Doron Rabin

Current Practice in the Timing of Surgical Intervention in Spinal Cord Injury

Study Design. Systematic review of the literature and prospective survey study. Objective. To characterize expert opinion regarding the timing of surgery for decompression of the injured spinal cord and critically summarize the evidence for early surgical intervention for acute spinal cord injury (SCI). Summary of Background Data. The optimal timing of decompressive surgery for acute SCI is controversial, resulting in considerable variability in clinical practice. Moreover, the current opinion of spine surgeons regarding the optimal timing of surgery after SCI is unknown. Methods. We undertook a systematic review of the applied preclinical and clinical published data regarding the timing of decompression following SCI. A 20-question survey was sent to orthopedic and neurosurgical spine surgeons across the world. Response frequencies were compiled for respondent demographics and preference for timing of surgical decompression in 6 distinct clinical scenarios. &khgr;2 statistics were used to compare response frequencies based on specialty and fellowship training. Results. A total of 971 spine surgeons responded to the survey. In almost every clinical scenario, with the exception of central cord syndrome, the majority of respondents (≥80%) preferred to decompress the spinal cord within 24 hours. A complete cervical SCI would preferably be decompressed within 6 hours by 46.2% of respondents, but 72.9% would operate within 6 hours for an incomplete SCI in an otherwise identical clinical scenario. Conclusion. The majority of spine surgeons prefer to decompress the acutely injured spinal cord within 24 hours. The majority of spine surgeons prefer to decompress the cervical spine for patients with complete or incomplete cervical SCI within 24 hours. Early decompression (within 24 hours) should be considered as part of the therapeutic management of any patient with SCI, particularly those with cervical SCI. Very early decompression (within 12 hours) should be considered for a patient with an incomplete cervical SCI (with the possible exception of central cord syndrome).

An instrument to measure the health status in children with hydrocephalus: the Hydrocephalus Outcome Questionnaire

Object. In the measurement of clinical outcome in pediatric patients with hydrocephalus the conditions effects on a childs physical, emotional, cognitive, and social health are frequently ignored. The authors developed a quantitative health status measure, the Hydrocephalus Outcome Questionnaire (HOQ), designed specifically for children with hydrocephalus, which can be completed by the childrens parents. Methods. The standardized steps in the development of a health status measure were followed. Item generation required involvement of health professionals and focus groups with parents of children with hydrocephalus. A comprehensive list of 165 unique health status items was thus generated. To streamline the list, questionnaires were sent to 69 sets of parents to solicit their opinions regarding the most important of these health issues, and the 51 most significant items were then selected to represent the following health domains: physical, social-emotional, and cognitive. In another cohort of 90 sets of parents, the 51-item questionnaire was then tested for reliability and construct validity against the following independent measures of specific components of health: Health Utilities Index, Wide Range Achievement Reading Test, Strengths and Difficulties Questionnaires, and Functional Independence Measure for Children. The HOQ took approximately 10 to 15 minutes for the parents to complete and demonstrated excellent test-retest reliability (0.93, 95% confidence interval [CI] 0.88-0.96), interrater reliability (0.88, 95% CI 0.79-0.93), and internal consistency (Cronbach alpha 0.94). Pearson correlation testing demonstrated very good construct validity between domain scores and their respective independent measures. Conclusions. The HOQ for children with hydrocephalus demonstrated excellent reliability and validity properties. This tool will be valuable for a wide range of clinical research projects in pediatric hydrocephalus.

