Editorial Commentary: How to Pass Go After Medial Patellofemoral Ligament Reconstruction.

CORR Synthesis: Can Guided Growth for Angular Deformity Correction Be Applied to Management of Pediatric Patellofemoral Instability?

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.

The Value of Minimal Clinically Important Difference, Substantial Clinical Benefit, and Patient-Acceptable Symptomatic State for Commonly Used Patient-Reported Outcomes in Recurrent Patellar Instability Patients After Medial Patellofemoral Ligament Reconstruction and Tibial Tubercle Transfer

Femoral Tunnel Placement in Medial Patellofemoral Ligament Reconstruction (SS-76)

The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint to lateral patellar translation and is often disrupted by lateral patellar dislocation. Surgical management for recurrent patellar instability focuses on restoring the MPFL function with repair or reconstruction techniques. Recent studies have favored reconstruction over repair; however, long-term comparative studies are limited. To compare long-term clinical outcomes, complications, and recurrence rates of isolated MPFL reconstruction and MPFL repair for recurrent lateral patellar instability. Cohort study; Level of evidence, 3. A total of 55 patients (n = 58 knees) with recurrent lateral patellar instability were treated between 2005 and 2012 with either MPFL repair or MPFL reconstruction. The exclusion criteria were previous or concomitant tibial tubercle osteotomy or trochleoplasty and follow-up of <8 years. Pre- and postoperative descriptive, surgical, imaging, and clinical data were recorded for each patient. MPFL repair was performed on 26 patients (n = 29 knees; 14 women, 15 men), with a mean age of 18.4 years. MPFL reconstruction was performed on 29 patients (n = 29 knees; 18 women, 11 men), with a mean age of 18.2 years. At a mean follow-up of 12 years (range, 8.3-18.9 years), the reconstruction group had a significantly lower rate of recurrent dislocation compared with the repair group (14% vs 41%; P = .019). There were no differences in the number of preoperative dislocations or tibial tubercle-trochlear groove distance. The reconstruction group had significantly more time from initial injury to surgery compared with the repair group (median, 1460 days vs 627 days; P = .007). There were no differences in postoperative Tegner, Lysholm, or Kujala scores at the final follow-up. In addition, no statistically significant differences were detected in return to sport (RTS) rates (repair [81%] vs reconstruction [75%]; P = .610) or reoperation rates for recurrent instability (repair [21%] vs reconstruction [7%]; P = .13). MPFL repair resulted in a nearly 3-fold higher rate of recurrent patellar dislocation (41% vs 14%) at the long-term follow-up compared with MPFL reconstruction. Given this disparate rate, the authors recommend MPFL reconstruction over repair because of the lower failure rate and similar, if not superior, clinical outcomes and RTS.

Objectives:Medial patellofemoral ligament (MPFL) reconstruction is the standard of care surgical treatment for recurrent patellar instability. Recurrent patellar instability is common after a first-time dislocation in the skeletally immature population. Adult-type reconstruction techniques are often avoided in skeletally immature patients due to the proximity of the femoral insertion of the MFPL to the distal femoral physis. It is currently unclear how outcomes of MPFL reconstruction in skeletally immature patients compare to those for skeletally mature patients. The objective of this study is to present the outcomes of isolated MPFL reconstruction in skeletally immature patients and compare their findings to a skeletally mature population.Methods:Patients were identified from an institutional patellofemoral registry who underwent isolated MPFL reconstruction from March 2014 to July 2018. Demographic, radiographic, and knee-specific patient-reported outcome measures (PROMs) were collected prior to surgery. Follow-up data collection included knee surveys collected at 1 and 2-years following MPFL reconstruction. Additionally, return to sport rates and episodes of re-dislocations were also collected. Comparisons of demographic and clinical data were made between skeletally immature and mature patients. Sub-analysis was performed on outcomes in skeletally immature patients who underwent MPFL reconstruction where the graft was placed distal to the physis to avoid the growth plate versus those who had standard placement of the graft. Baseline factors were analyzed using independent samples t-tests or chi-square analysis. Longitudinal analysis of knee PROMs was conducted using generalized estimating equation (GEE) modeling. Statistical significance was defined as p-values of 0.05 or less.Results:The study cohort included 107 patients (25 skeletally immature, 82 skeletally mature). Mean age of the study groups was 13.8 years in the immature group (range 11-15) and 21.3 in the mature group (range 14-34). No differences in sex (72% female in both groups) or obesity (0% vs. 8%) was observed between immature and mature patients. Radiographic measures of Caton-Deschamps Index (1.18 in both groups), TT-TG (14.9 vs. 14.8), and Dejour classification (P=0.328) also saw no differences between groups. Longitudinal outcomes in KOOS QoL, IKDC, KOOS PS, and Kujala surveys found no differences between immature versus mature patients over time. However, higher PediFABS was observed in the immature group versus mature at baseline (21.6 vs. 11.9, P<0.001), 1-year (18.1 vs. 11.5, P=0.006), and 2-years (22.4 vs. 11.5, P=0.003). Low incidence of post-operative dislocation and a high return to sport rate was observed in both skeletally immature and mature patients. No statistical differences were observed in all outcomes between immature patients who had standard graft placement and those where the graft was placed distal to the physis.Conclusion:Controversy exists in how best to treat the skeletally immature patient with recurrent lateral patellar instability. Due to the risk of injury to the growth plate, many believe it is best to wait to stabilize these patients until they have stopped growing. However, given the high risk of cartilage injury with each dislocation and the long term sequelae of such injuries in these young knees, the risk of waiting may be high. This study demonstrates similar outcomes and recurrence rates in skeletally immature patients with those seen in the mature population without disturbance or injury to the growth plates.Figure 1.Figure 2.

