Background The aim of this study was to compare the fit of two femoral nail designs with a 100 cm and 150 cm radius of curvature (RoC) and examine the implant deformation as surrogate measure for fit within the femoral canal. Methods Seven paired fresh-frozen human cadaveric femurs were investigated by insertion of either a long Trochanteric Femoral Nail - ADVANCED Proximal Femoral Nailing System (TFNA) or a Proximal Femoral Nail Antirotation System (PFNA) with an RoC of the nails 100 cm and 150 cm, respectively. Nails stiffness was measured before insertion via 3-point bending. Nail fit and deflection were analysed using computed tomography scans before nail insertion, after full intramedullary insertion and its rotational alignment with the femoral neck axis. Findings Bending stiffness of the two nail types was similar (P = 0.308). A significantly higher deflection of PFNA versus TFNA was detected post insertion and rotational alignment (P = 0.037) with proximal nail end registration only, and trend wise higher when registering both nail ends (P = 0.070). Deflection after compared to the pre-rotational alignment state was large for both nails, but not significant for both registration techniques (P ≥ 0.270). Interpretation Although bending stiffness of both nails was similar, the larger RoC of the PFNA resulted in significantly bigger deflection in comparison to TFNA before and after final rotational alignment of the nail with the femoral neck axis. This suggests that an implant with a 100 cm RoC more closely reflects the femoral anatomy.

BACKGROUND:Intramedullary nailing is the standard treatment method of femoral shaft fractures with generally satisfying results. However, recent clinical studies reported a possible radius of curvature (RoC) mismatch between treated femora and existing intramedullary implants. The aim of this biomechanical study was to compare the anatomical fit of two femoral nail designs with a 100 cm and 150 cm RoC and examine the implant deflection as a surrogate measure for the fit within the medullary canal. METHODS:Seven paired fresh-frozen human cadaveric femora were investigated by insertion of either a long Trochanteric Femoral Nail - ADVANCED Proximal Femoral Nailing System (TFNA) or a long Proximal Femoral Nail Antirotation System (PFNA) with RoCs of the nails 100 cm and 150 cm, respectively. Nails stiffness was measured before insertion via three-point bending. Nail anatomical fit and deflection were analysed using computed tomography scans before insertion and then at full insertion before and after axial rotation of the nail for alignment of the proximal locking element axis with the femoral neck axis and the centre of the femoral head. FINDINGS:Bending stiffness of the two nail types was similar (P = 0.308). A significantly higher deflection of PFNA versus TFNA was detected at full insertion with axial rotational nail alignment when proximal nail end registration was applied (P = 0.043), and trend wise higher when both ends registration was implemented (P = 0.063). INTERPRETATION:Although the bending stiffness of both intramedullary nails was similar, the larger RoC of the PFNA resulted in significantly bigger deflection in comparison to TFNA at full insertion before and after final axial rotation of the nail for alignment of the proximal locking element axis with the femoral neck axis and the centre of the femoral head. This suggests that an implant with a 100 cm RoC reflects better the femoral anatomy.

The management of fracture-related infection (FRI) with Debridement, Antibiotics, Irrigation, and Implant Retention (DAIR) is an appealing option, but its suitability is restricted to a relatively narrow proportion of patients. This study aimed to create a large animal model of DAIR after FRI and to evaluate outcomes after early (2 weeks) and delayed (5 weeks) DAIR. Additionally, intramedullary lavage (IML) of the intramedullary canal (IMC) is introduced as a novel technique to remove infected tissue. Our findings showed that DAIR failed to resolve infections in both early and delayed groups, whilst IML significantly reduced bacterial counts, leading to culture-negative results in the soft tissue and bone marrow. IML did not compromise long-term bone healing as revealed by an implant load sensor on the plate. In conclusion, DAIR was successfully achieved in a new large animal model with minimal losses. The IML method improves treatment efficacy, potentially broadening the range of patients suitable for DAIR.

