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We tested if the movement slowness of individuals with Parkinson's disease is related to their decreased ability to generate adequate net torques and linearly coordinate them between joints. This cross-sectional study included ten individuals with Parkinson's disease and ten healthy individuals. They performed planar movements with a reversal over three target distances. We calculated joint kinematics of the elbow and shoulder using spatial orientation. The muscle, interaction, and net torques were integrated into the acceleration/deceleration phases of the fingertip speed. We calculated the linear correlations of those torques between joints. Both groups modulated the elbow and shoulder net torques with target distances. They linearly coupled the production of torques. Both groups did not modulate the interaction torques. The movement slowness in Parkinson's disease was related to the difficulty in generating the appropriate muscle and net torques in the task. The interaction torques do not seem to play any role in movement control.

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BACKGROUND: Fractures of the capitellum are rare in children. The purpose of this study was to report fracture characteristics, treatment, and outcomes of pediatric capitellar fractures at a single children's hospital. We also aimed to update the classification of these fractures based on a large sample size by revising the Murthy (Boston) classification. METHODS: In a retrospective study at a single tertiary care children's hospital, fractures of the capitellum in patients below 18 years of age were queried and reviewed for demographics, injury characteristics, imaging, treatment, outcomes, and complications. Three surgeons reviewed all imaging to classify the fractures and assess interobserver and intraobserver reliability. RESULTS: Forty-four patients (25 male) with capitellar fractures with a mean age of 11.7±3.7 years were identified. Seven fractures did not belong to an existing type and were grouped into a new type IV capitellar fracture, defined as LCL avulsions with extension to the articular surface of the capitellum. We found good to excellent inter-rater and intrarater reliability for the new classification system. Our raters believed that cross-sectional imaging was essential to classifying fractures in 84% of the cases. Thirty-three of 44 patients underwent early surgical intervention, with favorable outcomes. Five patients presented late with substantial elbow contracture and malunion and were treated surgically with the excision of the fragment. CONCLUSIONS: The new classification of pediatric capitellar fractures is more comprehensive and offers good to excellent reliability. We found excellent outcomes in the majority of cases with early diagnosis and management, but substantial risk for complications with missed and delayed diagnosis. Malunion and subsequent loss of ROM were the most common presentations of a missed diagnosis, which can be surgically treated with favorable outcomes. LEVEL OF EVIDENCE: Level III-retrospective cohort study.

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OBJECTIVES: Lateral humeral condyle fractures account for 12% to 17% of all distal humerus fractures in children, and usually occur as an isolated injury or are associated with radial neck and/or proximal ulna fractures. The presentation with a concomitant dislocation of the elbow is rare. Therefore, literature on young patients with this uncommon combination is sparse and mostly limited to case reports and small case series. The aim of the present study is to identify the best treatment strategy for this injury, recognize potential risk factors for the development of complications, and identify predictors of outcome. METHODS: This is a multicenter retrospective review of electronic and written medical records for skeletally immature patients who were diagnosed with a lateral condyle fracture of the humerus associated with elbow dislocation (ED). Data recorded included patient demographics, fracture classification, direction of the dislocation, treatment strategy, time to union, elbow range of motion, complications, and additional procedures. The modified Flynn criteria were used to determine the outcomes. RESULTS: We identified 23 patients who presented to 3 institutions with a concomitant lateral humeral condyle fractures and an ED. The mean age at the time of injury was 8.7 years (range: 6 to 13 y). The median time from injury to surgery was 1 day (interquartile range: 0.5, minimum to maximum: 0 to 29 d). The median follow-up was 24 weeks (interquartile range: 16, minimum to maximum: 4 to 120 wk). The injury occurred more commonly in males (79%) with Weiss type 3 fractures. The direction of the dislocation was posterior or posteromedial in most cases. Open reduction through a modified Kocher lateral approach and fixation with either Kirschner wires (N = 12) or cannulated screws (N = 9) was the preferred method of treatment. Eight patients (34.8%) developed complications, including persistent elbow stiffness (N = 5), elbow instability (N = 1), and avascular necrosis (N = 2). There were no cases of delayed union, nonunion, malunion, heterotopic ossification, neurological injury, or hardware failure. Patients treated with casting or Kirschner wire fixation had a significantly increased rate of elbow stiffness compared with screw fixation (50%, 25%, and 11%, respectively, P = 0.015). According to Flynn's criteria, 65% of the patients had good or excellent outcomes, and 35% had poor. CONCLUSION: The findings of this study demonstrate a higher than previously described rate of complications in children with lateral condyle humerus fracture associated with ED, including persistent elbow stiffness, avascular necrosis, and chronic elbow instability, leading to unsatisfactory clinical outcomes in over one-third of the cases. Our findings suggest that the internal fixation with screws, combined with a shorter postoperative immobilization period (2 wk) may lead to improved clinical outcomes. LEVEL OF EVIDENCE: Level III-therapeutic, case series.

