Lateral Patellar Instability

Patellofemoral positioning CT protocol has diagnostic ability to differentiate patellar maltracking phenotype

Introduction

Traditional radiographs often fail to capture the dynamic nature of patellar maltracking in patellofemoral pain syndrome (PFPS) and patellar instability, necessitating improved diagnostic protocols. This study aimed to: (1) introduce a CT protocol with scans at three knee positions (45° flexion, extension, and extension with quadriceps contraction), (2) assess how positioning influences patellofemoral indices measured from radiographs and CT, and (3) to evaluate the protocol's ability to classify maltracking phenotypes: dislocator, subluxator, or symptomatic without dislocation/subluxation (Neither).

Methods

Patients who underwent surgery for PFPS from April to December 2022 were retrospectively reviewed. Patellofemoral indices from the three scans within the CT protocol were compared among themselves and with standard radiographs. Patients were grouped by maltracking phenotype, and their patellofemoral indices on radiographs and CT were compared to determine which imaging modality best distinguished the phenotypes. Statistical analyses included bivariate and multivariate logistic regression.

Results

The study included 65 patients (51 females, 14 males) with mean age of 27. Patellofemoral indices measured on CT-45° versus CT-Extended differed significantly (p < 0.05), indicated the influence of knee position. Quadriceps contraction further worsened most indices, highlighting the importance of load-bearing conditions. Radiographs and CT-45° had limited capability to differentiate Dislocator, Subluxator, and Neither, but CT-Extended and CT-Quad showed significant differences among these groups. Multivariate analysis identified four independent predictors of patellar maltracking severity (p < 0.05): (1) Lateral Offset and (2) Insall-Salvati Ratio measured on CT-Extended, as changes in (3) Lateral Offset and (4) Lateral patellofemoral angle (LPFA) between extension and quadriceps contraction.

Conclusions

Radiographs alone cannot reliably distinguish Dislocator, Subluxator, and Neither. A dedicated CT protocol featuring scans in neutral extension and with quadriceps contraction better delineates patellofemoral maltracking phenotypes and offers improved diagnostic accuracy in PFPS. This approach may guide tailored interventions to address distinct underlying mechanics of each phenotype.

Level of evidence

III.

Femoral anteversion angle is more advantageous than TT-TG distance in evaluating patellar dislocation: A retrospective cohort study

PURPOSE

The purpose of this study is to report the parameter characteristics of the femoral anteversion angle (FAA) and tibial tubercle-trochlear groove (TT-TG) distance in patients with patellar instability compared to healthy individuals and to evaluate their reliability in predicting patellar dislocation, providing potential indications for osteotomy.

METHODS

A retrospective collection of consecutive patients with patellar instability constituted the study group, while individuals without patellofemoral disorder served as the control group. Measurement of the FAA and TT-TG distance were conducted by lower extremity computed tomography scans and knees with true patellar dislocation were recorded. The diagnostic capability of the FAA and TT-TG distance was assessed using receiver operating characteristic curves and area under the curve (AUC), determining the pathological values by sensitivity and specificity.

RESULTS

The FAA (21.6 ± 9.0°) and TT-TG distance (20.1 ± 4.8 mm) in the study group were significantly greater than the control group (10.6 ± 7.9° and 15.6 ± 4.6 mm, respectively) (p < 0.001). The AUCs for patellar dislocation were 0.869 for FAA and 0.712 for TT-TG distance, with pathological cut-off values of 18.2° and 18.2 mm, respectively. The odds ratios for FAA and TT-TG distance were 1.185 and 1.125, respectively (p < 0.05).

CONCLUSIONS

Patients with patellar instability exhibited significantly greater FAA and TT-TG distance compared to healthy individuals. The FAA demonstrated superior predictive capability for patellar dislocation compared to the TT-TG distance. The FAA (>18.2°) measured by surgical transepicondylar axis and TT-TG distance (>18.2 mm) were the potential pathological thresholds. Additionally, an increase of 1° in FAA and 1 mm in TT-TG distance was associated with a 18.5% and 12.5% increased risk of patellar dislocation, respectively. Surgeons should be aware of the risk of patellar dislocation associated with rotational malalignment.

LEVEL OF EVIDENCE

Level III.

Isolated Medial Patellofemoral Ligament Reconstruction Under Increased Femoral Anteversion Is Associated With Increased Contact Pressure of Medial Patellofemoral Facet at Deep Flexion Angle: A Cadaveric Study

PURPOSE

To analyze (1) whether isolated medial patellofemoral ligament (MPFL) reconstruction in increased femoral anteversion could replicate the patellofemoral (PF) pressure pattern of a hypothetical normal population and (2) the change of PF pressure according to MPFL state under the same anteversion setting.

