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Accolade IIFemoral Hip Stem Design rationale

Accolade II femoral hip stem Design rationaleDesigned to fit more patients,designed to fit your approach.2

Accolade II femoral hip stem Design rationaleAddressing modern demandswith novel technology.The global THA population is evolving to includea younger1, more active2, and more demanding3patient. Many femoral stem designs on the markettoday predate the emergence of this novel demand.Subsequently, an opportunity to enhance theconventional femoral stem design exists.Conventional tapered wedge femoral stems haveachieved popularity due to their simplicity andexcellent clinical results4,5. Despite these results,literature indicates that there are still unmetclinical needs6,7,8. Incidence of subsidence6, distalonly implant engagement7, and peri-prostheticfracture8 suggest a clinical need for an improvedimplant fit for this novel patient population.Stryker, along with key industry leaders, embarkedto develop a novel femoral stem. This designwould build from the sound principles of taperedwedge philosophy to meet the unique needs ofthe current patient population. At the heart ofthis development was a unique technology calledStryker Orthopaedic Modeling and Analytics,or SOMA. As a system that enables populationbased design, SOMA has powerful functionalitywith which to design, model, and analyze novelorthopaedic devices.Stryker utilized SOMA technology to design anovel stem building upon the conventional taperedwedge femoral design, incorporating uniquefeatures to allow for an enhanced implant fit intoday’s patient population9. By establishing anincreased canal fit and fill9, Accolade II has beenshown to allow for improved stability10, decreasedintraoperative femoral fractures11, as well asexcellent survivorship and functional outcomes12,13,ultimately leading to satisfied patients13,14.3

Accolade II femoral hip stem Design rationaleSOMA technologyUtilizing the proprietary SOMA technology, Stryker was able to complete one of the largest proximalfemoral bone morphology studies ever undertaken13. An illustrated look at the process bywhich SOMA technology is employed in implant design is described below.4CT acquisitionSegmentationAnalysisThe SOMA database continues toaquire new CT scans, and currentlycontains over 16,500 bones14Once acquired, all bones aresegmented into inner andouter corticesUsing SOMA tools, bonemorphology can be studied in ahighly accurate and reproduciblemanner.Design inputValidationThe results of these studies, such as thepopulation Canal Flare Index, can beutilized in implant designThe resulting implant design canthen be validated using SOMA fittingtools.

Accolade II femoral hip stem Design rationaleThree key SOMA-designed featuresBone morphology data allowed Stryker an unprecedented look at femoral anatomy, andassisted in the design of a novel femoral stem. The SOMA input* was instrumental in theestablishment of three key design features of Accolade II:Unique size-specific medial curvatureincreasing proximal conformity to improve primarystability14,15Enhanced proximal-distal proportions16shown to mimic canal anatomy to avoid distal onlyengagement and achieve cortical fit8,16Optimized stem lengthenables muscle-sparing approaches withoutsacrificing stability15,17*SOMA-design of Accolade II based on 556 CT scans.5

Accolade II femoral hip stem Design rationaleUnique size-specific medial curvatureInitial stability is critical to long-term implantperformance6. Early subsidence and micromotionhas been established as a strong indicator for implantfailure6. Initial stability may be increased by creatinga higher conformity between the implant and thefemoral cortices, leading to a larger areaof contact19.Analyzing the SOMA morphology study data*, it wasobserved that a constant medial curvature may notallow for a conforming canal fit throughout varyingfemoral sizes.This population-based input influenced Stryker toincorporate the market’s first size-specific medialcurvature into Accolade II. This feature was designedto enable a more conforming proximal cortical fit15,which has been shown to allow for improved implantstability19.Using femurs from the SOMA database*, fit patterns of Accolade II can be comparedto conventional tapered wedge designs. The three examples below illustrate howAccolade II achieves a more conforming canal fit throughout varying bone sizes.Small femurAccolade II6Large femurMedium femurConventionaltapered wedgeAccolade IIConventionaltapered wedgeAccolade IIConventionaltapered wedge

Accolade II femoral hip stem Design rationaleEnhanced proximal-distal proportionsDistal-only engaged femoral stems can experience stress shielding19and consequently may lead to elevated failure rates due to looseningand migration9. In order to better mimic the femoral anatomy andavoid distal-only engagement, a more anatomic implant growth rateis needed.Utilizing the SOMA femoral morphology study*, a moreanthropomorphic proximal-distal stem growth rate was identified.This rate led to enhanced implant proportions13, as the distalgeometry of Accolade II increases in size less than the proximalgeometry. These proportions enable Accolade II to achieve asignificantly better canal fit and fill,9 and Accolade II has shown adecreased incidence of distal-only engagement9.Comparing implant fitIn the graph above, the proximal (P) and distal (D) measurements of a population of 556 femurs were plotted (blackdots) against the corresponding stem diameters of Accolade II (gold) and a conventional tapered wedge design (grey).Accolade II achieved more fully-conforming and proximal-only fit types compared to the conventional design, whilesubsequently reducing distal-only fit by 14%.167

Accolade II femoral hip stem Design rationaleOptimized stem lengthPopularity of muscle-sparing approaches and bone conserving fundamentals have led to a trend inshortening of stem length20. However, there exists a complex relationship between stem length andimplant stability20. Shortening stem length without geometry optimization has been shownto increase the potential for micromotion20, which is a strong indicator for implant failure6.Accolade II utilized the SOMA database* and stability analyses to establish an optimized length foreach stem size which not only accommodates muscle-sparing approaches20, but demonstratedimproved initial stability10.“simply shortening a standard tapered wedge designmay reduce the primary stability”17Mean % of HA coated stem surfacethat experienced micromotion 50μm1750%48.6% 12%44.6% 14%40.0% 12%35%Shortened tapered wedge stemConventional tapered wedge stemAccolade II8

Accolade II femoral hip stem Design rationaleDesigned to fit your approachMuscle-sparing surgical approaches continue to gain popularity,due to the potential patient benefits of faster recovery21,22, lesspain21,22 and greater satisfaction23.Stryker’s portfolio of muscle-sparing techniques features moderninstrumentation and dynamic Medical Education programs tosupport the Direct Anterior Approach and theDirect Superior Approach.The new Direct Superior Approach was designed for surgeons whoprefer the fundamentals and familiarity of the posterior approach,but seek to provide the next evolution in muscle-sparing THAsurgical techniques for their patients.Stryker has developed a training platform to help surgeons duringthe learning curve of a new surgical approach, Stryker’s TrainingAcademy.For access to Stryker’s Training Academy, contactyour local Stryker sales representative.9

Accolade II femoral hip stem Design rationaleClinical performance“Significantly better overall canal fit”9than conventional tapered wedge designover400,000implanted worldwide24over16,500bones*survivorshipfor Accolade II pursuantto a 3.5-year mean study12in SOMA database14less than0.1mmsubsidence pursuant to2-year RSA study101099.2%5xless intraoperativefracturesobserved compared toconventional tapered wedge11

Accolade II femoral hip stem Design rationale11