LONG TERM RESULTS OF REVISION TOTAL HIP ARTHROPLASTY

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1 LONG TERM RESULTS OF REVISION TOTAL HIP ARTHROPLASTY D. J. ENGELBRECHT, F. A. WEBER, M. B. E. SWEET, I. JAKIM From the University ofthe Witwatersrand, Johannesburg A total of 138 revision hip arthroplasties in 134 patients, all operated upon by one surgeon, were followed for an average of 7.4 years. The overall results were reasonable, with good to excellent Mayo hip scores in 62% and little or no pain in 86%. These results were independent of body weight, age, primary diagnosis and type of arthroplasty used. The incidence of radiologlcal loosening was alarming, though comparable to that found in other series. Our findings indicate that it may be wise to replace both components even when, after careful assessment before and during operation, one of them seems to be securely fixed. The need for revision operations after total hip arthroplasty has increased with the widening of the indications for primary replacement. Both the complexity of the procedure and the potential for complications exceed those for primary arthroplasty. We have analysed patient satisfaction and the clinical and radiological outcome of a series of revision arthroplasties followed for an average of 7.4 years. MATERIALS AND METHODS From 1973 to 1985, 193 cemented total hip arthroplasties were revised for mechanical failure after between one and 16 years (average 5.6 years). A total of 138 hips in 134 patients (mean age 59.2, range 25 to 85 years) were available for study at 3 to 15.5 years (average 7.4 years) after revision ; 15 had died from unrelated causes and there was one pen-operative death ; 22 could not be traced and 17 had undergone further surgery, including removal ofprostheses for deep sepsis in three. The modes D. J. Engelbrecht, FCS, Lecturer and Consultant Orthopaedic Surgeon F. A. Weber, FRCS, Consultant Orthopaedic Surgeon M. B. E. Sweet, MB, PhD, Reader in Experimental Orthopaedics and Consultant Orthopaedic Surgeon I. Jakim, MD, Senior Lecturer, Senior Consultant and Head of Department Department of Orthopaedic Surgery, University of the Witwatersrand Medical School, 7 York Road, Parktown 2193, Republic of South Africa. Correspondence should be sent to Dr I. Jakim British Editorial Society ofbone and Joint Surgery 030l-620X/90/lOl6 $2.00 JBoneJointSurgfBr] 1990; 72-B: of mechanical failure had included symptomatic aseptic loosening (1 12 patients), fracture of one or both components (9), and recurrent dislocation (9). All the failed prostheses were conventional total hip replacements fixed with polymethylmethacrylate, and included McKee- Farrar (21), Charnley (48) and MUller (69) prostheses. Six patients had been converted from excisional arthroplasty for previous failure of total hip arthroplasty. Of the 1 12 with component loosening, 27 had cup loosening, 20 had femoral stem loosening and 65 had loosening of both components. Before revision, sepsis was excluded by clinical examination, blood investigations including ESR, FBC, and serum iron studies (Weber and Lautenbach 1986), radiological examination including scintigraphy and, in suspicious cases, hip aspiration. Clinical and radiological data were used to compute individual Mayo hip scores with the dual aims of critical overall evaluation (Pellicci et al 1985) and of comparison with other series. All data were computerised and subjected to statistical analysis. Radiographs were taken by standard techniques and corrections for magnification, rotation and summation of errors were made by the methods of Sutherland et al (1982). The following features were recorded from an anteroposterior radiograph of the pelvis: Acetabular side a) cup inclination to the horizontal; b) presence, location and width of radiolucent lines; c) acetabular component coverage (Sutherland et al 1982); d) migration of the acetabular component (Callaghan et al 1985). VOL. 72-B, No. 1, JANUARY

