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Gender specific High flex knee replacement

Dr.A.K.VenkatachalamMS, DNB, FRCS, MCh Orth

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Knee replacement – basic facts

Nearly 30000 people undergo joint replacements in India per year with a 25% increase each year.

Knee osteoarthritis is the commonest indication for joint replacement.

Two thirds of population undergoing a TKR are women.

Requirements for TKR

Arthritis, injuries, infection cause deterioration of cartilage causing bone to grind on bone leading to severe pain.

Historically implants for TKR have been designed based upon an average between the size of women’s and men’s knees.

Knee replacements- Implant features so far

Knee implants come in various sizesMerely using a different size does not

address the shape differences.

Short comings of using Non gender specific knees

Even though most women are happy with their results after TKR, some still have residual pain in the front of the knee around the knee cap

Or they say their artificial knee doesn’t feel or move the way of their own knee when it was healthy.

Gender differences between men and women

Women are not smaller versions of menThey are shaped differentlyAlthough Women can wear men’s clothes and

shoes, they prefer to wear specially designed apparel.

Total knee replacement (TKR) involves resurfacing the worn out ends with metal and plastic implants.

Differences in bones, ligaments and tissues of men & women

Structure of the knee joint

Composed of three bones lower end of the

femur( thigh bone) Upper end of the leg

bone( tibia) Knee cap( patella)

All the bones are held together by tendons and ligaments and cushioned by cartilage.

Gender specific kneeTwo distinct populations: women and men

•Pioneering research conducted by Zimmer has mapped the anatomical differences between Female and male knees, laying the foundation for the design and development of gender solutions high-flex femoral implants.

•Three-dimensional CT data was collected and analyzed for more than 800 femurs and patellas.

Gender specific knee

Significant differences were identified between female and male knee anatomy.

Plotting M/L and A/P dimensions of the distal femur reveals two distinct populations: female and male.

Implant designs that distinguish between female and male anatomical differences allow for improved implant fit and fewer intraoperative adjustments..

Gender specific knee

Gender solutions high-flex femoral implants address the distinctive differences typically found in the female anatomy.

Historically we have shaped the patients to fit the implants. Now we have implants shaped to fit the patients.”

Gender specific knee

Anterior Flange ThicknessResearch has shown that the female knee has a less-pronounced anterior condyle than

males. This less-pronounced anterior condyle results in less bone being resected from the female knee:

0.8mm less on the lateral condyle (p < 0.02).13 1.3mm less on the medial condyle (p < 0.01).13

Gender Solutions High-Flex Femoral Implants address the distinctive anterior condyle differences by:

o Reducing the anterior flange thickness of the implant.o Recessing the patellar sulcus.o Retaining the clinically successful NexGen patellar articulation.o Avoiding overstuffing that may limit postoperative range of motion 14,15 that can

occur when placing a traditional implant on a resected female knee.

when placing a traditional implant on a resected female knee.

Anterior Flange Width The femoral anterior resection of the female bone is narrower than the male femoral

anterior resection.

Gender specific knee

Increased Trochlear Groove Angle

Patellar maltracking remains a concern —particularly with females —following total knee arthroplasty.5

Research documents that women have a statistically significant higher Q-angle than men.6,7,8

Gender Solutions High-Flex Femoral Implants replicate the distinct Q-angle difference by increasing the trochlear groove angle of the implant three degrees

Gender specific knee

CT data documents distinctive shape differences in female and male distal femurs.12,13 Female femurs are:

More trapezoidal-shaped. Narrower in the M/L dimension when compared to a male femur of the same A/P

dimension When a traditional implant is placed onto a resected female knee: The implant may overhang the bone at the distal, anterior, and posterior M/L

interfaces, which may lead to soft-tissue irritation and affect soft-tissue balancing.1,3,4 The surgeon may be faced with intra-operative adjustments to compensate for the

overhang. Gender Solutions High-Flex Femoral Implants have been narrowed medio-laterally. This allows surgeons to address the female population with unprecedented accuracy.

Gender specific knee

Femoral Mapping—Applying the Science

To address the issue of overhang in female knee arthroplasty, Zimmer has devised a unique patent pending method for predetermining the contour of a resected bone and the fit of an implant on the bone, and applied this novel method in its development of the Gender Solutions High-Flex Femoral Implant.

A traditional implant overhangs female bone as shown in red. Zimmer Gender Solutions High-Flex implant on female bone shows

little to no overhang as shown in the lower model.

Salient features of Gender specific knee

More natural movementThinner profile – so that the knees will not feel

bulky and cause less pain and increase functionContoured shape to match more closely the

narrower anatomy of the female knee. This provides for a more precise fit and prevent overhanging the bone and press and damage surrounding ligaments and tendons.

Advantages

Allows full knee bending or flexion upto 155 degrees which is necessary for activities like sitting on a low chair or on the floor, climbing stairs, gardening

Can be placed with Minimally invasive solutions procedures which typically offer smaller scars, shorter hospitalization and quicker recovery.

Minimally invasive high flex TKR

Patients squatting after High flexion TKR

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