Limitations and Ceiling Effects of Circumferential Minimally Invasive Surgical (cMIS) Techniques for the Treatment of Adult Scoliosis - Analysis of a 6-Year Experience

Presented at SMISS Annual Forum 2013
By Neel Anand MD
With Eli Baron MD, Babak Khandehroo MD, Sheila Kahwaty PA-C,

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

Introduction: Minimally invasive approaches to the surgical correction of Adult scoliosis have been gaining popularity over the last several years. cMIS techniques have previously been shown to achieve comparable deformity correction in both sagittal and coronal plane. However, the capability of these techniques and their limitations and the potential for ceiling effects have been a big concern for surgeons in preoperative planning of these new techniques.

Methods: 125 patients with adult scoliosis (Cobb angle>15 degrees) undergoing MIS instrumentation and fusion of 3 and more levels were studied retrospectively. An additional inclusion criterion that was the ability to measure Sagittal vertical alignment (SVA), Pelvic Incidence (PI) and Lumbar Lordosis (LL) on each X-ray (pre-op and the last available follow-up visits) included 80 patients for this study. Deformities included Degenerative Scoliosis (43), Idiopathic Scoliosis (32) and Iatrogenic Scoliosis (5). All underwent all or a combination of 3 MIS techniques: Percutaneous Pedicle screw Instrumentation (79), DLIF(65) and AxiaLIF(29). None of our patients underwent any kind of osteotomy or facet resection. Coronal Cobb Angle, SVA, PI and LL of the spine were evaluated on full-spine AP and lateral X-ray in a standardized upright position preoperatively and postoperatively. All measurements were performed with use of a software program.

Results: Mean age was 62.8 years (21-85).  An average of 6.8 levels (3-16) were fused with mean follow-up of 30 months (3-76). Comparing preoperative and postoperative spinopelvic parameters revealed: The mean pre-op COBB angle was corrected 61% (p< 0.01): from 34.7 degrees (15-73.5) to 13.4 degrees (0-31.3) at the last follow-up. A ceiling effect of 42 degrees for Cobb angle correction was noted. There was a linear relation between pre-op and post-op sagittal alignment with a limitation of 110mm to correct the pre-op SVA to the normal range (0 +/- 50) after surgery. In all patients the mean pre-op SVA significantly decreased from 60mm (11.5-151mm) to 27.4mm (0-84mm) postoperatively (p< 0.01). The mean pre-op PI-LL mismatch was significantly corrected from 13.8 degrees to 9.5 degrees after surgery (p< 0.01). A ceiling effect of 25.2 degrees for PI-LL mismatch correction was noted.

Conclusion: Our data indicate that cMIS techniques for scoliosis correction have some limitations and ceiling effects. Surgeons should consider these limitations for preoperative planning and deliberation of additional techniques as needed to achieve ideal correction in selected patients.