Abstract
Of the 11 054 Charnley low-frictional torque arthroplasties carried out at our hospital between 1962 and 1977, 110 (94 patients) had a minimum follow-up of 30 years with a mean of 32.3 years (30.0 to 40.5). The mean age of the patients at operation was 43.3 years (17.0 to 65.0) and 75.7 years (51.0 to 97.0) at follow-up. Overall, 90% of hips (99) were free from pain and activity was reported as normal in 58% of the patients.
A total of 13 hips (11.8%) were revised at a mean follow-up of 32.3 years (30.0 to 39.5), with wear and loosening of the acetabular component as the main indications.
The clinical results did not reflect the mechanical state of the implant. Follow-up with sequential radiographs of good quality is essential. Revision for radiological changes alone must be accepted if gross loss of bone stock is to be avoided.
Improvements in the design, materials and operative technique, based on the long-term outcome, are highlighted.
The Charnley low-frictional torque arthroplasty (DePuy International, Leeds, United Kingdom) was introduced into routine clinical practice in November 1962. Its fundamental principles remain unchanged. A small head of 22.225 mm diameter articulates with a thick ultra-high-molecular-weight polyethylene (UHMWPE) acetabular component, both components being cemented with polymethylmethacrylate (PMMA) to ensure the largest possible area of load distribution.1 Using a routine transtrochanteric approach, the operation is carried out in a clean-air enclosure with total-body exhaust suits.
The results of operations performed between November 1962 and December 1965, with a follow-up of four to seven years, were published by Charnley in 1972.2 More recently, survival patterns to 38 years have been reported.3
Our aim is to present the clinical results and radiological appearance in patients with a minimum follow-up of 30 years and to establish the correlation between them.
Patients and Methods
We examined the records of all the patients who underwent primary low frictional arthroplasty between December 1962 and December 1977 at Wrightington Hospital and sought the help of the Office of National Statistics to trace those who did not attend for follow-up.
During the 15-year period, 11 054 low-frictional arthroplasties were carried out by more than 130 surgeons. Detailed clinical and radiological information was available for 89 patients (105 low-frictional arthroplasties). We were able to trace a further five each with one arthroplasty) in whom the information was incomplete. In three, only the most recent radiographs at 32, 34 and 35 years were available and were included in the radiological studies. One died after follow-up for 36 years. The clinical result, as reported by a relative, was excellent and a radiograph after 30 years was available. The details were included in the clinical and radiological studies.
One low-frictional arthroplasty included in our study was revised at 33 years at another hospital for wear and fracture of the acetabular component.4
The 94 patients (110 low-frictional arthroplasties) in this study had a mean age at operation of 43.3 years (17.0 to 65.0) and mean weight of 64.0 kg (48 to 96). The mean follow-up was for 32.3 years (30.0 to 40.5) and the mean age of the patients at follow-up was 75.7 years (51.0 to 97.0). The underlying pathology of the hip is shown in Table I and previous operations in Table II.
Table I.
Details of the underlying pathology of the hip (in some patients more than one diagnosis applied)
| Number (%) | |
|---|---|
| Osteoarthritis | |
| Primary | 35 (31.8) |
| Secondary | |
| Congenital dislocation, dysplasia, subluxation | 23 (21) |
| Perthe’s disease | 6 (5.5) |
| Slipped upper femoral epiphysis | 6 (5.5) |
| Infection | 5 (4.5) |
| Avascular necrosis | 4 (3.6) |
| Fractured neck of femur | 7 (6.4) |
| Rheumatoid arthritis | 17 (15.5) |
| Ankylosing spondylitis | 8 (7.3) |
| Idiopathic protrusio | 2 (1.8) |
| Unspecified | 4 (3.6) |
Table II.
Details of previous operations
| Procedure | Number (%) |
|---|---|
| Femoral osteotomy | 7 (6.4) |
| Open reduction of hip | 5 (4.5) |
| Acetabular component arthroplasty | 3 (2.7) |
| Fracture fixation | 2 (1.8) |
Operative details.
