Purpose: The Lenke classification has established criteria which designate the proximal thoracic (PT) curve as structural (Lenke 2). However, this classification may overestimate the necessity to include the proximal thoracic curve in the fusion construct. The objective of this study was to compare the incidence of fusing the PT curve for true Lenke 2 curve patterns, comparing a time period when the classification was not utilized and when it was first used.

Method: A retrospective review of a consecutive series of patients with adolescent idiopathic scoliosis (AIS) at a single institution from 1996–2000 (early group) and from 2002–2004 (late group) were reviewed. The curves were all classified by the Lenke classification retrospectively. Patients were also grouped into those who have had inclusion of the PT curve (+PT fusion) and those who did not (−PT fusion).

Results: There were 44 in the early group and 33 in the late group. There were no differences in the early and late groups with respect to age (14.3 vs. 14.4yrs), gender (79.5% vs. 69.7% female), BMI (21.7 vs. 22.4kg/cm2), the preoperative PT magnitude (40.0° vs. 38.6°), curve flexibility (16.0% vs. 14.5%), the main thoracic (MT) magnitude (63.4° vs. 62.7°), T1 tilt (7.3° vs. 5.2°), pre-operative clavicle angle (1.0° vs. −0.2°), and preoperative shoulder height (1.2 vs. −0.8mm. The early group had fusion of the PT less often (36% vs. 57%)(p< 0.05) which resulted in a greater residual PT curve (26.5 vs. 22.2°), MT curve (33.8 vs. 27.8°), and a greater clavicle angle (4.6 vs. 2.5°)(p< 0.05). At two years the PT continued to be significantly greater in the early group (28.6 vs. 22.8°)(p< 0.05), however T1 tilt (8.8 vs. 8.1°), clavicle angle (1.3 vs. 1.0°), and shoulder height (3.5 vs. 4.7mm) were the same.

Conclusion: The application of the Lenke classification system for AIS increases the likelihood of instrumenting a PT curve resulting in improved postoperative PT curve magnitude. However, similar shoulder balance, T1 tilt and clavicle angle were seen compared between groups. The classification system should be used to guide decision making, however, other parameters should be evaluated when deciding when to instrument a PT curve.

Purpose: Few studies have analyzed spinal cord monitoring (SCM) during spine deformity surgery when neural axis abnormalities (NAA) are present. Our purpose was to compare the effectiveness of SCM between NAA and AIS patients.

Methods: This is a retrospective review of all patients from 1993–2002 with an isolated NAA who had SCM during spinal deformity surgery. These were compared to a randomly selected group of AIS patients during the same time period when techniques for somatosensory-evoked potentials (SSEP) and motor-evoked potential (MEP) monitoring remained the same.

Results: There were 41 NAA patients and 139 AIS patients. The age at surgery was similar (14.4 vs. 14.5 yrs), but there were more males (48.8 vs. 18.7%)* in the NAA group. For NAA patients, the most common abnormalities were syringomyelia (n=29) and tethered cord (n=5) for which 68% required neurosurgery. The preoperative curve magnitude was greater in the NAA group (65.9° vs 59.6°)* but there were no differences in surgical time (39.6 vs. 35.9 min/level) and estimated blood loss (99.4 vs. 82.0 cc/level) between the groups. There was a trend towards more surgical complications in the NAA group (7.3 vs. 3.6%). Good baseline values were achieved less often in the NAA group for SSEPs (85% vs 99%)* and MEPs (83% vs 100%)*. Significant deviations from baseline values were seen more often in the NAA group for SSEP (5.0% vs. 1.4%)* and MEP (4.0% vs. 2.5%)*. * (p< 0.05)

Conclusions: Obtaining baseline SCM values was more difficult and deviations from baseline were more common in the NAA patients when compared to AIS patients. However, SCM did not miss a neurologic injury and was found to be very useful and necessary during spine deformity surgery in the NAA population.