Abstract. Objective. To compare the periprosthetic fracture mechanics between a collared and collarless fully coated cementless femoral stem in a composite femur. Methods. Two groups of six composite femurs (‘Osteoporotic femur’, SawBones, WA USA) were implanted with either a collared (collared group) or collarless (collarless group) cementless femoral stem which was otherwise identical by a single experienced surgeon. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording was used to identify fracture mechanism. Fracture torque and angular displacement were measured and rotational work and system stiffness were estimated for each trial. Results were compared between collared and collarless group and the comparison was evaluated against previously published work using fresh frozen femurs and the same protocol. Results. In composite femur testing median fracture torque (IQR) was greater with a collared versus collarless implant (48.41 [42.60 to 50.27] Nm versus 45.12 [39.13 to 48.09] Nm, p= 0.4). Median rotational displacement (IQR) was less with a collared versus collarless implant (0.29 [0.27 to 0.31] radians versus 0.33 [0.32 to 0.34] radians, p= 0.07). Estimated rotary work was similar between groups (5.76 [4.92 to 6.64] J versus 5.21 [4.25 to 6.04] J, p= 0.4). Torsional stiffness was greater with a collared versus collarless implant (158.36 [152.61, 163.54] Nm per radian versus 138.79 [122.53, 140.59] Nm per radian, p= 0.5). Collarless stems were seen to move independently of the femur and fracture patterns originated at the calcar. Conclusions. Testing with composite femurs using an established protocol produced similar results to previously published studies using human femurs, but the difference between collared and collarless stems was smaller. The internal homogenous foam material in composite femurs does not accurately represent the heterogeneous cancellous bone which supports a femoral stem in vivo and may lead to overestimation of implant stability. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Periprosthetic femoral fractures can occur as a complication of total hip arthroplasty and are often challenging to treat as the mechanical scenario is influenced by the presence of the metal prosthesis within the bone. This research focuses on finding the optimum fixation for transverse, Vancouver type B1 periprosthetic fractures, stabilised using locking plates and secured using screws. The aim of this study was to experimentally validate a computer model of a human femur, develop that model to represent a periprosthetic femoral fracture fixation and show how the model could be used to indicate differences between plating techniques. In the first development stage, both a laboratory model and a finite element model were developed to evaluate the mechanical behaviour of an intact composite femur under axial loading. Axial strains were recorded along the medial length of the femur in both cases and compared to provide validation for the computational model predications. The computational intact femur model was then modified to include a cemented total hip replacement, and further adapted to include a periprosthetic fracture stabilised using a locking plate, with unicortical screws above, and bicortical screws below the transverse fracture. For the intact femur case, the experimental and computational strain patterns correlated well with an average difference of 16%. Following the inclusion of the stem, there was a reduction in the strain in the region of the prosthesis reducing by an average of 45%. There was also a large increase in bulk stiffness with the introduction of the prosthesis. When the fracture and plate fixation were included, there was little difference in the proximal strain where the stem dominated, and the strains in the distal region were found to be highly sensitive to the distribution of the screws. The results of this study indicate that screw configuration is an important factor in periprosthetic fracture fixation. A laboratory model of the periprosthetic facture case is now under development to further validate the computational models and the two approaches will then be used to determine optimum fixation methods for a range of clinical scenarios

Tibial periprosthetic fracture is an important complication of the Oxford Unicompartmental Knee Replacement (OUKR). Primary fixation of cementless OUKR tibial components relies on the interference-fit of the ‘keel’ and a slot in the proximal tibia. Clinically used double blade keel saws (DKS) create slots with two grooves, generating stress concentrations where fractures may initiate. This study aimed to investigate slot factors that may influence incidence of tibial periprosthetic fractures. Slots were made in PCF20 polyurethane foam using the DKS plus/minus adjuvant rasping, single blade keel saw (SKS), and rasp-only. Round and square slots were machined with milling cutters. Compact tensile tests were conducted per ASTM E399 to determine tensile load to fracture (TLTF) and results were validated using bovine tibia. Cementless OUKR components were implanted into slots in custom polyurethane blocks and compressed to failure to determine anatomical load to fracture (ALTF). A custom MATLAB program calculated slot roundness from cross-sectional images. Round slots had higher TLTF (29.5N, SD=2.7) than square (25.2N, SD=1.7, p<0.05) and DKS slots (23.3N, SD=2.7, p<0.0001). Fractures occurred at the round slot apices, square slot corners, and deepest DKS slot grooves. ALTF was not significantly different between square and round slots. Adjuvant rasping made DKS slots significantly rounder, resulting in significantly higher TLTF, but rasping did not increase ALTF. ALTF was significantly higher for SKS (850N, SD=133, p<0.01) and rasp-only (912N, SD=100, p<0.001) slots compared to standard DKS slots (703N, SD=81). Round keel slots minimise stress concentrations and increase TLTF but do not increase ALTF. The SKS and rasp-only slots retain material at slot ends and have significantly higher ALTF. Future studies should assess saw blades that retain material and round slot ends to evaluate if their use may significantly reduce the incidence of tibial periprosthetic fracture

