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Short cementless hip stem conserves bone in young patients, uses 3-point fixation
Mayo and Mayo-like designs show good clinical results at 2- to 3-year follow-up.
Uncemented bone-preserving short stem hip prostheses are among the choices available for young patients requiring a hip replacement.
“The short stem is an option,” Christoph Eingartner, MD, said. “It is a straightforward technique for a metaphyseal-fixed stem, and the hip stem orientation is also easy.”
One advantage of using a short femoral stem is that it conserves the greater trochanter and the ring of the femoral neck, Eingartner said at the 9th Annual Advances in Arthritis, Arthroplasty and Trauma Course.
Sparing bone and tissue
The biomechanical principles of the short hip stem are well understood, he said.
“It is a bone-preserving implant … and it allows for tissue-sparing techniques like the anterior or anterolateral approaches, and it is easy to perform through the less-invasive approaches,” he said.
The concept of a short femoral stem with three points of fixation that combat lateral stem antetorsion originated in the mid-’80s with the Mayo stem (Zimmer) designed by Bernard F. Morrey, MD. Today, other hip components such as the Metha (Aesculap) or Nanos (Smith & Nephew) femoral components successfully use the same short-stem principles, Eingartner explained.
Other “clinically proven” straight stems, including the Trilock (DePuy) and Taperloc (Biomet), recently became available in shorter versions.
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Results are in
Favorable 2- to 3-year results are available for some Mayo-derived prostheses. “But there are no long-term results with all those stems except the Mayo stem,” which has more than 10 years’ follow-up, he said.
When implanting a short-stem femoral prosthesis, surgeons should follow the direction of the femoral neck in both the anteroposterior and lateral planes to obtain proper orientation of the stem in the femoral canal, he added.
Surgical technique
Attaining optimal stem orientation can be performed by gradually opening up the femoral canal with an awl. When doing that, the optimal direction of the implant becomes evident by following the femoral neck to the dorsolateral cortex, Eingartner said.
He also suggested that surgeons “palpate the dorsal neck cortex in order to get an idea of the correct direction.”
To position the prosthesis, “It is important to orient it at the lateral aspect of the osteotomy with respect to the insertion depth,” Eingartner said. He recommended using an image intensifier during the early part of the learning curve for these short-stem procedures.
“For the Metha short stem, several modular neck options are available in order to address offset, antetorsion and leg length properly,” Eingartner told Orthopaedics Today Europe. “Support by hip navigation is also available to have all the geometric information available when deciding upon the modular neck component.”
The current generation of the Mayo-derived stems is designed with a distal curve that helps mitigate problems, like lateral femoral perforation, which are sometimes seen with short but straighter femoral stems, Eingartner noted.
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Images: Eingartner C |
For more information:
- Christoph Eingartner, MD, medical director, Caritas Hospital, can be reached at the Unit for Trauma and Reconstructive Surgery, Uhlandstrasse 7, Bad Mergentheim, Germany; +49-7931-58-3001; e-mail: christoph.eingartner@ckbm.de. He has no direct financial interest in any products or companies mentioned in this article.
Reference:
- Eingartner C. Short stem techniques in THA. Presented at the 9th Annual Advances in Arthritis, Arthroplasty and Trauma Course. Sept. 10-12, 2008. Arlington, U.S.A.