2 42 D. J. ENGELBRECHT, F. A. WEBER, M. B. E. SWEET, I. JAKIM Femoral side a) varus/valgus inclination; b) vertical subsidence (measured from the inferior margin of the collar of the prosthesis to the top of the lesser trochanter). A difference of 5 mm or more between the immediate postoperative measurement and subsequent measurements was considered to indicate subsidence (Callaghan et al 1985 ; Brand, Pedersen and Yoder 1986); c) presence, location and width of radiolucencies at the cement- bone and the cement-prosthesis interfaces; d) presence of fractures in the cement mantle. Bone quality Bone stock was assessed as good or poor (Callaghan et al 1985) by comparison of radiographs taken at the time of revision with those taken at follow-up. Operative technique. All operations were done by one experienced surgeon (FAW), thus eliminating the influence of the learning curve (Eftekhar and Tzitzikalakis 1986), and were performed in a laminar flow theatre augmented by body exhaust equipment. Pen-operative antibiotics were given. Trochantenic osteotomy was routine ; the tnochanter was re-attached by wines (61 hips), U bolts (19 hips) on wines and Charnley staples (58 hips). Cement was removed using power instruments on standard revision instruments. Anterior windows made for removal of distal broken stems and any accidental penfonations were gnafted with autogenous bone. Cane was taken to extend the new stem beyond any window. After removal of all cement, the femonal and acetabulan beds were prepared to maximise the shear strength of the cement-bone interface (Halawa et al 1978), and gentamycin-impnegnated cement was introduced using pressunisation. The acetabulum alone was revised in 18 hips, and the femonal component only was replaced in 15 hips. Mullen prostheses were used in 22 hips, the Gnobbelaan prosthesis in 24, Charnley components in 56, and the Ceraver-Osteal cemented stem with a titanium screw-in cup in 36. All femoral stems were cemented. For acetabulan revision, a reconstruction ring and cemented cup was used in 19, and combined with allograft in nine; allognaft was used with cement in six, and a cementless titanium screw-in cup and allograft augmented with autogenous graft in 12. Operating time averaged four houns when both components were replaced, and three hours when one component was revised. Patients received an average of 4 units of blood. Bacteriological cultures were taken during operation. Postoperative management. Most patients were mobilised within 48 hours and used crutches for six weeks, but when there had been technical difficulty with neattachment of the greaten trochanten, patients were kept in bed in abduction for 10 to 21 days. They were then mobilised on crutches until there was radiological evidence of union or until abductor function was considered satisfactory. No anticoagulant therapy was given, but graduated elastic stockings were worn for six weeks. RESULTS Systemic complications. Of the 134 patients reviewed, five (3.7%) developed pulmonary embolism ; the one penoperative death was attributed to this complication. Table I. Results related to the revision of a single or both components (number and percentage of whole series) Good or excellent Fair Poor Local complications. The three patients with deep infection, from whom the prostheses were removed, were excluded from the detailed review, but gave an overall known incidence of 1.6% in 193 hips. In the 138 hips reviewed there was only one superficial wound infection, with a fj-haemolytic streptococcus, that resolved with local treatment. Fracture of the femonal shaft occurred after operation in two osteoporotic patients (1.4%); they were treated by plating and bone graft. There were four dislocations (2.9%), one of which has persisted. Table H. Correlation of the final Mayo hip score with age (number, per cent) Age In years <45 45t o65 >65 Goodorexcellent Fair Poor Late complications. Non-union ofthe trochanten was seen in 31 hips (22.5%); there was no statistical correlation with the clinical scone. Pain related to the trochanten was found in eight patients (6%). Removal of the wine was necessary in five (3.7%) and re-operation in an attempt to re-attach the trochanter was done in five (3.7%), of which three united. There was a definite correlation between dislocation and trochantenic detachment with more than 2 cm of separation. THE JOURNAL OF BONE AND JOINT SURGERY

3 LONG TERM RESULTS OF REVISION TOTAL HIP ARTHROPLASTY 43 Ectopic bone formation was observed in 55 hips; grade 1 in 23, grade 2 in nine, grade 3 in 16 and grade 4 in seven (Bnooker et al 1973). There was no correlation between grades 3 and 4 ectopic bone formation and poor hip scones : 15 had good results, four fair and four had poor results). Table III. Correlation of the final Mayo hip score with the primary diagnosis (number, per cent) Osteoarthritis Post-traumatic Other Good or excellent Fair Poor Definitive failures. Of the whole series of 193 hips, 17 (8.8%) had needed a further operation : 14 for mechanical failure and three for deep sepsis. Latest assessment. Ofthe 134 patients, 123 (92%)neported satisfactory reduction of pain, the others being unhappy with the degree of pain relief. Similarly, 120 (90%) were happy with their functional improvement. In netrospect, however, only 84.5% of the patients necalled satisfactory pain relief