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Poong-Gi Ahn, Keung Nyun Kim, Sung Whan Moon and Keun Su Kim

Object

This was a retrospective clinical study in which the follow-up period exceeded 2 years. The authors investigated the time course of radiographic changes in the cervical range of motion (ROM) and sagittal alignment after cervical total disc replacement involving the ProDisc-C artificial disc.

Methods

Eighteen patients who underwent C5–6 total disc replacement were followed for an average of 27 months. Cervical neutral and flexion-extension lateral radiographs were obtained before and at 1 and 3 months after surgery for early-phase observations and at the last follow-up for late-phase observation. Segmental ROM values in the treated, superior, and inferior adjacent segments were measured. For whole-neck motion, C2–7 ROM was also measured. The percentage contributions of ROM at functional and adjacent segments to whole-neck motion were calculated. For evaluating sagittal alignment, C2–7 and C5–6 Cobb angles were measured. All data from ProDisc-C arthroplasty were compared with the results obtained in 22 patients who underwent C5–6 interbody fusion in which a Solis cage was used and who were followed for an average of 25 months

Results

In the ProDisc-C group, C2–7 and C5–6 ROM significantly decreased in the early phase after surgery and returned to preoperative levels in the late phase. Both superior and inferior adjacent segments showed significantly decreased ROM in the acute phase after surgery and returned to the preoperative values in the late phase. In terms of contributions to whole-neck motion, the ROM of the functional and adjacent segments did not change significantly compared with the preoperative ROM. In the cage group, C2–7 ROM was also significantly decreased in the early phase after surgery and returned to preoperative levels at the late phase. Both superior and inferior adjacent segments exhibited significantly increased ROM and percentage contributions to whole-neck motion in the early and late phases. Sagittal alignment of the whole cervical spine became significantly more lordotic in the late phase in the ProDisc-C group. The C5–6 Cobb angle became significantly lordotic in the ProDisc-C group, whereas there was no significant change in C5–6 Cobb angle in the cage group.

Conclusions

In the early phase after ProDisc-C replacement, the ROM of the entire neck as well as functional and adjacent segments decreased but, at the late phase, they returned to the preoperative state. Contributions of functional and adjacent segments to whole-neck motion were not changed after ProDisc-C replacement. Adjacent-segmental motion could be saved by ProDisc-C replacement instead of interbody cage fusion. Segmental degenerative kyphosis was significantly corrected in patients who underwent ProDisc-C replacement.

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Jeong Yoon Park, Yong Eun Cho, Sung Uk Kuh, Jun Hyung Cho, Dong Kyu Chin, Byung Ho Jin and Keun Su Kim

Object.

The purpose of this study was to evaluate the correlation between adjacent-segment degeneration (ASD) and pelvic parameters in the patients with spondylolytic spondylolisthesis. Sagittal balance is the most important risk and prognostic factor in the development of ASD. The pelvic incidence angle (PIA) is an important anatomical parameter in determining the sagittal curvature of the spine and in the individual variability of the sacral slope and the lordotic curve. Thus, the authors evaluated the relationship between the pelvic parameters and the ASD.

Methods.

Among 132 patients with spondylolytic spondylolisthesis who underwent surgery at their institution, the authors selected patients in whom a one-stage, single-level, 360° fixation procedure was performed for Grade I spondylolisthesis and who underwent follow-up for more than 1 year. Parameters in 34 patients satisfied these conditions. Of the 34 patients, seven had ASD (Group 1) and 27 patients did not have ASD (Group 2). The investigators measured degree of spondylolisthesis, lordotic angle, sacral slope angle (SSA), pelvic tilt angle (PTA), PIA, and additional parameters pre-and postoperatively. The radiographic data were reviewed retrospectively.

Results.

The population consisted of nine men and 25 women whose mean age was 48.9 ± 9 years (± standard deviation) (range 28–65 years). Seven patients developed ASD after undergoing fusion. Of all the parameters, pre-and postoperative degree of spondylolisthesis, segmental lordosis, lordotic angle, SSA, preoperative PTA, and pre-operative PIA did not differ significantly between the two groups; only postoperative PTA and PIA were significantly different.

Conclusions.

The development of ASD is closely related to postoperative PIA and PTA, not preoperative PIA and PTA. The measurement of postoperative PIA can be used as a new indirect method to predict the ASD.

