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Chi Heon Kim, Chun-Kee Chung, June Sic Kim, Tae Ahn Jahng, June Ho Lee and In Chan Song

Object

Recently, diffusion tensor (DT) imaging was introduced to demonstrate white matter tracts. However, research interest has focused on the anatomical rather than the functional aspects of this imaging modality. The authors undertook a functional analysis of DT imaging to determine the relationship between weakness and changes on DT images.

Methods

Diffusion tensor images were obtained in 23 patients with lesions located adjacent to the pyramidal tract. Patients were classified according to their motor deficit. Axial magnetic resonance image sections through the maximum tumor diameters were selected and the mean apparent diffusion coefficients (ADCs) and mean fractional anisotropies (FAs) were measured. One ovoid region of interest (ovROI) was placed in the center of the pyramidal tract and another was designed to include the whole pyramidal tract at the same axial level (wROI). To determine intraobserver variability, a single neurosurgeon measured mean ADCs and FAs four times by using these two different ROI types without knowledge of any clinical information. To determine interobserver variability, a second neurosurgeon who was also unaware of any clinical information measured the mean ADCs and FAs by using the wROI method.

The five measurements produced the same results. The mean FA at the lesion side of the pyramidal tract was significantly lower in patients with weakness (p < 0.01). Little intraobserver measurement variability occurred using the ovROI method, and no interobserver variability occurred using the wROI method.

Conclusions

Motor weakness was significantly related to a low mean FA in the pyramidal tract on the lesion side. Designing an ROI that includes the whole pyramidal tract is an easier and more reproducible method than using an ovROI method.

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Sung Bae Park, Tae-Ahn Jahng, Chi Heon Kim and Chun Kee Chung

Object

The aim of this study was to describe a novel technique for laminoplasty in which translaminar screws are used in the thoracic and lumbar spine.

Methods

The authors first performed a morphometric study in 20 control individuals using 3D reconstructed CT scans and spine simulation software to measure the lengths and diameters of the spaces available for translaminar screw placement from the T-1 to S-1.

Based on the results of the morphometric study, the authors then attempted translaminar screw fixation in 5 patients (April 2007–July 2007) after en bloc laminectomy in the thoracic and lumbar regions. All patients had intradural lesions: 3 schwannomas, 1 cavernoma, and 1 arachnoid cyst.

Results

The morphometric study in control individuals revealed that the safe trajectories for simulated screws measured 25–30 mm in length and 8–11 mm in diameter in the thoracic region (T1–12) and 26–34 mm in length and 6–7 mm in diameter in the lumbosacral region (L1–S1). This morphometric and simulation study showed that translaminar screw placement would be possible in practice.

Five patients underwent en bloc laminoplasty and translaminar screw fixation in which the screws measured 2.7 mm in diameter and 24 or 26 mm in length. Sixteen attempts at translaminar fixation were made in 8 vertebrae. Fourteen translaminar screws were successfully placed at the thoracic and lumbar levels. Two microplates had to be used because the laminae were too thin and narrow after further laminectomy with undercutting. There were no complications associated with the translaminar screws.

The mean follow-up period was 14.5 months. There was no screw breakage or displacement. Solid osseous fusion was documented in 2 patients who underwent CT scanning 15 months postoperatively.

Conclusions

The authors found that the laminoplasty and translaminar screw technique is feasible in the thoracic and lumbar regions, but further studies are needed to analyze the biomechanical effects and long-term outcomes in a large number of patients.

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Soo Eon Lee, Chun Kee Chung and Tae Ahn Jahng

Object

The purpose of cervical total disc replacement (TDR) is to decrease the incidence of adjacent segment disease through motion preservation. Heterotopic ossification (HO) is a well-known complication after hip and knee arthroplasties. There are few reports regarding HO in patients undergoing cervical TDR, however; and the occurrence of HO and its effects on cervical motion have rarely been reported. Moreover, temporal progression of HO has not been fully addressed. One goal of this study involved determining the incidence of HO following cervical TDR, as identified from plain radiographs, and demonstrating the progression of HO during the follow-up period. A second goal consisted of determining whether segmental motion could be preserved and identifying the relationship between HO and clinical outcomes.

Methods

The authors conducted a retrospective clinical and radiological study of 28 consecutive patients who underwent cervical TDR with Mobi-C prostheses (LDR Medical) between September 2006 and October 2008. Radiological outcomes were evaluated using lateral dynamic radiographs obtained preoperatively and at 1, 3, 6, 12, and 24 months postoperatively. The occurrence of HO was interpreted on lateral radiographs using the McAfee classification. Cervical range of motion (ROM) was also measured. The visual analog scale (VAS) and Neck Disability Index (NDI) were used to evaluate clinical outcome.

