Minimally Invasive Transforaminal Lumbar Interbody Fusion: Meta-Analyses Of The Fusion Rates. What is the optimal graft material?

Presented at SMISS Annual Forum 2014
By Marjan Alimi MD
With Roger Härtl MD, Yu Moriguchi MD, PhD, Avelino Parajón MD, Paul Christos PhD, Jose Torres-Campa MD, Rodrigo Navarro-Ramirez MD,

Disclosures: Marjan Alimi MD None. Roger Härtl MD B; Brainlab, DePuy-Synthes, Ulrich, Yu Moriguchi MD, PhD None, Avelino Parajón MD None, Paul Christos PhD None, Jose Torres-Campa MD None, Rodrigo Navarro-Ramirez MD None,

Introduction:
Minimally Invasive Transforaminal Lumbar Interbody Fusion (MIS TLIF) is an increasingly popular technique for treatment of various pathologies of the spine. Different graft materials are being used for fusion.

Aims/Objectives:
Comparison of the fusion rate between different graft materials used in MIS TLIF, via meta-analysis of the published literature.

Methods:
A Medline search was performed to identify the studies reporting on the fusion rate of MIS TLIF using different graft materials. A database was created including patient demographics, per-operative data, type of graft material, clinical outcome, fusion rate and duration of follow-up. Certain study groups were defined based on the type of graft utilized. Meta-analysis of the fusion rate was performed using the StatsDirect statistical software.

Results:
Forty series with a total of 1320 patients were included. Age and sex distribution were homogeneous in almost all series. The most frequent operated level was L4/L5. Implanted cages were made of PEEK, titanium, or hydrosorb. Significant improvement in clinical scores was observed in all studies. Fusion rates were high, regardless of the type of the graft, ranging from 92% to 99%, in different studies. Comparison of the series with rhBMP (38% of patients) and with non-rhBMP grafts (62% of patients) showed global fusion rates of 97% and 95%, respectively. The difference between the groups increased over time, reaching a maximum at 1 year (rhBMP group 99%, non-rhBMP group 93%). Comparisons of patients with iliac bone graft and those with other non-rhBMP grafts showed fusion rate of 93% for iliac crest and 92% for those with other non-rhBMP grafts. The lowest fusion rate was observed with isolated utilization of autologous local bone (92%). Addition of non-rhBMP grafts to the local bone increased the fusion rate up to 93% and addition of rhBMP to local bone increased it up to 95%. Combination of non-rhBMP with rhBMP and local bone resulted in the highest fusion rate (99%). The median complication rate was 8.82%, varying between 0% and 35.71%.

Conclusions:
Utilization of rhBMP for MIS TLIF resulted in higher fusion rates. Isolated use of local bone resulted in the lowest. Addition of allograft, bone substitutes and/or demineralized bone to local bone increased the fusion rate moderately. Given the potential complications of iliac bone harvesting and rhBMP, the decision on the type of graft material should be individualized. When rhBMP used, efforts should be made to use the lowest possible amount.