Revision knee arthroplasty is a complex procedure with the number and cost of knee revision procedures performed per year expected to rise. Few studies have examined adverse events following revision arthroplasty. The objective of this study was to determine rates of serious adverse events in patients undergoing revision knee arthroplasty with consideration of the indication for revision (urgent versus elective indications) and to compare these with primary arthroplasty and re-revision arthroplasty. Patients undergoing primary knee arthroplasty were identified in the UK Hospital Episode Statistics. Subsequent revision and re-revision arthroplasty procedures in the same patients and same knee were identified. The primary outcome was 90-day mortality and a logistic regression model was used to investigate factors associated with 90-day mortality and secondary adverse outcomes including infection (undergoing surgery), pulmonary embolism, myocardial infarction, stroke. Urgent indications for revision arthroplasty were defined as infection or fracture, and all other indications were included in the elective indications cohort. 939,021 primary knee arthroplasty cases were included of which 40,854 underwent subsequent revision arthroplasty, and 9,100 underwent re-revision arthroplasty. Revision surgery for elective indications was associated with a 90-day rate of mortality of 0.44% (135/30,826; 95% CI 0.37-0.52) which was comparable to primary knee arthroplasty (0.46%; 4,292/939,021; 95% CI 0.44-0.47). Revision arthroplasty for infection, however, was associated with a much higher mortality of 2.04% (184/9037; 95% CI 1.75-2.35; odds ratio [OR] 3.54; 95% CI 2.81-4.46), as was revision for periprosthetic fracture at 5.25% (52/991; 95% CI 3.94-6.82; OR 6.23; 95% CI 4.39-8.85). Higher rates of pulmonary embolism, myocardial infarction, and stroke were also observed in the infection and fracture cohort. These findings highlight the burden of complications associated with revision knee arthroplasty. They will inform shared decision-making for patients considering revision knee arthroplasty for elective indications. Patients presenting with infection of a knee arthroplasty or a periprosthetic fracture are at very high risk of adverse events. It is important that acute hospital services and tertiary referral centres caring for these patients are appropriately supported to ensure appropriate urgency and an anticipation for increased care requirements

