The Biomechanical analysis of arm swing during gait in the elbow stiffness

Background and purpose: The arm swing plays a role in gait by assisting the forward movement with the maintenance of the trunk balance. This study evaluates the biomechanical characteristics of the shoulder and elbow and their alteration in elbow stiffness. Materials and methods: The study included (1) biomechanical analysis and (2) computational musculoskeletal modeling based on motion tracking. This biomechanical study included eight fresh frozen specimens from individuals of both genders. Analysis was performed using Tekscan, and biomechanical analysis was performed with a custom-designed jig system with gravity-assisted muscle contracture. Fifteen participants without musculoskeletal or gait disorders were included for computational modeling. Three-dimensional (3D) motion tracking system using three Azure Kinect was used to obtain information for the 3D location of each joint. Computational modeling using The AnyBody Modeling System was performed to calculate the joint moment and range of motion during the arm swing of the gait. Results: In biomechanical study, stage 2 contact pressure was significantly increased compared with stage 0 (mean contact pressure in the resting position, P<0.0001; mean contact pressure in the passive swing, P=0.039; peak contact pressure in the passive swing, P <0.007). In the computational modeling results, the elbow range of motion (ROM) of flexion–extension in stages 1 and 2 was significantly increased compared with stage 0 in the nondominant arm as the control group (stage 0 vs 1, P <0.001; stage 0 vs 2, P=0.008). Shoulder ROM of flexion–extension in stage 2 was significantly increased compared with stage 0 (stage 0 vs 2 in dominant, P<0.001; stage 0 vs stage 2 in nondominant, P<0.001). The joint moment of the elbow in flexion–extension was significantly increased in stages 1 and 2 compared with stage 0 in the dominant arm (stage 0 vs 1, P=0.029; stage 0 vs 2, P<0.001) and in the nondominant arm (stage 0 vs 1, P=0.001; stage 0 vs 2, P<0.001). The joint moment of shoulder in flexion–extension in stage 2 was significantly increased compared with stage 0 in the dominant (stage 0 vs 1, P=0.569; stage 0 vs 2, P=0.005) and nondominant (stage 0 vs 1, P=0.039; stage 0 vs 2, P=0.015) arms. Conclusions: The elbow bears the load created by gravity and muscle contracture in the resting and dynamic arm swing movement. Elbow joint stiffness increases the load-bearing in the resting position and the dynamic arm swing motion. The ipsilateral and contralateral shoulder joint seems to compensate for the decreased elbow motion by increasing the ROM of the shoulder joint. Therefore, the moment of both shoulder joints was also increased. Clinical relevance: The current study showed that elbow stiffness should be managed not only for pain relief and limited motion but also to delay the arthritic process.Docto

The forearm interosseous ligament: comparative mechanical properties of the proximal, central, and distal bands

We compared the mechanical properties of the three parts of interosseous membranes in 12 fresh-frozen specimens. The proximal, central and distal bands of interosseous membranes were tested in a universal testing machine. Tensile strength, ultimate strain, ultimate load and elastic modulus were measured and compared. The stress?strain relationship curves of these bands were similar to those of ligaments. Tensile strength, ultimate load and elastic modulus were significantly higher in the central band than in the proximal and distal bands. Ultimate strain was significantly lower in the central band than in proximal and distal bands. We conclude that the interosseous membrane is similar to ligaments in structure with each band having distinct characteristics. The findings may aid in clinical choice of proper grafts used for interosseous membrane reconstruction

Subacromial bursal preservation can enhance rotator cuff tendon regeneration: a comparative rat supraspinatus tendon defect model study

Background: The role of subacromial bursa in rotator cuff surgery is unknown. This study aimed to assess the subacromial bursa's role in the healing of supraspinatus tendon injury in a rat model. Methods: Twenty-three male Sprague-Dawley rats (9 weeks old; weight, approximately 296 g) were used in this study. Three rats used as biomechanical study controls were killed at 12 weeks of age. A supraspinatus tendon defect was made bilaterally in 20 rats, whereas an additional subacromial bursa sectioning was performed on the left side. Six rats were killed for biomechanical testing and 4 were killed for histologic observation at 3 and 9 weeks, respectively. Results: The regenerated tendon in the bursal preservation group showed significantly superior biomechanical properties in maximum load to failure at 3 and 9 weeks and stiffness at 9 weeks after surgery compared with the bursal removal group. The modified Bonar scale scores showed better regenerated supraspinatus tendons in the bursal preservation group. Conclusion: The present study found that the subacromial bursa plays an important role in rotator cuff regeneration in this rat supraspinatus injury model. Extensive bursectomy of the subacromial bursa may not be recommended in rotator cuff repair surgery, though future in vivo human studies are needed to confirm these observations. (c) 2020 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved