12.50 Dislocations of the hip and femoral head fractures

Hip dislocations are commonly associated with other local and regional fractures and injuries resulting in a high risk of chronic disability and early or accelerated degenerative joint disease.

Avascular necrosis of the femoral head is a common complication of hip dislocation and a knowledge of the blood supply to the femoral head is therefore essential.

The main source of intraosseous blood supply of the weight-bearing portion of the femoral head is the deep branch of the medial femoral circumflex artery (MFCA) which gives rise to several ‘terminal’ superior retinaculum vessels. The deep branch of the MCFA passes between the psoas tendon laterally and pectineus medially, and runs laterally on the inferior border of obturator externus, which it crosses posteriorly, coming to lie between quadratus femoris and the inferior gemellus. It courses anterior to the inferior and superior gemellus muscles and the interposed obturator internus tendon (i.e. deep to these structures as seen from a posterior surgical approach) and enters the hip capsule just above the superior gemellus muscle, and distal to the piriformis tendon. The terminal retinacular vessels course towards the femoral head, bound to the femoral neck by the reflected fibres of the hip capsule.

The inferior gluteal artery may often anastomose with the MFCA through a branch that runs along the piriformis tendon, but the lateral femoral circumflex artery provides little contribution to the vascularity of the femoral head. A portion of the femoral head around the attachment of the ligamentum teres to the fovea is supplied by the medial epiphyseal branch of the acetabular branch of the obturator artery in the young.

The underlying cause of dislocations and fracture–dislocations of the hip is high-energy force dissipation. The relationship of the pelvis to the vector of force through the femur will determine whether an anterior dislocation, posterior dislocation, or fracture–dislocation will occur.

Most patients presenting with dislocations and fracture–dislocations of the hip have a history of severe trauma with a high force dissipation, such as:

Because of high force dissipation, victims in motor vehicle collisions may suffer multiple injuries and other occupants of the same vehicle may suffer the same fate.

An accurate history is invaluable and must be sought from the ambulance officers or those delivering the patient to hospital:

The high force dissipation involved in hip dislocation requires that medical staff should follow the principles of the early management of these injuries recommended by the Advanced Trauma Life Support method. Patients should undergo a thorough secondary examination initially to look for injuries to other organ systems and should be reviewed clinically over the next few days to exclude missed diagnoses.

Patients with a hip dislocation commonly present with:

The positional deformity of a posterior hip dislocation is one of flexion, adduction, and internal rotation. In the presence of an anterior dislocation, the hip typically assumes a position of external rotation abduction and some extension. When ipsilateral fractures of the femoral shaft or neck occur, however, the leg may assume a near-normal position and the diagnosis of hip dislocation may be missed.

Knowledge of the mechanism of injury should alert medical staff to possible associated injuries for which a careful search must be made. Opposing forces of an impact to the knee at one end of the leg and the momentum of the body at the other can result in injury anywhere between those two points. Abrasions and lacerations over the patella or proximal anterior tibia may indicate the site of force application. Injuries about the knee include proximal tibial fractures, patellar fractures, osteochondral fractures of the patellar and distal femoral articular surfaces, and distal femoral fractures. Patellar and knee ligament injuries may lead to instability of the knee which must be carefully assessed. The pelvis and spine must be examined thoroughly to exclude pelvic fractures, pelvic ring disruption, and spinal injuries.

A detailed assessment must be made for neurological injuries and if these are present they must be documented before and after reduction of the hip. Sciatic nerve injuries, particularly of the peroneal component, occur commonly in hip dislocations. Injuries to the lumbosacral trunk may accompany disruptions of the pelvic ring and spinal nerve root injuries may be present in patients with vertebral fractures.

All patients subject to severe trauma should have radiographs of the cervical spine and chest, and an anteroposterior view of the pelvis, as recommended in the Advanced Trauma Life Support method.

