Comparison of Great Toe Extension, Ankle Dorsiflexion, and Eversion Strength in Individuals With and Without L4–5, L5–S1 Disc Herniation

Ankle eversion strength Dorsiflexion strength Great toe extension strength Intervertebral disc height Lumbar disc herniationBackground: Lumbar disc herniation (LDH) can cause distal lower-extremity weakness through nerve root compression.Specifically, compression of the L5 nerve root may cause weakness in great toe extension (GTE), ankle dorsiflexion (DF), and eversion (EV).Although magnetic resonance imaging (MRI)-derived disc height reflects structural degeneration, few studies have quantitatively examined the association between disc height and L5-innervated muscle strength in individuals with LDH.Objects: This study compared GTE, DF, and EV strength between individuals with LDH and healthy controls and examined the association between MRI-derived disc height and muscle strength within the LDH group.Methods: Thirty participants were divided into two groups: individuals with LDH (n = 15) and healthy controls (n = 15).GTE, DF, and EV strengths were measured using a digital dynamometer.In the LDH group, lumbar MRI was analyzed to measure anterior, middle, and posterior disc heights at both L4-5 and L5-S1.Results: GTE, DF, and EV strength were significantly lower in individuals with LDH than in healthy controls (all p < 0.001).After adjustment for visual analogue scale, the betweengroup differences in normalized GTE, DF, and EV strength remained significant.Within the LDH group, posterior disc height at L4-5 was positively correlated with GTE and DF strength, while posterior disc height at L5-S1 was positively correlated with EV strength (r = 0.532, 0.613, and 0.631, respectively; p < 0.001, respectively).Conclusion: Individuals with LDH showed significantly lower GTE, DF, and EV strength than healthy controls.Within the LDH group, posterior disc height was positively correlated with GTE and DF strength at L4-5 and with EV strength at L5-S1.