Abstract. Background/Objectives. The incidence of reverse total shoulder replacement (rTSR) implantation is increasing globally, but apprehension exists regarding complications and associated challenges. We retrospectively analysed the senior author's series of rTSR from a tertiary centre using the VAIOS shoulder system, a modular 4th generation implant. We hypothesised that the revision rTSR cohort would have less favourable outcomes and more complications. Methods. 114 patients underwent rTSR with the VAIOS system, over 7 years. The primary outcome was implant survival. Secondary outcomes were Oxford shoulder scores (OSS), radiographic analysis (scapular notching, tuberosity osteolysis, and periprosthetic radiolucent lines) and complications. Results. There were 55 Primary rTSR, 31 Revision rTSR and 28 Trauma rTSR. Implant survival: Primary rTSR- 0 revisions, average 3.35-year follow-up. Revision rTSR-1 revision (4.17%), average 3.52-year follow-up. Trauma rTSR- 1 revision (3.57%), average 4.56-year follow-up OSS: Average OSS improved from 15.39 to 33.8 (Primary rTSR) and from 15.11 to 29.1 (Revision rTSR). Average post-operative OSS for the Trauma rTSR was 31.4 Radiological analysis and complications: Low incidence of scapular notching One hairline fracture below the tip of stem, noted incidentally, which required no treatment. One periprosthetic fracture after alcohol related fall. Treated non-surgically One joint infection requiring two-stage revision to rTSR. One dislocation noted at 2 year follow up. This patient had undergone nerve grafting within 6 months of rTSR for axillary nerve injury sustained during the original fracture dislocation. One acromial fracture with tibial and distal humeral fracture after a fall. Conclusions. The 4th generation modular VAIOS implant is a reliable option for various indications. The revision rTSR cohort had favourable outcomes with low complication rates. In this series, early-to-medium term results suggest lower revision rates and good functional outcomes when compared to published reports. We plan to monitor long-term implant survivorship and patient reported outcomes. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty, particularly for low volume surgeons. The recent introduction of robotic-arm assisted systems has allowed for increased accuracy, however new systems typically have learning curves. The objective of this study was to determine the learning curve of a robotic-arm assisted system for UKA. Methods A total of 152 consecutive robotic-arm assisted primary medial UKA were performed by five surgeons between 2017 and 2021. Operative times, implant positioning, reoperations and patient-reported outcome measures (PROMS; Oxford Knee Score, EuroQol-5D, and Forgotten Joint Score) were recorded. There was a learning curve of 11 cases with the system that was associated with increased operative time (13 minutes, p<0.01) and improved insert sizing over time (p=0.03). There was no difference in implant survival (98.2%) between learning and proficiency phases (p = 0.15), and no difference in survivorship between ‘high’ and ‘low’ usage surgeons (p = 0.23) at 36 months. There were no differences in PROMS related to the learning curve. This suggested that the learning curve did not lead to early adverse effects in this patient cohort. The introduction of a robotic-arm assisted UKA system led to learning curves for operative time and implant sizing, but there was no effect on patient outcomes at early follow- up. The short learning curve was independent of UKA usage and indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons

Total joint replacement (TJR) was one of the most revolutionary breakthroughs in joint surgery. The majority studies had shown that most implants could last about 25 years, anyway, there is still variation in the longevity of implants. In US, for all the hip revisions from 2012 to 2017 in the United States, 12.0% of the patients were diagnosed as aseptic loosening. Variable studies have showed that any factor that could cause a systemic or partial bone loss, might be the risk of periprosthetic osteolysis and aseptic loosening. Breast cancer is the most frequent malignancy in women, more than 2.1 million women were newly diagnosed with breast cancer, 626,679 women with breast cancer died in 2018. It's been reported that the mean incidence of THA was 0.29% for medicare population with breast cancer in USA, of which the incidence was 3.46% in Norwegian. However, the effects of breast cancer chemotherapy and hormonotherapy, such as aromatase inhibitors (AI), significantly increased the risk of osteoporosis, and had been proved to become a great threat to hip implants survival. In this case, a 46-year-old female undertook chemotherapy and hormonotherapy of breast cancer 3 years after her primary THA, was diagnosed with aseptic loosening of the hip prosthesis. Her treatment was summarized and analyzed. Breast cancer chemotherapy and hormonotherapy might be a threat to the stability of THA prosthesis. More attention should be paid when a THA paitent occurred with breast cancer. More studies about the effect of breast cancer treatments on skeleton are required