after their primary procedure, and 85.7% satisfactory functional improvement. Table IV Correlation of overall Mayo hip score with the radiological score for the femoral stem (number, per cent) Probably loose Probably stable Goodorexcellent Fair Poor Mayo hip scores were good to excellent in 62%, fair in 18%, and poor in 20%. Of the 18 hips in which the acetabular component only was nevised, nine had poor results. Where the femonal stem only was replaced (15 hips) thene wene three poor results. Where both components were revised 73 out of 105 hips did well (Table I). The differences between these groups were statistically significant, indicating that betten results can be anticipated when both components are revised. Of the 115 (86%) patients with little or no pain, 23 limped severely. In 17 this was due to limb length discrepancy of over 2 cm, and in six there was abductor insuffiency. Of the 14 patients with moderate pain, eight limped badly and six slightly. All five patients with severe pain limped badly. The time to revision (mean 5.6 years), body weight, age (Table II), primary diagnosis and the presence of associated medical problems had no statistically significant effect upon the final assessment. Although the incidence of poor results was higher (1 7 of 61, 28%) in those patients revised within 5.6 years of the primary arthroplasty than in those revised later (eight of 64, 12.5%), this diffenence was not statistically significant. Of the patients weighing more than 86 kg, four of 29 (14%) did badly, while 10 of 36 (28%) weighing less than 65 kg scored poorly. Although suggestive, this diffenence was not significant (p = 0.607), and may be related to restriction of activity in obese individuals. White (1988) found no correlation between increased weight and poor clinical result. An apparently greaten proportion of patients undergoing revision for conditions other than osteoarthnitis on post-traumatic arthritis had poor results (Table III); however, this difference was not significant (p = 0.232). There was no correlation between clinical outcome and the type of acetabular reconstruction. Radiological assessment. The radiological assessment for the femoral component suggested that 43 stems were loose : there were six cases ofsubsidence, five with cement cracks and 32 with complete radiolucency widen than 1 mm in any one zone. There was a strong correlation between radiological loosening and clinical result (Table IV). A varus stem correlated strongly with a poor femoral scone (p = 0.004). On the acetabular side the scones indicated probable loosening of 53 components; there were 13 cases of component migration, of which 10 were titanium screwin cups. There were 40 cases (six titanium screw-in cups) with complete nadiolucent lines greaten than 2 mm in any one zone. There was a higher rate of loosening, as determined radiologically, in the screw-in, non-cemented acetabular components (p = 0.017). An important finding was that we were unable to show any difference in the clinical outcome whether the cup was radiologically loose or not. The smaller the lever arm ratio between abductor and body-weight lever arms ( < 1.35) the better the radiological result ; this was statistically significant (p = 0.035). Evaluation of bone stock in the acetabulan bed showed a correlation between radiological loosening and poor bone stock (p = 0.014). In those cases of acetabular loosening in which the acetabular component only had been revised, four of nine femoral stems displayed radiological loosening, compared with two of 1 1 in cases where both components had been revised in order to achieve component compatibility. In revisions for aseptic loosening of the stem in which only the femoral component had been revised, four of six cups were radiologically loose compared to one of six when both components had been replaced. Although these figures suggest that both components should be revised, in most cases the numbers VOL. 72-B, No. 1, JANUARY 1990