METHODS

Ten fresh-frozen cadaveric knees were used. Experiments were performed from knee flexion 0° to 90° with 3 MPFL state (intact, released, and reconstructed) and 3 anteversion (initial state, 10° and 20° more increased). Medial and lateral PF joint contact pressures were measured at each point.

RESULTS

At 0° flexion, lateral PF pressure was increased to 62.1 ± 7.8 psi in 10° and 67.3 ± 13.5 psi in 20° more increased anteversion, compared with 43.2 ± 8.6 psi of hypothetical normal population (P .027 and .004, respectively). At 30° flexion, medial PF pressure was decreased to 31.3 ± 11.9 psi in 10° and 27.3 ± 17.5 psi in 20° more increased anteversion, compared with 44.1 ± 10.3 psi of hypothetical normal population (P .009 and .027, respectively). Within the same femoral anteversion, when anteversion was increased 10° and 20° more than the initial state, medial facet pressure after MPFL reconstruction at 90° flexion was increased from 28.7 ± 11.4 psi to 40.0 ± 9.9 psi and 16.7 ± 10.8 psi to 33.9 ± 15.0 psi compared with the intact MPFL (P .047 and <.001, respectively).

CONCLUSIONS

Biomechanically, isolated MPFL reconstruction under increased femoral anteversion was unable to replicate the state of a hypothetical normal population. Even when comparing within the same femoral anteversion, isolated MPFL reconstruction at increased femoral anteversion caused medial PF overpressure at 90° flexion angle.

CLINICAL RELEVANCE

When performing MPFL reconstruction for recurrent patellar dislocation, femoral anteversion should be assessed. Increased femoral anteversion can cause overpressure on the medial facet after isolated MPFL reconstruction.

Femoral inherent torsion is more accurate than femoral anteversion angle in evaluating femoral torsion to determine whether combine derotational distal femoral osteotomy or not

BACKGROUND

Previous view is that femoral anteversion angle (FAA) is equivalent to femoral torsion (FT) and as an indication for derotational distal femoral osteotomy (DDFO) combined with medial patellofemoral ligament reconstruction (MPFLR), but posterior femoral condylar deformity affects FAA. Therefore, FAA is not accurate in assessing FT. Whether the femoral inherent torsion (FIT), which avoids the influence of the posterior condyle, can better reflect FT during surgery remains unknown. Meanwhile, the impact of the posterior femoral condyle on surgical outcomes remains unclear.

METHODS

Twenty-five patellar dislocation (PD) patients from 2017 to 2021 were conducted. All patients underwent both preoperative and postoperative computed tomography scans. Categorized by posterior condylar angle (PCA), they were divided into Group A (PCA ≤ 6.4°) and Group B (PCA > 6.4°). Radiographic measurements included FAA, femoral inherent torsion (FIT), patellar tilt angle, congruence angle and tibial tubercle-trochlear groove distance. For clinical outcomes, the Kujula score, Lysholm score, IKDC score to reflect the knee function. The Tegner activity score was used to assess the activity level. The VAS score was used to assess the pain control.

RESULTS

In both groups, the postoperative radiographic outcomes demonstrated a statistically significant improvement. Preoperatively, the FAA was similar in the two groups, but the FIT was greater in the Group A (21.7° ± 1.2° vs 18.4° ± 1 .3°, P < 0.001). However, there was no statistically significant difference between them in the postoperative period (7.4° ± 1.5° vs 7.1° ± 1.8°). In terms of clinical outcomes, both groups demonstrated a significant improvement in the postoperative period. However, the scores of the Group A significantly better (Kujula: 85.7 ± 5.0 vs 79.6 ± 4.8, P = 0.005; Lysholm: 86.8 ± 5.3 vs 80.2 ± 5.7, P = 0.006; IKDC: 86.1 ± 8.8 vs 75.5 ± 7.6, P = 0.004).

CONCLUSION

FIT may be a more reliable indicator than FAA for evaluating FT in PD to determine whether combine DDFO or not, especially in the presence of posterior femoral condylar deformity. Posterior femoral condylar deformity appeared to result in a pseudo-increase in FAA. Simultaneous evaluation of FIT and FAA to identify true posterior condylar deformity offers the potential to prevent enlargement of DDFO and enable precision treatment.

Returning to pre-injury level of sports before 9 months after medial patellofemoral ligament reconstruction increases the incidence of anterior knee pain in young patients

PURPOSE

This study aimed to identify the risk factors for anterior knee pain (AKP) after medial patellofemoral ligament reconstruction (MPFLR).