Unicompartmental knee arthroplasty (UKA) is associated with a higher risk of revision compared with total knee arthroplasty (TKA). The outcomes of knee arthroplasty are typically presented as implant survival or incidence of revision after a set number of years, which can be difficult for patients and clinicians to conceptualise. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more relatable estimate of risk projection over a patient's remaining lifetime, and make comparisons to TKA. All primary UKAS performed from 1999 to 2019 (n=13,481) captured by the New Zealand Joint Registry (NZJR) were included. The lifetime risk of revision was calculated and stratified by age, gender and American Society of Anesthesiologists (ASA) status. The lifetime risk of revision for UKA was highest in the youngest patients (46-50 years; 40.4%) and lowest in the oldest patients (86-90 years; 3.7%). Lifetime risk of revision was higher for females (range 4.3%-43.4% cf. males 2.9%-37.4%) and patients with higher ASA status (ASA 3-4 range 8.8%-41.2% cf. ASA 1 1.8%-29.8%), regardless of age. The lifetime risk of UKA was two-fold higher than TKA (ranging from 3.7%-40.4% UKA, 1.6%-22.4% TKA) across all age groups. Increased risk of revision in the younger patients was associated with aseptic loosening in both males and females, and pain in females. Periprosthetic joint infections (PJI) accounted for 4% of all UKA revisions, in contrast to 27% for TKA; risk of PJI was higher for males than females for both procedures. The lifetime risk of revision is a more meaningful measure of arthroplasty outcomes and can aid with patient counselling prior to UKA. Findings from this study show the increased lifetime risk of UKA revision for younger patients, females and those with higher ASA status

The most common reason for revision surgery of total hip replacements is aseptic loosening of implants secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can cause pseudotumour formation. As revision surgery is associated with higher mortality and infection, it is important to understand the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4) has been shown to mediate immune responses to cobalt ions. Statin use in epidemiological studies has been associated with reduced risk of revision surgery. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses and there is evidence that statins can modulate TLR4 activity. This study investigates simvastatin's effect on orthopaedic biomaterial-mediated changes in protein expression of key inflammatory markers and soluble-ICAM-1 (sICAM-1), an angiogenic factor implicated in pseudotumour formation. Human macrophage THP-1 cells were pre-incubated with 50µM simvastatin for 2-hours or a vehicle control (VC), before being exposed to 0.75mM cobalt chloride, 50μm3 per cell zirconium oxide or LPS as a positive control, in addition to a further 24-hour co-incubation with 50µM simvastatin or VC. Interleukin −8 (IL-8), sICAM-1, chemokine ligand 2 (CCL2), CCL3 and CCL4 protein secretion was measured by enzyme-linked immunosorbent assay (ELISA). GraphPad Prism 10 was used for statistical analysis including a one-way ANOVA. Pre-treatment with simvastatin significantly reduced LPS and cobalt-mediated IL-8 secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells. Pre-treatment with simvastatin significantly reduced LPS-mediated but not cobalt ion-mediated CCL2 (n=3) and CCL3 protein (n=3) secretion in THP-1 cells. Simvastatin significantly reduced zirconium oxide-mediated CCL4 secretion (n=3). Simvastatin significantly reduced cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving implant failure

