Abstract
Introduction
We report the outcomes of minimally invasive technique for posterior lumbar interbody fusion (PLIF) procedure using Hollow Modular Anchorage (HMA) screws supplemented by routine pedicle screw fixation (Dynesis).
Patients and Methods
Seventy-nine patients, who had undergone PLIF procedure using HMA screws supplemented by pedicle screw fixation, were included. Patients deemed suitable for surgery following discography under sedation, with Marcaine instillation establishing reducibility of the listhesis and temporary relief of symptoms. Clinical outcome included visual analogue scale scores for leg pain and back pain, Oswestry Disability Index (ODI) and SF-36 questionnaires.
Results
Average age was 59 (range: 27-85). Mean follow- up was 5 years (range: 1-10). All cases went into union. None were lost to follow-up. Average length of stay was 24 hours (18-72 hours). All clinical parameters improved except SF-36. Mean ODI improved from 54 (range: 44-89) preoperatively to 33 (17-55) postoperatively (statistically significant, p=0.004). Back pain relief improved in visual analogue scale from average of 68 (range: 60-100) preoperatively to 37 postoperatively (range: 8:46) (statistically significant, p= 0.022). Leg pain relief improved from 53 (range: 31-100) preoperatively to 28 postoperatively (range: 4:60) (statistically significant, p= 0.007). Although mean SF-36 score improved from 37 (range: 10-41) preoperatively to 47 (range: 53-94) postoperatively (statistically insignificant, p=0.592).
Complications included: one infection required removal of implant; two temporary motor weaknesses related to L5 nerve root; four required removal of the pedicle screw due to pain or loosening.
Discussion
Our results are encouraging. Interbody HMA screws are porous hollow titanium screws with favourable biomechanical characteristics. Rather than square cages, they permit accurate placement of implant. Dynesys offers the option of extension and flexible support for the adjacent segment.
Conclusion
PLIF supplemented with pedicle fixation is a reliable and safe procedure for degenerative spondylolisthesis. SF-36 is less sensitive for assessing spinal surgery outcome.
