Introduction: Between 1987 and 1997 we implanted 319 primary hybrid total hip arthroplasties in 289 patients using the ‘Plasmacup’ (B. Braun Ltd, Sheffield) with a conventional metal on polyethylene articulation. We have observed a high revision rate with this implant recently and therefore undertook a clinical review of this cohort.

Patients and Methods: The indications for surgery were osteoarthritis (223), secondary arthritis (83), inflammatory arthritis (10), and others (3). 17 patients have died and 20 have been lost to follow up. Survival analysis was calculated using implant failure defined as revision (including liner exchange), and includes the censored patients outlined above. Assessment of complications in surviving implants was made using AP radiographs of the hip.

Results: The cup survival rate (Kaplan-Meier method) was 91% at 10 years (95%CI ± 4%) and 67% at 13 years (95%CI +/−9%). The stem survival rate was 96% at 10 years (95%CI +/−3%) and 87% at 13 years (95%CI +/−7%). The median wear in cup revisions for osteolysis was 2.4mm (IQR 1.0–3.2mm), and the median wear in surviving cups was 1.3 mm (IQR 0.8 1.9mm), and was an independent predictor of failure (Cox: p=0.001). There have been 57 revisions (35 cup only, 18 cup and stem, 4 stem only). Indications for revision were osteolysis or loosening (34), wear (18), and infection (5). In surviving cups (214), 29 have expansile acetabular osteolysis and 8 have linear osteolysis. In surviving stems (244), 14 have expansile osteolysis and 23 have linear osteolysis.

Conclusions: There is a high late failure rate of the plasma cup using a conventional metal on polyethylene articulation. Patients with this implant/bearing combination should be closely monitored, particularly after 10 years.

Purpose: To assess the outcome of patients with an infected TKA who developed complex wounds requiring surgical intervention in our institution.

Methods: The computerised local database was searched for patients recorded as having complex knee wounds associated with an infected TKA. Fifteen patients operated on between 1997 and 2007 were retrospectively reviewed. Data including the limb salvage rate, type of soft tissue surgery performed, local wound complications, and re-implantation rate were recorded. Average follow up was 3.2 years. Three patients had died at the time of review.

Results: Eleven out of 15 patients had been referred to our centre from other hospitals with an infected TKA. Fourteen patients were treated with two stage revision surgery. The remaining patient had direct exchange of the infected implant. Mean age at the time of surgery to address the soft tissue defect was 69.6 years.

Nine patients required a medial gastrocnemius flap. Three patients received fasciocutaneous flaps (one bipedicle); one patient was managed with a tissue expander pre-operatively; one with a split skin graft, and one patient required perforating skin incisions in order to close the wound. 60% of patients developed local wound complications and 27% required further soft tissue procedures.

The overall limb salvage rate was 73.3% (four patients required an above knee amputation for persistent infection). Five patients had successful re-implantation surgery. Four patients had arthrodesis surgery with successful eradication of infection. Two patients developed chronic infection.

Conclusions: Intensive specialist input from plastic and orthopaedic surgeons is required with such difficult cases. Contrary to recent literature, the risk of failure may be higher than previously thought. Patients should be fully counselled pre-operatively about the risks of such procedures.

Introduction: The concept that aseptic loosening is a function of polyethylene wear has led to the introduction of cross-linked polyethylene in THA. We studied the relationship between polyethylene wear rate and aseptic loosening to model the potential effects of wear-reducing strategies on the failure rate for each prosthetic component.

Methods: 350 subjects who had previously undergone Charnley THA were divided into 3 groups: Controls (n=273); isolated femoral stem looseners (n=43); and isolated cup looseners (n=34). Polyethylene wear was measured using a validated method (EBRA). The relationship between wear rate and loosening was examined using logistic regression analysis, and estimates of the effect of wear rate modulation made using odds-ratios (OR ).

Results: The median annual wear rate in the controls (0.07mm) was lower than both stem looseners (0.09mm, p=0.002) and cup looseners (0.18mm, p< 0.001). The OR of cup loosening increased 4.7 times per standard deviation (SD) increase in wear rate above the reference (control) population (p< 0.001). The OR of stem loosening increased 1.7 times per SD, but was not independent of other risk factors (p> 0.05). The potential reduction in risk of loosening was calculated using the following formula: (OR ^SD2)/(OR ^SD1), where 1 and 2 are the predicted mean z-score wear rates of modified versus conventional polyethylene. Thus, for a 25% or 50% reduction in wear rate, the incidence of cup loosening may reduce by 71% and 293%, respectively. The rate of stem loosening may reduce by 7% and 17%, respectively.

