Dual energy X-ray absorptiometry (DXA) is a precise tool for measuring bone mineral density (BMD) around total joint prostheses. The Hologic ‘metal-removal hip’ analysis package (Hologic Inc, Waltham, Massachusetts) is a DOS-based analysis platform that has been previously validated for measurement of pelvic and proximal BMD after total hip arthroplasty (THA). This software has undergone a change in the operating platform to a Windows-based system that has also incorporated changes to DXA image manipulation on-screen. These changes may affect the magnitude of random error (precision) and systematic error (bias) when compared with measurements made using the previously validated DOS-based system. These factors could influence interpretation of longitudinal studies commenced using the DOS system and later completed using the Windows system. The aims of this study were to compare the precision and bias of pelvic and femoral periprosthetic BMD measurements made using the Windows versus the DOS analysis platform of the Hologic ‘metal-removal hip’ software. A total of 29 subjects (17 men and 12 women) with a mean age of 51years (SD±10), who had undergone hybrid THA using a cemented stem and uncemented cup. Subjects underwent duplicate DXA scans of the hemipelvis and proximal femur taken on the same day after a period for repositioning.. Scans were obtained with the patient lying supine in the scanner with the legs in extension and the foot in a neutral position. Scans were carried out using the same Hologic QDR 4500-A fan-beam densitometer in ‘metal-removal hip’ scanning mode. The DXA scan acquisitions were analysed using both the DOS and the Windows versions of the analysis software. The same observer made all analyses (NRS). Pelvic scans were analysed using a four region of interest model and femoral scans were analysed using a seven region of interest model. Precision was expressed as coefficient of variation (CV%) and compared between methods using the F-test. Systematic bias was examined using the Bland and Altman method and paired t-test. The CV% for the pelvic regions of interest (n=4) varied from 3.92 to 8.54 and from 2.36 to 5.96 for the Windows and DOS systems, respectively. The CV% for the net pelvic region was 3.04 and 2.36 for Windows versus DOS, respectively (F- test, p> 0.05). The CV% for the femoral regions of interest (n=7) varied from 1.58 to 4.14 and from 1.84 to 4.65 for the Windows and DOS systems, respectively. The CV% for the net femoral region was 1.75 and 1.51 for Windows versus DOS, respectively (F- test, p> 0.05). Absolute BMD values for the net pelvic region were similar (Bland-Altman, Windows minus DOS value mean = -1.0%, 95% CI −7.5 to 5.6; t-test p.0.05). Absolute BMD values for the net femoral region were also similar (Bland-Altman, Windows minus DOS value mean = 1.3%, 95% CI −8.3 to 10.8; t-test p.0.05). In summary precision of the measurements using the 2 operating systems was similar and there was no systematic bias between methods. These data suggest that scans analysed using each platform may be used interchangeably within the same study subjects, without the need of a calibration correction.

Bisphosphonates reduce peri-prosthetic bone loss in the short term after total hip replacement but the mid- and longer term effects are not known. The aims of this randomised trial were to examine the effect of a single dose of 90 mg of pamidronate on the clinical and radiological outcome and peri-prosthetic bone mineral density in 50 patients (56 hips) over a five-year period, following total hip replacement.

At five years, 37 patients (42 hips) returned for assessment. The Harris hip scores were similar in the pamidronate and placebo groups throughout the study. Also at five years, four patients, two from each group had osteolytic lesions on plain radiography. These were located around the acetabular component in three patients and in the femoral calcar in one. The femoral and acetabular peri-prosthetic bone mineral density in the pamidronate group and the control group was similar at five years.

Pamidronate given as a single post-operative dose does not appear to influence the clinical outcome or prevent the development of osteolytic lesions at five years after total hip replacement.

Aims and Objectives Hybrid hip replacement became popular in some centres for younger patients with expected lower rates of acetabular loosening and subsequent revision. We have previously reported our 5 year results and now have further follow-up data on the same cohort of patients.

Materials and Methods 86 uncemented acetabular components of the same design were implanted into 68 patients between 1992 and 1997 who were prospectively followed with respect to clinical outcome, polyethylene wear and intention to revise as a definition of failure.

Results Data is available on 73 acetabular cups with a mean follow-up of 9.5 years. The failure rate is 22%. 9 patients have been revised and 7 further patients await revision for polyethylene wear and osteolysis which in some cases has been very aggressive. Further patients have advanced wear and early lysis which is under close observation.

