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A Minimally Invasive
Preserving Solution
The optimal reconstruction of the individual anatomy and biomechanics of each patient is a crucial part in THA. The SMS femoral stem has been designed to meet today’s THA challenges in a growing patient population [1].
SMS is a bone-preserving short metaphyseal-fitting cementless femoral stem, available in both collarless and collared versions. The stem is designed to achieve a more physiological proximal load transfer and restore the individual anatomy of the patient [1, 2]. The SMS’s stem design has been determined and validated based on the analysis of anthropometric data of hundreds of 3D femoral models collected in the MyBody database [2, 3].
As part of the P-Family Hip System, together with AMIStem-P and QUADRA-P, SMS represents a valuable solution for patients with good bone quality, especially young and active patients with Dorr A and B+ femurs. SMS’s reduced length design and distinctive curvature allow this stem to be the optimal choice for all MIS procedures, such as the AMIS approach.
SMS’s optimized design, characterized by an anatomic shape and a distinctive curvature, has been conceived to easily position the implant according to the AMIS technique and potentially reduce the risk of calcar fractures. Thanks to the high fit and fill, the stem adapts its position to the morphology of the proximal femur of the patient by means of a methapyseal press-fit in the intertrochanteric region. MectaGrip coating strengthens the bone-implant interface, resulting in a potentially improved load transfer [4,5].
The SMS’s shortened stem length and reduced distal geometry allow for preservation of more bone tissue distally than a traditional primary stem, while ensuring an efficient restoration of the joint biomechanics and leaving more options for any potential future revision surgery.
The SMS’s reduced length design and distinctive curvature allow this stem to be the optimal choice for all MIS procedures. Both the instruments and implants have been specifically designed to reduce the risk of damaging soft tissues when using the MIS techniques, especially the AMIS approach.
Literature tells us that femoral offset should increase progressively with stem size.[6]
The SMS’s comprehensive product range and anatomically progressive head center growth help to obtain an efficient restoration of the joint biomechanics in a wider patient population.
* The CT and MRI scans contained in the “MyBody” database are anonymous and do not permit in any way the identification of patients. Medacta recognizes the importance of personal data protection and considers
that preserving the confidentiality of personal data is one of the main objectives of its activity, in compliance with any applicable privacy law and regulation.
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15 STANDARD sizes (from 1 to 15) with 135° CCD angle
15 LATERALIZED sizes (from 1 to 15) with 127° CCD angle
The SMS comprehensive product range and anatomically progressive head center growth (≈1mm/size) help to obtain an efficient restoration of the joint biomechanics in a wide patient population [6].
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Vertical offset does not change when adding lateral offset for each implant size; therefore, the leg length is not affected when changing from standard to lateralized stem.
The collar is designed to be positioned at a 1 mm distance from the medial calcar. In this condition, load transfers through the triple taper body of the stem and the biomechanical behavior are identical to a collarless stem. In the case of implant subsidence, the collar comes in contact with the calcar bone, thus contributing to axial and rotational stability of the stem.
SMS is made of Ti-6Al-7Nb Alloy (ISO 5832-11) and is sandblasted along its length, producing a surface roughness between 2.5 and 6 μm. Successively, a 300 µm layer of MectaGrip, pure Titanium deposited via Plasma Spray (PS) technology, and an 80 µm outer coating of hydroxyapatite (HA) are applied on the shaft, except for the polished distal tip.
MECTAGRIP
MectaGrip is a coating treatment of commercially pure titanium deposited via a plasma spray (PS) technology. Plasma spray coating is one of the most clinically proven surfaces to achieve sound fixation in cementless THA.
Professor William Walsh’s animal study demonstrates how a surface treated with MectaGrip coating can achieve a stronger bone-implant interface compared to a surface treated with hydroxyapatite only.[4,5]
The distinctive anatomical curvature in the frontal and transverse planes has been conceived to allow for an optimal stem fit along the calcar arch, enhance load transfer laterally, and potentially reduce the risk of perioperative fracture.
The SMS’s anatomical calcar curvature in the frontal plane is proven by the successful clinical experience of the AMIStem and QUADRA femoral stem design.
The distal curvature of the stem changes with a medially-relieved distal geometry, while keeping a continuous lateral curvature.
