Purpose: To detect alteration of the fatty component by measuring the in vivo lipid and water content of normal-looking femoral heads of patients with and without risk for avascular necrosis (AVN) by using proton MR spectroscopy (MRS). Materials and Methods: Marrow composition was measured by proton MRS (TR/TE = 5000/20 msec) in a sample volume placed in the epiphysis of the intact femoral heads of patients with unilateral osteonecrosis of the hip (group 1, N = 61, then excluding the post-traumatic or steroid user, final N = 45) and age-matched controls (group 2, N = 49). Three response variables were derived from MRS: the lipid linewidth (LW), water LW, and lipid/water ratio. Results: Of the three variables, the lipid and water LWs differed significantly between groups (P < 0.001 and P = 0.05, respectively; t-test). The lipid/water ratio had border-line significance (P = 0.06). The three variables differed significantly between groups when multivariate regression (P < 0.0001) was analyzed; and age and sex had no significant effect on the three dependent variables. Conclusion: Proton MRS can depict alteration in the lipid and water composition of normal-looking femoral heads with and without AVN on the contralateral hip. Proton MRS may be a potential tool for investigating of the femoral head component in vivo and predicting the risk for development of AVN.
