IMAST 2022: Instrumented posterolateral fusion associated with similar patient outcomes but lower reoperation rate compared with unistrumented posterolateral fusion

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Andreas K. Andresen

Although there was no difference in patient reported outcomes (PROs) between those who underwent surgery for decompression with instrumented posterolateral fusion (IPLF) and those with uninstrumented posterolateral fusion (UPLF) at two-year follow-up, patients who underwent UPLF had a higher rate of reoperation than those with IPLF. This is according to new research, presented by Andreas K. Andresen (University of Southern Denmark, Odense, Denmark), and which won Best Clinical Paper at the Scoliosis Research Society’s 29th International Meeting on Advanced Spine Techniques (IMAST 2022; 6–9 April; Miami, USA).

The prospective, randomised, investigator-blinded single centre study sought to investigate the fusion rates between IPLF and UPLF in patients suffering from symptomatic degenerative spondylolisthesis.

The researchers note that “although IPLF is standard of care in North America, in Scandinavia uninstrumented fusion is often the treatment of choice for degenerative spondylolisthesis in patients aged over 60 years”.

From December 2016 to October 2019, Andresen et al conducted an open-label, single centre trial on patients with symptomatic single-level degenerative spondylolisthesis of 3mm or more. All patients had undergone at least 12 weeks of unsuccessful conservative treatment prior to enrolment. Patients were randomly assigned 1:1 to decompression with IPLF or UPLF.

The primary outcome measure was the Oswestry Disability Index (ODI). Secondary outcome measures were changes in EuroQoL5D-3L (EQ-5D), Visual Analogue Scale (VAS) for back and leg pain, ShortForm-36 (SF-36) PCS and MCS, and Zurich Claudication Questionnaire (ZCQ), duration of surgery, length of stay in hospital and reoperation rates within two years. Fusion rates were evaluated by fine-slice CT-scans at 12-months post op.

A total of 108 patients were included in the study, 54 in each group. There were no differences in the baseline demographics or PROs between the two groups. Two patients (4%) in the IPLF and one patient (2%) in the UPLF and had an intraoperative dural tear (p=0.56). There were no statistical differences found in PROs between the two groups at any time point.

In addition, the research showed a fusion rate of 94.3% in the IPLF group and 31.37% in the UPLF group (p<0.001). There was one re-operation (2%) in the IPLF group and seven reoperations (13%) in the UPLF group (p<0.05).

Speaking to Spinal News International, Andresen said: “In our study we investigated the addition of pedicle screw instrumentation in elderly patients who required fusion surgery due to degenerative spondylolisthesis. In our institution, due to a perceived risk of complications and reoperations due to screw pull-out and poor fusion in elderly, the standard fusion method in patients above 60 years of age have been uninstrumented.

“This has changed since the study was performed, and the results started to be processed. There were no reoperations due to screw pull-out, or any adjacent level disease within the two-year study period. We will of course have to investigate the longer-term outcome, to evaluate the durability of the two types of fusion.”


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