Aims

Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA).

Objectives

We used the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man (NJR) to investigate the risk of revision due to prosthetic joint infection (PJI) for patients undergoing primary and revision hip arthroplasty, the changes in risk over time, and the overall burden created by PJI.

Choice of implant for patients aged sixty-five years or younger requiring hip arthroplasty is a topic of current debate, those in favor of resurfacing maintain it offers a greater range of motion and activity. We examined the Oxford Hip Score's (OHS) and Duke Activity Status Index (DASI) of patients undergoing either total hip replacement (THR) using an Elite Plus Stem, or hip resurfacing using a Birmingham Hip Resurfacing (BHR).

The THR cohort comprised 34 implants (4 bilateral), 17 men, 17 women, mean age 56.08 years. The resurfacing cohort comprised 27 implants (3 bilateral), 18 men, 9 women, mean age 50.51 years. The mean difference calculated between pre- and post-operative OHS was 22.08 and 25.33 for the THR and resurfacing cohorts respectively. The mean Duke score was 42.3 and 53 for the cohorts respectively.

Using the pre-operative and post-operative change in Oxford Hip Scores, no statistically significant difference was found between the THR and resurfacing cohorts (p = 0.2891). There was a statistically difference found between the THR and resurfacing cohorts with regards to activity using post-operative Duke scores, (p = 0.0047).

This study has emphasized the use of the DASI, a pure activity score, in hip research. In terms of reducing pain, both prostheses appear equally effective. With regards to activity, as evidenced by utilizing a pure activity score, the resurfacing cohort faired better. Our study suggests at one year post-op, young patients with a resurfacing have a greater activity level than those with a THR.

Aim: To identify the microbiology of infected knee arthroplasty, emerging patterns of resistance over the last decade, and suggest appropriate empirical treatment.

Methods: A retrospective analysis was conducted of 121 patients with microbiologically proven infection, who underwent revision TKA between 1994–2008. The causative organism was identified from microbiological samples and the corresponding sensitivities recorded. The data was then collated to determine the most common causative organisms, changing patterns of antibiotic resistance over the time frame, and the antibiotics currently most effective at treating deep infection. A theoretical model combining gentamicin with other antibiotics was used to determine the most effective antibiotics for use as empirical treatments.

Results: Coagulase negative Staphylococcus (CNS) was the most common causative organism (49%). Staphylococcus aureus (SA) accounted for 13% of cases. The prevalence of CNS appears to be increasing, while that of SA and other organisms is decreasing. Vancomycin and teicoplanin were the most effective antibiotics with overall sensitivity rates of 100% and 96% respectively. Levels of resistance were significantly higher among the antibiotics more commonly used in the community. Antimicrobial resistance was higher when the causative organism was CNS, suggesting that multi-drug resistant CNS is becoming a problem in knee arthroplasty. Our theoretical model showed that gentamicin combined with vancomycin would be the most effective empirical treatment.

Conclusion: Understanding the microbiology of deep infection of the knee allows surgeons to treat this complication as effectively as possible. Vancomycin and teicoplanin appear to be the most effective antimicrobials, with relative invulnerability to the development of resistance. Given the effectiveness of these antibiotics, the use of vancomycin in gentamicin bone cement, combined with IV teicoplanin potentially allows for infected knee arthoplasties to be treated with a one-stage procedure. The rational use of antibiotics may help limit the amount of antibiotic resistance which develops in the future.

Introduction: Hip resurfacing arthroplasty is increasing in popularity, particularly in young and active patients. One unique advantage is retention of upper femoral bone stock with the hypothesis of easy revision should the resurfacing fail. The pupose of this study was to document the complexity or otherwise of our early experience with failed hip resurfacing.

Methods: We retrospectively reviewed all the patients who had revision surgery for failed hip resurfacing arthroplasty at our institution.

Results: Eleven patients with mean age of 52.8 years underwent revision of resurfacing at a mean time of 21.2 months following primary surgery. Revision was performed for deep infection in 4, cup loosening in 4 and 1 patient each for femoral neck fracture, avascular necrosis, and femoral loosening. For the 4 patients with cup loosening, the acetabular component was revised in 3 using a dysplasia Birmingham cup while 1 patient had both components revised. Of the 4 patients with deep infection, 3 had both components revised as one-stage revision with cemented components and 1 patient had a pseudarthosis. For the 3 cases with femoral loosening, neck fracture or avascular necrosis only the femoral component was revised using a cemented stem. Bone grafting was performed in 1 patient who had revision for loosening of acetabular cup with protrusio.

Conclusion: Acetabular failure appears to be equally common as femoral failure in resurfacing arthroplasty. Revision of both aseptic and septic failure appears to be relatively straightforward with primary implants used in all cases.

Objectives: Dislocation is one of the common complications of total hip Arthroplasty. Posterolateral approach and small femoral heads have been shown to be high-risk factors for dislocation of the implanted total hip prosthesis. The use of a posterior capsulorraphy has also shown to decrease the rate of dislocation with a posterolateral approach. The objective of this study was to evaluate the early dislocation rate using size 22 mm head and a Posterolateral approach augmented with a posterior capsulorraphy.