Discussion: The use of cross-linked-polyethylene has the potential for a major impact on the incidence of cemented cup loosening. However their effect on femoral stem loosening may be limited.

Aims: Dislocation is one of the commonest complications following total hip arthroplasty. A significant proportion of these patients go on to have recurrent dislocations. Many factors have been identified as contributing to the risk of dislocation but treatment of recurrent dislocation is challenging. The use of semicaptive acetabular components is a potential solution to the problem of recurrent dislocation but there are few studies into the efficacy of these implants.

Methods: Patients who underwent revision of their total hip arthroplasty to a semi-captive socket at the Lower Limb Arthroplasty Unit, Northern General Hospital, Sheffield between 2001 and March 2006 were studied. A proforma was designed and data was obtained from patients’ medical records. The number of dislocations both prior to revision to a semi-captive component and the following revision to a semi-captive acetabular component were recorded including the method of reduction Reasons for revision and the number and reasons for previous revisions were noted.

Results: Average time of follow up was 22 months (range 2 months – 5 years 1 month). Following revision of total hip arthroplasty to a semi-captive component, 78% suffered no further dislocations. Of those patients who went on to redislocate, three went on to have recurrent dislocations and all were reduced by closed reduction. One patient redislocated and underwent a second revision to a semi-captive acetabular component, which was successful and underwent no further dislocations.

Discussion. The results of this study show the use of semicaptive acetabular components in revision surgery for dislocation following total hip arthroplasty to be a highly effective solution to the problem of recurrent dislocation.

Aseptic loosening due to periprosthetic bone loss is a major cause of implant failure after total hip arthroplasty (THA). Interleukin 1-B (IL-1B) is thought to play a role in aseptic loosening by stimulating the activity of osteoclasts, the main bone resorbing cell type. A restriction fragment length polymorphism due to a C/T single base variation at +3954 in exon 5 of the IL-1B gene has been associated with differences in susceptibility to chronic periodontitis, a condition associated with bone loss. In this study we tested whether carriage of the C and T alleles at this site resulted in differential risk of aseptic loosening in 481 Caucasians (214 failed versus 267 radiologically intact implants) at 11.7± 4.1 years following primary cemented THA for osteoarthritis. Genomic DNA extracted from peripheral blood was genotyped using the Taqman 5′ nuclease method. Carriage rates were calculated and analysed using the 2 test.

In the intact implant group the frequency of the T allele was 0.253. The distribution of the C and T alleles was 147:105:15 (CC:CT:TT, respectively). In the failed implant group the frequency of the T allele was 0.241). The distribution of the C and T alleles was 124:77:13. The carriage rate of the T alleles in each group was 44.9% and 42.1%, respectively (odds-ratio P> 0.05). The genotype frequencies were in Hardy-Weinberg equilibrium for both intact and loose implant populations (Chi-squared P> 0.05).

Using the multivariate Cox proportional hazards model significant risk factors for loosening of both implant components included gender and age at THA (P< 0.05). However, carriage of the +3954 allele was not a significant independent risk factor for aseptic loosening (P> 0.05). Our data suggests that the IL-1B gene restriction fragment length polymorphism at +3954 does not influence the risk of aseptic loosening after THA.

Aims: Cementing techniques in arthroplasty affect the outcome of the procedure. Pressurisation is used to improve the cement/bone interface, relying on ante-grade pressure against a resisting force. It is known that ultra high molecular weight polyethylene (UHMWPE) leaves particulate debris, which may lead to aseptic loosening, suggesting a biodegradable cement restrictor may be better. We compared cement restrictor migration at insertion between two types of restrictors, to find if they behaved in a similar fashion.

Methods: A prospective, randomised study with 16 patients per group was compared. Each group was allocated either a UHMWPE or a biodegradable restrictor, inserted according to the manufacturer’s instructions. All procedures used the same approach by one of two surgeons using a cemented polished, tapered stem prosthesis. At insertion the restrictor depth was measured from a fixed reference point, prior to cement introduction, which allowed comparison with post-operative standardised EBRA radiographs. By measuring stem lengths we were able to calculate the individual magnification and hence increase the accuracy of restrictor migration measurement.

Results: In each group 15 patients completed the study. The results showed a marked significance, with mean migrations of 3.0cm vs. 0.5cm (biodegradable vs. UHMWPE). Mann-Whitney U test gives a value for p< 0.002. The medians (2.9vs.0.4), standard deviations (1.8 vs.0.4) and ranges (0.6–6.4 vs.0–1.2) were also significant.

