Current concepts of lateral patella dislocation

Classification of Lateral Patellar Instability in Children and Adolescents

There is significant heterogeneity in the literature related to the causes and treatment of patellar instability. To address the multifactorial issue of patellar instability, the first task is to classify the instability pattern. Once a classification system is developed, future studies can differentiate between treatment recommendations and outcomes for each instability pattern. Existing classification systems do not include the entire spectrum of patellar instability patterns. The aim of this article is to review the nomenclature and existing patellar instability classification systems and analyze the different patterns into a comprehensive system.

RANDOMIZED PROSPECTIVE STUDY ON TRAUMATIC PATELLAR DISLOCATION: CONSERVATIVE TREATMENT VERSUS RECONSTRUCTION OF THE MEDIAL PATELLOFEMORAL LIGAMENT USING THE PATELLAR TENDON, WITH A MINIMUM OF TWO YEARS OF FOLLOW-UP

Objective: The aim of this study was to compare the surgical results from reconstruction of the medial patellofemoral ligament (MPFL) with non-operative treatment of primary patellar dislocation. Methods: Thirty-nine patients (41 knees) with patellar dislocation were randomized into two groups. One group was treated conservatively (immobilization and physiotherapy) and other was treated surgically with reconstruction of the MPFL, and the results were evaluated with a minimum follow-up of two years. The Kujala questionnaire was applied to assess pain and quality of life, and recurrences were evaluated. Pearson's chi-square test and Fisher's exact test were used in the statistical evaluation. Results: The statistical analysis showed that the mean Kujala score was significantly lower in the conservative group (70.8), compared with the mean value in the surgical group (88.9), with p = 0.001. The surgical group presented a higher percentage of “good/excellent” Kujala score results (71.43%) than in the conservative group (25.0%), with p = 0.003. The conservative group presented a greater number of recurrences (35% of the cases), while in the surgical group there were no reports of recurrences and/or subluxation. Conclusions: Treatment with reconstruction of the medial patellofemoral ligament using the patellar tendon produced better results, based on the analysis of post-treatment recurrences and the better final results from the Kujala questionnaire after a minimum follow-up period of two years.

Multiligamentous injuries and knee dislocations

Complex capsular ligamentous structures contribute to stability of the knee joint. Simultaneous injury of two or more knee ligaments, aside from concurrent tears involving the anterior cruciate and medial collateral ligaments, is considered to be associated with femorotibial knee dislocations. Proximal tibiofibular joint dislocations are not always easily recognized and may be overlooked or missed. Patellofemoral dislocations can be transient with MR imaging sometimes required to reach the diagnosis. In this article, the authors describe the mechanism of injury, ligamentous disruptions, imaging, and treatment options of various types of knee dislocations including injuries of the femorotibial, proximal tibiofibular, and patellofemoral joints.

Medial Patellofemoral Ligament Reconstruction in a Below-Knee Amputee

Patellar instability is a common finding in patients with below-knee amputation and yet management options are not commonly described in the literature. We describe the first reported case of a medial patellofemoral ligament reconstruction using allograft in a patient with a below-knee amputation. Clinical outcome at two-year follow-up remains very good.

Accuracy of femoral tunnel placement in medial patellofemoral ligament reconstruction: the effect of a nearly true-lateral fluoroscopic view

BACKGROUND

Reconstruction of the medial patellofemoral ligament (MPFL) is an established operative procedure for patients with recurrent episodes of lateral patellar instability. However, recent articles have reported remarkable complication rates, with nonanatomic femoral tunnel positioning in up to 64% of patients.

PURPOSE

To evaluate the sensitivity of femoral tunnel placement using lateral fluoroscopic guidance to minor degrees of deviation from the true-lateral view using established radiographic landmarks.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six human cadaveric femora were used for this study. A 6-mm radiopaque eyelet was used to mark the native femoral insertion of the MPFL according to previously described radiographic landmarks. Radiographic landmarks were also applied with the femur positioned in 2.5° and 5° of internal and external rotation, respectively, and with the femur in 2.5° and 5° of hip abduction and adduction, respectively. The distance between the center of the 6-mm eyelet to the center of the native femoral MPFL insertion, as established in the true-lateral view, was measured and determined as the degree of shift in each position.

RESULTS

Hip adduction, abduction, and internal and external rotations of 2.5° resulted in a shift from the native femoral MPFL insertion point to a more distal (adduction), proximal (abduction), anterior (internal rotation), and posterior location (external rotation) of 2.7 ± 0.7, 2.0 ± 0.7, 2.7 ± 1.1, and 3.0 ± 1.3 mm, respectively (all P < .05). Malpositioning increased to a distance of 5.0 ± 0.7 mm distally, 3.6 ± 1.0 mm proximally, 5.2 ± 0.8 mm anteriorly, and 6.2 ± 0.6 mm posteriorly to the native insertion point when the attachment was marked with 5° of divergence from the true-lateral view (all P < .05).

CONCLUSION

The results of this study indicate the high sensitivity of femoral tunnel placement using lateral fluoroscopic guidance to minor degrees of deviation from the true-lateral view.

CLINICAL RELEVANCE

The study highlights the importance of an exact lateral view when fluoroscopic guidance is used for femoral tunnel positioning in the daily practice of MPFL reconstruction, and a possible explanation for the high incidence of nonanatomic tunnel placement is suggested.

Current Concepts for Patellar Dislocation

Context:

Patellar dislocation usually occurs to the lateral side, leading to ruptures of the Medial Patellofemoral Ligament (MPFL) in about 90% of the cases. Even though several prognostic factors are identified for patellofemoral instability after patellar dislocation so far, the appropriate therapy remains a controversial issue.

Evidence Acquisition:

Authors searched the Medline library for studies on both surgical and conservative treatment for patellar dislocation and patellofemoral instability. Additionally, the reference list of each article was searched for additional studies.

Results:

A thorough analysis of the anatomical risk factors with a particular focus on patella alta, increased Tibial Tuberosity-Trochlear Groove (TT-TG) distance, trochlear dysplasia as well as torsional abnormalities should be performed early after the first dislocation to allow adequate patient counseling. Summarizing the results of all published randomized clinical trials and comparing surgical and conservative treatment after the first-time patellar dislocation until today indicated no significant evident difference for children, adolescents, and adults. Therefore, nonoperative treatment was indicated after a first-time patellar dislocation in the vast majority of patients.

Conclusions:

Surgical treatment for patellar dislocation is indicated primarily in case of relevant concomitant injuries such as osteochondral fractures, and secondarily for recurrent dislocations.

Are the osseous and tendinous-cartilaginous tibial tuberosity-trochlear groove distances the same on CT and MRI?

OBJECTIVE

To verify whether the tibial tuberosity-trochlear groove distance (TT-TG) and the tendinous-cartilaginous TT-TG (the distance between the patellar tendon and trochlear groove: PT-TG) are identical using computed tomography (CT) and magnetic resonance imaging (MRI) techniques.

SUBJECTS AND METHODS

The TT-TG and PT-TG distances were measured on the same knee samples by three observers (two measurements per observer) using CT and MRI scans collected retrospectively. The reproducibility of the measurements was assessed using the interclass correlation coefficient (ICC). The means and standard deviations of four measurements were calculated for each patient. A paired t-test was used to assess differences between measurements.

RESULTS

Fifty knee samples (32 with patellar instability and 18 with other conditions) were evaluated. The inter- and intraobserver reliability was excellent for all four measurements (>0.8). On average, the TT-TG distance on MRI was 3.1-3.6 mm smaller than that on CT, and the PT-TG distance on MRI was 1.0-3.4 mm larger than the TT-TG distance on MRI.

