Expandable Technology in Minimally Invasive TLIF

International Society for the Advancement of Spine Surgery (ISASS17) Meeting Highlight

Insertion of static interbody cages during minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) is challenging, particularly at the L4-L5-S1 levels.

As Choll W. Kim, MD, PhD commented during his presentation at the 17th Annual ISASS Meeting, “It can be very difficult to insert a relatively large cage through the small window of a posterior annulotomy.” One means to achieve this is through the use of specialized expander implants that are inserted in a collapsed state. After insertion of the implant into the interbody space, incremental expansion facilitates optimal endplate contact within the larger anterior interbody space.

Dr. Kim is Associate Clinical Professor at the University of California-San Diego, the Director of the Minimally Invasive Spine Program at the Spine Institute of San Diego, and serves as Chair of the MIS Committee for the International Society for the Advancement of Spine Surgery (ISASS).

He reported findings from a prospective longitudinal study involving 25 patients (30 levels) who underwent MIS TLIF with an in situ expandable interbody device that was combined with supplemental transpedicular posterior stabilization. In addition to collecting pre-operative clinical and radiographic data, the study reported on follow-up data collected at 6 weeks, 12 months, and through 24 months post-operatively.
Imagery equipment showing a spinal fluoroscopyDr. Kim reported the findings were clinically meaningful, and most were statistically significant.Photo Source:123RF.com.

Study Results

Nearly two-thirds of the patients (64%) were female, and the average patient age was 52.6 (+12.9) years. Twenty of the 25 patients underwent one-level fusion, predominantly at L4-L5, and the other 5 had a two-level fusion procedure; most often at L4-S1.

Dr. Kim reported the findings were clinically meaningful, and most were statistically significant. Although there were no statistically significant differences in length of hospital stay between one-level versus two-level procedures, there were significant differences in mean operative time (152.1 + 86.9 vs 298.8 + 125.4 minutes) and in estimated blood loss (57.0 + 49.9 vs. 212.5 + 103.1 cc) (P<0.01).

There were significant differences in mean visual analogue scale (VAS), Oswestry Disability Index (ODI) and 36-Item Short Form Survey (SF-36) scores. All scores on VAS and ODI decreased significantly from pre-operative to all post-operative time intervals (P<0.05). Mean VAS low back pain decreased from 59.1 + 27.4 to 28.5 + 29.2 at 24 months, and ODI decreased from 44.5 + 16.6 to 19.1 + 15.4 (P=0.00). The SF-36 Physical Component score significantly increased from 31.4 + 5.6 to 44.1 + 11.6, and the SF-36 Mental Component score increased from 45.4 + 13.0 to 53.5 + 10.3 (P<0.01).

There were significant increases in both intervertebral disc height (6.9 + 2.4 vs 12.0 + 1.1 mm) and neuroforaminal height (15.9 + 6.5 vs 19.7 + 3.9 mm), both of which were maintained throughout 24 months (P<0.01). At 24-month follow-up, 96% of operative levels demonstrated radiographic evidence of successful fusion. None of the 25 patients required reoperation, and there were no device-related complications.


Dr. Kim concluded that the use of an expandable interbody device for MIS TLIF is safe and effective, enabling significant improvements in terms of intervertebral disc and neuroforaminal height restoration and high fusion rates.

Updated on: 05/04/19
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