Evaluation of the biomaterial-interface of screw threads in patients having clinical pain.

Fixation devices are normally anchored and stabilized with the use of metallic screws. Under normal circumstances, the patient has no adverse response to the fixation device. However, there are some patients that experience a significant amount of pain and the hardware needs to removed. Removal of the hardware, alleviates the pain. The tissues adjacent to the implanted devices were harvested and analyzed histochemically for cellular detail and immunochemically for the presence of PGE2. These tissues were compared with tissues retrieved from nonpainful stable fixation devices that were removed when they no longer were needed for stabilization. The results showed radiographically the presence of osteolysis in the area of the screw thread in patients with clinical pain. Also, histologically there was a presence of synovial-like granuloma tissue possibly produced by the micromotion of the loosened screw. When the tissues were analysed qualitatively by ELISA for PGE2 they had a statistically significant amount in comparison with tissue retrieved from patients with no clinical pain. The presence of PGE2 in the tissues suggest that this inflammatory mediator is produced in tissues adjacent to unstable devices and may mediate the osteolysis associated with the late implant failure and clinical pain.