The predictive value of multifidus degeneration in osteoporotic vertebral compression fracture patients with kyphosis deformity.

Background context: Osteoporotic vertebral compression fracture (OVCF) causes pain, kyphosis and neurological damage, which significantly affect patients' quality of life. Patients with OVCF are often elderly and have severe osteoporosis, which makes preoperative symptom more serious, postoperative recovery worse and the incidence of postoperative complications high. The paraspinal muscles have been well studied in adult spinal deformities, but there is no conclusive evidence that their findings can be applied to OVCF. The purpose of this study was to evaluate the associations between multifidus (MF) parameters including fat infiltration (FI), relative functional sectional area (rFCSA), relative gross cross-sectional area (rGCSA) and the sagittal parameters, symptom score, and postoperative complications.

Purpose: To figure out the potential associations between multifidus muscle (MF) degeneration and patients' quality of life (QoL), sagittal parameters and mechanical complications in osteoporotic vertebral compression fracture (OVCF) patients with kyphosis deformity.

Study design: Retrospective cohort study PATIENT SAMPLE: OVCF patients with kyphosis deformity who underwent corrective surgery between 2008 to 2021.

Outcome measurements: MF fat infiltration (MFFI), relative functional cross-sectional area (MFrFCSA), MF relative gross cross-sectional area (MFrGCSA), VAS, ODI, JOA, SRS-22, preoperative, postoperative and last-follow up spine sagittal parameters, postoperative mechanical complications.

Methods: The study included 108 OVCF patients with kyphosis deformity who underwent corrective surgery and were followed for 2 years. MRI were performed preoperatively to evaluate the paraspinal muscle morphology, including MF fat infiltration (MFFI), relative functional cross-sectional area (MFrFCSA), and MF relative gross cross-sectional area (MFrGCSA). VAS, ODI, JOA, and SRS-22 were conducted preoperatively. Preoperative, postoperative and last-follow up spine sagittal parameters were recorded, as well as sagittal balance, loss of correction results and improvement and deterioration of sagittal parameters. The occurrence of postoperative mechanical complications, including adjacent segment disease, screw loosening, proximal junctional kyphosis, and distal junctional problem were recorded. We analyzed the relationship between MF degeneration and the above parameters.

Results: Strong correlation was observed in VAS and MFFI (rr=0.597, p=.000),MF rFCSA (rr=-0.520, p=.001) and MF rGCSA (rr=-0.461, p=.005), as well as ODI and MF rFCSA (rr=-0.336, p=.042). Preoperatively, strong correlations were observed between MF rFCSA and LL (rr=-0.320, p=.010), TLK (rr=-0.271, p=.026), TK (rr=-0.251,p=.048). MF rGCSA and LL (rr=-0.259, p=.039), TLK (rr=-0.247, p=.043), TK (rr=-0.273, p=.030), GK (rr=-0.381, p=.002) were also strongly correlated. Our study showed strong correlations between MF FI and TLK loss (rr=0.406, p=.003), TK loss (rr=0.332, p=.045);MF rGCSA and SVA loss (rr =-0.367, p=.050), TPA loss (rr =-0.404, p=.030); MF rGCSA and TPA loss (rr =-0.401, p=.031), MF FI and GK loss(rr =0.397, p=.027). MF FI was significantly higher in the complication-presence group(p=.045).

Conclusions: Multifidus degeneration is significantly associated with QoL, sagittal parameters and mechanical complications in OVCF patients with kyphosis deformity. The pathological changes of paravertebral muscles should be included in the surgical strategy and postoperative paravertebral muscle rehabilitation should be adopted to improve the clinical outcomes of OVCF patients.