METHODS

Patients aged 15-35 years who underwent isolated MPFLR between 2012 and 2022 were included in the study. These patients were divided into two groups (AKP and control group). Patient demographics and preoperative and postoperative clinical outcomes between the two groups were assessed and compared. Univariate logistic regression analysis was performed to explore the potential risk factors associated with postoperative AKP. Subgroup analysis stratified the results based on the time to return to sports (RTS) (>9 and ≤9 months). Furthermore, Spearman correlation analysis was performed to investigate the association between Kujala score and time to RTS.

RESULTS

A total of 206 patients were included (AKP, n = 59; control, n = 147). At the 2-year follow-up, patients with AKP demonstrated a shorter duration in returning to their pre-injury activity level compared to those without AKP (9.0 ± 3.6 vs. 10.3 ± 2.7 months, p < 0.05). RTS earlier than 9 months after MPFLR was the only significant risk factor associated with postoperative AKP (odds ratio, 2.13, 95% confidence interval, 1.03-4.39; p < 0.05). Further subgroup analysis revealed that patient RTS earlier than 9 months exhibited worse patient-reported outcomes in both the total cohort and control group (p < 0.05). Furthermore, among patient RTS within 9 months, a longer recovery duration before RTS strongly correlated with a higher Kujala score (R = 0.670, p < 0.001).

CONCLUSIONS

Young patients who RTS at their pre-injury levels before 9 months after MPFLR have a higher incidence of postoperative AKP and poorer functional outcomes compared to those who delay their return. Specifically, within the first 9 months after MPFLR, the earlier the RTS, the more severe the AKP symptoms. Careful consideration of the timing for RTS may help reduce the incidence of postoperative AKP.

LEVEL OF EVIDENCE

Level III.

The Effects of Inaccurate Femoral Tunnel Placement During Medial Patellofemoral Ligament Reconstruction on Midterm Clinical Outcomes in Treatment of Recurrent Patellar Dislocation

BACKGROUND

There is a lack of evidence and continuous debate on whether femoral tunnel displacement substantially influences the clinical efficacy of medial patellofemoral ligament reconstruction (MPFL-R) in addressing recurrent patellar dislocation.

PURPOSE

To investigate possible associations between inaccurate femoral tunnel placement during MPFL-R and clinical outcomes, with a specific focus on proximal tunnel malpositioning.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who were diagnosed with recurrent patellar dislocation and underwent MPFL-R were retrospectively analyzed. A true lateral view on 3-dimensional computed tomography was obtained, and the distance from the center of the femoral tunnel to the Schöttle point (DF-to-S) was measured. Accordingly, femoral tunnels were divided into the suboptimal group (DF-to-S > 10 mm) and the optimal group (DF-to-S≤ 10 mm). Patient data were collected and pathoanatomic risk factors were evaluated. Clinical assessments included patient-reported outcome measures, including the International Knee Documentation Committee (IKDC), Kujala, Lysholm, and Tegner scores; subjective satisfaction; and postoperative complications. A subgroup analysis was performed between proximally malpositioned tunnels and tunnels lying in other directions.

RESULTS

A total of 112 patients (112 knees) were included, with 34 in the suboptimal group and 78 in the optimal group. Patient characteristics and pathoanatomic abnormalities were comparable between the 2 arms, with mean follow-ups of 52.90 ± 23.80 months and 60.14 ± 27.88 months in the suboptimal and optimal groups, respectively (P = .259). At the final follow-up, inferior IKDC (76.3 ± 12.8 vs 85.9 ± 6.3; P < .001), Kujala (87.7 ± 9.3 vs 93.8 ± 4.9; P = .001), and Lysholm (87.0 ± 11.8 vs 94.5 ± 5.3; P = .001) scores and subjective satisfaction (8.2 ± 1.4 vs 9.3 ± 0.9; P < .001) were observed in the suboptimal group compared with the optimal group. Lower proportions of patients met the minimal clinically important difference for the IKDC (82.4% vs 100.0%; P = .001) and Lysholm (79.4% vs 98.7%; P = .001) scores in the suboptimal group compared with the optimal group. Subgroup analysis demonstrated that the final IKDC (P = .002), Kujala (P = .001), and Lysholm (P = .001) scores and subjective satisfaction (P = .031) were statistically worse in the proximally located group, with insignificant improvements compared with preoperative levels. The suboptimal group showed a higher rate of overall complications, and anterior knee pain was more often reported in the proximally located subgroup.

