Severe Hemodynamic Collapse During Humerus Stabilization with Photodynamic Implant: A Report of Two Cases.

CASE: We present 2 cases of severe hemodynamic collapse during prophylactic stabilization of impending pathologic humerus fractures using a photodynamic bone stabilization device. Both events occurred when the monomer was infused under pressure into a balloon catheter. CONCLUSION: We suspect that an increase in intramedullary pressure during balloon expansion may cause adverse systemic effects similar to fat embolism or bone cement implantation syndrome. Appropriate communication with the anesthesia team, invasive hemodynamic monitoring, and prophylactic vent hole creation may help mitigate or manage these adverse systemic effects.

A Morphometric Study of Olecranon Fossa of Adult Human Humerus of Bangladeshi Population.

Olecranon fossa is the largest fossa among the three fossae of the humerus. It is present in the lower end of the posterior surface just above the trochlea. Osteometry of olecranon fossa is important since their fractures occur in 10.0% of upper limb fractures. The aim of this study was to measure different parameters of olecranon fossa. This study was taken from 100 (right=43 and left=57) samples were selected through the purposive sampling technique for this cross-sectional descriptive study which was carried out in the Department of Anatomy, Mymensingh Medical College, Mymensingh, Bangladesh from July 2021 to June 2022. Any damaged, unossified bones or fractured bones were excluded. Data were tabulated and statistically analyzed using Microsoft Excel and SPSS software. The mean ±SD vertical diameter of the olecranon fossa of the right humeri was 16.858±2.623mm and the left humeri were 17.071±2.905mm. The mean ±SD width of the olecranon fossa of the right humeri was 24.239±2.520mm and the left humeri were 24.509±2.692mm. The mean ±SD maximum depth of the olecranon fossa of the right humeri was 13.442±1.688mm and the left humeri were 13.124±1.733mm. The anatomical knowledge of the olecranon fossa is beneficial for anthropologists, orthopedic surgeons and radiologists in cases of olecranon fractures of the humerus.

Functional and oncological outcomes of patients with proximal humerus osteosarcoma managed by limb salvage.

BACKGROUND: Osteosarcoma is the most common primary bone malignancy in skeletally immature patients. The proximal humerus is the third most common site of osteosarcoma. The literature shows a paucity of published data concerning the outcome of proximal humerus osteosarcoma managed by limb salvage. The purpose of this study was to answer the following questions: (1) do patients with proximal humerus osteosarcoma managed by limb salvage and neoadjuvant chemotherapy show good functional and oncological outcomes, and (2) are there any prognostic factors that are associated with better oncological and functional outcomes? MATERIALS AND METHODS: The study was a retrospective case series study assessing the overall outcome of 34 patients with proximal humerus osteosarcoma. Eighteen patients were males (53%) while 16 were females. Biological reconstruction was done in 15 patients (44%), while nonbiological reconstruction was done in 19 patients. Resections were mainly intraarticular (82%). Functional outcome was assessed using the Musculoskeletal Tumor Society (MSTS) score, while oncological outcome was assessed based on local recurrence and development of chest metastasis. Comparisons between quantitative variables were done using the nonparametric Mann-Whitney test. To compare categorical data, the chi-square (χ2) test was performed. The exact test was used instead when the expected frequency was less than 5. Correlations between quantitative variables were examined using the Spearman correlation coefficient. RESULTS: The mean MSTS score was 25.5 (range 23-29). A younger age was statistically correlated with a poorer MSTS score (P = 0.0016). Six patients out of 34 (17.6%) had local recurrence and four of them (67%) were treated by forequarter amputation. 41% of patients developed chest metastasis, and the majority of them were treated by chemotherapy (71%). In comparison with patients with osteosarcoma at other sites who were also managed in our institution, proximal humerus osteosarcoma patients showed higher incidence rates of local recurrence and chest metastasis along with lower 5-year patient and limb survivorships compared to distal femur, proximal tibia and proximal femur osteosarcoma patients. CONCLUSION: Treatment of osteosarcoma of the proximal humerus by limb salvage and chemotherapy yields a good functional outcome. The method of reconstruction does not impact the resultant function. The 5-year survivorship of these patients is 65%. Younger patients have a better oncological outcome and an inferior functional outcome. LEVEL OF EVIDENCE: Level IV therapeutic study.

