The effect of interspinous ligament integrity on adjacent segment instability after lumbar instrumentation and laminectomy--an experimental study in porcine model.
Eight fresh porcine lumbar spines received a posterior instrumentation at L4-L5 using pedicle screw-rod system. Each specimen was tested utilizing laminectomies of varying extent. Group A (Integrity) preserved the spinous process and interspinous ligament; Group B (Partial laminectomy) removed the inferior portion of L4 spinous process and preserved the interspinous ligament of L3-L4; Group C (Complete laminectomy) removed the entire L4 spinous process. Hydraulic testing machine was used to generate an increasing moment up to 8400 N mm in flexion and extension. The intervertebral displacement on the superior adjacent disc between L3-L4 was measured using an extensometer. Under extension, no significant difference in the intervertebral displacement was observed among three different models of laminectomy. However, under flexion, the intervertebral displacement on adjacent disc with complete laminectomy was statistically larger than those of integrity and partial laminectomies (P=0.000976 and P=0.0363, respectively). No difference was found between integrity and partial laminectomy groups (P>0.05). This study implies that an instrumented spine with integrity of posterior complex is less likely to develop adjacent instability than a spine with destruction of the anchoring point for supraspinous ligament.
Chen
Lih-Huei
LH
Department of Orthopaedic Surgery, Chang Gung Memorial Hospital, Kweishan, Taoyuan, Taiwan.
Lai
Po-Liang
PL
Tai
Ching-Lung
CL
Niu
Chi-Chien
CC
Fu
Tsai-Sheng
TS
Chen
Wen-Jer
WJ
D000818:Animals; D001860:Bone Plates / Q000009:adverse effects; D001863:Bone Screws / Q000009:adverse effects*; D019245:Compressive Strength; D004195:Disease Models, Animal; D066298:In Vitro Techniques; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D007796:Laminectomy / Q000009:adverse effects; D008022:Ligaments / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology* / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation; D013552:Swine