| PCL injuries are an increasingly recognized cause of knee instability in the practice of orthopaedic surgery and sports medicine. Clinical interest in these injuries has been increasing over the last several decades as knowledge and understanding of the biomechanical consequences and surgical reconstruction options have progressed. Much work has been done through anatomy dissections and anatomical sectioning studies and biomechanics to improve our understanding of native PCL function as well as the importance of the secondary stabilizers. In addition, several reconstructive techniques for both isolated and combined PCL reconstruction have been evaluated and compared and can assist us in making a more informed clinical decision for the management of these, often difficult to treat, injuries.The purpose of this study was to approach the biomechanical function of PCL and its different bundles, examine the impact of PCL rupture on biomechanical and histological features and type II collagen levels using biomechanical, histologic, and immunohistochemical testing and, if possible, to further explore the influence mechanism of PCL rupture on the medial femoral condyle cartilage. Chapter One Effect of PCL rupture on biomechanical features of the medial femoral condyleObjective The purpose of this study was to compare biomechanical features of the medial femoral condyle among PCL intact, partial PCL rupture and complete PCL rupture, approach the biomechanical function of PCL and its different bundles and examine the biomechanical impact of PCL rupture.Materials Twelve fresh human cadaveric knee specimens were subjected to different load (200N,400N,600N,800N) at 0,30,60, and 90 of knee flexion. A combined quadriceps/hamstring load (400/200 N) was used to simulated muscle loads. Four surgical treatments-PCL intact(12 samples), ALB rupture(6 samples), PMB rupture(6 samples) and PCL rupture(12 samples) were tested in sequential order. During the test, strain of anterior, middle and posterior part of the medial femoral condyle were calculated.Results (1) At 0-degree knee flexion, compression strain was noted in anterior, middle and posterior part of the medial femoral condyle under any loading conditions. At 30-degree knee flexion, tension strain was founded in anterior part of the medial femoral condyle under any loading conditions and compression strain was founded in middle and posterior part of the medial femoral condyle under any loading conditions. At 60-and 90-degree knee flexion, tension strain was recorded in anterior and middle part of the medial femoral condyle under any loading conditions and compression strain was recorded in posterior part of the medial femoral condyle under any loading conditions. (2) At 0-degree knee flexion, no significant difference of strain of the medial femoral condyle was noted between PCL intact and ALB rupture under any loading conditions (P>0.05). Compared to PCL intact, PMB rupture and PCL rupture had higher strain of the medial femoral condyle under all loading conditions (P?0.05). Compared to ALB rupture, PMB rupture and PCL rupture had higher strain of the medial femoral condyle under all loading conditions (P<0.05). Compared to PMB rupture, PCL rupture had higher strain of the medial femoral condyle under individual loading conditions rather than under all loading conditions. (3) At 30-,60-and 90-degree knee flexion, compared to PCL intact, ALB rupture had higher strain of the medial femoral condyle under 600N and 800N load rather than under 200N and 400N load. No significant difference of strain of the medial femoral condyle was founded between PCL intact and PMB rupture under any loading conditions (P>0.05). However, PCL rupture had higher strain of the medial femoral condyle than PCL intact under all loading conditions.Compared to ALB rupture, PCL rupture had no higher strain of the medial femoral condyle under individual loading conditions rather than under all loading conditions. Compared to PMB rupture, ALB rupture had higher strain of the medial femoral condyle under 600N and 800N load rather than under 200N and 400N load. Furthermore, PCL rupture had higher strain of the medial femoral condyle than PMB rupture under all loading conditions.Conclusions Our data suggest that PMB are the major stabilizing bundles of PCL toward full extension, ALB are the major stabilizing bundles of PCL toward knee flexion and both bundles function through the ROM in a codominant fashion. Partial and complete rupture of PCL may have hazardous biomechanical impacts on each part of the medial femoral condyle during normal movement.Chapter Two Effect and mechanism of PCL rupture on histological features of the medial femoral condyleObjective The purpose of the study was to investigate the effect of PCL rupture on histological features of the medial femoral condyle and approach the possible mechanism of the association between PCL rupture and osteoarthritis.Methods Following transection of PCL of unilateral knee (experimental groups) and sham operation of another knee (control groups) in posterior leg, the 48 male rabbits were sacrificed at 4,8,16 and 24 weeks after surgery. Gross pathological observation, hematoxylin-eosin and toluidine blue staining for histological evaluation and immunohistochemistry analyses for OPN and MMP-13 were performed on the medial femoral condyle cartilage.Results (1) Gross observation:As time passed, cartilage appeared to be yellowish-white, lackluster and its appearance displayed significant cracks and cartilage defects, osteophyte-like structures were observed in the medial femoral condyle after PCL rupture. At 4,8,16,24 weeks postoperatively, gross