title: Biomechanical evaluation of segmental instability in degenerative lumbar spondylolisthesis.
abstract: Here we investigated the biomechanical properties of spinal segments in patients with degenerative lumbar spondylolisthesis (DLS) using a novel intraoperative measurement system. The measurement system comprised spinous process holders, a motion generator, a load cell, an optical displacement transducer, and a computer. Cyclic displacement of the holders produced flexion-extension of the segment with all ligamentous structures intact. Stiffness, absorption energy (AE), and neutral zone (NZ) were determined from the load-deformation data. Forty-one patients with DLS (M/F = 15/26, mean age 68.6 years; Group D) were studied. Adjacent segments with normal discs in six patients (M/F = 3/3, mean age 35 years) were included as a control group (Group N). Flexion stiffness was significantly lower in Group D than in Group N. The NZ, however, was significantly greater in Group D than in Group N. Thus, compared to normal segments, spinal segments with DLS had a lower flexion stiffness and a higher NZ. NZs in Group D were, however, widely distributed compared to those in Group N that showed NZ <2 mm/N in all cases, suggesting that the segment with DLS is not always unstable and that the segments with NZ >2 mm/N can be considered as unstable.
authors.affiliation: Niigata Spine Surgery Center, 2-5-22 Nishi-machi, Niigata 950-0165, Japan. kazu3795jp@yahoo.co.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hasegewa
authors.forename: Ko
authors.initials: K
authors.lastname: Kitahara
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hara
authors.forename: Ko
authors.initials: K
authors.lastname: Takano
authors.forename: Haruka
authors.initials: H
authors.lastname: Shimoda
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry / Q000295:instrumentation / Q000379:methods; D001696:Biomechanical Phenomena / Q000502:physiology; D004548:Elasticity / Q000502:physiology; D001330:Electronic Data Processing / Q000295:instrumentation / Q000379:methods; D004582:Electronics, Medical / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000639:trends; D007403:Intervertebral Disc / Q000503:physiopathology; D007593:Joint Instability / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D008022:Ligaments / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods*; D009068:Movement / Q000502:physiology; D018583:Pliability; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods; D013168:Spondylolisthesis / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D013314:Stress, Mechanical; D013718:Tensile Strength; D014160:Transducers, Pressure / Q000639:trends; D016474:Weight-Bearing / Q000502:physiology