Posterior transpediculate Zielke instrumentation in spondylolisthesis.

Between July 1987 and June 1989, 82 patients with spondylolisthesis (degenerative in 49, isthmic in 33) underwent Zielke posterior transpediculate instrumentation. One-level fusion was performed in 42 patients, two-level fusion in 32 patients, and three-level fusion in 8 patients. A supplemental allograft using frozen femoral heads was implanted in seven of the patients who underwent three-level fusion. The follow-up period ranged from 1.3 to 3 years (average, 1.7 years). Overall, 90.2% of the patients achieved solid fusion, and 85.4% had a good to excellent clinical result. Complications included nerve injury (one patient), rod breakage (four patients), nut loosening (11 patients), screw loosening (two patients), and screw breakage (three patients). The high incidence of instrumentation-related complications indicated that this technique must be further modified and refined.