Heritage meets progress
AMIStem-P is the evolution of a successful and proven femoral stem concept, originally born to simplify the AMIS approach without compromising implant stability.
On the basis of the remarkable clinical heritage of AMIStem-H, AMIStem-P was developed with the goal of providing an improved load transfer through the application of a state-of-the-art coating (MectaGrip) on the proximal part of the stem, to be able to better address the modern challenges in THA. The AMIStem-P System features also a collared (AMIStem-P Collared) and a cemented (AMIStem-C) version.
AMIStem-P maintains the same geometry as the AMIStem-H. Its triple tapered design characterized by a reduced lateral flare and an optimized length, which allows for reduced bone removal and for an easier stem implantation when utilizing the AMIS approach without compromising implant stability based on the clinical experience of straight, rectangular cementless hip stems.
AMIStem-H’s solid clinical history[1,2,3] laid the groundwork for the development of AMIStem-P.
Since 2009 more than 150,000 cementless AMIStem have been implanted:
MectaGrip coating aims to provide an enhanced proximal fill at the metaphyseal level, and a mechanically stronger bone implant interface, this results in potentially improved load transfer.[4]
The whole endosteal part of the stem is Hydroxyapatite coated.[5,6,7,8,9]
Young and active patients are the toughest challenge in THA today. The revision rate for patients younger than 55 years is significantly higher across pathologies.[17]
Mechanically stronger bone implant interface can help meet these challenges allowing higher loads to be transferred.
Literature tells us that femoral offset should increase progressively with stem size. AMIStem’s neck length increases size by size to allow for anatomical head center growth and to efficiently restore the hip joint biomechanics in a growing patient population. Vertical offset does not change when adding lateral offset for each size implant, thus leg length is not affected when changing from standard to lateralized.
11 Standard sizes (from 00 to 9) with a 135° CCD angle
9 Lateralized sizes (from 0 to 8) with a 127° CCD angle
11 Standard sizes (from 00 to 9) with a 135° CCD angle
9 Lateralized sizes (from 0 to 8) with a 127° CCD angle
9 Standard sizes (from 0 to 8) with a 135° neck-shaft angle
9 Lateralized sizes (from 0 to 8) with a 127° neck-shaft angle
AMIStem-P and AMIStem-P Collared are made of Titanium Niobium Alloy (Iso 5832-11) and sandblasted along its length, producing a surface with 2.5 to 6µm roughness. Successively a layer of MectaGrip, 300µm of pure Titanium deposited through Plasma Spray technology, is applied on the proximal 50% of the stem. Finally, 80µm of Hydroxyapatite (HA) is applied to the entire length of the stem.
MECTAGRIP
Professor William Walsh’s animal study[4] demonstrates how a surface treated with MectaGrip coating can achieve a stronger bone implant interface compared to a surface treated with Hydroxyapatite alone.
AMIStem-C is made of mirror polished High Nitrogen Stainless Steel.
NECK
The mirror polished surface helps minimize soft tissue damage and liner wear.
SHAPE
The triple tapered design provides axial and rotational stability.[11,12]
The trapezoidal shaped cross-section is designed to help promote effective stability and facilitate preservation of bone vascularization, since the diaphysis is not completely filled.[13,14,15]
TIP
The bullet-shaped distal tip facilitates insertion and decreases risk of damaging the inner cortex.
SURFACE TREATMENT
AMIStem-P & AMIStem-P Collared: macrostructures help increase stability and enhance contact surface area by 10-15%.[12]
AMIStem-C: mirror polished surface helps to prevent the formation of cracks or gaps in the cement mantle.[6]
COLLARED OPTION
Helps to prevent subsidence in patients with Dorr Type C bone and helps increase rotational stability.
The anterior approach, supported by years of clinical experience[16], 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, to make it more straightforward and enhance 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 surgeon. AMIStem-P will enter you into Medacta International’s world of the AMIS Experience.
[1] Everett S, Afzal I, Dora C, Crawfurd E, Field R. Medacta AMIStem: International, Multicentre, Prospective, Observational Study - ODEP Study 5 Year Results. EFORT 2017 Vienna.
[2] Viè P. AMIStem-H Radiological Assessment 5 Years Outcomes. Data on file: Medacta.
[3] Retrospective and prospective study to evaluate the AMISTEM H performance”, study approved by Swiss Ethic (Zurich canton) on 24 of March 2016 (BASEC-Nr 2015-00132).
[4] Prof. W.R. Walsh. Evaluation of implant fixation in an ovine model. Data on file: Medacta.
[5] Bonnomet F, Delaunay C, Simon P, Lefebvre Y, Clavert P, Kapandji AI, Kempf JF. Comportement d’un tige fémoral droite en arthroplastie totale primaire non cimentée de la hance chez les patients de moins de 65 ans. Rev de Chir Orthop 2001; 87:802-814.
[6] Hardy DC, Frayssinet P, Guilhem A, Lafontaine MA, Delince PE. Bonding of Hydroxyapatite Coated Femoral Prostheses. J Bone Joint Surg Br. 1991 Sep; 73(5):732-40.
[7] Hardy DCR, Delince PE. Aspects Radiologiques de l’Arthroplastie Fémorale Revetue d’Hydroxyapatite et correspondence Histologiques Acta Orthop Belg. 1993; 59(1):229-334.
[8] Hardy DCR, Frayssinet P, Delince PE. Projection d’Hydroxyapatite sur Prothèses Articulaires : Progrès ou Illusion ? Acta Orthop Belg. 1993; 59(1):98-103.
[9] 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.
[10] 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.
[11] Heidelberg Lab-Report. Orthopädische Universitätsklinik Heidelberg, 2008. Data on file:Medacta.
[12] 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.
[13] Moreau P. Cementless HA coated Quadra stem - 7 Years Clinical Outcomes. M.O.R.E. Journal, 2012 Jan; 2:3-6.
[14] Zweymüller K. 20 years of Zweymüller cement free hip endoprosthesis. Jatros Orthopädie 1999 Dez; 5:2-7.
[15] Dorn U, Kiss H, Engelhardt C, Dohnalek C, Steindl M, Zweymüller K. Results of Femoral Revision THR using the SLR stem: Minimum 2 years follow-up. 20 years of Zweymüller hip endoprosthesis, 4th Vienna Symposium. Zweymüller K (ed) – Bern; Göttingen; Toronto; Seattle: Huber, 2002.
[16] AMIS Publication Review – M.O.R.E. Journal Supplement, April 2016. 99.98.publ rev.01
[17] Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty Annual Report 2017, AOA, Adelaide. Table HT17 and Figure HT7