Conclusion The prosthesis studied has a high failure rate. Patients often report few symptoms until advanced osteolysis has occurred. We recommend that all patients with this type of prosthesis be recalled for frequent radiological review and report on an implant which seems to be failing unacceptably early.

Peri-prosthetic bone loss may contribute to aseptic loosening after THA. The aims of this randomised controlled trial extension study were to study the effect of pamidronate therapy on Peri-prosthetic bone mineral density (BMD) and Peri-prosthetic osteolysis over 5 years after primary THA.

50 patients were enrolled in the study in 1998. All received a hybrid THA (Ultima-TPS stem, Plasmacup) for osteoarthritis. Subjects were randomised to receive either 90mg of pamidronate or placebo by intravenous infusion on the 5^th post-operative day. At 5 years 36 patients (41 Hips: placebo n=21, pamidronate n=20) returned for measurement of BMD and clinical and plain radiographic assessment. Five patients had died and nine had withdrawn from the study.

The effect of pamidronate in maintaining femoral bone mass in the region of the calcar previously reported at 2 years was maintained at 5 years (Gruen zone 6 pamidronate versus placebo ANOVA P=0.038; Gruen zone 7 ANOVA P=0.048). No differences in pelvic BMD were found between treatment groups at 5 years. Harris hip scores used to evaluate clinical outcome did not show any significant difference between the 2 groups over the 5-year period. (Mann Whitney p> 0.05). Isolated expansile osteolytic lesions were identified on AP radiographs of the hip at 5 years in 4 patients (2 placebo, 2 pamidronate; P> 0.05). One patient had a 5x9mm lytic lesion in the region of the femoral calcar, and 3 patients had pelvic lytic lesions in the region of the acetabular dome (largest measuring 20x10mm).

Single-dose peri-operative pamidronate therapy preserves femoral calcar bone mass over a 5 year period after THA. However, although the number of subjects with osteolysis is small, we have seen no difference in the rate of osteolytic lesions between treatment groups. Long term study of this patient group is required to examine the rate of aseptic loosening between the treatment groups.

The pattern and magnitude of pelvic periprosthetic bone loss around cementless metal-backed acetabular implants have previously been described. The pattern of periprosthetic BMD change around cemented all-polyethylene acetabular implants is unreported. The aims of this study were to determine the precision of pelvic BMD measurements around the Charnley cup and to examine the longitudinal pattern of BMD change over the first 2 years after surgery.

19 subjects who had previously received a Charnley cup for osteoarthritis underwent duplicate measurements of pelvic BMD after repositioning using an Hologic QDR 4500A densitometer. Scan analysis was carried out using a 4-region of interest model according to a protocol previously described. In-vivo precision was expressed as coefficient of variation (CV%) for each region of interest. The precision of pelvic periprosthetic BMD measurements were 7.7%, 9.8%, 10.8%, and 9.9% for regions 1 to 4, respectively.

Longitudinal BMD changes were measured over a 2 year period in 32 patients (mean age 74 years; 22 women) undergoing cemented THA for unilateral osteoarthritis (17 right-sided). Transient decreases in BMD were observed in regions 2 and 3 (behind the dome of the implant) at 3 months (−9.0% and −13.2%, respectively; P< 0.05) and at 1 year (−8.1% and −9.3%; P< 0.05). By 2 years there had been some recovery in bone mass (BMD−6.9% and −2.6% respectively). No significant changes in BMD for regions 1 and 4 (located at the rim of the implant) were found.

The precision of pelvic periprosthetic BMD measurements for the cemented Charnley cup are poorer than those we have previously reported for cementless cups and may be due, in part, to cement artifact. The pattern of BMD change observed for the Charnley implant suggests that load transfer between the implant and the pelvis occurs principally at the implant rim. The magnitude of bone loss is similar to that we have previously reported for cementless metal-backed acetabular implants.

The Exeter (Howmedica Ltd) and Ultima-TPS (Depuy Ltd) implants are both collarless, polished, double-tapered, cemented femoral implants. The Exeter is manufactured in stainless steel and has an excellent long-term survivorship. The Ultima-TPS is manufactured in cobalt-chrome and has been recently introduced. The aim of this study was to compare the early performance of these implants in a 2-year randomised clinical trial.