SMS’s reduced distal geometry and shortened length allow for easy insertion, regardless of the surgical approach, prevent distal fixation and minimize the risk of thigh pain.
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Triple tapered design with a trapezoidal cross-section provides axial and rotational stability, and a high fit & fill in the metaphysis, enabling proximal transfer of force.[7,8,9,10]
The MectaGrip coating enhances proximal fit at the metaphyseal level, and creates a stronger bone-implant interface, allowing for an improved load transfer [4, 5,7,11,12,13]. Professor William Walsh’s animal study demonstrates how a surface treated with MectaGrip coating can achieve a stronger bone-implant interface compared to a surface treated with hydroxyapatite only [5].
The anterior approach, supported by years of clinical experience[14], is the only technique that follows an intermuscular and internervous path, potentially reducing the risk of damage to periarticular structures such as muscles, tendons, vessels and nerves. Convinced of the value of the anterior approach for improving patient well-being, but at the same time acknowledging the potential challenges in its adoption, an international group of expert surgeons, in collaboration with Medacta, set out to optimize and standardize the anterior approach, with the aim of making it more straightforward and enhancing its reproducibility.
The result of this collaboration was the AMIS (Anterior Minimally Invasive Surgery) technique, created in 2004, along with the development of dedicated instrumentation to facilitate the procedure. Today, the AMIS technique has evolved into the AMIS Experience and is now more than just a surgical technique. The AMIS Experience is a complete set of services that delivers healthcare efficiencies, including economic and commercial advantages, to the hospital and the surgeon. SMS will introduce you to Medacta International’s world of the AMIS Experience.
The SMS is part of the P-Family Hip System, which is the core of the Medacta Hip Implants portfolio. The Medacta offering embraces a Personalized Medicine Vision with a comprehensive platform for a personalized care experience with a Holistic Approach. Innovative implants, surgical technique and technologies bring value throughout the entire patient journey.
[1] Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty Annual Report 2020, AOA, Adelaide.
[2] Data on file: Medacta.
[3] J. Eijkenboom, P. Tomaszewski, D. Janssen, N. Verdonschot. Short Medacta Stem Pre-clinical assessment of bone remodeling and in growth potential - a finite element analysis.
[4] Walsh WR et al, Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone. Journal of Orthopaedic Surgery and Research (2020) 15:177.
[5] Comparison of titanium coatings for cementless fixation in an ovine model – Medacta M.O.R.E. Journal White Papaer (October 2019) – Pr. Walsh study.
[6] Piriou P, Bugyan H, Casalonga D, Lizée E, Trojani C, Versier G. Can hip anatomy be reconstructed with femoral components having only one neck morphology? A study on 466 hips. J Arthroplasty. 2013 Aug;28(7):1185-91.
[7] Moreau P. Cementless HA coated Quadra stem - 7 Years Clinical Outcomes. M.O.R.E. Journal, 2012 Jan; 2:3-6.
[8] Zweymüller K. 20 years of Zweymüller cement free hip endoprosthesis. Jatros Orthopädie 1999 Dez; 5:2-7.
[9] Heidelberg Lab-Report. Orthopädische Universitätsklinik Heidelberg, 2008. Data on file: Medacta.
[10] Löhr JF, Schütz U, Drobny T, Munzinger U. Revision Arthroplasty with the SLR-Revision Shaft. 20 years of Zweymüller hip endoprosthesis, 4th Vienna Symposium. Zweymüller K (ed) – Bern; Göttingen; Toronto; Seattle: Huber, 2002.
[11] Hardy DCR, Delince PE. Aspects Radiologiques de l’Arthroplastie Fémorale Revetue d’Hydroxyapatite et correspondence Histologiques Acta Orthop Belg. 1993; 59(1):229-334.
[12] Hardy DCR, Frayssinet P, Delince PE. Projection d’Hydroxyapatite sur Prothèses Articulaires: Progrès ou Illusion? Acta Orthop Belg. 1993; 59(1):98-103.
[13] Fraissinet P, Hardy D, Conte P, Delince P, Guilhem A, Bonel G. Histological analysis of the bone-prosthesis interface after implantation in humans of prostheses coated with hydroxyapatite. The journal of Orthop Surg. 1993; 7(3):246-53.
[14] AMIS Publication Review – M.O.R.E. Journal Supplement, April 2016. 99.98.publ rev.01.
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