Aims. The study objective was to prospectively assess clinical outcomes for a pilot cohort of tibial shaft fractures treated with a new tibial nailing system that produces controlled axial interfragmentary micromotion. The hypothesis was that axial micromotion enhances fracture healing compared to static interlocking. Methods. Patients were treated in a single level I trauma centre over a 2.5-year period. Group allocation was not randomized; both the micromotion nail and standard-of-care static locking nails (control group) were commercially available and selected at the discretion of the treating surgeons. Injury risk levels were quantified using the Nonunion Risk Determination (NURD) score. Radiological healing was assessed until 24 weeks or clinical union. Low-dose CT scans were acquired at 12 weeks and virtual mechanical testing was performed to objectively assess structural bone healing. Results. A total of 37 micromotion patients and 46 control patients were evaluated. There were no significant differences between groups in terms of age, sex, the proportion of open fractures, or NURD score. There were no nonunions (0%) in the micromotion group versus five (11%) in the control group. The proportion of fractures united was significantly higher in the micromotion group compared to control at 12 weeks (54% vs 30% united; p = 0.043), 18 weeks (81% vs 59%; p = 0.034), and 24 weeks (97% vs 74%; p = 0.005). Structural bone healing scores as assessed by CT scans tended to be higher with micromotion compared to control and this difference reached significance in patients who had biological comorbidities such as smoking. Conclusion. In this pilot study, micromotion fixation was associated with improved healing compared to standard tibial nailing. Further prospective clinical studies will be needed to assess the strength and generalizability of any potential benefits of micromotion fixation. Cite this article: Bone Jt Open 2021;2(10):825–833

Extracorporeal irradiation and re-implantation of a bone segment is a technique employed in bone sarcoma surgery for limb salvage in the setting of reasonable bone stock. There is neither consensus nor rationale given for the dosage of irradiation used in previous studies, with values of up to 300Gy applied. We investigated the influence of extracorporeal irradiation on the elastic and viscoelastic properties of bone. Bone specimens were extracted from mature cattle and subdivided into thirteen groups; twelve groups exposed to increasing levels of irradiation and a control group. The specimens, once irradiated, underwent mechanical testing in saline at 37°C. Mechanical properties were calculated by experimental means which included Young's Modulus, Poisson's Ratio, Dissipation Factor, Storage Modulus, Loss Modulus and Dynamic Modulus. These were all obtained for comparison of the irradiated specimens to the control group. We found there to be a statistically significant increase in Poisson's ratio after increasing irradiation doses up to 300Gy were applied. However, there was negligible change in all other mechanical properties of bone that were assessed. Therefore, we conclude that the overall mechanical effect of high levels of extracorporeal irradiation (300Gy) is minute, and can be administered to reduce the risk of malignancy recurrence

Introduction. Our unit has extensive experience with the use of Ilizarov circular frames for acute fracture and nonunion surgery. We have observed and analysed fracture healing patterns which question the role of relative stability in fracture healing and we offer limb mechanical axis restoration as a more important determinant. Aim. To assess for the presence of external callus, when only relative stability has been achieved but with anatomical restoration of the mechanical axis (ARMA). Methods. We retrospectively reviewed diametaphyseal proximal and distal tibial fractures treated with Ilizarov frame fixation in our unit between 2009 and 2017. We also reviewed cases where the Ilizarov frame technique had been used for complex femoral and humeral non-unions. Radiographs in 4 views were reviewed to assess bone healing, the presence of external callus and correction of lower limb mechanical axis. Results. 45 tibial plateau fractures, 42 distal tibial fractures and 20 humeral and 3 femoral non-unions were reviewed. Where ARMA was achieved, bone healing was observed to occur without external callus. ARMA proved more challenging in the distal tibia and where ARMA was not achieved external callus was visible during fracture healing. Conclusion. ARMA bone healing is reliable and occurs without formation of external callus, despite relative stability. This would suggest that external callus is produced not in response to just the magnitude of strain but also the direction of strain. Restoration of the mechanical axis is an important step in achieving union and needs to be considered when fixing fractures or treating non-unions