The anteroposterior radiograph of the pelvis must be scrutinized systematically for evidence of hip dislocation. Check for:

A series of pelvic radiographs, as described by Letournel and Judet, should be obtained when a hip dislocations is recognized, to improve the accuracy of diagnosis of associated fractures and the presence of incarcerated fragments in the hip joint. These additional views include an anteroposterior view of the hemipelvis and two 45-degree oblique views (Judet views), all centred on the femoral head. The pelvic series of radiographs allows an assessment to be made of the anterior and posterior walls and columns of the acetabulum. The three radiographs provide a profile of the anterior, middle, and posterior portion of the hip joint, which can be used to assess the integrity of the femoral head and acetabular surfaces. The three views can also be used to diagnose incarcerated fragments in the hip joint, as shown by incongruity of the joint, but only when the fragments are larger than 2mm. The Judet views are commonly omitted because of pain. Appropriate analgesia, however, is an integral part of resuscitation and the assistance of an anaesthetist may be sought when analgesia is inadequate. If the patient still cannot be positioned correctly for the Judet views, despite these measures, then the views should be taken under anaesthesia before a reduction is performed.

Repeat radiographs must be obtained immediately after reduction to determine the following:

It is imperative for the plain radiographs to be interpreted precisely to diagnose all associated fractures and any incarcerated fragments in the hip joint. This information is essential for an accurate classification of the hip dislocation, and hence the choice of appropriate treatment and operative approach when surgery is indicated.

The benefits of computed tomography (CT) compared with plain radiography include

The additional information provided by CT therefore improves the assessment of the size and displacement of fractures of the femoral head and the acetabular wall and hence the stability of the hip joint. Measurement of the percentage of remaining posterior acetabulum on axial CT scans after posterior dislocation of the hip provides a useful determinant of the stability of the joint (Figure 12.50.2). The incidence of instability is high when the remaining posterior articular surface is less than 34%. Hips with greater than 55% of the remaining posterior acetabulum will be stable.

Routine CT scanning has been recommended after successful closed reduction of hip dislocations and prior to planned open reduction, when closed reduction is unsuccessful. However, CT scanning may not be necessary after concentric reduction of simple (type I) posterior hip dislocations assessed on plain radiography. Nevertheless, the usefulness of CT scanning remains undisputed following dislocations of the hip associated with fractures or in the presence of an irreducible hip dislocation.

Magnetic resonance imaging (MRI) offers improved imaging of soft tissues compared with CT scanning. MRI scanning may be useful in the following:

From a practical perspective, MRI has limited usefulness in the initial evaluation of the multiply injured patient, because the procedure severely restricts access to the patient. MRI, however, may become a useful option after the patient is clinically stable.

Hip dislocations are classified as posterior or anterior, according to the position of the femoral head. The previously recognized term of ‘central’ dislocation has been superseded by a more comprehensive classification of acetabular fractures (AO Comprehensive Classification of Fractures of the Pelvis and Acetabulum). This subset of dislocations is discussed separately under acetabular fractures.

Thompson and Epstein subclassified posterior dislocations of the hip into five types. More recently described an improved subclassification of posterior hip dislocations that combined clinical and radiological findings, thereby providing a basic indication of treatment (Table 12.50.1).

The clinical findings included:

Radiological findings included:

Epstein subclassified anterior hip dislocations (Figure 12.50.3) into five types, but the subclassification took no consideration of the postproduction radiological findings and provided no benefit in determining the choice of treatment, outcome or prognosis. Consequently, a preferred subclassification is that of which follows the same pattern used for posterior dislocations (see Table 12.50.1).

Early diagnosis and treatment is essential for the patient with a hip dislocation. Avascular necrosis of the femoral head correlates strongly with the duration of an unreduced hip dislocation. Prompt reduction of a dislocated hip is therefore mandatory. Epstein reported markedly improved long-term results with immediate open reduction compared with closed treatment. However, those improved results may have resulted from a visual clearance of loose bodies, from the hip joint, which could not be radiologically demonstrated at that time. The advent of CT scanning for postproduction assessment after hip reduction nullifies the advantage of visual assessment of loose bodies during open reduction. Most authors now favour an immediate attempt at closed reduction.

