Posterior hip dislocation

　　1. Etiology

　　Mostly caused by indirect violence.

　　2. Pathogenesis

　　Mostly caused by indirect violence. When the hip joint is flexed, adducted, and the femoral shaft is internally rotated, the superior lateral part of the femoral head has exceeded the posterior edge of the acetabulum, and the anterior edge of the femoral neck is close to the anterior edge of the acetabulum, forming a lever with this point as the fulcrum. When a strong impact occurs at the front of the knee (such as when one leg is placed on the other leg while riding in a car, and the car suddenly brakes, causing the passenger's knee to hit the back of the front seat, etc.), the femoral shaft continues to internally rotate and adduct, and the femoral head is punctured through the posterior wall of the joint capsule due to the lever action, dislocating from the acetabulum, forming a dislocation. Hip joint posterior dislocation may occur occasionally due to human contact in sports, such as in football when 'blocking the ball', the hand, knee, and hip are slightly adducted, and a sudden violent force acts on the posterior part of the sacrum or pelvis, which can cause hip joint posterior dislocation. Hip joint dislocation caused by traffic accidents is common when the splash guard contacts the knee or femur, and the violence is transmitted to the hip joint through these anatomical structures, so attention is paid to knee or femur injury while ignoring hip joint dislocation. Due to the associated femoral shaft fracture with hip joint posterior dislocation, hip dislocation may be missed, and the internal rotation of the distal fracture segment is considered as the abduction of the femoral shaft fracture. However, detailed clinical examination can discover the external rotation deformity of hip dislocation, and X-ray films can make the diagnosis more clear.

　　1. Fracture:Hip dislocation may be complicated by acetabular fracture or femoral head fracture, and occasionally, fractures of the femoral shaft may occur simultaneously with hip dislocation.

　　2. Nerve injury:In about 10% of patients with posterior hip dislocation, the sciatic nerve may be bruised by the posteriorly and superiorly displaced femoral head or acetabular fracture fragment, causing paresis of the affected side. After reduction of dislocation, paresis gradually recovers in about 3/4 of cases. If there is no improvement in paresis after reduction of hip dislocation, and it is suspected that a large or comminuted acetabular margin fracture fragment is continuously compressing the nerve, early surgical exploration is needed.

　　3. Ischemic necrosis of the femoral head:Joint capsule tears and patellar ligament ruptures caused by inevitable hip dislocation may affect the blood supply of the femoral head, with 10% to 20% of cases developing ischemic necrosis. Changes can be seen on X-ray films around 12 months, and it has been confirmed that early reduction can shorten the time of femoral head blood circulation damage, which is the most effective method to prevent femoral head necrosis. Clinical manifestations include persistent discomfort in the inguinal region and internal rotation pain in the hip, with limited movement. If measures are ineffective, necrosis continues to worsen, eventually leading to severe traumatic arthritis. Severe pain may require joint fusion and artificial joint replacement.

　　4. Traumatic arthritis:This is a late complication, which is an inevitable result of ischemic necrosis. It can also occur in patients with hip dislocation and articular surface fracture. Generally speaking, patients should avoid excessive weight-bearing for 2 to 3 years after reduction of dislocation to delay or alleviate the occurrence of traumatic arthritis.

　　5. Recurrence of dislocation:Whether by manual reduction or surgical reduction, there is a possibility of recurrence of dislocation. Although the incidence is low, vigilance should still be raised.

　　There is a clear and relatively serious history of trauma. Due to the integrity of the anterior iliofemoral ligament, the affected limb produces flexion, adduction, and internal rotation deformity. If the iliofemoral ligament is simultaneously ruptured (such cases are rare), the affected limb will be externally rotated, the affected part will be painful, joint function will be impaired, and there will be elastic fixation. The affected limb will be shortened, and the femoral head can be palpated as elevated in the buttocks. The greater trochanter is above the Nelaton line. X-ray examination shows that the femoral head is located above the acetabulum.

　　Classification: Thompson and Epstein classify hip posterior dislocation into 5 types

　　Type I:Dislocation with or without minor fractures.

　　Type II:Dislocation with a large isolated fracture of the posterior acetabular margin.

　　Type III:Dislocation with comminuted fracture of the posterior acetabular margin, with or without large fracture fragments.

　　Type IV:Dislocation with acetabular bottom fracture.

　　Type V:Dislocation with femoral head fracture.

