Cementless acetabular replacement in patients with rheumatoid arthritisA 6- to 14-year prospective study

The Journal of Arthroplasty Vol. 18 No. 1 2003

Cementless Acetabular Replacement in Patients With Rheumatoid Arthritis A 6- to 14-Year Prospective Study M. Katsimihas, MRCS(Ed), A. H. Taylor, FRCS, M. B. Lee, MSc, P. P. Sarangi, MD, FRCS, and I. D. Learmonth, FRCS, FCS(SA) Orth

Abstract: Sixty-three consecutive patients who had 82 Harris-Galante porous acetabular cups (HGP1) (Zimmer Inc, Warsaw, IN) implanted for the treatment of rheumatoid arthritis were prospectively assessed since 1986. At last examination, 12 patients (16 hips) had died, and 1 patient (1 hip) was lost to follow-up. A total of 65 hips in 50 patients were available for the latest review. The follow-up period was 6.8 years to 14 years (mean, 9.1 years). There had been 6 revisions: 1 for deep infection and 5 for polyethylene cup wear. Survivorship analysis for all failures estimated that 75% of hips would still be revision-free after 4,558 days (12.5 years). Polyethylene wear has been identified in a further 7 cases at last examination. The average linear cup wear per year was 0.05 mm(range, 0.00 – 0.66 mm). There were no cases of acetabular loosening or acetabular migration. These results demonstrate the excellent durability of fixation of the HGP1 cups in patients with rheumatoid arthritis. However, a 32-mm head should probably not be used with this cup given the high associated incidence of polyethylene wear. Key words: rheumatoid arthritis, total hip replacement, uncemented acetabular prosthesis, Harris-Galante porous acetabular cups. Copyright 2003, Elsevier Science (USA). All rights reserved.

Cemented total hip arthroplasty (THA) has traditionally been considered the gold standard for the treatment of end stage disease of the hip joint due to rheumatoid arthritis (RA) [1–3]. However, a high rate of aseptic loosening of acetabular components has been described, and there have been reports of

femoral component loosening. Poss and Maloney et al [2] described a 78% incidence of increasing radiolucency around cemented acetabular components in RA at 6 to 11 years after surgery, although none had been revised. The purpose of this prospective study was to evaluate the medium-term results (6 to 14 years after surgery) using the Harris-Galante porous cup (HGP1) in a group of 50 patients with RA who underwent hybrid THA. The early results of this cohort of patients previously reported by Learmonth and Sarangi et al [4] were satisfactory.

From the Department of Orthopaedic Surgery, Avon Orthopaedic Centre, Southmead Hospital, Westbury-on-Trym, Bristol, BS10 5NB, United Kingdom. Submitted May 11, 2001; accepted May 31, 2002. No benefits or funds were received in support of this study. Reprint requests: M. Katsimihas, MRCSEd, Department of Orthopaedic Surgery, Winford Unit, Avon Orthopaedic Centre, Southmead Hospital, Westbury-on-Trym, Bristol, BS10 5NB, United Kingdom. E-mail: [email protected] Copyright 2003, Elsevier Science (USA). All rights reserved. 0883-5403/03/1801-0003$35.00/0 doi:10.1054/arth.2003.50012

Materials and Methods The HGP1 acetabular component is a hemispheric titanium cup, fully covered by clinched and entan-

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Cementless Acetabular Replacement • Katsimihas et al.

