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Long-term results of cemented Charnley low-friction arthroplasty in patients aged less than 30 years
The Journal of Arthroplasty Vol. 13 No. 2 t998
L o n g - t e r m Results of C e m e n t e d Charnley L o w - f r i c t i o n A r t h r o p l a s t y in Patients A g e d Less Than 30 Years David H. Sochart,
FRCS, and Martyn
L. P o r t e r , F R C S O r t h
Abstract: The results of cemented Charnley low-friction arthroplasty in patients aged less than 30 years are presem:ed. Eighty-three arthroplasties were performed on 55 patients with an average age of 24.9 years (range, 17-29 years) and an average follow-up period of 240 months (20 years; range, 62-360 months). There were 2 nonfatal pulmonary emboli, 2 castes of deep sepsis, and 3 fractured femoral implants. Twenty-eight acetabnlar components migrated (34%), 25 have been revised (30%), and the average annual acetabular wear rate was 0.12 ram. Sixteen femoral implants subsided (19%), and fracture of the tip of the cement mantle occurred in 8 hips (10%). Nineteen femoral components (23%) were revised; femoral osteolysis was seen in 15 hips (18%) and changes in the calcar in 33 (38%). Acetabular component survivorship was 92% (95% confidence interval, 85-98%) at 10 years, 70% (60-81%) at 20 years, and 68% (57-79%) at 25 years, with the figures for the femoral implant being 93% (87-98%), 76% (66-86%), and 73% (62-85%), respectively. Key words: Charnle} arthroplasty, young patients, revision, survivorship.
There h a v e b e e n few reports of the results of total hip arthroplasty (THA) p e r f o r m e d prior to the age of 30 because such patients are rarely e n c o u n t e r e d . The majority of previously published studies report high rates of b o t h loosening and revision, with the p o o r e s t results occurring in the y o u n g e s t patients [1-4]. M a n y of these series, however, can be criticized, as t h e y are based on the use of multiple i m p l a n t designs [3,5,6], small n u m b e r s of patients [1,7,8], or short follow-up periods [1,3,9]. The high reported failure rate is often attributed to a greater level of activity achieved following successful arthroplasty in y o u n g adults. This results in increased d e m a n d s on the implant, ultimately leading to wear, loosening, a n d early m e c h a n i c a l failure. As a result of the findings reported in these earlier
studies, m a n y surgeons h a v e b e e n reluctant to p e r f o r m arthroplasty on these y o u n g patients, despite the fact that the lack of standardization in these studies m a k e s it difficult to d r a w definite conclusions as to the true o u t c o m e of arthroplasty in this patient group. The p r e s e n t e d series avoids m a n y of these pitfalls, as it reports the use of a single design of implant and standard surgical technique, allied to long-term follow-up evaluation, and is, as far as we are aware, the largest reported series to date.
Materials and Methods All patients w h o u n d e r w e n t THA prior to the age of 30 years w e r e identified f r o m the clinical database at the Centre for Hip Surgery. A total of 93 arthroplasties h a d b e e n p e r f o r m e d on 61 patients w h o s e original case notes and radiographs were t h e n retrieved. Two patients (3 arthroplasties) died within 3 years of operation and 4 patients (7 arthroplasties) w e r e lost to follow-up evaluation
From the Centre for Hip Surgery, Wrightington Hospital Appley Bridge, Wigan, Lancashire, United Kingdom.
Reprint requests: David H. Sochart, FRCS, 7 Woodlea, Walkden Road, Worsley, Manchester, United Kingdom M28 2QJ. Copyright © 1998 Churchill Livingstone. 0883-5403/1302-000155.00/0
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within 2 years and could not be traced. These 6 patients (10 arthroplasties) were therefore excluded from further analysis, leaving 83 arthroplasties in 55 patients. Eleven more patients (17 arthroplasties) were known to have died during the study period but had remained under follow-up evaluation until close to the time of death. The cause and date of death were established, and their general practitioners were interviewed to determine whether further surgery had been performed. The majority of the surviving patients continued to return for regular follow-up evaluation at a clinic, and those who had been lost were traced via the National Health Service Central Register at the Office for National Statistics. All living patients were contacted, initially by questionnaire and then by telephone consultation. Those living outside of the region forwarded radiographs taken at their local hospital, and the remainder attended specific research clinics for clinical and radiologic assessment. Pre- and postoperative pain, function, and range of motion were graded using the 6-digit scale of Merle D'Aubignd and Postel [10] as modified by Charnley [11]. This extension of the scoring system includes an assessment of preoperative disability with the addition of an alphabetical prefix (A, B, or C) to the numerical classification. Patients in category A had involvement of only 1 hip, with B denoting bilateral hip involvement. Patients in category C had some other factor that contributed to the failure to achieve normal locomotion, such as polyarticular arthritis or neurologic dysfunction. There were 12 patients with ankylosing spondylitis (20 arthroplasties), 10 with congenital dislocation of the hip (13 arthroplasties), 24 with rheumatoid arthritis (39 arthroplasties), and 9 with degenerative arthrosis (11 arthroplasties). Of the patients with degenerative arthrosis, 3 had avascular necrosis (4 hips), 4 were post-traumatic (4 hips), and 2 had a metabolic disorder (3 hips). Thirteen hips (16%) had undergone 14 previous surgical procedures: 6 osteotomies, 5 hemiarthroplasties, and 3 open reductions. The majority of the patients undergoing surgery during this study were selected using the pseudarthrosis test [12]. An arthroplasty was undertaken only if the preoperative function and pain grades indicated that the patient's status would be improved by performing a Girdlestone excision arthroplasty (pseudarthrosis). The rationale was that even if the prosthesis were to fail and subsequently be removed, the patient would still have benefited. This meant that the patients selected, although young, tended to be severely disabled by their hip disease.
All operations were performed in a CharnleyHoworth laminar-flow clean-air enclosure (Howorth Engineering, Brinscall, Blackburn, UK), introduced in 1966, with the surgeons later wearing full-body exhaust suits following their introduction in 1970. A lateral approach was used, with a planar trochanteric osteotomy and standard Charnley reattachment with stainless-steel wires. Charnley prostheses (Thackray, Leeds, UK) were used in all cases and consisted of a tapered monobloc stainless-steel femoral stem with a 22.25-mm head. This formed a low-friction torque articulation with an unflanged ultrahigh-molecular-weight polyethylene acetabular component with an integral wire marker. Both components were cemented using radiopaque selfcuring polymethyl methacrylate cement, which was inserted and pressurized digitally, without prior occlusion of the distal femoral intramedullary canal. An anteroposterior radiograph of the replaced hip was obtained immediately following operation, with further radiographs being taken prior to hospital discharge and at each subsequent clinic visit. Patients returned annually for the first 10 years and then on alternate years. These anteroposterior films of the pelvis were taken to show both hips by a standard technique of centering the beam above the pubic symphysis with the hips in extension and neutral rotation, with the patellas pointing upward. The radiographs were examined for evidence of demarcation of the acetabular components recorded in the zones described by DeLee and Charnley [13], with loosening being assessed according to the criteria of Hodgkinson et al. [14]. Any acetabular component that was associated with a continuous radiolucent line in all 3 zones (grade 3), irrespective of its thickness, or that had changed position or migrated (grade 4) was considered to be loose. Migration of the cup was assessed on sequential radiographs by comparing the vertical distance from the center of the cup, measured using the integral wire marker, to a horizontal line joining the 2 anatomic teardrops. Wear of the acetabular components was measured using a graded circular gauge that takes into account the magnification differences between radiographs by using the standard 22.25-ram femoral head size as a reference [ 15,16]. The femoral components were assessed for demarcation and endosteolysis using the zonal system of Gruen et al. [17] and by identifying any of the features associated with loosening as described by Loudon and Older [ 18]. Definite loosening was said to be present if there had been subsidence of more than 5 mm or in the presence of continuous demarcation around the stem. Probable loosening was
HipArthroplasty in Patients Under 30
defined as subsidence of 2-5 m m or the presence of a radiolucent line surrounding 50% or m o r e of the stem (3 zones). Heterotopic ossification was classified using the Brooker system [19], but no specific prophylactic measures were used to prevent its formation. The Kaplan-Meier m e t h o d [20] was used to calculate the probability of retention of the original prosthesis from the time of initial operation until one of three separate endpoints: all revisions for w h a t e v e r reason; revision of the femoral stem; or revision of the acetabular c o m p o n e n t . Ninety-five percent confidence intervals were calculated and the chi-square test was used to assess the statistical significance (P < .05) of radiologic features with regard to the likelihood of revision.
