An evaluation of the effectiveness of medial patellofemoral ligament reconstruction using an anatomical tunnel site

PROMIS physical function and pain perform poorly psychometrically in patients undergoing medial patellofemoral ligament reconstruction

PURPOSE

The purpose of this study was to assess the validity, floor and ceiling effects, and dimensionality of PROMIS Physical Function (PF) and Pain compared to legacy patient reported outcome (PRO) measures in patients undergoing medial patellofemoral ligament (MPFL) reconstruction.

METHODS

Patients who underwent MPFL reconstruction between 2018 to 2020 were retrospectively reviewed. Preoperatively, patients completed the IKDC, VR-12, Kujala, SF-12, KOOS JR, PROMIS PF and Pain surveys. Inter-survey convergence was assessed with Spearman correlations. Psychometric analysis included investigations of inter-survey convergent validity, intra-survey floor and ceiling effects, and Rasch analyses with person-item fit and iterative question elimination model fit testing.

RESULTS

A total of 76 patients (mean age: 22.6 ± 8.4 years) who completed preoperative surveys were included (compliance: 91.7-96.2%). Preoperatively, age was significantly associated with both PROMIS PF (coefficient:  - 0.291, P = 0.005) and Pain scores (coefficient: 0.294, P = 0.002). PROMIS PF had a Very Good correlation with IKDC and PROMIS Pain had a Very Good correlation with KOOS JR. Other correlations ranged from Poor to Good. No significant floor or ceiling effects were observed for any PRO. On iterative question elimination Rasch modelling, only two questions from PROMIS PF remained after 6 rounds of elimination while PROMIS Pain had no questions remaining after 3 rounds of elimination.

CONCLUSION

Preoperative PROMIS PF and Pain provided only Fair to Good correlations with most legacy PROs. Although no significant floor and ceiling effects were observed, PROMIS PF and Pain did not perform well psychometrically in this population of patients undergoing MPFL reconstruction. These results suggest PROMIS questionnaires should be used with caution in this population, especially if used in isolation, when discussing clinical expectations with patients. The authors recommend continued use of legacy PROs specific to assessment of patellar instability and function that have established validity in patellar instability populations.

LEVEL OF EVIDENCE

Level IV.

Isolated medial patellofemoral reconstruction outcomes: A systematic review and meta-analysis

BACKGROUND

Treatment of patellar instability remains up for debate, and a combination of tibial tubercle osteotomy and medial patellofemoral ligament reconstruction (MPFLr) of the medial patellofemoral ligament (MPFL) has become the mainstay treatment for recurrent lateral patellar dislocation. Due to limited small studies, there remains a variety of surgical techniques still being practiced. The use of MPFL reconstruction, in isolation, has demonstrated promise.

PURPOSE

The purpose of this systematic review and meta-analysis is to investigate if isolated medial patellofemoral ligament reconstruction (iMPFLr) can safely and efficaciously restore knee stability and to present the patient demographics, surgical techniques, graft choices, clinical outcomes, and complications after iMPFLr for recurrent patellar dislocation (RPD).

METHODS

A review of the current literature according to Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, yielded 299 abstracts. Twenty-seven articles met the inclusion/exclusion criteria accounting for 1200 patients. Data was pooled and analyzed focusing on patient demographics, graft type used, Kujala, International Knee Documentation Committee (IKDC), Lysholm, Tegner, and complications.

RESULTS

Across all studies the weighted mean age was found to be an average of 24.5 years, BMI was 24.9 kg/m2, follow-up was 47.3 months, as 67% were female, TT-TG distance was 15.3 mm, and Caton Deschamps index 1.11. The pooled effect size difference of pre versus post assessment of Kujala was -2.8, IKDC was -4.5, Lysholm was -6.4, and Tegner was -0.74. The pooled complication rate was found to be 8% across all included studies. A subgroup analysis was also performed, specifically looking at how single bundle, double bundle, gracilis, semitendinosus and knee angle during fixation effect outcome data.

CONCLUSION

This systematic review and meta-analysis demonstrates that isolated MPFL reconstruction is a safe and effective treatment for recurrent patellar dislocations. Given the efficacy of isolated MPFL reconstruction, future investigations should aim to uncover the exact TT-TG distance, trochlear dysplasia, and patella alta grade for selecting patients to undergo this procedure. Furthermore, more primary research needs to be conducted on this topic due to the overall lack of published data from randomized controlled studies and no broad standardization of outcome measurements.

LEVEL OF EVIDENCE

(4) Systematic Review and Meta-Analysis.

Patella alta and increased TT-TG distance do not adversely affect patient-reported outcomes following isolated MPFL reconstruction: A systematic review

OBJECTIVES

To analyze the effect of patellofemoral anatomical variations (patella alta, increased tibial tubercle-trochlear groove [TT-TG] distance, and trochlear dysplasia) on clinical outcomes after isolated medial patellofemoral ligament (MPFL) reconstruction.

METHODS

A comprehensive search from PubMed, Embase, and the Cochrane Library databases was conducted to identify studies that compared outcomes based on the presence or absence of patella alta, elevated tibial tubercle-trochlear groove (TT-TG) distance, and/or trochlear dysplasia. Exclusion criteria included reviews and meta-analyses, studies that included patients who underwent associated bony procedures, and those reporting outcomes after isolated MPFL reconstruction with no comparison between varying anatomical groups.

RESULTS

After application of selection criteria, 19 studies were included. Patella alta was not predictive of failure or poorer outcomes among 13 studies; however, 2 studies demonstrated poorer patient-reported outcome scores and/or higher failure rates with increasing patellar height. Increasing TT-TG distance demonstrated a statistically significant correlation with poorer outcomes in only one study, whereas 12 other studies showed no association. Trochlear dysplasia resulted in worse outcomes and greater failure rates in 6 studies, while 10 studies showed no statistically significant correlation between trochlear dysplasia and postoperative outcomes.

CONCLUSION

Patella alta and increased TT-TG distance did not adversely affect outcomes following isolated MPFL reconstruction in the preponderance of reviewed studies. Data are mixed regarding the impact of trochlear dysplasia on the outcomes of isolated MPFL reconstruction.

LEVEL OF EVIDENCE

IV.

Adding Tibial Tuberosity Medialization to Medial Patellofemoral Ligament Reconstruction Reduces Lateral Patellar Maltracking During Multidirectional Motion in a Computational Simulation Model

Purpose

To determine whether adding tibial tuberosity medialization to medial patellofemoral ligament (MPFL) reconstruction reduces lateral patellar maltracking during a dynamic multidirectional activity and to investigate when medial patellofemoral contact pressures are elevated during daily activities, such as squatting.

