Biomechanical analysis of nonreamed tibial intramedullary nailing after simulated transverse fracture and fibulectomy

A tibial shaft fracture model was created to study the effects of an intramedullary nail and partial fibulectomy on fracture loading. Cadaveric lower extremities were instrumented with strain gages and subjected to biomechanical testing. A nonreamed nail was inserted into each tibia using only the proximal locking screws. Each specimen was tested under six conditions: intact tibia; intact tibia with nail; fractured tibia with nail removed and fibula intact; fractured tibia with nail and fibula intact; fractured tibia with nail and partial fibulectomy; and fractured tibia with partial fibulectomy and nail removed. In the intact tibia the anterior cortices were in relative tension compared with the posterior cortex. After transverse fracture this relative tension was increased. Inserting the nail after fracture significantly increased anteromedial and anterolateral compressive strains and decreased posterior strains. Performing a partial fibulectomy in the fractured tibia with a nail had no significant effect on the strain patterns. These results confirm the relative anterior tension present in the intact tibia and demonstrate an increase in this anterior tension following transverse fracture. Performing a partial fibulectomy or inserting an intramedullary nail increased anterior compressive loading. This loading alteration may be responsible for the clinical success seen using these treatment methods.

An anatomic study of the subscapularis tendon and myotendinous junction

The subscapularis muscle and tendon were studied in 25 cadaveric specimens. The subscaputaris insertion into the proximal humerus and its musculolendinous junction was defined. We found that the subscapularis muscle had a gradual formation of the musculotendinous junction and, in contrast to classical descriptions, inserted into the humerus as both tendon and muscle. The musculotendinous junction was fully formed 2 cm from the lesser tuberosity. The superior 60% of the muscle's insertion inserted into the lesser tuberosity as tendon. The remaining insertion consisted of muscle and was below the lesser tuberosity. The anterior humeral circumflex vessels and the axillary nerve marked the inferior aspect of the subscapularis muscle at the anterior aspect of the quadrangular space. The vessels then coursed laterally and superiorly onto the anterior surface of the muscle insertion coursing over the division between the tendinous and muscular portions. Proper identification of these relationships can prevent complications in shoulder surgery.

The anterior humeral circumflex vessels and the axillary nerve. An anatomic study

The anatomic relationship between the anterior humeral circumflex vessels and the axillary nerve was studied in 24 fresh-frozen cadaveric four-quarter shoulder specimens. Each shoulder was exposed through a standard deltopectoral incision, and the axillary nerve, anterior humeral circumflex vessels, and bicipital groove were identified. The perpendicular distance from the medial border of the bicipital groove to a point where the vessels crossed anterior to the nerve measured 2.6 +/- 0.4 cm (range, 2.1-3.6 cm). The perpendicular distance from the medial aspect of the bicipital groove to the point where the axillary nerve crossed the inferior border of the subscapularis and thus entered the quadrangular space was 3.0 +/- 0.5 cm (range, 2.1-4.4 cm). The anterior humeral circumflex vessels were easily located in all specimens, and the axillary nerve could be identified by its relationship to the vessels as described above, thus providing the operating surgeon with a consistent and reliable method of recognizing this nerve during anterior shoulder procedures. In addition, the axillary nerve was palpable in all specimens by sweeping the index finger in a medial-to-lateral direction along the inferior border of the subscapularis.

Cervical spondylolysis. Report of two cases

Two cases of cervical spondylolysis are presented. Both cases were discovered during radiographic examination after incidental trauma. The first patient experienced transient quadriplegia that spontaneously resolved and the other experienced only neck pain. Further radiographic evaluation of the first patient revealed significant spinal cord compromise, ultimately requiring decompression and fusion. The second patient's cervical spine proved stable to dynamic studies and was without cord compromise.