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Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2016)

The articular cartilage and underlying subchondral plate, comprised of calcified cartilage and a continuous plate of subchondral bone, form the osteochondral unit which bears and transmits the load as well as maintains low hydraulic conductivity and permeability. Age-related degeneration transitions to osteoarthritis (OA) a disease that results in degeneration of articular cartilage and abnormality of the

subchondral plate. The mechanism of this transition is not well known, and likely involves interplay between both the bone and the cartilage. This dissertation aims to delineate the biological and structural changes that occur in the osteochondral interface with age-related degeneration and disease, to help gain a better understanding of the pathogenesis.

3-D morphometric analyses of the subchondral plate in microCT indicated that the tidemark was disrupted and roughened in the early stage of degeneration. Investigating the subchondral plate in histology and with Digital Volumetric Imaging revealed that the disruptions were often caused by penetrating vascular channels that are involved in bone remodeling, which become larger and more abnormal in morphology in early degeneration stages. The penetration and disruption of the tidemark was found to occur in an earlier stage than large changes in the chondrocyte organization and fissuring of the articular cartilage matrix, known hallmarks of OA. Because the disrupted interface can potentially compromise the subchondral plate’s ability to act as a barrier to water and solutes, there is the potential of a mechanism where remodeling of the subchondral plate leads to more catabolism and fluid depressurization in the cartilage.

These studies provide new technical developments in the ability to analyze three-dimensional datasets computationally, and reduce them to morphometric parameters, allowing a multiscale assessment of the tissue depending on the region of focus and size of targeted objects. They provide quantitative confirmation of known histological hallmarks of degeneration and OA in both the cartilage and subchondral plate. Additionally, they provide novel 3-D information about the structure of the human subchondral plate in degeneration and OA, which has been mostly limited to studies of normal tissue in the past.

    Cover page: Structural Deterioration of Human Articular Cartilage and Subchondral Plate
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2014)

    Background

    Osteochondral allograft (OCA) transplantation is an effective treatment for defects in the medial femoral condyle (MFC), but the procedure is limited by a shortage of grafts. Lateral femoral condyles (LFCs) differ in geometry from MFCs but may be a suitable graft source. The difference between articular surface locations of the knee can be evaluated with micro-computed tomography imaging and 3-dimensional image analysis.

    Hypothesis

    LFC OCAs inserted into MFC lesions can provide a cartilage surface match comparable with those provided by MFC allografts.

    Study design

    Controlled laboratory study.

    Methods

    Twenty MFCs and 10 LFCs were divided into 3 groups: 10 MFC recipients (MFCr), 10 MFC donors (MFCd), and 10 LFC donors (LFCd). A 20-mm defect was created in the weightbearing portion of the MFCr. Two grafts, 1 MFCd and 1 LFCd, were implanted sequentially into each MFCr. Micro-computed tomography (μCT) images of the MFCr were acquired and analyzed to compare the topography of the original recipient site with the MFCd- and LFCd-repaired sites. Three-dimensional transformations were defined to register the defect site in the 3 scans of each MFCr. Vertical deviations from each voxel of the graft cartilage surface, relative to the intact recipient cartilage surface, were calculated and assessed as root mean square deviation and percentage graft area that was proud, sunk, and within the "acceptable" distance (±1.00 mm). The effect of repair (with MFC vs with LFC) on each of the surface match parameters is presented as mean ± SD and was assessed by t test: height deviation over area (root mean square, mm), graft area acceptable (%), area unacceptably proud (%), area unacceptably sunk (%), step-off height over circumference (root mean square, mm), graft circumference acceptable (%), circumference unacceptably proud (%), and circumference unacceptably sunk (%). Percentage data were arcsin transformed before statistical testing. An alpha level of 0.05 was used to conclude if variations were statistically significant.

    Results

    MFCr defects were filled with both orthotopic MFCd and nonorthotopic LFCd. Registered μCT images of the MFCr illustrate the cartilage surface contour in the sagittal and coronal planes, in the original intact condyle, as well as after OCA repairs. Specimen-specific surface color maps for the MFCr after implant of the MFCd and after implant of LFCd were generally similar, with some deviation near the edges. On average, the MFCr site exhibited a typical contour, and the MFCd and LFCd were slightly elevated. Both types of OCA-MFCd and LFCd-matched well, showing overall height deviations of 0.63 mm for area and 0.47 mm for step-off, with no significant difference between MFCd and LFCd (P = .92 and .57, respectively) and acceptable deviation based on area (87.6% overall) and step-off (96.7% overall), with no significant difference between MFCd and LFCd (P = .87 and .22, respectively). A small portion of the implant was proud (12.1% of area and 2.6% of circumference step-off height), with no significant difference between MFCd and LFCd (P = .26 and .27, respectively). A very small portion of the implant area and edge was sunk (0.3% of area and 0.6% of circumference), with no significant difference between MFCd and LFCd (P = .29 and .86, respectively).

    Conclusion/clinical relevance

    The achievement of excellent OCA surface match with an MFCd or LFCd graft into the common MFCr site suggests that nonorthotopic LFC OCAs are acceptable graft options for MFC defects.
      Cover page: Osteochondral Allograft Transplant to the Medial Femoral Condyle Using a Medial or Lateral Femoral Condyle Allograft
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