Clinical outcomes during the learning curve of MIDline Lumbar Fusion (MIDLF®) using the cortical bone trajectory

The objective of this study is to review the clinical outcomes of a novel minimally invasive surgery (MIS) technique for the treatment of instability of the lumbar spine using the cortical bone trajectory (CBT). We present a prospective review of the clinical outcomes from the first 25 consecutive cases in a single unit during the initial learning phase.

The investigation group included the first 25 patients (eight males and 17 females) who underwent MIDLF® since the introduction of this technique in a single unit. All patients were operated on by the same surgeon. Patients' demographics, as well as duration their surgery, intraoperative blood loss, duration of hospitalization, and complications were analyzed. From the patients' satisfaction survey; pre and post-operative analgesics use, visual analogue scale (VAS) score for both back pain and radicular symptoms, as well as the Oswestry disability index (ODI) were measured and analyzed.

There was a clear improvement in all measured parameters. The median intraoperative blood loss was 250 ml (200-700) with an average operative time of 190 (±46) and 237 (±14) min for one- and two-level fixation respectively and a median hospital stay of 2 days (1-12) inclusive of the day of surgery. The mean preoperative ODI was 59 % (±18.7) versus 34 % (±19.5) post-operatively. In this series, 84 % of the patients (n = 21) reported a significant reduction in the use of analgesia, and 44 % (n = 11) reported total freedom from intake of painkillers. The median postoperative pain-free walking distance increased from 50 (0-3520) to 1000 (0-8880) yards. Three complications were reported without any significant postoperative morbidity. While in this case series the preoperative ODI and back pain VAS significantly predicted the post-operative variable, the same could not be demonstrated for leg pain, preoperative walking distance, number of pain killers, or the patient body mass index (BMI).

Our results indicate that lumbar instrumentation using CBT is safe and effective with comparable results to those published for posterior lumbar interbody fusion (PLIF) even with the learning curve of new procedures. Patients who underwent a MIDLF® needed a shorter operative time, and they were mobilized and discharged quicker, with figures almost similar to those from non-instrumented surgery. While in this case series the preoperative ODI and back pain VAS significantly predicted the post-operative variable, the same could not be demonstrated for leg pain, preoperative walking distance, number of pain killers, or the patient BMI. Larger studies with longer follow-up are needed in order to better understand and assess the possible advantages of this technique.