Ideally, a closed reduction should be performed under general anaesthesia if an anaesthetist is readily available. The reduction can be performed under intravenous analgesia and sedation just as easily in a well-equipped emergency department as in an operating room. Patients already intubated for the treatment of closed head injuries can have an immediate closed reduction of the hip. Patients undergoing a general anaesthetic for treatment of multiple injuries should have a closed reduction of the hip performed first.

If it is not possible for a patient to undergo an immediate general anaesthetic, then a closed reduction can be attempted in the emergency department. Only one attempt at closed reduction should be made, and only once the patient is adequately sedated. Forceful attempts at closed reduction should be avoided when the patient is inadequately sedated as further damage to articular cartilage can result. If the attempt at closed reduction is unsuccessful, the patient should undergo a closed reduction in the operating room under general anaesthesia and complete muscle paralysis. If a closed reduction is still unsuccessful, an immediate open reduction must be performed.

Before progressing to open reduction, the full pelvic series of radiographs must be available. Irreducible hip dislocations may be associated with the following:

An accurate diagnosis of associated pathology is essential for preoperative planning of surgical approaches. For example:

Standard principles of reduction of a dislocated joint should be followed:

Successful reduction is usually evidenced by an audible or palpable ‘clunk’, return of a leg to a normal position, and immediate relief of pain when the patient is awake.

Stimson described a gravity reduction technique in which the affected leg is left hanging off the end of the barouche or operating table, with the hip and knee in a position of 90 degrees of flexion. With one hand on the front of the ankle and the other on the calf of the affected leg, the surgeon can easily control the position of the leg, while directing an anterior reduction forced to the hip. In this technique the surgeon has the advantage of working in line with gravity.

An alternative method of production was described by Allis. In this technique, which is the author’s preferred choice, the patient is left supine. The surgeon stands over the patient and pulls on the affected leg, against gravity, in the line of the deformity. When necessary, an assistant can apply countertraction to the pelvis. In large patients, when a lot of force is required, the assistant can gain a better hold by placing a towel over the skin first, before applying counter traction. The surgeon places one hand behind the calf and the other hand over the front of the ankle of the affected leg. By this means the position of the leg can be controlled, while an anterior reduction force is applied through the hip. When the surgeon has to apply greater force, various techniques can be used to gain a mechanical advantage. Bending forward at the waist, the surgeon can strut one elbow on an ipsilateral knee, placing the volar aspect of the forearm under the calf of the patient’s affected leg. An anterior reduction force can then be applied by the surgeon flexing that elbow (Figure 12.50.4). When even greater force is required, the surgeon can use this same technique bilaterally. The ankle of the patient’s affected leg is propped between the surgeon’s knee and forearm. The patient’s calf is supported in the surgeon’s hands. An anterior reduction force can then be applied by the surgeon clasping both hands together and flexing both elbows (Figure 12.50.5). These techniques allow the surgeon to use safe back practices by applying traction through a technique of elbow flexion and not through back extension.

After reduction of the hip has been verified radiographically, the stability of the hip must be assessed clinically, under continued sedation or anaesthesia (Box 12.50.3). This assessment is contraindicated in the presence of radiographic evidence of instability, including large displaced fractures of the posterior or posterosuperior acetabular wall, displaced fractures of the acetabular columns, or in the presence of a femoral neck fracture. The assessment of stability is made by applying a strong posteriorly directed force through the knee, with the hip flexed to 90 degrees in a neutral position of rotation and abduction/abduction. If any evidence of subluxation is detected, a CT scan is required.

