A Comparison of Outcome between Isobar TTL and Conventional Transforaminal Lumbar Interbody Fusion
Authors: Kumar Naresh 
Published: May 2015

Background Spine fusion using posterior instrumentation is currently considered the gold standard in surgical treatment for degenerative disease of the lumbar spine. Treatment-related problems for spinal fusion include stiffness, pseudoarthrosis, mechanical failure, and “adjacent segment disease (ASD).” The Isobar TTL is a form of pedicle screw–based dynamic stabilization (PDS) device. Several studies have shown the Isobar TTL to have good short-term outcomes in terms of fusion and decreasing the incidence of ASD. However, there are limited studies comparing the functional outcomes of the Isobar TTL with the conventional two-level transforaminal interbody fusion (TLIF). Methods This is a retrospective analysis of spine fusion and hybrid fusion cases done for degenerative lumbar disease in our institution during 2009 to 2012. Functional outcomes were measured preoperatively and at 12 and 24 months postoperatively using a 100-scaled visual analogue score (VAS), Oswestry Disability Index (ODI), and Short-Form 36 (SF-36) mental and physical components. Radiographic parameters to assess for ASD were also measured on standing lumbar films. These included disc height at the level of dynamic stabilization, disc height of the adjacent levels, foraminal height of the index level and adjacent levels, adjacent level disc angle, lumbar lordosis, and sacral slope. t test was used to analyze the data. p value of < 0.05 was determined significant. Results A total of 30 cases were studied, 15 of which used Isobar TTL (Scient'x USA, Maitland, Florida, United States) treatment and 15 underwent a two-level TLIF. Mean length of follow-up was 24 months. VAS and ODI scores were slightly lower in the TLIF group at 12 and 24 months postoperatively ( p = 0.86). The SF-36 mental component was 5.51 points higher in the Isobar TTL group at 12 months post-op but was closer to TLIF values by the end of 24 months ( p = 0.8). SF-36 physical component was higher in the TLIF at both 12 ( p = 0.91) and 24 months ( p = 0.37). Disc height showed deterioration in both groups at 12 months postoperatively with a greater reduction in height in the Isobar TTL group ( p = 0.71). Disc angle was better preserved in the Isobar TTL group with an improvement of 1.3 and 0.61 degrees at 12 and 24 months, respectively. Lumbar lordosis was better preserved in the TLIF group with an increment of 1.36 degrees at 12 months ( p = 0.3) and 2.56 degrees at 24 months ( p = 0.77). The Isobar TTL group showed an initial reduction in lumbar lordosis by 3.4 degrees. This improved by 1.49 degrees at the end of 24 months. Among the radiographic parameters, only sacral slope was found to have a significant difference between the Isobar TTL and TLIF groups (mean difference 5.53, p = 0.03). Operation time was longer by 90.83 minutes in the Isobar TTL group ( p = 0.09). The duration of hospital stay was the same for all the patients with an average of 8.83 ± 5.71 days ( p = 0.94). Conclusions The Isobar TTL is a valid treatment option in the management of degenerative lumbar disease. Short-term results of the Isobar TTL are comparable to a two-level conventional TLIF in terms of functional and radiographic outcomes.