65 patients with unilateral hip osteoarthritis were randomised to receive either the Exeter or TPS stem. All received a Charnley Cup. Outcome measures included the Oxford Hip Questionnaire, proximal femoral bone mineral density (BMD) measured by dual energy x-ray absorptiometry, and implant subsidence measured using EBRA. At 2 years 43 patients (66%) were reviewed. 22 patients (mean age 70 years, 16 female, BMI 27.9Kg/m²) received the TPS implant, and 21 patients (mean age 70 years, 15 female, BMI 28.9Kg/m²) received the Exeter implant. 19 patients withdrew for reasons unrelated to the study, 2 died, and 1 was withdrawn after deep wound infection.

Complete Oxford hip scores were available pre-operatively and at 2 years in 37 patients (n=20 TPS). Median (IQR) pre-operative hip scores were 51 (43 to 54) and 48 (36 to 53) for the TPS and Exeter implants, respectively. At 2 years the hip scores improved to 24 (18 to 31) and 22 (16 to 31), respectively. There were no differences in scores between groups at each time-point. There were no differences in BMD between groups at pre-operative baseline, 3 months, 1 and 2 years (Gruen zones 1–7, all time-points; n=19 TPS, n=13 Exeter implants: P> 0.05). Maximum bone loss was seen in Gruen zone 7 at 2 years for bone implants (TPS-11%, Exeter -14%, P> 0.05). Measurement of subsidence over 2 years using EBRA was possible in 20 patients (n=7 TPS, n=13 Exeter). Mean subsidence at 2 years was 1.62mm for the TPS implant and 1.60mm for the Exeter implant (P> 0.05). There was no plain radiographic evidence of osteolysis in either group.

These data suggest that the early performance of the two implants studied is similar. However, long-term survivorship data is required to confirm their equivalency.

In-vitro evidence suggests that wear debris can alter osteoblast function resulting in decreased bone matrix production and negative remodelling balance. FRZB encodes for Secreted Frizzled-Related Protein 3 which may play a role in bone formation and osteoarthritis. This study was undertaken to investigate whether the recently described single nucleotide polymorphisms (SNPs) at positions [+6] and [+109] of the FRZB gene are associated with osteolysis after THA.

Genomic DNA was extracted from 481 North European Caucasians at a mean of 12 years following cemented THA for idiopathic osteoarthritis. The control group consisted of 267 subjects and the osteolysis group 214 subjects. The [+6] and [+109] FRZB SNPs were genotyped using standard techniques.

For the FRZB [+6] SNP, the rare T allele was significantly over-represented in control versus the osteolysis group (χ² test for trend, p=0.02,). The odds ratio for osteolysis associated with carriage of the [+6] T-allele versus the [+6] C-allele was 0.58 (95%CI 0.36 to 0.94), p=0.03. The odds ratio for osteolysis associated with carriage of the [+109] G-allele versus the [+109] C-allele was 0.66 (0.38 to 1.12), p=0.15. A number of covariates have previously been described in this cohort and after adjustment for the effects of these covariates, the odds ratio for osteolysis with carriage of the [+6] T-allele was 0.69 (0.42–1.16).

We found that the FRZB [+6] T-allele is less common in subjects with osteolysis after THA versus controls, suggesting that allelic variants of genes associated with bone formation pathways may have a role in modulating the risk of osteolysis. However its loss of significance after correction for other factors suggests an interaction between this allele and other risk factors in osteolysis.

The use of prolonged courses of parenteral or oral antibiotic therapy in the management of two stage revision of infected total knee arthroplasty is reported by all major series.

We present a series of 59 consecutive patients, all with microbiologically proven deep infection managed at our unit where a prolonged course of antibiotic therapy has not been routinely used. The mean follow-up is 56.4 months (range 24–114 months). Of the 38 patients undergoing a staged exchange, infection was successfully eradicated in 34 patients (89%) with recurrent or persistent infection in 4 (11%). The infection cure rate in our series is similar that reported elsewhere.

A prolonged course of antibiotic therapy does not seem to alter the incidence of recurrent or persistent infection. The costs of antibiotic administration are high, both to the patient and care facility. It may be unnecessary.

