Biomechanical Effects of Facet Capsule Injuries in Posterior Lumbar Fusion Operations.

Park, Seung Won; Kim, Young Baeg; Hwang, Sung Nam; Choi, Duck Young; Kwon, Jeong Taik; Min, Byung Kook; Suk, Jong Sik

Original Article

Journal of Korean Neurosurgical Society 2001;30(3): 358-365.

Seung Won Park, Young Baeg Kim, Sung Nam Hwang, Duck Young Choi, Jeong Taik Kwon, Byung Kook Min, Jong Sik Suk

Department of Neurosurgery, College of Medicine, Chung-Ang University, Seoul, Korea.

ABSTRACT

OBJECTIVE
S: Although posterior lumbar fusion operations had been reported to accelerate spinal degeneration, there have been only a few studies for their biomechanical effects. We have studied the change of motion range at the vertebral joint one level above the fusion(UVJ) in pedicle screw fixation group(PSF)(n=13) where facet capsule was destroyed and in posterior lumbar interbody fusion group(PLIF)(n=8) where it was spared. PATIENTS AND METHODS:The patients were divided into early(3 to 6 months) and late(over 12 months) according to postoperative follow-up period. The flexion, extension and flexion-extension angles(FA, EA, FEA) were measured at the UVJ with pre-operative, early and late post-operative films.
RESULTS
Mean age and male to female ratio were 52.7+/-9.3 and 1:3.2. Mean follow-up periods were 144.1+/-30.0 and 528.8+/-160.3 days in early and late groups, respectively. The FEA and FA in the late PSF(11.8+/-3.1, 8.5+/-2.9) were significantly greater than pre-operative angles(7.8+/-3.9, 5.1+/-3.7)(p<0.01, p<0.05). All angles in the PLIF showed no significant changes with time. The FEA and FA in the late PSF(11.8+/-3.1, 8.5+/-2.9) were significantly greater than those of the late PLIF(7.6+/-2.3, 3.4+/-2.0)(p<0.01, p<0.001). All angles at early follow-up period were similar between PSF and PLIF. The EA showed no significant change in relation with follow-up period or fusion method.
CONCLUSION
As a result, the facet capsule injury in pedicle screw fixation seems to be related with increased flexion angle or degeneration of the adjacent joint above the fused vertebra in the late phase.

Key Words: Pedicle screw fixation; Posterior lumbar interbody fusion; Facet capsules; Motion range; Degeneration