A prospective study of Charnley low friction arthroplasty in patients under the age of 51 at the time of surgery.

1092 patients, 668 women and 424 men, mean age 41 years (12–51) at the time of surgery had 1434 Charnley low-friction arthroplasties carried out between November 1962 and December 1990. At mean follow-up 14.2 years (1 – 32), 742 patients (973 hips) are still attending and patients’ satisfaction with the outcome is 96.2%. Survivorship was 95.24% at 10 years and 58.67% at 27 years.

Patients who had had previous hip surgery had revision rate 24.8% compared with 14.1%. Patients with rheumatoid arthritis had fewer revisions than those with developmental hip dysplasia or primary osteoarthritis. Large 43 mm diameter cup gave lower revisions for aseptic cup loosening as compared with 40mm cup. Presence and preservation of subchondral plate, rim support compared to medialization of the cup, use of acetabular cement pressurizer and the reduced diameter neck (10mm) all made a contribution to reducing the incidence of revisions for aseptic cup loosening. Closing the medullary canal with bone block reduced the incidence of aseptic stem loosening. Use of the brace reamers did not affect the outcome and there appears to have been no advantage with the flanged stem.

The long-term problem was the increasing incidence of revisions for aseptic cup loosening. This was exponentially related to the depth of cup penetration by the head of the femoral component.

The long term clinical results of the Charnley LFA remain excellent even in young patients. Rim support of the cup, preservation of the subchondral bone of the acetabulum, cup flange and pressurising of the acetabular cement all make a significant contribution. Distal closure of the medullary canal and central position of the stem are of benefit, but reaming the medullary canal to cortex must be avoided. The long-term problem has been highlighted again as: wear and cup loosening.

We retrospectively analysed three hundred and one infected total hip replacements. Infection was defined on the basis of the surgeons clinical impression. This included a thorough history and physical examination, laboratory and radiographic evaluation. Peri operative findings were also taken into consideration.

Despite the overt appearances of sepsis fifty seven of these three hundred and one cases demonstrated no bacterial growth. These were excluded from the microbiological analysis.

The remaining two hundred and forty four cases oven bacteriological evidence of deep infection. Thirty seven cases grew two different organisms both of which were felt to be clinically significant. The remainder grew a single organism. Hence a total two hundred and eighty one bacteriological isolates were grown.

Coagulase negative staphylococcus accounted for 54.8%, staphylococcus aureus 13.5%, streptococci 8.9%, Escherichia coli 6.1% and diptheroids 2.5%.These organisms were plated out in a standard fashion against a variety of antimicrobial agents.

We analysed ten antibiotics and their sensitivity profiles against the spectrum of organisms demonstrated by this series.

Best antimicrobial coverage by a single antibiotic was afforded by fucidic acid (85.3%) and erythromycin (79.6%). Gentamicin was found to be sensitive to only 76.1% of the bacteria present at the time of revision for deep infection.

Combining gentamicin with other antibiotics improved the theoretical coverage. A combination of gentamicin and fucidic acid demonstrated a 97.5% coverage. Gentamicin with erythromycin gave 95.2%.

When treating the infected arthroplasty it may be beneficial to add extra antibiotics to bone cement. This may either be to the cement spacer in a two stage revision or to the definitive cement in a single stage revision. We would suggest that fucidic acid or erythromycin would be good candidates for this. These candidates should also be considered when designing the next generation of combination antibiotic acrylic bone cements.

Bacterial resistance in joint replacement surgery is an emerging problem. A review of the bacteriology from infected revisions performed at Wrightington over the past 5 years has shown that the most common organism is coagulase negative staphylococcus (59%), followed by staphylococcus aureus (17%).

The sensitivity profiles are shown below.

Gentamicin is the most commonly pre formulated antibiotic added to acrylic bone cement. The above data clearly demonstrates that for 32% of infected cases gentamicin alone is inadequate prophylaxis. As a consequence of this the use of additional antibiotics for resistant cases is becoming commonplace.

The aim of this study was to investigate the mechanical properties of additional antibiotics in acrylic bone cement.

