Factors of cage migration after posterior lumbar interbody fusion and strategies for reoperation
Objective To analyze the main influencing factors of cage migration after posterior lumbar interbody fusion and the strategies for reoperation.Methods A retrospective analysis was conducted on 1 214 patients with degenerative lumbar dis-eases who underwent posterior lumbar decompression pedicle screw fixation interbody fusion surgery from January 2017 to De-cember 2021.Patients with backward displacement of the metal marker at the posterior margin of cage ≥2 mm at the first postop-erative lateral X-ray and postoperative follow-up were labeled as cage displacement group,and 100 patients without cage migra-tion were randomly selected as the non-migration group.The basic information of the two groups of patients,the average inter-vertebral height before and after surgery,lumbar lordosis angle,difference in intervertebral disc height before and after fusion,screw loosening,cage insertion depth,and number of fused segments were compared.Results All patients were followed up for an average of 11.3 months,ranging from 6 to 18 months.Postoperative cage migration occurred in 21 cases,of which 4 cases required reoperation.The segments for reoperation were L3 4 in 1 case,L4 5 in 2 cases,and L5S,in 1 case.One case experienced cage migration again after the first revision surgery,necessitating a second revision surgery.The mean intervertebral height be-fore and after surgery in the cage migration group(n=21)was higher than that in the non-migration group(n=100),with statisti-cally significant differences(P＜0.05),indicating that choosing a relatively smaller cage is a factor influencing migration.In addi-tion,osteoporosis,insufficient insertion depth,screw loosening,pear-shaped intervertebral space,and cage migration after long-segment fixation also had significantly higher probabilities,with statistically significant differences(P＜0.05).Conclusion cage migration after posterior lumbar interbody fusion surgery is the result of multiple factors.Osteoporosis,relatively smaller cage,insufficient insertion depth,"pear-shaped"intervertebral space,long-segment fixation,and loosening of internal fixation are the main risk factors for cage migration after fusion.Revision surgery should identify the main factors causing cage migration and develop individualized reoperation plans.The key factors for successful revision surgery include the removal of the cage without additional injury,re-preparation of the intervertebral space and pedicle,and restoration of lumbar lordosis angle.
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