Patellar instability

Introduction to humeral instability Unstablepatella is a common cause of anterior knee pain and is a common disease of the patellofemoral joint. It is an important cause of patellofemoral softening or patellofemoral osteoarthritis, advances in biomechanics and imaging techniques, and clinical detection methods. The diversification has gradually made people realize that the degenerative changes of the patellofemoral joint are mostly caused by the instability of the patellofemoral joint or the instability of the humerus caused by the tibiofibular line. For example, the humeral deviation, the sacral tilt, the humerus high, the humeral subluxation. Wait. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific people Mode of infection: non-infectious Complications: dislocation of the humerus

Cause of instability of the humerus

(1) Causes of the disease

The cause of instability of the patellofemoral joint, the cause of humeral deviation or subluxation, actually includes the abnormality of each structure in the anterior knee region, which is broadly divided into four categories:

1. Abnormalities in the quadriceps and its dilatation include atrophy or dysplasia of the medial femoral muscle, relaxation of the medial support ligament, rupture or tear, lateral support ligament tension and high tibia.

2. Knee joint line abnormalities include an increase in Q angle, as well as knee, valgus and knee flexion.

3. Abnormal shape of the humerus such as patella bipartite (Fig. 1), heteromorphic tibia (III, IV).

4. Congenital factors mainly refer to dysplasia of the femoral condyle, secondary deformation or abnormal shape of the femoral condyle.

The common feature of all these changes is that the patellofemoral joint loses its normal structure, causing an abnormal tensile stress acting on the tibia, or an abnormal trajectory of the tibia, which makes the humerus unstable.

(two) pathogenesis

1. Static factors: mainly including patellar ligament, internal and external support ligament, tendon bundle, femur, external malleolus, etc., patellar ligament mainly restricts humerus uplift; inner and lateral support ligaments restrict lateral displacement of humerus; The bundle also has the effect of reinforcing the outer upper part of the humerus. Therefore, the restriction mechanism of the lateral aspect of the tibia is stronger than the medial side. When the knee joint is in the extended position and the quadriceps are relaxed, the tibia is slightly outwardly displaced. The inner and outer sidewalls of the trochlear groove have Limiting the lateral slip of the humerus, when the sulcus angle is increased, that is, the groove becomes shallow or the femoral condyle is poorly developed, the tibia loses this restriction and is prone to dislocation. In addition, the length of the longitudinal axis of the normal human tibia and The length of the ankle is almost equal. When the ankle is longer than the humerus, it is a high level of the humerus and is also a factor of instability of the tibia.

2. Dynamic factors: mainly refers to the role of the quadriceps muscle. The oblique muscle fibers of the medial femoral muscle are attached to the inner edge of the humerus. When the muscle contracts, there is an effect of pulling the tibia inward. This is an antagonistic movement of the humerus. The important dynamic factor for stabilizing the tibia. The Q-angle (quadriceps-angle) refers to the angle formed by the line connecting the anterior superior iliac spine to the center of the tibia and the center line of the tibia to the center of the tibial tuberosity. The normal Q angle is 5°-10 °, if the Q angle is greater than 15°, the quadriceps contraction will produce a component force that moves the tibia outward. As the Q angle increases, the component force that pulls the tibia outward increases gradually, and the stability of the tibia is also increased. worse and worse.

Prevention of humeral instability

Preventive work begins with the details of life.

Tibial instability Complications Dislocation of the humerus

The complication is dislocation of the tibia. Secondly, the symptoms of the disease are often not serious in the early stage. The rest or general painkillers can be relieved. The lesions continue to develop under the "hidden state" until the development of patellofemoral arthritis. In severe cases, the knee flexion and extension activities are limited, not one leg. Stand up. When tibiofemoral arthritis has developed in the late stage, the cartilage and subchondral bone in the lesion area have been significantly damaged, and the cartilage has no ability to regenerate. In addition, the disease is also easy to merge with meniscus injury and traumatic arthritis.

Symptoms of unstable humerus Common symptoms Powerless joint relaxation Q angle abnormal underarm pain Joint swelling strabismus

1. Symptoms of unstable humerus

(1) Pain: It is the most common main symptom, usually its nature is not constant, but its location is in the anterior region of the knee. It is more common in the anterior aspect of the knee. Pain can be aggravated by excessive activity, especially up and down the stairs. Or more obvious when prolonged flexion and extension activities.