Methods

Seven computational models representing knees with patellar instability, including lateral patellar maltracking, were evaluated following simulated MPFL reconstruction (bisect offset index > .75). Tibial tuberosity medialization was added to MPFL reconstruction for each model. Patellar tracking during multidirectional motion was evaluated by simulating pivot landing. Analysis of pivoting focused on early flexion (5° to 40°). Patellofemoral contact pressures during daily function were evaluated by simulating knee squatting. Data were analyzed with paired comparisons between MPFL reconstruction with and without tuberosity medialization.

Results

The patella dislocated during pivoting for 2 models with an isolated MPFL reconstruction and for 1 model including tibial tuberosity medialization. Adding tibial tuberosity medialization to MPFL reconstruction significantly decreased bisect offset index by ∼0.1 from 5° to 40° (P < .03). For knee squatting, medializing the tibial tuberosity significantly increased maximum medial contract pressure by ∼0.5 MPa from 30° to 85° (P < .05) but did not significantly influence maximum lateral pressure.

Conclusions

In this study of simulated multidirectional motion, MPFL reconstruction did not sufficiently constrain the patella for some knees. Adding tibial tuberosity medialization to MPFL reconstruction in these models reduced lateral patellar maltracking during multidirectional motion but increased pressure applied to medial cartilage during squatting.

Clinical Relevance

After establishing the influence of tibial tuberosity medialization on patellar maltracking for an idealized population, as was done in the current study, future simulation studies can be performed to better determine the anatomical characteristics of patients for whom tibial tuberosity medialization is needed to reduce the risk of postoperative patellar maltracking.

Accuracy of femoral tunnel positioning in medial patellofemoral ligament reconstruction: anatomic insertion leads to better clinical outcome

PURPOSE

The medial patello-femoral ligament (MPFL) is considered the primary restraint against patellar dislocation and its reconstruction is indicated in recurrent patellar instability. An anatomical positioning of MPFL femoral insertion is recommended to achieve satisfactory clinical outcomes and prevent osteoarthritis (OA) due to an altered kinematics. The purpose of the study was first to assess the relationship between correct femoral tunnel position and better clinical outcomes and lower patellofemoral osteoarthritis rate. Second, correlation of outcomes with factors potentially affecting the results, such as the type of graft, patellar height and trochlear dysplasia.

METHODS

Fifty-three patients (58 knees) who underwent MPFL reconstruction between 2009 and 2018 by a senior knee surgeon were retrospectively evaluated. Knee radiographs were performed before surgery, 12 months later and at last follow-up to assess trochlear dysplasia, patellar height and patellofemoral OA. The tibial tuberosity-trochlear groove (TT-TG) value was measured on a CT scan. The accuracy of graft positioning was evaluated on sagittal radiographs according to Schöttle et al. Subjective outcomes were collected before surgery, at 12 months and at last follow-up using several validated scores.

RESULTS

Forty-six patients (51 knees) with a mean age of 24.1 ± 7.4 years were included in the study. Mean follow-up was 8.9 ± 2.1 years. A significant improvement in all clinical scores was observed at 12 months and final follow-up. Anatomic Insertion (AI) of reconstructed MPFL was considered optimal in 33 (64.7%) and sub-optimal in 18 (35.3%) patients. Sub-optimal AI resulted in lower Kujala, IKCD and higher VAS score (p < 0.01); moreover, for every 1 mm distance in any direction from the ideal insertion, a decrease of 0.8 [95% CI (-1.4; -0.2)] in Kujala score and 0.8 [95% CI (-1.3; -0.3)] in IKDC was observed. At final follow-up, 8 patients presented patellofemoral OA Iwano grade 3 (15.7%): although that incidence did not correlate to graft positioning, the use the artificial ligament in all these cases appeared to be significant.

CONCLUSION

The present study confirms the importance of an optimal anatomic femoral insertion in MPFL reconstruction, reporting a significant positive correlation between graft positioning and clinical outcome. No significant correlations were found between anatomic insertion and patello-femoral OA development.

LEVEL OF EVIDENCE

IV.

Isolated medial patellofemoral ligament reconstruction results in similar postoperative outcomes as medial patellofemoral ligament reconstruction and tibial-tubercle osteotomy: a systematic review and meta-analysis

PURPOSE

To determine the effect of isolated medial patellofemoral ligament reconstruction (MPFLR) versus concomitant MPFLR and tibial-tubercle osteotomy (TTO) on patient-reported functional outcomes, rate of patellar redislocation, and rate of return to sport in skeletally mature patients with recurrent patellar instability and lateralization as defined by elevated tibial-tubercle trochlear groove (TT-TG) distance.

METHODS

Three databases MEDLINE, PubMed and EMBASE were searched from inception to July 10th, 2022 for literature outlining the management of patients with TT-TG indices greater than 15 mm with either isolated MPFLR or concomitant MPFLR and TTO procedures. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on functional outcomes via the Kujala anterior knee pain score, redislocation rates, return to sport rates, and complications were recorded. The MINORS score was used for all studies to perform a quality assessment of included studies.

RESULTS

A total of 31 studies comprising 1405 patients (1452 knees) were included in this review. The mean Kujala score in 13 studies comprising 848 total patients in the isolated MPFLR group was 85.0 (range 80.9-97.5) compared to a score of 83.7 (range 77.2-94.0) in 14 studies comprising 459 patients in the concomitant group. The mean pooled redislocation rate in 19 studies examining isolated MPFLR procedures comprising 948 patients was 3.1% (95% CI 2.1-4.4%, I² = 7%) as opposed to 3.2% (95% CI 1.9-5.0%, I² = 0%) in 15 studies comprising 486 patients in the concomitant group. The mean pooled return to sport rate in seven studies with 472 total patients in the isolated MPFLR group was 82% (95% CI 78-86%, I² = 16%) compared to a score of 92% (95% CI 78-99%, I² = 58%) in four studies comprising 54 patients in the concomitant group. There were similar complication rates between both treatment groups, including range of motion deficits, fractures, infections, and graft failures.

CONCLUSION

Isolated MPFLR leads to similar anterior knee pain, similar redislocation rates and lower return to sport rates than concomitant MPFLR and TTO procedures in patients with TT-TG distances greater than 15 mm. Information from this review can aid surgeons in their decision to choose MPFLR versus concomitant procedures for this patient population, and can also guide future studies on this topic.

