Introduction: Bone stock and cement-bone interface in revision total hip replacement (THR) for deep infection have never been investigated in the literature, while they are known to be important for aseptic loosening. The purpose of this study was to assess preoperative bone stock and immediate postoperative cement-bone interface as factors affecting infection control and mechanical outcome after revision THR for deep infection.

Methods: This study included 115 cases in which revision THR with antibiotic-loaded cement was operated for infected hip replacement by a single surgeon with minimal follow-up of five years (range 5–27 years). Preoperative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localized cavitation, Grade 3: Extensive bone loss). The immediate postoperative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap> 1mm, Grade D< 1mm). These two factors were analysed with regard to infection control and mechanical survival of implants after surgery.

Results: Bone stock did not have significant influence on infection control while it affected mechanical outcome. The cement-bone interface was an affecting factor for not only the mechanical survival of implants but also the cure of infection.

Discussion: There was a good chance of curing the infection even with extensive bone loss. Good cement fixation was an important factor with regard to infection control as well as the mechanical survival of implants. The results suggested that it might be important to shield the medullary space from the infected joint space with antibiotic-loaded cement.

Introduction: The long term success of impaction grafting depends on the remodelling process during incorporation. This project was devised to characterise any differences in the biochemical markers of bone turnover following revision hip arthroplasty performed with or without impaction grafting.

Methods: 87 patients were entered into this prospective study and grouped according to whether impaction allograft was used or not. Biochemical markers of bone turnover were assessed pre-operatively and post-operatively on day 2, day 9, week 6, 6 months and 1 year. Osteocalcin, procollagen type-I N-terminal propeptide and bone specific alkaline phosphatase were measured as bone formation markers. C-telopeptide, pyridinoline and deoxypyridinoline were measured as bone resorption markers.

Results: All patients had a successful outcome at one year. 50 patients with radiologically defined host-graft union were compared with 37 patients who did not receive an allograft. Markers of bone formation tended to rise by day 9 but the rise in osteocalcin was delayed in the graft group and was significantly lower at 6 months in comparison to the non-graft group (p=0.002). Alkaline phosphatase levels remained significantly elevated at one year in the graft group (p=0.027) whilst levels in the non-graft group had normalised. Markers of bone resorption also rise in both groups but with no significant differences between the groups.

Discussion: Following impaction grafting, new bone formation may be delayed in comparison to revisions performed without graft. The pattern of markers of bone resorption did not differ significantly between the groups suggesting that there is no large scale resorption of the impacted allograft in these cases.

These results provide a biochemical insight into the bone formation and bone resorption processes during allograft incorporation.

Introduction: In the United Kingdom, the wait for hip or knee joint replacement surgery can be particularly long. There are conflicting research accounts whether debilitating symptoms, such as pain and the effects on physical function and quality of life deteriorate or remain the same in individuals who are on the waiting list for hip or knee joint replacement. This study was conducted to investigate the severity of pain, level of physical function and quality of life amongst adults with osteoarthritis awaiting hip or knee joint replacement.

Methods: A longitudinal study was undertaken in the North West of England during 2003–2005. A total of 105 patients listed for primary hip or knee joint replacement were recruited, interviewed at baseline, and followed-up at three, six and nine months, or until their joint replacement. Measurement tools used were a visual analogue scale (VAS), Western Ontario McMaster’s University (WOMAC) Osteoarthritis Index and the Medical Outcomes Study Short Form Health Survey (SF-36).

Results: High levels of pain and poor physical function and quality of life were experienced by patients on the waiting list for joint replacement. At the three month follow-up (n=84) changes in VAS pain scores (0.6; 95% CIs mean difference 0.3,1.0); WOMAC pain scores (1.2 (95% CIs mean difference 0.7, 1.8) and WOMAC physical function scores (4.8; 95% CIs mean difference 2.8, 6.7) were significantly worse compared to baseline. However, there were minimal changes in quality of life as measured by the SF-36 while on the waiting list.

