The management of femoral bone loss is challenging during revision hip arthroplasty. In patients with Paprosky grade IIIB and IV defects, obtaining fixation and rotational stability using traditional surgical constructs is difficult. The use of a custom-made internal proximal femoral replacement prostheses has been proposed as a solution in patients, with severe femoral bone stock loss. However, there is a paucity in the literature on their use and long-term outcomes. We report on the clinical and radiological results of our cohort.

We retrospectively reviewed all patients who underwent internal proximal femoral replacement for revision hip arthroplasty between April 1996 and April 2019. All patients had at least 2 years of follow-up time.

160 patients underwent limb salvage at our institution using internal proximal femoral replacement. The mean follow-up was 79.7 months (S.D 41.3). Indications for revision included periprosthetic fractures, aseptic loosening, and deep infection. The mean Oxford hip score increased from 13.8 (0–22) to 31.5 (18–43) (paired t-test, p < 0.001). Kaplan-Meier prosthesis survival analysis with revision as the endpoint was 87% at 5 years. None required revision of the femoral stem. There were four dislocations (5%) and there was failure to eradicate the deep infection in four.

This technique allows instant distal fixation, allowing for early mobilisation. Long-term clinical and radiological outcomes are encouraging and the complication rates are acceptable for this patient group.

Aims

Young adults undergoing total hip arthroplasty (THA) largely have different indications for surgery, preoperative function, and postoperative goals compared to a standard patient group. The aim of our study was to describe young adult THA preoperative function and quality of life, and to assess postoperative satisfaction and compare this with functional outcome measures.

Custom acetabular components have become an established method of treating massive acetabular bone defects in hip arthroplasty. Complication rates, however, remain high and migration of the cup is still reported. Ischial screw fixation (IF) has been demonstrated to improve mechanical stability for non-custom, revision arthroplasty cup fixation. We hypothesise that ischial fixation through the flange of a custom acetabular component aids in anti-rotational stability and prevention of cup migration.

Electronic patient records were used to identify a consecutive series of 49 custom implants in 46 patients from 2016 to 2022 in a unit specializing in complex joint reconstruction. IF was defined as a minimum of one screw inserted into the ischium passing through a hole in a flange on the custom cup.

The mean follow-up time was 30 months. IF was used in 36 cups. There was no IF in 13 cups. No difference was found between groups in age (68.9 vs. 66.3, P = 0.48), BMI (32.3 vs. 28.2, P = 0.11) or number of consecutively implanted cups (3.2 vs. 3.6, P = 0.43). Aseptic loosening with massive bone loss was the primary indication for revision. There existed no difference in Paprosky grade between the groups (P = 0.1). 14.2% of hips underwent revision and 22.4% had at least one dislocation event.

No ischial fixation was associated with a higher risk of cup migration (6/13 vs. 2/36, X2 = 11.5, P = 0.0007). Cup migration was associated with an increased risk for all cause revision (4/8 vs. 3/38, X2 = 9.96, P = 0.0016, but not with dislocation (3/8 vs. 8/41, X2 = 1.2, P = 0.26).

The results suggest that failure to achieve adequate ischial fixation, with screws passing through the flange of the custom component into the ischium, increases the risk of cup migration, which, in turn, is a risk factor for revision.

3D printing acetabular cups offers the theoretical advantage of enhanced bony fixation due to greater design control of the porous implant surfaces. Analysing retrieved 3D printed implants can help determine whether this design intent has been achieved.

We sectioned 14 off-the-shelf retrieved acetabular cups for histological analysis; 7 cups had been 3D printed and 7 had been conventionally manufactured. Some of the most commonly used contemporary designs were represented in both groups, which were removed due to either aseptic loosening, unexplained pain, infection or dislocation. Clinical data was collected for all implants, including their age, gender, and time to revision.

Bone ingrowth was evaluated using microscopic assessment and two primary outcome measures: 1) bone area fraction and 2) extent of bone ingrowth.

