Soft tissue reactions following metal-on-metal arthroplasty of the hip have been under discussion in recent times. The phenomenon has been observed since the advent of arthroplasty, but the particular nature of metal-on-metal (MoM) resurfacing or total hip arthroplasty (THA), and the associated shedding of metal particles in high wear states, appears to excite a more aggressive response. Recent reports suggest involvement of muscle groups on a wide scale, and some cases of neurovascular involvement. It is not known which reactions require widespread muscle excision, and which cases may be adequately addressed by bearing exchange alone. We report three cases of soft tissue reaction (pseudotumour) following MoM hip resurfacing all managed with revision to ceramic-on-ceramic (CoC) THA with minimal soft tissue excision. All patients were female with ages at original operation of 49, 52 and 58 years. Time to revision surgery was 85, 28 and 66 months respectively.

Prosthesis revision resulted in progressive and satisfactory resolution of the pseudotumour. We propose that in the early stages, pseudotumour following MoM hip resurfacing can be adequately managed with revision to ceramic-bearing THA with minimal soft tissue excision, rather than revision with extensive soft tissue debridement that has been recently described.

Manual templating using transparencies allows preoperative visualisation of anatomy and prosthesis size, as well as ease of exchange from prosthesis type to another. Most UK hospitals have converted X-ray provision to Picture Archiving and Communication Systems (PACS), necessitating the use of digital templating.

We assessed the accuracy and speed of templating for hip replacement on 36 occasions in 12 patients listed for hip replacement, using final component choice as an indicator of accuracy. Each hip was templated using, “Orthoview,” templating programme

without initial scaling and

A two pence coin taped to the lateral aspect of the thigh at the level of the greater trochanter was used for scaling purposes.

Our results showed acetate templating to be most accurate, correlating identically with the prosthesis stem size in 9/12 cases, and with the acetabulum reamed size on 10/12 occasions. Acetate templating was also the most accurate method when allowing for +/− one size difference, being within +/− one size in all 12/12 cases for both stem size and acetabulum size. In comparison, both scaled and non scaled Orthoview templating correlated with the correct femoral prosthesis size in 5/12 patients. The acetabulum ream size was correctly templated in 10/12 patients using unscaled Orthoview, and 8/12 patients using scaled Orthoview. Additionally, Orthoview templating took a mean of 6 minutes, whereas manual templating can be achieved in under 30 seconds.

Manual templating of scaled PACS images using transparencies conferred considerable advantages in terms of accuracy and speed. Moreover, this method allows a hands-on assessment of the forthcoming surgical procedure immediately prior to the operation, as well as late changes in implant choice. We recommend the continuation of manual templating using modern scaled digital images.

To assess the outcome of knee “arthrodesis” using cemented Endo-Model knee fusion nail in failed Total Knee Replacement (TKR) with significant bone loss due to infection. This is a retrospective case study of seven patients with infected TKR and multiple surgeries with significant bone loss.

All patients had antibiotic loaded cement with a temporary K-nail as a first stage procedure to eradicate infection. All seven patients had “arthrodesis” performed using cemented modular Endo-Model Knee Fusion nail (Waldemar Link, Hamburg) by the senior author. Cement was used to hold the stems in the diaphyses and not used around the coupling mechanism. The “arthrodesis” relied entirely on the coupling mechanism which has been shown to have good axial and torsional rigidity by mechanical testing. Outcome was assessed using pre and post Visual Analogue Score (VAS).

Mean age was 72.3 years(62–86). Mean follow up was 39.6 months (7–68). The VAS pain score improved from pre-operative mean score of 7.9 to a postoperative score of 1.5. One patient suffered fracture of femoral cement mantle at 50 months who underwent a technically easy exchange revision. One patient had recurrent infection with distal femoral fracture at 36 months and was revised to distal femoral replacement.

The Endo-Model knee arthrodesis nail restores limb lengths, has good early results in terms of pain relief and provides a stable knee “arthrodesis” in cases where there is significant bone loss and extensor mechanism insufficiency following an infected TKR.

Introduction: Of all hip arthroplasties conducted annually, a proportion will subsequently require revision for aseptic loosening and periprosthetic osteolysis. Osteolysis may develop ‘silently’ and monitoring of patients is recommended. This should include x-rays as progressive changes in size of a lesion may indicate a potential failure. Area measurement of osteolysis has been achieved in a number of ways but with techniques that are not readily available in routine clinical practice. The aim of this study was to develop a method for routine assessment of hip arthroplasty to quantify osteolytic changes seen on x-ray, applicable by any health professional and with good inter-observer reliability.

Methods: A morphometric grid is superimposed on an object of interest and the number of test points that fall within a defined area counted. A specialized grid was developed and initial testing was conducted on twenty simulated osteolytic lesions. Subsequent testing was on thirty-five arthroplasty x-rays with evidence of osteolytic lesions. Four observers recorded the number of crosses seen over each lesion. The observers were representative of health professions and levels of experience involved in arthroplasty review.

Data was analysed for both inter-observer and test-retest reliability using the intra-class correlation coefficient and the Bland-Altman method (use of two methods provides a better estimation of accuracy).

Results: The results for intra-class correlation coefficients on both simulated and actual lesions were all excellent (range 0.90 to 0.98) as confirmed by visual representation using the Bland-Altman method.

