5/10/2013 Pediatric ACL injuries: non-operative vs. operative risks - - PowerPoint PPT Presentation

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Dynamic Evaluation of Pivot-Shift Kinematics in Physeal-Sparing Pediatric Anterior Cruciate Ligament Reconstruction Techniques

Mark Sena James Chen, MD Ryan Dellamaggioria, MD Dezba G. Coughlin, PhD Jeffrey C. Lotz, PhD Brian T. Feeley, MD Mark Sena PhD candidate Orthopaedic Bioengineering Lab Advisers: Jeffrey Lotz Brian Feeley

May 10, 2013 Orthopaedic Surgery

Am J Sports Med. 2013 Apr; 41(4):826-34

Pediatric ACL injuries: non-operative vs. operative risks

avoiding or delaying surgery

recurrent instability inability to return to play

Graf 2002, Mizuta 1995

meniscus / chondral damage

Lawrence 2011, Millet 2002

traditional (trans-physeal) ACL-R

varus / valgus deformity tibial recurvatum leg length discrepancy

Kocher 2002 (Herodicus survey) Koman 1999, Lipscomb 1986

…(trans) fixation hardware …large tunnels (>7% physis) …graft overtensioning

Janarv 1998, Edwards 2001

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% medial mensicus tears

Lawrence et. al., AJSM 2011

tear grade

Koman and Sanders, JBJS 1999 Koman and Sanders, JBJS 1999

Fabricant et al., JBJS 2013

Physeal-sparing ACL reconstruction: good outcomes, but…best choice?

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All Epiphyseal femur: epiphyseal tunnel tibia: epiphyseal tunnel (Partial) Trans-Tibial femur: over-the-top tibia: vertical tunnel Iliotibial Band femur: ITB over-the-top tibia: intermeniscal ligament

Illustrations by Rosanna Wustrack, MD.

“anatomic” (but technical) “anatomic” (but technical) non-anatomic fem. non-anatomic fem. non-anatomic non-anatomic extra-articular restraint extra-articular restraint

Kennedy et al., Am J Sports Med. 2011

reduced translation reduced translation reduced translation reduced translation

• ver-constrained

translation

• ver-constrained

translation increased rotation increased rotation reduced rotation reduced rotation

• ver-constrained

rotation

• ver-constrained

rotation

ITB TT AE

Research question: How do Peds techniques affect dynamic stability?

Pivot-shift test for rotational stability

Axial force, valgus and rotary torques Flexion subluxation / reduction

Clinical sign of symptomatic instability

Designed to mimic ‘giving way’

Galway 1972

+ Pivot correlates with poor outcome

Kocher 2004, Leitze 2005, Jonsson 2004

However, low sensitivity in the clinic

patient guarding, depends on IT-band

Bach 1988

poor reliability, various techniques

Noyes 1991 Lachman Pivot-shift satisfaction ✗ ✔ giving way ✗ ✔ activity limitation ✗ ✔ knee function ✗ ✔ Lysholm score ✗ ✔

Kocher et al. abd. add. neut.

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Bach et al.

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desired characteristics manual + quantitative

reliable quantitative known loads dynamic accessible

Lopomo et al.

good fair poor

Pivot-shift: challenging in the laboratory

desired characteristics manual + quantitative C.P.M. + valgus robot + load cell valgus & ITB weights

reliable quantitative known loads dynamic accessible

Lopomo et al. Musahl et al. Kanamori et al. Markolf et al.

good fair poor

Pivot-shift: challenging in the laboratory Hypothesis: The AE technique best restores native pivot-shift kinematics

…as determined by four outcome variables

Anterior Displacement (AD) [mm] Internal Rotation (IR) [deg] Posterior Translational Velocity (PTV) [mm/s] External Rotational Velocity (ERV) [deg/s]

…as determined by a “Knee Stability Index”

combines AD, IR, PTV, ERV into a single value (KSI)

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constant-tension spring constant-tension spring

force length

Mechanical Pivot-Shift Device Mechanical Pivot-Shift Device

MPSD Experimental Design: ACL intact, transected, reconstructed

6 knees, 5 conditions

intact, ACL-transected AE, TT, ITB (randomized)

position spring endpoints

femur: antero-lateral tibia: postero-lateral

perform test per condition

passive flexion (baseline) flexion with device (3x)

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Optotrak PC digitizing probe

external fixator (Synthes)

attach spring to tibia / femur

Optotrak™ motion capture

measure joint motion measure spring position

load cell (not shown)

measure forces / moments

spring (constant tension)

supplies forces / moments

• ptical

markers ex-fix

5/10/2013 3 Anterior Displacement (AD) Internal Rotation (IR)

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2 4 6 8 10 12

Intact Deficient TT ITB AE

** *

AD

∆d

5 10 15 20 25

** *

Intact Deficient TT ITB AE

IR

∆θ

* p<0.05

Posterior Translation Velocity (PTV) External Rotational Velocity (ERV)

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10 20 30 40 50 60 70 80

**

PTV

v

40 80 120 160 200

**

n.d.

ERV

ω

* p<0.05

Knee Stability Index (KSI):

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KSI = 4.0 AD’ + 2.5 PTV’ - 2.3 IR’ - 0.3 ERV’

‘most’ deficient 100 ‘most’ intact

• 20

20 40 60 80 100 Deficient TT ITB AE

AD PTV IR ERV logistic regression logistic regression KSI

KSI

deficient intact

*

* p<0.05

In summary…

All techniques improved stability metrics

reduced deficient values by 18-78%

• nly TT did not significantly reduce ERV

Iliotibial Band (ITB) reconstruction

• ver-constrained AD (-52%) and IR (-38%)

KSI (0.8)

Partial Trans-Tibial (TT) reconstruction

best restored AD (5%) and IR (-6%) highest KSI (13.3)

All Epiphyseal (AE) reconstruction

best restored PTV (-9%) and ERV (1%) lowest KSI (-4.0)

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5/10/2013 4 In summary…

Limitations

Adult specimens for Peds techniques Time zero study MPSD requires (gentle) manual flexion MPSD not yet validated by others

Conclusions

Operative treatment good outcomes Kinematics depend on technique ITB extra-articular constraint … further study AE (most anatomic) improved dynamic stability

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Key references and Acknowledgements

Fabricant et al., J Bone Joint Surg Am. 2013 Lawrence et al., Am J Sports Med. 2011 Kocher et al., J Pediatr Orthop. 2002 Koman and Sanders, J Bone Joint Surg Am, 1999 Kennedy et al., Am J Sports Med. 2011 Galway et al., J. Bone Joint Surg. 1972 Kocher et al., Am J Sports Med. 2004 Noyes et al., Am J Sports Med.1991 Lopomo et al., Knee Surg Sports Traumatol Arthrosc 2013 Musahl et al., Knee Surg Sports Traumatol Arthrosc. 2010 Kanamori et al, Arthroscopy. 2000 Markolf et al., J Bone Joint Surg Am. 2008 This material is based on work supported by the National Science Foundation Graduate Research Fellowship (Sena, MP)

MPSD Device Design: continuous flexion, prescribed loads

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flexion angle (deg) tibial force (N)

20 40 60 20 40 60

flexion angle (deg) tibial moment (N•m)

20 40 60 2 4 6 8 10 axial compression (40-50 N) valgus torque (6-8 N•m)