| Part one The Changes of Torsional Alignment of Hindlimb in Growing Rabbits after Patellar DislocationObjective:The dysplasia of femoral trochlea and patella has been considered as the risk factors for patellar dislocation.On the other hand,animal studies had shown early patellar dislocation can lead to the dysplasia of femoral trochlea and patella.Torsional malalignment of hindlimb has also been considered as a risk factor for patellar dislocation.But the influence of patellar dislocation on the development of torsional alignment of hindlimb remains unknown.The angle of femoral version and tibial torsion represent the torsional alignment of hindlimb.The present study aims to investigate whether the torsional alteration of the hindlimb occurs after patellar dislocation in growing rabbits and try to discuss the influence of patellar dislocation on the growth of torsional alignment of lower limb.Methods:In the present study,30 one-month-old rabbits were included.The experimental group consisted of 30 left knees of rabbits which were underwent the surgery for patellar lateral dislocation.The control group consisted of 30 right knees of the rabbits which no surgical procedure was performed.The Computed Tomography(CT)scan was performed after the surgery and at the point the rabbits were skeletal mature(5 months post-surgery).The angles of femoral version and tibial torsion were measured using a three-dimensional method.The results were expressed as mean ±standard deviation.The angles of femoral version and tibial torsion between the control group and the experimental group were evaluated by Student's t test.A P value<0.05 was determined as statistically significant.Results:After the surgery,the femoral version and tibial torsion in the experimental and control group were not significantly different.When the rabbits were mature(5 months after the surgery),the femoral anteversion(positive)turned to be femoral retroversion(negative).At that time,the angle of femoral version in the experimental group(-5.50±6.13°)was significantly different from that in the control group(-10.90±4.74°)(P<0.05).But the angle of tibial torsion in the experimental group(7.17±7.25°)and control group(4.47±6.34°)were not significantly different(P=0.144).Summary:From this study,patellar dislocation can lead to alteration of femoral version in growing rabbits.So early patellar dislocation may affect on lower extremity alignment.Part two The Osteogenesis of the Subchondral Bone Tissue in Femoral Trochlea of Growing Rabbits after Patellar DislocationObjective:The patellar dislocation is a common disease for children and adolescents.Patients with patellar dislocation often have femoral trochlear dysplasia.On the other hand,animal studies had verified that patellar dislocation can led to femoral trochlear dysplasia.But the mechanism is still unclear.Bone Morphogenetic Protein 2(BMP-2)increase the expression of the Runt-related transcription factor 2(RunX-2).They promote the expression of osteogenic genes,secretion of Alkaline Phosphatase(ALP)and differentiation from mesenchymal stem cells to osteoblasts.However,after early patellar dislocation,whether the osteogenic level of femoral trochlea and the expression level of BMP-2,RunX-2 and ALP changes is unknown.The present study used the models for patellar dislocation of growing rabbits.The morphology of femoral trochlea,the indices of bone trabecula,and the expression level of BMP-2?RunX-2 and ALP after early patellar dislocation were observed.The mechanism of the formation of femoral trochlear dysplasia after early patellar dislocation was discussed.Methods:The present study contained thirty two-month-old rabbits.The experimental group composed of left knees(with surgery for patellar dislocation)and the control group consisted of the right knees(without any surgical procedure).The rabbits were sacrificed at two weeks(10 rabbits),six weeks(10 rabbits),and ten weeks(10 rabbits)after the surgery.Then the distal femurs were achieved for Micro-computed tomography scanning(Micro-CT)for testing Bone Volume Fraction(BV/TV)?Trabecular number(Tb.N)?Trabecular thickness(Tb.Th)and Trabecular Separation(Tb.Sp).The immunohistochemical staining of ALP,BMP-2 and RunX-2 was also tested.The bone tissue under the cartilage of the femoral trochlea was tested with quantitative reverse transcriptase-polymerase chain reaction(qRT-PCR)for testing the expression of BMP-2 and RunX-2.The difference of the quantitative data between the experimental group and the control group were evaluated by Student's t test by GraphPad PRISM 8.0.A P value<0.05 was considered significantly different.Results:1.Measurements by Micro-CT:Six and ten weeks after surgery,the depth of femoral trochlea in the experimental group was lower significantly than that of the control group.The sulcus angle in the experimental group was higher than that of the control group significantly.The ROI of the experimental group showed significantly lower BV/TV,Tb.N,Tb.Th and significantly higher Tb.Sp(P<0.05).Two weeks after surgery,the above indices were not significantly different between two groups.2.Immunohistochemical staining and qRT-PCR:Two weeks and four weeks after the surgery,the Mean Optical Density(MOD)for ALP,BMP-2 and RunX-2 in the subchondral bone of femoral trochlea of the experimental group was significantly lower than those of the control group(P<0.05).The qRT-PCR also showed significantly lower expression of BMP-2 and RunX-2 in the subchondral bone of femoral trochlea in the experimental group(P<0.05).But ten weeks after patellar dislocation,those indices were not significantly between two groups.Summary:The osteogenic level of subchondral bone tissue in femoral trochlea after patellar dislocation in growing New