CONCLUSION

The osseous TT-TG and tendinous-cartilaginous PT-TG distances determined by CT and MRI were not identical.

Surgical versus conservative treatment of primary patellar dislocation. A systematic review and meta-analysis

PURPOSE

The purpose of this study was to determine the efficacy of surgical and conservative treatment in the prevention of recurrence after primary patellar dislocation.

METHODS

Studies were searched on MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and CINHAL from their inception to April 2015. All randomized controlled clinical trials comparing surgical versus conservative treatment after first patellar dislocation were included. Primary outcomes were: recurrent dislocation, subluxation, overall instability and subsequent surgery. Secondary outcomes included imaging, and subjective and objective clinical assessment tools. Methodological quality of the studies was assessed using Cochrane Collaboration's "Risk of Bias" tool. Pooled analyses were reported as risk ratio (RR) using a random effects model. Continuous data were reported as standardized mean difference (SMD) and 95 % confidence intervals (CIs). Heterogeneity was assessed using I².

RESULTS

Nine studies were included in the meta-analyses. Methodological quality of the studies was moderate to low. Meta-analyses showed that surgical treatment significantly reduces the redislocation rate (RR = 0.62; 95% CI = 0.39, 0.98, p = 0.04) and provides better results on Hughston VAS score (SMD = -0.32; 95% CI = -0.61, -0.03; p = 0.03) and running (OR = -0.52; 95% CI = 0.31, 0.88; p = 0.01). Conservative treatment showed less occurrence of minor complications (OR = 3.46; 95% CI = 2.08, 5.77; p = 0.01) and better results in the figure-of-8 run test (SMD = 0.42; 95% CI = 0.06, 0.77; p = 0.02) and in the squat down test (SMD = -0.45; 95% CI = -0.81, -0.10; p < 0.00001). No other significant differences could be found.

CONCLUSIONS

Based on the available data, surgical treatment of primary patella dislocation significantly reduces the risk of patella redislocation.

[Reconstruction of the medial patellofemoral ligament using autologous gracilis tendon in an implant-free technique on the patellar side]

OBJECTIVE

Anatomic reconstruction of the medial patellofemoral ligament using autologous gracilis tendon in an implant-free technique on the patellar side to regain patellofemoral stability.

INDICATIONS

Recurrent dislocations, primary dislocation with high risk of recurrence, and dislocations with (osteo-)chondral flake fractures. As combined approach together with other procedures (trochleoplasty, tibial tubercle osteotomy). Revisions.

CONTRAINDICATIONS

As an isolated procedure in patients with high degrees of trochlear dysplasia, chronic dislocation of the patella, and patellofemoral maltracking without instability.

SURGICAL TECHNIQUE

Harvesting of the gracilis tendon. Drilling of a V-shaped tunnel with a special aiming device in anatomic position on the medial side of the patella. Drilling of a femoral tunnel in anatomic position under fluoroscopic control. Passage of the graft, arthroscopic-guided tensioning, and femoral fixation with a biodegradable interference screw.

POSTOPERATIVE MANAGEMENT

Partial weight bearing (20 kg) for 1-2 weeks. No limitation in range of motion. No orthosis. Specific sports allowed after approximately 3 months.

RESULTS

Perioperative complications associated specifically with the technique were observed in 1.0% (7 of 729 cases). In a series of 72 consecutive cases from May 2010 to October 2010, the following were recorded after 4.0 ± 0.1 years: recurrent dislocations in 3.2%, a Tegner activity score of 5.1 ± 1.8, and subjective satisfaction in 92% (follow-up rate 87.5%). No fracture of the patella was seen in any of our patients.

Epidemiology of Patellofemoral Instability Injuries Among High School Athletes in the United States

BACKGROUND

Patellofemoral instability injuries, including dislocations and subluxations, are relatively rare in the general population but are believed to be much more common in young athletic patient populations, such as high school athletes. In spite of the relatively high risk, the epidemiology of such injuries in this population has not been clearly elucidated.

PURPOSE

To provide a comprehensive understanding of the epidemiology of patellofemoral instability injuries among high school athletes in the United States.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Data were obtained from the National High School Sports-Related Injury Surveillance System, High School RIO (Reporting Information Online), an Internet-based sports injury surveillance system. Athletic trainers from high schools across the country uploaded data regarding athlete exposures (defined as practice or game participation) and injuries across 22 sports from 2007-2008 through 2012-2013. Data were collected regarding athlete demographics, injury mechanism and details, practice versus competition, return to sport, and the need for surgery.

RESULTS

A total of 421 patellar instability (143 dislocations and 278 subluxations) injuries occurred during 21,556,515 athlete exposures (AEs) during the study period, for an overall injury rate of 1.95 per 100,000 AEs. The highest injury rates were noted in girls' gymnastics (6.19 per 100,000 AEs), boys' football (4.10), and boys' wrestling (3.45). The overall injury rate was significantly lower for girls than boys (1.66 and 2.15, respectively; rate ratio [RR], 0.77; 95% CI, 0.62-0.94). In contrast, among only the sex-comparable sports, the injury rate was higher for girls than boys (1.47 and 0.88, respectively; RR, 1.67; 95% CI, 1.19-2.34). The rate of injury was higher in competition (3.72) than practice (1.34) (RR, 2.78; 95% CI, 2.29-3.36). A no-contact injury mechanism was the most commonly reported mechanism (37.8% of injuries), followed by player-to-player contact (36.8%). When all contact subcategories are combined, the overall contact mechanism represents 59.3% of injuries. Return to play after a patellofemoral instability injury occurred within 3 weeks for 59.5% of athletes. Return to play in >3 weeks (16.0%) and loss of the remainder of the season (20.0%) were less common outcomes.

CONCLUSION

Patellofemoral instability injury rates vary by sport, sex, and type of exposure (competition vs practice). A better understanding of such patterns of patellofemoral instability injury will help drive formulation of new injury prevention strategies and decrease the risk for patellofemoral instability injury among high school athletes.

Medial patellofemoral ligament tears in the setting of multiligament knee injuries rarely cause patellar instability

BACKGROUND

Multiligament knee injuries (MLKIs) can also involve the medial patellofemoral ligament (MPFL), but there is a paucity of information regarding prevalence and relevance of MPFL involvement in this setting.

PURPOSE

(1) To identify the prevalence of MPFL injury in MLKIs, (2) to determine whether an MPFL tear results in symptomatic patellar instability, and (3) to report clinical and functional outcomes of patients with and without MPFL tears after MLKI surgical reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The records of all patients who underwent surgical reconstruction of MLKI (defined as a grade 3 injury of ≥2 ligaments) at a single institution from 2007 to 2010 were reviewed. Age, sex, knee dislocation classification (according to Schenck), and MRI findings were documented. All preoperative MRI scans were reviewed by an experienced musculoskeletal radiologist to determine the presence or absence of MPFL involvement. If an MPFL tear was present, its anatomic location and severity as well as the presence of patellar or lateral femoral condyle bone bruises were documented. Inclusion criteria included (1) MLKI treated at a single institution, (2) presence of MPFL tear on preoperative MRI, and (3) minimum 2-year clinical follow-up. Patellar instability symptoms were assessed with the Kujala Knee Questionnaire. Functional outcomes were measured using the International Knee Documentation Committee (IKDC) score. IKDC scores were compared between patients who sustained MLKIs with and without MPFL tears. There were 21 patients in each group.

