Hip dislocation is a term used to describe the medical situation where the proximal end of the femur and the hollow socket of the pelvis become disjointed.
A dislocation of the hip is usually painful and the affected individual is not able to move the leg. In the case of a posterior dislocation, the affected limb may appear shorter and bend inward, whereas an anterior dislocation will cause it to bend outward. When an injury to the associated nerve occurs, the side of the foot or ankle may be numb .
Hip dislocations can be diagnosed using different imaging techniques which include X-rays, computed tomography scan (CT), and magnetic resonance imaging (MRI).
An x-ray examination of the anteroposterior (AP), lateral side, including both internal and external oblique imaging of the femur assists in diagnosing the condition . A complete X-ray evaluation of the affected hip is required in other to determine the extent and type of the dislocation. The anteroposterior view of the pelvis may reveal the size and appearance of the femoral head. In addition, the positioning of the femoral head in association with the acetabulum is assessed to determine whether surgery is required. Fractures of the acetabulum, femoral head or neck are better evaluated with lateral and oblique views. During hip dislocation management, post-reduction x-rays are important in order to evaluate the progress of the bone attachment (which is referred to as reduction process) and to identify loose bone fragments or fractures that may interfere with the completion of the reduction process or cause post-reduction complications.
Another technique for diagnosing a hip dislocation is the CT scan . The choice of CT scan technique in the workup of hip dislocation is controversial, however, cases with closed reduction failure or an asymmetric joint space may necessitate the use of the technique. A CT scan assists in diagnosing loose bodies such as damaged soft tissues and fragments that can impair closed reduction; it is also useful to evaluate acetabular fractures.
Hip dislocation may also be diagnosed by magnetic resonance imaging. This technique is recommended in an acute hip dislocation with associated conditions, such as labral tears or cartilaginous loose bodies. Osteonecrosis which develops as a complication of the dislocation may also be diagnosed using an MRI after 4-6 weeks and is subsequently repeated after 3 months.
Generally, patients with hip dislocation are managed based on the diagnosis. In cases where there are no other damages or injuries to the hips, the femoral head is adjusted into the pelvis quickly (a process that is referred to as reduction) . The delay in this process may result in avascular necrosis or osteonecrosis. Surgery may not be required. Patients may be given local or general anesthesia before the reduction process. Also, sedatives and muscle relaxants may be indicated, in other to allow for proper manipulation of the femur by the clinicians . Hip joint reduction is usually done with the patient lying on a flat, rigid board facing up, and the hip is gently flexed, while the femur is pulled upwards. In cases of injury damage to the femoral head, nerves, acetabulum, as well as the presence of loose bone fragments at the hip joint, which may slow the reduction process, surgery may be indicated.
Patients with a posterior hip dislocation may be able to walk after 5-7 days following reduction. Some patients with severe cases may permanently require mobile aid to walk. After reduction, patients are not encouraged to engage in continuous bed rest, since it can increase chances of complications such as the formation of blood clots. Following surgery, physiotherapy activities such as passive exercise are employed to exercise the hip joint either manually or with the aid of a continuous passive motion machine.
The prognosis of hip dislocation depends on the nature and extent of the damage to the hip joint. The prognosis of anterior dislocations of the femoral head which do not include a fracture or injury is better than the prognosis of cases that affect the posterior end. Other factors such as osteonecrosis, arthritis, duration until resolution and injury severity play a major role in the determination of the outcome . However, the reduction timing during treatment is considered to be the most important factor in the prognosis of the hip dislocation.
Following a hip dislocation, osteonecrosis may develop on the femoral head, which may result in a poor outcome. Previous studies reported an incidence rate of 4.8% and 52.9% in osteonecrosis development arising from the hip reduction before or after 6 hours of injury respectively. Symptoms of osteonecrosis arise most frequently within 2 years after the injury; sometimes, osteonecrosis may be observed as late as 5 years following the initial injury. Therefore, a proper management of patients with hip dislocation alongside imaging techniques in other to prevent osteonecrosis are important .
Arthritis may develop after hip dislocation, and it is the most common complication of the condition. This complication affects the prognostic outcome negatively. In addition, the sciatic nerve may also be affected due to the fracture or dislocation of the hip. In cases where nerve function is impaired after resolution, an examination is necessary .
