✓ Postoperative sagittal-plane cervical spine deformities are a concern when laminectomy is performed for tumor resection in the spinal cord. These deformities appear to occur more commonly after resection of intramedullary spinal cord lesions, compared with laminectomy for stenosis caused by degenerative spinal conditions. Postlaminectomy deformities are most common in pediatric patients with an immature skeletal system, but are also more common in young adults (< 25 years of age) in comparison with older adults. The extent of laminectomy and facetectomy, number of laminae removed, location of laminectomy, preoperative loss of lordosis, and postoperative radiation therapy in the spine have all been reported to influence the risk of postlaminectomy spinal deformities. When these occur, patients should be monitored closely with serial imaging studies, because a significant percentage will have progressive deformities. These can range from focal kyphosis to more complicated swan-neck deformities. General indications for surgical intervention include progressive deformity, axial pain in the area, and neurological symptoms attributable to the deformity. Surgical options include anterior, posterior, and combined anterior–posterior procedures. The authors have reviewed the literature on postlaminectomy kyphosis as it relates to resection of cervical spinal cord tumors, and they summarize some general factors to consider when treating these patients.
Daniel R. Fassett, Randy Clark, Douglas L. Brockmeyer, and Meic H. Schmidt
Michael A. Finn, Daniel R. Fassett, Todd D. Mccall, Randy Clark, Andrew T. Dailey, and Darrel S. Brodke
Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link.
Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested.
All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct.
All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.
Edward F. Chang, Aaron Clark, Randy L. Jensen, Mark Bernstein, Abhijit Guha, Giorgio Carrabba, Debabrata Mukhopadhyay, Won Kim, Linda M. Liau, Susan M. Chang, Justin S. Smith, Mitchel S. Berger, and Michael W. McDermott
Medical and surgical management of low-grade gliomas (LGGs) is complicated by a highly variable clinical course. The authors recently developed a preoperative scoring system to prognosticate outcomes of progression and survival in a cohort of patients treated at a single institution (University of California, San Francisco [UCSF]). The objective of this study was to validate the scoring system in a large patient group drawn from multiple external institutions.
Clinical data from 3 outside institutions (University of Utah, Toronto Western Hospital, and University of California, Los Angeles) were collected for 256 patients (external validation set). Patients were assigned a prognostic score based upon the sum of points assigned to the presence of each of the 4 following factors: 1) location of tumor in presumed eloquent cortex, 2) Karnofsky Performance Scale (KPS) Score ≤ 80, 3) age > 50 years, and 4) maximum diameter > 4 cm. A chi-square analysis was used to analyze categorical differences between the institutions; Cox proportional hazard modeling was used to confirm that the individual factors were associated with shorter overall survival (OS) and progression-free survival (PFS); and Kaplan–Meier curves estimated OS and PFS for the score groups. Differences between score groups were analyzed by the log-rank test.
The median OS duration was 120 months, and there was no significant difference in survival between the institutions. Cox proportional hazard modeling confirmed that the 4 components of the UCSF Low-Grade Glioma Scoring System were associated with lower OS in the external validation set; presumed eloquent location (hazard ratio [HR] 2.04, 95% CI 1.28–2.56), KPS score ≤ 80 (HR 5.88, 95% CI 2.44–13.7), age > 50 years (HR 1.82, 95% CI 1.02–3.23), and maximum tumor diameter > 4 cm (HR 2.63, 95% CI 1.58–4.35). The stratification of patients based on scores generated groups (0–4) with statistically different OS and PFS estimates (p < 0.0001, log-rank test). Lastly, the UCSF patient group (construction set) was combined with the external validation set (total of 537 patients) and analyzed for OS and PFS. For all patients, the 5-year survival probability was 0.79; the 5-year cumulative OS probabilities stratified by score group were: score of 0, 0.98; score of 1, 0.90; score of 2, 0.81; score of 3, 0.53; and score of 4, 0.46.
The UCSF scoring system accurately predicted OS and PFS in an external large, multiinstitutional population of patients with LGGs. The strengths of this system include ease of use and ability to be applied preoperatively, with the eventual goal of aiding in the design of individualized treatment plans for patients with LGG at diagnosis.