The postoperative assessment of fracture healing remains a clinical challenge despite established treatment standards. The lack of reliable information on the mechanical stability of the fracture complicates individualized follow-up care. This increases the risk of delayed mobilization, implant overload or late detection of healing complications.Sensor-based implants, such as the AO Fracture Monitor enable objective, continuous measurement of implant load, offering a novel approach to evaluating the healing process. Preclinical studies demonstrate a significant correlation between mechanical load and radiological healing parameters, confirming the potential of instrumented implants for diagnostic and preventive applications. Initial clinical data are currently being collected as part of a multicenter study. Additional application areas, such as spinal fusion and hip fracture treatment are the focus of ongoing research and commercial development efforts.Continuous data acquisition enables uninterrupted remote monitoring, independent of scheduled follow-up examinations. This opens new possibilities for dynamic adjustment of treatment protocols, early detection of complications and targeted rehabilitation management; however, integrating such systems into routine clinical practice poses substantial regulatory and procedural challenges. Current studies therefore provide an essential foundation for the gradual establishment of personalized follow-up strategies in routine clinical care.

Die postoperative Beurteilung der Frakturheilung stellt trotz etablierter Behandlungsstandards weiterhin eine klinische Herausforderung dar. Mangels verfügbarer belastbarer Informationen zur mechanischen Stabilität der Fraktur ist eine individuell optimierte Nachsorge erschwert. Dies birgt das Risiko einer verzögerten Mobilisation oder einer Überlastung des Implantats sowie eines verspäteten Erkennens von Heilungskomplikationen. Sensorbasierte Implantate wie der AO-Frakturmonitor ermöglichen eine objektive, kontinuierliche Erfassung der Implantatbelastung und bieten einen neuartigen Zugang zur Bewertung des Heilungsverlaufs. Präklinische Studien belegen eine signifikante Korrelation zwischen mechanischer Belastung und radiologischen Heilungsparametern und bestätigen das Potenzial instrumentierter Implantate für diagnostische und präventive Anwendungen. Erste klinische Daten werden derzeit im Rahmen einer multizentrischen Studie erhoben. Weitere Anwendungsfelder wie die spinale Fusion oder die Versorgung von Hüftfrakturen sind Gegenstand laufender Forschungs- und Entwicklungsaktivitäten. Die kontinuierliche Datenerhebung erlaubt ein lückenloses Remote Monitoring – unabhängig von zeitlich limitierten Kontrolluntersuchungen. Dies eröffnet neue Möglichkeiten zur dynamischen Anpassung von Therapieschemata, zur frühzeitigen Detektion von Komplikationen und zur gezielten Steuerung der Rehabilitation. Die Integration solcher Systeme in die klinische Routine ist jedoch mit erheblichen regulatorischen und prozessualen Herausforderungen verbunden. Die in der Durchführung befindliche Studie bildet eine essenzielle Grundlage für die schrittweise Etablierung personalisierter Nachsorgekonzepte im klinischen Alltag.

PURPOSE:This study investigated the formation of fracture repair tissue in response to 2.5-25% strain magnitudes under immediate and delayed loading in a large animal model with monotonically increasing interfragmentary strain. METHODS:Experimental osteotomies were created in ten sheep and were instrumented with an active fixator that generated a gradient (2.5-25%) of interfragmentary strain across the osteotomy. Sheep were randomly assigned to an immediate-loading (from day 1 post-surgery) group or a delayed-loading (from day 22 post-surgery) group. Five weeks post-surgery, the tibiae were scanned using high-resolution computed tomography (CT). CT images were subsequently sliced at different strain levels. For each two-dimensional slice, we evaluated the area and density of fracture repair tissue within the osteotomy and the radial span of the periosteal tissue. Repeated-measures ANOVA tested the effects of strain magnitude and loading protocol on these parameters. RESULTS:The area and density of osteotomy repair tissue were highest at 2.5% of strain for both groups and significantly decreased when strain increased (p ≤ 0.015). In contrast, periosteal tissue span increased with strain (p < 0.001) and was significantly larger in the immediate-loading group (p < 0.01). CONCLUSION:Our study demonstrates the combined effect of strain (2.5-25%) and the timing of loading on bone healing. We observed two strain-related healing responses: up to ~ 7.5% strain, callus formed between the cortices, while higher strain shifted calcified repair tissue toward external callus. In this experimental model, strains below 25% provided a potent healing environment when stimulation was applied during the early healing stage.

