Biomedical subjects

Mark B Hurtig

Publications and source records attributed to Mark B Hurtig.

8 recordsLinked to original sources

PubMed2006

Osteochondral graft fixation using a bioresorbable bone cement.

Multiple osteochondral grafts can be used to resurface large joint defects in both humans and horses. In humans, immediate postoperative weight bearing can be prevented, however in the equine, it is unavoidable. Early weight bearing can create detrimental graft micromotion. The aim of this study was to investigate the role of a bioresorbable cement in improving the initial stability of multiple osteochondral graft repairs of large subchondral cystic lesions in the horse. Configurations employed for filling a 20mm diameter cylindrical defect included: (A) twelve 4.5mm diameter grafts with cement, (B) five 6.5mm diameter grafts with cement, (C) four each of 4.5mm and 6.5mm grafts with cement and (D) cement only. Intact bone slices (E) were also tested. Push-out tests were used to quantify construct to host sidewall interface fixation. Configuration (A) proved clinically impractical (n=3). Configurations (B) (n=6), and (C) (n=4) had statistically similar interface stiffnesses and failure stresses (43+/-8 and 30+/-12 MPa and 0.96+/-0.1 and 1.2+/-0.3 Mpa, respectively) suggesting that they are equally susceptible to interface movement in the immediate postoperative period. By way of comparison, defects filled only with cement had an average stiffness of 53+/-7MPa and failure stress of 1.8+/-0.3 MPa (n=6) while the intact femoral condyle demonstrated a stiffness of 108+/-7 MPa and failure stress of 18+/-0.4 MPa (n=6). Cement augmentation improved immediate postoperative stability of multiple osteochondral graft constructs over uncemented constructs, although in all cases the observed moduli of elasticity and yield stress values were lower than those observed for cement only and intact bone test specimens. (all numbers are mean+/-SEM).

Absorbable Implants↗

PubMed2006

Characterization of experimentally induced post-traumatic osteoarthritis in the medial femorotibial joint of horses.

OBJECTIVE: To study osteoarthritis in the equine medial femorotibial (MFT) joint after a single traumatic injury. ANIMALS: 10 mature horses. PROCEDURE: In vitro explant cultures were used to determine injury threshold for stifle joint cartilage. Contusive impacts were applied to the medial femoral condyle (MFC), and horses were followed for 84 (n = 5) and 180 days (5). Synovial fluid samples were collected every 14 days for determination of sulphated glycosaminoglycan (sGAG) concentrations. Radiographic and lameness evaluations were performed. Gross and histologic descriptions, and immunohistochemistry, cartilage sGAG content determination, and cartilage aggregate modulus determination were performed at the MFC impact site (MFCi), MFC nonimpact site (MFCn), and medial tibial plateau (MTP). RESULTS: Synovial fluid sGAG concentration decreased significantly on days 14, 28, 42, and 56 in all horses. Macroscopic and microscopic articular lesions developed within all MFT joints. No radiographic abnormalities were observed. Mild lameness was evident in several horses. No significant differences were found between short-term and longterm cohorts of horses with respect to histologic scores and TUNEL results. On immunohistochemistry, MFCi was positive for COL2-(3/4)C(short). International Cartilage Repair Society scores differed significantly between short-term and long-term cohorts of horses. In all horses, sGAG concentrations were significantly decreased at the MFCi, compared with the MFCn. CONCLUSIONS AND CLINICAL RELEVANCE: Use of contusive impacts on the MFC of horses results in cartilage lesions that are similar to those described clinically, supporting trauma as a contributing factor in the natural pathogenesis of osteoarthritis.

Animals↗

PubMed2005

Influence of species and anatomical location on chondrocyte expansion.

BACKGROUND: Bovine articular cartilage is often used to study chondrocytes in vitro. It is difficult to correlate in vitro studies using bovine chondrocytes with in vivo studies using other species such as rabbits and sheep. The aim of this investigation was to study the effect of species, anatomical location and exogenous growth factors on chondrocyte proliferation in vitro. METHODS: Equine (EQ), bovine (BO) and ovine (OV) articular chondrocytes from metacarpophalangeal (fetlock (F)), shoulder (S) and knee (K) joints were cultured in tissue culture flasks. Growth factors (rh-FGFb: 10 ng/ml; rh-TGFbeta: 5 ng/ml) were added to the cultures at days 2 and 4. On day 6, cells were counted and flow cytometry analysis was performed to determine cell size and granularity. A three factor ANOVA with paired Tukey's correction was used for statistical analysis. RESULTS: After 6 days in culture, cell numbers had increased in control groups of EQ-F, OV-S, OV-F and BO-F chondrocytes. The addition of rh-FGFb led to the highest increase in cell numbers in the BO-F, followed by EQ-F and OV-S chondrocytes. The addition of rh-TGFbeta increased cell numbers in EQ-S and EQ-F chondrocytes, but showed nearly no effect on EQ-K, OV-K, OV-S, OV-F and BO-F chondrocytes. There was an overall difference with the addition of growth factors between the different species and joints. CONCLUSION: Different proliferation profiles of chondrocytes from the various joints were found. Therefore, we recommend performing in vitro studies using the species and site where subsequent in vivo studies are planned.

