Fractures of the femoral head
Dr. KS Dhillon
Introduction
Fractures of the femoral head are uncommon but severe injuries of the proximal femur, that typically occur after posterior dislocation of the hip joint [1–3]. Birkett was the first to discover and document femoral head fractures while performing a post-mortem dissection in 1869 [4].
The incidence of this rare injury has increased steadily in recent years. This is most likely due to the higher number of motor vehicle accidents and enhanced survival of polytraumatized patients [5].
Treatment of this injury ranges from simple closed reduction to a surgical approach, where an open reduction and internal fixation of the fracture is carried out. Sometimes the fracture fragment is removed. Associated femoral neck or acetabular fractures have to be treated [6-8].
The fractures can be associated with serious long-term complications such as osteonecrosis of the femoral head, posttraumatic osteoarthritis, and
heterotopic ossification. These complications often lead to poor functional outcomes and unsatisfactory clinical results [9–11].
Mechanism of injury
Fractures of the femoral head usually occur with posterior hip dislocations and/or with fractures of the acetabulum [12].
The incidence of fractures of the femoral head in patients with posterior hip dislocation is approximately 5–15% [1–3,13–15]. The fracture of the femoral head is caused by shear forces along the femoral axis against the acetabular rim, as the femoral head exits the acetabulum [16]. Impression fractures caused by anterior or central hip dislocation or isolated fractures are less frequent [17-19].
Fractures of the femoral head occur mostly after high-energy trauma, typically in the form of motor vehicle accidents or fall from a significant height. About two thirds of patients are young adults. Associated injuries such as acetabular fractures are extremely common [20].
Blood supply
Ninety percent of the blood supply to the femoral head comes via an intracapsular plexus surrounding the femoral neck. The blood supply originates from two branches of the femoral artery, namely the medial circumflex artery and the lateral circumflex artery. Ten percent of the blood supply comes via the foveal artery which originates from the obturator artery. The foveal artery runs through the ligamentum teres and supplies the perifoveal area.
Classification systems
Stewart and Milford in 1954 described four grades of hip joint dislocation (fig 1). In type 1 there was no acetabular fracture or only a minor chip fracture. In type there 2 there is a posterior rim fracture and the hip is stable after reduction. In type 3 there is a posterior rim fracture with hip instability after reduction. In type 4 there is dislocation with femoral head or neck fracture [21].
Fig 1
Pipkin [22] classified fractures of the femoral head by their location and the presence of any associated fractures (fig 2).
Fig 2
He divided the femoral head fracture into one of four types: type I is defined as fracture inferior to the fovea, type II is defined as fracture extended superior to the fovea, type III is a type I or type II fracture associated with a femoral neck fracture, and type IV is a type I or type II fracture associated with an acetabular fracture. Pipkin used the fovea capitis as the landmark between type I and type II fractures. The ligamentum capitis femoris is attached to the inferior fragment in type II injuries, and this often results in substantial rotation of this fragment. As a result of this, the rotated caudal segment with its attached ligamentum may prevent a reduction of the cranial head segment [22].
The Pipkin classification has become the most frequently used classification system for fractures of the femoral head.
There is a better outcome with Pipkin type I and type II fractures when compared to Pipkin III and IV fractures [23].
Some authors regard the Brumback classification (fig 3) as more accurate and clinically valid as compared to the Pipkin classification [24]. The classification system of Brumback et al [25] also considers the direction of the dislocation, joint stability, and severity of the acetabular fracture. In addition, the Brumback classification provides a prognostic value, with patients suffering from type 3B and type 5 injuries faring the worst, and patients with type 2B fractures having the best physical outcomes [9].
Brumback classification of dorsal hip luxations and fractures of the femoral head
Fig 3
Clinical Evaluation and Diagnosis
The posterior hip dislocation usually presents with shortening of the lower limb. The limb is held in flexed, adducted, and internally rotated position. In patients with large acetabular wall fractures, little to no rotational asymmetry is seen. In patients with anterior dislocation, the limb is flexed, abducted, and externally rotated. The Ipsilateral knee is assessed for ligamentous stability. A rapid neurovascular examination is carried out including pulses, capillary refill, and skin temperature. In this type of trauma, the sciatic nerve is often injured [2].
Fracture dislocation is usually evident on an anterior-posterior (AP) pelvic radiograph. If a posterior dislocation of the femoral head is present, an AP pelvic radiograph will usually show a superiorly displaced femoral head, a void in the acetabular socket, and a disruption of Shenton’s line.
Additional pelvic inlet and outlet views and 45° oblique views, as described by Judet and Letournel [26], can be obtained if necessary.
If concomitant injuries, such as acetabular fractures are present, additional iliac and obturator oblique views should be performed.
A CT scan with appropriate reconstructions should be performed to obtain all the essential information for the diagnosis of a femoral head fracture. After the successful closed reduction, a CT scan should be performed routinely. The CT scan will provide essential information about the structure of the femoral head fracture, fracture displacement, and potential fracture fragments in the joint space.
Magnetic resonance imaging (MRI) can be done to detect an avulsion of the acetabular labrum and to make an early diagnosis of femoral head necrosis [5].
