Minimum 5-year follow-up of anterior column structural allografts in the thoracic and lumbar spine

Study Design. An analysis of consecutive adult patients treated surgically with anterior column structural allografts for sagittal plane abnormalities . Objectives. To evaluate the effectiveness of anterior structural allografts in maintaining long-term sagittal plane correction when combined with post erior spinal fusion and posterior segmental spinal instrumentation and to a ssess anterior allograft incorporation into adjacent vertebral bodies a min imum of 5 years after implantation. Summary of Background Data. There is no study in the literature in which in corporation and remodeling of anterior column structural allografts with mi nimum 5-year follow-up are assessed. Do they collapse or resorb or sustain stress fractures between a 2-year and 5-year follow-up? Methods. Twenty-three consecutive adult patients (mean age, 45 years; range , 25-63 years) had a combination of anterior structural fresh-frozen allogr aft plus posterior autogenous grafting and posterior segmental spinal instr umentation performed from June 1988 through August 1992. All patients had s agittal plane abnormalities, and all surgeries were performed by the same s urgeon, Twenty of the 23 patients returned for follow-up examinations for a t least 5 years (average, 7 +/- 3 years; range, 5 +/- 4-10 +/- 3 years). Di agnoses included kyphoscoliosis (n = 8), spondylolisthesis (n = 3), degener ative disc disease (n = 3), and acute or chronic fracture (n = 6). The allo grafts spanned only disc spaces in 16 patients, and vertebral bodies and di sc spaces in 4 patients. Forty disc spaces and four vertebral bodies were g rafted, and 67 structural allografts were placed. Upright radiographs were analyzed before surgery, immediately after surgery, and at final follow-up examination to assess the degree of anterior allograft incorporation and ma intenance of sagittal correction. A strict 4-point grading system was used. Two independent observers, not involved with surgical procedures, analyzed the radiographic results. Results. Of the 67 structural allografts, 66 (98.5%) showed incorporation. Both observers concluded that none of the 67 structural allografts showed e vidence of collapse. In all grafted levels and in any patient, there was no difference in sagittal plane measurements obtained immediately after surge ry and those obtained at follow-up examinations 2 years and 5 or more years after surgery. Conclusions. Anterior fresh-frozen structural allo graft works effectively in the long term to maintain correction of sagittal plane abnormalities if combined with posterior fusion and instrumentation. A minimum of 5 years af ter surgery, there is a high rate of structural allograft incorporation int o the adjacent vertebral bodies.