P R O D U C T R A T I O N A L E

E C H E L O N ® P R I M A R Y H I P S Y S T E M

A D D R E S S I N G

C L I N I C A L I S S U E S

O F C E M E N T L E S S

H I P

A R T H R O P L A S T Y

Echelon Primary Total Hip System

Cementless total hip arthroplasty has provided aproven method of treatment for several decades.

The Echelon Primary Hip system incorporatesthe design concepts learned throughout thisperiod to offer a femoral implant system thataddresses the clinical needs of both surgeons and patients alike.

By offering dual offset implants in 1 mm incre-ments and simple yet precise instrumentation,the Echelon Primary Hip system offers the surgeon unprecedented intraoperative flexibility.For the patient, Echelon Primary stems aredesigned with the goal of providing long-term,pain-free restoration of joint function and normal hip biomechanics.

1

STANDARD OFFSETHIGH OFFSET

2

System Features

The Echelon Primary total hip system has been designedto simply address the clinical issues surrounding totalhip arthroplasty.

Well-Designed ImplantsMany surgeons favor a cylindrical stem design. Stems of this configuration have shown excellent long-term clinical results using diaphyseal biologicfixation.1, 2, 3 An extensively porous coated cylindricalstem offers many advantages.

• Solid fixation in the consistent cannular portion of the diaphysis.

• Simple, reproducible surgical technique.• Proven long-term clinical results.

Echelon implants also incorporate many design featuresthat help the clinical success of the prosthesis.

• 1 mm increment sizes to precisely fit theimplant to the patient, and not the other way around.

• Dual offsets for proper joint tension.

• Optimized medial curve to fill theproximal femur and avoid confusion.

• Threaded driver hole that accepts a locking stem inserter for implant control during insertion.

Surgical TechniqueEchelon instruments have been designed to provide exact and reproducible results. Sharp reamers in 0.5 mm increments allow precise preparation of the femoral canal and permit the surgeon to choose the amount of press fit. Precision ground broaches easily prepare the proximal femur for the implant.

A simple surgical technique avoids OR confusion.The prosthesis that is implanted is the same size as the final reamer and broach that are used.

3

Comprehensive SystemEchelon Primary implants are part of a family offemoral stems that address primary and revisionsituations. With one set of instruments, a varietyof stems can be implanted.

Acetabular OptionsReflection® Acetabular SystemReflection acetabular shells and liners offer the perfect complement to the Echelon system.Available in a variety of options, each Reflectionshell has a polished inner surface and uses theMicroStable® liner locking mechanism whichsecurely holds a selection of liners.

Femoral Head OptionsCobalt Chrome and Zirconia femoral heads precisely fit the 12/14 taper onthe Echelon Primary stem.

Smith & Nephew femoral heads offer an additional 19 mm of adjustment to ensure proper joint tension.

POROUS PRIMARY

CEMENTED REVISION

POROUS REVISION

4

Addressing Implant Fixation

MICROMOTION

Mic

rom

otio

n (µ

m)

120.0

100.0

80.0

60.0

40.0

20.0

00.0

Trial number1 2 3 4

This 2-3 bead layer coating has 30% average porosityand 270 microns averagepore size which has beenshown to be successful inbone in-growth.6

Immediate and continued fixation of a total jointprosthesis has been correlated to the long-term clinical success of an implant.4 Rough porouscoating covers 2/3 of the Echelon Primary stem,along with distal flutes to help the implant achieveshort-term and long-term biological fixation.

Porous CoatingCircumferential rough porous coating of sintered beads (RoughCoatTM) covering 2/3 of the stem increases the friction between the implantand bone, improving implant stability and provid-ing a porous surface for bone ingrowth. This helpsreduce the initial movement of the prosthesis andresults in implant stability which contributes to a lower incidence of pain.5

Rotational Stabil ityDistal flutes help increase rotational stability byproviding immediate fixation upon implantation.The flutes on the distal portion of the stem are .25 mm larger than the porous coated diameter to provide extra penetration into the cortical bone for instant stability of the implant.