gled commercially pure titanium fibers in a fibermetal pad. The pad has a thickness of 1.6-mm, a density of 50%, and an average pore size of 350 ␮m. Eighty-two cementless acetabular components were inserted in 63 patients with RA between 1986 and 1993. There were 22 men and 41 woman, with a mean age at the time of the index operation of 54.7 years (range, 25– 80 years). Eighteen patients underwent bilateral total hip arthroplasties, of whom 5 patients were under 50 years of age. Of the 46 patients who had unilateral THA, 15 were younger than 50 years old. Fifty-seven patients were classified as Charnley grade C, 5 as grade B, and 1 as grade A. Thirty-six cups were inserted with line-to-line reaming, and 46 of the cups were inserted into an acetabulum under-reamed by 1 or 2 mm. Acetabular bone grafting was performed in 20 hips. There were 38 Muller stems* inserted, 18 Exeter,† 15 CPT,‡ 7 Corin Muller,§ 2 Charnley,㛳 1 Sheehan,¶ and 1 Harris-Galante stem.# All stems were cemented with the exception of the 1 HarrisGalante stem. Immediate postoperative radiographs were available for all patients. The average follow-up time was 9.1 years (SD, 2.3 years). Of the total of 63 patients initially included in the preliminary study by Learmonth and Sarangi et al [4], 12 patients (16 hips) had died, and 1 patient (1 hip) was lost to follow-up. Therefore, 65 hips in 50 patients were available for review. Patients were assessed clinically and radiologically at 3, 6, and 12 months, and annually thereafter. All radiographs were standardized anteroposterior and lateral views. Radiographic assessment for radiolucent lines around the socket was based on the method described by DeLee and Charnley [5], with radiographic loosening of the acetabular component defined as a progressive circumferential radiolucency greater than 2 mm. Acetabular cup migration was assessed according to the criteria of Massin, Schmidt, and Engh [6]. Wear of the polyethylene liner was estimated by measuring the distance between the center of the femoral head and the acetabular component metal shell and comparing the most recent with the first postoperative radiograph. A reduction in the distance of more than 1 mm in any of the 3 zones indicated wear. The interobserver and intraobserver errors were estimated using separate measurements taken at 2-week intervals by the authors (MK, AT). *Muller, Protek, Bern, Switzerland, †Exeter, Howmedica, Rutherford, NJ, ‡CPT, Zimmer (UK), Swindon, UK, §Corin Muller, Corin Medical Ltd, Cirencester, UK, 㛳Charnley, Thackery, Rutherford, NJ, ¶Sheehan, Zimmer Inc, Warsaw, IN, #HarrisGalante, Zimmer Inc, Warsaw, IN.

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Heterotopic bone formation was classified according to the system of Brooker and Bowerman et al [7]. In addition, the presence of screw fracture, screw lysis, bone resorption (osteolysis), and any progression were recorded. The Harris Hip Score (HHS), was used for clinical evaluation. The survival time was defined as the length of time (in days) from the date of the operation to the date of revision. The survival times for hips that had not yet required a revision at the last follow-up appointment were calculated as the length of time from the date of operation to the date of last examination and were treated as censored observations. Deaths without revision were treated as censored observations at date of death. Estimates of revision-free survival at a given time point were constructed using Greenwoods’s formula to calculate the standard errors.

Results After surgery, 9 patients developed deep vein thrombosis and 1 had a nonfatal pulmonary embolus. There were 4 cases of superficial wound infections, which were treated successfully using antibiotics. Two patients developed early deep wound infections; 1 of these patients underwent a 2-stage revision and the second was treated using a Girldestone procedure. Of the 11 hips inserted via the posterior approach, 1 dislocated. There were no deaths associated with the index THAs. The average preoperative HHS was 21.5 (range, 5–58); the score at final review was 81.5 (50 –100). The preoperative pain score was 5.8 (range, 0 –29), and the postoperative score was 40 (range, 30 – 44). The average acetabular cup angle was 40° (range, 17°–70°). Four acetabular cups were partly uncovered in zone A. Acetabular fixation was augmented with screws in 51 hips. There was 1 screw breakage, which occurred during its insertion. No screw radiolucencies were seen. All the bone grafts used were fully incorporated radiographically, and no obvious acetabular osteolytic areas were identified. There was no evidence of loosening or migration of the cup. Twelve nonprogressive radiolucent lines were present; 5 in zone A, 2 in zone B, and 5 in zone C. The excellent durability of fixation at 14.5years after surgery is shown in Fig 1. Polyethylene wear was seen radiographically in 12 liners (Table 1), 5 of which had been revised. The average linear cup wear per year was 0.05 mm (range, 0.00 – 0.66 mm). The interobserver and intraobserver errors were calculated and expressed as k values of 0.714 and 0.700, respectively, represent-

18 The Journal of Arthroplasty Vol. 18 No. 1 January 2003

Fig. 1. Radiographs of a woman (patient No. 1) with advanced rheumatoid arthritic changes of the left hip joint, treated with a left THA. (A) Anteroposterior radiograph showing advanced rheumatoid arthritis of the left hip joint before the THA was performed. (B) Anteroposterior and (C) lateral radiographs demonstrating the excellent durability of fixation of the HGP1 cup with a cemented 32-mm monobloc Muller stem 14.5 years after a left THA.

