Comparison of standard fusion with a "topping off" system in lumbar spine surgery: a protocol for a randomized controlled trial

Background: Fusion of lumbar spine segments is a well-established therapy for many pathologies. The procedure changes the biomechanics of the spine. Initial clinical benefits may be outweighed by ensuing damage to the adjacent segments. Various surgical devices and techniques have been developed to prevent this deterioration. "Topping off" systems combine rigid fusion with a flexible pedicle screw system to prevent adjacent segment disease (ASD). To date, there is no convincing evidence that these devices provide any patient benefits. Methods/Design: The study is designed as a randomized, therapy-controlled trial in a clinical care setting at a university hospital. Patients presenting to the outpatient clinic with degenerative disc disease or spondylolisthesis will be assessed against study inclusion and exclusion criteria. After randomization, the control group will undergo conventional fusion. The intervention group will undergo fusion with a supplemental flexible pedicle screw system to protect the adjacent segment ("topping off"). Follow-up examination will take place immediately after treatment during hospital stay, after 6 weeks, and then after 6, 12, 24 and 36 months. Subsequently, ongoing assessments will be performed annually. Outcome measurements will include quality of life and pain assessments using questionnaires (SF-36 (TM), ODI, COMI). In addition, clinical and radiologic ASD, work-related disability, and duration of work disability will be assessed. Inpatient and 6-month mortality, surgery-related data (e.g., intraoperative complications, blood loss, length of incision, surgical duration), postoperative complications, adverse events, and serious adverse events will be documented and monitored throughout the study. Cost-effectiveness analysis will also be provided. Discussion: New hybrid systems might improve the outcome of lumbar spine fusion. To date, there is no convincing published data on effectiveness or safety of these topping off systems. High quality data is required to evaluate the benefits and drawbacks of topping off devices. If only because these devices are quite expensive compared to conventional fusion implants, nonessential use should be avoided. In fact, these high costs necessitate efforts by health care providers to evaluate the effects of these implants. Randomized clinical trials are highly recommended to evaluate the benefits or harm to the patient.