Commentary & Perspective

Commentary & Perspective on
"Twenty-five-Year Results After Charnley Total Hip Arthroplasty in Patients Less than Fifty Years Old. A Concise Follow-up of a Previous Report"
by Jay D. Keener, MD, et al.
and on
"Results of Porous-Coated Anatomic Total Hip Arthroplasty without Cement at Fifteen Years. A Concise Follow-up of a Previous Report"
by J.A. Bojescul, MD, et al.

Commentary & Perspective by
Daniel J. Berry, MD*,
Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN

Two articles in the June 2003 issue of The Journal are long-term follow-up reports of total hip arthroplasty performed primarily in younger patients. Both articles, presented in The Journal's new concise format for follow-up reports, are updates of studies previously published in The Journal^1,2. Comparison of the two studies and independent evaluation of the findings of each allow the reader to draw valuable conclusions.

In "Twenty-five-Year Results After Charnley Total Hip Arthroplasty in Patients Less than Fifty Years Old," Keener et al. have provided detailed information pertaining to the durability of Charnley total hip arthroplasty in younger patients. It is notable that 69% (sixty-four) of the ninety-three prosthetic hips in their series were well-functioning at the latest follow-up evaluation or at the time of the patient's death. Of those that required revision only 5% required more than one revision arthroplasty. The authors have provided detailed data showing that these patients had retained a reasonable level of function at the most recent follow-up, but that level was less than that in normal subjects who were more than fifty-five years old. Importantly, Keener et al. demonstrated that the number of comorbidities in each patient and the presence of a musculoskeletal comorbidity had a significant effect on each WOMAC subscale score.

The article by Bojescul et al., "Results of Porous-Coated Anatomic Total Hip Arthroplasty without Cement at Fifteen Years," is a report of one of the longest-term studies in the literature on primary cementless total hip arthroplasty. The mean age of the patients at the time of the arthroplasty was fifty-eight years—relatively young—but the age range was broad (twenty-two to eighty-one years). The important findings of this study concern the fifteen-year survival rates of the primary arthroplasties: 80% were free of revision for any reason, 86% were free of revision of the acetabular component, and 92% were free of revision of the femoral component. These rates are not the best when compared with those in the most favorable reports of cemented arthroplasty, but when one considers that these are the results for a first-generation cementless implant, they are encouraging. In the entire original cohort of 100 Porous Coated Anatomic (PCA) total hip replacements in ninety-one patients, serial radiographs showed that, at an average follow-up of fifteen years, ninety-four of the femoral components had become bone-ingrown, one was stable with fibrous ingrowth, and five were unstable. With this first-generation femoral implant, at fifteen years 13% of patients (eight of sixty-four) had some thigh pain, but it should be noted that no hip in this series was revised specifically because of thigh pain. In contrast with the favorable outcome of durable femoral fixation, twenty-one acetabular components in the entire group ultimately demonstrated radiographic loosening. The acetabular loosening was associated with polyethylene wear. Loosening associated with marked polyethylene wear is more common with this particular cementless acetabular component (PCA) in comparison with some other cementless designs that tend to remain well fixed despite marked polyethylene wear and periprosthetic osteolysis. Of note, many of these acetabular components failed after ten years, while very few femoral stems were revised after ten years.

Several important conclusions emerge from an examination of both of these articles. The failure rate for the acetabular components, in both the cemented Charnley design as well as the cementless PCA design, was markedly higher than that for the femoral components. Failures of the acetabular component occurred in both groups predominantly because of loosening. It has been understood that acetabular loosening in cemented designs is, at least in part, related to polyethylene wear. Factors that contributed to failure of the acetabular components in the PCA series reported by Bojescul et al. were the combined use of a 32-mm femoral head and polyethylene that was sterilized with gamma radiation in air, which probably contributed to the high volumetric wear rate of the polyethylene, and, in this patient cohort, led to a high rate of acetabular revision because of loosening and/or associated osteolysis.

An important conclusion of both studies is that failure of the acetabular component because of either loosening (for cemented cups) or polyethylene wear with or without loosening (for uncemented sockets) remains a major problem in total hip arthroplasty performed in relatively young, active patients.

Cemented or uncemented fixation can provide low rates of femoral component loosening over the long term. The data in these two papers are consistent with those in many other studies with similar findings^3-5. It is, however, important to note that these findings are probably specific to the designs used: some cemented femoral implants have performed very well over the long term, whereas others have performed much less well than did the smooth flatback femoral stem used in the series of Charnley total hip arthroplasties reported by Keener et al. The relatively high rate of durable femoral fixation in the cementless series reported by Bojescul et al. demonstrates that even with a first-generation, proximally porous-coated uncemented implant design and the nascent surgical techniques for cementless arthroplasty (and the associated learning curve of the senior author), the durability of the femoral fixation was impressive. Notably, the femoral component, once bone ingrown, did not tend toward late loosening. It is likely that with the continued evolution of cementless implant designs and greater surgeon experience with these implants, the results of cementless femoral components will be even better than the already relatively good results reported in this series.

Finally, these two studies affirm the value of total hip arthroplasty, even in relatively young patients. Though both the cemented and cementless components used in these studies were early designs, the results indicate the benefits of their use in the great majority of patients. As with all good studies, these reports also reveal areas in which there is room for improvement: both series highlight the interrelated problems of bearing surface wear and acetabular component failure, which have become the focus of efforts made in the last decade to improve the results of total hip arthroplasty.

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Depuy/Johnson and Johnson). In addition, a commercial entity (Depuy/Johnson and Johnson) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Callaghan JJ, Forest EE, Olejniczak JP, Goetz DD, Johnston RC. Charnley total hip arthroplasty in patients less than fifty years old. A twenty to twenty-five-year follow-up note. J Bone Joint Surg Am. 1998;80:704-14.
2. Callaghan JJ, Dysart SH, Savory CG. The uncemented porous-coated anatomic total hip prosthesis. Two-year results of a prospective consecutive series. J Bone Joint Surg Am. 1988;70:337-46.
3. Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J Bone Joint Surg Am. 2002;84:171-7.
4. Geesink RG, Hoefnagels NH. Six-year results of hydroxyapatite-coated total hip replacement. J Bone Joint Surg Br. 1995;77:534-47.
5. Engh CA Jr, Culpepper WJ 2nd, Engh CA. Long-term results of use of the anatomic medullary locking prosthesis in total hip arthroplasty. J Bone Joint Surg Am. 1997;79:177-84.