Summary

This study aims to investigate the correlation between changes in patellar height, as measured by CD and IS ratios, and patient-reported outcomes (PROs) following DFO

Abstract

Introduction

Distal femoral osteotomy (DFO) is an established surgical intervention aimed at correcting malalignment in the knee, which can alleviate pain and improve function in patients with lateral compartment osteoarthritis or valgus deformities. It is also utilized for lateral patellar instability. Despite its benefits, the impact of DFO on patellar height, specifically as measured by the Caton-Deschamps (CD) index and the Insall-Salvati (IS) ratio, remains unclear. Changes in patellar height can influence knee biomechanics and potentially affect clinical outcomes and patient satisfaction. This study aims to investigate the correlation between changes in patellar height, as measured by CD and IS ratios, and patient-reported outcomes (PROs) following DFO

Methods

Patients undergoing DFO from January 2010 to August 2023 were identified. Indications for DFO included valgus alignment with mLDFA < 86, osteoarthritis of the lateral compartment and patellar instability. Exclusion criteria included individuals without pre-operative and post-operative lateral radiographs of the knee, or patients with less than 2 years of follow-up. Demographic data including sex, age, and body mass index (BMI) at time of surgery was obtained. Outcomes were assessed using follow-up questionnaires that evaluated symptom resolution, patient satisfaction, Tegner Activity Scale, IKDC, KOOS, Lysholm score, and return to sport. Radiological measurements including CD and IS ratios were obtained using both pre-operative and post-operative lateral radiographs of the knee.

Results

The final size of the cohort was 52 patients who underwent DFO. 31 (59.6%) patients completed PROs. Average age was 33.9 ± 9.9 years. The average degree of correction was 6.69± 3.37 and all of the DFOs included were lateral opening wedge osteotomies. The cohort was 38.5% male and the average BMI was 30.2 ± 5.4 kg/m2. We found no significant difference in pre-operative versus post-operative CDI in patients undergoing DFO (0.979 ± 0.196 vs. 1.002 ± 0.171, p=0.203). There was no significant difference in pre-operative versus post-operative IS in patients undergoing DFO (1.271 ± 0.223 vs. 1.2664 ± 0.206, p=0.768). A linear regression analysis controlling for age, sex and BMI found no significant correlation between change in pre-operative to post-operative patellar height (b=0.163, p=0.174). Linear regression analyses controlling for age, sex and BMI found no significant correlation between change in pre-operative to post-operative CD or IS values and functional outcome scores at final follow up including IKDC, Lysholm, VAS pain at final follow up, VAS satisfaction at final follow up, Tegner score at final follow-up, VAS sports, KOOS Symptoms, KOOS Pain, KOOS ADL, KOOS Sports, and KOOS QoL. A logistic regression analysis controlling for age, sex and BMI found no significant correlation between change in patellar height (CD and IS) and return to sport (p=0.506 and p=0.803, respectively).

Discussion And Conclusion

In this study, we found no significant difference in pre-operative and post-operative patellar height in patients who underwent DFO for coronal malalignment. Additionally, we found no correlation between the change in CD and IS ratio and patient-reported outcomes (PROs) following DFO. Our findings suggest that alterations in patellar height in patients undergoing DFO does not affect clinical outcomes such as pain, function, and return to sports in this patient population. These results indicate that while patellar height measurements can provide valuable insights into knee biomechanics, they may not be predictive of overall patient satisfaction and symptom resolution post-DFO. Further research with larger sample sizes and longer follow-up periods is warranted to validate these findings and explore other potential factors influencing postoperative outcomes.