Although the use of either unilateral or bilateral segmental pedicular instrumentation with transforaminal lumbar interbody fusion (TLIF) is effective in the treatment of lumbar spondylosis, patients who underwent TLIF buttressed by unilateral instrumentation were 7 times more likely to suffer pseudarthrosis and were more likely to require a reoperation.

Jeremy Steinberger, MD, Icahn School of Medicine at Mount Sinai, New York, New York, USA, presented the results of a prospective cohort study that looked at the incidence of complications in patients with lumbar spondylosis who underwent TLIF with either unilateral or bilateral instrumentation.

The study included 80 consecutive patients (40 men and 40 women), with a mean age of 44.2 years (range, 24–68 years). Patients were excluded from the study if they had an infection, tumor, spondylolisthesis, or fracture. All patients underwent 1- or 2-level TLIF between October 2007 and November 2009 for either degenerative disc disease or lumbar spondylosis. All surgeries were performed by the same 2 surgeons.

At admission to the study, patients were randomized to TLIF using unilateral (n = 40) or bilateral (n = 40) pedicle screw fixation and fusion with titanium screws. To ensure a tight fit of the graft into the disc space, compression was applied to the screws above and below the level of the TLIF. A sponge was placed into the interbody cage and into the intertransverse process spaces.

To compare outcomes between the 2 groups, patients were followed at week 2, months 3 and 6, year 1, and then biannually. At 6-month follow-up, the 36-item Short-Form Health Survey (SF-36) scores were obtained.

Radiographic data was also obtained at each follow-up period and evaluated by a single designated film reviewer. Fusion was assessed on anteroposterior /lateral x-rays by the presence of newly formed trabeculated bone between 2 adjacent fusion segments. In unclear cases, computed tomography was used. Other imaging (eg, magnetic resonance imaging) was used if indicated by a patient's clinical course. After one year, if bony healing had not occurred, radiographic pseudarthrosis was documented.

With a mean follow-up of 52 months (range 37 to 63 months), the study showed that all patients after TLIF, regardless of screw type, had a significant physical improvement as measured by SF-36 (P < .001). Also, significantly more patients treated with TLIF using unilateral instrumentation developed pseudarthrosis compared with patients treated with bilateral instrumentation (17.5% vs 2.5%; P = .05). For patients undergoing TLIF with unilateral pedicle screw instrumentation, the relative risk of developing pseudarthrosis was 7.

Under multivariate analysis, unilateral instrumentation (P = .021) and sex (P = .002) were found to be independent predictors for developing pseudarthrosis. According to Dr Steinberger, when unilateral pedicle screws are used, decreased rates of fusion occur because the screws do not appear to stabilize the TLIF construct as well as bilateral constructs.