femoral notching in total knee arthroplasty

FEMORAL NOTCHING in TOTAL KNEE ARTHROPLASTY

By

Ihab El-Desouky (M.D.)

Kasr Alainy School of MedicinePelvis and joint Reconstruction Unit

July 2016

Femoral Notching in Total Knee Arthroplasty• Definition: Violation of the anterior cortex (+/-

medulla)of the distal femur during preparation in TKR.

• Hirsh et al (1981) by

FOUR CASES.

was 1st to associate

notching with

supracondylar

fracture in TKR.

Then ;

Femoral Notching in Total Knee Arthroplasty

Early reports: • Culp et al. (1987): 61 fractures

with 27 cases showed notching.

• Aaron et al.,(1987) five cases 42% of deep resection of trochlea.

• Ritter et al., (1988) one case (of 180 notched femur)

• Madsen et al., (1989) two cases.

• Figgie et al., (1990) eight (of 20 notched femur) • Healy et al,. (1993) two cases ( of 7 factured femora)

Femoral Notching in Total Knee ArthroplastyNon-stop:deep resection of the anterior femoral cortex causes stress-riser and fracture.

1-Clinical hypothesis : Culp et al., (1987): 3mm notching---29.2 reduction of the torsional strength.

2-Biomechanical studies: Lesh et al,. (2000) paired human cadaver femora (Rt and Lt of same specimen) -----TKR one with notching and one without: ----bending and torsion-----fracture.

---------- ----------Results.


Non-stop: deep resection of the anterior femoral cortex causes stress-riser and fracture.

Lesh et al,. (2000) Results: Notching decreases bending strength to fracture by

18 % and torsion by 40%

Fracture configuration of fracture: notched; cortical defect and non-notched: mid-shaft

Shawen et al (2003) cadaveric femora---- 3-mm anterior cortical notch

reduced torsional load to failure by 31%. BUT added other variables ( bone mass by DEXA + distal femur cortical geometry by polar moment of inertia by CT)

3- Finite element analysis : Zalzal et al., (2006) 3-D computer aided

design: computer software –femoral model during gait ---model for TKR --

notches (shallow or deep, with sharp or smooth corners, proximity of the notch)

Femoral Notching in Total Knee ArthroplastyNon-stop: deep resection of the anterior femoral cortex causes stress-riser and fracture.

Zalzal et al (2006) : Finite Element Analysis: High stresses at

1- Deep notch (h) (more than 3mm)2-Sharp corners of the notch (r )3-Close proximity of the notch to implant(L)

Colour differentiation for more stresses with close implant


Stop sign: before final move.

1-Epidemiology:

-Supra-condylar femoral # after TKR= 0.3- 2.5 % of all cases(400.000/year in USA, 2/3 are females, National Center for Health Statistics).

-Anterior femoral notching incidence in some recent studies:

• Ritter et al., (2005-USA) 325/ 1089 TKR= 30%

• Gujarathi et al., (2009- UK) 72/200 TKR= 41%


Incidence of #

Notched #Incidence of #

Non-Notched #

No. of # / total

Study

0.48%250.13%732/5233Merkel and Johnson 1986

1.4%80.8%514/567Figge, 1990

%0.091%0.0912/1089Ritter, 2005

0.5%11%23/200Gujarathi, 2009

Stop sign: before final move.1-Epidemiology:

-Supra-condylar femoral # following ant. notching:


Stop sign2-Classification system: Tayside classification 2009(Scotland );

I: violation of the outer table

II: violation of the outer and the inner tables

III: violation up to 25% of the medullary canal

(from the inner table to the center of the medullary canal);

IV: violation up to 50% of the medullary canal

-Grade II = 3 mm violation

of the cortex in other studies.

-Grades III and IV are the risky groups.

Femoral Notching in Total Knee ArthroplastyStop sign

3-Risk factors for supracondylar femoral fractures, in decreasing order (Multi-factorial)OsteopeniaRheumatoid arthritisSteroid useNeurologic disordersRevision TKRFemale genderSeventh decade of lifeDistal femoral osteolysisAnterior femoral notching +/- AND

Mismatch of the elastic modulus Rotationally constrained componentsDelayed bone remodeling due to vascular compromise at the surgical site.Hole in navigation systems

So still notching is a controversial issue for supra-condylar fracture.


Run again:-A clear conflict between the clinical ,biomechanical and finite element analysis.

-Hoffmann et al, (2012) series of 36 # , 9 (25%) with notching:

• Length of time from initial TKA to fracture was shorter

• distance from the anterior flange ofthe femoral component to the fracture (smaller short segmentfixation) was significantly reduced. more challenging to treat.

• An avoidable factor, other factors can’t be avoided( age , gender, oseoporosis---)

-Minoda et al., (2013): Computer Assisted Study--- more notching with navigation system.

-Lee et al., (2015): a retrospective study of 148 TKA ( 70 conventional and 78 navigated) ---- notching in 4 conventional (5.7%) and 13 navigated (16.7)

Anterior femoral bowing of the distal femur observed in 61.5%


Factors affecting the anterior femoral cut and notching:

1-Patient-related :

1- Anterior femoral bowing:


Stop sign


• Take Home Massage:• Notching should be avoided.

• patients who sustain inadvertentnotching that they should have additional protection inthe early postoperative period, and to consider the use afemoral component with stem as a means to bypass thestress riser of the anterior cortical notch. Mostimportant, authors believe that an anterior cortical notchshould be considered as a contraindication for manipulation of the knee prosthesis in the earlypostoperative period

femoral notching in total knee arthroplasty

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