Regulatory bodies impose stringent pre-market controls to certify the safety and compatibility of medical devices. However, internationally recognized standard tests may be expensive, time consuming and challenging for orthopedic implants because of many possible sizes and configurations. In addition, cost and time of standard testing may endanger the feasibility of custom-device production obtained through innovative manufacturing technologies like 3d printing. Modeling and simulation (M&S) tools could be used by manufactures and at point-of-care to improve design confidence and reliability, accelerate design cycles and processes, and optimize the amount of physical testing to be conducted. We propose an integrated cloud platform to perform in silico testing for orthopedic devices, assessing mechanical safety and electromagnetic compatibility, in line with recognized standards and regulatory guidelines. The . InSilicoTrials.com. platform contains two M&S tools for orthopedic devices: CONSELF and NuMRis. CONSELF (. conself.com. ) uses Salome-Meca 2017 to compute static implant stresses and strains on metallic orthopedic devices, following the requirements and considerations of ASTM F2996-20 for non-modular hip femoral stems and ASTM F3161-16 for total knee femoral components. Simulation results were consistent with those reported in the two standards. NuMRis (. numris.insilicomri.com. ) uses ANSYS HFSS and ANSYS Mechanical 2019R3 to compute radio-frequency energy absorption and induced heating in 1.5T and 3T MRI coils, replicating the ASTM F2182-19e2 Standard Test Method. Simulation results were validated against in vitro measurements. The integrated M&S workflow on the cloud platform allows the user to upload the 3D geometry and the material properties of the orthopedic device to be tested, automatically set up the standard testing scenarios, run simulations and process outcome, with the option to summarize the results in accordance with current FDA guidance on M&S reporting. The easy-to-use interfaces of InSilicoTrials tools run through commercial web browsers, requiring no specific expertise in computational methods or additional on-premise software and hardware resources, since all simulations are run remotely on cloud infrastructure. The integrated cloud platform can be used to evaluate design alternatives, test multi-configuration devices, perform multi-objective design optimization and identify worst-case scenarios within a family of implant sizes, or to assess the safety and compatibility of custom-made orthopedic devices. InSilicoTrials.com. is the first cloud platform offering a collection of M&S tools to perform in silico standard testing for orthopedic devices. The proposed tools allow to assess mechanical safety and electromagnetic compatibility before prototyping, preventing risks and criticalities for the patient, and helping manufacturers and point-of-care to accelerate time and reduce costs during the device development. The proposed platform promotes the broader adoption of digital evidence in preclinical trials, supporting the device submission process and pre-market regulatory evaluation, and helping secure regulatory approval

Repeat revision hip replacements can lead to severe bone loss necessitating salvage procedures such as proximal or total femoral replacement. We present medium term outcomes from our experience of the Limb Preservation System (LPS) in patients with failed revision hip arthroplasties. All patients undergoing proximal femoral or total femoral replacement from 2003–2007 at our unit were reviewed. Data was collected preoperatively and at annual assessment post procedure for a minimum of 5 years. This included clinical review, functional outcome scores (WOMAC, Oxford Hip Score, Harris Hip Score) and radiographic evaluation. A total of 17 patients underwent femoral replacement (13 proximal, 4 total) using the LPS during the study period. Within this cohort there were 13 males and 4 females with a mean age of 64 years (range 47–86). Median follow up was 7 years (range 5–9 years). Primary diagnoses were DDH (7), Primary OA (5), RA (2), proximal femoral fracture (2) and phocomelia (1). Five patients (29%) required further revision surgery for infection (2 patients) or recurrent dislocations (3 patients). No stems required revision due to aseptic loosening or stem failure at 5–9 years. Compared to preoperative assessment, there was significant improvement in median outcome scores at 5 years (WOMAC increased by 33 points, Oxford hip score by16 points and Harris hip score by 43 points). 82% of patients maintained functional independence at latest review. The Limb Preservation System offers a salvage procedure for failed revision total hip arthroplasty with significant symptom and functional improvement in most patients at medium term follow up

Summary. The dGEMRIC index correlates more strongly with the pattern of radiographic joint space narrowing in hip osteoarthritis at five year follow-up than morphological measurements of the proximal femur. It therefore offers potential to refine predictive models of hip osteoarthritis progression. Introduction. Longitudinal general population studies have shown that femoroacetabular impingement increases the risk of developing hip osteoarthritis, however, morphological parameters have a low positive predictive value. Arthroscopic debridement of impingement lesions has been proposed as a potential strategy for the prevention of osteoarthritis, however, the development of such strategies requires the identification of individuals at high risk of disease progression. We investigated whether delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) predicts disease progression. This imaging modality is an indirect measure of cartilage glycosaminoglycan content. Patients and Methods. 34 asymptomatic individuals from a longitudinal cohort study (sibkids) were assessed at baseline with the collection of Patient Reported Outcome Measures (PROMs), anteroposterior and cross-table lateral radiographs, 3D morphological MRI, and dGEMRIC at 3T of their index hip. A dGEMRIC index was calculated as a ratio of the anterosuperior acetabular cartilage T1 relaxation time and the total femoral and acetabular cartilage T1 relaxation time. 29 individuals were followed up at 5 years for repeat assessment (average age 51 years and range 36 to 67). Radiological measurements were made by a single observer using in house Hipmorf software. Radiographic disease progression was assessed using minimum joint space width (JSW), lateral sourcil JSW, and medial sourcil JSW. These were measured on baseline and five year follow-up anteroposterior radiographs with an intra-observer ICC of 0.916. Alpha angle measurements were made by the same observer on radiographs and MRI radial slices with an intra-observer ICC of 0.926. Results. Mean minimum JSW for the cohort fell by 0.16mm over five years (p=0.024). Baseline dGEMRIC index did not correlate with change in minimum JSW (r=0.031 p=0.873). There was a moderate correlation between baseline dGEMRIC and the direction of JSW loss (change in JSW at the lateral sourcil minus change in JSW at the medial sourcil) (r=0.561 p=0.002). There was a weak correlation between the change in Non-Arthritic Hip Score and baseline dGEMRIC (r=0.256 P=0.180). Maximum alpha angle measured on baseline MRI radial slices did not correlate with change in minimum JSW and weakly correlated with the direction of JSW narrowing (r=0.273 p=0.160). Conclusion. A low dGEMRIC index indicates reduced glycosaminoglycan concentration in the anterosuperior acetabular cartilage compared with the total femoral and acetabular cartilage. This correlates with lateral JSW narrowing relative to medial JSW narrowing as osteoarthritis progresses. The dGEMRIC index correlates better with osteoarthritis progression than alpha angle measurements and offers the potential to refine a predictive model for osteoarthritis progression to aid patient selection for clinical trials

