STUDY DESIGN: The somatosensory afferent units in the sacroiliac joint of an animal model were investigated using an electrophysiologic technique. OBJECTIVES: To identify the mechanosensitive receptive fields in the sacroiliac joint, and to determine their distribution and characteristics. SUMMARY OF BACKGROUND DATA: The sacroiliac joint is considered to be a source of lower back pain. Although there have been clinical studies on the diagnosis of sacroiliac joint pain, no satisfactory diagnostic method other than joint blocks has been reported. It still is not clear whether the sacroiliac joints actually transmit pain to the central nervous system. The sensory innervation of the sacroiliac joint has not been fully characterized neurophysiologically. METHODS: Experiments were performed on 10 adult cats weighing 2.6 to 4 kg. The animals were anesthetized with intravenous sodium pentobarbital. An L4-L7 laminectomy was performed. The L4-L6 dorsal roots were cut at their proximal ends, split, and draped over a bipolar recording electrode. Glass probes were used to search the sacroiliac joint and adjacent tissues for mechanosensitive units. When units were identified, they were stimulated electrically to obtain conduction velocities and by Semmes-Weinstein monofilaments to determine mechanical thresholds. RESULTS: In the sacroiliac joint and adjacent muscles, 29 discrete mechanosensitive units were identified. Of these 29 units, 26 were found in the posterior sacroiliac ligament and the remaining 3 in the adjacent muscles. Also, 16 units (55%) were identified in the proximal third of the sacroiliac joint. Conduction velocities of the units ranged from 3.1 to 22 m/second (average, 9.2 m/second), and 26 units were group III. Mechanical thresholds of the units ranged from 4.6 to 164.3 g (average, 69.7 g). Whereas 28 units (96.6%) had thresholds higher than 7 g, one unit (3.4%) had a threshold lower than 7 g. CONCLUSIONS: Group III units with mechanical thresholds higher than 7 g may serve as nociceptors, and units with thresholds of lower than 7 g may serve as proprioceptors. The current study showed that most of the units in the sacroiliac joint were high-threshold group III units that perhaps had a nociceptive function. This result suggests that the sacroiliac joint may be a source of lower back pain in humans. This study also showed that the sacroiliac joint has little proprioceptive function.
STUDY DESIGN: The somatosensory afferent units in the sacroiliac joint of an animal model were investigated using an electrophysiologic technique. OBJECTIVES: To identify the mechanosensitive receptive fields in the sacroiliac joint, and to determine their distribution and characteristics. SUMMARY OF BACKGROUND DATA: The sacroiliac joint is considered to be a source of lower back pain. Although there have been clinical studies on the diagnosis of sacroiliac joint pain, no satisfactory diagnostic method other than joint blocks has been reported. It still is not clear whether the sacroiliac joints actually transmit pain to the central nervous system. The sensory innervation of the sacroiliac joint has not been fully characterized neurophysiologically. METHODS: Experiments were performed on 10 adult cats weighing 2.6 to 4 kg. The animals were anesthetized with intravenous sodium pentobarbital. An L4-L7 laminectomy was performed. The L4-L6 dorsal roots were cut at their proximal ends, split, and draped over a bipolar recording electrode. Glass probes were used to search the sacroiliac joint and adjacent tissues for mechanosensitive units. When units were identified, they were stimulated electrically to obtain conduction velocities and by Semmes-Weinstein monofilaments to determine mechanical thresholds. RESULTS: In the sacroiliac joint and adjacent muscles, 29 discrete mechanosensitive units were identified. Of these 29 units, 26 were found in the posterior sacroiliac ligament and the remaining 3 in the adjacent muscles. Also, 16 units (55%) were identified in the proximal third of the sacroiliac joint. Conduction velocities of the units ranged from 3.1 to 22 m/second (average, 9.2 m/second), and 26 units were group III. Mechanical thresholds of the units ranged from 4.6 to 164.3 g (average, 69.7 g). Whereas 28 units (96.6%) had thresholds higher than 7 g, one unit (3.4%) had a threshold lower than 7 g. CONCLUSIONS: Group III units with mechanical thresholds higher than 7 g may serve as nociceptors, and units with thresholds of lower than 7 g may serve as proprioceptors. The current study showed that most of the units in the sacroiliac joint were high-threshold group III units that perhaps had a nociceptive function. This result suggests that the sacroiliac joint may be a source of lower back pain in humans. This study also showed that the sacroiliac joint has little proprioceptive function.
Authors: Christian E Althoff; Matthias Bollow; Eugen Feist; Stephan R Marticorena-Garcia; Iris Eshed; Torsten Diekhoff; Bernd Hamm; Kay Geert A Hermann Journal: Clin Rheumatol Date: 2015-04-22 Impact factor: 2.980
Authors: David W Polly; John Swofford; Peter G Whang; Clay J Frank; John A Glaser; Robert P Limoni; Daniel J Cher; Kathryn D Wine; Jonathan N Sembrano Journal: Int J Spine Surg Date: 2016-08-23