Establishing the Minimum Clinically Important Difference, Patient Acceptable Symptomatic State, and Substantial Clinical Benefit After Isolated Medial Patellofemoral Ligament Reconstruction.

Medial patellofemoral ligament (MPFL) reconstruction has recently been broadly accepted as primary surgical treatment in adults. Reconstruction techniques with osseous fixation in femur cannot be used for patients with open growth plates. Operative treatment of patella instability in children therefore is a challenge and requires alternative MPFL reconstruction techniques. Limited knowledge exists concerning outcome after MPFL reconstruction in children and adolescents. This study present clinical outcome in a consecutive single clinic series of children treated with paediatric MPFL reconstruction using a soft tissue femoral fixation technique. Twenty-four MPFL reconstructions in 20 operated children aged 8-16 were included in the study. Indication for surgery was two or more patella dislocations. MPFL reconstruction was performed by looping the released gracilis tendon around the adductor magnus tendon insertion and through drill holes in the proximal medial patella edge. Clinical outcome was evaluated by Kujala score and NRS pain score preoperatively, at 1-year follow-up and final follow-up at 39 months. Outcome was compared with a cohort of 179 adult patients with recurrent patella instability operated with an adult MPFL reconstruction technique. Kujala score improved from 61 (13) to 81 (16). NRS pain score improved from 3.0 (3.1) to 1.5 (1.3) in activity. Four patients (20%) experienced redislocation within the first postoperative year compared with 5% in an adult patient population. Five patients (25%) experienced subluxations. One patient with a redislocation was re-operated with adult MPFL reconstruction technique. Cartilage injury was seen in six patients. There are clinical relevant improvements in knee function and pain after MPFL reconstruction in paediatric patients. Patella stability after MPFL reconstruction using femoral soft tissue graft fixation in paediatric patients was inferior to MPFL reconstruction using bony femoral fixation in adult patients. Case-Control study, Level III.

Objectives:Medial patellofemoral ligament (MPFL) reconstruction is an effective surgicalprocedure for patients with recurrent lateral dislocations. Outcomemeasurements can identify the success of a surgical procedure but areshifting away from absolute values or deltas of patient-reported outcomes(PROs) towards the minimal clinically important difference (MCID),substantial clinical benefit (SCB), and patient acceptable symptomatic state(PASS), representing the smallest clinical improvement that patientsperceive as important, the threshold at which patients notice a considerableimprovement, and patient satisfaction with their outcome, respectively. Toour knowledge no prior study has defined these thresholds in MPFLreconstruction patients.Methods:An institutional database was reviewed for patients who underwent primaryMPFL reconstruction between August 2015 to February 2018 with a minimum6-month follow-up. IKDC, Kujala and KOOS were administered to all patientspre-operatively and at 6-months and 1-year post-operatively. An anchor-basedapproach with a receiver-operator curve/area under the curve analysis usingthe Youden index was performed to calculate the MCID, SCB and PASS. Thepredictive power was determined to be acceptable with AUC≥70% and excellentwith AUC≥80%.Results:From 2015 to 2018, 93 of 162 patients (mean age 23.7±10.1 years; 25 males, 68females) completed for 6-month follow-up. At 6-months follow-up, SCB andPASS were defined with acceptable predictive power for all scores listed,while MCID achieved this for KOOS pain and sports subscores only (Table 1).At 1-year follow-up, SCB and PASS were each defined with acceptablepredictive power for all scores listed, while MCID achieved this mark forKOOS pain and quality of life subscores as well as both Kujala scales.Conclusion:This study establishes MCID, SCB and PASS for IKDC, Kujala, and KOOSsubscores at 6-months and 1-year postoperatively with excellent predictivepower for 19/23 PROMs investigated at 1-year. These findings representimportant benchmarks in patients undergoing primary MPFL reconstruction.

