Mosaic Arthroplasty is a well-accepted surgical approach to treating focal cartilage defects of the knee. However, the task of creating the mosaic of osteochondral grafts that optimally restores the cartilage surface is technically demanding. Conventional techniques require the surgeon to reconstruct a complex, three-dimensional surface by eye and experience only. There is evidence that this type of procedure is sensitive to technique: grafts that are transplanted proud of the native cartilage surface tend to show evidence of cartilage fissuring and fibrillation prematurely. Two computer-assisted techniques (navigation by optical tracking and guidance by patient-specific templates) were investigated to determine whether they would have a beneficial effect on surgical execution, and whether any differences in execution had any correlation to surgical outcome. The experimental work can be broken into two parts: an in vitro study that compared the accuracy of execution of an optically navigated group versus a template guided group, and an in vivo animal trial that compared both computer assisted techniques to the conventional, non-assisted approach. The results of the pilot study indicated that, while there were higher errors in the individual measures of position, orientation, and plug depth in the optically navigated group, there was no significant difference in the overall fidelity of the geometric surface produced between the two groups. The results of the animal trial indicated that both computer assisted techniques produced morphological results that were superior to the conventional technique. The two computer-assisted techniques also showed a significantly better treatment effect as seen by their higher histological scoring. Furthermore, a significant linear correlation was found between morphological results and histological score. Overall, the experiments demonstrated that surgeons and patients could potentially benefit from the use of computer-assisted techniques in the short term. Further work is required to prove long-term beneficial effect. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-11-02 20:50:33.957

One major barrier that prevents cartilage integration following mosaic arthroplasty is the presence of a zone of chondrocyte death (ZCD) that is generated upon osteochondral graft harvest, which can extend up to 400 μm into the cartilaginous portion of the graft. In order for cartilage integration to occur, chondrocytes must be present at the graft periphery; however chondrocyte migration through the ZCD to the graft periphery is inhibited by the dense extracellular matrix (ECM) of cartilage. The purpose of this study was to develop a method for increasing the number of chondrocytes within the ZCD and at the periphery of a cartilage graft. This method used a combination of collagenase treatment (as a means of degrading the ECM within the ZCD) and chondrocyte chemotaxis (as a means of improving chondrocyte migration into the ZCD and to the cartilage periphery). Results indicate that treating bovine articular cartilage with 0.6 % collagenase for 10 min decreased with extent of the ZCD by approximately 35% (collagenase: 109 ± 13 μm; control: 175 ± 13 μm). Each of the chemotactic agents tested (PDGF-bb, bFGF, and IGF-I) were found to induce bovine chondrocyte chemotaxis at concentrations of 25 ng/mL in modified Boyden chamber experiments. However, in bovine articular cartilage samples that were pre-treated with collagenase (0.6% for 10 min), supplementation with 25 ng/mL of either PDGF-bb or bFGF had no apparent effect on the ZCD relative to samples treated only with collagenase (PDGF-bb: 85 ± 10 μm; bFGF: 88 ± 10 μm). Alternatively, bovine articular cartilage samples pre-treated with collagenase (0.6% for 10 min) and supplementation with 25 ng/mL IGF-I resulted in an approximately 65% reduction in the ZCD relative to samples treated only with collagenase (IGF-1: 38 ± 5 μm). Thus, treating osteochondral grafts with collagenase and IGF-1 induces chondrocyte repopulation of the zone of chondrocyte death generated by osteochondral graft harvesting, and could enhance cartilage integration after implantation. / Thesis (Master, Chemical Engineering) -- Queen's University, 2009-12-21 20:16:05.815

Computer assisted mosaic arthroplasty (CAMA) is a surgical technique that transplants cylindrical osteochondral grafts to repair damaged cartilage. An earlier in vivo study on sheep showed that short-term clinical outcomes are improved with the use of computer assistance, as compared to the conventional technique. This thesis reports on a study comparing three mosaic arthroplasty techniques -- one conventional and two computer assisted -- on human anatomy. This in vitro study used solid foam femur models modified to incorporate simulated cartilage defects. There were five participating surgeons ranging from a third year resident to a senior orthopedic surgeon. Each of the five participating surgeons performed a total of nine trials. There were three distinct sets of identical solid foam femur models with simulated cartilage defects. Three surgical techniques (conventional, opto-electronic, and patient-specific template) were performed on each. Several measures were made to compare surgical techniques: operative time; surface congruency; defect coverage; graft surface area either too high or too low; air volume below the grafts; and distance and angle of the grafts from the surgical plan. The patient-specific template and opto-electronic techniques resulted in improved surface congruency, defect surface coverage, graft surface within 0.50mm recessed and 0.25mm proud of the original surface, and below-graft air gap volume in comparison to the conventional technique. However, the conventional technique had a shorter operative time. The patient-specific template technique had less variance in surface congruency and shorter operative time than did the opto-electronic technique. / Thesis (Master, Computing) -- Queen's University, 2013-11-28 17:06:06.961