A PROSPECTIVE RANDOMIZED TRIAL OF CORE DECOMPRESSION VERSUS CORE DECOMPRESSION AND CEMENT PACKING FOR PRE-COLLAPSE OSTEONECROSIS OF THE FEMORAL HEAD

Abstract

Introduction: Osteoneocrosis of the femoral head (ONFH) is difficult to treat as collapse frequently occurs after core decompression. This may be due to the failure to provide structural support during revascularization and healing after core decompression. Cement (PMMA) packing for giant cell tumors of bone has been shown to provide adequate support of the subchondral bone. This study was undertaken to determine whether or not the addition of PMMA packing provides any benefit to the outcome of core decompression for ONFH. Secondary objectives were to assess various factors for prognostic significance.

Materials and Methods: A prospective, randomized trial of core decompression ± cement (PMMA) packing for ARCO stage I or II ONFH was conducted. Outcome measures were: radiographic (XR) progression, conversion to hip arthroplasty (THA), WOMAC, SF 36, and Harris Hip scores (HHS). Survivorship analysis using Kaplan-Meier estimates was performed.

Results: The time to XR progression at 3 years for the core vs. core + PMMA cohorts was 42 ± 11 mo vs. 45 ± 12 mo, p=0.68, respectively. The time to THA at 3 yrs for the core vs. core± PMMA groups was 42 ± 11 mo vs. 67 ± 12 mo, p=0.17, respectively. Comparing pre vs.1 year postoperative WOMAC scores, for the core + PMMA group, there were statistically significant improvements in pain (p=0.082), stiffness (p=0.03), physical function (p= 0.05) and total score (p=0.03) whereas for the core decompression group, there was no significant difference noted among the same domains (p=0.06, 0.25, 0.74, 0.88) respectively. The SF 36 role physical domain score was higher for the core + PMMA group at 1 year (p=0.07) and 15 mos (p=0.09) but was no different at 3 yrs (p=85). For the physical function and bodily physical domains, there was no difference at any time point. The factors of smoking (y/n) p=0.003, location (central/ medial/lateral) p=0.03, per cent femoral head involvement (< 15, 15–30, > 30%) p=0.05, age (< 40, ≥40 yrs), and necrotic arc (< 40, ≥40) p=0.005, were significant predictors for XR progression on univariate analysis but upon Cox multivariate regression, only age (p=0.09), smoking (p=0.07), and necrotic arc (p=0.04) remained independently, statistically significant.

Discussion: The addition of PMMA packing to core decompression for pre-collapse ONFH (ARCO I/II) does not improve the outcome of treatment as measured by XR progression and conversion to THA. There is a benefit to PMMA packing for pain relief at 12–15 mos. as measured by the mean WOMAC, HHS and SF 36/role physical scores but this benefit ceases at 3 years after treatment. Age ≥40 years, smoking, and necrotic arc ≥40 are all predictive of eventual progression of disease on XR.