Introduction. Osteoporosis is a metabolic disease of the bone responsible for a loss of bone resistance and an increase in fracture risk. World Health Organization (WHO) estimations are about 6.3 millions of femoral neck fractures in the world by 2050. These estimations make osteoporosis a real problem in term of public health. Knowledge in biological tissues mechanical behaviour and its evolution with age are important for the design of diagnosis and therapeutic tools. From the mechanical aspect, bone resistance is dependent on bone density, bone architecture and bone tissue quality. If the importance of bone density and bone architecture has been well explored, the bone tissue quality still remains unstudied because of the lack of biomechanical tools suitable for testing bone at this microscopic dimension. Therefore the goal of this study is to estimate the osteoporotic cancellous bone tissue mechanical behaviour at its microscopic scale, using an approach coupling mechanical assays and digital reconstruction. Materials and methods. The experimental study is based on cancellous bone tissue extracted from human femoral head. Forty 8mm diameters bone cylinders have been removed from femoral head explanted after a femoral neck fracture treated by arthroplasty. These cylinders have been submitted to a digitally controlled compressive trial. Before and after the trials, microscanner analyses with an 8 μm spatial resolution have been realized in order to determine the micro structural parameters. The cylinders have been rebuilt with the digital model-building in order to estimate the mechanical behaviour and the bone quality. Results. The results will be presented from a macroscopic and microscopic point of view and will show the relationship between gender and age of the patients. At the macroscopic scale, we will look at that apparent young modulus heterogeneity and the cracking strength. At the microscopic scale, we will confirm that the cancellous bone tissue mechanical behaviour is close to the Haversian bone tissue mechanical behaviour. Finally, the parametric study will permit us to point out the main microstructural components influencing cancellous bone tissue quality. Conclusion. This study allows a precise estimation of the osteoporotic cancellous bone tissue mechanical behaviour. It seems to be a great step in the understanding of this disease and it could probably lead to great improvements in the diagnosis, prognostic, medical and surgical approaches of osteoporosis

Introduction. Fracture healing is governed by biological and mechanical factors. Circular frames are one method to fix fractures. Recently, the number of frame designs that are available has increased and these different designs may have different effects on the mechanical environment created. The senior author has been concerned by the stability of the construction when a short frame is used. This study examined the stability of different frames and the possible use of additional 7th struts to aid stability. Method. The frame configuration was modified with increasing strut angles from 15° − 70°. Each frame was cyclically tested in compression to 200N. The Taylor Spatial Frame was retested with the addition of a seventh strut. Results. Frame stability significantly deteriorated with shorter struts. This was particularly apparent at angles less than 30°. Stiffness was significantly improved with the addition of a seventh strut. Conclusions. Ring-strut angle, plays a significant factor in hexapod frame stability. Stability can be improved with the addition of a seventh strut. This may be particularly important in the paediatric community and in frame around the thigh were a larger ring may increase the strut angle

The previous bioabsorbable plates have had several issues with regard to clinical usage for fractures. The aims of this study were to demonstrate the clinical results of novel bioabsorbable plates made of hydroxyapatite/poly-L-lactide and titanium plates for metacarpal fractures and to compare mechanical properties of them in a fracture model. The subjects were 33 metacarpal diaphyseal fractures of 27 consecutive patients treated with bioabsorbable plates. The mean age was 35.8 (17–78), 22 male and 5 female was included. The mean follow up period was 7.4months (2–14). All cases achieved bone union, and there were no complication especially for aseptic swelling etc. Furthermore, we compared the mechanical properties of bioabsorbable and titanium plates. There were no significant differences in 6 month postoperative clinical results including total range of active motion and % of the contralateral grip strength between patients receiving bioabsorbable and titanium plates. The bending strength and stiffness of one-third tubular bioabsorbable plate constructs were comparable with those of titanium plates for 1.5mm screws, and those of semi-tubular bioabsorbable plates were comparable with those of titanium plates for 2.0mm screws. The torsional strength of semi-tubular bioabsorbable plates was significantly greater than that of titanium plates for 2.0mm screws