scores of the medial femoral condyle cartilage in the experiment group were significantly higher than in the controls (P<0.05). There was statistical difference in the gross scores of the experiment group among different time points postoperatively. (2)HE and toluidine blue staining:After PCL rupture, the scores for structure range from irregular to complete disorganization of the cartilage, scores for cellularity range from hypocellularity to large decrease in chondrocytes, scores for stainability range from small decrease in color to no stainability over time. There was a significant time-dependent increase of Mankin score in the medial femoral condyle cartilage from 4 to 24 weeks postoperatively (p<0.05). (3) Mankin score:At 4,8,16,24 weeks postoperatively, Mankin score of the medial femoral condyle cartilage in the experiment group were significantly higher than in the controls (P<0.05). There was statistical difference in the Mankin score of the experiment group among different time points postoperatively. (4) Expression of OPN:OPN levels increased over time in the the medial femoral condyle cartilage and statistical significance was reached for weeks 4-24 compared to the normal cartilage (P<0.05). OPN levels at 8, 16,24 weeks postoperatively were significantly higher than that at 4 weeks postoperatively (P<0.05). There were no signifigant differences between 8 weeks postoperatively and 16 weeks postoperatively (P>0.05). OPN levels at 8,16 weeks postoperatively were significantly lower than that at 24 weeks postoperatively (P<0.05). OPN levels were maximal at week 24. (5) Expression of MMP-13:At 4,8,16,24 weeks postoperatively, MMP-13 levels of the medial femoral condyle cartilage in the experiment group were significantly higher than in the controls (P<0.05). MMP-13 levels at 8,16,24 weeks postoperatively were significantly higher than that at 4 weeks postoperatively (P<0.05). There were no signifigant differences between 8 weeks postoperatively and 24 weeks postoperatively (P>0.05). MMP-13 levels at 8,24 weeks postoperatively were significantly lower than that at 16 weeks postoperatively (P<0.05). MMP-13 levels were maximal at week 16 and decreased slightly at week 24. (6) Correlation Analysis:In addition, articular cartilage OPN levels of medial femoral condyle showed a positive correlation with macroscopic grade (Spearman's rho=0.880, p<0.05) and Mankin score (Spearman's rho=0.871, p<0.05). In addition, the articular cartilage levels of MMP-13 also correlated with macroscopic grade (Spearman's rho=0.840, p<0.05) and Mankin score (Spearman's rho=0.817, p<0.05).Conclusion These observations reveal that PCL rupture results in the rapid development of degenerative changes characteristic of OA in medial femoral condyle cartilage. Elevated levels of OPN and MMP-13 may contribute to the knee damage and cartilage degeneration induced by PCL rupture.Chapter Three Effect of PCL rupture on type II collagen levels of the medial femoral condyle cartilage and its related factorsObjective To investigate effects of PCL rupture on type?collagen levels of high-weight-bearing and low-weight-bearing articular cartilage of the medial femoral condyle and explored the changes of type?collagen following PCL rupture and its relationship with mechanical and biochemical factors.Methods Following transection of PCL of unilateral knee (experimental groups) and sham operation of another knee (control groups) in posterior leg, the 48 male rabbits were sacrificed at 4,8,16 and 24 weeks after surgery. Immunohistochemistry analyses for type II collagen was performed on the high-weight-bearing and low-weight-bearing articular cartilage of the medial femoral condyle.Results Compared to high-weight-bearing and low-weight-bearing articular cartilage of control groups, the integrated optical density (IOD) of type II collagen in high-weight-bearing cartilage rather than in low-weight-bearing cartilage at 4 weeks postoperatively was significantly lower (P?0.05). Compared to low-weight-bearing articular cartilage of experimental groups, the IOD of type II collagen in high-weight-bearing cartilage at 4 weeks postoperatively was significantly lower (P<0.05). At 8,16,24 weeks postoperatively, the IOD of type II collagen in high-weight-bearing and low-weight-bearing cartilage of experimental groups was markedly lower than that in high-weight-bearing and low-weight-bearing articular cartilage of control groups, high-weight-bearing cartilage of experimental groups had lower IOD of type II collagen compared with low-weight-bearing articular cartilage of experimental groups. With further analysis comparing the change of IOD of type?collagen in high-weight-bearing and low-weight-bearing cartilage, the results showed that PCL rupture timedependently decreased the expression of type II collagen. Lower type II collagen levels was associated with the mechanical factors rather than biochemical factors at 4 weeks postoperatively and its levels was associated with the mechanical factors and biochemical factors at 8,16,24 weeks postoperatively. The mechanical factors were responsible for the majority of degradation of cartilage matrix at 8 weeks postoperatively, the biochemical factors were responsible for the majority of degradation of cartilage matrix at 16 weeks postoperatively and were responsible for the vast majority of degradation of cartilage matrix at 24 weeks postoperatively.Conclusion PCL rupture could timedependently decrease the expression of type?collagen, which related to the mechanical factors in the early stage of rupture and biochemical factors in the late stage of rupture. |
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