This study investigated the formation of fracture repair tissue in response to 2.5–25

Freehand distal interlocking of intramedullary nails remains a challenging task. Recently, a new training device for digitally enhanced hands-on surgical training (DEHST) was introduced, potentially improving surgical skills needed for distal interlocking. To evaluate whether training with DEHST enhances the performance of novices (first-year residents without surgical experience in freehand distal nail interlocking). Twenty novices were randomly assigned to two groups and performed distal interlocking of a tibia nail in mock operation under operation-room-like conditions. Participants in Group 1 were trained with DEHST (five distal interlocking attempts, 1 h of training), while those in Group 2 did not receive training. Time, number of X-rays shots, hole roundness in the X-rays projection and hit rates were compared between the groups. Time to complete the task [414.7 s (range 290–615)] and X-rays exposure [17.8 µGcm2 (range 9.8–26.4)] were significantly lower in Group 1 compared to Group 2 [623.4 s (range 339–1215), p = 0.041 and 32.6 µGcm2 (range 16.1–55.3), p = 0.003]. Hole projections were significantly rounder in Group 1 [95.0

Osteosynthesis aims to maintain fracture reduction until bone healing occurs, which is not achieved in case of mechanical fixation failure. One form of failure is plastic plate bending due to overloading, occurring in up to 17% of midshaft fracture cases and often necessitating reoperation. This study aimed to replicate in-vivo conditions in a cadaveric experiment and to validate a finite element (FE) simulation to predict plastic plate bending.Six cadaveric bones were used to replicate an established ovine tibial osteotomy model with locking plates in-vitro with two implant materials (titanium, steel) and three fracture gap sizes (30, 60, 80 mm). The constructs were tested monotonically until plastic plate deformation under axial compression. Specimen-specific FE models were created from CT images. Implant material properties were determined using uniaxial tensile testing of dog bone shaped samples. The experimental tests were replicated in the simulations. Stiffness, yield, and maximum loads were compared between the experiment and FE models.Implant material properties (Young's modulus and yield stress) for steel and titanium were 184 GPa and 875 MPa, and 105 GPa and 761 MPa, respectively. Yield and maximum loads of constructs ranged between 469–491 N and 652–683 N, and 759–995 N and 1252–1600 N for steel and titanium fixations, respectively. FE models accurately and quantitatively correctly predicted experimental results for stiffness (R2=0.96), yield (R2=0.97), and ultimate load (R2=0.97).FE simulations accurately predicted plastic plate bending in osteosynthesis constructs. Construct behavior was predominantly driven by the implant itself, highlighting the importance of modelling correct material properties of metal. The validated FE models could predict subject-specific load bearing capacity of osteosyntheses in vivo in preclinical or clinical studies.Acknowledgements: This study was supported by the AO Foundation via the AOTRAUMA Network (Grant No.: AR2021_03).

Introduction: The management of fractured bones is a key domain within orthopedic trauma surgery, with the prevention of delayed healing and non-unions forming a core challenge. This study evaluates the efficacy of the AO Fracture Monitor in conjunction with biomechanical simulations to better understand the local mechanics of fracture gaps, which is crucial for comprehending mechanotransduction, a key factor in bone healing. Through a series of experiments and corresponding simulations, the study tests four hypotheses to determine the relationship between physical measurements and the predictive power of biomechanical models.Methods: Employing the AO Fracture Monitor and Digital Image Correlation techniques, the study demonstrates a significant correlation between the surface strain of implants and interfragmentary movements. This provides a foundation for utilizing one-dimensional AO Fracture Monitor measurements to predict three-dimensional fracture behavior, thereby linking mechanical loading with fracture gap dynamics. Moreover, the research establishes that finite element simulations of bone-implant systems can be effectively validated using experimental data, underpinning the accuracy of simulations in replicating physical behaviors.Results and Discussion: The findings endorse the combined use of monitoring technologies and simulations to infer the local mechanical conditions at the fracture site, offering a potential leap in personalized therapy for bone healing. Clinically, this approach can enhance treatment outcomes by refining the assessment precision in trauma trials, fostering the early detection of healing disturbances, and guiding improvements in future implant design. Ultimately, this study paves the way for more sophisticated patient monitoring and tailored interventions, promising to elevate the standard of care in orthopedic trauma surgery.