(2) Playing "soft legs": When playing "giving way", when the weight is walking, the moment of knee joint appears weak, unstable, and sometimes the patient can fall. This phenomenon is often due to the stock The head muscles are weak, or because the humerus of the subluxation slides out of the intercondylar groove.

(3) pseudo-incarceration: pseudo-incarceration (pseudolocking) refers to the momentary non-autonomous limiting obstacle that occurs when the knee is stretched. When the weight-bearing knee joint is flexed to the extension position, the semi-dislocated tibia slides into the pulley groove. This phenomenon often occurs, and it is often necessary to distinguish the true incarceration caused by the twisted or loose body of the meniscus tear or displacement.

2. Symptoms of unstable humerus

(1) quadriceps atrophy: quadriceps atrophy is a common sign of knee joint disease, and the performance is more obvious when the knee extension device appears dysfunction, with the medial femoral muscle as the weight.

(2) Swelling: In severe cases of unstable humerus, quadriceps weakness, resulting in synovitis, joint swelling, and floating sputum test.

(3) squint of the humerus: the squinting knee has a knee valgus, a high tibia, an enlarged anterior femoral angle, a knee deformity such as an excessive humerus, and a line of weakness, in order to maintain a normal step. The tibia of the tibia is tilted to the medial side and is a common factor in the instability of the tibia.

(4) Trajectory test: the patient sits on the edge of the bed, the lower legs sag, the knee flexes 90°, the knee joint is slowly extended, and the trajectory of the tibia is observed as a straight line. If there is an outward sliding, it is positive. Specific signs of instability of the tibia.

(5) tenderness: more distributed in the inner edge of the humerus and the medial support zone. When the examiner presses the patient's tibia and performs the extension and flexion test, it can induce subgingival pain. The clinical tenderness is sometimes associated with the painful part of the patient's complaint. Not consistent.

(6) Pressing sound: When the knee joint is in the straight position, press the tibia and move it up, down, left and right. You can feel or hear the renailate crepitation under the tibia, accompanied by soreness, knee You can also feel or hear the press sound when the joint is actively flexing and flexing.

(7) Fear sign: The patient's knee joint is in a mild flexion position. When the examiner pushes out the tibia to induce subluxation or dislocation, the patient develops fear and pain, which causes the knee joint to flex and exacerbate the pain (Fig. 2). The apprehension sign is also a specific sign of instability of the tibia.

(8) Increased lateral mobility of the humerus or joint relaxation: the range of the passive movement of the humerus in the normal knee joint is not more than 1/2 of its own width, and the range of the lateral movement of the humerus is smaller when the knee is 30°. The joint is slack, and the degree to which the tibia can move to the outside is divided into 3 degrees:

I degree: The center of the humerus is on the inside or axis of the axis of the lower limb.

II degree: The center of the humerus is located outside the axis.

III degree: The inner edge of the humerus crosses the axis of the lower limb.

(9) Q angle abnormality: Q angle is an important index to measure the tibial line of force. The internal rotation of the femur and the external rotation of the humerus can increase the Q angle and cause the sacrum to tilt.

Unstable sacral examination

X-ray examination of the patellofemoral joint is a common method for diagnosing instability of the tibia. It usually includes the orthotopic position of the knee joint, the lateral position and the axial image of the patellofemoral joint. The latter is more meaningful in the diagnosis of patellofemoral joint disease.

1. Orthotopic position: the patient is supine, the feet are close together, the toes are up, the quadriceps are completely relaxed, and the front and back are taken. Observe:

(1) Tibial position: The center point of the normal tibia should be located on the inner or lower side of the lower limb.

(2) Tibial height: The lower tibia of the normal humerus is located just above the line connecting the lowest points of the femoral condyles on both sides, and the lower pole is on the near side of the line. The distance above 20 mm is the high tibia.

(3) The shape of the tibia and fibula: stunted or deformed.

2. Lateral position: It can show signs of osteochondral sclerosis and osteoarthrosis of the humerus. It is often used to judge the presence or absence of high tibia and humerus height measurement. The measurement methods used by different scholars are not the same.

(1) Blumensaat method: When the knee flexion of the patient is 30°, the triangular hard line projected at the top of the intercondylar fossa is called the Ludloff triangle, and the extension line is forwarded at the bottom edge. The normal humerus should be The lines intersect, if the lower pole of the tibia is more than 5 mm proximal to the line, it is the high tibia (Figure 4).