Phagocytosis of wear particles by perimplant macrophages results in cytokine release and osteoclast activation and osteolysis. Some investigators have proposed that this response may be mediated by adherent endotoxin. The aim of this study was to determine the role of endotoxin in modulating pro-inflammatory cytokine mRNA expression of macrophages when stimulated with titanium particles using relative quantitative real-time polymerase chain reaction (rqRT-PCR)

Human peripheral blood mononuclear cells were isolated from healthy subjects and plated in chamber slides. Three types of titanium particles were prepared; commercially pure titanium particles (cpTi), endotoxin stripped particles and endotoxin stripped particles with endotoxin (LPS) added back. Endotoxin levels of 450, 0 and 140 Eu/ml respectively were confirmed by high sensitivity Limulus Amebocyte Lysate assay. Macrophages were stimulated with particle concentrations of 0, 8.3, 83 and 830 particles per cell at time points 0 and 3 hours. LPS (200ng/ml) was used as a positive control. rqRT-PCR was performed using standard techniques.

Stimulation of human macrophages with cpTi demonstrated a significant dose dependent increase in TNFα, IL-1A, IL-1B and, IL-6. (Kruskal-Wallis p=0.01, p=0.017, p=0.001 and p=0.013 respectively). IL-18 mRNA levels were not increased (P> 0.05). The expression of mRNA following stimulation with the highest dose of titanium particles was similar to that following LPS stimulation. Endotoxin-free cpTi particles did not elicit any increase in mRNA expression above base line levels (P > 0.05, all cytokines). This lack of response was rescued in endotoxin-stripped particles with LPS added back. Particle dose dependent increases in cytokine mRNA levels were observed for TNFα, IL-1A, IL-1B and, IL-6 mRNA but not IL-18 (p=0.01, p=0.01, p=0.01, p=0.05 and p=0.> 0.05 respectively).

Our results show that adherent endotoxin plays a role in modulating particle induced pro-inflammatory cytokine mRNA expression in-vitro. Further study is required in evaluating the role of adherent endotoxin in vivo

Cytokine mediated activation of osteoclasts can lead to peri-implant osteolysis and aseptic loosening. The aim of this study was to determine the IL-1β and TNFα mRNA cytokine expression profile of human macrophages when stimulated with polyethylene particles using relative quantitative real-time polymerase chain reaction (rqRT-PCR).

Human peripheral blood monocytes or human monocytes from the cell line THP-1 were used in this study. rqRT-PCR conditions were optimized by stimulating human macrophages with 200ng/ml lipopolysaccharide (LPS). The median CV% value for duplicate measures was 12.6 (range 4.5–54). Stimulation assays were performed using unfractionated endotoxin-free commercial polyethylene particles (median size 7μm); or fractionated particles (size range 0.1–1.2μm). Human macrophages were stimulated with high dose unfractionated polyethylene particles at 0, 3500 or 10500 mm³/cell or with fractionated polyethylene particles at 0 and 100mm³/cell at time points 0 and 3 hours. Low dose unfractionated polyethylene stimulation was performed on THP-1 cells at 0, 50, 100, 1000 and 10000 mm³/cell. In all experiments LPS stimulation was used as a positive control. RNA was extracted and rqRT-PCR was performed using standard techniques

High dose unfractionated polyethylene stimulation did not result in a significant difference in cytokine mRNA levels between groups. Using fractionated polyethylene, a small increase in IL-1β mRNA was identified (21% versus maximal stimulation using LPS). Low dose unfractionated polyethylene stimulation of THP-1 cells demonstrated dose dependent decreases in TNFα and IL-1β mRNA expression that was not due to inhibition of RNA extraction or a decrease of cell viability.

Endotoxin-free polyethylene particles do not appear to be a major stimulus for IL-1β and TNFα mRNA production as measured by rqRT-PCR. We did observe a small positive effect on IL-1β mRNA expression using a fractionated polyethylene stimulus. However it remains unclear whether this effect is due to fractionation of particles into the submicron range or is due to introduction of endotoxin during the filtration process.

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery.

The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years.

Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.

We report the results of the revision of 123 acetabular components for aseptic loosening treated by impaction bone grafting using frozen, morsellised, irradiated femoral heads and cemented sockets. This is the first large series using this technique to be reported. A survivorship of 88% with revision as the end-point after a mean of five years is comparable with that of other series.

All major studies have incorporated the use of prolonged courses of parenteral or oral antibiotic therapy in the management of two-stage revision of an infected total knee arthroplasty. We present a series of 59 consecutive patients, all with microbiologically-proven deep infection of a total knee arthroplasty, in whom a prolonged course of antibiotic therapy was not routinely used. The mean follow-up was 56.4 months (24 to 114).