Methods: Questionnaire and case notes review of 148 patients operated at one institution by 3 different senior surgeons from Aug’03 to Jan’05. A posterior capsulorraphy was performed in all the patients. The primary outcome measure was the dislocation of the prosthetic hip within the first year of surgery.

Results: 4 of the 148 patients (2.7%) had an episode of dislocation during the first year of surgery. 3 patients were treated conservatively and 1 required operative intervention in the form of PLAD. Radiographic analysis of this patient showed excessive anteversion of the socket(28⁰⁾.

Conclusions: Studies have consistently shown an increased rate of dislocation with a Posterolateral approach and use of a size 22mm head. A recently published study by Berry et.al has shown a 12.1% dislocation rate with the use of this approach and size 22mm head. However posterior capsulorraphy was not performed in patients in this study group. Our study shows that performing a posterior capsulorraphy can reduce early dislocation rates using Posterolateral approach and size 22 mm head. The dislocation rate (2.7%) is comparable to any other approach and the use of a larger head size.

These patients continue to be monitored to evaluate long term outcomes with this approach. (301 words)

Aim of the study: To evaluate the results of metal-on-metal resurfacing hip arthropalsty in young patients

Materials and Methods: Between February 2000 and December 2004, this operation was performed in 181 patients (205 hips) using the posterior approach. The main indications were osteoarthritis, osteonecrosis, hip dysplasia, post-traumatic arthritis, perthe’s disease and slipped capital femoral epiphysis. There were 142 males and 39 females aged 26 to 68 years (average 47.4 years). 136 patients had a minimum 3 year follow-up (range 1–5 years). Clinical and radiological evaluation was performed at 3 months, 1 year, 2 years and 5 years from time of surgery. All patients were scored using the Charnley’s modification of Merle d’Aubigne score preoperatively and at last follow-up. Radiological evaluation included grading acetabular and femoral zones for loosening, determining stem-shaft angle, hip ratio. The endpoint for outcome evaluation was revision which was two in this series. Survivourship analysis was performed by Kaplan-Meier analysis. The results in our patients were encouraging with most returning to sporting activities at an average of 12 months. 1 patient with bilateral hip resurfacing had evidence of osteolysis after surgery and had occasional hip pain until last follow-up. Complications like neck fracture, heterotrophic ossification were not seen in our series.

Conclusion: Early results of metal-on-metal resufacing arthroplasty in our series are encouraging. Continued follow-up and evaluation remains important to determine the long term results of this operation.

We wanted to know if a mobile bearing Total Knee Arthroplasty was able to cope with rotation of the tibial tray about the femoral prosthesis, by studying the tibio-femoral and patello-femoral joints.

This was a kinematic study that used a mobile bearing TKA mounted on a jig that allowed rotation of the tibial tray. The TKA was moved through a 90° range of flexion and we used photography to record the effects at the tibio-femoral and patello-femoral joints. We found that with a fixed tibia, increasing the degree of external rotation increased the degree of medial femoral condyle lift off from the polyethylene insert which was complete at 25° of tibial tray external rotation. The lift off increased with the degree of flexion. The patello-femoral joint remained congruent. If the rotated tibial tray was mounted on a tibia that was allowed to freely rotate, it led to congruity at the tibio-femoral joint. Now we found that there was medial facet impingement and lateral facet lift off of the patella button in extension and flexion.

We concluded that this mobile bearing prosthesis did not cope well with rotation of the tibial tray. The relatively low congruency at the tibio-femoral articulation meant that there was a reduced “driving force” at the tibio-femoral joint resulting in less than adequate rotation of the mobile polyethylene insert. We feel that the tibial tray must be placed in neutral to the femoral prosthesis and failure to do so will result in abnormal polyethylene loading that would increase wear and may culminate in early prosthesis revision.

The use of rim mesh to augment acetabular defects at the time of revision hip surgery is a valuable technique. Where acetabular containment is compromised by segmental rim defects, it can be achieved by using a flexible wire mesh fixed to the wall of the ilium by multiple screws. Morsilised bone graft is then impacted onto the acetabular bed and wire mesh thus creating a new hemi-spherical acetabular bed for cementation of a new socket.

Standard AP and lateral radiographs are acceptable methods for assessing conventional socket revisions. However if a rim mesh has been used the mesh itself will obscure the socket and both columns of the acetabulum making interpretation difficult. We have modified the Judet views classically used in acetabular fracture surgery to allow better imaging of the socket. The views taken are dependant upon rim mesh position at surgery. Technique: Positioning for posterior acetabular rim mesh

From the supine position the patient is rotated 45° so that the side under examination is raised. Radiolucent pads are used to support the pelvis and leg. The hips and knees should not be flexed.

