Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing.

OBJECTIVES: Modern metal-on-metal (MoM) hip resurfacing arthroplasty (HRA), while achieving good results with well-orientated, well-designed components in ideal patients, is contraindicated in women, men with head size under 50 mm, or metal hypersensitivity. These patients currently have no access to the benefits of HRA. Highly crosslinked polyethylene (XLPE) has demonstrated clinical success in total hip arthroplasty (THA) and, when used in HRA, potentially reduces metal ion-related sequelae. We report the early performance of HRA using a direct-to-bone cementless mono-bloc XLPE component coupled with a cobalt-chrome femoral head, in the patient group for whom HRA is currently contraindicated. METHODS: This is a cross-sectional, observational assessment of 88 consecutive metal-on-XLPE HRAs performed in 84 patients between 2015 and 2018 in three centres (three surgeons, including the designer surgeon). Mean follow-up is 1.6 years (0.7 to 3.9). Mean age at operation was 56 years (sd 11; 21 to 82), and 73% of implantations were in female patients. All patients were individually counselled, and a detailed informed consent was obtained prior to operation. Primary resurfacing was carried out in 85 hips, and three cases involved revision of previous MoM HRA. Clinical, radiological, and Oxford Hip Score (OHS) assessments were studied, along with implant survival. RESULTS: There was no loss to follow-up and no actual or impending revision or reoperation. Median OHS increased from 24 (interquartile range (IQR) 20 to 28) preoperatively to 48 (IQR 46 to 48) at the latest follow-up (48 being the best possible score). Radiographs showed one patient had a head-neck junction lucency. No other radiolucency, osteolysis, component migration, or femoral neck thinning was noted. CONCLUSION: The results in this small consecutive cohort suggest that metal-on-monobloc-XLPE HRA is successful in the short term and merits further investigation as a conservative alternative to the current accepted standard of stemmed THA. However, we would stress that survival data with longer-term follow-up are needed prior to widespread adoption.Cite this article: R. B. C. Treacy, J. P. Holland, J. Daniel, H. Ziaee, D. J. W. McMinn. Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing. Bone Joint Res 2019;8:443-450. DOI: 10.1302/2046-3758.810.BJR-2019-0060.R1.

Asynchronous Bilateral Total Knee Arthroplasty: Predictors of the Functional Outcome and Patient Satisfaction for the Second Knee Replacement.

BACKGROUND: The primary aim of this study is to identify independent preoperative predictors of outcome and patient satisfaction for the second total knee arthroplasty (TKA). METHODS: A retrospective cohort of 454 patients undergoing an asynchronous (6 weeks or more apart) bilateral primary TKA were identified from an arthroplasty database. Patient demographics, comorbidities, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-12 scores were collected preoperatively and 1 year postoperatively. Overall patient satisfaction was assessed at 1 year. RESULTS: The 1 year WOMAC pain score (P = .01), and improvement in WOMAC pain (P < .001) and functional (P = .002) scores were significantly lower for the second TKA. Worse preoperative WOMAC pain, function, and stiffness scores were demonstrated to be independent predictors of improvement in the WOMAC pain, function, and stiffness scores, respectively, for both the first and second TKA. The overall rate of satisfaction with the first TKA was 94.0% and 94.7% for the second TKA (P = .67). The rate of satisfaction for the second TKA was 77.8% for patients that were dissatisfied with their first TKA, which was an independent predictor of dissatisfaction (P = .02). CONCLUSION: Improvement in pain and function is less with the second TKA, but the satisfaction rate remains similar. There are common independent predictors for change in the WOMAC score for the first and second TKA; however, the predictors of satisfaction were different with no common factors. Patients that were dissatisfied with their first TKA were more likely to be dissatisfied with their second TKA. LEVEL OF EVIDENCE II: Prognostic retrospective cohort study.

An Overview and Predictors of Achieving the Postoperative Ceiling Effect of the WOMAC Score Following Total Knee Arthroplasty.