Introduction and Objective. Total joint replacement is indicated for osteoarthritis where conservative treatment has failed, and in the UK the number of patients requiring hip and knee replacements is set to increase with an ageing population. Survival of total hip replacements is around 85% at 20 years with the most common reason for revision being aseptic loosening of the implant secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can also cause pseudotumour formation. As revision surgery is associated with higher morbidity, mortality, infection rates, venous thromboembolism, resource demand and poorer subsequent function it is important to understand the mechanisms underlying the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4), an innate immune receptor, has been demonstrated to mediate deleterious immune responses by the Tyson-Capper research group, including inflammatory cytokine interleukin-8 (IL-8) secretion. Statin use in epidemiological studies has been associated with reduced overall risk of revision surgery after hip replacement. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses which can lead to osteolysis and pseudotumour formation. As literature from cardiological investigations demonstrate that statins can reduce the expression and responsiveness of TLR4, this could be an exciting mechanism to exploit to reduce the host immune response to orthopaedic wear debris, thereby improving implant survival by reducing immune mediated osteolysis. This ongoing study investigates simvastatin's effect on cobalt ion-mediated changes in gene and protein expression of interleukin-8 and soluble-ICAM-1 (sICAM-1) which is an angiogenic factor implicated in pseudotumour formation. Materials and Methods. TLR4-expressing human monocyte/macrophage THP-1 cells were pre-incubated with 50μM simvastatin for 2-hours or a vehicle control, before being exposed to exposed to 0.75mM cobalt chloride, in addition to a further 24-hour co-incubation with 50μM simvastatin or vehicle control. IL-8 protein and sICAM-1 secretion was measured by enzyme-linked immunosorbent assay (ELISA). Gene expression changes were quantified by TaqMan-based real time polymerase chain reaction. Results. Pre-treatment with simvastatin significantly reduced cobalt-mediated IL-8 protein secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells (p-value<0.0001). Work will be undertaken to determine changes in gene expression, the role of TLR4 in these responses and the effect of simvastatin on additional inflammatory markers. Conclusions. Simvastatin significantly reduces cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving aseptic loosening and pseudotumour formation

Abstract. Shoulder replacements have evolved and current 4th generation implants allow intraoperative flexibility to perform anatomic, reverse, trauma, and revision shoulder arthroplasty. Despite high success rates with shoulder arthroplasty, complication rates high as 10–15% have been reported and progressive glenoid loosening remains a concern. Objectives. To report medium term outcomes following 4th generation VAIOS® shoulder replacement. Methods. We retrospectively analysed prospectively collected data following VAIOS® shoulder arthroplasty performed by the senior author between 2014–2020. This included anatomical (TSR), reverse(rTSR), revision and trauma shoulder replacements. The primary outcome was implant survival (Kaplan-Meier analysis). Secondary outcomes were Oxford Shoulder Scores (OSS), radiological outcomes and complications. Results. 172 patients met our inclusion criteria with 114 rTSR, 38 anatomical TSR, and 20 hemiarthroplasty. Reverse TSR- 55 primary, 31 revision, 28 for trauma. Primary rTSR- 0 revisions, average 3.35-year follow-up. Revision rTSR-1 revision (4.17%), average 3.52-year follow-up. Trauma rTSR- 1 revision (3.57%), average 4.56-year follow-up OSS: Average OSS improved from 15.39 to 33.8 (Primary rTSR) and from 15.11 to 29.1 (Revision rTSR). Trauma rTSR-Average post-operative OSS was 31.4 Anatomical TSR38 patients underwent primary anatomical TSR, 8 were revisions following hemiarthroplasty. In 16/38 patients, glenoid bone loss was addressed by bone grafting before implantation of the metal back glenoid component. Mean age at time of surgery was 68.3 years (53 – 81 years). Mean follow-up was 34 months (12 – 62 months). The average Oxford shoulder score improved from 14 (7–30) to 30 (9–48). There were 3 revisions (7.8%); two following subscapularis failure requiring revision conversion to reverse shoulder replacement and one for glenoid graft failure. Conclusions. The medium-term results of the VAIOS® system suggest much lower revision rates across multiple configurations of the system than previously reported, as well as a low incidence of scapular notching. This system allows conversion to rTSR during primary and revision surgery