Repeat Cerebrospinal Fluid Shunt Infection in Children

Background: In this study, we investigated the treatment of cerebrospinal fluid (CSF) shunt infection and the risk factors for repeat shunt infection (RSI) in a cohort of children treated at the Hospital for Sick Children, Toronto, Canada. Methods: Between 1996 and 2000, a total of 51 children were identified with shunt infection (mean age 5.8 years). The medical records of these children were reviewed to identify cases of RSI within 6 months of the initial shunt infection (ISI). Results: In the 51 ISIs, the infecting organisms were coagulase-negative Staphylococcus (43.1%), Staphylococcus aureus (37.3%) and others (19.6%). The initial mode of treatment of the shunt infection was using an external ventricular drain (EVD) with removal of the shunt apparatus (54.9%), externalization of the shunt (37.3%) or shunt removal only (7.8%). The mean number of days of external CSF drainage (either EVD or externalized shunt) was 11.2 days. Ten patients (19.6%) developed RSI. The actuarial risk of RSI plateaued after 90 days at 24.4%. The following variables were tested as risk factors for RSI using survival analysis, although none reached statistical significance: initial organism (p = 0.09), age (p = 0.42), etiology of hydrocephalus (p = 0.45), number of days of CSF drainage (p = 0.45), type of surgical treatment of the ISI (p = 0.58) and the presence of bacteriologically positive CSF at ISI (p = 0.85). Conclusions: The risk of RSI is substantial and greater effort needs to be directed towards understanding the risk factors. Such studies will need a greater sample size in order to obtain sufficient statistical power.

Reliability of quantitative magnetic resonance imaging methods in the assessment of spinal canal stenosis and cord compression in cervical myelopathy.

Study Design. Prospective, blinded reliability study of quantitative magnetic resonance imaging (MRI) measures in patients with cervical myelopathy. Objective. To assess the intra- and interobserver reliability of commonly used quantitative MRI measures such as transverse area (TA) of spinal cord, compression ratio (CR), maximum canal compromise (MCC), and maximum spinal cord compression (MSCC). Summary of Background Data. There is no consensus on an optimal quantitative MRI method(s) in assessing canal stenosis and cord compression. Methods. Seven surgeons performed measurements on 17 digital MR images, on 4 separate occasions. The degree of stenosis was evaluated by measuring TA and CR on axial T2, MCC, and MSCC on midsagittal T1- and T2-weighted MRI sequences, respectively. Statistical analyses included repeated-measures analysis of variance and intraclass correlation coefficients (ICCs). Results. The mean ± SD for intraobserver ICC was 0.88 ± 0.1 for MCC, 0.76 ± 0.08 for MSCC, 0.92 ± 0.07 for TA, and 0.82 ± 0.13 for CR. In addition, the interobserver ICC was 0.75 ± 0.04 for MCC, 0.79 ± 0.09 for MSCC, 0.80 ± 0.05 for CR, and 0.86 ± 0.03 for TA. Higher degree of canal compromise (MCC) was associated with lower modified version of Japanese Orthopaedic Association Scale score (P = 0.05). Also, a strong association was found between MSCC and lower modified version of Japanese Orthopaedic Association Scale score, greater number of steps, and longer walking time (P < 0.05). Conclusion. All 4 measurement techniques demonstrated a good to moderately high degree of intra- and interobserver reliability. Highest reliability was noted in the assessment of T2-weighted sequences and axial MRI. Our results show that the measurements of MCC, MSCC, and CR are sufficiently reliable and correlate well with clinical severity of cervical myelopathy.

Analysis of in vivo kinematics of 3 different cervical devices: Bryan disc, ProDisc-C, and Prestige LP disc.

OBJECT Cervical arthroplasty has emerged as a means of preventing adjacent segment disease by preserving motion, restoring sagittal balance, and mimicking natural spinal kinematics. The purpose of this retrospective in vivo study was to characterize the impact of arthroplasty on sagittal balance and segmental kinematics of the cervical spine. METHODS Sixty patients receiving the Bryan disc, ProDisc-C, or Prestige LP disc were retrospectively analyzed. Only single-level arthroplasty cases were included in this study. Lateral dynamic radiographs of the cervical spine were evaluated using quantitative measurement analysis software to determine the kinematics at the index level both preoperatively and 1 year postoperatively. Collected parameters included range of motion (ROM), disc angles, shell angles, anterior and posterior disc heights (ADHs/PDHs), translation, and center of rotation (COR). Preoperative and postoperative data were compared using the Student t-test, with p < 0.05 indicating significance. RESULTS The Bryan and Prestige LP discs preserved motion, whereas the ProDisc-C increased segmental ROM from extension to flexion. Following surgery, the Bryan disc exhibited significant shell angle kyphosis, while ProDisc-C and Prestige LP retained lordosis. Both ADHs and PDHs decreased following insertion of the Bryan disc. In contrast, the ProDisc-C increased the ADHs and PDHs by 80% and 52%, respectively, and the Prestige LP disc increased the ADHs and PDHs by 20%. Only the ProDisc-C demonstrated significant translation of 0.7 mm. The ProDisc-C shifted the COR x by 0.9 mm anteriorly, while the Prestige LP disc demonstrated a significant superior shift of 2.2 mm in COR y. CONCLUSIONS All discs adequately maintained ROM at the surgical level. The greatest difference among the 3 devices was in the disc height and index angle measurements.