LEVEL OF EVIDENCE

Level IV.

Protocols of rehabilitation and return to sport, and clinical outcomes after medial patellofemoral ligament reconstruction with and without tibial tuberosity osteotomy: a systematic review

PURPOSE

No consensus exists on rehabilitation programmes after medial patellofemoral ligament reconstruction (MPFLR) with or without tibial tuberosity osteotomy (TTO). This systematic review examined the content and timeline of rehabilitation (weightbearing, range of motion [ROM] and exercise therapy) and return to sport (RTS), as well as patient-reported outcomes after MPFLR with or without TTO.

METHODS

The PubMed, Cochrane Library, Web of Sciences, CINAHL and SPORTDiscus databases were searched from inception to December 2021. Studies that reported postoperative rehabilitation programmes and patient-reported outcomes for patients aged ≥ 18 years who underwent MPFLR with or without concomitant TTO were included.

RESULTS

Eighty-five studies were included, 57 of which were case series and only one randomised controlled trial on rehabilitation programmes. Non-weightbearing was set within one week post-operatively in approximately 80% of weightbearing programmes for MPFLR without and with TTO. Joint immobilisation was set within one week post-operatively in 65.3% and 93.8% of programmes for MPFLR without and with TTO, respectively. Weightbearing and ROM (≤ 90°) restriction were within three weeks post-operatively for > 50% of the programmes. Quadriceps strengthening was the most cited exercise therapy (33 programmes), most often initiated within two weeks post-operatively. However, few other exercise programmes were cited (only nine programmes). RTS was mostly noted at six months post-operatively (35 programmes). The weighted mean Kujala score was 87.4 points.

CONCLUSION

Regardless of TTO addition to MPFLR, most studies restricted weightbearing and ROM only in the early post-operative period, with seemingly favourable clinical results. Limited information was available on post-operative exercise therapy.

Inconsistencies in Reporting Risk Factors for Medial Patellofemoral Ligament Reconstruction Failure: A Systematic Review

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is a common surgical treatment for patients with recurrent patellar instability. A variety of risk factors, such as age, trochlear dysplasia, patella alta, and increased tibial tubercle-trochlear groove (TT-TG) distance, have been identified and may lead to postoperative failure or poor outcomes.

PURPOSE

While a large number of risk factors have been identified, significant heterogeneity exists in evaluating and reporting these risk factors in the literature. The goal of this study was to perform a systematic review to determine risk factors associated with worse outcomes after MPFL reconstruction and their consistency of being controlled for or analyzed among studies.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review of the literature was performed using the MEDLINE database to identify relevant clinical outcome studies after MPFL reconstruction for recurrent patellar instability. Eligible studies were evaluated for risk factors that were associated with MPFL failure, defined as recurrent instability or lack of improvement on patient-reported outcome (PRO) scores. Each study was then evaluated for inclusion of these risk factors.

RESULTS

Ten studies were included in the final analysis, comprising 1287 knees from 1275 patients who underwent isolated MPFL reconstruction. Of these 10 studies, 8 defined outcomes based on PROs and 3 defined outcomes based on postoperative recurrent instability (1 study included both outcomes). In the PRO failure group, 12 risk factors were found across all studies: trochlear dysplasia, trochlear bump height, elevated TT-TG, patellar tilt, hyperlaxity, age at first dislocation, age at surgery, body mass index, bilateral symptoms, WARPS/STAID score (weak atraumatic, risky anatomy, pain, and subluxation/strong, traumatic, anatomy normal, instability, and dislocation), femoral tunnel malposition, and femoral tunnel widening. In the recurrent instability failure group, 7 risk factors were found across all studies: trochlear dysplasia, bump height, patella alta, higher sulcus angle, higher congruence angle, preoperative J sign, and femoral tunnel malposition. Trochlear dysplasia and femoral tunnel malposition were consistently cited in several studies as risk factors for worse PROs and higher rates of recurrent instability. Patella alta was indicated as a significant risk factor for recurrent instability in 1 of 2 studies analyzing postoperative instability failures and was not associated with worse PROs in any of the studies analyzed. Similarly, elevated TT-TG distance was not a significant risk factor in any of the studies that analyzed recurrent instability as the failure endpoint.

CONCLUSION

While various risk factors are postulated to affect outcomes after MPFL reconstruction, there remains inconsistency within the literature regarding the inclusion of all risk factors in a given analysis. Furthermore, the significance of these risk factors varies among studies in terms of whether they affect postoperative outcomes. We found that more severe trochlear dysplasia (types C and D) and femoral tunnel malposition (>10 mm from Schöttle's point) appear to have the most consistent effect on producing higher rates of recurrent dislocation as well as worse PROs. Despite this, the role of concomitant bony procedures to adjust certain pathoanatomic risk factors in addition to MPFL reconstruction remains unknown. Future high-level studies must be conducted that respect the multifactorial nature of patellar instability and should analyze all risk factors (demographic, anatomic, and radiographic) reported to affect outcomes.

Allograft Medial Patellofemoral Ligament Reconstruction in Adolescent Patients Results in a Low Recurrence Rate of Patellar Dislocation or Subluxation at Midterm Follow-Up

PURPOSE

To evaluate rates of recurrent instability in adolescent patients with medial patellofemoral ligament (MPFL) reconstruction with allograft and associations of anatomic risk factors with complications.

METHODS

A retrospective review identified patients of a single surgeon who underwent MPFL reconstruction with allograft for recurrent patellar instability with minimum 2-year follow-up. Surgical management was recommended after a minimum 6 weeks of nonoperative management and included MPFL reconstruction with gracilis allograft using a double-bundle technique. Preoperative radiographs were evaluated to assess physeal closure, lower-extremity alignment, trochlear morphology, and Insall-Salvati and Caton-Deschamps ratios. Magnetic resonance images were reviewed to evaluate the MPFL, trochlear morphology, and tibial tubercle trochlear groove distance (TT-TG). Descriptive statistics were used to characterize data. The primary outcome was recurrent instability.