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OBJECTIVES: The primary objective of the present study is to compare the radiographic outcomes and complications of two different techniques for lateral closing-wedge osteotomy in pediatric patients with cubitus varus. METHODS: We retrospectively identified patients treated at five tertiary care institutions: 17 underwent the Kirschner-wire (KW) technique, and 15 patients were treated with the mini external fixator (MEF) technique. Demographic data, previous treatment, pre- and postoperative carrying angle (CA), complications and additional procedures were recorded. Radiographic evaluation included assessment of the humerus-elbow-wrist angle (HEW), and the lateral prominence index (LPI). RESULTS: Patients treated with both KW and MEF achieved significant improvements in clinical alignment (mean pre-op CA -16 ± 6.1 degrees to mean post-op 8.9 ± 5.3 degrees, P < 0.001). There were no differences in final radiographic alignment or radiographic union time; however, time to achieve full elbow motion was faster in the MEF group (13.6 versus 34.3 weeks, P = 0.4547). Two patients (11.8%) in the KW group experienced complications, including one superficial infection and one failed correction that required unplanned revision surgery. Eleven patients in the MEF group underwent a planned second surgical procedure for hardware removal. CONCLUSIONS: Both fixation techniques are effective at correcting cubitus varus in the pediatric population. The MEF technique may have the advantage of shorter recovery of elbow range of motion but may require sedation for hardware removal. The KW technique may present a slightly higher complication rate.

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BACKGROUND: Classic orthopaedic teaching states a high risk of pediatric acute compartment syndrome (PACS) and other adverse outcomes to be associated with pediatric floating elbow injuries. However, more recent data suggest otherwise. This study aims to evaluate treatment approaches and outcomes of pediatric floating elbow injuries and accurately determine the rate of associated PACS. METHODS: A multicenter retrospective database was created to review patients below 18 years old who presented between 2014 and 2019 with floating elbow injuries. Patient demographics, injury characteristics, treatment course, and outcomes were evaluated. A severity classification (Children's Orthopaedic Trauma and Infection Consortium for Evidence-Based Studies) was established: class 1 injuries included Gartland 1 supracondylar fracture, class 2 included Gartland 2 supracondylar fracture, and class 3 included Gartland 3 or 4 supracondylar or t-condylar fracture. Subclasses A and B were based on displacement of the distal fracture. RESULTS: Four hundred fifty four patients were evaluated across 15 institutions. The cohort was 51% male and a median of 6.8 years old at injury. Thirteen patients (2.9%) presented without a palpable or dopplerable pulse, all having class 3 injuries. Ninety patients (20.0%) presented with nerve injuries, which were more common in class 3 injuries ( P <0.001). Only 14 (3.1%) had persistent nerve injuries at the final follow-up. Displacement largely dictated whether the distal injury was treated with fixation ( P <0.001) or immobilization only. Open reduction rate of the proximal fracture was 7.7% overall. There was 1 case (0.2%) of PACS involving displaced proximal and distal fractures. The median length of follow-up was 2.5 months. Modified Flynn outcomes at the last clinical visit were excellent/good in 315 patients (70%). More severe injuries had less good/excellent outcomes than less severe injuries ( P =0.030). CONCLUSIONS: This multicenter study of a large cohort of pediatric floating elbow injuries identified a low rate of PACS (0.2%). Closed treatment of the distal fracture was more frequently performed for nondisplaced fractures. Nerve and vascular injury rates were consistent with those of isolated component fractures and were associated with fracture displacement. The Children's Orthopaedic Trauma and Infection Consortium for Evidence-based Studies classification was an effective predictor of outcomes. LEVEL OF EVIDENCE: Level IV.