The acetabulum was curetted in 20 hips and in 90, Charnley acetabular reamers located through the pilot hole were used. Extra anchoring holes for injection of cement were used in 72, one hole in five, two in 15, three in 40, and more than three in 12. The original scalloped-edge (non-flanged) acetabular component was used in all cases. This was a standard 43 mm diameter implant in 71 and a small 40 mm diameter version in 39. Plain CMW cement (CMW Laboratories; DePuy International, Blackpool, United Kingdom) was used in all cases. It was spoon-mixed in an open bowl with barium sulphate powder added as the opacifier. The acetabulum was washed with normal saline and dried with a swab before finger-packing the cement, which was pressurised with the component. This was medialised5 in 58 and placed within the rim in 51. One cup was not fully contained within the acetabulum. Bone grafting was not used. The medullary canal was prepared with broaches in 68 hips and brace reamers in 42. It was washed with saline and dried with a swab. Cement was thumb-packed in all cases. The medullary canal was not sealed off distally except in four hips in which a bone block with proximal venting was used.6
A monoblock, polished, stainless-steel femoral component was used in all cases. In 80 this was the original ‘flat-back’ design in EN58J (the standard quality for a stainless steel implant). The other 30 were ‘round-back’, with matt finish in 316L stainless steel (21 standard, 6 three-quarter neck length, 2 ‘extra heavy’ and 1 CDH).
Clinical assessment was according to Merle d’Aubigné and Postel7 as modified by Charnley.2 The Charnley ABC categories2 were used to assess the function of walking in which grade ‘A’ denoted involvement of only one hip and no other factors affecting the ability to walk, grade ‘B’ denoted involvement of both hips and no other factors and grade ‘C’, the presence of other factors, such as cardiovascular or respiratory disability, as well as hip problems. The radiological appearance of the bone-cement interface of the components was determined according to the method of Hodgkinson, Shelley and Wroblewski8 and Harris, McCarthy and O’Neill9 respectively. Wear of the acetabular component was measured as described by Griffith et al.10
The indications for revision and the findings at revision were recorded.
Results
Clinical.
At the latest follow-up, 90% of the hips (99) were reported to be free from pain, 6% (seven) had occasional discomfort and 4% (four) had pain on activity. Functional activity was considered to be normal in 58% (64 hips). In 26% (29 hips) support for walking was required and in 15% (17 hips), activities were limited. Between operation and follow-up the number of Charnley grade A hips had decreased from 25 (23%) to 12 (11%), grade B from 56 (51%) to 46 (42%), and grade C had increased from 29 (26%) to 52 (47%).
Radiological appearance.
The anteroposterior (AP) radiographs showed 70 femoral components to be in the neutral position, 30 in valgus and ten in varus. Post-operative complications, early and late, are given in Tables III and IV. Radiographs at one year showed that 38 acetabular components (34.5%) had a perfect cement-bone interface and no demarcation and 70 (63.6%) had demarcation which involved the outer-third in 49, the outer two-thirds in 15 and was complete in six. None, however exceeded 1 mm and all components were therefore classified as secure. One acetabular component was radiologically loose (0.9%) and one had migrated (0.9%).8 On the latest radiographs, which included cases before revision, 73 hips (66.4%) had a secure acetabular component, four (3.6%) had no demarcation of the cement-bone interface, 69 (62.7%) had various degrees of demarcation (outer-third in 35, two-thirds in 20 and complete demarcation in 14), but none exceeded 1 mm.8
Table III.
Details of complications occurring within one year
| Complication | Number (%) |
|---|---|
| Delayed wound healing | 2 (1.8) |
| Trochanteric nonunion | 2 (1.8) |
| Deep-vein thrombosis | 1 (0.9) |
| Pulmonary embolism | 9 (8.2) |
| Urinary retention | 3 (2.7) |
| Chest infection | 2 (1.8) |
Table IV.
