Factors Influencing Surgical Decision-Making in the Posterior Laminectomy With Fixation for Degenerative Cervical Myelopathy (POLYFIX-DCM) Trial: Survey Study (Preprint)

Background:
Degenerative cervical myelopathy (DCM) is estimated to affect 2% of the adult population. DCM is caused when degenerative processes stress and injure the spinal cord. Surgery to remove stress on the spinal cord is the mainstay of treatment. A range of techniques are in use. Whilst various factors are described to inform their selection, there is no consensus and limited comparative evidence.

Objective:
Here, we report on a study of the principal investigators of the NIHR POLYFIX-DCM clinical trial, exploring decision-making with a focus on laminectomy versus laminectomy and fusion.

Methods:
A series of 7 cases were shared with 24 principal investigators using SurveyMonkey (California USA). Each case consisted of a mid-sagittal T2-weighted MRI and lateral cervical x-rays in flexion and extension. Surgeons were asked if their preferred approach was anterior or posterior. If posterior, they were asked whether they preferred to instrument and whether they had equipoise to randomise in NIHR POLYFIX DCM. Variance in decision making was then explored using factors reported to inform decision making, such as alignment, location of compression, number of levels operated, presence of mobile spondylolisthesis and patient age.

Results:
The majority of PIs (53%) completed the survey. Overall PIs favoured a posterior approach (75%) with instrumentation (66%) and would randomise most (62%) cases. Factors reported to inform decision making poorly explained variance in responses in both univariate testing and with a multivariate model (R2= 0.1). Only surgeon experience >5 years and orthopaedic specialty training background were significant predictors, both associated with an anterior approach [OR – 1.255, p = 0.019 and OR - 1.344, p=0.007 respectively] and fusion for posterior procedures [OR – 0.628, p<0.001 and OR – 1.344, p<0.001 respectively]. Surgeon experience also significantly affected the openness to randomise, with those of >5 years’ experience less likely to randomise (OR -0.68, p<0.001).

Conclusions:
In this representative sample of spine surgeons in the UK.In the UK, there is no consensus on surgical strategy, including the role of instrumented fusion following posterior decompression. Overall, there is clinical equipoise, and conceptually a randomised controlled trial appears feasible. This sets the premise for NIHR POLYFIX DCM.