Aims. The aim of this study was to assess the incidence of reinfection in patients after two-stage revision of an infected megaprosthesis (MPR) implanted after resection of a bone tumour. Methods. A retrospective study was carried out of 186 patients from 16 bone sarcoma centres treated between January 2010 and December 2020. The median age at the time of tumour diagnosis was 26 years (IQR 17 to 33); 69 (37.1%) patients were female, and 117 (62.9%) were male. Results. A total of 186 patients with chronic MPR infections were included. Median follow-up was 68 months (IQR 31 to 105). The most represented sites of MPR were distal femur in 93 cases (50.0%) and proximal tibia in 53 cases (28.5%). Polymicrobial infections were seen in 34 cases (18.3%). The most frequent isolated pathogens were staphylococci. Difficult-to-treat (DTT) pathogens were isolated in 50 cases (26.9%). The estimated infection recurrence (IR) rate was 39.1% at five years and 50.0% at ten years. A higher IR rate was found in DTT PJI compared to non-DTT infections (p = 0.019). Polymicrobial infections also showed a higher rate of infection recurrence (p = 0.046). Conclusion. This study suggests that an infected MPR treated by two-stage revision and ultimately reimplantation with a MPR can be successful, but the surgeon must be aware of a high recurrence rate compared to those seen with infected conventional implants. Cite this article: Bone Joint J 2025;107-B(2):253–260

Background. Total Hip Arthroplasty (THA) has long been the standard treatment for cases in which non-surgical alternatives have failed to improve pain and function in hip osteoarthritis (OA) patients. Outcomes from THA have improved over time with better surgical techniques and improved implant designs. While conventional neck-sacrificing implants have been associated with favorable outcomes, there is evidence to suggest biomechanical advantages of newer, femoral neck-preserving short-stem implants, including the Corin MiniHip. However, there is a still a gap of knowledge regarding the potential benefits of the MiniHip stem over conventional neck-sacrificing stems in regards to patient-reported outcomes (PROs). In this study, we investigated the differences between a neck-sacrificing stem design and neck-preserving short-stem design (MiniHip, Corin Inc.) arthroplasty concerning PROs, and considering the known features of the short stem design, we hypothesized that MiniHip THA would be associated with improved PROs in comparison to a neck-sacrificing implant system. We further sought to investigate gender effects related to MiniHip or conventional stem surgery. Methods. Neck-sacrificing implant patients (n=90, age 57±7.9 years, female=58, male=32) and a matched (matching criteria: follow-up period, BMI, age) cohort group of MiniHip patients (n=105, age 55.16±9.88 years, female: 25, male: 80) reported both pre-operative and post-operative Hip disability and Osteoarthritis Outcome Scores (HOOS) at a minimum interval of 6 months post-operatively and up to three years postoperatively. We applied MANCOVA analysis to compare patient-reported outcome subscores from each group using follow-up period as a covariate and employing gender as an additional grouping factor to evaluate gender effects. Statistical significance was set at α=0.05 and Bonferroni corrections were applied to account for multiple comparisons. Results. There was a main effect of time, showing that all HOOS subscores of both groups increased significantly after surgery (p<0.001). There was a main effect of surgery for subscores Symptoms (p=0.038), ADL (p=0.046), and Sports and Recreation (p=0.039). There was a gender effect only for the subscore Symptoms (p=0.007). There were significant time by surgery interactions for HOOS subscores Symptoms (p=0.002), Pain (p=.009), Sports and Recreation (p=0.004), and QOL (p<0.001) subscores. We also observed a significant time by gender interaction effect for all HOOS subscores (p<0.001). Discussion. The interaction effects regarding most HOOS subscores and surgery/implant type indicate an advantage of MiniHip surgery regarding post-operative reported outcomes. The observed results may be due to previously described improved physiological loading and native hip structure preservation with neck-preserving short-stem designs. While longer-term studies are required for further investigation, evidence suggests the MiniHip may provide a significant benefit to primary THA patients. The additional gender/time interaction effect observed in our study highlights the necessity to consider potential sex differences regarding both the potential/expected improvement in PROs from THA and the requirement to account for such differences when designing osteoarthritis outcome studies based on PROs

Background

Recent studies indicate the benefits of total hip arthroplasty (THA) by using femoral neck-preserving short-stem implants (March et al 1999). These benefits rely on the preservation of native hip structure and improved physiological loading.

