Kaufman, Kenton

Background: Spasticity after upper motor neuron injury (stroke, spinal cord injury, etc.) alters muscle activity and induces long-term structural remodeling of skeletal muscle [1]. Elbow flexors, including the biceps brachii, are frequently affected, leading to abnormal tone, involuntary co-contraction, and impaired elbow function. Hyper-selective neurectomy (HSN) is a well-established surgical technique that has gained renewed clinical adoption with advances in anatomic understanding and intraoperative nerve mapping [2], yet its effects on muscle properties are poorly defined. Objective: The purpose of this study was to define pre- vs. post-HSN differences in muscle gene expression, sarcomere length, and clinical outcomes of the spastic human biceps. Methods: Individuals with elbow flexor spasticity undergoing a planned two-stage HSN were prospectively enrolled (n=10). Stage 1 released the elbow flexors and provided a pre-biopsy; Stage 2, performed ~3 months later to treat the forearm flexors, provided a second exposure to the biceps and a second biopsy. In both stages, biceps biopsies were obtained with customized clamps [3] at predefined elbow angles (50°, 90°, 135°), fixed, and analyzed for sarcomere length [4]. Total RNA was extracted from pre- and post-HSN biceps samples to characterize transcriptional changes. Clinical spasticity was assessed before Stage 1 and again before Stage 2 using the Modified Ashworth Scale (MAS). Data were compared using repeated-measures models, and single-cell transcriptional changes were analyzed using established analytical pipelines. Results: Sarcomere length (SL) increased significantly after HSN at all joint angles. At 50°, SL increased from 2.45 ± 0.18 µm pre-HSN to 3.05 ± 0.28 µm post-HSN; at 90°, from 2.70 ± 0.29 µm to 2.91 ± 0.16 µm; and at 135°, from 2.72 ± 0.36 µm to 3.24 ± 0.32 µm (all p < 0.05). Clinical spasticity assessment improved significantly as well (p < 0.05), with MAS scores decreasing from 1.89± 0.93 to 0.35 ± 0.53. RNA sequencing revealed changes in key pathways and overall gene expression patterns such as enhanced inflammatory response through increased cytokine production and fibroblast proliferation, leading to elevated collagen synthesis and subsequent fibrosis. We also observed upregulated immune modulation and chemotaxis, while pathways involved in mitochondrial respiration, muscle development, and cellular homeostasis were downregulated. At the transcript level, HSN led to decreased inflammation and adipogenesis, while promoting increased extracellular matrix assembly, and vascular formation. Conclusion: HSN produced coordinated improvements across structural, clinical, and transcriptional levels in the spastic human biceps muscle. Sarcomere lengths increased toward longer resting lengths at all joint angles, clinical spasticity decreased significantly, and RNA sequencing revealed distinct post-operative transcriptional remodeling. The longer sarcomere length and decreased spasticity should contribute to improved patient function after HSN. References: 1. Lieber RL et al. Muscle Nerve. 2002;26:98–105. 2. Leclercq C et al. Hand Clin. 2018;34:537–545. 3. Lieber RL et al. J Neurophysiol. 1994;71:874–881. 4. Ward SR et al. J Biomech. 2009;42:193–196. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Background: In recent years, the prevalence of medial ulnar collateral ligament injuries has increased in throwers of all ages and skill levels. The motusBASEBALL sensor possesses an inertial measurement unit (IMU) that has been developed and applied to the throwing arm to allow for measurements of several objective parameters, which may prove beneficial for monitoring, rehabilitation, and injury prevention in the throwing athlete. However, the reliability, consistency, and validity of the IMU have not been independently assessed. Purpose: To evaluate the reliability, consistency, and validity of the motusBASEBALL sensor compared with the historic gold standard of marker-based motion capture. Study Design: Controlled laboratory study. Methods: A total of 10 healthy male baseball athletes with varsity-level high school experience volunteered to participate in this study. Participants were fitted with 37 retroreflective markers for motion capture and the motusBASEBALL IMU sensor. Participants threw 5 fastballs at maximum effort, with measurements recorded simultaneously by motion capture and the IMU. Arm slot, arm speed, arm stress, and shoulder rotation were measured and compared. Results: Of the 4 metrics generated by the IMU, significant differences were found for 3 of the throwing metrics compared with motion capture including arm slot (5.0°± 6.1°; P = .037), elbow varus torque (9.4 ± 12.0 N·m; P = .037), and shoulder rotation (6.3°± 6.1°; P = .014). Arm speed did not demonstrate a statistically significant difference (29.2 ± 96.8 rpm; P = .375). The IMU consistently underreported pitching performance values. Shoulder rotation exhibited excellent reliability with <5° of error, and arm slot demonstrated good reliability with <10° of error. Arm stress and arm speed were less reliable. Conclusion: The IMU was not accurate or valid for arm slot, arm stress, and shoulder rotation compared with marker-based motion capture. It was relatively accurate for arm speed. Despite its lack of validity, it was consistent and reliable for arm speed and shoulder rotation and relatively reliable for arm slot and arm stress. Caution should be used when comparing values provided by this IMU to the gold standard of marker-based motion capture. Clinical Relevance: IMU technology has potential to be used in monitoring, rehabilitation, and injury prevention in throwing athletes if valid. This study demonstrates that the values provided by the IMU should not be considered equivalent to those generated by the gold standard of marker-based motion capture; however, there may still be a role for this technology when relying on its internal consistency for intrathrower comparisons and tracking.

Objectives: The current standard of care for an amputee is a socket-based prostheses. An osseointegrated implant (OI) is an alternative for prosthetic attachment. Osseointegration addresses reported problems related to wearing a socket interface, such as skin issues, discomfort, diminished function, quality of life, prosthetic use, and abandonment. The purpose of this report is to systematically review current literature regarding OI to identify and categorize the reported clinically relevant outcome measures, rate the quality of available evidence, and synthesize the findings. Data sources: A multidisciplinary team used PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methods. Search methodology was based on identifying clinically relevant articles. Three databases were searched: PubMed, CINAHL, and Web of Science. Study Selection: Clinical studies with aggregated data reporting at least 1 clinically relevant outcome measure were included. Data Extraction: The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criterion was used for critical appraisal and recommendations. Conclusions: This review identified 21 clinically relevant observational studies. Outcome measures were categorized into the following 9 categories: vibratory stimulation, complications, biomechanics, economics, patient-reported outcome measures, electromyography, x-ray, physical functional performance, and energy consumption. This systematic review consisted of Level III and IV observational studies. Homogeneous outcome measures with strong psychometric properties across prospective studies do not exist to date. Higher-level, prospective, randomized, long-term, clinically relevant trials are needed to prove efficacy of OI compared with socket prosthetic attachment. Osseointegration was at least equivalent to sockets in most studies. In some cases, it was superior. Osseointegration represents a promising alternative to socket prosthetic attachments for extremity amputees. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.