The Echelon design was compared to a 5/8 porous coatedcylindrical prosthesis for rotational stability. The distal flutesof the Echelon stem allowed significantly less rotationalmicromotion compared to the scratch fit of the 5/8 porouscoated prosthesis.7

Echelon5/8 coated stem reamed .5 mm5/8 coated stem reamed line-to-line

Distal flutes that are .25 mmlarger than the core diameter help achieve immediate implant fixation.

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Proximal Fil lThe proximal body of the Echelon Primary stem wasdesigned to work in conjunction with distal fixation.Based on a study of more than 100 radiographs, theproximal geometry of the stem provides optimum fill and easy insertion of the implant. This isaccomplished by incorporating a 3˚ A-P proximal flare and an optimized medial curve.

A .5 mm press-fit is achieved between the broach and the implant providing an interference fit and enhancing initial fixation.

Reducing Stem StiffnessThe effect of stem stiffness has been a concern of the long-term fixation of cylindrical stems. By design, cylindrical stems achieve tight distal fixation.However, this may lead to remodeling of the proximalfemur. Although this has not led to significantclinical problems, researchers have concluded that the performance of distal fixation stems can be enhanced with increased stem flexibility.8

Furthermore, by optimizing the porous coatinglength and overall stem length, tight distal fixationcan be achieved with less bone resorptive remodeling.9

This provides for a more anatomic fit of theprosthesis which may also reduce thigh pain.

Standard/ PorousHigh Offset Stem Coating

Size Length Length

11-12 130 mm 90 mm

13-14 140 mm 96 mm

15-17 150 mm 102 mm

18-19 160 mm 108 mm

LENGTH MEASUREMENTS

Echelon Primary stems are proportionally sized to better match patient anatomy and conserve bone.

Echelon has a 3˚ proximal anterior/posterior flare toimprove proximal fill, without preventingimplant seating.

Design features such as the coronal slot help decrease theoverall stiffness of the stem which maylead to less proximalstress shielding anddecreased end-of-stemthigh pain.

Medial curves start at a higher locationthan other designs to avoid impingement.One optimized medial curve reduces O.R.confusion and delays.

30 20 10 0mm

Design 1

Design 2

11.8 mm

Echelon

6

Addressing Range of Motion

Maximizing the patient’s range of motion (ROM) without impingement of the prosthesis is an important clinical goal in preventing:10

• Increased poly debris which could lead to osteolysis

• Subluxation and possible joint dislocation• Prosthetic loosening• Dislodgement of a modular acetabular liner

Echelon Primary stems have been designed toaddress these range of motion issues throughimplant design.

Neck GeometryOptimizing neck geometry increases range of motion. The circulotrapezoidal neck on theEchelon Primary stem is designed to provide a greater range of motion than a circular neck. By using more material in the medial/lateraldirection where fatigue requirements are higher, and less material in the anterior/posterior direction where demands are smaller, the range of motion is maximized.

Head and Neck SizeProsthesis ROM correlates with the ratio of head diameter to neck thickness. It has been suggested that the minimum recommended ratio to achieve adequate range of motion is 2 to 1.11 To achieve the recommended ratio with a 28 mm head, the maximum neckdiameter should be 14 mm. The circulotrape-zoidal neck on the Echelon Primary helpsminimize neck thickness, thereby increasing ROM and reducing impingement which could lead to dislocation.

Cross-section comparison of optimized (circulotrapezoidal) and cylindrical necks.

Cylindrical

Circulotrapezoidal

L

A P

M

128û

Effect of neck size on ROM.

144û

Circulotrapezoidal Neck

Cylindrical Neck

7

144û

Large exposed tapers or skirted heads decrease prosthesis ROM up to 40 percent.12

102û 118û118°102°

144°

Optimized 12/14 TaperThe size of a taper connection affects ROM. EchelonPrimary stems have an optimized 12/14 taper that is buried inside the femoral head for increased rangeof motion compared to other taper designs. A largetaper that is exposed beyond the femoral head mayimpinge on the cup, limiting ROM. Skirted headsalso have a negative impact on range of motion.

