Implant design may influence delayed heterotopic ossification after total disk arthroplasty in lumbar spine.

BACKGROUND: As total disk arthroplasty (TDA) gains increasing acceptance as an alternative to fusion for degenerative disk disease of the lumbar spine, new complications are encountered by the physicians during and after the procedure. We hereby report a complication after TDA in the lumbar spine that is in variance from previously proposed theories and suggests the possibility of implant design as one of the etiologic factors. The purpose of the present submission is to report a case of delayed heterotopic ossification (HO) after TDA that suggests that the keel-based design of the implant might have contributed to the etiology.

CASE DESCRIPTION: The patient underwent TDA for L3-4 degenerative disk disease and had fusion surgery for L5-S1 disease about 6 months later. During follow-up, development of significant HO was noticed at the L3 and L4 level. Radiologic studies revealed the origin of HO to be the keel cut made in the body of L3 to accommodate the keel-based artificial disk.

CONCLUSION: The exact etiology of HO after TDA is not clear. The presented anecdote points toward vertebral body trauma due to the design of the implant as a possible factor that needs to be studied more elaborately.