Zealand white rabbits is low,which is related to the significantly decreased expression level of osteogenesis related BMP-2,RunX-2 and ALP.These may relate to trochlear dysplasia after early patellar dislocation.Part three The Morphology of Patella Changed Significantly after Soft Tissue Correction for Children with Recurrent Patellar DislocationObjective:Although morphological improvement of femoral trochlea has been investigated in children with patellar dislocation after surgery,whether the patella shape changed under the same condition is still unknown.The purpose of the study was to investigate the changes of patellar morphology in transverse plane following surgical correction of recurrent patellar dislocation in children.Methods:A total of 22 patients with a mean age of 9.9 years(7 to 12)were included.All had unilateral recurrent patellar dislocation.The knees with recurrent patellar dislocation were treated with medial patellar retinaculum plasty and defined as the affected side.The contralateral knees with no symptom of patellar instability were considered as the unaffected side.All patients were treated between October 2014 and August 2018.Axial CT(Computed Tomography)scans were undertaken in all patients to assess the patellar morphological characteristics on a particular axial image preoperatively and at the final follow-up.Student's t test was used to test the difference of the numerical variables.A P value<0.05 was determined as statistically significant.The results are expressed as mean ± standard deviation.Results:There were not significant differences about patellar transverse diameter,thickness and Wiberg angle between affected side and unaffected side before surgery and at the last follow-up respectively(The mean followup period:28.0 ± 3.3 months).However,before surgery,the Wiberg-index in the affected side(0.74 ± 0.06)was significantly different from that in the unaffected side(0.64 ± 0.04).At the last follow-up,the Wiberg-index in the affected side(0.67 ± 0.05)and the unaffected side(0.65 ± 0.04)were not significantly different.Also,in the affected side,the Wiberg-index at the last follow-up was significantly lower than that before surgery(P<0.05).The Wiberg-index in the unaffected side was not significantly different before surgery and at the last follow-up.Summary:The patellar morphology can change significantly after surgical procedures in children with patellar recurrent dislocation whose epiphysis is not close.Part four Anatomical Medial Patellofemoral Ligament Reconstruction for Developmental Patellar Dislocation:Two-Strand Grafts versus Four-Strand GraftsObjective:Medial patellofemoral ligament(MPFL)reconstruction is the main treatment for patellar dislocation.The methods for fixation at patellar side for reconstruction are various,each has its own characteristics.We invented a new fixation method with a certain bone-graft area,less bone loss and no implant.The present study described the new fixation using semi patellar tunnel for anatomical MPFL reconstruction.The purpose of this study was to describe two anatomical MPFL reconstruction methods with the new fixation:reconstruction with two-strand grafts and reconstruction with four-strand grafts and to evaluate the clinical and radiological results.Methods:From January 2010 to January 2013,patients who sustained developmental patellar dislocation and met inclusion criteria were included in the study and divided into two groups randomly to undergo MPFL reconstruction either by two-strand grafts(T group)or four-strand grafts(F group).Patients were followed up 1 month,12 month,24 months,and 36 months postoperatively.The apprehension test was applied to test patellar stability.The Kujala score,Lysholm score,and Crosby-Insall grading were used to evaluate the function of the affected knee.The patellar congruence and patellar tilt angle were used to measure the morphology of the patellofemoral joint.In addition,patients'subjective assessments and complications were recorded.Results:Thirty-eight patients in T group and 38 patients in F group were followed for at least 36 months.The apprehension test was positive in all patients preoperatively but was negative at follow-up.The Kujala score,Lysholm score,patellar congruence angle,and the patellar tilt angle of patients in both groups improved significantly at 36-month follow-up when compared with those assessed preoperatively.However,patients in the F group achieved better clinical results in terms of Kujala score,patellar congruence angle,patellar tilt angle,and Crosby-Insall grading when compared with those in the T group 36 months after the operation.Most patients(92%of patients in the T group and 97%of patients in the F group)were satisfied with the surgery.Summary:The anatomical MPFL reconstruction with two-strand grafts or four-strand grafts were both safe techniques for recurrent patellar dislocation with satisfactory clinical outcomes.The anatomical fixation with four strand grafts achieved better clinical and radiographic results in the follow-up,which may be a better reconstruction method.Conclusions:The early patellar dislocation can led to torsional malalignment of hindlimb and femoral trochlear dysplasia which is related to the low osteogenesis of subcondral bone.Clinically,the patellar morphology can change significantly after surgical procedures in children with patellar recurrent dislocation whose epiphysis is not closed.These findings show that patellar dislocation is a developmental disorder.The anatomical fixation with four-strand grafts achieved better clinical and radiographic results in the follow-up,which may be a better reconstruction method than the method using two-strand grafts. |
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