In Lenke type 1 or type 2 adolescent idiopathic scoliosis (AIS), significant correction of the main thoracic curve with relative under-correction of the proximal thoracic curve increases the incidence of postoperative shoulder height imbalance. This is the conclusion presented by Alex Sielatycki (Department of Orthopaedic Surgery, Columbia University, New York, USA) at the 25th International Meeting on Advanced Spine Techniques (IMAST; 11–14 July, Los Angeles, USA).
Of the importance of these findings, Sielatycki comments: “Postoperative shoulder height imbalance is a relatively common phenomenon after surgical correction of Lenke type 1 or 2 AIS, and when it occurs it can be particularly bothersome for patients and their families. We believe our findings are important in that they highlight the need to carefully assess the correction of both the main thoracic and proximal thoracic curves relative to each other. Our hope is that surgeons will use this information to guide their decision making and reduce the risk for shoulder imbalance.”
The study from Columbia University and the Harms Study Group sought to analyse how much the amount of curve correction of both main curves and proximal curves contributes to shoulder balance in patients with Lenke Type 1 and Type 2 AIS.
Thirteen surgeons reviewed preoperative and five year postoperative X-rays and clinical radiographs from a large, multicentre database (the Harms Study Group) of 145 Lenke type 1 or type 2 AIS patients who were corrected with pedicle screw/ rod constructs. All patients had at least five years’ follow-up.
Using multivariate analysis to identify predictors of postoperative shoulder imbalance, the investigators report that shoulder imbalance was most common when the proximal curve was corrected less than 52%, and the main curve was corrected more than 53%. For these patients, only 41.3% had balanced shoulders, meaning almost 60% of this cohort had asymmetrical shoulders.
Postoperative shoulder height imbalance is a significant potential complication in scoliosis patients, Sielatycki informed the IMAST audience, and is reported in approximately 25–40% cases in the literature.
According to Sielatycki, while it is thought that a more cephalad upper instrumented vertebra is thought to mitigate this shoulder imbalance postoperatively, there is little attention paid to how much the amount of curve correction contributes to shoulder balance, and this is what attracted him and his colleagues to the research. Sielatycki explains, “Shoulder height imbalance is a relatively common problem following these operations, and there is relatively little attention given to the proper surgical techniques to reduce this complication.”
“As our manuscript mentions, many studies discuss choosing a more proximal UIV as a means to mitigate this risk, however our clinical experience has been that merely instrumenting a more cranial UIV does not itself reduce the risk for imbalanced shoulders. The indirect connection is that a more proximal UIV will allow the surgeon to control the proximal curve, however the real work comes with using corrective maneuvers (distraction across the concavity and compression across the convexity) to level the UIV and balance the shoulders.”
Speaking to Spinal News International about the clinical ramifications of his research, Sielatycki comments, “Achieving maximal thoracic curve correction and good shoulder height balance are two goals in AIS surgery that are somewhat at odds. Our study shows that when the main curve is maximally corrected, the risk for shoulder height imbalance is increased; particularly when the proximal curve is not adequately corrected. We are hopeful that findings of our study will provide useful information for scoliosis surgeons in achieving the goals of maximal curve correction as well good shoulder height balance.”
From Sielatycki et al’s research, the influence of degree of curve correction proved to be great in determining shoulder imbalance. In contrast, Sielatycki explained that “A more proximal upper instrumented vertebra (UIV) did not show any difference in average correction of that proximal curve, and also the UIV did not influence which correction category each patient fell into.”
Five years on from surgery, 93 (64%) of the 145 patients analysed in the study had balanced shoulders. Where the proximal curve had been corrected more than 52%, this rose to 79.7% with balanced shoulders, meaning only 20% were unbalanced (the flip-side of this being that for patients with a proximal curve correction of less than 52%, almost half—46%—had unbalanced shoulders).
Large corrections of the main thoracic curve (greater than 53%), coupled with a relatively small proximal curve correction (less than 52%) led to more than half of patients having unbalanced shoulders (59.7% asymmetrical; 41.3% balanced). However, under-correcting both the proximal and main curve—by less than 52% and 53% respectively—resulted in patients with balanced shoulder 87% of the time.
Sielatycki concluded his talk with the advice: “You really need to pay careful attention to the correction of that proximal curve relative to the amount of correction of the main thoracic curve, whether its instrumented or not, and if you are instrumenting that proximal curve, you should take care to distract across the proximal concavity, and compress across the convexity to level the UIV, and achieve good postoperative shoulder height balance.”
For this research, Sielatycki and colleagues were awarded the Whitecloud Award for the Best Clinical Paper presented at IMAST 2018.
