Primary total hip arthroplasty after acetabular fracture.

In most cases, when THA is performed after an acetabular fracture, it is done to manage secondary degenerative change or, possibly, osteonecrosis of the femoral head. Secondary complicating factors may be encountered during the THA. After initial nonsurgical treatment of an acetabular fracture, an occult or frank acetabular nonunion and malunion are not uncommon and may extend to the residual pelvic ring. After surgical treatment, intrusive hardware, heterotopic bone, dense scar tissue, ischemic muscle or bone, and occult infection are additional hazards that may be encountered. When acute sciatic nerve palsy, whether induced traumatically or iatrogenically, accompanies the initial acetabular injury, the palsy is likely to be exacerbated during a subsequent THA. A careful clinical and radiographic evaluation is needed, along with the formulation of a detailed surgical strategy. The need for specialized arthroplasty instruments, fixation devices, and autograft or, occasionally, allograft has to be identified. When heterotopic bone is evident, an extensile approach may be needed to allow adequate exposure for its complete removal. After a bone defect and/or a nonunion with displacement has been characterized, one or more strategies for obliteration of the defect are considered; these include the use of impaction grafting, a structural graft, a cup inserted with multiple screws, mesh, or a suitable ring or other fixation device. Evaluation of results has shown that, overall, the late outcome of THA after acetabular fracture is inferior to that of arthroplasty performed because of degenerative arthritis. Although open reduction and internal fixation of an acute acetabular fracture was previously hypothesized as an effective way to improve the anticipated late outcome of THA by the elimination of a large fracture gap or the prevention of a potential nonunion, current observations do not support that hypothesis. An initial open reduction may compromise the outcome of a subsequent THA by compromising the blood supply of the acetabulum and by initiating the formation of scar tissue, heterotopic bone, or an occult or frank infection. For a highly selected group of especially severe acetabular fractures, particularly those in elderly patients, THA appears to be a promising therapeutic alternative.

Personal computer interface and software for the ZONAX microscope attachment controller.

We describe the hardware and software of a general-purpose interface that permits a personal computer (PC) running MS-DOS to control cytometric devices, e.g., a scanning stage, shutters, and focus motor attached to a microscope. This note explains how to use the interface to convert the ZONAX microscope attachment controller from 8080-based hardware control to PC-based control.