A comparison of single-rod instrumentation with double-rod instrumentationin adolescent idiopathic scoliosis

Study Design. A consecutive series of patients with idiopathic scoliosis tr eated with single-rod instrumentation was followed prospectively. Outcomes were compared with results obtained from a retrospective review of a consec utive series of patients treated with double-rod instrumentation. Objective. To compare single-rod instrumentation with segmental fixation wi th double-rod instrumentation for the treatment of adolescent idiopathic sc oliosis. Summary of Background Data. Mechanical testing of single-rod instrumentatio n with segmental fixation at every level showed it to be as resistant to to rsion as a double-rod construct. A clinical trial was initiated to document the clinical outcome in single-rod patients. Methods. A total of 43 of 51 consecutive patients underwent spinal fusion w ith a single rod. Outcome was evaluated at a minimum of 2 years after surge ry. The control group comprised 103 patients who had standard double-rod in strumentation at the same institution. Results. The single- and double-rod groups were similar with respect to age , sex, curve type, length of follow-up, curve magnitude, and best bend. For King Ill-V curves undergoing posterior spinal fusion, there was significan tly less blood loss in the single-rod group (703 mt vs 1011 mt), less cell saver collection (189 mt vs 367 mt), and less operating time (220 minutes v s 260 minutes). Blood loss and operating time were not different for patien ts with King I and King II curves. There were eight patients (19%) requirin g reoperation because of hardware-related problems in the single-rod group compared with four (4%) in the double-rod group. There were nine patients ( 21%) with broken rods in the single-rod group, six of whom were symptomatic and five of whom required reoperation. Two patients required multiple oper ations because of pseudarthrosis in the single-rod group. There were no bro ken rods in the double-rod group. The single-rod group had 2 early postoper ative infections and no late infections compared with 10 late infections in the double-rod group. There was a statistically significant relationship b etween hardware problems and fusion below L1 in the single-rod group. Conclusion, Because of rod failure, single-rod instrumentation should be co nsidered only in curves that can be instrumented to L1 and higher.