Vertical acetabular positioning with an inclinometer in total hip arthroplasty

Vertical acetabular implant positioning is an important technical aspect in total hip arthroplasty. To evaluate the potential benefit of an inclinometer, 50 cup insertions were done on a cadaver pelvis. Acetabular cup vertical angles averaged 44.4 degrees +/- 11.4 degrees by visuospatial perception and 42.2 degrees +/- 3.8 degrees with the inclinometer. All cups were within the safe angle range of 40 degrees to 49 degrees with the inclinometer compared with 64% of cups by visuospatial perception. Use of the inclinometer reduced variability by a factor of 2.0 to 4.5. The addition of an inclinometer for acetabular cup insertion increases the probability of positioning the cup within a vertical safe range during total hip arthroplasty on a cadaver pelvis, suggesting that it could be a useful adjunct in clinical practice.