Spinal epidural lipomatosis: case reports, literature review and meta-analysis.

BACKGROUND CONTEXT: Symptomatic spinal epidural lipomatosis (SEL), a rare cause of spinal cord compression, has most often been associated with exogenous steroid use. PURPOSE: Identify four associations with SEL, correlate the associated groups with level of disease and compare treatment with outcome data in these groups. STUDY DESIGN/SETTING: Case reports of three patients and analysis of 104 cases from the literature. PATIENT SAMPLE: Three patients from the senior author's practice. OUTCOME MEASURES: Not applicable. METHODS: The authors report three new cases of SEL not associated with steroid use. They review all available English literature and present a table of all 104 reported cases. RESULTS: The clinical course of three new patients is reported. CONCLUSIONS: Associated conditions are exogenous steroid use, obesity, endogenous steroid excess, and some remain idiopathic. Although SEL is a rare condition, our review of the literature reveals many more reported cases than previously thought. With increased awareness of this condition and improved imaging techniques, further studies of this disease should be undertaken.     

Radiographic verification of pedicle screw pilot hole placement using Kirshner wires versus beaded wires

STUDY DESIGN: Kappa statistics were used to compare the accuracy of two different techniques for verifying pedicle screw pilot hole placement in cadaveric vertebrae. OBJECTIVE: To determine whether clinicians radiographically detect misplaced pedicle screw holes with greater sensitivity and specificity when beaded wires rather than straight Kirschner wires are used. SUMMARY OF BACKGROUND DATA: Pedicle screws commonly are used in orthopedic surgery to obtain and maintain spinal stability. Pedicle screws are reportedly misplaced at a rate of 20% to 40%. Radiographic verification is commonly used to place pedicle screw pilot holes, but this technique is known to be less than 100% accurate. Computer-assisted techniques may allow more accurate screw placement, but these techniques require expensive equipment. METHODS: Pedicle screw pilot holes were drilled into 12 human lumbar and thoracic vertebrae. Some of the holes were misplaced deliberately so that they violated the pedicle walls. Lateral and posteroanterior radiographs of the vertebrae were evaluated by 13 experienced orthopedic spine surgeons and 3 inexperienced observers. At different times, the observers were shown radiographs depicting Kirschner wires or beaded wires placed in the pilot holes. Observers indicated whether they thought the pedicle screw pilot hole violated the pedicle. RESULTS: The sensitivity and specificity of using posteroanterior or lateral radiographs to detect misplaced pedicle screws were increased when beaded wires were placed in the pilot holes. CONCLUSIONS: Radiographic evaluation of beaded wires placed in pedicle screw pilot holes can be both sensitive and specific for misplaced screws. The highest sensitivity and specificity were found using posteroanterior radiographs.     

Sensitivity and specificity of dural sac and herniated disc dimensions in patients with low back-related leg pain

Narrow spinal canals or herniated discs can be associated with leg pain. However, it is not known whether quantitative measurements of the spinal canal or herniated disc are sensitive and specific for low back-related leg pain. The size and cross-sectional area of the dural sac and any herniated discs were measured from magnetic resonance imaging examinations of 22 asymptomatic individuals and 44 patients with sciatica. The sensitivity and specificity of these measurements were determined. In this small population of patients, a dural sac anteroposterior (AP) diameter of 10.2 mm at the L3-4, L4-5, or L5-S1 vertebral levels was 74% sensitive and 74% specific for leg pain. Based on measurements in symptomatic patients, a herniated disc with an AP diameter of approximately 3 mm was over 95% sensitive and 95% specific. However, if the AP diameters of herniated discs in symptomatic patients were compared with similar measurements in asymptomatic controls, the most sensitive and specific threshold value was 6.8 mm. These findings must be confirmed in a larger population before they are applied clinically. J. Magn. Reson. Imaging 2000;12:439-443.     

Thoracolumbar pseudarthrosis

Pseudarthrosis is the leading cause of failed spine fusion and is of paramount concern to surgeons attempting fusion procedures. Thus, it is essential to understand this complication to direct efficient and intelligent management. A review of various modalities in the identification and diagnosis of a pseudarthrosis is presented. In addition, its histologic features and classification system are discussed. Not all pseudarthroses need treatment. When treatment is considered, however, there are both nonoperative and operative strategies. Operative alternatives include posterolateral, anterior, or anterior-posterior combined fusions.     

Donor marrow-derived cells as immunogens and targets for the immune response to bone and skin allografts

The relative importance of donor marrow-derived cells in the immunogenicity of bone and skin allografts was compared. Radiation chimeras were created to have marrow-derived cells (MDCs) of a different genotype from their nonmarrow-derived cells (NMDCs). Such animals were used as donors of bone or skin for recipients chosen so that either the MDCs or the NMDCs of the graft would be incompatible. Immunogenicity was determined by measuring the recipient antibody response. The effect of the immune response on the bone graft (rejection) was determined by impaired bone healing. When MDCs alone were H-2 disparate with the recipient, bone grafts were immunogenic, and the bone graft healing was impaired. In contrast, skin grafts in the same combinations were immunogenic but were not rejected if the differences were only expressed on the MDCs of the graft. The role of NMDCs in all of these experiments was more difficult to interpret, but the results suggested that NMDCs are relatively unimportant for healing of bone grafts, although critical for rejection of skin grafts. We conclude that, unlike the situation with skin grafts, the major inducers and targets of the immune response to bone allografts are marrow derived.     

Posterior annular strains during discography

Discography is commonly used in the workup of back disorders. The clinical utility of the test is controversial, and little is known about mechanical changes that may occur in the disc during this exam. To quantify three-dimensional deformations of the posterior annulus during discography, and to examine some of the covariates that influence the deformations, displacements of the lumbar posterior annulus were measured during discographic injection for three different spinal positions. Disc bulge and annular strains were calculated from the displacements. The combined effect of disc pressurization, spine position, and location on the disc (lateral versus midline) explained much of the variation in the measured bulges and strains (r(2) = 0.56). Disc pressurization or spine position alone did not always have a significant effect on strains, and the strains and bulges were often influenced by the interactions between position of the spine, location of the disc, and pressurization. In clinical studies of discography, these results suggest that patient position during the examination should be standardized.