RESULTS

Over the 4-year study period, 30 of 51 patients (59%) treated surgically for a MLKI had MRI evidence of an MPFL tear. Nine were lost to follow-up, leaving 21 patients for review. There were 13 complete (62%), 5 high-grade partial (24%), and 3 partial (14%) MPFL tears. Sixteen of 21 tears (76%) occurred at the proximal third, with the remainder exhibiting diffuse signal abnormality consistent with tearing throughout the length of the MPFL. The superficial medial collateral ligament was involved in all patients. In no case was the MPFL repaired or reconstructed. At mean follow-up of 3.6 years (range, 2.0-5.7 years), only 1 of 21 patients (5%) complained of patellofemoral instability symptoms whereas 20 of 21 patients (95%) did not experience patellar subluxation or dislocation. No significant difference was found when IKDC scores were compared between patients with and without an MPFL tear (mean ± SD, 65.5 ± 22.9 vs 79.4 ± 16.1; P = .07).

CONCLUSION

MPFL tears occur frequently in patients with MLKI but rarely cause instability. In the majority of cases, MPFL tears do not need to be addressed at the time of surgery.

Evaluation and management of patellar instability in pediatric and adolescent athletes

CONTEXT

The rising popularity and intensity of youth sports has increased the incidence of patellar dislocation. These sports-related injuries may be associated with significant morbidity in the pediatric population. Treatment requires understanding and attention to the unique challenges in the skeletally immature patient.

EVIDENCE ACQUISITION

PubMed searches spanning 1970-2013.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

Although nonoperative approaches are most often suitable for first-time patellar dislocations, surgical treatment is recommended for acute fixation of displaced osteochondral fractures sustained during primary instability and for patellar realignment in the setting of recurrent instability. While a variety of procedures can prevent recurrence, the risk of complications is not minimal.

CONCLUSION

Patellar stabilization and realignment procedures in skeletally immature patients with recurrent patellar dislocation can effectively treat patellar instability without untoward effects on growth if careful surgical planning incorporates protection of growth parameters in the skeletally immature athlete.

Acute traumatic patellar dislocation

Inaugural traumatic patellar dislocation is most often due to trauma sustained during physical or sports activity. Two-thirds of acute patellar dislocations occur in young active patients (less than 20 years old). Non-contact knee sprain in flexion and valgus is the leading mechanism in patellar dislocation, accounting for as many as 93% of all cases. The strong displacement of the patella tears the medial stabilizing structures, and notably the medial patellofemoral ligament (MPFL), which is almost always injured in acute patellar dislocation, most frequently at its femoral attachment. Lateral patellar glide can be assessed with the knee in extension or 20° flexion. Displacement by more than 50% of the patellar width is considered abnormal and may induce apprehension. Plain X-ray and CT are mandatory to diagnose bony risk factors for patellar dislocation, such as trochlear dysplasia or increased tibial tubercle-trochlear groove distance (TT-TG), and plan correction. MRI gives information on cartilage and capsulo-ligamentous status for treatment planning: free bodies or osteochondral fracture have to be treated surgically. If patellar dislocation occurs in an anatomically normal knee and osteochondral fracture is ruled out on MRI, non-operative treatment is usually recommended.

Selective hemiepiphyseodesis for patellar instability with associated genu valgum

BACKGROUND/AIMS

Patellar instability limits activity and promotes arthritis. Correcting genu valgum with selective hemiepiphyseodesis can treat patellar instability.

METHODS

We retrospectively reviewed 26 knees with patellar instability and associated genu valgum that underwent hemiepiphyseodesis.

RESULTS

Average anatomic lateral distal femoral angle (aLDFA) significantly corrected. Symptoms improved in all patients. All competitive athletes returned to sports. One complication occurred.

CONCLUSIONS

In genu valgum, the patella seeks an abnormal mechanical axis, resulting in patellar instability. By correcting the mechanical axis with hemiepiphyseodesis, patellar instability symptoms improve and patients return to sports. Complications are rare. Selective hemiepiphyseodesis is recommended when treating patellar instability with associated genu valgum.

Biomechanical comparison of patellar fixation techniques in medial patellofemoral ligament reconstruction

BACKGROUND

Multiple techniques for reconstruction of the medial patellofemoral ligament (MPFL) have been described; however, little is known about the biomechanical properties of these techniques. Fixation of the graft to the patella has not been studied in a human cadaveric model.

HYPOTHESIS/PURPOSE

The purpose of this study was to compare the ultimate failure load and stiffness of 2 different MPFL patellar fixation techniques: suture anchor fixation and interference screw fixation. The null hypothesis was that the suture anchor group would show no difference in the ultimate failure load and stiffness compared with the interference screw group.

STUDY DESIGN

Controlled laboratory study.

METHODS

Reconstruction of the MPFL with semitendinosus autografts was performed in 8 pairs of fresh-frozen cadaveric knees (16 knees total; mean age, 55.8±7.7 years). The specimens were randomly assigned to 2 groups of 8 specimens each based on the method used to fix the graft to the medial patella: suture anchor or interference screw fixation. Each reconstruction technique was performed on 1 knee from the same cadaveric specimen. Suture anchor reconstruction was completed with 2 parallel 3.0-mm biocomposite suture anchors. Interference screw fixation was accomplished with two 4.75-mm biocomposite interference screws docked in parallel tunnels. The reconstructions were cyclically loaded for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 6 mm/s with a line of pull parallel to the anchors or interference screws. Ultimate failure load (N), stiffness (N/mm), and mode of failure were recorded for each specimen.

RESULTS

The suture anchor group had a significantly lower mean failure load (201.54±63.14 N) than the interference screw group (299.25±99.87 N) (P=.007). The suture anchor group also had significantly lower mean stiffness (20.60±6.78 N/mm) compared with the interference screw group (34.66±10.74 N/mm) (P=.007). The most common mode of failure in the suture anchor group was failure at the graft-suture interface. In the interference screw group, the most common mode of failure was the tendon graft pulling out of the tunnel.

CONCLUSION

Interference screw fixation to the medial patella was found to be significantly stronger than suture anchor fixation when comparing the ultimate failure load and stiffness.

CLINICAL RELEVANCE

This study compares the biomechanical properties of 2 commonly used methods for patellar graft fixation in MPFL reconstruction surgery. It supports the use of interference screw fixation based on the ultimate load and stiffness, although suture anchor fixation may be sufficient when compared with the native MPFL based on previously published data.

Introduction of a classification system for patients with patellofemoral instability (WARPS and STAID)

PURPOSE

The primary purpose of this paper is to introduce the WARPS/STAID classification system for patellofemoral instability. The secondary purpose is to establish the validity and reliability of the WARPS/STAID classification system.

METHODS

Patients (n = 31) with a confirmed diagnosis of patellofemoral instability underwent a thorough knee history and physical examination with 3 raters. The raters graded each component of the WARPS/STAID classification system on a visual analogue scale (VAS). A single Global VAS WARPS/STAID score was graded after all other components of the classification system were completed. Intraclass correlation coefficient (ICC 2, 3) was calculated for each metric of the classification scale and for the Global score. Concurrent validity was assessed by correlating the WARPS/STAID score with the Kujala score. Subjects were assigned to one of three categories (WARPS, STAID, or mixed characteristics) according to the Total WARPS/STAID score to determine the level of agreement between the three raters.

RESULTS

Intraclass correlation coefficient (ICC 2, 3) of the WARPS/STAID classification continuum ranged between 0.73 and 0.91 for the individual metrics of the classification. The ICC (2, 3) for the Global WARPS/STAID score was 0.75. The mean Kujala score (m = 61, SD 18) was significantly correlated with the total WARPS/STAID score (r = 0.387, p < 0.05). The majority of subjects were assigned to either the WARPS or STAID categories.

CONCLUSION

This study introduced the WARPS/STAID classification system and established both validity and reliability in subjects with patellofemoral instability.

LEVEL OF EVIDENCE

II.

