Disclosures Kinematic and Quantitative MR Imaging Evaluation of ACL - - PowerPoint PPT Presentation

5/10/2013 1

Kinematic and Quantitative MR Imaging Evaluation of ACL Reconstructions Using the Mini-Two Incision Method Compared to the Anteromedial Portal Technique

Drew A. Lansdown, MD Christina Allen, MD Samuel Wu Xiaojuan Li, PhD Benjamin Ma, MD

Disclosures

• Aided by a Resident Research Grant from the

Orthopaedic Research and Education Foundation.

• NIH/NIAMS P50-AR060752
• No other financial disclosures.

Background

• High prevalence of ACL

injury

– 95,000 new injuries yearly in the US1

• ACL serves as primary

restraint

– Resists anterior displacement of the tibia2 – Controls internal rotation of the tibia2

• ACL-deficient knee at high

risk of meniscal and articular cartilage injury3

1. Muneta et al. Arthroscopy. 1999. 2. Beynonn et al. AJSM. 2005. 3. Kannus et al. JBJS. 1987.

Background

• Several reconstruction

techniques exist

– Open, two-incision approach – Arthroscopic transtibial – Arthroscopic anteromedial portal – Arthroscopic mini-two incision

• Difference between

techniques primarily related to femoral tunnel positioning

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Background

• Increased risk of progression to

early-onset osteoarthritis even after ACL reconstruction1-3

– Result of initial injury? – Incomplete restoration of normal knee kinematics? – Progressive cascade?

• Transtibial reconstruction restores

anteroposterior stability

• Anteromedial reconstruction

– Results in improved rotational stability as compared to transtibial reconstruction – Leads to stable Lachman and restoration of anterior tibial translation4

1. Lohmander, et al. Arthritis & Rheumatism. 2004. 2. Von Porat, et al. An of Rheum Disease. 2004. 3. Andriacchi, et al. Ann of BME, 2004. 4. Carpenter, et al. Arthroscopy. 2009. 5. Theologis, et al. Arthroscopy. 2010.

Mini-Two Incision Reconstruction

• Femoral footprint

is visualized arthroscopically

• 1-2 cm incision
• ver lateral femur
• Guide pin through

lateral femoral cortex into notch

• Retrograde drill

produces femoral tunnel

1. Lubowitz et al. Arthroscopy. 2011.

Theoretical Advantages1

• Direct visualization of tunnel starting and exit

points may allow for improved positioning

• Tunnel length is longer than that created by

anteromedial portal technique

• Minimizes risk of lateral wall blowout
• Procedure performed with knee flexed at 90

degrees, which may allow for improved visualization of anatomic landmarks

1. Lubowitz et al. Arthroscopy. 2010.

Hypotheses

• Tibiofemoral cartilage contact area is not

significantly different between the mini-two incision reconstruction and the contralateral knee

• The mini-two incision reconstruction technique

more closely restores the cartilage contact area as compared to the anteromedial portal technique.

• The mini-two incision reconstruction results in

the restoration of normal translation and rotational parameters

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Patient Selection

INCLUSION CRITERIA

18 -50 years old 12-24 months post-op Mini-two incision reconstruction

EXCLUSION CRITERIA

Associated ligamentous injury Meniscal repair or debridement greater than 20% History of inflammatory arthropathy Previous surgery on either knee

Patient Characteristics

MT Reconstruction AM Reconstruction Number of patients 7 12 Mean age (Range) 30.85 yrs 32 yrs Mean time from surgery (Range) 15.57 months (13-19) 12 months Graft type Hamstring autograft (7) Hamstring autograft (8) PT allograft (3) Achilles allograft (1)

Data Acquisition

• 3T GE Signa MR scanner
• Sagittal fat-suppressed

T2-weighted images

• Surgical and

contralateral knees imaged

• Full extension
• 30°-40° flexion

Imaging Parameters Repetition time (TR) 4000 ms Echo time (TE) 50.96 ms Field of View 16 cm Matrix size 512 x 256 Slice thickness 1.5 mm

Image Processing

• In-house Matlab

software

• ROIs defined

– Posterior aspect of femoral condyles – Tibia – Cartilage contact – Midline axis

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Image Processing

• In-house Matlab

software

• ROIs defined

– Posterior aspect of femoral condyles – Tibia – Cartilage contact – Midline axis

Image Processing

• In-house Matlab

software

• ROIs defined

– Posterior aspect of femoral condyles – Tibia – Cartilage contact – Midline axis

Image Processing

• In-house Matlab

software

• ROIs defined

– Posterior aspect of femoral condyles – Tibia – Cartilage contact – Midline axis

Image Processing

• In-house Matlab

software

• ROIs defined

– Posterior aspect of femoral condyles – Tibia – Cartilage contact – Midline axis

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Registration

• Tibia ROIs

registered in flexion and extension with iterative closest point algorithm

Registration

• Femoral condyles

modeled as spheres

Registration

• Axes for femur set

as central axis of spheres, defined central axis of femur and cross product of these two axes

Contact Area

• All points from defined

splines are connected with a set of triangles

• Area is calculated as the

summation of the triangles

• Contact centroid is the

centroid of the triangles

• Translation defined

according to tibial axis

5/10/2013 6 Rotational and Translational Parameters Are Similar in MT and AM Reconstructions

Internal Tibial Rotation (Degrees) (Mean [SD]) Anterior Tibial Translation (mm) (Mean [SD]) MT Reconstructed 0.24 (8.2)

• 0.05 (2.3)

MT Normal 3.4 (6.8) 0.01 (1.3) AM Reconstructed 3.1 (5.6) 0.7 (2.7) AM Normal 2.3 (5.4) 1.3 (5.4) MT = Mini-two incision method AM = Anteromedial portal technique p = 0.55 p = 0.36 p = 0.38 p = 0.33

Cartilage Contact Area

Medial – Extension Medial – Flexion Lateral – Extension Lateral - Flexion MT Recon vs MT Control 90.5% ¥ (4.8%) 86.3%¥ (7.3%) 101.3% (13.6%) 99.4% (14.0%) AM Recon vs AM Control 99.2% (13.1%) 109.3% (27.1%) 111.8% (29.7%) 111.2%¥ (18.9%)

p = 0.0040 p = 0.0025 p = 0.03

Medial compartment contact areas are significantly lower in both flexion and extension

Medial Contact Centroid Is Abnormal

• Shifted laterally in both flexion and extension

relative to the contralateral knee

– 9.1 mm in flexion (p = 0.02) – 8.9 mm in extension (p = 0.05)

• AM reconstructions show lateral contact

centroid shift anteriorly in flexion and extension

Conclusions

• MT reconstruction restores kinematic parameters
• Cartilage contact area in the medial compartment is

significantly decreased following MT reconstruction

• No difference in cartilage contact area with AM

reconstruction

• Contact centroid is shifted laterally for the medial

compartment with the MT reconstruction

• Contact changes may be responsible for early

degenerative changes despite reconstruction

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Acknowledgements

• Christina Allen, MD
• Benjamin Ma, MD
• Xiaojuan Li, PhD
• Samuel Wu
• Will Schairer
• Lee Jae Morse, MD