Discussion: Regular follow-up of hip arthroplasty with x-ray ensures that changes are monitored even when symptoms are absent. We believe that this tool can improve the process through quantitative assessment of osteolytic lesions. The scientific development supports the reliability of the tool when used by a number of raters and the simplicity of application makes it a useful addition to an arthroplasty clinic.

Introduction: Avascular necrosis of the femoral head may play a role in failure of the femoral component in metal on metal hip resurfacing arthroplasty. The purpose of our study was to determine, prospectively, femoral head perfusion during hip resurfacing arthroplasty in the posterior and anterolateral approaches.

Methods: 20 hip resurfacing arthroplasties were performed in 19 patients between September 2005 and March 2006 by two different surgeons; one using the extended posterior approach and the other an anterolateral approach. There were an equal number of procedures for each approach. 1.5 gms of intravenous cefuroxime was administered following caspsulectomy and relocation of the femoral head. After 5 minutes the femoral head was dislocated and prepared as routine for the operation. Bone from the top of the femoral head and reamings were sent for assay to determine the concentration of cefuroxime. The average time taken to prepare the femur and take samples was 8.5 minutes.

Results: The concentration of cefuroxime in bone was significantly greater when using the anterolateral approach (mean 15.7mg/kg; CI 12.3 – 19.1) compared to the posterior approach (mean 5.6mg/kg; CI 3.5 – 7.8; p< 0.001). In one patient, who had the operation through a posterior approach, cefuroxime was undetectable.

Discussion: The posterior approach is associated with a significant reduction in the blood supply to the femoral head during hip resurfacing arthroplasty. This may be a cause for avascular necrosis and potential failure of the femoral component in this procedure.

Aim: To assess the outcome of knee arthrodesis using cemented Endo-Model knee fusion nail in failed total knee arthroplasty with significant bone loss due to infection.

Methods: A Retrospective case study of seven patients with infected TKR and multiple surgeries and significant bone loss (Type III AORI classification). All patients had antibiotic loaded cement with a temporary K-nail as a first stage procedure to eradicate infection. All seven patients had arthrodesis performed using cemented modular Endo-Model Knee Fusion nail (Waldemar Link, Hamburg) by senior author (RSJ). The arthrodesis relied on the strong coupling mechanism of the nail and not on bony union, providing pain relief while mainting leg length. Outcomes assessed using pre–and post Visual Analogue Score (VAS) and Oxford knee scores.

Results: Mean age 76.8 years (62–85). Mean follow up 23.7 months (3–42). The mean VAS pain score improved from 7.6 (6.5–8.5) pre-operatively to 1.1 (0–3.2) post-operatively. The mean post-operative Oxford score was 30.3 (27–36). One patient required revision for asceptic loosening. All but one of the patients thought that arthrodesis was preferable to amputation post-operatively.

Conclusion: The Endo-Model knee fusion nail has good early results in terms of pain relief and knee arthrodesis where there is significant bone loss and extensor mechanism insufficiency following an infected total knee replacement.

Hip resurfacing is a relatively new concept in hip arthroplasty, but is being performed more frequently in the United Kingdom.

We compared anteroposterior radiographs of 30 patients who had undergone cemented hip resurfacing (Cormet) with those of 30 patients who had undergone uncemented hip resurfacing (Cormet). All operations were performed using the anterolateral approach. We measured the acetabular offset, femoral offset, stem shaft angle, medialisation of the cup, head/neck ratio, cup height, leg length, and the implant seating pre-operatively, immediately postoperatively and one year postoperatively. The data were analysed by paired t-tests.

There were no significant differences between any of the measurements at all three time periods. This demonstrates no loss of offset, no femoral neck thinning and no leg length reduction. We note a smaller femoral offset and a reduction on average of 2mm in seating of the femoral implant in the uncemented group as compared to the cemented group. This we attribute to movement of the femoral implant in the first year post-operatively, and as such restoration of the femoral offset to the pre-operative level.

We conclude that uncemented hip resurfacing does not show any statistical benefit over cemented hip resurfacing, although we did observe a more accurate reproducible femoral offset with better seating of the implant in the uncemented group. We also note that there was no neck thinning in any of these patients at one year post-operatively.

Introduction: Dividing the short external rotators 2 cm from their insertion into the femur should preserve the deep branch of the medial femoral circumflex artery. Our aim was to determine, prospectively, femoral head perfusion during hip resurfacing arthroplasty comparing two posterior approaches.

Methods: 20 hip resurfacing arthroplasties were performed in 20 patients by two different surgeons between September 2005 and November 2006. Patients were divided into two equal groups according to approach. One surgeon used the extended posterior approach and the other a modified posterior approach. Intravenous cefuroxime was administered in every case following capsulectomy and relocation of the femoral head. After 5 minutes the femoral head was dislocated and prepared as routine for the operation. Bone from the top of the femoral head and reamings were sent for assay to determine the concentration of cefuroxime.

Results: There was no statistical difference between the concentration of cefuroxime in bone when using the modified posterior approach (mean 5.6mg/kg; CI 3.6 – 7.8) compared to the extended posterior approach (mean 5.6; CI 3.5 – 7.8; p=0.95). In one patient, who had the operation through the posterior approach, cefuroxime was undetectable.