Discussion: The often long wait for joint replacement surgery and deterioration in pain and physical function has highlighted the need for active management by health professionals while patients are on the waiting list. There needs to be a clinical reassessment of patients by health professionals while on the waiting list for joint replacement.

Bone morphogenic proteins (BMPs) are members of the transforming growth factor beta (TGF-beta) family and play a central role in bone formation. These morpho-gens are known to be present in bone matrix however the characteristics of their release during the grafting process has not previously been defined. The aim of this study was to determine the release BMP-7 (osteogenic protein; OP-1) from cancellous allograft that occurs during impaction grafting for revision hip arthroplasty.

Forty, 10mm cubes of cancellous bone were accurately cut from the central region of 7 fresh frozen femoral heads. The cubes were centrifuged and washed to remove the marrow contents. The cubes were then individually washed and the fluid assayed for BMP-7 activity using a commercially available enzyme linked immuno-sorbent assay kit (Raybiotech Inc.). The cubes were then divided into 4 groups with samples from each femoral head in each group. Each group was subjected to strain of either 20%, 40%, 60% or 80% using a material testing machine. The cubes were then individually washed again and the wash fluid analysed for BMP-7 activity.

BMP-7 activity was found to be present in all groups. Release of BMP-7 was found to increase with increasing strain. At 80% strain the mean concentration of BMP-7 released (830 pg/g) was 58% greater than that released at 60% strain (527 pg/g), 150% greater than the concentration at 40% strain (333 pg/g) and 476% greater than at 20% strain (144 pg/g). The differences between release at 80% and 40% strain and between 80% and 20% strain were statistically significant (p=0.036, p=0.002).

Activity of BMP-7 in fresh frozen cancellous allograft bone has not previously been demonstrated. This study shows that the freezing and storage of femoral heads allows some maintenance of biological activity. Furthermore we have shown that BMP-7 may be released in proportion to the strain applied to the bone. This confirms that the process of impaction of bone morsels during revision hip arthroplasty may release BMPs that could aid in the incorporation and remodelling of the allograft.

Fifty-seven revision total knee arthroplasties were performed in our hospital using the TC3 system between 1995 and 1997. Twelve patients died. Forty-five patients were followed up for an average of 5.6 years (range 4 – 7 years). No patients were lost to follow-up.

All patients were clinically and radiologically evaluated. A postal patient satisfaction questionnaire was completed. Two patients were revised; one for infection and one for instability. Survivorship using revision as the end point was 93.3% at 7 years.

Indications for revision were infection (4;9%), instability (38;84%), pain and stiffness (3;7%). 32 (71%) patients were satisfied with their outcome, 7 (16%) were noncommittal and 6 (13%) were disappointed at 5 years. We have analysed the 13 dissatisfied patients and highlight the lessons learned.

Pain and stiffness are not good indications for revision; insert thickness of more than 17.5mm is suggestive of elevation of the joint-line; instead the femoral component should be distalised; step wedges should be used in preference to angular wedges; Always long stem the tibial implant if augments are used; stems should be canal filling with adequate grip on the diaphysis.

We suggest the above lessons we have learned from our initial revision arthroplasty learning curve may correlate to the clinical outcome of this small group of dissatisfied patients.

Introduction: In attempting to unravel the complex cellular responses leading to prosthetic loosening investigators have been limited to studying gene expression of extracellular molecules about which most is known whereas new microarray technology allows simultaneous expression profiling of thousands of genes from a complex sample such as the membrane formed around loosened hip prostheses.

Methods: Two groups of 8 patients were recruited who have undergone primary total hip arthroplasty for osteoarthritis and subsequently developed either septic or aseptic loosening +/− osteolysis. The control group consisted of one group of 5 patients with the same initial diagnosis who had undergone identical procedures, developed no clinical or radiological signs of aseptic or septic loosening, but had come to revision surgery for other complications as defined by the Swedish Hip register: fracture without previous osteolysis, dislocation, technical error, implant fracture, polyethylene wear or pain. Periprosthetic membrane was harvested at the time of revision surgery and subjected to RNA extraction. cDNA was then synthesized and hybridised to a Human Genome u95 Genechip ® array which contains a complete set of known human genes. Data normalisation, data filtering and pattern identification was performed using Genechip®3.1 software (Affymetrix, Santa Clara, CA).

