Cost of instrumentation found to have no impact on cosmetic results for Lenke type 1A and B curves

One physician labeled the only correlation between cost density and radiographic improvement ‘weak.’

Increasing costs of instrumentation does not correlate with cosmetic outcome in patients with adolescent idiopathic scoliosis, according to a recent study of individuals with Lenke type 1A and B curves.

The findings were presented by Scott Yang, MD, at the North American Spine Society 25th Annual Meeting in Orlando, Fla.

“Cosmesis is a very important concern for many adolescents, and Lenke type 1A and B curves have a particularly disfiguring curve with rib prominence, shoulder imbalance, a trunk shift, and waistline asymmetry,” Yang said. “The question we set out to propose was: Does the cost of instrumentation, correlate with improved radiographic or cosmetic outcome in adolescent idiopathic scoliosis?”

Yang noted the only statistically significant correlation that his study found between cost and radiographic deformity measures was in Cobb angle correction – but he also noted the correlation was “rather weak.”

A retrospective study

Yang’s group performed a retrospective study of 58 Lenke type 1A and B right thoracic curves from Scolisoft, an online, multicenter database. Follow-up included 6 months of complete radiographic and photographic data. Total cost of the instrumentation – hooks and pedicle screws – was used as a calculation of cost, and the study’s outcome measure was cost density — defined as the total cost of instrumentation divided by the number of vertebrae fused.

To gauge cosmetic improvements, Yang’s group looked at preoperative and postoperative photographic measurements which included trunk shift, waistline asymmetry and shoulder balance.

“The radiographic measures used in our study were standard deformity measurements, including preoperative and follow-up measurements of coronal and sagittal measurements,” Yang added. “These were correlated with cost.”

Yang reported an average patient age of 14.9 years, with an average cost of instrumentation being $12,662. He also pointed out a “significant range” in costs for the same type of Lenke 1 curve, with costs of instrumentation ranging from $6,769 to $21,274.

Only a weak correlation

When the radiographic deformity measures were correlated with cost, Yang reported finding there was no statistically significant difference in any change in deformity measures preoperatively and postoperatively – with the exception of the weak correlation for the Cobb angle.

Within the photographic results, the group noted there was no statistically significant correlation between cosmetic outcomes and cost density. Yang did stress, however, that the interobserver and intraobserver variability of the measurements were excellent as measured by the interclass correlation coefficient.

The importance of cosmesis

“We know from the literature that increasing pedicle screw implant density is correlated with improved major Cobb angle corrections,” Yang said. “Pedicle screws improve major and minor curve coronal corrections compared to previous constructs.”

Still, he added, his study found that cost had no correlation with cosmetic results. This distinction is important, Yang noted, because it raises the question of whether or not high pedicle screw implant density is necessary in correcting Lenke type 1A and B curves.

“As you all know, the more pedicle screws that are implanted, the higher the rate of complications can occur,” he said.

Though the study’s weaknesses included a short follow-up time frame and no involvement of a formal cost analysis, Yang said its strength was in the fact that it was the first to compare cost and cosmetic outcome.

“The coronal Cobb angle correction improves slightly with cost density of implantation, however we saw no improvement in cosmetic outcome with increasing cost,” Yang concluded. “In consideration of surgical instrumentation, high-density pedicle screw implantation may not be necessary in Lenke 1A and B curves if we consider the outcomes of cosmesis.”

“The surgeon should take into consideration the importance of cosmetic outcome and cost effectiveness in deciding instrumentation strategy,” he added. – by Robert Press

References:

• Yang S. Right adolescent idiopathic thoracic curve (Lenke 1A and B): Does cost of instrumentation and implant density improve radiographic and cosmetic parameters? Paper #214. Presented at the North American Spine Society 25th Annual Meeting. October 5-9, 2010. Orlando, Fla.
• Clements DH, et al. Correlation of scoliosis curve correction with the number and type of fixation anchors. Spine. 2009; 15;34(20):2147-2150.

• Scott Yang, MD, can be reached at SY2W@hscmail.mcc.virginia.edu.
  Disclosure: Yang has no relevant financial disclosures.