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

Abstract

Background: Medial patellofemoral ligament reconstruction (MPFLR) is widely used to treat patellofemoral instability. However, it is still unclear when a concomitant bony procedure is needed. Purpose: To evaluate the therapeutic efficacy of isolated MPFLR for recurrent patellar lateral dislocation and to identify the prognostic factors for clinical outcomes. Study Design: Case series; Level of evidence, 4. Methods: A total of 237 patients who had undergone unilateral isolated MPFLR between January 2011 and December 2016 were included. Patellar tracking (J sign) and radiologic information including patellar height, trochlear dysplasia, tibial tubercle–trochlear groove distance, and patellar tilt was collected preoperatively, and the Kujala and International Knee Documentation Committee (IKDC) functional scores were used to assess postoperative recovery. Failure was defined as redislocation or patient-reported and clinically confirmed patellar instability. The influence of radiologic features and the J sign on knee functional scores was explored via subgroup analysis. Potential prognostic factors were explored using univariate and multivariate regression analyses, and risk factors for a positive J sign were evaluated using Spearman coefficient correlation analysis. Results: The mean ± SD follow-up period was 70.67 ± 18.05 months (range, 36-108 months). From preoperatively to final follow-up, all patients had statistically and clinically significant improvements in the Kujala score (from 51.43 ± 6.87 to 88.52 ± 4.83; P < .001) and IKDC score (from 49.78 ± 6.05 to 81.16 ± 4.20; P < .001). Subgroup analysis indicated no significant difference in functional score improvements based on radiologic features or the J sign. Overall, 20 knees (8.4%) experienced postoperative failure: 11 with redislocation and 9 with patellar instability. A preoperative positive J sign was shown to be an independent prognostic factor for postoperative failure via logistic regression analyses: univariate (odds ratio, 3.340; 95% CI, 1.316-8.480; P = .011) and multivariate (odds ratio, 3.038; 95% CI, 1.179-7.827; P = .021). In addition, the J sign was closely associated with patellar height ( r S, 0.159; P = .014) and trochlear dysplasia ( r S, 0.235; P < .001). Conclusion: Isolated MPFLR appears to be an effective strategy for recurrent patellar lateral dislocation, with significant functional improvement and a low failure rate. A preoperative positive J sign was identified as a potential prognostic risk factor for postoperative failure.

Patellar Instability

“…Although failure risk was not associated with radiographic features (patellar height, trochlear dysplasia, TT-TG distance, patellar tilt), the presence of a preoperative J-sign was associated with a 3-fold increased risk of postoperative instability. The authors also found a significant association between a J-sign and both a CDI value of ≥1.2 and trochlear dysplasia 50 . Similarly, Sappey-Marinier et al reported that the presence of a preoperative J-sign or CDI ≥1.3 was predictive of failure, although no correlation was found between these 2 predictors 51 .…”

“…Patellar dislocation recurrence may occur after surgical stabilization. In an analysis of 237 patients who underwent unilateral isolated MPFL reconstruction, Zhao et al aimed to identify factors associated with recurrent lateral PI 50 . Although all included patients demonstrated clinical improvements in Kujala and International Knee Documentation Committee scores, 20 patients (8.4%) experienced some type of failure (redislocation or subjective instability) up to 5 years postoperatively.…”

Does Tibial Tuberosity Osteotomy Improve Outcomes When Combined With Medial Patellofemoral Ligament Reconstruction in the Presence of Increased Tibial Tuberosity–Trochlear Groove Distance? A Systematic Review and Meta-analysis

“…One study was published in 2022, 17 5 studies were published in 2021, 12,15,27,41,48 3 studies were published in 2020, 2,37,47 2 studies were published in 2019, 8,26 1 in 2017, 22 and 1 in 2014 21 ; 7 studies were judged to be of level 3 evidence, 2,12,15,21,27,37,47 and 6 studies had level 4 evidence. 8,17,22,26,41,48 The mean age of the overall cohort in the 13 studies was 24.1 years, and the mean follow-up was 3.8 years. Within the included studies, 386 patients (406 knees) had a TT-TG >20 mm; of these patients, 276 had undergone MPFLR+TTO, and 110 had undergone iMPFLR.…”

“…Most studies used the Caton-Deschamps index, yy with the exception of Sisa ´k et al 37 and Matsushita et al, 22 who used the Insall-Salvati ratio. TT-TG was measured using magnetic resonance imaging 2,8,12,17,37 or computed tomography 15,21,22,26,27,41,47,48 axial superimposed images. The studies used variations of the technique used by Matsushita et al, 22 who employed Photoshop software (Adobe, Inc) to superimpose an image of a line going through the deepest point of the trochlear groove to an image of a line though the center of the tibial tuberosity perpendicular to the posterior condylar line and measured the distance between the 2.…”

Insall proximal realignment with/without tibial tubercle osteotomy for recurrent patellar instability yields acceptable medium- to long-term results but risk of osteoarthritis progression is considerable

“…This difference in findings might be due to the inclusion of TTO in the current treatment strategy. In comparison, studies applying modern MPFL-R - regardless of pathoanatomic features of treated knees - redislocation and/or subluxation rates between 3.4% and 8.4% [ 18 , 43 ] have been seen. One of the few other studies reporting both on luxation and subluxation rates after MPFL-R with/without TTO is that by Enderlein et al [ 15 ].…”