What does inability to walk on heels indicate in a patient with lumbar radiculopathy?

Inability to Walk on Heels in Lumbar Radiculopathy

Inability to walk on heels in a patient with lumbar radiculopathy indicates L4 or L5 nerve root involvement, most commonly L5 radiculopathy. This finding represents weakness in the tibialis anterior and other ankle dorsiflexor muscles, which are primarily innervated by the L4 and L5 nerve roots.

Clinical Significance of Heel Walking Impairment

• Heel walking tests the functional integrity of the L4-L5 nerve roots by assessing ankle dorsiflexion strength, particularly of the tibialis anterior muscle 1
• This test is part of the comprehensive neurological examination for patients with suspected lumbar radiculopathy and helps localize the level of nerve root impingement 1
• When a patient cannot walk on their heels, this suggests weakness in the muscles responsible for ankle dorsiflexion, which is a key motor function of the L4 and L5 nerve roots 1

Neuroanatomical Correlation

• L4 nerve root: Primarily innervates the tibialis anterior muscle, which is essential for ankle dorsiflexion and heel walking 1
• L5 nerve root: Contributes to ankle dorsiflexion and also innervates the extensor hallucis longus and extensor digitorum longus 1
• The inability to walk on heels helps differentiate L4/L5 radiculopathy from S1 radiculopathy (where toe walking would be affected instead) 1, 2

Diagnostic Context

• This clinical finding should be interpreted alongside other neurological signs such as sensory changes, reflex abnormalities, and other motor deficits 1, 2
• Sensory deficits in the L5 distribution (lateral leg and dorsum of foot) often accompany motor weakness in L5 radiculopathy 1, 2
• For L4 radiculopathy, sensory deficits typically affect the medial leg and ankle region 1
• The patellar reflex may be diminished in L4 radiculopathy, while reflexes are typically preserved in isolated L5 radiculopathy 1, 2

Clinical Evaluation Algorithm

1. Assess heel walking ability: Patient stands and attempts to walk on heels with toes raised 1
2. Grade muscle strength of ankle dorsiflexion on a 0-5 scale 2
3. Test related muscle groups:
   • Extensor hallucis longus (L5) - great toe extension 1
   • Extensor digitorum longus (L5) - toe extension 1
   • Tibialis anterior (L4/L5) - ankle dorsiflexion and inversion 1
4. Assess corresponding sensory distributions and reflexes 1, 2
5. Correlate with imaging findings (MRI preferred) if surgery or intervention is being considered 1

Diagnostic Pitfalls and Caveats

• Inability to walk on heels is not pathognomonic for radiculopathy and can occur in other conditions such as peripheral neuropathy or myopathy 2
• Clinical tests for radiculopathy, including heel walking, have relatively low individual diagnostic accuracy when used in isolation 2
• The overall clinical evaluation combining multiple tests has better diagnostic accuracy than any single test 2
• Imaging findings often do not correlate perfectly with clinical symptoms - many asymptomatic individuals have disc herniations on imaging 1
• Non-adjacent disc herniations can occasionally cause radicular symptoms at lower levels (e.g., an L2/3 disc herniation causing L5 radiculopathy) 3

Management Implications

• Identification of the specific nerve root involvement helps guide targeted treatment approaches 4
• Most cases of lumbar radiculopathy with motor weakness will improve with conservative management within 4-6 weeks 1, 4
• Persistent motor weakness, especially if progressive, may indicate the need for surgical intervention 1
• For chronic cases with persistent motor deficits, a more comprehensive rehabilitation approach may be needed 4