Measurement of whole-body human centers of gravity and moments of inertia.

With the inclusion of women in combat aircraft, the question of safe ejection seat operation has been raised. The potential expanded population of combat pilots would include both smaller and larger ejection seat occupants, which could significantly affect seat performance. The method developed to measure human whole-body CG and MOI used a scale, a knife edge balance, and an inverted torsional pendulum. Subjects' moments of inertia were measured along six different axes. The inertia tensor was calculated from these values, and principal moments of inertia were then derived. Thirty-eight antropometric measurements were also taken for each subject to provide a means for direct correlation of inertial properties to body dimensions and for modeling purposes. Data collected in this study has been used to validate whole-body mass properties predictions. In addition, data will be used to improve Air Force and Navy ejection seat trajectory models for the expanded population.

Contamination risks from a high-speed bone burr.

STUDY DESIGN: The authors recorded the contamination rate at a mock surgical site below a high-speed burr creating debris from a fresh-frozen allograft specimen. OBJECTIVES: To document possible contamination rates associated with high-speed burr use. SUMMARY OF BACKGROUND DATA: The literature contained no studies addressing a known rate of contamination from high-speed burr use. METHODS: Samples of debris were collected in a mock-up of an operation involving bone burring. Set distances were maintained between objects within the field. High-speed bone burring was performed on fresh-frozen allograft bone specimens, and falling debris was collected on sterile culture plates. Control specimens were obtained randomly. Two hundred test and 20 control samples were collected by means of standard sterile techniques. RESULTS: Thirty-five percent of the cultured specimens from the test group grew skin flora, compared with 10% from the control group (P = 0.02). CONCLUSIONS: The authors propose that the higher contamination rate in the experimental samples resulted from airborne bone chips striking nonsterile surfaces before landing on the culture plates. Such contamination may increase the risk of wound infection.

Management of intraoperative femur fractures associated with revision hip arthroplasty.

Femoral fractures sustained during revision total hip arthroplasty (THA) are a serious complication. The incidence of intraoperative femur fractures in the period from 1982 to 1986 was ten in 159 (6.3%) THA revisions. The patients were treated primarily by surgical stabilization with compression plates and screws. All of the fractures healed, but of the ten, only six patients ultimately regained satisfactory THA function.

Reapproximation of femoral anatomy in a young hip arthroplasty patient. A case report.

A 33-year-old white man with a total hip arthroplasty presented with a malunion deformity of his femur following a fracture. Careful reapproximation of normal anatomy was achieved through a corrective angled osteotomy procedure. An attempt was made to reduce anticipated risks associated with future revision arthroplasty, and the patient's difficulties in ambulation were alleviated.

Effects of electromyographic biofeedback on reaction time and movement time.

The effects of electromyographic (EMG) biofeedback on reaction time (RT) and movement time (MT) were investigated utilizing 42 right-handed, male subjects from a university population. Subjects were randomly divided into three groups, a control group and two experimental groups. Both experimental groups were exposed to their EMG signals from their triceps brachii during the task, one experimental group received written information explaining the purpose of the EMG was to improve performance through biofeedback. Reaction times of the first block of 25 trials were significantly faster than those on the subsequent three blocks of trials for all groups. This provided evidence of learning. No other significant effects for reaction times were observed. Mean movement time for the EMG-only group was significantly slower than the means of either the Control group or EMG-Biofeedback group, with no difference between the latter two. The differences between experimental groups may have been related to alteration of strategy, anxiety, motivation.