(2) Labelle and Laurin method: the patient bends the knee 90°, takes the lateral image, and leads the distal end along the femoral cortex. Normally, 97% of the upper tibia passes through this line. Above this line is the high tibia, on the contrary, low. This line is the lower tibia (Figure 5).

(3) Insall and Salvati method (ratio method): photographing the lateral position of the knee at 30°, measuring the length of the ankle (Lt), that is, from the lower edge of the humerus to the upper edge of the humerus nodule, and then measuring the longest diagonal of the tibia. The length (Lp), the ratio of the two (Lt/Lp), the normal value is 0.8 to 1.2, greater than 1.2 for the high tibia, and less than 0.8 for the lower tibia (Figure 6).

(4) Blackburne-Peel method: take a 30° lateral image of the knee, measure the vertical distance from the lower edge of the tibial articular surface to the tibial plateau (A), and then measure the length of the tibial articular surface (B). The normal A/B ratio is 0.8, greater than 1.0 for the high tibia (Figure 7).

(5) Pediatric high-level measurement method (midpoint method): Find the midpoint (F) of the lower femoral condyle in the lateral radiograph, the midpoint (T) of the supraorbital humerus and the long axis of the humerus The midpoint (P) of the line, the ratio of PT to FT is 0.9 to 1.1 for normal knee flexion of 50° to 150°, the tibia is higher when the ratio is greater than 1.2, and the lower is less than 0.8 (Fig. 8).

3. Axial position (temporomandibular joint occlusion): Axial X-ray examination is more important in the diagnosis of patellofemoral joint stability. It can be used not only to understand whether the patellofemoral relationship is suitable, but also to identify the trabecular bone of the lateral aspect of the humerus. The direction changes and there is no excessive lateral-pressure syndrome.

Since Settegast proposed the use of axial position to detect the patellofemoral joint in 1921, many improved inspection methods and techniques have appeared. However, due to the different knee angles adopted by different scholars, the measured values are not the same. The author's method is The patient is placed on his back, and the knee joint is fixed and fixed at a 30° position with a special posture frame to relax the quadriceps muscle. The X-ray tube is placed at the distal side of the patellofemoral joint so that the emitted beam is parallel to the tibia. The axis is placed on the proximal side of the patellofemoral joint so that the film and the X-ray beam and the humeral surface are at an angle of 90° (Fig. 9). The test items and methods are as follows:

(1) Groove angle: On the X-ray film of the patellofemoral joint, the lowest point from the femoral intercondylar groove is inward, and the highest point of the external condyle draws two straight lines, the angle of which is called the groove angle or the tread angle of the pulley (sulcus Angle, SA), the size of the groove angle represents the depth of the intercondylar sulcus and the development of the trochlear (Fig. 10A).

(2) Suitable angle: the angle formed by the corner line of the groove angle and the line connecting the top of the groove and the lower pole of the tibia is called the congruence angle (CA). The angle is located at the inner side of the angle line and is at the negative angle. Positive angle, which represents the relative positional relationship between the tibia and the femur. Usually, the lower part of the humerus is located inside the corner line, that is, the angle is normal and the negative angle is normal (Fig. 10B).

(3) lateral patellofemoral angle: the angle between the highest point of the femur and the anterior line of the lateral tibia is the lateral patellofemoral angle. Normally, the opening is outward. If the opening is inward or the two lines are parallel, it means The tibia has a lateral tilt (Figure 11).

(4) Tibial tilt angle: the angle formed by the line connecting the highest point of the femur and the maximum transverse diameter of the tibiofibular cut, which increases, indicating an increase in the inclination of the tibia (Fig. 12).

(5) External dislocation of the humerus: the highest point of the femoral condyle is the vertical line connecting the highest point of the femur, and the distance between the vertical line and the inner edge of the tibia is the extensor of the humerus, and the inner edge of the humerus is close to the vertical line. It is normal to be on the vertical line or across the vertical line, and away from the vertical line to indicate that the humerus has moved outward (Figure 13).

(6) depth index: the vertical distance between the length of the humerus and the axis of the lower tibia to the transverse axis is the depth of the tibia; the length of the line connecting the highest point of the femur and the outer iliac crest is connected to the line from the lowest point of the trochlear groove. The vertical distance ratio is the pulley depth (Fig. 14). According to Ficat's measurement, the depth index of the tibia is normally 3.6 to 4.2, and the pulley depth index is 5.3 ± 1.2.

