Kinematic Knee Alignment

Stefano Bini, MD

The Permanente Medical Group

East Bay

Outcomes

• TKA survivorship >90% at 10 years

• Design issues largely resolved

Heresy!

Not ….

Nor…

A problem to solve….

Reason for aseptic revisions (N=1154)

June 5, 2014

Table 3. Reasons for Revision

Reasons for Revision1 N (%)

Instability 352 (30.5%)

Pain 342 (29.6%)

Aseptic Loosening 295 (25.6%)

Arthrofibrosis 207 (17.7%)

Osteolysis 38 (3.3%)

Femoral Fracture 37 (3.2%)

Hematoma 34 (3.0%)

352 342

295207

109

Instability PainASL Stiffness

Patient Reported Outcomes

• Registries

–UK, NZ

• 20-25% of patients dissatisfied

Patient Reported Outcomes

• Canada

–Bourne

• 1703 TKAs

–19% unsatisfied

–72-86% reporting pain relief

–ADLs 70-84%

Patient Reported Outcomes

• USA

• How are our BEST (?) US surgeons doing:– Parvizi, Numley, Berend,

Lombardi, Clohisy, Hamilton, Della Valle, Barrack• 661 young active patients

• 66% normal

• 33% persistent pain

• 41% stiff

• 33% noise/grinding

TKA ROM

• 115 degree is about the best published averages

– Mai, Caldwell et all Orthopedics 2012

TKA: an opportunity

Improving mechanical alignment

• Custom Cutting Guides– Fewer instruments,

greater accuracy, shorter operative time

• Primary goal– Better alignment

through 3-D imaging

• Assumption:

• Better mechanical alignment would lead to better clinical outcomes

Clinical Results

• Mechanical Alignment

• Conventional vs. CAS

Study Alignment KSS Flexion

Dutton Conventional 152 NA

CAS 152 NA

Matziolis Conventional 144 109

CAS 149 108

Stulberg Conventional 147 116

CAS 147 117

Lets reconsider…

• “The definition of insanity is doing the same thing over and over again and expecting different results”

What could be done differently?

What if….

• We are not aligning them correctly?

– The mechanical axis is not the right axis?

– The Transepicondylar axis is not the rotational axis of the knee?

– The gaps should not be balanced?

– The femur is not externally rotated 3 degrees?

Heresy!

Kinematic Alignment

• Goal– Align the kinematic axis of the prosthetic femoral

component with the patient’s pre-arthritic kinematic axis

• Assumption– If the surfaces of the implants are where the original

pre-arthritic knee used to be the component will be coaxial to the kinematic axis

• Expectation– Improved patient reported outcomes because the

knee is anatomically balanced throughout the arc of motion.

Kinematic Alignment

• Concerns

– The “normal knee” tibial joint line is in varus

– The “normal knee” femoral joint line is in valgus

– The “normal knee” posterior condylar axis is in internal rotation relative to the TE axis

– Kinematic alignment forces us to place components outside the accepted parameters of “normal TKA”

Achieving Kinematic alignment

• Femoral alignment

– Resect amounts of bone from the distal andposterior femur medially and laterally as thick as the components you are putting in (after adjusting the cuts for cartilage loss).

Posterior condylar axis and the tibia

What are the assumptions of orthodoxy?

• Mechanical alignment is normal

• Perpendicular placement of the joint line to the mechanical axis of the tibia is a good thing

• The Transepicondylar axis is the rotational axis of the knee

• Balancing gaps is good

• Balancing that requires selective soft tissue “releases” is appropriate– Collateral ligaments contract

Mechanical Alignment is “Normal”

Mechanical Alignment is rare

• Eckhoff JBJS 2005– CT scanograms – 180 NORMAL ASX

knees– 2% neutral

mechanical axis– 76% deviation >

3deg from neutral

Perpendicular placement of the tibia to its mechanical axis is good… +/- 3 deg

• Bellemans CORR 2012

– WB XRs

– 32% men varus >= 3 deg from neutral

– 17% of women varus >=3 deg from neutral

Tibia is in varus for a reason….

3-5 deg

Axis of Rotation

• The cylindrical axis of the femur is the axis about which the tibia flexes and extends

• Transepicondylar axis vs. Cylindrical axis– 23 healthy patients 3D CT

analysis– Average error from Transverse

axis is 5 deg• SD 1.6 deg• Range 1.8 to 11.3 deg

– Proximal and anterior to the Cylindrical axis in all knees• Ekhoff JBJS 2005, CORR 2007

Balancing gaps is good

Balanced Gaps ?