Results

The mean follow-up period was 21.6 ± 7.0 months, and the mean occurrence of HO was at 8.0 ± 6.6 months postoperatively. At the last follow-up, 18 (64.3%) of 28 patients had HO: Grade I, 6 patients; Grade II, 8 patients; Grade III, 3 patients; and Grade IV, 1 patient. Heterotopic ossification progression was proportional to the duration of follow-up; HO was present in 3 (10.7%) of 28 patients at 1 month; 7 (25.0%) of 28 patients at 3 months; 11 (42.3%) of 26 patients at 6 months; 15 (62.5%) of 24 patients at 12 months; and 17 (77.3%) of 22 patients at 24 months. Cervical ROM was preserved in Grades I and II HO but was restricted in Grades III and IV HO. Clinical improvement according to the VAS and NDI was not significantly correlated with the occurrence of HO.

Conclusions

The overall incidence of HO after cervical TDR was relatively high. Moreover, HO began unexpectedly to appear early after surgery. Heterotopic ossification progression was proportional to the time that had elapsed postoperatively. Grade III or IV HO can restrict the cervical ROM and may lead to spontaneous fusion; however, the occurrence of HO did not affect clinical outcome. The results of this study indicate that a high incidence of HO with the possibility of spontaneous fusion is to be expected during long-term follow-up and should be considered before performing cervical TDR.

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Soo Eon Lee, Chun Kee Chung, Tae-Ahn Jahng and Hyun-Jib Kim

Object

Although laminectomy is an effective surgical technique for the treatment of multilevel cervical stenotic lesions, postoperative kyphosis and neurological deterioration have been frequently reported after laminectomy. Hence, laminectomy without fusion is seldom performed nowadays. However, the clinical impression from the long-term follow-up of patients who had undergone laminectomy does not support that postoperative kyphosis is common in patients with ossification of the posterior longitudinal ligament (OPLL). In this paper, the authors assessed the long-term outcome of laminectomy for cervical OPLL in terms of the changes in the cervical curvature and in the neurological status.

Methods

The authors retrospectively reviewed medical records and radiological images in patients who had undergone cervical laminectomy between 1999 and 2009. The preoperative and the final follow-up status recovery rate were assessed using the Japanese Orthopaedic Association (JOA) scale. The cervical global angle and range of motion (ROM) were measured preoperatively and at the last follow-up. The cervical spine was classified into 3 types: lordotic, straight, and kyphotic.

Results

A total of 34 patients were available for medical record review and telephone interviews. There were 28 men and 6 women, whose mean age at the time of surgery was 57.8 years. The mean follow-up period was 57.5 months. The mean preoperative JOA score was 10.7, and the JOA score at the last follow-up was significantly improved to 14.3 (p < 0.001) with a recovery rate of 56.3%. The JOA score at each postoperative follow-up point increased until 6 years postoperatively; thereafter, it gradually decreased. The mean preoperative global angle was −11.3° and the most recent global angle was −8.4°. The preoperative ROM was 33.9° and the most recent ROM was 27.4°. There was no statistical significance in the change of cervical curvature or ROM. Preoperatively, 29 of the 34 patients had a lordotic cervical curvature and 5 patients had a straight spine. At last follow-up, 24 patients had a lordotic curvature, 3 patients changed from lordosis to kyphosis, and 7 patients had a straight spine. One patient whose cervical curvature changed from lordosis to kyphosis during the follow-up period underwent cervical fusion 9 years after the laminectomy procedure.

Conclusions

The long-term outcome of laminectomy for cervical OPLL is satisfactory in terms of the clinical and radiological aspects. The risk of postlaminectomy kyphosis was not high, raising the possibility that the OPLL itself may serve as a support for the spinal column.

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Soo Eon Lee, Tae-Ahn Jahng and Hyun-Jib Kim

Object

Spinal stenosis with degenerative lumbar scoliosis (DLS) mostly occurs in the elderly population (typically > 65 years old), causing pain in the legs and back, claudication, and spinal deformity. The surgical strategy for DLS is controversial concerning the surgical approach, fusion area, decompression area, correction methods, and ideal angle of curve correction. A nonfusion stabilization system with motion preservation has been recently used for degenerative spinal diseases with favorable outcomes. This study attempted to analyze surgical outcomes after decompression and nonfusion stabilization for spinal stenosis with a mild to moderate degree of DLS.

Methods

Twenty-eight patients (21 women and 7 men, with a mean age of 65.3 years) with spinal stenosis and DLS who underwent decompressive surgery and nonfusion stabilization with the Dynesys system were included in this study. Medical records and radiological studies were reviewed to access clinical and radiological outcomes and surgery-related complications.

