, Volume 472, Issue 3, pp 943-950
Date: 26 Oct 2013

Long-term Results and Bone Remodeling After THA With a Short, Metaphyseal-fitting Anatomic Cementless Stem

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Topic
Hip

Abstract

Background

Long-term results of standard total hip arthroplasty (THA) in young patients were not optimal. There are a number of reported disadvantages to longer cementless stems in THA including thigh pain and proximal stress shielding. However, it is unknown whether a short, metaphyseal-fitting anatomic stem without diaphyseal fixation, which represents a possible alternative, will maintain fixation over the longer term.

Question/purposes

We therefore evaluated long-term (1) clinical results using validated scoring instruments; (2) osseointegration and bone remodeling; (3) complications; and (4) rates of revision and osteolysis in patients younger than 65 years who underwent THA with a short, metaphyseal-fitting anatomic cementless stem.

Methods

We reviewed 500 patients (630 hips) younger than 65 years (mean age at surgery, 52.7 years) who underwent THA with the Immediate Postoperative Stability stem (IPS; DePuy, Leeds, UK) by one surgeon (Y-HK) from January 1995 to March 2002. Demographic data, Harris hip score, WOMAC score, UCLA activity score, and radiographic data were recorded. All patients underwent dual-energy x-ray absorptiometry scanning of the acetabulum and proximal femur at 2 weeks after the operation and at final followup to determine stress shielding. Thigh pain was specifically investigated and scored by patients on a visual analog scale. Other complications were recorded. We determined component survival rates at 15 years using revision and aseptic loosening as end points. Minimum followup was 11 years (mean, 15.8 years; range, 11–18 years).

Results

The clinical and functional results improved significantly for the Harris hip score, WOMAC, and UCLA activity scores (p < 0.001). At latest followup, mean Harris hip, WOMAC, and UCLA activity scores were 94 (range, 71–100), 15 (range, 5–29), and 7.9 (range, 6–9) points, respectively. All hips had osseous integration of the acetabular and femoral components. No patients had thigh pain. Four hips (0.6%) had deep infection and four (0.6%) had a recurrent dislocation. No patients had Grade 3 stress shielding. Fifteen-year survival rates were 98.7% (95% confidence interval [CI], 0.95–1.00) for the acetabular component and 99.4% (95% CI, 0.97–1.00) for the femoral component with revision as the end point and 100% (95% CI, 0.98–1.00) for both components with aseptic loosening as the end point.

Conclusions

The short, metaphyseal-fitting anatomic cementless femoral stem provided stable fixation without relying on diaphyseal fixation in younger patients, suggesting metaphyseal fitting alone is sufficient in young patients who have good bone quality. Because we observed no thigh pain and little stress shielding in our patients, modifying the distal stem design as is done with this implant might be advantageous, but this would need to be determined in future comparative studies.

Level of Evidence

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Each author certifies that he or she, or a member of his or her immediate family, has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
A comment to this article is available at http://dx.doi.org/10.1007/s11999-013-3402-z.