| Objective：Chronic patellar dislocation is more common in clinical.Many researchers consider this disease have diverse pathogenesis. Theybelieve that femoral trochlear dysplasia is the important cause for habitualpatellar dislocation. Femoral trochlear dysplasia is a anatomicalmorphological abnormality in the geometrical concave and in its depth at thefront part of the trochlear groove. In patients with patellar dislocation, femoraltrochlear dysplasia is a common phenomena with incidence. However, peoplehave little cognition about femoral trochlear dysplasia at the moment. It is notquite clear about the pathogenesis and mechanism. The aim of this study wasto investigate the effects of patellar dislocation on femoral trochlear dysplasiaby animal experiments.Methods：Forty1-month-old New Zealand White rabbits (provided byAnimal Test Center of Hebei Medical University) of both sexes, weighingfrom290g to320g, were randomly divided into two groups, with each groupcontaining20rabbits. They were raised under the same conditions in singlecage for each animal. The feedstuff used was the standard complete feedstuffprovided by the center and the water fed with tap water. Before the surgery,the left knees of rabbits in sham surgery Group and experimental group wereshaved and sanitized following the routine procedures and the right kneeswere used as controls. A surgery was performed under sterile conditions andintravenous anesthesia (su mian xin0.2ml/kg). After anesthesia, a longitudinalincision of about3cm in length was cut at the front middle line of the leftknees of the rabbits in sham surgery Group and experimental group.Layer-by-layer incision of skin and subcutaneous tissue was performedconsecutively to reveal capsule. Incisions of2cm was made at the capsule at1.5cm from the upper edge of the patella along the bilateral of the patellar ligament. For animals in sham surgery Group, a sham surgery was performedfor the left knee. After the bilateral joint capsule was cut, the incised jointcapsule and the skin wound were closed in layers with3-0nylon sutures. Thisgroup is sham surgery group; Incisions of2cm were cut longitudinally alongthe bilateral joint capsule of the patella of the left knee for animals inexperimental group. The lateral joint capsule was sutured overlapping to makethe patella completely dislocated and that it cannot return to the normalposition during active and passive knee extension and flexion in experimentalgroup. The right knees of animals in two groups were used as control group.After the surgery they were raised under the same conditions in single cagefor each animal. The parameters used from CT scans include sulcus angle,trochlear width and trochlear depth1month and3months after the surgerypostoperatively, imaging femoral trochlea of sham surgery Group,experimental group and cntrol group by CT scans provided the measurementof sulcus angle, trochlear width and trochlear depth.Rabbits were sacrificed3months after the surgery by air venous embolism. The anatomicmorphological changes in the femoral trochlea were observed visually and thechanges in the cartilage tissues of the femoral trochlea and the patella wererecorded. A sharp scalpel was then used to take the cartilage tissues at thefemoral trochlea and the patella of rabbits of sham surgery Group,experimental group and control group respectively. They were made intotissue blocks of about0.5×0.5×0.5cm and stained with hematoxylin and eosinor toluidine blue and observed the changes of the femoral trochlea andpatella by Microscopy.Results: The average value of sulcus angle was113.99°±1.58°in shamsurgery group and114.47°±1.69°in experimental group and113.64°±1.46°incontrol group1month after the surgery. There was no statistical difference inthe average values of Sulcus angle in the three groups1month after thesurgery (P>0.05).The average value of trochlear width was6.86±0.14mm insham surgery group and7.77±0.12mm in experimental group1month after thesurgery. This set of data revealed significant difference of sulcus angle average value between the sham surgery group and the experimentalgroup(P<0.05). The average value of trochlear width was6.78±0.14mm°incontrol group. there were no differences between the sham surgery Group andthe control group(P>0.05).however, there were significantly different betweenthe sham surgery Group and the control group(P<0.05). The average value oftrochlear depth was2.04±0.08mm in sham surgery group and2.00±0.04mm inexperimental group and2.04±0.08mm in control group1month after thesurgery. There was no statistical difference in the average values of trochleardepth in the three groups1month after the surgery (P>0.05). The averagevalue of sulcus angle was respectively135.33°±1.77°,158.72°±4.10°,135.68°±2.16°in sham surgery group, experimental group and control group3month after the surgery. This set of data revealed significant difference ofsulcus angle average value between the sham surgery group and theexperimental group(P<0.05), and there were no differences between the shamsurgery Group and the control group(P>0.05). The average value of trochlearwidth was Respectively7.13±0.21mm,9.16±4.13mm,7.15±0.18mm in shamsurgery group, experimental group and control group3month after the surgery.This set of data revealed significant difference of trochlear width averagevalue between the sham surgery group and the experimental group(P<0.05),and there were no differences between the sham surgery Group and thecontrol group(P>0.05).The average value of trochlear depth was113.99°±1.58°in sham surgery group and114.47°±1.69°in experimental groupand113.64°±1.46°in control group3month after the surgery. This set of datarevealed significant difference of trochlear depth average value between thesham surgery group and the experimental group(P<0.05), and there were nodifferences between the sham surgery Group and the control group(P>0.05).Cross-sectional anatomy in the experimental group3months after thesurgery: The lateral femoral trochlea were low, shallow, and wide. Thetrochlear groove were shallow. The bulge of the lateral femoral trochlear facetwas not obvious compared with the internal trochlear facet. The shamsurgery group and Control group: The shape of the femoral trochlea were normal, the trochlear groove had normal depth. The lateral femoral trochlearfacet was usually higher and more protruded than the internal trochlearfacet.Visual Observation in tne experimental group: the trochlear groove wereshallow, wide, and low. Lateral femoral trochlea was low, and height oftrochlear groove was reduced. The hyperosteogeny of the femoral trochleawas obvious. The articular cartilage surface was rough and uneven with dimcolor. Cracks and defects could be see. The sham surgery group and Controlgroup: The knee joint did not show any inflammatory change. The appearanceof the femoral trochlea was normal and the surface of the articular cartilagewas smooth. The luster was bright. There were no cracks or softened parts.The patellofemoral joint was closely connected, and the joint parts werecompatible to each other. Histochemistry Preparation of Pathological Sectionsin experimental Group: The articular cartilage of femoral trochlea and thepatellar cartilage at the surgery side of the animals were thin and rough. Therewere partially peeled off cartilage that resulted in defective areas withdifferent formed and sized cartilage cells and irregular arrangements. Themain growth direction was changed, and the four structural layers were noteasily identified. The sham surgery group and Control group: The HE stainingwas homogeneous. The surface of the articular cartilage was smooth and thecells were orderly and regularly arranged with basically the same size. Thesuperficial cells were fusiform and nearly longitudinally arranged. The cells inthe transition layer were round in shape and dispersed sparsely, while they arecylindrical in shape in the radiation layer. The cells in the calcification layerwere relatively large and sparsely dispersed. The four layers were clearlydistinguishable.Conclusions: Secondary femoral trochlear dysplasia may be caused bypatellar dislocation in a normally developing femoral trochlea and patellardislocation may be one of the causes of femoral trochlear dysplasia. |
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