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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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Seung-Jae Hyun, Ki-Jeong Kim, and Tae-Ahn Jahng

OBJECTIVE

No reports have investigated how cervical reconstructive surgery affects global sagittal alignment (GSA), including the lower extremities, and health-related quality of life (HRQOL). The study was aimed at elucidating the effects of cervical reconstruction on GSA and HRQOL.

METHODS

Twenty-three patients who underwent reconstructive surgery for cervical kyphosis were divided into a head-balanced group (n = 13) and a trunk-balanced group (n = 10) according to the values of the C7 plumb line, T1 slope (T1S), and pelvic incidence minus lumbar lordosis (PI-LL). Head-balanced patients are those with a negative C7 sagittal vertical axis (SVA), a larger LL than PI, and a low T1S. Trunk-balanced patients are those with a positive SVAC7, a normal PI-LL, and a normal to high T1S. Various sagittal Cobb angles, SVA, and lower-extremity alignment parameters were measured before and after surgery using whole-body stereoradiography.

RESULTS

Cervical malalignment was corrected to achieve cervical sagittal balance and occiput-trunk (OT) concordance (center of gravity [COG]–C7 SVA < 30 mm). Significant changes in the upper cervical spine and thoracolumbar spine were observed in the head-balanced group, but no significant change in lumbopelvic alignment was observed in the trunk-balanced group. Lower-extremity alignment did not change substantially in either group. HRQOL scores improved significantly after surgery in both groups. SVACOG–C7 and SVAC2–7 were negatively and positively correlated with the 36-Item Short-Form Health Survey physical component score and Neck Disability Index, respectively. The visual analog scale for back pain, Oswestry Disability Index, and PI-LL mismatch improved significantly in the head-balanced group after cervical reconstruction surgery.

CONCLUSIONS

Patients with cervical kyphosis exhibited compensatory changes in the upper cervical spine and thoracolumbar spine, instead of in the lower extremities. These compensatory mechanisms resolved reciprocally in a different fashion in the head- and trunk-balanced groups. HRQOL scores improved significantly with GSA restoration and OT concordance following cervical reconstruction.

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Jong-myung Jung, Seung-Jae Hyun, Ki-Jeong Kim, and Tae-Ahn Jahng

OBJECTIVE

This study investigated the incidence and risk factors of rod fracture (RF) after multiple-rod constructs (MRCs) for adult spinal deformity (ASD) surgery.

METHODS

A single-center, single-surgeon consecutive series of adult patients who underwent posterior thoracolumbar fusion at 4 or more levels using MRCs after osteotomy with at least 1 year of follow-up were retrospectively reviewed. Patient characteristics, radiological parameters, operative data, and clinical outcomes (on the Scoliosis Research Society-22r questionnaire) were analyzed at baseline and follow-up.

RESULTS

Seventy-six patients were enrolled in this study. RF occurred in 9 patients (11.8%), with all cases involving partial rod breakage. Seven patients (9.2%) underwent revision surgery. There were no significant differences in baseline demographic characteristics, radiological parameters, and surgical factors between the RF and non-RF groups. Multivariable analysis revealed that interbody fusion at the L5–S1 and L4–S1 levels could significantly reduce the occurrence of RF after MRCs for ASD (adjusted odds ratios 0.070 and 0.035, respectively). The RF group had significantly worse function score (mean 2.9 ± 0.8 vs 3.5 ± 0.7) and pain score (mean 2.8 ± 1.0 vs 3.5 ± 0.8) compared with the non-RF group at last visit.

CONCLUSIONS

RF occurred in 11.8% of patients with MRCs after ASD surgery. Most RFs occurred at the lumbosacral junction or adjacent level (77%). Interbody fusion at the lumbosacral junction (L5–S1 or L4–S1 level) could significantly prevent the occurrence of RF after MRCs for ASD.

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Sang-Hyun Han, Seung-Jae Hyun, Tae-Ahn Jahng, and Ki-Jeong Kim

Spontaneous bilateral pedicle fractures of the lumbar spine are rare, and an optimal surgical treatment has not been suggested. The authors report the case of a 50-year-old woman who presented with low-back pain and right leg radiating pain of 1 year’s duration. Radiological studies revealed a spontaneous bilateral pedicle fracture of L-5. All efforts at conservative treatment failed, and the patient underwent surgery for osteosynthesis of the fractured pedicle using bilateral pedicle screws connected with a bent rod. Her low-back and right leg pain were relieved postoperatively. A CT scan performed 3 months postoperatively revealed the disappearance of the pedicle fracture gap and presence of newly formed bony trabeculation. In rare cases of spontaneous bilateral pedicle fracture of the lumbar spine, osteosynthesis of the fractured pedicle using bilateral pedicle screws and a bent rod is a motion-preserving technique that may be an effective option when conservative management has failed.