Discussion: The similarity in femoral head perfusion between approaches suggests the blood supply is further impaired by capsulectomy rather than by damaging the MFCA alone.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Materials and Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 781 procedures in 676 patients have been recorded (54% posterior approach, 40% antero-lateral, 6% Ganz approach). The mean follow-up is 2.5 years (0.1–9.7 yrs) and the mean postoperative HHS is 85.9 (range 25–100). The mean age at surgery was 54.2 years. 60% of implantations were on male patients. The principal diagnosis was; OA 87%, RA 5%, AVN, post-traumatic OA and DDH 2% each, Perthes 1% and the remainder 1%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.6 degrees. Uncemented heads (a recent innovation) were used in 7%. Kaplan-Meier survivorship is 93% at 9 years. In the OA subgroup 3.3% have been revised, approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Conclusions: The results of this cohort (which includes the learning period of the contributing surgeons) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Sub-classification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

The treatment of bony defects of the tibia at the time of revision total knee replacement is controversial. The place of compacted morsellised bone graft is becoming established, particularly in contained defects. It has previously been shown that the initial stability of impaction-grafted trays in the contained defects is equivalent to that of an uncemented primary knee replacement. However, there is little biomechanical evidence on which to base a decision in the treatment of uncontained defects. We undertook a laboratory-based biomechanical study comparing three methods of graft containment in segmental medial tibial defects and compared them with the use of a modular metal augment to bypass the defect.

Using resin models of the proximal tibia with medial defects representing either 46% or 65% of the medial cortical rim, repair of the defect was accomplished using mesh, cement or a novel bag technique, after which impaction bone grafting was used to fill the contained defects and a tibial component was cemented in place. As a control, a cemented tibial component with modular metal augments was used in identical defects. All specimens were submitted to cyclical mechanical loading, during which cyclical and permanent tray displacement were determined.

The results showed satisfactory stability with all the techniques except the bone bag method. Using metal augments gave the highest initial stability, but obviously lacked any potential for bone restoration.

Introduction: etiology of late infection after arthroplasty can be difficult to establish. Histology is the gold standard for infection in patients without inflammatory arthritis but diagnosis in inflammatory arthritis depends on culture (Atkins et al). Real-time PCR offers a rapid and direct assessment for staphylococci and enterococci infection but has not been widely assessed.

The aims of this study were

to develop the Roche lightcycler Staphylococcal and Enterococcal PCR kits to facilitate diagnosis of hip and knee prosthetic infections

Methods: uplicate, multiple tissue samples were taken (with separate sterile instruments) at the 1^st stage of revision after informed consent. One set were cultured and results interpreted by the Oxford criteria. The second set were extracted using the Qiagen DNA kit, purified (in-house method) and tested using the Roche lightcycler kits.

Results:53 patients undergoing 2 stage revision for suspected infection were recruited.15 (28.3%) had negative histology and no inflammatory arthritis; 3 with single positive cultures and negative PCR – considered contaminants.

29 patients had non-inflammatory arthritis. 14/18 (77.8%) with positive cultures had staphylococci +/or enterococci isolated and 10 PCR results correlated. The other 11 patients had negative cultures.

9 patients had inflammatory arthritis. Six were culture negative and of the other three, 2 were positive for staphylococci on culture with 1 positive by PCR.

Discussion: Negative staphylococcal PCR correlates with the isolation of staphylococci from only one sample. This agrees with the Oxford criteria that such samples may be considered contaminants. Additional positives detected by staphylococcal PCR alone are rare.

Enterococcal PCR confirmed culture positivity in 2/3 patients. An additional 5 positive PCR’s were obtained from patients’ culture negative for enterococci. It is not clear if these are false positives or more sensitive detection of enterococcal isolation.

Restoration of hip biomechanics is an important determinant of outcome in hip replacement. Pre-operative templating is considered important in preoperative planning, and this trend is likely to develop further to satisfy consumer demand and to facilitate navigated surgery, particularly as digitisation of radiographs becomes established.

We aimed to establish how closely natural femoral offset could be reproduced using the manufacturers’ templates for 10 femoral stems in common use in the U.K.

The most frequently used femoral components from the U.K. national joint registry and uncemented) were identified, and the CPS-Plus stem was added, as this is in use in our unit. A series of 24 consecutive pre-operative radiographs from patients who had undergone unilateral total hip replacement for unilateral osteoarthritis of the hip were reviewed.

The non-operated on side of the pelvic radiographs was templated as described by Schmalzreid. 3 surgeons of variable experience (junior trainee, senior trainee, consultant) performed the assessment. The standard deviation of change in offset between the templated centre of rotation and the normal centre of rotation of the set of radiographs for each prosthesis was then calculated allowing a ranking.

The most accurate template was the CPS with a mean standard deviation of 1.92mm followed in rank order by: CPT 2.21mm, C Stem 2.42mm, Stanmore 3.02 mm Exeter 3.06 mm, ABG II 3.54mm, Charnley 3.54 mm, Corail 3.63 mm, Furlong HAC 4.2 mm and Furlong modular 4.86mm.

There is wide variation in the ability of the femoral templates to reproduce normal femoral anatomy in a series of standard pre-operative hip radiographs. The more modern cemented polished tapered stems with high modularity appear best able to reproduce femoral offset. Nevertheless, some older monoblock stems, despite poor templating characteristics, are known to be associated with acceptable clinical results. The coming years are likely to be witness to changes in patient expectations and radiograph storage. Implant design and digital templates will need to improve apace with these changes, to ensure accurate preoperative planning.