Results Eighty-three cemented Charnley low-friction arthroplasties were p e r f o r m e d on 55 patients w h o were aged less t h a n 30 years at the time of surgery (Table 1). There were 21 m e n (31 arthroplasties) and 34 w o m e n (52 arthroplasties), with 28 palients (48%) undergoing staged bilateral procedures. All of the patients have b e e n followed up to the present day or until the time of death or revision of both of the original components. The average age at the time of operation was 24.9 years (range, 17-29 years) and the average follow-up period was; 240 m o n t h s (20 years; range, 62-360 months). Eleven patients (17 arthroplasties) had died, only 1 of w h o m had u n d e r g o n e revision surgery. Thirty-five patients (64%} were in C h a m l e y category C, 11
Table 1. Patient Details, Radiologic Findings, and Revision Rates AS No. of patients 12 No. of hips 20 Average age (y) 25.5 Acetabular revision 4 Acetabular migration 7 Total w e a r (ram) 2.25 Average w e a r (mm/y) 0.09 Eemoral revision 2 Osteolysis 2 Calcar changes 7 Subsidence 4 Cement tip fracture 2 Heterotopic ossification 4 Cortical h y p e r t r o p h y 7
CDH
RA
10 13 24.2 6 6 2.8 0.15 3 2 6 4 2 5 l0
24 49 24.7 7 7 1.8 0.09 8 6 17 6 2 12 9
OA
Total
9 55 11 83 25.2 24.9 8 25 (30%) 8 28 (34%) 3.8 2.4 0.24 0.12 6 19 (23%) 5 15 (18%) 3 33 (40%) 2 16 ( I 9 % ) 2 8 (10%) 6 27 (33%) 6 32 (39%)
AS, ankylosing spondylitis; CDH, congenitaI dislocation of the hip; RA, r h e u m a t o i d arthritis; OA, osteoarthritis (degenerative arthrosis).
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(20%) were in category B, and only 9 (16%) had unilateral hip disease and were in category A. Three patients developed superficial w o u n d infections treated successfully with antibiotics, and 2 developed late deep sepsis requiring revision of both components. Both of these patients had r h e u m a t o i d arthritis, with 1 undergoing revision at 5 years (the shortest follow-up period in the series), and the other at l0 years. There were 2 cases of nonfata! p u l m o n a r y emboli, with no other d o c u m e n t e d cases of deep vein thrombosis or perioperative fatality. There were no cases of nerve palsy or early dislocation, but there were 2 late dislocations. These were associated with m a r k e d acetabular wear, for which acetabular revision was performed, 1 at 16 years and the other after 18 years. Fracture of the femoral implant occurred in 3 hips (4%) and was associated with aseptic loosening and loss of support of the proximal portion of the stem. All 3 hips were revised, 8, 15, and 19 years from the time of index operation. Following surgery, all patients experienced marked improvements with respect to levels of pain, function, and range of hip m o v e m e n t . The preoperative pain score averaged 3.6 (range, 2-6) and improved to 5.9 (range, 5-6), with all patients having little or no pain and 95% being entirely pain-free (79 arthroplasties in 52 patients). The score for function was originally designed for use only in patients with monarticular hip disease and tends to decline naturally with aging and with the progression of polyarticular disease. It can, however, act as a useful indicator of the initial effect of surgery and improved from an average of 2.4 (range, 1-5) to 4.9 (range, 1-6). Cumulative range of hip m o v e m e n t increased from an average of 2.2 (range, 1-6) to an average of 5.0 (range, 2-6), representing an improvem e n t from an average range of m o t i o n of 60°-100 ° to one of 210 °. Thirty-five acetabular c o m p o n e n t s (42%) had no evidence of radiologic demarcation, 15 had demarcation in 1 zone, and 4 had 2 affected zones. Only 1 patient had demarcation in all 3 acetabular zones w i t h o u t evidence of migration [14]. Twenty-eight c o m p o n e n t s (34%) had migrated an average of 8 m m (range, 2-20 mm), in addition to having radiolucent demarcation, and 21 of these have b e e n revised. Two of the implants that migrated were the result of deep sepsis, and 8 of the surviving components are currently radiologically loose. A total of 27 acetabular components (33 % ) had u n d e r g o n e aseptic loosening. Twenty- five acetabular c o m p o n e n t s (30 %) have b e e n revised, at an average of 162 m o n t h s (13.5 years; range, 62-344 months) from the time of
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index arthroplasty. Nineteen were revised for aseptic loosening (23%) and 2 following deep sepsis, all of which had migrated. The remaining 4 were revised for excessive wear, 2 of which were associated with recurrent dislocation. The total a m o u n t of acetabular wear averaged 2.4 m m (range, 0-7.21 mm), and the average a n n u a l wear rate for the entire series was 0. i2 m m (range, 0-0.55 mm). The annual wear rate for surviving c o m p o n e n t s was 0.08 m m (range, 0-0.35 mm), and that for revised c o m p o n e n t s was 0.22 m m (range, 0.05-0.55 mm). This difference was statistically significant (P < .0 i). The alignment of the femoral c o m p o n e n t was neutral in 46 hips, valgus in 23, and varus in 14, but there was n o statistical difference in survivorship b e t w e e n these 3 groups (P = .3). Fifty-five femoral stems (66 % ) had no evidence of radiologic demarca tion, 12 had nonprogressive demarcation in only 1 Gruen zone, and 8 in 2 zones. Eight femoral components had demarcation in m o r e t h a n 3 zones and were radiologically loose. Subsidence occurred in a total of 16 hips (19%), although only 2 had subsided greater t h a n 5 m m and were definitely loose. A fracture of the tip of the c e m e n t mantle was seen in 8 hips (10%), 2 of which were the hips that had subsided m o r e t h a n 5 mm, with the r e m a i n d e r having all subsided less t h a n 5 ram. Osteolysis a r o u n d the femoral c o m p o n e n t occurred in 15 hips (18%), and changes in the calcar in 33 hips (40%). Twenty-six hips had loss of height of the calcar, and 7 had m a r k e d osteopenia. H y p e r t r o p h y of the femoral cortex at the level of the tip of the stem occurred in 32 hips (39%). Nineteen femoral c o m p o n e n t s (23%) were revised at an average of 166 m o n t h s (13.8 years; range, 62-245 months) from the time of index arthroplasty. Thirteen ( 16 %) were revised for aseptic loosening, 3 of which had an associated fracture of the femoral implant and 2 were revised following deep sepsis. Four c o m p o n e n t s were revised during surgery to replace a loose acetabulum, although these femoral implants were not actually loose but were replaced as they were t h o u g h t likely to have a damaged bearing surface. Only 2 of the surviving femoral implants are currently radiologically loose, giving an overall rate of aseptic femoral loosening of 18% (15 hips). Heterotopic ossification was seen in 27 hips (33%). Nineteen had Brooker class 1 changes and 5 were in class 2. There were no cases of b o n y ankylosis (class 4), and only 3 had class 3 changes, which caused slight reduction in the range of hip m o v e m e n t . Displacement of the trochanter occurred in 7 hips
(8%) and breakage of the wires in l l hips (13%). Four hips (5%) required further surgery as a consequence of wire breakage, 3 undergoing wire removal and 1 trochanteric reattachment. Survivorship of the femoral c o m p o n e n t was 93 % (95% confidence interval 8 7 - 9 8 % ) at 10 years, 76% ( 6 6 - 8 6 % ) at 20 years, and 73% (62-85%) at 25 years, with the corresponding values for the acetabulum being 92% (85-98%), 70% (60-81%), and 68% (57-79%), respectively. The survivorship for both of the original c o m p o n e n t s at 10 years was 89% (82-96%), and at 25 years was 65% (54-76%) (Figs. 1, 2).
Discussion Patients aged less than 30 years w h o require THA form only a small fraction of the typical arthroplasty population, even at specialist tertiary referral units. Only 93 of the 10,469 arthroplasties p e r f o r m e d at this institution during the study period were in such patients, accounting for less t h a n 1% of all cases. The scarcity of these patients is reflected in the limited n u m b e r s of previously reported studies, which usually consist of small n u m b e r s of patients, on w h o m a variety of implants have been used. Follow-up periods are often short, with m a n y patients being lost, as the y o u n g patient population is more mobile in response to family or occupational necessity t h a n their older counterparts. The poor early results reported in the literature led m a n y surgeons to r e c o m m e n d o s t e o t o m y and arthrodesis as alternatives [6,21,22], but these are not appropriate for all patients, such as those with bilateral disease. The worst results were reported in the youngest patients and those w h o had u n d e r g o n e previous operations [1,3,4,6], and arthroplasty was reserved for the patients w h o were most severely disabled by their hip disease. These motivated y o u n g patients were, however, willing to accept the high perceived risks of implant loosening and the likelih o o d of ultimate revision surgery, in exchange for the pain relief and i m p r o v e m e n t s in function that successful arthroplasty could offer them. In studies of patients aged less t h a n 45 years at the time of operation, White reported a revision rate of 14% at 7.5 years [23]. Dorr et al. reported a revision rate of 19% at only 4.5 years, with 45% of the surviving implants showing radiologic signs of impending failure [3]. Sharp and Porter reported a 14% revision rate at 6 years in patients aged less than 40 years and implicated r h e u m a t o i d arthritis as the main cause of loosening [24], and Williams and McCullough reported loosening in 24.6% of hips at
HipArthroplasty in Patients Under 30 82
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Fig. l. TWenty-five-year survivorship curves (K~plan-Meier) for the femoral and acetabular components, both individually (A, B) and in combination (C), with tile 95 % confidence intervals and number of hips surviving, given at 5-year intervals.
