The role of distraction in improving the space available for the cord in cervical spondylosis.

STUDY DESIGN: This study analyzed the effects of distraction via strut graft insertion on the canal dimensions in spondylotic human cadaver cervical spines. Transverse and anteroposterior diameters and cross-sectional areas were measured by transverse computed tomography imaging before and after distraction without direct decompression. OBJECTIVES: This experiment was designed to address whether distraction across the disc space without direct canal decompression can improve the space available for the cord. SUMMARY OF BACKGROUND DATA: Smith-Robinson anterior discectomy and fusion have been shown to improve clinical symptoms of radiculopathy and myelopathy even in the absence of direct decompression. This has been postulated to be the result of gradual resorption of intruding osteophytes. However, the immediate effects of indirect distraction alone have not been previously investigated. METHODS: Four cadaver spines from elderly donors were harvested intact. The transverse diameter, anteroposterior diameter, and cross-sectional area of the spinal canal were measured before and after discectomy and distraction via insertion of fibular strut graft by digitization of contiguous computed tomography scan slices. RESULTS: The spinal canal dimensions before distraction were found to vary in a sinusoidal pattern around the disc space, with the maximum measurements located at the pedicle and the minimum measurements at the spondylotic ridge above or below the disc space. Distraction via strut graft insertion significantly increased the anteroposterior diameter and cross-sectional area, but had a negligible effect on transverse diameter. CONCLUSIONS: Anterior discectomy and distraction with a strut graft can significantly improve the space available for the cord in cervical spondylosis. Osteophyte debridement, which risks iatrogenic injury to the cord, may not always be necessary for improving clinical radiculopathy and myelopathy.

Does the angle of the computed tomographic scan change spinal canal measurements?

Computed tomographic scanning at 0 degrees, 10 degrees, and 20 degrees was used on two human cadaver cervical spines to determine whether altering the scan angle affects spinal canal measurement. Maximum anteroposterior diameter, cross-sectional area, and transverse diameter were determined by digitization of the scans. Both spines exhibited a regular sinusoidal pattern of variation in anteroposterior diameter and cross-sectional area, with less of a pattern for transverse diameter. The maximum values occurred around the discs in the normal spine, moving to just below the pedicle in the spondylotic spine. Minimum values were at the pedicle in the normal spine and near the discs in the spondylotic spine. Changing the computed tomographic scan angle to 10 degrees in either a cephalad or caudad direction had a negligible effect on the pattern or absolute values for any dimension in either spine. Changing the angle to 20 degrees in either direction significantly and irregularly altered both the pattern and values of anteroposterior diameter and cross-sectional area in both spines. There was little effect on transverse diameter. It was concluded that comparison of different scans should be interpreted with caution unless the change in angulation is 10 degrees or less.

Biomechanical comparison of single- and double-pin fixation for acute slipped capital femoral epiphysis.

Biomechanics of pin fixation for acute slipped capital femoral epiphysis (SCFE) was studied in an in vitro immature canine model. Acute SCFE were created in 24 paired femurs. The paired specimens were pinned with either one or two pins and loaded to failure. Strength and stiffness of the paired limbs were expressed as percentages of the loads necessary to create the initial SCFE in the intact specimen. Strength and stiffness were equivalent statistically for the intact physis and the fractured physis fixed with two pins. Single pinning was only 83% as strong and 78% as stiff as the intact physeal plate. Double-pin fixation is recommended over single-pin fixation for acute SCFE. These data, however, should not be extrapolated to the clinical situation of fixation for chronic SCFE.

Traction force profiles associated with the use of a fracture table: a preliminary report.

A load cell was developed that can reliably monitor longitudinal traction forces applied to limbs during several different orthopaedic procedures. This permitted determination of tensile loads and the effects of patient limb positions on tension magnitudes. The relationships between the magnitude and duration of applied tension to functional nerve changes were also studied. This preliminary report reviews traction force data on seven patients for eight operations. Mean peak loads for femoral, tibial, and hip procedures were 686, 356, and 306 N, respectively. Adduction of the limb around a fixed peroneal post caused great increases in traction forces.

Vitamin D deficiency rickets. A report on three cases.

A resurgence of classic vitamin D deficiency rickets has been noted in the recent pediatric literature, but no mention of it appears in recent orthopedic journals. Three cases of vitamin D deficiency rickets occurred in children whose ages ranged from 14 to 17 months. Similar to the experience of others, all three occurrences were in young black children who were sustained on breast milk for prolonged periods (9-17 months). Differing from other cases in the recent literature, the patients' families were not consuming vitamin D deficient diets to comply with religious beliefs. Simple treatment with vitamin D supplementation was effective once the diagnosis was established.