Can autologous bone culture predict spinal fusion capacity?

The capacity of the individual patient to initiate osteoblast proliferation as a predictor for successful lumbar spinal fusion has not yet been report ed. The objectives of this study were, first, to analyze the relationship b etween in vitro osteoblast proliferation and clinical bony fusion in the in dividual patient in order to predict the fusion outcome and, second, to mea sure the effect of preoperative tobacco smoking on osteoblast proliferation . Sixty-one patients (mean age 46 years) underwent posterolateral lumbar fu sion in the period 1994-1995. Thirty-eight patients received CD pedicle scr ew implants and 23 received posterolateral fusions alone. During surgery, a utogenous iliac bone was harvested and 1 g of trabecular bone without blood or bone marrow was then isolated for cell culturing. The cultures were cla ssified as excellent (confluence within 4 weeks), good (confluence between 4 and 6 weeks) and poor (no or poor growth). Spine fusion was evaluated by two independent observers from plain anterior-posterior, lateral, and flexi on/extension radiographs taken I year postoperatively, and the functional o utcome was measured by the Dallas Pain Questionnaire (DPQ). Twenty-three pa tients had excellent, 19 good, and 1' poor in vitro osteoblast proliferatio n. Bony fusion was obtained in 77% of patients: 83% in the CD instrumentati on group and 70% in the non-instrumentation group (NS). There was no signif icant correlation between osteoblast proliferation and spinal fusion or fun ctional outcomes when analyzing the CD instrumentation and non-instrumentat ion groups together or separately. Elderly patients had a significantly poo rer osteoblast proliferation than younger patients (P < 0.008). Preoperativ e tobacco consumption had no discernible effect on osteoblast proliferation , and no correlation between smoking and fusion was found. Further refineme nt of autologous osteoblast culturing may provide a biological tool for sel ection of patients who require biological enhancement of their bone fusion capacity. The poorer osteoblast proliferation related to advanced age suppo rts the important negative biological influence of age on bony fusion. Howe ver, with more sensitive testing and better discrimination, other results a re possible - or can in any event not be excluded.