Accuracy and reliability of MRI quantitative measurements to assess spinal cord compression in cervical spondylotic myelopathy: a prospective study

Study type: Reliability study Introduction: Cervical spondylotic myelopathy (CSM) is the most common spinal cord disorder in persons more than 55 years old. Despite multiple neuroimaging approaches proposed to quantify the spinal cord compromise in CSM patients, magnetic resonance imaging (MRI) remains the procedure of choice by providing helpful information for clinical decision making, determining optimal subpopulations for treatment, and selecting the optimal treatment strategies. However, the validity, reliability, and accuracy of the MRI quantitative measurements have not yet been addressed. Objective: To assess the intra- and inter-observer reliability of MRI quantitative measurements of the spinal cord compromise in CSM patients. Methods: Seventeen CSM patients (13 male) of mean age 54.5 years old were selected from the AOSpine North America database. The patients had different combinations of stenotic levels (1–4 levels) and the clinical severity (range mJOA baseline: 8–18). Asymptomatic or previous surgically treated CSM, active infection, neoplastic disease, rheumatoid arthritis, ankylosing spondylitis, trauma, or concomitant lumbar stenosis were excluded. The patients underwent preoperative MRI using 1.5T (15 patients) and 3T (two patients) scanner, including mid-sagittal T1-weighted, axial and mid-sagittal T2-weighted series. MRI data were analyzed (Mango 2.0 software; Multi-Image Analysis GUI) by four blind raters in three different sessions. Four measurements were analysed: transverse area (TA) (Figure 1), compression ratio (CR) (Figure 2), maximal canal compromise (MCC), and maximal spinal cord compression (MSCC) (Figure 3). The differences for each measurement were evaluated using mixed-effect ANOVA models (ratter, session, ratter x session). The intra- and inter-rater reliability was evaluated with intraclass correlation coefficients (ICC) (Figure 4).Figure 1 Transverse area (TA)Figure 2 Compression ratio (CR = AP/W)Figure 3 Maximal canal compromise (MCC), and maximal spinal cord compression (MSCC). MCC(%) = 1−[Dx/(Da+Db)/2] × 100%; MSCC(%) = 1−[dx/(da+db)/2] × 100%Figure 4 Intraclass correlation coefficients (ICC) Results: The principal findings were: (i) for TA (71.48 ± 12.99mm2), the intra-rater agreement was 0.97 (95% CI, range 0.94–0.99) and the inter-rater agreement was 0.76 (95% CI, range 0.49–0.90); (ii) for CR (0.35 ± 0.04%), 0.94 (95% CI, range 0.88–0.98), and 0.79 (95% CI, range 0.57–0.91) respectively; (iii) for MCC (83.21 ± 2.08%), 0.95 (95% CI, range 0.89–0.98), and 0.64 (95% CI, range 0.28–0.85) respectively; and (iv) for MSCC (82.87 ± 1.52%), 0.93 (95% CI, range 0.86–0.97), and 0.84 (95% CI, range 0.65–0.93) respectively. Conclusions: Our data suggest that three out of four measurements (TA, CR and MSCC) have acceptable intra- and interreliability coefficients (ICC > 0.75). However, for the maximal canal compromise measure, although the intrareliability was acceptable, the inter-rater reliability was not acceptable (0.64). Based on this study, we recommend that three MRI measures: transverse area, compression ratio and maximal spinal cord compression should be used in the imaging assessment of the spinal cord in CSM patients.

