Medial Patellofemoral Ligament Augmentation Repair for Primary Patellar Dislocation With Concomitant Chondral or Osteochondral Injury in Children and Adolescents: Outcomes at Minimum 2-Year Follow-up

Background

Treatment of primary patellar dislocation (PPD) with chondral or osteochondral injury without patellar stabilization in the adolescent population may lead to unsatisfactory outcomes. Surgical treatment, with or without traditional medial patellofemoral ligament (MPFL) reconstruction, is a topic of interest.

Purpose

To compare postoperative outcomes and rates of patellar redislocation and return to the operating room (OR) in patients who sustained a PPD with chondral or osteochondral injury and were surgically treated with versus without suture tape augmentation repair of the MPFL.

Study Design

Cohort study; Level of evidence, 3.

Methods

Adolescents who sustained a PPD with chondral or osteochondral injury confirmed via magnetic resonance imaging (MRI) and who were treated by a single surgeon between January 2009 and November 2020 were retrospectively reviewed. Patients were grouped into those who underwent chondral or osteochondral treatment with suture tape augmentation repair of the MPFL (ST group; n = 20) and those who did not have suture tape augmentation or repair (no-ST group; n = 20; 11 patients within the no-ST group did undergo medial imbrication). Demographic characteristics, postoperative knee range of motion, pre- and postoperative radiographic measurements, and preoperative MRI parameters were recorded, and minimum 2-year patient-reported outcomes were collected. Data were compared between the ST and no-ST groups.

Results

The mean patient age was 15.02 years (range, 12.64-17.61 years) in the ST group and 14.18 years (range, 10.56-16.38 years) in the no-ST group, with a mean follow-up of 3.63 years (range, 2.01-6.11 years) in the ST group and 4.98 years (range, 2.23-9.03 years) in the no-ST group. Significantly more patients returned to the OR in the no-ST group compared with the ST group (7 [35%] vs 0 [0%]; P = .008). Further patellar stabilization with an MPFL allograft (n = 5) and manipulation under anesthesia (n = 2) were reasons for returning to the OR. There were no redislocation events in the ST group.

Conclusion

Treating PPDs with chondral or osteochondral injury using suture tape to augment and repair the MPFL has promising advantages over not repairing it-including lower rates of postoperative patellar instability and return to the OR.

Derotational distal femur osteotomy with medial patellofemoral ligament reconstruction can get good outcomes in the treatment of recurrent patellar dislocation with excessive TT-TG and increased femoral anteversion

Background

Surgery is the main treatment for recurrent patellar dislocation (PD). However, due to the complexity of anatomical factors, there is still a lack of consensus on the choice of combined surgical methods. This study aimed to compare the clinical and radiological outcomes of medial patellofemoral ligament reconstruction combined with derotational distal femur osteotomies (MPFLR + DDFO) and combined with tibial tubercle osteotomies (MPFLR + TTO) for recurrent PD with increased femoral anteversion angles (FAA) and excessive tibial tubercle-trochlear groove (TT-TG) distance.

Methods

In this retrospective analysis, MPFLR + DDFO and MPFLR + TTO patients from 2015 to 2020 were included. Group A (MPFLR + DDFO, n = 42) and B (MPFLR + TTO, n = 46) were formed. Clinical outcomes included physical examinations, functional outcomes (Kujala, Lysholm, International Knee Documentation Committee (IKDC), visual analog scale (VAS) and intermittent and persistent osteoarthritis pain scale (ICOAP), Tegner scores), and complications. The Caton-Deschamps index (CD-I), patellar title angle, patellar congruence angle, patella-trochlear groove distance, TT-TG distance, and FAA were used to assess radiological outcomes.

Results

All clinical outcomes improved significantly in both groups, but Group A had significantly better postoperative scores than Group B (Kujala: 89.8 ± 6.4 vs. 82.9 ± 7.4, P < 0.01; Lysholm: 90.9 ± 5.1 vs. 81.3 ± 6.3, P = 0.02; IKDC: 87.3 ± 9.0 vs. 82.7 ± 8.0, P < 0.01; Tegner: 6.0 (5.0, 9.0) vs. 5.0 (4.0, 8.0), P = 0.01). However, there was no significant difference in the VAS and ICOAP scores between the two groups. No dislocation recurrences occurred. Radiological outcomes improved significantly in both groups, but Group A had better outcomes. After surgery, the patellar height of 88.5% (23/26) patients in Group A and 82.8% (24/29) patients in Group B was restored to normal (the Caton-Deschamps index <1.2).

Conclusions

Both MPFLR + TTO and MPFLR + DDFO obtained satisfactory clinical and radiological outcomes in the treatment of recurrent PD with increased FAA and excessive TT-TG. However, the outcomes of MPFLR + DDFO were better and should be considered a priority. MPFLR + TTO may be not necessary for such patients.

Reliability of Tibial Tubercle-Trochlear Groove Distance for Assessing Tibial Tubercle Lateralization: A Study Comparing Different Anatomic References

Background

The tibial tubercle-trochlear groove (TT-TG) distance is a measurement used to quantitatively assess tibial tubercle lateralization (TTL), and it has important reference value for the treatment of patellar dislocation (PD). However, TT-TG distance accuracy has been questioned, so many new parameters have been proposed.

Purpose

To compare which of the TT-TG, tibial tubercle-midepicondyle (TT-ME), tibial tubercle-Roman arch (TT-RA), tibial tubercle-tibial intercondylar midpoint (TT-TIM), and tibial tubercle-mid inter-epicondyle trochlea intersection (TT-MIELTI) distances better reflect TTL in patients with PD.

Study Design

Cohort study (diagnosis); Level of evidence, 3.

Methods

A total of 96 patients who had undergone surgery for PD and 96 patients without PD (controls) were included in the study. The patients had all undergone computed tomography examination. The TT-TG, TT-ME, TT-RA, TT-TIM, TT-MIELTI distances and the TTL distance were measured independently by 2 surgeons in a blinded and randomized fashion. The t test was used to detect whether the parameters were significantly different between the 2 groups. The TTL distance was used as a reference value for lateralization of tibial tubercle. Pearson correlation coefficients were calculated to determine correlations between the defined measurements.

Results

The intra- and interobserver reliability of the defined measurements was excellent. All parameters except for TT-TIM distance were significantly larger in the PD group than the control group (P < .01 for all). There was a moderate correlation (r = 0.601) between the TT-TG distance and TTL, and other parameters were less correlated with TTL.

Conclusion

Among 5 the parameters tested, the TT-TG distance still had the highest correlation with TTL and was able to reflect TTL better in patients with PD. The role of TT-TIM distance in the assessment of PD needs further study.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Epidemiology of patellar dislocations in the United States from 2001 to 2020: results of a national emergency department database

OBJECTIVES

Recent studies have shown an increasing incidence of patellar dislocations among children and adolescents. Updated, population-based studies of all patellar dislocations in the United States (US), however, are lacking. This study investigated recent trends in injury rates and demographics among patients sustaining patellar dislocations in the US from 2001 to 2020.

METHODS

This descriptive epidemiologic study retrospectively analyzed the National Electronic Injury Surveillance System (NEISS) database to identify cases of acute patellar dislocations presenting to US Emergency Departments (EDs) from 2001 to 2020. Annual, overall, and age-adjusted incidence rates (IRs, expressed per 100,000 at-risk person-years) and additional patient/injury characteristics were analyzed. Average annual percent change (AAPC) estimates are presented to indicate the magnitude/direction of trends in annual injury rates.

RESULTS

An estimated total of 159,529 patellar dislocations occurred over the study period for an overall IR of 2.58 (95% CI = 2.04-3.12). Accounting for population growth, the overall annual incidence increased significantly from 2.61 in 2001 to 3.0 in 2020 (AAPC = 2.8, p < 0.0001). When considering sex and age, statistically significant increases in annual IRs were observed among males aged 10-19 years (AAPC = 3.8, p < 0.0001), females aged 10-19 years (AAPC = 5.3, p < 0.0001), and females aged 20-29 years (AAPC = 3.5, p = 0.0152), while no significant changes were observed in any other age groups. Two-thirds of patellar dislocations involved sports-related injury mechanisms. The annual incidence of both sports-related and non-sports-related injuries increased significantly over the study period (sports-related: AAPC = 2.6, p = 0.0001; non-sports-related: AAPC = 3.4, p = 0.0001). Athletic patellar dislocations occurred most commonly in basketball and dance.

CONCLUSION

The number of patients sustaining patellar dislocations is increasing in the US. Similar increasing trends were observed in both males and females aged 10-19 years, whereas injury rates increased in the third decade only among females. A large percentage of injuries occur during athletic activity, but both sports- and non-sports-related patellar dislocations are on the rise.

Management of patellar instability in skeletally immature patients

Surgical intervention is the treatment of choice for recurrent lateral patellar instability. Surgery should be considered for first time lateral patella dislocations with osteochondral fractures or underlying anatomical risk factors. Primary repair and nonanatomical imbrications/reconstructions have fallen out of favor due to abnormal biomechanics and high rates of recurrence. Anatomical reconstruction of the MPFL using a variety of auto and allograft tissues have yielded good outcomes and low redislocation rates. Physeal sparing MPFL reconstruction techniques under radiological control are safe and do not cause growth disturbance. Allografts may be indicated for hyperlax patients. Although no clear cutoff points exist, correction of valgus and excessive femoral anteversion should be considered when indicated. Osteochondral and chondral injuries are common and should be addressed during surgery for instability.

Acute Treatment of Osteochondral Detachment Following Patellar Dislocation: Clinical and Short-Term MRI Follow-Up

BACKGROUND

The aim of our study is to emphasizes the significance of prompt diagnosis and intervention in younger patients affected by osteochondral detachment after patellar dislocation, where the first objective is to minimize in the shortest possible time complications and ingravescence. The method involves a clinical patient assessment and MRI follow-up in subjects who underwent to an immediate surgical intervention for osteochondral damage.

METHODS

From January 2020 to December 2022, 22 patellar dislocation cases were assessed; osteochondral lesions were identified in 12 (54%) patients; nine of these patients were treated immediately with knee arthroscopy, while in seven instances the osteochondral fragment was reattached using bioabsorbable pins. Post-operative clinical evaluations were conducted at one-, three-, and six-month intervals; finally, a six-month post-operative MRI was performed for all surgically treated patients.

RESULTS

The MRI evaluations, conducted six months post-operation for all seven patients, indicated successful integration of the reattached osteochondral fragment. Every patient returned to their pre-injury activities after surgery. However, two of them reported mild pain in the anterior region of the knee post-surgery.

CONCLUSIONS

in young patients, swift diagnosis and immediate surgical intervention for osteochondral detachment resulting from patellar dislocation are crucial. This approach has been identified as the best practice, since it substantially minimizes immediate functional restrictions and significantly lowers the long-term risk of femoral-patellar osteoarthritis.

