Factors Affecting Learning Curve in Endoscopic Lumbar Discectomy using Interlaminar Approach / 대한척추외과학회지

STUDY DESIGN: A retrospective study OBJECTIVES: To try and find the best surgical technique by analyzing the real-time video taken during a percutaneous endoscopic interlaminar lumbar discectomy. SUMMARY OF LITERATURE REVIEW: A percutaneous endoscopic lumbar discectomy, using an interlaminar approach, has superior aspects, such as anatomical similarity with that of open spinal surgery, and applicability regardless of the herniated level. However, the technical difficulty can be an obstacle to shortening of the learning-curve. MATERIALS AND METHODS: Between January 2005 and January 2006, 56 patients who were underwent an operation at our hospital, due to single level (L4-5 or L5-S1) herniated lumbar disc disease, by one surgeon, and were selected for this study. The procedure was divided by the approach; either ligament flavum resection, partial removal of the lamina or root identification and discectomy. By analyzing the real-time video taken during the operation, as well as checking the time taken for each procedure, the factors influencing the prolongation of surgery time can be sought, and efforts made to shorten the operation time. RESULTS: The mean operation time was 65 minutes (28 minutes~127 minutes). The mean operation times in patients either requiring or not requiring partial removal of the lamina were 84 minutes (45 minutes~127 minutes) and 45 minutes (28 minutes~91 minutes), respectively, and also showed a statistically significant correlation (p=0.023). The mean operation times for the first and last 10 cases were 107 and 48 minutes, respectively. 3 cases needed revision open surgery due to failed symptom resolution. The procedures affecting a prolonged operation time were partial removal the lamina and ligament flavum resection. The time required for ligament flavum resection plateaued after 20 cases, and that for partial removal of the lamina reached plateau after 19 cases. CONCLUSIONS: By overcoming such technical problems, shortening of the learning-curve for a percutaneous endoscopic interlaminar lumbar discectomy was possible.

The Posterior Fixation of Thoracolumbar Burst Fracture using Pedicle Screws and Caudal Offset Sublaminar Hooks / 대한척추외과학회지

STUDY DESIGN: A retrospective study. OBJECTIVES: We analyzed the clinical results of thoracolumbar burst fractures, managed by posterior fixation of 2 segments above and 1 segment below, using an offset sublaminar hook. SUMMARY OF LITERATURE REVIEW: Mono-segment fixation above and below the injured vertebra, using posterior pedicle screw fixation, has the benefit of saving the uninjured mobile lumbar segment in thoracolumbar junction burst fracture patients. However, in a severely comminuted vertebral body, mono-segment fixation may not prevent loss of correction and metal failure. Options for such cases are additional anterior column support or long segment fixation, including 2 segments above and 1 below the injured vertebra. Instead of fixing 2 segments below the fracture level, fixation of one segment below, using the offset sublaminar hook, can save the uninjured segment, especially in the upper lumbar segment, with greater fixation strength than mono-segmental screws only. MATERIAL AND METHOD: The study included eleven patients with a thoracolumbar junction burst fracture, which underwent posterior fixation using pedicle screws in 2 segments above and 1 segment below, aided by an offset sublaminar hook. The mean follow-up period was 30.7 months (range, 24 to 58 months). Radiographs taken at follow-up were evaluated for implant loosening, correction loss, change in pedicle screw angle, and loss of vertebral height, adjacent segment instability and junctional degenerative change. The clinical results were collected in out-patient department. RESULTS: No implant loosening was noted. No case showed adjacent instability, acceleration of junctional degenerative change at the lower end of lumbar segment or hook dislodgement. Also, there were no junctional area related symptoms. CONCLUSION: For posterior surgery of thoracolumbar burst fractures, this construct, fixing 2 segments above and 1 segment below injured vertebra, aided by an offset sublaminar hook, was satisfactory in maintaining fracture reduction, and showed no instability or acceleration of degeneration on adjacent segnents.

Factors Affecting Segmental Lordotic Angle After Posterior Lumbar Interbody Fusion Using Metal Cage / 대한척추외과학회지

STUDY DESIGN: This is a retrospective study. OBJECTIVES: We tried to find out what kind of factors affect the segmental lordotic angle improvement after performing posterior lumbar interbody (PLIF) fusion using a metal cage. The study was done using radiographic measurements. SUMMARY OF LITERATURE REVIEW: For degenerative spinal disease, PLIF with using a metal cage is an effective way to fuse and restore segmental lordosis of the lumbar spine. MATERIALS AND METHODS: The study included 104 patients (65 males, 39 females). Radiographs of the antero-posterior, lateral, flexion and extension views that were taken during the preoperative period and the follow-up 6 months were evaluated for the L4-5 segmental lordosis angle, cage invagination, cage position and disc height. Then, statistical analysis was performed using the Pearson method to determine which factors affected the segmental lordotic angle correction. RESULTS: The increase of the anterior disc height on the postoperative lateral radiograph (gamma=0.303, p<0.01) and the increase of lordosis on the preoperative extension radiograph (gamma=0.384, p<0.01) showed statistically positive correlation with the increase of the postoperative segmental lordosis angle. When comparing between the 4 degrees and 8 degrees cages, the more angle the cage had, the more segmental angle was restored and this was statistically correlated (P<0.05). However, the amount of segmental lordosis angle correction was not as much as the angle of the cage that was used. Other factors such as cage invagination and cage position didn't show statistical correlation. CONCLUSIONS: Posterior lumbar interbody fusion using a metal cage is useful method for restoring the lumbar segmental lordosis angle only if the disc is flexible enough to be distracted (ED note: distracted is the word you want?) sufficiently intraoperatively or if it allows good segmental lordosis, as seen on the preoperative extension radiograph. Correction of the segmental lordosis angle using a wedged cage with a larger angle was not always satisfactory because it did not restore as much angle as the angle of cage that was used.