CONCLUSION

Inaccurate femoral tunnel positioning was associated with inferior midterm subjective functional scores and a higher rate of postoperative complications after MPFL-R. Proximal displacement in particular was associated with adverse clinical outcomes.

The Norwegian version of the Norwich Patellar Instability score has good validity and moderate reproducibility

Purpose

To translate and adapt the Norwich Patellar Instability (NPI) score into Norwegian, and second, to examine the psychometric properties of the Norwegian version (NPI-No).

Methods

NPI was translated according to international guidelines. A cohort of 107 patients surgically treated for recurrent patellofemoral instability completed NPI-No, related questionnaires and functional tests prior to and six months post-surgery. Validity (face, content and construct validity), internal consistency (Cronbach's alpha [α]), test-retest reliability (intraclass correlation coefficient [ICC]], measurement error (standard error of measurement [SEM] and smallest detectable change at individual [SDCind] and group level [SDCgroup]) and construct validity (hypotheses testing; independent t tests, Pearson's r) were examined.

Results

NPI-No had good face and content validity. Internal consistency was satisfactory (α = 0.88), test-retest reliability was moderate ICC2.1 0.65 (95% confidence interval = 0.47-0.77) and measurement error low (SEM = 7.8). SDCind was 21.7 points and SDCgroup was 2.8. Seven of the 10 hypotheses about construct validity were confirmed. While there was no ceiling effect pre- or post-operatively, a substantial floor effect (28%) was observed at the 6-month follow-up.

Conclusion

The NPI-No is valid for assessment of self-perceived patellar instability before and after surgery in Norwegian patients. However, reproducibility was found to be only moderate. This study adds further knowledge about the measurement properties of the NPI.

Level of Evidence

Level II.

Predicting two-year return-to-sport failure after medial patellofemoral ligament reconstruction in patellar dislocation patients with bone abnormalities

PURPOSE

To develop a comprehensive and validated personalized scoring system based on anatomical characteristics to predict the probability of failure to return to sport after medial patellofemoral ligament reconstruction in patients with patellar dislocation.

METHODS

312 patients with medial patellofemoral ligament reconstruction in our hospital from 2013 to 2023 were included. Demographic and anatomical characteristics were collected retrospectively. A backward stepwise approach was used to identify independent predictors, and a nomogram was constructed to predict the probability of recurrence. The predictive performance was evaluated by receiver operating characteristic curves, calibration diagram and decision curve analysis.

RESULTS

Multivariate analysis showed that increased tibial tubercle-trochlear groove (TT-TG) distance, trochlear dysplasia, increased femoral anteversion angle, and patellar alta were independent risk factors for failure of return to sport after medial patellofemoral ligament reconstruction. Validation of this column graph in the training cohort and validation cohort showed strong predictive power, with areas under the curve of 0.850 and 0.844, respectively. The nomogram has good calibration and good clinical practicability.

CONCLUSION

The study developed a personalized predictive nomogram with 4 predictors (increased TT-TG distance, trochlear dysplasia, increased femoral anteversion angle, and patellar alta) that allowed surgeons to stratify the risk of failure to return to sport after medial patellofemoral ligament reconstruction and recommend skeletal surgery for patients with these factors.

LEVEL OF EVIDENCE

Level III.

Decreased femoral trochlea axial orientation corrected by derotational distal femur osteotomy in patients with patellar dislocation yields satisfactory outcomes

PURPOSE

The femoral trochlea axial orientation has been shown to be a better predictor of patellar dislocation than the femoral anteversion angle. However, no study has investigated the importance of the femoral trochlea axial orientation in the surgical treatment of patellar dislocation. It is aimed to explore the pathological threshold of the femoral trochlea axial orientation and its guiding implications for surgical interventions in the study.

METHODS

Sixty-four patients with patellar dislocation and 64 controls were included for measurement of the femoral trochlea axial orientation. The ability to predict the patellar dislocation and the pathologic threshold of the femoral trochlea axial orientation were evaluated using the receiver operating characteristic curve. One hundred patients with medial patellofemoral ligament reconstruction and 25 patients with derotational distal femur osteotomy were divided into two groups based on the femoral trochlea axial orientation cut-off value and their postoperative knee functions, and patellar tilt angles were compared.

RESULTS

There were significant differences in the femoral trochlea axial orientation (60.8 ± 7.9 vs. 67.8 ± 4.6, p < 0.05) between patients with patellar dislocation and the normal population. The sensitivity and specificity of the femoral trochlea axial orientation were 0.641 and 0.813, respectively, at the femoral trochlea axial orientation smaller than 63.8°. Amongst patients having had isolated medial patellofemoral ligament reconstruction with decreased femoral trochlea axial orientation, knee function was poorer after surgery. The prognosis of patients with the femoral trochlea axial orientation correction in derotational distal femur osteotomy was better than that for patients without correction.

