RESUMEN
This study had two purposes: first, to determine how femoral attachment location affects the load sharing between the two bundles of a Y-type posterior cruciate ligament reconstruction, and second, to determine how the bundles, separately and in combination, control posterior tibial translation throughout the full range of knee flexion. One and two-bundle reconstructions were performed in 12 cadaveric knees. The one-bundle reconstructions were attached within the femoral posterior cruciate ligament footprint at one of three locations, high and shallow (S1), mid and shallow (S2), or mid and deep (D). The two-bundle reconstructions comprised an S1 bundle with either an S2 or a D bundle. Posterior translation and bundle tension were measured as the knee was flexed from full extension to 1,200 of flexion while a posterior force of either 50 or 100 N was applied to the proximal tibia. The shallow one-bundle reconstruction restored posterior translation to within 2 mm of that of the intact knee over the entire range of knee flexion. The deep reconstruction did not control abnormal posterior translation above 45 degrees. The tension in the shallow bundles increased with knee flexion, and the deep bundle tension remained nearly constant throughout knee flexion. Both two-bundle reconstructions controlled posterior translation, but with different load-sharing characteristics. The S1-S2 configuration resisted posterior tibial translation as both bundles became taut in flexion. In contrast, the S1-D configuration resisted posterior translation in a reciprocal fashion with the D bundle tension being the greatest in extension and the S1 bundle tension being the greatest tension in flexion.
Asunto(s)
Ortopedia/métodos , Procedimientos de Cirugía Plástica , Ligamento Cruzado Posterior/cirugía , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Fenómenos Biomecánicos , Cadáver , Femenino , Fémur/cirugía , Humanos , Masculino , Persona de Mediana Edad , Rango del Movimiento Articular , Análisis de Regresión , Tendones/cirugíaRESUMEN
The management of hip instability in myelomeningocele patients is controversial. The purpose of this study is to review our long-term results of isolated Chiari osteotomies in the treatment of hip instability in children with myelomeningocele. Between 1975 and 1988, 11 patients underwent 13 Chiari osteotomies for reducible hip subluxation or dislocation and acetabular deficiency. The patients returned for follow-up clinical examinations, interviews, and radiographs. The average age at the time of surgery was 9.4 years (range, 5-18). The average age at follow-up was 18 years (range, 13-23). The average follow-up was 11.4 years (range, 2-18). The mean preoperative center-edge (CE) angle was -38 degrees. The mean immediate postoperative CE angle was 41 degrees. At final follow-up, the mean CE angle was 4.6 degrees. Only three of the 10 hips had a normal CE angle of > or = 25 degrees. The Chiari osteotomy alone did not achieve long-term hip stability in the majority of patients. Several, if not most, of our patients may progress to frank dislocation with longer follow-up.
Asunto(s)
Articulación de la Cadera/cirugía , Inestabilidad de la Articulación/cirugía , Meningomielocele/cirugía , Osteotomía/métodos , Adolescente , Niño , Preescolar , Femenino , Estudios de Seguimiento , Marcha , Luxación de la Cadera/etiología , Luxación de la Cadera/cirugía , Articulación de la Cadera/diagnóstico por imagen , Humanos , Inestabilidad de la Articulación/etiología , Locomoción , Masculino , Meningomielocele/complicaciones , Radiografía , Rango del Movimiento ArticularRESUMEN
GH-binding proteins (GH-BP) have recently been discovered in human plasma, but their biological function is unknown. The high affinity GH-BP is related to the GH receptor and may modulate the interaction of GH with tissue receptors, whereas the low affinity GH-BP should be inert in this regard. Modulation of receptor binding probably results in modulation of GH bioactivity. To address these issues, we examined the effects of purified GH-BPs as well as whole plasma on GH binding to receptors in human, rabbit, and female rat liver and in rat adipocytes. High affinity BP inhibited binding of GH to receptors in a dose-dependent fashion. Substantial inhibition was observed within the physiological range of BP concentrations; human liver and rat adipocytes were the most sensitive in this regard. In contrast, the low affinity BP had no effect on receptor binding of GH. Whole human plasma also inhibited GH binding to receptors. This effect could be attributed to its content of GH-BP, since removal or primary absence of the BP from plasma abolished its inhibitory effect. Purified high affinity BP also inhibited GH-dependent insulin-like growth factor-I production by cultured human fibroblasts to a degree comparable to receptor inhibition. We conclude that the circulating high affinity GH-BP, by sequestering GH, substantially interferes with binding of GH to its receptor, and that the well known inhibitory effect of plasma in RRAs for GH is largely due to this BP. GH action in human fibroblasts in vitro is similarly inhibited by this BP.