Feasibility of Translaminar Screw Placement in Korean Population: Morphometric Analysis of Cervical Spine

PURPOSE: To analyze the feasibility of unilateral and bilateral translaminar screw placement in Koran population, and compare the acceptance rate using previously reported data in American population. MATERIALS AND METHODS: The translaminar lengths, thickness, heights, and sagittal-diagonal measurements were performed. The feasibility analysis was performed using unilateral and bilateral 3.5 mm cervical screw placement on the CT scans within 0.5 mm of safety margin. We also performed radiographic analysis of the morphometric dimensions and the feasibility of unilateral and bilateral translaminar screw placement at C3-C7. RESULTS: Korean population had similar or significantly shorter translaminar lengths and thickness (lengths and thickness in C7 among males; lengths in C6-C7 and thickness in C4 among females) than American population, but had similar or significantly longer translaminar heights and sagittal-diagonal measurements (heights in C3-C7 and sagittal-diagonal measurements in C3-C6 among males; heights in C7 and sagittal-diagonal measurements in C3-C7 among females). Unilaterally, translaminar screw acceptance rates in C3-C7 were similar between Korean and American male population, but the rates in C4-C6 were significantly smaller between Korean and American female population. Bilaterally, translaminar screw acceptance rates in C3 and C5-C6 were significantly larger between Korean and American male population, but the rates in C3-C7 were similar between Korean and American female population. CONCLUSION: The feasibility of unilateral and bilateral translaminar screw placement is different depending on different ethnics. Subaxial cervical unilateral translaminar screw placement among Korean male population and bilateral placement at C4-C7 among Korean female population are more acceptable than American population.

Slip Reduction Rate between Minimal Invasive and Conventional Unilateral Transforaminal Interbody Fusion in Patients with Low-Grade Isthmic Spondylolisthesis

OBJECTIVE: To compare the slip reduction rate and clinical outcomes between unilateral conventional transforaminal lumbar interbody fusion (conventional TLIF) and unilateral minimal invasive TLIF (minimal TLIF) with pedicle screw fixation for treatment of one level low-grade symptomatic isthmic spondylolisthesis. METHODS: Between February 2008 and April 2012, 25 patients with low-grade isthmic spondylolisthesis underwent conventional TLIF (12 patients) and minimal TLIF (13 patients) in single university hospital by a single surgeon. Lateral radiographs of lumbar spine were taken 12 months after surgery to analyze the degree of slip reduction and the clinical outcome. All measurements were performed by a single observer. RESULTS: The demographic data between conventional TLIF and minimal TLIF were not different. Slip percentage was reduced from 15.00% to 8.33% in conventional TLIF, and from 14.15% to 9.62% in minimal TLIF. In both groups, slip percentage was significantly improved postoperatively (p=0.002), but no significant intergroup differences of slip percentage in preoperative and postoperative were found. The reduction rate also not different between conventional TLIF (45.41+/-28.80%) and minimal TLIF (32.91+/-32.12%, p=0.318). CONCLUSION: Conventional TLIF and minimal TLIF with pedicle screw fixation showed good slip reduction in patients with one level low-grade symptomatic isthmic spondylolisthesis. The slip percentage and reduction rate were similar in the conventional TLIF and minimal TLIF.