Fat in the lumbar multifidus muscles - predictive value and change following disc prosthesis surgery and multidisciplinary rehabilitation in patients with chronic low back pain and degenerative disc: 2-year follow-up of a randomized trial

Abstract

BackgroundEvidence is lacking on whether fat infiltration in the multifidus muscles affects outcomes after total disc replacement (TDR) surgery and if it develops after surgery. The aims of this study were 1) to investigate whether pre-treatment multifidus muscle fat infiltration predicts outcome 2 years after treatment with TDR surgery or multidisciplinary rehabilitation, and 2) to compare changes in multifidus muscle fat infiltration from pre-treatment to 2-year follow-up between the two treatment groups.MethodsThe study is secondary analysis of data from a trial with 2-year follow-up of patients with chronic low back pain (LBP) and degenerative disc randomized to TDR surgery or multidisciplinary rehabilitation. We analyzed (aim 1) patients with both magnetic resonance imaging (MRI) at pre-treatment and valid data on outcome measures at 2-year follow-up (predictor analysis), and (aim 2) patients with MRI at both pre-treatment and 2-year follow-up. Outcome measures were visual analogue scale (VAS) for LBP, Oswestry Disability Index (ODI), work status and muscle fat infiltration on MRI. Patients with pre-treatment MRI and 2-year outcome data on VAS for LBP (n = 144), ODI (n = 147), and work status (n = 137) were analyzed for prediction purposes. At 2-year follow-up, 126 patients had another MRI scan, and change in muscle fat infiltration was compared between the two treatment groups. Three radiologists visually quantified multifidus muscle fat in the three lower lumbar levels on MRI as <20% (grade 0), 20–50% (grade 1), or >50% (grade 2) of the muscle cross-section containing fat. Regression analysis and a mid-P exact test were carried out.ResultsGrade 0 pre-treatment multifidus muscle fat predicted better clinical results at 2-year follow-up after TDR surgery (all outcomes) but not after rehabilitation. At 2-year follow-up, increased fat infiltration was more common in the surgery group (intention-to-treat p = 0.03, per protocol p = 0.08) where it was related to worse pain and ODI.ConclusionsPatients with less fat infiltration of multifidus muscles before TDR surgery had better outcomes at 2-year follow-up, but findings also indicated a negative influence of TDR surgery on back muscle morphology in some patients. The rehabilitation group maintained their muscular morphology and were unaffected by pre-treatment multifidus muscle fat.Trial registration NCT 00394732 (retrospectively registered October 31, 2006).

Does pre-operative multifidus morphology on MRI predict clinical outcomes in adults following surgical treatment for degenerative lumbar spine disease? A systematic review

“…Of the six included studies, three were retrospective cohort studies [16][17][18], two were prospective cohort studies [15,19], and one was a secondary analysis of a previous randomised control trial [13]. Two studies examined the effect of pre-operative fat infiltration on improvement in LBP (Visual Analogue Scale [VAS]) only [17,18], two studies examined the effect of pre-operative fat infiltration on improvement in both LBP (VAS) and disability (Oswestry Disability Index [ODI]) [13,15], one study examined the effect of both pre-operative fat infiltration and cross-sectional area on improvement in disability (ODI) only [19], and one study examined the effect of pre-operative cross-sectional area on improvement in disability (ODI) only [16]. No studies examined the effect of multifidus cross-sectional area on LBP rating scales.…”

“…All included studies examined multifidus morphology using validated methods of imaging and grading; however, only two studies used identical methods of grading [17,18]. For quantification of fat infiltration, two studies used pixel intensity to estimate grade of fat infiltration [17,18] and three studies used a semi-quantitative visual method [13,15,19]. For measurement of cross-sectional area, both studies used manual tracing of muscle cross-sectional area from a digital image [16,19].…”

“…The results of the risk of bias assessment are reported in Table 3. Overall, two of the included studies were at high risk of bias [15,16] and four were considered to be at low risk of bias [13,[17][18][19]. Generally, the QUIPS tool domains at greatest risk of bias were study confounding with three studies being at moderate-to-high risk of selection bias [15,16,18] and study attrition with three studies being at moderate-to-high risk of attrition bias [16][17][18].…”

“…Alternatively, in cases where conservative treatment has failed or in those with concurrent spinal stenosis or radiculopathy, surgical management may be considered [8]. At present, there is some evidence to suggest that changes in the morphology of multifidus following a surgical procedure are associated with worse clinical outcomes, although the magnitude of this effect is unclear [10][11][12][13][14]. Furthermore, the association between the pre-operative morphological condition of multifidus and post-operative clinical outcomes is not well described [15][16][17][18][19].…”

The Implications of Paraspinal Muscle Atrophy in Low Back Pain, Thoracolumbar Pathology, and Clinical Outcomes After Spine Surgery: A Review of the Literature

“…35 compared to those with increased multifidus muscle fat in 1 or 2 levels. 37 The Relationship Between Paraspinal Muscle Atrophy and Failed Back Surgery…”