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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.

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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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Sanghyun Han, Seung-Jae Hyun, Ki-Jeong Kim, Tae-Ahn Jahng, and Hyun-Jib Kim

OBJECTIVE

Posterior column osteotomy (PCO) has been known to provide an angular change (AC) of approximately 10° in sagittal plane deformity. However, whether PCO can actually obtain an AC of ≥ 10° depending on the particular level in the lumbar spine and which factors can effect a gain of ≥ 10° AC after PCO remain to be elucidated. The aim of this study was to identify the factors that effect a gain of ≥ 10° AC through PCO by comparing radiographic measurements between an AC group and a control group before and after adult spinal deformity (ASD) surgery.

METHODS

Forty consecutive patients who underwent multilevel PCOs for ASD at a single institution between 2012 and 2016 were included in this study. PCO was performed in 142 disc space levels in the lumbar spine. The authors defined the disc space level that obtained ≥ 10° AC in the sagittal plane by PCO as the AC group and the remaining patients as controls. The modified Pfirrmann grade, surgical level, implementation of the transforaminal lumbar interbody fusion (TLIF), and radiographic measurements were compared between the groups.

RESULTS

There were 67 levels in the AC group and 75 in the control group. Multivariate analysis identified the surgical level at L4–5 (OR 3.802, 95% CI 1.127–12.827, p = 0.031), performing TLIF with PCO (OR 3.303, 95% CI 1.258–8.674, p = 0.015), and a preoperative kyphotic disc space angle (OR 1.397, 95% CI 1.231–1.585, p < 0.001) as the factors that significantly effected ≥ 10° AC in the sagittal plane after PCO.

CONCLUSIONS

In ASD surgery, PCO cannot always achieve ≥ 10° AC in the sagittal plane. The factors that effected ≥ 10° AC in PCO for ASD were surgical level at L4–5, performing TLIF with PCO, and the preoperative kyphotic disc space angle.

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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, 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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Young-Seop Park, Seung-Jae Hyun, Ho Yong Choi, Ki-Jeong Kim, and Tae-Ahn Jahng

OBJECTIVE

The aim of this study was to investigate the risk of upper instrumented vertebra (UIV) fractures associated with UIV screw fixation (unicortical vs bicortical) and polymethylmethacrylate (PMMA) augmentation after adult spinal deformity surgery.

METHODS

A single-center, single-surgeon consecutive series of adult patients who underwent lumbar fusion for ≥ 4 levels (that is, the lower instrumented vertebra at the sacrum or pelvis and the UIV of the thoracolumbar spine [T9–L2]) were retrospectively reviewed. Age, sex, follow-up duration, sagittal UIV angle immediately postoperatively including several balance-related parameters (lumbar lordosis [LL], pelvic incidence, and sagittal vertical axis), bone mineral density, UIV screw fixation type, UIV PMMA augmentation, and UIV fracture were evaluated. Patients were divided into 3 groups: Group U, 15 patients with unicortical screw fixation at the UIV; Group P, 16 with bicortical screw fixation and PMMA augmentation at the UIV; and Group B, 21 with bicortical screw fixation without PMMA augmentation at the UIV.

RESULTS

The mean number of levels fused was 6.5 ± 2.5, 7.5 ± 2.5, and 6.5 ± 2.5; the median age was 50 ± 29, 72 ± 6, and 59 ± 24 years; and the mean follow-up was 31.5 ± 23.5, 13 ± 6, and 24 ± 17.5 months in Groups U, P, and B, respectively (p > 0.05). There were no significant differences in balance-related parameters (LL, sagittal vertical axis, pelvic incidence–LL, and so on) among the groups. UIV fracture rates in Groups U (0%), P (31.3%), and B (42.9%) increased in sequence by group (p = 0.006). UIV bicortical screw fixation increased the risk for UIV fracture (OR 5.39; p = 0.02).

CONCLUSIONS

Bicortical screw fixation at the UIV is a major risk factor for early UIV compression fracture, regardless of whether a thoracolumbosacral orthosis is used. To reduce the proximal junctional failure, unicortical screw fixation at the UIV is essential in adult spinal deformity correction surgery.