Cemented, polished, tapered stems have produced excellent results, but some early failures occur in younger patients. The CPS-Plus stem (Plus Orthopedics AG, Switzerland) is a polished double taper with rectangular cross section for improved rotational stability. A unique proximal stem centraliser increases cement pressurisation, assists alignment and creates an even cement mantle.

Radiostereometric analysis has demonstrated linear subsidence in a vertical plane, without any rotation or tilt. These features should improve implant durability. Midterm (5 years) results of a prospective international multicentre study are presented.

Materials and Methods: 222 patients (230 hips) were recruited to this IRB-approved study at three centres in the UK and two in Norway. Clinical and radiographic outcomes were assessed at regular intervals.

Results: 160 hips in 153 patients were available for full clinical and radiographic evaluation. 27 patients have died, 30 patients were unable to attend (outcome known) and 12 patients have not reached 5 years follow-up.

The mean Harris hip score improved from 42 preoperatively to 91. There have been no revisions for aseptic loosening and none of the stems have radiographic evidence of loosening. There has been one revision for deep sepsis. With revision for aseptic loosening as an endpoint, stem survivorship is 100%.

Conclusion: The design of the CPS-Plus stem attempts to address the issues of cement pressurization, rotational stability, and subsidence. Earlier laboratory studies have now been supplemented by this clinical evaluation, performed in a number of different centres by several surgeons, and the midterm results are very encouraging.

Introduction: NICE guidelines (2000) stipulated three-year follow-up data compatible with satisfactory performance at 10 years as a minimum requirement for hip implants. We reviewed the performance of two devices in use in our department which fell outside these requirements. The Cenator cup (Corin Medical) is a cemented device, and the EPF cup (Plus Orthopedics) is uncemented (equatorially expanded, screw option, polished inside, porous HA coated).

Patients and Methods: 117 Cenator and 110 EPF cups inserted during the period 12/09/2000–28/01/2003 were assessed at 3 years by the following: Oxford Hip Score, satisfaction (visual analogue scale), details of femoral component, age, sex, BMI and any complications. Radiological assessment included Charnley Grade, concentricity, superior cover, cup inclination, migration, radiolucent lines, and linear wear at 3 years. Statistical associations with radiolucent lines or linear wear were calculated.

Results: The mean age of patients with Cenator cups was 81 (range 61–102) and EPF cups 67 (39–86). Oxford Hip Scores averaged 10 (0–41)(Cenator) and 7 (0–29)(EPF). Cup inclination range was 30–65° (mean 47). Linear wear > 1mm was observed in 18 Cenator and 53 EPF cups. Early radiolucent lines behind EPF cups closed (all cases), and superior cover improved in 8%. Progressive radiolucencies > 1mm were seen behind 37 Cenator cups. One of each type was revised for deep sepsis. Four other minor reoperations occurred. Statistical association was demonstrated between superior cover and progressive radiolucencies (Cenator), and between sex, cup size and inclination and linear wear (EPF).

Discussion: Crucial markers of prognosis were observed (progressive radiolucencies and linear wear) but survivorship at three years for aseptic loosening was 100%. Our results indicate satisfactory performance at three years in accordance with NICE guidelines, and suggest acceptability of both devices. Our methods may be applicable to similar implants currently in use but not yet endorsed by suitable published outcome data.

Aim: Avascular necrosis of the femoral head is believed to play a role in failure of the femoral component in metal on metal hip resurfacing arthroplasty. The purpose of our study was to determine, prospectively, femoral head perfusion during hip resurfacing arthroplasty in the posterior and anterolateral approaches.

Methods: 20 hip resurfacing arthroplasties were performed in 19 patients between September 2005 and April 2006. Patients were divided into two groups according to approach. An equal number of operations were performed by two different surgeons; one using the extended posterior approach and the other an anterolateral approach. Intravenous cefuroxime was administered in every case following capsulectomy and relocation of the femoral head. After 5 minutes the femoral head was dislocated and prepared as routine for the operation. Bone from the top of the femoral head and reamings were sent for assay to determine the concentration of cefuroxime.

Results: The concentration of cefuroxime in bone was significantly greater when using the anterolateral approach (mean 15.7mg/kg; CI 12.3 to 19.1) compared to the posterior approach (mean 5.6mg/kg, CI 3.5 to 7.8; p< 0.001). In one patient, who had the operation through a posterior approach, cefuroxime was undetectable.

Conclusion: The posterior approach is associated with a significant reduction in the blood supply to the femoral head during hip resurfacing arthroplasty. This may be a cause for avascular necrosis and potential failure of the femoral component in this procedure.

The visco-elastic behaviour of acrylic bone cement is a key feature of cement-implant performance. The ability of the cement to creep in conjunction with a force-closed design of stem (collarless polished taper) affords protection of the vital bone-cement interface. Most surgeons in the UK use antibiotic-laden PMMA in primary total joint arthroplasty. In revision surgery the use of bespoke antibiotic-cement combinations is common.

The aim of this study was to elicit the effect of antibiotics upon the physical properties of bone cement.

Methods: The static properties of the cements were assessed following protocols described in ISO 5833: 2002, while the viscoelastic properties of the cement were measured with in-house developed apparatus in quasi-static conditions. Creep tests were performed in four point bending configuration over a 72 hour period in physiological conditions. Porosity was measured on the mid cross section of the creep samples using a digital image technique.

The cements used were Palacos R40 and Palacos R with gentamicin. The antibiotics added included fucidin, erythromycin, teicoplanin and vancomycin in 500mg powder aliquots up to a maximum of 1g per 40 g mix.