The additively manufactured cups were revised after a median (IQR) time of 24.9 months (20.5 to 45.6) from patients with a median (IQR) age of 61.1 years (48.4 to 71.9), while the conventional cups had a median (IQR) time to revision of 46.3 months (34.7 to 49.1, p = 0.366) and had been retrieved from patients with a median age of 66.0 years (56.9 to 68.9, p = 0.999).

The additively and conventionally manufactured implants had a median (IQR) bone area fraction of 65.7% (36.4 to 90.6) and 33.9% (21.9 to 50.0), respectively (p < 0.001).

A significantly greater amount of bone ingrowth was measured into the backside of the additively manufactured acetabular cups, compared to their conventional counterparts (p < 0.001). Bone occupied a median of 60.0% and 5.7% of the porous depth in the additively manufactured and conventional cups, respectively.

3D printed components were found to achieve a greater amount of bone ingrowth than their conventionally manufactured counterparts, suggesting that the complex porous structures generated through this manufacturing technique may encourage greater osteointegration.

Ceramic bearing fractures are rare events, but mandate revision and implantation of new bearings. Revisions using metal heads have been reported to lead to gross volumetric head wear (due to abrasive retained ceramic micro-debris), cobalt toxicity, multi-organ failure and death. Such complications are widely published (50+ reports), yet we know that patients continue to be put at risk. Using data from the NJR and AOANJRR, this study seeks to compare the risk of re-revision and death by revision bearing combination following a ceramic bearing fracture.

Data were extracted from the NJR and AOANJRR, identifying revisions for ceramic bearing fracture. Subsequent outcomes of survival, re-revision and death were compared between revision bearing combinations (ceramic-on-ceramic, ceramic-on-polyethylene, and metal-on-polyethylene).

366 cases were available for analysis from the NJR dataset (MoP=34, CoP=112, CoC=221) and 174 from the AOANJRR dataset (MoP=17, CoP=44, CoC=113). The overall incidence rate of adverse outcome (revision or death) was 0.65 for metal heads and 0.23 for ceramic head articulations (p=0.0012) across the whole time period (NJR). Kaplan-Meir survival estimates demonstrate an increased risk of both re-revision and death where a metal head has been used vs a ceramic head following revision for ceramic fracture.

There are few decisions in arthroplasty surgery that can lead to serious harm or death for our patients, but revision using a metal head following ceramic bearing fracture is one of them. This study enhances the signal of what is already known but previously only reported as inherently low-level evidence (case reports and small series) due to event rarity. Use of a metal head in revision for ceramic fracture represents an avoidable patient safety issue, which revision guidelines should seek to address.

Aims

Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning.

Aims

Minimally manipulated cells, such as autologous bone marrow concentrates (BMC), have been investigated in orthopaedics as both a primary therapeutic and augmentation to existing restoration procedures. However, the efficacy of BMC in combination with tissue engineering is still unclear. In this study, we aimed to determine whether the addition of BMC to an osteochondral scaffold is safe and can improve the repair of large osteochondral defects when compared to the scaffold alone.

Aims

The aim of this study was to present the first retrieval analysis findings of PRECICE STRYDE intermedullary nails removed from patients, providing useful information in the post-market surveillance of these recently introduced devices.

Aims

The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.

Aims

Periprosthetic joint infection (PJI) is a debilitating condition with a substantial socioeconomic burden. A novel autologous blood glue (ABG) has been developed, which can be prepared during surgery and sprayed onto prostheses at the time of implantation. The ABG can potentially provide an antimicrobial coating which will be effective in preventing PJI, not only by providing a physical barrier but also by eluting a well-known antibiotic. Hence, this study aimed to assess the antimicrobial effectiveness of ABG when impregnated with gentamicin and stem cells.

Aims

For cementless implants, stability is initially attained by an interference fit into the bone and osteo-integration may be encouraged by coating the implant with bioactive substances. Blood based autologous glue provides an easy, cost-effective way of obtaining high concentrations of growth factors for tissue healing and regeneration with the intention of spraying it onto the implant surface during surgery. The aim of this study was to incorporate nucleated cells from autologous bone marrow (BM) aspirate into gels made from the patient’s own blood, and to investigate the effects of incorporating three different concentrations of platelet rich plasma (PRP) on the proliferation and viability of the cells in the gel.

