Very low dislocation rate and good clinical outcome after Bereiter trochleoplasty and additional procedures following the Copenhagen patella-femoral instability algorithm: One- and two-years outcomes from a consecutive cohort of 368 cases.

Purpose: Patello-femoral instability (PFI) is often caused by predisposing factors, with trochlea dysplasia (TD) as the most prominent. Untreated patellar instability leads to impaired function and an increased risk of patellofemoral osteoarthritis. Since 2009 patients with PFI have been treated according to the Copenhagen PFI algorithm, where underlying osseous predisposing factors are addressed. The aim of this study was to report the two-year outcome after Bereiter trochleoplasty (TP) for high grade TD in a cohort of 368 consecutive patients treated according to the Copenhagen PFI algorithm from 2011 to 2021.

Methods: This was a register study evaluating a consecutive cohort of patients with high grade TD undergoing Bereiter trochleoplasty and additional procedures following the Copenhagen PFI algorithm. Outcomes were the Kujala score, the Knee Osteoarthritis Outcome Score (KOOS) and the Lysholm score collected preoperatively and after 1 and 2 years.

Results: From January 2011 to September 2021, 368 Bereiter TPs were performed on 346 patients (99 males, 225 females and 44 bilateral surgeries). Four knees (1.1%) experienced a re-dislocation. There were statistically significant (p < 0.0001) and clinically relevant improvements in all patients reported outcome measure (PROM)-scores 1 and 2 years after surgery. Over 2 years Kujala score improved mean (95% confidence interval) 18.7 (16.5-20.9), KOOS QoL 31.0 (28.0-34.0) and Lysholm score 20.0 (17.1-22.9).

Conclusions: Patients with high grade TD treated with Bereiter TP and additional procedures according to the Copenhagen PFI algorithm showed low re-dislocation rate and statistically significant and clinically relevant improvement in patient reported outcome 1 and 2 years after treatment.

Level of evidence: Level II.