Osteointegration of an uncemented modular revision stem implanted during revision hip surgery

Though mid-term survival rates of over 95% in several series have been published, there is still a paucity of related literature regarding the role of vertical stem instability in the osteointegration of fluted tapered stems. This paper presents a comprehensive and prospective assessment on short-term experiences with uncemented modular femoral stem in the treatment of defective femur during revision surgery of total hip replacement.

Clinical and radiological monitoring of 20 consecutive patients with implanted tapered fluted revision stem (Lima Corporate, Udine, Italy) was of 27 months in average (20-35 months). The average pre-operative Merle d'Aubigné and Postel method score was 6.3 points (3-10 points). The frequency of femur defects, classified according to Paprosky, was IIIA = 9 and IIIB = 11.

During last follow-up, the Merle d'Aubigné and Postel hip score was on average 11.7 (6-16 points). Compared to post-operation radiograph, stem migration of 1.9 mm (0-11 mm) on average was found. This vertical stem migration was observed only when comparing hip radiographs immediately after surgery, and at 6 weeks post-surgery. The Paprosky IIIA defects group, presented a subsided stem by an average of 1.5 mm. In the group of Paprosky IIIB defects, the stem subsidence was on average 2.3 mm. All 20 patients in the study showed excellent osteointegration of the uncemented revision modular stem.

This study found and excellent osteointegration of the Lima uncemented tapered fluted revision modular stem in defective femur with a cortical bone segment present in the diaphyseal isthmus area. The initial vertical instability leading to stem migrating during the first six weeks following surgery did not, however, affect its osteointegration.