4.5 years, b u t in 4 3 . 5 % of implants that h a d b e e n in place longer t h a n 5 years {25]. Revision was perf o r m e d in 2 1 % of patients aged less t h a n 30 years in a series reported by Chandler et al. {1], w i t h Joshi et al. also Iinding p o o r e r results in the u n d e r - 3 0 age group [4]. A recent study by Torchia et al. r e p o r t e d a
revision rate of 4 3 % at 12.6 years in patients aged less t h a n 20 years [61, but the series contained a wide range of prostheses a n d underlying pathologies including t u m o r cases. The complication rates in the current series were low, with no fatal p u l m o n a r y emboli, two nonfatal
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emboli, and no other recorded cases of deep vein thrombosis. There w e r e no early dislocations a n d 2 late cases that w e r e associated with m a r k e d acetabular wear. This reflects the fact that the majority of the operations w e r e p e r f o r m e d either by the late Professor J o h n Charnley or by his senior colleagues, using a standardized surgical technique. Fracture of the femoral prosthesis occurred in 3 patients (4%), but the strength of the m o d e r n C h a m l e y implants has b e e n increased following the introduction of i m p r o v e d materials, a n d stem breakage has n o w b e e n eradicated [26,27]. All patients e x p e r i e n c e d m a r k e d pain relief, with 95% being pain-free, w h i c h is consistent with the rates of 8 9 - 9 5 % reported in other series [4,28-31]. The range of hip m o v e m e n t increased to an average of 210 ° in keeping with previous studies [23,26,29,31,32] a n d the i m p r o v e m e n t in function, a l t h o u g h obvious, was t e m p e r e d by the fact that the majority of patients h a d polyarticular disease. The rate of revision of the acetabular c o m p o n e n t was 30% at an average follow-up period of 20 years, w h i c h is better t h a n the 4 3 % at 12.6 years reported by Torchia et al. [6] or the 36% at 16 years reported by Joshi et al. [4]. The average a n n u a l acetabular w e a r rate for the entire series was 0.12 m m , in keeping with previously reported rates of 0.1-0.16 m m [28-30,33,34]. The average a n n u a l w e a r rate of 0.22 m m for revised c o m p o n e n t s was also similar to the reported rates of 0.19-0.21 m m for e x p l a n t e d
cups [15,35], a n d the difference in w e a r rates b e t w e e n surviving c o m p o n e n t s and the original cups that h a d required revision was highly statistically significant ( P < .01). This confirms a link b e t w e e n increased rates of acetabular w e a r and the d e v e l o p m e n t of c o m p o n e n t loosening, ultimately leading to revision, as has previously b e e n suggested by Wroblewski [32]. There was also an association b e t w e e n a n y evidence of acetabular d e m a r c a t i o n at 1 year and eventual c o m p o n e n t migration (P = .004) and revision (P = .004), as previously reported by Joshi et al. [4]. There was no association, in this series, b e t w e e n previous hip surgery a n d eventual revision (P = .7), as has b e e n suggested in earlier studies [1,3,4,6]. Femoral c o m p o n e n t revision was p e r f o r m e d in 2 3 % of hips, w h i c h was higher t h a n in m o s t series looking at the o u t c o m e of arthroplasty in older patients, but l o w e r t h a n the rates of 2 5 - 2 8 % at only 11 years reported in patients with j u v e n i l e - o n s e t r h e u m a t o i d arthritis [36, 37]. The subsidence rate of 19% was lower t h a n the rates of 2 5 - 4 0 % in m o s t l o n g - t e r m series [2,18,30,32,38], and the 10% rate of c e m e n t tip fracture was similar to the reported rates of 7 - 1 5 % [2,6,30,32,38]. H y p e r t r o p h y of the femoral cortex at the level of the tip of the prosthesis occurred in 39% of hips and was higher t h a n the reported rates of 1 6 - 2 9 % [4,26,32]. N o n e of these radiologic features was associated with an increased
HipArthroplasty in Patients Under 30 risk of revision, w i t h P v a l u e s of 0.06, 0.4, a n d 0.06, respectively. Osteolysis a r o u n d t h e f e m o r a l c o m p o n e n t was seen i n 18% of hips, w h i c h is higher t h a n rates i n most other series ranging from 3% to 10% [4,26,28,34], b u t is similar to t h e rates of 1 7 . 5 - 2 1 % i n t h e l o n g - l e r m studies r e p o r t e d b y W r o b l e w s k i a n d S i n e y {30,32]. The d e v e l o p m e n t of osteolysis was associated w i t h a h i g h a v e r a g e a n n u a l a c e t a b u l a r w e a r rate (P < .0 l) a n d its p r e s e n c e w a s also s t r o n g l y associated w i t h f e m o r a l l o o s e n i n g a n d i m p l a n t r e v i s i o n (P < .01), c o n f i r m i n g t h e l i n k b e t w e e n t h e g e n e r a t i o n of p o l y e t h y l e n e w e a r debris, t h e d e v e l o p m e n t of osteolysis, a n d f e m o r a l i m p l a n t l o o s e n i n g . C h a n g e s i n t h e m e d i a l f e m o r a l calcar o c c u r r e d i n 4 0 % of ]:tips, w i t h rates of 2 4 - 4 4 % h a v i n g b e e n r e p o r t e d i n p r e v i o u s series {4,6,26,32]. The d e v e l o p m e n t of calcar c h a n g e s was associated w i t h a h i g h a c e t a b u l a r w e a r rate (P < .01) b u t w a s n o t associated w i t h a n i n c r e a s e d risk of f e m o r a l i m p l a n t l o o s e n i n g (P = .07) or r e v i s i o n (P = .08). The c e m e n t e d C h a r n l e y l o w - f r i c t i o n a r t h r o p l a s t y p e r f o r m e d well u p to 25 years i n this g r o u p of active y o u n g p a t i e n t s . S u r v i v o r s h i p of t h e a c e t a b u l a r c o m p o n e n t was 9 2 % ( 9 5 % c o n f i d e n c e i n t e r v a l , 8 5 9 8 % ) at 10 years a n d 6 8 % ( 5 7 - 7 9 % ) at 25 years, w i t h t h e figures for t h e f e m o r a l c o m p o n e n t b e i n g 9 3 % ( 8 7 - 9 8 % ) a n d 7 3 % ( 6 2 - 8 5 % ) , respectively. The major factors d e t e r m i n i n g t h e l o n g e v i t y of t h e
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i m p l a n t w e r e l o o s e n i n g , m i g r a t i o n , a n d r e v i s i o n of t h e a c e t a b u l a r c o m p o n e n t , w h i c h w e r e associated w i t h a n i n c r e a s e d a v e r a g e a n n u a l w e a r rate. A n i n c r e a s e d rate of a c e t a b u l a r w e a r was also associated w i t h t h e d e v e l o p m e n t of f e m o r a l osteolysis, w h i c h c o n t r i b u t e d to f e m o r a l l o o s e n i n g a n d revision. The results of this l o n g - t e r m s t u d y s h o w t h e v a l u e of t h e use of a single, tried a n d tested, i m p l a n t design a n d surgical t e c h n i q u e , r e s u l t i n g i n l o w c o m p l i c a t i o n rates a n d c o m p o n e n t s u r v i v o r s h i p exc e e d i n g t h o s e r e p o r t e d i n earlier series. Y o u n g p a t i e n t s h a v e l o n g b e e n a c c e p t e d as b e i n g at h i g h e r risk of i m p l a n t l o o s e n i n g a n d failure, b u t t h e 25y e a r results i n t h e c u r r e n t series w e r e satisfactory (Tables 2, 3). I m p r o v e m e n t s i n c e m e n t i n g techn i q u e s {27,39], i m p l a n t materials, a n d p r o s t h e t i c design {18,26] are likely to result i n e v e n b e t t e r results for the f e m o r a l c o m p o n e n t s i n t h e f u t u r e . The c u r r e n t a i m of r e s e a r c h i n a r t h r o p l a s t y s u r g e r y s h o u l d t h e r e f o r e be to r e d u c e t h e i n c i d e n c e of a c e t a b u l a r c o m p o n e n t l o o s e n i n g , w h i c h a p p e a r s to be closely r e l a t e d to t h e issue of w e a r rates. The use of t h e s m a l l - d i a m e t e r h e a d size is c e n t r a l to t h e C h a r n l e y c o n c e p t of l o w - f r i c t i o n t o r q u e a n d c o n t r i b utes to l o w e r rates of l o o s e n i n g a n d debris g e n e r a t i o n [40,41], w i t h the v a l u e of i m p r o v e d b e a r i n g surfaces s u c h as ceramics c u r r e n t l y u n d e r i n v e s t i g a tion. The results of t h e c u r r e n t s t u d y are e n c o u r a g -
