Do Hyper-Lordotic Cages Help Create and Maintain Sagittal Alignment with MIS Correction of Adult Scoliosis?

Presented at SMISS Annual Forum 2014
By Neel Anand MD
With Eli M. Baron MD, Babak Khandehroo MD, Shiela Kahwaty PA-C,

Disclosures: Neel Anand MD None Eli Baron MD , Babak Khandehroo MD None, Shiela Kahwaty PA-C None,

Introduction:
The inability to correct and maintain sagittal alignment has been a major criticism of MIS techniques in the correction of adult spinal deformity. Recently, hyperlordotic interbody cages using the minimally invasive direct lateral transpsoas approach have been used to improve sagittal balance.

Aims/Objectives:
This study was conducted to assess the efficacy of hyperlordotic cage techniques in MIS correction of adult scoliosis.

Methods:
This is a retrospective study of 44 consecutive patients (mean age: 65yrs, range 48-84) with adult scoliosis who underwent minimally invasive lateral approach using hyperlordotic (12 degree) cages as part of their MIS technique for the treatment of spinal deformity. This cohort included 17 adult idiopathic scoliosis and 27 degenerative scoliosis patients. These patients were compared to a previously published cohort of patients treated with 6 degree interbody cages. All radiographic parameters including segmental interbody angle, regional lordosis(L1-S1) and sagittal alignment were measured with use of a software program on the 36” standing radiographs obtained preoperatively and postoperatively.

Results:
Mean follow-up was 16 months(3-24). Total of 157 levels were performed between T12 and L5 with 12 degree cages used at 130 lumbar interbody levels (mainly in L2-L3, L3-L4 and L4-L5), and 6 degree cages used at 27 levels (at T12-L1 and L1-2). At L5-S1 an ALIF was done. The mean pre-op segmental lordotic angles at L2-3, L3-4, and L4-5 were: 3.2°, 3.5°, and 6.9°, respectively. The mean post-implantation segmental lordotic angles significantly increased in all levels as 12.61°, 13° and 13.8° respectively. The pre-op regional lordosis of 52.5° was maintained at 53° at the last follow-up. The mean pre-op sagittal alignment, which was 57.3mm (13-110), was improved to 28mm(0-51.1) postoperatively and maintain at 24.6mm(0-51.5) at the last follow-up. This was compared to the past published 6 degree cage cohort whose preop SVA was 60mm(11 - 151) with postop 27.4mm(0 to 84). When we compared patients with pre-op SVA of greater than 80mm a significant difference was noted. The hyperlordotic cages cohort showed an SVA improvement from 93mm to 31mm as compared to the 6 degree cage cohort who improved from 113mm to 58.3mm.

Conclusions:
Our study shows that hyper-lordotic cages significantly increase operative level segmental lordosis. This 12-degree cage effect was significant in patients with major pre-op sagittal malalignment when compared to the use of 6-degree cages. Hence judicious use of hyperlordotic cages in patients with significant sagittal imbalance may help to create normal sagittal alignment.