Long-term Osseous Remodeling after Femoral Head-neck Junction Osteochondroplasty

OBJECTIVES: Cam-type femoroacetabular impingement (FAI) is characterized by bony deformity of the proximal femoral head-neck junction. Osteochondroplasty at this level removes the impinging bone and has been associated with excellent clinical outcomes. Little is known about how the resection site remodels over long periods of time. Our objective was to describe the osseous remodeling of the femoral head-neck junction after osteochondroplasty at longterm follow-up (minimum of 7-years follow-up). METHODS: A retrospective review of all patients that underwent femoral head-neck osteochondroplasty between October 2004 and December 2006 at our institution was performed. All patients with a minimum 7-year frog-leg lateral radiographic follow-up were included. Head-neck offset (HNO), head-neck offset ratio (HNOR) and α angle were measured on all frog-leg lateral radiographs preoperatively and postoperatively. The degree of cortical remodeling at the osetochondroplasty site was also graded as either none (no sclerotic margin was noted at the resection site), partial (sclerosis was present but in ), or (a continuous cortical line was noted) on the frog-leg lateral radiograph. A paired sample t-test was used for all continuous variables. Longitudinal analyses for HNO, HNOR and α angle were carried out using repeated measures ANOVA. An a priori power analysis utilizing data from a previous short-term study showed that 17 hips were required in order to obtain a power > 85% to find a change in HNOR of 0.02. RESULTS: Eighteen hips, 10 left and 8 right, in 17 patients met inclusion criteria. The average age at the time of surgery was 26.8±SD10.3 years (range, 14-43 years) including nine females and eight males. Average radiographic follow-up was 112.1± SD17.4 months (range, 84-143 months). Initial radiographic correction of the cam-deformity was significant for HNO (7.0±SD2.5 vs. 11.3±SD2.5, p < .001), HNOR (0.12±.04 vs. 0.20±.04, p < .001), and α angle (53.2±14.0 vs. 38.9±5.7, p < .001). A small and gradual change in HNO (11.29±SD2.50 vs. 10.56±SD7.16), HNOR (0.199±.039 vs. 0.195±.138) and α angle (38.92±5.70 vs. 39.36±16.68) was observed across longitudinal follow-up but was not statistically significant (p = .645, p = .851; and p = .835; respectively) (see Figure 1). Only two hips (11%) demonstrated a decrease in HNOR > 0.02. One of these hips had an osteophyte in a patient with progression of osteoarthritis who subsequently underwent total hip arthroplasty three months later. After removing the osteoarthritic patient as an outlier, we continued to observe only small and gradual change in HNO (11.27±SD2.59 vs. 12.13±SD3.56), HNOR (0.20±SD.04 vs. 0.22±SD.70), and α angle (38.8±SD5.9 vs. 35.4±SD4.7) that was not statistically significant (p = 0.631, p = 0.312, p = 0.162; respectively). Recorticalization was present in 78% of hips (13 partial and 1) at an average follow-up of 22.8 months (range, 10-36 months). Recorticalization was present in 100% of hips (6 partial and 12 ) at final follow-up. CONCLUSION: Our study of osseous remodeling of the femoral head-neck junction after osteochondroplasty demonstrated insignificant postoperative changes in HNO, HNOR, and α angle over long-term follow-up. The head-neck junction predictably remodeled to cortical bone at the resection site. This study provides us with additional confidence that an osteochodroplasty at the femoral head-neck junction is durable over long periods of time.