All data were analysed using ANOVA with Bonfer-roni post-hoc test. Pearson’s correlation coefficient was used to investigate the association between physical factors (SPSS).

Results: The static and working properties did not vary significantly with antibiotic additions. The mean creep of the cement increased in line with the amount of antibiotic added. The specific antibiotic was not relevant. The differences were statistically significant. Mean porosity also increased with antibiotic mass. There was a linear relationship between cement porosity and creep!

Conclusions: Despite modern mixing techniques the porosity of bone cement increases with antibiotic additions. This increased porosity is related to the greater creep seen in the cement. Surgeons should apply these findings when planning revision hip surgery.

Introduction: The advent of metal on metal resurfacing in the United Kingdom has resulted in increasing interest in the procedure. The operation is more demanding than primary joint replacement and the complications involved are frequently peculiar to the technique. We present a single-surgeon series from a district hospital performed within the ambit of a larger multicentre study.

Method: Data on 83 cases in 80 patients (51 males, 29 females, age 34y–68y, mean age 50.6y) were collected. Patients were reviewed preoperatively and postoperatively at 6 months and annually (mean 21 months, range 1–60 months). At review Harris Hip scores were recorded with a radiological assessment to assess implant orientation. Technical difficulties with implant insertion were recorded. All cases were approached via an anterolateral exposure.

Results: Postoperative scores improved dramatically in nearly all cases. There was persistent pain in two cases, one of spinal origin, the other unexplained. 2 loose femoral components were revised at 2 and 3 years respectively years leaving the intact cup. 1 cup rotated slightly over 3 months and stopped, 4 cups were incompletely seated and 1 femoral component was inserted in slight varus. All remain asymptomatic to date. There was one unrelated death (mesenteric infarction) and no femoral neck fractures.

Discussion: Resurfacing arthroplasty is technically more demanding than total hip replacement and the exchange of experiences via a multicentre user group is important. The conservative nature of the device means that revision for fractured neck of femur (commonest cause of failure) to a stemmed implant retaining the cup is relatively easy. The results of this series are encouraging.

The visco-elastic behaviour of cement, is a key feature of cement-implant performance in total hip arthroplasty.

The aim of this study was to describe the creep behaviour of the leading plain bone cements under standardised physiological in-vitro conditions.

Methods: Cements were mixed under vacuum conditions as per manufacturers instructions. Moulds were used to to produce beams of standard dimensions. These were stored in saline at 37oC for 21 days to ensure thorough polymerisation. Under the same conditions, the beams were tested for 72 hours in a 12-station quasi-static creep rig, using a four-point bending configuration. The rig applied a constant stress of 8MPa to each beam and the deflection was recorded at 8-minute intervals by a data-logging device. The porosity was measured in the mid-cross section of each beam sample using a digital image technique.

The cements tested were Palacos R, CMW1 and Smartset GHV and Surgical Simplex P.

All data were analysed using ANOVA with Bonfer-roni post-hoc test (SPSS).

Results: Palacos R exhibited the highest mean deflection at 72 hours (0.86+/- 0.21mm) followed by Surgical Simplex P (0.85 +/- 0.18mm), CMW1 (0.72 +/- 0.09mm) and Smartset GHV (0.60 +/- 0.16mm). The difference between the two DePuy cements and Palacos R (p=0.03) and Surgical Simplex P (p=0.04) were statistically sig-nificant. None of the beams failed during the test. The creep behaviour correlated with the cross-sectional porosity measurements.

Conclusions: This study has shown that there are sig-nificant differences in the creep bahaviour of the leading medium and high viscosity bone cements. In particular Palacos R and Surgical Simplex P demonstrate ‘High’ creep and the DePuy cements ‘Low’ creep. Creep appears sensitive to subtle changes in the composition of the material. This may be reflected in the clinical behaviour of different bone cements and stresses the importance of the time-dependent properties of PMMA.

Introduction Resurfacing hip arthroplasty is becoming an increasingly popular option in the management of hip arthritis in younger individuals. Large series from units pioneering the technique have yielded encouraging results, but smaller units have reported alarming complication rates in recent years. We report a single-surgeon series performed from within the ambit of a multicentre trial.

Method Data on 49 cases in 46 patients (28 males, 18 females, age 34–68, mean 50.6) were collected. Harris Hip scores were obtained preoperatively and at follow-up (6, 12, 24, 36 and 48 months, mean 16.2). Radiological assessment included evaluation of component position and possible migration. Technical difficulties with implant insertion were recorded.

Results Postoperative hip scores improved dramatically in 47 cases. 3 patients have thigh pain. In one case rotational displacement of the cup occurred over 3 months. This is asymptomatic. In 2 cases there was minor femoral neck notching during surgery, without complications. One femoral component was inserted in slight varus. There was incomplete seating of the acetabulum in 4 cases, without complications. Lateral guide pin protrusion occurred into the tissues during surgery in 2 cases, and this pin is no longer used. Painless clicking, possibly due to impingement, has been noted in 4 cases. There was 1 death, due to total mesenteric infarction. There have been no femoral neck fractures and no revisions in these cases, all performed via the anterolateral approach.