Clinical outcomes of derotational femoral osteotomy combined with medial patellofemoral ligament reconstruction in patients with patellar dislocation and increased femoral anteversion unaffected by the pattern of distribution of femoral torsion

PURPOSE

The aim of this study was to evaluate the clinical effect of derotational femoral osteotomy combined with medial patellofemoral ligament reconstruction for patellar dislocation and the effect of the distribution of femoral torsion at different segments on postoperative function.

METHODS

Forty-two patients with patellar dislocation who underwent derotational femoral osteotomy from 2017 to 2021 were retrospectively analysed. All patients received computed tomography scans from the hip to the knee to evaluate correction of the femoral anteversion (FA) angle, patellar tilt angle (PTA) and congruence angle (CA) after derotational femoral osteotomy. Subjective scores, such as the Kujala, Lysholm, International Knee Documentation Committee (IKDC), Tegner and visual analog scale (VAS) scores, were used to evaluate knee function before and after the operation. Patients with supracondylar torsion > distal torsion were categorized into the supracondylar torsion group and patients with distal torsion > supracondylar torsion were categorized into the distal torsion group. Subgroup analyses were performed.

RESULTS

No presentation of redislocation occurred in these patients at the minimum 2-year follow-up visit. The mean preoperative FA angle in the supracondylar torsion group was 30.2° ± 4.2°, and the mean postoperative FA angle was 14.5° ± 2.5° (p < 0.001). The mean preoperative FA angle was 26.7° ± 1.4° and the mean postoperative FA angle was 14.1° ± 1.4° in the distal torsion group. In addition, postoperative PTA and CA were significantly corrected in both groups (p < 0.001). The postoperative Kujala, Lysholm, IKDC, Tegner and VAS scores were significantly improved in both groups (p < 0.001). Subgroup analyses showed a higher preoperative FA in the supracondylar torsion group and a higher occurrence of high-grade trochlear dysplasia in the distal torsion group. However, there was no significant difference in their postoperative clinical outcomes.

CONCLUSION

Through a minimum of 2-year follow-up visits of patients with patellar dislocation and increased FA, it was found that derotational femoral osteotomy could significantly reduce FA and improve subjective knee function. The pattern of torsion distribution did not significantly affect the clinical outcomes of derotational femoral osteotomy. These findings readvised orthopaedic surgeons that derotational femoral osteotomy remains the preferred procedure for correcting rotational malalignment, but that they should be more cautious about its indications.

LEVEL OF EVIDENCE

Level IV.

Patellar Dislocation in Adolescent Patients: Influence on Cartilage Properties Based on T1ρ Relaxation Times

BACKGROUND

Adolescents who experience a patellar dislocation have an elevated risk of patellofemoral posttraumatic osteoarthritis. Magnetic resonance imaging (MRI)-based T1ρ relaxation times were measured for adolescents to evaluate patellofemoral cartilage after patellar dislocation. Long T1ρ relaxation times are an indicator of cartilage degradation.

HYPOTHESIS

The primary hypothesis is that patellofemoral cartilage T1ρ relaxation times will be elevated in the acute phase after patellar dislocation. The secondary hypothesis is that T1ρ relaxation times will be higher for knees with multiple rather than single dislocations due to repeated traumatic injury.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In total, 23 adolescents being treated for a recent patellar dislocation, 13 for a first-time dislocation (47 ± 38 days since most recent dislocation) and 10 for multiple dislocations (55 ± 24 days since most recent dislocation), and 10 healthy controls participated in MRI-based T1ρ relaxation time mapping. For multiple regions of the patellofemoral joint, mean T1ρ values were compared between the 3 groups with multiple group comparisons and post hoc tests. T1ρ relaxation times were also correlated against measures of patellofemoral anatomy and alignment for single and multiple dislocations. Statistical significance was set at P < .05.

RESULTS

T1ρ relaxation times were significantly longer for injured knees (single and multiple dislocations) than controls at the medial and central patella and central trochlear groove. For the regions on the patella, significant differences between injured and control knees exceeded 15%. No significant differences were identified between single and multiple dislocations. For the initial dislocation group, T1ρ relaxation times within multiple regions of the patellofemoral joint were significantly correlated with lateral patellar alignment or patellar height.

CONCLUSION

Elevated patellofemoral cartilage T1ρ relaxation times are consistent with a high risk of long-term patellofemoral osteoarthritis for adolescents who experience patellar dislocations. T1ρ relaxation times were elevated for multiple regions of patellofemoral cartilage. T1ρ relaxation times were expected to increase with additional dislocation episodes, but relaxation times after single and multiple dislocations were similar. After a first dislocation, parameters related to patellar maltracking were correlated with cartilage degradation.

Comparison of Bone Bruise Pattern Epidemiology between Anterior Cruciate Ligament Rupture and Patellar Dislocation Patients-Implications of Injury Mechanism

Different bone bruise patterns observed using magnetic resonance imaging (MRI) after non-contact anterior cruciate ligament (ACL) rupture and lateral patellar dislocation may indicate different knee injury mechanisms. In this study, 77 ACL ruptures and 77 patellar dislocations in knee MR images taken from patients with bone bruises at our institution between August 2020 and March 2022 were selected and analyzed. In order to determine typical bone bruising patterns following by ACL rupture and patellar dislocation, sagittal- and transverse-plane images were used to determine bone bruise locations in the directions of medial-lateral and superior-inferior with MR images. The presence, intensity, and location of the bone bruises in specific areas of the femur and tibial after ACL rupture and patellar dislocation were recorded. Relative bone bruise patterns after ACL rupture and patellar dislocation were classified. The results showed that there were four kinds of bone bruise patterns (1-, 2-, 3-, and 4- bone bruises) after ACL rupture. The most common two patterns after ACL rupture were 3- bone bruises (including the lateral femoral condyle and both the lateral-medial tibial plateau, LF + BT; both the lateral-medial femoral condyle and the lateral tibial plateau, BF + LT; and the medial femoral condyle and both the medial and lateral tibial plateau, MF + BT) followed by 4- bone bruises (both the lateral-medial femoral condyle and the tibial plateau, BF + BT), 2- bone bruises (the lateral femoral condyle and tibial plateau, LF + LT; the medial femoral condyle and the lateral tibial plateau, MF + LT; the lateral femoral condyle and the medial tibial plateau, LF + MT; the medial femoral condyle and the tibial plateau, MF + MT; both the lateral-medial tibial plateau, 0 + BT), and 1- bone bruise (only the lateral tibial plateau, 0 + LT). There was only a 1- bone bruise (the latera femoral condyle and medial patella bone bruise) for patellar dislocation, and the most common pattern of patellar dislocation was in the inferior medial patella and the lateral anterior inferior femur. The results suggested that bone bruise patterns after ACL rupture and patellar dislocation are completely different. There were four kinds of bone bruise patterns after non-contact ACL rupture, while there was only one kind of bone bruise pattern after patellar dislocation in patients, which was in the inferior medial patella and lateral anterior inferior femur.

Healing of a bone-exposed soft tissue defect after surgical correction of traumatic patellar dislocation: A case report

RATIONALE

Reconstructive surgery is widely considered the primary treatment for soft tissue defects around the knee owing to its high flexibility. However, in our recent case study, we explored an alternative approach using decellularized collagen dressings, which proved highly effective in healing a soft tissue defect involving bone exposure following surgical correction of a traumatic patellar dislocation.

PATIENT CONCERNS

A 65-year-old male with a traumatic patellar dislocation in the lower extremity failed to approximate the wound after surgical correction. The patient refused additional surgical reconstruction because of the potential risks of multiple operative complications.

DIAGNOSES

Traumatic patellar dislocation complicated by exposed bone following surgical treatment was made.

INTERVENTIONS

The procedure was performed using ABCcolla® Collagen Matrix (ACRO Biomedical, Taiwan), an acellular dermal matrix made from a decellularized native porcine collagen scaffold dressing. Collagen dressings were applied to the soft tissue defect, and biointegration was observed in the wound area of bone exposure.

OUTCOMES

Through the application of ABCcolla® Collagen Matrix (ACRO Biomedical, Taiwan) and diligent wound care for a total of 105 days, the patient healed successfully and achieved partial functional recovery after undergoing rehabilitation. During recent outpatient clinic visits, the patient is now able to ambulate independently with the aid of crutches.

LESSONS

Collagen dressings circumvent the potential risks and complications associated with multiple surgical procedures. We believe that the utilization of collagen dressings, combined with careful wound management, could serve as a promising alternative treatment option for patients with soft tissue defects around the knee in the future.

The Novelty of Orthopedic Rehabilitation After Conservative Management for Patellar Dislocation With Partial Tear of Medial Meniscus and Early Osteoarthritis in a 31-Year-Old Female

Primary patellar dislocation or first-time patellar dislocation is the second most frequent cause of knee injuries which overall accounts for about 3% of other knee injuries. The patellofemoral joint is formed by the patella connecting to the femoral trochlea and creates both static and dynamic structures of the knee. There are basically three types of patellar dislocation: superior, lateral, and medial. The lateral dislocation is the most frequent one. Females are more vulnerable and are at higher risk than males. Muscular weakness or muscular imbalance leads to patellar instability, and ultimately to dislocation. The recurrence rate after primary patellar dislocation is 15-60%. This case report is of a 31-year-old female with patella dislocation with a medial meniscal tear and a case of early osteoarthritis for whom we planned goal-oriented physiotherapy rehabilitation week-wise and progressed every week. The assessment was taken before and after physiotherapy rehabilitation. The patient was managed conservatively with a long knee brace, and physiotherapy started after one month. Due to prolonged immobilization, the patient suffered from quadriceps muscle atrophy. The physiotherapist focused on biomechanism and got the expected results in pain reduction, regaining strength, and improving range of motion, and the patient was able to walk properly without taking any support after rehabilitation.

Association Between Femoral Anteversion and Distal Femoral Morphology in Patients With Patellar Dislocation and Trochlear Dysplasia

Background

Increased femoral anteversion (FA) is reportedly associated with patellar dislocation (PD) and trochlear dysplasia (TD), and the increase in FA may occur at different segments of the femur. In addition, TD is associated with dysplasia of the posterior femoral condyle. Among patients with PD, whether FA is greater with or without TD remains unclear.

Purpose

To explore differences in FA and torsion distribution at different femoral sections among patients with PD and TD, patients with PD and no TD, and sex- and age-matched controls and to investigate the association between FA and distal femoral morphology.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

This study involved 132 knees: 44 knees with PD and TD, 44 knees with PD but no TD, and 44 control knees. FA, proximal torsion (PT), middle torsion (MT), distal torsion (DT), and distal femoral morphology were measured. Differences were investigated by 1-way analysis of variance. Pearson correlation analysis was conducted to explore the association between FA and each parameter.