According to the authors, 80 cases (35 males, 45 females) had normal patellofemoral joints (all subjects had no history of knee pain, no positive signs, age 18 to 40 years old): the groove angle was 138 ° ± 6 °(x±s), suitable angle is -8°±9° (x±s); lateral patellofemoral angle is 7.8°±3.1° (x±s); tibia inclination angle is 11°±2.5° (x± s), 92% of the inner edge of the humerus is in the vertical line or on the vertical line, 8% is on the outside of the vertical line, but the distance is no more than 2mm.

The purpose of X-ray measurement of the patellofemoral joint is to determine the relative positional relationship between the tibia and the femur in the patellofemoral joint, and to judge different diseases according to different changes, including: the deviation of the humerus (extension of the tibia); the inclination of the tibia (outside The patellofemoral angle, the sacral tilt angle), the humerus, the anatomical change of the intercondylar sulcus and the developmental condition (ditch angle, suitable angle, depth index), these indicators reflect the stability of the patellofemoral joint to varying degrees, the author is based on normal The measurement of the patellofemoral joint is considered to be suitable for the angular measurement mark. In addition to reflecting the tibial offset, it can reflect the fit of the trough depth and the groove angle to the tibia. In addition, the lateral patellofemoral angle is more repeatable. In the diagnosis of unstable humerus, it is more practical for the angle and lateral patellofemoral angle.

4. Articular angiography of unstable humerus: It can not only observe the changes of patella cartilage through double contrast of knee joint, but also compare the support ligaments on both sides of the tibia and diagnose synovial fold syndrome, except for other lesions and CT examination of joints. The diagnosis of stable tibia often requires more integration with other methods of examination.

5. Arthroscopic instability of the humerus: This is an invasive examination method. The examiner can directly observe the positional relationship between the tibia and the femur, the trajectory of the tibia, and the extent, extent and location of the injury of the tibia and femur. It is helpful to choose the appropriate surgical method, predict the possibility of successful operation, and more importantly, to determine whether there are other intra-articular disorders, such as meniscus tear, synovial fold, synovitis, exfoliative chondritis, Free body, etc., can also be treated accordingly when the lesion is clearly defined.

Jackson divides the articular cartilage into three types according to the degree of articular cartilage changes:

Type I: The iliac cartilage surface has a localized softening lesion.

Type II: The cartilage surface of the humerus has cracks and erosion damage, while the femoral condyle surface is normal.

Type III: In addition to type II changes, there is also a disruptive change in the femoral condyle.

6. CT or MRI examination of unstable humerus: the application of computed tomography and magnetic resonance imaging technology makes the diagnosis of patellofemoral joint instability more accurate, avoiding the overlap and distortion of common X-ray images, because the patellofemoral joint is at 0 When the temperature is ~20° (straight position), most of the humerus is in the shallowest trochlear of the intercondylar groove. In this position, the quadriceps and the medial and lateral support ligaments are relaxed, and the patellofemoral joints are relatively unstable. Therefore, the commissural joint of the patellofemoral joint was taken at a position within 20° of knee flexion, and the positive rate of patella instability was the highest. However, in fact, the flexion of the knee joint at 20° was difficult to project the patellofemoral joint. Often unclear, difficult to measure, and with CT or MRI technology, in the knee joint straight position, the quadriceps relax, cross-sectional scan of the middle part of the humeral joint, clear image, good repeatability, easy to measure and calculate, is A powerful diagnostic tool for unstable humerus.

Diagnostic diagnosis of humerus instability

diagnosis

According to medical history, clinical manifestations, X-ray examination and X-ray measurement, especially arthroscopy, CT and MRI examination can establish a clinical diagnosis.

Differential diagnosis

In terms of diagnosis, the disease needs to be identified with a variety of diseases, including:

1. Congenital discoid meniscus hypertrophy;

2, congenital knee dislocation;

3. Intralateral and lateral meniscus injury;

4, meniscus calcification;

5, meniscus ossification;

6, exfoliative osteochondritis;

7. Synovial chondromatosis;

8, joint synovial fold syndrome;

9, semitendinosus and semimembranosus tendon slippage;

10, femoral biceps tendon slip and so on.

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