Scientific Article   |    
Mechano-Acoustic Diagnosis of Cartilage Degeneration and Repair
Mikko S. Laasanen, MSc; Juha Töyräs, PhD; Anna I. Vasara, MD; Mika M. Hyttinen, MD; Simo Saarakkala, BSc; Jani Hirvonen, BSc(Eng); Jukka S. Jurvelin, PhD; Ilkka Kiviranta, MD, PhD
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Corresponding author: Jukka S. Jurvelin, PhD
Department of Applied Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland. E-mail address: jukka.jurvelin@uku.fi

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Technology Agency (TEKES) Projects 2893 and 40819/00, Kuopio University Hospital (EVO 5173), Finland; The Graduate School for Musculoskeletal Diseases, Finland; Finnish Cultural Foundation of Northern Savo, Jyväskylä Central Hospital (TEVO B51). None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

J Bone Joint Surg Am, 2003 Apr 01;85(suppl 2):78-84
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Background: The combined use of high-frequency ultrasound and mechanical indentation has been suggested for the evaluation of cartilage integrity. In this study, we investigated the usefulness of high-resolution B-mode ultrasound imaging and quantitative mechanical measurements for the diagnosis of cartilage degeneration and for monitoring tissue-healing after autologous chondrocyte transplantation.

Methods: In the first study, osteochondral samples (n = 32) were obtained from the lateral facet of a bovine patella, and the samples were visually classified as intact (n = 13) or degenerated (n = 19) and were graded with use of the Mankin scoring system. Samples were imaged with use of a 20-MHz ultrasound instrument, and the dynamic modulus (Edyn) of cartilage was determined in unconfined compression with use of a high-resolution materials tester. In the second study, cartilage chondrocytes were harvested from the low-weight-bearing area of six-month-old porcine knee joints and cultured. A month later, a cartilage lesion was created on the facet of the femoral trochlea and was repaired with use of the autologous chondrocyte transplantation technique (n = 10). Three months later, to estimate cartilage Edyn, the repair tissue, the adjacent cartilage, and the sham-operated contralateral joint cartilage (control) were analyzed in situ with an arthroscopic indentation instrument. Subsequently, the same sites were imaged with ultrasound.

Results: All visually degenerated bovine samples (mean Mankin score = 4) and five visually normal samples (Mankin score = 1) showed reduced Edyn (<2.1 MPa) as compared with histologically normal cartilage (Edyn = 13.8 ± 3.2 MPa, Mankin score = 0). Cartilage stiffness, as shown by the indenter force, was lower (0.6 ± 0.3 N, p < 0.05, Wilcoxon's signed-rank test) in the porcine tissue repaired with autologous chondrocyte transplantation than it was in the adjacent (1.6 ± 0.1 N) or the control (1.9 ± 0.4 N) tissue. The superficial and internal structure of the degenerated and repaired tissue, including the subchondral erosion at the repair site, was sensitively demonstrated by the ultrasound imaging.

Conclusions: Measurement of cartilage Edyn is an objective method with which to follow changes in the mechanical integrity of cartilage. B-mode ultrasound imaging offers detailed information on the structural properties of cartilage and subchondral bone.

Clinical Relevance: Mechanical indentation and ultrasound imaging complement each other and provide information on the functional and structural integrity of cartilage and subchondral bone. Combined use of these techniques may provide a means for the early diagnosis of cartilage degeneration and for the monitoring of tissue healing after repair surgery.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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