　　In addition, the injuries causing hip dislocation are all relatively strong, so there may also be fractures of the ipsilateral femur, injury to the sciatic nerve, and shock. Dehne and Immermann collected 42 cases of ipsilateral femoral fracture and dislocation, and in 17 of the 42 cases, the hip joint function had become irreversible after 4 to 6 months after the injury, and the dislocation was discovered. Therefore, in the treatment of such injury patients, it is necessary to take X-ray films as much as possible to determine the situation of ipsilateral or contralateral fracture or dislocation, sciatic nerve injury, which is often transient or incomplete. Aufranc, Narton, and Row observed that about 27% of patients with hip posterior dislocation had sciatic nerve involvement signs early on, of which 69% were transient, and only 29% were persistent incomplete injuries. The injury with the most frequent is the rupture of the peroneal nerve. The shock caused by dislocation should be paid attention to, in order to prevent missing diagnosis and treatment.

　　This disease is caused by direct trauma, such as falls, falls, or emergency braking while driving. Hip dislocation caused by traffic accidents. Therefore, attention should be paid to lifestyle, high-risk workers such as construction workers, miners, and drivers are prone to injury, and protection should be paid attention to during the work process. Stay calm when facing things, avoid emotional excitement to produce conflict and lead to this disease. In addition, early discovery, early diagnosis, and early treatment are also of great significance for the prevention of this disease.

　　1. X-ray examination:X-ray films are the most basic method for diagnosing hip dislocation and fracture, and most X-ray films of hip dislocation can be correctly displayed. However, the hip joint structure is complex, and the anterior and posterior structures overlap. Although most X-ray films of hip fractures can determine the presence or absence of fracture, it is difficult to show the exact degree, exact location, exact direction of displacement, and the relationship with the joint capsule.

　　2. Routine CT:Routine CT can make a correct diagnosis for most hip dislocations, and its advantage over X-ray is that it can clearly show the direction and degree of dislocation, and more importantly, it can clearly and accurately show the presence of bone fragments within the hip joint, which directly determines the patient's treatment plan and prognosis.

　　1. What foods are good for the body for hip joint posterior dislocation

　　Increase nutrition, eat more protein-rich foods such as fish, eggs, soy products, and appropriately increase calcium. Drink more water, eat more vegetables and fruits such as green vegetables, celery, bananas, etc.

　　2. What foods should not be eaten for the best hip joint posterior dislocation

　　Avoid spicy foods: such as chili, mustard, etc. Habits such as smoking and drinking should be quit.

　　(The above information is for reference only, please consult a doctor for details.)

　　First, treatment

　　Immediate manual reduction should be performed for fresh hip joint posterior dislocation, even if there is acetabular or femoral head fracture, it should be immediately corrected. Closed reduction can only be tried once or twice, and if it fails, open reduction should be performed to prevent further damage to the femoral head.

　　1. Type I posterior dislocation:Emergency department visit for dislocation, first give sedatives and analgesics in the emergency room, and perform manual reduction. If the reduction fails, do not generally repeat the attempt multiple times. At this time, the patient is taken to the operating room and a closed reduction is performed again under general anesthesia. If it still fails, open reduction should be performed. Causes of failure of closed reduction: the femoral head passes through the joint capsule to form a loop, the piriformis, obturator, and upper and lower adductor muscles are embedded, the acetabular rim lip is torn; acetabular cartilage碎片 and femoral head fracture fragments block. After reduction of dislocation, the pelvic anteroposterior radiograph should be taken again to observe whether the hip joint space is consistent with the normal side. If the medial joint space is widened, it indicates that there are residual bone cartilage fragments within the joint, and a pelvic CT scan may be necessary for further diagnosis. Fracture fragments embedded between the femoral head and acetabular articular surface can be surgically removed.

　　(1) Closed reduction method:

　　①Allis technique reduction: The patient lies on a low flat bed or on the ground, the operator stands next to the affected hip, an assistant fixes the pelvis, the operator holds the ankle of the affected limb with one hand, and the other forearm is flexed and wrapped around the trochanter, gently flexing the hip and knee to 90° to relax the iliofemoral ligament and hip muscles. Then, the forearm wrapped around the trochanter is used to exert a continuous upward traction along the long axis of the femur, while the hand holding the ankle presses down on the lower leg, and the femur is rotated inward and outward to allow the femoral head to return from the torn joint capsule fissure to within the capsule. At this point, it is often felt or heard that the femoral head clicks into the acetabulum, the deformity disappears, and then the affected limb is extended and abducted. The key to the success of this operation is gentle and stable technique to relax the muscles and alleviate pain. If the muscle relaxation is not sufficient, the operator cannot pull the femoral head close to the acetabulum. The other assistant can use their hand to push the greater trochanter forward and downward to assist in reduction.