Axial knee radiographs: consistency across clinic sites

PURPOSE

(1) Do radiographic protocols for knee axial images vary across different clinic locations? (2) Does variability between radiographic positioning protocols (knee flexion angle, beam positioning) yield different radiographic measurements that could influence clinical assumptions?

METHODS

Radiographic positioning, including beam angle and knee flexion, was measured using a photograph taken of a phantom leg and (human) model set-up. An axial radiograph of a phantom leg was taken at seven different outpatients musculoskeletal clinics to assess patella position (lateral tilt/translation). The phantom leg patella was placed in an abnormal position for the radiographic image across all sites.

RESULTS

Knee flexion<30° was less accurate in obtaining requested knee flexion than higher knee flexion angles (phantom limb error averaged 6°, range 4°-7° human model error averaged 15°, range 11°-25°). Of the five sites utilizing a 'Merchants' axial radiographs, the congruence angle varied from +12° to +29°, being normal at one site (+12°) and abnormal (>+16°) at three sites, and negative at one site (-15°).

CONCLUSIONS

Radiographic protocols for knee axial imaging are inconsistent in radiographic positioning and imaging. This variability can lead to disparity in radiographic image results used for clinical decision-making. Standardization of radiographic positioning would yield more consistent imaging of patella position in early flexion, increasing clinical utility and accuracy.

Which patellae are likely to redislocate?

PURPOSE

The purpose of this study was to identify the risk factors for recurrent lateral patellar dislocations and to incorporate those factors into a patellar instability severity score.

METHODS

Sixty-one patients [male/female 35/26; median age 19 years (range 9-51 years)] formed the study group for this investigation. Within the study group, 40 patients experienced a patellar redislocation within 24 months after the primary dislocation, whereas 21 patients, who were assessed after a median follow-up of 37 months (range 24-60 months), had not experienced a subsequent episode of lateral patellar instability. In all patients, age at the time of the primary dislocation, gender, the affected body side, body mass index, bilateral instability, physical activity according to Baecke's questionnaire, the grade of trochlear dysplasia, patellar height, tibial tuberosity-trochlear groove (TT-TG) distance, and patellar tilt were assessed. The odds ratio (OR) of each factor with regard to the patellar redislocation was calculated using contingency tables. Based on these data, a "patellar instability severity score" was calculated.

RESULTS

The patellar instability severity score has six factors: age, bilateral instability, the severity of trochlear dysplasia, patella alta, TT-TG distance, and patellar tilt; the total possible score is seven. Reapplying this score to the study population revealed a median score of 4 points (range 2-7) for those patients with an early episode of patellar redislocation and a median score of 3 points (range 1-6) for those without a redislocation (p=0.0004). The OR for recurrent dislocations was 4.88 (95% CI 1.57-15.17) for the patients who scored 4 or more points when compared with the patients who scored 3 or fewer points (p=0.0064).

CONCLUSION

Based on the individual patient data, the patellar instability severity score allows an initial risk assessment for experiencing a recurrent patellar dislocation and might help differentiate between responders and non-responders to conservative treatment after primary lateral patellar instability.

LEVEL OF EVIDENCE

Case-control study, Level III.

Medial capsule reefing in patellar instability

PURPOSE

The efficacy of medial capsule reefing in the treatment of patellar instability is well documented. Aim of the present study was to prospectively evaluate the outcomes of an all-arthroscopic medial capsule reefing technique in young patients with painful patella syndrome and potential patellar instability.

METHODS

Thirty patients with painful patellar syndrome and potential patellar instability having undergone a minimum of 6 months of intensive rehabilitation were enrolled in the present study. All subjects were evaluated with physical examination, clinical and functional outcomes and complete imaging study.

RESULTS

All patients were reviewed at an intermediate follow-up of 72 months. Average Kujala score improved from 72.9±15.0 to 88.4±7.6 (p<0.0001), average Larsen score from 15.0±2.5 to 17.2±2.2 (p<0.002), average Lysholm from 63.8±16.7 to 87.9±11.7 (p<0.0001) and average Fulkerson score from 69.5±21.5 to 90.8±9.8 (p<0.0001). No intraoperative or postoperative complications were recorded. Ninety per cent of patients were very satisfied or satisfied with their functional result. Twenty-eight patients were reviewed at the final follow-up, 120 months after surgery. Average Kujala was 87.7±8.8 (p<0.0001), average Larsen was 16.8±2.7 (p<0.01), average Lysholm was 87.6±14.3 (p<0.0001), and average Fulkerson was 87.2±13.9 (p<0.0001). Almost 86% of patients were very satisfied or satisfied with their result. However, slight deterioration of the outcomes over time was observed.

CONCLUSION

At the final follow-up, the outcomes of all-arthroscopic technique were significantly improved from preoperative values; however, they were slightly inferior at the 72 months follow-up. This slight deterioration of the outcomes may be the consequence of the reduction in physical activities.

LEVEL OF EVIDENCE

Case series, Level IV.

Medial retinacular flap advancement and arthroscopic lateral release for symptomatic chronic patellar lateral subluxation with tilting

PURPOSE

The purpose of this study was to investigate outcomes of surgical treatment in patients with symptomatic chronic patellar lateral subluxation with tilting.

METHODS

Thirty-two patients (38 knees) underwent arthroscopic lateral release and mini-open advancement of medial retinacular flap for the treatment of symptomatic chronic patellar lateral subluxation with tilting with a mean follow-up of 52.0±11.4 months. The mean age at surgery was 24.7±8.8 years, and the duration of symptoms was 4.8±4.1 years. The patellofemoral function of the knee was evaluated before surgery and at the clinical follow-up using the Kujala functional score.

RESULTS

Thirty-six knees (95%) showed excellent or good results after surgery. Two knees with grade IV chondromalacia of the patella had fair results with persistent apprehension signs and persistent pain. The Kujala patellofemoral functional scores improved by an average of 20.9 points from a mean value of 71.8±12.1 preoperatively to 92.7±10.7 postoperatively (P<0.01). Radiographically, there were significant improvements in congruence angle from 23.4°±7.9° preoperatively to -7.2°±6.4° postoperatively (P<0.01) and in the lateral patellofemoral angle from -8.6°±6.8° preoperatively to 6.3°±4.2° postoperatively (P<0.01).

CONCLUSIONS

Medial retinacular flap advancement and arthroscopic lateral release offer a promising treatment for symptomatic chronic patellar lateral subluxation and tilt without frank traumatic episode.

LEVEL OF EVIDENCE

Retrospective study, Level IV.

Comparison operative and conservative management for primary patellar dislocation: an up-to-date meta-analysis

PURPOSE

The aim of this review was to compare the clinical outcomes between operative and conservative management for primary patella dislocation (PPD).

METHODS

PubMed Medline, EMBASE, Google scholar, and the Cochrane Library were systematically searched for randomized controlled trials that compared operative technique versus conservative technique for PPD. The results of eligible studies were independently extracted and analyzed according to the following: patient's satisfaction, Kujala score, Tegner score, and redislocation rate. Random-effect and fixed-effect models were adopted to calculate the weight mean difference and the odds ratio for continuous and dichotomous variables with 95 % confidence interval.

RESULTS

Seven studies met the inclusion criteria, resulting in 402 (216 surgery and 186 conservation) patients available for the present study. A meta-analysis showed no significant differences between the two treatment groups in terms of patient's satisfaction and Kujala score. However, significant differences in Tegner score (P < 0.00001) and redislocation rate (P = 0.002) were observed in favor of surgical treatment. In the subgroup analysis, surgical intervention achieved higher (P = 0.002) Kujala score in short term (<5 years), while conservation gained advantage (P = 0.003) in long term (>5 years). There was no significant difference in dislocation rate in long term.