Table 2. Life-table Analysis for Femoral Components (<30 Years of Age: Stems) Years Since Operation
No. of Hips
No. of Failures
No. Withdrawn
No. Lost to Follow-up Evaluation
No. at Risk
0-i 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 I0-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20 20-21 21-22 22-23 23-24 24-25
83 83 83 83 83 83 82 82 82 80 79 77 76 75 74 7I 70 67 63 56 50 43 41 31 27
0 0 0 0 0 1 0 0 2 1 2 1 0 I 0 1 2 1 1 2 3 0 0 1 0
0 0 0 0 0 0 0 0 0 0 0 0 1 0 3 0 1 3 6 4 4 2 10 3 10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
83 83 83 83 83 83 82 82 82 80 79 77 75.5 75 72.5 71 69.5 65.5 60 54 48 42 36 29.5 22
AnnualFailure Annual Success Rate (%) Rate (%) 0 0 0 0 0 1.2 0 0 2.4 1.3 2.5 1.3 0 1.3 0 1.4 2.9 1.5 1.7 3.7 6.3 0 0 3.4 0
100 100 100 I00 100 98.8 100 100 97.6 98.8 97.5 98.7 100 98.7 100 98.6 97.1 98.5 98.3 96.3 93.8 100 i00 96.6 100
Survival Rate (%)
SE
100 100 100 I00 100 98.8 98.8 98.8 96.4 95.2 92.8 91.6 91.6 90.4 90.4 89.1 86.5 85.2 83.8 80.7 75.6 75.6 75.6 73.1 73.1
0 0 0 0 0 1.2 1.2 1.2 2.1 2.4 2.8 3.1l 3.1 3.2 3.2 3.4 3.8 4 4. l 4.5 5.1 5.1 5.I 5.5 5.5
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The Journal of Arthroplasty Vol. 13 No. 2 February 1998 Table 3. L i f e - t a b l e A n a l y s i s for A c e t a b u l a r C o m p o n e n t s ( < 3 0 Years of Age: C u p s )
Years Since Operation
No. of Hips
No. of Failures
No. Withdrawn
No. Lost to Follow-up Evaluation
No. at Risk
A n n u a l Failure Rate (%)
Annual Success Rate (%)
Survival Rate (%)
SE
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 I7-18 18-19 19-20 20-21 21-22 22-23 23-24 24-25
83 83 83 83 83 83 82 82 82 79 78 76 73 72 71 68 67 61 58 52 48 41 40 31 29
0 0 0 0 0 1 0 0 3 1 2 3 0 1 0 1 5 0 3 1 2 0 i 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1 0 3 0 1 3 3 3 5 1 8 2 11
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
83 83 83 83 83 83 82 82 82 79 78 76 72.5 72 69.5 68 66.5 59.5 56.5 50.5 45.5 40.5 36 30 23.5
0 0 0 0 0 1.2 0 0 3.7 1.3 2.6 4 0 1.4 0 1.5 7.5 0 5.3 2 4.4 0 2.8 0 0
100 100 100 100 100 98.8 100 100 96.3 98.7 97.4 96.1 100 98.6 100 98.5 92.5 100 94.7 98 95.6 100 97.2 I00 i00
100 100 100 100 100 98.8 98.8 98.8 95.2 94 91.6 88 88 86.7 86.7 85.5 79 79 74.8 73.4 70.l 70.1 68.2 68.2 68.2
0 0 0 0 0 1.2 1.2 1.2 2.4 2.6 3.1 3.6 3.6 3.7 3.7 3.9 4.5 4.5 4.9 5 5.3 5.3 5.3 5.5 5.5
ing and the pessimism with which arthroplasty in patients aged less than 30 has traditionally been viewed should n o w be reconsidered.
References 1. C h a n d l e r H, R e i n e c k T, W i x s o n R, M c C a r t h y J: Total hip r e p l a c e m e n t s i n p a t i e n t s y o u n g e r t h a n t h i r t y years old. J B o n e J o i n t Surg 6 3 A : 1 4 2 6 , 1981 2. K a v a n a g h B, Wallrichs S, Dewitz M e t al: C h a r n l e y l o w - f r i c t i o n a r t h r o p l a s t y of t h e hip. J A r t h r o p l a s t y 9:229, 1 9 9 4 3. D o r r L, Takei G, C o n a t y P: Total h i p a r t h r o p l a s t y in p a t i e n t s less t h a n forty-five years old. J B o n e J o i n t Surg 65A:474, 1983 4. J o s h i A, P o r t e r M, Trail I e t al: Long t e r m results of Charnley low-friction arthroplasty in young patients. J B o n e J o i n t Surg 75B:616, 1993 5. Collis DK: C e m e n t e d t o t a l h i p r e p l a c e m e n t i n p a t i e n t s w h o are less t h a n fifty years old. J B o n e J o i n t Surg 66A:353, I 9 8 4 6. Torchia ME, KIassen RA, B i a n c o AJ: Total h i p a r t h r o plasty w i t h c e m e n t i n p a t i e n t s less t h a n t w e n t y years old. J B o n e J o i n t Surg 78A:995, 1996 7. Cage DJN, G r a n b e r r y W, Tullos H: L o n g - t e r m results of t o t a l a r t h r o p l a s t y i n a d o l e s c e n t s w i t h d e b i l i t a t i n g p o l y a r t h r o p a t h y . Clin O r t h o p 283:156, 1992 8. L e a r m o n t h I, H e y w o o d A, Kaye J, Dall D: Radiological l o o s e n i n g after c e m e n t e d h i p r e p l a c e m e n t for j u v e n i l e c h r o n i c arthritis. J B o n e J o i n t Surg 71B:209, 1989
9. Bisla R, Inglis A, R a n a w a t C: J o i n t r e p l a c e m e n t s u r g e r y in p a t i e n t s u n d e r thirty. J B o n e J o i n t Surg 58A:1098, 1976 i 0 . M e r l e D ' A u b i g n e R, Postel M: F u n c t i o n a l results of hip a r t h r o p l a s t y w i t h acrylic prosthesis. J B o n e J o i n t Surg 36A:451, 1954 1 i. C h a r n l e y J: A r t h r o p l a s t y of t h e hip: a n e w o p e r a t i o n . L a n c e t 1129, 1961 12. Halley DK, C h a r n l e y J: Results of l o w - f r i c t i o n a r t h r o plasty i n p a t i e n t s t h i r t y years of age or y o u n g e r . Clin O r t h o p 112:180, 1975 I3. DeLee JG, C h a r n l e y J: Radiological d e m a r c a t i o n of c e m e n t e d sockets i n total h i p r e p l a c e m e n t . Clin Ort h o p 121:20, 1976 14. H o d g k i n s o n JP, Shelley P, W r o b l e w s k i BM: T h e correlation between the roentgenographic appearance and o p e r a t i v e findings at t h e b o n e c e m e n t j u n c t i o n of t h e socket i n C h a r n l e y l o w - f r i c t i o n a r t h r o p l a s t i e s . Clin O r t h o p 228:105, 1988 15. Isaac G, W r o b l e w s k i BM, A t k i n s o n J, D o w s o n D: A tribological s t u d y of r e t r i e v e d h i p p r o s t h e s e s . Clin O r t h o p 2 7 6 : I 15, 1992 16. Griffith M, S e i d e n s t e i n M, Williams D, C h a r n l e y J: Socket w e a r i n C h a r n l e y l o w - f r i c t i o n a r t h r o p l a s t y of t h e hip. Clin O r t h o p 137:37, I 9 7 8 17. G r u e n TE, McNeice GM, A m s t u t z HC: M o d e s of failure of c e m e n t e d s t e m - t y p e f e m o r a l c o m p o n e n t s . Clin O r t h o p 141:17, 1979 18. L o u d o n J, Older M: S u b s i d e n c e of t h e f e m o r a l c o m p o n e n t r e l a t e d to l o n g - t e r m o u t c o m e of h i p replacem e n t . J B o n e J o i n t Surg 71B:624, 1989
HipArthroplasty in Patients Under 30 19. Brooker A, Bowerman J, Robinson R, Riley L: Ectopic ossification following total hip replacement. J Bone Joint Surg 55A:1629, 1973 20. Kaplan EL, Meier P: Nonparametric estimation from incomplete observations. A m Stat Assoc J 53:457, 1958 21. Poss R: The role of osteotomy in the treatment of osteoarthritis of the hip. J Bone Joint Surg 66A: 144, i984 22. Sponseller P, McBeath A, Perpich M: Hip arthrodesis in young patients. J Bone Joint Surg 66A:853, 1984 23. White SH: The fate of cemented total hip arthroplasty in young patients. Clin Orthop 231:29, 1988 24. Sharp D, Porter KM: The Charnley total hip arthroplasty in patients under age forty. Clin Orthop 201:51, 1985 25. Williams W, McCullough CJ: Results of cemented total hip replacement in juvenille chronic arthritis. J Bone Joint Surg 75B:872, 1993 26. Dall D, Learmonth I, Solomon M e t al: Fracture and loosening of Charnley femoral stems. J Bone Joint Surg 75B:259, I993 27. Wroblewski BM, Van Der Rijt A: Intramedullary cancellous bone block to improve femoral stem fixation in Charnley low-friction arthroplasty. J Bone Joint Surg 66B:639, I984 28. Sullivan PM, MacKenzie J, Callaghan J, Johnston RC: Total hip arthroplasty with cement in patients who are less than fifty years old. J Bone Joint Surg 76A:863, 1994 29. Charnley J, Cupic Z: The nine- and ten-year results of the low-friction arthroplasty of the hip. Clin Orthop 95:9, 1973