In absence of available quantitative measures, the assessment of fracture healing based on clinical examination and X-rays remains a subjective matter. Lacking reliable information on the state of healing, rehabilitation is hardly individualized and mostly follows non evidence-based protocols building on common guidelines and personal experience. Measurement of fracture stiffness has been demonstrated as a valid outcome measure for the maturity of the repair tissue but so far has not found its way to clinical application outside the research space. However, with the recent technological advancements and trends towards digital health care, this seems about to change with new generations of instrumented implants – often unfortunately termed “smart implants” – being developed as medical devices.The AO Fracture Monitor is a novel, active, implantable sensor system designed to provide an objective measure for the assessment of fracture healing progression (1). It consists of an implantable sensor that is attached to conventional locking plates and continuously measures implant load during physiological weight bearing. Data is recorded and processed in real-time on the implant, from where it is wirelessly transmitted to a cloud application via the patient's smartphone. Thus, the system allows for timely, remote and X-ray free provision of feedback upon the mechanical competence of the repair tissue to support therapeutic decision making and individualized aftercare.The device has been developed according to medical device standards and underwent extensive verification and validation, including an in-vivo study in an ovine tibial osteotomy model, that confirmed the device's capability to depict the course of fracture healing as well as its long-term technical performance. Currently a multi-center clinical investigation is underway to demonstrate clinical safety of the novel implant system. Rendering the progression of bone fracture healing assessable, the AO Fracture Monitor carries potential to enhance today's postoperative care of fracture patients.

Bone fracture healing is a complex physiological process influenced by biomechanical and biomolecular factors. Mechanical stability is crucial for successful healing, and disruptions can lead to delayed healing or nonunion. Bone commonly heals itself through secondary fracture healing, which is governed by the mechanical strain at the fracture site. To investigate these phenomena, a validated methodology for capturing the mechanoregulatory process in specimen-specific models of fracture healing could provide insight into the healing process. This study implemented a prognostic healing simulation framework to predict healing trajectories based on mechanical stimuli. Sixteen sheep were subjected to a 3 mm transverse tibial mid-shaft osteotomy, stabilized with a custom plate, and equipped with displacement transducer sensors to measure interfragmentary motion over 8 weeks. Computed tomography scans were used to create specimen-specific bone geometries for finite element analysis. Virtual mechanical testing was performed iteratively to calculate strains in the callus region, which guided tissue differentiation and consequently, healing. The predicted healing outcomes were compared to continuous in vivo sensor data, providing a unique validation data set. Healing times derived from the in vivo sensor and in silico sensor showed no significant differences, suggesting the potential for these predictive models to inform clinical assessments and improve nonunion risk evaluations. This study represents a crucial step towards establishing trustworthy computational models of bone healing and translating these to the preclinical and clinical setting, enhancing our understanding of fracture healing mechanisms. Clinical significance: Prognostic bone fracture healing simulation could assist in non-union diagnosis and prediction.

Reliable and timely assessment of bone union between vertebrae is considered a key challenge after spinal fusion surgery. Recently, a novel sensor concept demonstrated the ability to objectively assess posterolateral fusion based on continuous implant load monitoring. The aim of this study was to investigate systematically the concept in a mono-segmental fusion model using an updated sensor setup. Three sheep underwent bilateral facetectomy at level L2-L3 and L4-L5. The segments were stabilized using two unconnected pedicle-screw-rod constructs per level. Sensing devices were attached to the rods between each pedicle screw pair and the loads were continuously monitored over 16 weeks. After euthanasia, the spines were biomechanically tested for their range of motion and high-resolution CT scans were performed to confirm the fusion success. After an initial increase in implant load until reaching a maximum (100 %) at approximately week 4, eleven out of twelve sensors measured a constant decrease in implant load to 52 +/- 9 % at euthanasia. One sensor measurement was compromised by newly forming bone growing against the sensor clamp. Bridging bone at each facet and minor remnant segmental motion (<0.7 degrees) confirmed the fusion of all motion segments. Data obtained by continuous measurement of implant loading of spinal screw-rod constructs enables objective monitoring of spinal fusion progression. The sensor concept provides valuable real-time information, offering quantifiable data as an alternative to traditional imaging techniques. However, the design of the current sensor concept needs to be matured, tailored to, and validated for the human spine.

Background: Locked plating for distal femur fractures is widely recommended and used. We systematically reviewed clinical studies assessing the benefits and harms of fracture fixation with locked plates in AO/OTA Type 32 and 33 femur fractures. Methods: A comprehensive literature search of PubMed, Embase, Cinahl, Web of Science, and the Cochrane Database was performed. The studies included randomized and non-randomized clinical trials, observational studies, and case series involving patients with distal femur fractures. Studies of other fracture patterns, studies conducted on children, pathological fractures, cadaveric studies, animal models, and those with non-clinical study designs were excluded. Results: 53 studies with 1788 patients were found to satisfy the inclusion and exclusion criteria. The most common harms were nonunion (14.8%), malunion (13%), fixation failure (5.3%), infection (3.7%), and symptomatic implant (3.1%). Time to full weight-bearing ranged from 5 to 24 weeks, averaging 12.3 weeks. The average duration of follow-up was 18.18 months, ranging from 0.5 to 108 months. Surgical time ranged between 40 and 540 min, with an average of 141 min. The length of stay in days was 12.7, ranging from 1 to 61. The average plate length was ten holes, ranging from 5 to 20 holes. Conclusion: This review aimed to systematically synthesize the available evidence on the risk associated with locked plating osteosynthesis in distal femur fractures. Nonunion is the most common harm and is the primary cause of reoperation. The overall combined risk of a major and critical complication (i.e., requiring reoperation) is approximately 20%.

