LUMBAR INTERVERTEBRAL DISC TRANSFER - A CANINE STUDY

Study Design. Degenerative lumbar disc disease has been implicated as a cause of low back pain. Current treatment options for low back pain involve nonphysiologic fusion of the involved segments and have variab le success rates. This is an experimental study of lumbar intervertebr al disc transplantation using a canine surgical model. Objectives. Thi s study evaluated the feasibility of lumbar disc transplantation and i ts effects on disc metabolism and morphology. Method. Eight mature mon grel dogs underwent disc transfer surgeries, in which the L2-L3 and L4 -L5 intervertebral discs, with a small segment of adjacent superior an d inferior vertebral body, were removed and transposed. The transplant ed discs were stabilized by plates or by a flexible cable wire constru ct using Songer cables (DANEK, Inc., Memphis, TN). Unrestricted activi ty was allowed postoperatively. At 4 months, the spines were harvested , and the transplanted discs were evaluated biochemically and histolog ically. Intervening nontransplanted discs served as viable controls an d thrice-frozen discs served as nonviable controls. Cell viability was assessed by measuring proteoglycan synthesis and DNA content. Results . Proteoglycan synthesis (S-35 uptake normalized to DNA content) was m aintained in transplanted anulus fibrosus tissue, but was decreased in nucleus pulposus samples (P < 0.05). DNA content was not altered sign ificantly in the transplanted discs. Histologic analysis of the transp lanted discs showed revascularization and remodeling of the bone adjac ent to the disc and preservation of the lamellar architecture of the a nulus fibrosus. The transplanted nucleus pulposus samples had chondroc yte-like cells present, but the staining characteristics of the nucleu s material was variable. The contour of the transplanted disc endplate s was irregular in all specimens. Conclusions. The structure and funct ion of autograft intervertebral discs were maintained after disc trans fer surgery; the transplant discs, however, were not completely normal in either their morphology or their metabolic functioning.