ing good agreement between the first and second occasions of measurements. The average age of the patients with wear was 44.5 years and of those without wear was 52.7 years. No femoral stems failed although 4 monobloc prostheses were revised to allow the femoral head size to be reduced from 32 to 28 mm at the time of acetabular revision. Thus, there were 6 hip revisions in total, 1 of which (patient No. 1) was for early deep infection. The other 5 revisions were for polyethylene wear as noted above. Patient No. 2 had bilateral THA in

1986 with 32-mm monobloc Muller stems. These were revised for acetabular wear at 12.5 years and 12.9 years, with revision of the well-fixed stems to allow downsizing of the femoral heads to 28mm (Fig. 2). Patient No. 3 had revision at 10 years, with removal of 2 acetabular screws. The liner was exchanged and the 32-mm head Muller femoral stem was revised to an Exeter stem with a 28-mm head (Fig. 3). In patient No. 4, the uncemented HarrisGalante stem remained in situ, and the head size was reduced from 32 to 28mm, 8.5 years after

Cementless Acetabular Replacement • Katsimihas et al. Table 1. Liner Wear and Associated Head and Cup Size

Stem Type

Head Size (mm)

Muller

32

Harris-Galante Exeter

32 32 28

Sheehan

22

Acetabular Cup Size (mm) Awaiting Revision

Revised

48⫻1 54⫻1 56⫻1 52 56 50 52 52

2 1 1 1

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survivor function is given in Fig. 5. There were too few revisions performed during the study period to estimate the median revision-free survival. It was estimated that 75% of hips would still be revisionfree after 4,558 days (12.5 years). Distal femoral stem cortical hypertrophy was seen in 8 cases, all of which had a Muller monobloc stem in situ. There was 1 case of detachment of the greater trochanter. Five cases of heterotopic ossification were seen, 2 Brooker grade I, 2 Brooker grade II, and 1 Brooker grade III.

Discussion primary THA (Fig. 4). Finally, patient No. 5 had the liner exchanged and the well-fixed 32-mm Muller stem revised to an Exeter stem 12 years after surgery to allow downsizing of the head. A plot of the

Several studies of cemented THAs have shown a reduction in the incidence of femoral stem aseptic loosening with modern cementing techniques, but

Fig. 2. Radiographs of a man (patient No. 2) who developed bilateral polyethylene wear of the acetabular liner, and subsequently underwent bilateral hip joint revisions to exchange the worn polyethylene liners and to downsize the femoral heads by revising the Muller stems. (A) Anteroposterior radiograph of the pelvis showing bilateral polyethylene wear 12.5 years following THA, with HGP1 cups and 32-mm head Muller femoral stems. The excellent durability of the cups is demonstrated as is the excellent fixation of the Muller stems. (B) Radiograph of the right hip showing obvious polyethylene wear of the liner. (C) Anteroposterior radiograph of the pelvis following bilateral hip joint revisions for polyethylene wear. In addition to the exchange of the worn liners, the well-fixed Muller stems were exchanged to Exeter stems to downsize the heads from 32 to 28 mm.

20 The Journal of Arthroplasty Vol. 18 No. 1 January 2003

Fig. 3. Radiographs of a woman (patient No. 3) who, 10 years after primary THA, presented with polyethylene wear of the acetabular liner and underwent revision surgery. (A) Anteroposterior radiograph of the left primary THA 10 years after surgery, showing a thin and worn acetabular polyethylene liner. There is also screw penetration in zone A of the acetabulum, but the HGP1 cup fixation is excellent. (B) Anteroposterior radiograph of the left hip after revision. The worn acetabular liner was exchanged and the well-fixed 32-mm monobloc Muller stem was revised to an Exeter stem with a 28-mm head. In addition, the screw from zone A and 1 screw from zone B of the acetabulum have been removed.

