Opposition Transfer Using the Extensor Indicis Muscle and the Extensor Pollicis Brevis Tendon.

Purpose: This study aimed to introduce a novel technique using the extensor pollicis brevis and extensor indicis proprius tendons as power sources for thumb opposition reconstruction in cases of severe carpal tunnel syndrome (CTS) associated with thenar muscle atrophy. Furthermore, the efficacy of this novel method and the traditional Camitz technique was compared. Methods: Patients with severe CTS and thumb opposition dysfunction who underwent surgery using the novel technique (n = 7 and 9 surgeries) or the Camitz technique (n = 8 and 8 surgeries) were included in the analysis. The pre- and postoperative palmar abduction angle, thumb-ring finger opposition angle, and Kapandji score were assessed. The repeated measures analysis of variance and the Mann-Whitney U test were used for statistical analysis. Results: The novel technique was associated with a significant postoperative improvement in palmar abduction angle, thumb-ring finger opposition angle, and Kapandji score. In particular, the thumb-ring finger opposition angle of patients who underwent surgery using this technique was superior to that of patients who underwent surgery using the Camitz technique. Therefore, the novel technique was highly effective in improving thumb pronation. Conclusion: The novel technique using the extensor pollicis brevis and extensor indicis proprius tendons is promising for thumb opposition reconstruction in severe CTS cases. Unlike the traditional Camitz technique, this approach promotes stable thumb opposition function without requiring a pulley, thereby yielding satisfactory outcomes. Nevertheless, further studies with a larger sample size should be conducted to validate these findings. Type of study/level of evidence: Therapeutic 4; Surgical technique.

Relationship between Ear Temperature, Behaviour and Stress Hormones in Guinea Pigs (Cavia porcellus) during Different Interactive Activities in Zoos.

Guinea pigs (Cavia porcellus) are used for interactive activities in zoos; therefore, it is important to investigate their welfare. This study aimed to evaluate the validity of measuring the guinea pigs' body temperature of guinea pigs through the ear canal and investigate the relationship among changes in the expression of negative behavior, changes in body temperature, and changes in salivary cortisol concentration, and examine the effects of different interactive activities. In the normal interactive activities performed at the site, the decreased body temperature of pigs was observed over time. In contrast, increased body temperature was observed in excessive interactive activities, which are not recommended. Among the negative behaviors, "Head turning" and "Locomotion" increased significantly in excessive interactions compared to normal interactions, but "Head tossing" decreased significantly over time in both types of interactions. "Freezing" was observed only in excessive interactions. Salivary cortisol concentration increased significantly for all activities. Investigating the relationship between the individual expression of negative behavior and changes in body temperature and changes cortisol level made it possible to uncover the potential for inferring an animal's physiological state. Combining ear temperature monitoring and behavioral observation during zoo interaction activities is recommended as an ethical and scientifically supported practice.

Long-term changes in bone mineral density following adolescent idiopathic scoliosis surgery: a minimum 34-year follow-up.

PURPOSE: To investigate longitudinal changes in bone mineral density (BMD) in middle-aged female patients who underwent spinal fusion for adolescent idiopathic scoliosis (AIS). METHODS: The study subjects were 229 female patients who were diagnosed with AIS and underwent spinal fusion between 1968 and 1988. A two-step survey study was conducted on 19 female AIS patients. BMD, Z-scores, T-scores, and the prevalence of osteoporosis and osteopenia were compared between the initial (2014-2016) and second (2022) surveys. Correlations between the annual changes in Z-scores and T-scores with radiographic parameters, body mass index (BMI), and the number of remaining mobile discs were analyzed. RESULTS: BMD decreased significantly from the initial (0.802 ± 0.120 g/cm2) to the second survey (0.631 ± 0.101 g/cm2; p < 0.001). Z-scores decreased from 0.12 ± 1.09 to - 0.14 ± 1.04, while T-scores decreased significantly from - 0.70 ± 1.07 to - 1.77 ± 1.11 (p < 0.001). The prevalence of osteopenia and osteoporosis increased significantly from 36.8% to 89.5% (p = 0.002), but the increase in osteoporosis alone was not statistically significant (5.3% to 26.3%; p = 0.180). Moderate negative correlations were found between annual changes in Z-scores and both main thoracic (MT) curve (r = - 0.539; p = 0.017) and lumbar curve (r = - 0.410; p = 0.081). The annual change in T-scores showed a moderate negative correlation with the MT curve (r = - 0.411; p = 0.081). CONCLUSION: Significant reductions in BMD and an increased prevalence of osteopenia and osteoporosis were observed in middle-aged female AIS patients who had undergone spinal fusion. The decline in Z-scores in patients with AIS suggested that there was an accelerated loss of BMD compared with the general population. Larger residual curves could pose an added osteoporosis risk. Further research is needed to understand if the onset of osteoporosis in AIS patients is attributable to the condition itself or the surgical intervention.

