Interobserver and intraobserver variability in the identification of the Lenke classification lumbar modifier in adolescent idiopathic scoliosis.

STUDY DESIGN: Interobserver and intraobserver reliability study for the identification of the Lenke classification lumbar modifier by a panel of experts compared with a computer algorithm. OBJECTIVES: To measure the variability of the Lenke classification lumbar modifier and determine if computer assistance using 3-dimensional spine models can improve the reliability of classification. SUMMARY OF BACKGROUND DATA: The lumbar modifier has been proposed to subclassify Lenke scoliotic curve types into A, B, and C on the basis of the relationship between the central sacral vertical line (CSVL) and the apical lumbar vertebra. Landmarks for identification of the CSVL have not been clearly defined, and the reliability of the actual CSVL position and lumbar modifier selection have never been tested independently. Therefore, the value of the lumbar modifier for curve classification remains unknown. METHODS: The preoperative radiographs of 68 patients with adolescent idiopathic scoliosis presenting a Lenke type 1 curve were measured manually twice by 6 members of the Scoliosis Research Society 3-dimensional classification committee at 6 months interval. Intraobserver and interobserver reliability was quantified using the percentage of agreement and kappa statistics. In addition, the lumbar curve of all subjects was reconstructed in 3-dimension using a stereoradiographic technique and was submitted to a computer algorithm to infer the lumbar modifier according to measurements from the pedicles. RESULTS: Interobserver rates for the first trial showed a mean kappa value of 0.56. Second trial rates were higher with a mean kappa value of 0.64. Intraobserver rates were evaluated at a mean kappa value of 0.69. The computer algorithm was successful in identifying the lumbar curve type and was in agreement with the observers by a proportion up to 93%. CONCLUSIONS: Agreement between and within observers for the Lenke lumbar modifier is only moderate to substantial with manual methods. Computer assistance with 3-dimensional models of the spine has the potential to decrease this variability.

Changes in load distribution in the knee after opening-wedge or closing-wedge high tibial osteotomy.

The treatment of unicompartmental osteoarthritis of the knee by high tibial osteotomy has been carried out by closing-wedge osteotomy. The advantages for opening-wedge osteotomy are ease of procedure and improved correction with comparable short-term to midterm results. It is not known how the opening-wedge high tibial osteotomy procedure alters the load distribution between the medial and lateral compartments of the knee. The current biomechanical study investigated opening-wedge vs closing-wedge osteotomies in 5 pairs of cadaver knees. The results showed that at 5 degrees osteotomy, the closing-wedge provided superior results of load transfer from medial to lateral compartment than that seen with opening-wedge, but at 10 degrees osteotomy, there was no significant difference in load transfer in the knee compartments between the 2 surgery modes.

Long-term outcome in neuromuscular scoliosis fused only to lumbar 5.

STUDY DESIGN: Outcomes are retrospectively compared for patients with neuromuscular scoliosis after instrumented surgery and fusion to the pelvis versus lumbar 5 fusion alone. OBJECTIVES: To compare outcomes for patients with neuromuscular scoliosis for correction of scoliosis, lumbar 5 tilt, and pelvic obliquity after instrumented surgery and pelvic fusion, and by fusion only to lumbar 5. SUMMARY OF BACKGROUND DATA: Correction of scoliosis and pelvic obliquity in neuromuscular disease using spinal instrumentation is an accepted surgical procedure. Controversy remains concerning the caudal extent of fusion and instrumentation to lumbar 5 or to the sacrum. METHODS: Patients with progressive neuromuscular scoliosis underwent spinal fusion with segmental instrumentation using a U-rod terminating in pedicle screw fixation at L5. Similar patients underwent spinal fusion with a unit rod and sacral fusion. RESULTS: From 1998 to 2002, 55 patients with neuromuscular scoliosis underwent instrumentation and L5 fusion with the U-rod or to the sacrum with the unit rod. Initial and long-term corrections of scoliosis and pelvic obliquity were similar in both groups. CONCLUSIONS: Instrumentation and fusion to L5 is a less technically difficult procedure, requires less surgical time, has decreased blood loss, and less risk of infection compared to instrumented pelvic fusion. Postoperative and long-term follow-up indicates that L5 fusion can correct scoliosis and pelvic obliquity, comparable to results of sacrum fusion.

A biomechanical study of posterior spinal instrumentation using pedicle screws with and without cross-links.

OBJECTIVE: It is not clear from the studies reported in the literature whether the addition of cross-links to bilateral pedicle screws increases the stiffness of the construct significantly to fix multilevel vertebral bodies. The current study addresses the question of how cross-links change the rotational stiffness of constructs with 6, 12, and 20 pedicle screws. METHODS: Seven thoracolumbar 10-level spine segments (T4-L1), from individuals of average age 72 years (range 46-83 years), were instrumented with pedicle screws (6, 12, and 20) and tested in torsion with and without cross-links. As the cadaver specimens had signs of osteopenia, constructs consisting of 10 wood blocks 35 x 35 x 78 mm (weight x height x length) were also tested following an identical protocol as in the cadavers to prove the concept. RESULTS: For both wood blocks and cadavers, the rotational stiffness increased linearly with number of screws with and without cross-links. Two cross-links increased rotational stiffness significantly for both 12 and 20 screws (nonsignificant for 6 screws) for wood block constructs. However, the rotational stiffness values of the cadaver constructs with or without cross-links failed to show any significant differences. CONCLUSIONS: This work has raised the need for developing a suitable animal model for the study of multilevel vertebral bodies to simulate the fixation of scoliosis corrections.