Successful reduction of a dislocated hip and grading of the dislocation should be immediately confirmed with plain radiographs, including an anteroposterior and lateral view of the hip and an anteroposterior view of the pelvis. The radiographs should be carefully reviewed for evidence of incongruence or fractures of the acetabulum, femoral head, or femoral neck. If a previously unrecognized fracture of the acetabulum is diagnosed, additional Judet views should be obtained. A CT scan of the involved hip should be obtained for all dislocations of the hip associated with fractures (Levin types II–V) or when the presence of an intra-articular loose body is suspected.

Following closed reduction and assessment of hip stability, the affected leg is placed in traction. If the hip is stable, simple skin traction will suffice. If the hip is unstable, skeletal traction should be used. A posteriorly unstable hip should be treated in external rotation. An anteriorly unstable hip should be treated in internal rotation. Rotation of the hip can be controlled by applying a traction cord to one end of the traction pin. Placement of a traction pin must be correctly inclined to achieve this.

Widening of the hip joint is not radiographically (Box 12.50.4) evident on plain radiographs when fragments measuring 2mm are present in the hip joint. Therefore widening of the joint space on plain radiographs is a poor indicator of small loose bodies within the traumatized hip joint. Furthermore, although widening of the joint space is demonstrable when 4-mm fragments are interposed with in the hip joint, the widening does not equal the size of the fragment. There is a high risk of developing traumatic arthritis when patients with intra-articular fragments are treated in traction. Consequently it is imperative that the diagnosis of small loose bodies in the hip joint is not missed. Small loose bodies can be diagnosed by a CT scan taken with fine slices through the entire acetabulum. The scan should be processed for bone and soft tissue windows. When non-osseous loose bodies are present, MRI may be a useful alternative.

Once the radiographic imaging and clinical assessment of stability has been performed, the Levine grading of the dislocation can be completed. Management of the dislocation is largely determined by the Levine grading.

Type I injuries are pure dislocations or dislocations in which there is no significant associated fracture (Figure 12.50.6). A congruent reduction is obtained and the dislocation is stable after reduction. No surgical intervention is required. The patient is treated in gentle skin traction such as Hamilton–Russell traction. Active and passive range of motion exercises are permitted, but flexion beyond 90 degrees and internal rotation beyond 10 degrees are avoided for 6 weeks. Patients are mobilized weight-bearing as tolerated, once hip irritability resolves and leg control is regained.

In type II dislocations there is an irreducible hip dislocation (Figure 12.50.7). No significant associated fractures are present. The irreducibility is therefore due to the interposition of soft tissues, such as largely cartilaginous osteochondral loose bodies, the labrum, tendons, or muscle. An open reduction is required, with exposure of the hip joint on the side of the dislocation. If the hip remains unstable after reduction, further surgical exploration is required. If large tears of the capsule and labrum are present, these must be repaired. Concentric reduction of the hip joint must be confirmed radiologically in the operating room before surgical closure is performed.

In type II dislocations the hip is clinically unstable after reduction, or postproduction imaging demonstrates joint space widening or incarcerated fragments of bone or cartilage in the joint (Figure 12.50.8). The instability may be due to subluxation of the femoral head by incarcerated fragments, extensive labral detachment, or disruption of the capsuloligamentous attachments of the hip joint. Plain radiographs or CT scanning demonstrate bony fragments incarcerated in the articular space. Cartilage or soft tissue fragments are demonstrated best in MRI studies.

Minor capsuloligamentous disruptions or detachments of the acetabular labrum may be managed by non-surgical means, including bed rest or bracing of the hip within its stable arc of motion. Extensive labral tears may require surgical reattachment.

Fragments of tissue left incarcerated in the hip joint may damage the articular cartilage of the apposing femoral head and acetabulum. These fragments must be surgically cleared from the hip joint. Large fragments may be replaced where this is surgically possible. Smaller fragments must be removed, either arthroscopically or by an open procedure. When an open procedure is performed, the surgeon should choose the surgical exposure which offers the most direct approach to the offending fragment. Concentric reduction of the hip must be demonstrated radiographically before wound closure. The stable range of hip motion must be determined by stability examination before the patient leaves the operating room. Postoperatively the patient is placed in Hamilton–Russell traction. Active and passive range of motion exercises are permitted within the clinically determined stable range of hip motion. Once hip irritability resolves and leg control is regained patients are mobilized weight-bearing as tolerated. A hip brace may be used when the stable range of hip motion would leave the patient vulnerable to redislocation when walking.