Most dislocations involving the hip joint cause the head of the femur to be posteriorly shifted. The dislocations usually result from the flexing of both knee and the hip joint with pressure exerted to the knee. A hip dislocation may result from hitting the knee against a surface such as a car dashboard in a road traffic accident. Hip dislocations may also result from falls from a high altitude, such as during ladder climbing or through high-impact sports like wrestling, rugby, football and karate . Most often, the traumatic force which causes dislocation of the hip joint may also affect other body parts. The accident may simultaneously damage or dislocate the knee, arm, or legs of the affected individual. Sometimes, the neck or head may also be fractured. Children may be affected by a congenital dislocated hip bone, referred to as hip dysplasia . Undetected hip dysplasia may cause failure of the hip to develop normally.
In a dislocated hip, damage to the bones and to the related nerves, such as the sciatic nerve, may co-exist. Also, blood supply to the femoral head may be impaired, resulting into osteonecrosis.
Hip dislocations commonly occur among adults and rarely among young individuals. About 5% of the cases are observed in patients below the age of 14 years and mostly affect males, due to injury resulting from low-energy sporting games or falls . Only a few reports are available about the prevalence of hip dislocation among athletes and most cases (70%) result from road traffic accidents. Hip dislocations are commonly reported in sporting activities such as American football and rugby. In football, 3% of major injuries involve either a hip fracture or dislocation. Sports which include rugby, alpine skiing and snowboarding constitute the second most prevalent cause of hip dislocations .
Previous studies involving skiers and snowboarders reported a higher incidence of hip dislocation with or without a fracture among snowboarders when compared to skiers over a period of time . Also, cases of hip dislocations and fractures among drivers and equestrians have been reported .
Anatomically, the hip joint is a ball and socket type of joint, which is usually stable and allows for proper movement. Therefore, a dislocation of the hip joint occurs rarely. The disorder arises due to the effect of high pressure on the hip bone, particularly the femoral head; a fracture of the posterior acetabular wall can accompany the dislocation. Sometimes, the neck of the femur and the articular cartilage of the femur may be involved. Injuries causing bone or cartilage fragmentation may cause a deposition of comminuted bodies or particles at the hip joint .
There is no medical literature about preventing the occurrence of hip dislocation, however, individuals are encouraged to be cautious and avoid any possible injuries or accidents which can result in the condition. High-risk individuals, particularly athletes of physically demanding games are trained, guided, and advised to wear protective materials to avoid hip dislocation.
Some anatomical joints of the body such as the wrist, shoulder or ankle joint are prone to dislocation following accidental events. However, hip joint dislocation is relatively rare and is usually caused by accidents resulting from sports, road traffic accidnts and other physical activities . Severe traumatic conditions which are referred to as large-force traumas from accidents are usually the main factor causing hip dislocation . The traumatic conditions arise from a high-energy impact and may cause injury or dislocation of the hip. Sporting activities with increased risk for hip dislocation include American football, rugby, gymnastics (such as vaults, acrobatics, floor exercise, etc.), running, basketball, car race, equestrian sports (horse riding, polo, horse racing, etc.) and water and alpine skiing (snowboarding) .
The dislocation of the femoral bone may either be anterior or posterior. The posterior type of hip dislocation is the most common form in traumatic dislocations. The posterior hip dislocation is classified into different groups depending on the damaging effect of the injury on the bone.
Based on the radiographic features, Thompson-Epstein classified hip dislocation into:
Also, Steward and Milford classified hip dislocation based on the stability of functional hip:
Due to the morbidity and severe effect on the physical posture, which are commonly associated with hip dislocations, a proper management of the condition is very important. Prompt and proper treatment is necessary in other to prevent chronic sequelae such as avascular necrosis.
Hip dislocation results from the separation of the thighbone (femur) head from the pelvic bone (pelvis) socket. It is an uncommon condition and it is caused by severe injury. High-impact injuries resulting from accidents, which affect the hip joint, may result in the dislocation of the hip. The accident can be due to high-altitude falls, road traffic accidents or sporting activities including high-energy sports such as American football, rugby, football, skiing, and snowboarding.
Major symptoms of hip dislocation include severe pain of the affected leg, as patients are unable to move the leg. Injury that affects the associated sciatic nerve, may result in numbness or pain at the joint. Hip dislocations are diagnosed by the clinician after the previous history of the patient has been taken, including the nature of the injury that caused the condition. Various clinical investigations may be requested to evaluate the state of the dislocation. These investigations include x-rays, magnetic resonance imaging (MRI) and computed tomography (CT) scan. Clinical treatment in which the dislocated hip is re-joined or manipulated into the normal position is called reduction. The clinician may administer anesthesia or sedatives during treatment and may non-surgically manipulate the hip bones to the normal state. However, surgery may be required if there are complications due to bone fragments or loose bodies that can impair reduction process.