Spinal cord stimulation versus re-operation in patients with failed back surgery syndrome: an international multicenter randomized controlled trial (EVIDENCE study).

OBJECTIVE: This paper presents the protocol of the EVIDENCE study, a multicenter multinational randomized controlled trial to assess the effectiveness and cost-effectiveness of spinal cord stimulation (SCS) with rechargeable pulse generator versus re-operation through 36-month follow-up in patients with failed back surgery syndrome. STUDY DESIGN: Study subjects have neuropathic radicular leg pain exceeding or equaling any low back pain and meet specified entry criteria. One-to-one randomization is stratified by site and by one or more prior lumbosacral operations. The sample size of 132 subjects may be adjusted to between 100 and 200 subjects using a standard adaptive design statistical method with pre-defined rules. Crossover treatment is possible. Co-primary endpoints are proportion of subjects reporting ≥ 50% leg pain relief without crossover at 6 and at 24 months after SCS screening trial or re-operation. Insufficient pain relief constitutes failure of randomized treatment, as does crossover. Secondary endpoints include cost-effectiveness; relief of leg, back, and overall pain; change in disability and quality of life; and rate of crossover. We are collecting data on subject global impression of change, patient satisfaction with treatment, employment status, pain/paresthesia overlap, SCS programming, and adverse events. DISCUSSION: As the first multicenter randomized controlled trial of SCS versus re-operation and the first to use only rechargeable SCS pulse generators, the EVIDENCE study will provide up-to-date evidence on the treatment of failed back surgery syndrome.

A biorobotic structural model of the mammalian muscle spindle primary afferent response.

A biorobotic model of the mammalian muscle spindle Ia response was implemented in precision hardware. We derived engineering specifications from displacement, receptor potential, and Ia data in the muscle spindle literature, allowing reproduction of muscle spindle behavior directly in the robot's hardware; a linear actuator replicated intrafusal contractile behavior, a cantilever-based transducer reproduced sensory membrane depolarization, and a voltage-controlled oscillator encoded strain into a frequency signal. Aspects of muscle spindle behavior not intrinsic to the physical design were added in control software using an adaptation of Schaafsma's mathematical model. We tuned the response to biological ramp and hold metrics including peak, mean, dynamic index, time domain response, and sensory region displacement. The model was validated against biological Ia response to ramp and hold, sinusoidal and fusimotor inputs. The response with dynamic or static gamma motorneuron input was excellent across all studies. The passive spindle response matched well in five of the nine measures. Potential applications include basic science muscle spindle research and applied research in prosthetics and robotics.

The usefulness property of biorobotic sensorimotor models: A natural source of prosthetic designs.

This commentary addresses an additional feature of biorobotic modeling: usefulness in prosthetic design. By implementing structurally and behaviorally accurate models as prosthetics, biologically accurate restoration can be approximated. This has potential to reestablish important peripheral elements of the sensorimotor control system, including limb biomechanics, proprioception, and vision. Examples given include musculoskeletal prosthetics and retinal implants.