Results

FA was significantly larger in the PD with TD group (25.4° ± 4.7°) than in the other groups (controls: 18.9° ± 5.6°; PD without TD: 19.9° ± 4.8°) (P < .01). DT was significantly larger in the PD with TD group (15.8° ± 2.9°) than in the other groups (controls: 9.0° ± 4.3°; PD without TD: 8.8° ± 3.9°) (P < .01). In all 3 groups, FA was strongly positively correlated with DT (control, PD without TD, and PD with TD, respectively: r = 0.76, 0.80, and 0.88; P < .01), strongly positively correlated with the posteromedial condylar length (r = 0.48, 0.48, and 0.70; P < .01) and negatively correlated with the posterolateral condylar length (r = -0.30, -0.35, and -0.78, respectively; P < .05).

Conclusion

The increased FA in knees with TD was due mainly to DT rather than PT or MT, which may provide a reference for choosing the optimal position for femoral derotation osteotomy.

Cadaveric Study to Define the Anatomy of the Medial Patellofemoral Ligament (MPFL) and Its Variant Patterns

BACKGROUND

The medial patellofemoral ligament (MPFL) is one of the major soft tissue stabilizers on the medial side of the knee joint, extending from the medial condyle of the femur to the medial aspect of the patella. Different kinds of literature described different sizes and different origins and insertions of MPFL. Injury of MPFL causes patellar instability and dislocation. We reported the anatomy and morphology of MPFL and its implications in the repair of MPFL. The aim of the study was also to look at the variant forms of the MPFL.   Methodology: A total of 40 lower limbs fixed in formalin were dissected to study the MPFL of the knee. After reflecting the deep fascia and retinaculum on the medial side of the knee joint the MPFL was exposed. For better learning the lower medial part of vastus medialis was reflected, so that the part of MPFL undercover was exposed.

RESULTS

 Different forms of MPFL were seen like two straps 12.5%, broad rectangle 20%, and triangular shaped 67.5% MPFL. The origin of MPFL was found between the adductor tubercle and medial epicondyle of the femur and insertion was seen extending from the proximal medial half of the patella to the tendinous aponeurosis of vastus medialis obliquus (VMO) and vastus intermedius muscle (VIM).

CONCLUSIONS

This is the first study that described three variant patterns of MPFL in accordance with their morphological appearance. This knowledge will be helpful to the surgeons for easy identification and repair of the MPFL.

Traumatic Popliteal Artery Occlusion Following Lower Extremity Crush Injury Presenting With Isolated Patellar Dislocation

While traumatic popliteal artery injury historically has a low incidence, failure to acutely recognize the vascular insult poses a significant risk of limb loss and functional impairment. A 71-year-old male presented with left lower extremity pain in setting of a crush injury working underneath a vehicle resulting in an isolated lateral dislocation of his patella and complete occlusion of the distal popliteal artery. He was taken to the operating room for an in-situ bypass and four-compartment fasciotomy. His hospital stay included three staged washouts/debridements with eventual closure. He was discharged after 38 days to a rehabilitation facility with ability to self-ambulate with assistance within one month. This patient's presentation is unique for his isolated patellar dislocation without associated injuries characteristically associated with a traumatic vascular injury of the popliteal artery and serves to remind the importance of complete examination in the setting of blunt trauma.

Femoral Anteversion Measured by the Surgical Transepicondylar Axis Is Correlated with the Tibial Tubercle-Roman Arch Distance in Patients with Lateral Patellar Dislocation

Background and Objectives: Various predisposing factors for lateral patellar dislocation (LPD) have been identified, but the relation between femoral rotational deformity and the tibial tubercle-Roman arch (TT-RA) distance remains elusive. Materials and Methods: We conducted this study including 72 consecutive patients with unilateral LPD. Femoral anteversion was measured by the surgical transepicondylar axis (S-tAV), and the posterior condylar reference line (P-tAV), TT-RA distance, trochlear dysplasia, knee joint rotation, patellar height, and hip-knee-ankle angle were measured by CT images or by radiographs. The correlations among these parameters were analyzed, and the parameters were compared between patients with and without a pathological TT-RA distance. Binary regression analysis was performed, and receiver operating characteristic curves were obtained. Results: The TT-RA distance was correlated with S-tAV (r = 0.360, p = 0.002), but the correlation between P-tAV and the TT-RA distance was not significant. S-tAV had an AUC of 0.711 for predicting a pathological TT-RA, with a value of >18.6° indicating 54.8% sensitivity and 82.9% specificity. S-tAV revealed an OR of 1.13 (95% CI [1.04, 1.22], p = 0.003) with regard to the pathological TT-RA distance by an adjusted regression model. Conclusions: S-tAV was significantly correlated with the TT-RA distance, with a correlation coefficient of 0.360, and was identified as an independent risk factor for a pathological TT-RA distance. However, the TT-RA distance was found to be independent of P-tAV.

3D-printed individualized navigation template versus the fluoroscopic guide to defining the femoral tunnel for medial patellofemoral ligament reconstruction: A retrospective study

During medial patellofemoral ligament (MPFL) reconstruction, fluoroscopic determination of the femoral tunnel point is the most common method. However, there is a decrease in tunnel position accuracy due to rotation of the femur during fluoroscopy, as well as the damage to the operator from multiple fluoroscopies, whereas the 3D-printed individualized navigation template is not affected by this factor. This study focuses on the accuracy and early clinical efficacy of 2 different ways to determine the femoral tunnel (Schöttle point) for double-bundle isometric MPFL reconstruction. This is a retrospective study, conducted between 2016 and 2019, in which 60 patients with recurrent patellar dislocation were divided into 2 groups: 30 with MPFL reconstruction at the Schöttle point determined by 3D-printed individualized navigation template (group A) and 30 with MPFL reconstruction at the Schöttle point determined by fluoroscopic guidance (group B). The changes in patella congruence angle and patella tilt angle before and after surgery were assessed using computed tomography scans of the knee, knee function was assessed using the Kujala knee score and the international knee documentation committee (IKDC) score, and the 2 approaches were compared for the intraoperative establishment of the femoral tunnel position at a distance from Schöttle point. At a minimum of 3 years follow-up, patella tilt angle and patella congruence angle returned to normal levels and were statistically different from the preoperative range, with no significant differences between the 2 groups at the same period, and Kujala and IKDC scores of knee function were significantly improved in both groups after surgery. The mean Kujala and IKDC scores were statistically different between groups A and B at 3 and 6 months postoperatively. No statistically significant differences were seen between the 2 groups at the final follow-up. Both femoral tunnel localization approaches for double-bundle isometric MPFL reconstruction resulted in good knee function. At no < 3 years of follow-up, the use of a 3D-printed individualized navigation template did result in more accurate isometric points and higher knee function scores in the early postoperative period.

Prediction of Subsequent Contralateral Patellar Dislocation after First-Time Dislocation Based on Patellofemoral Morphologies

The subsequent dislocation of a contralateral patellofemoral joint sometimes occurs after a first-time lateral patellar dislocation (LPD). However, the anatomic risk factors for subsequent contralateral LPD remain elusive. This study included 17 patients with contralateral LPD and 34 unilateral patellar dislocators. The anatomic parameters of the contralateral patellofemoral joints were measured using CT images and radiographs that were obtained at the time of the first dislocation. The Wilcoxon rank-sum test was performed, and a binary regression model was established to identify the risk factors. The receiver operating characteristic curves and the area under the curve (AUC) were analyzed. The tibial tubercle-Roman arch (TT-RA) distance was significantly different between patients with and without contralateral LPD (24.1 vs. 19.5 mm, p < 0.001). The hip−knee−ankle (HKA) angle, patellar tilt, congruence angle, and patellar displacement were greater in the study group than in the control group (p < 0.05). The TT-RA distance revealed an OR of 1.35 (95% CI (1.26−1.44]), p < 0.001) and an AUC of 0.727 for predicting contralateral LPD. The HKA angle revealed an OR of 1.74 (95% CI (1.51−2.00), p < 0.001) and an AUC of 0.797. The Patellar tilt, congruence angle, and patellar displacement had AUC values of 0.703, 0.725, and 0.817 for predicting contralateral LPD, respectively. In conclusion, the contralateral patellofemoral anatomic parameters were significantly different between patients with and without subsequent contralateral LPD. Increased TT-RA distance and excessive valgus deformity were risk factors and could serve as predictors for contralateral LPD. At first-time dislocation, the abnormal position of the patella relative to the trochlea may also be an important cause of subsequent LPD.

The Tibial Tuberosity-Rotational Angle as a Novel Predisposing Parameter for Patellar Dislocation

Background

The tibial tuberosity (TT) in the axial plane is located on a curved line along the anterior cortex of the proximal tibia. Therefore, the linear measurement of TT position may not fully reflect TT malposition.

Purpose

To introduce TT-rotational angle (TT-RA) as a new anatomical parameter, which means the rotation of the TT relative to the dorsal condylar line of the tibia, and to validate its predictive value for patellar dislocation.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were 46 patients with a history of patellar dislocation and 46 age- and sex-matched controls who underwent axial magnetic resonance imaging. Seven radiological parameters were measured and compared between the 2 groups, including TT-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance, TT-PCL ratio, TT lateralization (TTL), trochlear groove medialization (TGM), TT-RA, trochlear groove-posterior condylar axis angle (TG-PCA), and knee rotation. The predictive values of parameters for patellar dislocation were assessed using multiple logistic regression analysis.

Results

The intra- and interobserver correlation coefficients for measuring the radiographic parameters showed good to excellent values., respectively. There were significant differences in the TT-TG distance (13.9 vs 6.8 mm; P < .001), TT-RA (16.0° vs 9.1°; P < .001), TG-PCA (93.7° vs 95.4°; P = .017), and knee rotation (0.9° vs 5.3°; P < .001) between the 2 groups. However, there was no significant difference in TT-PCL distance (20.7 vs 19.4 mm; P = .075), TT-PCL ratio (28.0% vs 26.6%; P = .136), TTL (65.7% vs 64.9%; P = .270), or TGM (54.9% vs 55.0%; P = .923). Multivariable analysis showed that 3 parameters were significantly associated with patellar dislocation: TT-RA (OR, 1.57; P < .001), TT-TG distance (OR, 1.52; P = .002), and knee rotation (OR, 0.75; P = .022).

Conclusion

The TT-RA was a reliable predisposing parameter of patellar instability. It can be an alternative method of measurement when the TT-TG distance is not clearly defined.

