The science of pinning the neck of the femur.

Experiments show that the cancellum of some femoral heads and of the trochanteric region is too weak to support a nail. A simple classification of traumatic femoral neck fractures is presented. These are either vertical or, less commonly, transversely disposed. Either type may be undisplaced, impacted, or displaced. For adequate fixation of undisplaced vertical and all displaced fractures a nail plate is essential. For undisplaced transverse fractures and impacted vertical fractures two screws usually suffice. Impacted transverse fractures require no active treatment. Hammering nails into the femoral head can cause fractures of the articular cartilage, split the femoral head in two, lead to avulsion of articular cartilage under the weight-bearing area, and osteoarthrosis. Early weight-bearing on weak implants can be disastrous. For the unsolved fracture a sliding pin compressing the fragments should be used. In a series of 54 displaced fractures so treated, 50 united. Prosthetic replacement should be reserved for patients with poor-quality bone. Children are best treated with a Coventry lag screw. Non-union after internal fixation in young patients should be salvaged by an excisional osteotomy, but a prosthesis is the answer for elderly patients. Late segmental collapse is explained in terms of contact stresses.