Discussion Resurfacing arthroplasty is more technically demanding than total hip replacement. All cases in this series were entered in a multicentre analysis, the benefits have including regular contact with other surgeons. The procedure is conservative on the femoral side at least, and conversion to hip replacement in the event of future femoral component loosening or neck fracture should be easy, although the results of articulation between a new stemmed device and an old (worn) cup are not known. The results of this single-surgeon series from a DGH, performed within the ambit of a large multi-centre analysis, have been encouraging.

Background Prescriptive guidelines for selection of implants for hip arthroplasty are likely to become increasingly established, on grounds of safety, cost and effectiveness. Such guidelines were introduced in the UK by the National Institute of Clinical Excellence (NICE) in 2000. Most departments were non-compliant in one or more respects, and knowledge of the recommendations was limited among clinicians. Concern exists that the recommendations may replace the Bolam Test in cases of clinical negligence in future.

Materials and Methods The recommendations of NICE, from the initial documentation to the present, were scrutinised alongside experience of other nationally-funded or managed healthcare systems in Europe and North America. The evolution of guidance from 1999 onwards, together with the areas of potential difficulty were identified.

Results Potential difficulties were encountered in relation to a number of implants in widespread use in the UK, particularly in relation to the choice of acetabular component (cup), despite the fact that cup loosening accounts for a third of revisions. The use of cup and stem from different manufacturers was also identified as a cause of concern.

Discussion Departments face a choice of adopting the recommendations of NICE in their entirety or continuing with established practice, with the attendant risk of future litigation should certain implants prove to be unacceptable as clinical results become available through the National Registry. Continuation with established practice may be acceptable, even in respect of implants not recommended by NICE, provided data collection activity is maintained. We propose an algorithm through which individual departments may maintain compliance with NICE without altering departmental practice.

Introduction The CPS-Plus stem (Endoplus UK) is a polished double-taper with rectangular cross section maintained throughout for rotational stability. There are 5 stem sizes with proportionate offset, and 5 neck length options. A unique proximal stem centraliser has been shown to increase proximal cement pressurisation during insertion in-vitro, also assists with alignment of the stem and helps create an even cement mantle. RSA analysis has demonstrated linear subsidence in a vertical plane, without posterior head migration and valgus tilt.

We report a multi-centre prospective clinical trial. 231 hips in 223 patients have been entered into the study. 151 of these have reached 3 years follow-up.

Method Patients were recruited by surgeons working at three centres in the UK, and two in Norway. Merle d Aubigne and Postel, Harris, and Oxford hip scores were recorded pre-operatively and at follow-up (3, 6, 12, 24, 36, 60 months). Radiographic assessment included evaluation of subsidence and the presence of any radiolucencies.

Results Hip scores have been very satisfactory. Radiological subsidence is less than 1.5mm in over 95% of cases and only one stem has subsided more than 3mm. There has been one revision for deep sepsis, 7 dislocations and one femoral fracture, but none of these complications were related to the choice of femoral component. There have been no revisions for aseptic loosening. Kaplan Meier survivorship analysis at 36 months for aseptic stem loosening is 0.997 (95% CI 0.977 – 1) and for all-cause revision is 0.981 (95% CI 0.958 – 1). 53 hips had reached 5-year follow-up at 30/9/04.

Discussion The tradition of polished tapered stems arose from serendipity and most results have been excellent. The CPS-Plus stem represents an attempt to re-examine the issues relating to rotational stability, subsidence, cement pressurisation and offset. Earlier laboratory studies have now been supplemented by this clinical evaluation, performed in a number of different centres by several surgeons, and the evidence is encouraging.

In particular, the RSA subsidence characteristics, cement pressurisation and rotational stability already associated with this implant in-vitro have been supported by excellent survivorship analysis, and the authors believe that increasing familiarity with the concepts raised by this implant will result in clinical benefits in relation to polished taper cemented stem longevity.

Introduction: The CPS-Plus stem (Endoplus UK) is a polished double-taper with a rectangular cross section maintained throughout for rotational stability. There are 5 stem sizes with proportionate offset, together with 5 neck length options, and a unique proximal stem centraliser which has been shown to increase proximal cement pressurisation during insertion in-vitro, assists with alignment of the stem and helps create an even cement mantle. RSA analysis has demonstrated linear subsidence in a vertical plane, without the posterior head migration and valgus tilt associated with other designs.

Data on the CPS-Plus stem has been obtained from a multi-centre prospective clinical trial. 231 hips in 223 patients have been entered into the study. 151 of these have reached 3 years follow-up.

Method: Patients were recruited by surgeons working at three centres in the UK and two in Norway. Merle d Aubigne and Postel, Harris, and Oxford hip scores were recorded pre-operatively and at follow-up (3, 6, 12, 24, 36, 60 months). Radiographic assessment included evaluation of subsidence and the presence of any radiolucencies.

Results: Objective and subjective scoring have indicated very satisfactory results. Radiological subsidence is less than 1.5mm in over 95% of cases and only one stem has subsided more than 3mm. There has been one revision for deep sepsis, 7 dislocations and one femoral fracture, but none of these complications were related to the choice of femoral component. There have been no revisions for aseptic loosening. Kaplan Meier survivorship analysis at 36 months for aseptic stem loosening is 0.997 (95% CI 0.977 – 1) and for all-cause revision is 0.981 (95% CI 0.958 – 1).

Discussion: The tradition of polished tapered stems arose from serendipity and most results have been excellent. The CPS-Plus stem represents an attempt to re-examine the issues relating to rotational stability, subsidence, cement pressurisation and offset. Earlier laboratory studies have now been supplemented by this clinical evaluation, performed in a number of different centres by several surgeons, and the evidence is encouraging.

