| disease | Hip Dislocation |
The hip joint has a stable structure, and dislocation can only be caused by a strong external force. It is a serious injury. At the same time as dislocation, soft tissue injury is also severe, and it is often combined with injuries in other parts or multiple injuries. Therefore, most patients are active young adults. Generally, it is divided into three types: anterior, posterior, and central dislocation. If the femoral head is located in front of the Nelaton line (the line connecting the anterior superior iliac spine and the ischial tuberosity) after dislocation, it is an anterior dislocation. If the dislocation is behind this line, it is a posterior dislocation. If the femoral head is pushed toward the midline, breaking through the acetabulum and entering the pelvis, it is a central dislocation. Among the three types, posterior dislocation is the most common. This injury should be treated as an emergency, and the earlier the reduction, the better the outcome.
bubble_chart Etiology
Dislocations are classified into three types: anterior, posterior, and central dislocations, with posterior dislocations being the most common. Posterior dislocation occurs when the hip joint is flexed and adducted, and a violent force along the long axis of the femur can cause ligament tears, allowing the femoral head to break through the joint capsule posteriorly, resulting in posterior dislocation. If the hip joint is in a flexed and grade I adducted position, the same force can cause a fracture of the posterior rim of the acetabulum, leading to posterior dislocation of the femoral head. When the hip joint is in a neutral or grade I abducted position, violent force can cause an acetabular fracture, and the femoral head may shift towards the pelvic cavity along the fracture line, known as central dislocation, which is rare. If the hip joint is in an abducted position, the greater trochanter of the femur may collide with the superior rim of the acetabulum, and continued abduction with this as a fulcrum can result in anterior dislocation due to a violent force along the long axis of the femoral head. The femoral head may come to rest in the obturator foramen or on the pubic crest. Anterior dislocation can also occur in a squatting position with legs abducted, such as during the collapse of a cave dwelling.
bubble_chart Clinical Manifestations1. Posterior dislocation
(1) History of injury with the hip in a flexed and adducted position.
(2) Hip pain and limited movement.
(3) Specific signs of dislocation: The hip is elastically fixed in a flexed, adducted, and internally rotated position, with the toe touching the dorsum of the healthy foot, and the affected limb appears shortened. The joint space in the groin is empty, and the femoral head can be palpated as a bulge posterior to the ilium. The greater trochanter is displaced upward, above the iliosacral line (the line connecting the anterior superior iliac spine and the ischial tuberosity, known as Nelaton's line).
(4) Sometimes complicated by sciatic nerve injury and fracture of the posterior superior rim of the acetabulum. In advanced stages, it may be complicated by femoral head necrosis.
(5) X-ray examination can determine the type of dislocation and the presence of fractures, and differentiate it from femoral neck fracture.
2. In anterior dislocation, the hip joint presents with flexion, abduction, and external rotation deformity. The affected limb is rarely shortened, and the greater trochanter is also prominent, but not as obvious as in posterior dislocation. It may be located below the iliosacral line, and the femoral head can be palpated anterior to the obturator foramen.
3. Central dislocation deformity is not obvious. In severe cases, the affected limb may be shortened, with the lower limb internally rotated and adducted, and the greater trochanter may not be visible due to cryptorchidism, with limited hip joint movement. Clinically, diagnosis often requires X-ray examination. It is often associated with acetabular fracture, and may involve injury to the sciatic nerve and pelvic organs. In advanced stages, it may be complicated by traumatic arthritis.
There is a clear history of trauma, with significant pain at the affected area and limited movement. The affected limb is shortened, and the hip joint exhibits a deformity of flexion, adduction, and internal rotation. The dislocated femoral head can be palpated in the buttock, with noticeable upward displacement of the greater trochanter. Diagnosis can be confirmed by X-ray examination.
bubble_chart Treatment Measures
1. Treatment of fresh dislocation
(1) Reduction methods for posterior dislocation
① Question mark method (Bigelow's method)
Under spinal anesthesia, the patient lies supine, an assistant fixes the pelvis, and the hip and knee are flexed to 90 degrees. The surgeon holds the affected limb's ankle with one hand and places the other forearm under the popliteal fossa to apply upward traction. Initially, the hip joint is flexed, adducted, and internally rotated (to move the femoral head away from the ilium). Then, while maintaining traction, the joint is externally rotated, abducted, extended, and the femoral head is guided into the acetabulum to achieve reduction (the assistant can help push the femoral head into the acetabulum). The continuous movement of the thigh during reduction resembles a "?" shape, hence the name "question mark method." For left posterior dislocation, the thigh's movement resembles a forward "question mark," while for right posterior dislocation, it resembles a backward "question mark."
② Allis method
The patient lies supine, with the assistant's actions and the surgeon's position as described above. During reduction, the surgeon first flexes the affected hip and knee to 90° to relax the iliofemoral ligament and knee flexors. Then, one hand presses the lower leg downward, while the other forearm pulls upward from behind the knee, moving the femoral head forward toward the posterior joint capsule's tear. Simultaneously, the femur is rotated internally and externally to guide the femoral head into the acetabulum. The assistant can also push the femoral head into the acetabulum. A distinct sound or sensation is often heard or felt during reduction. This method is relatively safe.
Immobilization: After reduction, a unilateral hip spica cast can be applied for 4–5 weeks (or the affected limb can be immobilized in grade I abduction and internal rotation using sandbags while lying flat). Early mobilization with crutches is allowed, but weight-bearing on the affected side should be avoided. After 6–8 weeks, an X-ray should confirm the absence of femoral head necrosis before weight-bearing is permitted.
④ Indications for surgical reduction
If manual reduction fails, timely surgical reduction should be considered. Large fractures of the acetabular rim require surgical reduction and internal fixation.
(2) The treatment principles for anterior dislocation are similar, with only the direction of manipulation being opposite. Post-reduction management is also the same.
(3) Central dislocation should be reduced using bone traction for 4–6 weeks. If severe traumatic arthritis develops in advanced stages, artificial joint replacement or arthrodesis may be considered.
2. For old hip dislocations, reduction is difficult due to fibrous scar tissue filling the acetabulum and soft tissue contractures. The treatment approach depends on the duration of dislocation, local pathology, and the patient's condition. For dislocations less than three months old, manual reduction may be attempted. Bone traction is applied for 1–2 weeks to pull the femoral head down to the acetabular rim. Under anesthesia, gentle manipulation is performed to loosen adhesions. Once sufficient mobility is achieved, reduction is performed using the same methods as for fresh dislocations. However, excessive force should be avoided to prevent fractures. If manual reduction fails or the dislocation is older than three months, surgical reduction is necessary. For severe joint surface damage, hip arthrodesis or artificial joint replacement may be considered based on the patient's occupation.
sciatic nerve injury
