616 - Learning Curve of a Minimally Invasive Technique for Percutaneous Pedi...

General Session: MIS-2

Presented by: H. Nicola - View Audio/Video Presentation (Members Only)


H. Nicola(1), M. Da Silva(2), D. Onay(2)

(1) Hospital San Juan de Dios, Spine Surgery, Caracas, Venezuela
(2) Clinica Sanatrix, Caracas, Venezuela


Background and Purpose: Minimally invasive posterior lumbar fusion using tubular retractor system has been well reported. Supporters have claimed that this technique reduce soft-tissue trauma, blood loss, postoperative pain, transfusion needs and the length of hospital stay, as compared with reports describing the traditional open procedure. However, very few studies have evaluated the learning curve of this technically demanding surgery. The purpose of this study is to report our clinical experience and evaluate the learning curve of MIS-TLIF based on perioperative variables and clinical and radiologic outcomes.

Methods: Between 2008 and 2015, a total of 246 consecutive patients with LDD underwent 1-level TLIF by 2 surgeons in 1 hospital. Surgery was performed using tubular retractor system for TLIF technique and spinal instrumentation with PPS. Patients were followed up for more than 1 year (average follow-up 32 months). Operative and fluoroscopy duration, blood loss, complications and ambulation recovery time were recorded. Clinical results were assessed using Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS). Radiographic images were obtained preoperatively and during follow-up to evaluate fusion and migration rate.

Results: The learning curve was assessed using a curve fitting regression analysis. Operative time gradually decreased and the asymptote was achieved at the 64th case; therefore, 64 patients were defined as the “early” group and the subsequent 182 cases were defined as the “late” group for comparison. Comparing both groups demographics were similar. For operative parameters, 4 variables showed differences between the 2 groups: mean operative duration, fluoroscopy duration, ambulation recovery time and complication rate. Operative time was significantly shorter in the late group (152 min) than the early group (235 min), and blood loss during the operation was significantly reduced in the late group (70 ml) compared with the early group (160 mL). Fluoroscopy Mean time was 3,25 minutes in early group and 1,7 minutes in later one. Ambulation recovery time significantly decreased from 2.3 day in the early group to 1.2 in the late group. We found in the early group 10 complications (18,51%): 1 severe radicular damage, 2 durotomy, 1 symptomatic cage migrations, 1 bone graft migration, 3 screws malposition and 2 converted to open; and in the latter group, there were 11 complications (6,79%): 3 durotomy, 1 symptomatic cage migrations, 1 asymptomatic cage migrations, 4 screws malposition and 2 converted to open. At the final follow-up, for clinical outcome parameters, ODI and VAS scores for lower back pain and radiating pain did not differ between the 2 groups. ODI significantly decreased from an average of 44 at the preoperative stage to 11 at the final follow-up. Average VAS scores for lower back pain and radiating pain also significantly decreased from an average of 7.6 to 2.4 and 7.1 to 1.4. For radiological outcome, both groups showed similar good fusion rates.

Conclusions: Although it is not easy to reach the proficiency in MIS TLIF technique, in our study the latter patients benefited from shorter operative and fluoroscopy duration, ambulation time and complication rate. This means that after the initial learning curve this technique could be an effective and reliable option for the surgical treatment of LDD.