Results: This has revealed the involvement of a large number of genes coding for transcriptional regulators upstream from the extracellular and cell-cell signalling molecules already known to be involved in osteolysis and deep infection and which may ultimately control the responses to wear particles and bacterial challenge. Differential expression of genes involved in cell survival and death, cell growth regulation, cell metabolism, inflammation and immune response was found. Most interestingly pathways for control of local bone resorption and inflammatory response have been shown to be highly activated.

Conclusions: The identification of these new pathogenetic mechanisms of total hip replacement failure make new indicators of disease susceptibility and prognosis plus new drug targets direct possibilities.

Introduction: We describe the association between postoperative femoral stem radiological appearances and aseptic failure of THA (total hip arthroplasty).

Methods: A retrospective review of records and radiographs of all patients attending for follow-up between August 2002 and August 2003 who had a cemented Charnley femoral stem and either a cemented polyethylene acetabular cup inserted. Femoral stem aseptic loosening was defined either by findings at revision surgery, the definite radiographic loosening criteria of Harris or progressive endosteal cavitation across zones as described by Gruen. Well-fixed control THA’s were defined as those that demonstrated none of the radiographic features of aseptic loosening or ‘at risk’ signs as described by Wroblewski. Parameters measured were: Alignment, Barrack grade of cementation, cement mantle width of the cement mantle and the presence and width of any radiolucent lines

Results: 63 hips were entered into the aseptic failure group and 138 into the control group. The alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was statistically associated with failure in Gruen zones 6 (p=0.040) and Gruen zone 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). The grade of cementation as measured by the Barrack grade was strongly associated with failure for grades C (p=0.001) and D (p=0.001).

Discussion and conclusion: This study has demonstrated that easily applied radiological criteria can be used to identify ‘at risk’ Charnley THA’s from the immediate post-operative AP radiograph.

Previous attempts to assess the comfort and protection afforded by surgical gowns have been extremely simplistic and limited in their nature relying on a single and subjective linear scoring system. We have performed a comfort assessment comparison between the Charnley exhaust suit, disposable gown plus visor and the Stryker Steri-Shield system using a newly developed objective multi-dimensional validated ergonomic tool.

A prospective, comparative study was conducted using a modification of the Comfort Rating Scales (CRS) designed to measure wearable comfort of computer devices during physical activity across 6 dimensions. These dimensions are emotion, attachment, harm, perceived change, movement and anxiety.

10 theatre staff were recruited to the study and completed modified CRS scores on three separate occasions after having worn a disposable surgical gown plus mask with visor, a Charnley exhaust suit and a Stryker Steri-Shield system. The total mean CRS for a disposable gown plus visor was 16.1 with a mean dimensional score of 2.7 (range: 0.2 – 8.4), for the Charnley system the values were 51.4 and 8.6 (range: 5.9 – 12.8) respectively and for the Stryker Steri-Shield 15.4 and 2.6 (range: 0.8–5.6).

Although disposable, impermeable gown plus visor or the Steri-Shield system provide a similar level of comfort, the modified CRS has demonstrated that over 6 dimensions of measurable comfort the Steri-Shield system provides the least variation in comfort and as such may offer the best combination of comfort, protective qualities and form or style of personal protection systems for lower limb arthroplasty operations.

Purpose Coagulase negative staphylococci (CNS) have been one of the major pathogens responsible for prosthetic joint infections, and are showing increasing multiple-antibiotics resistance. Intact cell mass spectrometry (ICMS), based on the analysis of bacterial surface proteins, has been recognised as a new technique for identification of micro-organisms. The aim of this study was to evaluate the ability of ICMS for species level identification of clinical CNS isolates.