CONCLUSIONS

The femoral trochlea axial orientation had good predictive efficiency for patellar dislocation. Isolated medial patellofemoral ligament reconstruction is not sufficiently effective for patients with patellar dislocation and decreased femoral trochlea axial orientation. Patients with a decreased femoral trochlea axial orientation can have better surgical outcomes after correction by derotational distal femur osteotomy.

LEVEL OF EVIDENCE

Level III.

Is kinesiophobia associated with functional outcome measures in patients following medial patellofemoral ligament reconstruction?

BACKGROUND

This study aimed to investigate the potential relationship between kinesiophobia and functional outcomes in patients following medial patellofemoral ligament reconstruction (MPFLr).

METHODS

Twenty-one patients (six males, 15 females) who underwent MPFLr between 2016 and 2020, (23.57 ± 9.49 years old) with a mean follow up period of 52.33 ± 24.82 months were included in the study. Following an assessment of patellar stability and alignment, kinesiophobia levels, function and balance were measured. The kinesiophobia was measured using the Tampa Scale of Kinesiophobia, while functional outcomes were assessed with the single-leg hop test, Y-Balance test and single-leg sway index. The self-reported function was measured by Kujala patellofemoral score and Lysholm knee score.

RESULTS

The patients exhibited kinesiophobia scores of 43.10 ± 6.90. A negative correlation existed between kinesiophobia and both the Kujala scores (r = -0.75, P < 0.001) and the Lysholm scores (r = -0.79, P < 0.001). Moderate negative correlations were observed between kinesiophobia and the single-leg hop distance (r = -0.64, P < 0.01), as well as in Y-Balance test anterior reach distance (r = -0.51, P < 0.01) and posterolateral reach distance (r = -0.55, P < 0.01). Additionally, a low negative correlation was noted between kinesiophobia and Y-Balance test posteromedial reach distances (r = -0.43, P = 0.05), as well as the total sway index (r = -0.46, P = 0.04).

CONCLUSIONS

A high level of kinesiophobia was strongly correlated with self-reported functional scores and moderately correlated with measured functional outcomes. The findings underscore a notable prevalence of kinesiophobia following biomechanically successful MPFLr. Investigating the impact of kinesiophobia on outcomes after MPFLr may provide a better understanding of patient recovery.

Impact of sex and age on the lateralisation of the tibial tubercle in normal paediatric and adolescent populations

PURPOSE

Numerous methods have been proposed to characterise tubercle lateralisation. However, their normal values and related changes remain unclear. Accordingly, it was aimed to determine the potential sex and age effects and determined the optimal individualised method of diagnosing lateralisation of the tibial tubercle in patients with recurrent patellar dislocation (RPD).

METHODS

Measurements included the tibial tubercle-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance and tibial tubercle lateralisation (TTL); and the proximal tibial width (PTW), trochlear width (TW) and trochlear dysplasia index (TDI), for adjustment. A two-way analysis of variance was used to determine the effect of age, sex and their interaction within the normal group. When the age effect was statistically significant, a nonlinear regression was created. Areas under the receiver-operating characteristic curve (AUCs) were calculated to assess diagnostic accuracy.

RESULTS

A total of 277 normal participants (mean [SD] age, 13.5 [2.6] years; 125 [45.1%] female) and 227 patients with RPD (mean [SD] age, 13.5 [2.6] years; 161 [58.1%] female) were analysed. It was found that in the normal group, in patients aged 7-10, TT-PCL distance (p = 0.006), TTL (p = 0.007) and TT-PCL/PTW (p < 0.001) were significantly larger in females than in males. A significant sex effect was also detected on TT-TG/TW (p = 0.014). TT-TG distance, TT-PCL distance, TTL and TT-PCL/PTW (in male patients) approached an established normal adult value of 12.3 mm, 20.9 mm, 0.64 and 0.28, respectively, with increasing age (p < 0.001). The AUC was greater for TT-TG/TDI and TT-TG/TW (p ≤ 0.01) and TT-TG/TDI outperformed TT-TG/TW in patients aged 15-18 (p = 0.004).

CONCLUSIONS

Tubercle lateralisation increased with age and was affected by sex, with the exception of TT-TG distance and TT-TG/TDI. TT-TG/TDI is the optimal method of diagnosing a lateralized tibial tubercle in patients with RPD. These findings assist with the evaluation of tubercle lateralisation in that they provide a proper protocol for paediatric and adolescent populations with RPD; and thus, will help determine whether medial tubercle transfer should be included among the tailored surgical procedures considered for the treatment of patients with RPD.