[Effectiveness comparison of ultrasound-guided closed reduction and Kirschner wire fixation for different unstable humeral lateralcondylar fractures of children].

Objective: To compare the effectiveness of ultrasound-guided closed reduction and Kirschner wire fixation for different unstable humeral lateralcondylar fractures of children. Methods: The clinical data of 94 children with unstable humeral lateralcondylar fractures admitted to three medical centers between January 2021 and October 2022 were retrospectively analyzed. The children were divided into three groups according to the Song classification and whether the elbow joint was dislocated or not, including 42 cases of Song 4 type (group A), 38 cases of Song 5 type (group B), and 14 cases of elbow joint dislocation (group C). There was no significant difference in gender, age, side, cause of injury, and time from injury to operation among the three groups ( P>0.05). All children were treated with ultrasound-guided closed reduction and Kirschner wire fixation. The operation time and complications of the three groups were recorded and compared, and the failure of closed reduction was evaluated by ultrasound. X-ray examination was performed at last follow-up to measure the Baumann angle, condylar angle, carrying angle, and lateral osteophyte of the affected side; the extension, flexion, pronation, and supination range of motion of the affected elbow joint were measured; the function of the elbow joint was evaluated by Mayo score. Results: The operation time in group A was significantly longer than that in groups B and C ( P<0.05). There were 7, 2, and 5 cases of closed reduction failure in groups A, B, and C, respectively, and there was no significant difference in the incidence of the closed reduction failure ( P>0.05). All patients were followed up 6-28 months, with an average of 15.7 months. There was no significant difference in the follow-up time among the three groups ( P>0.05). Complications: in group A, there were 2 cases of delayed union, 4 cases of needle tract infection, 1 case of trochlear necrosis, and 39 cases of lateral osteophyte; in group B, there was 1 case of malunion, 5 cases of needle tract infection, 1 case of redisplacement, and 26 cases of lateral osteophyte; in group C, there were 2 cases of needle tract infection and 10 cases of lateral osteophyte. There was no significant difference in the incidence of complications among the three groups ( P>0.05). No cubitus varus or cubitus valgus deformity was found in all patients. At last follow-up, except that the condylar angle in group A was significantly greater than that in groups B and C ( P<0.05), there was no significant difference in other imaging indicators, elbow range of motion, or Mayo score between groups ( P>0.05). Conclusion: The Song type 4 of humeral lateralcondylar fracture treated with ultrasound-guided closed reduction and Kirschner wire fixation has a longer operation time, more postoperative complications, and is more prone to lateral osteophyte.

Resection Arthroplasty Is a Valuable Strategy for Humeroradial Synostosis - A Case Report.

A 15-year-old girl with humeroradial synostosis since birth underwent a resection arthroplasty. A trapezoidal resection osteotomy of approximately 2 cm was performed at the anterior part of the bone flexure. This resulted at 18 months in an elbow arc of motion of 60°-110° and forearm pronation/supination of 40° and 60° without postoperative complications and improved disabilities of the arm, shoulder and hand and Hand 20 scores. Radiographic analysis revealed a humeroradial joint with a maintained pseudarthrosis and hinged motion at the humeroulnar joint. When performed by an experienced surgeon, resection arthroplasty corrects humeroradial synostosis, resulting in improvement in range of motion and quality of life. Level of Evidence: Level V (Therapeutic).

AI-assisted Analysis to Facilitate Detection of Humeral Lesions on Chest Radiographs.

