We previously reported the average ten-year results associated with the use of porous-coated noncemented acetabular shells that were placed at a high hip center at the time of revision total hip arthroplasty in thirty-four patients (thirty-six hips) with severe acetabular bone loss. We now report the average 16.8-year results for twenty-one patients (twenty-three hips). Of the original cohort of forty-four patients (forty-six hips), thirty-nine patients (forty-one hips; 89%) retained the shell. Two shells (4.3%) were revised because of aseptic loosening, and three (6.5%) were revised because of infection. Six femoral components were revised because of femoral osteolysis, and seven were revised because of aseptic loosening without osteolysis. On the basis of our results after an average duration of follow-up of 16.8 years, we believe that the placement of an uncemented acetabular component at a high hip center continues to be an excellent technique for revision total hip arthroplasty in selected patients with severe acetabular bone loss.
Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.
1 Kelly J. Hendricks, MD Department of Orthopaedic Surgery, University of Kansas Medical Center, MS 3017, 3905 Rainbow Boulevard, Kansas City, KS 66210. E-mail address for K.J. Hendricks: firstname.lastname@example.org
2 William H. Harris, MD, DSc Harris Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, 55 Fruit Street GRJ 1126, Boston, MA, 02114. E-mail address for W.H. Harris: email@example.com
We previously reported the results of revision total hip arthroplasty after an average duration of follow-up of 10.4 years (range, 8.5 to 12.7 years) for thirty-four patients (thirty-six hips), from an original pool of forty-four patients (forty-six hips), in whom a cementless acetabular component (Harris-Galante I or Harris-Galante II; Zimmer, Warsaw, Indiana) was placed at least 35 mm proximal to the interteardrop line because of severely compromised bone stock1. All components but one were fixed with multiple screws after line-to-line reaming of the acetabulum (Fig. 1). The average hip center was 43 mm (range, 37 to 77 mm) proximal to the interteardrop line. The femoral component was revised simultaneously in thirty-three of the forty-six hips, but no well-fixed femoral components were revised. The mean age of the patients at the time of the revision surgery was fifty-two years (range, twenty-five to eighty-one years).
At the time of the ten-year follow-up, one of the original forty-six hips had undergone re-revision of the acetabular shell because of aseptic loosening, with one additional shell scheduled for re-revision because of aseptic loosening. In three other hips, the acetabular shell had been removed because of infection. Nonprogressive pelvic osteolysis was noted in two of the thirty-six hips that were followed for ten years or more, and two hips demonstrated a continuous nonprogressive radiolucent line about the acetabular component. The mean Harris hip score was 81 points (range, 56 to 100 points).
The central purpose of the present report is to update the results of acetabular reconstruction with use of one type of cementless acetabular component, placed at a high hip center, after a mean duration of follow-up of 16.8 years (range, fifteen to 17.9 years). We also report the results for the femoral components, which were quite varied in design, fixation method, and duration in situ.
Of the original group of forty-four patients (forty-six hips), twelve patients (twelve hips) had died, two patients (two hips) were too ill to return for follow-up, four patients (four hips) were lost to follow-up, and five patients (five hips) had undergone re-revision of the acetabular shell, leaving twenty-one patients (twenty-three hips) available for the present study. The two patients (two hips) who were too ill to return for follow-up had not required repeat revision. In the group of twelve patients (twelve hips) who had died prior to the minimum fifteen-year follow-up, the average interval from the index revision to the time of death was 9.82 years (range, four to fourteen years) and no patient had undergone re-revision or reoperation for any reason. Twenty-one hips had current radiographs and clinical follow-up, one had clinical follow-up only, and one had radiographic follow-up only. In the case of the one patient who lacked current radiographs, the most recent radiographs (made eleven years after the index revision) demonstrated no osteolysis or evidence of cup loosening. In the case of the one patient without current clinical follow-up, the most recent Harris hip score (determined twelve years after the index revision) was 84 points.
Clinical and radiographic data on the twenty-one patients (twenty-three hips) had been collected prospectively, and the minimum fifteen-year data were evaluated retrospectively. The average age of the patients at the time of the latest follow-up was 64.9 years (range, forty-four to eighty-nine years). Institutional review board approval was obtained before the start of this study.