Aims

The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components.

Objectives

The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities.

Background

In the late 1980's Michael Freeman conceived the idea that knee replacement would most closely replicate the natural knee joint, if the medial Tibio-Femoral articulation was configured as a “ball-in-socket”. Over the last three decades, medial rotation and medial pivot designs have proved successful in clinical use. Freeman's final iteration of the medial ball-in-socket concept was the Medial Sphere knee. We report the three-year survivorship, clinical outcomes, patient reported outcome measures (PROMs) and radiographic analysis of this implant in a multi-centre, multi-surgeon, prospective observational study.

Objectives

The Attune total knee arthroplasty (TKA) has been used in over 600 000 patients worldwide. Registry data show good clinical outcome; however, concerns over the cement-tibial interface have been reported. We used retrieval analysis to give further insight into this controversial topic.

Objectives

Previous studies have suggested that metal-on-metal (MoM) Pinnacle (DePuy Synthes, Warsaw, Indiana) hip arthroplasties implanted after 2006 exhibit higher failure rates. This was attributed to the production of implants with reduced diametrical clearances between their bearing surfaces, which, it was speculated, were outside manufacturing tolerances. This study aimed to better understand the performance of Pinnacle Systems manufactured before and after this event.

Objectives

The Precice nail is the latest intramedullary lengthening nail with excellent early outcomes. Implant complications have led to modification of the nail design. The aim of this study was to perform a retrieval study of Precice nails following lower-limb lengthening and to assess macroscopical and microscopical changes to the implants and evaluate differences following design modification, with the aim of identifying potential surgical, implant, and patient risk factors.

Introduction

Modular-neck hips have twice the rate of revision compared to fixed stems. Metal related pathology is the second most common reason for revision of implants featuring titanium stems with cobalt chrome necks. We aimed to understand the in-vivo performance of current designs and explore the rationale for their continued use.

Introduction

Numerous studies have reported on clinically significant volumes of material loss and corrosion at the head-stem junction of metal-on-metal (MOM) hips; less is understood about metal-on-polyethylene (MOP) hips. We compared the effect of bearing type (MOM vs MOP) on taper material loss for a hip system of a single design (DePuy Pinnacle).

Additive manufacturing has enabled a radical change in how surgeons reconstruct massive acetabular defects in revision hip surgery. We report on the early clinical and radiological results from our methods for surgical planning, design, and implantation of 3D printed trabecular titanium implants in a cohort of patients with large unclassifiable pelvic defects.

We set up a prospective investigation involving 7 consecutive patients. Inclusion criteria was the following: 1) A history of previous total hip replacement; and 2) Current imaging showing at least a Paprosky 3B defect. Planned acetabular inclination and version was 40° and 20° respectively. Post operatively all patients had a CT scan which was analysed with software to determine component position and compared to planned. Outpatient review was done at 2 weeks (For wound), 6 weeks (for weight bearing and fixation) and 52 weeks (for fixation and infection) post-operative.

The median age at surgery was: 65 years (40–78). The median bone defect volume was 140cm³. Median surgery length was 5.2 hours (3–6.25). Median blood loss was 1300mL (450– 2000). Radiologically, components were stable and no screw breakages were identified. Achieved inclination was 41.0° (29.0–55.6) and achieved version was 15.8° (3.8–43.6). Median Oxford Hip score improved from 9 (2–44) to 25 (18–32).

We have demonstrated a new series of pre, intra and post-operative methods for reconstruction of unclassifiable acetabular bony defects. Initial clinical and radiological results are excellent considering the severity of the bony defects. We recommend the use of our or similar methods when trying to reconstruct these defects.

Several implants have a proven track record of durability and function in patients over many years. As manufacturers' patents expire it is understandable that cheaper generic copies would be considered. There is currently no established, independent method of determining design equivalence between generic and branded orthopaedic implants.

