Effect of displacement of fractures of the greater tuberosity on the mechanics of the shoulder.

Using a dynamic biomechanical model of malunion of the shoulder, we have determined the change in deltoid force required for abduction with various combinations of superior and posterior displacement of fractures of the greater tuberosity of the humerus. We tested eight fresh human cadaver shoulders in a dynamic shoulder-testing apparatus during cycles of glenohumeral abduction from 0 degrees to 90 degrees. The greater tuberosities were osteotomised and stabilised to represent malunion with combinations of superior and posterior displacements of 1 cm and less. The peak force was measured for each displacement in each specimen and statistically compared with values of no displacement using a repeated-measures analysis of variance. The abduction force was significantly increased by 16% (p = 0.006) and 27% (p = 0.0001) by superior displacements of 0.5 cm and 1 cm, respectively, while combined superior and posterior displacement of 1 cm gave an increase in force of 29% (p = 0.001). While treatment criteria for acceptable residual displacement of the greater tuberosity are widely used, there is little information on the direct biomechanical effects of displacement on shoulder mechanics. Although the results of conservative treatment are influenced by a number of factors, including associated injuries, rehabilitation and the pre-existing function of the shoulder, our data suggest that small amounts of residual displacement may alter the balance of forces required to elevate the arm at the glenohumeral joint.

Nonarticular proximal tibia fractures: treatment options and decision making.

Nonarticular proximal-third fractures account for 5% to 11% of tibial shaft injuries and occur as a result of a variety of mechanisms. Treatment is more challenging than for more distal fractures, and the rates of compartment syndrome and arterial injury are higher, especially for displaced fractures. Closed management often leads to varus malunion, especially when the fibula is intact. Closed treatment should therefore be reserved for nondisplaced or minimally displaced fractures with little soft-tissue injury. Plating of the proximal tibia has become a less popular alternative because of the high incidence of infection and fixation failure. However, judicious use of lateral plates as an adjunct to medial external fixation in comminuted fractures can be effective. External fixation remains the most versatile method. It is indicated for fractures with short proximal fragments and in cases of extensive soft-tissue injury that would preclude use of other surgical techniques. Temporary joint-spanning external fixation has a role in the initial management of certain fracture patterns, particularly when accompanied by severe soft-tissue injury. Although intramedullary nailing can lead to valgus malunion in a sizable percentage of patients with this injury, it can be useful for stabilizing fractures with proximal fragments longer than 5 to 6 cm. Placing the entry portal more proximal and lateral, locking in extension, and using specific techniques, such as blocking screws, can improve alignment after nailing. Use of an algorithm that takes into account the severity of soft-tissue injury, the length of the fracture fragment, and the degree of fracture stability allows effective decision making among current treatment techniques.

'Floating pelvis'. A combination of bilateral hip dislocation with a lumbar ligamentous disruption.

A patient is described with a ligamentous disruption at the L4/L5 level in association with bilateral, traumatic dislocations of the hip. The diagnostic evaluation, acute intervention, and definitive stabilisation are reported. The unstable spine posed a problem in treatment with regard to the timing and technique of the reduction of the hips.