Acta chirurgiae orthopaedicae
et traumatologiae Čechoslovaca

Acta Chir Orthop Traumatol Cech. 2008; 75(5):339-346 | DOI: 10.55095/achot2008/062

Comparison of Hydroxyapatite-Coated Stems in Total Hip Arthroplasty after a Minimum 10-Years Follow-upOriginal papers

J. GALLO^1,*, I. LANDOR², I. ČECHOVÁ¹, D. JAHODA²

¹ Department of Orthopedics, University Hospital, Faculty of Medicine and Dentistry, Palacký University, Olomouc, Czech Republic

² First Orthopedic Clinic, Charles University, Prague, Czech Republic

PURPOSE OF THE STUDY:
Hydroxypatite coating (HAC) was introduced into total hip arthroplasty (THA) practice to improve the fixation interface between bone and prosthesis. To test this assumption however, long-term follow-up investigations are needed. In this study, we present data for two consecutive series of THA stems with HAC and a minimum ten-year follow-up.

MATERIAL:
Overall, 249 patients (271 hips) were included in the study, of these 122 (135 hips) had Walter hip arthroplasty (WHA group) with a two-layered TiO2/HAC at the proximal part of the stem and 127 (136 hips) had ABG I prostheses (ABG I group) with a single-layered HAC at the proximal part of the stem. Mean length of follow-up was 11.4 years (0.8-13) and 9.8 years (4-12) in WHA and ABG I groups, respectively. Mean age at the time of surgery was 62 years (23-79) and 47 years (21-65) in WHA and ABG I groups, respectively.

METHODS:
Probabilities of implant survival were estimated using the Kaplan-Meier method. Radiographic data were included to construct the worst-case scenario. Differences in survival curves were evaluated by Gehan's Wilcoxon test. Harris hip score was used to compare preoperative status with that of final follow-up.

RESULTS:
The overall survival of WHA was significantly better than the ABG I (0.85 versus 0.66; p < 0.05). The main reason for a high revision rate in ABG I was periprosthetic osteolysis followed by aseptic loosening. With regard to stems, the survivorship curve for the Walter stem was significantly better than for the ABG I stem even when radiographic results were included (p = 0.0002). In the WHA group, two stems (1.5%) were revised due to sepsis, in contrast to thirty-one stems (23.5%) revised in the ABG I group due to osteolysis and aseptic loosening (p < 0.05). Significant improvement was achieved in both groups under study in terms of Harris hip score.

DISCUSSION:
Data presented here appear surprising at first glance because the differences between the stems under study are only minor. The failure in ABG I was most probably caused by poor polyethylene quality and poor locking mechanism of polyethylene liner in the metallic shell. In addition, HAC used in ABG I prosthesis was not able to prevent the development of polyethylene disease stimulated by high wear rate.

CONCLUSION:
This study revealed excellent survivorship for WHA stems after a minimum ten-year survival and significantly poorer survivorship for the ABG I stems. This may be explained at least particularly by combined two-layered HAC used in WHA stems which provide simultaneously endurable bone interlocking and effective barrier against expansion of polyethylene disease.

Keywords: total hip replacement, hydroxyapatite, Walter hip arthroplasty, ABG I, survival analysis, polyethylene disease, osteolysis

Accepted: July 15, 2008; Published: October 1, 2008  Show citation