Combined effect of DBM, PRP, and bone marrow fluid on bone union in a rat posterolateral fusion model.

Platelet-rich plasma (PRP) promotes bone union through osteoinduction. We investigated whether adding demineralized bone matrix (DBM), derived naturally from biomaterial and with various growth factors, for osteoconductivity and bone marrow fluid for osteogenesis results in different bone unions. Eight-week-old male Sprague-Dawley rats were divided into four groups of five based on transplantation material: sham control (C group); DBM alone (D group); DBM + PRP (DP group); and DBM + PRP + bone marrow fluid (DPB group). After posterolateral fusion at L3-5, postoperative weekly CT imaging determined average number of bone union in facet joints (4 joints × 5 animals = 20 joints) and bone formation. Pathological evaluation and bone strength were assessed using 3-point bending two weeks postoperatively. Facet joint bone union at four weeks postoperatively was 4/20 (20%, DP group) and 8/20 (40%, DPB group) joints. Six weeks postoperatively, it was 7/20 (35%, D group), 12/20 (60%, DP group), and 16/20 (80%, DPB group). Eight weeks postoperatively, it was 13/20 (65%, D group), 17/20 (85%, DP group), and 20/20 (100%, DPB group), suggesting that DPB > DP > D > C. Bone formation and bone strength showed a similar DPB > DP > D > C group trend. Adding PRP and bone marrow fluid to DBM promotes bone union and strength.

Radioulnar Instability and Ulnar Stump Stabilization in Distal Radio Ulnar Joint Arthritis: A Cadaver Study.

BACKGROUND: Salvage procedures for distal radioulnar joint (DRUJ) arthritis, like the Darrach or Sauvé-Kapandji (S-K) procedures, often result in extensor tendon ruptures at the ulnar stump. Radioulnar instability is considered the underlying cause and stump stabilization techniques are employed. This study investigated radioulnar instability, extensor tendon irritation, and the effectiveness of stump stabilization techniques following salvage procedures. METHODS: Six upper limbs from three cadavers were used. Forearm rotation was measured using magnetic position sensors to assess radial movement. The Darrach procedure was performed on two limbs, comparing radial motion ranges for different ulnar osteotomy positions. The risk of tendon rupture was assessed with applied weight. The S-K procedure was performed on four limbs, evaluating stump stabilization techniques and radial movement distance underweight. RESULTS: Proximal osteotomy positions increased radial motion range. Extensor tendon irritation occurred when the load was applied to the volar and ulnar sides, particularly with a pronated forearm. Stump stabilization techniques did not significantly contribute to ulnar stump stabilization. CONCLUSIONS: Proximal ulnar osteotomy positions in DRUJ salvage procedures led to increased radioulnar instability and potential complications. Load application on the volar and ulnar sides, especially in a pronated forearm, increased the risk of tendon rupture. Stump stabilization techniques showed limited utility in stabilizing the ulnar stump or reducing complications. These findings can inform strategies for minimizing complications in DRUJ salvage procedures.

Health-Related Quality of Life of Patients With Adolescent Idiopathic Scoliosis at Least 40 Years After Surgery.