CONCLUSIONS

Surgical treatment might provide better clinical results in short term. More persuasive evidence is still needed to proof the effect of surgical management in long time.

Evaluation of medial patellofemoral ligament tears after acute lateral patellar dislocation: comparison of high-frequency ultrasound and MR

OBJECTIVES

The purpose of this study was to compare the diagnostic performance of high-frequency ultrasound with MR in the evaluation of medial patellofemoral ligament (MPFL) lesions after acute lateral patellar dislocation (LPD).

METHODS

High-frequency ultrasound and MR images were prospectively obtained in 97 consecutive patients with acute LPD. Images were acquired using standardised protocols and were independently evaluated by two radiologists. The MPFL was assessed at three sites (patellar insertion, femoral attachment, and mid-substance) for signs of injury.

RESULTS

Of a total of 291 sites in 97 MPFLs, 127 showed proven MPFL tear at surgery, including 51 sites of complete tear and 76 sites of partial tear. In a site-based analysis, the sensitivity, specificity, and accuracy of high-frequency ultrasound was 90.8%, 96.3%, and 94.6%, respectively, for partial MPFL tear and 86.3%, 96.3%, and 94%, respectively, for complete tear. For MR, the sensitivity, specificity, and accuracy was 81.6%, 95.7%, and 91.3%, respectively, for partial MPFL tear and 80.4%, 95.7%, and 92.1%, respectively, for complete tear. There was no statistical difference between high-frequency ultrasound and MR in the assessment of partial (P = 0.1, 0.777, 0.155) or complete (P = 0.425, 0.777, 0.449) MPFL lesions. Interobserver agreement was very good for high-frequency ultrasound and good for MR.

CONCLUSIONS

Data suggest that high-frequency ultrasound and MR have similar diagnostic performance in the evaluation of MPFL lesions after acute LPD.

KEY POINTS

• High-frequency ultrasound and MR were able to detect MPFL lesions after acute lateral patellar dislocation. • High-frequency ultrasound and MR showed similarly high accuracy in diagnosing MPFL lesions. • Interobserver agreement was very good for high-frequency ultrasound and good for MR.

Return to activity after medial patellofemoral ligament repair or reconstruction

PURPOSE

This study aimed to determine the ability of patients to return to activity after medial patellofemoral ligament (MPFL) reconstruction or repair for patellar instability.

METHODS

A systematic review was performed using multiple databases. Studies reporting outcomes with Tegner scores after repair or reconstruction of the MPFL were included. Surgical technique, Tegner scores, and episodes of recurrent patellar instability were recorded.

RESULTS

Ten articles with a total of 402 patients were included. The mean preoperative Tegner score was 4.7 (2.9 to 7.5). The mean postoperative Tegner score was 5.8 (4.0 to 7.7). Forty-nine patients (12.2%) had a recurrent episode of instability, 11 of whom required additional corrective procedures. There was a statistically significant larger failure rate among those who underwent MPFL repair (26.9%) than those who underwent reconstruction (6.6%) or medial retinacular repair/plication (16.5%).

CONCLUSIONS

Recurrent dislocation was higher in patients who underwent MPFL repair rather than reconstruction. However, repair and reconstruction had similar Tegner scores. Repair or reconstruction of the soft tissue structures contributing to patellofemoral instability is successful in returning patients to preinjury activity levels.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II, III, and IV studies.

Clinical and Functional Outcomes following Primary Repair versus Reconstruction of the Medial Patellofemoral Ligament for Recurrent Patellar Instability

Background. The purpose of this study was to compare outcomes of medial patellofemoral ligament (MPFL) repair or reconstruction. Methods. Fourteen knees that underwent MPFL repair and nine (F5, M4) knees that underwent reconstruction at our institution were evaluated for objective and subjective outcomes. The mean age at operation was 20.1 years for repair and 19.8 years for reconstruction. All patients had a minimum of 2 years of follow-up (range: 24-75 months). Patient subjective outcomes were obtained using the International Knee Documentation Committee (IKDC) and Kujala patellofemoral subjective evaluations, as well as Visual Analog (VAS) and Tegner Activity Scales. Bilateral isometric quadriceps strength and vastus medialis obliquus (VMO) and vastus lateralis (VL) surface EMG were measured during maximal isometric quadriceps contractions at 30° and 60° of flexion. Results. There were no redislocations in either group. There was no difference in IKDC (P = 0.16), Kujala (P = 0.43), Tegner (P = 0.12), or VAS (P = 0.05) scores at follow-up. There were no differences between repair and reconstruction in torque generation of the involved side at 30° (P = 0.96) and 60° (P = 0.99). In addition, there was no side to side difference in torque generation or surface EMG activation of VL or VMO. Conclusions. There were minimal differences found between patients undergoing MPFL repair and MPFL reconstruction for the objective and subjective evaluations in this study.

Operative versus conservative treatment for patellar dislocation: a meta-analysis of 7 randomized controlled trials

Purpose

Patellofemoral pathology is common, and patellofemoral dislocation mainly affects adolescents and young adults. We conducted a meta-analysis exclusively of RCTs to compare the clinical outcomes of patellar dislocation patients managed operatively versus non-operatively.

Methods

After systematic review of electronic databases and websites, a total of 7 RCTs reporting data on 402 subjects were included. The methodological quality of the literature was assessed using the PEDro critical appraisal tool. Mean differences (MDs) and risk ratio (RR) were calculated for the pooled effects. Heterogeneity was assessed using the I² test.

Results

Data synthesis showed a lower rate of recurrent patellar dislocation post-treatment in patients managed operatively compared to non-operatively (P = 0.01).

Conclusion

The results suggest a difference in outcomes between the treatment strategies. However the limited number of studies and high risk of inherent bias indicate that future studies involving more patients in better-designed randomized controlled trials will be required.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8011948721221355.

Long-term outcome after operative treatment of traumatic patellar dislocation in adolescents

OBJECTIVES

Retrospective evaluation of the long-term outcomes after surgical treatment of traumatic patellar dislocations in adolescents and identification of possible predictive factors of poor outcomes.

DESIGN

Retrospective clinical study.

SETTING

University Clinic, Level I Trauma Center.

PATIENTS

All 33 adolescents, with a mean age of 14.8 years, who were treated surgically after traumatic patellar dislocation between 1994 and 2006, were involved in this study.

INTERVENTION

Mini-open medial reefing and arthroscopic lateral release.

MAIN OUTCOME MEASUREMENTS

The clinical outcome was evaluated with the visual analogue scale, the Lysholm score, the Kujala score, and the Tegner activity level scale. On preoperative radiographs and magnetic resonance imaging scans, trochlear dysplasia and patella alta were assessed. The variables analyzed were sex, associated osteochondral injuries, the number of redislocations before surgery, and the number of redislocations after surgery.

RESULTS

At the mean follow-up of 9.8 years, the mean Lysholm score was 82.6, the mean Kujala score was 84.4, the mean Tegner activity level was 4.8, and the mean visual analogue scale was 0.2. We found no significant differences in the subgroups regarding functional outcomes. Fifteen patients with patella alta and 4 patients with trochlear dysplasia were assessed radiologically. Redislocations after surgery were observed in 4 patients, 2 of them were female patients who exhibited quadriceps angles requiring tibial tubercle osteotomy to be performed after maturation.

CONCLUSIONS

The techniques of mini-open medial reefing and lateral release demonstrate a good functional long-term outcome and effectively prevent recurrent instability. The major predictive factor for poor outcomes and redislocations is an inadequately addressed pathology.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The incidence of trochlear dysplasia in anterior cruciate ligament tears

PURPOSE

The purpose of the present epidemiologic study is to record the radiographic presence of trochlear dysplasia and patella alta in patients who undergo anterior cruciate ligament (ACL) reconstruction as a potential underlying factor for post-operative anterior knee pain (AKP).