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The skeletal muscle contraction is determined by cross-bridge formation between the myosin heads and the actin active sites. When the muscle contracts, it shortens, increasing its longitudinal shear elastic modulus ([Formula: see text]). Structurally, skeletal muscle can be considered analogous to the molecular receptors that form receptor-ligand complexes and exhibit specific ligand-binding dynamics. In this context, this work aims to apply elastography and the ligand-binding framework to approach the possible intrinsic mechanisms behind muscle synergism. Based on the short-range stiffness principle and the acoustic-elasticity theory, we define the coefficient [Formula: see text], which is directly related to the fraction saturation of molecular receptors and links the relative longitudinal deformation of the muscle to its [Formula: see text]. We show that such a coefficient can be obtained directly from [Formula: see text] estimates, thus calculating it for the biceps brachii, brachioradialis, and brachialis muscles during isometric elbow flexion torque (τ) ramps. The resulting [Formula: see text] curves were analyzed by conventional characterization methods of receptor-ligand systems to study the dynamical behavior of each muscle. The results showed that, depending on muscle, [Formula: see text] exhibits typical ligand-binding dynamics during joint torque production. Therefore, the above indicates that these different behaviors describe the longitudinal shortening pattern of each muscle during load sharing. As a plausible interpretation, we suggested that this could be related to the binding kinetics of the cross-bridges during their synergistic action as torque increases. Likewise, it shows that elastography could be useful to assess contractile processes at different scales related to the change in the mechanical properties of skeletal muscle.

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Abstract The authors present an atypical case of a left elbow complex fracture with extensive loss of bone and muscle tissue. The patient was submitted to several surgical procedures, which resulted in a total arthroplasty of the left elbow with triceps reconstruction using a semitendinosus muscle tendon graft.

Resumo Os autores apresentam um caso atípico de fratura complexa do cotovelo esquerdo com perda extensa de tecido ósseo e muscular. O paciente foi submetido a diversos procedimentos cirúrgicos, que resultaram em uma artroplastia total do cotovelo esquerdo associada à reconstrução do tríceps com enxerto do tendão do músculo semitendíneo.

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Abstract Acute distal biceps injuries clinically present with sudden pain and acute loss of flexion and supination strength. The main injury mechanism occurs during the eccentric load of the biceps. The hook test is the most significant examination test, presenting the highest sensibility and specificity for this lesion. Magnetic resonance imaging, the gold standard imaging test, can provide information regarding integrity and identify partial and/or complete tears. The surgical treatment uses an anterior or double approach and several reattachment techniques. Although there is no clinical evidence to recommend one fixation method over the other, biomechanical studies show that the cortical button resists better to failure. Although surgical treatment led to an 89% rate of return to work in 14 weeks, the recovery of high sports performance occurred in 1 year, with unsustainable outcomes.

Resumo As lesões agudas do tendão distal do bíceps se apresentam, clinicamente, com uma dor súbita associada a perda aguda de força de flexão e supinação. Seu principal mecanismo de lesão ocorre durante contração excêntrica do bíceps. O "Hook Test" é o principal teste semiológico, sendo o mais sensível e específico. A ressonância magnética, exame padrão ouro para o diagnóstico, pode fornecer informações sobre a integridade, identificando as lesões parciais e/ou completas. O tratamento cirúrgico pode ser realizado por duas vias principais: anterior e por dupla via porém as técnicas de reinserção tendínea são diversas não havendo evidência clínica que recomende um método de fixação em detrimento ao outro; embora o botão cortical apresente maior resistência a falha nos estudos biomecânicos. Com o tratamento cirúrgico o retorno as atividades laborais foi de 89% em 14 semanas (média) porém ao esporte de alto rendimento o prazo foi longo, média de 1 ano, e não duradouro.

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