Method A total of 50 CNS strains from revision joint replacement operations were studied. ICMS and commercial identification kits were used for identification of those CNS. The commercial kits were used following the manufacturer’s recommendations. For ICMS, single colonies were smeared onto five spots on a sample slide. After drying, a 1 μl of aliquot of matrix solution was added to each spot. Analysis of strains was performed using a Kompact MALDI 2 linear, time of flight mass spectrometer and 3-ns pulse width nitrogen laser light. Combined spectra were constructed from 100 shots at each spot on the sample slide.

Results In this study, the commercial kit did not require any special equipment, but required overnight incubation and could not identify at least seven strains. On the other hand, the ICMS method was rapid, accurate and highly reproducible. The mass: charge spectra produced by ICMS contained potential biomarker peaks that could be used for species level identification.

Conclusions ICMS has the potential as a powerful tool for species level identification of clinical CNS isolates in terms of rapidity, accuracy and cost effectiveness. This study suggested that ICMS is a possible new method of identifying causative organism in infected joint replacements.

Introduction: Non-steroidal anti-inflammatory drugs (NSAIDs) are inhibitors of cyclooxygenase activity and are potential therapeutic agents in the prevention of aseptic loosening. Cigarette smoking is a risk factor for decreased proximal femur bone density. We investigated whether the clinical variables of NSAID usage and cigarette smoking are possibly linked to aseptic loosening around total hip arthroplasty (THA).

Methods: Retrospective review of records and radiographs of all patients attending for follow-up between August 2002 and 2003 who had undergone THA. Age, gender, primary and revision surgery details, radiographic parameters as detailed above, smoking history and NSAID usage history were recorded. Logistic regression analysis was used to determine the presence of associations.

Results: 224 patients were recruited to the study: 143 to the control group with a mean time of THR survival of 14.6 years and 81 to the aseptic group with a mean time to THR failure of 5.1 years. 130 patients had never smoked, 69 were ex-smokers and 25 were smokers (average of 15.5 cigarettes/day). 13.6% of patients in the study group were smokers and 10.5% in the control group. The average duration of NSAID usage pre-operatively was 3.4 years and post-operatively was 4.4 years. Using the logistic regression model, amount of cigarettes smoked, years as a non-smoker and length of usage of NSAID were not found to be associated with aseptic loosening

Discussion and conclusions: We found no such statistically significant relationship with regards to smoking habit or NSAID usage as either protective or risk factors.

Aim: To undertake clinical and radiological assessment of the TCIII prosthesis for Revision total knee arthroplasty with survivorship analysis.

Methods: We reviewed the clinical and radiological outcome of 57 Total Condylar III (TCIII) prostheses used for revision knee arthroplasty performed between December1995 and December1997 at Wrightington hospital. Twelve patients (12 knees) had died. At a mean follow-up of 6.75 years (range, 5–8years) 45 knees in 43 patients were available for review. None were lost to follow-up. There were 23 women and 20 men, with a mean age of 73 years. Radiographs were analysed for component position, alignment and bone-cement radio-lucencies.

Results: The reason for revision was instability in 38 knees, infection in 4 knees, pain in 2 knees and stiffness in one knee. The mean preoperative Hospital for Special Surgery HSS score was 36, improving to 70 after revision at latest review(p=< 0.001). The mean postoperative range of movement was 95 degrees. 2 prostheses were revised, one for infection and another for instability, Survival analysis using the Kaplan Meier method provided a cumulative survival rate of 95.56 % at 8 years.

Conclusion: The clinical and radiological results of our study support the continued use of the TCIII prostheses in revision total knee arthroplasty with satisfactory outcome in the medium term.

Introduction. Preoperative bone stock and cement-bone interface in revision total hip replacement (THR) for deep infection have never been investigated while they are both well known to be important for mechanical outcome after revision THR for aseptic loosening.

Purpose. The purpose of this study was to assess pre-operative bone stock and immediate postoperative cement-bone interface as factors affecting infection control after one stage revision THR for deep infection.