BACKGROUND: To describe the ceiling effect for the components of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and identify preoperative independent predictors for patients who achieve maximal scores (ceiling effect) after total knee arthroplasty (TKA). METHODS: A retrospective cohort of 2589 patients undergoing a primary TKA were identified from an established arthroplasty database. Patient demographics, WOMAC and Short Form 12 (SF-12) scores were collected preoperatively and 1 year postoperatively. Logistic regression analysis was used to identify independent preoperative predictors of patients achieving ceiling scores. RESULTS: The ceiling effect was 26.8% (n = 695) for the pain score, 6.4% (n = 165) for the function score, and 21.2% (n = 548) for the stiffness score. Lower body mass index (P = .001), absence of gastric ulceration (P = .04), absence of anemia (P = .02), absence of depression (P = .004), and absence of back pain (P < .001) and better preoperative WOMAC pain and SF-12 physical (P = .01) and mental (P < .001) scores were associated with a ceiling WOMAC pain score. Male gender (P = .03), lower body mass index (P = .040), absence of gastric ulceration (P = .004), and absence of back pain (P < .001) and better preoperative SF-12 physical (P = .02) scores were associated with a ceiling WOMAC function score. Male gender (P = .001), absence of back pain (P < .001), and better preoperative WOMAC stiffness score (P = .005) and SF-12 mental (P = .001) scores were associated with a ceiling WOMAC stiffness score. CONCLUSION: The WOMAC pain and stiffness components demonstrated a high ceiling effect but in contrast the functional score had a low ceiling effect. The absence of back pain was a common predictive factor for all 3 components and had the greatest impact upon the likelihood of achieving a ceiling score.

Mechanical properties of cancellous bone from the acetabulum in relation to acetabular shell fixation and compared with the corresponding femoral head.

To gain initial stability for cementless fixation the acetabular components of a total hip replacement are press-fit into the acetabulum. Uneven stiffness of the acetabular bone will result in irregular deformation of the shell which may hinder insertion of the liner or lead to premature loosening. To investigate this, we removed bone cores from the ilium, ischium and pubis within each acetabulum and from selected sites in corresponding femoral heads from four cadavers for mechanical testing in unconfined compression. From a stress-relaxation test over 300 s, the residual stress, its percentage of the initial stress and the stress half-life were calculated. Maximum modulus, yield stress and energy to yield (resilience) were calculated from a load-displacement test. Acetabular bone had a modulus about 10-20%, yield stress about 25% and resilience about 40% of the values for the femoral head. The stress half-life was typically between 2-4 s and the residual stress was about 60% of peak stress in both acetabulum and femur. Pubic bone was mechanically the poorest. These results may explain uneven deformation of press-fit acetabular shells as they are inserted. The measured half-life of stress-relaxation indicates that waiting a few minutes between insertion of the shell and the liner may allow seating of a poorly congruent liner.

Effect of cobalt-mediated Toll-like receptor 4 activation on inflammatory responses in endothelial cells.

Cobalt-containing metal-on-metal hip replacements are associated with adverse reactions to metal debris (ARMD), including inflammatory pseudotumours, osteolysis, and aseptic implant loosening. The exact cellular and molecular mechanisms leading to these responses are unknown. Cobaltions (Co2+) activate human Toll-like receptor 4 (TLR4), an innate immune receptor responsible for inflammatory responses to Gram negative bacterial lipopolysaccharide (LPS).We investigated the effect of Co2+-mediated TLR4 activation on human microvascular endothelial cells (HMEC-1), focusing on the secretion of key inflammatory cytokines and expression of adhesion molecules. We also studied the role of TLR4 in Co2+-mediated adhesion molecule expression in MonoMac 6 macrophages.We show that Co2+ increases secretion of inflammatory cytokines, including IL-6 and IL-8, in HMEC-1. The effects are TLR4-dependent as they can be prevented with a small molecule TLR4 antagonist. Increased TLR4-dependent expression of intercellular adhesion molecule 1 (ICAM1) was also observed in endothelial cells and macrophages. Furthermore, we demonstrate for the first time that Co2+ activation of TLR4 upregulates secretion of a soluble adhesion molecule, sICAM-1, in both endothelial cells and macrophages. Although sICAM-1 can be generated through activity of matrix metalloproteinase-9 (MMP-9), we did not find any changes in MMP9 expression following Co2+ stimulation.In summary we show that Co2+ can induce endothelial inflammation via activation of TLR4. We also identify a role for TLR4 in Co2+-mediated changes in adhesion molecule expression. Finally, sICAM-1 is a novel target for further investigation in ARMD studies.

Cobalt ions recruit inflammatory cells in vitro through human Toll-like receptor 4.