METHODS

All consecutive cases of skeletally-mature ACL-deficient knees that would undergo ACL reconstruction in three different hospitals were prospectively included during a six-month period. Inclusion criteria were acute and sub-acute ACL injury with no previous ipsilateral knee operation. Patients with chronic ACL tears, prior-to-ACL-injury history of patellar instability or other PF disorders were excluded from the study.

RESULTS

A total of 299 knees were included (mean age 32 ± ten years). Forty-four (14.7 %) knees had a positive 'crossing sign' in the lateral X-rays and 255 (85.3 %) had no sign of trochlear dysplasia (p < 0.01). Among the cases with trochlear dysplasia, 41 (93 %) had type A trochlear dysplasia with the presence only of the 'crossing sign' and three (7 %) had type C trochlear dysplasia. Patellar height results included a mean Caton-Deschamps index of 1.0 ± 0.14 (0.5-1.4). Twenty (6.6 %) knees had an index of less than 0.8, and two (0.6 %) knees had an index less than 0.6. In contrast, 15 (5.0 %) knees had an abnormal value of more than 1.2, indicating patella alta.

CONCLUSIONS

The most important finding of the study is the increased prevalence of trochlear dysplasia and patella alta in patients with ACL injury, when compared to the incidence of trochlear dysplasia and patella alta in the general population in the literature. This finding could sound as an alert of a possible additional risk factor for post-operative anterior knee pain after ACL reconstruction.

Osteochondral injury after acute patellar dislocation in children and adolescents

BACKGROUND

Acute patellar dislocation (APD) is a common injury in the pediatric patient population and may be associated with a spectrum of soft tissue and osteochondral injuries. This study describes the incidence of osteochondral fracture and associated injury patterns in a pediatric population after first-time APD and assesses functional outcomes after treatment.

METHODS

One hundred twenty-two patients, aged 11 to 18 years, who were evaluated after first-time APD over a 10-year period were identified, 46 of whom had confirmed osteochondral injury on magnetic resonance imaging (MRI). Demographic data, including knee affected, mechanism of injury, recurrent dislocation, operations performed, and condition at last follow-up, were retrieved from the medical record. Operative reports and MRI were used to characterize the location of osteochondral injury. The functional outcome of each patient with an osteochondral fracture was assessed using the Pedi-IKDC questionnaire.

RESULTS

Forty-six patients, mean age 14.6 years (range, 11 to 18 y), were included. Osteochondral fracture occurred at the patella in 35 patients (76%), the lateral femoral condyle in 11 patients (24%), and at both locations in 3 patients (6.5%). In 21 patients (44%), MRI confirmed osteochondral injury despite the plain radiograph interpretation as negative for fracture. Twenty-six patients (68%) subsequently underwent surgery after injury. Injury to the medial patellofemoral ligament was identified on MRI in 97.8% of patients (45/46). Fifteen patients (32.6%) underwent a concomitant medial repair at the time of surgery. Osteochondral injury to the distal femur on average had a lower International Knee Documentation Committee score than patellar injuries (72.3±18 vs. 91.1±10.2, P<0.003). Femoral osteochondral injury involving the weight-bearing surface (75.27±18.19) scored lower than non-weight-bearing surface injuries (93.22±7.47; P<0.001).

CONCLUSIONS

The incidence of osteochondral injury associated with APD is high. Osteochondral fractures may initially go unrecognized on plain radiographs. Patients with weight-bearing lateral femoral condyle injuries had lower short-term functional scores, suggesting that outcomes depend on location of injury.

LEVEL OF EVIDENCE

Level IV, diagnostic and therapeutic study.

Variation in tibial tubercle-trochlear groove measurement as a function of age, sex, size, and patellar instability

BACKGROUND

The tibial tubercle-trochlear groove (TT-TG) measurement was developed to quantify morphologic abnormalities about the knee associated with patellar instability and to help guide surgical decision making.

PURPOSE

To assess variations in TT-TG as a function of patient age and size in a population of patients with patellar instability compared with those with no instability.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

All patients younger than 20 years who underwent surgery for patellar instability from 2010 to 2012 were included in this retrospective study. A total of 180 patients with no history of patellar instability or patellofemoral complaints were used as a control group. The TT-TG was measured on magnetic resonance axial images using the centers of the tibial tubercle and the trochlear groove. Data were normalized based on patient height, weight, body mass index (BMI), and femur width. Alpha was set at P < .05 to declare significance.

RESULTS

The average age of the 45 patellar instability patients was 15.4 years (range, 10-18 years), their mean TT-TG was 16.3 mm (range, 6.5-26 mm), and 51% were male. By comparison, the mean age of the control group was 16 years (range, 10-19 years), the mean TT-TG was 11.7 mm (range, 3-22 mm), and 58% were male. The TT-TG and the normalized TT-TG for height, weight, BMI, and femur width were all greater in the patellar instability group compared with the control group (P ≤ .001). Thirty-one percent of patients had a TT-TG greater than 20 mm in the instability group compared with 3% in the control group (P < .05, specificity 97%, sensitivity 31%). The TT-TG was found to increase as a function of height in both groups (r = 0.14, P = .04) and decreased with age only in the instability group (r = -0.3, P = .04).

CONCLUSION

An elevated TT-TG is associated with patellar instability both in pediatric and adolescent patients. However, this measurement varies as a function of patient age and height, with each centimeter in height increasing the TT-TG by 0.12. Normalization of TT-TG to patient height may control for size variations and should be undertaken in the work-up and management of patients with patellar instability.

Femoral tunnel enlargement after medial patellofemoral ligament reconstruction: prevalence, risk factors, and clinical effect

BACKGROUND

In recent years, significantly more attention has been focused on the role of the medial patellofemoral ligament (MPFL) in patellar stability, and MPFL reconstruction has become a mainstay of surgical treatment of episodic patellar dislocations. Although previously described in detail after reconstruction of the anterior cruciate ligament, tunnel enlargement has not been investigated after MPFL reconstruction.

HYPOTHESES

(1) Femoral tunnel enlargement occurs after MPFL reconstruction. (2) Patella alta, trochlear dysplasia, and tunnel malposition are risk factors for tunnel enlargement. (3) The presence of tunnel enlargement is not associated with recurrent dislocations or poorer patient-reported outcome scores after MPFL reconstruction.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Fifty-five of 59 knees treated for episodic patellar dislocations with MPFL reconstruction between 2005 and 2010 were evaluated at 1 year postoperatively for the presence of tunnel enlargement on lateral radiographs. Tunnel enlargement was defined as a tunnel area greater than 2 times that of the original tunnel. Knees with tunnel enlargement at 1 year were compared with those without tunnel enlargement. Patients were assessed for recurrent subluxations or dislocations at a mean of 3 years postoperatively, and patient-reported outcome scores were assessed in a subset of patients at a mean of 3.7 years postoperatively.

RESULTS

Tunnel enlargement was noted in 23 knees (41.8%). No differences in patient age or body mass index were noted between the 2 groups. The mean patellar height was significantly higher in the enlarged tunnel group (P = .03). A higher prevalence of trochlear dysplasia or tunnel malposition was not demonstrated in the enlarged tunnel group. Patient-reported outcome scores and the risk of recurrent patellar instability were equal in the 2 groups.

CONCLUSION

Femoral tunnel enlargement after MPFL reconstruction is common, with patients with patella alta at an increased risk. The influence of tunnel malposition and trochlear dysplasia on this condition requires further research. Recurrent instability and patient-reported outcome scores are not affected by tunnel enlargement.