• AAHKS 2014

• Roth JD et all

– normal knee

– Extension 0

• 0.5 mm laxity

– Flexion 90

• 3.0 mm varus

• 1.5 mm valgus

Balanced Gaps?

• Yes in full extension

– Stable at heel strike

• No in 90 of flexion

– Should be a couple of mm of laxity on the lateral side to allow roll back and establish “normal” balance

Is it time to revisit alignment?

• Mechanical alignment was a solution to a problem that has been mostly solved by improved biomaterials and engineering

PSG: KA vs. Conventional

• Dossett, Orthopedics 2012

– RCT Kinematic with PSGs vs. Conventional

– 41 patients in each arm

outcome Kinematic Conventional

P value

WOMAC 12 +/_14.8

28 +/-18.5 <.000

Oxford 8 +/- 9.1 15 +/- 8.9 <0.001

Combined KSS

174 +/-31.3

149 +/-35.3

<0.001

Extension 0.7 +/- 1.7 0.8 +/- 2.2 .734

Flexion 120 +/-9.2

115 +/-12.3

0.43

Op. time 106 +/-20 127 +/- 24 <0.000

Variation in alignment = natural

• Dossett Orthopedics 2012

• Standardized CT scanogram alignment methodology

Sagittal plane angle Kinematic Conventional Difference

p

Femoral component and anatomic axis of femur

9.8 +/-6.0

4.6 +/-4.5 5.2 <0.000

Tibial tray and anatomic axis of tibia

-5.0 +/-5.4

-3.0 +/-4.7

-2.0 0.035

Outliers in Kinematic Knee

Howell

• 214 Kinematic TKAs, patient specific guides

– 3 year follow up, 75% varus outlier (>3 deg)

– No failures, OKS 43

• 101 consecutive patients

– Generic instruments used for kinematic alignment

– Oxford knee score average 42 (max 48)

• No difference for outliers > 3 deg varus

Alignment and survivorship

• Malkani JBJS 1995 Mayo experience

• 168 consecutive TKA, 119 10+ year follow up

• 96% survivorship, 4/6 revision for patella

• Tibial alignment– 43% > 4 deg varus

– 10% >7 deg of varus

• Femoral alignment– 54% > 6 deg of valgus

– 10% > 11 deg of valgus

Alignmet >3 deg is bad

• Mel Ritter 2011 JBJS

• 6070 knees,

• 54 (0.89%) failure rate

• Tibia <90, Femur >8 valgus: 8.7% failure rate

• Neutral mechanical but non pp joint line– 3.2% failure (p=0.4922 NS) if

tibia vara

“Mal”alignment >3 deg

• Mel Ritter 2011 JBJS

• Goniometer readings from standing XRs– 54 failures TOTAL (0.89%)

– Mean duration of f/up was 7.6 years

– Mean time to failure is 5.2 years (+-3.6) • HR is a time dependent

statistic

KA vs. Conventional vs. PSGs

• Nunley KS 2014

– Berend, Howell, Lombardi, Barrack

– Retrospective independent review comparing consecutive TKAs in mechanically aligned TKA (custom guides N=107; and conventional N= 341) to Kinematic alignment with custom guides (N=87)

– 1 year min f/up

• Patient satisfaction and residual symptoms

KA vs. Conventional vs. PSGs

• Nunley KS 2014• NS: pain in last 30 days, grinding, swelling, problems in and

out of car, or chair or using stairs, limp, participation in preferred activity

score Kinematic Mechanical P value

Satisfied overall

98% 94% 0.19

Pain relief 100% 95% 0.03

Knee normal 90% 77% 0.01

ADL 93% 92% 0.77

Stiffness 20% 30% 0.04

So how did we solve his problem?

Kinematic Knee

Challenge Assumptions

Summary

• TKA as an unsolved problem

• Traditional alignment techniques may be part of the problem

• Kinematic alignment is one solution

• Kinematic alignment is evolutionary

– Not revolutionary

• Kinematic alignment is in evolution

– Instrumentation evolving with the concepts

Final thoughts…

• Follow the discussion

• Form your own opinion

• Go on: be a heretic!

Thank you for your attention

Consider Kinematic Alignment

• Kinematic alignment is the restoration of the pre-arthritic joint line and rotational axis of the knee.– me

• Kinematically aligned TKA restores function by aligning the femoral and tibial components to the “normal” or pre-arthritic joint line of the knee.– Stephen Howell MD

Who’se idea was it?

• Dr Hungerford MD and Krackow– Porous Coated Anatomical knee (PCA)

• Dr Tilmann Callies, Prof H Windhagen– Hannover

– Stryker Shape Match

• Dr Stephen Howell, MD PhD– Sacramento

– OTIS