Bishop, Allen T.

BACKGROUND: The application of vascularized rib grafts in spine surgery has been limited to the treatment of kyphosis with anterior placement of the rib graft to facilitate anterior spine arthrodesis. The outcomes following use of vascularized rib grafts in complex spinal reconstruction have not been adequately evaluated. The purpose of this study was to determine the results, including the time to osseous union and complications, following anterior or posterior placement of pedicled vascularized rib grafts for complex spinal reconstruction. METHODS: The medical records and images of all patients in whom a vascularized rib graft had been used for a multisegmental spine reconstruction at a single institution between 1994 and 2004 were retrospectively reviewed. Eighteen patients (mean age, 45.3 years) who had been followed for an average of 31.8 months were identified. Details regarding indications, the levels that were spanned, the graft length, the time to union, and complications were evaluated. RESULTS: The preoperative diagnoses included metastatic or primary tumor (thirteen patients) and progressive kyphosis secondary to chronic osteomyelitis (two), injury (one), congenital anomalies (one), or implant failure (one). On the average, 4.4 levels were fused and 1.9 vertebral bodies were excised. All eighteen arthrodeses included various forms of allograft and/or autograft material, and instrumentation was used, in addition to the vascularized rib graft, in twelve patients. The mean rib length was 16.1 cm, and a rib between the fifth and eleventh ribs, inclusive, was used, depending on the location of the spinal reconstruction. The average time to union was 6.8 months, and all rib grafts united. There were no complications specific to the rib-harvesting procedure. CONCLUSIONS: The use of a vascularized rib graft in complex spinal reconstruction adds little time to the overall procedure, is associated with low morbidity, and appears to offer substantial benefits to the patient.

The physical attributes of the three capitohamate interosseous ligaments were tested in a computer-controlled multi-axis testing machine using 12 human cadaver specimens. After an intact test run, selected ligaments were cut in random sequence and the test repeated. The remaining ligaments were tested to failure with servohydrolic stress at 5 mm/second. In the intact joint complex, the average dorsopalmar rotational displacement was approximately 9° in each direction. Under the load limit, the dorsopalmar translational displacement averaged 0.9 mm and 0.5 mm respectively, proximal–distal translational displacement averaged 0.8 mm and 0.4 mm respectively, and distractional displacement averaged 0.3 mm. Based on the sequential sectioning it was found that the dorsal ligament provided 76% (SD 14) of the rotational resistance with palmar rotation of the capitate and 44% (SD 19) of translational constraint with palmar translation of the capitate. The deep ligament provided 51% (SD 15) of the rotational resistance with dorsal rotation of the capitate and 63% (SD 24) of translational resistance with dorsal translation of the capitate. With proximal—distal translation, the dorsal ligament was the most important constraint in each direction. In resisting distraction, each of the three ligaments was equally effective. Failure testing showed the deep ligament was strongest at 289 N, followed by the palmar at 171 N and the dorsal at 133 N.

A relationship between gout and Kienböck’s disease has been proposed on the basis of a previously published case report. A review of patients at our institution identified a single case with the combination of both Kienböck’s disease and gout. We believe that the association is coincidental.

An ex vivo rabbit tibia perfusion model was developed to investigate the vascular reactivity and vascular endothelial function of bone tissue. The tibiae of 36 adult New Zealand rabbits were isolated and perfused through the cannulated nutrient artery at a constant flow rate in an organ chamber. The increase in perfusion pressure caused by graded doses of norepinephrine produced a dose response curve, which was first recorded under control condition, and then during perfusion with acetylcholine (ACh), N G -monomethyl-L-arginine acetate (L-NMMA), and/or L-arginine (nitric oxide precursor) infusion. The optimal flow rate for rabbit tibia was 0.3 to 0.4 ml/min, depending on the weight of the tibia. The perfusion baseline and the norepinephrine dose-response curve (NEDRC) remained stable for at least eight hours. Acetylcholine (1 × 10-5 M ) infusion attenuated the NEDRC (33 ± 5%) for 1.5 hours. Thereafter, the vasorelaxant effect of ACh diminished due to depletion of nitric oxide, and ultimately caused an increase in the NEDRC due to a vasoconstrictive action. The rebound vasoconstriction did not occur in the presence of constant L-arginine infusion, which maintained nitric oxide production, and ACh continued to attenuate the NEDRC (36 ± 4.5%) for at least eight hours. L-NMMA, which inhibits the synthesis of nitric oxide, increased the vasoconstrictive effect of norepinephrine significantly (155 ± 16%). The rabbit tibia ex vivo model seems ideal for the study of bone vascular bed activity, due to its stable baseline, reliable NEDRC and cost efficiency. We have further demonstrated that the intraosseous vascular endothelium of rabbit tibia produces nitric oxide as one method of regulating bone perfusion.