Adult spinal deformity

● adult spinal deformity (ASD) encompasses scoliosis and sagittal imbalance

sagittal balance correlates with quality of life measures

● basic spine measurements needed: LL, PI, PT, ± SVA

● major alignment objectives (most valid for age 50–60 years): LL = PI ± 9°, PT < 20°, SVA < 5 cm

Adult spinal deformity or adult degenerative scoliosis, is a broad term that refers to a wide spectrum of structural abnormalities of a mature spine.

The term “adult degenerative scoliosis” (ADS) (as distinguished from Juvenile idiopathic scoliosis (IJS)) is often used interchangeably with ASD.

Definition of adult degenerative scoliosis:

Adult degenerative scoliosis is a spinal deformity with Cobb angle > 10 º 1) in a skeletally mature individual 2). in a skeletally mature individual. ADS may be the result of childhood idiopathic scoliosis persisting into adulthood, or maybe de novo.

This condition also goes by the name, “de novo” scoliosis. As the name implies, this variety begins in the adult patient due to degeneration of the discs, arthritis of the adjacent facet joints and collapse and wedging of the disc spaces.

It encompasses abnormality in the coronal plane (scoliosis) and sagittal imbalance.

see Adult spinal deformity epidemiology.

A survey of neurosurgeon AANS membership assessed the deformity knowledge base and impact of current training, education, and practice experience to identify opportunities for improved education. Eleven questions developed and agreed upon by experienced spinal deformity surgeons tested ASD knowledge and were subgrouped into 5 categories:

1) radiology/spino-pelvic alignment

2) health-related quality of life

3) surgical indications

4) operative technique

5) clinical evaluation.

Chi-square analysis was used to compare differences based on participant demographic characteristics (years of practice, spinal surgery fellowship training, percentage of practice comprising spinal surgery).

Responses were received from 1456 neurosurgeons. Of these respondents, 57% had practiced less than 10 years, 20% had completed a spine fellowship, and 32% devoted more than 75% of their practice to spine. The overall correct answer percentage was 42%. Radiology/spinal pelvic alignment questions had the lowest percentage of correct answers (38%), while clinical evaluation and surgical indications questions had the highest percentage (44%). More than 10 years in practice, completion of a spine fellowship, and more than 75% spine practice were associated with greater overall percentage correct (p < 0.001). More than 10 years in practice was significantly associated with increased percentage of correct answers in 4 of 5 categories. Spine fellowship and more than 75% spine practice were significantly associated with increased percentage correct in all categories. Interestingly, the highest error was seen in risk for postoperative coronal imbalance, with a very low rate of correct responses (15%) and not significantly improved with fellowship (18%, p = 0.08).

The results of this survey suggest that ASD knowledge could be improved in neurosurgery. Knowledge may be augmented with neurosurgical experience, spinal surgery fellowships, and spinal specialization.

Neurosurgical education should particularly focus on radiology/spinal pelvic alignment, especially pelvic obliquity and coronal imbalance and operative techniques for ASD 3).

In 1994 Dubousset 4) described the concept of “cone of economy” which is a range of spinal alignment in which a minimum of muscle activity is required to maintain balance. Quantification of severity of spinal deformity and classification helps guide appropriate treatment paradigms.

A literature analysis highlighted several classification schemes developed for degenerative scoliosis patients: the Simmons classification system, the Aebi system, the Faldini working classification system, the Schwab system, and the Scoliosis Research Society system 5).

see Adult spinal deformity etiology.

ADS tends to progress at an average rate of 3° per year (range: 1–6°). Factors associated with higher rates of progression: Cobb angle > 30°, apical rotation > Grade II (on the Nash-Moe system, which is falling into disuse), lateral listhesis > 6 mm, and an intercrest line through L5. Factors not correlated with rate of progression: age and gender. Controversial associations: osteopenia.

High-Frequency Spinal Cord Stimulation for the Treatment of Primarily Axial Back Pain due to Degenerative Scoliosis with Spinopelvic Imbalance 6).

Cobb JR. Outline for the study of scoliosis. American Academy of Orthopaedic Surgeons Instr Course Lect. 1948;5:261–275
Silva FE, Lenke LG. Adult degenerative scoliosis: evaluation and management. Neurosurg Focus. 2010 Mar;28(3):E1. doi: 10.3171/2010.1.FOCUS09271. PubMed PMID: 20192655.
Clark AJ, Garcia RM, Keefe MK, Koski TR, Rosner MK, Smith JS, Cheng JS, Shaffrey CI, McCormick PC, Ames CP; , and the International Spine Study Group. Results of the AANS membership survey of adult spinal deformity knowledge: impact of training, practice experience, and assessment of potential areas for improved education. J Neurosurg Spine. 2014 Jul 18:1-8. [Epub ahead of print] PubMed PMID: 25036219.
Dubousset J, Weinstein SL. Three-dimensional anal- ysis of the scoliotic deformity. In: The pediatric spine: Principles and practice. New York, NY: Raven Press; 1994:479–496
Faldini C, Di Martino A, De Fine M, Miscione MT, Calamelli C, Mazzotti A, Perna F. Current classification systems for adult degenerative scoliosis. Musculoskelet Surg. 2013 Apr;97(1):1-8. doi: 10.1007/s12306-013-0245-4. Epub 2013 Apr 4. Review. PubMed PMID: 23553440.
Tate Q, House LM, McCormick ZL, Mahan MA. High-Frequency Spinal Cord Stimulation for the Treatment of Primarily Axial Back Pain due to Degenerative Scoliosis with Spinopelvic Imbalance: Case Report. Pain Med. 2019 Mar 11. pii: pnz043. doi: 10.1093/pm/pnz043. [Epub ahead of print] PubMed PMID: 30856267.
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