Purpose To develop an artificial intelligence (AI) system for humeral tumor detection on chest radiographs (CRs) and evaluate the impact on reader performance. Materials and Methods In this retrospective study, 14 709 CRs (January 2000 to December 2021) were collected from 13 468 patients, including CT-proven normal (n = 13 116) and humeral tumor (n = 1593) cases. The data were divided into training and test groups. A novel training method called false-positive activation area reduction (FPAR) was introduced to enhance the diagnostic performance by focusing on the humeral region. The AI program and 10 radiologists were assessed using holdout test set 1, wherein the radiologists were tested twice (with and without AI test results). The performance of the AI system was evaluated using holdout test set 2, comprising 10 497 normal images. Receiver operating characteristic analyses were conducted for evaluating model performance. Results FPAR application in the AI program improved its performance compared with a conventional model based on the area under the receiver operating characteristic curve (0.87 vs 0.82, P = .04). The proposed AI system also demonstrated improved tumor localization accuracy (80% vs 57%, P < .001). In holdout test set 2, the proposed AI system exhibited a false-positive rate of 2%. AI assistance improved the radiologists' sensitivity, specificity, and accuracy by 8.9%, 1.2%, and 3.5%, respectively (P < .05 for all). Conclusion The proposed AI tool incorporating FPAR improved humeral tumor detection on CRs and reduced false-positive results in tumor visualization. It may serve as a supportive diagnostic tool to alert radiologists about humeral abnormalities. Keywords: Artificial Intelligence, Conventional Radiography, Humerus, Machine Learning, Shoulder, Tumor Supplemental material is available for this article. © RSNA, 2024.

Long-standing Nonunited Fracture Lateral Humeral Condyle in Children. Evaluating a Two-stage Surgical Treatment Strategy With Critical Review.

OBJECTIVE: This work aimed to evaluate the results of using a 2-stage surgical treatment strategy without doing anterior transposition of the ulnar nerve (ATUN) for cases with long-standing nonunited fracture lateral humeral condyle (LHC) in children, accompanied by a critical review. METHODS: A consecutive 12 children with a long-standing ">2 years" nonunited LHC with evident radiologic gross anatomic distortion of the elbow were included in this study. A 2-stage surgical treatment strategy was applied, wherein the first stage, open functional reduction, osteosynthesis, and iliac bone graft were done. Then after 6 months, the second stage surgery was carried out in the form of supracondylar humeral corrective osteotomy if the cubitus valgus angle was ≥20 degrees. ATUN was not done for any of the cases even with those having ulnar nerve dysfunction. RESULTS: Union took place in 11 out of the 12 cases after a mean follow-up period of 11 weeks (range: 8 to 14 wk; SD: 1.6). All the 7 cases showed preoperative ulnar nerve dysfunction and reported clinical recovery at the end of their follow-up. CONCLUSIONS: Two-stage surgical treatment strategy without ATUN is a convenient, reproducible, and successful line of treatment for children presented with longstanding nonunited LHC with anatomically distorted elbow. LEVEL OF EVIDENCE: Level IV-case series.

The Gartland classification for expediting supracondylar humerus fracture triage: a collaborative approach to structured reporting between pediatric radiologists and orthopedists.

BACKGROUND: The modified Gartland classification is an important tool for evaluation of pediatric supracondylar humerus fractures (SCHF) because it can direct treatment decisions. Gartland type I can be managed outpatient, while emergent surgical consult occurs with type II and III. This study assesses the interobserver reliability of the Gartland classification between pediatric radiologists and orthopedic providers. METHODS: A retrospective review of 320 children diagnosed with a SCHF at a single tertiary children's hospital during 2022 was conducted. The Gartland classification documented in the radiographic report by a pediatric radiologist and the classification documented in the first encounter with an orthopedic provider was collected. Kappa value was used to assess interobserver reliability of classifications between radiologists and orthopedic providers. A second group of 76 Gartland type I SCHF from 2015, prior to our institution's implementation of structured reporting, was reviewed for comparison of unnecessary orthopedic consults at initial presentation. RESULTS: The Gartland classification has excellent interobserver reliability between radiologists and orthopedic providers with 90 % (289/320) agreement and kappa of 0.854 (confidence interval: 0.805-0.903). The most frequent disagreement that occurred was fractures classified as type II by radiology and type III by orthopedics. There were similar rates of consults for the 2015 and 2022 cohorts (p = 0.26). CONCLUSION: The Gartland classification system is a reliable and effective tool for communication between radiologists and orthopedic providers. Implementing a structured reporting system has the potential to improve triage efficiency for SCHF.

