Constrained testing conditions affect the axial rotation response of lumbar functional spinal units.

STUDY DESIGN: Human cadaveric spine specimens were tested in axial rotation using constrained and unconstrained methods. OBJECTIVES: To determine the degree to which constrained methods affect the response of the functional spinal unit in axial rotation at lumbar and lumbosacral levels. SUMMARY OF BACKGROUND DATA: A substantial controversy exists in the literature regarding the appropriateness of different testing methods. No study has been found in which the effect of constraint on axial rotation behavior was objectively examined. METHODS: Ten human cadaveric spine specimens (five L3-L4, five L5-S1) were tested in axial rotation, using both constrained and unconstrained methods. In the unconstrained test, pure moments were applied to the upper vertebra, and its complete three-dimensional motion was measured using an optoelectronic camera system. In the constrained test, the specimens were loaded in a fixed-axis servohydraulic test machine individually around five rotational axis positions within the vertebral body, and the rotational motion was measured. RESULTS: The rotational angles in the constrained tests were not different among the five rotational axis positions. However, the maximum rotation from the five axis positions was approximately 40% greater than the minimum rotation, a significant difference. The axial rotational motion of the unconstrained tests was always less than the maximum rotation measured in the constrained test. However, the total rotational angle using the helical axis of motion was not significantly different from the constrained angles. CONCLUSIONS: The large differences between maximum and minimum rotation angles demonstrate that the behavior of the functional spinal unit in axial rotation is sensitive to the axis's position but the location of the axis is not repeatable. This supports the use of unconstrained methods in spinal testing.

Melorheostosis of the hand with complicating bony spur formation and bursal inflammation: diagnosis and treatment.

A 37-year old woman presented with intolerable pain associated with a slowly growing mass on the dorsum of the right hand. The radiographs were characteristic of melorheostosis involving the third and fourth metacarpals, with a cortical bony projection extending from the base of the third metacarpal eroding slightly into the fourth metacarpal, associated with bursal formation. Magnetic resonance imaging (MRI) demonstrated an inflamed bursal collection adjacent to the spur. This region corresponded to the patient's severe clinical, focal pain. To our knowledge, this is the first case report in which melorheostosis of the hand has been associated with bony spur formation and complicated by an inflamed bursa.

The role of supplemental translaminar screws in anterior lumbar interbody fixation: a biomechanical study.

The immediate stabilization provided by anterior interbody cage fixation is often questioned. Therefore, the role of supplementary posterior fixation, particularly minimally invasive techniques such as translaminar screws, is relevant. The purpose of this biomechanical study was to determine the immediate three-dimensional flexibility of the lumbar spine, using six human cadaveric functional spinal units, in four different conditions: (1) intact, (2) fixed with translaminar screws (TLS), (3) instrumented with anterior interbody cage insertion with the BAK system and (4) instrumented with BAK cage with additional TLS fixation. Flexibility was determined in each testing condition by measuring the vertebral motions under applied pure moments (i.e. flexion-extension, bilateral axial rotation, bilateral lateral bending) in an unconstrained manner. Anterior fixation with the BAK alone provided significant stability in flexion and lateral bending. Additional posterior TLS significantly reduced the motion in extension and axial rotation. TLS fixation alone resulted in smaller rotations than BAK fixation in all loading directions. Based on these results, it seems that interbody cage fixation with the BAK system stabilizes the spine in some, but not all, loading directions. The problematic loading directions of extension and axial rotation can be substantially stabilized by using translaminar screw fixation. However, one should emphasize that the degree of stability needed to achieve solid fusion is not known.

Imaging features of pseudoaneurysms of the hand in children and adults.

OBJECTIVE: Our objective was to review the imaging features of pseudoaneurysms of the hand in 25 patients. The patients presented with a mass, peripheral paresthesia, or ischemia. Pseudoaneurysm of the hand is a rare and often clinically unsuspected diagnosis. Correct diagnosis is important because there are risks for distal embolic disease with ischemia or gangrene of the fingers, ulnar or digital nerve dysfunction, rupture, or bone erosion and joint destruction. Scant reports appear in the world literature, and this report is the first review, to our knowledge, of the imaging features. The cause may be a history of a single direct trauma or chronic trauma, as seen in patients with hypothenar or thenar hammer syndrome. CONCLUSION: Awareness of the specific imaging appearances of pseudoaneurysms of the hand and their complications may improve the accuracy of radiologic diagnosis, advance the preoperative workup, and prevent possible clinical complications such as digital gangrene, nerve dysfunction, and aneurysm rupture.