Introduction and Objective. The aim of this study was to evaluate whether CT-based pre-operative planning, integrated with intra-operative navigation could improve glenoid baseplate fixation and positioning by increasing screw length, reducing number of screws required to obtain fixation and increasing the use of augmented baseplate to gain the desired positioning. Reverse total shoulder arthroplasty (RSA) successfully restores shoulder function in different conditions. Glenoid baseplate fixation and positioning seem to be the most important factors influencing RSA survival. When scapular anatomy is distorted (primitive or secondary), optimal baseplate positioning and secure screw purchase can be challenging. Materials and Methods. Twenty patients who underwent navigated RSA (oct 2018 and feb 2019) were compared retrospectively with twenty patients operated on with a conventional technique. All the procedures were performed by the same surgeon, using the same implant in cases of eccentric osteoarthritis or complete cuff tear. Exclusion criteria were: other diagnosis as proximal humeral fractures, post-traumatic OA previously treated operatively with hardware retention, revision shoulder arthroplasty. Results. The NAV procedure required mean 11 (range 7–16) minutes more to performed than the conventional procedure. Mean screw length was significantly longer in the navigation group (35.5+4.4 mm vs 29.9+3.6 mm; p . .001). Significant higher rate of optimal fixation using 2 screws only (17 vs 3 cases, p . .019) and higher rate of augmented baseplate usage (13 vs 4 cases, p . .009) was also present in the navigation group. Signficant difference there is all in function outcomes, DASH score is 15.7 vs 29.4 and constant scale 78.1 vs 69.8. Conclusions. The glenoid component positioning in RSA is crucial to prevent failure, loosening and biomechanical mismatch, coverage by the baseplate of the glenoid surface, version, inclination and offset are all essential for implant survival. This study showed how useful 3D CT-based planning helps in identifying the best position of the metaglena and the usefulness of receiving directly in the operation theater real-time feedback on the change in position. This study shows promising results, suggesting that improved baseplate and screw positioning and fixation is possible when computer-assisted implantation is used in RSA comparing to a conventional procedure

Introduction and Objective. The surgical strategy for acetabular component revision is determined by available host bone stock. Acetabular bone deficiencies vary from cavitary or segmental defects to complete discontinuity. For segmental acetabular defects with more than 50% of the graft supporting the cup it is recommended the application of reinforcement ring or ilioischial antiprotrusio devices. Acetabular reconstruction with the use of the antiprotrusion cage (APC) and allografts represents a reliable procedure to manage severe periprosthetic deficiencies with highly successful long-term outcomes in revision arthroplasty. Objective. We present our experience, results, critical issues and technical innovations aimed at improving survival rates of antiprotrusio cages. Materials and Methods. From 2004 to 2019 we performed 69 revisions of the acetabulum using defrosted morcellized bone graft and the Burch Schneider anti-protrusion cage. The approach was direct lateral in 25 cases, direct anterior in 44. Patients were re-evaluated with standard radiography and clinical examination. Results. Eight patients died from causes not related to surgery, and two patients were not available for follow up. Five patients were reviewed for, respectively, non-osseointegration of the ring, post-traumatic loosening with rupture of the screws preceded by the appearance of supero-medial radiolucency, post-traumatic rupture of the distal flange, post-traumatic rupture of the cemented polyethylene-ceramic insert, and dislocation treated with new dual-mobility insert. Among these cases, the first three did not show macroscopic signs of osseointegration of the ring, and the only areas of stability were represented by the bone-cement contact at the holes in the ring. Although radiographic studies have shown fast remodeling of the bone graft and the implant survival range from 70% to 100% in the 10-year follow up, the actual osseointegration of the ring has yet to be clarified. To improve osseointegration of the currently available APC whose metal surface in contact with the bone is sandblasted, we combined the main features of the APC design long validated by surgical experience with the 3D-Metal Technology for high porosity of the external surface already applied to and validated with the press fit cups. The new APC design is produced with the 3D-Metal technology using Titanium alloy (Ti6Al4V ELI) that Improves fatigue resistance, primary stability and favorable environment for bone graft ingrowth. We preview the results of the first cases with short-term follow up. Conclusions. Acetabular reconstruction with impacted morcellized bone graft and APC is a current and reliable surgical technique that allows the restoration of bone loss with a high survival rate of the implant in the medium to long term. The new 3D Metal Cage is designed to offer high friction for the initial stability. The high porosity of the 3D Metal structure creates a favorable environment for bone growth, thus providing valid secondary fixation reproducing the results achieved with the 3D metal press fit cup