A Pilot Study on the Reliability of Ultrasound-Based Assessment of Patella Diameter and Sulcus Angle

This pilot study aimed to determine the reliability of a newly developed ultrasound-based protocol for the assessment of patella diameter and sulcus angle. The diameter of the patella expressed in mm and the sulcus angle, expressed in degrees were measured in the right knee in 12 healthy participants (eight women and four men) in two separate sessions by two examiners (experienced rater and inexperienced rater) using ultrasonography according to a developed standardized protocol. The reliability was determined on the calculated intraclass correlation coefficient, ICC, expressed as a 95% confidence interval (lower bound, upper bound). For the patella diameter measurement, intra-rater and inter-rater reliability were good to excellent, with the ICC exceeding 0.836-0.998 and 0.859-0.997, respectively. The intra-rater and inter-rater reliability of the sulcus measurement was moderate to excellent, as the ICC amounted to 0.559-0.993 and 0.559-0.990, respectively. The reliability of both measures increased with the experience of the examiner. Therefore, it was determined that the newly developed protocol for an ultrasound-based assessment of patella diameter and sulcus angle is reliable. Further studies validating their clinical use should be carried out.

A Novel Heterozygous ACAN Variant in a Short Patient Born Small for Gestational Age with Recurrent Patellar Dislocation: A Case Report

ACAN variants can manifest as various clinical features, including short stature, advanced bone age (BA), and skeletal defects. Here, we report rare clinical manifestations of ACAN defects in a 9 year, 5 month-old girl born small for gestational age (SGA), who presented with short stature, and was initially diagnosed with idiopathic growth hormone deficiency. She displayed several dysmorphic features, including genu valgum, cubitus valgus, and recurrent patellar dislocations. She presented with progressive advancement of BA compared with chronological age. Whole exome sequencing confirmed the presence of a novel heterozygous nonsense variant, c.1968C>G, p.(Tyr656*), in ACAN. ACAN variants should be considered in short stature patients born SGA with joint problems, particularly those with recurrent patellar dislocation and genu valgum.

Reconceptualization of Trochlear Dysplasia in Patients With Recurrent Patellar Dislocation Using 3-Dimensional Models

Background

Common classification schemes, measurements, and surgical planning for trochlear dysplasia are predicated on 2-dimensional imaging views.

Purpose

To investigate patellofemoral joint osseous anatomy using 3-dimensional (3D) printed models to describe osseous anatomic trochlear variations in patients with recurrent patellar dislocation.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Computed tomography scans were obtained from 20 patients with recurrent patellar dislocation and 10 healthy control knees, and 3D prints generated from these computed tomography scans were studied with respect to mediolateral positioning of the proximal trochlear groove and groove obliquity as well as changes in the appearance, height, and orientation of the medial and lateral trochlear ridges. Each trochlea was centered with respect to a vertical line perpendicular to the distal femoral condyles and through the central intercondylar notch roof, with the 3D models resting on their posterior femoral condyles. A novel 3D measurement method was devised to assess groove obliquity, termed the entry point-transition point (EP-TP) angle. The EP was defined as the midpoint of the flattened region of the proximal trochlea where the lateral and medial ridges of the proximal trochlea meet, and the TP was the point along the trochlear groove at which the groove shape changes from an oblique orientation proximally to one more vertical distally. Measurements were obtained by 3 reviewers, and reliability analyses were performed.

Results

With the dysplastic knees arranged according to flattening of the trochleas, increased obliquity of the trochlear grooves was observed, as reflected by increased EP-TP angles as well as more lateral patellar EPs into the proximal trochleas of these recurrent patellar dislocation knees when compared with the control knees. The degree of trochlear dysplasia (according to the Dejour classification and trochlear flatness in the frontal and axial planes) was associated with diminished prominence of the lateral trochlear convexity, increasingly lateralized proximal trochlear EPs, increased trochlear groove obliquity, lateral trochlear curvature, and progressive medial ridge deformity.

Conclusion

The 3D reproductions enabled unique conceptualization of trochlear deformity associated with recurrent patellar dislocation.

Pathological Thresholds of Segmental Femoral Torsion in Patients With Patellar Dislocation: Influence on Patellofemoral Malalignment

Background

Femoral torsion can be evaluated from different femoral segments. The pathological thresholds for femoral torsion of different segments and the influence of segmental femoral torsion on patellofemoral alignment remain unknown.

Purpose

To compare femoral torsion between patients with recurrent patellar dislocation and healthy individuals, to determine the statistical physiological range and pathological thresholds of femoral torsion in different segments, and to investigate the influence of femoral torsion on patellofemoral malalignment.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

We retrospectively reviewed the records of patients with patellar dislocation who received surgical treatment in our department between 2019 and 2020. Healthy participants were recruited as the control group. The control patients were asymptomatic and had no history of lower extremity disorders. The differences in femoral torsion between the study and control groups were compared. The diagnostic capacity of femoral torsion in different segments and their correlation with patellar tilt were investigated. The mean value and 95% CI of femoral torsion in different segments were established using data from healthy volunteers.

Results

A total of 60 patients with patellar dislocation and 100 healthy volunteers were included in this study. The total, mid, and distal femoral torsion values differed significantly between the study and control groups (P < .01). Total femoral torsion had the highest diagnostic value (area under the receiver operating curve = 0.733). Total torsion (r = 0.432; P < .001), mid torsion (r = 0.242; P = .002), and distal torsion (r = 0.324; P < .001) showed significant correlations with patellar tilt. The pathological thresholds of excessive femoral torsion of the total, proximal, mid, and distal femoral segments were 24.73°, 46.68°, –6.55°, and 14.92°, respectively.

Conclusion

Patients with patellar dislocation had greater femoral torsion than healthy individuals in multiple femoral segments. Excessive mid, distal, and total torsion was associated with more significant patellar tilt.

Tibial Tubercle to Trochlear Groove Distance Measured by Posterior Condylar Reference Line on MRI Can Over-Evaluate Lateralization Deformity of Tibial Tubercle in Patients with Recurrent Patellar Dislocation

Background: The tibial tubercle to trochlear groove (TT-TG) distance is currently considered as an indication for tibial tubercle osteotomy. While the influence of femoral condylar morphology on such measurement remains unclear. Methods: A total of 86 patients with patellar dislocation (PD) and 86 healthy individuals were enrolled. Femoral condylar morphology and the TT-TG distance measured by anatomical transepicondylar axis (TT-TGa), by surgical transepicondylar axis (TT-TGs), and by posterior condylar reference line (TT-TGp) were assessed by MRI. Unpaired t-test, Spearman, and Pearson correlation analysis were conducted. We determined the pathological value of the parameters and established a binary regression model. Results: The interclass correlation coefficients of all the TT-TG distances were greater than 0.75 in all types of trochlear dysplasia. The lateral/posterior femoral condyle was shorter and the medial/posterior condyle was longer in the study group (28.5 ± 3.3 and 35.2 ± 2.8, respectively) than in the control group (30.9 ± 2.7 and 33.5 ± 2.3, respectively). In the study group, the TT-TGp distance was greater than TT-TGs and TT-TGa distance (p < 0.001). The pathological value of the TT-TG distance was 13.0 mm. Each TT-TG distance revealed a significant OR with regard to PD. Conclusion: The TT-TGa, TT-TGs, and TT-TGp distance can be reliably measured by MRI even in patients with trochlear dysplasia. While the TT-TGp distance may overestimate the lateralization deformity of the tibial tubercle. Posterior femoral condylar dysplasia may be a reason for such overestimating. These findings have not been correlated to clinical outcomes and further studies are required.

Reliability of the Tibial Tubercle-Roman Arch Distance for Evaluating Tibial Tubercle Malposition and Predicting Patellar Dislocation via Magnetic Resonance Imaging

Background:

The tibial tubercle (TT)–trochlear groove (TT-TG) distance has low reproducibility in patients with a dysplastic trochlea, whereas the clinical value of the TT–posterior cruciate ligament (TT-PCL) distance remains controversial.

Purposes:

To establish a method to assess the position of the TT on magnetic resonance imaging (MRI) scans using the TT–Roman arch (TT-RA) distance, compare this method with the TT-TG and TT-PCL distance, and provide the pathological threshold value of the TT-RA distance in patients with patellar dislocation.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

The TT-RA distance, TT-TG distance, and TT-PCL distance were measured on MRI scans in 70 patients with a history of patellar dislocation and 70 healthy individuals. Inter- and intraobserver reliability of each measurement parameter were evaluated. The discriminatory capacity and the interrelationship of the 3 measurement parameters were investigated using Pearson correlation and the receiver operating characteristic curve. The pathological threshold values of these measurements were calculated according to the data of healthy individuals. Finally, logistic regression analysis was performed using these values.

Results:

Patients with patellar dislocation had a greater TT-RA distance compared with healthy individuals (18.05 ± 4.16 vs 13.86 ± 2.90 mm; P < .001). The TT-RA distance had a stronger diagnostic capacity, with an area under the curve of 0.802 compared with 0.625 for TT-PCL distance. Excellent reproducibility was seen for TT-RA distance measurement at any degree of trochlear dysplasia (all intraclass correlation coefficients [ICCs] >0.90). The inter- and intraobserver ICCs of the TT-TG distance measurements were extremely low for Dejour type D dysplasia (ICC, 0.509 and 0.616, respectively). The pathological TT-RA distance threshold was calculated as 19.5 mm. Logistic regression showed that patients with a TT-RA distance >19.5 mm were 11.7 times more likely to sustain patellar dislocation than were those with TT-RA distance less than this value.

Conclusion:

The TT-RA distance was a more reliable parameter with which to evaluate TT position than was TT-TG distance in patients with trochlear dysplasia. The TT-PCL distance was the least reliable among the 3 parameters studied.

Changes in Anatomic Risk Factors for Patellar Instability During Skeletal Growth and Maturation

BACKGROUND

Several anatomic risk factors have been identified in the pathogenesis of patellofemoral instability. The literature is sparce regarding how these anatomic risk factors change during skeletal growth and development.

HYPOTHESIS

The anatomic risk factors associated with patellar instability change significantly during skeletal growth and maturation with different patterns in male versus female patients.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Magnetic resonance imaging data from 240 unique, asymptomatic knees (7-18 years of age; 50% female) were used to measure patellar height (Caton-Deschamps index), lateral patellar tilt angle, trochlear height, trochlear groove depth, trochlear sulcus angle, and tibial tubercle-trochlear groove (TT-TG) distance. Linear regression was used to test the associations between age and anatomic findings. Two-way analysis of variance with Holm-Šídák post hoc test was used to compare anatomic characteristics between sexes in 3 age groups: prepubertal school-aged children (7-10 years old), early adolescents (11-14 years old), and late adolescents (15-18 years old).