In particular, the RSA subsidence characteristics, cement pressurisation and rotational stability already associated with this implant in-vitro have been supported by excellent survivorship analysis, and the authors believe that increasing familiarity with the concepts raised by this implant will result in clinical benefits in relation to polished taper cemented stem longevity.

The static properties of bone cements have been widely reported in the literature (Lewis, 1997, Khun, 2000, Armstrong 2002). Commercial bone cements are expected to perform above the minimum values in static tests specified by ISO 5833: 2002. It has been suggested that the viscoelastic properties of bone cement, such as creep and stress relaxation, might bear more relevance to the in-vivo behaviour of the cement-implant construct (Lee 2002). This study aimed to compare numerous properties of Simplex P, Simplex Antibiotic and Simplex Tobramycin and identify those properties most sensitive to subtle changes in cement composition. The three cements were chosen on the basis that they are characterised by the same liquid and powder compositions, the only difference being represented by the type and amount of added antibiotics. In Simplex Antibiotic the additives are 0.5g Erythromycin and 3 million I.U. Colistin, while in Antibiotic Simplex with Tobramycin the only additive is 0.5g of Tobramycin. The static properties of the cements were assessed following protocols described in ISO 5833: 2002, while the viscoelastic properties of the cement were measured with in-house developed apparatus in quasi-static conditions. Creep and stress relaxation tests were performed in four point bending configuration. Porosity was measured on the mid cross section of the creep samples using a digital image technique. All cements exhibited properties compatible with the ISO standard, but in plain Simplex the ISO minimum for bending and compressive strength was within the variation of the batches tested. Bending strength measurements were the least sensitive to differences in the cements. Plain Simplex displayed lower bending and compressive strength but higher bending modulus than the antibiotic laden options. The bending modulus could only discriminate between Simplex P and Simplex Antibiotic (p=0.02). Differences in the compressive strength of the three cements were significant, with the plain option being the weakest. Stress relaxation only discriminated between plain and Tobramycin loaded cement (p=0.028), while creep was more sensitive to differences and allowed distinction between plain and antibiotic loaded bone cements. The creep behaviour correlated with the cross sectional porosity measurements. This study demonstrated that the static tests specified by the current international standard are not as sensitive to subtle changes in the composition of the material as the time temperature dependent parameters characteristic of creep and stress relaxation. The authors advocate the evaluation of time and temperature dependent characteristics as a complement to the current standard.

Introduction: In-vivo elution studies on Antibiotic-loaded Bone Cement (ABC) have concentrated on the short to medium term. This unit has previously described gentamicin release from cement during revision surgery and its presence in the joint aspirates of THAs at up to 12 years. We elected to study the late elutional behaviour of gentamicin-loaded cement in THA.

Methods: 51 patients undergoing revision THA surgery, for aseptic failure, at our centre were studied. Details of the original operation and the subsequent clinical and radiographic course were noted. Pre-operative urine samples and intra-operative joint fluid aspirates (prior to cement disruption) were assayed for their gentamicin concentrations using a fluorescence polarisation immunoassay (Abbott TDX). Cement samples underwent a Bacillus subtilis agar plate inhibition bioassay to assess for antimicrobial activity.

Results: Urine samples were obtained in 43 (84%) of the cases. All were negative for gentamicin (sensitivity level of 0.06 mg/L). Cement samples were retrieved in 36 cases (71%) and all of these (100%) demonstrated significant antimicrobial activity when compared to a standard 10 mg gentamicin disc. In 25 cases (49%) the joints were aspirated and 8 (32%) of these had a gentamicin concentration > 0.1 mg/L. The concentrations however were all below the Minimum Inhibitory Concentration (MIC) for intermediate sensitivity organisms. The longest interval between the primary and revision operations, in these positive cases was 25 years!

Conclusions: This study uniquely demonstrates sequestration of gentamicin within cement for up to 27 years. In addition, one third of joint aspirates had detectable though subtherapeutic gentamicin concentrations at up to 25 years. There was no evidence of late systemic release. These low concentrations of antibiotics, released after many years, are probably a potent stimulus to the emergence of resistant organisms. The use of antibiotic-loaded bone cement in primary THA remains controversial and requires further scrutiny.

Revision hip surgery is becoming increasingly common, 300 procedures being performed in 2001 at our institution. In order to achieve a good outcome bone stock needs to be of good quantity frequently necessitating the use of impaction bone grafting using allograft bone.

Donor bone may frequently take three months before it becomes available for use due to the stringent screening procedure. Donor patients must have a clean bill of health, swabs taken at the time of surgery must obviously demonstrate no growth and blood samples taken at donation and an interval of three months, free from viral infectious diseases. It is thus easy to see the lag from the time of donation to availability and why, with increasing demand, need for allograft bone is rapidly exceeding supply.

We need to look for an alternative supply of human bone allograft.

We have compared the harvest of bone at the time of primary total knee replacement with that of the femoral head by both mass and volume. Sixty consecutive patients undergoing primary hip or knee arthroplasty were included in the study, and the masses and volume of the femoral heads compared with that of the total bone cuts in knee arthroplasty. The type of knee replacement used was documented as was whether the femoral head had had a bone block removed. It was found that the mass of femoral heads was 81g, that of knee cuts 95g this is a statistically significant difference; the volume of femoral heads 66ml and that of knee cuts 75ml.

