A 30-mm Cemented Stem Extension Provides Adequate Fixation of the Tibial Component in Revision Knee Arthroplasty

The optimal stem length and method of fixation for the tibial component in revision knee arthroplasty remains controversial. The use of a cemented 30-mm stem extension provides certain advantages compared with other methods of fixation, but there are few published results. We therefore asked (1) what is the survivorship (with respect to loosening and repeat revision) of tibial component revisions when a 30-mm stem extension is used; and (2) what factors are associated with the appearance tibial radiolucent lines? We retrospectively reviewed 54 patients (58 knees) with fixation of the revision tibial component with a 30-mm cemented stem extension; another seven patients died and 11 patients had these components but were lost to followup. These implants represented 74% of our tibial revisions during the period in question (76 of 103); general indications for using them were need for a varus-valgus constrained liner or proximal bone loss requiring a metaphyseal cone or metal augment with an intact diaphysis. The Anderson Orthopaedic Research Institute tibial defect was Grade 1 in 37, 2A in 10, 2B in four, and Grade 3 in seven knees; constrained liners were used in 34% (20 of 58 knees). Patients were evaluated and followed for a mean of 5 years (range, 2-12 years). There were no revisions for tibial component loosening. One patient had d,bridement and liner exchange for late infection. Radiolucent lines were seen in 25 tibial components but only eight knees had radiolucencies in four or more zones. There were significantly fewer radiolucencies in revisions that used metaphyseal cones (20 in eight knees with cones compared with 53 in 17 without, p = 0.013). The cemented 30-mm tibial stem extension provided excellent fixation in knee revision arthroplasty, even with metaphyseal defects and constrained polyethylene liners, although this series included relatively few patients with severe tibial defects. Longer followup is required for patients with radiolucent lines to confirm that the fixation will remain durable. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.