RESULTS

Patellar height (female sex), lateral patellar tilt angle (male sex), and trochlear sulcus angle (both sexes) decreased with age (P < .001). Trochlear height, depth, and TT-TG distance increased with age in both male and female participants (P < .02). Male participants had a larger sulcus angle (by 5.3°± 1.6° at age 11-14 years) and greater trochlear height (by >5 mm across medial, central, and lateral regions at age 15-18 years) than age-matched female participants (P < .01). We found no other sex-related differences in quantified anatomic features (P > .1).

CONCLUSION

The findings partially support our hypothesis indicating significant age-related changes in all quantified features, which were not different between male and female participants except for trochlear sulcus angle in early adolescence and trochlear height in late adolescence. In general, the majority of anatomic risk factors for patellar instability change with maturity in a direction that assists in reducing the risk of patellar instability and/or dislocation. The only outlier is the TT-TG distance, which increased by age, and in our oldest cohort of patients, the mean fell below the normal adult range. The current observations highlight the importance of age in the interpretation of risk for injury as well as the need for further studies to identify intrinsic and extrinsic factors that may result in abnormal development of these anatomic features during skeletal growth and maturation.

Osteochondral Fractures in Acute Patellar Dislocations in Adolescents: Midterm Results of Surgical Treatment

Background:

Osteochondral fractures (OCFs) are common injuries during acute patellar dislocation (APD), carrying a high risk of early joint deterioration if left untreated. The recommended approach is reduction and stable fixation; however, data on the results of such treatment are limited.

Purpose:

To evaluate midterm results of fixation of APD-related OCFs in adolescents and to identify predictive factors for poor outcomes.

Study Design:

Case series; Level of evidence, 4.

Methods:

This was a retrospective analysis of adolescent patients who underwent internal fixation of APD-related OCFs between 2004 and 2015 at a single tertiary pediatric trauma center. The primary outcome variables included Knee injury and Osteoarthritis Outcome Score (KOOS), patient satisfaction (0-10 scale), and sports participation compared with preoperative level. Secondary outcome variables included relationship between final results and OCF location (patellofemoral vs tibiofemoral), surgical delay (>6 weeks), and patellar instability after OCF fixation. OCF healing was evaluated using magnetic resonance imaging (MRI).

Results:

Included were 40 patients (19 female, 21 male) with 42 OCFs (29 patellar OCFs, 13 lateral femoral condyle OCFs). The median patient age at surgery was 14.5 years (interquartile range [IQR], 13-15.5 years), and median follow-up was 76 months (IQR, 52.5-95 months). Recurrence of patellar instability occurred in 27.5% of patients. Median overall KOOS was 93.8 (IQR, 90.8-97.6); KOOS–Symptoms, 92.9 (IQR, 85.7-96.4); KOOS–Pain, 97.2 (IQR, 91.7-100); KOOS–Activities of Daily Living, 100 (IQR, 97.1-100); KOOS–Sports, 90 (IQR, 80-100); and KOOS–Quality of Life, 78.1 (IQR, 56.2-87.5). Median satisfaction score was 8 (IQR, 8-9), and 16 patients (40%) returned to sports participation at their preinjury level. MRI scans revealed a 100% rate of bone healing. Abnormalities exceeding the fracture area were evident on MRI scans in 86.5% of patients. Recurrence of patellar instability (even after surgical fixation) and unstable patella at final follow-up were independent predictors of worse results after OCF fixation.

Conclusion:

In the current study, reduction and internal fixation for APD-related OCF in adolescents yielded favorable midterm outcomes. Recurrence of dislocation and persistent patellar instability jeopardized clinical results.

The Increased Tibiofemoral Rotation: A Potential Contributing Factor for Patellar Maltracking in Patients with Recurrent Patellar Dislocation

OBJECTIVE

The purpose of this study was to analyze the relationship between tibiofemoral rotation and patellar maltracking in patients with recurrent patellar dislocation.

METHODS

A total of 143 consecutive knees (118 patients) with clinically diagnosed recurrent patellar dislocation from January 2018 to December 2019 were retrospectively analyzed. Patellar tilt angle and bisect offset index were recorded on axial CT to assesses the severity of patellar maltracking. Tibiofemoral rotation angle is measured by comparing the angle between the posterior femoral and tibial condylar lines on three-dimensional CT. The Pearson correlation was calculated to investigate the association between tibiofemoral rotation angle and patellar maltracking. Patients were divided into the rotation group (≥15°) and control group (<15°) based on the value of tibiofemoral rotation and a further comparison was performed. To further clarify the complicated relationship among tibial tubercle-trochlear groove (TT-TG), tibial tubercle-posterior cruciate ligament distance (TT-PCL), tibiofemoral rotation, and patellar maltracking, patients were divided into four subgroups according to the value of TT-TG and TT-PCL.

RESULTS

The mean preoperative tibiofemoral rotation angle was 12° ± 6° (range, 0°-31°). Pearson correlation between patellar maltracking parameters (bisect offset index, patellar tilt angle) and various bony deformities found that the tibiofemoral rotation angle was moderately correlated with bisect offset index (r = 0.451, p < 0.001) and patellar tilt angle (r = 0.462, p < 0.001). Further results demonstrated that bisect offset index (152.1 vs 121.2, p < 0.001) and patellar tilt angle (41.2° vs 33.5°, p < 0.001) were significantly higher in the rotation group than that in control group. For patients with a TT-TG distance of >20 mm, the increased TT-TG distance was mainly caused by tibiofemoral rotation angle in group C (TT-TG > 20 mm, TT-PCL < 24 mm) and predominantly induced by tibial tubercle lateralization in group D (TT-TG > 20 mm, TT-PCL > 24 mm). Bisect offset index and patellar tilt angle were significantly higher in the group C than group D.

CONCLUSION

The increased tibiofemoral rotation angle is associated with patellar maltracking in patients with recurrent patellar dislocation. Patients with increased tibiofemoral rotation angle usually have more severe patellar maltracking.

Elevated Patellofemoral and Tibiofemoral T1ρ Relaxation Times Following a First Time Patellar Dislocation

OBJECTIVE

The study was performed to evaluate cartilage within the knee following a first-time patellar dislocation, using elevated MRI-based T1ρ relaxation times as an indicator of low proteoglycan concentration. The hypothesis is that MRI-based T1ρ relaxation times for patellofemoral and tibiofemoral cartilage are significantly longer for knees being treated for patellar dislocation than for healthy control knees.

DESIGN

Twenty-one subjects being treated for a first-time, unilateral dislocation of the patella and 16 healthy controls participated in MRI-based T1ρ relaxation time mapping. Mean relaxation times were quantified for patellofemoral and tibiofemoral regions for injured knees, the contralateral knees, and healthy controls. T1ρ values for each region were compared between the 3 groups with generalized estimating equations. Linear regressions were also performed to correlate T1ρ relaxation times with time from injury.

RESULTS

The knees with a disloction had longer T1ρ relaxation times than the contralateral knees and control group at the medial patella and longer relaxation times than the control group at the lateral tibia (P < 0.05). T1ρ relaxation times at the medial patella also decreased with time from injury (r² = 0.21, P = 0.037).

CONCLUSIONS

Compositional changes to cartilage on the medial patella are related to traumatic impact during a dislocation. Potential exists for cartilage properties at the medial patella to improve with time. Cartilage degradation at the lateral tibia is not directly related to traumatic impact. The current baseline data are a starting point to characterize the pathway from a first-time dislocation to progressive cartilage degradation and osteoarthritis.

A Randomized Controlled Trial Comparing a Patella-Stabilizing, Motion-Restricting Knee Brace Versus a Neoprene Nonhinged Knee Brace After a First-Time Traumatic Patellar Dislocation

BACKGROUND

A traumatic lateral patellar dislocation is a common injury in adolescents and young adults. The majority of first-time dislocations can be treated nonoperatively. Various types of knee braces are used for nonoperative treatment, but evidence on the most preferable bracing method is lacking.

PURPOSE

To evaluate the efficacy of a patella-stabilizing, motion-restricting knee brace versus a neoprene nonhinged knee brace for the treatment of a first-time traumatic patellar dislocation at 3 years of follow-up.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 101 skeletally mature patients with a first-time traumatic patellar dislocation were enrolled in the study. After exclusion criteria were applied, 79 patients with a first-time traumatic patellar dislocation were randomized and allocated into 2 study groups: group A, with a patella-stabilizing, motion-restricting knee brace (hinged to allow knee range of motion [ROM] of 0°-30°) and group B, with a neoprene nonhinged knee brace (not restricting any knee motion). Both groups received similar physical therapy instructions and were advised to use the brace continuously for 4 weeks. Overall, 64 patients completed the trial.

RESULTS

The redislocation rate in group A was 34.4% (11/32) and in group B it was 37.5% (12/32) (risk difference, -3.1% [95% CI, -26.6% to 20.3%]; P = .794). Patients in group A had less knee ROM than those in group B at 4 weeks (90° vs 115°, respectively; P < .001) and 3 months (125° vs 133°, respectively; P = .028). Patients in group A had more quadriceps muscle atrophy than patients in group B at 4 weeks (24/32 vs 16/32, respectively; P = .048) and 3 months. At 6 months, patients in group B reported better functional outcomes than patients in group A (Kujala score mean difference, 4.6; P = .012), although no clinically relevant difference was found at 3 years.

CONCLUSION

The use of a patella-stabilizing, motion-restricting knee brace for 4 weeks after a first-time traumatic patellar dislocation did not result in a statistically significant reduction in redislocations versus a neoprene nonhinged knee brace, although this trial was underpowered to detect more modest differences. Knee immobilization was associated with quadriceps muscle atrophy, less knee ROM, and worse functional outcomes in the first 6 months after the injury.

REGISTRATION

NCT01344915 (ClinicalTrials.gov identifier).

Utility of Diagnostic Ultrasound in the Assessment of Patellar Instability

Background

The use of imaging to diagnose patellofemoral instability is often limited by the inability to dynamically load the joint during assessment. Therefore, the diagnosis is typically based on physical examination using the glide test to assess and quantify lateral patellar translation. However, precise quantification with this technique remains difficult.

Purpose

To quantify patellar position using ultrasound imaging under dynamic loading conditions to distinguish between knees with and without medial patellofemoral complex (MPFC) injury.

Study Design

Controlled laboratory study.

Methods

In 10 cadaveric knees, the medial patellofemoral distance was measured to quantify patellar position from 0° to 40° of knee flexion at 10° increments. Knees were evaluated at each flexion angle under unloaded conditions and with 20 N of laterally directed force on the patella to mimic the glide test. Patellar position measurements were made on ultrasound images obtained before and after MPFC transection and compared for significant differences. To determine the ability of medial patellofemoral measurements to differentiate between MPFC-intact and MPFC-deficient states, area under the receiver operating characteristic (ROC) curve analysis and the Delong test were used. The optimal cutoff value to distinguish between the deficient and intact states was determined using the Youden J statistic.

