Prospective evaluation of a 3-blade speculum cannula for minimally invasive lumbar microdiscectomy

Minimally invasive spine technology is still in an evolutionary stage. This prospective study reports the technical feasibility, benefits, and limitations of using a 3-blade speculum cannula for minimally invasive lumbar microdiscectomies. We studied 52 consecutive patients, 24 males and 28 females, with a mean age of 36.1 years (range 20 to 68 years) and body mass index of 29.6 who underwent a microdiscectomy using this access device that opened to create a cylindrical working channel. We prospectively documented the length of the incision, estimated blood loss, length of surgery, outcomes using the visual analog scale for leg pain, and complications. The average incision length was 20.9 mm (range 13 to 30 mm). Average blood loss was less than 50 mL. Ninty-six percent of the patients had complete resolution of their radicular leg pain with improved mean visual analog scale scores from 8 to 0.3 postoperatively (P<0.5). Mean surgical time decreased with experience from 135 minutes for the first 15 patients, 103 minutes for the next 22, and 75.2 minutes for the last 15, to an overall mean of 108 minutes (range 51 to 188 minutes) and a 56% decrease for the last 38 patients. Body mass index did not affect surgical time or incision length. Seventy-five percent of the patients were discharged on the day of surgery and the remainder within 23 hours. Two symptomatic hematomas required reoperation using the retractor at 3 days and 4 weeks postoperatively. This new speculum minimal access device was effective for lumbar microdiscectomy in limiting the size of the incision without the need for sequential dilation, providing excellent visualization with the aid of a microscope, allowing same-day discharge after surgery, and demonstrating improved outcomes even in obese patients. This device may provide insights for the improvement of design considerations for other minimally invasive access devices.