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30. Wroblewski BM, Siney PD: Charnley low-friction arthroplasty in the young patient. Clin Orthop 285: 45, I992 31. Wroblewski BM, Siney PD: Charnley low-friction arthroplasty of the hip. Clin Orthop 292:191, i993 32. Wroblewski BM: 15- to 21-year results of the Charnley low-friction arthroplasty. Clin Orthop 211:30, 1986 33. Charnley J, Halley D: Rate of wear in total hip replacement. Clin Orthop 112:170, 1975 34. Halley D, Wroblewski BM: Long-term results of lowfriction arthroplasty in patients 30 years of age or younger. Clin Orthop 21 I:43, 1986 35. Wroblewski BM: Direction and rate of socket wear it, Charnley low-friction arthroplasty. J Bone Joint Surg 67B:757, 1985 36. Swann M: Total hip replacement for juvenile chronic arthritis. Clin Exp Rheum 11 (suppl):$47, 1993 37. Witt JD, Swann M, AnseI1 BM: Total hip replacemem: for juvenille chronic arthritis. J Bone Joint Surg 73B:770, 1991 38. N e u m a n n L, Freund K, Sorensen K: Total hip arthroplasty with the Charnley prosthesis in patients 55 years old and less. J Bone Joint Surg 78A:73, 1996 39. Barrack R, Mulroy R, Harris W: Improved cementing techniques and femoral component loosening in young patients with hip arthroplasty. J Bone Joint Surg 74B:385, 1992 40. Charnley J, Kamangar A, Longfield M: The optimum size of prosthetic heads in relation to the wear of plastic sockets in total replacement of the hip. Med Biol Eng 7:31, 1969 41. Morrey B, Ilstrup D: Size of the femoral head and acetabular revision in total hip arthroplasty. J Bone Joint Surg 71A:50, 1989
L o n g - t e r m Results of C e m e n t e d Charnley L o w - f r i c t i o n A r t h r o p l a s t y in Patients A g e d Less Than 30 Years David H. Sochart,
FRCS, and Martyn
L. P o r t e r , F R C S O r t h
Abstract: The results of cemented Charnley low-friction arthroplasty in patients aged less than 30 years are presem:ed. Eighty-three arthroplasties were performed on 55 patients with an average age of 24.9 years (range, 17-29 years) and an average follow-up period of 240 months (20 years; range, 62-360 months). There were 2 nonfatal pulmonary emboli, 2 castes of deep sepsis, and 3 fractured femoral implants. Twenty-eight acetabnlar components migrated (34%), 25 have been revised (30%), and the average annual acetabular wear rate was 0.12 ram. Sixteen femoral implants subsided (19%), and fracture of the tip of the cement mantle occurred in 8 hips (10%). Nineteen femoral components (23%) were revised; femoral osteolysis was seen in 15 hips (18%) and changes in the calcar in 33 (38%). Acetabular component survivorship was 92% (95% confidence interval, 85-98%) at 10 years, 70% (60-81%) at 20 years, and 68% (57-79%) at 25 years, with the figures for the femoral implant being 93% (87-98%), 76% (66-86%), and 73% (62-85%), respectively. Key words: Charnle} arthroplasty, young patients, revision, survivorship.
There h a v e b e e n few reports of the results of total hip arthroplasty (THA) p e r f o r m e d prior to the age of 30 because such patients are rarely e n c o u n t e r e d . The majority of previously published studies report high rates of b o t h loosening and revision, with the p o o r e s t results occurring in the y o u n g e s t patients [1-4]. M a n y of these series, however, can be criticized, as t h e y are based on the use of multiple i m p l a n t designs [3,5,6], small n u m b e r s of patients [1,7,8], or short follow-up periods [1,3,9]. The high reported failure rate is often attributed to a greater level of activity achieved following successful arthroplasty in y o u n g adults. This results in increased d e m a n d s on the implant, ultimately leading to wear, loosening, a n d early m e c h a n i c a l failure. As a result of the findings reported in these earlier
studies, m a n y surgeons h a v e b e e n reluctant to p e r f o r m arthroplasty on these y o u n g patients, despite the fact that the lack of standardization in these studies m a k e s it difficult to d r a w definite conclusions as to the true o u t c o m e of arthroplasty in this patient group. The p r e s e n t e d series avoids m a n y of these pitfalls, as it reports the use of a single design of implant and standard surgical technique, allied to long-term follow-up evaluation, and is, as far as we are aware, the largest reported series to date.
Materials and Methods All patients w h o u n d e r w e n t THA prior to the age of 30 years w e r e identified f r o m the clinical database at the Centre for Hip Surgery. A total of 93 arthroplasties h a d b e e n p e r f o r m e d on 61 patients w h o s e original case notes and radiographs were t h e n retrieved. Two patients (3 arthroplasties) died within 3 years of operation and 4 patients (7 arthroplasties) w e r e lost to follow-up evaluation
From the Centre for Hip Surgery, Wrightington Hospital Appley Bridge, Wigan, Lancashire, United Kingdom.
Reprint requests: David H. Sochart, FRCS, 7 Woodlea, Walkden Road, Worsley, Manchester, United Kingdom M28 2QJ. Copyright © 1998 Churchill Livingstone. 0883-5403/1302-000155.00/0
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within 2 years and could not be traced. These 6 patients (10 arthroplasties) were therefore excluded from further analysis, leaving 83 arthroplasties in 55 patients. Eleven more patients (17 arthroplasties) were known to have died during the study period but had remained under follow-up evaluation until close to the time of death. The cause and date of death were established, and their general practitioners were interviewed to determine whether further surgery had been performed. The majority of the surviving patients continued to return for regular follow-up evaluation at a clinic, and those who had been lost were traced via the National Health Service Central Register at the Office for National Statistics. All living patients were contacted, initially by questionnaire and then by telephone consultation. Those living outside of the region forwarded radiographs taken at their local hospital, and the remainder attended specific research clinics for clinical and radiologic assessment. Pre- and postoperative pain, function, and range of motion were graded using the 6-digit scale of Merle D'Aubignd and Postel [10] as modified by Charnley [11]. This extension of the scoring system includes an assessment of preoperative disability with the addition of an alphabetical prefix (A, B, or C) to the numerical classification. Patients in category A had involvement of only 1 hip, with B denoting bilateral hip involvement. Patients in category C had some other factor that contributed to the failure to achieve normal locomotion, such as polyarticular arthritis or neurologic dysfunction. There were 12 patients with ankylosing spondylitis (20 arthroplasties), 10 with congenital dislocation of the hip (13 arthroplasties), 24 with rheumatoid arthritis (39 arthroplasties), and 9 with degenerative arthrosis (11 arthroplasties). Of the patients with degenerative arthrosis, 3 had avascular necrosis (4 hips), 4 were post-traumatic (4 hips), and 2 had a metabolic disorder (3 hips). Thirteen hips (16%) had undergone 14 previous surgical procedures: 6 osteotomies, 5 hemiarthroplasties, and 3 open reductions. The majority of the patients undergoing surgery during this study were selected using the pseudarthrosis test [12]. An arthroplasty was undertaken only if the preoperative function and pain grades indicated that the patient's status would be improved by performing a Girdlestone excision arthroplasty (pseudarthrosis). The rationale was that even if the prosthesis were to fail and subsequently be removed, the patient would still have benefited. This meant that the patients selected, although young, tended to be severely disabled by their hip disease.