Metal-on-metal (MoM) hip replacements, often manufactured from a cobalt-chrome alloy, are associated with adverse reactions including soft tissue necrosis and osteolysis. Histopathological analysis of MoM peri-implant tissues reveals an inflammatory cell infiltrate that includes macrophages, monocytes and neutrophils. Toll-like receptor 4 (TLR4) is an innate immune receptor activated by bacterial lipopolysaccharide. Recent studies have demonstrated that cobalt ions from metal-on-metal joints also activate human TLR4, increasing cellular secretion of inflammatory chemokines including interleukin-8 (IL-8, CXCL8) and CCL2. Chemokines recruit immune cells to the site of inflammation, and their overall effect depends on the chemokine profile produced. This study investigated the effect of cobalt on the secretion of inflammatory cytokines CCL20 and IL-6. The chemotactic potential of conditioned media from a cobalt-stimulated human monocyte cell line on primary monocytes and neutrophils was investigated using an in vitro transwell migration assay. The role of TLR4 in observed effects was studied using a small molecule TLR4-specific antagonist. Cobalt ions significantly increased release of CCL2 and IL-6 by MonoMac 6 cells (P<0.001). Conditioned media from cobalt-stimulated cells significantly increased monocyte and neutrophil chemotaxis in vitro (P<0.001). These effects were abrogated by the TLR4 antagonist (P<0.001) suggesting that they occur through cobalt activation of TLR4. This study demonstrates the role of TLR4 in cobalt-mediated immune cell chemotaxis and provides a potential mechanism by which cobalt ions may contribute to the immune cell infiltrate surrounding failed metal hip replacements. It also highlights the TLR4 signalling pathway as a potential therapeutic target in preventing cobalt-mediated inflammation.

Anterior knee symptoms after S-ROM hinge implantation.

PURPOSE: To evaluate the performance of a canal filling hinge device for complex knee arthroplasty. METHODS: Thirty-seven (4 primary hinge implantation and 33 revision cases) patients who had undergone arthroplasty with the S-ROM third generation hinge device for a combination of massive bone loss or ligamentous insufficiency were prospectively examined with a minimum of 5-year follow-up. Median age at surgery was 72 years (range: 43 to 87 years). Principal indications included aseptic loosening or massive osteolysis (24 cases), infection (8 cases) and periprosthetic fracture (4 cases). All patients exhibited either grade 2 (N = 12) or grade 3 (N = 25) AORI bone loss or a grade 3 medial ligament deficiency. RESULTS: One patient experienced implant failure (71 months), and one patient suffered late deep infection (36 months). Mean WOMAC score improved from 27 to 62. Four patients required patellar resurfacing for persistent pain. The 5-year survivorship was 86%. CONCLUSIONS: While the S-ROM device may offer satisfactory medium term outcome for complex end stage knee disease, we report a high rate of debilitating anterior knee symptoms.

Use of porous trabecular metal augments with impaction bone grafting in management of acetabular bone loss.

BACKGROUND: The use of impaction grafting in revisions with larger acetabular bone defects has mixed outcomes and sometimes high failures rates. PATIENTS AND METHODS: This prospective, single-center study involved a consecutive series of 24 patients who underwent complex reconstruction of the acetabulum using a trabecular metal augment, impaction bone grafting, and a cemented high-density polyethylene cup. Patients were followed for median 5 (3-7) years. RESULTS: The 2-year WOMAC pain, function, and stiffness scores improved, as did certain components (bodily pain, physical function, role physical, role emotional, physical component score, and social function) of the SF-36 (p < 0.05). 23 of the patients were very satisfied with the overall outcome of the surgery and would have undergone the surgery again for a similar problem, and 19 reported great improvement in their quality of life after surgery. Radiographs at the latest follow-up revealed incorporation of the augment with mean change in acetabular component inclination of less than 1 degree (p > 0.05) and cup migration of less than 5 mm in both horizontal and vertical axes (p > 0.05). 1 patient required further revision at 13 months and was found to have a fractured augment at re-revision. INTERPRETATION: This study shows that trabecular metal augments are effective in filling the bone defect and provide a stable foundation for impaction bone grafting. We found satisfactory clinical and radiographic results using this technique, with low failure rate at a median follow-up time of 5 years.

Functional outcome following aseptic single-stage revision knee arthroplasty.

PURPOSE: This study attempts to quantify the influence of constraint and various indications upon functional outcome following aseptic first-time revision knee arthroplasty. METHODS: A single-centre prospective study was performed to examine the outcome for 175 consecutive total revision knee replacements performed between 2003 and 2008 with a minimum follow-up of 2 years. Patient-reported outcome data were used to determine the influence of final level of component constraint, its relationship with primary indication for surgery and the predictor variable for functional outcome at 1 year. RESULTS: All patients were found to have a significant improvement for WOMAC pain, function and stiffness score and physical functioning, role physical, bodily pain and social functioning components of SF-36 score. About 69% were satisfied with the overall procedure. WOMAC function, pain and stiffness score was significantly worse for patients revised for instability (27%) compared to that for aseptic loosening (46%). A significantly higher proportion of patients were satisfied with the procedure, had a better quality of life and would have the surgery again in the aseptic loosening group as compared to the instability group. Revision to a higher level of constraint did not improve knee function irrespective of the primary indication for surgery. CONCLUSION: This study has found that revision for instability, irrespective of choice of new device, was met with significantly poorer functional outcome. The level of constraint did not influence functional outcome. LEVEL OF EVIDENCE: II.

