IMAST 2022: New research highlights high failure rates of anterior VBT for Lenke 1/2 curves with lumbar C modifier

Joshua Pahys

Anterior vertebral body tethering (VBT) for Lenke 1/2 curves with lumbar C modifier is associated with significantly higher failure rates if both curves are tethered and the preoperative triradiate cartilage is open, a recent study has found.

The results of the study—a retrospective review of a single-centre database—were presented by Joshua Pahys (Shriners Hospitals for Children, Philadelphia, USA) at the Scoliosis Research Society’s 29th International Meeting on Advanced Spine Techniques (IMAST 2022; 6–9 April; Miami, USA).

Speaking to Spinal News International, Pahys said: “This study is one of the first to report on the outcomes of single vs. bilateral VBTs for idiopathic scoliosis. While we initially thought VBT was ideal in patients who had significant growth remaining (those with an open triradiate cartilage), our research has shown that these patients were at the greatest risk for requiring revision surgery.

“These results helped us evolve our treatment of these patients, and how we counsel families. Our team currently advocates for thoracic posterior spinal fusion (PSF) over VBT for Lenke 1 and 2 curves due to the higher reoperation rates with VBT and relatively minimal motion loss seen with thoracic PSF. We feel it is important to continue to objectively evaluate the results of this novel procedure to improve patient outcomes moving forward.”

The study included 197 adolescent idiopathic scoliosis (AIS) patients with Lenke 1/2 curves who had a minimum of two year follow-up. Patients were grouped based on preoperative lumbar modifier A/B (n=128) or C (n=69). The total C group (CT) was further subdivided into single-sided VBT (CS, n=47) vs. bilateral thoracic and lumbar VBT (CB, n=22).

The preoperative lumbar Cobb was larger for CT (37°) vs. AB (29°, p<0.01), but all other preoperative radiographic and demographic data was similar between all groups. All groups had similar preoperative skeletal maturity scores (Sanders, Risser, and open triradiate cartilage [TRC]). At two years postoperatively, the CT group had a larger lumbar Cobb (18.5°) vs. AB (14.7°), p=0.05.

Reoperation rates were significantly higher in the C group undergoing bilateral VBT (CB) compared to AB (31% vs. 14%, p=0.05), primarily for overcorrection. Patients with preoperative open TRC vs. closed TRC had significantly increased revision rates for all groups: AB: 27%: CT: 52%; CS: 40%; CB: 86%; p<0.001.

The majority of revisions were for overcorrection, and six patients (AB: n=3; CT: n=3) required a fusion. Coronal thoracic Cobb>35° was present in 20% of AB vs. 17% of CT patients (p=0.3) and coronal lumbar Cobb>35° was present in 4% of AB vs. 6% of CT patients (p=0.3) at last visit.


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