All operations were performed in a CharnleyHoworth laminar-flow clean-air enclosure (Howorth Engineering, Brinscall, Blackburn, UK), introduced in 1966, with the surgeons later wearing full-body exhaust suits following their introduction in 1970. A lateral approach was used, with a planar trochanteric osteotomy and standard Charnley reattachment with stainless-steel wires. Charnley prostheses (Thackray, Leeds, UK) were used in all cases and consisted of a tapered monobloc stainless-steel femoral stem with a 22.25-mm head. This formed a low-friction torque articulation with an unflanged ultrahigh-molecular-weight polyethylene acetabular component with an integral wire marker. Both components were cemented using radiopaque selfcuring polymethyl methacrylate cement, which was inserted and pressurized digitally, without prior occlusion of the distal femoral intramedullary canal. An anteroposterior radiograph of the replaced hip was obtained immediately following operation, with further radiographs being taken prior to hospital discharge and at each subsequent clinic visit. Patients returned annually for the first 10 years and then on alternate years. These anteroposterior films of the pelvis were taken to show both hips by a standard technique of centering the beam above the pubic symphysis with the hips in extension and neutral rotation, with the patellas pointing upward. The radiographs were examined for evidence of demarcation of the acetabular components recorded in the zones described by DeLee and Charnley [13], with loosening being assessed according to the criteria of Hodgkinson et al. [14]. Any acetabular component that was associated with a continuous radiolucent line in all 3 zones (grade 3), irrespective of its thickness, or that had changed position or migrated (grade 4) was considered to be loose. Migration of the cup was assessed on sequential radiographs by comparing the vertical distance from the center of the cup, measured using the integral wire marker, to a horizontal line joining the 2 anatomic teardrops. Wear of the acetabular components was measured using a graded circular gauge that takes into account the magnification differences between radiographs by using the standard 22.25-ram femoral head size as a reference [ 15,16]. The femoral components were assessed for demarcation and endosteolysis using the zonal system of Gruen et al. [17] and by identifying any of the features associated with loosening as described by Loudon and Older [ 18]. Definite loosening was said to be present if there had been subsidence of more than 5 mm or in the presence of continuous demarcation around the stem. Probable loosening was
HipArthroplasty in Patients Under 30
defined as subsidence of 2-5 m m or the presence of a radiolucent line surrounding 50% or m o r e of the stem (3 zones). Heterotopic ossification was classified using the Brooker system [19], but no specific prophylactic measures were used to prevent its formation. The Kaplan-Meier m e t h o d [20] was used to calculate the probability of retention of the original prosthesis from the time of initial operation until one of three separate endpoints: all revisions for w h a t e v e r reason; revision of the femoral stem; or revision of the acetabular c o m p o n e n t . Ninety-five percent confidence intervals were calculated and the chi-square test was used to assess the statistical significance (P < .05) of radiologic features with regard to the likelihood of revision.
Results Eighty-three cemented Charnley low-friction arthroplasties were p e r f o r m e d on 55 patients w h o were aged less t h a n 30 years at the time of surgery (Table 1). There were 21 m e n (31 arthroplasties) and 34 w o m e n (52 arthroplasties), with 28 palients (48%) undergoing staged bilateral procedures. All of the patients have b e e n followed up to the present day or until the time of death or revision of both of the original components. The average age at the time of operation was 24.9 years (range, 17-29 years) and the average follow-up period was; 240 m o n t h s (20 years; range, 62-360 months). Eleven patients (17 arthroplasties) had died, only 1 of w h o m had u n d e r g o n e revision surgery. Thirty-five patients (64%} were in C h a m l e y category C, 11
Table 1. Patient Details, Radiologic Findings, and Revision Rates AS No. of patients 12 No. of hips 20 Average age (y) 25.5 Acetabular revision 4 Acetabular migration 7 Total w e a r (ram) 2.25 Average w e a r (mm/y) 0.09 Eemoral revision 2 Osteolysis 2 Calcar changes 7 Subsidence 4 Cement tip fracture 2 Heterotopic ossification 4 Cortical h y p e r t r o p h y 7
CDH
RA
10 13 24.2 6 6 2.8 0.15 3 2 6 4 2 5 l0
24 49 24.7 7 7 1.8 0.09 8 6 17 6 2 12 9
OA
Total
9 55 11 83 25.2 24.9 8 25 (30%) 8 28 (34%) 3.8 2.4 0.24 0.12 6 19 (23%) 5 15 (18%) 3 33 (40%) 2 16 ( I 9 % ) 2 8 (10%) 6 27 (33%) 6 32 (39%)
AS, ankylosing spondylitis; CDH, congenitaI dislocation of the hip; RA, r h e u m a t o i d arthritis; OA, osteoarthritis (degenerative arthrosis).
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(20%) were in category B, and only 9 (16%) had unilateral hip disease and were in category A. Three patients developed superficial w o u n d infections treated successfully with antibiotics, and 2 developed late deep sepsis requiring revision of both components. Both of these patients had r h e u m a t o i d arthritis, with 1 undergoing revision at 5 years (the shortest follow-up period in the series), and the other at l0 years. There were 2 cases of nonfata! p u l m o n a r y emboli, with no other d o c u m e n t e d cases of deep vein thrombosis or perioperative fatality. There were no cases of nerve palsy or early dislocation, but there were 2 late dislocations. These were associated with m a r k e d acetabular wear, for which acetabular revision was performed, 1 at 16 years and the other after 18 years. Fracture of the femoral implant occurred in 3 hips (4%) and was associated with aseptic loosening and loss of support of the proximal portion of the stem. All 3 hips were revised, 8, 15, and 19 years from the time of index operation. Following surgery, all patients experienced marked improvements with respect to levels of pain, function, and range of hip m o v e m e n t . The preoperative pain score averaged 3.6 (range, 2-6) and improved to 5.9 (range, 5-6), with all patients having little or no pain and 95% being entirely pain-free (79 arthroplasties in 52 patients). The score for function was originally designed for use only in patients with monarticular hip disease and tends to decline naturally with aging and with the progression of polyarticular disease. It can, however, act as a useful indicator of the initial effect of surgery and improved from an average of 2.4 (range, 1-5) to 4.9 (range, 1-6). Cumulative range of hip m o v e m e n t increased from an average of 2.2 (range, 1-6) to an average of 5.0 (range, 2-6), representing an improvem e n t from an average range of m o t i o n of 60°-100 ° to one of 210 °. Thirty-five acetabular c o m p o n e n t s (42%) had no evidence of radiologic demarcation, 15 had demarcation in 1 zone, and 4 had 2 affected zones. Only 1 patient had demarcation in all 3 acetabular zones w i t h o u t evidence of migration [14]. Twenty-eight c o m p o n e n t s (34%) had migrated an average of 8 m m (range, 2-20 mm), in addition to having radiolucent demarcation, and 21 of these have b e e n revised. Two of the implants that migrated were the result of deep sepsis, and 8 of the surviving components are currently radiologically loose. A total of 27 acetabular components (33 % ) had u n d e r g o n e aseptic loosening. Twenty- five acetabular c o m p o n e n t s (30 %) have b e e n revised, at an average of 162 m o n t h s (13.5 years; range, 62-344 months) from the time of
