L3 vertebrectomy noted with L2-L4 cage insitu. There is anterior and posterior instrumented fusion from L1 to L5 with bilateral rods and pedicle screws. A right lateral rod with screws is seen at L1 and L5. There is abnormal low T1, high T2 and Stir signal centred around the L2-L4 cage. This lobulated fluid signal tracks into the L3/L4 disc and laterally into the left psoas muscle which shows mostly heterogenous post contrast enhancement with smaller non enhancing necrotic areas. This is highly concerning for infection. The described findings were not present on the March 2020 study and is new. The collection extends along the inferior medial margin of psoas without clear encroachment into the spinal canal or posterior elements.
There is no evidence of macroscopic local disease recurrence.
Satisfactory appearances of the posterior rods and pedicle screws. The spinal canal dimensions appear adequate with no central canal stenosis. There is moderate bilateral (left >right) lateral recess narrowing at L4-L5, with potential irritation of the left L5 nerve root as seen previously. Small posterior annular tear of the L5/S1 disc with no overt disc bulge.
Conclusion:
Abnormal fluid signal centred around the L2-L4 cage tracking into the L3/L4 disc and left psoas muscle. The findings are highly concerning for loosening with infection of the cage device. Image guided biopsy of the left psoas collection is feasible if definitive microbiological confirmation is needed.