Type IV dislocations are associated with fractures of the acetabulum requiring reconstruction to restore joint congruity or hip stability (Figure 12.50.9). Prolonged dislocation of the hip joint should be prevented whenever possible. The author initially places the patient in skeletal traction and performs a gentle closed reduction at the time of insertion of the traction pin. Definitive surgical management should be dictated by the acetabular fracture and not the hip dislocation.

Type V dislocations are associated with fractures of the femoral neck (Figure 12.50.10) or femoral head (Figure 12.50.11). The mechanism of injury in femoral head fractures is the same as that of hip dislocations. Typically the injury occurs with the femur in a neutral position with reference to abduction and relatively less flexion than in pure dislocations of the hip.

The majority of hip dislocations are posterior. The incidence of femoral head fractures associated with posterior dislocations has been reported at 7–13%. Femoral head fractures have been reported in up to 68% of anterior hip dislocations, but the number of reported cases is small. Femoral head fractures may result from indentation (Figure 12.50.12) or cleavage (Figures 12.50.11 and 12.50.13) of the femoral head by the acetabular lip at the time of dislocation, or from avulsion by the teres ligament.

Pipkin classified cleavage fractures of a femoral head into four types according to the position of the fracture and the presence of a femoral neck or acetabular fracture (Table 12.50.2). In a type I injury the fracture of the femoral head is caudad to the fovea (Figure 12.50.14 and 15A). In type II injuries the fracture of the femoral head is cephalad to the fovea (Figures 12.50.11 and 12.50.15B). A type III injury is a type I or a type II fracture with an associated fracture of the femoral neck that results in a segmental fracture of the femoral head (Figure 12.50.15C). A type IV injury has an associated fracture of the acetabular rim (Figures 12.50.13 and 12.50.15D).

Type 1 Pipkin fractures have been treated by closed reduction and traction. If postproduction radiographs demonstrate incongruence of the hip or the presence of intra-articular fragments, operative excision was previously recommended. Following experience gained in surgical hip dislocation the preferred treatment is open reduction and internal fixation for non-comminuted fractures sufficiently large to provide purchase for screw fixation.

Type II Pipkin fractures have been treated by closed reduction and traction, closed reduction and excision of the fragments, or open reduction and internal fixation. Following reduction the patient is treated in traction and early range of motion exercises are commenced.

Type III Pipkin fractures have been treated by closed reduction and traction, closed reduction and excision of the fragment, open reduction and internal fixation, and primary arthroplasty. Any attempt at closed reduction must be performed gently to avoid displacement of a femoral neck fracture, or the production of an iatrogenic fracture. If the attempt at reduction is unsuccessful, the surgeon should proceed to open reduction rather than resort to an excessively forceful closed reduction.

Type IV Pipkin fractures have been treated by closed reduction and traction, closed reduction and excision of the fragment, and open reduction and internal fixation. The acetabular fractures should dictate the treatment protocol. Undisplaced acetabular fractures may be treated non-operatively. When the indications for open reduction and internal fixation of the acetabulum are present, the fracture should be treated operatively and the femoral fracture can then be treated along the lines of type I and II fractures. Postoperative management is determined by the acetabular fracture.