Of the 38 patients who underwent a staged exchange, infection was successfully eradicated in 34 (89%) but recurrent or persistent infection was present in four (11%). Our rate of cure for infection is similar to that reported elsewhere. We conclude that a prolonged course of antibiotic therapy seems not to alter the incidence of recurrent or persistent infection. The costs of the administration of antibiotics are high and such a regime may be unnecessary.

A two-stage procedure was carried out on 57 patients with confirmed infection in a hip replacement. Allograft bone was used in the second stage. Pathogenic organisms were identified in all patients. In stage 1, the prosthesis was removed together with infected tissue. Antibiotics were added to customised cement beads. Systemic antibiotics were not used. At the second stage, 45 of the patients had either acetabular impaction grafting, femoral impaction grafting or a combination; 12 had a massive allograft.

Eight patients suffered recurrent infection (14%), in six with the original infecting organism. The risk factors for re-infection were multiple previous procedures and highly resistant organisms. We believe that systemic antibiotic therapy should be considered for these patients. Allograft bone is shown to be a useful adjunct in most infected hip replacements with considerable loss of bone stock.

Between April 1992 and November 1998 we used 34 massive proximal femoral allografts for femoral reconstruction at revision hip arthroplasty. Seven patients have died and two have been lost to follow-up. There were thus 25 grafts in 24 patients for review. The mean follow-up was 53 months (16 to 101). By the time of the review two patients had undergone a further revision for failure of the allograft. Another had required secondary plating and grafting at the graft-host junction for symptomatic nonunion. One had recurrence of deep sepsis and was being managed conservatively.

Trochanteric union was considered to have occurred radiologically in 16 of the 25 grafts and union at the host-graft junction in 20. Resorption of the allograft was significant in only two hips. We recommend this technique in cases in which femoral bone loss has been catastrophic.

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.

Purpose: The role of hip aspiration as a preoperative investigation for the painful hip remains controversial. Since 1999, we have performed hip aspiration under local anaesthetics in the X-ray department. This paper reviews our experience with this technique.

Results: Hip aspirations were carried out subsequently on 182 patients from November 1999 to November 2002. Out of 68 patients that underwent revision hip surgery, 63 were included in the study. Three of the five patients excluded had received antibiotics at induction prior to obtaining the operative samples and two did not have any operative samples taken at the time of surgery. Fifteen (23.8%) of the 63 hips were found to be infected based on operative tissue cultures. The sensitivity and specificity of the test were 80% and 87.5%, respectively. Positive and negative predictive values were 66.6% and 93.3% respectively and the accuracy was 85.7%.

Conclusion: Hip aspiration in the Radiology department is a simple, cost effective and reliable preoperative test when used selectively. When used in combination with other laboratory and radiological investigation it can act as an important preoperative investigation in the diagnosis of sepsis. There is an added advantage of identifying the microorganism along with its antibiotic sensitivities. This can guide clinicians in choosing the correct antibiotic for the cement and also for the postoperative antibiotic therapy.

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.

One of the major surgical challenges at revision arthroplasty is the management of bone stock loss in the acetabulum.

There are several options available for reconstruction; cemented sockets within thick cement mantles, custom sockets jumbo uncemented sockets, support rings and bone grafting. Slooff and others have shown good results with impaction grafting.(JBJS 80B 1998)

If one is to use bone graft, does the preparation of the graft have any effect on the graft itself? There are a number of ways bone can be presented, freeze dried, fresh frozen or frozen irradiated. Concerns have been raised that irradiated bone has an altered and weakened structure. There is a paucity of clinical results on this subject. In this study we present a series of patients using gamma irradiated bone for reconstruction.23% of the cases reconstructions secondary to failure due to sepsis.

Between 1987 and 2000 192 revision arthroplasties in 165 patients were performed with irradiated morcellised bone allograft for acetabular reconstruction. Only those patients with a minimum follow up of 24 months were reviewed. Clinical and radiological follow up was achieved in 130 hips in 115 patients. 9 patients had died at a range of 1 to 66 months after surgery. There were 23 (17%) re-revisions of the acetabular component. Of these 13 were for deep sepsis, 5 for persistent early dislocation and 4 for aseptic loosening. Of those hips revised for infection there was a 13% re-revision rate for reinfection. There was only one catastrophic failure of the graft and only three re-revisions for aseptic loosening to date.

We feel that impaction grafting of the acetabulum is a useful technique for reconstruction even when the index arthroplasty failed for sepsis. We have found no evidence to show that gamma irradiated bone performs any worse than other types of allograft bone.

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.