Stepwise reduction of bone mineral density increases the risk of cage subsidence in oblique lumbar interbody fusion patients biomechanically: an in-silico study.

BACKGROUND: Cage subsidence causes poor prognoses in patients treated by oblique lumbar interbody fusion (OLIF). Deterioration of the biomechanical environment initially triggers cage subsidence, and patients with low bone mineral density (BMD) suffer a higher risk of cage subsidence. However, whether low BMD increases the risk of cage subsidence by deteriorating the local biomechanical environment has not been clearly identified. METHODS: OLIF without additional fixation (stand-alone, S-A) and with different additional fixation devices (AFDs), including anterolateral single rod screws (ALSRs) and bilateral pedicle screws (BPSs) fixation, was simulated in the L4-L5 segment of a well-validated finite element model. The biomechanical effects of different BMDs were investigated by adjusting the material properties of bony structures. Biomechanical indicators related to cage subsidence were computed and recorded under different directional moments. RESULTS: Overall, low BMD triggers stress concentration in surgical segment, the highest equivalent stress can be observed in osteoporosis models under most loading conditions. Compared with the flexion-extension loading condition, this variation tendency was more pronounced under bending and rotation loading conditions. In addition, AFDs obviously reduced the stress concentration on both bony endplates and the OLIF cage, and the maximum stress on ALSRs was evidently higher than that on BPSs under almost all loading conditions. CONCLUSIONS: Stepwise reduction of BMD increases the risk of a poor local biomechanical environment in OLIF patients, and regular anti-osteoporosis therapy should be considered an effective method to biomechanically optimize the prognosis of OLIF patients.

Negative pressure pulmonary edema after percutaneous endoscopic interlaminar lumbar discectomy-a case report.

BACKGROUND: Negative pressure pulmonary edema (NPPE) is a rare complication that is more prevalent in young patients. NPPE usually results from acute upper airway obstruction, which is most commonly caused by laryngospasm during extubation. NPPE is characterized by the sudden onset of coughing, hemoptysis, tachycardia, tachypnea, and hypoxia, and is dramatically improved with supportive care, which prevents severe sequelae. To our knowledge, there is no report of a patient developing NPPE after percutaneous endoscopic interlaminar lumbar discectomy. CASE PRESENTATION: Herein, we report the case of a 22-year-old amateur basketball player with L5/S1 disc herniation who developed NPPE during extubation after general anesthesia for a minimally invasive spinal surgery (percutaneous endoscopic interlaminar lumbar discectomy). The NPPE was treated by maintaining the airway patency, applying positive-pressure ventilation, administering dexamethasone and antibiotics, and limiting the volume of fluid infused. The patient had an uneventful postoperative course, and was discharged to his home on postoperative day 3. CONCLUSIONS: Although NPPE is an infrequent complication, especially in patients undergoing percutaneous endoscopic interlaminar lumbar discectomy, this case report highlights the importance of early diagnosis and prompt treatment of NPPE to prevent the development of potentially fatal complications.