The 7 antibiotics listed above were selected on the basis of sensitivity to organisms isolated at revision for deep infection. Each was added at a loading of 1g active to CMW1 RO (plain) and CMW1 G (gentamicin). The antibiotics were mixed with the polymer by hand. The cement was then mixed as per manufacturer’s instructions.

Dough and setting times were noted. Standard samples were produced using ISO approved moulds. Each antibiotic/cement combination was tested for compression strength, impact strength and flexural strength.

All antibiotic/cement combinations performed as well as the control mix when tested for compression and impact strength. The flexural strength results for fusidic acid and erythromycin when added to acrylic cement were comparable to the control mix. Flucloxacillin, clindamycin and teicoplanin did lower the flexural strength to just below acceptable limits. However Vancomycin when added at 1g active reduced the flexural strength of acrylic bone cement significantly.

Although vancomycin may remain one of the last bastions of antibiotic therapy our study suggests that’s its addition to acrylic bone cement significantly weakens its mechanical properties. We would advise caution in its use as this may reduce the chances of long term success when undertaking revision for deep infection.

Objective: To study the incidence of MRSA (Methicillin resistant Staphylococcus aureus) at pre-operative screening and relate this to positive cultures of the tissue in joint replacement surgery.

Setting: Elective joint replacement centre with routine MRSA screening facility.

Design: Retrospective review of MRSA screening and positive tissue samples taken during one year period from 1.11.99 to 31.10.00 in hip and knee replacements.

Results: Eighteen (18) out of the 2867(0.7%) screens performed on patients undergoing joint replacement surgery had MRSA isolated from one source or other. However, no MRSA was found from tissue samples taken during the surgery. But 63 isolates from 499 tissue samples (12.6%) were reported as coagulase negative staphylococcus, out of which 28(44%) were resistant to Methicillin.

After observing the incidence of Methicillin resistant coagulase negative staphylococcus during one year, we reviewed the tissue culture reports in revision hip replacements from May 1974 till July 1999. Two hundred ninety-one (291) positive organisms were isolated from 337 cultures, out of which 57.5% were coagulase negative staphylococcus 11.9% staphylococcus aureus. Methicillin resistance was noted in 30.8% of coagulase negative staphylococcus as opposed to 6% of staphylococcus aureus.

Conclusion: Staphylococcus epidermidis is the most prevalent and persistent species on human skin and mucous membranes, constituting 65–90% of all staphylococci (Mandell, Douglas & Bennett, 2000). Since a majority of isolation in tissue samples constitute methicillin resistant coagulase negative staphylococcus, would it be more appropriate to screen for Methicillin resistant Staphylococcus epidermidis (MRSE), rather than MRSA, in patients undergoing joint replacement surgery?

We reviewed prospectively cemented stem revision in 106 patients with severe femoral endosteal bone lysis without infection. Bone grafts were not used in any of the patients. The minimum follow-up was three years (mean 6 years 4 months). At the last review 76.4% of the patients were free of pain and 17.9% had only mild or occasional discomfort; radiographs showed well-fixed stable stems in 101 (95.3%). An intramedullary cement plug was used at revision to improve stability in 97.7%. There was new endosteal osteolysis after revision in 17 patients; only two had severe changes. Seven hips (6.6%) required a second revision; only four of these (3.8%) were for stem loosening. Survivorship of the revised stem, using radiological evidence of stem loosening as the end point, was 95.8% at seven years. The results of stem revision arthroplasty using cement in the presence of massive endosteal cavitation are satisfactory.

We reviewed the records and radiographs of 387 cemented revisions of aseptic loose sockets after total hip replacement at a mean follow-up of 5.5 years. The clinical results were satisfactory, but at the last radiological assessment 38 sockets (9.8%) had a continuous zone of demarcation greater than 1 mm thick and another 35 (9%) showed migration. Poor acetabular bone stock had a profound influence on the outcome of revision surgery, but the results of cemented revision were comparable to those reported for cementless revision at similar mean follow-up.

We reviewed 54 patients at a mean follow-up of 4 years 4 months after rerevisions for failure of Charnley low-friction arthroplasty. Rerevision for aseptic loosening in 26 hips was satisfactory; there were no clinical failures and at the latest radiological assessment only one stem and three sockets showed signs of loosening. By contrast, nine of 20 multiple revisions for recurrent dislocation failed, as did five of eight multiple revisions for deep infection. There was radiological evidence of loosening in one stem and nine sockets in the former group and in three stems and five sockets in the latter.

