Letter to the Editor Comparison of acetabular reamings during hip resurfacing versus uncemented total hip arthoplasty

1. SA Brennan, JA Harty, C Gormley, SK O’Rourke. Comparison of acetabular reamings during hip resurfacing versus uncemented total hip arthoplasty. J Orthop Surg (Hong Kong) 2009;17:42–6. To the Editor: We read with interest the article by Brennan et al.1 They concluded that: “In hip resurfacing, the use of an appropriately small femoral component avoids oversizing the acetabular component and removal of excessive bone stock.” This was based on the finding that “The mean weight of acetabular reamings was not significantly different between patients undergoing hip resurfacing and uncemented total hip arthroplasty (THA).” We have 3 concerns. First, the sample size was small and hence no significant difference between the 2 groups may merely represent a type-II error. Second, the surgeons involved were not blinded and this may have inadvertently affected decisions on the amount of reaming. Third, this study was not randomised and “obese elderly women at risk of femoral neck fracture and patients with large subchondral pseudocysts or a history of avascular necrosis of the femoral head were assigned to uncemented THA.” The uncemented THA group is by definition more likely to have lower bone density (weight per unit of volume) than the resurfacing group. Therefore, an equal bone volume/stock removed from patients in the uncemented THA group would have less weight compared to those in the resurfacing group, making the validity of any comparisons questionable.