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index arthroplasty. Nineteen were revised for aseptic loosening (23%) and 2 following deep sepsis, all of which had migrated. The remaining 4 were revised for excessive wear, 2 of which were associated with recurrent dislocation. The total a m o u n t of acetabular wear averaged 2.4 m m (range, 0-7.21 mm), and the average a n n u a l wear rate for the entire series was 0. i2 m m (range, 0-0.55 mm). The annual wear rate for surviving c o m p o n e n t s was 0.08 m m (range, 0-0.35 mm), and that for revised c o m p o n e n t s was 0.22 m m (range, 0.05-0.55 mm). This difference was statistically significant (P < .0 i). The alignment of the femoral c o m p o n e n t was neutral in 46 hips, valgus in 23, and varus in 14, but there was n o statistical difference in survivorship b e t w e e n these 3 groups (P = .3). Fifty-five femoral stems (66 % ) had no evidence of radiologic demarca tion, 12 had nonprogressive demarcation in only 1 Gruen zone, and 8 in 2 zones. Eight femoral components had demarcation in m o r e t h a n 3 zones and were radiologically loose. Subsidence occurred in a total of 16 hips (19%), although only 2 had subsided greater t h a n 5 m m and were definitely loose. A fracture of the tip of the c e m e n t mantle was seen in 8 hips (10%), 2 of which were the hips that had subsided m o r e t h a n 5 mm, with the r e m a i n d e r having all subsided less t h a n 5 ram. Osteolysis a r o u n d the femoral c o m p o n e n t occurred in 15 hips (18%), and changes in the calcar in 33 hips (40%). Twenty-six hips had loss of height of the calcar, and 7 had m a r k e d osteopenia. H y p e r t r o p h y of the femoral cortex at the level of the tip of the stem occurred in 32 hips (39%). Nineteen femoral c o m p o n e n t s (23%) were revised at an average of 166 m o n t h s (13.8 years; range, 62-245 months) from the time of index arthroplasty. Thirteen ( 16 %) were revised for aseptic loosening, 3 of which had an associated fracture of the femoral implant and 2 were revised following deep sepsis. Four c o m p o n e n t s were revised during surgery to replace a loose acetabulum, although these femoral implants were not actually loose but were replaced as they were t h o u g h t likely to have a damaged bearing surface. Only 2 of the surviving femoral implants are currently radiologically loose, giving an overall rate of aseptic femoral loosening of 18% (15 hips). Heterotopic ossification was seen in 27 hips (33%). Nineteen had Brooker class 1 changes and 5 were in class 2. There were no cases of b o n y ankylosis (class 4), and only 3 had class 3 changes, which caused slight reduction in the range of hip m o v e m e n t . Displacement of the trochanter occurred in 7 hips
(8%) and breakage of the wires in l l hips (13%). Four hips (5%) required further surgery as a consequence of wire breakage, 3 undergoing wire removal and 1 trochanteric reattachment. Survivorship of the femoral c o m p o n e n t was 93 % (95% confidence interval 8 7 - 9 8 % ) at 10 years, 76% ( 6 6 - 8 6 % ) at 20 years, and 73% (62-85%) at 25 years, with the corresponding values for the acetabulum being 92% (85-98%), 70% (60-81%), and 68% (57-79%), respectively. The survivorship for both of the original c o m p o n e n t s at 10 years was 89% (82-96%), and at 25 years was 65% (54-76%) (Figs. 1, 2).
Discussion Patients aged less than 30 years w h o require THA form only a small fraction of the typical arthroplasty population, even at specialist tertiary referral units. Only 93 of the 10,469 arthroplasties p e r f o r m e d at this institution during the study period were in such patients, accounting for less t h a n 1% of all cases. The scarcity of these patients is reflected in the limited n u m b e r s of previously reported studies, which usually consist of small n u m b e r s of patients, on w h o m a variety of implants have been used. Follow-up periods are often short, with m a n y patients being lost, as the y o u n g patient population is more mobile in response to family or occupational necessity t h a n their older counterparts. The poor early results reported in the literature led m a n y surgeons to r e c o m m e n d o s t e o t o m y and arthrodesis as alternatives [6,21,22], but these are not appropriate for all patients, such as those with bilateral disease. The worst results were reported in the youngest patients and those w h o had u n d e r g o n e previous operations [1,3,4,6], and arthroplasty was reserved for the patients w h o were most severely disabled by their hip disease. These motivated y o u n g patients were, however, willing to accept the high perceived risks of implant loosening and the likelih o o d of ultimate revision surgery, in exchange for the pain relief and i m p r o v e m e n t s in function that successful arthroplasty could offer them. In studies of patients aged less t h a n 45 years at the time of operation, White reported a revision rate of 14% at 7.5 years [23]. Dorr et al. reported a revision rate of 19% at only 4.5 years, with 45% of the surviving implants showing radiologic signs of impending failure [3]. Sharp and Porter reported a 14% revision rate at 6 years in patients aged less than 40 years and implicated r h e u m a t o i d arthritis as the main cause of loosening [24], and Williams and McCullough reported loosening in 24.6% of hips at
HipArthroplasty in Patients Under 30 82
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76
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60
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59
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Fig. l. TWenty-five-year survivorship curves (K~plan-Meier) for the femoral and acetabular components, both individually (A, B) and in combination (C), with tile 95 % confidence intervals and number of hips surviving, given at 5-year intervals.
4.5 years, b u t in 4 3 . 5 % of implants that h a d b e e n in place longer t h a n 5 years {25]. Revision was perf o r m e d in 2 1 % of patients aged less t h a n 30 years in a series reported by Chandler et al. {1], w i t h Joshi et al. also Iinding p o o r e r results in the u n d e r - 3 0 age group [4]. A recent study by Torchia et al. r e p o r t e d a
revision rate of 4 3 % at 12.6 years in patients aged less t h a n 20 years [61, but the series contained a wide range of prostheses a n d underlying pathologies including t u m o r cases. The complication rates in the current series were low, with no fatal p u l m o n a r y emboli, two nonfatal
128
The Journal of Arthroplasty Vol. 13 No. 2 February 1998
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Years Fig. 2. Combined 25-year survivorship curve showing the outcome for the acetabular and femoral components both individually and together.
emboli, and no other recorded cases of deep vein thrombosis. There w e r e no early dislocations a n d 2 late cases that w e r e associated with m a r k e d acetabular wear. This reflects the fact that the majority of the operations w e r e p e r f o r m e d either by the late Professor J o h n Charnley or by his senior colleagues, using a standardized surgical technique. Fracture of the femoral prosthesis occurred in 3 patients (4%), but the strength of the m o d e r n C h a m l e y implants has b e e n increased following the introduction of i m p r o v e d materials, a n d stem breakage has n o w b e e n eradicated [26,27]. All patients e x p e r i e n c e d m a r k e d pain relief, with 95% being pain-free, w h i c h is consistent with the rates of 8 9 - 9 5 % reported in other series [4,28-31]. The range of hip m o v e m e n t increased to an average of 210 ° in keeping with previous studies [23,26,29,31,32] a n d the i m p r o v e m e n t in function, a l t h o u g h obvious, was t e m p e r e d by the fact that the majority of patients h a d polyarticular disease. The rate of revision of the acetabular c o m p o n e n t was 30% at an average follow-up period of 20 years, w h i c h is better t h a n the 4 3 % at 12.6 years reported by Torchia et al. [6] or the 36% at 16 years reported by Joshi et al. [4]. The average a n n u a l acetabular w e a r rate for the entire series was 0.12 m m , in keeping with previously reported rates of 0.1-0.16 m m [28-30,33,34]. The average a n n u a l w e a r rate of 0.22 m m for revised c o m p o n e n t s was also similar to the reported rates of 0.19-0.21 m m for e x p l a n t e d