these have failed to demonstrate any significant reduction of the rate of acetabular component loosening [8,9]. A greater incidence of both acetabular and femoral loosening has been reported in patients with RA compared with those suffering from osteoarthritis [2,9,10,11,12]. This may be related to periarticular osteopenia, which has been associated with inactivity, medication (steroid and antimetabolites), regional hyperaemia, and increased bone turnover [13]. Unger and Inglis et al [14] reported a revision rate of 7.2 % for cemented acetabular loosening in RA, and 16% of the nonrevised hips were noted to be loose. Severt and Wood et al [15] followed up on 75 primary cemented THAs, for an average of 7.4 years. Revision THA’s were performed for acetabular loosening in 4 hips (5%) and femoral loosening in 1 hip (1%). Roentgenographic evidence of loosening was seen in a further 6 acetabular components (8%), in 3 femoral components (4%), and in both the femoral and acetabular component of 1 hip (1.3%). Previously, one of the authors [16] compared the clinical and radiologic results of primary Charnley low-friction arthroplasties in 517 osteoarthritic hips

with 55 rheumatoid hips. Radiologic review at a mean follow-up of 7.5 years identified a 4-fold increase in the incidence of significant migration (⬎4 mm) of the unrevised cups in the rheumatoid group. Lachiewicz and McCaskill et al [10] noted that 26% of the acetabular components and 8% of the femoral components were loose at approximately 6 years after surgery using cemented prosthesis in patients with RA. In a recent study, Creighton and Callaghan et al [17] reported an overall rate of 8% (8 of 98) radiographic loosening of the acetabular component and 16% (8 of 49) in those patients whose implant had been in situ for at least 10 years. The study showed the long-term durability of cemented total hip prosthesis in patients who have RA, although radiographic loosening of the acetabular component remained the major long-term problem. Loosening of the acetabular component remains the major long-term problem following THA in patients with RA. As a possible solution to the problem of mechanical loosening, porous-coated cups were introduced in the mid 1980s. Initially early encouraging results were reported by Cracchiolo, Severt, and Moreland [18] and Lachie-

Cementless Acetabular Replacement • Katsimihas et al.

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Fig. 4. Radiographs of a woman (patient 4) who developed polyethylene wear 8.5 years after primary uncemented THA of the left hip. (A) Radiographic view of the left hip joint 8.5 years after primary THA demonstrates acetabular liner wear.The acetabular cup fixation is excellent. (B) Postrevision anteroposterior radiograph of the left hip; at revision, the polyethylene liner was exchanged and the 32-mm head of the uncemented stem was downsized to a 28-mm head.

wicz [19]. Erwin and Morscher [8] suggested that uncemented hemispheric cups were superior to cemented cups or to other types of uncemented cups, especially in osteopenic patients with RA. Conversely, Kirk and Rorabeck et al [20], in a study comparing cemented and uncemented cups in RA, found no difference in clinical outcome between the 2 groups.

Fig. 5. Kaplan-Meier survival estimate of time to revision with a 95% confidence interval (n ⫽ 82 hips).

This study reviews the medium-term follow-up results in a large cohort of patients with RA in whom a cementless cup was used. Currently, no cup shows radiographic evidence of loosening or migration. Nine cups show radiolucent lines, but these are all nonprogressive. In the five that were revised for polyethylene wear, none of the of the metal shells were clinically loose at the time of

22 The Journal of Arthroplasty Vol. 18 No. 1 January 2003 revision surgery, and all remain in situ. It has been suggested that augmenting the primary fixation of uncemented acetabular component with screws is unnecessary, because any stability achieved by bone screws is short lived and does not affect the final stability of the implant [21]. We found no difference between the acetabular components that were fixed with screws and those that were not. The deep infection rate was 1.5 %, which is comparable with those in other studies [2]. The main problem encountered in this study was a high rate of polyethylene wear, which was associated with a 32-mm head size and thin polyethylene. In the latest follow-up examination, 7 cups showed evidence of polyethylene wear; 5 of these were associated with 32-mm heads, 1 with a 28mm, and 1 with a 22-mm head size femoral stem. Although the overall average linear annual wear was not excessively high, it is well documented that the 32-mm head size is associated with higher rates of volumetric wear than either a 28-mm or a 22-mm head [22]. All these patients remain asymptomatic and have been placed on a waiting list for revision of the acetabular liner; they are being carefully monitored radiographically and clinically in the interim. Long-term radiographic follow-up is necessary to identify acetabular cup wear, especially in asymptomatic patients. This ensures that revision of the polyethylene liner is performed before the metal shell is damaged or wear-induced osteolysis of the acetabular or femoral component compromises the fixation of either component. A 32-mm head should probably not be used with this cup because of the high associated incidence of polyethylene wear, because this results in an unacceptably reduced thickness (⬍8 mm) of the polyethylene liner.

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