The innervation of the axillary arch determined by surface stimulodetection electromyography.

The axillary arch (AA) is a muscular anatomical variation in the fossa axillaris that has been extensively studied in cadaveric specimens. Within these dissections, different innervations of the AA have been proposed, but this has never been explored in vivo. Knowledge of the innervation of the AA is required in order to better understand its function (e.g. predisposition for certain sports and/or activities, understanding shoulder injuries in overhead sports). Here, we report on the use of surface stimulodetection electromyography (SSEMG) to resolve the innervation of the AA in 20 subjects (12 women, eight men - mean age of 21.3 ± 2.7 years) with a uni- or bilateral AA. SSEMG of each muscle [M. latissimus dorsi (MLD) and M. pectoralis major] was performed with a four-channel electrostimulation measuring system in order to determine the innervation of the AA. The results showed co-contraction of the MLD in 85% of the subjects after AA stimulation. In the remaining subjects, no specific localized response was observed due to non-specific nerve stimulation, inherent to the proximity of the brachial plexus in these individuals. Our findings demonstrate that SSEMG exploration offers a practical and reliable tool for investigating anatomical aspects of muscle innervation in vivo. Using this approach, we conclude that the AA receives the same innervation as the MLD (the N. thoracodorsalis), and may be considered a muscular extension of the latter.

Functional anatomy of the dorsal hood or the hand: correlation of ultrasound and MR findings with cadaveric dissection.

The main aim of this study was to provide an overview of the anatomy of the dorsal hood (DH) based on the dissection of sixteen cadaver hands, correlated with magnetic resonance (MR) and ultrasound findings. A secondary aim was to assess the function of components of the DH. Sixteen embalmed hands were evaluated by MRI and ultrasound before being dissected. Each hand was photographed during each stage of dissection. Secondly we evaluated the role of the different structures of the DH in the stability of the extensor tendon by transection of the different components alternatively at the ulnar and radial sides. MR, ultrasound, and dissection showed that the extensor tendon (ET) is stabilized by the sagittal band (SB) at the level of the metacarpophalangeal (MCP) joint and more distally by the transverse and the oblique bands, respectively. Transection of the radial SB of the second finger leads systematically to ulnar dislocation of the ET. The transection of the ulnar DH does not lead to instability of the ET. The SB is the most important structure of the DH in the stability of the ET at the MCP level. Rupture of the radial SB of the second finger leads systematically to ulnar dislocation of the ET.

Sonography of the finger flexor and extensor system at the hand and wrist level: findings in volunteers and anatomical correlation in cadavers.

We present a review of sonography of the flexor and extensor system of the hand and wrist in volunteers and cadavers. CT tenography also was performed in cadaveric specimens. Anatomical structures of the extensor system that were assessed with sonography included the extensor tendons and insertions, retinaculum, and dorsal hood. On the flexor side, the variable relationship between the flexor superficialis and profundus could be appreciated. Volar plates, tendon insertions, and annular pulleys could also be investigated. Sonography can show details of the finger flexor and extensor system.

Prevalence and MRI-anatomic correlation of bone cysts in osteoarthritic knees.

OBJECTIVE: The objectives of this study were to determine the prevalence of cysts in the weight-bearing areas and interspinous bone cysts in tibial plateau specimens derived from knees with advanced osteoarthritis, to perform MRI-anatomic correlation of these cysts, and to define their histologic characteristics. MATERIALS AND METHODS: Forty-two tibial plateau specimens were recovered from patients undergoing total knee replacement surgery for severe osteoarthritis (14 men and 28 women; mean age, 74 years; age range, 58-87 years). The tibial specimens underwent MRI with T1- and T2-weighted MR sequences. No radiographic data were available before MRI. Tibial specimens were sectioned using a high-speed rotating diamond disk into 3-mm-thick slices. MR images and anatomic specimens were analyzed for the presence of cysts in the interspinous and weight-bearing areas. Histologic staining methods included routine Harris hematoxylin stain, trichrome stain, and Alcian blue-PAS stain. RESULTS: Twenty-three (54%) of 42 specimens contained one or more cystic areas, with a total of 30 cystic areas. The cysts were distributed in the weight-bearing area (14/30) and interspinous area (16/30). All cysts seen on the anatomic slices could also be depicted on both MRI sequences. Histologic findings were identical for all noncommunicating cysts and revealed necrotic bone fragments with dead denuclearized cells. The cavities were surrounded by a layer of fibrous connective tissue containing adipocytes and osteoblasts. No evidence of epithelial components was found in the lining of the cavities. CONCLUSION: Interspinous and weight-bearing tibial cysts are common in severe knee osteoarthritis. The cysts contain necrotic bone fragments and are lined by a nonepithelial fibrous wall. Our findings support the hypothesis that interspinous cysts could result from repetitive bone stresses through the cruciate ligaments. Our findings do not support the use of the term "herniation cyst."