The femoral head centre is rarely level with the tip of the GT.

Presenting Author – Sanjeev Gupta
Introduction The superior tip of the Greater Trochanter (GT) is commonly used as an intraoperative reference for restoring leg length during total hip arthroplasty. The aim of this study was to quantify the height of the native femoral head centre relative to the superior tip of the GT in a series of 519 non-arthritic femurs, using 3D imaging. Methods Pre-operatively, 519 patients with unilateral osteoarthritis had CT scans performed as part of their routine planning for THR. Within the 3D planning, each patient had the height of their contralateral, non-arthritic, femoral head centre calculated in relation to the superior tip of the GT. This distance was matched on the diseased side during the 3D templating. If the head centre was below the tip of GT it was assigned a negative value. Results The mean height of the native femoral head centre relative to the superior tip of the GT was -7.3mm (SD = 5.1). The range was -27.1mm to 9.8mm. Conclusions • The height of the femoral head centre relative to the GT is variable and rarely sits level with the superior tip. • On average, it is 7mm below the GT. • Surgeons should be aware of this when intraoperatively restoring leg length and should avoid generalised assumptions regarding patient anatomy.