Teres minor muscle and related anatomy.

BACKGROUND: The purpose of this study was to describe the complex anatomy surrounding the teres minor muscle. METHODS: Thirty-one cadaveric human shoulders were dissected. Qualitative fascial and neurovascular anatomy were described. Location of motor nerves to teres minor were measured in reference to local anatomy. RESULTS: Fascial anatomy of the posterior shoulder had 2 distinct and equally common variants, 1 of which demonstrated a stout, inflexible fascial compartment enveloping the teres minor muscle. The other had a continuous fascia enveloping both the infraspinatus and teres minor muscles. In both variants, the primary nerve to teres minor traveled around a fascial sling, becoming sub-fascial at an average of 44 mm (range, 25-68) medial to the teres minor's insertion. The nerve took its most angulated course as it entered the fascial sling. Smaller accessory innervation of teres minor began, on average, 30 mm (range, 15-48) medial to the muscle's lateral insertion. None of the accessory motor nerves coursed deep to the fascial sling nor to the distinct teres minor fascial compartment. CONCLUSION: A stout fascial sling may be the potential site of greatest compression and tethering of the primary motor nerve to teres minor. Additional lateral accessory motor nerves to teres minor remained extra-fascial and took a less angulated path. Half of the shoulders demonstrated a separate teres minor fascial compartment. An improved understanding of the fascial anatomy and innervation pattern of the teres minor muscle may help clinicians who treat patients with symptomatic isolated teres minor muscle atrophy.

Insertional anatomy of the triceps brachii tendon.

HYPOTHESIS: Triceps tendon anatomy is important for surgical approaches to the elbow and tendon repair. The purpose of this study is to describe both the qualitative and quantitative anatomy of the triceps brachii tendon insertion. MATERIALS AND METHODS: Thirty-six elbows were dissected from twenty-three cadavers. Dimensions of the triceps tendon proper, lateral triceps expansion, and tendon insertion were measured. The central triceps tendon morphology was described. RESULTS: All specimens showed a distinct lateral tendon expansion continuous with the anconeus fascia (mean width, 16.8 mm). The mean width of the proper triceps tendon was 23.7 mm. The mean maximum olecranon width was 26.9 mm. The ratio of the triceps tendon width to the olecranon width averaged 0.88. The mean thickness of the central tendon insertion was 6.8 mm. The medial triceps tendon showed a distinct, rolled medial edge and an insertion consistently confluent with the central tendon. The triceps footprint insertion was dome shaped. The mean insertional width and length of the tendon proper were 20.9 mm and 13.4 mm, respectively. The mean distance from the olecranon tip to the tendon was 14.8 mm. The tendon width, thickness, and insertional dimensions correlated with the olecranon width. CONCLUSIONS: The lateral triceps expansion is a consistent anatomic finding with a width that is approximately 70% of the width of the central tendon. The triceps insertion has a broad width and narrow thickness that expands distally and correlates with the size of the olecranon. Knowledge of this anatomy will help the surgeon optimize surgical approaches and triceps repair techniques.

Unilateral proximal bifurcation of the femur.

We present a case report of a boy with a unilateral bifurcation of the proximal femur with a bifid femoral neck and 2 femoral heads. The patient had no other musculoskeletal or neurovascular abnormalities. One femoral head articulated with the acetabulum but the nonarticulating, larger head was better developed. The articulating head and neck were resected and the nonarticulating head was reduced. This hip then continued to develop well. This is the first report of such a phenomenon in the scientific literature.

Shear stress alters the expression of myelin-associated glycoprotein (MAG) and myelin basic protein (MBP) in Schwann cells.

Schwann cells within a peripheral nerve respond robustly after an axonal injury. Recent results have revealed that Schwann cells undergo concurrent proliferation and apoptosis after a chronic nerve injury that is independent of axonal pathology. Although the exact nature of the stimulus that produces this Schwann cell response remains unknown, we postulated that this response may be triggered directly by mechanical stimuli. Thus, we sought to determine how pure Schwann cells responded to a sustained shear stress in the form of laminar fluid flow by evaluating for proliferation, expression of S-100, myelin-associated glycoprotein (MAG), and myelin basic protein (MBP). Immunohistochemistry demonstrated that the Schwann cells were positive for S-100, MAG, and MBP in greater than 99% of the experimental cells. Stimulated cells also revealed an increased rate of proliferation by as much as 100% (p<.001). The mRNA expression of MAG and MBP was down-regulated by 21% (p<.035) and 18% (p<.015), respectively, in experimental cells from RT-PCR assays. Furthermore, Western blot showed a down-regulation in MAG and MBP protein expression by 29% (p<.035) and 35% (p<.02), respectively. This study provides novel information regarding Schwann cell direct response to this physical stimulus that is not secondary to an axonal injury.

Total elbow arthroplasty: current indications, factors affecting outcomes, and follow-up results.

Indications for total elbow arthroplasty (TEA) are expanding in light of newly published follow-up studies. The unique characteristics of the pathologic condition, appropriate patient selection, suitable choice of prosthesis, and proper surgical technique are critical factors that have a large impact on the ultimate results of TEA for any indication. This article addresses these factors as they relate to various indications and presents a review of the recently published results of the 10-year follow-up studies for TEA.

Optimization of Schwann cell adhesion in response to shear stress in an in vitro model for peripheral nerve tissue engineering.

The design of nerve guidance channels (NGCs) is evolving to produce a favorable environment for neural regeneration. We created an in vitro model to evaluate the interactions between three centrally important components of this altered host environment: (1). Schwann cells, (2). substrate, and (3). sustained mechanical stimulus in the form of shear stress with laminar fluid flow. Preconfluent Schwann cells were plated on slides coated either with laminin, poly-D-lysine, type IV collagen, or fibronectin. These slides were placed into custom-designed, parallel-plate, flow chambers and were administered laminar fluid flow at a rate of 15 mL/min for 2 h. Schwann cell adhesion assays demonstrated that laminin (mean, 86.1%; SEM, 4.47%) and fibronectin (mean, 81.7%; SEM, 3.24%) were statistically superior to collagen type IV (mean, 57.7%; SEM, 3.96%) and poly-D-lysine (mean, 58.0%; SEM, 4.97%) (p < 0.001). Fibronectin (mean, 12.20%; SEM, 0.374%) induced statistically greater Schwann cell proliferation than did laminin (mean, 8.14%; SEM, 0.682%) (p < 0.001). Therefore, we recommend that fibronectin should be used as an important component of NGCs with further in vivo studies. As mechanical stress is an integral part of the host environment, our study is the first to incorporate this factor into an in vitro model for peripheral nerve tissue engineering.