Classification

Associated fractures typically guide the treatment of a hip dislocation, and therefore classification systems that separate the injuries on this basis can be quite helpful. There are four categories of hip dislocations:

1. 
   

   Hip dislocation without fractures

   
   
2. 
   

   Hip dislocation with fracture of the acetabulum

   
   
3. 
   

   Hip dislocation with fracture of the femoral head

   
   
4. 
   

   Hip dislocation with fractures of the femoral head and acetabulum

As acetabular fractures were addressed in Chapter 23, this chapter focuses on hip dislocation, with or without fracture of the femoral head. In addition to associated fractures, noting the location of the displaced femoral head is also important in guiding the treatment of the injury, as well as providing effective communication between physicians. As stated above, displacement is typically posterior (89–92%), but anterior (8–11%) and rarely inferior (obturator) dislocations do occur.2,6 Medial dislocations involve a fracture of the quadrilateral surface of the acetabulum, and are discussed in Chapter 23 with acetabular fractures. The literature contains reports of a “floating pelvis” (bilateral hip dislocations and an unstable lumbar spine injury) as well as bilateral hip dislocations. The bilateral hip dislocation can involve opposite directions of displacement between the two sides, and is commonly associated with a motorcycle accident.7–12

As previously mentioned, a femoral head fracture may be a component of the injury pattern, and can be hard to recognize on plain imaging. The incidence of a femoral head fracture in conjunction with a hip dislocation is 16%. As dislocations are usually posterior, it is the anteromedial femoral head that fails due to shear forces as the femoral head displaces past the posterior wall of the acetabulum (Fig. 24.2). The exact location and size of the anteromedial fragment is related to the position of the extremity at the time of injury.13 Although anterior dislocation of the hip is rare, it is associated with a higher likelihood of femoral head fracture; in such cases this is usually an infrafoveal impaction fracture.6 Femoral head fractures have been classified by Pipkin13 according to their location in relation to the fovea as well as by the presence of associated injuries (Fig. 24.3 and Table 24.1).

The Pipkin type I fracture is distinguished from the type II fracture based on the relationship and integrity of the ligamentum teres to the head fragment that remains in the acetabulum. In the type I fracture, the ligamentum teres ruptures as the femoral head dislocates and fractures, and the resultant fragment is caudal to the insertion of the ligamentum teres to the femoral head. Typically this caudal fragment does retain a small periosteal or capsular pedicle of soft tissue. In the type II fracture, the ligamentum teres remains attached to the fragment as the femoral head dislocates and fractures. The type III situation is complicated by the presence of a concomitant femoral neck fracture, and the type IV is associated with an acetabular fracture. During a posterior dislocation, the anteromedial head experiences a shear force as it impacts the posterior rim of the acetabulum. An obturator oblique radiograph is particularly helpful in evaluating the anteromedial femoral head (Fig. 24.4). Impaction injuries and subtle concomitant fractures are best examined with a computed tomography (CT) scan of the pelvis.

Nonoperative Treatment

Closed Reduction of Posterior Hip Dislocation

Upon identification of a hip dislocation, a closed reduction should be promptly performed. Concomitant fractures of the acetabulum and femoral head are not contraindications to a closed reduction. Furthermore, an expedient closed reduction is necessary whether or not operative intervention is required for the injury pattern.

Closed reduction of the hip is ideally done with the patient deeply sedated or under general anesthesia. When the plan is to perform a closed reduction in the operating room, the patient should be asked to give prior consent for an open reduction in the event that the closed manipulation is not successful. Re-creating the position of dislocation by placing the hip in a flexed, internally rotated and adducted position is typically necessary to have the femoral head clear the posterior rim of the acetabulum during reduction. With the leg in this position, a distally directed axial force in line with the femoral shaft pulls the femoral head over the rim of the acetabulum, and the joint reactive forces produced by the musculature at the hip will generate a congruent reduction if there are no free osteochondral fragments interposed.

The Bigelow maneuver is perhaps the most commonly performed technique, ideally with three practitioners collaborating to perform the reduction. The patient is placed in the supine position. One assistant provides countertraction with downward pressure on the anterosuperior iliac spines, and the other spots the orthopaedist as they stand over the patient on the bed, grasping the knee from posteriorly, pulling axial traction on the femur on a hip that is flexed, adducted, and alternatively internally and externally rotated gently (Fig. 24.5).

With the Allis maneuver, an assistant stabilizes the pelvis while the reducer pulls in-line traction. The hip is flexed to 90 degrees and gentle alternating internal and external rotation helps coax the hip back into position (Fig. 24.6).

The Stimson method entails the patient lying prone with the affected extremity hanging off the end of the exam table. The hip and knee are flexed to 90 degrees and a downward force is applied to the calf (Fig. 24.7).14 This can often only be tolerated under general anesthesia.

Closed Reduction of Anterior or Inferior Hip Dislocation

Traction and counter traction are also used for an anterior hip dislocation. Allis also described this maneuver, detailing that traction should be applied distally with gentle flexion and internal rotation of the hip. Extension can also be helpful with an anterior dislocation. The reduction of the inferior dislocation involves the above maneuvers with a modification added by Walker, which involves a lateralizing force on the proximal femur. The lateralizing force can be provided by a sheet wrapped around the inner aspect of the proximal femur, with the two ends of the sheet lateral to the patient.

Regardless of the type of dislocation or technique applied, a slow, constant force that fatigues the hip musculature of a relaxed patient is essential. The goal is to have a successful reduction without incurring additional articular or bony injury. If the reduction attempt under conscious sedation is unsuccessful, further manipulations under conscious sedation should not be performed so as to avoid further trauma to the hip. The reasons for an unsuccessful closed reduction include inadequate muscular paralysis, “buttonholing” of the femoral head through the capsular tissues producing entrapment of the head, and ligamentous or bony injuries of the extremity preventing safe or effective traction on the limb (Fig. 24.8).

If unsuccessful, a manipulative reduction under general anesthesia should be the next step, and the surgeon should be prepared to perform an open reduction of the hip, as well as treat any associated injuries in this setting. A Schanz pin in the proximal femur at the level of the lesser trochanter is a helpful manipulative tool for a successful closed reduction, particularly in the presence of a diaphyseal femoral fracture. For the isolated dislocation, however, if adequate relaxation was achieved with conscious sedation and the reduction attempt was unsuccessful, it is unlikely that the attempt under general anesthesia will produce a different result. Thus, the surgeon should be prepared to perform an open reduction if the patient is taken to the operating room.

After a successful closed reduction, radiographic and CT imaging should be performed to determine if there is an associated femoral head or acetabular fracture. If this workup is negative, the patient may be made weight bearing as tolerated with an assistive device as necessary. If instability remains a concern, an examination under anesthesia can provide useful information. If re-creating the position of instability and applying an axial force can produce subluxation of the femoral head within the acetabulum, then repair of the injured structures is necessary. Closed treatment entails giving the patient an explanation of the injury as well as information about which provocative positions to avoid. The use of an abduction orthosis is rarely of benefit, and an ambulatory aid can be discontinued as soon as tolerated.

Patients with small avulsions of the posterior wall as well as small, caudal femoral head fractures can typically be treated with the above protocol as well. Closed treatment is only appropriate in the concentrically reduced hip with a femoral head fracture that is small, infrafoveal, displaced < 1 mm, and not associated with intra-articular debris (Fig. 24.9).

Related posts:

Treatment of Fractures in Geriatric Patients Care of the Soft Tissue Envelope Musculoskeletal Infection Associated with Skeletal Trauma Distal Humeral Fractures Femoral Neck Fractures Pelvic Ring Injuries

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