We acquired 10 boxed, as manufactured components consisting of the generic OptiStem XTR model (n=5) and branded Exeter (n=5) femoral stems. Two examiners were blinded to the implant design and independently measured the mass, volume, trunnion surface topography, roughness, trunnion cone angle, CCD angle and femoral offset using peer-reviewed methods. We then compared the stems using these parameters.

We found that the OptiStems (1) were lighter (p<0.001) (2) had a rougher trunnion surface (p<0.001) with a greater spacing and depth of the machined threads (p<0.001), (3) had greater trunnion cone angles (p=0.007) and (4) a smaller radius at the top of the trunnion (p=0.007). There was no difference for stem volume (p=0.643), CCD angle (p=0.788) or offset (p=0.993).

This study is the first independent investigation of the equivalence of a generic orthopaedic implant to its branded design. We found a clear difference in trunnion roughness, trunnion cone angle and radius, and implant mass when comparing the two generic and branded stem designs. All implants require standard regulatory processes to be followed. It does not appear feasible that generic implants can be manufactured to predictability guarantee the same performance as generic drugs.

We found a number of physical differences between the generic and branded implants. Whilst both designs are likely to work in clinical practice, they are different.

Dual mobility (DM) cups are designed to improve stability, however have been associated with increased risk of impingement that can ultimately result in intraprosthetic dislocation. It is speculated that the femoral neck plays a role in their performance. We investigated the effect of neck topography on the wear of new-generation liners.

This was a retrieval study involving 70 DM cups implanted with liners made of highly crosslinked polyethylene and paired with two neck types: either highly polished (n=35) or rough necks (n=35). The median time of implantation was 30 months.

The rim edge of all inserts was investigated by two examiners for evidence of contact with the femoral neck, presenting as deformation of the polyethylene. A high precision roundness machine and micro-CT scans of the components were used to measure the size of the deformations observed.

28 of the 35 (80%) DM liners paired with rougher necks had evidence of neck impingement resulting in a raised lip, whilst 8 out of 35 (23%) liners paired with smooth necks had a raised lip; this difference was significant (p<0.0001). The repeatability and the inter-observer reproducibility of the deformation scores was found to be substantial κ >0.70. The height of the raised rims of the DM cups paired with rough necks had a median (range) of 139 µm (72–255), whilst had a median (range) of 52 µm (45–90) with smooth necks, the difference between the groups was significant (p<0.0001).

Liner rim deformation resulting from contact with the femoral neck likely begins during early in-vivo function.

Rough necks can increase the damage on the polyethylene rim in dual-mobility bearing, which may lead to loss of the retentive power of these components over time.

Trunnionosis, due to mechanical wear and/or corrosion at the head stem taper junction, can occur in metal on polyethylene (MOP) hip implants. In some patients this results in severe soft tissue destruction or Adverse Reaction to Metal Debris (ARMD). The amount of material required to cause ARMD is unknown but analyses of retrieved hips may provide the answer to this clinically important question.

We collected implants from 20 patients with failed hips with MOP bearings, revised due to ARMD. We collected clinical, imaging and blood test data. We graded the severity of taper corrosion (1 to 4), and quantified the volume of material loss from this junction. We compared our results with previous data collected for metal-on-metal (MOM) hips.

The median time to revision of the MOP hips was 51.3 (23.1–56.4) months. All head tapers were moderately to severely corroded with a median corrosion score of 4. The median (range) of total material loss at the taper of the MOP hips was 3.9 mm³ (2.96 – 7.85 mm³) and the material loss rate was 1.4 mm³ / year (0.56 – 1.82).

Comparison with MOM hips revealed no significant difference in taper material loss (p=0.7344) with a median rate of 0.81 mm³ / year (0.01–3.45).

We are the first to quantify the volume of material loss at the head taper of hip implants with MOP bearings that were revised due to trunnionosis. This data indicates that a clinically significant dose of cobalt and chromium to induce ARMD is approximately 1.4 mm³ / year.

We have identified a clinically significant volume of taper material loss in MOP hips.

Introduction

The Precice nail is the latest intramedullary lengthening nail with excellent early outcomes. Implant complications have led to modification of the nail design. The aim of this study was to perform a retrieval study of Precice nails following lower limb lengthening. To assess macroscopic and microscopic changes to the implants and assess differences following design modification, with identification of potential surgical, implant and patient risk factors.