AnteversionIt is not necessary to build anteversion into the neck of the stem to maximize range of motion. Built-in anteversion does not increase range ofmotion – it merely shifts the location of the ROM. With proper neck, taper, and acetabular liner geometry, a neutral stem neck can provide a greater ROM than a stem with a circular neck and built-in anteversion.

ROM for neutral circulotrapezoidal neck and antevertedcircular neck were mapped on a two-dimensional plane.

ECHELON 0 DEG

CYLINDRICAL �NECK DESIGN 10 DEG

FLEXION EXTENSION

ABDUCTION

ADDUCTION

Many details were considered when designing the Echelon Primary femoral implants. Clinicalperformance along with surgical concerns havebeen addressed in the implant design.

Femoral OffsetFemoral offset is an important clinical require-ment of proper joint function. When offset is not restored, medialization of the femur can occur resulting in impingement and possibleinstability.13 Furthermore, when offset is notrestored at the time of surgery, laxity of the soft tissues can occur resulting in weakness and possible dislocation.

Echelon Primary stems are offered in StandardOffset and High Offset configurations to provideproper joint tension without affecting leg lengthor surgical technique.

Femoral neck lengths are based on the Spectron®

Total Hip System which has 20 years of excellentclinical results.

Size RangeEchelon Primary stems are proportionally sized.Larger diameter stems are longer and have moreneck offset to accommodate the natural anatomy.

Distal Bullet TipThe bullet tip reduces the stress between the distal implant tip and the bone to minimize end-of-stem thigh pain.

Addressing Implant Design

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Implants are offered in 1 mmincrements (11-19 mm) tobetter fit the patient.

11 mm

19 mm

Driving PlatformThe Echelon implants feature a threaded drivingplatform with an elliptical slot for rotational andaxial implant control during insertion.

Shoulder ReliefA rounded shoulder has been incorporated into the design to ease insertion of the implant into the femur and reduce impingement of theimplant into the greater trochanter which could cause fracture of the bone.

MaterialAll Echelon implants are manufactured fromCobalt Chromium which allows for extensiveporous coating of the stem.

To address stiffness concerns of Cobalt Chrome,the Echelon design was tested in a 4-point bendconfiguration. The Echelon stem demonstrated areduced stiffness when tested in anterior/posteriorand medial/lateral directions.14

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STEM STIFFNESS

N/m

m

6000

5000

4000

3000

2000

1000

05/8 Coated Stem (13.5 mm) Echelon (15 mm)

A/P M/L

A four-point bend test was used to compare the stemstiffness of the Echelon design to a commonly usedfemoral implant.

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Addressing Surgical Instrument Design

Surgical instrument design is as equally important as the design of the implant itself. Echelon instruments have been designed to provide a simple, exact and reproducible surgical experience.

Proximal ReamerA special reamer has been designed to open theproximal femur to ensure that subsequent reamingstays lateral. This proximal reamer can also be usedto remove sclerotic bone.

ReamersSharp femoral reamers are available in .5 mmincrements for exact preparation of the femoralcanal. Clear depth marks indicate the appropriatereaming depth.

BroachesEchelon broaches feature a tooth pattern that has been ground on a 5 axis machine. This tooth arrangement helps move bone chips up and out of the femoral canal which makes bone preparation straightforward and facilitates cleaning.

Broach HandlesSecurely locking broach handles with a wide striking platform and a quick connect/disconnectfacilitate easy broaching of the femoral canal.

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Trial NecksTo avoid confusion, Echelon trial necks are designed to work with the corresponding size of broach. Magnets are also embedded into the trial neck so that it stays in place when put through trial range of motion.

Trial HeadsA wide variety of trial heads are available (22, 26, 28, 32 mm) to address soft tissue variability and surgeon preference. Femoral heads along with the optimized 12/14 taper have been designed to reduce the number of skirted femoral heads.

Stem InserterStem implantation is made easy with a rigid,threaded attachment mechanism. The locking stem inserter provides maximum control duringimplant seating.

