5/10/2013 Disclosures Kinematic and Quantitative MR Imaging Evaluation of ACL Reconstructions Using the Mini-Two Incision Method • Aided by a Resident Research Grant from the Compared to the Anteromedial Portal Technique Orthopaedic Research and Education Foundation. • NIH/NIAMS P50-AR060752 • No other financial disclosures. Drew A. Lansdown, MD Christina Allen, MD Samuel Wu Xiaojuan Li, PhD Benjamin Ma, MD Background Background • High prevalence of ACL • Several reconstruction injury techniques exist – 95,000 new injuries yearly in – Open, two-incision the US 1 approach • ACL serves as primary – Arthroscopic transtibial restraint – Arthroscopic – Resists anterior anteromedial portal displacement of the tibia 2 – Arthroscopic mini-two – Controls internal rotation of incision the tibia 2 • Difference between • ACL-deficient knee at high techniques primarily risk of meniscal and articular cartilage injury 3 1. Muneta et al. Arthroscopy. 1999. related to femoral tunnel 2. Beynonn et al. AJSM. 2005. positioning 3. Kannus et al. JBJS. 1987. 1
5/10/2013 Background Mini-Two Incision Reconstruction • Increased risk of progression to early-onset osteoarthritis even • Femoral footprint after ACL reconstruction 1-3 is visualized – Result of initial injury? arthroscopically – Incomplete restoration of normal • 1-2 cm incision knee kinematics? – Progressive cascade? over lateral femur • Transtibial reconstruction restores • Guide pin through anteroposterior stability lateral femoral • Anteromedial reconstruction cortex into notch – Results in improved rotational • Retrograde drill stability as compared to produces femoral transtibial reconstruction tunnel – Leads to stable Lachman and restoration of anterior tibial translation 4 1. Lohmander, et al. Arthritis & Rheumatism. 2004. 1. Lubowitz et al. Arthroscopy. 2011. 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. Theoretical Advantages 1 Hypotheses • Tibiofemoral cartilage contact area is not • Direct visualization of tunnel starting and exit significantly different between the mini-two points may allow for improved positioning incision reconstruction and the contralateral knee • Tunnel length is longer than that created by • The mini-two incision reconstruction technique anteromedial portal technique more closely restores the cartilage contact area • Minimizes risk of lateral wall blowout as compared to the anteromedial portal technique. • Procedure performed with knee flexed at 90 • The mini-two incision reconstruction results in degrees, which may allow for improved the restoration of normal translation and visualization of anatomic landmarks rotational parameters 1. Lubowitz et al. Arthroscopy. 2010. 2
5/10/2013 Patient Selection Patient Characteristics EXCLUSION CRITERIA INCLUSION CRITERIA MT Reconstruction AM Reconstruction Number of patients 7 12 Associated ligamentous injury Mean age (Range) 30.85 yrs 32 yrs 18 -50 years old Meniscal repair or debridement Mean time from surgery 15.57 months (13-19) 12 months greater than 20% (Range) 12-24 months post-op Graft type Hamstring autograft (7) Hamstring autograft (8) PT allograft (3) History of inflammatory Achilles allograft (1) arthropathy Mini-two incision reconstruction Previous surgery on either knee Data Acquisition Image Processing Imaging Parameters • 3T GE Signa MR scanner • In-house Matlab Repetition 4000 ms software • Sagittal fat-suppressed time (TR) Echo time (TE) 50.96 ms • ROIs defined T 2 -weighted images Field of View 16 cm – Posterior aspect of • Surgical and Matrix size 512 x 256 femoral condyles contralateral knees Slice thickness 1.5 mm – Tibia imaged – Cartilage contact • Full extension – Midline axis • 30°-40° flexion 3
5/10/2013 Image Processing Image Processing • In-house Matlab • In-house Matlab software software • ROIs defined • ROIs defined – Posterior aspect of – Posterior aspect of femoral condyles femoral condyles – Tibia – Tibia – Cartilage contact – Cartilage contact – Midline axis – Midline axis Image Processing Image Processing • In-house Matlab • In-house Matlab software software • ROIs defined • ROIs defined – Posterior aspect of – Posterior aspect of femoral condyles femoral condyles – Tibia – Tibia – Cartilage contact – Cartilage contact – Midline axis – Midline axis 4
5/10/2013 Registration Registration • Tibia ROIs • Femoral condyles registered in modeled as spheres flexion and extension with iterative closest point algorithm Registration Contact Area • All points from defined • Axes for femur set splines are connected as central axis of with a set of triangles spheres, defined • Area is calculated as the central axis of summation of the femur and cross triangles product of these • Contact centroid is the two axes centroid of the triangles • Translation defined according to tibial axis 5
5/10/2013 Rotational and Translational Parameters Are Cartilage Contact Area Similar in MT and AM Reconstructions Medial – Medial – Lateral – Lateral - Extension Flexion Extension Flexion Internal Tibial Rotation Anterior Tibial Translation (mm) (Degrees) (Mean [SD]) (Mean [SD]) MT Recon 90.5% ¥ 86.3% ¥ 101.3% 99.4% vs (4.8%) (7.3%) (13.6%) (14.0%) MT Reconstructed 0.24 (8.2) -0.05 (2.3) MT Control p = 0.33 p = 0.55 p = 0.0025 p = 0.0040 MT Normal 3.4 (6.8) 0.01 (1.3) AM Recon 111.2% ¥ 99.2% 109.3% 111.8% AM Reconstructed 3.1 (5.6) 0.7 (2.7) vs p = 0.36 p = 0.38 (13.1%) (27.1%) (29.7%) (18.9%) AM Control AM Normal 2.3 (5.4) 1.3 (5.4) p = 0.03 Medial compartment contact areas are MT = Mini-two incision method AM = Anteromedial portal technique significantly lower in both flexion and extension Medial Contact Centroid Is Abnormal Conclusions • MT reconstruction restores kinematic parameters • Shifted laterally in both flexion and extension • Cartilage contact area in the medial compartment is relative to the contralateral knee significantly decreased following MT reconstruction – 9.1 mm in flexion (p = 0.02) • No difference in cartilage contact area with AM – 8.9 mm in extension (p = 0.05) reconstruction • Contact centroid is shifted laterally for the medial • AM reconstructions show lateral contact compartment with the MT reconstruction centroid shift anteriorly in flexion and • Contact changes may be responsible for early extension degenerative changes despite reconstruction 6
5/10/2013 Acknowledgements • Christina Allen, MD • Benjamin Ma, MD • Xiaojuan Li, PhD • Samuel Wu • Will Schairer • Lee Jae Morse, MD 7
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