Physical examination was performed, radiographs were made, and clinical evaluations (including determination of the Harris hip score2 and the University of California at Los Angeles [UCLA]3 functional index) were performed. Designation of radiographic signs of loosening and evaluation of radiolucent lines were performed according to previously published criteria4. All radiolucent zones measuring >3 mm in width were considered to represent osteolysis. The locations of periacetabular radiolucencies were described according to the system of DeLee and Charnley5. The distance proximal to the interteardrop line and the lateral distance from a vertical line from the lateral edge of the teardrop were used as references to determine vertical and horizontal displacement of the hip center. Migration of ≥4 mm or an angular change of >5° was deemed to be evidence of migration of the acetabular component. Linear head penetration was measured with use of the computer-assisted methods of Livermore et al.6. For patients who underwent exchange of the acetabular liner, the final radiograph that had been made before acetabular exchange was used to determine the femoral head penetration before reoperation and thus the wear rate. Measurements of position, linear wear, and osteolysis were performed as described in our previous report1. Acetabular bone deficiency at the time of the index operation was classified according to both the American Academy of Orthopaedic Surgeons (AAOS)7 and Tanzer systems8. According to the AAOS system, there were two stage-1, seven stage-2, and thirty-seven stage-3 hips. According to the Tanzer system, there were two stage-I, five stage-II, nineteen stage-IIIA, eighteen stage-IIIB, and two stage-IV hips.
For the twenty patients (twenty-two hips) with the acetabular shell still in place who had calculation of the Harris hip score at the time of the latest evaluation, the average score improved from 52 points preoperatively to 73 points (range, 44 to 98) at the time of the most recent follow-up. Seven hips were rated as poor (Harris hip score, <70). Of these seven hips, four were in four patients with femoral osteolysis associated with a loose femoral component, two were in patients who were substantially compromised by chronic low-back pain, and one was in a patient who had had a stroke and had markedly reduced activity.
In the entire group of forty-six hips, five acetabular shells (10.9%) had been re-revised because of aseptic loosening (two shells) or infection (three shells). The two re-revisions that were performed because of aseptic loosening had been done at sixty-nine and 121 months after the index revision. Both shells had migrated medially into the pelvis. One shell, in addition to being loose, demonstrated substantial periprosthetic osteolysis accompanied by a continuous radiolucent line. The shell that was re-revised at sixty-nine months after the index revision had been placed 42.5 mm proximal to the interteardrop line in a hip with Paprosky grade-IIIB bone stock9, and had had little intrinsic stability at the time of the index revision. The shell that was re-revised at 121 months had been placed 52 mm proximal to the interteardrop line in a hip with Paprosky grade-IIIA9 bone stock. Neither of these shells had contact with the pubis. Seven additional hips underwent isolated exchange of the polyethylene liner with retention of the acetabular shell. Two of these seven exchanges were performed because of liner wear. One other liner was exchanged to cross-linked polyethylene incidentally at the time of bone-grafting for the treatment of a pubic stress fracture. No osteolysis was evident radiographically around either the femoral or the acetabular component. The four remaining liners were exchanged for a cross-linked polyethylene liner incidentally at the time of femoral revision. Of the twenty-three hips with a minimum of fifteen years of follow-up, four had radiolucent lines in one acetabular zone5, three had radiolucent lines in two zones, and four had radiolucent lines in all three zones. Of the four hips with radiolucent lines in all three zones, none had a continuous radiolucent line and none had migration of the shell.
For the entire study group of forty-six hips, at an average of 16.8 years after the index revision, Kaplan-Meier analysis revealed a survival rate of 93% with revision of the acetabular shell because of aseptic loosening as the end point (Fig. 2), 89% with revision of the shell for any reason as the end point, and 74% with repeat acetabular surgery for any reason as the end point (Fig. 3).
In the original cohort of forty-six hips, sixteen femoral components (35%) had been revised by the time of the minimum fifteen-year follow-up; specifically, three femoral components (6.5%) had been re-revised because of infection, six (13%) had been re-revised because of femoral osteolysis, and seven (15%) had been re-revised because of aseptic loosening without osteolysis. The revisions that were performed because of osteolysis were done at an average of nine years (range, 5.5 to 14.5 years) after the index revision in hips with proximal osteolysis in Gruen zones 1, 2, and 7. The seven revisions that were performed because of aseptic loosening were done at an average of 11.7 years (range, 5.75 to 15.8 years) after the index revision.