Dual-taper implants provide surgeons with options to optimise patients' anatomy intraoperatively but are at risk of early revision due to adverse tissue reactions to corrosion debris. Risk factors for failure and linkage with symptoms however are not fully understood. We related retrieval findings to clinical and implant variables.

This study involved 88 failed dual-taper implants with TMZF femoral stems and cobalt-chromium necks, revised for pain, elevated Co (median = 7.3μg/L) and Cr (median = 2.15μg/L) ions levels and fluid collection on MRI.

Stem-neck surfaces were assessed for: 1) severity of corrosion using a published visual method and 2) severity of material lost and location of damage with a roundness-measuring machine. Five traces were taken on each round section of the taper surface at 45° increments to compute the relative depth of damage. The total area of these traces provided a measure of surface damage for comparative purposes.

The stem-neck taper junctions were severely corroded; the deepest areas of damage were on the inferior-proximal and superior-distal part of the necks, compatible with cantilever bending. Elemental analysis revealed chromium rich deposits indicative of corrosion processes and metal transfer from the stem to the neck.

There was a positive correlation between the severity of damage and time of implantation (p<0.0001). Co and Cr levels in the blood were also strongly correlated (p<0.0001, p=0.0002). No other implant or patient variables were linked.

The stem-neck junction was severely corroded in all cases. The severity and location of the areas of surface damage did not link with implant or patient characteristics in this big cohort suggesting that the design and material combination is the predominant source of failure in these designs.

Dual-taper hips are severely corroded at the stem-neck junction; this appears to be due to the use of a TMZF alloy stem paired with CoCrMo necks.

Circulating cobalt and chromium from metal-on-metal implants cause rare but fatal autopsy-diagnosed cardiotoxicity. Concern exists that milder cardiotoxicity may be common and under-recognized. Unacceptably high failure rates of metal-on-metal hip implants have prompted regulatory authorities to issue worldwide safety alerts. Despite this, approximately 1 million patients continue to live with metal-on-metal implants, putting them at risk of systemic toxicity. Although blood cobalt and chromium levels are easily measured and track local toxicity, no non-invasive tests for organ deposition exist.

We recently demonstrated the utilisation of a T2* protocol (cardiovascular MRI) to detect cobalt and chromium deposition within the liver of a patient with elevated blood cobalt levels (confirmed by liver biopsy tissue analysis and X-ray fluorescence spectroscopy).

We sought to detect and constrain the correlation between blood metal ions and a comprehensive panel of established markers of early cardiotoxicity. In addition we applied T2* protocols with the aim of detecting cardiac metal deposition.

90 patients were recruited through RNOH clinics into this prospective single centre blinded study. Patients were divided into 3 age and gender-matched groups according to type of implant and blood metal ion levels as follows: [Group A] Non-metal bearing hip implants; [Group B] Metal-on-metal implants, low blood metal ion levels (<7ppb); and [Group C] Metal-on-metal implants, high blood levels (>7ppb).

All underwent detailed cardiovascular phenotyping using cardiac MRI (with T2*, T1 and ECV mapping, in addition to LV size and ejection fraction), advanced echocardiography (LV size and ejection fraction), and cardiac blood biomarker (Troponin and BNP) sampling in the same sitting at the Heart Hospital London. Primary outcomes were pre-specified. See study flow diagram – figure 1. (The study was registered with clinicaltrials.gov: NCT02331264).

Blood cobalt levels were significantly different between groups (0.17ppb (range 0·10–0·47, SD 0·08) vs. 2·47 (0·72–6·9, SD 1·81) vs. 30·0 (7·54–118.0, SD 29·1) respectively for groups A, B and C).

No significant between-group differences were found for LV size, ejection fraction (CMR or echocardiography), LA size, T1, T2*, ECV, BNP or troponin, with all results within normal ranges. There was no relationship between blood cobalt levels and either left ventricular ejection fraction or T2* (r=-0·022 and r=-0·108 respectively). Although small, the study was sufficiently powered to detect, as a minimum, a difference in ejection fraction of 4.8% (Cohen's d effect size 0·8).

