Arthroscopic surgery for synovial chondroma of the subacromial bursa with non-traumatic shoulder subluxation complications:Two case reports

BACKGROUND Synovial chondromatosis is a disease originating from the synovium and characterized by the presence of metaplastic cartilaginous nodules in synovial cavities.The exact prevalence of synovial chondromatosis remains unknown,and the involvement of the shoulder joint is very rare.Synovial chondromatosis accompanied by subluxation of the humeral head without a history of trauma is rarely encountered,and to our knowledge,no published reports describe this condition.CASE SUMMARY We present two cases of synovial chondromatosis in the shoulder joint,accompanied by subluxation of the humeral head,in two arthroscopically managed adult patients.We performed arthroscopic labrum fixation and removal of the loose body from the shoulder joint.To identify primary and secondary categories,pathological analysis was arranged.Clinical and radiographic evaluations at the 1-mo follow-up were satisfactory.CONCLUSION The biomechanical function of the shoulder joint requires attention,especially following the detection of loose bodies,as observed with synovial chondroma occurring in rare sites.Arthroscopic management is successful in patients with synovial chondromatosis combined with shoulder subluxation.

New treatment of patellar instability after total knee arthroplasty: A case report and review of literature

BACKGROUND Patellar instability is an uncommon complication after total knee arthroplasty(TKA).Partial lateral patella facetectomy(LPF)with lateral retinaculum release treatment of patellar instability is rarely reported.CASE SUMMARY We present a case of patellar instability 8 mo after primary TKA.Treatment of this complication was adapted to address the cause of the dislocation.To eliminate patellar instability,we restored the vastus medialis and performed LPF with lateral retinaculum release.We achieved normal patellar tracking.Clinical and radiographic evaluations at the 1-year postoperative follow-up were satisfactory.CONCLUSION LPF with lateral retinaculum release represents a promising option to restore central patellar tracking in patients with patellar instability after TKA in cases without component malposition.

Cross-sectional Anatomy of Ilium for Guiding Acetabular Component Placement Using High Hip Center Technique in Asian Population

Background：Many clinical studies have been published involving the use of a high hip center （HHC）,achieved good follow-up.However,there is a little anatomic guidance in the literature regarding the amount of bone stock available for initial implant coverage in this area of the ilium.The purpose of this study was to evaluate the thickness and width of the human ilium and related acetabular cup coverage for guiding acetabular component placement in HHC.Methods：A total of 120 normal hips in 60 cases of adult patients from lower extremities computer tomographic angiography Digital Imaging and Communications in Medicine data were chosen for the study.After importing the data to the mimics software,we chose the cross sections every 5-mm increments from the rotational center of the hip to the cephalic of the ilium according the body sagittal axis,then we measured the thickness and width of the ilium for each cross section in axial plane,calculated the cup coverage at each chosen section.Results：At the acetabular dome,the mean thickness and width of the ilium were 49.71 ± 4.88 mm and 38.92 ± 3.67 mm,respectively,whereas at 1 cm above the dome,decreased to 41.35 ± 5.13 and 31.13 ± 3.37 respectively,and 2 cm above the dome,decreased to 31.25 ± 4.04 and 26.65 ± 3.43,respectively.Acetabular cup averaged coverage for 40-,50-,and 60-mm hemispheric shells,was 100%,89%,and 44% at the acetabular dome,100%,43.7%,and 27.5% for 1 cm above the dome,and 37.5%,21.9%,and 14.2% for 2 cm above the dome.Conclusions：HHC reconstructions within 1cm above the acetabular dome will be an acceptable and smaller diameter prosthesis would be better.

Three-dimensional reconstruction method for measuring the knee valgus angle of the femur in northern Chinese adults

The purpose of this study was to establish a method for measuring the knee valgus angle from the ana- tomical and mechanical axes on three-dimensional reconstruction imaging models, and to use this method for estimating an average knee valgus angle value for northern Chinese adults. Computed tomographic angiography data in DICOM format for 128 normal femurs from 64 adult subjects were chosen for analysis. After the femur images were subjected to three-dimensional reconstruction, the deepest point in the intercondylar notch （point A）, the midpoint of the medullary cavity 20 cm above the knee-joint line （point B）, and the landmark of the femoral head rotation center （point C） were identified on each three-dimensional model. The knee valgus angle was defined as the angle enclosed by the distal femoral anatomical axis （line AB） and the femoral mechanical axis （line AC）. The average （mean＋SD） of knee valgus angle for the 128 femurs was 6.20°±1.20° （range, 3.05° to 10.64°）. Significant positive correlations were found between the knee valgus angles of the right and left sides and between the knee valgus angle and age. During total knee arthroplasty, choosing a valgus cut angle of approximately 6° may achieve a good result in reestablishing the natural mechanical alignment of the lower extremity for patients of northern Chinese ethnicity. Larger valgus cut angles should be chosen for older patients.