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 following scaling and then manually scaled images on a computer screen superimposing acetate templates in the traditional fashion. 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.
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).
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.
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 To analyse results together with bacteriological and histological findings.
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.
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.
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%.
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.
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).
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.
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).
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.
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.
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.
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.
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.
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.