STUDY DESIGN: Retrospective study. OBJECTIVE: The aim was to clarify the health-related quality of life (QOL) of patients who had adolescent idiopathic scoliosis (AIS) at a minimum of 40 years after surgery. SUMMARY OF BACKGROUND DATA: The postoperative health-related QOL of middle-aged patients with AIS has been reported to be good, but that of middle-aged and older patients with AIS has yet to be completely explored. MATERIALS AND METHODS: We included 179 patients with AIS who underwent spinal fusion(s) between 1968 and 1982. We conducted three surveys in 2009, 2014, and 2022. Patients self-administered both the Scoliosis Research Society-22 and the Roland-Morris Disability questionnaires three times (in 2009, 2014, and 2022) and the Oswestry Disability Index (ODI) questionnaire was self-administered in 2014 and 2022. We considered patients who responded to all three surveys in 2009, 2014, and 2022. RESULTS: For the Scoliosis Research Society-22 questionnaires, no significant differences were detected among the three time points (2009, 2014, and 2022) for total scores, function domain, pain domain, self-image domain, mental domain, or satisfaction domain. The results of the Roland-Morris Disability Questionnaire were also not significantly different among the surveys over time. The ODI questionnaires revealed a significant worsening of the 2022 results compared with the 2014 results. Eight patients (29.6%) who had an ODI deterioration of 10% or more had numerically fewer mobile lumbar disks than those with <10% deterioration of the ODI, although the difference did not reach statistical significance. CONCLUSION: Among patients with AIS who underwent spinal fusion(s) between 1968 and 1982, we found health-related QOL to be maintained over the last 13 years. Relatively good QOL was appreciated in this population of patients who are now middle-aged and older.

Analgesic effects and arthritic changes following intra-articular injection of diclofenac etalhyaluronate in a rat knee osteoarthritis model.

BACKGROUND: Diclofenac etalhyaluronate (DF-HA) is a recently developed analgesic conjugate of diclofenac and hyaluronic acid that has analgesic and anti-inflammatory effects on acute arthritis. In this study, we investigated its analgesic effect on osteoarthritis, using a rat model of monoiodoacetate (MIA). METHODS: We injected MIA into the right knees of eight 6-weeks-old male Sprague-Dawley rats. Four weeks later, rats were randomly injected with DF-HA or vehicle into the right knee. Seven weeks after the MIA injection, fluorogold (FG) and sterile saline were injected into the right knees of all the rats. We assessed hyperalgesia with weekly von Frey tests for 8 weeks after MIA administration. We took the right knee computed tomography (CT) as radiographical evaluation every 2 weeks. All rats were sacrificed 8 weeks after administration of MIA for histological evaluation of the right knee and immunohistochemical evaluation of the DRG and spinal cord. We also evaluated the number of FG-labeled calcitonin gene-related peptide (CGRP)-immunoreactive(ir) neurons in the dorsal root ganglion (DRG) and ionized calcium-binding adapter molecule 1 (Iba1)-ir microglia in the spinal cord. RESULTS: Administration of DF-HA significantly improved pain sensitivity and reduced CGRP and Iba1 expression in the DRG and spinal cord, respectively. However, computed tomography and histological evaluation of the right knee showed similar levels of joint deformity, despite DF-HA administration. CONCLUSION: DF-HA exerted analgesic effects on osteoarthritic pain, but did not affect joint deformity.

The Effect of an Additional Core Suture During Pulvertaft Tendon Repair: A Fresh-Frozen Cadaver Study.

PURPOSE: Pulvertaft tendon repair is a strong suture technique; however, proper tendon tension is impaired by repair site elongation. Therefore, methods to reduce postoperative elongation are warranted. This study aimed to determine the effects of additional core sutures during Pulvertaft tendon repair on repair site elongation and rupture strength. METHODS: A total of 48 finger extensor tendons were harvested from fresh-frozen cadavers, and tendons with similar diameters were paired. The 24 pairs of tendons were divided into the following 4 groups: group I, 3 interlaced weaves only; group II, 3 interlaced weaves and 2 core suture strands with 4-0 nylon; group III, 3 interlaced weaves and 2 core suture strands with 4-0 FiberWire; and group IV, 4 interlaced weaves only. Each sutured tendon was placed in a Universal Testing Machine, and repair site elongation after repeated traction loads and rupture strength were measured. RESULTS: The mean elongation values were 2.74 ± 0.84 mm, 1.80 ± 0.16 mm, 1.60 ± 0.18 mm, and 1.92 ± 0.18 mm for groups I, II, III, and IV, respectively. The elongation values were significantly lower in groups II, III, and IV than in group I. The mean rupture strengths were 64.9 ± 16.0 N, 94.8 ± 17.2 N, 110.9 ± 21.3 N, and 104.9 ± 17.5 N for groups I, II, III, and IV, respectively. Rupture strengths were significantly higher for groups III and IV than for group I. CONCLUSIONS: After adding core sutures during Pulvertaft tendon repair, the elongation amount decreased, and the rupture strength improved. CLINICAL RELEVANCE: The study showed the effect of additional core sutures during Pulvertaft tendon repair, suggesting that it could be useful in reducing postoperative tendon elongation when extensor tendon transfers are performed.