RESULTS

20 patients (24 knees; 18 knees in 14 females and 6 knees in 6 males; average age 15.7 years; range 11.5 to 19.6) underwent MPFL reconstruction with allograft (mean ± standard deviation follow-up 5.2 ± 1.7 years; range 2.2 to 8.1). Physes were open in 9 knees. The Insall-Salvati ratio was 1.09 ± 0.16, and the Caton-Deschamps index was 1.17 ± 0.15. Preoperatively, 19 patients were noted to have trochlear dysplasia, and TT-TG was 15.3 ± 3.9 mm. Three of 4 knees (16.7%) with non-hardware-related complications had open physes: 3 (12.5%) had recurrent instability, 2 of which underwent subsequent operation, and 1 sustained a patella fracture after a fall, requiring open reduction and internal fixation. The average Insall-Salvati ratio of these 4 patients was 1.21 ± 0.20, Caton-Deschamps index was 1.18 ± 0.17, and TT-TG was 17.5 ± 3.3 mm, none of which were statistically different from the group without complications. There were no clinically noted growth disturbances postoperatively.

CONCLUSIONS

MPFL reconstruction using allograft tissue may be performed safely in the pediatric and adolescent population with good outcomes at midterm follow-up, few complications, and a low rate of recurrent instability.

LEVEL OF EVIDENCE

IV, case series.

Biomechanical Comparison of 2 Patellar Fixation Techniques in Medial Patellofemoral Ligament Reconstruction: Transosseous Sutures vs Suture Anchors

Background

Multiple techniques for fixing a graft to the patella in medial patellofemoral ligament (MPFL) reconstruction have been described; however, no single technique has been shown to be superior to another.

Purpose/Hypothesis

The purpose of this study was to compare the biomechanical performance of 2 different patellar fixation techniques: suture anchor (SA) and transosseous suture (TS) fixation. The hypothesis was that there would be no significant differences between the groups in ultimate failure load, stiffness, or elongation.

Study Design

Controlled laboratory study.

Methods

In this study, a new TS technique was biomechanically compared with the SA technique for MPFL reconstruction using 24 fresh-frozen mature porcine patellae and porcine flexor profundus tendons. The specimens were randomized into 2 groups undergoing MPFL reconstruction using either the SA technique or the TS technique (n = 12 per group). Fixation with TS was completed using 3 No. 2 UltraBraid sutures and three 2-mm transosseous tunnels. SA reconstruction was completed using 2 parallel 3.5-mm titanium SAs with 2 No. 2 UltraBraid sutures. We preconditioned each graft using a force between 5 and 20 N before cyclic loading. Then, the specimens were biomechanically tested (1000 cycles; 5-100 N; 1 Hz) and loaded under tension at 200 mm/min until failure. The ultimate failure load, stiffness, elongation, and failure mode were recorded for each specimen. The Shapiro-Wilk test and independent t tests were used to assess the data.

Results

The TS technique resulted in a significantly higher mean failure load than did the SA technique (496.18 ± 93.15 vs 399.43 ± 105.35 N; P = .03). The TS technique resulted in less stiffness than did the SA technique (55.42 ± 7.92 vs 72.11 ± 10.64 N/mm; P < .01). There was no significant difference between the groups in elongation. None of the graft fixation/patellar complexes failed during cyclic testing in either group. During the load-to-failure test, the most common mode of failure in the SA group was an anchor being pulled out of the bone, whereas that in the TS group was rupture of the suture material.

Conclusion

MPFL reconstruction with 3 TSs provided a higher load to failure than did the commonly used fixation method involving SAs.

Factors Influencing Graft Function following MPFL Reconstruction: A Dynamic Simulation Study

Medial patellofemoral ligament (MPFL) reconstruction is currently the primary surgical procedure for treating recurrent lateral patellar instability. The understanding of graft function has largely been based on studies performed with normal knees. The current study was performed to characterize graft function following MPFL reconstruction, focusing on the influence of pathologic anatomy on graft tension, variations with knee flexion, and the influence on patellar tracking. Knee squatting was simulated with 15 multibody dynamic simulation models representing knees being treated for recurrent lateral patellar instability. Squatting was simulated in a preoperative condition and following MPFL reconstruction with a hamstrings tendon graft set to allow 0.5 quadrants of lateral patellar translation with the knee at 30 degrees of flexion. Linear regressions were performed to relate maximum tension in the graft to parameters of knee anatomy. Repeated measures comparisons evaluated variations in patellar tracking at 5-degree increments of knee flexion. Maximum graft tension was significantly correlated with a parameter characterizing lateral position of the tibial tuberosity (maximum lateral tibial tuberosity to posterior cruciate ligament attachment distance, r ² = 0.73, p < 0.001). No significant correlations were identified for parameters related to trochlear dysplasia (lateral trochlear inclination) or patella alta (Caton-Deschamps index and patellotrochlear index). Graft tension peaked at low flexion angles and was minimal by 30 degrees of flexion. MPFL reconstruction decreased lateral patellar shift (bisect offset index) compared with preoperative tracking at all flexion angles from 0 to 50 degrees of flexion, except 45 degrees. At 0 degrees, the average bisect offset index decreased from 0.81 for the preoperative condition to 0.71. The results indicate that tension within an MPFL graft increases with the lateral position of the tibial tuberosity. The graft tension peaks at low flexion angles and decreases lateral patellar maltracking. The factors that influence graft function following MPFL reconstruction need to be understood to limit patellar maltracking without overloading the graft or over constraining the patella.

Patellar Tendon Shortening for Treatment of Patella Alta in Skeletally Immature Patients With Patellar Instability

Aberrant anatomy, such as patella alta, can be a risk factor for recurrent patellar instability or inferior clinical outcomes after medial patellofemoral ligament reconstruction. In patients with significant patella alta (Caton Deschamps Index >1.2), tibial tubercle distalization may be considered to improve outcomes. However, despite patellar instability commonly affecting pediatric patients, a distalization osteotomy is not feasible in this patient population due to the presence of open physes. Our article presents a technique describing an alternative soft-tissue distalization approach whereby patellar height is decreased by shortening the patellar tendon.

Tibial Tubercle-Midepicondyle Distance Can Be a Better Index to Predict the Outcome of Medial Patellofemoral Ligament Reconstruction Than Tibial Tubercle-Trochlear Groove Distance

Purpose

To compare the clinical utility of tibial tubercle-midepicondyle (TT-ME) and tibial tubercle-trochlear groove (TT-TG) distances in predicting the risk for recurrent instability after isolated MPFL reconstruction.

