Effects of hypertonia on contracture development in rat spinal cord injury.

Abstract

STUDY DESIGN:

Experimental animal study.

OBJECTIVES:

Spastic hypertonia is originally believed to cause contractures from clinical observations. Botulinum toxin is effective for the treatment of spasticity and is widely used in patients who have joints with contractures. Using an established rat model with knee contractures after spinal cord injuries, we aimed to verify whether hypertonia contributes to contracture development, and the botulinum toxin improves structural changes in muscles and joint components responsible for contractures.

SETTING:

University laboratory in Japan.

METHODS:

To evaluate the effect of hypertonia on contracture development, the rats received botulinum toxin injections after spinal cord injuries. Knee extension motion was measured with a goniometer applying a standardized torque under anesthesia, and the contribution by muscle or non-muscle structures to contractures were calculated by measuring joint motion before and after the myotomies. We quantitatively measured the muscle atrophy, muscle fibrosis, and synovial intima length.

RESULTS:

Botulinum toxin injections significantly improved contractures, whereas did not completely prevent contracture development. Botulinum toxin was effective in improving the muscular factor, but little difference in the articular factor. Spinal cord injuries induced muscle atrophy, and botulinum toxin significantly accelerated muscle atrophy and fibrosis. The synovial intima length decreased significantly after spinal cord injuries, and botulinum toxin did not improve this shortening.

CONCLUSIONS:

This animal study provides new evidence that hypertonia is not the sole cause rather is the partial contributor of contractures after spinal cord injuries. Furthermore, botulinum toxin has adverse effects in the muscle.

• Authors: Hideki Moriyama, Junya Ozawa, Takumi Yakuwa, Shota Inoue, Taisei Wakigawa, Nobuhiro Kito, Yoshitada Sakai, Toshihiro Akisue
• Journal: Spinal cord (Spinal Cord) Vol. 57 Issue 10 Pg. 850-857 (Oct 2019) ISSN: 1476-5624 [Electronic] England
• PMID: 31201373 (Publication Type: Journal Article)

Chemical References

• Neuromuscular Agents
• Botulinum Toxins, Type A

Topics

• Animals
• Botulinum Toxins, Type A (pharmacology)
• Contracture (etiology)
• Male
• Muscle Hypertonia (etiology)
• Neuromuscular Agents (pharmacology)
• Range of Motion, Articular (drug effects)
• Rats
• Rats, Wistar
• Spinal Cord Injuries (complications)