Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five L2-3, five L4-5) were tested. From each cadaver spine, one motion segment was fixed with a pair of cylindrical cages (BAK, Sulzer Medica) and the other with paired rectangular cages (Rotafix, Corin Spinal). Each specimen was tested in an unconstrained state, after cage introduction and after additional posterior translaminar screw fixation. The range of motion (ROM) in flexion-extension, lateral bending, and rotation was tested in a materials testing machine, with +/- 5 Nm cyclical load over 10 sec per cycle; data from the third cycle was captured for analysis. RESULTS: ROM in all directions was significantly reduced (p < 0.05) with both types of cages. There was no significant difference in reduction of ROM in flexion-extension (p = 0.6) and rotation (p = 0.92) between the two cage groups, but stability in lateral bending was marginally superior with the rectangular cages (p = 0.11). Additional posterior fixation further reduced the ROM significantly (p < 0.05) in most directions in both cage groups, but did not show any difference between the cage groups. CONCLUSIONS: There was no significant difference in immediate stability in any direction between the threaded cylindrical cage and the new design of the rectangular cage with endplate teeth

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Cervical spine trauma

Cervical spine trauma is a common problem with a wide range of severity from minor ligamentous injury to frank osteo-ligamentous instability with spinal cord injury. The emergent evaluation of patients at risk relies on standardized clinical and radiographic protocols to identify injuries; elucidate associated pathology; classify injuries; and predict instability, treatment and outcomes. The unique anatomy of each region of the cervical spine demands a review of each segment individually. This article examines both upper cervical spine injuries, as well as subaxial spine trauma. The purpose of this article is to provide a review of the broad topic of cervical spine trauma with reference to the classic literature, as well as to summarize all recently available literature on each topic

Pelvic or lumbar fixation for the surgical management of scoliosis in duchenne muscular dystrophy.

STUDY DESIGN: This retrospective study evaluates two groups of patients with scoliosis and Duchenne muscular dystrophy, treated with two different surgical stabilization methods. OBJECTIVE: To determine whether fixation to the sacropelvis is always necessary for adequate stabilization of scoliosis in Duchenne muscular dystrophy. SUMMARY OF BACKGROUND DATA: Pelvic fixation is generally recommended for scoliosis in Duchenne muscular dystrophy. Recent studies describe a more selective approach toward lumbar or pelvic fixation. Pelvic fixation is reserved for larger curves and established pelvic tilt. METHODS: Fifty cases of Duchenne muscular dystrophy, operated in two different centers and followed up for a minimum of 3 years, were reviewed. In the first group (Oswestry), 31 patients had fixation to the pelvis, using standard Luque instrumentation and pelvic fixation. The Galveston technique was used in 9 cases and L-rod configuration in 22 cases. In the second group (Nottingham), 19 cases had fixation to L5 using pedicle screws in the lumbar spine and sublaminar wires in the thoracic spine. These cases were operated on early, usually shortly after becoming wheelchair dependent. RESULTS: In the pelvic fixation group, the mean age at the time of surgery was 14 years, and forced vital capacity was 44%. The mean Cobb angle and pelvic obliquity were 48 degrees and 19.8 degrees at the time of surgery, 16.7 degrees and 7.2 degrees immediately after surgery, and 22 degrees and 11.6 degrees at the final follow-up (mean 4.6 years), respectively. The mean blood loss was 4.1 L, and the average hospital stay was 17 days. There were five major complications, including a deep wound infection in one case, revision of instrumentation prominence at the proximal end in two cases, and loosening of pelvic fixation in two cases. In the lumbar fixation group, the mean age at the time of surgery was 11.7 years, and forced vital capacity was 58%. The mean Cobb angle and pelvic obliquity were 19.8 degrees and 9 degrees at the time of surgery, 3.2 degrees and 2.2 degrees immediately after surgery, and 5.2 degrees and 2.9 degrees at the final follow-up (mean 3.5 years), respectively. The mean estimated blood loss (3.3 L) and mean hospital stay (7.7 days) were much less compared with the pelvic fixation group. Pelvic obliquity was corrected and maintained below 10 degrees in all but two cases, who had an initial pelvic obliquity exceeding 20 degrees. One patient had instrumentation failure at the proximal end, and one had a deep wound infection. CONCLUSION: Lumbar fixation to L5 is adequate if the surgery is performed early, soon after becoming wheelchair bound, and with smaller curves and minimal pelvic obliquity. Use of pedicle screws in lumbar spine provides a solid foundation to maintain the correction over the period of relatively short life expectancy of these children. Pelvic fixation may be necessary in older children, who have larger curves and established pelvic obliquity. In the presence of deteriorating lung function, this is associated with a greater morbidity and higher complication rate