Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability: Influence of Persistent Postoperative Apprehension and J-Sign

Background: Patients with recurrent instability underwent isolated medial patellofemoral ligament (MPFL) reconstruction regardless of anatomic risk factors within the confines of strict exclusion criteria. Previous publications from this cohort have been limited in the ability to identify risk factors for failure of isolated MPFL reconstruction when recurrent instability was defined as the only mode of failure, likely because of the small patient numbers who experienced this outcome. Purpose: To investigate whether persistence of postoperative apprehension and J-sign indicate suboptimal outcomes after isolated MPFL reconstruction and to determine if they may help identify patients who need bony realignment in addition to a soft tissue stabilization. Study Design: Case series; Level of evidence, 4 Methods: Patients with recurrent patellar instability were prospectively enrolled from March 2014 to December 2019 and underwent primary, unilateral MPFL reconstruction by the senior author within the confines of strict exclusion criteria. Imaging measurements were obtained at baseline. Patient-reported outcome measures (PROMs) were collected at baseline and annually. Recurrent instability events (patellar dislocations or subluxations), return-to-sport (RTS) rates, presence of postoperative apprehension, and J-sign were collected at 1- and 2-year follow-ups. Results: A total of 138 knees (72% female; mean age, 20.1 ± 6.1 years) underwent isolated MPFL reconstruction between March 2014 and December 2019. The mean Beighton score was 5.3 ± 3.0, and knee hyperextension beyond 0° was 5.4° ± 2.8°. Of the knees evaluated, 95 (81%) had a preoperative J-sign and 89 (65%) had preoperative knee hyperextension. At 2 years, recurrent instability was reported in 6 knees (5%), postoperative apprehension in 9 knees (8%), and a postoperative J-sign in 44 knees (37%). No patients with postoperative apprehension reported recurrent instability. At 2 years, 89% of patients were able to RTS. Patients with both preoperative knee hyperextension and postoperative apprehension had worse RTS rates compared with patients without either ( P = .034). Patients with postoperative J-signs had a significantly worse International Knee Documentation Committee score ( P = .022), Knee injury and Osteoarthritis Outcome Score Physical Function Short Form score ( P = .011), and Kujala score ( P = .035) at the 2-year follow-up. For patients with recurrent instability or postoperative apprehension, the Kujala score was statistically significantly lower at 1 year compared with those without (84.9 vs 91.7; P = .019). Conclusion: In this prospective study of knees undergoing isolated MPFL reconstruction for recurrent patellofemoral instability, patients with postoperative J-signs showed worse PROMs at 2 years, a higher percentage of patients with preoperative knee hyperextension and postoperative apprehension did not RTS, and patients with postoperative apprehension did not experience recurrent instability. These findings support the need to further investigate if postoperative J-sign and apprehension may be important markers of suboptimal outcomes after isolated MPFL reconstruction for recurrent instability, which in turn may help identify patients who may benefit from concomitant bony realignment procedures at the time of their index procedure.