Abstract
Modularity in femoral revision stems was developed to reduce subsidence, leg length discrepancy and dislocation experienced in revision surgery. The Wagner SL Revision Stem (Zimmer, Warsaw, IN) has been known for excellent bony fixation and proximal bony regeneration, but the third-generation proportional neck offset and 135° neck-shaft angle has an unknown track record. Our aim is to study the effect of these design modifications on stem subsidence, dislocation rate and stem survival.
We reviewed 76 consecutive femoral revisions (70 patients; 50 M: 20 W; 67.7 yo [range; 37.7 – 86.6 yo]) with the Wagner SL implanted at our institution (2004–2012). No patient was lost to follow-up, but nine had died, and one patient was excluded for a Paprosky type I femoral bone defect. This leaves us 66 hips (60 patients) at 2 to 9.5 years of follow-up (mean 55 months; range, 24–114 months). Indications for revisions included aseptic stem loosening (62.1%), infection (13.6%), acetabular loosening (12.1%), recurrent dislocation (4.5%), periprosthetic (4.5%) and stem fracture (1.5%), and chondrolysis (1.5%). Patients were actively followed up at regular intervals to ascertain revision status and outcome measures including the Merle d'Aubigné (n=53), WOMAC questionnaires (n=59) and radiographs (n=66). Radiographs were evaluated for stem subsidence (mm).
One of the surviving 66 stems was revised for recurrent deep infection (1.5%). No patient underwent revision of the femoral stem for aseptic loosening or subsidence. The mean preoperative WOMAC scores (P: 12.8; S: 5.6; F: 51.8) had improved significantly at follow-up (P: 9.7;, S: 4.3; F: 37.6) (p<0.05). The mean Merle D'Aubigné score went from a pre-op of 8.2 (SD: 2.8; range 1 to 14) to a mean of 15.3 (SD: 2.6; range 7 to 18) (p<0,05) at the latest follow-up. During the follow-up period, 3 hips dislocated (4.5%). Each event happened prior to six months after surgery. Only one of these cases dislocated twice. Closed reduction was performed in all cases. None required revision surgery subsequently, and they all remained stable. The stem survivorship is 98.4% at 5 years (0.95 CI: 93–100) and 97.4% at 7.5 years (0.95 CI: 88.9–100). Stem subsidence of 0 to 5 mm was considered as not clinically significant (n=20; 30%). Stem subsidence of 5 to 10 mm occurred in 5 hips (7.6%)and stem subsidence greater than 10 mm only occurred in one hips (1.5%).
The third generation Wagner SL conical revision femoral stem has a lower rate of complication than its preceding generations, and is comparable to modular stems performance reported in current literature. These results motivate the authors to continue using monoblock conical revision femoral stems.