Details of late complications
| Complications | Number (%) |
|---|---|
| Dislocation | 4 (3.6) |
| Infection | 2 (1.8) |
| Loose acetabular component | 31 (28.2) |
| Loose femoral component | 8 (7.3) |
| Fractured femoral component | 1 (0.9) |
The mean rate of penetration of the acetabular component for the whole group was 0.06 mm/year (0.01 to 0.23) with a mean total penetration of 2.07 mm (0.4 to 7.0). Secure components had a lower mean rate of penetration of 0.0567 mm/year (0.011 to 0.233) and a lower mean total penetration of 1.8 mm (0.4 to 6.0) as compared with loose and migrated components which had a mean rate of 0.0812 mm/year (0.02 to 0.278) and a total mean penetration of 2.62 mm (0.7 to 7.0).
There were no cases of endosteal cavitation of the femur within one year. In four hips (3.6%) there was cortical thickening at the tip of the stem.
At the latest follow-up, 99 (90.0%) hips showed a normal appearance, while 11 (10.0%) showed endosteal cavitation almost exclusively in the proximal zones 2 and 7 of Gruen, McNiece and Amstutz,11 which was interpreted as the consequence of strain shielding of the proximal femur. Distal cortical thickening was present in 27 hips (24.5%) and absent in the remaining 83 (75.5%). Two femoral components (1.8%) were definitely loose and 12 (10.9%) were possibly loose.9
The correlation between the clinical results2,7 and the radiological appearance8,9,11 is shown in Figure 1a for the acetabular component and Figure 1b for the femoral component. On the acetabular side the mean scores for pain, function and movement for the secure components were 5.8 (4 to 6), 4.6 (2 to 6), and 4.7 (3 to 6) whereas for the loose components the mean scores were 5.6 (4 to 6), 4.4 (2 to 6), and 4.2 (3 to 6), respectively. On the femoral side, the mean scores for secure components were 5.7 (4 to 6), 5.1 (2 to 6), and 5.1 (3 to 6) whereas for loose components they were 4.2 (4 to 5), 3.9 (3 to 5), and 4.1 (3 to 5), respectively.
Fig. 1a, Fig. 1b
Bar charts showing a) comparison of the clinical results in patients with radiologically secure and loose acetabular components and b) the comparison of the clinical results in patients with radiologically secure and loose femoral components.
A total of 13 low-frictional arthroplasties (11.8%) had been revised (Table V) at a mean follow-up of 32.3 years (30.0 to 39.5), two (1.8%) for late deep infection, five (4.5%) for loosening of the acetabular component (including a worn fractured component4 revised at another hospital), four (3.6%) for loosening of both components, one (0.9%) for loosening and one (0.9%) for fracture of the femoral component.
Table V.
Details of revisions
| Cause | Number (%) |
|---|---|
| Deep infection | 2 (1.8) |
| Loose, worn, fractured acetabular component | 5 (4.5) |
| Both components loose | 4 (3.6) |
| Loose femoral component | 1 (0.9) |
| Fractured femoral component | 1 (0.9) |
Discussion
The clinical success of the Charnley low-frictional arthroplasty continues, with a follow-up beyond 40 years and the hallmark of that success is freedom from pain.
The level of activity at this length of follow-up reflects age and medical comorbidities. The clinical results do not reflect the mechanical state of the implant. Radiologically loose and even migrating acetabular components cannot be identified or distinguished from secure acetabular components by reference to the clinical results (Fig. 1a).
Radiologically loose femoral components may be symptomatic (Fig. 1b), probably because of the pistoning effect of the stem-cement composite giving increased intramedullary pressure. Understanding the mechanics of a cemented femoral component has proved to be of great benefit.12
Wear and loosening of the acetabular component are the main indications for revision. Loosening, however, may not be progressive, especially in patients with declining function. Monitoring and the taking of good quality radiographs are essential and timely intervention will avoid major mechanical problems.