Material and methods. This study included 115 cases which satisfied following conditions; a) One stage revision THRs for deep infection were carried out by a single surgeon. b) Follow-up of more than five years was done. Preoperative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localized cavitation, Grade 3: Extensive bone loss). Immediate postoperative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap within 1mm, Grade D: Gap more than 1mm). These two factors were analyzed in view of infection control after surgery.

Results. Preoperative bone stock did not show significant influence on infection control. Immediate postoperative cement-bone interface was an affecting factor for cure of infection.

Conclusion. There was a good chance of cure of infection even in cases with significant bone loss. Good cement fixation appeared to be important in view of infection control. The results suggested the importance of shielding of medullary space with antibiotic-loaded cement from infected joint space in revision THR for infection.

We describe the association between immediate postoperative radiological appearances and early aseptic failure of THA having compensated for the methodological flaws in previous similar studies. 63 hips were entered into the aseptic failure group and 138 into the control group. Alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was associated with failure in Gruen zones 6 (p=0.040) and 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). Grade of cementation was associated with failure for Barrack grades C (p=0.001) and D (p=0.001). This study has demonstrated that easily applied radiological criteria can be used to identify at risk THAs from the immediate post-operative AP radiograph.

Aim: To undertake clinical and radiological assessment of the TCIII prosthesis for Revision total knee arthroplasty with minimum 5 year follow-up.

Methods: We reviewed 57 Total Condylar III (TCIII) prostheses used for revision knee arthroplasty performed between December1995 and December1997 at Wrightington hospital. Twelve patients (12 knees) had died. At a mean follow-up of 6.75 years (range, 5–8years) 45 knees in 43 patients were available for review. None were lost to follow-up. There were 23 women and 20 men, with a mean age of 73 years. Radiographs were analyzed for component position, alignment and bone-cement radiolucencies.

Results: The reason for revision was instability in 38 knees, infection in 4 knees, pain in 2 knees and stiffness in one knee. The mean preoperative Hospital for Special Surgery HSS score was 36, improving to 70 after revision at latest review (p=< 0.001). The mean postoperative range of movement was 95 degrees. 2 prostheses were revised; one for infection and another for instability. Survival analysis using the Kaplan Meier method provided a cumulative survival rate of 95.56 % at 8 years.

Conclusion: Our study supports the continued use of the TCIII prostheses in revision total knee arthroplasty, wherein the ligaments can be balanced, with satisfactory outcome in the medium term.

Introduction and Aims: Official governmental data indicates that infection rates for hip and knee replacement vary between zero and eight percent between institutions with and average rate of between one and two percent. Despite an apparent increase in our understanding of infection and increased use of antibiotics, decontamination and surgical technology infection remains a major problem, accounting for up to 10% of all revision procedures. The aim of this paper is to review where infection comes from, what turns a contamination into an infection and how infection can be avoided.

Method: The organisms causing contamination of 125 primary joint replacements have been studied prospectively and compared to the organisms found at 334 revisions for deep infection. The antibiotic sensitivities, virulence and genetic ability to produce biofilms have been studied. The use of pre-operative screening for MRSA in 9000 patients undergoing elective surgery is compared to 2500 microbiological specimens taken for possible infection during the same time period to assess the importance of MRSA in prosthetic infection. The genetic susceptibility to infection, relationship between post-operative pyrexia and deep prosthetic infection and the use of blood transfusion and infection is investigated.

Results: At least 70% of all primary joint replacements are contaminated with bacteria. The commonest contaminant is Staph. epidermidis, which is the commonest organism causing deep infection. The Staph. epidermidis causing deep infection is genetically a much stronger producer of biofilms than other strains of Staph. epidermidis. Five percent of the contaminating Staph. epidermidis is multi-resistant to antibiotics and is not susceptible to routine antibiotic prophylaxis. In our institution all elective patients are screened for MRSA. One percent of patients are carriers. Deep infection with MRSA is uncommon, with MRSA accounting for less than 2% of cases, however infection with Staph. epidermidis is the most common accounting for 60% of all infection, but of concern is that 55% of all infecting Staph. epidermidis is methicillin-resistant. The organism of concern is therefore MRSE not MRSA. Post-operative pyrexia actually protects against infection. The temperature charts of 40 patients who subsequently developed deep infection when compared to the charts of 200 patients without deep infection indicates that a low post-operative temperature is associated with an increased risk of infection, possibly indicating depressed immunity. Post-operative blood transfusion in 100 patients is shown to decrease immunity and increase nosocomial infection and wound healing problems, indicating that the immune modulation at the time of surgery is probably a major factor in post-operative infection. Finally, comprehensive genetic studies in patients undergoing long-term follow-up at Wrightington indicate definite genetic susceptibility to deep infection in certain patient groups.