Emergency treatment
Fracture-dislocation of the hip joint needs emergency treatment. An immediate closed reduction is indicated even if a femoral head fracture is present. Reduction is performed under sedation in the emergency department. Delay of the reduction must be avoided to minimize the risk of osteonecrosis of the femoral head [27]. After a successful reduction, new radiographs and a CT scan of the hip should be done to evaluate the femoral head and other associated injuries.
When there is a contraindication for closed reduction such as concomitant femoral neck fracture or when the dislocation remains irreducible due to a rotation of the fracture fragment around the ligament of the head of the femur, impaction of soft tissues or an osteochondral fragment [22], an urgent open reduction is indicated.
Definitive treatment
Non-surgical treatment
The Pipkin classification can be useful in guiding the appropriate treatment approach for femoral head fractures. Pipkin I and II fractures can be treated non-surgically if closed reduction achieves a residual displacement of the bone fragment of 1 mm or less and an anatomically congruent hip joint without fragment interposition. In the past, most femoral head fractures were treated with prolonged bed rest and axial traction after closed reduction [22,28]. With this treatment approach, fairly poor results have been reported [13]. Nowadays, partial weight-bearing with crutches for a minimum of six weeks is recommended [25,29]. Adduction and internal rotation beyond neutral should be restricted for about two months [5]. Radiographs are repeated to evaluate maintenance of hip reduction and hip joint congruency. Radiographs are usually done after one, three, and six weeks, as well as at three months. Pipkin type 4 fractures with nondisplaced and small fracture fragments can also be treated non-surgically.
Surgical treatment
Patients in whom after close reduction a displacement of less than1 mm
displacement cannot be achieved, surgical treatment would be indicated. In patients with Pipkin type I and type II fractures where surgery is indicated, open reduction and internal fixation (ORIF) is recommended. This is usually done with countersunk screws or headless compression screws.
Headless compression screws have the advantage that they can be placed subchondrally, without causing damage to the articular cartilage [8,30]
Bio-absorbable screws can also be used to fix femoral head fractures. These bio-degradable screws provide fewer artifacts during magnetic resonance imaging. Hermus et al [31] and Prokop et al [32] reported on the use of bio-absorbable screws for the fixation of femoral head fractures.
In Pipkin type I injuries with small fragments outside the weight-bearing zone removal of the fractured fragment can be done.
General Pipkin type III injuries have a poor prognosis [24]. Such injuries are treated by immediate open reduction and internal fixation. Close reduction is not feasible since there is a neck fracture.
In younger patients, ORIF of the femoral neck and head fracture is performed. A hemiarthroplasty or a total hip arthroplasty is performed in senescent patients with signs of advanced arthritis and low physical demands [33]. A hemiarthroplasty can only be done if there is no acetabular fracture.
Pipkin IV fractures are addressed in tandem with the associated acetabular fracture. If the femoral head and acetabular fracture are not displaced, a non-operative approach with restricted weight-bearing is recommended. If the fractures are displaced, ORIF of the fractures is carried out.
Complications
Isolated fractures of the femoral head carry the risk of a variety of complications. The most frequent early complications in surgical cases of femoral head fractures are postoperative infections with a rate of about 3.2%. Sciatic nerve injury occurs in 4.0% of all fracture dislocations [24]. Major late complications include avascular necrosis with an incidence of about 11.8%, posttraumatic arthritis with an incidence of 20%, and heterotopic ossification with a 16.8% incidence [24]. Another common complication is coxa magna which occurs in 27% of the cases with radiographic follow-up averaging two years and six months [34]. Decreased internal rotation is another complication. It may not be clinically problematic or cause disability.
Prognosis
There are 2 problems when trying to analyze the prognosis of femoral head fractures i.e inadequate follow-up in the percentage of patients within the study series and the lack of a uniform classification system with satisfactory inter-observer and intra-observer reliability [35].
The most commonly used criteria for functional assessment following fractures of the femoral head was established by Thompson and Epstein [12]. It included the radiographic outcome as well as residual pain and range of motion of the hip joint. Giannoudis et al [24] in a systematic review analyzed the outcome of femoral head fractures using Thompson and Epstein’s criteria. The outcome was excellent in 14.3%, good in 39.8%, fair in 19.3%, and poor in 26.5% of the patients. Surprisingly, the authors found no statistical difference in the outcome among Pipkin subtypes. The analysis, however, revealed a tendency towards a superior outcome in Pipkin type I and II fractures, as compared to Pipkin type III and IV fractures. The data published by Giannoudis et al [24] are based on a
rather small number of patients. There was an absence of a validated outcome instrument and a lack of high-quality randomized control studies.
Conclusion
Fractures of the femoral head are uncommon. They usually occur with posterior dislocation of the hip from high-energy trauma. Treatment is conservative in cases of non-displaced fractures with intact joint congruity. For displaced fractures, surgical treatment is usually necessary. Surgical treatment involves open reduction and internal fixation of the fractured segments. Sometimes surgery is necessary for the removal of small bone fragments. In the elderly population where there is a fracture of the neck, a hemiarthroplasty or total hip replacement may be necessary. Hemiarthroplasty cannot be carried out if there is a fracture of the acetabulum.
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