Identifying a Reliable Intra-articular Landmark to Avoid Vascular Injury During Transacetabular Screw Fixation: A 3D Computed Tomography Study.

Introduction: Vascular injury during acetabular screw fixation is a life-threatening complication of total hip arthroplasty. This study uses three-dimensional computed tomography to (1) measure absolute distance from the external iliac artery (EIA) to the acetabulum, (2) determine available bone stock along the EIA path, and (3) create a novel acetabular vascular risk map.

Methods: A retrospective radiographic study was conducted using three-dimensional CT. Placement of four 6.5-mm screws in a radial projection from the acetabulum toward the EIA was simulated. The initial screw (Sc1) was placed anteriorly at the center of the anterior labral sulcus. The terminal screw (Sc4) was placed such that any screw placed further posteriorly would not be in contact with the EIA. The shortest distance to the EIA (AD) and acetabular bone depth (BD) were measured.

Results: Fifty patients (100 hips) were included with an average age of 61.9 ± 15.4 years and average body mass index (BMI) of 27.5 ± 5.3 kg/m2. The mean AD at Sc1 was 25.1 ± 2.3 mm (range: 15.4 to 34.9), increasing to 71.5 ± 7.8 mm (range: 21.0 to 144.9) at Sc4. Mean BD at Sc1 was 4.6 ± 0.8 mm (range: 1.4 to 32.0), increasing to 20.1 ± 5.5 mm (range: 2.1 to 36.3) at Sc4. On univariate analysis, male patients demonstrated greater AD and BD at all screw positions. Multiple linear regression revealed an inverse correlation between age and AD and a direct correlation between weight and AD (P value <0.005).

Conclusion: This study identifies the tip of the cotyloid fossa as a reliable intra-articular landmark during total hip arthroplasty. Surgeons should remain wary of potential vascular injury during transacetabular screw fixation, particularly when operating on elderly, female patients.