cups [15,35], a n d the difference in w e a r rates b e t w e e n surviving c o m p o n e n t s and the original cups that h a d required revision was highly statistically significant ( P < .01). This confirms a link b e t w e e n increased rates of acetabular w e a r and the d e v e l o p m e n t of c o m p o n e n t loosening, ultimately leading to revision, as has previously b e e n suggested by Wroblewski [32]. There was also an association b e t w e e n a n y evidence of acetabular d e m a r c a t i o n at 1 year and eventual c o m p o n e n t migration (P = .004) and revision (P = .004), as previously reported by Joshi et al. [4]. There was no association, in this series, b e t w e e n previous hip surgery a n d eventual revision (P = .7), as has b e e n suggested in earlier studies [1,3,4,6]. Femoral c o m p o n e n t revision was p e r f o r m e d in 2 3 % of hips, w h i c h was higher t h a n in m o s t series looking at the o u t c o m e of arthroplasty in older patients, but l o w e r t h a n the rates of 2 5 - 2 8 % at only 11 years reported in patients with j u v e n i l e - o n s e t r h e u m a t o i d arthritis [36, 37]. The subsidence rate of 19% was lower t h a n the rates of 2 5 - 4 0 % in m o s t l o n g - t e r m series [2,18,30,32,38], and the 10% rate of c e m e n t tip fracture was similar to the reported rates of 7 - 1 5 % [2,6,30,32,38]. H y p e r t r o p h y of the femoral cortex at the level of the tip of the prosthesis occurred in 39% of hips and was higher t h a n the reported rates of 1 6 - 2 9 % [4,26,32]. N o n e of these radiologic features was associated with an increased
HipArthroplasty in Patients Under 30 risk of revision, w i t h P v a l u e s of 0.06, 0.4, a n d 0.06, respectively. Osteolysis a r o u n d t h e f e m o r a l c o m p o n e n t was seen i n 18% of hips, w h i c h is higher t h a n rates i n most other series ranging from 3% to 10% [4,26,28,34], b u t is similar to t h e rates of 1 7 . 5 - 2 1 % i n t h e l o n g - l e r m studies r e p o r t e d b y W r o b l e w s k i a n d S i n e y {30,32]. The d e v e l o p m e n t of osteolysis was associated w i t h a h i g h a v e r a g e a n n u a l a c e t a b u l a r w e a r rate (P < .0 l) a n d its p r e s e n c e w a s also s t r o n g l y associated w i t h f e m o r a l l o o s e n i n g a n d i m p l a n t r e v i s i o n (P < .01), c o n f i r m i n g t h e l i n k b e t w e e n t h e g e n e r a t i o n of p o l y e t h y l e n e w e a r debris, t h e d e v e l o p m e n t of osteolysis, a n d f e m o r a l i m p l a n t l o o s e n i n g . C h a n g e s i n t h e m e d i a l f e m o r a l calcar o c c u r r e d i n 4 0 % of ]:tips, w i t h rates of 2 4 - 4 4 % h a v i n g b e e n r e p o r t e d i n p r e v i o u s series {4,6,26,32]. The d e v e l o p m e n t of calcar c h a n g e s was associated w i t h a h i g h a c e t a b u l a r w e a r rate (P < .01) b u t w a s n o t associated w i t h a n i n c r e a s e d risk of f e m o r a l i m p l a n t l o o s e n i n g (P = .07) or r e v i s i o n (P = .08). The c e m e n t e d C h a r n l e y l o w - f r i c t i o n a r t h r o p l a s t y p e r f o r m e d well u p to 25 years i n this g r o u p of active y o u n g p a t i e n t s . S u r v i v o r s h i p of t h e a c e t a b u l a r c o m p o n e n t was 9 2 % ( 9 5 % c o n f i d e n c e i n t e r v a l , 8 5 9 8 % ) at 10 years a n d 6 8 % ( 5 7 - 7 9 % ) at 25 years, w i t h t h e figures for t h e f e m o r a l c o m p o n e n t b e i n g 9 3 % ( 8 7 - 9 8 % ) a n d 7 3 % ( 6 2 - 8 5 % ) , respectively. The major factors d e t e r m i n i n g t h e l o n g e v i t y of t h e
•
Sochart and Porter
129
i m p l a n t w e r e l o o s e n i n g , m i g r a t i o n , a n d r e v i s i o n of t h e a c e t a b u l a r c o m p o n e n t , w h i c h w e r e associated w i t h a n i n c r e a s e d a v e r a g e a n n u a l w e a r rate. A n i n c r e a s e d rate of a c e t a b u l a r w e a r was also associated w i t h t h e d e v e l o p m e n t of f e m o r a l osteolysis, w h i c h c o n t r i b u t e d to f e m o r a l l o o s e n i n g a n d revision. The results of this l o n g - t e r m s t u d y s h o w t h e v a l u e of t h e use of a single, tried a n d tested, i m p l a n t design a n d surgical t e c h n i q u e , r e s u l t i n g i n l o w c o m p l i c a t i o n rates a n d c o m p o n e n t s u r v i v o r s h i p exc e e d i n g t h o s e r e p o r t e d i n earlier series. Y o u n g p a t i e n t s h a v e l o n g b e e n a c c e p t e d as b e i n g at h i g h e r risk of i m p l a n t l o o s e n i n g a n d failure, b u t t h e 25y e a r results i n t h e c u r r e n t series w e r e satisfactory (Tables 2, 3). I m p r o v e m e n t s i n c e m e n t i n g techn i q u e s {27,39], i m p l a n t materials, a n d p r o s t h e t i c design {18,26] are likely to result i n e v e n b e t t e r results for the f e m o r a l c o m p o n e n t s i n t h e f u t u r e . The c u r r e n t a i m of r e s e a r c h i n a r t h r o p l a s t y s u r g e r y s h o u l d t h e r e f o r e be to r e d u c e t h e i n c i d e n c e of a c e t a b u l a r c o m p o n e n t l o o s e n i n g , w h i c h a p p e a r s to be closely r e l a t e d to t h e issue of w e a r rates. The use of t h e s m a l l - d i a m e t e r h e a d size is c e n t r a l to t h e C h a r n l e y c o n c e p t of l o w - f r i c t i o n t o r q u e a n d c o n t r i b utes to l o w e r rates of l o o s e n i n g a n d debris g e n e r a t i o n [40,41], w i t h the v a l u e of i m p r o v e d b e a r i n g surfaces s u c h as ceramics c u r r e n t l y u n d e r i n v e s t i g a tion. The results of t h e c u r r e n t s t u d y are e n c o u r a g -
Table 2. Life-table Analysis for Femoral Components (<30 Years of Age: Stems) Years Since Operation
No. of Hips
No. of Failures
No. Withdrawn
No. Lost to Follow-up Evaluation
No. at Risk
0-i 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 I0-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20 20-21 21-22 22-23 23-24 24-25
83 83 83 83 83 83 82 82 82 80 79 77 76 75 74 7I 70 67 63 56 50 43 41 31 27
0 0 0 0 0 1 0 0 2 1 2 1 0 I 0 1 2 1 1 2 3 0 0 1 0
0 0 0 0 0 0 0 0 0 0 0 0 1 0 3 0 1 3 6 4 4 2 10 3 10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
83 83 83 83 83 83 82 82 82 80 79 77 75.5 75 72.5 71 69.5 65.5 60 54 48 42 36 29.5 22
AnnualFailure Annual Success Rate (%) Rate (%) 0 0 0 0 0 1.2 0 0 2.4 1.3 2.5 1.3 0 1.3 0 1.4 2.9 1.5 1.7 3.7 6.3 0 0 3.4 0
100 100 100 I00 100 98.8 100 100 97.6 98.8 97.5 98.7 100 98.7 100 98.6 97.1 98.5 98.3 96.3 93.8 100 i00 96.6 100
Survival Rate (%)
SE
100 100 100 I00 100 98.8 98.8 98.8 96.4 95.2 92.8 91.6 91.6 90.4 90.4 89.1 86.5 85.2 83.8 80.7 75.6 75.6 75.6 73.1 73.1
0 0 0 0 0 1.2 1.2 1.2 2.1 2.4 2.8 3.1l 3.1 3.2 3.2 3.4 3.8 4 4. l 4.5 5.1 5.1 5.I 5.5 5.5
130
The Journal of Arthroplasty Vol. 13 No. 2 February 1998 Table 3. L i f e - t a b l e A n a l y s i s for A c e t a b u l a r C o m p o n e n t s ( < 3 0 Years of Age: C u p s )
Years Since Operation
No. of Hips
No. of Failures
No. Withdrawn
No. Lost to Follow-up Evaluation
No. at Risk
A n n u a l Failure Rate (%)
Annual Success Rate (%)
Survival Rate (%)
SE
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 I7-18 18-19 19-20 20-21 21-22 22-23 23-24 24-25
83 83 83 83 83 83 82 82 82 79 78 76 73 72 71 68 67 61 58 52 48 41 40 31 29
0 0 0 0 0 1 0 0 3 1 2 3 0 1 0 1 5 0 3 1 2 0 i 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1 0 3 0 1 3 3 3 5 1 8 2 11
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
83 83 83 83 83 83 82 82 82 79 78 76 72.5 72 69.5 68 66.5 59.5 56.5 50.5 45.5 40.5 36 30 23.5
0 0 0 0 0 1.2 0 0 3.7 1.3 2.6 4 0 1.4 0 1.5 7.5 0 5.3 2 4.4 0 2.8 0 0
100 100 100 100 100 98.8 100 100 96.3 98.7 97.4 96.1 100 98.6 100 98.5 92.5 100 94.7 98 95.6 100 97.2 I00 i00
100 100 100 100 100 98.8 98.8 98.8 95.2 94 91.6 88 88 86.7 86.7 85.5 79 79 74.8 73.4 70.l 70.1 68.2 68.2 68.2
0 0 0 0 0 1.2 1.2 1.2 2.4 2.6 3.1 3.6 3.6 3.7 3.7 3.9 4.5 4.5 4.9 5 5.3 5.3 5.3 5.5 5.5
ing and the pessimism with which arthroplasty in patients aged less than 30 has traditionally been viewed should n o w be reconsidered.
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