Recovery of Forearm Bone Strength After Plate Removal: A Finite Element Analysis Study.

PURPOSE: The purpose of this study was to estimate the bone strength after plate removal over time and to investigate the progression of bone strength recovery. METHODS: A consecutive series of 31 patients was investigated to evaluate bone strength before and after forearm plate removal. Patients who were included underwent plate fixation for forearm diaphyseal fractures and were scheduled for plate removal. Computed tomography (CT) scans of the entire length of the bilateral forearms were taken before plate removal and at 1, 3, and 6 months after surgery. Patient-specific CT-based finite element analysis was used to predict the forearm bone fracture strength against an axial load (N), defined as the bone strength. Bone strength was estimated by patient-specific CT-based finite element analysis at each time point. RESULTS: The mean age of the patients was 40.4 years. The mean time between plate fixation and removal was 27.5 months. Bone strength before the removal was estimated as reduced to 47% of that of the uninjured side. This was constant regardless of age group, involvement of the radius or ulna, Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification, open fracture, or type of plate. Bone strength at 1, 3, and 6 months after removal was estimated to be 66%, 85%, and 97%, respectively. The bone strength of the distal ulna was weaker than that at the other sites in the forearm and showed delayed recovery. CONCLUSIONS: Bone strength after plate removal showed recovery within 3-6 months and was fully recovered by 6 months. The degree of recovery of bone atrophy varies from site to site, and patients should be careful about refracture after removal. CLINICAL RELEVANCE: Clinicians should be aware that bone strength may not be sufficiently restored even 6 months after plate removal of forearm fractures.

Frozen vein wrapping for chronic nerve constriction injury reduces sciatic nerve allodynia in a rat model.

BACKGROUND: Autologous vein wrapping (VW) is used in the treatment of recurrent chronic constriction neuropathy and traumatic peripheral nerve injury. However, use of autologous veins is limited by the inability to obtain longer veins of sufficient length for larger sites. Frozen allograft tissue has several advantages, including its availability for large grafts, avoidance of donor-site morbidity, and shorter operation time. Here, we investigated the effect of frozen vein wrapping (FVW) in Wistar rats as a model of sciatic nerve injury. RESULTS: The rats were grouped by treatment as (i) untreated after chronic constriction injury surgery (CCI; control group), (ii) treated with vein wrapping using freshly isolated vein (VW), and (iii) treated with vein wrapping using frozen vein (FVW). Mechanical allodynia was assessed with von Frey filaments on postoperative days (PODs) 1, 3, 5, 7, and 14. Gene expression of HO-1 was evaluated by quantitative polymerase chain reaction (qPCR). The response of heme oxygenase-1 gene, Hmox-1, expression to VW and FVW was assessed by RT-PCR. Both VW and FVW significantly increased withdrawal threshold levels compared to the untreated control group on POD 1, 3, and 5. Both VW and FVW also showed increased HO-1 expression compared to the CCI group. CONCLUSIONS: FVW increased the withdrawal threshold similar to VW in a rat CCI model for short periods. Frozen vein wrapping using vein allograft without donor site morbidity may be an alternative therapeutic option.

Updates on cadaver surgical training in Japan: a systematic facility at Chiba University.

Cadaver surgical training (CST), which ensures medical safety by improving the skills of surgeons, is popular overseas. However, training involves ethical issues given the use of cadavers. In 2012, the Japan Surgical Society and the Japanese Association of Anatomists compiled and opened the "Guidelines for Cadaver Dissection in Education and Research of Clinical Medicine (Guideline 2012)" to the public. This has allowed Japan to conduct CST or research under the regulations of Postmortem Examination and Corpse Preservation Act and the Body Donation Act. However, its dissemination has been sluggish. The Clinical Anatomy Lab (CAL), established in 2010 at Chiba University, is a facility for conducting CST and research. In the 11 years since its inception, 250 programs have been implemented. Orthopedics had the most implemented in the clinical field, with 120 (48%), followed by emergency and critical care medicine with 27 (10.8%), and neurological surgery with 27 (10. 8%). Based on the purpose of the training, the most common objective for the programs (approximately 83%) was education. Further, the highest number of programs was recorded in 2018 (34) and participants in 2017 (631). The implementation of CST requires more than just guiding surgeons to a dissection practice room. There are several methods of preserving cadavers to make them suitable for CST. For various surgical simulations, an operating table is more suitable than a dissection table. The current paper provides information on how to implement CST in universities that have so far only worked on anatomy education for medical students.

