ACCURACY OF ACETABULAR REAMERS IN TOTAL HIP ARTHROPLASTY.

Introduction: Serial reamers of incremental diameter are used in the preparation of the acetabulum in Total Hip Arthroplasty. If the reamer is blunt then the size of the reamed acetabulum may not accurately represent the size of the last reamer used. This inaccuracy may then adversely affect implant selection or implantation. Methods: Traditional debris-retaining cheese grater ace-tabular reamers were used to create a cavity in a foam block, following a standardised technique. A casting was then made of the cavity, the diameter of the cast measured and compared to that of the reamer. Accuracy was defined as the difference between the observed and expected diameters. Measurements were collected for five different hip systems (78 reamers in total) Results: Sixty-four out of the seventy-eight reamer tested were inaccurate. There was a significant difference between groups. Only reamers from one of the five systems tested consistently created cavities which accurately matched their stated size. Two systems consistently produced a cavity that was at least 1mm smaller than intended. In the majority of cases the mid-range reamers, sizes (46–52mm) were the most inaccurate. Discussion: The majority of acetabular reamers in our study were inaccurate. If this is unintentional, it suggests reamers may become increasingly blunt with use and should be calibrated, sharpened or replaced.