Methods

A consecutive series of patients with recurrent patellar dislocation who underwent isolated MPFL reconstruction made up the study population. The patients were followed for a minimum of 2 years. In assessment of surgical outcome, the patient was deemed to exhibit “postoperative recurrent patellar instability” when ≥1 of the following 3 conditions was identified: redislocation, positive apprehension sign, and positive J-sign (manifestation of abnormal patellar tracking). As for radiological parameters for position of the tibial tubercle, TT-ME distance (transverse distance between the tibial tubercle and midpoint of the transepicondylar line) and TT-TG distance were measured on axial computed tomography images. The clinical utility as a factor to predict the outcome of MPFL reconstruction was compared between the 2 distances using receiver operating characteristic (ROC) analysis. In addition, various radiological indices potentially influencing the surgical outcome were subjected to multivariable logistic regression analysis.

Results

We examined 38 knees in 38 patients with a mean age at surgery of 17.6 years. Postoperative recurrent patellar instability was encountered in 8 of the 38 knees. The ROC curve analysis showed the TT-ME distance to be a significantly better indicator in predicting surgical outcome than the TT-TG distance (P = .001). The univariate analysis for radiological factors demonstrated that the TT-ME distance was significantly associated with postoperative recurrent patellar instability (odds ratio 1.42, P = .012) whereas all other factors including the TT-TG distance did not correlate with recurrent instability. The multivariable logistic regression analysis revealed that only the TT-ME distance was significantly associated with recurrent instability (P = .035).

Conclusions

Analysis of our patient population undergoing isolated MPFL reconstruction showed that the TT-ME distance was a significantly better indicator than the TT-TG distance to predict the risk for recurrent instability after isolated MPFL reconstruction performed for patellar instability.

Level of Evidence

Level IV, therapeutic case series.

Psychometric properties of the Norwich Patellar Instability Score in people with recurrent patellar dislocation

BACKGROUND

Patellar dislocations account for two percent of all knee injuries with a 17% chance of re-dislocation. There are few validated scores specific to instability. One of these is the Norwich Patellar Instability Score. There has been limited assessment of the validity, floor-ceiling effect and responsiveness of the Norwich Patellar Instability (NPI) Score from an independent centre. The purpose of this paper is to address this limitation.

METHODS

Data from 90 patients referred to a tertiary referral patellofemoral clinic were analysed. All routinely completed data including NPI Score, Kujala Patellofemoral Disorder Score, and demographic outcomes during appointments, up to 36 months following initial clinical assessment was analysed. Convergent validity was assessed by correlating outcomes of the Kujala Patellofemoral Disorder Score to the NPI Score. Effect size (ES) was determined between baseline to 12-month and 12 to 36-month assessments to determine responsiveness. Floor-ceiling effect was evaluated at baseline, 12-month and 12 to 36-month follow-up.

RESULTS

NPI Score demonstrated good convergent validity to the Kujala Patellofemoral Disorder Score (p < .001; 95% confidence interval (CI): -0.71 to -0.52). NPI Score demonstrated good responsiveness to change both between baseline to 12 months (ES: 0.43; 95% CI: 0.42 to 0.10) and 12 to 36 months (ES: 0.67; 95% CI: 0.60 to 0.15). Whilst the NPI Score did not demonstrate a ceiling effect, there was moderate risk of a floor-effect where 13% of the cohort reported the lowest levels of NPI scores.

CONCLUSIONS

The NPI Score is a valid and responsive outcome for people with recurrent patellar dislocation.

Generalized joint hypermobility does not influence clinical outcomes following isolated MPFL reconstruction for patellofemoral instability

PURPOSE

Generalized joint hypermobility (GJH) has frequently been described as a risk factor for patellofemoral instability; however, only a few primary research studies have demonstrated any evidence of a relationship. The primary purpose of this study was to determine if isolated proximal soft tissue stabilization for patellofemoral instability is as successful in patients with GJH compared those without, as measured by disease-specific quality-of-life (QOL), symptom scores and functional outcomes. The secondary purpose was to determine if clinical and patient-reported outcomes were influenced by patient demographic factors in the presence of joint hypermobility.

METHODS

Between 2009 and 2014, data were collected on 174/193 knees (92% follow-up) following an isolated medial patellofemoral ligament reconstruction (MPFL-R). Patients with a Beighton score of 4 or greater were classified as positive for GJH, and any score of 3 or less was classified as negative. Pre- and post-operative Banff Patella Instability Instrument (BPII) scores were compared using a two-sample t test to determine the influence of GJH on QOL. The relationship between the Beighton score, and demographic and clinical factors was explored using correlational analysis. Functional testing including balance and single-leg hop testing was conducted 1 and 2 years post-operatively. Limb symmetry and mean limb-to-limb performance differences were calculated.

RESULTS

In this cohort of isolated MPFL reconstructions, 55.1% had a positive Beighton score. There were seven surgical failures (3.6%). There was no evidence of a relationship between a positive Beighton score and pre-operative BPII scores, post-operative BPII scores or post-operative symptom scores. GJH did not correlate significantly with any post-operative functional testing measures. A positive Beighton score was inversely related to patient age and more prevalent in females.

CONCLUSIONS

This study determined that the presence of GJH did not influence disease-specific quality of life, physical symptom score or functional outcomes following MPFL reconstruction.

LEVEL OF EVIDENCE

III.

Recurrent patellar dislocations: trochleoplasty improves the results of medial patellofemoral ligament surgery only in severe trochlear dysplasia

PURPOSE

Medial patellofemoral ligament (MPFL) surgery combined with trochleoplasty (TP), is often performed to restore the normal patellofemoral biomechanics avoiding recurrent lateral patellar dislocation (LPD) in patients with trochlear dysplasia (TD). However, it is still unclear whether combining TP and MPFL surgery would be more beneficial than performing MPFL surgery on its own. This meta-analysis quantitatively synthesizes and compares published data on the outcomes of recurrent LPD treatment using MPFL surgery without or with TP in patients affected by TD.

METHODS

A systematic literature search about the treatment of recurrent LPD in the presence of TD was conducted. The primary outcome was redislocation rate, analyzed for different types of TD. Kujala, and IKDC scores, as well as complication rate, were also analyzed through a separate meta-analysis.

RESULTS

No statistically significant difference was found in the overall redislocation rate of MPFL surgery without and with TP. There was, however, a statistically significant difference (p < 0.001) in redislocation rate after MPFL surgery without TP between patients with type A or B TD (2.7%) and in patients with type C or D TD (18.6%). In the analysis for every single type of TD, the following results were obtained: redislocation rate of 1.8% in type A, 3.2% in type B, 11.9% in type C, and 7.4% in type D. A statistically significant difference in the complication rate, favouring MPFL surgery without TP, was documented. Both surgical approaches provided a significant improvement with no difference in Kujala and IKDC scores. These results were confirmed when data were analyzed including only patients with type B, C, or D TD, or without additional bone remodelling procedures.