Tissue reaction to UHMWPE wear particles is unlikely to be the cause of loosening of components. The exponential correlation between the depth of penetration of the acetabular component and the incidence of migration13 is not reflected in the incidence of aseptic loosening of the femoral component.14 Impingement of the neck of the femoral component on the rim of the polyethylene15 is more likely to be the cause. Reduction of the diameter of the neck of the femoral component stem from 12.5 mm to 10 mm has lowered the incidence of migration of the acetabular component, at comparable depths of penetration, by a mean of 54%.16 Also, the additional benefit of the low-wearing alumina cross-linked polyethylene combination is notable.17
The longest follow-up results are in young patients and have been achieved with the earliest design, materials and operative technique, all supporting the original Charnley concept. Evolutionary development, based on the concept has allowed the logical introduction of improvements. We recommend early revision in patients with radiological evidence of loosening of either component. For a young patient total hip arthroplasty is merely the beginning of treatment.
The study was supported by the Peter Kersahw and John Charnley Trusts.
We thank the surgeons who carried out the operations and to the Office of National Statistics for their help in tracing patients.
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
1 Charnley J. Low friction arthroplasty of the hip: theory and practice. Berlin etc: Springer-Verlag, 1979:12. Google Scholar
2 Charnley J. The long-term results of low-friction arthroplasty of the hip performed as a primary intervention. J Bone Joint Surg [Br]1972;54-B:61–76. Google Scholar
3 Wroblewski BM, Siney PD, Fleming PA. Charnley low-friction arthroplasty: survival patterns to 38 years. J Bone Joint Surg [Br]2007;89-B:1015–18. Google Scholar
4 Wroblewski BM, Siney PD, Fleming PA. Wear and fracture of the acetabular cup in Charnley low-friction arthroplasty. J Arthroplasty1998;13:132–7. Google Scholar
5 Charnley J. Total prosthetic replacement of the hip: in relation to physiotherapy. Physiotherapy1968;54:406–11. Google Scholar
6 Wroblewski BM, van der Riti AJ. Intramedullary cancellous bone block to improve femoral stem fixation in the Charnley low-friction arthroplasty. J Bone Joint Surg [Br]1984;66-B:639–44. Google Scholar
7 Merle d’Aubigné M, Postel M. Functional results of hip arthroplasty with acrylic prosthesis. J Bone Joint Surg [Am]1954;36-A:451–75. Google Scholar
8 Hodgkinson JP, Shelley P, Wroblewski BM. The correlation between roentgen-ographic appearances and operative findings at the bone-cement junction of the socket in the Charnley low-friction arthroplasties. Clin Orthop1988;228:105–9. Google Scholar
9 Harris WH, McCarthy JC, O’Neill DA. Femoral component loosening using contemporary techniques of femoral cement fixation. J Bone Joint Surg [Am]1982;64-A:1063–7. Google Scholar
10 Griffith MJ, Seidenstein MK, Williams D, Charnley J. Socket wear in Charnley low friction arthroplasty of the hip. Clin Orthop1978;137:37–47. Google Scholar
11 Gruen TA, McNiece GM, Amstutz HC. “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop1979;141:17–27. Google Scholar
12 Wroblewski BM, Siney PD, Fleming PA. Triple tapered polished cemented stem in total hip arthroplasty: rationale for the design, surgical technique and 7 years of clinical experience. J Arthroplasty2001;16(Suppl 1):37–41. Google Scholar
13 Wroblewski BM. Charnley low friction arthroplasty in patients under the age of 40 years. In: Sevastik J, Goldie I, eds. The young patients with degenerative joint disease. Stockholm: Almquist & Wiksell, 1985:197–201. Google Scholar
14 Wroblewski BM, Siney PD, Fleming PA. Wear of the cup in the Charnley LFA in the young patient. J Bone Joint Surg [Br]2004;86-B:498–503. Google Scholar
15 Wroblewski BM. Direction and rate of socket wear in the Charnley low-friction arthroplasty. J Bone Joint Surg [Br]1985;67-B:757–61. Google Scholar
16 Wroblewski BM, Siney PD, Fleming PA. Reduced diameter of the neck of the stem and its effect on the incidence of radiographic cup loosening and revisions in Charnley low-frictional torque arthroplasty. J Arthroplasty2009;24:10–14. Google Scholar
17 Wroblewski BM, SIney PD, Fleming PA. Charnley low friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene: a 10 year follow-up. J Bone Joint Surg [Br]1999;81-B:54–5. Google Scholar