Guidelines for cadaver dissection in education and research of clinical medicine (The Japan Surgical Society and The Japanese Association of Anatomists).

This article translates the guidelines for cadaver surgical training (CST) published in 2012 by Japan Surgical Society (JSS) and Japanese Association of Anatomists from Japanese to English. These guidelines are based on Japanese laws and enable the usage of donated cadavers for CST and clinical research. The following are the conditions to implement the activities outlined in the guidelines. The aim is to improve medicine and to contribute to social welfare. Activities should only be carried out at medical or dental universities under the centralized control by the department of anatomy under the regulation of Japanese law. Upon the usage of cadavers, registered donors must provide a written informed-consent for their body to be used for CST and other activities of clinical medicine. Commercial use of cadavers and profit-based CST is strongly prohibited. Moreover, all the cadaver-related activities except for the commercial-based ones require the approval of the University's Institutional Review Board (IRB) before implementation. The expert committee organized at each university for the implementation of CST should summarize the implementation of the program and report the details of the training program, operating costs, and conflicts of interest to the CST Promotion Committee of JSS.

Guidelines for cadaver dissection in education and research of clinical medicine (The Japan Surgical Society and The Japanese Association of Anatomists).

This article translates the guidelines for cadaver surgical training (CST) published in 2012 by Japan Surgical Society (JSS) and Japanese Association of Anatomists from Japanese to English. These guidelines are based on Japanese laws and enable the usage of donated cadavers for CST and clinical research. The following are the conditions to implement the activities outlined in the guidelines. The aim is to improve medicine and to contribute to social welfare. Activities should only be carried out at medical or dental universities under the centralized control by the department of anatomy under the regulation of Japanese law. Upon the usage of cadavers, registered donors must provide a written informed-consent for their body to be used for CST and other activities of clinical medicine. Commercial use of cadavers and profit-based CST is strongly prohibited. Moreover, all the cadaver-related activities except for the commercial-based ones require the approval of the University's Institutional Review Board (IRB) before implementation. The expert committee organized at each university for the implementation of CST should summarize the implementation of the program and report the details of the training program, operating costs, and conflicts of interest to the CST Promotion Committee of JSS.

Intra-articular injection of monoiodoacetate induces diverse hip osteoarthritis in rats, depending on its dose.

BACKGROUND: Monoiodoacetate (MIA)-induced arthritis models are used widely in osteoarthritis (OA) research to develop effective conservative treatments for hip OA, as an alternative to joint replacement surgery. In joint OA models, such as the MIA-induced knee OA model, various doses of MIA are utilized, depending on the purpose of the research. So far, only 2 mg of MIA has been used for MIA-induced hip OA research. We hypothesized that the amount of MIA should be adjusted according to the osteoarthritis model under investigation. We performed radiographic and histological evaluations in rats for hip OA models induced by different doses of MIA. METHODS: One hundred and eighty right hips of six-week-old, male Sprague-Dawley rats (n = 30 rats per group) were treated with either a single intra-articular injection of various doses of MIA (0.25, 0.5, 1.0, 2.0, and 4.0 mg) dissolved in 25 µl of sterile saline (MIA group), or with 25 µl of sterile saline alone (Sham group). Radiographic and histological evaluations of the hip joint were performed at one, two, four, eight, and 12 weeks after administration (n = 6 rats per group per time point). RESULTS: OA changes progressed from 1 week after administration in the 1.0-mg, 2.0-mg, and 4.0-mg MIA groups. The degree of OA changes increased as the dose of MIA increased. The 0.25-mg and 0.5-mg MIA groups presented fewer OA changes than the 2.0-mg and 4.0-mg MIA groups during the entire study period (up to 12 weeks). The administration of 0.25 mg and 0.5 mg of MIA-induced both radiographic and histological OA changes in a time-dependent manner, whereas more than 2 mg of MIA provoked end-stage OA at 8 weeks after injection. Absolute, dose-dependent histopathological OA changes were observed 4 weeks after MIA administration. CONCLUSIONS: Intra-articular MIA injection to the hip joints of rats induced diverse OA changes dose-dependently. Research for developing novel conservative treatments for hip OA and intractable pain should consider the pathological condition when determining the dose of MIA to be employed.