Primary stability in locking plate fixation for proximal humeral fractures may be increased by using an additional nail osteosynthesis in combination with locking plate osteosynthesis-A biomechanical comparison.

BACKGROUND: Stability is regarded as an important factor for proper healing and avoiding secondary dislocation in osteoporotic fractures of the proximal humerus. Several surgical techniques have been proposed for treatment, including intramedullary nail osteosynthesis and locking plate fixation. This study introduces a novel approach that combines both techniques and compares its primary stability with conventional methods. METHODS: The study involved 25 osteoporotic humeri with two-part fracture models, which were randomly assigned to locking-plate fixation, intramedullary nailing, or a combination of both techniques. The specimens were subjected to sinusoidal loading at 250 N in 20° abduction for 5000 cycles and then to quasi-static loading until failure. Fracture movement, failure mode, and failure load were measured and compared among the groups. FINDINGS: The groups fixated with intramedullary nailing and the groups fixated with intramedullary nailing and locking plate fixation showed significantly lower fracture motion than the group using locking plate fixation only (p < 0.005) and significantly higher load to failure (p = 0.007 and p = 0.0062, respectively). There was no significant difference between the group using intramedullary nailing and the group using locking-plate fixation and intramedullary nailing in fracture movement or load-to-failure (p > 0.005). INTERPRETATION: The results indicate that locking plate fixation provides less primary stability than intramedullary nailing or the combined of both techniques. This combined approach may offer advantages as a treatment for complex proximal humeral fractures in osteoporotic bone, and specific implants should be developed to ensure optimal treatment.

Five-Year Follow-Up of Surgery vs Functional Bracing for Closed Displaced Humeral Shaft Fractures.

This study compares outcomes of surgery and functional bracing for closed humeral shaft fractures after 5 years of follow-up.

[A multicenter clinical study on the treatment of lateral epicondylitis of humerus by manipulation].

OBJECTIVE: To investigate clinical effect of tendons pulling,poking and kneading for the treatment of external humeral epicondylitis. METHODS: From January 2018 to December 2021,a multicenter randomized controlled study was performed to collect 192 patients with external humeral epicondylitis in Wangjing Hospital,Beijing Dianli Hospital,and Beijing Fengsheng Osteotraumatology Hospital,respectively,and they were divided into treatment group and control group by random number table method. There were 96 patients in treatment group,including 36 males and 60 females,aged from 28 to 60 years old with an average of (41.20±5.50) years old;the course of disease ranged from 1 to 14 days with an average of (5.24±1.35) days;they were treated once every other day for 2 weeks. There were 96 patients in control group ,including 33 males and 63 females,aged from 26 to 60 years old with an average of (43.35±7.75) years old;the course of disease ranged from 1 to 14 days with an average of (5.86±1.48) days;they were treated with topical voltaalin combined with elbow joint fixation for 2 weeks. Visual analogue scale (VAS) and Hospital for Surgery Scoring System (HSS) elbow pronation and supination angles,wrist metacarpal flexion and dorsal extension angles,elbow tenderness between two groups were compared before treatment and at 1,3,5,7,11 and 13 days after treatment;Hospital for Surgery Scoring System 2 (HSS2) was compared before treatment and the final treatment. RESULTS: All patients were followed up for 10 to 14 days with an average of (12±1.6) days. VAS between treatment group and control group before treatment were 6.83±1.36 and 6.79±1.58,respectively,and decreased to 1.49±1.09 and 2.11±1.81 after the final treatment. VAS of treatment group were significantly lower than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). HSS between two groups were 61.73±11.00 and 36.47±12.45 before treatment,respectively,and increased to 94.42±5.9 and 91.44±9.11 at the final treatment. HSS of treatment group were significantly higher than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). On the 5th day after treatment,the external and internal rotation angles of elbow in treatment group were (66.41±12.69) ° and (66.35±13.54) °,while those in control group were (62.08±16.03) ° and (61.77±16.35) °. On the 7th day after treatment,the external and internal rotation angles of elbow were (69.79±12.64) ° and (70.02±13.55) ° in treatment group,and (65.28±15.86) ° and (65.09±16.67) ° in control group. Elbow joint motion in treatment group was higher than that in control group (P<0.05). On the 5th day after treatment,angles of wrist dorsiflexion and palm flexion were (39.43±15.94) ° and (46.68±11.10) ° in treatment group,and (38.51±18.49) ° and (44.27±13.58) ° in control group. On the 7th day after treatment,angles of wrist dorsiflexion and palm flexion were (42.52±16.50) ° and (49.23±10.96) ° in treatment group,and (41.18±20.09) ° and (46.64±14.63) ° in control group. The motion of wrist joint in treatment group was higher than that in control group (P<0.05). On the 13th day after treatment,HSS2 in treatment group 93.61±6.32 were higher than those in control group 92.06±7.94(P<0.05). There was no significant difference in elbow tenderness between two groups at each time point (P>0.05). CONCLUSION: Voltaren external treatment combined with elbow fixation and tendons pulling,poking and kneading could effectively improve symptoms of external humeral epicondylitis. Compared with voltaren external treatment,tendons pulling,poking and kneading has advantages of longer analgesic time and better elbow function recovery.

