Study design: Prospective observational cohort study.
Objective: Comparison of clinical and radiological outcomes of single-level open versus minimally invasive (MIS) transforaminal lumbar interbody fusion (TLIF) at 6 months and 2-year follow-up. There is recognition that more data are required to ascertain the benefits and risks of MIS vis-a-vis open TLIF. This study aims to report on one of the largest currently available series comparing the clinical and radiological outcomes of the two procedures with a minimum follow-up of 2 years.
Methods: From January 2002 to March 2008, 144 single-level open and MIS TLIF were performed at our centre, with 72 patients in each group. Clinical outcomes were based on patient-reported outcome measures recorded at the Orthopaedic Diagnostic Centre by independent assessors before surgery, at 6 months and 2 years post-operatively. These were visual analogue scores (VAS) for back and leg pain, Oswestry disability index (ODI), short form-36 (SF-36), North American Spine Society (NASS) scores for neurogenic symptoms, returning to full function, and patient rating of the overall result of surgery. Radiological fusion based on the Bridwell grading system was also assessed at 6 months and 2 years post-operatively by independent assessors.
Results: In terms of demographics, the two groups were similar in terms of patient sample size, age, gender, body mass index (BMI), spinal levels operated, and all the clinical outcome measures (p > 0.05). Perioperative analysis revealed that MIS cases have comparable operative duration (open: 181.8 min, MIS: 166.4 min, p > 0.05), longer fluoroscopic time (open: 17.6 s, MIS: 49.0 s, p < 0.05), less intra-operative blood loss (open: 447.4 ml, MIS: 50.6 ml, p < 0.05) and no post-operative drainage (open: 528.9 ml, MIS: 0 ml, p < 0.05). MIS patients needed less morphine (open: 33.5 mg, MIS: 3.4 mg, p < 0.05) and were able to ambulate (open: 3.4 days, MIS: 1.2 days, p < 0.05) and be discharged from hospital earlier (open: 6.8 days, MIS: 3.2 days, p < 0.05). At 6 months, clinical outcome analysis showed both groups improving significantly (>50.0%) and similarly in terms of VAS, ODI, SF-36, return to full function and patient rating (p > 0.05). Radiological analysis showed similar grade 1 fusion rates (open: 52.2%, MIS: 59.4%, p > 0.05) with small percentage of patients developing asymptomatic cage migration (open: 8.7%, MIS: 5.8%, p > 0.05). One major complication (open: myocardial infarction, MIS: screw malpositioning requiring subsequent revision) and two minor complications in each group (open: pneumonia and post-surgery anemia, MIS: incidental durotomy and pneumonia) were noted. At 2 years, continued improvements were observed in both groups as compared to the preoperative state (p > 0.05), with 50.8% of open and 58% of MIS TLIF patients returning to full function (p > 0.05). Almost all patients have Grade 1 fusion (open: 98.5 %, MIS: 97.0%, p > 0.05) with minimal new cage migration (open: 1.4 %, MIS: 0%, p > 0.05).
Conclusions: MIS TLIF is a safe option for lumbar fusion, and when compared to open TLIF, has similar operative duration, good clinical and radiological outcomes, with additional significant benefits of less perioperative blood loss and pain, earlier rehabilitation, and a shorter hospitalization.