Conclusion: We do not understand prosthetic infection. We screen and worry about the wrong organisms, we wrongly worry about post-operative pyrexia, we increase the susceptibility of our patients to infection by blood transfusion and give the wrong antibiotics. We may be able to completely avoid infection if we redirect our efforts and stop relying on powerful broad spectrum antibiotics alone.

Aims: Tumour necrosis factor-alpha is a proinflammatory cytokine that has been implicated in the inflammatory response to bacterial infection and wear debris particles around loosened total hip replacements (THR). Individual TNF responses to such stimuli may be dictated by genetic variation and we have studied the effect of single nucleotide polymorphisms (SNPs) within the TNF gene.

Methods: We performed a case control study of 9 SNPs (−1031, −863, −857, −376, −308, −238, +489, +851 and +1304) for possible association with deep sepsis or aseptic loosening. All patients included in the study were Caucasian and had had a cemented Charnley THR. Cases consisted of 44 patients with early aseptic loosening and 30 patients with microbiological evidence at surgery of deep infection. Controls consisted of 85 THRs that were clinically asymptomatic for over 10 years and demonstrated no radiographic features of aseptic loosening. DNA was extracted from venous blood and genotyped by Snapshot assay.

Results: Genotype and allele frequencies for all SNPs were in Hardy-Weinberg equilibrium between THR controls and a random sample of UK Caucasians. A significant association was found for the -863 SNP and aseptic loosening (p< 0.05; OR=2.36; 95% CI: 0.976 – 5.71). A trend towards association was found between the -863A SNP and deep infection (p=0.80; OR=2.42; CI: 0.800 – 7.34).

Conclusions: Genetic polymorphism of TNF-alpha may play a significant role in THR aseptic loosening and possibly in deep infection. SNP markers may serve as predictors of implant survival and response to therapy such as anti-TNF treatment.

Introduction and Aims: The aim of this study was to evaluate the efficacy of one stage revision THA for deep infection with a long-term follow-up.

Method: One stage revision THA for deep infection was carried out in 273 joints on 262 patients by the senior author between 1974 and 2000. All infected hip replacements were primarily treated with one stage revision THA, regardless of microorganisms at the authors’ unit unless bone stock in the hips was too poor for implant fixation. This study included 162 revisions in 154 patients for which a minimum follow-up of five years (range 5.1 to 27.6 years; average 12.3 years) had been done. Fifty-two cases (32.1 %) had had discharging sinus by the time of revision surgery for infection.

Results: One hundred and thirty eight (85.2 %) hips were free of infection at the time of the latest follow-up. Twenty cases (12.3 %) had reoperation for recurrent infection. Four hips (2.5%) maintained their implants with the evidence of infection. Twenty-two cases (13.6 %) showed radiological loosening. Thirteen cases (8.0 %) were revised again for reasons other than infection (12 for aseptic loosening and one for dislocation).

Conclusion: Deep infection is one of the most serious complications after total hip arthroplasty (THA). This study presented the longest follow-up, with a large number of cases in revision THA for deep infection. The results suggested that one stage revision was an effective treatment for deep infection of hip arthroplasty.

Introduction and Aims: The purpose of this study was to assess pre-operative bone stock and immediate postoperative cement-bone interface as factors affecting infection control and mechanical outcome after one stage revision THR for deep infection.