Animals↗

PubMed2005

Comparison of intraosseous and intravenous infusion of technetium Tc 99m pertechnate in the distal portion of forelimbs in standing horses by use of scintigraphic imaging.

OBJECTIVE: To describe and compare the distribution of technetium Tc 99m (99mTc) pertechnate following intraosseous or i.v. injection (with or without use of a tourniquet) in the distal portion of the forelimb in standing horses. ANIMALS: 4 horses. PROCEDURE: Each horse received 4 forelimb treatments in random sequence: intraosseous infusion with tourniquet application (IOT), intraosseous infusion without tourniquet application, i.v infusion with tourniquet application (IVT), and i.v. infusion without tourniquet application. Dynamic nuclear scintigraphic imaging of the third metacarpal bone, proximal and middle phalanges, and distal phalanx was performed from the start of each treatment until 1 hour after infusion was completed. Radionuclide activity was compared within and between treatment groups. RESULTS: Tourniquet application was necessary to maintain high levels of radionuclide activity in the distal portion of the forelimb after intraosseous or i.v. infusion with 99mTc pertechnate; IVT and IOT treatments resulted in similar radionuclide activity in the proximal and middle phalanges and distal phalanx. Of the 4 treatments, there was significantly higher radionuclide activity in the distal aspect of the third metacarpal bone after the IOT treatment. CONCLUSIONS AND CLINICAL RELEVANCE: By use of a tourniquet, radionuclide administration via the intraosseous or i.v. routes resulted in effective perfusion of the distal portion of the forelimb and similar distribution of the agent in the phalanges of horses. Further studies are required to ascertain whether these findings apply to delivery of therapeutic agents in infected tissues via IOT or IVT.

Animals↗

PubMed2004

Manual punch versus power harvesting of osteochondral grafts.

PURPOSE: The purpose of the study was to analyze the effect on chondrocyte viability of 2 existing methods of harvesting osteochondral grafts used for articular cartilage resurfacing. TYPE OF STUDY: Acute animal experiment. METHODS: Power (P) trephine versus manual (M) punch harvesting was tested; 2.7-mm and 4.5-mm dowels were harvested from 8 femoral trochlea from 4 sheep using the Acufex MosaicPlasty system (Andover, MA). Grafts were harvested perpendicular to the articular surface to a depth of 10 mm under constant saline irrigation. Power trephine grafts (n = 46, 2.7 P; n = 45, 4.5 P) were harvested by coupling the serrated trephine to a standard orthopaedic nitrogen powered drill. Manual punch grafts (n = 41, 2.7 M; n=33, 4.5 M) were harvested by malleting the punch to the required depth, minimizing rocking, and only slightly turning the punch on removal. Five 40-microm-thick fresh cartilage sections oriented perpendicular to the articular surface were obtained from each graft and then stained with Syto 13 and ethidium bromide vital stains, and the proportion of live cells per field and physical damage were compared between groups. Masson's trichrome stain was used on paraffin-embedded histologic sections. RESULTS: Power harvesting was technically more difficult and resulted in more gross and light microscopic damage to the osteochondral grafts. Chondrocyte viability was significantly greater for manual punch versus power harvesting of both graft sizes (P <.005). Chondrocyte viability was greater for 4.5 P versus 2.7 P grafts (P <.005), but no difference was found between the 2.7 M and 4.5 M groups (P =.357). CONCLUSIONS: Chondrocyte viability is significantly greater using manual punch versus serrated power trephines when harvesting osteochondral grafts for cartilage resurfacing procedures. Power trephines should not be used for this procedure. CLINICAL RELEVANCE: This study shows that the original method (power trephine) of harvesting osteochondral grafts results in great loss of chondrocyte viability versus manual punch harvesting and should no longer be used.

Animals↗

PubMed2003

Development of a solid-phase assay for measurement of sulfated glycosaminoglycan concentrations in equine synovial fluid.

