Michael Schendel

Learn More
Facet forces, longitudinal ligament loads, and vertebral body motion were experimentally measured in five fresh human lumbar spine segments, L1-L2. Strain gages on the bone surface were used to quantify facet loads. Buckle transducers were used to measure anterior and posterior longitudinal ligament loads. The three-dimensional motion of the motion segment(More)
The parameters in adolescent idiopathic scoliosis correction (longitudinal height gain, coronal and sagittal plane changes) that correlate most closely with an increase in thoracic volume are reported. With pre- and postoperative radiographs of matched patients having straight Harrington distraction rods and contoured Luque rods, coordinates were digitized(More)
Long levels of spinal instrumentation and fusion are common in surgery for spinal deformity. The effect on the remaining mobile segments is not well understood. The changes in lumbar facet loading and lumbosacral motion were evaluated as the number of immobilized levels increased. Four fresh canine cadaveric spines from T6 to sacrum were used. Lumbosacral(More)
STUDY DESIGN For in vitro studies, there is no basis for choosing a "load control study" over a "displacement control" study. This study qualitatively compared results from in vitro and in vivo tests, allowing the authors to address the experimental assumptions that in vitro testing contributes to the understanding of the in vivo condition. OBJECTIVES To(More)
Ten consecutive patients with adolescent idiopathic scoliosis and King-Moe curve Types II and III, scheduled consecutively for Cotrel-Dubousset instrumentation, underwent pre- and postoperative computed tomography scans with axial slices through each vertebra, and including the pelvis. Vertebral rotation was measured and referenced to the pelvis. Average(More)
The motion and facet load changes at the adjacent segment after lumbosacral immobilization (with different angles) were quantified in vitro using canine spines. Changes were examined under flexion, extension, and lateral bending. An increase (extension: 62%; flexion: 85%; left bend: 30%; right bend 26%) in motion at the adjacent segment was found for all(More)
Although the normal sagittal profile of the thoracolumbar spine has been described, this has been obtained primarily by using young individuals standing. We sought to describe the sagittal profile of the thoracolumbar spine in an older population in the supine cross-table lateral position compared with that standing. We enrolled 50 volunteers with no(More)
STUDY DESIGN Eighteen patients with adolescent idiopathic scoliosis treated with ISOLA instrumentation and 13 treated with Cotrel-Dubousset instrumentation were studied before and after surgery with computed tomography scans. OBJECTIVES To analyze and compare the immediate change in chest volume of patients treated with the derotation method of(More)
STUDY DESIGN In vivo, canine lumbar spine intervertebral motion was measured before and after instrumentation of caudal segments. The three-dimensional kinematics of the intervertebral joint were described using helical axes and Fourier series. OBJECTIVE The in vivo three-dimensional kinematics of the intervertebral joint were measured and described. An(More)
Using an instrumented spatial linkage, a method for measuring intervertebral motion in vivo was developed and used on six dogs. The segmental motion was recorded as the animals were exercised in routine functions. The standing posture was found to be a repeatable position. During walking, the average excursion between opposing facets was 3.4 +/- 1.3 mm, as(More)