Kingsbury G. Heiple

Contribution of collagen and mineral to the elastic-plastic properties of bone

Tension testing of wet bovine haversian cortical bone demonstrated marked plastic behavior. Progressive surface decalcification of this bone with dilute hydrochloric acid resulted in progressive decreases in the tension yield point and the ultimate stress with no change in the yield strain or ultimate strain unless decalcification was complete. The slope of the plastic region remained identical throughout decalcification. These findings are consistent with an elastic-perfectly plastic model for the mineral phase of bone tissue in which the mineral contributes the major portion of the tension yield strength. The slope or stiffness of the plastic region of the stress-strain curve is a function only of the properties of collagen, which itself plays a minor role in the tension yield strength of bone.

Bone Strength: The Effect Of Screw Holes

1. In dogs, redrilling a screw hole after removal of the screw did not improve final repair as judged by both histological examination and biomechanical testing.2. The screw holes, despite the radiolucency apparent on roentgenograms were rapidly filled with dense woven bone, and then were slowly rem

Prognosis in septic arthritis of the hip in children.

Thirty-eight children (39 hips) with septic arthritis have been reviewed in an effort to determine the factors most important to prognosis of the hip joint. The younger patients, 3 or more years later, had poorer results by roentgenographic classification. This was particularly true of patients under one year of age. Longer duration of disease from clinical onset to initiation of therapy also resulted in a poorer result. The outcome could not be clearly correlated with the causative organism or with open as opposed to closed treatment although the policy of management was strongly biased to open drainage. Sixty per cent of the infections were caused by Staphylococcus aureaus and the majority of the other cases by Streptococcus pyogenes and Hemophilus influenzae. The nonstaphylococcal organisms may be less destructive to the femoral head in infants.

Knee function after patellectomy and cruciform repair of the extensor mechanism.

When patellectomy is performed, the objectives should include restoration of a moment arm, centralization of the extensor mechanism, adequate range of motion, and cosmesis. The cruciate repair of the extensor mechanism described in this report has been developed to meet the aforementioned objectives. Eight patients with 12 patellectomies described herein were examined with Cybex testing of the knee at a follow-up period of 18 months to 20 years (mean, 56 months). A four-quadrant tissue dissection of the patellar soft-tissue enclosure was reconstructed in a cruciform pants-over-vest fashion, with the superomedial flap containing the vastus medialis insertion on top. This soft-tissue patella attempts to provide a greater moment arm than simpler repairs. This study examines whether this construct restored the torque of extension while concomitantly facilitating centralization of the extensor mechanism. Cybex testing of both knees examined both extensor and flexor function with specific regard to the ratio of extensor to flexor forces. Patients with patellectomies had few subjective complaints, with a mean knee score of 94 (median, 100). The extensor torque was not completely restored and there was a moderate decrease in the quadriceps function, both subjectively and objectively as measured by Cybex testing. The authors also found that in patients with unilateral patellectomies, the ratios of extension to flexion function, a parameter not yet reported in the literature, were significantly different between the normal and patellectomized knees. The same extension to flexion ratios were seen in patients with bilateral patellectomies. Because patients with patellar pathology requiring patellectomy frequently have chronic and bilateral disease, comparative functional evaluation may be difficult.(ABSTRACT TRUNCATED AT 250 WORDS)