Medial patellofemoral ligament: anatomy, injury and treatment in the adolescent knee

PURPOSE OF REVIEW

Traumatic and nontraumatic patellofemoral instability (PFI) in children and adolescents is a complex problem. It is determined by a large number of mechanical and pathomorphologic conditions, mainly seen in nontraumatic dislocations.

RECENT FINDINGS

Although conservative treatment with a short immobilization, followed by early passive motion and isometric quadriceps strengthening, can be considered in real traumatic dislocations without any cartilaginous injury, a surgical intervention should be considered in atraumatic cases. As 90% of PFI are nontraumatic and correlated with skeletal deformities, the redislocation rate is reported to be up to 80% after initial conservative treatment. To optimize the results, the causing disorder for PFI has to be considered imperatively. In addition to bony disorder, further risk factors have to be taken into consideration for determining the optimal time for surgery. As biomechanical and clinical studies have shown the importance of the medial patellofemoral complex, especially the medial patellofemoral ligament (MPFL), against patellar lateralization, the reconstruction or minimally invasive double-bundle reconstruction of the MPFL is the main surgical technique to treat PFI in children, as it can be used even in open epiphysial cartilage. Further surgical interventions correcting bone deformities, such as trochleoplasty or tibial tubercle osteotomies addressing lower limb deformities, should be performed after closure of the epiphysial cartilage.

SUMMARY

It is the goal of this overview to explain the pathoanatomy of PFI, the demanding clinical and radiological examinations and treatment options.

Surgical versus non-surgical management for primary patellar dislocations: an up-to-date meta-analysis

The aim of this up-to-date meta-analysis was to compare the effects of surgical versus non-surgical treatment of patients following primary patellar dislocation and to provide the best evidence currently available. A comprehensive literature search was conducted using multiple databases, including Medline, Embase, and Cochrane Registry of Clinical Trials. All databases were searched from the earliest records to May 2013. Eligible studies were selected, and data were extracted by two independent investigators. The primary outcome variable was the frequency of recurrent patellar dislocation. The other outcomes included knee function scores, patient-rated outcomes, and radiographic examination. If appropriate, meta-analysis of these variables was performed. Nine independent trials were found to match the inclusion criteria. The pooled results demonstrated that the incidence of recurrent patellar dislocation and Hughston visual analog scale was significantly lower in the surgical treatment group than that in the non-surgical treatment group (P < 0.05). There was no statistically significant difference between the two treatment groups in frequency of subsequent surgical interventions, percentage of excellent or good subjective opinion, Kujala score, pain score on visual analog scale, and severity of patellofemoral joint osteoarthrosis (P > 0.05). This up-to-date meta-analysis indicates that surgical treatment was associated with a lower risk of recurrent patellar dislocation, but a lower Hughston VAS than non-surgical treatment for primary patellar dislocation. More large high-quality trials and further studies are needed to overcome the limitations of small sample sizes, and varieties of different surgical procedures or non-surgical management strategies adopted in the included trials.

Lateral patellar retinaculum reconstruction for medial patellar instability following lateral retinacular release: a case report

Lateral retinacular release is still being performed in patients with recurrent patellar dislocation as an additional procedure with distal realignment or medial patellofemoral ligament (MPFL) reconstruction. However, consensus remains lacking regarding suitable indications for lateral retinacular release. A 20-year-old woman presented with patellar instability in both medial and lateral directions after undergoing lateral retinacular release with MPFL reconstruction. She displayed inherent systemic joint laxity meeting all seven Carter-Wilkinson criteria. Simultaneous MPFL revision and lateral retinaculum reconstruction successfully improved patellar instability in both directions. This case provides an example of iatrogenic medial patellar instability after failed lateral retinacular release.

Sonography on injury of the medial patellofemoral ligament after acute traumatic lateral patellar dislocation: Injury patterns and correlation analysis with injury of articular cartilage of the inferomedial patella

OBJECTIVE

The purpose of this study was to investigate the accuracy of high-frequency ultrasonography in the diagnosis of injuries of medial patellofemoral ligaments (MPFLs), analyse the characteristics of MPFL injury and correlations between injury of the MPFL and articular cartilage of the inferomedial patella in patients with acute traumatic lateral patellar dislocation.

METHODS

High-frequency sonographic images of 49 patients with acute traumatic lateral patellar dislocations treated surgically were reviewed. The χ(2) tests were performed for statistical analysis.

RESULTS

Twenty-eight cases of complete MPFL tear and 21 cases of partial MPFL tear were identified in operation, with 27 cases of MPFL tear located at their femoral attachment, 21 cases of tear at the patellar attachment and one case of midsubstance tear. The diagnostic accuracy of sonography regarding partial MPFL tear and complete MPFL tear was 89.8% and 89.8%. Among the patients with MPFL tear at the patellar attachment, eight and six cases were concomitant with chondral and osteochondral lesions in the inferomedial patella, respectively, in contrast to nine and six cases in patients with MPFL tear at the femoral attachment, respectively. There was no significant difference between the two locations described above regarding the prevalence rates of chondral or osteochondral lesions of the inferomedial patella (P=0.732, P=0.614). Among the patients with complete MPFL tear, 12 and 10 cases were concomitant with chondral and osteochondral lesions in the inferomedial patella, respectively, while six and two cases were concomitant with partial MPFL tear. There was no significant difference between the two types of injuries discussed above on the prevalence rates of chondral lesions of the inferomedial patella (P=0.305), but the prevalence rate of osteochondral lesions between the two types of injuries discussed above was statistically different (P=0.035).

CONCLUSIONS

The MPFL is most easily injured at the femoral attachment, secondly at the patellar attachment. High-frequency ultrasonography is an accurate method in the diagnosis of an MPFL tear. There are neither significant differences on the prevalence rates of chondral or osteochondral lesions of the inferomedial patella between locations of MPFL injuries, nor significant difference on the prevalence rates of chondral lesions between MPFL injury types; but the complete MPFL tear is more often concomitant with inferomedial patellar osteochondral lesions than the partial MPFL tear.

Treatment options for patellofemoral instability in sports traumatology

Patellofemoral instability not only involves lateral patellar dislocation, patellar mal-tracking or subluxation but can also cause a limiting disability for sports activities. Its underlying causes are known as morphological anomalies of the patellofemoral joint or the mechanical axis, femorotibial malrotation, variants of the knee extensor apparatus, and ligamentous insufficiencies often accompanied by poor proprioception. Athletes with such predisposing factors are either suffering from unspecific anterior knee pain or from slightly traumatic or recurrent lateral patellar dislocation Treatment options of patellar instability are vast, and need to be tailored individually depending on the athlete’s history, age, complaints and physical demands. Different conservative and surgical treatment options are reviewed and discussed, especially limited expectations after surgery.

The contemporary management of anterior knee pain and patellofemoral instability

In this review the evidence for the management of patients with patellofemoral disorders is presented confined to anterior knee pain and patellar dislocation (excluding patellofemoral arthritis). Patients present along a spectrum of these two problems and are best managed with both problems considered. The key to managing these patients is by improving muscle function, the patient losing weight (if overweight), and judicious use of analgesics if pain is an important feature. Hypermobility syndrome should always be looked for since this is a prognostic indicator for a poor operative outcome. Operations should be reserved for those with correctable anatomical abnormalities that have failed conservative therapy. The current dominant operation is a medial patellofemoral ligament reconstruction.