The volumes of bone available from knee arthroplasty cuts are at least comparable femoral heads obtained using hip replacement and could, perhaps, provide a realistic source of bone allograft.

Aims: The aim of this study was to reassess whether the use of a Ôone knife techniqueñ can be considered as safe as the current practice of using separate skin and inside knives for elective orthopaedic surgery. Methods: A tatal of 609 knife blades from 203 elective orthopaedic operations consisting of equal numbers of skin, inside and control blades, were cultured using direct and enrichment media. Results: Thirty-one skin blades (15.3%), 22 inside blades (10.8%) and 13 control blades (6.4%) gave bacterial growth. In only 3 cases (1.4%) skin and inside knife cultures grew corresponding organisms. However, in the presence of skin knife contamination the same organism was found on 10% of inside blades. It remains to be seen whether in the remaining 90% contamination of deeper layers was prevented by changing the knife after the skin incision, since the incidence of late deep sepsis is not yet known in these cases. Conclusions: The organisms cultured in this study were predominantly coagulase-negative staphylococci, known to be major culprits in early and late peripros-thetic infection. Our study suggests that the rationale for separate skin and inside knives can be supported, since the cost of a single deep infection in human and þnancial terms can be considerable

Introduction: Impaction grafting has become a popular technique to revise implants. The Norwegian Arthroplasty Registry reports its use for a third of all revisions. Yet, the technique is seen as demanding. A particular challenge is to achieve sufficient mechanical stability of the construction. This work tests two hypotheses: (1) Graft compaction is an important determinant of mechanical stability, and (2) Graft compaction depends on compaction effort and graft properties. Methods: Impaction grafting surgery was simulated in laboratory experiments using artificial bones with realistic elastic properties (Sawbones, Malmö, Sweden). Bone stock was restored with compacted morsellised graft, and the joint reconstructed with a cemented implant. The implant was loaded cyclically and its migration relative to bone measured. In a second study, morsellised bone of various particle sizes and bone densities, with or without added ceramic bone substitutes, was compacted into a cylindrical mould by impaction of a plunger by a dropping weight. Plunger displacement was measured continuously. Results: Initial mechanical stability of the prostheses correlated most strongly with degree of graft compaction achieved. Graft compaction to similar strength was achieved with less energy for morsellised bone with larger particles, higher density, or bone mixed with ceramic substitutes. Conclusion: Initial mechanical stability of impaction-grafted joint reconstructions depends largely on degree of graft compaction achieved by the surgeon. Compaction depends partly on the vigour of impaction, and partly on graft quality. Higher bone density, larger particle size and mixing with ceramic particles all help to facilitate graft compaction, giving a stronger compacted mass with less effort.

Introduction: There are approximately 50000 hip and knee arthroplasties performed in the UK every year. With this increasing number the prevalence of periprosthetic fractures is also rising. These are often challenging problems with increased morbidity and mortality. The use of cortical strut allografts in periprosthetic fractures was first reported in the early 90’s with favourable results.The aim of this study was to assess the radiological outcome of cortical strut allografts used as the treatment for periprosthetic fractures of the femur in patients presenting to our institution.

Patients & Methods: 17 patients with who had received strut allografts as part of their treatment for a periprosthetic fracture of the femur were identified. 13 fractures were around a total hip replacement and 4 around other femoral implants (2 long stemmed TKR’s and 2 fracture fixation devices).

We undertook a radiological evaluation of this technique. We assessed fracture union and strut allograft incorporation using the radiological criteria of Emerson et al. The procedure was deemed a success if the fracture had united, with evidence of graft incorporation with a stable implant. We also undertook a notes review identifying any risk factors and any previous surgery.

Results: Two patients died in the early post-operative period. 15 patients were available for analysis. The average length of radiographic review was 16 months. 11/15 procedures (73%) were deemed a success. All these showed evidence of graft incorporation which was time dependent. There were four failures. In one patient the struts fractured at two months. There were three cases of deep sepsis, this required amputation in one and excision arthroplasty in two.

Conclusion: Cortical strut allografts are a good technique for the management of periprosthetic fractures of the femur. As well as providing initial support they also become incorporated which improves the host bone stock.

Retrospective review of 25 patients over 65 years of age with unilateral acetabular fractures managed conservatively showed that seven of the 23 survivors (30%) had an unacceptable functional result. Poor results were associated with: displaced posterior column fractures, osteoporosis, femoral head fracture, delayed diagnosis, inadequate radiographs, inappropriate or too brief traction, and early weight-bearing. In this age group acetabular fractures tend to be low-velocity injuries of osteoporotic bone and are not comparable with those in younger patients.

Using a simple method of quantifying fracture healing, 53 patients who had limb fractures and also severe head injuries were studied; they were compared with 30 patients who had limb fractures but no head injury. Those with head injuries had a greater healing response and united more rapidly. Radiological and histological analysis revealed that the terms "myositis ossificans" and "heterotopic bone" may be more appropriate than "fracture callus" to describe the healing response in these patients.

We report a series of 12 Silastic interposition arthroplasties of the shoulder. There was a very high incidence of dislocation or fragmentation (50%) leading to early failure of the device in seven patients. Our analysis suggests that the operation should be restricted to rheumatoid arthritic shoulders in which there is no loss of bone or distortion of the humeral head.