Biomechanical assessment of the first dorsal compartment of the wrist: A fresh cadaver study with relevance to de Quervain's disease.

Resistance of de Quervain's disease to conservative treatment has been associated with an intertendinous septum in the first compartment. This study aimed to investigate the relationship between intertendinous septum's presence or absence, internal pressure and wrist positon in the first compartment. Fourteen arms were obtained from seven fresh frozen cadavers. A pressure sensor was inserted into the first compartment; if a septum was present, the pressure sensor was inserted into the abductor pollicis longus (APL) side and the extensor pollicis brevis (EPB) side, respectively. Three wrist positions were also tested: neutral, 45° flexion, and 45° extension. Intertendinous septa were present in seven wrists. The average pressure change in the first compartment measured on the EPB side of a present septum was significantly greater than that measured on the APL side of a present septum or where no septum existed: no septum = 54.6 ± 48.3 kPa; septum, EPB = 81.7 ± 76.5 kPa; and septum, APL = 32.8 ± 37.4 kPa. The average pressure change was also significantly greater in the flexion wrist position relative to the neutral and extension positions: neutral = 36.3 ± 58.0 kPa; 45° flexion = 79.5 ± 65.9 kPa; and 45° extension = 50.4 ± 42.6 kPa. Clear relationships existed between (1) the presence of a septum and increased internal pressure on the EPB side in the first compartment and (2) increased internal pressure with the wrist at 45° flexion compared with the neutral and extension position.

Usage of cadavers in surgical training and research in Japan over the past decade.

The "Guidelines for Cadaver Dissection in Education and Research of Clinical Medicine" drafted by the Japan Surgical Society (JSS) and the Japanese Association of Anatomists in 2012 helped dispel legal concerns over cadaver surgical training (CST) and the usage of donated human bodies for research and development (R&D) in the country. Subsequently, in the fiscal year 2018, the Ministry of Health, Labour and Welfare increased the funding for CST, prompting its wider implementation. This study analyzed data obtained in 2012-2021 through the reporting system of the JSS-CST Promotion Committee to map the usage of cadavers for clinical purposes, specifically education and R&D, in Japan. We found that the number of medical universities using cadavers for CST and R&D programs was just 5 in 2012, and it reached 38 for the decade. Thus, about half of Japan's medical universities implemented such programs over the period. Meanwhile, the total number of programs was 1,173. In the clinical field, the highest number of programs were implemented in orthopedics (27%), followed by surgery (21%), and neurosurgery (12%). Based on the purpose, the most common objective of the programs (approximately 70%) was acquiring advanced surgical techniques. Further, the highest number of programs and participants were recorded in 2019 (295 programs, 6,537 participants). Thus, the guidelines helped expand cadaver usage for clinical purposes in Japan. To further promote the clinical usage of cadavers in medical and dental universities throughout Japan, sharing know-how on operating cadaver laboratories and building understanding among the general public is recommended.

Determinants of fracture type in the proximal femur: Biomechanical study of fresh frozen cadavers and finite element models.

BACKGROUND: Proximal femur fractures are usually categorized as either a cervical or trochanteric fracture, but the relationship between fracture type and fall direction is not clear. By cadaveric mechanical testing and finite element analysis (FEA), the aims of this research were to verify the factors that define the proximal femur fracture type and to clarify the change in stress distribution based on fall direction. METHODS: From fresh frozen cadavers, we obtained 26 proximal femora including ten pairs of 20 femora. We conducted quasi-static compression tests in two fall patterns (lateral and posterolateral), and identified the fracture type. We then examined the relationship between fracture type and the following explanatory variables: age, sex, neck shaft angle, femoral neck length, bone mineral density (cervical and trochanteric), and fall direction. In addition, for the ten pairs of femurs, the effect of fall direction on fracture type was examined by comparing the left and right sides. In addition, we generated the proximal femur finite element (FE) models from computed tomography data to simulate and verify the change of external force in different fall directions. RESULTS: In mechanical tests, only fall direction was found to have a significant relationship with fracture type (p = 0.0227). The posterolateral fall group had a significantly higher incidence of trochanteric fractures than lateral fall group (p = 0.0325). According to FEA, the equivalent stress in the lateral fall was found to be more concentrated in the cervical area than in the posterolateral fall. CONCLUSION: In proximal femur fractures, fall direction was significantly associated with fracture type; in particular, trochanteric fractures were more likely to occur following a posterolateral fall than a lateral fall.