I congratulate the Scoli-RISK-1 Study Group for presenting their findings with regard to neurogenic complications following surgery for complex adult spinal deformity. This group was formed specifically to prospectively investigate and accurately report motor deficits following 3-column osteotomies in complex thoracolumbar deformity surgery. The inclusion criteria cover anatomic areas between the C7 and L5 levels. Thus, these osteotomies occur at the cauda equina/root or spinal cord level, where neurologic consequences and potential for recovery are notably different. These surgical procedures are demanding on the patient as well as the surgeon and surgical team. Safety is improved by using spinal monitoring, which is sensitive for spinal cord issues (motor and sensory columns) but is less reliable for nerve root injury. Minor and major complications can be expected in 3 out of 4 patients treated with posterior 3-column osteotomy1,2.
The authors elected to measure lower-extremity motor complications using a validated measurement tool employed primarily for spinal cord injury from trauma—i.e., the American Spinal Injury Association (ASIA) lower extremity motor score (LEMS). The LEMS component measures motor function in the lower-extremity myotomes of L2-S1, applying the well-known muscle-strength grading of 0 to 53. The sensory component of the ASIA grading system was not reported in this study. As quantifiable data, the LEMS score has utility, but the exact nature of the deficit is not always clear. For example, an LEMS score of 45, which represents a 5-point decline compared with normal, would be assigned to a complete unilateral foot drop (L5). From the study’s data, it is not possible to say whether a 1 to 5, 6 to 10, or >10-point decline is due to a deficit of the root alone, the spinal cord and root, or the spinal cord alone. Notwithstanding that, a larger decline of >10 points is likely to indicate a spinal cord complication.
The rate of decline in motor function immediately following surgery was 23% in this study. This is about 2 to 2.5 times higher than what was found in retrospective series4,5. This difference is due to this study’s design, the ASIA LEMS grading, and the prospective inclusion of cases from several international spine surgeons and centers. The 23% rate means that 1 of 5 patients who have a posterior 3-column osteotomy between C7 and L5 can expect to have a postoperative motor deficit, and about half of these deficits will persist for 2 years. As stated by the authors, this information is of value for perioperative counseling but whether to undergo an operation with this degree of risk is a weighty decision for older adults (median age in this study, 60 years; maximum, 80 years). It is imperative for the surgeon to have a frank discussion and describe the potential complications to the patient. It should be noted that the rates of neurologic deficits in this cohort were presented by authors who are expert surgeons and who perform this procedure commonly. The implication is that a spine surgeon performing the occasional 3-column osteotomy may have an even higher motor deficit rate.
Despite the higher rate of motor deficits, about half improved over 2 years with function returning to baseline or normal. At 2-year follow-up, the residual motor deficits had an occurrence rate of 10.0% compared with preoperative values. This 10.0% rate of neurologic complications is similar to the 2-year rates reported in several retrospective studies4,5. This recovery is somewhat surprising given that 61% of the procedures were revisions that included osteotomy for adult spinal deformity. Such a recovery course suggests that the neurologic deficits were partial motor root lesions or partial cord syndromes. Of 4 cases with a ≥10-point drop in the LEMS, 2 improved to baseline and 1 was lost to follow-up. In the remaining case, the LEMS score only partially improved to 40 points. In all cases with abnormal neurologic follow-up data, recovery tends to plateau at about 6 months.
Despite the prospective study design, 62 (23%) of 271 data points were missing at 2 years, and there were other omissions at 6 weeks and 6 months. Despite multiple ASIA LEMS certified examiners, interobserver error rates were not stated. The mean LEMS for the group with preoperative neurologic abnormalities changed from 43.79 preoperatively to 46.12 at 2 years, and the mean score for the preoperative normal group changed from 50.00 to 49.66. One would expect some error in rating between examiners. With such small changes, the potential for interobserver bias could significantly affect these results.
I look forward to future analyses.
1. Smith JS, Shaffrey CI, Klineberg E, Lafage V, Schwab F, Lafage R, Kim HJ, Hostin R, Mundis GM Jr, Gupta M, Liabaud B, Scheer JK, Diebo BG, Protopsaltis TS, Kelly MP, Deviren V, Hart R, Burton D, Bess S, Ames CP; on behalf of the International Spine Study Group. Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up. J Neurosurg Spine. 2017 Oct;27(4):444-57. Epub 2017 Feb 17.
2. Pellisé F, Vila-Casademunt A, Núñez-Pereira S, Domingo-Sàbat M, Bagó J, Vidal X, Alanay A, Acaroglu E, Kleinstück F, Obeid I, Pérez-Grueso FJS, Lafage V, Bess S, Ames C, Mannion AF; European Spine Study Group. The Adult Deformity Surgery Complexity Index (ADSCI): a valid tool to quantify the complexity of posterior adult spinal deformity surgery and predict postoperative complications. Spine J. 2017 Jul 4:S1529–9430(17)30316-9. Epub 2017 Jul 4.
3. Kirshblum SC, Burns SP, Biering-Sorensen F, Donovan W, Graves DE, Jha A, Johansen M, Jones L, Krassioukov A, Mulcahey MJ, Schmidt-Read M, Waring W. International standards for neurological classification of spinal cord injury (revised 2011). J Spinal Cord Med. 2011 Nov;34(6):535-46. Epub 2012 Feb 15.
4. Boachie-Adjei O, Ferguson JA, Pigeon RG, Peskin MR. Transpedicular lumbar wedge resection osteotomy for fixed sagittal imbalance: surgical technique and early results. Spine (Phila Pa 1976). 2006 Feb 15;31(4):485-92. Epub 2006 Feb 17.
5. Buchowski JM, Bridwell KH, Lenke LG, Kuhns CA, Lehman RA Jr, Kim YJ, Stewart D, Baldus C. Neurologic complications of lumbar pedicle subtraction osteotomy: a 10-year assessment. Spine (Phila Pa 1976). 2007 Sep 15;32(20):2245-52. Epub 2007 Sep 18.