Results

Fifty-nine segments were decompressed and stabilized without fusion in 28 patients, consisting of 1 segmental stabilization in 8 patients (28.6%, L4–5), 2 segmental stabilizations in 11 patients (39.3%, L3–5), 3 segmental stabilizations in 7 patients (25.0%, L2–5 in 6 patients, L3–S1 in 1 patient), and 4 segmental stabilizations in 2 patients (7.1%, L2–S1 in 1 patient, L1–5 in 1 patient). The mean follow-up period was 30.7 months. Radiologically, the mean lumbar scoliotic angle was 13.7° before surgery, 5.1° at 3 months postoperatively, 3.8° at 12 months postoperatively, 4.2° at 24 months postoperatively, and 3.9° at the last follow-up, which was statistically significant (p < 0.05). Lumbar lordosis and range of motion were preserved. The score on the visual analog scale for leg and back pain significantly decreased, and the Oswestry Disability Index significantly improved after surgery. There were no newly developed neurological deficits or aggravation of neurological symptoms. A radiolucent line around the pedicle screw was observed in 4 patients (14.2%) with 5 screws (2.8%).

Conclusions

Adding nonfusion stabilization after decompressive surgery resulted in a safe and effective procedure for elderly patients with lumbar stenosis with a mild to moderate scoliosis angle (< 30°). Statistically significant improvement of the clinical outcome was obtained at the last follow-up evaluation with no progression of the degenerative scoliosis.

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Christopher I. Shaffrey and Justin S. Smith

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Chang-Hyun Lee, Jaebong Lee, James D. Kang, Seung-Jae Hyun, Ki-Jeong Kim, Tae-Ahn Jahng and Hyun-Jib Kim

OBJECT

Posterior cervical surgery, expansive laminoplasty (EL) or laminectomy followed by fusion (LF), is usually performed in patients with multilevel (≥ 3) cervical spondylotic myelopathy (CSM). However, the superiority of either of these techniques is still open to debate. The aim of this study was to compare clinical outcomes and postoperative kyphosis in patients undergoing EL versus LF by performing a meta-analysis.

METHODS

Included in the meta-analysis were all studies of EL versus LF in adults with multilevel CSM in MEDLINE (PubMed), EMBASE, and the Cochrane library. A random-effects model was applied to pool data using the mean difference (MD) for continuous outcomes, such as the Japanese Orthopaedic Association (JOA) grade, the cervical curvature index (CCI), and the visual analog scale (VAS) score for neck pain.

RESULTS

Seven studies comprising 302 and 290 patients treated with EL and LF, respectively, were included in the final analyses. Both treatment groups showed slight cervical lordosis and moderate neck pain in the baseline state. Both groups were similarly improved in JOA grade (MD 0.09, 95% CI −0.37 to 0.54, p = 0.07) and neck pain VAS score (MD −0.33, 95% CI −1.50 to 0.84, p = 0.58). Both groups evenly lost cervical lordosis. In the LF group lordosis seemed to be preserved in long-term follow-up studies, although the difference between the 2 treatment groups was not statistically significant.

CONCLUSIONS

Both EL and LF lead to clinical improvement and loss of lordosis evenly. There is no evidence to support EL over LF in the treatment of multilevel CSM. Any superiority between EL and LF remains in question, although the LF group shows favorable long-term results.

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Chang Hwan Pang, Soo Eon Lee, Chang Hyeun Kim, Jeong Eun Kim, Hyun-Seung Kang, Chul-Kee Park, Sun Ha Paek, Chi Heon Kim, Tae-Ahn Jahng, Jin Wook Kim, Yong Hwy Kim, Dong Gyu Kim, Chun Kee Chung, Hee-Won Jung and Heon Yoo

OBJECT

There is inconsistency among the perioperative management strategies currently used for chronic subdural hematoma (cSDH). Moreover, postoperative complications such as acute intracranial bleeding and cSDH recurrence affect clinical outcome of cSDH surgery. This study evaluated the risk factors associated with acute intracranial bleeding and cSDH recurrence and identified an effective perioperative strategy for cSDH patients.

METHODS

A retrospective study of patients who underwent bur hole craniostomy for cSDH between 2008 and 2012 was performed.

RESULTS

A consecutive series of 303 cSDH patients (234 males and 69 females; mean age 67.17 years) was analyzed. Postoperative acute intracranial bleeding developed in 14 patients (4.57%) within a mean of 3.07 days and recurrence was observed in 37 patients (12.21%) within a mean of 31.69 days (range 10–104 days) after initial bur hole craniostomy. The comorbidities of hematological disease and prior shunt surgery were clinical factors associated with acute bleeding. There was a significant risk of recurrence in patients with diabetes mellitus, but recurrence did not affect the final neurological outcome (p = 0.776). Surgical details, including the number of operative bur holes, saline irrigation of the hematoma cavity, use of a drain, and type of postoperative ambulation, were not significantly associated with outcome. However, a large amount of drainage was associated with postoperative acute bleeding.

