The Incidence of Recurrent Instability After Medial Retinacular Repair, Quadriceps Tendon Femoral Ligament Reconstruction, and the Roux Goldthwait Patellar Tendon Transfer for Patellar Instability

BACKGROUND: For skeletally immature patients with recurrent patellofemoral instability, numerous soft tissue procedures have been described to stabilize the patella while protecting the physis, with varied success rates and no clear superiority of a given procedure. Cases characterized by habitual instability or severe patellofemoral dysmorphology often warrant multiple simultaneous procedures to correct both proximal and distal malalignment. HYPOTHESIS/PURPOSE: To determine the incidence of recurrent instability and post-operative complications in a series of patients treated with (1) quadriceps tendon femoral ligament reconstruction (QTFLR) and medial retinacular repair (MRR), or (2) QTFLR and Roux-Goldthwait patellar tendon transfer (RG) with or without MMR; and to compare these outcomes to those for isolated MRR. METHODS: Eligible participants were retrospectively identified from surgeon records based on diagnosis of patellar instability, surgical treatment with MRR, QTFLR, RG, or a combination of these procedures, and minimum follow-up of 6 months. The medical records of included participants were reviewed to collect demographic data and document post-operative complications and recurrent instability. The presence of skeletal immaturity, patella alta, trochlear dysplasia, and elevated TT-TG were determined from radiographs and MRI. Statistical analysis included independent t-tests, rank sum procedure, and Chi-square analysis for univariate analysis, and stepwise binary logistic regression analysis to determine predictors of recurrent instability and complications. RESULTS: Seventy patients (41 females, 29 males) were included with a mean age of 16.4 years and mean follow-up of 3.5 years. The QTFLR + MRR group (n=11) had 36.3% incidence of recurrent instability (dislocation in 3, subluxation in 1) and 9.1% incidence of complications. The QTFLR + RG ± MRR group (n=13) had 23.1% incidence of recurrent instability (no dislocations, subluxation in 3) and 7.7% incidence of complications. The isolated MRR group (n=46) had a 23.9% incidence of recurrent instability (dislocation in 7, subluxation in 4) and 15.2% incidence of complications. There was a significantly higher presence of trochlear dysplasia (p<0.001) and elevated TT-TG (p=0.004) in the combination procedure group compared to the isolated MRR group. Elevated TT-TG and skeletal immaturity were significantly associated with post-operative subluxation in the isolated MRR group. No other factors were predictive of recurrent instability or post-operative complications for any groups. CONCLUSION: The incidence of recurrent instability after combined soft tissue procedures for patellar instability ranged from 23-36%, similar to the incidence of recurrent instability of 24% for isolated MRR despite the combined procedure group having a higher presence of trochlear dysplasia and elevated TT-TG distance.