Despite proven advantages, pulsatile lavage seems to be used infrequently during preparation in cemented total knee arthroplasty. This remains irritating, as the technique has been suggested to improve radiological survival in cemented TKA, where aseptic loosening of the tibial component represents the main reason for revision. Furthermore, there may be a potential improvement of fixation strength for the tibial tray achieved by increased cement penetration. In this study, the influence of pulsed lavage on mechanical stability of the tibial component and bone cement penetration was analyzed in a cadaveric setting. Six pairs of cadaveric, proximal tibia specimen underwent computed tomography (CT) for assessment of bone mineral density (BMD) and exclusion of osseous lesions. Following surgical preparation, in one side of a pair, the tibial surface was irrigated using 1800ml normal saline and pulsatile lavage, while in the other side syringe lavage using the identical amount of fluid was applied. After careful drying, bone cement was hand-pressurized on the bone surface, tibial components were inserted and impacted in an identical way. After curing of cement, specimen underwent a postimplantation CT analysis). Cement distrubution was then assessed using a three-dimenionsional visualization software. Trabecular bone, cement and implant were segmented based on an automatic thresholding algorithm, which had been validated in a previous study. This allowed to determine median cement penetration for the entire cemented area. Furthermore, fixation strength of the tibial trays was determined by a vertical pull-out test using a servohydraulic material testing machine. Testing was performed under displacement control at a rate of 0,5mm/sec until implant failure. Data was described by median and range. Results were compared by a Wilcoxon matched pairs signed rank test with a type 1 error probability of 5 %. Median pull-out forces in the pulsed lavage group were 1275N (range 864–1391) and 568N (range 243–683) in the syringe lavage group (p=0.031). Cement penetration was likewise increased (p=0.031) in the pulsed lavage group (1.32mm; range 0.86–1.94), when compared to the syringe irrigated group (0.79mm; range 0.51–1.66). Failure occurred in the pulsatile lavage group at the implant-cement interface and in the syringe lavage group at the bone-cement interface, which indicates the weakness of the latter. Altogether, improved mechanical stability of the tibial implant and likewise increased bone cement interdigitation could be demonstrated in the current study, when pulsed lavage is implemented. Enhanced fixation strength was suggested being a key to improved survival of the implant. If this is the case, pulsatile lavage should be considered being a mandatory preparation step when cementing tibial components in TKA

The ratio of the incidence of trochanteric to cervical fractures increased with age in the elderly female population, but the reason for this fact remain unclear. The purposes of this study were to investigate whether or not there are specificities of the local distribution of mechanical properties at the trochanteric region of the elderly female using a scanning acoustic microscope (SAM). Human proximal femurs were harvested from seven female cadavers (67–88 years) and proximal femur was coronally sectioned into halves across the center of neck. The surface of the coronal section was polished in order to achieve flat surfaces of smoothness well below the surface resolution in scanning with SAM. Bone tissue density and elastic modulus were calculated from the acquired SAM data. Mechanical properties were measured at the lateral and medial trochanter. Cortical bone tissue of the lateral trochanter had significantly lower elastic modulus than that of the medial trochanter in the all specimen over 70s(p<0.05). Trabecular bone tissue of proximal region of the lateral trochanter had significantly lower elastic modulus than that of distal region in all 80s specimens (p<0.05). Decrease of the elastic modulus of cortical bone in the lateral trochanter and low value of the elastic modulus of trabecular bone in the proximal region of the lateral trochanter may be related to the increase of the ratio of trochanteric to cervical fractures with age in the elderly female population

