Introduction: Osteolysis is a silent disease with few clinical symptoms until significant bone loss has occurred. Advanced osteolysis, with associated bone loss, can make revision surgery more difficult and compromise the ultimate outcome. In order to delineate the natural history of screw osteolysis in the AMK (Anatomic Modular Knee, Depuy) TKA, a cohort of patient were followed prospectively to determine the incidence and progression of osteolysis.

Methods: Between October 1987 and November 1992, 370 patients had 450 uncemented AMK TKA performed at a single institution. Attempts were made to contact all patients in 1993 and 228 patients (280 TKA) agreed to participate in the study. Flouroscopically guided tangential views of the tibial tray were performed and any osteolysis was catalogued by location and graded based on the classification of Lewis et al. Eighty-seven knees had osteolysis for an incidence of 31%, with 52 line, 23 cyst, and 12 cavity. The patients with osteolysis were reassessed 3 years later. No progression was noted in patients with line osteolysis, but two patients with cyst and two patients with cavity had progressive osteolysis. Five knees had been revised for symptomatic osteolysis.

This cohort was reassessed by chart and radiograph review in 2000. All patients who initially had cavitary osteolysis had been revised. In addition, 13 patients with cyst osteolysis progressed to cavity and ten knees had been revised. Of the 52 knees that had line osteolysis, 21 progressed to cyst or cavity and 15 knees were revised. Furthermore, 57 additional knees had developed osteolysis with 24 knees being revised.

Osteolysis in the AMK is a silent and progressive disorder. We were unable to identify any risk factors that would classify certain patients as at risk for osteolysis. Consequently, we recommend regular periodic follow up in order to recognize osteolysis early.