Lateral retinacular release in concordance with medial patellofemoral ligament reconstruction in patients with recurrent patellar instability: A computational model

Background: There is a higher rate of failure of isolated MPFL reconstruction in skeletally immature patients with patellar instability compared to skeletally mature patients. Genu valgum is a known risk factor for patellar instability. There is potential for concomitant surgical correction of genu valgum to achieve better clinical outcomes and to decrease failure rates of MPFL reconstruction. Purpose: To evaluate outcomes of combined medial patellofemoral ligament (MPFL) reconstruction and implant-mediated guided growth (IMGG) in skeletally immature patients with patellar instability and genu valgum. Study Design: Case series; Level of evidence, 4. Methods: In a multicenter study, all skeletally immature patients with recurrent patellar instability and genu valgum who underwent MPFL reconstruction using hamstring graft and IMGG using a transphyseal screw or tension band plate for the distal femur and/or proximal tibia were included. The knee valgus angle and mechanical axis were measured on full-length radiographs and anatomic risk factors were measured on MRI. Patients were followed until correction of their lower limb alignment and implant removal or until skeletal maturity. Clinical outcomes, including complications, were analyzed. Results: A total of 31 patients (37 knees) were included in the study. The mean age and skeletal age of the cohort were 12.4 and 12.9 years, respectively. Simultaneous MPFL reconstruction and IMGG were performed in 26 of 37 knees; 11 underwent staged procedures. Twenty knees had transphyseal screws and 17 knees had tension band plates for IMGG. The knee valgus corrected from a mean of 12.4° to 5.1° in 12.1 months. Implants were removed from 22 of 37 knees once genu valgum was corrected. There was no significant difference (P = .65) in the correction rate between plates (0.7 deg/month) and screws (0.6 deg/month). Ten complications occurred in 4 patients (7 knees) and included 5 patellar redislocations, 2 rebound valgus, 1 varus overcorrection, 1 knee arthrofibrosis, and 1 implant loosening. For children <10 years of age, 3 of 6 (50%) knees had patellar redislocations and 5 of 6 knees had a complication. This was statistically significant (P = .003) compared with patients >10 years of age. Similarly, for patients with bilateral knee involvement, 5 of 12 (42%) knees had patellar redislocations and a total of 8 complications occurred in this subset. This was statistically significant (P < .001) compared with patients with unilateral involvement. Conclusion: IMGG with plates or screws in the setting of combined MPFL reconstruction improves genu valgum. Children <10 years of age and those with bilateral instability with genu valgum remain difficult subsets to treat with higher complication rates.

Widespread Implementation of Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Maintains Functional Outcomes at Midterm to Long-Term Follow-up While Decreasing Complication Rates: A Systematic Review

The principal aim of this study was to report the outcomes of medial patellofemoral ligament (MPFL) reconstruction, used as either an isolated procedure or in combination with another stabilization procedure, for the primary treatment of recurrent patellar instability. Between 2007 and 2012, 45 patients with recurrent patellar instability and no prior stabilization surgery had an MPFL reconstruction by a single surgeon, either as an isolated procedure or in combination with another stabilization procedure. Questionnaires detailing patellar instability since surgery, knee pain, ability to negotiate stairs, and sports participation were completed, and data regarding examination and radiological findings were collected from the medical record. A total of 36 (80%) patients completed the questionnaire at a mean of 3.1 years (minimum 1 year), whilst a further 11% had clinical follow-up of greater than 1 year. Four patients were excluded due to lack of adequate follow-up. Thirty-one patients had an isolated MPFL reconstruction and none had further patellar instability. Of the ten patients who had a combined procedure, one experienced recurrent instability. Return to sport rates were 81 and 57% for the isolated and combined groups, respectively, with the majority returning to strenuous sport (81 and 57%, respectively). Most patients (96 and 80%) could negotiate stairs without difficulty, whilst 38 and 40% reported some degree of anterior knee pain. This study shows that satisfactory results can be obtained using MPFL reconstruction either in isolation or in combination to treat recurrent patellar instability. Whether the indications for an isolated MPFL can be extended further remains unclear. III.