OBJECTIVE: To develop a new 1,9-dimethylmethylene blue (DMMB) assay for measurement of sulfated glycosaminoglycan (sGAG) concentrations in equine synovial fluid (SF) by use of membrane technology and to compare the assay's ability to measure sGAG concentrations with that of 2 other established DMMB assays. SAMPLE POPULATION: 25 samples of SF collected from affected joints of 14 horses and 13 samples of SF collected from nonaffected (control) joints of 4 horses. PROCEDURE: A solid-phase DMMB assay was developed to measure sGAG concentrations in SE Results for the assay were then compared with results obtained by use of the direct spectrophotometric method (ie, Famdale method) and microplate DMMB assay. RESULTS: The solid-phase assay and direct spectrophotometric assay measured the same sGAG concentrations in identical equine SF, but those concentrations differed significantly from results obtained by use of the microplate DMMB assay. All other aspects of the solid-phase DMMB assay were comparable to both the direct spectrophotometric and microplate DMMB assays. CONCLUSIONS AND CLINICAL RELEVANCE: The new solid-phase assay can be used interchangeably with the direct spectrophotometric method to measure sGAG concentrations in equine SF samples, but it cannot be interchanged with the microplate DMMB assay. Results can be rapidly obtained with the solid-phase assay. Also, the solid-phase assay can detect nanogram quantities of sGAGs in SF, circumvent the problem of premature precipitation of sGAG-dye complexes, and provide quantitative or qualitative results. The solid-phase assay may replace other DMMB assays for measuring sGAG concentrations in SF obtained from horses.

Animals↗

PubMed2003

Assessment of three variations of the 1,9-dimethylmethylene blue assay for measurement of sulfated glycosaminoglycan concentrations in equine synovial fluid.

OBJECTIVE: To determine whether 3 variations of the 1,9-dimethylmethylene blue (DMMB) assay yield comparable results when measuring sulfated glycosaminoglycan (sGAG) concentrations in equine synovial fluid (SF). SAMPLE POPULATION: 25 samples of SF collected from affected joints of 13 horses and 13 samples of SF collected from nonaffected (control) joints of 4 horses. PROCEDURE: Sulfated glycosaminoglycan concentrations were measured by the direct spectrophotometric (ie, Farndale), microplate, and indirect DMMB assays in samples of SF collected from normal and affected joints and in samples digested with nucleases, papain, and hyaluronidase. RESULTS: All 3 assays reacted similarly to standard solutions of sGAGs and digestion of SF samples with nucleases, papain, and hyaluronidase. Nucleic acids were not important interfering substances, and papain and hyaluronidase could not be used interchangeably to digest SE All 3 assays proved to have satisfactory precision (SD < 10%), but each DMMB assay resulted in significantly different measures of sGAG in equine SF. CONCLUSIONS AND CLINICAL RELEVANCE: Samples of SF should be digested with papain or hyaluronidase prior to measurement via DMMB assay. Researchers currently are unable to compare clinical information when variations of the DMMB assay are used, because each DMMB assay yields substantially different sGAG concentrations in SF. Of the 3 assays examined here, we recommend use of the direct spectrophotometric DMMB assay.

Animals↗

PubMedDate not supplied

Cylindrical press-fit osteochondral allografts for resurfacing the equine metatarsophalangeal joint.

OBJECTIVE: To investigate the feasibility of resurfacing the equine fetlock joint using cylindrical, orthotopic, press-fit, osteochondral allografts. STUDY DESIGN: Experimental study. ANIMALS: Ten mature, mixed-breed horses. METHODS: Cylindrical, osteochondral grafts (6.5-mm diameter) were harvested aseptically from cadaveric equine metatarsophalangeal joints. Allografts were transplanted into 6 horses; 4 horses were sham operated. The surgical approach involved creation of a bone block at the origin of the medial collateral ligament and luxation of the metatarsophalangeal joint. Grafts were placed into the medial and lateral metatarsal condyles. Radiographs were taken at 8 and 25 weeks, and lameness was evaluated at 25 weeks. Horses were killed at 25 weeks. Analyses included gross evaluation, microradiography, paravital staining, light microscopy, and cartilage biochemistry. RESULTS: No complications occurred that could be attributed to the surgical procedure. Graft congruency with the surrounding articular cartilage was fair to excellent. Two horses were sound at 25 weeks. Most grafts had more than 90% articular cartilage coverage, and histologic and microradiographic analysis revealed good graft incorporation and articular cartilage survival. Sulphated glycosaminoglycan concentration was decreased in grafted tissue. CONCLUSIONS: We attribute the viability of osteochondral allografts in the equine fetlock to adequate congruency, stable graft fixation, and the use of orthotopic tissue. Host response to the allograft bone tissue did not affect cartilage viability. CLINICAL RELEVANCE: Before clinical use, improvements to instrumentation are required that would decrease damage to grafts and minimize technique-associated incongruencies of the articular surface at the time of grafting. Larger grafts would also likely be required to resurface a greater surface area.

Animals↗