Freehand distal interlocking of intramedullary nails remains a challenging task. If not performed correctly it can be a time consuming and radiation expensive procedure. Recently, the AO Research Institute developed a new training device for Digitally Enhanced Hands-on Surgical Training (DEHST) that features practical skills training augmented with digital technologies, potentially improving surgical skills needed for distal interlocking. Aim of the study: To evaluate weather training with DEHST enhances the performance of novices without surgical experience in free-hand distal nail interlocking compared to a non-trained group of novices. 20 novices were assigned in two groups and performed distal interlocking of a tibia nail in an artificial bone model. Group 1: DEHST trained novices (virtual locking of five nail holes during one hour of training). Group 2: untrained novices without DEHST training. Time, number of x-rays, nail hole roundness, critical events and success rates were compared between the groups. Time to complete the task (sec.) and x-ray exposure (µGcm2) were significantly lower in Group1 414.7 (290–615) and 17.8 (9.8–26.4) compared to Group2 623.4 (339–1215) and 32.6 (16.1–55.3); p=0.041 and 0.003. Perfect circle roundness (%) was 95.0 (91.1–98.0) in Group 1 and 80.8 (70.1–88.9) in Group 2; p<0.001. In Group 1 90% of the participants achieved successful completion of the task (hit the nail with the drill), whereas only 60% of the participants in group 2 achieved this; p=0.121. Training with DEHST significantly enhances the performance of novices without surgical experience in distal interlocking of intramedullary nails. Besides radiation exposure and operation time the com-plication rate during the operation can be significantly reduced.

BACKGROUND AND OBJECTIVES:Fractures of the proximal humerus are common, particularly in elderly populations. Anatomical locking plates target stabilization with a multitude of screws spanning into the humeral head. Sound implant placement and screw length determination are key for a successful clinical outcome but are difficult to obtain from planar X-rays. A novel implant positioning technology for proximal humerus plating (Xin1) outputs screw lengths suggestions and plate position based on hole projections in conventional X-ray images. This study investigated the performance of a prototype Xin1 system in a postmortem (in vitro) experiment as well as in a clinical handling test.MATERIALS AND METHODS:For in vitro testing, twelve shoulders from six anatomical specimens were randomized into two groups to compare the Xin1 technique to the conventional operation in terms of surgical precision, procedure time and X-ray exposure. For the clinical trial, 11 patients undergoing plating of the proximal humerus were included. The aim was to investigate clinical handling of the Xin1 marker clip and to retrospectively evaluate the system performance in a real-life fracture situation. Image pairs before and after insertion of the proximal screws were retrospectively processed to investigate the influence of potential bone fragment shifts on the system output.RESULTS:In the postmortem experiment, the use of the system significantly improved the surgical precision (52% error reduction), procedure time (38% shorter) and radiation exposure (64% less X-rays). Clinical handling demonstrated seamless embedding of the marker clip into existing clinical workflows without adverse events reported. Retrospective X-ray analysis on six eligible patients revealed differences in the calculated screw lengths of ≤2 mm before and after screw insertion for five patients. In one patient, the screw lengths differed up to 8 mm, which might indicate displacement of the head fragment.CONCLUSIONS:Results suggest a strong potential of the Xin1 assistance technology to enhance the surgical procedure and patient outcomes in the rising incidence of osteoporotic humeral fractures. Robust performance in a real-life fracture situation was observed. In-depth validation of the system is, however, needed before placing it into clinical practice.