At the time of the final follow-up, Kaplan-Meier analysis revealed a survival rate of 61% with revision or removal of either the femoral or the acetabular component for any reason as the end point, 69.6% with aseptic loosening of either the femoral or the acetabular component as the end point, and 81.5% with reoperations of the acetabular component because of aseptic failure (i.e., shell revision or liner revision) as the end point.
Dislocation occurred in five hips (10.9%) at an average of one year (range, 0.25 to four years) after the index revision. Four of the five hips with dislocation had had a trochanteric advancement, whereas one had not. Two hips with a single dislocation and two hips with recurrent dislocations were successfully treated with closed reduction and bracing. The fifth hip was in a patient who had a complex problem involving prior tuberculosis, a failed cup arthroplasty, and a failed total hip replacement. The index revision was followed by infection and recurrent dislocations. This patient eventually required a resection arthroplasty to control the infection.
The femoral head penetration rate averaged 0.16 mm/yr (range, 0.027 to 0.287 mm/yr) among the twenty-two hips with radiographs at the minimum fifteen-year follow-up, whereas the ten-year follow-up penetration rate had averaged 0.17 mm/yr. No hip center changed by >3 mm as compared with the position on the initial index postoperative radiograph in any of the hips that were evaluated. The hip center in this group averaged 43.5 mm (range, 37 to 77 mm) proximal to the interteardrop line on the immediate preoperative radiograph and 38.6 (range, 34 to 74 mm) at the time of the most recent evaluation.
In the interval between the ten-year report and the present report, no new osteolytic lesions developed and no radiographically evident progression of the extant lesions occurred.
The cementless acetabular shell that was evaluated in the present study, when placed at a high hip center, demonstrated good performance and a low rate of mechanical, radiographic, or clinical loosening at an average of 16.8 years follow-up, despite the severe bone loss that was present at the time of the index revision in many cases.
Infection (prevalence, 6.5%) was the most common reason for removal of the acetabular shell in our series. Dislocation occurred in five hips (10.9%), four of which did not require additional surgery. Because of the historically high rate of dislocation after revision hip surgery, we now routinely increase the femoral head size (to >32 mm) at the time of revision for any reason, not just acetabular failure. However, this is not always possible with a high hip center because of the relative paucity of bone proximally in the ilium, which may mandate the use of a smaller acetabular component. For this reason, we advocate the use of a large acetabular component placed against host bone whenever possible10,11; however, in cases of severe bone loss, a high hip center may be the preferred reconstructive option.
The rate of femoral head penetration in the present series was higher than the rates that have been reported by some investigators for polyethylene that has been sterilized with gamma radiation in air. This raises the question that placement at a high hip center may increase the wear rate of conventional polyethylene. The hips in the present study were not generally placed lateral to the original hip center, and trochanteric advancements were performed to keep the joint-reaction forces low and to optimize hip biomechanics. Independent of whether or not the high hip center is causally related to an increase in wear of gamma-in-air-irradiated polyethylene or whether other factors could be involved, we recommend the use of alternate bearing surfaces for high hip center reconstructions. This would allow for the placement of a more wear-resistant bearing surface (and preferably, if possible, one that would allow for the use of a larger femoral head as well). Despite these higher penetration rates, the prevalence of pelvic osteolysis was low and none of our patients in this small group demonstrated progression of osteolytic lesions during the interval from the ten to the fifteen-year follow-up as judged on the basis of plain radiographs. We attribute the discrepancy between a higher penetration rate (increased polyethylene wear) and the absence of new or progressive osteolytic lesions to three possible explanations. First, the higher penetration rate extended over the first decade with only a low prevalence of osteolysis. Second, the activity levels of the patients were likely reduced both by increasing age and by the effects of the revision hip operations. Third, only plain radiographs were used to detect osteolysis, a notably inaccurate method.
On the basis of our results and those of others12-14, we recommend and continue to use uncemented acetabular components, augmented with multiple screws and placed at a high hip center, for acetabular revision in selected patients with severe acetabular bone deficiency. ▪
Dearborn JT, Harris WH. High placement of an acetabular component inserted without cement in a revision total hip arthroplasty. Results after a mean of ten years. J Bone Joint Surg Am. 1999;81:469-80.
In support of their research for or preparation of this manuscript, one or more of the authors received grants or outside funding from the William H. Harris Foundation. In addition, one or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Zimmer, Inc.). Also, a commercial entity (Zimmer, Inc.) 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 authors are affiliated or associated.
* Original Publication Cited Here...
Investigation performed at the Department of Orthopaedic Surgery and the Harris Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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