LEVEL OF EVIDENCE

Level III.

Predicting the Probability of Recurrence Based on Individualized Risk Factors After Primary Lateral Patellar Dislocation Treated Nonoperatively

PURPOSE

To develop a comprehensive and effective personalized scoring system on the basis of demographic and clinical characteristics for predicting recurrence probability in patients with primary lateral patellar dislocation (LPD).

METHODS

Participants included 261 primary patients with LPD with 2-year minimum follow-up from our hospital across 2013 to 2020. Demographic and clinical characteristics were collected retrospectively. The backward stepwise method was performed to identify independent predictors and construct a nomogram to predict the probability of recurrence. The predictive performance was assessed by receiver operating characteristic curves, calibration plots, and decision curve analysis.

RESULTS

After variables selection, 6 independent predictors of recurrence (skeletal maturity, trochlear dysplasia, tibial tuberosity-trochlear groove distance, mechanical axis deviation, Insall-Salvati index, and patellar tilt) were enrolled in our model. Validation of this nomogram in both training and validation cohort revealed powerful predictive ability, with an area under the curve of 0.962 and 0.977, respectively. The nomogram also showed great calibration and good clinical practicability.

CONCLUSIONS

Our study presented a nomogram that incorporates 6 independent risk factors (skeletal maturity, trochlear dysplasia, tibial tuberosity-trochlear groove distance, mechanical axis deviation, Insall-Salvati index, and patellar tilt), which can be conveniently used to accurately predicts the risk of recurrence after primary LPD in individual cases.

LEVEL OF EVIDENCE

Level III, retrospective comparative prognostic study.

Medial Patellofemoral Complex Reconstruction (Combined Reconstruction of Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament) With Semitendinosus Autograft Resulted in Similar Clinical and Radiographic Outcomes to Medial Patellofemoral Ligament Reconstruction in Treating Recurrent Patellar Dislocation

PURPOSE

To compare clinical and radiographic outcomes of medial patellofemoral ligament reconstruction (MPFL-R) and medial patellofemoral complex reconstruction (MPFC-R) for recurrent patellar dislocation. Outcome measures were compared based on the Insall-Salvati index.

METHODS

Patients who were diagnosed with recurrent patellar dislocation and underwent either MPFL-R or MPFC-R (combined reconstruction of MPFL and medial quadriceps tendon-femoral ligament) were retrospectively analyzed. Group allocation was based on surgical procedure and patient characteristics were collected. Clinical assessments included patient-reported outcome measures (PROMs) and return-to-sports rates. Minimal clinically important difference analysis was performed. A subgroup analysis of PROMs was carried out between patients with an Insall-Salvati index ≤1.2 versus >1.2. The patellar tilt angle, lateral patellar displacement, and bisect offset ratio were measured pre- and postsurgery. Functional failures and complications were assessed.

RESULTS

Overall, 70 patients (72 knees) in the MPFL-R group and 58 patients (61 knees) in the MPFC-R group were included. Patient characteristics were comparable between the groups. At a minimum follow-up of 24 (mean, 50.6 ± 22.1) months, all PROMs were substantially improved (P < .001), without significant intergroup differences. The percentages of patients reaching the minimal clinically important difference were similar after MPFL-R and MPFC-R: 98.6% versus 93.4% (International Knee Documentation Committee), 97.2% versus 98.4% (Lysholm), 98.6% versus 100% (Kujala), and 77.8% versus 72.1% (Tegner). The subgroup analysis based on patellar height and the return-to-sport rates also suggested comparable results. Radiographic evaluation demonstrated significantly smaller lateral patellar displacements (P = .004) and bisect offset ratios (P < .001) but similar patellar tilt angles after MPFC-R. Four (5.6%) patients receiving MPFL-R and 2 (3.3%) patients receiving MPFC-R reported recurrence of functional instability, without statistically significant difference.

CONCLUSIONS

MPFC-R resulted in similar overall clinical and radiographic outcomes to MPFL-R in treating recurrent patellar dislocation. MPFC-R might not provide additional benefits for patients with an Insall-Salvati index >1.2.

LEVEL OF EVIDENCE

Level IV, therapeutic, retrospective cohort study.

