We have developed a new drug delivery system using porous apatite-wollastonite glass ceramic (A-W GC) to treat osteomyelitis. A-W GC (porosity, 70% and 20% to 30%), or porous hydroxyapatite (HA) blocks (porosity 35% to 48%) used as controls, were soaked in mixtures of two antibiotics, isepamicin sulphate (ISP) and cefmetazole (CMZ) under high vacuum. We evaluated the release concentrations of the antibiotics from the blocks. The bactericidal concentration of ISP from A-W GC was maintained for more than 42 days, but that from HA decreased to below the detection limit after 28 days. The concentrations of CMZ from both materials were lower than those of ISP. An in vivo study using rabbit femora showed that an osseous concentration of ISP was maintained at eight weeks after implantation. Osteoconduction of the A-W GC block was good. Four patients with infected hip arthroplasties and one with osteomyelitis of the tibia have been treated with the new delivery system with excellent results

We report the results of cancellous femoral impaction grafting with cement in revision hip arthroplasty in all patients from one centre who had undergone surgery more than five years previously. A total of 32 surgeons undertook femoral impaction grafting in 207 patients (226 hips). There were no deaths attributable to the revision surgery; 33 patients with 35 functioning hips died with less than five years’ follow-up. One patient was lost to follow-up. Two hips (1%) developed early postoperative infection. Of the 12 stems which underwent a further surgical procedure for aseptic failure, ten were for femoral fracture and two for loosening. Survivorship with any further femoral operation as the endpoint was 90.5% (confidence intervals, 82 to 98) and using femoral reoperation for symptomatic aseptic loosening as the endpoint, the survivorship was 99.1% (confidence intervals, 96 to 100) at 10 to 11 years. As a consequence of the experience in this series, we have modified our technique with an increased use of longer stems with impacted allograft. Long stems are indicated when the host bone around the tip of a short stem is compromised, in patients with major loss of bone stock, or when a femoral fracture occurs

Total hip and total knee arthroplasty both provide a considerable improvement in quality of life, but there is no evidence to suggest that one is more successful than the other. We studied 72 patients in a prospective trial before and after total hip or total knee replacement. We recorded scores for disability and distress derived from the Harris hip score and the British Orthopaedic Association knee assessment score, and used them to generate quality of life (QoL) scores using the Rosser Index Matrix immediately before and at one year after surgery. The patients awaiting knee replacement had significantly lower QoL scores than those awaiting hip replacement (p = 0.011). The QoL scores at one year were high and almost identical for both groups (p = 0.46). Further analysis showed that gender and weight were not significant predictors of improvement of QoL scores, but age (p = 0.03) and whether the hip or knee was replaced (p = 0.006) were significant factors

Aims

The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA).

Metal-on-metal (MOM) bearings for hip arthroplasty are increasing in popularity. Concern remains, however, regarding the potential toxicological effects of the metal ions which these bearings release. The serum levels of cobalt and chromium in 22 patients who had undergone MOM resurfacing arthroplasty were compared with a matched group of 22 patients who had undergone 28 mm MOM total hip arthroplasty (THA). At a median of 16 months (7 to 56) after resurfacing arthroplasty, we found the median serum levels of cobalt and chromium to be 38 nmol/l (14 to 44) and 53 nmol/l (23 to 165) respectively. These were significantly greater than the levels after 28 mm MOM THA which were 22 nmol/l (15 to 87, p = 0.021) and 19 nmol/l (2 to 58, p < 0.001) respectively. Since the upper limit for normal patients without implants is typically 5 nmol/l, both groups had significantly raised levels of metal ions. MOM bearings of large diameter, however, result in a greater systemic exposure of cobalt and chromium ions than bearings of small diameter. This may be of relevance for potential long-term side-effects. It is not known to what extent this difference is due to corrosion of the surfaces of the component or of the wear particles produced

Three radiological methods are commonly used to assess the outcome of total hip replacement (THR). They aim to record the appearance of lucent areas and migration of the prosthesis in a reproducible manner. Two of them were designed to monitor the implant through time and one to grade the quality of cementing. We have measured the level of inter- and intraobserver agreement in all three systems. We randomised 30 patients to receive either finger packing or retrograde gun cementing during Charnley hip replacements. The postoperative departmental radiographs were evaluated in a blinded study by two orthopaedic trainees, two consultants and two experts in THR. The trainees and consultants repeated the exercise at least two weeks later. We used the unweighted kappa statistic to establish the levels of agreement. In general, intraobserver agreement was moderate but interobserver agreement was poor, with levels similar to or less than those expected by chance. Our results indicate that such systems cannot provide reliable data from centres in different parts of the world, with various levels of surgeon evaluating radiographs at differing time intervals. We discuss the problem and suggest some methods of improvement