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Keun Su Kim, S. Tim Yoon, Jin Soo Park, Jun Li, Moon Soo Park and William C. Hutton

Object. Systemic nicotine has been hypothesized to cause degeneration of the intervertebral disc which in turn decreases vascular supply to the disc through a cholinergic receptor—mediated process. Another possible mechanism may be through direct regulatory effects on disc cells. In this study, the authors tested the hypothesis that nicotine adversely affects nucleus pulposus cells by directly inhibiting proteoglycan synthesis and gene expression of type II collagen (Phase I study). They also assessed the hypothesis that nicotine inhibits the bone morphogenetic protein (BMP)—2-induced upregulation of extracellular matrix (Phase II study).

Methods. Cells were isolated from nucleus pulposus obtained in rat lumbar discs and cultured on a monolayer. Media were treated with nicotine and/or recombinant human (rh)BMP-2 for 7 days. Sulfated glycosaminoglycan (SO4-GAG) in media was quantified using 1,9-dimethylmethylene blue (DMMB) assay. Gene assay of types I and II collagen, Sox9, and glyceraldehyde-3-phosphate dehydrogenase were quantified using reverse transcriptase—polymerase chain reaction (RT-PCR) and real time PCR. In the Phase I study, nicotine-treated (100 µg/ml) and nontreated cells were compared. The s-GAG production and messenger RNA (mRNA) of type II collagen and Sox9 decreased significantly in the nicotine-treated group. In the Phase II study, five groups were compared: 1) nontreatment; 2) rhBMP-2 only (100 ng/ml); and 3–5) with rhBMP-2 (100 ng/ml) and increasing doses of nicotine (1 [third group], 10, [fourth group], 100 [fifth group] µg/ml). The SO4-GAG production and mRNA of type II collagen and Sox9 decreased significantly in the groups treated with rhBMP-2 combined with 10 and 100 µg/ml of nicotine compared with the group treated with rhBMP-2.

Conclusions. The results of this study raise the possibility that nicotine may contribute to the process of disc degeneration by a direct effect on the nucleus pulposus cells, possibly by antagonizing the effect of BMP-2.

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Un Yong Choi, Jeong Yoon Park, Kyung Hyun Kim, Sung Uk Kuh, Dong Kyu Chin, Keun Su Kim and Yong Eun Cho

Object

Clinical results for unilateral pedicle screw fixation after lumbar interbody fusion have been reported to be as good as those for bilateral instrumentation. However, no studies have directly compared unilateral and bilateral percutaneous pedicle screw fixation after minimally invasive surgery (MIS) for transforaminal lumbar interbody fusion (TLIF). The purpose of this study was to determine whether unilateral percutaneous pedicle screw fixation is comparable with bilateral percutaneous pedicle screw fixation in 1-segment MIS TLIF.

Methods

This was a prospective randomized study of 53 patients who underwent unilateral or bilateral percutaneous pedicle screw fixation after MIS TLIF for 1-segment lumbar degenerative disc disease. Twenty-six patients were assigned to a unilateral percutaneous pedicle screw fixation group and 27 patients were assigned to a bilateral percutaneous pedicle screw fixation group. Operative time, blood loss, clinical outcomes (that is, Oswestry Disability Index [ODI] and visual analog scale [VAS] scores), complication rates, and fusion rates were assessed using CT scanning 2 years after surgical treatment.

Results

The 2 groups were similar in age, sex, preoperative diagnosis, and operated level, and they did not differ significantly in the length of follow-up (27.5 [Group 1] vs 28.9 [Group 2] months) or clinical results. Both groups showed substantial improvements in VAS and ODI scores 2 years after surgical treatment. The groups differed significantly in operative time (unilateral 84.2 minutes; bilateral 137.6 minutes), blood loss (unilateral 92.7 ml; bilateral, 232.0 ml), fusion rate (unilateral 84.6%; bilateral 96.3%), and postoperative scoliotic change (unilateral 23.1%; bilateral 3.7%).

Conclusions

Unilateral and bilateral screw fixation after MIS TLIF produced similar clinical results. Although perioperative results were better with unilateral screw fixation, the long-term results were better with bilateral screw fixation, suggesting bilateral screw fixation is a better choice after MIS TLIF.