Biomechanical comparison of calf and human spines.

Given the limited availability of human cadaveric specimens and their potential risk of infection, calf spines have been used as substitutes for human spines in the evaluation of spinal implants. Few biomechanical data comparing calf and human spines are available, however. The purpose of this study was to determine the biomechanical properties of the calf spine and to compare them with properties previously reported for the human spine. We determined the range of motion neutral zone, and stiffness of thoracic and lumbar calf spines (T6 to L6) under pure moment loading in flexion-extension, axial rotation, and lateral bending. These properties were shown to be similar to those of the human spine. The results suggest that the calf spine can be used as a substitute for the human spine in some in vitro tests.

Formalin fixation strongly influences biomechanical properties of the spine.

As fresh human cadaveric spine specimens for in vitro testing are hard to obtain and carry a potential risk of infection, the possibility of using embalmed spine specimens has been considered. The cross-linking effect of formalin fixation, however, raises uncertainties regarding the biomechanical likeness of preserved specimens. They have been reported to be stiffer, but no quantitative data exist. The purpose of this study was to determine the biomechanical differences between fresh and formalin-fixed spine specimens, using L1-2 motion segments from six 16-week-old calf spines. The range of motion and neutral zone were determined in flexion-/extension, left/right axial rotation, and right/left lateral bleeding. The range of motion decreased in the formalin fixed specimens by as much as 80%, and the neutral zone by as much as 96%. The results of this study therefore imply that, for biomechanical testing, formalin-fixed specimens are not representative of the in vivo conditions.

The thoracodorsal artery perforator flap with a vascularized scapular segment for reconstruction of a composite lower extremity defect.

High-energy trauma resulting in a composite defect of the lower extremity confronts the microvascular surgeon with more difficulties than do free flap reconstruction elsewhere in the body, since the choice of distant recipient vessels is particularly difficult. Combining principles of perforator flap surgery with those of composite tissue transfer, we designed a thoracodorsal artery perforator flap with a vascularized bone segment from the scapula for reconstruction of a composite lower extremity defect in a patient following a paragliding accident. This is the first report on the application of a composite thoracodorsal artery perforator flap with vascularized scapula in lower extremity reconstruction. Among its multiple advantages, such as preservation of latissimus dorsi function, it is a good tool for one-stage reconstruction of traumatic composite lower extremity defects because its low donor site morbidity and long vascular pedicle enables anastomosis placement outside the zone of injury.

Load-displacement properties of the thoracolumbar calf spine: experimental results and comparison to known human data.

The availability of human cadaveric spine specimens for in vitro tests is limited and the risk of infection is now of vital concern. As an alternative or supplement, calf spines have been used as models for human spines, in particular to evaluate spinal implants. However, neither qualitative nor quantitative biomechanical data on calf spines are available for comparison with data on human specimens. The purpose of this study was to determine the fundamental biomechanical properties of calf spines and to compare them with existing data from human specimens. Range of motion, neutral zone, and stiffness properties of thoracolumbar calf spines (T6-L6) were determined under pure moment loading in flexion and extension, axial left/right rotation and right/left lateral bending. Biomechanical similarities were observed between the calf and reported human data, most notably in axial rotation and lateral bending. Range of motion in the lumbar spine in flexion and extension was somewhat less in the calf than that typically reported for the human, though still within the range. These results suggest that the calf spine can be considered on a limited basis as a model for the human spine in certain in vitro tests.