Multifidus Muscle Atrophy Predicts Spinal Cage Subsidence After Lumbar Fusion

Degenerative lumbar spondylolisthesis (DLS) is a common degenerative disease that causes low back pain and lower extremity pain. Transforaminal Lumbar Interbody Fusion (TLIF) is an effective surgical method for treating this condition. However, postoperative complications exist, such as cage subsidence, whose causes are complex. This study investigated the characteristics and risk factors of cage subsidence after TLIF in DLS patients.

A total of 131 TLIF patients were divided into the subsidence group (subsidence group, n=39) and the non-subsidence group (non-subsidence group, n=92). General patient data were collected, including sex, age, body mass index (BMI), surgical time, intraoperative blood loss, hypertension and diabetes. The imaging data collected included the degree of multifidus muscle atrophy (MMA) at the surgical segment preoperatively; the lumbar lordosis angle, segmental lordosis angle, and intervertebral height before surgery, immediately after surgery, and 12 months postoperatively. Univariable analysis and multivariable logistic regression analysis were used to identify independent risk factors for subsidence after TLIF in patients with DLS.

The degree of MMA before surgery in the subsidence group was significantly greater than that in the non-subsidence group (p< 0.001). There were statistically significant differences in the final follow-up Visual Analogue Scale (VAS) scores for lower back pain and postoperative Oswestry Disability Index (ODI) scores between the two groups. Intervertebral height correction (OR=11.19, p=0.0001), segmental lordosis angle correction (OR=3.43, p=0.0001), and MMA (OR=0.73, p=0.003) were all independent risk factors for cage subsidence.

Intervertebral height correction, segmental lordosis angle correction and MMA were identified as independent risk factors for cage subsidence after TLIF in patients with DLS. In clinical practice, preoperative physiotherapy and core muscle strengthening training aimed at improving the quality of the multifidus muscle can reduce MMA. Meanwhile, selecting an appropriate height for the interbody fusion cage and avoiding excessive correction of the lordotic angle can be used to reduce the incidence of interbody fusion cage subsidence after TLIF and improve patients' clinical outcomes.