Better Balance for Patients with Lumbar AIS

Kwan et al. present an interesting concept for balancing surgical-magnitude Lenke type-5 and 6 curves using an intraoperative technique based on calculations from preoperative side-bending radiographs followed by intraoperative measurements relative to a crossbar. Postoperative coronal imbalance is often difficult to predict and control in such patients, and the authors give surgeons a pragmatic intraoperative tool to predict satisfactory alignment, which achieved that result at a minimum of 2 years postoperatively in 37 of 39 patients. After a few simple preoperative calculations have been performed, comparison with the intraoperative crossbar on fluoroscopy can quickly allow the surgeon to adjust the correction of the major curve, if necessary, to obtain the postoperative standing balance desired. The authors have further refined previous work by Tolo and others1 for application in patients with adolescent idiopathic scoliosis (AIS) who are not undergoing fusion to the pelvis. Rather than relying on “eyeball verification” of intraoperative radiographic alignment, the more quantitative technique presented by Kwan et al. is likely to achieve a more reproducible long-term result, benefiting patients seeking treatment of their scoliotic curves. Surgeons adopting this technique will undoubtedly become facile with it and find additional uses for it. For example, given the study’s findings that failure to match the intraoperative lowest instrumented vertebra (LIV) tilt angle (β angle) to the preoperative supine right-sided-bending (RSB) LIV tilt angle adjusted for pelvic obliquity (PO) (α angle) yields persistent coronal imbalance due to under- or overcorrection of the thoracolumbar/lumbar (TL/L) curve, one can postulate that this technique may also assist in the complex and controversial choice between L3 and L4 as the LIV for Lenke-5 and 6 curve types, thereby potentially eliminating the need for revision surgery for persistent and symptomatic postoperative coronal imbalance2.