Positioning for anterior acetabular rim mesh

From the supine position the patient is rotated 45° so the non affected side is raised. Using radiolucent pads the pelvis is supported. The femur should not be flexed and externally rotated as they would be for an oblique hip

The film is centred approximately 2cm below the ASIS of the hip being examined.

These views of the hip allow complete imaging of the socket and the reconstructive construct. Radiographic evaluation of the bone graft and bone cement-graft interface can be reliably made.

We would recommend these views for the radiographic follow up of socket revisions involving the rim mesh technique.

In 1999 a statement of best practice in primary total hip replacement was approved by the Council of the British Orthopaedic Association and by the British Hip Society to provide a basis for regional and national auditable standards. We have compared practice in the North West of England to this document to ascertain adherence to this guide to best practice.

86 surgeons from 26 hospitals were included in the study. A mean of 93.3% of operations were performed in the surgeon’s usual theatre. All of these theatres had vertical laminar air flow systems. 42.2% of respondents routinely used exhaust suits. 68.1% of respondents routinely used impermeable disposable gowns, 26.1% used impermeable reusable gowns. The Charnley femoral and acetabular prostheses were the most commonly used prostheses.

All surgeons use some form of anti-thromboembolic prophylaxis. 66.2% use a combination of both mechanical and chemical means. All surgeons used antibiotic prophylaxis. The most popular choice of antibiotic was a cephalosporin. 70.7% used a three-dose regime over 24 hours. 2.6% of surgeons continued antibiotic prophylaxis for 48 hours after surgery. 93.7% of surgeons routinely use antibiotic-loaded cement.All surgeons routinely cleaned, irrigated and dried the acetabulum and femur before cement insertion. Only one surgeon did not use any form of femoral canal occlusion. 69.4% used an intramedullary bone block. Retrograde filling of the femoral shaft by means of a cement gun was practised by 65.1%.

This study has demonstrated considerable variation of practice in THA across the North West region and significant divergence from the statement of best practice approved by the BOA and BHS. The introduction of a properly funded national hip register will surely help to clarify the effect of such diverse practice on patient outcome. We would recommend that all trusts locally audit their practices and correlate them to these nationally agreed guidelines.

A secure bone/cement interface at the bone cement junction is an important requirement for the long-term success in the cemented hip arthroplasty. Cementing techniques have evolved and now involve pressurisation of the acetabulum and femur. It can be difficult to get a complete rim seal and hence adequate pressurisation due to the unique anatomy of the acetabulum and the contyloid notch.

Several acetabular pressurisers are commercially available.

We have developed an instrument for controlled and reproducible cement pressurisation in the acetabulum before socket insertion. It is a T-bar incorporating a central plunger, which protrudes from an outer sleeve when force is applied. The protrusion of the central plunger and hence the amount of force applied can be limited by a stop-sleeve.

A laboratory saw bone model was designed to assess this system and compare it with two existing pressurisers. A polypropylene model of the acetabulum was used. Included in the model were two 1.3mm diameter capillary outlets, one at its pole and one at a point close to its rim opposite the cotyloid notch. Water was free to flow through the capillaries at a pressure of 13.5” WG to represent blood flow. 5 test per pressuriser were performed.

CMW 1 Gentamicin bone cement was mixed as per manufacturers instruction in a Vacuum Mix system. The cement was then pressurised using one of three systems; the Depuy T handle pressuriser, the Exeter pressuriser and our new instrument.

The cement mantle produced with the Depuy T-handle and the Exeter pressuriser was thicker at the pole than the rim and the cement intrusion was not consistent nor reproducible. The new pressurizer produced a cement mantle equal at the pole and the rim to within 1mm. A reproducible cement mantle compatible to the shape of the socket and with cement intrusion of 5mm (+/− 1mm) could be achieved. We recommend the use of this pressuriser.

Introduction: Long-term, aseptic loosening is the central problem for total hip replacements (THR)1. Several studies have suggested the possibility of predicting long-term loosening of femoral components (after about 7 years) by assessment of the short-term migration pattern (1 – 2 years) using radiostereometric analysis (RSA)2. During the past 2 years, we have been conducting an RSA study of the Elite Plus (DePuy) femoral component migration in 25 (8M, 17F) primary THR patients (mean age 61 years).

Results: The Table below shows the mean and SD of the stem centroid migrations after 12 months. The mean subsidence rate of 0.71 mm/year (15 patients) during the first month reduced to 0.16 mm/year, (22 patients) during the following two months. By the latter half of the first postoperative year, the mean rate had reduced to 0.13 mm/year.

Discussion: A study by the Oxford group (Alfaro-Adrian et al.³ ) compared the migration of 19 Elite Plus stems with 32 Exeter (Howmedica) stems over a two year period. After 1 year, there is a remarkable similarity in the subsidence, lateral migration and internal rotation between the two groups. However, combining the posterior and anterior migrations in the present study, the mean posterior migration was 0.15 mm. This is about half of that measured by the Oxford group (0.28 mm). Furthermore, the present study shows that varus rotation is predominant – compared to valgus rotation in the Oxford group’s study.