Treatment of a fractured humerus and partially torn supraspinatus tendon in a professional boxer with liquid platelet-rich fibrin and heat-coagulated albumin gel: a case report.

INTRODUCTION: Fractures with delayed healing can be a serious complication, especially for athletes depending on quick return to sports. To our knowledge, no cases of increased healing of delayed union fractures with autologous biomedical interventions have been reported. CASE PRESENTATION: A 33-year-old Swedish professional boxer with a fractured humerus with a delayed union and a partially torn supraspinatus tendon was treated with injections of liquid platelet-rich fibrin and heat-coagulated albumin gel. He recovered almost completely from both injuries in only 1 month and could return to professional boxing in 3 months. CONCLUSION: This case raises the hypothesis that liquid platelet-rich fibrin and heat-coagulated albumin gel may be an effective, minimally invasive intervention in fractures with a delayed union. Further research is required to test this theory.

The importance of interdigitating screw fixation of the trochlea in double plate osteosynthesis of low transcondylar distal humerus fractures: A biomechanical study.

OBJECTIVE: The trochlea is of great importance for the stability of the elbow and its fixation in low transcondylar fractures of the distal humerus is especially challenging. The aim of this study was to determine the optimal trochlea fixation in double plate osteosynthesis of intraarticular distal humerus fractures. METHODS: A low transcondylar, C3-type distal humerus fracture was created in 20 fresh-frozen human cadaveric humeri. The samples were then randomly divided into two groups of 10 specimens each. Double plate osteosynthesis was performed in both groups. In group A, the two most distal screws of the lateral plate were inserted into the trochlea fragment. In group B, these screws did not extend into the trochlea. Displacement under cyclic loading and ultimate failure loads were determined for all specimens. RESULTS: Group A showed significantly less displacement under cyclic loading in each measurement interval (0.92 mm vs. 1.53 mm after 100 cycles, p = 0 0.006; 1.10 mm vs. 1.84 mm after 1000 cycles, p = 0.007; 1.18 mm vs. 1.98 mm after 2000 cycles, p = 0.008). The ultimate failure load was significantly higher in group A than in group B (345.61 ± 120.389 N vs. 238.42 ± 131.61 N, p = 0.037). CONCLUSIONS: Fixation of the trochlea with interdigitating screws in double plate osteosynthesis of low-condylar type C distal humerus fractures results in superior construct stability. LEVEL OF EVIDENCE: not applicable (biomechanical).

Outcome determinants for coronal shear fractures of the distal humerus.