　　② Bigelow's manual reduction: The patient lies on their back, the assistant fixes the pelvis with both hands on the anterior superior iliac spines, the operator holds the ankle of the affected limb with one hand and places the other forearm under the flexed knee of the patient, along the direction of the patient's deformation, applies a longitudinal traction, and then maintains the position of adduction and internal rotation, flexing the hip to 90° or more. Then abduct, external rotate, and extend the hip joint, so that the femoral head enters the acetabulum. This is a method of drawing a question mark, with the left side being a positive question mark and the right side being a negative question mark. This method must be very stable and cannot be forceful, as the lever action may occur.

　　Possible fracture of the femoral neck.

　　③ Stimson's gravity reduction method: The patient lies prone on the operating table or car, the affected limb hangs down outside the edge of the table, the operator holds the lower leg to flex the hip and knee joints to 90°, an assistant fixes the pelvis, applies a longitudinal downward traction to the distal end of the flexed knee joint, and gently rotates the femur to assist in reduction.

　　Among the above three methods, methods 1 and 3 are more stable and safe.

　　④ Postoperative management: After manual reduction in patients with simple posterior hip dislocation, skin traction can be used for fixation in a mild abduction position for 3 to 4 weeks. They can walk with crutches and move around, but the affected limb should not bear weight for 2 to 3 months to prevent the avascular femoral head from collapsing under pressure. An X-ray film of the hip should be taken every 2 months after the injury, and it can be proven that the blood supply of the femoral head is good and there is no avascular necrosis within about 1 year, and then they can gradually return to normal activity.

　　It has been confirmed that early reduction can shorten the time of blood circulation damage in the femoral head, which is the most effective method to prevent avascular necrosis of the femoral head. In the review of 128 cases of dislocation and fracture-dislocation, Stenart and Milford found that the prognosis of patients who were复位 after more than 24 hours was poor. In their report, avascular necrosis accounted for 15.5% in closed reduction, 40% in open reduction, and the total incidence of avascular necrosis was 21.2%. In Brav's report on 262 cases of dislocation and fracture-dislocation, it was found that the incidence of avascular necrosis was 17.6% in the hip joints reduced within 12 hours after injury, but it reached 56.9% in the hip joints reduced after 12 hours. Houguard and Thomsen reported that the incidence of avascular necrosis was 4% in the hip joints reduced within 6 hours, but it reached 58% in those reduced more than 6 hours.

　　(2) Open reduction: For cases where manual reduction is not possible, early surgical open reduction should be performed, and the Kocher-Langebeck incision is preferred. However, during the operation, from the initial fascial incision to the exposure of the sciatic nerve, it is necessary to pay attention to prevent injury to the sciatic nerve. The sciatic nerve may be located in front of the femoral head or transferred to the back. The femoral head may penetrate the abductor muscle group or be located between the short external rotator muscle groups. In the initial segment of the incision, the sciatic nerve should be identified first, and then during the manual reduction of the hip joint and the stripping of the posterior joint capsule, attention should be paid to protect the sciatic nerve. In addition, during the operation, it is necessary to follow the protection of the residual blood supply of the femoral head, such as retaining the 1 cm attachment of the piriformis and obturator internus muscles to the piriform fossa when cutting them; retaining the integrity of the quadratus femoris muscle to avoid injury to the terminal branches of the medial circumflex femoral artery, preventing interference with the subarticular support band vessels, and retaining the joint capsule attached to the neck of the femur. Clearing the hematoma, torn labrum, and bone cartilage fragments, and exposing the acetabulum. Finally, the operator uses one finger to protect the sciatic nerve and the other hand to guide the femoral head back into the acetabulum, while the assistant performs a longitudinal traction in the 90° flexion of the hip and knee. Repair the attachments of the piriformis and obturator internus muscles. Postoperative management is the same as that for manual reduction.

　　2. Types II, III, and IV posterior dislocations:For types II, III, and IV posterior dislocations, manual reduction should be performed as soon as possible, as the possibility of femoral head avascular necrosis significantly increases after more than 12 hours. Once the femoral head is accurately reduced, for acetabular posterior margin fractures with surgical indications, the open reduction can be postponed for 5-10 days. During this period, X-ray films and pelvic CT scans are used to further determine the surgical plan.