CONCLUSION

Isolated MPFL is as effective as combined TP and MPFL surgery in preventing redislocation and improving clinical and functional outcomes in patients with recurrent LPD and knees affected by moderate TD. However, in case of severe TD, the redislocation rate is lower when TP is performed in combination with MPFL surgery, although with comparable clinical outcomes and a higher risk of post-operative range of motion (ROM) limitation.

LEVEL OF EVIDENCE

Systematic review and meta-analysis, Level IV.

Influence of Risky Pathoanatomy and Demographic Factors on Clinical Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction: A Regression Analysis

BACKGROUND

Multiple studies have demonstrated that a number of demographic and pathoanatomic characteristics are associated with patellofemoral instability, recurrence of instability, and less satisfactory results following medial patellofemoral ligament reconstruction (MPFL-R). Despite the growing volume of research, the relationship of risk factors to patient-reported outcome after MPFL-R is unclear.

PURPOSE

To determine if certain pathoanatomic and demographic factors predict disease-specific quality-of-life outcome after isolated MPFL-R for symptomatic patellofemoral instability.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The study analyzed 224 isolated MPFL-Rs. Demographic data were collected, including age at first dislocation, sex, and presence of bilateral instability. Pathoanatomic risk factors included the presence of high-grade trochlear dysplasia, tibial tubercle-trochlear groove (TT-TG) distance, patella alta ratio, Beighton score, and patellar tilt. Other factors included femoral tunnel position accuracy and WARPS/STAID score. Descriptive analyses were conducted, followed by calculation of individual Spearman rank correlation coefficients for the predictor variables versus the Banff Patellofemoral Instability Instrument (BPII) scores. A multivariable regression with stepwise selection was employed to establish the final model predicting BPII score, with all significant variables for alpha ≤ .05 included in the final model.

RESULTS

The cohort of 224 patients included 66 (29.5%) males and 158 (70.5%) females, with a mean age of 24.1 years and a mean body mass index of 23.9 kg/m². The mean age of first patellar dislocation was 15.7 years, and 41.4% of patients had bilateral instability. Pathoanatomic variables within the cohort included the following: high-grade trochlear dysplasia = 41%; mean TT-TG = 14.6 mm, with 16.8% of patients demonstrating a TT-TG ≥18 mm; mean Caton-Deschamps ratio = 1.09, with 22% of patients demonstrating a ratio ≥1.2; and positive Beighton score = 37.5%. The mean BPII score at postoperative 2 years was 67.1 out of 100. A stepwise elimination in the regression model demonstrated no statistically significant 3- or 2-way relationships. Assessment of individual variables indicated that bilateral symptoms (P = .004), higher age at first dislocation (P = .024), and femoral tunnel position >10 mm from the Schöttle point (P = .042) were statistically significant predictors of lower quality-of-life scores. The R² value for the regression analysis model was 0.07.

CONCLUSION

In this large cohort of patients undergoing isolated MPFL-R for symptomatic lateral patellofemoral instability, a multivariable forward stepwise regression demonstrated that bilateral symptoms, femoral tunnel position, and age at first dislocation were statistically significant predictors of lower postoperative BPII scores. No anatomic risk factors were predictive of quality-of-life outcome score 2 years after MPFL-R surgery. The R² value indicated that there were many other important contributing factors affecting BPII outcome scores than those explored in this study.

Tibial Tubercle Osteotomy and Medial Patellofemoral Ligament Imbrication for Patellar Instability Due to Trochlear Dysplasia

Background:

The treatment of patellar instability in the setting of trochlear dysplasia is challenging.

Purpose/Hypothesis:

The purpose of this study was to evaluate outcomes for the treatment of recurrent patellar dislocations due to trochlear dysplasia using anteromedialization tibial tubercle osteotomy combined with medial patellofemoral ligament (MPFL) imbrication. We hypothesized that the treatment of patellar instability with tibial tubercle osteotomy and MPFL imbrication would result in improved patient satisfaction and decrease patellar instability events in patients with prior instability and trochlear dysplasia.

Study Design:

Case series; Level of evidence, 4.

Methods:

We performed a retrospective analysis of patients who underwent MPFL imbrication and concomitant anteromedialization tibial tubercle osteotomy for recurrent patellofemoral instability at a single institution. The minimum follow-up was 1 year. Patient demographic information including age at the time of surgery, sex, body mass index (BMI), tibial tubercle–trochlear groove (TT-TG) distance, and grade of trochlear dysplasia was collected along with relevant operative data. Postoperatively, recurrent dislocation events as well as Knee injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Index, and Kujala scores were collected, and satisfaction was ascertained by asking patients whether they would undergo the procedure again.

Results:

A total of 37 knees from 31 patients (23 female) with a mean follow-up of 3.8 years (range, 1-8.9 years) were included. The mean patient age was 28.8 years (range, 14-45 years), the mean BMI was 24 kg/m² (range, 20-38 kg/m²), and the mean preoperative TT-TG distance was 18.9 mm (range, 8.4-32.4 mm). Two knees were classified as low-grade trochlear dysplasia (Dejour A) and 35 as high-grade trochlear dysplasia (Dejour B-D). At final follow-up, patients reported mean KOOS subscale scores of 86.5 (Pain), 79.8 (Symptoms), 93.9 (Activities of Daily Living), 74.3 (Sports/Recreation), and 61.9 (Quality of Life), as well as a mean Kujala score of 81.3. Mean patient satisfaction was 8.3 of 10. The majority of knees (86.5%; 32/37) remained stable without recurrent instability after this procedure, while 13.5% (5 knees) suffered a recurrent dislocation, with 2 requiring revision surgery. Eight knees (21.6%) underwent subsequent hardware removal.

Conclusion:

Anteromedialization tibial tubercle osteotomy with MPFL imbrication can improve recurrent patellofemoral instability and provide significant clinical benefit to patients with trochlear dysplasia.

The Medial Patellofemoral Ligament Is a Dynamic and Anisometric Structure: An In Vivo Study on Length Changes and Isometry

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is associated with a high rate of complications, including recurrent instability and persistent knee pain. Technical errors are among the primary causes of these complications. Understanding the effect of adjusting patellofemoral attachments on length change patterns may help surgeons to optimize graft placement during MPFL reconstruction and to reduce graft failure rates.