Anteversion HandlesA simple, knurled handle threads into both the broach handle and stem inserter giving extra visualization and control during preparation and implantation.

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Addressing Surgical Technique

STEP 1.RESECT FEMORAL NECK WITH THE OSTEOTOMY GUIDE.

STEP 2.OPEN FEMORAL CANAL WITH BOX OSTEOTOME.

STEP 3.PERFORM INITIAL FEMORAL REAMING WITHCANAL FINDER AND MODULAR T-HANDLE.

STEP 4.REAM CANAL IN 0.5 MM INCREMENTS TO SELECTED SIZE.

STEP 5.BROACH FEMUR TO SIZE DETERMINED BY LAST REAMER USED.

3

4

5

13

STEP 6.REAM THE CALCAR BONE WITH THE CALCAR REAMER, IF NECESSARY.

STEP 7.PLACE THE TRIAL NECK ON THE BROACH AND PERFORM TRIAL REDUCTION.

STEP 8.ASSEMBLE THE IMPLANT TO THE THREADED STEMINSERTER.

STEP 9.SEAT THE IMPLANT TO THE DESIRED LEVEL.

STEP 10.PERFORM FINAL TRIAL REDUCTION.

STEP 11.ASSEMBLE THE FEMORALHEAD ON TO THE STEM.

Echelon, RoughCoat, Spectron, Reflection and Micro Stable are trademarks of Smith & Nephew, Inc. ©2000 Smith & Nephew, Inc. 04/00 7138-0649

Smith & Nephew, Inc. • 1450 Brooks Road • Memphis, TN 38116 U.S.A.(901) 396-2121 • For information: 1-800-821-5700 • For orders and order inquiries: 1-800-238-7538

www.smithnephew.com/echelon

POROUS / PRIMARY

POROUS / REVISION

CEMENTED / REVISION

REFERENCES

1. Engh, C., et al, Cementless Total Hip Arthroplasty Using the Anatomic Medullary Locking Stem, CORR, Number 249, December 1989.

2. Orthopedics Today, May 1997.

3. Engh, C., et al, Porous-Coated Total Hip Replacement, CORR, Number 298, January, 1994.

4. Whiteside, L. et al, The Effect of Collar and Distal Stem Fixation on Micromotion of the Femoral Stem in Uncemented Total Hip

Arthroplasty, CORR, Number 239, February, 1989

5. Bobyn J., et al, Producing and Avoiding Stress Shielding, CORR, Number 274, January 1992.

6. Kienapfel, H., et al, Implant Fixation by Bone Ingrowth, J of Arthroplasty, Vol. 14, No. 3, April, 1999.

7. Daigle, K. et al, Axial Insertion and Torque Testing of Two Fluted-Slotted Distal Designs, and Porous Coated Model in Simulated Cancellous

Bone, Smith & Nephew Technical Report, OR-96-15, March, 1996.

8. Otani, T., et al, Effects of Femoral Component Material Properties on Cementless Fixation in Total Hip, JOA, Vol. 8 Number 1, 1993.

9. Nishii, T., et al, Longitudinal Evaluation of Time Related Bone Remodeling After Cementless THA, CORR, Number 339, June, 1997.

10. Impingement in THA: The Effect of Neck Geometry and Acetabular Design, Smith & Nephew Technical Publication, September 1998.

11. Chandler, D., et al, Prosthetic Hip Range of Motion and Impingement, The Effects of Head and Neck Geometry, CORR. Number 166,

June 1982, pp. 284-291.

12. The Effect of Hip Implant Design Factors on the Incidence of Early Impingement, Smith & Nephew Technical Publication, December 1998.

13. McGrory, B., et al, Effect of Femoral Offset on Range of Motion and Abductor Muscle Strength After Total Hip Arthroplasty, JBJS, Vol. 77-B.

Number 6, November 1995.

14. Daigle, K, Flexibility Analysis, Smith & Nephew Technical Memo, TM105801, April, 1998.