The most important issue in the assessment of fracture healing is to acquire information about the restoration of the mechanical integrity of bone. Many researchers have attempted to monitor stiffness either directly or indirectly for the purpose of assessing strength, as strength has been impossible to assess directly in clinical practice. The purpose of this study was thus to determine the relationship between bending stiffness and strength using mechanical testing at different times during the healing process. Unilateral, transverse, mid-tibial osteotomies with a 2-mm gap were performed in 28 rabbits. The osteotomy site was stabilized using a double-bar external fixator. The animals were divided into four groups (n=7/group/time point; 4, 6, 8 and 12 weeks). A series of images from micro-computed tomography of the gap was evaluated to detect the stage of fracture healing and a 4-point bending test was performed to measure stiffness and strength. Formation of cortex and medullary canal at the gap was seen in the 12-week group and would represent the remodeling stage. In addition, the relationship between stiffness and strength remained almost linear until at least 12 weeks. However, stiffness recovered much more rapidly than strength. Strength was not fully restored until the later stages of fracture healing. However, the current study demonstrated that stiffness could be monitored as a surrogate marker of strength until at least the remodeling stage

Improving periprosthetic bone is essential for implant fixation and reducing peri-implant fracture risk. This studied examined the individual and combined effects of iPTH and mechanical loading at the cellular, molecular, and tissue level for periprosthetic cancellous bone. Adult rabbits had a porous titanium implant inserted bilaterally on the cancellous bone beneath a mechanical loading device on the distal lateral femur. The right femur was loaded daily, the left femur received a sham loading device, and half of the rabbits received daily PTH. Periprosthetic bone was processed up to 28 days for qPCR, histology, and uCT analysis. We observed an increase in cellular and molecular markers of osteoblast activity and decrease in adipocytic markers for both treatments, with small additional effects in the combined group. Loading and iPTH led to a decrease and increase, respectively, in osteoclast number, acting through changes in RANKL/OPG expression. Changes in SOST and beta-catenin mRNA levels suggested an integral role for the Wnt pathway. We observed strong singular effects on BV/TV of both loading (1.53 fold) and iPTH (1.54 fold). Combined treatment showed a small additive effect on bone volume. In conclusion, loading and iPTH act through a pro-osteoblastic/anti-adipocytic response and through control of bone turnover via changes in the RANKL/OPG pathway. These changes led to a small additional, but not synergistic, increase in bone volume with the combined therapy

Introduction. Short-segment posterior instrumentation for spine fractures is threatened by unacceptable failure rates. Two important design objectives of pedicle screws, bending and pullout strength, may conflict with each other. Hypothesis. Multiobjective optimization study with artificial neural network (ANN) algorithm and genetic algorithm (GA). Materials & Methods. Three-dimensional finite element (FE) methods were applied to investigate the optimal designs of pedicle screws with an outer diameter of 7 mm using a multiobjective approach for these two objectives. Based on the FE results on an L25 orthogonal array, two objective functions were developed by an ANN algorithm. Then, the trade-off solutions known as Pareto optima were explored by a GA. The optimal design was validated by mechanical tests. Results. The knee solutions of the Pareto fronts had simultaneous high bending and pullout strength ranging from 92 to 94 percent of their maxima. The corresponding range of the design parameters was 3.8 to 4.06 mm for inner diameter and 3.21 to 3.3 mm for pitch; 0 mm for beginning position of conical angle, 0.4 mm for proximal root radius, 5 degrees for proximal half angle, and 0.1 mm for thread width. The optimal design was well validated by mechanical tests, comparing with commercially available pedicle screws. Discussion & Conclusions. The optimal design of pedicle screws obtained could achieve an ideal with high mechanical performance in both bending and pullout tests