We reviewed 351 cemented revisions of femoral stems performed for aseptic loosening. At a mean of six years after the revision operation 72.1% of the patients were pain-free and 21.4% had only mild or occasional discomfort. The latest radiographs showed definite stem loosening in 10 (2.8%) and 20 hips (5.7%) had required rerevision, only nine (2.6%) of which were for mechanical failure of the stem. Survivorship analysis, taking the end point as rerevision of the stem, gave 97.0% survival at eight years and 91.6% at 11 years. Excellent results both clinically and radiologically can be achieved by cemented revision of the femoral stem for aseptic loosening.

We assessed 41 patients with rheumatoid arthritis (47 hips) who had had revision hip arthroplasty, at an average follow-up of 7 years 4 months (2 to 19). The clinical results were excellent or satisfactory in 43 hips. Radiologically, 45 stems were secure. Fifteen sockets (36.6%) were radiologically loose. Three hips required rerevision. Socket failure is the predominant problem in rheumatoid patients after cemented revision arthroplasty.

We report a prospective study of 57 one-stage cemented revisions of total hip replacement for deep infection with an actively discharging sinus. The average follow-up was 7 years 4 months. Seven patients had required rerevisions, but at latest follow-up, infection was under control in 49 (86%). A discharging sinus is not, in itself, a contraindication to one-stage revision of a hip replacement.

A flanged socket was introduced by Sir John Charnley for use in his low-friction hip arthroplasty in 1976. Experimental evidence has suggested that the flange offers an advantage in terms of cement pressurisation at the time of implantation. We have reviewed 302 primary Charnley arthroplasties followed for 9 to 11 years to determine the effect of the flanged socket on the radiological appearance. The incidence of radiological demarcation at the cement-bone interface is significantly reduced in early radiographs after the use of a flanged socket, and the advantage is maintained in the long-term results.

Laboratory wear testing of ultra high molecular weight polyethylene from 12 Charnley acetabular cups, removed after periods of up to 17.5 years showed that the large patient-to-patient variations in clinical penetration rate cannot be explained by batch-to-batch variation in the wear resistance of the material. Nor was there any evidence of a time-dependent degradation in wear resistance of the material.

In a prospective study, a double crossover wire with a compression spring was used to re-attach 52 un-united trochanters at revision operations on total hip arthroplasties. Bony union was achieved in 42 (81%) and was not influenced by the duration of the nonunion or the separation gap. The new method compared favourably with earlier revisions at which other methods of trochanteric re-attachment had been used.

A retrospective review of 72 cases of Charnley low friction arthroplasty revised for stem loosening, has identified a number of "at risk" factors. These were: previous hip surgery and, in radiographs taken at one year, demarcation of the distal cement and fracture of the cement near the tip of the stem. Separation of the back of the stem from the cement, as an isolated feature, was not considered significant. Endosteal cavitation of the femoral shaft, rare in the first year, indicated loosening of some duration. Patients whose radiographs show the "at risk" changes, should be followed-up indefinitely in order to plan timely revision and avoid gross loss of the femoral bone stock.

An experimental evaluation was made of the efficacy of an unflanged cup, an ogee-flanged cup and the Exeter pressuriser in the pressurisation of acetabular cement. Only a very modest injection pressure could be generated through an unflanged socket and even this was readily lost as the socket "bottomed out". The ogee-flanged socket gave a consistently high injection pressure which could be maintained throughout the process of polymerisation. The Exeter pressuriser gave marginally better results. Of the two cements tested, Palacos with gentamicin showed better intrusion than CMW Type 1 cement, but it also allowed greater extrusion once pressure was released. The importance of maintaining a continuous pressure on the cement throughout polymerisation is emphasised.

We report a retrospective review of 127 low friction arthroplasties carried out for the failure of a previous hip operation. After an average follow-up of 10.4 years, 20% of cases required further revision, over half of them for deep infection. We estimated from the radiographic appearances that eventual failure by loosening was probable in 58% on the femoral side and 56% on the acetabular side of the arthroplasties.