Results

A significant increase in medial patellofemoral distance was observed in the MPFC-deficient state as compared with the intact state at all flexion angles (P = .005 to P < .001). When compared with the intact state, MPFC deficiency increased medial patellofemoral distance by 32.8% (6 mm) at 20° of knee flexion under 20-N load. Based on ROC analysis and the J statistic, the optimal threshold for identifying MPFC injury was 19.2 mm of medial patellofemoral distance at 20° of flexion under dynamic loading conditions (area under the ROC curve = 0.93, sensitivity = 77.8%, specificity = 100%, accuracy = 88.9%).

Conclusion

Using dynamic ultrasound assessment, we found that medial patellofemoral distance significantly increases with disruption of the MPFC.

Clinical Relevance

Dynamic ultrasound measurements can be used to accurately detect the presence of complete MPFC injury.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Evaluation and management of patellar instability

Patellar instability is a common clinical problem that primarily affects the adolescent and young adult population. The demographic and anatomic risk factors that predispose patients to patellar instability are multifactorial and include young age, female sex, trochlear dysplasia, elevated tibial tubercle to trochlear groove distance (TT-TG), patella alta, femoral and tibial malalignment, ligamentous laxity, and lack of neuromuscular control. There have been substantial efforts to predict which patients who sustain a first-time dislocation will go on to incur additional dislocations. This is particularly important because with each dislocation event, there is a significant risk of injury to the patellofemoral joint including both medial patellofemoral ligament (MPFL) stretch or rupture and damage to the cartilage which can range from simple fissures to full-thickness cartilage defects and osteochondral fractures. Prediction models have demonstrated that amongst first time dislocators, young patients with trochlear dysplasia are at the highest risk for redislocation. The current standard of care for treatment of first-time dislocators without a loose body or osteochondral fracture is nonoperative management. However, recently there has been a focus on implementing a risk-stratified approach to the surgical indications for a first-time dislocator as the high-risk population might be better treated with early surgical stabilization to prevent or reduce their risk of recurrent dislocation and its associated morbidity. Likewise, for patients with recurrent dislocations, it remains to be determined whether an isolated MPFL reconstruction is sufficient for high-risk patients with several poor prognostic risk factors or if bony realignment procedures should be implemented concurrently.

Medial patellofemoral ligament reconstruction: A review

INTRODUCTION

Reconstruction of the medial patellofemoral ligament (MPFL) is an effective surgical method for the treatment of lateral patellar instability. At present, there is not much controversies regarding the femoral attachment, however, the controversies regarding patellar attachment versus attachment, number of graft strands, tension, isometry and so on. The following electronic databases will be searched: PubMed, the Cochrane Library, Embase, Web of Science, Medline. We will consider articles published between database initiation and March 2021. MPFL in the subject heading will be included in the study. Language is limited to English. Research selection, data extraction, and research quality assessment were independently completed by 2 researchers.

CONCLUSIONS

MPFL reconstruction is a reliable technique for the treatment of patellofemoral instability. The Schöttle point is still the mainstream method for locating the femoral attachment, the patellar attachment for single-bundle is located at the junction of the proximal one third and the distal two third of the longitudinal axis of the patella. For double-bundles, one is located in the proximal one third of the medial patellar edge and another is in the center of the patellar edge. Meanwhile, the adjustment of graft tension during operation is very important.

Portuguese Translation and Cross-Cultural Adaption of the Banff Patella Instability Instrument

Objective  To translate into Brazilian Portuguese and to cross-culturally adapt the Banff Questionnaire for Patellar Instability.

Methods  The translation and cross-cultural adaptation followed the linguistic validation process proposed by international guidelines, which consists of six steps: translation, synthesis, back-translation, review by an expert committee, pretest, and final report presentation to the authors of the original questionnaire. Literate patients with recurrent patellar instability, older than 12 years of age, who signed the informed consent form or had it signed by a legal guardian were included in the study. Patients with neurological or systemic comorbidities were excluded from the study.

Results  A total of 62 patients (18 males and 44 females) were included in the study. Discrepancies observed during the processes of translation and harmonization of the back-translations were modified with no need for reformulation. No pretest version replacements were required.

Conclusion  The Banff Questionnaire for Patellar Instability has been successfully translated and cross-culturally adapted into Brazilian Portuguese, so it can be used to assess patients with patellar instability who speak this language.

Patient-Reported Outcomes After a Modified Albee Procedure

Background:

Trochlear dysplasia (TD) is a recognized condition that can become a risk factor for patellofemoral instability. A modified Albee osteotomy procedure using a trapezoidal-shaped wedge to elevate the lateral wall of the trochlea can be used with the goal of preventing further dislocation. However, outcomes studies are lacking, and scores on patient-reported outcome measures (PROMs) are largely unknown.

Purpose/Hypothesis:

The purpose of this study was to identify PROM scores for the Kujala Anterior Knee Pain Scale (AKPS), International Knee Documentation Committee (IKDC), Activity Rating System (ARS), and 100-point pain visual analog scale (VAS) for patients having undergone the modified Albee osteotomy. The hypothesis was that patients will have acceptable pain and function at mid- to long-term follow-up.

Study Design:

Case series; Level of evidence, 4.

Methods:

From 1999 to 2017, a total of 46 consecutive patients (49 knees) underwent a modified Albee procedure by a single surgeon at a single health care system. These 46 patients were contacted and asked to complete the AKPS, IKDC, ARS, and pain VAS. Additional demographic information was obtained via chart review. Frequencies and rates for categorical variables and means and standard deviations for continuous variables of the demographics and PROM scores were calculated.

Results:

PROM scores were obtained in 28 (30 knees; 61%) of the 46 patients. At minimum follow-up of 82 months, the mean scores were 78.5 ± 18.2 for AKPS, 61.2 ± 11.4 for IKDC, 5.2 ± 5.3 for ARS, and 24.4 ± 28.7 for VAS pain. Notably, only 1 of the 28 patients reported a patellofemoral dislocation since surgery, and this was an isolated incident without further instability.

Conclusion:

A modified Albee trochlear osteotomy can be a successful adjunctive procedure to prevent recurrent patellar dislocations in patients with mild TD. However, owing to the loss of one-third of patient follow-up scores and the absence of baseline function scores in this study, the procedure deserves further investigation as a way to address a particularly difficult dilemma for a select subset of patients with patellofemoral instability.

Magnetic Resonance Imaging of Patellofemoral Morphometry Reveals Age and Gender Variations in the Knees of Children and Adolescents

Background: The morphology and alignment of the patellofemoral joint are crucial risk factors for patellar instability, and the incidence of acute primary patellar dislocation is the highest in women in their second decade of life. The purpose of the study was to analyze age and gender variations of the patellofemoral joint using magnetic resonance imaging (MRI). Methods: A total of 852 patients aged between 4 and 18 years with a history of knee MRI examinations were screened for eligibility and 663 patients (470 males, 193 females) were included. Patients were divided into groups according to age and sex. The age group was divided into five groups (Group 1, 4–6 years; Group 2, 7–9 years; Group 3, 10–12 years; Group 4, 13–15 years; and Group 5, 16–18 years). Three orthopaedic surgeons measured MRI parameters reflecting the patellofemoral morphology (sulcus angle, lateral trochlear inclination, trochlear facet symmetry, and femoral depth) and alignment (tibial tuberosity–trochlear groove distance, percent sulcus location, and percent tibia tuberosity location). Results: Parameters including tibial tuberosity–trochlear groove distance, sulcus angle, percent tibial tuberosity location, trochlear facet symmetry, and femoral depth showed significant differences between the age groups (p < 0.05). The sulcus angle decreased fin Group 2, and the femoral depth showed an increasing trend with aging in male patients. However, the sulcus angle in females decreased first and then increased in Group 3 as the inflection point. The femoral depth showed an opposite pattern. Conclusions: Patellofemoral morphometry showed age and gender variation. Notably, the sulcus angle and femoral depth were significantly different between males and females and changed according to the development. These findings may reflect the sex difference and peak incidence of the patellar instability risk. Understanding the morphological changes and differences of the patellofemoral joint may facilitate the diagnosis of patellofemoral pathologies.

Comparing Nonoperative Treatment, MPFL Repair, and MPFL Reconstruction for Patients With Patellar Dislocation: A Systematic Review and Network Meta-analysis

Background:

Medial patellofemoral ligament (MPFL) reconstruction, MPFL repair, and nonoperative treatment are important treatments for patients with patellar dislocation. However, it is unclear which treatment leads to better outcomes.

Purpose:

To determine the efficacy and safety of the 3 treatments in the treatment of patellar dislocation and compare the effect of MPFL reconstruction with MPFL repair, MPFL reconstruction with nonoperative treatment, and MPFL repair with nonoperative treatment.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

The PubMed, Web of Science, Cochrane Library, Embase, CNKI (China National Knowledge Infrastructure), and Wanfang databases were searched from inception to December 2020. Included were clinical studies that described the efficacy and safety of 2 of the 3 treatments, studies directly comparing the clinical effects of the 2 operative techniques, or studies comparing the effects of reconstruction or repair with nonoperative treatment. Two reviewers independently extracted data and assessed the quality of the included studies with the Cochrane risk-of-bias tools. The outcomes evaluated were postoperative redislocation rate, revision rate, complications, and Kujala score. We used traditional direct pairwise meta-analysis as well as network meta-analysis for comprehensive efficacy of all 3 treatment measures.

Results:

Twelve studies were included: 5 compared MPFL reconstruction with MPFL repair, 2 compared MPFL reconstruction with nonoperative treatment, and 5 compared MPFL repair with nonoperative treatment. The risk of bias was serious in 4, moderate in 4 and low in 4 articles. MPFL reconstruction led to significantly reduced redislocation and improved Kujala scores compared with MPFL repair and nonoperative treatment. MPFL repair led to reduced redislocation rates compared with nonoperative treatment but did not show an obvious benefit in primary dislocations. There was no significant difference among the 3 treatments in terms of revision rate and incidence of complications, although we found that treatment-related complications were least likely to occur in nonoperative treatment.

Conclusion:

The results of this review indicate that MPFL reconstruction decreases recurrent dislocation compared with MPFL repair or nonoperative treatment, but it has a higher possibility of complications. MPFL repair resulted in less postoperative redislocation than nonoperative treatment but did not show an obvious benefit in primary dislocation.

Neglected Locked Patellar Dislocation in an Adult Female: Report of a Rare Case

Introduction

Dislocation of patella is a very common injury which usually reduces spontaneously or can be reduced easily using gentle manipulation. Irreducible patellar dislocations are rare and usually result due to either rotation of patella along the horizontal or vertical axis or due to bony impaction. Neglected locked patellar dislocations are extremely rare injuries presenting additional challenges.