Conclusions: In this study, the biodegradable restrictor used was found to allow significantly more migration than the UHMWPE one used. Although there are positive advantages in avoiding the use of UHMWPE restrictors, further advances need to be made before abandoning it completely.

Polyethylene wear particle-induced osteolysis is a major cause of implant failure after total hip arthroplasty (THA). Tumour necrosis factor (TNF) is a pro-inflammatory cytokine that is thought to play a pivotal role in this process. We have recently shown that carriage of the −238 ‘A’ allele in the TNF gene promoter is associated with a higher rate of osteolysis after THA versus carriage of the [more common] ‘G’ allele. The aim of this study was to determine the effect of this polymorphism on TNF gene transcriptional activation in response to polyethylene particle stimulation using a luciferase reporter gene assay.

A 691 bp fragment (−585 to +106) of the TNF gene was amplified by polymerase chain reaction and directionally cloned into the PGL3.basic vector (Promega, Madison, WI). Insert sequences were checked using an ABI 377 DNA sequencer (PE Applied Biosystems, Foster City, CA). RAW264.7 murine macrophage-like cells in rapid growth phase were transfected with plasmids containing either the TNF-238G allele or the TNF-238A allele. pTK-RL (Promega), that expresses the Renilla luciferase gene under the control of Herpes simplex virus minimal promoter, was used as a transfection control. The cells were then either left unstimulated or were induced using polyethylene particles generated from a hip simulator. Lipopolysaccharide (LPS) and LTA (Lipoteichoic acid) were used as positive controls. Luciferase reporter activity was measured after 4 hours (Dual luciferase assay, Promega Corp., Southampton, U.K.) and the relative firefly luciferase activity was calculated. Results were analysed using repeated measures ANOVA.

Polyethylene particle stimulation at concentrations of 0, 1, 15, and 30mg/mL resulted in relative luciferase activities (mean (SD)) of 21.4 (2.9), 36.2 (8.2), 45.9 (11.1), and 40.7 (5.1) for the −238A allele; and 19.7 (5.0), 26.4 (8.0), 35.9 (2.3), and 32.4 (2.4) for the −238G allele (ANOVA P=0.01). LPS and LTA stimulation also resulted in increased reporter activity for −238A versus −238G (ANOVA P=0.02 and P=0.04, respectively).

The promoter allele TNF-238A results in higher levels of transcriptional activation versus the TNF-238G allele in response to a clinically relevant stimulus, and provides functional evidence for the significance of this polymorphism in the development of osteolysis after THA.

The Huckstep ( Bbraun Medical) interlocking hip prosthesis has been used in the Sheffield Lower Limb Arthroplasty Unit in cases of complex primary and revision hip arthroplasty since 1996. We reviewed the outcomes in cases performed prior to October 2001.

Eighty cases were identified. Of these, eight died within one year of surgery, four of which were in the peri operative period. A further thirteen were lost to follow up in the first year due to medical deterioration, move from area or refusal to attend. The remaining 57 patients had a mean time to follow up of 34 months (12–81m).

As a primary prosthesis the Huckstep was used to allow corrective osteotomy. In revision cases it was employed to bypass periprosthetic fractures and fragile proximal femoral bone, in cases requiring extended trochanteric osteotomy to facilitate cement removal, and to enable use of bulk proximal femoral allograft. The use of the Huckstep was planned pre operatively in 67 cases and as a salvage option in 13.The design of the implant allowed a stable construct without the need for bone cement which could interpose and prevent bone healing or graft incorporation. It avoids problems incurred in pressurising cement or impaction grafting against fragile bone.

Complications included infection requiring further surgery (5), dislocation (5), periprosthetic fracture (2), screw breakage (4), and mechanical failure (2). Eleven patients required further revision surgery. The apparently high complication rate reflects the complex nature of the surgery and the high degree of co morbidity in the elderly patient group.

In conclusion, we have found the Huckstep hip prosthesis to be a useful option in cases of complex hip surgery. Whilst the long term outcome is as yet unknown, our short term results show it to have allowed healing of fractures, osteotomy sites and cortical defects, allograft incorporation and replenishing of bone stock, hence facilitating further arthroplasty surgery.

Tumour necrosis factor-α (TNF) is thought to play a role in aseptic loosening, the major cause of implant failure after total hip arthroplasty (THA). Natural sequence variations at –238 and –308 in the promoter region of the TNF gene are associated with differences in the susceptibility and severity of several TNF-mediated diseases. We tested whether carriage of the [less common] ‘A’ allele at –238 and –308 are associated with aseptic loosening after THA.