Posterior hip dislocations may result in impaction (Figure 12.50.12) or cleavage fractures (Figures 12.50.13 and 12.50.14) of the femoral head that lie anteriorly. A surgical hip dislocation is ideal for operative reduction and internal fixation of these fractures and provides ready ease of access to the whole femoral head (Figure 12.50.16). Ganz and Beck have modified the technique by incorporating a step-cut of the greater trochanter. Placing the distal half of the trochanteric osteotomy deeper than the proximal portion, the intervening step between the two provides a mechanical block to proximal migration of the osteotomized trochanter after internal fixation. The patient’s ipsilateral knee is flexed and the tibial shaft used as a reference to the plane of the osteotomy. In contrast, anterior hip dislocations are characterized by cleavage or impaction fractures on the posterosuperior and lateral portion of the femoral head.

Treatment goals of anatomical reduction, restoration of hip joint stability, and removal of all interposed bone fragments have resulted in an improved prognosis of femoral head fractures. In general, the outcomes of Pipkin type I and II fractures are similar and are better than those of Pipkin type III and IV fractures.

The sciatic nerve is frequently injured in hip dislocations. The peroneal component is most commonly affected. The reported incidence varies from 8–19% of patients with hip dislocation. Damage to the nerve may be secondary to pressure ischaemia or directly from laceration or impalement by bone fragments. Nerve tissue has little tolerance to ischaemia. Posterior hip dislocations with neurological deficit of the sciatic nerve should therefore be reduced as a surgical emergency. Increasing sciatic nerve dysfunction in the presence of displaced posterior wall or transverse acetabular fractures should be treated emergently by acute open reduction and internal fixation of the fracture. Paresis may develop acutely after reduction of a hip dislocation and warrants surgical exploration. Causes include:

Posterior hip dislocations commonly results from a forceful blow to the front of the knee. Concomitant injuries may therefore occur to the patella, the femoral or tibial condyles, or to the knee ligaments. Posterior cruciate ligament injuries and posterolateral rotatory instability are the most common ligamentous injuries associated with posterior hip dislocation. Associated collateral knee ligament injury may occur when the causative force is applied to the tibia and not directly to the knee.

Avascular necrosis of the femoral head occurs more commonly after posterior hip dislocations than after anterior dislocation. The reported incidence after posterior hip dislocation varies from 3–50%. Changes occur in the extraosseous blood flow of the common femoral and circumflex vessels to dislocated hips. Internal rotation of the femur, posterior dislocation of the hip, and lateral displacement of the femur produces traction to the deep branch of the medial circumflex femoral artery, which have shown to be the major blood supply to the weight bearing portion of the femoral head. Delay in reduction may lead to avascular necrosis by prolonging ischaemia and by causing progressive arterial damage in the common femoral and circumflex vessels. The commencement of early weight bearing does not increase the incidence of avascular necrosis but may modify the severity of this complaint.

Recurrent hip dislocation may result from a deficiency of the bony and capsuloligamentous restraints of the hip joint, or an alteration of local muscle forces. Impaction fractures of the femoral head may also lead to recurrent dislocation in a manner similar to dislocation of the humeral head resulting from a Hill–Sachs lesion.

The reported incidence of heterotopic bone formation associated with hip dislocation is 2%. The incidence increases after open reduction of dislocations, open reduction and internal fixation of associated fractures, delayed surgery, and in patients with a hip injury. Surgical excision may be warranted when heterotopic bone formation is disabling, but should be delayed until the process is quiescent. A bone scan may be helpful to confirm this.

The reported incidence of post-traumatic arthritis following uncomplicated hip dislocation varies around 11–16%. When hip dislocation is associated with acetabular fractures the incidence of post-traumatic arthritis rises markedly and has reached 88% in severe acetabular fractures. The incidence of post-traumatic arthritis decreased to 10% or less with accurate open reduction and internal fixation of acetabular fractures, but increased with age.

Appropriate management of hip dislocation requires a clear understanding of the mechanisms of injury, early recognition of systemic injuries, accurate diagnosis and grading of dislocations, and prompt effective treatment. Problems and complications must be anticipated to prevent their occurrence or to allow early and effective treatment when they occur. A comprehensive approach to the injury complexes associated with hip dislocation is mandatory for an effective outcome of treatment.