Diseases of the proximal femur and femoroacetabular joint are becoming ever more prevalent in patients with end-stage renal disease due to the pathology associated with hemodialysis (HD).1 As such, joint arthroplasty procedures are becoming increasingly popular in this patient population. In fact, patients undergoing long-term HD are more likely to receive a total hip arthroplasty (THA) compared with the general population.2 Patients with renal failure on HD often undergo cemented femoral component fixation in the setting of joint arthroplasty procedures. The concerns regarding implant choice primarily center on the compromising biomechanical changes in bone of HD patients. Pathology associated with long-term HD, such as renal osteodystrophy, steroid use, and amyloid deposition are believed to increase the risk of mechanical complications in cementless implants, such as inadequate initial component stability, and insufficient bony ingrowth causing early failure.3–8
Nevertheless, uncemented femoral components have been used in patients on long-term HD with varying results.5,7,9 In some reports, however, the outcomes in regard to loosening and survivorship have been similar to cemented components.1,7 These findings suggest that initial component stability and bony ingrowth are sufficient, despite the altered biomechanical properties of the hemodialyzed bone.
This systematic review was conducted to investigate the results of uncemented hip arthroplasty in long-term HD patients, with a special emphasis on fixation of the femoral component. The research questions formulated were: (1) What are the rates of aseptic component loosening? (2) What are revision rates of uncemented components due to aseptic loosening in long-term HD patients?
MATERIALS AND METHODS
Search Strategy and Criteria
The study was exempt by the Institutional Review Board. We conducted a combined search of Medline, Ovid, Medscape, Web of Science, Google Scholar databases for clinical studies reporting clinical results of hip hemiarthroplasty (HA) or THA in patients on long-term HD. The search strategy combined the following keywords: hip, arthroplasty, hemodialysis, uncemented, cemented, and renal failure. The reference lists of each of the studies were reviewed to identify any additional relevant studies. The reference lists of each of the studies were reviewed to identify any additional relevant studies.
Studies meeting the following inclusion criteria were included in the review: (1) clinical studies reporting mechanical complications of cemented or uncemented hip HA or THA in HD patients, and (2) patients with end-stage renal disease managed with HD at the time of the procedure. Exclusion criteria were: (1) non-English language studies, (2) abstract-only publications, (3) studies including revision cases, (4) studies without HD patients, (5) studies containing previously published data, (6) studies on implants other than conventional unipolar or bipolar HA or THA (e.g., resurfacing hip arthroplasty), and (7) studies other than clinical studies such as reviews, case reports, and expert opinions.
Data were extracted by one of the investigators (MGS) and checked for accuracy by a second investigator (SRH). The information retrieved from each study included the following information: title, author, year, location, sample size, mean age, average length of follow-up, and study design. Information from each study also included patient characteristics, component information, and duration of HD, radiographic evidence of loosening, and revision of the femoral component for aseptic loosening. The time from initial operation to revision was recorded whenever possible. No attempts were made to contact the corresponding authors to obtain missing data.
The quality of the studies reviewed was assessed with the Methodological Index for Non-randomized Studies (MINORS) instrument10 (Table 1) and the Center for Evidence-Based Medicine’s (CEBM’s) Levels of Evidence Scale11 (Table 2). MINORS is a valid instrument designed to assesses methodological quality of nonrandomized surgical studies and consists of 12 items, the first eight being specifically for noncomparative studies. The items are scored 0 (not reported), 1 (reported but inadequate), or 2 (reported and adequate). The global ideal score for noncomparative studies is 16. The CEBM Levels of Evidence Scale assesses quality based on study design, with case series receiving lower rankings. The same investigators mentioned earlier scored the studies. The investigators resolved any rating discrepancies through verbal discussion to reach a consensus regarding all studies.
All data were tabulated in Microsoft Excel (2012 version; Microsoft, Redmond, WA) Data pooling (metaanalysis) was not performed because the studies were retrospective, heterogeneous, and diverse in their inclusion and exclusion criteria. We therefore present our results as ranges of survivorship (or reoperation frequencies).
