[Minimally Invasive Posterior Lumbar Interbody Fusion and Instrumentation - Outcomes at 24-Month Follow-up]

PURPOSE OF THE STUDY Minimally invasive posterior lumbar interbody fusion and percutaneous instrumentation were introduced in the clinical practice with the aim to reduce the damage to musculoligamentous structures associated with open surgeries. The purpose of the study is to evaluate the clinical outcomes, radiological results and complications of the group of patients operated with the use of the minimally invasive posterior lumbar interbody fusion technique. MATERIAL AND METHODS The group of 31 patients operated for lumbar degenerative disc disease was followed-up prospectively. The surgical technique included a unilateral microsurgical decompression of the spinal canal with the insertion of interbody cages supplemented by percutaneous transpedicular fixation. The clinical outcomes were evaluated by means of the Oswestry Disability Index (ODI), Macnab classification, VAS score for low back pain (VAS LBP) and lower extremity pain (VAS LE) at 2, 6, 12 and 24 months postoperatively. The success rate of interbody fusion and complications was also assessed. RESULTS The inclusion criteria were met by 29 patients. The mean preoperative ODI score of 68.4 decreased to 25.1 at two-year follow-up (p 0.001). Based on the modified Macnab scale excellent and good outcomes were achieved at two-year-followup by 82.4% patients. The mean value of VAS LBP score decreased from 6.2 to 2.1 and in case of VAS LE from 5.38 to 1.34 (p ˂ 0.001). The mean time of operation was 157 minutes. Solid interbody fusion was achieved in 80% of patients. In one case, revision surgery for dislocation of the interbody cage was performed one year after the operation. A total of five misplaced transpedicular screws (5.2%) were recorded. DISCUSSION Dorsal minimally invasive spinal operational techniques, when compared with the open surgery, result in less iatrogenic injury to paravertebral muscles. From a short-term perspective, there is also less blood loss and lower frequency of infectious complications. Together with the reduction of postoperative pain and shorter hospital stay, they enable faster recovery and rehabilitation with comparable clinical effectiveness of the procedure. Apart from the above-mentioned benefits, also some shortcomings are discussed such as higher frequency of complications, longer time of operation, higher occurrence of implant malposition and higher exposure of the patient and the surgeon to radiation. CONCLUSIONS The minimally invasive posterior lumbar interbody fusion technique resulted in a statistically significant clinical improvement in the ODI, Macnab scale, VAS LBP and VAS LE scores. The percutaneous instrumentation technique shows an acceptable rate of incorrectly inserted screws. Key words: degenerative disc disease, minimally invasive spinal surgery, posterior lumbar interbody fusion, spine stabilization, lumbar interbody fusion complications.