Thoracic zygapophyseal joint pain patterns. A study in normal volunteers

Nine asymptomatic volunteers underwent 40 provocative intra-articular injections of the thoracic zygapophyseal joints.

The purpose of the study was to isolate and stimulate the thoracic zygapophyseal joints via fluoroscopically guided intra-articular injections to determine whether they are potential pain generators.

Experimentally, the cervical and lumbar zygapophyseal joints have been shown to produce pain, and tentative referral patterns have been established. Referral patterns based on stimulation of the thoracic zygapophyseal joints have not been previously reported.

Four subjects underwent right-sided T3-T4, T5-T6, T7-T8, and T9-T10 joint injections, and four subjects underwent left-sided T4-T5, T6-T7, T8-T9, and T10-T11 joint injections. One subject underwent both the right- and left-sided joint injections. The zygapophyseal joints were injected with contrast medium only, and the quality, intensity, and distribution of evoked pain was recorded.

In this asymptomatic population, 72.5% of joints injected produced a sensation/pain that was different from the sensation of needle advancement through the soft tissues. In 27.5% of joints injected, there was no evoked pain despite adequate capsular distension. Evoked referral patterns were consistent in all subjects. Significant overlap occurred in the referral patterns, with most thoracic regions sharing 3-5 different joint referral zones.

This study provides preliminary confirmation that the thoracic zygapophyseal joints can cause both local and referred pain. A referral pain diagram has been constructed.