PURPOSE: Coronal shear fractures of the distal humerus involving the capitellum and trochlea are rare injuries. Internal fixation with headless compression screws provides a stable construct facilitating early mobilisation. Our study aimed to identify the key determinants of both radiological and functional outcomes of patients with distal humerus coronal shear fractures treated with internal fixation. METHODS: A retrospective analysis of 61 patients with distal humerus coronal shear fractures who were treated surgically was done. Demographics, fracture morphology, time to surgery, operative details such as surgical approach and implant used, quality of reduction, time to union, and associated complications from hospital records. Radiological outcomes were assessed using plain radiographs, and the functional outcomes were by Oxford Elbow Score (OES) and Mayo Elbow Performance Index (MEPI). RESULTS: Patients with anatomical reduction of the fracture had better functional outcomes and range of motion. The presence of posterior comminution of capitellum resulted in poorer outcomes (p = 0.03). Delayed presentation did not alter the outcome when the anatomical reduction was achieved. Myositis ossificans was noted in nine patients and non-union in five patients. Two patients developed avascular necrosis of the capitellum and arthritis of the elbow joint. CONCLUSION: Anatomical reduction and posterior comminution are the two key determinants of the functional outcome in these coronal shear fractures of the distal humerus. Early mobilisation following a stable fixation is crucial in achieving a good outcome.

Results of Allografts and Synthetic Grafts in Humeral Simple Bone Cysts.

PURPOSE OF THE STUDY: Simple bone cysts (SBCs) are the most common benign bone lesions in childhood. There are many different methods in the treatment of SBCs. There is no consensus on which method to use in the treatment. In this study, we compared the results of allogeneic bone graft or synthetic bone graft in addition to fl exible intramedullary nail (FIN) for SBC located in the humerus. MATERIAL AND METHODS: This retrospective study comparing the data of 19 (group 1: 8 curettage, allograft and FIN; group 2: 11 curettage, synthetic graft and FIN) patients with a mean age of 11.4 (6 to 26; seven female, twelve male) who were surgically treated in our hospital for humeral SBC between April 2014 and January 2020. Patient data included age, sex, anatomical side, stage of the cyst, pathological fracture, previous treatments and complications. RESULTS: The mean follow-up period was 33.7 months (12 to 61). The average last follow-up Musculoskeletal Tumor Society functional scores for groups 1 and 2 were 27.8 (20 to 30) and 28.6 (21 to 30) (P > 0.05). Complete or signifi cant partial radiographic healing rates were achieved in group 1 (75%) compared with group 2 (81.9%). The reoperation rates for groups 1 and 2 were 62.5% (5/8; three for nails removed, two for recurrence) and 36.3% (4/11; two for nails removed, two for recurrence). One patient in group 2 had a 15° varus deformity due to recurrence. No other complications were observed. CONCLUSIONS: The combination of curettage-grafonage FIN is a common treatment method in recent years, as it provides early cyst healing and limb mobilization in SBCs located in the upper extremity. For defects after curettage of the bone cysts, allogeneic or synthetic grafts (granule b-tricalcium phospate) which have similar results in terms of healing can be used as an alternative to each other. KEY WORDS: allografts, bone cysts, bone nails, synthetic grafts, humerus.

Postmenopausal women with normal BMD who have fractures have deteriorated bone microarchitecture: A prospective analysis from The OFELY study.

Most postmenopausal women who sustain fragility fracture (Fx) have their areal bone mineral density (BMD) above the osteoporosis threshold. A sizeable proportion of them have normal aBMD. This study aimed to prospectively investigate the association of fragility Fx with bone microarchitecture (MA) assessed by high-resolution peripheral computed tomography (HR-pQCT) in postmenopausal women without low BMD. At the 14th annual follow-up of the OFELY study, we measured bone MA at the distal radius and tibia with HR-pQCT in addition to areal BMD with DXA, in 586 postmenopausal women. Among them, 166 (29 %) women, mean (SD) age 65 (8) yr, had normal BMD defined as a T score ≥ -1 at the lumbar spine, femoral neck, and total hip. During a median [IQR] 15 [14-15] yr of follow-up, 46 of those women sustained incident fragility Fx, including 19 women with a major osteoporotic Fx (clinical spine, forearm, proximal humerus, hip). Women who sustained Fx did not differ for age, BMI, tobacco and alcohol use, diabetes, falls, FRAX®, aBMD, and TBS compared with women without incident Fx. In contrast, they had significant impairment of volumetric densities, cortical area (Ct. Ar) and thickness (Ct. Th), stiffness (K), and estimated failure load (FL) at the radius compared with women without incident Fx. At the radius, each SD decrease of volumetric densities, Ct.Ar, Ct.Th, K, and estimated FL were significantly associated with an increased risk of all fragility fractures with hazard ratios (HR) from 1.44 to 1.56 and of major osteoporotic fractures (HR from 1.66 to 2.57). Lesser impairment of bone MA was seen at the tibia. We conclude that even in women with normal areal BMD fragility fractures are associated with deterioration of bone microarchitecture.

