An Assessment of Hip Strength, Patient Reported Outcomes, and Plasma Inflammatory Biomarkers After Surgical Correction for Symptomatic Femoroacetabular Impingement

OBJECTIVES: Patients with Femoroacetabular impingement (FAI) have been shown to have elevated circulating biomarkers of inflammation and cartilage catabolism, but little is known about whether corrective surgical intervention improves objective measures of hip strength and inflammation. This study measured several variables including pain, function, quality of life, symptoms, hip strength, and inflammatory and cartilage biomarkers in a cohort of subjects undergoing FAI surgery and postoperative (postop) rehabilitation. We hypothesized that surgical FAI repair and completion of a postop rehabilitation program will significantly improve patient reported outcomes (PROs), increase hip flexion and abduction strength measures, and decrease biomarkers of inflammation and cartilage degradation. METHODS: This study was approved by the University of Michigan Medical School IRB (HUM00055335). Male and female patients aged 16-40 years of age, with symptomatic FAI diagnosed by concordant history, physical examination, and imaging findings were eligible for inclusion. Subjects who have undergone previous hip surgery, have a global overcoverage deformity, dysplasia, or degenerative chondral changes greater than Tonnis grade I were excluded. A single, fellowship trained, sports medicine orthopaedic surgeon performed all surgical procedures, and patients underwent a standardized postop rehabilitation program. HOOS questionnaires were assessed at each subject’s preoperative visit (preop), and at 2, 14, 26, and 52 weeks postop. Hip flexion, abduction, and extension were measured at each time point using a BioDex isokinetic dynamometer. High sensitivity C-reactive protein (HS-CRP) and cartilage oligomeric matrix protein (COMP) were measured in plasma using ELISAs. Differences between preop and postop time points were assessed using a mixed-effects model, and data are reported as mean±95% CI. RESULTS: A total of 11 males and 6 females completed the study. Mean age of subjects was 25.2±3.8 years (range 16.0-38.0 years) and BMI of 24.2±2.0 kg/m2 (range 18.1-33.6 kg/m2). For most HOOS subscales, there was a decrease in score at 2 weeks postop, and by 14 weeks activities of daily living (ADL) improved by 18%, pain by 34%, quality of life by 69%, sport and recreation by 36%, and symptoms by 28% compared to preop values (Figure 1A-E). These improvements in HOOS subscales persisted for the duration of the study period (Figure 1A-E). No differences in hip flexion strength were observed, while extension was 20% and 31% significantly higher than preop values at 26 and 52 weeks, and for abduction patients were 34% stronger than preop values at 52 weeks. No differences in HS-CRP or COMP were observed (Figure 1F-J). CONCLUSION: In support of our hypothesis, we observed significant improvements in PROs of hip function, although changes in PROs preceded improvements in objective measures of hip extension and abduction strength. Despite improvements in other planes, no changes in hip flexion were observed. Plasma biomarkers of hip inflammation and cartilage turnover were not reduced by surgical intervention and rehabilitation. FAI surgery and postop rehabilitation is effective at treating pain, and improving patient reported quality of life and symptoms, with modest improvements in hip strength. However, the surgical correction of pathological hip anatomy and improvements in hip strength did not lead to significant differences in markers of inflammation or cartilage turnover.