Clinical and Radiological Outcomes After Combined ACL and MPFL Reconstruction Versus Isolated ACL Reconstruction for ACL Injury With Patellar Instability

BACKGROUND

An anterior cruciate ligament (ACL) injury accompanied by patellar instability (PI) is a topic that has gained orthopaedic surgeons' attention recently. Untreated PI is reportedly associated with worse clinical outcomes after isolated ACL reconstruction (ACLR) in patients after an ACL injury with PI. Nevertheless, the appropriate surgical approach and its long-term therapeutic effects in these patients remain unclear.

PURPOSE

(1) To compare the clinical and radiological outcomes between isolated ACLR (iACLR) and combined ACLR and medial patellofemoral ligament reconstruction (cAMR) in patients after an ACL injury with PI and (2) to explore the correlations between these 2 procedures and clinical and radiological outcomes.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 106 patients diagnosed with an ACL injury accompanied by PI between January 2016 and April 2021 were analyzed in this study. There were 34 patients excluded because of missing postoperative radiological data. Among the remaining 72 patients, 34 patients underwent iACLR, while 38 patients underwent cAMR. Demographic characteristics, intraoperative findings, and patient-reported outcomes (Lysholm score, subjective International Knee Documentation Committee score, and Tegner activity score) were prospectively collected. Patellar alignment parameters and worsening patellofemoral osteoarthritis (PFOA) features (evaluated with the modified Whole-Organ Magnetic Resonance Imaging Score) were analyzed longitudinally on magnetic resonance imaging. The Kujala score was used to evaluate the functional recovery of the patellofemoral joint, and redislocations of the patella were prospectively recorded. Finally, multivariate logistic regression analysis was used to explore the correlations between these 2 procedures and clinical (not achieving the minimal detectable change [MDC] for the Lysholm score) and radiological (worsening PFOA features) outcomes.

RESULTS

The mean follow-up duration was 28.9 ± 6.2 and 27.1 ± 6.8 months for the iACLR and cAMR groups, respectively (P = .231). Significantly higher Lysholm scores (88.3 ± 9.9 vs 82.1 ± 11.1, respectively; P = .016) and subjective International Knee Documentation Committee scores (83.6 ± 11.9 vs 78.3 ± 10.2, respectively; P = .046) were detected in the cAMR group compared with the iACLR group postoperatively. The rates of return to preinjury sports were 20.6% and 44.7% in the iACLR and cAMR groups, respectively (difference, 24.1% [95% CI, 3.3%-45.0%]; P = .030). Moreover, the rates of worsening PFOA features were 44.1% and 18.4% in the iACLR and cAMR groups, respectively (difference, 25.7% [95% CI, 4.9%-46.4%]; P = .018). In addition, significantly higher Kujala scores (87.9 ± 11.3 vs 80.1 ± 12.0, respectively; P = .006), lower redislocation rates (0.0% vs 11.8%, respectively; difference, 11.8% [95% CI, 0.9%-22.6%]; P = .045), and significantly better patellar alignment were detected in the cAMR group compared with the iACLR group postoperatively. Furthermore, multivariate logistic regression analysis determined that iACLR and partial lateral meniscectomy were significantly correlated with not achieving the MDC for the Lysholm score and worsening PFOA features in our study population.

CONCLUSION

In patients after an ACL injury with PI, cAMR yielded better clinical and radiological outcomes compared with iACLR, with better patellar stability and a lower proportion of worsening PFOA features. Furthermore, not achieving the MDC for the Lysholm score and worsening PFOA features were significantly correlated with iACLR and partial lateral meniscectomy. Our study suggests that cAMR may be a more appropriate procedure for patients after an ACL injury with PI, which warrants further high-level clinical evidence.

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 malalignment: A common disorder associated with knee pain

Pain-associated knee joint disorders are common in daily life. Practically, knee pain should be divided into the origin from the isolated tibiofemoral (TF), isolated patellofemoral (PF) joint, or a combination thereof. The TF joint controls the actions of level walking, while the PF joint controls knee flexion-extension. Owing to its sufficient inherent stability, non-traumatic disorders of the isolated TF joint in young individuals are uncommon. In contrast, because of its insufficient inherent stability, non-traumatic disorders of the isolated PF joint are common in young individuals. Patellar malalignment (PM) associated with knee pain is common in all age groups, and the most common predisposing factor is imbalanced peripatellar soft-tissue tension. The outward forces acting on the patella are caused by pulling from the quadriceps femoris during knee flexion to extension (manifested by the quadriceps angle [Q-angle]), and sliding backward of the iliotibial band (ITB) during knee extension to flexion. Once the muscle power of the vastus medialis (especially the vastus medialis obliquus [VMO]) decreases, which lowers the counteracting effect against outward forces, the patella displaces or rotates laterally. The reduced contact surface between the patella and the femoral condyle significantly increases the compressive pressure and injures the articular cartilage. Subsequently, progressive PF degeneration occurs. Although other factors may also cause PM, they are relatively uncommon. In principle, nonsurgical treatment of PM should be considered first, while surgical treatment should follow established indications. Some nonsurgical techniques are currently widely used that feature high satisfaction rates. Surgical techniques are continuously being developed, and their success rates have gradually improved. This study aimed to review the current literature for relevant studies and report related publications of the author's institution to emphasize the universality and importance of PM management. Conceptually, simply focusing on problems of the TF joint cannot treat all knee disorders.

Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia

PURPOSE

The purpose of this study was to evaluate the clinical outcomes of medial patellofemoral ligament (MPFL) reconstruction combined with derotational distal femur osteotomy in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia.

METHODS

Between 2015 and 2020, 64 patients (64 knees) with recurrent patellar dislocation, who had excessive femoral anteversion angle (≥ 25°) and trochlear dysplasia and were surgically treated using derotational distal femur osteotomy and MPFL reconstruction, were eligible for this retrospective study. These patients were assigned to two groups according to the grade of trochlear dysplasia. Group A (type A trochlear dysplasia, n = 33) and Group B (type B, C, D trochlear dysplasia, n = 31). Preoperative and postoperative patellar tilt angle (PTA), Caton-Deschamps index (CD-I), tibial tubercle-trochlear groove (TT-TG) distance and femoral anteversion angle were evaluated. Patient outcomes were assessed using the preoperative and postoperative International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, Tegner score, and visual analog scale (VAS) score.

RESULTS

A total of 64 patients (64 knees) were evaluated in this study, with a mean follow-up period of 28.4 ± 3.6 months. There were no cases of wound infection, osteotomy site fractures, deep venous thrombosis of the lower extremities, or re-dislocation in the two groups during the postoperative follow-up period. All patients returned to full extension and flexion. The postoperative Tegner score, Lysholm score, Kujala score, IKDC score, VAS score, PTA, CD-I, TT-TG distance, and femoral anteversion angle were significantly improved compared with the preoperative status (P < 0.05). There was no significant difference between the two groups (n.s.).

CONCLUSION

MPFL reconstruction combined with derotational distal femur osteotomy showed satisfactory clinical outcomes during follow-up in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. Even patients with high-grade trochlear dysplasia showed satisfactory results. For those patients, additional surgery is not necessary.

LEVEL OF EVIDENCE

Level III.

Correlation between flat foot and patellar instability in adolescents and analysis of related risk factors

INTRODUCTION

Flatfoot and patellar instability are both developmental limb deformities that occur frequently in adolescents. A high number of patients with both diseases can be seen in clinic, and there are no studies showing a correlation between the two. The goal of this study is to investigate the association between developmental patellar instability and flat feet in adolescents and its associated risk factors.

METHODS

This experiment uses a cross-sectional study to select 74 adolescent patients with flat foot from a randomly selected middle school in this city since December 2021 and obtain relevant data. SPSS26.0 statistical software was used for data analysis. Quantitative data were expressed as mean ± standard deviation, and Pearson correlation coefficient was used for analysis. p < 0.05 indicates a statistically significant difference.

RESULTS

A total of 74 people (40 men and 34 women) were included in this study. The correlation coefficients between Meary angle, Pitch angle, calcaneal valgus angle, CSI, BMI, and Beighton scores and knee joint Q angle are 0.358 (p < 0.01), -0.312 (p < 0.01), 0.403 (p < 0.01), 0.596 (p < 0.01), 0.427 (p < 0.01), and 0.293 (p < 0.05), respectively, indicating that flat foot, overweight, and Beighton scores are all correlated with Q angle. The correlation coefficients between Meary angle, Pitch angle, calcaneal valgus angle, CSI, and BMI were 0.431 (p < 0.01), -0.399 (p < 0.01), 0.319 (p < 0.01), and 0.563 (p < 0.01), respectively, indicating a correlation between flat foot and BMI. The correlation coefficients between Meary's angle, Pitch's angle, calcaneal valgus angle, CSI, and Beighton's score were 0.207 (p > 0.05), -0.240 (p < 0.05), 0.204 (p > 0.05), and 0.413 (p < 0.01), respectively, indicating a correlation between flat foot and Beighton's score.

CONCLUSION

We believe that there is a significant correlation between adolescent flatfoot and patellar instability. Excessive weight and ligamental laxity during adolescent development are among the risk factors for flatfoot and patellar instability.