The most important issue in the assessment of fracture healing is to acquire information about the restoration of the mechanical integrity of bone. Echo tracking (ET) can noninvasively measure the displacement of a certain point on the bone surface under a load. Echo tracking has been used to assess the bone deformation angle of the fracture healing site. Although this method can be used to evaluate bending stiffness, previous studies have not validated the accuracy of bending stiffness. The purpose of the present study is to ensure the accuracy of bending stiffness as measured by ET. A four-point bending test of the gap-healing model in rabbit tibiae was performed to measure bending stiffness. Echo tracking probes were used to measure stiffness, and the results were compared with results of stiffness measurements performed using laser displacement gauges. The relationship between the stiffness measured by these two devices was completely linear, indicating that the ET method could precisely measure bone stiffness

Introduction. In order to prepare hamstring autograft, suture fixation to the tendon is required to secure and handle the tendon during harvest and preparation. We use a simple, grasping suture which doesn't require suture of the tendon, thus saving time and avoiding violation of the graft itself. We present this technique, with results of mechanical testing compared to a standard whip suture, traditionally used to handle hamstring autograft. Methods and materials. Twelve uniform ovine flexor tendons were prepared. A number two braided polyester suture was used in all cases. Six tendons were prepared with a standard, non-locking whip-suture, maintaining uniformity of suture bite and working length between samples. Six tendons were prepared with the utility suture, also taking care to maintain uniformity. The suture was applied by tying the thread around the tendon with a single-throw granny knot then symmetrically wrapping the suture ends from proximal to distal and securing with another single throw, allowing compression of the tendon with longitudinal tension on the suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Peak load values and load/displacement curves were acquired and results analysed with a two-sample T-test assuming significance at P<0.05. Results. Modes of failure between the groups, as characterised by the load/displacement curves were quite distinct. Peak load to failure was lower in the utility suture group but all failures occurred when the suture snapped. Thus the peak load to failure of the suture/tendon construct exceeded the breaking strain of the suture material. Conclusion. The grasping utility suture described here is sufficiently strong to harvest and handle hamstring autograft without passing a needle through the graft, saving time and avoiding violation of the graft itself. The lower loads at failure, despite failure occurring due to suture snapping, may reflect differing knot orientation between groups

Aim

To investigate the biomechanical behaviours of the TL-Hex & Taylor Spatial Frame (TSF) Hexapod external fixators, with comparison to traditional ring-fixator constructs.

Exercise deters systemic diseases such as osteoporosis, sarcopenia, diabetes and obesity. Brief daily periods of low intensity vibration (LIV; <0.4g) is anabolic to bone and muscle, an adaptive response achieved in part by biasing mesenchymal stem cell (MSC) fate selection towards forming higher order connective tissues. In the clinic, LIV has protected the musculoskeletal system even under severe challenges such as Crohn Disease, Cerebral Palsy, and end-stage renal disease. Low magnitude mechanical signals also suppress adipogenesis in the mouse, with reductions in subcutaneous and visceral fat. The starkly distinct response of these tissues (augment bone & muscle; suppress fat) suggests that LIV influences the differentiation pathway of MSCs. Extending this diet induced obesity model to 7 months increased total adiposity, accelerated age-related loss of trabecular bone and severely reduced B & T-cell number in the marrow and blood, shifting hematopoietic stem cells (HSC) towards the myeloid lineage. LIV introduced at 4 months rescued bone and B-cells to those levels measured in regular diet controls. These data emphasise why inactivity can promote osteoporosis, diabetes and obesity, and why a sedentary individual is predisposed to disease sequelae. Protection of MSC and HSC populations by mechanical signals may represent a unique strategy by which adiposity can be suppressed, the immune system protected, and a musculoskeletal system enhanced

Introduction

The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.

Introduction

Total leg muscle function in hip OA patients is not well studied. We used a test-retest protocol to evaluate the reproducibility of single- and multi-joint peak muscle torque and rapid torque development in a group of 40–65 yr old hip patients. Both peak torque and torque development are outcome measures associated with functional performance during activities of daily living.

