Causes of lower extremity weaknesses after posterior lumbar spine fusion surgery and therapeutic effects of active surgical exploration

Background This study was aimed at investigating the causes of lower extremity weaknesses after posterior lumbar spine fusion surgery and looking at subsequent treatment strategies. Methods Patients who underwent posterior lumbar spine fusion surgery in the Peking University First Hospital between January 2009 and December 2018 were counted. Those who needed secondary surgery because of subsequent lower extremity weaknesses were selected. CT scans and MRIs were used to evaluate the reasons for weaknesses before secondary surgery. Muscle strength was evaluated after surgery. Results Thirty patients (30/4078, 0.74%) required a secondary surgery because of lower extremity weaknesses after posterior lumbar spine fusion surgery. The main causes of weakness were (1) internal fixation malposition and loosening (11 patients, 36%), (2) epidural hematomas (9 patients, 30%), (3) insufficient decompression (5 patients, 17%), and (4) nerve root edemas (5 patients, 17%). Weakness occurred on average 2.9 days after surgery (1–9 days). Twenty-seven patients (90%) got improved muscle strength after their secondary surgery. Conclusions Iatrogenic neurologic deficits and lower extremity weaknesses were rare complications after posterior lumbar spine fusion surgeries, but important to recognize and manage. The main causes of weakness were internal fixation malposition and loosening, epidural hematomas, insufficient decompression, or root edemas. There may be positive, therapeutic effects to subsequent, active surgical exploration.