The leakage pathway and effect of needle gauge on degree of disc injury post anular puncture: a comparative study using aged human and adolescent porcine discs.

STUDY DESIGN An in vitro biomechanical study using aged human and adolescent porcine discs. OBJECTIVES To find the leakage pathway and effect of needle gauge on the degree of disc injury post anular puncture. SUMMARY OF BACKGROUND DATA Spinal needles are widely used for minimal invasive disc surgeries and disc degeneration/regeneration research. Applications of anular puncture require different diameters of spinal needles. However, the effect of needle diameters on the disc injury has not been systematically studied yet. METHODS Four groups of experiments were conducted: 1) porcine thoracic disc, 2) human thoracic disc, 3) porcine thoracic disc with 200 N external loading, and 4) porcine lumbar discs. The disc was punctured consecutively with needles from smaller diameter to larger diameter. After each anular puncture, the quantitative discomanometry technique was conducted to quantify the disc rupture pressure and volume. The association between needle gauge and rupture pressure and volume was analyzed. RESULTS The degree of disc injury increased with the diameter of needle. For an aged human thoracic disc, the anulus fibrosus cannot hold pressure more than 2 MPa after a 21-gauge-needle-anular-puncture. The leakage pathway of injected saline was through the anular fissure but was through the endplate when the disc was next to an osteoporotic vertebrae. The pressure holding power of porcine disc is stronger than of human disc. The rupture pressure of porcine lumbar disc is higher than of porcine thoracic disc. The axial compressive external loading increased the disc rupture pressure. The rupture volumes were not affected by the dimension of injury fissure. The rupture volume was at level of 0.3 mL without external loading and at 0.2 mL with external loading. CONCLUSION A spinal needle of < or = 22 gauge and injection volume of < or = 0.2 mL are recommended to prevent postsurgery leakage.