Anterior column reconstruction of the thoracolumbar spine with a new modular PEEK vertebral body replacement device: retrospective clinical and radiologic cohort analysis of 48 cases with 1.7-years follow-up.

PURPOSE: To evaluate whether a new PEEK vertebral body replacement can maintain the sagittal alignment as an anterior column reconstruction device in thoracic and lumbar spinal defects due to trauma or tumor. METHODS: Retrospective review of 48 patients who underwent a corpectomy between T5 and L5 due to trauma or tumor and were stabilized with the new PEEK vertebral body replacement, between 2013 and 2017. We excluded patients who underwent a corpectomy for infection or degenerative disease and patients without complete follow-up in our institution. The primary outcome was the bi-segmental kyphotic angle (BKA). Secondary outcomes were the assessment of pedicle screw loosening, cage height, and subsidence or tilting of the cage. The clinical outcomes were assessed through the COMI-Score, EuroQol-5D, and Karnofsky indexes. Bony fusion and complications were registered. RESULTS: After the surgery BKA decreased by 12.1° (p < 0.001). At the end of the follow-up, we observed a mean loss of reduction of 1.6° (p = 0.002). This was accompanied by an increase in subsidence of 2.1 mm (p < 0.001) and mean tilting of the cage of 1.4° (p = 0.003). The height of the cage and other parameters did not experience any changes. Clinically, the COMI-Score (p = 0.02) and the EuroQol-5D Index (p = 0.012) showed significant improvement, same as Karnofsky-Index (p = 0.015) at final follow-up. The fusion rate according to Bridwell was 92.1%. The 2% late complications were related to implant malpositioning. CONCLUSION: The new PEEK expandable vertebral body replacement is effective and safe in thoracic and lumbar anterior column reconstruction in tumor and trauma diseases.

Mechanical failure of 113 uncemented modular revision femoral components.

AIMS: We evaluated a large database with mechanical failure of a single uncemented modular femoral component, used in revision hip arthroplasty, as the end point and compared them to a control group treated with the same implant. Patient- and implant-specific risk factors for implant failure were analyzed. METHODS: All cases of a fractured uncemented modular revision femoral component from one manufacturer until April 2017 were identified and the total number of implants sold until April 2017 was used to calculate the fracture rate. The manufacturer provided data on patient demographics, time to failure, and implant details for all notified fractured devices. Patient- and implant-specific risk factors were evaluated using a logistic regression model with multiple imputations and compared to data from a previously published reference group, where no fractures had been observed. The results of a retrieval analysis of the fractured implants, performed by the manufacturer, were available for evaluation. RESULTS: There were 113 recorded cases with fracture at the modular junction, resulting in a calculated fracture rate of 0.30% (113/37,600). The fracture rate of the implant without signs of improper use was 0.11% (41/37,600). In 79% (89/113) of cases with a failed implant, either a lateralized (high offset) neck segment, an extralong head, or the combination of both were used. Logistic regression analysis revealed male sex, high body mass index (BMI), straight component design, and small neck segments were significant risk factors for failure. Investigation of the implants (76/113) showed at least one sign of improper use in 72 cases. CONCLUSION: Implant failure at the modular junction is associated with patient- and implant-specific risk factors as well as technical errors during implantation. Whenever possible, the use of short and lateralized neck segments should be avoided with this revision system. Implantation instructions and contraindications need to be adhered to and respected. Cite this article: Bone Joint J 2020;102-B(5):573-579.