gms | German Medical Science

Objective: MIS-HLIF is a hybrid of the PLIF- and the TLIF-procedure. The approach utilizes a standard unilateral midline approach for decompression, but bilateral (ipsilateral and contralateral crossover) facetotomy and discectomy. The ipsilateral facetotomy is later employed to implant a specially designed cage. Using navigation pedicle screws are placed in a vertical (dorsoventral) vector ipsilaterally and in conventional percutaneous dorsolateral technique on the contralateral side. This study reports that preoperative simulation accelerates MIS-HLIF and reduces the radiation exposure for the staff.

Method: Developing the SOP for MIS-HLIF 163 patients with single-level degenerative lumbar spondylolisthesis underwent treatment so far. Previous quality assurance study of MIS-HLIF, Numeric rating scale (NRS), Oswestry disability index (ODI) and core outcome measures index (COMI) were assed for the first 23 patients preoperatively as well as 6 weeks, 3 months, 6 months and 1 year after surgery. For these patients, segmental realignment was statistically objectified using Boxall's method. Furthermore, the surgery time as well as radiation exposure of staff was assed and compared to in-house conventional open and MIS-TLIF. P<0.05 was considered significant.

Results: Previous outcome evaluation in the first 23 patients showed significant improvement of NRS, COMI and ODI scores at all postoperative follow-up time points (p<0.05). Postoperative statistical evaluation of x-ray data from these patients further showed a significant reduction of olisthesis from an average of 22% preoperatively to 9% postoperatively (p<0.01). The average blood loss was less than 500 ml. After establishing a preoperative simulation in the SOP mean surgical time (by one surgeon) decreased from 180 (SD 27) to 140 minutes (SD 30) and mean radiation exposure for staff was reduced from 570 (SD 110) to 350 centigray/ cm² (SD 50) significantly in the last 33 cases. Compared with in house patients after MIS-TLIF: (720 centigray/ cm², SD 90) and after TLIF: (420 centigray/ cm², SD 30).

Conclusions: MIS-HLIF is combining advantages of the PLIF and TLIF procedure and ist outcome is not inferior. The preoperative software-assisted simulation of the cage concerning the sagittal balance reduces the surgical time and radiation exposure for the staff. Based on preoperative imaging data this simulation suggests the optimal height of the device so it must not be defined intraoperatively via x-ray.