The difficulty in detecting bone growth after spine fusion is a known challenge. While newer imaging modalities such as thin-slice CT scans have added to the surgeon’s toolset, it adds significant cost and radiation exposure to patients who have continuing pain after their initial fusion surgery.1 The patented2 IntelliRodTM system is based on measuring strain in a rod-based pedicle screw system. The microelectronic sensor can be clamped on a rod at the time of initial surgery to monitor load in the rod.
Routine post-operative visits would include the reading of the strain in the implanted rod using wireless inductive coupling to both power the internal circuit and transmit the encoded strain signal. The strain is an indicator of the load on the rod which in turn is a function of the bone growth achieved in the fusion3. Comparing the immediate post-operative strain level to the subsequent strain at 6 weeks, 3 months, and 6 months or more during the post-operative course will be expected to indicate the patterns shown in the graph depicting fusion or lack of fusion.
1 Goldstein C., Drew B. When is a Spine Fused? Injury, Int. J. Care Injured. 42 2011: 306-313.
2 US Patent 7,357,037
3Floerkemeier T., et al.Telemetric in vivo measurement of compressive forces during consolidation in a rabbit model.19(3) 2011: 173-183.