Load-bearing characteristics of lumbar facets in normal and surgically altered spinal segments

An in-vitro experimental study was carried out to measure the induced loading on human lumbar facets due to varying amounts of compressive axial load. Testing was done on L2-L3 and L4-L5 spinal motion segments obtained from cadavers at autopsy. The compressive loading was applied to the spinal specimens in first a neutral position and then in an extended position. The motion segments were tested in a normal state and after facetectomy of the left facet. Contact pressures were quantified using pressure-sensitive film. This film was inserted between the articulating surfaces of the two facet joints prior to placing axial loads on the motion segments. In addition to recording pressure, the film was also used to quantify contact area. This provided sufficient information to compute the total facet loadings for all cases studied. Results of this study show how facet loads, peak pressures and contact areas change with respect to the various loads, positions and states studied. In particular this study shows that the absolute facet loads remain relatively constant with increasing segmental compressive loads such that the facet load expressed as a percent of load applied to the segment decreases with increasing axial loads. It also shows that the contact area moves cranially at L2-L3 and caudally at L4-L5 with increasing loads in extension. Furthermore, this study indicates that the load on the remaining facet is reduced substantially after a facetectomy although peak pressure increases. Finally, this study demonstrates the substantial difference in facet loadings between L2-L3 segments and L4-L5 segments.

The isolated fracture of the ulnar shaft. Treatment without immobilization

The isolated fracture of the ulnar shaft is notorious for prolonged healing time. Over a twenty-seven-month period, seventy-one such fractures were treated at our institution. The initial twelve fractures were immobilized with the standard axilla-to-palm plaster cast. They had an average healing time of 10.5 weeks and a non-union rate of 8 per cent. The remaining fifty-nine fractures were treated without a cast or with a cast or splint for no longer than two weeks after injury and then mobilization as tolerated. In this group the average healing time was 6.7 weeks and there were no non-unions. The motion at the wrist and elbow was always regained, and the average loss of forearm rotation was 5 degrees.

Reduction of plasma levels of betathromboglobulin and platelet factor 4 during hemodialysis: a possible role for a short acting inhibitor of platelet aggregation

Plasma levels of the platelet markers betathromboglobulin and platelet factor 4 are elevated in patients with chronic renal failure, and their levels in hemodialysis patients increase further during exposure to the dialysis membrane. The effectiveness of a short acting inhibitor of platelet aggregation in reducing the blood levels of betathromboglobulin and platelet factor 4 was assessed by means of a double blind cross over study. A statistically significant reduction of betathromboglobulin and platelet factor 4 levels was observed during treatment with the platelet inhibitor.

Pyogenic infections of the pubic symphysis

Four cases of Pseudomonas aeruginosa infection of the pubic symphysis occurred in intravenous abusers of pentazocine hydrochloride and pyribenzamine. Symptoms included suprapubic pain when walking, bilateral inguinal pain, and pain caused by hip flexion and rotation. Cultures of material taken by joint aspiration and open biopsy yielded P. aeruginosa in three patients and P. aeruginosa, P. maltophilia, and Corynebacterium in the fourth. All four responded to antibiotic treatment and open debridement but were lost to follow-up. Recent reports of P. aeruginosa arthritis in intravenous drug abusers are discussed. The concept of infective synchondritis as a distinct entity is suggested.

A perfusion method of incubation to demonstrate horseradish peroxidase in bone

A perfusion method of incubation to show horseradish peroxidase in the bone of young mice is presented. After perfusion fixation, the incubation medium is perfused from the descending aorta into the entire lower half of the animal. From the vessels there is good penetration of the medium into all tissues. This allows the preparation of any one perfused bone to ground-, semithin-, and ultrathin sections. Differences in peroxidase distribution in the entire bone suggest regional differences in vascular supply. The tracer enzyme diffuses freely from the vessels into the extracellular fluid of bone. 3 min. after injection, peroxidase is found between all bone lining cells and in osteocyte lacunae.