Abstract. Objective. To estimate the effect of calcar collar contact on periprosthetic fracture mechanics using a collared fully coated cementless femoral stem. Methods. Three groups of six composite femurs were implanted with a fully coated collared cementless femoral stem. Neck resection was increased between groups (group 1 = normal, group 2 = 3mm additional, group 3 = 6mm additional), to simulate failure to obtain calcar collar contact. Periprosthetic fractures of the femur were simulated using a previously published technique. Fracture torque and rotational displacement were measured and torsional stiffness and rotational work prior to fracture were estimated. High speed video recording identified if collar to calcar contact (CCC) occurred. Results between trials where calcar contact did and did not occur where compared using Mann-Whitney U tests. Results. Where CCC occurred versus where no CCC occurred, fracture torque was greater (47.33 [41.03 to 50.45] Nm versus 38.26 [33.70 to 43.60] Nm, p= 0.05), Rotational displacement was less (0.29 [0.27 to 0.39] rad versus 0.37 [0.33 to 0.49] rad, p= 0.07), torsional stiffness was greater (151.38 [123.04 to 160.42] rad. Nm-1 versus 96.86 [84.65 to 112.98] rad.Nm-1, p <0.01) and rotational work was similar (5.88 [4.67, 6.90] J versus 5.31 [4.40, 6.56] J, p= 0.6). Conclusions. Resistance to fracture and construct stiffness increased when a collared cementless stem made contact with the femoral calcar prior to fracture. These results demonstrate that calcar-collar contact and not a calcar collar per se, is crucial to maximising the protective effect of a medial calcar collar on the risk of post-operative periprosthetic fractures of the femur. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objective. To estimate the effect of calcar collar separation on the likelihood of calcar collar contact during in vitro periprosthetic fracture. Methods. Three groups of six composite femurs were implanted with a collared cementless femoral stem. Neck resection was increased between groups (group 1 = normal, group 2 = 3mm additional, group 3 = 6mm additional), to simulate failure to obtain calcar collar contact. Prior to each trial, the distances between anterior (ACC) and posterior (PCC) collar and the calcar were measured. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording identified when collar to calcar contact (CCC) occurred. The ACC and PCC were compared between trials where the CCC was and was not achieved. Regression estimated the odds of failing to achieve CCC for a given ACC or PCC. Results. CCC was achieved prior to fracture in all cases in group one, 50% in group two and 0% in group three. The median (range) ACC for those trials where CCC was achieved was 0.40 (0.00, 3.37) mm versus 6.15 (3.06 to 6.88) mm, where CCC was not achieved (p <0.01). The median (range) PCC for those trials where CCC was achieved was 0.85 (0.00 to 3.71) mm versus 5.97 (2.23 to 7.46) mm, where CCC was not achieved (p <0.01). Binomial logistic regression estimated risk of failure to obtain CCC increased 3.8 fold (95% confidence interval 1.6 to 30.2, p <0.05) for each millimetre of PCC. Conclusions. Increased separation between collar and calcar reduced the likelihood of calcar collar contact during a simulated periprosthetic fracture of the femur. Surgeons should aim to achieve a calcar-collar distance of less than 1mm following implantation to ensure calcar collar contact during periprosthetic femoral fracture and to reduce the risk of fracture. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Introduction. In general the life expectancy of population is improving. This is causing to increase case load of peri-prosthesis fractures after joint replacements. We present our results of peri-prosthesis fracture around hip managed by revision arthroplasty. Methods. A retrospective analysis of 24 consecutive patients of periprosthetic hip fracture treated with a revision arthroplasty at Major Trauma Centre between February 2021 and January 2022. Results. 12 male and 12 female patients, average age 78 years. 3 fractures around BHR prosthesis, 2 type A, 15 type B and 3 of type C (Vancouver). The surgery was done in an average 6 days after injury (range 1–14). 6 patients died in follow up, 1 patient contracted infection, 2 developed LLD and 1 patient had multiple dislocations. 6 patients had revision using endo-prosthesis. Advanced age with peri-prosthesis fracture has increased risk of mortality (average age 84.5 years). Conclusion. Endo-prosthesis replacement had higher risk of dislocation, infection and mortality. Overall patients do well after a revision arthroplasty for periprosthetic hip fracture. 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 and Objective. Interest for direct anterior approach (DAA) in hip hemiarthroplasty (HHA) has greatly increased in recent years, however which is the best surgical approach in hip replacement treating femoral neck fractures (FNFs) is already unclear. The aim of this study is to perform a radiographic and perioperative complications analysis by comparing the direct anterior approach (DAA) with the direct lateral approach (DLA) in patients treated with hemiarthroplasty for FNFs. Materials and Methods. Patients with FNFs surgically treated between 2016–2020 with HHA were enrolled. The radiographical outcomes of DAA and DLA are compared. Several peri-operative and post-operative variables were evaluated: mean surgery time, complications as periprosthetic fractures or episodes of dislocation, the average of post-operative diaphyseal filling of the stem (Canal Fill Index, CFI), the extent of heterotopic ossification (HO) (simplified Broker classification) and metadiaphiseal bone loss (Paprosky classification) within one year from surgery. Results. 86 patients underwent HHA by DAA and 80 patients by DLA. The two groups are qualitatively comparable. No statistically significate differences were showed in all variables analyzed (p>0.05). The average of surgical time of DAA were 61 minutes compared to 67 of DLA. No differences were showed in the post-operative CFI (DAA 0.71 ± 6.1; DLA 0.76 ± 13.5), the extent of the HO (DAA 79.07% low; DLA 75% low) and metadiaphiseal bone loss (DAA Grade I 91.86%; DLA Grade I 93.75%). Regarding perioperative complications, we have discovered only one periprosthetic fracture each group. Although there was no statistically significant difference, we highlighted a higher number of dislocations in the group of DLA (2 episodes vs no one). Conclusions. In this study we have shown that the DAA is an adequate surgical choice comparing with the classical DLA for FNFs treated with HHA. The analysis of our radiographic parameters and perioperative complications have not shown a significant difference between the two surgical approach. This study is limited by a purely radiographic analysis without addition of clinical parameters