Oxidation and fusion defects synergistically accelerate polyethylene failure in knee replacement.

We have previously reported upon a cohort of patients with premature failure of such material and postulated upon the impact of abnormally high concentrations of type 2 fusion defects whereby there is a lack of particle cohesion due to incomplete diffusion. In vivo oxidation has been purported to underscore the premature failure of polyethylene. The mechanism of such remains poorly delineated. New data has now been obtained by determining substrata oxidative profiles of 10 failed Kinemax Plus modular tibial insert analyses in conjunction with fusion defect detection. The full thickness of a series of cores was analysed using infra-red spectroscopy to identify higher levels of oxidation in loaded used material at both the articulating and non-articulating regions. A comparison was made to an unused control. Articulating, loaded, areas exhibited greater local concentrations of oxidised material and wider variation of such consistent with the higher presence of fusion defects. Subsurface analysis confirmed the presence of a major oxidative peak 2mm below the surface for all loaded areas irrespective of wear. Additionally we were able to identify a second major oxidative focus about halfway between the inferior (tibial baseplate) surface and the articulating area. We believe that the combination of high oxidation and fusion defects represents a second high stress zone consistent with the observation of tibial baseplate polyethylene dissociation and backside wear with resultant catastrophic material failure.

Outcome of hip resurfacing in obese patients.

The effect of obesity on outcome for patients undergoing hip resurfacing has been evaluated. Pre and post-operative objective patient scored outcomes for a group of 181 cases of hip resurfacing performed over a three year period were collected. Cases have been stratified by body mass index (BMI) with evaluation of post-operative complications. Patient outcomes included: SF-36, WOMAC, and satisfaction scores, and were compared pre-operatively, and at one year. We found an increased rate of wound complications in the obese group (BMI > 30) with 4 cases of prolonged wound drainage and 2 superficial infections, compared to none in the non-obese group. A similar improvement in SF-36, WOMAC and patient satisfaction was found for both groups. No increase in the risk of femoral neck fracture or aseptic loosening was seen in the obese group. These results suggest excellent early outcomes for obese patients undergoing hip resurfacing with no added risk of early failure.

Cadaveric hands-on training for surgical specialties: is this back to the future for surgical skills development?

INTRODUCTION: Delivery of surgical care is linked intricately to technical proficiency. Recent legislative changes in the United Kingdom have facilitated the introduction of new teaching methods. This article is a review of our experience with a cadaver laboratory housed within a tertiary referral hospital and assesses the impact of such for the future delivery of surgical care in the United Kingdom. MATERIALS AND METHODS: We describe in this article the logistics of setting up and running a fresh frozen cadaver laboratory, the governance arrangements in place, the performance of the facility in the first 2 years, and the feedback from the participants. RESULTS: The center hosts approximately 60 courses per year across a range of surgical disciplines that have received excellent feedback. Support from the Trust Board, local charities, multidisciplinary faculty, and the industry underpinned by robust governance has resulted in a successful venture. CONCLUSIONS: Hands-on training is increasingly relevant in craft specialties. After the introduction of the European working time directive, there is clear evidence of reduction in time spent performing live surgical procedures by trainees. There has been an explosion in the introduction of new surgical technology and marked expansion in the instrumentation that accompanies such procedures. Greater scrutiny of surgical outcomes is now in the public domain. To embrace and maximize patient benefit successfully, it is mandatory that the surgeon of the future will require access to dedicated near patient surgical training in specific skills without jeopardizing patient care.

Socio-economic impact of Birmingham hip resurfacing on patient employment after ten years.

Birmingham hip resurfacing is an attractive option for treatment of arthritis in young and active patients. The aim of this study was to assess the socio-economic impact of Birmingham hip resurfacing on their employment and work intensity at ten years. A cohort of 90 consecutive patients with 100 Birmingham hip resurfacing, performed by single surgeon, were reviewed prospectively. The mean age was 51 years at surgery. Prospective review was undertaken from surgery until the tenth post-operative year. Overall, 90% of patients were in the same employment following surgery. Two patients who were employed before surgery were unemployed. Three patients had to decrease their work intensity but were still employed. Three out of five disabled patients regained employment following surgery. Seventy-eight patients were able to continue their employment with no or minimal restriction. Birmingham hip resurfacing allows the majority of patients to continue their same employment at similar intensity ten years following surgery.