　　For patients with posterior dislocation and acetabular margin fractures of types II, III, and IV, if the fracture fragments are very small and closed reduction is good, the postoperative traction time should be extended to 4-6 weeks. For patients with poor reduction of fracture fragments, the fracture fragments are compressed into the gluteus maximus muscle belly by the posteriorly displaced femoral head, and the bone fragments cannot be reduced through joint traction or the posterior wall fracture exceeds more than half of the articular surface, leading to joint instability of types II, III, and IV dislocation, and non-concentric reduction of fractures due to bone fragments left in the joint. In such cases, a posterior hip joint incision should be made for surgical removal. For large isolated fracture fragments of types II, III, and IV posterior dislocation, cancellous bone compression screws can be used for fixation; for comminuted bone fragments of type III posterior dislocation, they should be excised, and iliac bone grafting should be performed to repair the posterior wall of the acetabulum, followed by the application of reconstruction plates and screws along the ischial tuberosity to the lateral iliac bone to fix them. For patients with posterior column acetabular fracture associated with type IV posterior dislocation, the articular surface can be reduced by prying, and then reconstruction plates and screws can be used for fixation. For patients with sciatic nerve symptoms, simultaneous exploration should be performed. The sooner the surgery is performed, the better, and it is best not to exceed 3 weeks.

　　3. Type V posterior dislocation with femoral head fracture:Posterior hip dislocation with femoral head fracture is relatively rare and occurs during the dislocation process when the hip joint is flexed beyond the posterior edge of the acetabulum, causing shearing injury. The small fracture fragment below the femoral head usually has no soft tissue attachment, while the larger fracture fragments are often connected to the acetabulum by the round ligament.

　　4. Old Hip Dislocation:Dislocation exceeding 3 weeks is considered old. After 3 months, the soft tissue injury has healed in a deformed state: the hematoma within the acetabulum and fissures has transformed from granulation tissue to solid fibrous tissue, the incision of the joint capsule has healed around the base of the femoral neck, the femoral head is adhered to an abnormal position by a large amount of scar tissue, and the muscles around the joint also become contracted. These pathological changes are sufficient to prevent the reduction of the femoral head. At the same time, due to the long-term non-weight-bearing of the affected limb, bone demineralization occurs, particularly evident in the intertrochanteric and femoral neck areas, making fractures more likely during manual reduction. Therefore, in the past, it was commonly advocated to perform open reduction for old dislocations. In recent years, with the development of integrated traditional Chinese and Western medicine therapy, manual reduction has been successfully performed for some patients with old dislocations.

　　(1) Manual Reduction: For simple, non-complex avulsion fractures (without bone or blood clot ossification), if the condition is within 3 months, manual reduction or bone traction followed by manual reduction can be attempted. During reduction, the joint should be fully mobilized, adhesions should be released, muscle contracture should be relieved, and only after the bony obstruction between the relative articular surfaces is completely eliminated can reduction be performed. The force applied during reduction should be coordinated and moderate, and it is crucial to avoid poor coordination and the use of force, as this may cause fractures or serious complications such as vascular and nerve injuries. If the dislocation has exceeded 3 months, and there has been repeated rough reduction after injury, the soft tissues around the joint become stiff, and the range of joint motion is minimal. In the elderly, due to the longer period of dislocation, bone atrophy due to disuse is evident, and X-ray films show widespread ossification shadows around the joint soft tissues, or there may be old dislocations with associated fractures, vascular, or nerve injuries. In such cases, it is not advisable to attempt manual reduction and surgical reduction or joint reconstruction surgery is more appropriate. Method: Perform bone traction first, gradually pulling the femoral head to the acetabular plane. Reduction should be done under adequate anesthesia. Before reduction, the hip should be massaged and moved in all directions to release the adhesions of the scar tissue on the femoral head, maximizing the range of motion of the femoral head, which is essential for successful reduction. Avoid using force during reduction and instead, use a continuous and strong traction and push method to reduce the femoral head.

　　(2) Open Reduction: For patients with long-standing dislocation, inability to reduce manually, or associated with fracture, surgical reduction should be performed. For patients with posterior dislocation, 2-3 weeks of bone traction (preferably using tibial tuberosity bone traction) must be used before surgery to gradually pull the femoral head to the acetabular plane, and then surgical reduction can be performed. The scar tissue inside the acetabulum must be completely removed. However, attention must be paid not to damage the articular cartilage surface. The saddle-shaped space caused by dislocation has been filled with scar tissue. The scar tissue in this space must also be completely removed to reduce the femoral head. Violence should be avoided during reduction to prevent flattening the acetabular margin, cracking the femoral head, or causing fractures of the femoral shaft or neck. The hip should be immobilized with a plaster brace for 3 weeks after surgery. Other treatments are the same as for fresh dislocations. If it is found during surgery that the articular surfaces of the femoral head and acetabulum have been severely damaged, joint fusion should be considered.

　　II. Prognosis

　　It may cause aseptic necrosis of the femoral head and late traumatic hip arthritis, and artificial femoral head replacement can be performed if necessary, with good results.