Abstract
BackgroundThe appropriate position of retractors to minimize the risk of femoral nerve palsy remains uncertain. The purpose of this imaging study was to evaluate the distance between the femoral nerve (FN) and anterior acetabulum (AA) in hip osteoarthritis (OA).MethodsForty-one patients with unilateral hip OA underwent magnetic resonance imaging. Three measurement levels were defined and the minimum distance between the femoral nerve (FN) margin and anterior acetabulum (AA) rim was measured on axial T1-weighted images on the OA and normal sides at each level, with reference to an advanced neurography view. The cross-sectional area (CSA) of the iliopsoas muscle was also measured at each level bilaterally by three observers. Distances and CSAs were compared between the OA and normal side. Multiple regression analysis was performed to identify variables associated with the distance in OA.ResultsThe mean minimum FN to AA distances in OA were 19.4 mm at the top of the anterior inferior iliac spine (AIIS), 24.3 mm at the bottom of the AIIS, and 21.0 mm at the tip of the greater trochanter. These distances were significantly shorter than in normal hips at the top and bottom of the AIIS, with mean differences of 1.6 and 5.8 mm, respectively (p = 0.012, p < 0.001). CSAs of the iliopsoas in OA were significantly smaller at all levels (all p < 0.001), with reductions of 10.5 to 17.9%. The CSA of the iliopsoas at the bottom of the AIIS was associated with the FN to AA distance at the same level (p = 0.026). Interobserver reliabilities for measurements were very good to perfect (intraclass correlation coefficients 0.897 to 0.966).ConclusionsTo minimize the risk of femoral nerve palsy, surgeons should consider the change of the femoral nerve to anterior acetabulum distance in osteoarthritic hip surgery.
Highlights
Femoral nerve palsy following total hip arthroplasty (THA) is a serious neurological complication with a rate of 0.01–2.27% [1,2,3] that results in quadriceps femoris weakness with inability to extend the knee, and sensory disturbances that affect the anteromedial thigh or medial leg [4]
There is little information regarding the distance in OA hips, preoperative muscle atrophy occurs in the lower extremity of patients with hip OA [6, 7], which suggests that the femoral nerve (FN) to AA distance, which is associated with iliopsoas thickness, may be shorter than in a normal hip
The objective of this study was to evaluate the distance between the FN and AA in OA hips, and to test the hypothesis that the FN becomes closer to the AA with an atrophic iliopsoas muscle in hip OA compared to a normal hip
Summary
Femoral nerve palsy following total hip arthroplasty (THA) is a serious neurological complication with a rate of 0.01–2.27% [1,2,3] that results in quadriceps femoris weakness with inability to extend the knee, and sensory disturbances that affect the anteromedial thigh or medial leg [4]. A cadaveric study showed that the FN was closest to the AA rim at 90° from the anterior superior iliac spine, which correlated positively with the thickness of the iliopsoas muscle and the femoral length [5] This indicated that placement of retractors at this point had a potential risk of femoral nerve injury during THA, especially in cases with a thin iliopsoas and short femoral length. The appropriate position of retractors to minimize the risk of femoral nerve palsy remains uncertain The purpose of this imaging study was to evaluate the distance between the femoral nerve (FN) and anterior acetabulum (AA) in hip osteoarthritis (OA)
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