However, further investigation is needed to compare the outcome of these implants versus the conventional neck-sacrificing stems particularly assessed by patient-reported outcomes (PROs). In this study, we have investigated the differences in PROs between a neck-sacrificing stem design and neck-preserving short stem design (MiniHip, Corin Inc.). We hypothesized higher PROs outcome in patients who received treatment by using neck-preserving implants.

Dual-mobility constructs (DMCs) are increasingly used for total hip replacement (THR) following hip fracture. The aims of this study were to identify whether there was a difference in all-cause construct survival following THR with a DMC (DMC-THR) or with a conventional construct following hip fracture, and to identify the expected net all-cause construct survival for DMC-THR performed for hip fracture. We performed a systematic review and meta-analysis of published studies (including joint registries) including DMC-THR for hip fracture which provided Kaplan-Meier (KM) survival estimates. The primary outcome was all-cause construct survival over time. 318 papers and 17 registry reports were identified. Three studies (two registry reports and one cohort study utilising joint registry data) met the inclusion criteria, including 8,834 DMC-THRs and 63,865 conventional THRs. Upon meta-analysis, DMC-THRs had lower all-cause construct survival. Five-year KM estimates (95% confidence intervals) were 95.3% (94.6–95.9%) for DMC-THR and 96.1% (95.9–96.3%) for conventional THR. These results suggest there is a small absolute but not clinically significant all-cause implant survival difference between THR with DMC and conventional implants following hip fracture. Given the higher comparative cost of DMC, this analysis does not support its routine use

Aims. Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia. Methods. In a cadaveric model, UKA and TKA procedures were performed on eight fresh-frozen knee specimens, using conventional (solid) and titanium lattice tibial implants. Stress at the bone-implant interfaces were measured and compared to the native knee. Results. Titanium lattice implants were able to restore the mechanical environment of the native tibia for both UKA and TKA designs. Maximum stress at the bone-implant interface ranged from 1.2 MPa to 3.3 MPa compared with 1.3 MPa to 2.7 MPa for the native tibia. The conventional solid UKA and TKA implants reduced the maximum stress in the bone by a factor of 10 and caused > 70% of bone surface area to be underloaded compared to the native tibia. Conclusion. Titanium lattice implants maintained the natural mechanical loading in the proximal tibia after UKA and TKA, but conventional solid implants did not. This is an exciting first step towards implants that maintain bone health, but such implants also have to meet fatigue and micromotion criteria to be clinically viable. Cite this article: Bone Joint Res 2022;11(2):91–101

Introduction. Achieving an appropriate primary stability after implantation is a prerequisite for the long-term viability of a dental implant. Virtual testing of the bone-implant construct can be performed with finite element (FE) simulation to predict primary stability prior to implantation. In order to be translated to clinical practice, such FE modeling must be based on clinically available imaging methods. The aim of this study was to validate an FE model of dental implant primary stability using cone beam computed tomography (CBCT) with ex vivo mechanical testing. Method. Three cadaveric mandibles (male donors, 87-97 years old) were scanned by CBCT. Twenty-three bone samples were extracted from the bones and conventional dental implants (Ø4.0mm, 9.5mm length) were inserted in each. The implanted specimens were tested under quasi-static bending-compression load (cf. ISO 14801). Sample-specific homogenized FE (hFE) models were created from the CBCT images and meshed with hexahedral elements. A non-linear constitutive model with element-wise density-based material properties was used to simulate bone and the implant was considered rigid. The experimental loading conditions were replicated in the FE model and the ultimate force was evaluated. Result. The experimental ultimate force ranged between 67 N and 789 N. The simulated ultimate force correlated better with the experimental ultimate force (R. 2. =0.71) than the peri-implant bone density (R. 2. =0.30). Conclusion. The developed hFE model was demonstrated to provide stronger prediction of primary stability than peri-implant bone density. Therefore, hFE Simulations based on this clinically available low-radiation imaging modality, is a promising technology that could be used in future as a surgery planning tool to assist the clinician in evaluating the load-bearing capacity of an implantation site. Acknowledgements. Funding: EU's Horizon 2020 grant No: 953128 (I-SMarD). Dental implants: THOMMEN Medical AG