PURPOSE

To determine the in vivo length changes of the MPFL during dynamic, weightbearing motion and to map the isometry of the 3-dimensional wrapping paths from various attachments on the medial femoral epicondyle to the patella.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Fifteen healthy participants were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion (full extension to ~110° of flexion). On the medial femoral epicondyle, 185 attachments were projected, including the anatomic MPFL footprint, which was divided into 5 attachments (central, proximal, distal, posterior, and anterior). The patellar MPFL area was divided into 3 possible attachments (proximal, central, and distal). The length changes of the shortest 3-dimensional wrapping paths of the various patellofemoral combinations were subsequently measured and mapped.

RESULTS

For the 3 patellar attachments, the most isometric attachment, with an approximate 4% length change, was located posterior and proximal to the anatomic femoral MPFL attachment, close to the adductor tubercle. Attachments proximal and anterior to the isometric area resulted in increasing lengths with increasing knee flexion, whereas distal and posterior attachments caused decreasing lengths with increasing knee flexion. The anatomic MPFL was tightest in extension, decreased in length until approximately 30° of flexion, and then stayed near isometric for the remainder of the motion. Changing both the femoral and patellar attachments significantly affected the length changes of the anatomic MPFL ( P < .001 for both).

CONCLUSION

The most isometric location for MPFL reconstruction was posterior and proximal to the anatomic femoral MPFL attachment. The anatomic MPFL is a dynamic, anisometric structure that was tight in extension and early flexion and near isometric beyond 30° of flexion.

CLINICAL RELEVANCE

Proximal and anterior MPFL tunnel positioning should be avoided, and the importance of anatomic MPFL reconstruction is underscored with the results found in this study.

Systematic Review of Medial Patellofemoral Ligament Reconstruction Techniques: Comparison of Patellar Bone Socket and Cortical Surface Fixation Techniques

PURPOSE

To compare patellar bone socket and cortical surface fixation techniques for isolated medial patellofemoral ligament (MPFL) reconstruction and determine whether there was a difference in (1) complication rates, including fracture of the patella; (2) redislocation rates; or (3) patient-reported outcomes.

METHODS

A literature search was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We included patients who underwent isolated MPFL reconstruction for recurrent patellar instability. Patients with confirmed concomitant or prior ipsilateral knee procedures, multiligament injury, or less than 3 months of follow-up were excluded. Risk-of-bias assessment was performed using the Methodological Index for Non-randomized Studies (MINORS) system. Studies were classified by surgical technique (patellar bone socket group [group S] vs cortical fixation group [group F]), and complications, redislocations, and patient-reported outcomes were collected.

RESULTS

A total of 29 studies yielded 981 patients with MPFL reconstruction for inclusion. Of the patients, 620 underwent a patellar bone socket technique and 361 underwent a cortical fixation technique. Patients ranged in age from 11 to 68 years. Patellar fracture rates ranged from 0% to 17% in group S and were 0% in all group F studies. Mean Kujala scores ranged from 83.5 to 93.6 in group S and from 84.4 to 94.5 in group F. Mean Lysholm scores ranged from 84.6 to 91.7 in group S and from 83.5 to 95 in group F. Redislocation rates ranged from 0% to 21% in group S and from 0% to 13% in group F. Although heterogeneous in nature, complication rates ranged from 0% to 28% in group S and from 0% to 4% in group F.

CONCLUSIONS

MPFL reconstruction techniques with patellar bone sockets showed a larger range of complication rates than cortical fixation techniques, although overall, complications remained uncommon. Clinically, the bone socket group had comparable postoperative redislocation rates and patient outcomes to the group treated with cortical fixation techniques.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I through IV studies.

Patellar Redislocation Rates and Clinical Outcomes After Medial Patellofemoral Ligament Reconstruction: Suture Anchor Versus Double Transpatellar Tunnel Fixation

BACKGROUND

Few studies to date have compared clinical outcomes in patients who have undergone medial patellofemoral ligament (MPFL) reconstruction using the suture anchor and double transpatellar tunnel fixation methods. This meta-analysis therefore compared the clinical results, including the patellar redislocation rate and improvement in functional scores, of suture anchor and double transpatellar tunnel fixation.

HYPOTHESIS

The recurrence rate and improvement in functional outcomes after surgery would be similar using the suture anchor and double transpatellar tunnel fixation methods.

STUDY DESIGN

Meta-analysis.

METHODS

Studies evaluating MPFL reconstruction using either the suture anchor or double transpatellar tunnel technique for patellar site fixation were included if they reported the patellar redislocation rate after surgery and/or validated patient-reported outcomes such as the Kujala and Lysholm scores.

RESULTS

Twenty-one studies were included in this meta-analysis. The mean patellar redislocation rates were similar using the suture anchor (3.2% [95% CI, 1.6%-6.2%]) and double transpatellar tunnel (3.4% [95% CI, 2.1%-5.4%]) techniques ( P = .879). The mean improvement in the Kujala score from before to after MPFL reconstruction was greater using the suture anchor (37.2 [95% CI, 31.1-43.4]) method than the double transpatellar tunnel method (28.7 [95% CI, 21.2-36.1]) ( P = .018). However, the mean improvement in the Lysholm score did not differ significantly using the 2 techniques.

CONCLUSION

The patellar redislocation rate did not differ significantly in patients who underwent MPFL reconstruction using the suture anchor and double transpatellar tunnel fixation methods. The suture anchor fixation method, however, resulted in a greater degree of improvement in patient-reported outcomes.

Single- and double-bundle medial patellofemoral ligament reconstruction procedures result in similar recurrent dislocation rates and improvements in knee function: a systematic review

PURPOSE

To evaluate medial patellofemoral ligament (MPFL) reconstruction using hamstring tendon autografts using single-bundle (SB) and double-bundle (DB) techniques, and compare the clinical outcomes including the Kujala score, postoperative apprehension, recurrent subluxation or dislocation, and complications.

METHODS

The PubMed, Embase, and Cochrane Library databases were searched for relevant literature using the terms ''medial patellofemoral ligament'' and ''MPFL''. The pooled mean values of improvement in the Kujala score were calculated by random effects meta-analysis. Unweighted estimates for the rates of postoperative apprehension, recurrent subluxation or dislocation, and complications were determined by dividing the total number of occurrences by the total number of knees.

RESULTS

Thirty-one articles were included, involving 1063 patients (1116 knees). Two hundred and forty-four patients (254 knees) underwent SB reconstruction, while 819 patients (862 knees) underwent DB reconstruction. The pooled mean values of Kujala score improvement were similar in the SB group (30.1; 95% CI 26.6-33.6) and DB group (30.7; 95% CI 27.7-33.7). The SB group had a significantly greater rate of postoperative apprehension (7.9%) than the DB group (4.1%; P = 0.014). There were no significant differences between the two groups in the rates of recurrent subluxation or dislocation (1.2 and 1.6%) and complications (10.6 and 7.7%).