4 44 D. J. ENGELBRECHT, F. A. WEBER, M. B. E. SWEET, I. JAKIM are too small for statistical evaluation. Intra-openative evaluation of loosening is probably unreliable. Whether or not patients were taking non-stenoidal anti-inflammatory agents made no difference (p = 0.57) to the radiological assessment of either the acetabulan or the femoral component. DISCUSSION Because little long-term follow-up data is available the final outcome of revision of a total hip arthnoplasty is uncertain. Short-to medium-term studies have reported varying degrees of success (Hunter et al 1979 ; Amstutz et al 1982 ; Callaghan et al 1985 ; Kavanagh, Ilstrup and Fitzgerald 1985 ; Pellicci et al 1985). Our series is most comparable to that of the longest published follow-up, Pellicci et al (1985) who followed 99 patients for 5 to 12.5 years. Radiolucent lines are common in revised arthroplasties, the incidence ranging from 20% to 61% on the acetabular side, and from 43% to 53% on the femonal side (Amstutz et al 1982; Pellicci et al 1982; Kavanagh et al 1985). This sign is probably only clinically significant if it is progressive (Carlsson and Gentz 1984 ; Pellicci et al 1985); but it must be considered indicative of eventual failure (Pellicci et al 1985). The incidence of radiolucencies in our series is similar to that in other published figures and suggests that the bone-cement interface after revision is such that long-term fixation will not equal that for primary arthnoplasty. The question of whether to replace one on both components at revision has been the subject of some debate. Kavanagh et al (1985) have advocated replacement of the loose component only. Where the femonal component only was replaced for femoral loosening, we found that 67% of the cups were radiologically loose at follow-up. This compared with 16% of cup loosening in cases where both components had been replaced. We share the opinion of O Neil and Harris (1984) that the presently available methods of pre- and intra-openative assessment of loosening are limited. It seems clean that whatever factors affecting the bone-cement interface are operative in any one patient (Ling 1986), these will not only have compromised the primary procedure, but will also influence any revision arthnoplasty. In addition to time-related failure of the unrevised component, a type of shielding effect may be operative. Thus peak stresses which were previously dissipated by one loose component are, after revision, transmitted by a well-fixed component without dissipation. Revision arthnoplasty calls for a wide exposure which, in our opinion, necessitates trochantenic osteotomy. The reported incidence of trochantenic non-union ranges from 3% to 27% (Goodman and Schatzker 1987; Schutzen and Harris 1988); we found an incidence of 22.5%, irrespective of the method of fixation. Separation of less than 1 cm was observed in half of the hips. The lack of any statistical correlation between non-union and a poor clinical result suggests that fibrous union can stabilise the trochantenic fragment, and that the abductons can adapt to this degree of shortening (Glassman, Engh and Bobyn 1987). It must be noted that all those hips which dislocated did so in the presence of trochantenic detachment of greaten than 2 cm. In our series 19% of those patients with little on no pain had a limp, which was generally due to limb length discrepancy ; we consider that stability should not be sacrificed for the sake oflimb length equality. We found a high rate of migration without radiolucency after the use ofself-tapping titanium screw-in cups, but this did not correlate with poor clinical results. Knahr et al (1987) have shown that cup migration with nadiolucent lines around an uncemented acetabulan component is indicative of progressive instability. However, in the absence of generally accepted criteria for the potential failure of non-cemented components, we adopted a conservative view in grading cases with migration of oven 5 mm, allotting each 0 points in the radiological score of the acetabulan component. On the acetabulan side there was a statistically significant correlation between bone stock and the radiological score, but this did not apply on the femonal side, whether the revision had been successful or not. This is in agreement with the findings of Goodman and Schatzker (1987). Despite steady advances in techniques for primary arthnoplasty, the potential for failure remains. All the operations in this series were performed by one surgeon and it is worth noting that the results were similar for each type of arthroplasty employed. Although revision arthnoplasty offers the patient the best chance of restoration of function and freedom from pain, the durability of the procedure remains doubtful. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. REFERENCES Amstutz HC, Ma SM, Jinn*h RH, Mal L Revision of aseptic loose total hip arthroplasties. C/in Orthop 1982; 170 : Brand RA, Pedersen DR, Yoder SA How definition of loosening affects the incidence of loose total hip reconstructions. C/in Orthop 1986; 210: Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr. Ectopic ossification following total hip replacement : incidence and a method of classification. I Bone Joint Surg [Am] 1973 ; 55-A: Carlsson AS, Gentz C-F. 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