This study compares outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual lag screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Technical factors associated with mechanical failure were also identified. All adult patients (>18yrs) with a subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Included patients underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022). Cox regression analysis was used to determine the risk of mechanical failure and technical predictors of failure. The study included 587 patients, 336 in the GN group (median age 82yrs, 73% female) and 251 in the IN group (median age 82yrs, 71% female). The IN group exhibited a higher prevalence of osteoporosis (p=0.002) and CKD□3 (p=0.007). There were no other baseline differences between groups. The risk of any mechanical failure was increased two-fold in the GN group (HR 2.51, p=0.020). Mechanical failure comprising screw cut-out (p=0.040), back-out (p=0.040) and nail breakage (p=0.51) was only observed in the GN group. The risk of peri-implant fracture was similar between the groups (HR 1.10, p=0.84). Technical predictors of mechanical included varus >5° for cut-out (HR 15.61, p=0.016), TAD>25mm for back-out (HR 9.41, p=0.020) and shortening >1cm for peri-implant fracture (HR 6.50, p=<0.001). Dual lag screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures

This study aimed to assess the outcomes of patients with complex rib fractures undergoing operative or non-operative management at our center over a six-year time period. Retrospective analysis was performed to identify all patients with complex rib fractures at our center from May 2016 to September 2022. Outcome measures included mechanical ventilation, tracheostomy, pneumonia, and mortality at one year. 388 patients with complex rib fractures were identified. 37 (10%) patients fulfilled criteria for surgical management and underwent rib fracture fixation; 351 patients were managed non-operatively with anaesthetic block or analgesia alone. The fixation group had a significantly higher proportion of patients with flail chest (30 (81%) vs 94 (27%), p<0.001) and were significantly more likely to require ICU admission (30 (81%) vs. 16 (5%), p<0.001) than the non-operative group. At one year follow-up, no significant differences were seen for mortality between these groups (1 (3%) vs. 27 (7%), p=0.276). Of the surgical management group, those that underwent fixation <72 hours post injury were significantly less likely to develop pneumonia than those who were delayed >72 hours (2 (18%) vs 15 (58%), p=0.038), with downward trends noted for ICU length of stay (6 vs 10 days, p=0.140) and duration of mechanical ventilation (5 vs 8 days, p=0.177); no significant differences were seen for tracheostomy (3 vs. 5, p=0.588) or mortality (0 vs 1, p=0.856). Surgical fixation of complex rib fractures improves outcomes in selected patient groups. Early surgical fixation led to reduced rates of pneumonia and may improve other outcome measures

Restoration of native Coronal Plane Alignment of the Knee (CPAK) phenotype is a strategy suggested to achieve better satisfaction. The aim of this study was to investigate the influence of changes in CPAK classification on patient-reported outcome measures (PROMs) and survivorship in a large cohort of manual mechanically aligned (MA) cemented TKAs. A retrospective analysis of 1062 consecutive cemented TKAs using MA philosophy at a single institution. Pre- and post-operative hip-knee-ankle radiographs were classified using the CPAK classification. Oxford Knee Score (OKS) and patient satisfaction (4-point-Likert scale) were collected prospectively. Implant survival data was obtained from our national arthroplasty database. We compared the outcomes of patients who maintained or changed their CPAK classification following TKA. Satisfaction was analysed using chi-square test, and OKS was analysed using Mann-Whitney test. Pre-operatively, most patients were CPAK type-I (38.8%). 85.5% of patients changed their CPAK type post-operatively, with CPAK type-V observed in 41.2% of these. Significantly better satisfaction (p=0.033) and OKS (p=0.021) were observed at one-year follow-up in patients who changed CPAK type, although the difference was below OKS minimally important clinical difference. There was no difference in satisfaction (p=0.73) and OKS (p=0.26) at one year between CPAK-V and non-V classifications. Post-operative CPAK type had no correlation with satisfaction and OKS. 12 TKAs (1.1%) were revised within 10 years (3 septic). In this large cohort of MA-TKA, excellent survivorship was observed at 10 years, with no demonstrable difference in outcome related to the final CPAK phenotype or change in phenotype