CONCLUSION

With variability in patient populations and surgical techniques, the DB procedure for isolated MPFL reconstruction demonstrates similar outcomes to the SB technique regarding improvement of knee function, recurrent subluxation or dislocation, and complications. The SB technique may have a greater risk of postoperative apprehension, whereas the DB technique may cause more stiffness.

LEVEL OF EVIDENCE

IV.

Return-to-Play Guidelines After Medial Patellofemoral Ligament Surgery for Recurrent Patellar Instability: A Systematic Review

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction and repair continue to gain acceptance as viable treatment options for recurrent patellar instability in patients who wish to return to sports after surgery. Return-to-play guidelines with objective or subjective criteria for athletes after MPFL surgery, however, have not been uniformly defined.

PURPOSE

To determine whether a concise and objective protocol exists that may help athletes return to their sport more safely after MPFL surgery.

STUDY DESIGN

Systematic review.

METHODS

The clinical evidence for return to play after MPFL reconstruction was evaluated through a systematic review of the literature. Studies that measured outcomes for isolated MPFL surgery with greater than a 12-month follow-up were included in our study. We analyzed each study for a return-to-play timeline, rehabilitation protocol, and any measurements used to determine a safe return to play after surgery.

RESULTS

Fifty-three studies met the inclusion criteria, with a total of 1756 patients and 1838 knees. The most commonly cited rehabilitation guidelines included weightbearing restrictions and range of motion restrictions in 90.6% and 84.9% of studies, respectively. Thirty-five of 53 studies (66.0%) included an expected timeline for either return to play or return to full activity. Ten of 53 studies (18.9%) in our analysis included either objective or subjective criteria to determine return to activity within their rehabilitation protocol.

CONCLUSION

Most studies in our analysis utilized time-based criteria for determining return to play after MPFL surgery, while only a minority utilized objective or subjective patient-centric criteria. Further investigation is needed to determine safe and effective guidelines for return to play after MPFL reconstruction and repair.

Functional testing and return to sport following stabilization surgery for recurrent lateral patellar instability in competitive athletes

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction and tibial tubercle osteotomy are commonly used to treat recurrent lateral patellar instability, yet there are limited available data on return to sport (RTS) following these procedures. The purpose of this study is to evaluate patient factors associated with excellent functional outcomes, including successful RTS, following surgical stabilization including MPFL reconstruction in competitive athletes with recurrent lateral patellar instability.

METHODS

Athletes undergoing primary MPFL reconstruction for recurrent lateral instability from 2005 to 2013 were identified at a single institution. Concomitant procedures, such as tibial tubercle osteotomy (TTO), were included. Patient demographic information, including BMI, gender, age, and pre-injury Tegner score, was recorded. In addition, radiographs were reviewed for pre-operative patellar height (Caton-Deschamps index) and trochlear dysplasia (Dejour classification). All patients underwent a standardized rehabilitation/post-operative protocol, with isokinetic strength and functional testing being performed at 6 months post-operatively. Final Tegner scores, RTS status, subjective instability ratings, and Kujala scores were collected at a minimum of 2 years. Chi-squared analysis for categorical variables and Wilcoxon rank-sum analysis for continuous variables were used to determine the relationship between the previously mentioned patient and knee characteristics with isokinetic data, RTS status, or Kujala scores.

RESULTS

Thirty-nine athletes (23 male, 16 female) at a mean age of 17.5 ± 2.9 years (range, 13-26) underwent primary MPFL reconstruction (32 autografts, seven allografts) for recurrent patellar instability with a mean follow-up of 47.0 ± 16.4 months. Sixteen patients (41%) underwent concomitant tibial tubercle osteotomies. Isokinetic data collected at 6 months post-operatively demonstrated mean knee flexion and extension strength deficits of 15.8 ± 10.1% and 21.4 ± 14.3%, respectively, compared to the contralateral leg (p < 0.001 for both). Patients who underwent concomitant tibial tubercle osteotomy (p = 0.04), males (p = 0.01) and those with patella alta (p = 0.04) had weaker 6-month isokinetic testing. Thirty-three of the thirty-nine (85%) athletes were able to RTS at a mean of 8.1 ± 3.9 months. Patients undergoing MPFL with concomitant TTO (p = 0.02) returned to sport at a slower rate. One patient (3%) reported an episode of recurrent dislocation requiring revision surgery. Kujala and Tegner scores at final follow-up were 91.1 ± 6.3 and 6 (range, 4-9), respectively.

CONCLUSION

Surgical stabilization including MFPL reconstruction for recurrent lateral patellar instability is an effective procedure for returning athletes to competitive sports. However, strength deficits persist at 6 months after surgery, especially in those undergoing concomitant TTO, which may delay return to sport. Physicians can use these results to counsel patients that return to competitive sports is safe with good clinical outcomes and low rate of recurrence at 4-year follow-up; however, predisposing factors, like a lateralized tibial tubercle, should be addressed if necessary, but athletes should be counselled that a slower recovery and longer return to sport time may be expected.

LEVEL OF EVIDENCE

IV.

A new minimally invasive surgical technique for medial retinaculum repair following traumatic patellar dislocation

A new surgical method is introduced offering a less invasive approach to reattach the medial retinaculum following acute patellar dislocation. This retrospective analysis comprised 12 cases of medial retinacular repair in 10 patients. The surgical technique achieved reinforced reattachment of the torn region of the medial retinaculum for improved patellar support and stabilization. During follow-up, no recurrent patellar dislocations occurred, except where one patient reported a subjective feeling of patellar dislocation. The average Kujala score for our sample group after 2 years was 89.2. A plethora of methods are described in the literature to repair a tear to the medial patellofemoral ligament, which attaches at the superomedial patella. However, it is our contention that traumatic patellar dislocation invariably results in osteochondral avulsion at the inferomedial patella, refuting medial patellofemoral ligament involvement, and, rather, implicating the inferior aspect of the deep layer of medial retinaculum. Our surgical technique enables stable fixation of the region, decreasing the rate of recurrent dislocations. No grafts are used, permitting tendinous and ligamentous anatomy to remain intact. We further postulate that performing a CT examination preoperatively may reduce time between diagnosis and surgery, in addition to locating fracture sites more precisely.