Effects of Minimally Invasive Lateral Lumbar Interbody Fusion with Accessory Rod Technique on Rod Fracture in Adult Spinal Deformity Surgery: Analysis of 239 Patients.

ABSTRACT

STUDY DESIGN: A retrospective study. OBJECTIVES: To analyze factors associated with rod fracture (RF) in adult spinal deformity (ASD), and to assess whether the accessory rod (AR) technique can reduce RF occurrence in deformity correction in the setting of minimally invasive lateral lumbar interbody fusion (LLIF). SUMMARY OF BACKGROUND DATA Instrumentation failure is the most common reason for revision surgery in ASD. Several RF reduction methods have been introduced. However, there are insufficient studies on postoperative RF after deformity correction using minimally invasive LLIF. METHODS: This study included 239 patients (average age 71.4 y and a minimum 2-year follow up) with ASD who underwent long-segment fusion from T10 to sacrum with sacropelvic fixation. Patients were classified into the non-RF group and the RF group. After logistic regression analysis of the risk factors for RF, subgroup analyses were performed; pedicle subtraction osteotomy (PSO) with 2-rod (P2 group) versus PSO with 2-rod and AR (P4 group), and LLIF with 2-rod (L2 group) versus LLIF with 2-rod and AR (L4 group). RESULTS: RF occurred in 50 patients (21%) at an average of 25 months. RF occurred more frequently in patients who underwent PSO than in those who underwent LLIF (P=0.002), and the use of the AR technique was significantly higher in the non-RF group (P<0.05).Following logistic regression analysis, preoperative PI-LL mismatch, PSO, and the AR technique were associated with RF. In subgroup analyses, RF incidence was 65% (24/37 cases) of P2 group, 8% (4/51 cases) of P4 group, and 21% (22/105 cases) of L2 group. In the L4 group, there was no RF. CONCLUSION: Minimally invasive multilevel LLIF with the AR technique is capable of as much LL correction as conventional PSO and appears to be an effective method for reducing RF.