Demystifying the Radial Nerve The Management of Radial Nerve Palsy in the Setting of Humeral Shaft Fracture.

The association of radial nerve palsy and humeral shaft fracture is well known. Primary exploration and fracture fixation is recommended for open fractures and vascular injury while expectant management remains the standard of care for closed injuries. In the absence of nerve recovery, exploration and reconstruction is recommended 3 to 5 months following injury. When direct repair or nerve grafting is unlikely to achieve a suitable outcome, nerve and tendon transfers are potential options for the restoration of wrist and finger extension.

Biomechanical comparison of composite and cadaveric humeri models in experiments on operated humeral shaft fractures.

A study was undertaken to determine how well contacting fracture fragments of composite bone replicated the behavior of fracture fragments in real bone. Ten composite and ten real humeral diaphyses were transected and reconstructed with limited-contact dynamic-compression plates. Two screws were placed on each side of the transection site and a calibrated electronic sensor sheet was placed between the imitated fracture fragments. After insertion of the distal screws, pressure measurements were made during insertion of the first proximal screw in compression mode, during insertion of the second screw in compression mode after loosening the first screw, and finally after retightening the first screw. The process was repeated after bending the plate. The contact area, the net compression force and the average compressive stress were computed and statistically compared. The composite bone and cadaveric bone differed in contact area and compressive stress but not in net compressive force. Plate bending did not produce a significant difference between composite and cadaveric bone. The results indicate that composite bone does not reproduce all the local fracture fragment conditions so that hardware testing in composite bone should proceed carefully. A gap between fracture fragments as is often used in comminuted fracture tests may remain as the most appropriate situation for fracture hardware testing.

Time-elapsed microstructural imaging of failure of the reverse shoulder implant.

BACKGROUND: Reverse Shoulder Arthroplasties (RSA) have become a primary choice for improving shoulder function and pain. However, the biomechanical failure mechanism of the humeral component is still unclear. The present study reports a novel protocol for microstructural imaging of the entire humerus implant under load before and after fracture. METHODS: A humerus specimen was obtained from a 75-year-old male donor. An expert surgeon implanted the specimen with a commonly used RSA implant (Aequalis reversed II, Stryker Orthopaedics, USA) and surgical procedure. The physiological glenohumeral contact force that maximized the distal implant migration was selected from a public repository ( orthoload.com ). Imaging and concomitant mechanical testing were performed using a large-volume micro-CT scanner (Nikon XT H 225 ST) and a custom-made compressive stage. Both when intact and once implanted, the specimen was tested under a pre-load and by imposing a constant deformation causing a physiological reaction load (650 N, 10 degrees adducted). The deformation of the implanted specimen was then increased up to fracture, which was identified by a sudden drop of the reaction force, and the specimen was then re-scanned. RESULTS: The specimen's stiffness decreased from 874 N/mm to 464 N/mm after implantation, producing movements of the bone-implant interface consistent with the implant's long-term stability reported in the literature. The micro-CT images displayed fracture of the tuberosity, caused by a combined compression and circumferential tension, induced by the distal migration of the implant. CONCLUSION: The developed protocol offers detailed information on implant mechanics under load relative to intact conditions and fracture, providing insights into the failure mechanics of RSA implants. This protocol can be used to inform future implant design and surgical technique improvements.