En bloc resection for metastatic spinal tumors: is it worth it?

Total en bloc spondylectomy (TES) for resection of spinal tumors is part of our armamentarium for potentially curing neoplastic disease in selected patients.5 The goal of surgery is to remove neoplastic tissue with clear margins and then to reconstruct the spine to provide neurological and mechanical stability. While technical advancements in surgery and increasing sophistication in chemotherapeutic agents and the delivery of radiation have made TES feasible, the morbidity rate remains relatively high. Patient selection is a key component to clinical success, where quality of life (QOL) must be balanced with quantity of life in the management of oncological disease. While TES of primary benign and malignant tumors in medically fit patients is accepted, controversy exists in cases of spinal metastatic disease that is distant from the primary neoplasm.1 Murakami et al.7 present their experience with TES in patients with distant spinal lesions metastasizing from adenocarcinoma of the lung. They retrospectively identified 6 patients managed with TES over a 10-year period. None of the patients had visceral metastasis and 2 patients had metastasis to 2 adjacent vertebral levels. Four patients had thoracic spinal metastasis while 2 had lumbar spinal metastasis. Five patients underwent preoperative intraarterial embolization of the surgical lesion. The authors report mean intraoperative blood loss of approximately 1 L and a mean operative time of 7 hours 20 minutes. There were 2 perioperative complications, a deep infection in a patient with a CSF leak and paralysis from a postoperative hematoma. At mean follow-up of 46 months, one patient had died with mediastinitis of postoperative infection 16 months after TES, and another patient died following a myocardial infarct 8 months after TES. The authors report that these deaths were not related to lung cancer. Of the 4 surviving patients, 2 had distant spinal metastases and 1 had lung metastasis. There are a number of limitations that make it difficult to draw any conclusions from the small case series. Only 6 patients were identified over a 10-year period, indicating that lung adenocarcinoma metastasis to the spine in the absence of visceral disease is rare, or, more likely, many eligible patients did not undergo TES. It was unclear if the surgical goal of negative margins was achieved, as no pathological description of the surgical specimen was included in the report. The preand postoperative functional status of patients was not described and no QOL measures were included. The authors employed a surgical strategy decision tool that stipulated that patients have a minimum Karnofsky Performance Scale score of 30 prior to consideration for surgery. Functional status prior to TES is essential to determining benefit to the individual, especially in oncology patients. Murakami et al.7 should be commended for their candor in describing perioperative complications following TES. Certainly the development of major perioperative complications in 2 of 6 patients raises concerns. Both complications (deep infection with CSF leakage and paralysis) would likely influence length of hospital stay, need for additional surgery, and overall QOL. The death that occurred in a patient with mediastinitis may not have been due to lung cancer recurrence, but could have been a delayed complication of the TES procedure itself. Ultimately, the morbidity and mortality profile described seems daunting in the absence of any data supporting improved QOL over alternative, less aggressive, surgical and medical treatment paradigms. The applicability of TES to distal spinal metastasis from lung adenocarcinoma remains very controversial. In contrast, en bloc resection of locally invasive Pancoast tumors does represent a reasonable approach to treat these challenging lesions and can be associated with gratifying long-term results.6 The principle of en bloc resection in the management of primary spinal tumors is well accepted in the literature. Prospective data indicate that en bloc resection with negative margins confers acceptable morbidity and long-term survival, whereas violating the margins may increase the risk of local recurrence.4 The objective for TES in patients with primary tumors becomes one of long-term survival, in addition to maintaining or improving QOL. Efforts to standardize the staging and surgical approach to these tumors1,2 should help optimize clinical results. In contrast to primary tumors, the goal of surgical management of spinal metastasis is primarily one of J Neurosurg Spine 13:411–413, 2010 See the corresponding article in this issue, pp 414–417.

