Lumbar interbody fusion is a common treatment for a variety of spinal pathologies.
The influence of interbody cage positioning on clinical outcomes following lumbar interbody fusion is not well understood, though it has been hypothesized that insufficient mechanical loading of the interbody graft can prevent proper fusion of the joint.
Lumbar interbody cages placed from an anterior or lateral approach are desirable due to their large size, providing a stable fusion environment. Posterior implants are typically limited by their access corridor. Expandable footprint TLIF interbodies may allow for a minimally invasive TLIF approach with the biomechanical benefits of an ALIF-sized graft; however this requires experimental investigation 1).
Anterior lumbar interbody fusion (ALIF).
Endoscopic assisted anterior lumbar interbody fusion (ALIF)
Axial lumbar interbody fusion (Ax-LIF)
In elderly patients with severe osteoporosis, instrumented lumbar interbody fusion may result in fixation failure or nonunion because of decreased pedicle screw pullout strength or increased interbody graft subsidence risk. Thus, given its many advantages, percutaneous pedicle screw fixation with cement augmentation can be an effective method to use in elderly patients.
The aim of a study was to determine if patients with lumbar intervertebral disc disease who achieve radiographic fusion after single-level lumbar interbody fusion have better clinical outcomes than patients with radiographic pseudarthrosis at 12 and 24 months postoperative.
Individual patient-level data of 4 randomized controlled trials (RCTs) were obtained from the Yale University Open Data Access Project project and analyzed. Clinical outcomes (Oswestry Disability Index [ODI]; Numeric Rating Scales [NRSs] for back and leg pain) were compared between patients with radiographically confirmed fusion and those with radiographic nonunion 1 and 2 years postoperative. The results of each study were first analyzed separately, and then were pooled by metaanalysis. The GRADE approach was applied to evaluate the level of evidence.
A total of 496 patients with clinical and radiographic data at 1- and 2-year follow-ups were identified. Of these, 5.5% (95% confidence interval: 3.7; 8.3) had radiographic nonunion which did not require reoperation. Patients with fusion had better improvements in ODI (P < 0.001) and NRS back pain scores (P < 0.001). The overall percentage of fused patients with ODI and NRS back pain scores that exceeded the criteria for minimal clinically important differences was also significantly higher than that of patients with nonunion (ODI, odds ratio [OR] = 2.7, P = 0.019; NRS back pain, OR = 3.5, P = 0.033). The predictive values of fusion for clinical outcomes, however, were poor, with low specificity and low negative predictive values.
The presence of radiographic fusion is clinically significant, as patients with fusion had better clinical outcomes at 1 and 2 years postoperative than those with nonunion; however, patient-centered clinical outcomes should also be taken into consideration as independent, complimentary variables when assessing treatment success 2).
The fusion rate in spinal surgery may vary in relation to the technique, and it remains unknown which surgical technique provides the best fusion rate and surgical outcomes. Lee et al., aimed to compare radiological and surgical results between three surgical techniques used for lumbar interbody fusión.
Seventy-seven patients diagnosed with degenerative lumbar spinal stenosis including spondylolytic lumbar spondylolisthesis. Patients were divided into three groups according to the surgical technique: anterior lumbar inter-body fusion (ALIF, n = 26), transforaminal lumbar inter-body fusion (TLIF, n = 21), and posterior lumbar inter-body fusion (PLIF, n = 30). Various radiological parameters were measured including fusion rates.
Significant changes after surgery were observed in the ALIF group for the percentage of vertebral body slippage, anterior disc height, posterior disc height, segmental, and segmental ROM. The fusion rate on CT scan at the final follow-up was 69.2% in the ALIF, 72.7% in the TLIF, and 64.3 % in the PLIF. The cage subsidence rate 2 years after surgery was 15.4% in the ALIF, 38.1% in the TLIF, and 10% in the PLIF.
ALIF was associated with better restoration of segmental lordosis. The fusion rate on CT scan and with segmental ROM did not differ between the three groups. TLIF was associated with a better post op VAS. PLIF showed the lowest cage subsidence rate. Therefore, it looks difficult to tell which surgical technique is better between the three groups as well as all the surgical procedures being equivocal in terms of fusion rate and outcomes 3).