Background and aims. Hallux rigidus in the metatarsophalangeal joint (MTPJ) can be treated with arthroplasty to reduce pain and enhance motion. Few studies have investigated the functionality and the survival of HemiCap arthroplasty. Primarily we aimed to examine the medium to long-term functionality and the degree of pain after surgery. Secondarily the failure and revision rate of HemiCap implants. Methods. A total of 106 patients were operated with HemiCap arthroplasty (n=114) from 2006 to 2014, median age 53 (16 to 80) years, 78 females, 37 dorsal flange (DF) implants. Patient charts were reviewed retrospectively to collect revision data. Pre operative Coughlin/Shurnas arthrosis degree, hallux valgus (HV), intermetatarsalintermetatarsal (IM) and Distal Metaphyseal Articular Angle (DMAA) angles was were measured. Pre- and post operative 3 weeks, 6 months, 1 and 2 year2-year pain levels of the first MTPJ by Visuel Analog Skala (VAS 1–10), American Orthopaedic Foot and Ankle Score (AOFAS 0 to 100 points) and, Range of Motion (ROM), were available for 51 patients. FortysevenForty-seven of the 70 available for reexamination partook in a cross sectional follow up where the Self-Reported Foot and Ankle Score (SEFAS 0–48 points) was added to the Patients Related Outcome Measures (PROMs). Statistics. Kaplan-Meier for survival analysis, adjusted for sex, radiological angles, degree of arthrosis and dorsal flange. Prospective PROMs and ROM compared by paired t-test. Results. At 3, 5 and 7 years we had an mean implant survival of 85%, 83% and 78%. Almost all were revised due to pain, one due to malalignment and one due to loosening of the Hemicap. Dorsal flange, gender, preoperative arthrosis degree, HV, IM or DMAA angles did not statistically influence the result. For those (n=23) that were re-examined, preoperative dorsal ROM changed from mean(sd) 21 (6) to 42 (18) degrees, VAS from 7 (2) to 2 (2) and AOFAS from 61 (11) to 87 (11) (p < 0.001). At mean 5 year follow up (n=47), mean (sd) dorsal ROM was 46 (17) degrees,. AOFAS was 84 (9), VAS 2 (1) and SEFAS 42 (6) points. The dorsal flange made no statistical significant difference for ROM or PROMs, but DF displayed 51 degrees of extension vs. 44 without (p=0.1). Periprostethic lucency (<2 mm) was observed in 27/47. Conclusions. In general, we saw an acceptable implant survival rate. We did not find any predictors that influenced implant failure and the design alterations with the dorsal flange are not evident clinically. Patients who were not revised had significantly less pain, greater ROM, and better overall foot and ankle conditions than preoperatively, but the data are biased by missing numbers and revisions

Background. Following endosteal uncemented orthopaedic device implantation, the initial implant/bone interface retains spaces and deficiencies further exacerbated by pressure necrosis and resultant bone resorption. This implant-bone space requires native bone infill through the process of de novo osteogenesis. New appositional bone formation on the implant surface is known as contact osteogenesis and is generated by osteogenic cells, including skeletal stem cells (SSCs), colonising the implant surface and depositing the extracellular bone matrix. Surface nanotopographies provide physical cues capable of triggering SSC differentiation into osteoblasts, thus inducing contact osteogenesis, translated clinically into enhanced osseointegration and attainment of secondary stability. The current study has investigated the in vitro and in vivo effects of unique nanotopographical pillar substrates on SSC phenotype and function. Methods. Adult human SSCs were immunoselected, enriched using STRO-1 antibody and cultured on control and test surfaces for 21 days in vitro. The test groups comprised Ti-coated substrates with planar or modified surfaces with nanopillar. Osteoinductive potential was analysed using qPCR and immunostaining to examine gene expression and protein synthesis. Results. Following in vitro (n=5) culture on nanopillars, the expression of osteogenic genes (ALP, Collagen 1, OPN and OCN) and of Osteopontin protein (a bone matrix protein), on Ti pillars were both significantly enhanced when compared to control or Ti planar surfaces. Conclusions. Discrete raised surface nanopillars modulate adult SSC populations in the absence of any chemical cues and enhance their osteogenic properties, an effect not observed on planar Ti constructs. Hence, these findings herald exciting opportunities to improve the implant surface design, implant osseointegration, and, ultimately, implant survival. Level of evidence. Original experimental study