Case Report

We are reporting a case of a 24-year female who presented to us 4 months after suffering a knee injury for which she received native treatment initially. On presentation, patient was able to walk with a limp and some discomfort but was unable to squat or sit cross-legged. Clinical examination revealed a patellar dislocation which was irreducible. On open reduction, the patella was found to be locked in the lateral gutter with rotation along its vertical axis and with an osteochondral fracture of its medial margin. There were a lot of fibrotic adhesions which required extensive release, following which the patella could be derotated and reduced into the trochlear groove. The medial retinaculum was repaired using transosseous sutures. Postoperatively, the patient developed wound edge necrosis which was managed with debridement and secondary suturing. At 1-year follow-up patient had almost full knee range of motion without any signs of patellar pain or instability and was able to squat and sit cross-legged.

Conclusion

Unlike acute irreducible patellar dislocations which can be managed easily with open reduction, a neglected dislocation necessitates wider surgical exposure and a lot of soft tissue releases, which may jeopardize vascularity of the soft tissues leading to wound healing problems. Release of all adhesions while taking care to prevent further chondral injury, adequate lateral retinacular release, derotation of patella to relocate it into trochlear groove, and meticulous medial retinacular repair is essential for a successful outcome.

Medial Patellofemoral Ligament Reconstruction for Adolescents With Acute First-Time Patellar Dislocation With an Associated Loose Body

BACKGROUND

The management of adolescents with acute first-time patellar dislocation with an associated loose body remains a debated topic. The rate of recurrent dislocation in these patients may be up to 61% if the medial patellofemoral ligament (MPFL) is repaired or not addressed surgically. To our knowledge, a prospective evaluation of MPFL reconstruction for adolescents with acute first-time patellar dislocation with an associated chondral or osteochondral loose body has not been previously performed.

PURPOSE/HYPOTHESIS

The purpose of this study was to analyze patients with a first-time patellar dislocation who required surgery for a loose body, comparing those who underwent MPFL repair or no treatment with those who underwent MPFL reconstruction during the index procedure. The hypothesis was that performing MPFL reconstruction would reduce the rate of recurrent instability and improve patient-reported outcomes compared with MPFL repair or no treatment. A secondary objective was to report outcomes of those patients who underwent reconstruction versus those who did not.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This was a prospective analysis of adolescents treated with MPFL reconstruction for acute first-time patellar dislocation with associated loose bodies between 2015 and 2017 at a single pediatric level 1 trauma center with minimum 2-year follow-up. Retrospective analysis was previously performed for a similar cohort of adolescents treated with MPFL repair or no treatment. Patient characteristic data, radiographic measurements, and surgical variables were compared. Primary outcome measures included recurrent subluxation or dislocation and the need for further stabilization procedures. Secondary outcomes included Kujala score, Single Assessment Numeric Evaluation score, patient satisfaction, and ability to return to sport.

RESULTS

A total of 76 patients were included, 30 in the MPFL reconstruction cohort and 46 in the MPFL repair or no-treatment cohort. The only difference noted in patient characteristic, radiographic, or surgical variables was a smaller Insall-Salvati ratio in the reconstruction group (1.29 vs 1.42; P = .011). Compared with MPFL repair or no treatment, MPFL reconstruction was associated with less recurrent instability (10.0% vs 58.7%; P < .001), fewer secondary procedures (6.7% vs 47.8%; P < .001), and more frequent return to sports (66.7% vs 39.1%; P = .003). No differences in patient-reported outcomes were noted.

CONCLUSION

Performing concomitant MPFL reconstruction in adolescents with first-time patellar dislocation and an intra-articular loose body results in a 5-fold reduction in recurrent instability, reduces the need for subsequent surgery, and improves patients' ability to return to sports compared with repairing or not treating the MPFL.

Changes in cartilage and subchondral bone in a growing rabbit experimental model of developmental trochlear dysplasia of the knee

Purpose: Trochlear dysplasia is one of the most frequent lower extremities deformities. Aim of this research was to investigate the changes in cartilage and subchondral bone of trochlea after patellar dislocation in growing rabbits. Materials and Methods: Ninety-six knees from 48 one-month-old rabbits were divided into two groups (experimental, control). Lateral patellar dislocation was established in the experimental group and distal femurs were collected at 4, 8, 12 and 24-week time points, respectively. General examination and histological observations were conducted to research the anatomical structure of the trochlear cartilage and subchondral bone. Structural parameters of trochlear subchondral bone were measured by MicroCT. Subsequently, the expression of TRPV4, collagen II and MMP-13 in cartilage were detected by western blot and RT-PCR analysis, respectively.Results: Subchondral bone loss was found in experimental group from 4 weeks after patellar dislocation, accompanied by increased TRAP-positive osteoclasts in subchondral bone. The trochlear dysplasia model was well established from 8 weeks after patellar dislocation. In addition, degeneration of cartilage was found from 8 weeks, accompanied by decreased expression of mechanically sensitive TRPV4 and collagen II, and increased expression of MMP-13.Conclusions: This study proved that trochlear dysplasia can be caused by patellar dislocation in growing rabbits, accompanied by significant subchondral bone loss. What is more, this study also shows that degenerative cartilage changes occur in the patellar dislocation model and become aggravated with time, accompanied by decreased TRPV4 and collagen II, but increased MMP-13.

Clinical Outcomes and Prognostic Factors in Patients With Recurrent Patellar Lateral Dislocation Treated With Isolated Medial Patellofemoral Ligament Reconstruction: A Retrospective Single-Center Analysis

Background

Medial patellofemoral ligament reconstruction (MPFLR) is widely used to treat patellofemoral instability. However, it is still unclear when a concomitant bony procedure is needed.

Purpose

To evaluate the therapeutic efficacy of isolated MPFLR for recurrent patellar lateral dislocation and to identify the prognostic factors for clinical outcomes.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 237 patients who had undergone unilateral isolated MPFLR between January 2011 and December 2016 were included. Patellar tracking (J sign) and radiologic information including patellar height, trochlear dysplasia, tibial tubercle-trochlear groove distance, and patellar tilt was collected preoperatively, and the Kujala and International Knee Documentation Committee (IKDC) functional scores were used to assess postoperative recovery. Failure was defined as redislocation or patient-reported and clinically confirmed patellar instability. The influence of radiologic features and the J sign on knee functional scores was explored via subgroup analysis. Potential prognostic factors were explored using univariate and multivariate regression analyses, and risk factors for a positive J sign were evaluated using Spearman coefficient correlation analysis.

Results

The mean ± SD follow-up period was 70.67 ± 18.05 months (range, 36-108 months). From preoperatively to final follow-up, all patients had statistically and clinically significant improvements in the Kujala score (from 51.43 ± 6.87 to 88.52 ± 4.83; P < .001) and IKDC score (from 49.78 ± 6.05 to 81.16 ± 4.20; P < .001). Subgroup analysis indicated no significant difference in functional score improvements based on radiologic features or the J sign. Overall, 20 knees (8.4%) experienced postoperative failure: 11 with redislocation and 9 with patellar instability. A preoperative positive J sign was shown to be an independent prognostic factor for postoperative failure via logistic regression analyses: univariate (odds ratio, 3.340; 95% CI, 1.316-8.480; P = .011) and multivariate (odds ratio, 3.038; 95% CI, 1.179-7.827; P = .021). In addition, the J sign was closely associated with patellar height (r _S, 0.159; P = .014) and trochlear dysplasia (r _S, 0.235; P < .001).

Conclusion

Isolated MPFLR appears to be an effective strategy for recurrent patellar lateral dislocation, with significant functional improvement and a low failure rate. A preoperative positive J sign was identified as a potential prognostic risk factor for postoperative failure.

Predicting Risk of Recurrent Patellofemoral Instability With Measurements of Extensor Mechanism Containment

BACKGROUND

Identifying risk factors for recurrent patellar dislocation after a primary dislocation may help guide initial treatment. Magnetic resonance imaging (MRI) measurements relating the alignment of the extensor mechanism to trochlear morphology have been shown to distinguish patients with dislocations from controls, but their usefulness in predicting the risk of a second dislocation is not known.

PURPOSE

To identify the association of novel MRI measures of patellar containment with recurrent instability in pediatric patients presenting with a first-time patellar dislocation.

STUDY DESIGN

Cohort study (Prognosis); Level of evidence, 3.

METHODS

The study was conducted at a tertiary care children's hospital (2005-2014) on patients (age, 8-19 years) with a first-time patellar dislocation. MRI measurements were made by 2 independent raters. Interobserver reliability was assessed for all measurements via an intraclass correlation coefficient (ICC). Only measurements with an ICC >0.8 were included. Univariable and multivariable logistic regression analyses were used to evaluate variables associated with recurrence.

RESULTS

A total of 165 patients with a median age of 14 years and a slight (57.6%) female predominance was identified. The median follow-up length of the whole cohort was 12.2 months (interquartile range, 1.6-37.1 months). Subsequent instability was documented in 98 patients (59.4%). MRI measurements with excellent correlation (ICC > 0.8) were the tibial tubercle to trochlear groove distance (TT-TG), the tangential axial width of the patella, the tangential axial trochlear width, the axial width of the patellar tendon beyond the lateral trochlear ridge (LTR), and the tibial tubercle to LTR distance. In univariate analysis, all mentioned MRI measurements had significant association with recurrent instability. However, after both backward and forward stepwise regression analyses, the tibial tubercle to LTR distance was the only independent predictor of recurrent instability (P = .003 in both). Patients with a tibial tubercle to LTR distance value greater than -1 mm had a significantly higher rate of recurrent patellar dislocation (72%).

CONCLUSION

Of numerous axial view MRI parameters, only the tibial tubercle to LTR distance demonstrated a statistically significant association with recurrent patellar instability upon multivariable logistic regression analysis during short-term follow-up of a pediatric population presenting with initial lateral patellar dislocation. Interobserver correlation of the tibial tubercle to LTR distance was good (ICC > 0.8) and similar to that of TT-TG.

Conservative versus repair of medial patellofemoral ligament for the treatment of patients with acute primary patellar dislocations: A systematic review and meta-analysis

PURPOSE

The aim of this study was to perform a meta-analysis to compare the effects of repair of medial patellofemoral ligament (MPFL) and conservative treatment in patients with acute primary patellar dislocation (PPD).

METHOD

The databases we used to search the studies included MEDILINE, EMBASE, and Cochrane registry of controlled clinical trials. Five randomized controlled studies comparing the effects of MPFL repair versus conservative treatment with 300 acute PPD patients were included in the present meta-analysis. Primary outcome was redislocation rate and secondary outcomes included Kujala score, percentage of excellent or good subjective opinion, Tegner activity score, and knee injury and osteoarthritis outcome score (KOOS; pain, symptoms, and activities of daily living).