Aims

The purpose of this study was to examine whether leg-length discrepancy (LLD) following unilateral total hip arthroplasty (THA) affects the incidence of contralateral head collapse and subsequent THA in patients with bilateral osteonecrosis, and to determine factors associated with subsequent collapse.

We report a series of 640 consecutive cervical hip fractures which were followed prospectively for two years after primary internal fixation with two hook-pins. Secondary arthroplasties were performed as salvage procedures in 75 cases and the early outcome of these was studied retrospectively. The mean time in hospital was 25 days for prosthetic replacement, though 60% of the patients had other medical conditions considered as risk factors. Mortality was 5% after six months and 8% after one year. Dislocation was seen in 11% and additional surgery was required in 4%. There was one case of deep infection and one supracondylar femoral fracture. In some cases there was considerable delay between the primary and secondary operation due to lack of awareness of functional deterioration, but although many patients had poor mobility before the secondary operation this was greatly improved within six weeks of the arthroplasty. We conclude that elective secondary hip arthroplasty for failure of fracture fixation is a safe and successful procedure. Once the decision to perform an arthroplasty is taken, this should be done without delay to avoid deterioration of function

Aseptic loosening is seen in a significant proportion of cemented total hip replacements (THR). In a small subgroup of patients who suffer early loosening polyethylene debris is unlikely to be responsible. We recently reported one case of allergic contact dermatitis to N,N-dimethylparatoluidine (DMT), an accelerator used in bone cement. We have therefore investigated this using skin-patch tests to a variety of substances including metals, polyethylene and the separated individual components of Simplex cement. We studied 70 patients, 15 with aseptic loosening less than two years after THR, 25 with satisfactory long-term cemented fixation, five with infected loosening of cemented THRs and 25 awaiting hip arthroplasty. We found seven positive reactions to DMT, all of them in patients with the rapid onset of aseptic loosening. Allergy to DMT is recognised in the dental profession in respect of the ‘denture sore mouth’ syndrome, and could also be an occupational hazard since some industrial glues contain DMT. Our results suggest the need for awareness of possible previous dental or occupational exposure to the constituents of bone cement. We recommend the use of skin-patch testing in high-risk cases

The fatigue failure of bone cement, leading to loosening of the stem, is likely to be one mode of failure of cemented total hip replacements. There is strong evidence that cracks in the cement are initiated at voids which act as stress risers, particularly at the cement-stem interface. The preferential formation of voids at this site results from shrinkage during polymerisation and the initiation of this process at the warmer cement-bone interface, which causes bone cement to shrink away from the stem. A reversal of the direction of polymerisation would shrink the cement on to the stem and reduce or eliminate the formation of voids at this interface. We have investigated this by implanting hip prostheses, at room temperature or preheated to 44°C, into human cadaver femora kept at 37°C. Two types of bone cement were either hand-mixed or vacuum-mixed before implantation. We found that the area of porosity at the cement-stem interface was dramatically reduced by preheating the stem and that the preheating temperature of 44°C determined by computer analysis of transient heat transfer was the minimum required to induce initial polymerisation at the cement-stem interface. Temperature measurements taken during these experiments in vitro showed that preheating of the stem caused a negligible increase in the temperature of the bone. Reduction of porosity at the cement-stem interface could significantly increase the life of hip arthroplasties

Fifty-nine cases of trochanteric wire revision following hip arthroplasty with trochanteric osteotomy and reattachment were identified and their outcome was studied. Two were infected and were excluded. Five were revised for instability: four became stable while one continued to have persistent dislocation. Fifty-two were revised for pain, 36 by removal of the trochanteric wire and 16 by reattachment of the greater trochanter. Successful relief of pain was obtained in less than half the cases. There was no difference in the incidence of back pain, wiring technique, trochanteric advancement, previous surgery to the same hip, trochanteric size or the pattern of wire breakage in the successfully treated group and the unsuccessful group. Neither was the removal of intact wire from a united trochanter any more certain of relieving pain than removal of broken wire from an un-united trochanter. Six patients later required revision for loosening or infection. These results indicate the need for full radiological and haematological investigation before exploration of the greater trochanter. At exploration for pain the wires should simply be removed as we could show no successful union after late reattachment of the trochanter in the absence of instability