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

Abstract. Objectives. Obesity is prevalent with nearly one third of the world's population being classified as obese. Total knee arthroplasty (TKA) is an effective treatment option for high BMI patients achieving similar outcomes to non-obese patients. However, increased rates of aseptic loosening in patients with a high BMI have been reported. In patients with high BMI/body mass there is an increase in strain placed on the implant fixation interfaces. As such component fixation is a potential concern when performing TKA in the obese patient. To address this concern the use of extended tibial stems in cemented implants or cementless fixation have been advocated. Extend tibial stems are thought to improve implant stability reducing the micromotion between interfaces and consequently the risk of aseptic loosening. Cementless implants, once biologic fixation is achieved, effectively integrate into bone eliminating an interface. This retrospective study compared the use of extended tibial stems and cementless implants to conventional cemented implants in high BMI patients. Methods. From a prospectively maintained database of 3239 primary Attune TKA (Depuy, Warsaw, Indiana), obese patients (body mass index (BMI) >30 kg/m²) were retrospectively reviewed. Two groups of patients 1) using a tibial stem extension [n=162] and 2) cementless fixation [n=163] were compared to 3) a control group (n=1426) with a standard tibial stem cemented implant. All operations were performed by or under the direct supervision of specialist arthroplasty surgeons. Analysis compared the groups with respect to class I, II, and III (BMI >30kg/m², >35 kg/m², >40 kg/m²) obesity. The primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups. Where radiographic images at greater than 3 months post-operatively were available, radiographs were examined to compare the presence of peri-implant radiolucent lines. Results. The mean follow-up of 4.8, 3.4, and 2.5 years for cemented, stemmed, and cementless groups respectively. In total there were 34 all-cause revisions across all the groups with revision rates of 4.55, 5.50, and 0.00 per 1000-implant-years for cemented, stemmed, and cementless groups respectively. Survival Analysis did not show any significant differences between the three groups for all-all cause revision. There were 6 revisions for aseptic loosening (5 tibial and 1 femoral); all of which were in the standard cemented implant group. In contrast there were no revisions in the stemmed or cementless implant groups, however, this was not significant on survival analysis. Analysis looking at class I, II, and III obesity also did not show any significant differences in survival for all cause revision or aseptic loosening. Conclusion. This retrospective analysis showed that there were no revisions required for aseptic loosening when either a cemented stemmed or cementless implant were used in obese patients. These findings are in line with other studies showing that cementless fixation or extended stem implants are a reasonable option in obese patients who represent an increasing cohort of patients requiring TKR. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Three-dimensional (3D) printing of porous titanium implants marks a revolution in orthopaedics, promising enhanced bony fixation whilst maintaining design equivalence with conventionally manufactured components. No retrieval study has investigated differences between implants manufactured using these two methods. Our study was the first to compare these two groups using novel non-destructive methods. Materials and methods. We investigated 16 retrieved acetabular cups divided into ‘3D printed’ (n = 6; Delta TT) and ‘conventional’ (n = 10; Pinnacle Porocoat). The groups were matched for age, time to revision, size and gender (Table 1). Reasons for revision included unexplained pain, aseptic loosening, infection and ARMD. Visual inspection was performed to evaluate tissue attachment. Micro-CT was used to assess clinically relevant morphometric features of the porous structure, such as porosity, depth of the porous layer, pore size and strut thickness. Scanning electron microscopy (SEM) was applied to evaluate the surface morphology. Results. Significant differences (p = 0.0002) were found for all morphometric parameters (Table 2). Microscopic analysis revealed uniform beads over the backside of conventional implants, due to the manufacturing technique (Figure 1a). Conversely, beads of random size were found on 3D printed implants, representing a by-product of the manufacturing process, where some starting powder particles are not completely fused together (Figure 1b). The two groups showed similar tissue attachment (3D printed 76.9 ± 27.1%; conventional 73.8 ± 12.2%; p = 0.2635). Conclusion. This was the first study to analyse retrieved 3D printed orthopaedic implants. Differences were found between these and conventional implants, but both literature and registry data do not suggest a short-mid-term clinical issue with 3D printed components. Similar tissue on growth suggested a comparable behaviour with bone in situ. The key difference is the presence of the particles on 3D printed implants, whose clinical significance needs to be investigated. For any figures or tables, please contact the authors directly

