Abstract
Introduction
Achieving primary and long-term stability of femoral implant is critical for THA. This can be influenced by the shape and location of surface preparation as well as geometry. The Corail® stem has developed in 1986 in France, which is a straight quadrangular, and full HA coated standard titanium alloy stem featuring a metaphyseal tulip flare in combination with horizontal and vertical grooves. We have performed 75 THAs using it since May 2013. The purpose of this study was to evaluate radiographic changes of femur over time in Japanese patients after THA using this HA coated stem.
Materials and Methods
Between May 2013 and September 2015, we implanted 75 THAs using a Corail® stem (DePuy-Synthes) in 66 patients. Their ages at operation were 47 to 93 years (avg. 66.5 years). Durations of follow up were 6 to 34 months after implantation (avg. 13.7 months). Acetabular components were standard titanium alloy, either 37 Pinnacle Porocoat®, 19 Pinnacle Gription® (DePuy-Synthes), 8 Ranawat®, 5 Regenerex®, or 6 G7® (Zimmer-Biomet) uncemented cups. Heads were either 73 BIOLOX delta® ceramic (CeramTec) or 2 CoCr. Liners were either 56 Marathon® (DePuy-Synthes) or 19 E1® HXLPE (Zimmer-Biomet). We studied 74 hips except one hip which was revised due to infection at the time of 3 weeks after surgery. Postoperative radiographic evaluations were done at the time of 2, 4, 6, 9, 12 months and then every 6 months thereafter. We examined cancellous condensation, radiolucent line, osteolysis, cortical hypertrophy and stress shielding using both of plain X-ray and Tomosynthesis (Shimadzu, Japan).
Results
The stem size included #8 in two hips, #9 in seven hips, #10 in eleven hips, #11 in twenty three hips, #12 in thirteen hips, #13 in ten hips, #14 in seven hips and #15 in one hip. Four periprosthetic fractures occurred during surgery. There were three subsidences in combination with radiolucent line at Gruen Zone 1 (Fig. 1, 2 and 3). The cancellous condensation was observed in 25% of all at the time of 2 months, 63% at 4 months, 87% at 6 months and 100% at 9 months after surgery at Gruen Zone 2, 3, 5 and 6 (Fig. 4, 5 and 6). At the latest follow-up, osteolysis, cortical hypertrophy and stress shielding were no evident in each hip.
Discussion
Primary stability of the Corail® stem must be achieved in a bed of cancellous bone. ARTRO group recommends that the correct size is the size that fills the femoral cavity to within 1 to 2mm distance from the cortices in templating process. We followed this indication intraoperatively in early days, but we experienced three subsided cases that might be caused by this indication. In present, we emphasize to gain the surgical tip to feel both axial and rotational stability by the final broach rather than the indication in templating process. Radiological appearance of the remaining cancellous bed shows 0.5 to 1mm distance from the cortices and we don't have any stem subsidence after we changed out previous surgical technique.
