Study design Report of case seriesObjective To report a problem with bioabsorbable poly-Llactide-co-D, L-lactide, PLDLLA, posterior lumbar instrumented fusion (PLIF) cage implants. Summary of background data Synthetic bioabsorbable implants have recently been introduced to spinal surgery and their indications and applications are still being explored. There is evidence that the use of bioabsorbable cages may be of benefit in interbody spinal fusion. Methods We present a case series of nine patients who have undergone PLIF with bioabsorbable cages in the lumbar spine. Results At follow-up over at least 1 year, four of these patients were found to have osteolysis around the implant on CT scanning. One of these patients underwent an operation to remove the cage and histology sent during surgery suggested that the implant had caused the bone loss and there was no evidence of infection. Another patient had ongoing pain in relation to the lysis, while the other two patients with lysis remained asymptomatic. Conclusions PLDLLA cage, which has high osteolytic nature, is considered not suitable as a fusion cage.