Commentary & Perspective

Commentary & Perspective on
"Comparison of Proximal Porous-Coated and Grit-Blasted Surfaces of Hydroxyapatite-Coated Stems"
by Ye-Yeon Won, MD, et al.

Commentary & Perspective by
John J. Callaghan, MD*,
University of Iowa Hospitals and Clinics, Iowa City, Iowa

In "Comparison of Proximal Porous-Coated and Grit-Blasted Surfaces on Hydroxyapatite-Coated Stems," Won, Dorr, and Wan evaluate the variable of porous-coated and nonporous-coated (grit-blasted) stems in relation to clinical and radiographic results at mean follow-up of 2.5 years. Their study is unique in that each patient had bilateral arthritis with the porous-coated stem implanted in one hip and the grit blasted stem implanted in the other, thus eliminating the potential selection biases of gender, age, weight, and activity level. The authors demonstrate no difference in clinical or radiographic results with identical bone remodeling around the implants during the 2.5-year average follow-up period.

The authors deserve great credit for performing this study in a prospective manner in patients with bilateral hip arthritis. All radiographs were reviewed independent of the surgeon. The authors rightfully conclude that with this particular proximally hydroxyapatite-coated implant, the presence of proximal porous coating had no effect on the clinical results or the radiographic evidence of fixation at 2.5 years after operation.

In addition to these findings, the authors note that a weakness of this study is the small numbers of patients (thirty-four hips in seventeen patients). I concur that a much larger series would be needed to ensure that their conclusions are not the result of a type-II statistical error. In addition, it would be appropriate to know the number of patients with bilateral hip arthritis who underwent bilateral procedures but would not agree to enter in the study. This would better allow the reader to determine the generalizability of the results of the study. A large percentage of the study group was male (more than two-thirds), and the average age was 62 years. It would be helpful to know the gender and age distribution of the surgeons' entire practice to put this study in proper perspective. In addition, it is unfortunate that these arthroplasties were performed while the surgeon was using the ill-fated Interop acetabular components (Centerpulse Orthopedics). This could confound the short-term and long-term evaluation of these stems.

Until the last paragraph, the authors are correct in explaining that these results should not be generalized to other stems. They have previously demonstrated that the results with the porous-coated version of this implant are better with rather than without hydroxyapatite coating, and this has not been the case for all implants. They have not performed a comparison of grit-blasted components with and without hydroxyapatite coating, so they should refrain from "inferring" that those results would be the same. I look forward to seeing a longer follow-up of this patient cohort to see if the results are similar at an extended period of follow-up.

*The author did not receive grants or outside funding in support of research or preparation of this manuscript. The author did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

Copyright © 2004 by the The Journal of Bone and Joint Surgery, Inc.