Elective orthopaedic procedures, and particularly total hip arthroplasty (THA), in octogenarians and nonagenarians patients are burdened of several implications. Besides the comorbidities and the anesthesiological issues, legal and ethical implications are present. Some literature data show the clinical improvement of THA in elderly patient but the psychological aspects are not yet evaluated. Aim of this study is to evaluate the clinical aspects and the psychological impact in daily living in octogenarians and nonagenarians patients addressing THA. We conducted a retrospective evaluation of 81 THA in 81 patients of age more than 85 years with a minimum follow-up of 6 months. Clinical aspects were evaluated using the Hip disability and Osteoarthritis Outcome Score (HOOS). The psychological issues were evaluated with the Short Form 12 (SF-12) using both the Physical Component Summary (PCS) and the Mental Component Summary (MCS). From the starter cohort of 81 patients, 8 patients were died for causes unrelated to surgery, 13 were lost to follow-up, 1 patient was revised for periprosthetic fracture; 59 patients composed the final cohort. Mean HOOS rased from 18,07 ± 17,81 to 92,36 ± 5,74 with statistically significant distribution both in the global score than in all of the different subscales. The PCS raised from 26,81 ± 10,81 to 51,86 ± 4,45 and The MCS raised from 34,84 ± 10,81 to 56,70 ± 5,04, but none of them showed a statistically significant distribution. THA in octogenarians and nonagenarians patients could be a safe procedure with positive results for clinical and psychological aspects

Previous scientific studies have highlighted how coupling is an important element affecting total hip arthroplasty's survival. This study aims to evaluate whether metal-on-metal (MOM) coupling could be a statistically significant risk factor. The data from the regional joint registry (Registro dell'Impiantologia Protesica Ortopedica, RIPO) was used for analysis. The data collection accuracy of this registry was 97.2% in 2017. We retrospective evaluate all MOM total hip arthroplasties (THAs) implanted in our department between January 01st 2000 and December 31st 2011. We used a control group composed by all other prosthesis implanted in our Department in the same time lapse. We registered 660 MOM THAs. Mean age of patients was 66.9 years. 603 patients have a >36mm head, while 78 a <36 mm one. Neck modularity was present in half of patients. 676 implants were cementless. We registered 69 revisions, especially due to aseptic mobilization (16 THAs), implant breakage (9 THAs) and periprosthetic fracture (6 THAs). The MOM THAs overall Kaplan-Meier survival rate was 87.2 at 15 years, and the difference between MOM THAs and other implants two curves is statistically significant (p<0.05). Male sex is a significant risk factors. Further evaluations are in progress to establish the presence of any additional risk factors. We think weight and/or BMI may be included in this category. Our study confirms the data currently present in the literature regarding a lower survival of metal-on-metal hip prostheses. The male sex is a statistically significant risk factor (p<0.05), while age, head size and modularity of the prosthetic neck are not statistically significant (p>0.05). Any new finds will be presented at the congress venue

Fragility ankles fractures in the geriatric population are challenging to manage, due to fracture instability, soft tissue compromise, patient co-morbidities. Traditional management options include open reduction internal fixation, or conservative treatment, both of which are fraught with high complication rates. We aimed to present functional outcomes of elderly patients with fragility ankle fractures treated with tibiotalocalcaneal nails. 171 patients received a tibiotalocalcaneal nail over a six-year period, but only twenty met the inclusion criteria of being over sixty and having poor bone stock, verified by radiological evidence of osteopenia or history of fragility fractures. Primary outcome was mortality risk from co-morbidities, according to the Charlson co-morbidity index (CCI), and patients’ post-operative mobility status compared to pre-operative mobility. Secondary outcomes include intra-operative and post-operative complications, six-month mortality rate, time to mobilisation and union. The mean age was 77.82 years old, five of whom are type 2 diabetics. The average CCI was 5.05. Thirteen patients returned to their pre-operative mobility state. Patients with low CCI are more likely to return to pre-operative mobility status (p=0.16; OR=4.00). Average time to bone union and mobilisation were 92.5 days and 7.63 days, respectively. Mean post-operative AOFAS ankle-hindfoot and Olerud-Molander scores were 53.0 (range 17-88) and 50.9 (range 20-85), respectively. There were four cases of broken distal locking screws, and four cases of superficial infection. Patients with high CCI were more likely to acquire superficial infections (p=0.264, OR=3.857). There were no deep infections, periprosthetic fractures, nail breakages, non-unions. TTC nailing is an effective treatment methodology for low-demand geriatric patients with fragility ankle fractures. This technique leads to low complication rates and early mobilisation. It is not a life-changing procedure, with many able to return to their pre-operative mobility status, which is important for preventing the loss of socioeconomic independence

