Anular incision technique on the strength and multidirectional flexibility of the healing intervertebral disc

Abstract

Study Design. This study used a sheep model to biomechanically analyze the healing strength of the anulus flbrosus after two types of anular incisions. Objective. This study evaluated whether the type of anular Incision made at the time or Itimbar discectomy plays a role in the subsequent healing strength of the anulus and the biomechanical flexibility of the corresponding motion segment. Methods. Two types of anulBr incision, a full thickness removal of s box or window of anulus and a full thickness straight transverse sift through the anulus, were made in the intarvartebral discs of 18 adult sheep. After healing times of 2, 4, and 6 weeks, the intervertebral discs were tested versus control levels for strength of anular healing and biomechawcal flexibility of the corresponding motion segment. Results. The box incised discs showed a significantly greater loss in strength during the early healing phase (2 to 4 weeks) and e longer response before recovering anuler strength when compared with the- slit- Inelsed discs. The type Df incision also affected the multidirectional flexibility of the motion segments in a diffarantiated manner. Larger amounts of motion were seen with the box Incision when compared with the slit incision at all time periods and in ell pure moments. Conclusion. Tha technique of anular incision plays a definite roEe in the liming and strength of subsequent anular healing. The box incision through the anulus led to significantly weaker healing than did the slit incision in the early healing phase (2 -4 weeks). Also, larger amounts of motion ware soon in the vertebral motion segments of those discs undergoing box Incision when compared with slit or control levels. © 1994, J.B. Lippincott Company.