Using best available technologies, exposure of patients with metal-on-metal hip implants to high (but not extreme) blood cobalt and chromium levels has no detectable effect on the heart. We believe these findings will offer reassurance to one million patients worldwide living with a metal-on-metal hip implant and will support clinicians caring for such patients.

For any figures or tables, please contact the authors directly by clicking on ‘Info & Metrics’ above to access author contact details.

Total hip arthroplasties are known to corrode predominantly at the taper junctions between Cobalt Chromium Molybedenum (CoCrMo) and Titanium (Ti) alloy components.

We aimed to understand the modes underlying clinically significant tissue reactions to metals from corroded implants by determining: (1) what type of metal is present in the tissues, (2) which cells contain the metal species and (3) how this compares with results from metal-on-metal (MOM) hip resurfacings (HRs).

This study involved periprosthetic tissue from patients that had undergone revision surgery due to adverse reactions to metal debris (ARMD) from dual-taper prostheses consisting of Ti-based alloy stems paired with CoCrMo necks. We used Synchrotron micro X-ray Fluorescence Spectroscopy (µXRF) and micro X-ray Absorption Near Edge Spectroscopy (µXANES) for detection of Co, Cr and Ti, and determination of their oxidation state.

Synchrotron radiation has shown that the chromium in tissues is Cr₂O₃ when derived from corroded CoCrMo/Ti junctions beside the CrPO₄ species found when hip implants release CoCrMo nanoparticles from their bearing surfaces (MoM HRs). Presence of Cr₂O₃ was associated with titanium oxide TiO₂. This may be the outcome of the chemical interaction between the two species. Histological examination showed corrosion products present within viable macrophages and in the extracellular connective tissue, Figure 1.

Understanding corrosion at taper junctions and the pathogenesis of the biological response is of significant clinical importance. This is the first study to co-register histology and metal distribution maps and to explore the potential synergy effect of CoCrMo with Ti alloy.

This study provides guidance for toxicological studies on wear/corrosion particles, how they stimulate the host response and the cellular mechanisms involved in the pathogenesis of ARMD.

For any figures or tables, please contact the authors directly by clicking on ‘Info & Metrics’ above to access author contact details.

Aims

The aim of this study was to compare the design of the generic OptiStem XTR femoral stem with the established Exeter femoral stem.

Objectives

Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces.

Introduction

THR is one of the most frequently performed operations nationally. A large number of prostheses are available, and the procedure is therefore associated with variation in practice and outcomes. NICE guidelines aim to standardise best practice, and are informed by separate, independent bodies, such as the NJR and ODEP, which monitor data about the implants used and their performance. This study aims to determine whether clinical practice and component use has changed since the publication of NJR data.

Introduction

The Birmingham Hip Resurfacing (Smith & Nephew London, UK) is the most popular hip resurfacing (HR) in the UK. However, it is now subject to two Medical Device Alerts (MDA) from the Medicines and Healthcare products Regulatory Agency (MHRA).

Introduction

Dual-mobility bearings increase the stable range of motion of total hip arthroplasty (THA) but are limited by the mechanical effects of a large diameter metal on polyethylene bearing which may cause high rates of wear from the surfaces of the polyethylene bearing and the head-stem taper. Improved polyethylene (PE) has reduced concern over bearing wear but the effects on the taper junction are unknown.

We aimed to better understand the effect of dual mobility bearings on fretting-corrosion damage to the taper junction by comparison to standard bearings.

Introduction

Surgical simulation and ‘virtual’ surgical tools are becoming recognised as essential aids for speciality training in Trauma & Orthopaedics, as evidenced by the BOA T&O Simulation Curriculum 2013^1,2. The current generation of hip arthroplasty simulators, including cadaveric workshops, offers the trainee limited exposure to reproducible real life bony pathology. We developed and implemented a novel training course using pathological dry bone models generated from real patient cases to support senior orthopaedic trainees and new consultants in developing knowledge and hands on skills in complex total hip arthroplasty.