Untreated acetabular dysplasia following treatment for developmental dysplasia of the hip (DDH) leads to early degenerative joint disease. Clinicians must accurately and reliably recognise dysplasia in order to intervene appropriately with secondary acetabular or femoral procedures. This study sought early predictors of residual dysplasia in order to establish empirically-based indications for treatment. DDH treated by closed or open reduction alone was reviewed. Residual hip dysplasia was defined according to the Severin classification at skeletal maturity. Future hip replacement in a subset of these patients was compared with the Severin classification. Serial measurements of acetabular development and subluxation of the femoral head were collected, as were the age at reduction, type of reduction, and Tonnis grade prior to reduction. These variables were used to predict the Severin classification. The mean age at reduction in 72 hips was 16 months (1 to 46). On the final radiograph, 47 hips (65%) were classified as Severin I/II, and 25 as Severin III/IV (35%). At 40 years after reduction, five of 43 hips (21%) had had a total hip replacement (THR). The Severin grade was predictive for THR. Early measurements of the acetabular index (AI) were predictive for Severin grade. For example, an AI of 35° or more at two years after reduction was associated with an 80% probability of becoming a Severin grade III/IV hip. This study links early acetabular remodelling, residual dysplasia at skeletal maturity and the long-term risk of THR. It presents evidence describing the diagnostic value of early predictors of residual dysplasia, and therefore, of the long-term risk of degenerative change

Reports of differing failure rates of total hip prostheses made of various metals prompted us to measure the size of metallic and polyethylene particulate debris around failed cemented arthroplasties. We used an isolation method, in which metallic debris was extracted from the tissues, and a non-isolation method of routine preparation for light and electron microscopy. Specimens were taken from 30 cases in which the femoral component was of titanium alloy (10), cobalt-chrome alloy (10), or stainless steel (10). The mean size of metallic particles with the isolation method was 0.8 to 1.0 microns by 1.5 to 1.8 microns. The non-isolation method gave a significantly smaller mean size of 0.3 to 0.4 microns by 0.6 to 0.7 microns. For each technique the particle sizes of the three metals were similar. The mean size of polyethylene particles was 2 to 4 microns by 8 to 13 microns. They were larger in tissue retrieved from failed titanium-alloy implants than from cobalt-chrome and stainless-steel implants. Our results suggest that factors other than the size of the metal particles, such as the constituents of the alloy, and the amount and speed of generation of debris, may be more important in the failure of hip replacements

We have reviewed 65 bipolar arthroplasties of the hip in 55 patients with osteoarthritis secondary to dysplasia. The mean age at operation was 56 years (42 to 79) and the mean period of follow-up was 7.2 years (5.0 to 13.0). The average Merle d’Aubigné and Postel score before operation was 10.3 and at final follow-up 15.0. There were excellent or good results in 42 hips (65%). Migration of the outer head was observed in 50 hips (77%), most often in the group with a centre-edge angle of less than 0°, an acetabular head index of less than 60%, coverage of the outer head by the original acetabulum of less than +10° and after bone grafting of the acetabulum. This migration was progressive in 31 (62%) of the 50 hips, with massive osteolysis of the acetabulum in eight. The extent and progression of migration were closely associated with this osteolysis. Four hips required revision for extensive migration of the outer head with destruction of the acetabulum or severe acetabular osteolysis, and nine hips are awaiting revision for failure of the bipolar prosthetic head. The overall failure rate was 18%. We report major problems after bipolar hip arthroplasty for osteoarthritis secondary to hip dysplasia with progressive migration of the outer head and massive acetabular osteolysis at five years or more after operation

Objectives

Little is known about tissue changes underlying bone marrow lesions (BMLs) in non-weight-bearing joints with osteoarthritis (OA). Our aim was to characterize BMLs in OA of the hand using dynamic histomorphometry. We therefore quantified bone turnover and angiogenesis in subchondral bone at the base of the thumb, and compared the findings with control bone from hip OA.