Learning Curve and Clinical Outcomes of Minimally Invasive Transforaminal Lumbar Interbody Fusion Our Experience in 86 Consecutive Cases

Study Design. Consecutive case series with prospective data collection. Objective. To define and analyze the learning curve for minimally invasive transforaminal lumbar interbody fusion (TLIF). Summary of Background Data. Minimally invasive TLIF using a unilateral approach has recently been gaining popularity because of its potential for minimizing soft-tissue damage and reducing recovery time. However, a steep learning curve has been described for surgeons first performing this technique. Methods. Eighty-six consecutive patients with degenerative lumbar diseases who were treated by TLIF were included in the study. Surgeries were performed using a tubular retractor, and a cage was inserted using a unilateral transforaminal approach by a single surgeon. The corresponding segments were fixed with percutaneous pedicle screws. Eighty-three patients were followed up for more than 1 year, and the average follow-up period was 25 months. Single-level TLIF was performed in 60 cases, single-level TLIF plus adjacent-level decompression was performed in 13 cases, and double-level TLIF was performed in 13 cases. Corrected operative time per level, operative blood loss, postoperative blood drainage, total blood loss, and ambulation recovery time were measured. Transfusion rates and complication incidence were also identified. Clinical results were assessed using the Oswestry Disability Index (ODI) and a visual analogue scale (VAS). The learning curve was assessed using a logarithmic curve-fit regression analysis. In the single-level TLIF group (n = 60), 22 patients were defined as the "early" group (among the first 30 cases of the series), and the subsequent 38 cases were defined as the "late" group for comparison. Results. Corrected operative time gradually decreased as the series progressed, and an asymptote was reached after about 30 cases. ODI significantly decreased from an average of 24 at the preoperative stage to 10 at the final follow-up. Average VAS scores for lower back pain and radiating pain also significantly decreased from an average of 5.2 to 1.9 and 6.8 to 0.9, respectively. In the single-level TLIF series, operative time was significantly shorter in the late group (183 +/- 23 min) than the early group (254 +/- 44 min), and blood loss during the operation was significantly reduced in the late group (292 +/- 280 mL) compared with the early group (508 +/- 278 mL). Ambulation recovery time significantly decreased from 2.4 +/- 0.6 days in the early group to 2.0 +/- 0.5 in the late group. ODI and VAS scores for lower back pain and radiating pain did not differ between the 2 groups. Conclusion. Although it is not easy to master the minimally invasive TLIF technique, the surgeon's experience with this operation correlated with reduced operation time and blood loss during surgery. After the initial learning curve, this technique could be an effective and reliable option for the surgical treatment of lumbar degenerative disease.