Despite past advances of implant technologies, complication rates of fixations remain high at challenging sites such as the proximal humerus [1]. These may not only be owed to the implant itself but also to dissatisfactory surgical execution of fracture reduction and implant positioning. Therefore, the aim of this study was to quantify the instrumentation accuracy of a highly standardised and guided procedure and its influence on the biomechanical outcome and predicted failure risk. Preoperative planning of osteotomies creating an unstable 3-part fracture and fixation with a locking plate was performed based on CT scans of eight pairs of low-density proximal humerus samples from elderly female donors (85.2±5.4 years). 3D-printed subject-specific guides were used to osteotomise and instrument the samples according to the pre-OP plan. Instrumentation accuracies in terms of screw lengths and orientations were evaluated by comparing post-OP CT scans with the pre-OP plan. The fixation constructs were biomechanically tested until cyclic cut-out failure [2]. Failure risks of the planned and the post-OP configurations were predicted using a validated sample-specific finite element (FE) simulation approach [2] and correlated with the experimental outcomes. Small deviations were found for the instrumented screw trajectories compared to the planned configuration in the proximal-distal (0.3±1.3º) and anterior-posterior directions (-1.7±1.8º), and for screw tip to joint distances (-0.3±1.1 mm). Significantly higher failure risk was predicted for the post-OP compared to the planned configurations (p<0.01) via FE. When incorporating the instrumentation inaccuracies, the biomechanical results could be predicted well with FE (R 2 =0.70). Despite the high instrumentation accuracy achieved using sophisticated subject-specific 3D-printed guides, even minor deviations from the pre-OP plan significantly increased the FE-predicted risk of failure. This underlines the importance of intraoperative guiding technology [3] in tandem with careful pre-OP planning to assist surgeons to achieve optimal outcomes. Acknowledgements This study was performed with the assistance of the AO Foundation via the AOTRAUMA Network.

Freehand distal interlocking of intramedullary nails is technical demanding and prone to handling issues. It requires the surgeon to precisely place a screw through the nail under x-ray. If not performed accurately it can be a time consuming and radiation expensive procedure. The aims of this study were to assess construct and face validity of a new training device for distal interlocking of intramedullary nails. 53 participants (29 novices and 24 experts) were included. Construct validity was evaluated by comparing simulator metrics (number of x-rays, nail hole roundness, drill tip position and accuracy of the drilled hole) between experts and novices. Face validity was evaluated by means of a questionnaire concerning training potential and quality of simulated reality using a 7-point Likert scale (range 1-7). Mean realism of the training device was rated 6.3 (range 4-7) and mean training potential as well as need for distal interlocking training was rated 6.5 (range 5-7) with no significant differences between experts and novices, p≥0.236. All participants stated that the simulator is useful for procedural training of distal nail interlocking, 96% would like to have it at their institution and 98% would recommend it to their colleagues. Total number of x-rays were significantly higher for novices (20.9±6.4 vs. 15.5±5.3), p=0.003. Successful task completion (hit the virtual nail hole with the drill) was significantly higher in experts (p=0.04; novices hit: n=12; 44,4%; experts hit: n=19; 83%). The evaluated training device for distal interlocking of intramedullary nails yielded high scores in terms of training capability and realism. Furthermore, construct validity was established as it reliably discriminates between experts and novices. Participants see a high further training potential as the system may be easily adapted to other surgical task requiring screw or pin position with the help of x-rays.

Background: The impact of the nail radius of curvature, as one of the most important design features in modern femoral nails on the ease of nail removal, remains unknown. Therefore, the aim of this study was to investigate force, energy, and nail deformation of different nail designs. Methods: Nail insertion and extraction was performed on six pairs of fresh-frozen human cadaveric femora on a material testing machine with two different nail systems - Trochanter femoral nail ADVANCEDTM Nailing System with a radius of curvature of 1.0 m and Proximal Femoral Nail Antirotation System with a radius of curvature of 1.5 m. Deformation was measured after insertion (plastic and elastic deformations) and extraction (plastic deformations). Findings: The peak force during nail removal was significantly lower in the first group (274.5 +/- 130.4 N) compared to the second group (695.2 +/- 158.8 N, p = 0.001). Plastic deformation was observed in all implants, being significantly larger in the Proximal Femoral Nail Antirotation System (p = 0.027). There was a strong positive correlation between the first peak force during nail removal and nail insertion (r = 0.802, p = 0.002) as well as between extracting energy and insertion energy (r = 0.943, p < 0.001). Interpretation: The results from this study showed that a radius of curvature of 1.0 m is easier to remove from the set of cadaver femora. Furthermore, our findings support the idea of further reducing the nail radius of curvature below 1.0 m in order to more closely match the anatomy of populations with strong-bowed femora.