# Importance of modifiable non-radiographic functional parameters for adult spinal deformity

## TL;DR

This study identifies non-radiographic physical parameters that correlate with the severity of adult spinal deformity and introduces a benchmark for treatment goals.

## Contribution

The study introduces the ASD-MJ index as a benchmark for modifiable clinical goals in treating adult spinal deformity.

## Key findings

- Subjects meeting the ASD-MJ goals showed significantly better radiographic and clinical outcomes.
- Key parameters like trunk muscle strength and knee extension were significantly different between robust and clinical ASD groups.
- The ASD-MJ index provides a measurable target for conservative and physical therapies in ASD patients.

## Abstract

We clarified non-radiographic physical parameters associated with the severity of adult spinal deformity (ASD) using community-dwelling adult volunteers. They were subjected to upright entire spine radiographs for standard radiographic parameters and the number of sagittal modifiers of SRS-Schwab ASD classification (Schwab-SM). Clinical evaluations included isometric muscle strength of trunk extensor (TEX), trunk flexor (TFL), quadriceps femoris (QF), gluteus maximus, and iliopsoas; range of motion (ROM) of hip, knee, ankle, and active back extension (BET); SF36 physical component score (PCS), VAS for back and knee pain, and the degree of ambulatory kyphosis (dTIA). Each muscle strength was calibrated by body weight (BW) and expressed as BW ratio. According to our previous study, dTIA ≥ 7.6° was defined as pathological and dTIA ≤ 3.5° as normal. A final total of 409 female volunteers were included, and their demographics were; age 67.0 ± 5.5 years, Schwab-SM 2.1 ± 1.8, TEX 0.90 ± 0.33BW, TFL 0.48 ± 0.15BW, QF 0.45 ± 0.19BW, PCS 33.5 ± 6.5. Subjects were classified as clinical ASD group (cASD, n = 10) with PCS ≤ 27(mean-1SD) and pathological dTIA, robust group (n = 19) with PCS ≥ 40 (mean + 1SD) and normal dTIA, and the rest (non-cASD, n = 338). Statistical analyses showed significant differences in TEX, TFL, QF, knee extension (KEX), and BET between robust and cASD, and the mean values of robust group (TEX ≥ 1.1BW, TFL ≥ 0.5BW, QF ≥ 0.5BW, KEX ≥ 0° and BET ≥ 14 cm) were used as ‘ASD-MJ’ index. Subjects with fully achieving ASD-MJ goals showed significantly better radiographic and clinical outcomes than those with unmet goals. In conclusion, upon prescribing conservative or physical therapies for ASD patients, modifiable clinical goals should be clarified, and ASD-MJ could be a benchmark.