Motion preservation following anterior cervical discectomy

Anterior cervical decompression is an accepted treatment option for the management of cervical radiculopathy and/or myelopathy secondary to degenerative disc disease. This procedure is usually followed by an interbody fusion, which may be supplemented with instrumentation.2 Concern regarding the potential for accelerated adjacent level degeneration with symptomatic axial pain or neural compromise prompted the development of cervical arthroplasty devices. A number of artificial cervical discs, with differing designs and biomechanical properties, aim to allow motion at the surgical level following cervical discectomy. Whereas early radiographic data confirm either preserved or increased range of motion (ROM) at the surgical level following arthroplasty, there are little data to support the use of one particular device over another. Ryu and colleagues8 examined the radiographic changes in the cervical spine at a minimum of 2 years follow-up after insertion of either a single-level Bryan disc (Medtronic Sofamor Danek) or a Prodisc-C disc (Synthes Spine). Consecutive patients undergoing insertion of either device were identified retrospectively. Clinical outcomes were measured with the visual analog scale and Neck Disability Index scores. Range of motion, functional spinal unit (FSU) height, and heterotopic ossification were measured on static and dynamic radiographs while facet arthrosis, disc degeneration, and uncinate degeneration were assessed on CT. Prosthesis size and positioning at the surgical level were recorded from anteroposterior and lateral radiographs. At final follow-up, the Bryan disc showed a smaller FSU angle but greater ROM than the Prodisc-C, but FSU height did not differ between the 2 prostheses. Adjacent level kinematics did not differ between the Bryan disc and Prodisc-C. Progression of facet arthrosis at the operative level was observed in 1 Bryan disc patient and 6 Prodisc-C patients. Heterotopic ossification at the surgical level was noted in 11 patients with Bryan discs and 8 with Prodisc-C discs, and appeared to be related to the presence of ossification of the posterior longitudinal ligament. The progression of adjacent level degenerative changes did not differ between the devices. The presence of facet degeneration or heterotopic ossification did not appear to affect the visual analog scale and Neck Disability Index scores. Although the data in the paper by Ryu et al.8 are interesting, this study has a number of important limitations. The strength of the conclusions is limited by the retrospective, consecutive patient design. Moreover, the relatively small number of patients enrolled in each group undermines statistical power. In addition, the results may be biased by differences in surgical experience with a given device. The authors acknowledge that the Prodisc-C was placed too far ventrally within the disc space in some instances. While suboptimal device placement may be a reality of the “learning curve,” presumably optimal placement is essential to producing optimal results, especially in the context of small sample sizes. Nonetheless, this study serves to highlight many of the issues surrounding cervical arthroplasty. Ryu et al.8 should be commended for including a broad spectrum of radiographic outcome measures and trying to relate these to in vivo clinical outcomes. Should arthroplasty devices maintain pathological ROM or restore it? What is the optimal balance between ROM and segmental alignment following insertion of an arthroplasty device? These questions are pertinent, as previous authors have questioned if device placement should optimize ROM or segmental alignment.7 Ryu et al. report that the Bryan disc conferred a smaller FSU angle and greater ROM at the surgical level in comparison to the ProdiscC, yet clinical outcomes did not differ significantly between the 2 groups. A recent randomized control trial reported no differences in clinical outcomes in patients treated with anterior cervical discectomy (ACD), anterior cervical discectomy and fusion (ACDF), and ACDF with instrumentation, despite radiographic evidence of kyphosis in the ACD group.9 Careful patient selection may be the most important factor in successful operative management of cervical radiculopathy and/or myelopathy.1,4 Comparisons between arthroplasty devices may be premature as it is yet unknown if motion preservation J Neurosurg Spine 13:297–298, 2010 See the corresponding article in this issue, pp 299–307.

Biomechanical evaluation of the ProDisc-C stability following graded posterior cervical injury

OBJECTIVEThere are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.METHODSFourteen human cadaveric cervical spines (C3-T1 or C2-7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.RESULTSRange of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).CONCLUSIONSForaminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.