Poster 248: Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle-Trochlear Groove Distance and Patellar Height: Differential Outcomes for Chondral Defects
Authors: Davies Michael , Propp Bennett E. , Marmor William , Wimberly Audrey , Nguyen Joseph T. , Stein Beth E. Shubin , Dennis Elizabeth R. 
Published: August 2024

Objectives:

Patellofemoral instability is a common injury seen in adolescents and young adults. More than 95% of patella dislocations result in an injury to the medial patellofemoral ligament (MPFL) and a large percentage of these patients also sustain cartilage injuries at the time of their dislocation. These chondral injuries range from cracks and fissures to full-thickness chondral shear injuries to osteochondral fractures. MPFL reconstruction is the standard of care treatment for patients with recurrent dislocations, but the impact of concomitant full-thickness chondral injuries on the patient-reported outcome measures (PROMs) in patients who undergo isolated MPFL reconstruction without bony realignment remains unclear. The purpose of this study is to compare PROMs between individuals who underwent isolated MPFL reconstruction with concomitant cartilage restoration to those patients whose cartilage injuries were not full-thickness and thus did not require a concomitant cartilage restoration procedure at the time of their MPFL reconstruction. We hypothesized that cartilage injury in patients with patellofemoral instability would result in worse preoperative PROMs compared to patients without chondral injury, and that these differences would be mitigated by concomitant surgical intervention to address chondral damage performed in addition to their MPFL reconstruction.

Methods:

Patients with recurrent patellar instability were collected in an institutional registry starting March 2014. Exclusion criteria included history of prior patella stabilization procedure, an off-loadable (inferior/lateral) Outerbridge grade 4 chondral defect, anterior knee pain >50% of their chief complaint and a “Jumping J” sign. All patients underwent primary, unilateral, isolated MPFL reconstruction regardless of their bony anatomy. PROMS, episodes of recurrent instability, and return to sports data were obtained at baseline and annually. Radiographic measurements were obtained at baseline. Cartilage lesion characteristics including location, Outerbridge grade, and lesion size were identified intraoperatively. Patients were retrospectively assigned to the cartilage intervention group if they underwent concomitant particulated juvenile cartilage allograft, osteochondral allograft, open reduction internal fixation, microfracture, or removal of loose body. Those without intervention or chondroplasty comprised the comparison group.

Results:

A total of 138 patients underwent isolated MPFL reconstruction between March 2014 and December 2019. Two patients were excluded from the study for concomitant anterior cruciate ligament reconstruction and meniscus repair, respectively. Twenty-two patients underwent concomitant cartilage restoration, while 114 patients underwent chondroplasty or no concomitant cartilage intervention. Average tourniquet time was significantly greater in the intervention group at 61.32 ± 20.18 minutes compared to 43.65 ± 9.71 minutes (p = 0.0002). 50 patients reached ≥ 5-years, of which 40 (80%) completed follow-up PROMs. A total of 119 patients reached ≥2-years, of which 89 (75%) completed follow-up PROMs. All PROMs improved over time except for Pediatric Functional Activity Brief Scale scores which had no change (P = 0.095). Baseline PROMs were significantly different between the intervention and no-intervention groups for Knee injury and Osteoarthritis Outcome Score – Quality of Life (KOOS-QoL), KOOS – Physical Function Shortform (KOOS-PS), and Kujala scores (p < 0.05) (Table 1). The baseline KOOS-QoL, KOOS-PS, and Kujala scores for the intervention group were 17.08 ± 15.93, 33.24 ± 15.81, and 49.80 ± 20.51, respectively, compared to 32.98 ± 20.53. 42.42 ± 12.58, and 60.05 ± 18.19 for the no-intervention group (Table 1). On average, those who received a concomitant cartilage restoration procedure scored lower on all three measures at baseline compared to those who did not receive intervention. There was no statistically significant difference in PROMs between the intervention and no-intervention groups at 2- or 5-year time points, nor in the change in outcomes scores between timepoints for the 2 groups (Table 2, Table 3).

Conclusions:

The treatment of cartilage lesions in addition to MPFL reconstruction for recurrent patellar instability resulted in similar improvement in PROMs when compared to isolated MPFL reconstruction without cartilage intervention at 2 and 5 years after surgery. This was true despite patients with cartilage injuries initially displaying significantly worse PROMs prior to surgery. We concluded that intervening with cartilage restoration in full-thickness cartilage lesions at the time of isolated MPFL reconstruction can result in equivalent outcomes and thus can mitigate the preoperative difference in PROMs seen between patients with significant chondral injuries at the time of presentation and those with isolated instability in the absence of a significant chondral injury. Future work will seek to confirm the durability of these results with longer term follow-up.