Seong Hoon Oh

A robot-assisted surgery system for spinal fusion

The goal of this work is to develop a robot-assisted surgery system for spinal fusion, which is composed of a robot, a surgical planning system, and an optical tracking system. The system plays roles of assisting surgeon for inserting a pedicle screw in spinal fusion. Compared to pure navigation systems as well as conventional methods for spinal fusion, it is able to achieve better accuracy through compensating for the portending movement of the surgical area. Furthermore, the robot can position and guide needles, drills, and other surgical instruments or conducts drilling/screwing directly. In preoperative surgery, the desired entry point, orientation, and depth of surgical tools for pedicle screw insertion are determined by the surgical planning system based on CT or MR images. Intra-operatively, the position information on the surgical instruments and the targeted surgical areas are obtained by the tracking system and, using that information, a robot conducts the preplanned operation depending on its role while compensating the movement of the surgical area. Two exemplary experiments employing the developed robot-assisted surgery system are conducted.

Development of SPINEBOT for spine surgery

In most spine surgeries, the physician directly performs the surgical operation with help of specially designed surgical tools along with off-line CT images and possibly with fluoroscopic images that provide the on-line status of current surgical operation for patient However, the surgical procedure generally requires accurate operational skills and intuition of the physician. Sometimes, trifling errors or misjudgments during surgical operation could result in unrecoverable damages to patients. To cope with these problems, robotic technology has been incorporated into the surgical operations in various levels. In this paper, a robotic system for percutaneous spine surgery, called SPlNEBOT, is developed. The expected roles of SPINEBOT are to provide the guide for the K-wire, to help the physician to locate and orient the position of surgery more accurately, and to compensate for respiration movement of the patients body during operation. A preliminary experiment has been conducted with a mockup environment of surgical operation. The experimental results confirm that the SPINEBOT is not only able to guide by accurately pointing and orienting the specified location, but also successfully compensate the emulated respiratory movement of the patient.

A Multi-center Clinical Study of Posterior Lumbar Interbody Fusion with the Expandable Stand-alone Cage (Tyche® Cage) for Degenerative Lumbar Spinal Disorders

OBJECTIVE This multi-center clinical study was designed to determine the long-term results of patients who received a one-level posterior lumbar interbody fusion with expandable cage (Tyche(R) cage) for degenerative spinal diseases during the same period in each hospital. METHODS Fifty-seven patients with low back pain who had a one-level posterior lumbar interbody fusion using a newly designed expandable cage were enrolled in this study at five centers from June 2003 to December 2004 and followed up for 24 months. Pain improvement was checked with a Visual Analogue Scale (VAS) and their disability was evaluated with the Oswestry Disability Index. Radiographs were obtained before and after surgery. At the final follow-up, dynamic stability, quality of bone fusion, interveretebral disc height, and lumbar lordosis were assessed. In some cases, a lumbar computed tomography scan was also obtained. RESULTS The mean VAS score of back pain was improved from 6.44 points preoperatively to 0.44 at the final visit and the score of sciatica was reduced from 4.84 to 0.26. Also, the Oswestry Disability Index was improved from 32.62 points preoperatively to 18.25 at the final visit. The fusion rate was 92.5%. Intervertebral disc height, recorded as 9.94+/-2.69 mm before surgery was increased to 12.23+/-3.31 mm at postoperative 1 month and was stabilized at 11.43+/-2.23 mm on final visit. The segmental angle of lordosis was changed significantly from 3.54+/-3.70 degrees before surgery to 6.37+/-3.97 degrees by 24 months postoperative, and total lumbar lordosis was 20.37+/-11.30 degrees preoperatively and 24.71+/-11.70 degrees at 24 months postoperative. CONCLUSION There have been no special complications regarding the expandable cage during the follow-up period and the results of this study demonstrates a high fusion rate and clinical success.

Efficacy and durability of the titanium mesh cage spacer combined with transarticular screw fixation for atlantoaxial instability in rheumatoid arthritis patients.

Study Design. A retrospective study. Objective. This retrospective investigation was conducted to determine efficacy and endurance of titanium mesh cage as a strut for interlaminar wiring by comparing with autologous iliac bone graft (AIBG). For patients with atlantoaxial instability (AAI), allograft bone was harvested on an interlaminar mesh cage and transarticular fixation (TAF) was performed. Summary of Background Data. There have been few studies about atlantoaxial fusion rate and advantages for titanium mesh cage from comparison with AIBG in rheumatoid arthritis (RA) patients. Methods. Between January 1998 and October 2007, 55 RA patients were surgically treated for AAI. Among them, 34 patients who underwent surgical treatment with TAF and interlaminar wiring using mesh cage packed with allograft, enrolled in this study (group I). For evaluation of bone fusion about mesh cage group, 21 RA patients who underwent TAF and interlaminar wiring with AIBG were also selected (group II). In both groups, radiologic evidence of bone fusion was assessed with measuring atlantodental interval. Patients were strongly encouraged to mobilize by postoperative 1 day with external cervical bracing. The mean follow-up period was 12.3 months (6–36 months). Results. Overall, bone fusion was achieved in 33 patients (97%) in group I. And, this was comparable with 100% of group II. There was no statistical difference in bone fusion rate. During the study period, there were 2 instrument-related complications of screw malposition and cable loosening. Conclusion. The results of this study in which mesh cage was used as an interlaminar spacer, showed immediate rigid fixation and successful bone union. We also could prevent donor site morbidities frequently seen in patients with surgical treatment for AAI.

Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability : Comparison with Bilateral Method

OBJECTIVE Bilateral C1-2 transarticular screw fixation (TAF) with interspinous wiring has been the best treatment for atlantoaxial instability (AAI). However, several factors may disturb satisfactory placement of bilateral screws. This study evaluates the usefulness of unilateral TAF when bilateral TAF is not available. METHODS Between January 2003 and December 2007, TAF was performed in 54 patients with AAI. Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months. RESULTS Unilateral TAF was performed in 27 patients (50%). The causes of unilateral TAF were anomalous course of vertebral artery in 20 patients (74%), severe degenerative arthritis in 3 (11%), fracture of C1 in 2, hemangioblastoma in one, and screw malposition in one. The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p=0.317). CONCLUSION Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement.

Subsidence of Cylindrical Cage (AMSLU™ Cage) : Postoperative 1 Year Follow-up of the Cervical Anterior Interbody Fusion

OBJECTIVE There are numerous reports on the primary stabilizing effects of the different cervical cages for cervical radiculopathy. But, little is known about the subsidence which may be clinical problem postoperatively. The goal of this study is to evaluate subsidence of cage and investigate the correlation between radiologic subsidence and clinical outcome. METHODS To assess possible subsidence, the authors investigated clinical and radiological results of the one-hundred patients who underwent anterior cervical fusion by using AMSLUtrade mark cage during the period between January 2003 and June 2005. Preoperative and postoperative lateral radiographs were measured for height of intervertebral disc space where cages were placed. Intervertebral disc space was measured by dividing the sum of anterior, posterior, and midpoint interbody distance by 3. Follow-up time was 6 to 12 months. Subsidence was defined as any change in at least one of our parameters of at least 3 mm. RESULTS Subsidence was found in 22 patients (22%). The mean value of subsidence was 2.21 mm, and mean subsidence rate was 22%. There were no cases of the clinical status deterioration during the follow-up period. No posterior or anterior migration was observed. CONCLUSION The phenomenon of subsidence is seen in substantial number of patients. Nevertheless, clinical and radiological results of the surgery were favorable. An excessive subsidence may result in hardware failure. Endplate preservation may enables us to control subsidence and reduce the number of complications.

Nucleoplasty as an Alternative Intradiscal Therapy: Indications and Technique

This study was designed to determine the outcome of treatment of herniated intervertebral discs with Nucleoplasty (Arthrocare Spine, Sunnyvale, CA, USA). Nucleoplasty, a minimally invasive procedure for treating the contained herniated intervertebral discs, was introduced recently. Nucleoplasty utilizes coblation technology for ablating and coagulating soft tissue for partial disc removal. Sixty-five patients underwent Nucleoplasty at Hanyang University Hospital from August 2000. All patients had axial pain, and 49 patients had accompanying radiating pain in the leg. The mean follow-up period was 6.2 months. Fifty-six patients underwent the one-level procedure, and nine patients underwent the two-level procedure. The operated levels were L2-3 in 4 cases, L3-4 in 3 cases, L4-5 in 36 cases, and L5-S in 3 cases. The average operation time was 46 min. Most patients underwent the procedure under local anesthesia and were discharged on the same day or the next day. Ruptured or migrated disc herniations, spinal stenosis, previous major spinal surgery, and definite radiological spinal instability were contraindications. A visual analogue scale (VAS) and the MacNab classification were used to measure symptoms at each visit. The subjects were 27 men and 19 women, with a mean age of 38.5 years at the time of surgery. The surgical results according to the MacNab classification were excellent or good in 54 cases, fair in 6 cases, and poor in 5 cases. The mean VAS score was 7.5 at the time of surgery and 2.2 at 1 month after the procedure. Most patients showed symptom improvement 1 or 2 days after surgery. Difficulties were found in targeting into and navigating in the L5-S level. Three patients underwent open discectomy and one patient received an epidural steroid injection during the follow-up period. One case of discitis was treated with intravenous antibiotics as a surgery-related complication. These results indicate that Nucleoplasty is a new and reliable addition to the armamentarium of minimally invasive disc surgery for contained herniated intervertebral discs. Patient selection is the most important key to successful surgical results.