Purpose: We have performed this study to compare the postoperative maximal flexion angle(MFA) of high-flex implants with that of conventional implants in PCL-substituted total knee arthroplasty(TKA). Materials and Methods: The staged sequential bilateral TKAs were performed in Group 1, 35 patients(70 knees) with osteoarthritis of both knee. The conventional implant and the high-flex implant were both used in each patient by randomized method. The postoperative MFA of both type of implants was measured and analyzed at 1 year after surgery. To evaluate unidentified factors that might influence the results, such as the differences derived from personal characteristics during postoperative rehabilitation process achieving the range of motion of knee, we also analyzed the other patient groups, which were composed of Group 2(10 patients, 20 knees) bilaterally operated with conventional implants, Group 3(7 patients, 14 knees) bilaterally with high-flex implants, Group 4(13 patients, 13 knees) unilaterally with conventional implants and Group 5(17 patients, 17 knees) unilaterally with high-flex implant. Results: In Group 1, the average postoperative MFA of high-flex implant and that of conventional implant showed no significant difference.(131.7 and 131.9 degree each) The average postoperative MFA in Group 1,2,3,4 and 5 showed no significant difference either. Conclusion: This study indicates that the high-flex implant alone does not seem to improve the MFA as compared to the conventional implant. The status of the contralateral knee and the personal characteristics during rehabilitation seem to be more important factors in increasing the maximal flexion

Aims. Radiostereometric analysis (RSA) studies of vitamin E-doped, highly crosslinked polyethylene (VEPE) liners show low head penetration rates in cementless acetabular components. There is, however, currently no data on cemented VEPE acetabular components in total hip arthroplasty (THA). The aim of this study was to evaluate the safety of a new cemented VEPE component, compared with a conventional polyethylene (PE) component regarding migration, head penetration, and clinical results. Patients and Methods. We enrolled 42 patients (21 male, 21 female) with osteoarthritis and a mean age of 67 years (. sd. 5), in a double-blinded, noninferiority, randomized controlled trial. The subjects were randomized in a 1:1 ratio to receive a reverse hybrid THA with a cemented component of either argon-gas gamma-sterilized PE component (controls) or VEPE, with identical geometry. The primary endpoint was proximal implant migration of the component at two years postoperatively measured with RSA. Secondary endpoints included total migration of the component, penetration of the femoral head into the component, and patient-reported outcome measurements. Results. In total, 19 control implants and 18 implants in the VEPE group were analyzed for the primary endpoint. We found a continuous proximal migration of the component in the VEPE group that was significantly higher with a difference at two years of a mean 0.21 mm (95% confidence interval (CI) 0.05 to 0.37; p = 0.013). The total migration was also significantly higher in the VEPE group, but femoral head penetration was lower. We found no difference in clinical outcomes between the groups. Conclusion. At two years, this cemented VEPE component, although having a low head penetration and excellent clinical results, failed to meet noninferiority compared with the conventional implant by a proximal migration above the proposed safety threshold of RSA. The early proximal migration pattern of the VEPE component is a reason for continued monitoring, although a specific threshold for proximal migration and risk for later failure cannot be defined and needs further study. Cite this article: Bone Joint J 2019;101-B:1192–1198

Background: Computer-assisted navigation systems are supposed to improve the precision of implant positioning and therefore the longevity of the knee arthroplasty. Several studies have demonstrated a better mechanical axis or axial component alignment in navigated compared to conventional TKA at least less outliers from a range of 3° of varus or valgus. It is still unclear wether navigation can improve rotational alignment. Materials and Methods: After informed consent 80 patients were randomized to navigated or conventional TKA. In all patients, a cemented, unconstrained, cruciate-retaining TKA with a rotating platform was implanted. A full-length standing and a lateral radiograph and CT Scans of the hip, knee and ankle joint were done 5 to 7 days postoperatively before discharge. Results: The navigated group showed a median deviation from the mechanical axis of 1,5° with a range between 5,9° valgus and 4,6 varus malalignment. The conventional implanted arthroplasties showed a median deviation from the mechanical axis of 1,6° with a range between 5,9° valgus and 7,2° varus malalignment. 5 navigated and 7 conventional implanted arthroplasties were outside a tolerance level of 3°. The femoral component showed a median deviation from the transepicondylar axis of 1,7° (range: 3,1° external rotation to 4,4° internal rotation) in the navigated group and of 1,0° (range: 3,4° external rotation to 4,3° internal rotation) in the conventional implantations. The tibial component showed a much greater range of rotational deviation from the medial third of the tuberosity in median 5,3° (range: 14,9° external rotation to 26° internal rotation) in the navigated group and 4,8° (range: 6,5° external rotation to 23,8° internal rotation) in the conventional implantations. Conclusion: We could not find a difference between Computer-assisted navigation and conventional implantation for rotational alignment of the femoral or tibial component. While the deviation from the transepicondylar axis was quite low and nearly all implantations were within a range of 3° of internal and external rotation there was a considerable range of deviation for the tibial rotational alignment