RESULTS

The outcome of the Kujala score was statistically significant between the two treatments and indicated that MPFL repair had a higher Kujala score than conservative treatment in patients with acute PPD. There was no significant difference between the two treatments regarding the redislocation rate (p = 0.32), percentage of excellent or good subjective opinion (p = 0.15), Tegner activity score (p = 0.24), and KOOS (p > 0.05).

CONCLUSIONS

Based on the available data, MPFL repair did not reduce the risk of redislocation nor did it produce any significantly better outcome based on the clinical manifestations, including anterior knee pain and knee activities. Only the Kujala score was improved by MPFL repair compared with conservative treatment.

Assessment and Trends of the Methodological Quality of the Top 50 Most Cited Articles on Patellar Instability

Background

Studies with a low level of evidence (LOE) have dominated the top cited research in many areas of orthopaedics. The wide range of treatment options for patellar instability necessitates an investigation to determine the types of studies that drive clinical practice.

Purpose

To determine (1) the top 50 most cited articles on patellar instability and (2) the correlation between the number of citations and LOE or methodological quality.

Study Design

Cross-sectional study.

Methods

The Scopus and Web of Science databases were assessed to determine the top 50 most cited articles on patellar instability between 1985 and 2019. Bibliographic information, number of citations, and LOE were collected. Methodological quality was calculated using the Modified Coleman Methodology Score (MCMS) and the Methodological Index for Non-Randomized Studies (MINORS). Mean citations and mean citation density (citations per year) were correlated with LOE, MCMS, and MINORS scores.

Results

Most studies were cadaveric (n = 10; 20.0%), published in the American Journal of Sports Medicine (n = 13; 26.0%), published between 2000 and 2009 (n = 41; 82.0%), and conducted in the United States (n = 17; 34.0%). The mean number of citations and the citation density were 158.61 ± 59.53 (range, 95.5-400.5) and 12.74 ± 5.12, respectively. The mean MCMS and MINORS scores were 59.62 ± 12.58 and 16.24 ± 3.72, respectively. No correlation was seen between mean number of citations or citation density versus LOE. A significant difference was found in the mean LOE of articles published between 1990 and 1999 (5.0 ± 0) versus those published between 2000 and 2009 (3.12 ± 1.38; P = .03) and between 2010 and 2019 (3.00 ± 1.10; P = .01).

Conclusion

There was a shift in research from anatomy toward outcomes in patellar instability; however, these articles demonstrated low LOE and methodological quality. Higher quality studies are necessary to establish informed standards of management of patellar instability.

Patellofemoral Dislocation Recurrence After a First Episode: A Case-Control Study

Background:

Lateral patellar dislocation can become a recurrent problem after the first episode. Identifying those patients who are at increased risk of redislocation is important for the treatment decision-making process.

Purpose:

To identify clinical and radiologic risk factors for recurrence of patellar dislocation after a first episode.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The study included patients with lateral patellar dislocation and a 1-year minimum follow-up who were seen between 2011 and 2018. Patients aged 10 to 65 years were included. Patient characteristics, physical examination (patellar apprehension, J sign), and radiographs were reviewed. The Caton-Deschamps and Insall-Salvati ratios were used to evaluate patella alta. High-grade trochlear dysplasia was defined as Dejour types B, C, and D.

Results:

A total of 130 patients (139 knees) with primary lateral patellar dislocation were included. Recurrent dislocation was seen in 83 knees (59.71%). Stepwise logistic regression analysis demonstrated that Caton-Deschamps ratio ≥1.15 (OR, 2.39; 95% CI, 1.09-5.22; P = .029), age <21 years (OR, 2.53; 95% CI, 1.11-5.77; P = .027), and high-grade trochlear dysplasia (OR, 4.17; 95% CI, 1.90-9.17; P < .001) were significantly associated with patellar redislocation. Based on the presence of these factors, the probability of dislocation after a first lateral patellar dislocation was 31.2% with no factors present, 36.6% with any 1 factor present, 71.7% with any 2 factors present, and 86.2% if all 3 conditions were present.

Conclusion:

The results of this study indicated that patella alta, high-grade trochlear dysplasia, and age <21 years were independent risk factors for patellar redislocation after a first episode, with an additive effect when they were present together. This may help to guide the type of treatment for these patients.

Characteristics of Osteochondral Fractures Caused by Patellar Dislocation

Background

Literature describing the anatomic characteristics of osteochondral fractures (OCFs) in the knee joint after patellar dislocation is scarce.

Purpose

To describe the patterns of OCFs in the knee joint after acute or recurrent patellar dislocation in a sample of patients from 2 orthopaedic trauma centers.

Study Design

Case series; Level of evidence, 4.

Methods

In this multicenter study, all patients who had International Classification of Diseases, 10th Revision, diagnostic codes S83.0 and M22.0 between 2012 and 2018 were screened. Of the 2181 patients with clinically diagnosed patellar dislocation, 1189 had undergone magnetic resonance imaging (MRI). Patients with diagnosed patellar dislocation and osteochondral fragment verified on MRI scans were included. Demographic and clinical data were collected from electronic patient records. OCF location and size were assessed from MRI scans. Results were further compared in subgroups by sex, skeletal maturity, and primary versus recurrent patellar dislocation.

Results

An OCF was detected in 134 patients with injured knees, all of whom were included in the final analysis. It occurred in the patella in 63% of patients, in the lateral femoral condyle in 34%, and in both locations in 3%. The median OCF size was 146 mm² (interquartile range, 105-262 mm²). There was no statistically significant difference in OCF size between patellar and lateral femoral condyle fractures. Patellar OCFs were more frequent in female than male patients (P = .009) and were larger after primary than recurrent dislocation (P = .040).

Conclusion

OCFs were mainly located in the medial facet of the patella and in the lateral femoral condyle, with these locations accounting for approximately two-thirds and one-third of all OCFs, respectively. Proportion of patellar OCF was higher in female than in male. Patellar OCFs may be larger after primary than recurrent dislocation.

Prevalence and Site of Medial Patellofemoral Ligament Injuries in Patients With Acute Lateral Patellar Dislocations: A Systematic Review and Meta-analysis

Background

Medial patellofemoral ligament (MPFL) injuries are common in patients with acute lateral patellar dislocations, but the pattern of MPFL injuries is unclear, especially with respect to patient age.

Purpose

The primary aim was to determine the prevalence of MPFL injuries according to the site of injury in patients with acute lateral patellar dislocations. The secondary aim was to compare the site of MPFL injuries in patients aged ≤16 versus >16 years.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic literature search was performed with PubMed, Embase, and CINAHL to identify articles published from January 1, 1999, to May 31, 2019, that examined the site of MPFL injuries in patients with acute patellar dislocations. The study design, sample size, age at injury, technique used for diagnosing MPFL injuries (magnetic resonance imaging, ultrasound, and/or surgery), and prevalence and site of MPFL injuries were extracted from each study. The pooled estimate of the proportion of MPFL injuries at each site was calculated (femur, patella, midsubstance, and combined sites of injury) as well as proportions stratified by age group (≤16 and >16 years).

Results

The literature search yielded 420 unique articles, of which 52 were screened for eligibility; of these, 17 were excluded. Thus, a total of 35 articles (2558 patients) were included in the final analysis. The overall prevalence of MPFL injuries was 94.7% (95% CI, 91.2%-96.8%). Most MPFL injuries occurred at the patella (37.1% [95% CI, 30.8%-43.9%]), followed by the femur (36.8% [95% CI, 31.0%-43.0%]), combined sites (25.1% [95% CI, 20.7%-30.1%]), and the midsubstance (15.6% [95% CI, 13.2%-18.4%]). In patients aged ≤16 years, most MPFL injuries occurred at the patella (39.3% [95% CI, 27.9%-51.9%]), and in patients aged >16 years, most MPFL injuries occurred at the femur (47.2% [95% CI, 40.6%-54.0%]).

Conclusion

The prevalence of MPFL injuries in patients with acute patellar dislocations varied by site of injury and by age. MPFL injuries at the patella were most prevalent overall and in children and adolescents, and MPFL injuries at the femur were more prevalent in adults.

Development of an innovative measurement method for patellar tracking disorder

In this study, we investigated whether the measurement of patellar tracking can be used as a diagnostic parameter of patellofemoral joint disease. Patellar tracking is defined as the movement of the patella in relation to the femorotibial joint within the full range of flexion and extension of the knee joint. The PubMed, EMBASE, Medline, PsychINFO, and AMED databases were used to find relevant articles. Analyzed were the patellar tracking coordinate system and the measurement objects, precision, methods used in those studies, as well as the results obtained. Origin points for coordinate systems varied across the studies. The research object and methods of patellar tracking varied in the studies. Most studies focused on a static description of the internal and external displacement and the internal and external inclination. The in vivo, noninvasive, and six degrees of freedom evaluation of patellar tracking reflect patellar motion more comprehensively, though each of these methods does so in different ways. Dynamic and quantitative evaluation of patellar tracking is still lacking in clinical work. Accurate and quantitative patellar tracking measurement could provide clinicians with a comprehensive evaluation of the stability of the knee joint.

Patellar Tendon Imbrication Is a Safe and Efficacious Technique to Shorten the Patellar Tendon in Patients With Patella Alta

Background

Patella alta has been noted to be a risk factor for recurrent patellar instability.

Purpose

We conducted a radiographic study to determine whether a patellar tendon imbrication technique normalizes patellar height as well as whether the shortened length is maintained at a minimum 2-year follow-up.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 54 consecutive patients were identified after a retrospective chart review was performed on patients who underwent patellar tendon imbrication between 2008 and 2013. Preoperative, 3 weeks postoperative, and minimum 2 years postoperative lateral radiographs were analyzed using Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) indices to determine the amount of shortening that was achieved after the procedure and to what degree that shortening was maintained at a minimum 2-year follow-up.

Results

A total of 27 patients (32 knees) completed a minimum 2-year follow-up. The mean patellar tendon length preoperatively was 6.1 cm (range, 5-8 cm). At 3 weeks and 2 years, the mean tendon lengths were 5.1 and 5.2 cm, respectively. Thus, the mean ± SD change in patellar tendon length from preoperative to 3 weeks postoperative was 0.97 ± 0.67 cm. IS, BP, and CD ratios had minimal change (loss of correction) from 3-week to 2-year follow-up; the delta values were 0.04, -0.03, and 0.09, respectively. There were no complications directly related to the technique.

Conclusion

Patellar tendon imbrication is a safe and effective procedure to correct patella alta in the setting of lateral patellar instability. On average, the technique allowed 1 cm of patellar tendon shortening and maintained the correction at a minimum 2-year follow-up. In the skeletally immature patient, this technique allows correction of patella alta by avoidance of a tibial tuberosity osteotomy.