Travis G. Maak*, Andrew P. Kraszewski§, Anil Ranawat§, Sherry I. Backus§, Howard J. Hillstrom§, Bryan T. Kelly§

* Joint Preservation Service, University of Utah, Salt Lake City, UT

§ Center for Hip Preservation, Hospital for Special Surgery, New York, NY

Disclosures !! Anil Ranawat: Conformis, MAKO, NOVA surgical, Linvatec,

Mitek !! Bryan T. Kelly: A2 Surgical, Pivot Medical, Smith & Nephew

!! Funding for this study was provided by Institute for Sports

Medicine Research & MAKO Surgical Corp.

Introduction ! There has been a recent interest in non-

arthritic hip pathologies such as femoral acetabular impingement (FAI)1,2.

!! Passive range-of-motion and static specialty tests are the cornerstones of diagnosis and assessment for treatment3.

!! Little information exists about the use of

dynamic measurements to assess lower extremity function in individuals with FAI4.

Specific Aims

!!Measure and identify objective and reliable kinematic and kinetic parameters to assess dynamic hip function

!!Examine differences in those joint

parameters between healthy individuals and those with FAI

Materials & Methods Study Design

Cross-sectional; 16 Subjects: 6 FAI, 10 Healthy FAI Inclusion Criteria

Positive impingement on clinical exam Evidence of cam-type impingement using AP and lateral

radiographs Measurement

Full-body 3D motion capture, force plates and instrumented stairs, 6 surface EMG of hip musculature

Functional Tasks

Repeated trials of three ADLs: 3-stair ascent (SA) 3-stair descent (SD) Sit-to-stand (STS)

Materials & Methods Data Processing !! Subject-specific inverse-dynamic

models in Visual3D

!! Output: 3-plane lower extremity kinematics and kinetics, MVIC-normalized EMG comparing averaged healthy bilateral and FAI limbs

!! Intra-subject Coefficient of Multiple Correlation (CMC)5

0 = Not repeatable 100 = Perfectly repeatable

Results

Age (yr)

Height (cm) Weight (kg) BMI (kg/m2)

FAI (6) 32 (10) 181 (6) 81.6 (11.5) 25.0 (3.9)

Healthy (10) 25 (4) 176 (7) 75.6 (12.3) 24.3 (3.6)

Hip Knee Ankle

Stair Ascent 100% 100% 92%

Stair Descent 92% 100% 88%

Sit to Stand 100% 96% 79%

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Hip

Fle

x-Ex

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lvis

Fle

x-Ex

t H

ip R

otat

ion

Stair Ascent Stair Descent Sit-to-Stand FA

I H

ealthy

Hip & Pelvis Kinematics

Stair Ascent ! Medial hamstring EMG activity in early SA

" FAI gluteus medius EMG activity during early SA

!"#$#%&'(&)$"(*+&)$

!"#$"(*+,%$-,.)'/+01$

FAI Healthy

Stair Descent " Gluteus medius EMG activity

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FAI Healthy

Sit to Stand " Internal hip rotation moment " Rectus femoris EMG activity during early STS

!"#$2(3'&)$4(.5/+)$

6+0(73)$25',750$"5.(0'$

FAI Healthy

Conclusions !! This study presents the first EMG data for FAI

subjects compared to healthy with 3D kinematics and kinetics during ADLs.

!! CMC values indicate very good measurement reliability for 3D kinematics, kinetics and EMG among healthy and FAI subjects.

!! FAI may exhibit decreased internal rotation moments with hip flexion during sit to stand

Conclusions !! Decreased gluteus medius activation may be an

impingement-related motor pattern change, disuse atrophy, or an antalgic response

!! Decreased rectus femoris and increased medial

hamstring activation may be a dynamic compensatory response to increased baseline pelvic flexion in symptomatic FAI subjects

!! Neuromuscular compensatory strategies may be identified that are not present with static measures including: focused quadriceps stretching, hamstring activation and strengthening, and hip abductor activation and strengthening

Acknowledgments

The authors would also like to thank Erin Magennis, Sarah Knapp, Priya Patel and Jennifer Stone for their extensive aid and

commitment to this project.

Literature Cited 1. Byrd JW, and Jones KS. Arthroscopy, 25(4):

365-8, 2009. 2. Kennedy, MJ, Lamontagne M, and Beaule

PE. Gait & Posture, 30(1): 41-4, 2009. 3. Kubiak-Langer M, Tannast M, Murphy SB et

al. Clin Orthop Relat Res, 458: 117-24, 2007. 4. Farquhar SJ, Reisman DS, and Snyder-

Mackler L. Phys Ther, 88(5): 567-79, 2008. 5. Kadaba MP, Ramakrishnan HK, Wootten

ME, et al. JOR, 7(6): 849-60, 1989

Thank You!