Abstract. Objectives. Currently, total hip replacement surgery is an effective treatment for osteoarthritis, where the damaged hip joint is replaced with an artificial joint. Stress shielding is a mechanical phenomenon that refers to the reduction of bone density as a result of altered stresses acting on the host bone. Due to solid metallic nature and high stiffness of the current orthopaedic prostheses, surrounding bones undergo too much bone resorption secondary to stress shielding. With the use of 3D printing technology such as selective laser melting (SLM), it is now possible to produce porous graded microstructure hip stems to mimics the surrounding bone tissue properties. Method. In this study we have compared the physical and mechanical properties of two triply periodic minimal surface (TPMS) lattice structure namely gyroid and diamond TPMS. Based on initial investigations, it was decided to design, and 3D print the gyroid and diamond scaffolds having pore size of 800 and 1100 um respectively. Scaffold of each type of structure were manufactured and were tested mechanically in compression (n=8), tension (n=5) and bending (n=1). Results. Upon FEA validation of the scaffold in Abaqus, the desired scaffold for hip implant application was evaluated to have a young's modules of 12.15 GPa, yield strength of 242 MPa and porosity of 55%. Topology and lattice optimization were performed using nTopology to design an optimised graded porous hip implant based on stress shielding reduction. It was understood that the designed optimised hip implant can reduce the stress shielding effect by more than 65% when compared to the conventional generic implant. Conclusions. The designed hip implant presented in this work shows clinical promise in reducing bone loss while having enhanced osseointegration with the surrounding cortical bones. Hence, this will help reduce the risk of periprosthetic fracture and the probability of revision surgery

The December 2024 Hip & Pelvis Roundup³⁶⁰ looks at: Total hip arthroplasty after femoral neck fractures versus osteoarthritis at one-year follow-up: a comparative, retrospective study; Excellent mid-term survival of a monoblock conical prosthesis in treating atypical and complex femoral anatomy with total hip arthroplasty; Hip arthroscopy for femoroacetabular impingement improves sexual function; Fast-track hip arthroplasty does not increase complication rates; Ten-year experience with same-day discharge outpatient total hip arthroplasty: patient demographics changed, but safe outcomes were maintained.

Hip fractures pose a major global health challenge, leading to high rates of morbidity and mortality, particularly among the elderly. With an ageing population, the incidence of these injuries is rising, exerting significant pressure on healthcare systems worldwide. Despite substantial research aimed at establishing best practice, several key areas remain the subject of ongoing debate. This article examines the latest evidence on the place of arthroplasty in the surgical treatment of hip fractures, with a particular focus on the choice of implant, the use of cemented versus uncemented fixation, and advances in perioperative care.

Cite this article: Bone Joint J 2024;106-B(12):1372–1376.

Aims

The mean age of patients undergoing total knee arthroplasty (TKA) has reduced with time. Younger patients have increased expectations following TKA. Aseptic loosening of the tibial component is the most common cause of failure of TKA in the UK. Interest in cementless TKA has re-emerged due to its encouraging results in the younger patient population. We review a large series of tantalum trabecular metal cementless implants in patients who are at the highest risk of revision surgery.

Stress shielding of the proximal femur occurs in stemmed implants. Resurfacing implant does not invade the intramedullary region. We studied the stress patterns in conventional and nonstemmed designs. Methods. FE model geometry was based on standard femur from the international Society of Biomechanics Mesh Repository. Loading simulated for one- legged stance with body weight of 826 N. 2 regions were defined, R1 (40 mm from tip of head) and R2 41 mm–150 mm) of the intramedullary part of the stemmed model's interface with bone. 2 different loading conditions bending and torsion were compared for stress and strain. The FE model was solved with ANSYS version 6.1 on a single processor NT station. Results. With conventional implants, stem shields cortical bone from being loaded. In nonstemmed implants, Von Misses stress contours show a similar distribution as intact bone, transferring loads to the cortical shell but with higher stresses and a maximum displacement of 17.39% higher than that of intact bone. 15–23 mm proximal to R2 and around 110 mm, region of the stem tip, there were higher stress and strain concentrations. Conclusion. Based on simulations, nonstemmed implants provide more physiological loading compared to conventional implants though stress shielding increases in region of the stem in resurfacing implant