Method: This study included 115 cases which satisfied the following conditions: 1) One stage revision THR for deep infection was the primary intervention for infected hip replacement by a single surgeon (BMW) unless the bone stock was too poor for fixing implants; 2) follow-up of more than five years; 3) A complete series of radiographs was available for radiological study including pre-operative and immediate post-operative ones. Pre-operative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localised cavitation, Grade 3: Extensive bone loss). The immediate post-operative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap> 1mm, Grade D< 1mm). These two factors were analysed with regard to infection control and the mechanical survival of implants after surgery.

Results: Bone stock did not have significant influence on infection control, while it did affect mechanical outcome. The cement-bone interface was an affecting factor for not only the mechanical survival of implants but also the cure of infection.

Conclusion: There was a good chance of curing the infection even with extensive bone loss. Good cement fixation was an important factor with regard to infection control, as well as the mechanical survival of implants. The results suggested that it was important to shield the medullary space from the infected joint space with antibiotic-loaded cement in revision THR for deep infection.

Purpose: In attempting to unravel the complex cellular responses leading to prosthetic loosening investigators have been limited to studying gene expression of extracellular molecules about which most is known whereas new microarray technology allows simultaneous expression profiling of thousands of genes from a complex sample such as the membrane formed around loosened hip prostheses.

Methods: Two groups of 8 patients were recruited who have undergone primary total hip arthroplasty for osteoarthritis and subsequently developed either septic or aseptic loosening +/− osteolysis. The control group consisted of one group of 5 patients with the same initial diagnosis who had undergone identical procedures, developed no clinical or radiological signs of aseptic or septic loosening, but had come to revision surgery for other complications as defined by the Swedish Hip register: fracture without previous osteolysis, dislocation, technical error, implant fracture, polyethylene wear or pain. Peri-prosthetic membrane was harvested at the time of revision surgery and subjected to RNA extraction. cDNA was then synthesized and hybridised to a Human Genome u95 Genechip ® array which contains a complete set of known human genes. Data normalisation, data filtering and pattern identification was performed using Genechip®3.1 software (Affymetrix, Santa Clara, CA).

Results: This has revealed the involvement of a large number of genes coding for transcriptional regulators upstream from the extracellular and cell-cell signalling molecules already known to be involved in osteolysis and deep infection and which may ultimately control the responses to wear particles and bacterial challenge. Differential expression of genes involved in cell survival and death, cell growth regulation, cell metabolism, inflammation and immune response was found. Most interestingly pathways for control of local bone resorption and inflammatory response have been shown to be highly activated.

Conclusions: The identification of these new pathogenetic mechanisms of total hip replacement failure make new indicators of disease susceptibility and prognosis plus new drug targets direct possibilities.

We explored the association of post-operative pyrexia following hip arthroplasty and the development of deep infection Method: The postoperative temperature records of 80 patient’s following primary hip replacement were retrospectively analysed. Thirty-one patients had revision surgery at a mean time interval of 37.2 months (range 5–74 months) for confirmed deep prosthetic infection. The control group of patients were asymptomatic at a mean follow-up of 31.5 months. There were 28 patients with an uneventful clinical outcome following surgery and 21 patients who had developed a systemic infection during their stay in hospital. The maximum daily temperature of each patient was recorded. Results: The mean peak temperature of patients with deep prosthetic infection was significantly lower then patients with a systemic infection or a normal clinical recovery following surgery (p=0.01). The difference between the peak post-operative temperature and the preoperative temperature was also significantly lower in patients who subsequently required revision surgery for prosthetic infection (p=0.007). Conclusion: Patients with deep prosthetic infection have a lower pyrexia response then patients with either an uneventful clinical recovery or the development of a systemic infection following total hip replacement. Pyrexia is part of the acute phase response following surgery is mediated by cytokines including IL-1 and IL-6, which are also involved in activation of the patients cellular and humoral immune response. A low pyrexia response following surgery may therefore also be suggestive of reduced acute phase response to the potential wound contamination produced during surgery with a consequence of subsequent prosthetic infection.