Habitual patellar dislocation

　　The etiology of habitual patellar dislocation is complex, and part of it may be related to trauma, high patella, maldevelopment of the femoral condyle, genu varum, maldevelopment of the medial quadriceps muscle, hypertrophy of the lateral quadriceps muscle, relaxation of the soft tissues on the medial side of the knee joint, and contraction of the lateral soft tissues. Abnormal development of the bone and surrounding soft tissues of the knee joint is an innate factor for the occurrence of habitual patellar dislocation, suggesting that habitual patellar dislocation may be related to genetic factors.

　　1. There is no obvious trauma to the knee joint, or the quadriceps femoris is strongly contracted, which can cause dislocation. Most patients often dislocate, and the patella dislocates to the lateral side of the femoral condyle when the knee is flexed, and naturally复位 when the knee is extended. The quadriceps femoris atrophy, extension of the knee is weak, easy to fall, but there is no obvious pain.

　　2. This disease is also prone to some postoperative complications, including recurrence of dislocation, knee hyperextension, limited flexion, osteoarthritis, etc. If the patellofemoral joint alignment is not good after surgery, it can lead to patellofemoral arthritis, leaving patellar pain. Therefore, during orthopedic correction, it is necessary to both effectively correct the dislocation and maintain the normal patellofemoral joint structure, keeping the patellofemoral joint alignment normal, and not leaving knee pain and patellofemoral arthritis after surgery, with a fast functional recovery.

　　The main symptoms of this disease are that when the patient flexes the knee, the patella slides away from the central position of the intercondylar fossa of the femur and moves towards the front of the lateral condyle of the femur, located on the lateral side of the knee joint. It not only affects the appearance of the knee but also greatly weakens the strength of the knee joint, affecting its normal function. Over time, it may induce osteoarthritis of the knee joint. The injured area is obviously swollen, the patella is tender, the movement is obviously restricted, the knee feels soft, walking is difficult, and the knee can be复位 by extending the knee and gently pushing with the hand. Arthroscopic examination and X-ray examination can show patellar dislocation.

　　For habitual dislocations caused by congenital causes, there are no effective preventive measures for this disease. Therefore, the prevention of this disease mainly focuses on traumatic causes of habitual dislocation. Avoiding trauma is the key to the prevention and treatment of the disease. In addition, attention should be paid to both effectively correcting the dislocation and maintaining the normal patellofemoral joint structure during orthopedic correction, keeping the patellofemoral joint alignment normal, and not leaving knee pain and patellofemoral arthritis after surgery, with a fast functional recovery.

　　1. X-ray examination of the patella

　　In the anteroposterior radiograph, the patella can be seen to have moved upwards and dislocated from the intercondylar fossa of the femur. In the lateral radiograph, it shows that the length of the patella is not equal to the length of the patellar ligament. Normally, the distance from the tibial tuberosity to the inferior margin of the patella (i.e., the length of the patellar ligament) is consistent with the length of the patella. If this distance is significantly greater than the length of the patella, it indicates an upward patellar dislocation. Routine X-ray examination is difficult to detect patellar lateral dislocation, and it is advisable to take a patellar axial radiograph in a flexed 20-30 degree position to determine whether there is a patellar dislocation. In the axial radiograph, first, connect the two prominent parts of the femoral condyles with a line A-A'. The second line B-B' is the connecting line of the lateral articular surface of the patella. The two lines intersect to form the patellofemoral angle. Normally, the patellofemoral angle opens to the lateral side. In patients with patellar lateral dislocation, the two lines are parallel or the patellofemoral angle opens medially. This oblique appearance indicates that there is a backward pulling force on the lateral side of the patella. Another manifestation is that the patella has moved outward from the normal central position in the femoral trochlea, becoming a subluxation. Sometimes both conditions exist simultaneously, which further increases the complexity of patellar dislocation.

　　2. Arthroscopic examination

　　Arthroscopic examination is mainly to evaluate the degree of joint cartilage damage, determine the type of surgery to be selected according to the degree of cartilage degeneration of the patella, and can be divided into four levels: 1st level, only cartilage softening, 2nd level, fibrosis lesions with a diameter less than 1.3cm, 3rd level, fibrosis lesions with a diameter greater than 1.3cm, 4th level, subchondral bone cortex exposed.

　　Increase the intake of high-fiber foods and fresh vegetables and fruits, maintain a balanced diet, including proteins, sugars, fats, vitamins, trace elements, and dietary fibers, etc., and combine meat and vegetables.

　　1. Soft tissue surgery

　　1. Tighten and suture the medial periosteum, joint capsule, and extensor part of the quadriceps muscle.

　　2. Periosteal transfer surgery (Campbell), transfer the medial periosteum and muscle pedicle (Krougius).

　　3. Tendon transfer surgery, transfer the medial hamstrings to strengthen the power of the hamstrings.

　　2. Lower end of the femur surgery

　　For patients with internal rotation of the lower end of the femur, genu varum, and underdevelopment of the external condyle of the femur, perform supracondylar osteotomy of the femur, and elevate the external condyle of the femur (Albee) separately.

　　3. Patellar ligament transfer surgery (Houser)

　　Perform the half-patellar ligament transfer surgery (Goldthwait) in children.

　　4. Patellofemoral Arthroplasty

　　Meng Jimao proposed that the local structural development deformity of habitual patellar dislocation varies from person to person, and it cannot be solved by a single operation. Comprehensive surgical treatment should be adopted according to different deformities, and the transfer of the medial vastus muscle to strengthen the medial traction force is advocated. The surgical method is:

　　1. Release the soft tissue of the lateral knee joint contracture.

　　2. Tighten the medial knee joint and move the insertion point of the medial vastus muscle to the lateral side of the patella.

　　3. Perform Houser surgery or Goldthwait surgery according to the specific situation.