Aims. Oxidised zirconium was introduced as a material for femoral components in total knee arthroplasty (TKA) as an attempt to reduce polyethylene wear. However, the long-term survival of this component is not known. . Methods. We performed a retrospective review of a prospectively collected database to assess the ten year survival and clinical and radiological outcomes of an oxidised zirconium total knee arthroplasty with the Genesis II prosthesis. . The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and a patient satisfaction scale were used to assess outcome. Results. A total of 303 consecutive TKAs were performed in 278 patients with a mean age of 68 years (45 to 89). The rate of survival ten years post-operatively as assessed using Kaplan–Meier analysis was 97% (95% confidence interval 94 to 99) with revision for any reason as the endpoint. There were no revisions for loosening, osteolysis or failure of the implant. There was a significant improvement in all components of the WOMAC score at final follow-up (p < 0.001). The mean individual components of the KOOS score for symptoms (82.4 points; 36 to 100), pain (87.5 points; 6 to 100), activities of daily life (84.9 points; 15 to 100) and quality of life (71.4 points; 6 to 100) were all at higher end of the scale. . Discussion. This study provides further supportive evidence that the oxidised zirconium TKA gives comparable rates of survival with other implants and excellent functional outcomes ten years post-operatively. Take home message: Total knee arthroplasty with an oxidised zirconium femoral component gives comparable long-term rates of survival and functional outcomes with conventional implants. . Cite this article: Bone Joint J 2016;98-B:58–64

Aims

Proper preoperative planning benefits fracture reduction, fixation, and stability in tibial plateau fracture surgery. We developed and clinically implemented a novel workflow for 3D surgical planning including patient-specific drilling guides in tibial plateau fracture surgery.

Introduction. PEEK-OPTIMA™ has been considered as an alternative to cobalt chrome in the femoral component of total knee replacements. Whole joint wear simulation studies of both the tibiofemoral and patellofemoral joints carried out to date have shown an equivalent wear rate of UHMWPE tibial and patella components against PEEK and cobalt chrome (CoCr) femoral components. In this study, the influence of third body wear on UHMWPE-on-PEEK was investigated, tests on UHMWPE-on-CoCr were carried out in parallel to compare PEEK to a conventional femoral component material. Methods. Wear simulation was carried out in simple geometry using a 6-station multi-directional pin-on-plate simulator. 5 scratches were created on each PEEK and CoCr plate perpendicular to the direction of the wear test using a diamond stylus to produce scratches with a geometry similar to that observed in retrieved CoCr femoral components. To investigate the influence of scratch lip height on wear, scratches of approximately 1, 2 and 4µm lip height were created. Wear simulation of GUR 1020 UHMWPE pins (conventional, non-sterile) against the plates was carried out for 1 million cycles (MC) using 17g/l bovine serum as a lubricant using kinematic conditions to replicate the average contact pressure and cross-shear in a total knee replacement. Wear of UHMWPE pins was measured gravimetrically and the surface topography of the plates assessed using a contacting Form Talysurf. Wear factors of the pins against the scratched plates were compared to unscratched controls (0µm lip height). Minimum n=3 for each condition and statistical analysis carried out using ANOVA with significance taken at p<0.05. Results. For the control tests (0µm lip height), the wear factor of UHMWPE pins was similar (p=0.64) against PEEK and CoCr plates. Against CoCr, with an increasing lip height, an exponential increase in wear factor of UHMWPE pins was observed; for PEEK, with increasing lip height, the wear factor did not show an exponential increase. When articulated against the largest scratches, 4µm, the wear factor of UHMWPE was significantly higher against CoCr than PEEK (p=0.01). At the conclusion of the study, on the PEEK plates, a polishing effect of the pin against the plates was observed and in the area of the wear test, the lip height of the scratches was lower than pre-test values; for the CoCr plates, no change in lip height was measured after 1MC wear simulation. Conclusion. The exponential relationship between scratch lip height in CoCr and wear of UHMWPE has previously been described. However, the trend in the wear of UHMWPE was different when articulating against scratched PEEK compared to CoCr, with a significantly higher wear factor of UHMWPE against CoCr than PEEK at a scratch lip height of 4µm. This study suggests that the third body wear behaviour of this all-polymer knee replacement will be different to that of conventional implant materials