Repair of lumbar spondylolysis with a hook-screw.

A hook-screw has been devised to link the vertebral arch and superior articular process across the defect of a spondylolysis. This method of direct repair overcomes the difficulty of fixation in dysplasia of the arch and avoids crossing the defect with a screw. Compression and a bone graft are applied to the defect to obtain union. This procedure has been used in 33 patients followed for an average period of 3.5 years, and has given satisfactory relief of back pain in 79% and radiographic fusion in 73%, with better results in patients under 20 years of age. Associated degeneration and instability of the disc spaces should be assessed before operation by magnetic resonance imaging so that a standard intervertebral fusion can be used if indicated rather than this direct approach to the lysis. The technical problems encountered and the recent addition of a compression spring to the hook-screw are described.