481 Caucasians (214 with failed implants versus 267 with radiologically intact implants) were recruited 11.7± 4.1 years after cemented THA for osteoarthritis. Genomic DNA was extracted from peripheral blood and genotyped for the –238 and –308 polymorphisms using the Taqman® 5′ nuclease method. 500 subjects from the local population were also genotyped using Taqman® to establish the background prevalence of the ‘A’ allele at each site.

The carriage rate of –238A was 8.8% in the background population and 10.9% in the THA controls (P> 0.05). –238A carriage in the loosening group was 17.3% (odds ratio 1.72, 95% confidence interval 1.02 to 2.90). Carriage was highest (20.5%) in subjects with loosening of both the femoral and pelvic implant components (odds ratio 2.12; 1.17 to 3.83). The association of –238A with aseptic loosening was independent of age, sex, and amount of implant wear (Cox hazard ratio 1.49 (1.04 to 2.13; P=0.03)). Carriage of –308A was not associated with aseptic loosening.

Genetic, as well as environmental factors, influence implant failure after THA. Whether the –238 polymorphism causes the biological change that predisposes to loosening, or is in linkage disequilibrium with such a locus, is not yet known.

Factors that allow the generation or ingression of wear particles at the implant-host interface after total hip arthroplasty (THA) may include early migration and periprosthetic bone loss. We have previously shown that a single 90mg dose of the bisphosphonate pamidronate prevents bone loss over 6 months after THA. In this 2 year randomised trial extension study we assessed the longer term effects of this intervention on bone loss and implant migration.

Twenty-two patients received 90mg of pamidronate and 22 received placebo at randomisation 5 days after surgery. Femoral and pelvic bone mineral density (BMD) was measured by dual energy x-ray absorptiometry (DXA) and implant migration was measured using the EBRA-Digital method over a 104 week period.

In the placebo group rapid periprosthetic bone loss occurred over the first 6 months. After this period a partial recovery in bone mass occurred in most regions. Patients in the pamidronate group had significantly less femoral, but not pelvic, bone loss than those give placebo (ANOVA P=0.02). Pamidronate was most effective in preventing bone loss in Gruen zones 6 and 7 (ANOVA P=0.004, and P=0.014, respectively). At week 104 the mean total stem migration was 1.77mm±0.27 and 1.62mm±0.37 for the placebo and pamidronate groups, respectively (P> 0.05). Total cup migration was 0.75mm±0.26 and 0.76mm±0.14, respectively (P> 0.05). Age at surgery accounted for 26% (linear regression r=−0.65, P=0.02) and 38% (r=−0.51, P=0.007) of the variability in stem and cup migration at week 104, with younger subjects experiencing greater migration. Stem migration at week 104 was also inversely related to the Barrack cement mantle grade (r=−0.66, r² 41%, P=0.0003). Implant migration was not significantly related to changes in periprosthetic bone mass.

Pamidronate therapy has a significant effect on bone mass, but not implant stability, after THA.Our findings suggest that the major determinants of early migration after THA are young patient age and poor cementing technique.

We aimed to determine whether acute periprosthetic bone loss at 1 year following THA may be predicted by early changes in markers of bone turnover, and prevented by a single 90 mg dose of pamidronate in a randomized trial of 46 men and women undergoing primary THA.

Femoral BMD was measured at postoperative baseline, and 6, 12, 26, and 52 weeks later using an Hologic 4500-A densitometer. Markers of bone turnover were measured at preoperative baseline and at 1, 6, 12, and 26 weeks.

Patients in the placebo group lost significantly more periprosthetic bone than those in the pamidronate group. The mean (±95% CI) difference in proximal femoral BMD (area under BMD change.time curve) between those receiving pamidronate and those receiving placebo was 1.84 (±1.29) g.weeks/cm² (P=0.02). A transient increase in all markers of bone turnover was seen in the placebo group, with peaks in osteoclast activity at 6 weeks, and peaks in osteoblast activity 12 weeks. Pamidronate therapy was associated with suppression of all markers of bone turnover with the exception of the resorption marker iFDpd (P< 0.05).

Using a multiple regression analysis model the AUC changes in bone markers predicted 42% of proximal femoral BMD change at 1 year (P=0.006). Using only change in 2 of the markers (PINP and iFDpd) at 6 weeks 28% of proximal femoral BMD change at 1 year could be predicted (P=0.01).

THA is associated with a transient increase in bone remodelling units and bone loss. The relationship between femoral bone loss and turnover markers in the placebo group suggests that the transient increase in these markers reflects local changes in BMD, and that pamidronate reduces bone loss by preventing increased local bone turnover.