Seungcheol Lee

CHARITE versus ProDisc: a comparative study of a minimum 3-year follow-up.

Study Design. A retrospective study. Objectives. To evaluate and compare clinical and radiologic outcomes of the CHARITÉ and ProDisc. Summary of Background Data. There is no clinical report comparing CHARITÉ and ProDisc. Methods. Among a total of 61 patients who underwent total disc replacement, 57 patients followed more than 3 years were enrolled. The CHARITÉ was used in 33 patients and ProDisc in 24. MRI follow-up was possible in 52 patients. Clinical and radiologic data including range of motion (ROM) and facet degeneration of the replaced segment, and degeneration of the disc at the adjacent level were evaluated. Results. Mean percentage improvement of Oswestry Disability Index (ODI) score was 78.9% in the CHARITÉ group and 75.8% in ProDisc group. The mean improvement of the Visual Analogue Scale (VAS) pain score was 72% in the CHARITÉ and 74.2% in ProDisc. There was no statistical difference between 2 groups in improvement rates either of the ODI scores and VAS scores. Degradation of the facets was seen in 36.4% of the CHARITÉ and 32% of the ProDisc. Degradation of disc degeneration at the adjacent level above the index level was seen in 19.4% in the CHARITÉ and 28.6% in the ProDisc. The degradation rates of facet joints and disc at adjacent segment between the 2 groups were not significantly different. Segmental ROM of the replaced segments was well preserved, but ROM of L5–S1 of the ProDisc was significantly less than that of the CHARITÉ. Conclusions. While clinical outcomes of both CHARITÉ and ProDisc groups were fairly good, the facet joint of the index level and the disc at the adjacent level showed an aggravation of the degenerative process in a significant number of patients, regardless of the device used, raising concerns of possible late consequences of total disc replacement, especially regarding facet arthrosis and adjacent segment disease.

Comparison of growth factor and cytokine expression in patients with degenerated disc disease and herniated nucleus pulposus

OBJECTIVES This study was conducted to investigate the expression of cytokines and growth factors in disc specimens obtained from patients with herniated nucleus pulposus (HNP) and degenerated disc disease (DDD). DESIGN AND METHODS MRI and Western blot analyses were performed to evaluate the levels of disc degeneration and the expression levels of cytokines and growth factors. RESULTS The levels of TNF-alpha and IL-8 were significantly greater in the DDD group than in the HNP group, but no statistical differences were observed in the expression of IL-1beta, IL-6 and IL-12 between the HNP and DDD groups. In addition, the expression of TGF beta, VEGF and NGF was significantly higher in the DDD group than in the HNP group. CONCLUSION The greater levels of cytokine and growth factor expression in the DDD group than in the HNP explain why discogenic patients usually have more severe back pain than patients with herniated discs.

Percutaneous Endoscopic Interlaminar Discectomy for Intracanalicular Disc Herniations At L5–S1 Using a Rigid Working Channel Endoscope

OBJECTIVE: Percutaneous endoscopic transforaminal discectomy is often used as a minimally invasive procedure for lumbar disc herniation. However, a transforaminal approach posts limitations at the L5–S1 level owing to anatomic constraints, such as a high iliac crest or small intervertebral foramen and especially for migrated large intracanalicular disc herniations. We discuss the procedure and clinical results of percutaneous endoscopic interlaminar discectomy using a rigid working channel endoscope at the L5–S1 level and the relevant surgical anatomy. METHODS: We performed percutaneous endoscopic discectomy through the interlaminar approach in 67 patients who satisfied our inclusion criteria during the period from March 2002 to November 2002. All procedures were performed under local anesthesia. Under fluoroscopic guidance, we performed discography using indigocarmine mixed with radio-opaque dye. The 6-mm working channel endoscope was then introduced into the epidural space. Herniated disc material was removed using forceps and laser under clear endoscopic visualization. We retrospectively evaluated the 65 cases with more than 1.5 years of follow-up. The patients were evaluated using the visual analogue scale (VAS) and the Oswestry Disability Index (ODI). RESULTS: VAS for leg pain (preoperative mean, 7.89; postoperative mean, 1.58) and ODI (preoperative mean, 57.43; postoperative mean, 11.52) showed statistically significant (P = 0.00) improvement in their values at the last follow-up examination compared with preoperative scores. Of the study group, 90.8% individuals showed favorable result. The mean hospital stay was 12 hours. The average time to return to work was 6.79 weeks. Complications included two cases of dural injury with cerebrospinal fluid leakage, nine cases of dysesthesia that were transient, and one case of recurrence. Two patients required conversion to open procedure at the initial operation. There was no evidence of infection in any patients. CONCLUSION: Percutaneous endoscopic interlaminar discectomy is a safe, effective, and minimally invasive procedure for the treatment of intracanalicular disc herniations at the L5–S1 level in properly selected cases, especially when the transforaminal approach is not possible because of anatomic constraints.