Sectioning the medial patellofemoral ligament alters patellofemoral joint kinematics and contact mechanics

Medial patellofemoral ligament (MPFL) disruption may alter patellofemoral joint (PFJ) kinematics and contact mechanics, potentially causing pain and joint degeneration. In this controlled laboratory study, we investigated the hypothesis that MPFL transection would change patellar tracking and PFJ contact pressures and increase the distance between the attachment points of the MPFL. Eight fresh frozen dissected cadaveric knees were mounted in a rig with the quadriceps and ITB loaded to 205 N. An optical tracking system measured joint kinematics, and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Length patterns of the distance between the femoral and patellar attachments of the MPFL were measured using a suture led to a linear displacement transducer. Measurements were repeated with the MPFL intact and following MPFL transection. A significant increase in the distance between the patellar and femoral MPFL attachment points was noted following transection (p < 0.05). MPFL transection resulted in significantly increased lateral translation and lateral tilt of the patella in early flexion (p < 0.05). Peak and mean medial PFJ contact pressures were significantly reduced and peak lateral contact pressures significantly elevated in early knee flexion following MPFL transection (p < 0.05). MPFL transection resulted in significant alterations to PFJ tracking and contact pressures, which may affect articular cartilage health.

Are the tubular grafts in the femoral tunnel in an anatomical or isometric position in the reconstruction of medial patellofemoral ligament?

PURPOSE

The purpose of this study was to evaluate the biomechanical results from the in vitro reconstruction of medial patellofemoral ligament (MPFL) using a navigation-assisted technique on a cadaveric model and its effects on patellar stability and kinematics. The authors investigated the hypothesis that patellar kinematics after reconstruction with a tubular graft are not optimal when compared with the original fan-shaped MPFL.

METHODS

In six fresh-frozen cadaveric knees, lateral loads (25 N) were applied on the patella at 0°, 30°, 60° and 90° of knee flexion in three different MPFL states: intact, cut and reconstructed. The arrangement allowed positional measurements of patellar motion to be tracked in six degrees of freedom. Medial to lateral patellar translation and patellar tilt were recorded. The kinematics after a technique of MPFL reconstruction, performed with a gracilis tendon in a blind femoral tunnel guided by navigation, were compared against kinematics recorded in the MPFL intact state. A temporary fixation of adequate tension to engage the lateral patellar facet in extension was applied to the MPFL and, after graft cycling, the final fixation was done at 70° knee flexion with an interference screw.

RESULTS

There was a comparable medial to lateral patellar translation and tilting of the patella in the MPFL-intact and the MPFL-reconstructed state. Static patellar translation in the MPFL-reconstructed state, with and without the application of load, was comparable to patellar translation in the MPFL-intact state. The dynamic patellofemoral shift kinematics recorded an under-constraint in early flexion and over-constraint in late flexion, while an opposite effect was recorded in patellar tilt. However, these differences were not statistically significant.

CONCLUSION

The study confirmed the major role of the MPFL in case of medial loading between 0° and 60°, by focusing on the importance of kinematically identifying the proper femoral point for fixation. While the study demonstrates the importance of kinematic determination of the proper femoral point of fixation, as the anatomical insertion remains difficult to identify. Even in dissected cadavers, the authors recorded a slightly anterior placement than native MPFL. After reconstruction, patellar stability in terms of lateral translation and tilt was similar to the intact MPFL, but patellar kinematics were not optimal with the use of a smaller and tubular graft than the native wider and fan-shaped MPFL.

Surgical treatment of a chronically fixed lateral patella dislocation in an adolescent patient

Acute patellar dislocation or subluxation is a common cause for knee injuries in the United States and accounts for 2% to 3% of all injuries. Up to 49% of patients will have recurrent subluxations or dislocations. Importance of both soft tissue (predominantly, the medial patellofemoral ligament, MPFL, which is responsible for 60% of the resistance to lateral dislocation) and bony constraint of femoral trochlea in preventing subluxation and dislocation is well documented. Acute patella dislocation will require closed reduction and management typically consist of conservative or surgical treatment depending on the symptoms and recurrence of instability. Most patients are diagnosed and treated in a timely manner. We present a 15 years old male with a missed traumatic lateral patella dislocation during childhood. The patient presented as an adolescent with a chronically fixed lateral patella dislocation and was management with surgery. The key steps in the surgical reconstruction of this patient required first mobilizing the patella with a lateral retinacular release and V-Y lengthening of the shortened or contracted quadriceps tendon. Then a combination of MPFL reconstruction using the semitendinosis autograft, tibial tubercle osteotomy with anterio-medialization, and lateral facetectomy was performed. At the one-year follow-up, our patient had improved knee range of motion and decrease in pain. Chronically fixed lateral dislocated patella is a rare and complex problem to manage in older patients that will require a thorough work-up and appropriate surgical planning along with reconstruction.

Medial patellofemoral ligament reconstruction: the superficial quad technique

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is a routine procedure for patellar instability. The majority of the techniques require hardware fixation or a bony procedure at the patella. However, most of the complications described in the literature can be attributed to patellar fixation. The "superficial quad technique" uses the superficial slip of the quadriceps tendon as the graft material, which provides a better anatomic match to the native MPFL.

HYPOTHESIS

The superficial quad technique provides anatomic patellar fixation without a bony procedure and without patellar complications.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The study included 32 patients (10 male, 22 female; mean age, 25 years) who underwent MPFL reconstruction using the superficial quad technique and who were followed for a mean duration of 38 months. Objective assessment was performed and Kujala scores were obtained preoperatively and at the time of final follow-up.

RESULTS

There were no patellar complications, including redislocation, in the present study. The mean Kujala score improved to 91.25 (range, 73-100) from a preoperative score of 49.31 (range, 23-62).

CONCLUSION

The results were comparable with those of other studies in the literature that used hamstring grafts, but without associated patellar complications. The superficial quad technique uses graft material that is a better anatomic match to the native MPFL. It provides anatomic patellar fixation without a bony procedure.

Predictors of recurrent instability after acute patellofemoral dislocation in pediatric and adolescent patients

BACKGROUND

Patellofemoral instability is common in the pediatric and adolescent population, yet prognosis after the first dislocation has been difficult to determine.

PURPOSE

To describe the demographics of pediatric and adolescent patients with a first-time patellofemoral dislocation and to determine predictors of recurrent instability.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A search of the Mayo Medical Index database between 1998 to 2010 was performed, and 2039 patients were identified. Inclusion criteria were (1) age 18 years or younger, (2) no history of patellofemoral subluxation/dislocation of the affected knee, (3) radiographs within 4 weeks of the initial instability episode, and (4) a dislocated patella requiring reduction or convincing history/findings suggestive of acute patellar dislocation (effusion/hemarthrosis, tenderness along medial parapatellar structures, and apprehension with lateral patellar translation). Radiographs were evaluated for trochlear dysplasia (Dejour classification) and patella alta (Caton-Deschamps and Insall-Salvati indices). Skeletal maturity was graded based on the distal femoral and proximal tibial physes (open, closing, or closed).

RESULTS

A total of 222 knees (120 male [54.1%] and 102 female [45.9%]) in 210 patients with an average age of 14.9 years (range, 9-18 years), met the inclusion criteria. Twenty-four patients (10.8%) underwent early surgery. All others were initially treated nonoperatively. Of the 198 patients in this group, 76 (38.4%) had recurrent instability, and 39 (51.3%) of these required surgical treatment. Recurrent instability was associated with trochlear dysplasia (P < .01). Patients with both immature physes and trochlear dysplasia had a recurrence rate of 69% (33/48), with a hazard ratio of 3.3. Age, sex, body mass index, and patella alta were not statistically associated with recurrent instability.

CONCLUSION

Nonoperative treatment for first-time patellofemoral dislocation resulted in a 62% success rate. However, skeletally immature patients with trochlear dysplasia had only a 31% success rate with nonoperative management. Nearly half of patients with recurrent instability required surgical intervention to gain stability.