Comparison of performance of conventional and minimally invasive surgery acetabular reamers

Acetabular reaming in minimally invasive surgery can be done using a newly designed minimally invasive reamer. The new minimally invasive reamer is narrower and chamfered, which results in two sharp edges. This design may result in acetabular cavities with less ideal spheres than those achieved with conventional reaming. We compared the acetabular shapes in nine pairs of cadaver acetabula. Minimally invasive reaming was performed in one acetabulum of each pair, and conventional reaming was performed on the contralateral side. A new digitizing technique, optical three-dimensional scanning, was applied to the reamed acetabula to determine the reamers' performance. Best-fit spheres were calculated for the reamed cavities, and all reamers were measured for exact dimensions. There were small deviations between the diameters of the reamer and the reamed cavity for the minimally invasive (mean, 0.1 mm; standard deviation, 0.5 mm) and conventional (mean, 0.3 mm; standard deviation, 0.4 mm) reamers. There were no significant differences between minimally invasive and conventional reaming. The mean differences between the reamer domes and the measured values showed a discrepancy of 2.2 mm (standard deviation, 0.08 mm) in the minimally invasive surgery group and 2.8 mm (standard deviation, 0.09 mm) in the conventional group. Although the acetabular reamer design has been modified, there were no significant differences in the acetabular shapes after minimally invasive or conventional reaming. LEVEL OF EVIDENCE: Therapeutic Study, Level II (prospective comparative study with no statistically significant difference). See the Guidelines for Authors for a complete description of levels of evidence.