Solid fusion after lumbosacral arthroplasty.

A 55-year-old female was diagnosed with L5-S1 degenerative disc disease (DDD). Initial scores by the visual analogue scale (VAS) were 5 (back) and 9 (leg) and the Oswestry disability index (ODI) was 32. Arthroplasty was performed. Clinical and radiographic monitoring took place thereafter at one month, three months, six months and annually. At one month, VAS scores were 2 (back) and 3 (leg), ODI was 12 and ROM was 2.1° by radiographs. At two years, VAS scores were 1 (back) and 2 (leg), ODI was 6 and ROM was approaching 0. Five years after surgery, the entire operated segment (L5-S1) was solidly fused. A malpositioned disc implant may impair normal spinal movement, culminating in heterotopic ossification or complete fusion of the operated segment.