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Research Papers

The Acute Effect of Bipolar Radiofrequency Energy Thermal Chondroplasty on Intrinsic Biomechanical Properties and Thickness of Chondromalacic Human Articular Cartilage

[+] Author and Article Information
Nicholas Dutcheshen

Doctor of Medicine, Medical Office Building, Suite 744, Orthopaedic Surgery, Beaumont Health System, 3535 W Thirteen Mile Road, Royal Oak, MI 48073ndutcheshen@yahoo.com

Tristan Maerz

 Master of Science in Biomedical Engineering, Orthopaedic Research, Beaumont Health System, 3811 W. Thirteen Mile Road, Royal Oak, MI 48073Tristan.Maerz@beaumont.edu

Patrick Rabban

 Bachelor of Science in Biomedical Engineering, Orthopaedic Research, Beaumont Health System, 3811 W. Thirteen Mile Road, Royal Oak, MI 48073prabban@umich.edu

Roger C. Haut

Doctor of Philosophy in Mechanics,  Orthopaedic Biomechanics Laboratories, Michigan State University, East Lansing, MI 48824haut@egr.msu.edu

Keith D. Button

Bachelor of Science in Mechanical Engineering, Orthopaedic Biomechanics Laboratories,  Michigan State University, East Lansing, MI 48824keithdbutton@gmail.com

Kevin C. Baker1

 Doctor of Philosophy in Biomedical Engineering, Research Institute, Suite 404, Orthopaedic Research, Beaumont Health System, 3811 W. Thirteen Mile Road, Royal Oak, MI 48073Kevin.Baker@beaumont.edu

Joseph Guettler

 Doctor of Medicine Orthopaedic Surgery, Beaumont Health System, 3535 W Thirteen Mile Road, Royal Oak, MI 48073jguettlermd@wideopenwest.com

1

Corresponding Author.

J Biomech Eng 134(8), 081007 (Aug 06, 2012) (7 pages) doi:10.1115/1.4007105 History: Received February 27, 2012; Revised June 25, 2012; Posted July 09, 2012; Published August 06, 2012; Online August 06, 2012

Radio frequency energy (RFE) thermal chondroplasty has been a widely-utilized method of cartilage debridement in the past. Little is known regarding its effect on tissue mechanics. This study investigated the acute biomechanical effects of bipolar RFE treatment on human chondromalacic cartilage. Articular cartilage specimens were extracted (n = 50) from femoral condyle samples of patients undergoing total knee arthroplasty. Chondromalacia was graded with the Outerbridge classification system. Tissue thicknesses were measured using a needle punch test. Specimens underwent pretreatment load-relaxation testing using a spherical indenter. Bipolar RFE treatment was applied for 45 s and the indentation protocol was repeated. Structural properties were derived from the force-time data. Mechanical properties were derived using a fibril-reinforced biphasic cartilage model. Statistics were performed using repeated measures ANOVA. Cartilage thickness decreased after RFE treatment from a mean of 2.61 mm to 2.20 mm in Grade II, II-III, and III specimens (P < 0.001 each). Peak force increased after RFE treatment from a mean of 3.91 N to 4.91 N in Grade II and III specimens (P = 0.002 and P = 0.003, respectively). Equilibrium force increased after RFE treatment from a mean of 0.236 N to 0.457 N (P < 0.001 each grade). Time constant decreased after RFE treatment from a mean of 0.392 to 0.234 (P < 0.001 for each grade). Matrix modulus increased in all specimens following RFE treatment from a mean 259.12 kPa to 523.36 kPa (P < 0.001 each grade). Collagen fibril modulus decreased in Grade II and II-III specimens from 60.50 MPa to 42.04 MPa (P < 0.001 and P = 0.005, respectively). Tissue permeability decreased in Grade II and III specimens from 2.04 *10−15 m4 /Ns to 0.91 *10−15 m4 /Ns (P < 0.001 and P = 0.009, respectively). RFE treatment decreased thickness, time constant, fibril modulus, permeability, but increased peak force, equilibrium force, and matrix modulus. While resistance to shear and tension could be compromised due to removal of the superficial layer and decreased fibril modulus, RFE treatment increases matrix modulus and decreases tissue permeability which may restore the load- bearing capacity of the cartilage.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Compressive indentation relaxation testing was performed on a custom-built stepper-motor driven mechanical testing system. A specimen stage was used to clamp the specimen while a spherical indenter interfacing with a load cell was displaced into cartilage immersed in a saline bath.

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Figure 2

Load Relaxation Plot from experimental and model data. Load relaxation data from indentation tests performed pretreatment (solid line) and post-treatment (dashed lined) was fitted to a fibril-reinforced, biphasic computational model of articular cartilage (pretreatment: circles; post-treatment: triangles) [46] to derive matrix modulus (Em ), collagen fibril modulus (Ef ), and tissue permeability (k).

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Figure 3

Cartilage thickness as determined by the needle punch test for Grade II, II-III, and III articular cartilage before and after RFE treatment. Cartilage thickness decreased a mean 15.91% (SD 0.67%) due to RFE treatment, and this decrease was significant in each grade (P < 0.001). * indicates P < 0.05.

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Figure 4

Peak force (a), Equilibrium Force (b), and Time Constant (c) (1/ln t in seconds and normalized by peak force) as determined by the indentation test for Grade II, II-III and III articular cartilage before and after RFE treatment. Peak force increased a mean 28.9% (SD 10.0%), equilibrium force increased a mean 99.9% (SD 26.1%), and Time constant decreased a mean 40.0% (SD 11.6%) due to RFE treatment. * indicates P < 0.05.

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Figure 5

Matrix modulus (Em ) (a), Fibril network modulus (Ef ) (b), and Permeability (c) of chondromalacic articular cartilage before and after RFE treatment. Em increased a mean 105.3% (SD 19.3%) (P < 0.001 each grade). Ef decreased significantly in Grade II and Grade II-III specimens (P < 0.001 and P = 0.005, respectively). Permeability decreased significantly in Grade II and Grade III specimens (P < 0.001 and P = 0.009, respectively). * indicates P < 0.05.

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