Introduction. The evaluation of treatment modalities for distal femur periprosthetic fractures (DFPF) post-total knee arthroplasty (TKA) has predominantly focused on functional and radiological outcomes in existing literature. This study aimed to comprehensively compare the functional and radiological efficacy of locking plate (LP) and retrograde intramedullary nail (IMN) treatments, while incorporating mortality rates. Method. Twenty patients (15 female, 5 male) with a minimum 24-month follow-up period, experiencing Lewis-Rorabeck type-2 DFPF after TKA were included. These patients underwent either LP (n=10) or IMN (n=10). The average follow-up duration was 48 months (range: 24–192). Treatment outcomes, including functional scores, alignment, union time, complications, and mortality rates, were assessed and compared between LP and IMN groups. Clinical examination findings pre-treatment and at final follow-up, along with two-way plain radiographs, were utilized. Statistical analyses comprised Student's t-test and Kaplan-Meier survival analysis with a 95% confidence interval. Result. At final follow-up, the LP group demonstrated a mean Knee Society score of 67.2 ± 16.1, while the IMN group exhibited a score of 72.8 ± 9.4(P = 0.58). No statistically significant differences were observed in alignment between the groups[aLDFA (anatomical lateral distal femoral angle), P = 0.31; aPDFA (anatomical posterior distal femoral angle), P = 0.73]. The mean time to union was 3.7 ± 0.8 months for LP and 3.9 ± 0.6 months for IMN (P = 0.62). Complications such as infection occurred in 1 LP patient, and non-union was observed in 2 LP patients, while no complications were noted in IMN group(P < 0.01). Mortality rates were notably lower in the IMN group compared to the LP group across various time intervals. Conclusion. Both LP and IMN treatments yielded similar functional scores, alignment, and union time for DFPF post-TKA. However, the lower incidence of complications and mortality rates associated with IMN treatment suggest its superiority in managing DFPF following TKA

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

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

Introduction. Femoral periprosthetic fractures above TKA are commonly treated with retrograde intramedullary nailing (IMN). This study determined if TKA design and liner type affect the minimum knee flexion required for retrograde nailing through a TKA. Methods. Twelve cadaveric specimens were prepared for six single radius (SR) TKAs and six asymmetric medial pivot (MP) TKAs. Trials with 9mm polyethylene liners were tested with cruciate retaining (CR), cruciate substituting (CS) and posterior stabilizing (PS) types. The knee was extended to identify the minimum knee flexion required to allow safe passage of the opening reamer while maintaining an optimal fluoroscopic starting point for retrograde nailing. Furthermore, the angle of axis deviation between the reamer and the femoral shaft was calculated from fluoroscopic images. Results. In all specimens, the reamer entry point was posterior to Blumensaat's line. In the SR TKA, the average flexion required was 70, 71 and 82 degrees for CR, CS and PS respectively. The required flexion in PS was significantly greater than the other designs (p=0.03). In the MP TKA, the average flexion required was 74, 84 and 123 degrees for CR, CS and PS respectively. The required flexion was significantly greater in CS and PS designs (p<0.0001). Femoral component size did not affect the minimum flexion required. Furthermore, the entry reamer required 9.2 (SR) and 12.5 (MP) degrees of posterior axis deviation from the femur. Conclusions. Our study illustrates four novel factors to consider when performing retrograde nailing through TKA. First, significant knee flexion is required to obtain an ideal radiographic starting point when retaining the liner. Second, PS implants require more flexion with both TKA designs. Third, femoral component size does not affect the flexion required. Fourth, there is a consistent posterior axis deviation of the entry reamer from the femoral shaft, explaining the commonly created extension deformity