CONCLUSIONS

Bur hole craniostomy is an effective surgical procedure for initial and recurrent cSDH. Patients with hematological disease or a history of prior shunt surgery are at risk for postoperative acute bleeding; therefore, these patients should be carefully monitored to avoid overdrainage. Surgeons should consider informing patients with diabetes mellitus that this comorbidity is associated with an increased likelihood of recurrence.

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Chang-Hyun Lee, Tae-Ahn Jahng, Seung-Jae Hyun, Chi Heon Kim, Sung-Bae Park, Ki-Jeong Kim, Chun Kee Chung, Hyun-Jib Kim and Soo-Eon Lee

OBJECTIVE

The Dynesys, a pedicle-based dynamic stabilization (PDS) system, was introduced to overcome the drawbacks of fusion procedures. Nevertheless, the theoretical advantages of PDS over fusion have not been clearly confirmed. The aim of this study was to compare clinical and radiological outcomes of patients who underwent PDS using the Dynesys system with those who underwent posterior lumbar interbody fusion (PLIF).

METHODS

The authors searched PubMed, Embase, Web of Science, and the Cochrane Database. Studies that reported outcomes of patients who underwent PDS or PLIF for the treatment of degenerative lumbar spinal disease were included. The primary efficacy end points were perioperative outcomes. The secondary efficacy end points were changes in the Oswestry Disability Index (ODI) and back and leg pain visual analog scale (VAS) scores and in range of motion (ROM) at the treated and adjacent segments. A meta-analysis was performed to calculate weighted mean differences (WMDs), 95% confidence intervals, Q statistics, and I2 values. Forest plots were constructed for each analysis group.

RESULTS

Of the 274 retrieved articles, 7 (which involved 506 participants [Dynesys, 250; PLIF, 256]) met the inclusion criteria. The Dynesys group showed a competitive advantage in mean surgery duration (20.73 minutes, 95% CI 8.76–32.70 minutes), blood loss (81.87 ml, 95% CI 45.11–118.63 ml), and length of hospital stay (1.32 days, 95% CI 0.23–2.41 days). Both the Dynesys and PLIF groups experienced improved ODI and VAS scores after 2 years of follow-up. Regarding the ODI and VAS scores, no statistically significant difference was noted according to surgical procedure (ODI: WMD 0.12, 95% CI −3.48 to 3.72; back pain VAS score: WMD −0.15; 95% CI −0.56 to 0.26; leg pain VAS score: WMD −0.07; 95% CI −0.47 to 0.32). The mean ROM at the adjacent segment increased in both groups, and there was no substantial difference between them (WMD 1.13; 95% CI −0.33 to 2.59). Although the United States is the biggest market for Dynesys, no eligible study from the United States was found, and 4 of 8 enrolled studies were performed in China. The results must be interpreted with caution because of publication bias. During Dynesys implantation, surgeons have to decide the length of the spacer and cord pretension. These values are debatable and can vary according to the surgeon's experience and the patient's condition. Differences between the surgical procedures were not considered in this study.

CONCLUSIONS

Fusion still remains the method of choice for advanced degeneration and gross instability. However, spinal degenerative disease with or without Grade I spondylolisthesis, particularly in patients who require a quicker recovery, will likely constitute the main indication for PDS using the Dynesys system.

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Soo Eon Lee, Tae-Ahn Jahng and Hyun Jib Kim

OBJECTIVE

The long-term effects on adjacent-segment pathology after nonfusion dynamic stabilization is unclear, and, in particular, changes at the adjacent facet joints have not been reported in a clinical study. This study aims to compare changes in the adjacent facet joints after lumbar spinal surgery.

METHODS

Patients who underwent monosegmental surgery at L4–5 with nonfusion dynamic stabilization using the Dynesys system (Dynesys group) or transforaminal lumbar interbody fusion with pedicle screw fixation (fusion group) were retrospectively compared. Facet joint degeneration was evaluated at each segment using the CT grading system.

RESULTS

The Dynesys group included 15 patients, while the fusion group included 22 patients. The preoperative facet joint degeneration CT grades were not different between the 2 groups. Compared with the preoperative CT grades, 1 side of the facet joints at L3–4 and L4–5 had significantly more degeneration in the Dynesys group. In the fusion group, significant facet joint degeneration developed on both sides at L2–3, L3–4, and L5–S1. The subjective back and leg pain scores were not different between the 2 groups during follow-up, but functional outcome based on the Oswestry Disability Index improved less in the fusion group than in the Dynesys group.

CONCLUSIONS

Nonfusion dynamic stabilization using the Dynesys system had a greater preventative effect on facet joint degeneration in comparison with that obtained using fusion surgery. The Dynesys system, however, resulted in facet joint degeneration at the instrumented segments and above. An improved physiological nonfusion dynamic stabilization system for lumbar spinal surgery should be developed.