From 36 articles identified in the original search, only eight studies met the inclusion criteria and were included for final analysis (Figure 1).1,3,5–9,12 Study characteristics of the selected articles are presented in Table 3 together with the scores used for quality appraisal. All of the eight studies were retrospective case series and were given a ranking of 4 in the CEBM scale. The average MINORS score for these studies was 7.1 with a range of 6 to 12. All included studies were published between 1994 and 2010. Of the studies, four were conducted in Japan, and two were from the United States. The remaining studies were conducted in Taiwan and the United Kingdom. Two studies reviewed patients undergoing HA,8,9 three reviewed THA,7 and three included both HA and THA.1,3,5
Femoral Component Outcome
All eight studies reported complications including aseptic loosening or stem migration (Table 4). Revision rates for aseptic loosening of the stem ranged from 0% to 100%. The longest identified follow-up of an uncemented femoral component was performed by Toomey and Toomey5 who followed patients for a minimum of 5 yr. None of the four uncemented femoral components were noted to show loosening. Nakai et al.12 evaluated 17 metal cancellous cementless Lübeck (MCCL) prostheses with no radiographic evidence of loosening at mean follow-up of 3.7 yr. Nagoya et al.1 followed a cohort of 11 primary extensively coated anatomic medullary locking (AML) stems for a minimum of 3 yr. None of the of stems followed for a median 8 yr were revised for aseptic loosening. Utilizing four different proximally porous coated femoral implants, Li et al.7 found radiographic loosening in only one hip when reviewed at a median of 7 yr postoperatively.
This systematic review evaluated the follow-up of primary, uncemented femoral components in patients on long-term HD. The literature regarding the durability of uncemented femoral components in this patient population was mixed in both quality and results. The current literature suggests, despite the poor quality of studies, that component stability and osseous integration are sufficient despite the altered biomechanical properties of hemodialyzed bone. However, the literature does not provide a clear recommendation on which method of fixation is best suited for this patient population. The varying outcomes reported in the literature reflect that the factors leading to early loosening of femoral components in dialyzed patients still remain unclear.
The wide array of results reveals the need for future research. All eight studies included in this review were case series. Based on the CEBM scale, these studies were ranked at only 4, which reflects lower quality. Thus, the results should not be ignored, but they should be implemented with caution. The MINORS score averaged 6.8, which also indicates that the quality of the studies was low and the results should be regarded carefully.
Three case studies were highly relevant in reporting the results of various uncemented femoral components.1,7,12 At a median follow-up of 8 yr, Nagoya et al.1 reported no loosening in 11 extensively porous coated femoral implants. Nakai et al.12 showed no radiographic evidence of loosening at mean follow-up of 3.7 yr in 17 patients treated with MCCL prosthesis. In 2010, Li et al.7 demonstrated bone-ingrowth stability in 95% (19 of 20) of hips utilizing four different proximally porous coated femoral implants. The results of these studies suggest that reliable, durable fixation from solid bony ingrowth can be obtained with a variety of cementless implant designs, ranging from proximally porous coated to extensively porous coated. Although the studies are still considered lower quality in design, the results are very promising and provide the foundation for a future prospective, randomized study.
As with other systematic reviews, the results are limited by the availability and quality of available data. This review looked at nonrandomized retrospective studies and thus is weakened by the limitations of nonrandomized study designs. Furthermore, not all necessary data required for comparison between studies were reported. Also, as with any systematic review, publication bias is always a concern. The literature review identified only eight studies meeting our inclusion criteria regarding the outcomes of uncemented femoral components in patients on long-term HD. It is possible that some important studies may have been missed, particularly ones with results that would affect the overall conclusions of this study. This review looked solely at studies published in the English language, and as such may add to the degree of publication bias.
The current literature suggests, despite the poor quality of studies, that component stability and osseous integration are sufficient despite the altered biomechanical properties of hemodialyzed bone. However, the literature does not provide a clear recommendation on which method of fixation is best suited for this patient population. The varying outcomes reported in the literature reflect that the factors leading to early loosening of femoral components in dialyzed patients still remain unclear. Case series cannot answer the question whether HD is a risk factor for component loosening as multivariate analysis is required.
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Keywords:Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved
hip; arthroplasty; hemodialysis; aseptic loosening; uncemented