The complex problem of the interprosthetic femoral fracture in the elderly patient.

An ageing population and greater number of hip and knee replacements performed have led to an increasing number of patients with ipsilateral hip and knee replacements in situ. This often physiologically suboptimal population is at risk for periprosthetic fracture. An interprosthetic femoral fracture represents a unique challenge to the surgeon and requires a detailed multidisciplinary management strategy involving both fracture fixation and often complex revision. We have identified the largest series to our knowledge of patients presenting for surgical management of an unstable fracture between a hip and knee prosthesis. Institutional approval was granted for prospective study of these patients. We present the detailed management, outcome and review the known literature of the best practice for such a complex surgical case. We have outlined 9 fractures in 8 patients presenting to a single trauma unit. A variety of surgical options, often more than one, were employed. One patient died during the study period. All fractures progressed to union. There was a female preponderance with a mean age of 78 years. All patients had established systemic and metabolic bone morbidity. We believe this fracture pattern presents to the general orthopaedic surgeon a unique challenge, which bridges the expertise of the trauma and revision surgical spectrum. It is obvious that this will become an increasing issue with the median age of the population increasing. This case series highlights the need for ready availability of biological, arthroplasty and trauma systems to address such.

Metal-on-metal total hip arthroplasty.

The effects of elevated levels of metal ions in patients who have undergone metal-on-metal total hip arthroplasty are not fully understood. The effects of femoral head size on serum metal-ion levels have been the subject of conflicting reports, and further investigation is needed to evaluate the impact of acetabular and femoral component alignment. The conduct of clinical trials of metal-on-metal total hip arthroplasties has been inadequate as few investigators have used a randomized controlled design to compare metal-on-metal bearings with other bearing surfaces. Additional clinical research needs to include appropriate validated patient-reported outcome measures, activity monitoring, and health economics.

Cup anteversion in hip resurfacing: validation of EBRA and the presentation of a simple clinical grading system.

The use of large metal on metal bearings has led to a reduction in the risk of dislocation post hip arthroplasty. Because of this, and also because of the technical difficulties associated with resurfacing surgery in particular, it could be argued that a less meticulous approach to acetabular cup placement has developed in comparison with conventional metal on polyethylene arthroplasty. Resurfacing cups may produce significant clinical problems when placed at the extremes of version, including increased production of metal debris and psoas tendonitis. Presented in this article is evidence that EBRA software (Einzel-Bild-Roentgen-Analysis, University of Innsbruck, Austria) can be used to reliably assess the version of resurfacing cups, when radiographs are of sufficient quality. The cups have characteristic appearances when placed at the extremes of version. These characteristics can allow the surgeon to identify poorly positioned cups without the use of software.

Hip flexion after Birmingham hip resurfacing: role of cup anteversion, anterior femoral head-neck offset, and head-neck ratio.

We aimed to investigate the factors affecting range of flexion after hip resurfacing. A total of 82 cases, operated by a single surgeon, were assessed at a mean of 43 months. The Einzel-Bild-Roentgen-Analysis for the acetabular cup software was used to measure socket orientation. Range of flexion had a moderate positive correlation with cup anteversion (R = 0.26, P = .017), weak but significant negative correlation with neck diameter (R = -0.23, P = .042), and none with anterior femoral head-neck offset. Using multivariate analysis that adjusted for age, sex, cup anteversion and inclination, head-neck offset ratio, head-neck ratio, and neck diameter, the only significant correlate of flexion was cup anteversion (P = .017). Care should be taken during cup placement to allow adequate anteversion to be maintained in Birmingham hip resurfacing because this can affect flexion range of motion.

Bone density of the femoral neck following Birmingham hip resurfacing.

BACKGROUND: Resurfacing is a popular alternative to a standard hip replacement in young arthritic patients. Despite bone preservation around the femoral component, there is little information regarding the bone quality. PATIENTS AND METHODS: 32 patients underwent consecutive Birmingham hip resurfacing. The bone density of the femoral neck was measured preoperatively and then at 6 weeks, 3 months, 1 year, and 2 years. The femoral neck was divided into regions of interest. Results were available for 27 hips in 26 patients. RESULTS: The overall femoral neck bone density showed a trend towards a decrease at 6 weeks and 3 months but returned to the preoperative level at 1 year, and was maintained at 2 years. The combined superior regions of the neck showed a statistically significant decrease in bone density at 6 weeks and 3 months. This returned to preoperative levels at 1 year and was maintained at 2 years. INTERPRETATION: Bone density appears to decrease at 6 weeks and 3 months, suggesting that care is necessary until bone density begins to recover.