Factors affecting prognosis of patients who underwent corpectomy and fusion for treatment of cervical ossification of the posterior longitudinal ligament: analysis of 47 patients.

Objective: Even though cervical ossification of the posterior longitudinal ligament (OPLL) has several unique clinical features compared with spondylotic myelopathy or cervical disc disease, there have been few reports about factors affecting prognosis after decompression using corpectomy. To clarify the prognostic factors for cervical OPLL, the authors analyzed the clinical and radiologic parameters of 47 patients retrospectively. Methods: The patients were classified into a good-prognosis group and a poor-prognosis group according to the changes of Nurick grade after operation. Age at operation, gender, preoperative Nurick grade, duration of symptoms, snake-eye appearance, occupying ratio, type of OPLL, Pavlov ratio, and double-layer sign did not affect the prognosis significantly. Results: Multiple logistic regression analysis revealed that diabetes mellitus (DM) was the only statistically significant factor predicting poor prognosis for the patients with cervical OPLL who underwent corpectomy and fusion. Conclusions: Surgeons do not have to be discouraged from performing anterior decompression for the patients with cervical OPLL on the basis of age, severity of disease (preoperative Nurick grade or occupying ratio), irreversible changes in gray matter of the spinal cord (snake-eye appearance), or duration of symptoms. We should direct our attention to DM as a potent risk factor for cervical OPLL and try to clarify the mechanism by which DM possibly affected the functional recovery of the patients.

Modified transcorporeal anterior cervical microforaminotomy for cervical radiculopathy: a technical note and early results

A prospective analysis of the first twenty patients operated for cervical radiculopathy by a new modification of transcorporeal anterior cervical foraminotomy technique. To evaluate early results of a functional disc surgery in which decompression for the cervical radiculopathy is done by drilling a hole in the upper vertebral body and most of the disc tissue is preserved. Earlier approaches to cervical disc surgery either advocated simple discectomy or discectomy with fusion, ultimately leading to loss of motion segment. Posterior foraminotomy does not address the more common anterior lesion. Twenty patients suffering from cervical radiculopathy not responding to conservative treatment were chosen for the new technique. Upper vertebral transcorporeal foraminotomy was performed with the modified technique in all the patients. All the patients experienced immediate/early relief of symptoms. No complications of vertebral artery injury, Horner’s syndrome or recurrent laryngeal nerve palsy were noted. Modified transcorporeal anterior cervical microforaminotomy is an effective treatment for cervical radiculopathy. It avoids unnecessary violation of the disc space and much of the bony stabilizers of the cervical spine. Short-term results of this technique are quite encouraging. Longer-term analysis can help in outlining the true benefits of this technique.

Hybrid linearization of a power system with FACTS devices for a small signal stability study

This paper deals with a hybrid linearization method of a power system with FACTS (flexible AC transmission system) devices. The linearized power system model provides useful information, which is necessary for the small signal stability study and the control design. Although the algebraic linearization method provides an accurate and parameterized linear system, it may incur computation burdens for the large power system with multiple FACTS devices. The numerical identification of linearized system by utilizing input-output numerical data is highly versatile. However, quite an amount of valuable information may not be fully utilized. In this paper, a hybrid method in which the algebraic and the numerical linearization technique are combined is presented. While both the power system and the FACTS devices are separately linearized by using algebraic method, the interaction terms between the power system and FACTS devices are numerically identified by adopting the quadratic optimization technique. The proposed hybrid linearization technique is tested on the WSCC system in which one TCSC (thyristor-controlled series capacitor) is installed. Both eigenvalue analysis and time-domain simulation results verify that the proposed method can effectively identify the linearized model of the power system with FACTS devices.