Background. Hip resurfacing has resurged in the last decade due to a renewed interest in metal on metal bearing. One of the proposed advantages is ease of revision of the femoral component. Short term functional results after femoral revision are similar to those after conventional total hip replacement. Survival and function after revision of the acetabular component only or of both components have not been reported. We aimed to assess hip function and implant survival after revision of the acetabular component for failed Birmingham hip resurfacing (BHR). Methods. The Oswestry Outcome Centre collected data prospectively on 5000 patients who underwent hip resurfacing between 1997 and 2002. Of these, 182 hips were revised: 42% had revision of the femoral component only, 8% revision of the acetabular component only, and 50% revision of both components. This study analyzed patients who had revision of the acetabular component, either in isolation or in combination with the femoral component. Results. In the isolated acetabular revision group the median Harris Hip Score was 74 at a mean of 4.5 years post-revision. In the both components revision group the median Harris hip score was 85 at a mean of 4 years. There was no significant difference in function between the groups. Kaplan-Meier survivor ship analysis after revision showed an average survival of 91% at 10 years. There was a significant difference between survival of isolated acetabular revision (75%) and both component revision (96%). Conclusions. Revision total hip replacement subsequent to failure of hip resurfacing has good outcome and good midterm survival. Isolated acetabular revision and revision of both components had similar function but survival was significantly worse in the isolated acetabular revision group

Summary Statement. Proximal femoral bony deficits present a surgical and biomechanical challenge to implant longevity in revision hip arthroplasty. This work finds comparable primary stability when a distally fixing tapered fluted stem was compared with a conical design in cadaveric tests. Introduction. Proximal bony deficits complicate revision hip surgery and compromise implant survival. Longer distally fixing stems which bypass such defects are therefore required to achieve stability compatible with bony ingrowth and implant longevity. Aims. It is hypothesised that a tapered stem will provide superior rotational stability to a conical design. This work therefore aims to compare the primary stability and biomechanical properties of a new design of tapered fluted modular femoral stem (Redapt®, Smith & Nephew) with that of a conical fluted stem (Restoration®, Stryker). Materials & Methods. 7 Pairs of cadaveric femora were obtained according to strict inclusion/exclusion criteria. Each underwent dual energy x-ray absorptiometry and calibration plain-film radiographs were taken. Digital templating was performed using TraumaCad (Voyant Health, Brainlab) to determine implant sizing. Both stems are fluted, modular and manufactured from titanium. The control stem (Restoration) featured a straight conical design and the investigation stem (Redapt) a straight tapered design. Implantation was performed by a revision arthroplasty surgeon familiar with both systems. Proximal bone deficiency was reproduced using an extended trochanteric osteotomy with removal of metaphyseal bone before reattaching the osteotomy. Primary stability in the axial, sagittal and coronal planes was assessed using micromotion transducers (HBM, Darmstadt, Germany) and also by Radiostereometric Analysis (RSA). RSA employs simultaneous biplanar radiographs to measure relative movement. Two 1mm tantalum beads were mounted on the prosthesis with the centre of the femoral head taken as the third reference point. Beads were placed proximally in the surrounding bone as rigid body markers. Each bone was potted according to the ISO standard for fatigue testing and cyclically loaded at 1Hz for at least 3 increments (750–350N, 1000–350N, 1500–350N) for 1000 cycles. RSA radiographs were taken at baseline and on completion of each cycle. A strain analysis was concurrently performed using a PhotoStress® (Vishay Precision Group, Raleigh, USA) photoelastic coating on the medial femoral cortex. Each bone was loaded intact and then with the prosthesis in-situ at 500N increments until strain fringes were identified. Once testing was completed, the stems were sectioned at the femoral isthmus and data is presented on the cross-sectional fit and fill observed. Results. Both stem designs showed comparable primary stability with all stems achieving clinically acceptable micromotion (<150 μm) when loaded at body weight. A larger proportion of the control stems remained stable as loading increased to x2-3 body weight. Transducer-recorded migration appeared greatest in the axial plane (y axis) with negligible distal movement in the coronal or sagittal planes. Point motion analysis (RSA) indicated most movement to be in the coronal plane (x-axis) whereas segment motion analysis showed rotation about the long axis of the prosthesis to be largest. Photoelastic strain patterns were transferred more distally in both designs, however substantial stress shielding was also observed. Discussion/Conclusion. Both designs achieved adequate distal fixation and primary stability under representative clinical loading conditions. This work supports the continued use of this novel stem design for revision surgery in the presence of extensive proximal bone loss