The superior analgesic effects of minodronate compared with other bisphosphonates has been previously reported. However, to our knowledge, there are no studies analyzing the analgesic effects of bisphosphonates on chronic pain. The purpose of the present study was to evaluate the analgesic effects of minodronate (MIN), alendronate (ALN), and pregabalin (PRG) on chronic pain caused by chronic constriction injury (CCI) of the sciatic nerve. Four-week-old female Wister rats underwent ovariectomy. At 8 weeks old, the left sciatic nerve was ligated to induce the chronic pain model (CCI side), and sham surgery was performed on the right posterior limb as a CCI control (control side). The rats were divided into the following four groups: 1) MIN group, administered with minodronate (0.15 mg/kg/week) (n = 10); 2) ALN group, administered with alendronate (0.15 mg/kg/week) (n = 10); 3) PRG group, administered with pregabalin (10 mg/kg) (n = 9); and 4) Control group, administered with vehicle (n = 10). Treatments were administered subcutaneously every week for 2 weeks immediately after CCI. To quantify the sensitivity to a tactile stimulus, paw withdrawal in response to a tactile stimulus was measured using von Frey filaments at 0, 1, and 2 weeks after CCI. Von Frey filaments were applied to the plantar surface of the hindpaws for 3 s, and this was repeated three times. Paw withdrawal in response to the stimulus was evaluated by scoring as follows: 0, no response; 1, a slow and/ or slight response to the stimulus; 2, a quick withdrawal response; 3, an intense withdrawal response away from the stimulus. The mean value of the score was adopted as the pain score. After evaluating the response, bilateral femurs were harvested for bone mineral density (BMD) measurements. The pain score of the CCI side was significantly higher than that of the sham side in all groups (p < 0.05) at each time point. The pain score for the MIN group, but not the ALN group, of the CCI side was significantly lower (p = 0.05) at 0 and 1 week after CCI. Total femoral BMD of the CCI side was significantly lower in the PRG and Control groups than those of the MIN and ALN groups (p < 0.05). No significant difference was identified for BMD between the MIN and ALN groups. Minodronate showed a significant analgesic effect on chronic pain and suppressed osteoporotic changes caused by CCI

One of the most controversial issues in total knee replacement is whether or not to resurface the patella. In order to determine the effects of different designs of femoral component on the conformity of the patellofemoral joint, five different knee prostheses were investigated. These were Low Contact Stress, the Miller-Galante II, the NexGen, the Porous-Coated Anatomic, and the Total Condylar prostheses. Three-dimensional models of the prostheses and a native patella were developed and assessed by computer. The conformity of the curvature of the five different prosthetic femoral components to their corresponding patellar implants and to the native patella at different angles of flexion was assessed by measuring the angles of intersection of tangential lines.

The Total Condylar prosthesis had the lowest conformity with the native patella (mean 8.58°; 0.14° to 29.9°) and with its own patellar component (mean 11.36°; 0.55° to 39.19°). In the other four prostheses, the conformity was better (mean 2.25°; 0.02° to 10.52°) when articulated with the corresponding patellar component. The Porous-Coated Anatomic femoral component showed better conformity (mean 6.51°; 0.07° to 9.89°) than the Miller-Galante II prosthesis (mean 11.20°; 5.80° to 16.72°) when tested with the native patella. Although the Nexgen prosthesis had less conformity with the native patella at a low angle of flexion, this improved at mid (mean 3.57°; 1.40° to 4.56°) or high angles of flexion (mean 4.54°; 0.91° to 9.39°), respectively. The Low Contact Stress femoral component had the best conformity with the native patella (mean 2.39°; 0.04° to 4.56°). There was no significant difference (p > 0.208) between the conformity when tested with the native patella or its own patellar component at any angle of flexion.

The geometry of the anterior flange of a femoral component affects the conformity of the patellofemoral joint when articulating with the native patella. A more anatomical design of femoral component is preferable if the surgeon decides not to resurface the patella at the time of operation.

A total of 20 pairs of fresh-frozen cadaver femurs were assigned to four alignment groups consisting of relative varus (10° and 20°) and relative valgus (10° and 20°), 75 composite femurs of two neck geometries were also used. In both the cadaver and the composite femurs, placing the component in 20° of valgus resulted in a significant increase in load to failure. Placing the component in 10° of valgus had no appreciable effect on increasing the load to failure except in the composite femurs with varus native femoral necks. Specimens in 10° of varus were significantly weaker than the neutrally-aligned specimens.

The results suggest that retention of the intact proximal femoral strength occurs at an implant angulation of ≥ 142°. However, the benefit of extreme valgus alignment may be outweighed in clinical practice by the risk of superior femoral neck notching, which was avoided in this study.