Objectives

Throughout the 20th Century, it has been postulated that the knee moves on the basis of a four-bar link mechanism composed of the cruciate ligaments, the femur and the tibia. As a consequence, the femur has been thought to roll back with flexion, and total knee arthroplasty (TKA) prostheses have been designed on this basis. Recent work, however, has proposed that at a position of between 0° and 120° the medial femoral condyle does not move anteroposteriorly whereas the lateral femoral condyle tends, but is not obliged, to roll back – a combination of movements which equates to tibial internal/ femoral external rotation with flexion. The aim of this paper was to assess if the articular geometry of the GMK Sphere TKA could recreate the natural knee movements in situ/in vivo.

Aims

There are many guidelines that help direct the management of patients with metal-on-metal (MOM) hip arthroplasties. We have undertaken a study to compare the management of patients with MOM hip arthroplasties in different countries.

Introduction

Uncertainties in the management of patients with MOM hip implants continue to be a problem for all surgeons. Guidelines vary and do not fully define or quantify thresholds. We aimed to assess the differences in decision-making amongst an international community of six specialist orthopaedic institutions.

Introduction

Recent studies on large diameter femoral head hip replacements have implicated the modular taper junction as one of the significant sources of wear and corrosion products and this has been attributed to increased torque and bending on the taper interface. The aim of this study was to assess the effect of frictional torque and bending moment on fretting corrosion at the taper junction and to investigate whether different material combinations also had an effect.

Introduction

The National Joint Registry (NJR) for England, Wales and Northern Ireland contributes important information on the performance of implants and surgeons. However, the quality of this data is not known. This study aimed to perform an independent validation of primary metal-on-metal hip procedures recorded on the NJR through linkage to the London Implant Retrieval Centre (LIRC).

Introduction

Retrieved metal-on-metal acetabular components are invaluable resources from which to investigate the wear behaviour of failed hip implants. New forensic and investigative techniques continue to be developed to help the surgeon further understand factors which contribute to early failure. We have developed a novel technique to locate the in vivo location of the primary wear scar of an explanted cup.

The aim of this study was to assess the effect of frictional torque and bending moment on fretting corrosion at the taper interface of a modular femoral component and to investigate whether different combinations of material also had an effect. The combinations we examined were 1) cobalt–chromium (CoCr) heads on CoCr stems 2) CoCr heads on titanium alloy (Ti) stems and 3) ceramic heads on CoCr stems.

In test 1 increasing torque was imposed by offsetting the stem in the anteroposterior plane in increments of 0 mm, 4 mm, 6 mm and 8 mm when the torque generated was equivalent to 0 Nm, 9 Nm, 14 Nm and 18 Nm.

In test 2 we investigated the effect of increasing the bending moment by offsetting the application of axial load from the midline in the mediolateral plane. Increments of offset equivalent to head + 0 mm, head + 7 mm and head + 14 mm were used.

Significantly higher currents and amplitudes were seen with increasing torque for all combinations of material. However, Ti stems showed the highest corrosion currents. Increased bending moments associated with using larger offset heads produced more corrosion: Ti stems generally performed worse than CoCr stems. Using ceramic heads did not prevent corrosion, but reduced it significantly in all loading configurations.

Cite this article: Bone Joint J 2015;97-B:463–72.

Introduction:

Non-invasive extendible endoprostheses (NIEE) were primarily developed for salvage after musculo-skeletal tumour surgery in the immature skeleton. However, they may also have a unique application to manage complex limb reconstruction in revision surgery to address limb-length inequality in the mature skeleton. The aim of this study is to present the minimum 2 –year results of using non-invasive extendible endoprostheses for complex lower limb reconstruction.

Introduction:

Pigmented Villonodular Synovitis (PVNS) is a rare inflammatory disorder of the synovium, bursa and tendon sheath. The objective of this study was to evaluate the long-term outcomes and morbidity associated with operative management of PVNS of the hand.

