Congenital patellar dislocation

The patella refers to the knee joint area of ​​the human body, and congenital patellar luxation means that a person's knee joint area cannot stand upright normally, causing difficulty in movement. Congenital patellar dislocation is a very rare phenomenon, and its cause is not particularly clear in current medicine. After congenital patellar dislocation occurs, a person's calf and thigh will be deformed. So how should congenital patellar dislocation be corrected?

Causes

The cause is unknown, but some patients have a genetic predisposition. Occasionally, other congenital malformations may occur. The outer edge of the patient's patella is closely connected to the iliotibial band, the iliotibial band is severely contracted, the quadriceps femoris is abnormally developed, the vastus medialis muscle is absent, and the patella is very small, causing the entire knee extensor mechanism to move outward, resulting in a series of deformities: flexion deformity of the hip and knee joints, knee valgus, tibial external rotation and excessive lumbar lordosis. The intercondylar notch of the femur is hypoplastic, but the bone ends are basically normal.

Clinical manifestations

After birth, one or both sides of the knee joint are found to have flexion contracture and cannot be straightened. The patella has moved to the outside of the femoral condyle, and the knee cannot be actively extended, and passive knee extension is also limited. Because the patella is small and the knee cannot be extended, it is not easy to palpate the patella on the outside of the femoral condyle in infants. The shadow of the knee extensor mechanism disappears on the lateral X-ray before the age of 2 years. After the age of 2, the patellar ossification center gradually appears, and the patella can be seen on the lateral side of the femoral condyle on the AP radiograph.

Disease treatment

Surgical treatment should be performed as early as possible to reconstruct the knee extension mechanism. With early treatment, knee joint function can be restored and the accompanying deformities can be gradually corrected with growth and development.

Surgical steps:

(I) Release all contracted tissues on the lateral side of the patella and prepare for reconstruction. The incision is made from the middle and lower side of the lateral thigh along the iliotibial band to the tibial tubercle.

The joint is bent inward, and the contracted tissue on the outside of the patella is fully loosened, including the outside of the patellar ligament. The distal end of the vastus lateralis muscle is cut longitudinally from the junction of the iliotibial band, the lateral edge of the quadriceps tendon and the outer edge of the patella, and freed upward for later use. The contracted iliotibial band is cut off, and if the biceps femoris is obviously contracted, it is lengthened. At this time, the contracted tissue on the outside of the patella has been completely loosened.

(ii) Repositioning of the patella: Make an incision along the inner edge of the patella between the rectus femoris and vastus medialis muscles. At this time, the patella can be repositioned between the femoral condyles. If the quadriceps tendon and patellar ligament are still not in a straight line and there is still force for external patellar dislocation when the knee is flexed, half of the lateral patellar ligament can be shifted to the inside until the tibial tuberosity is moved medially.

(III) Repair and suture the soft tissue, strengthen the knee extension mechanism, remove part of the loose joint capsule and synovium on the inside, and then tighten and suture them. After slightly freeing the vastus medialis muscle upward, the muscle belly tissue is used to cover the patella and sutured to the outer edge of the patella to strengthen the force that fixes the patella in the neutral position. The distal end of the released vastus lateralis muscle is shifted upward and sutured to the upper part of the quadriceps tendon to reduce the force pulling the patella outward. The redundant joint capsule and synovium on the inside were removed and the synovial defect on the outside was repaired. During the operation, the result was considered satisfactory if the knee joint was flexed 90° and the patella no longer slipped outward. The long leg was fixed with a plaster splint for 6 weeks after the operation. The quadriceps contraction function was exercised early, and knee flexion and extension activities were practiced after the plaster was removed.