Total Hip Replacement (THR) is one of the most successful operations in all of medicine, however surgeons just rely on their experience and expertise when choosing between cemented or cementless stem, without having any quantitative guidelines. The aim of this project is to provide clinicians with some tools to support in their decision making. A novel method based on bone mineral density (BMD) measurements and assessments was developed 1) to estimate the periprosthetic fracture risk (FR) while press-fitting cementless stem; 2) to evaluate post-operative bone remodeling in terms of BMD changes after primary THR. Data for 5 out of over 70 patients (already involved in a previous study. 1. ) that underwent primary THA in Iceland were selected for developing novel methods to assess intra-operative FR and bone mineral density (BMD) changes after the operation. For each patient three CT images were acquired (Philips Brilliance 64 Spiral-CT, 120 kVp, slice thickness: 1 mm, slice increment: 0.5 mm): pre-op, 24 hours and 1 year post-operative. Pre-op CT scan was used to create 3D finite element model (Materialise Mimics) of the proximal femur. The material properties were assigned based on Hounsfield Units. Different strategies were analyzed for simulating the press-fitting operation, developing what has already been done in prior study. 1. In the finite element simulation (Ansys Workbench), a pressure (related to the implant hammering force of 9.25 kN. 2. ) was applied around the femur's hollow for the stem and the distribution of maximum principal elastic strain over the bone was calculated. Assuming a critical failure value. 3. of 7300 με, the percentage of fractured elements was calculated (i.e. FR). Post 24 hours and Post 1 year CT images were co-registrated and compared (Materialise Mimics) in order to assess BMD changes. Successively, volumes of bone lost and bone gained were calculated and represented in a 3D model. Age and gender should not be taken as unique indicators to choose between implants typologies, since also three dimensional BMD distribution along with volume of cortical bone influence the risk of periprosthetic fractures. Highest FR values were experienced in the calcar-femorale zone and in similar location on the posterior side. BMD loss volume fractions after 1 year were usually higher than BMD gain ones. Consistently with prior studies. 4. , BMD loss was mainly concentrated around the proximal end (lesser trochanter area, outer bone). If present, BMD gain occurred at the distal end (below stem's tip) or proximally (lesser trochanter area, interface contact with the stem). The use of clinical data for BMD assessments serves as an important tool to develop a quantitative method which will support surgeons in their decisions, guiding them to the optimal implant for the patient. Knowing the risk of fracture if choosing a cementless stem and being aware of how the bone will remodel around the stem in one year's time can eventually lead to reduction in revisions and increased quality of life for the patient. Further work will target analysis of a larger cohort of patients and validate FE models

Objectives. Microindentation has the potential to measure the stiffness of an individual patient’s bone. Bone stiffness plays a crucial role in the press-fit stability of orthopaedic implants. Arming surgeons with accurate bone stiffness information may reduce surgical complications including periprosthetic fractures. The question addressed with this systematic review is whether microindentation can accurately measure cortical bone stiffness. Methods. A systematic review of all English language articles using a keyword search was undertaken using Medline, Embase, PubMed, Scopus and Cochrane databases. Studies that only used nanoindentation, cancellous bone or animal tissue were excluded. Results. A total of 1094 abstracts were retrieved and 32 papers were included in the analysis, 20 of which used reference point indentation, and 12 of which used traditional depth-sensing indentation. There are several factors that must be considered when using microindentation, such as tip size, depth and method of analysis. Only two studies validated microindentation against traditional mechanical testing techniques. Both studies used reference point indentation (RPI), with one showing that RPI parameters correlate well with mechanical testing, but the other suggested that they do not. Conclusion. Microindentation has been used in various studies to assess bone stiffness, but only two studies with conflicting results compared microindentation with traditional mechanical testing techniques. Further research, including more studies comparing microindentation with other mechanical testing methods, is needed before microindentation can be used reliably to calculate cortical bone stiffness. Cite this article: M. Arnold, S. Zhao, S. Ma, F. Giuliani, U. Hansen, J. P. Cobb, R. L. Abel, O. Boughton. Microindentation – a tool for measuring cortical bone stiffness? A systematic review. Bone Joint Res 2017;6:542–549. DOI: 10.1302/2046-3758.69.BJR-2016-0317.R2