Introduction:

Endoprosthetic replacement of the proximal femur is common in the management of bone tumours and failed revision arthroplasty. This study seeks to compare those patients undergoing acetabular resurfacing at the time of femoral replacement with those patients where the native acetabulum was preserved.

Introduction:

Distal femoral replacement is recognised as the optimum treatment for malignant distal femoral tumours. Aseptic loosening is known to be a major cause for failure in these implants. Studies have indicated that the HA coated collar promotes osteointegration and bony in growth. This study compares long term aseptic loosening in implants with HA coated collars to those without in the immature skeleton.

Introduction:

High failure rates with large diameter, metal on metal hip replacements have highlighted a potential issue with the head/stem taper junction as one of the significant sources of metal ion release. Postulated reasons as to why this may be such a problem with large head metal on metal hip replacements is due to the increased torque achieved by the larger head size. This may be responsible for applying greater micromotion between the head and stem taper and consequently greater amounts of fretting corrosion. The aim of this study was to perform short term in vitro electrochemical tests to assess the effect of increasing head diameter and torque on the fretting corrosion susceptibility of the head/stem taper interface and to investigate its effect on different material combinations.

Background

The changes in surface roughness occurring during the wear process at the bearing surface are of great importance in trying to understand the failure mechanism of large head metal-on-metal hip replacements. The aim of the study is to identify and characterise the areal surface parameter variation between the worn and unworn areas. Surface topography variations at the bearing surface have an effect on the lubrication regime [1]. In vitro tests of these components have suggested a “self-polishing” of the surface [2]. Traditionally Ra has been used as a descriptor of surface texture. Considering the high standard of manufacturing to which these components are produced, Ra is not sufficient to describe surface morphology which requires spatial information which can only be achieved through the use of areal parameters.

Introduction

Local recurrence of tumours along the biopsy tract is a known complication of percutaneous closed needle biopsy. Correct surgical management requires preoperative identification and excision of the biopsy tract at time of surgery. These tracts become increasingly difficult to identify with time, leading to risk of inadequate excision of the biopsy tract and recurrence of the tumour at the biopsy site.

There are several component position and design variables that increase the risk of edge loading and high wear in metal-on-metal hip resurfacing (MOM-HR). In this study we combined all of these variables to calculate the ‘contact patch to rim distance’ (CPRD) in patients undergoing revision of their MOM-HR. We then determined whether CPRD was more strongly correlated with component wear and blood metal ion levels, when compared to any other commonly reported clinical variable. This was a retrospective study of 168 consecutively collected MOM-HR retrieval cases. All relevant clinical data was documented, including pre-revision whole blood cobalt and chromium ion levels. Wear of the bearing surfaces was then measured using a roundness-measuring machine. We found four variables to be significantly (p < 0.05) correlated with component wear and blood metal ion levels: (1) cup inclination angle, (2) cup version angle, (3) arc of cover, and (4) CPRD. The correlations between CPRD and both wear and ion levels were significantly stronger than those seen with any other variable (all p < 0.0001). Our study has shown that CPRD is the best predictor of component wear and blood metal ion levels, and may therefore be a useful parameter to help determine those patients who are at risk of high wear and require more frequent clinical surveillance.

Material loss at the head-stem taper junction may contribute to the high early failure rates of stemmed large head metal-on-metal (LH-MOM) hip replacements. We sought to quantify both wear and corrosion and by doing so determine the main mechanism of material loss at the taper. This was a retrospective study of 78 patients having undergone revision of a LH-MOM hip replacement. All relevant clinical data was recorded. Corrosion was assessed using light microscopy and scanning electron microscopy, and graded according to a well-published classification system. We then measured the volumetric wear of the bearing and taper surfaces. Evidence of at least mild taper corrosion was seen in 90% cases, with 46% severely corroded. SEM confirmed the presence of corrosion debris, pits and fretting damage. However, volumetric wear of the taper surfaces was significantly lower than that of the bearing surfaces (p = 0.015). Our study supports corrosion as the predominant mechanism of material loss at the taper junction of LH-MOM hip replacements. Although the volume of material loss is low, the ionic products may be more biologically active compared to the particulate debris arising from the bearing surfaces.