Background: The comparative clinical outcome of medial retinaculum plication (MRP) versus medial patellofemoral ligament reconstruction (MPFLR) for recurrent patellar instability in adults is unknown. Hypothesis: Arthroscopic MRP can yield similar results to MPFLR for recurrent patellar instability in adults. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: One hundred patients with recurrent patellar instability were randomly divided into 2 groups receiving either arthroscopic MRP or MPFLR. Lateral release and anteromedial or distal tibial tubercle transfers were also performed as indicated. Follow-ups were performed at 12, 24, and 60 months postoperatively, and computed tomography (CT) was performed immediately after the operation and at follow-up. The passive patella glide test was performed before surgery and at each follow-up point. The degree of knee function was evaluated preoperatively and at 2 and 5 years postoperatively using the International Knee Documentation Committee (IKDC), Lysholm, and Kujala rating scales. Survival analysis was performed, and redislocation or multiple episodes of patellar instability were considered as indicating failure. Results: Forty-three patients in the MRP group and 45 patients in the MPFLR group were followed for 5 years and received complete evaluations. The correction of the static patellar position deteriorated over time in both groups, but significantly better results were observed for the MPFLR group. The results of the passive patella glide test indicated more stable patellae in the MPFLR group at each follow-up point. Functional evaluations at 2 and 5 years (final Lysholm score, 69.3 ± 6.9 vs 86.9 ± 6.1; Kujala score, 73.8 ± 5.5 vs 87.4 ± 5.7) revealed statistically significant superior results in the MPFLR group. Finally, 4 patients (9.3%) in the MRP group and 1 (2.2%) in the MPFLR group experienced episodes of redislocation, and 7 patients (16.3%) in the MRP group and 3 (6.7%) in the MPFLR group experienced multiple episodes of patellar instability (P = .037). Kaplan-Meier survival analysis and a log-rank test indicated better results and a significantly higher survival rate (P = .006) in the MPFLR group. Conclusion: MPFLR results in better static patellar position and functional outcome than MRP in the treatment of recurrent patellar dislocation in adults.

Objectives: Medial patellofemoral ligament (MPFL) reconstruction is used to address cases of recurrent patellar instability. Minimal clinically important difference (MCID) is an important marker that relays the smallest clinical improvement in which patients feel a significant change after surgery. MCID has been previously established for MPFL reconstruction after 6 months and 1 year. To date, no study has established MCID for patient reported outcomes 2 years after MPFL reconstruction. The purpose of this study is to define the MCID for the Kujala, International Knee Documentation Committee (IKDC), and Knee Injury and Osteoarthritis Outcome Score for Joint Reconstruction (KOOS JR) at minimum two-year follow-ups after isolated MPFL reconstruction. Methods: All patients undergoing isolated MPFL reconstruction for recurrent patellar instability at a single institution between December 2015-June 2021 were included. Patients with concomitant osseous procedures beyond chondroplasty and any ligamentous procedure were excluded. A distribution-based approach was used to calculate the MCID. This was performed by determining the standard deviation (SD) of the delta two-year patient reported outcome scores (PROS) and then multiplying the SD by 0.5. The number of patients achieving MCID were then presented as a percentage. Results: Eighty-six of 117 patients who underwent isolated MPFL reconstruction completed preoperative and a two-year follow-up PRO survey (59 female, 27 male; age 21.1 ± 8.7 years). For Kujala, the preoperative mean was 59.3 ± 17.1, two-year follow-up mean was 87.6 ± 13.6, and MCID was 9.2 with 88% of the cohort achieving MCID. For IKDC, preoperative mean was 50.2 ± 17.2, two-year mean was 80.5 ± 18.6, and MCID was 12.4 with 80% of patients achieving MCID. KOOS JR had a preoperative man of 66.0 ± 14.6, two-year follow-up mean of 88.8 ± 11.9, and MCID of 8.5 with 72% of patients meeting this MCID (Figure 1). Conclusions: At two years following MPFL reconstruction, the MCID’s for clinically relevant subjective PROS were 9.2 (Kujala), 12.5 (IKDC), and 8.5 (KOOS JR). MCID’s for MPFL reconstruction are already established for 6-month and 1-year time points, and this was the first presentation of two-year MCID values. Establishing the 2-year MCID for MPFL reconstruction gives surgeons another tool to use in the diagnoses of patellar instability patients who may be struggling post-operatively.