Femoral head anatomy, diagnosis and management

Authors: Olivia Ann Dunseath, Ibrahem Al-Obaidi, Luca Ignatius, Branavan Rudran, Chris Jordan

Abstract

Femoral head fractures are complex and severe injuries, usually associated with hip dislocation. They typically result from high-energy trauma. Therefore, a low index of suspicion is required for diagnosis in these contexts. Initial presentation can vary depending on coexisting injuries but is typically an emergency and requires immediate reduction of the joint. Delays result in worse outcomes for patients.Pelvic radiographs are recommended before and after joint reduction, with Judet, inlet and outlet views to identify any associated acetabular fracture and pelvic ring injury. Computed tomography helps determine the fracture configuration and classification, commonly using the Pipkin classification. Definitive fracture management depends on patient demographics, fracture pattern and associated injuries.Pipkin type I and II fractures with minimal displacement and an anatomically congruent hip joint may be treated conservatively. Otherwise, surgical open reduction internal fixation via the anterior approach is recommended. Young patients with Pipkin type III injuries usually require open reduction internal fixation via the anterior or posterior approach, while elderly patients may need total hip arthroplasty. Pipkin type IV fractures may require a combination of open reduction internal fixation approaches with or without trochanteric flip osteotomy.Femoral head fractures often have poor outcomes, with type III and IV fractures having worse outcomes than types I and II. Early complications include infection and sciatic nerve palsy. Late complications include avascular necrosis, heterotopic ossification and post-traumatic arthritis. This article considers the anatomy, diagnosis and evidence-based management strategies for femoral head fractures.

Introduction

Fractures of the femoral head are a rare traumatic injury of the proximal femur, occurring almost exclusively alongside hip dislocation, with a reported associated incidence of 5–15% (1). The stability of the hip joint means that a large amount of energy is required for disruption, meaning the mechanism of these injuries usually results from high-energy trauma such as road traffic accidents or falls from height. Approximately two-thirds of patients are young adults, and associated injuries occur in as many as 75% of the cases (2). This article considers the anatomy, diagnosis and evidence-based management strategies for femoral head fractures.

Important anatomy

The proximal femur’s bony anatomy comprises four main the femoral head, neck, greater trochanter, and lesser trochanter. The primary weight-bearing portion of the femoral head is the anterolateral aspect, which is coated with hyaline cartilage and articulates with the acetabulum to form the hip joint. All forces travelling between the spine and legs pass through this joint, making its stability crucial for supporting weight-bearing during walking. The femoral neck, narrower than the head, connects it to the shaft, while the trochanters act as attachment sites for muscles involved in joint movement.

There are three main sources of blood to the femoral the medial and lateral femoral circumflex arteries (branches of the deep femoral artery) and the foveal branch of the obturator artery (via the ligament of the head of the femur). The medial circumflex provides the majority of the blood supply, travelling posteriorly and proximally, whereas the lateral circumflex travels anteriorly and proximally up the femur (Fig. 1). Disruption of these vessels, as seen in femoral neck fractures, places the femoral head at risk of avascular necrosis.

Initial presentation and management

Due to the mechanism of injury, patients often present with multiple concomitant injuries. A thorough history and physical examination are essential to identify and manage life-threatening head, intra-abdominal, pelvic and chest trauma before the hip injury assessment (3, 4).

If the hip dislocates posteriorly, the limb appears shortened, flexed, adducted and internally rotated (5). Anterior dislocations may appear shortened, flexed, abducted and externally rotated (6). However, these presentations may be absent alongside coexisting femoral neck, head and acetabular fractures. A thorough examination of the ipsilateral limb and knee for ligament stability is essential, as dislocations often occur secondary to the knees hitting the dashboard during a road traffic accident (7). A focused neurovascular status of the injured leg is required, with particular attention given to the peroneal nerve division, as the sciatic nerve is commonly injured (8). The physician must continuously re-assess neurovascular status during admission.

Hip dislocation is an orthopaedic emergency. Regardless of a concomitant femoral head fracture, an immediate reduction must be performed as soon as the patient is clinically stable. Delay in diagnosis and reduction may result in complications such as avascular necrosis of the femoral head (9). An AP pelvic X-ray should be taken during the acute hospitalisation. Hip reduction must be performed under sedation in the emergency department or theatre using a recognised, safe method, typically involving longitudinal traction in line with the position of the affected lower extremity (4). Following reduction, radiographs are required to demonstrate concentric reduction, and stability is assessed while the patient is under sedation. If a femoral neck fracture coexists, closed reduction is contraindicated, requiring immediate surgical management.

Imaging

AP pelvis radiographs should be taken pre- and post-reduction of the dislocated hip. Additional Judet oblique radiographs reveal coexisting acetabulum fractures (10), while inlet and outlet views assess for concurrent pelvic ring injuries (11). When considering an impaction fracture, an X-ray alone will struggle to identify very small intra-articular loose fragments in the joint space of the hip, which, if left untreated, will complicate recovery (12). Therefore, CT imaging is an integral next step in the series of imaging required for diagnosing femoral head fractures and assessing fracture pattern, displacement and post-reduction congruity. Magnetic resonance imaging (MRI) is used for suspected associated soft tissue injuries and for assessing complications, such as avascular necrosis.

Radiographic classification of femoral head fractures

The Pipkin classification system, developed in 1957 from observations of 24 patients (25 femoral head fractures), is the most widely used system for radiographically classifying femoral head fractures (13). This system divides injuries into four groups depending on the fracture location on the femoral head and coexisting fractures (Table 1 and Fig. 2).

Brumback et al. (14) and Yoon et al. (15) have since proposed more comprehensive classifications. Brumback et al. considered the dislocation direction, joint stability and acetabular fracture severity, whereas Yoon et al. focused on the location, size and degree of fragmentation (Table 1). More recently, 3D mapping of fracture patterns has been used to identify mismatches between different classification systems, developing a more comprehensive and descriptive classification system based on morphometric features of femoral head fractures (16). However, their use requires caution due to the lack of robust validation (17). While most orthopaedic surgeons use the most established Pipkin classification system, the number of non-validated and inconsistent fracture classification schemes remains a barrier to the optimal management of femoral head fractures.

Definitive management of femoral head fractures

The definitive management of femoral head fractures remains controversial, with no gold standard. This is likely due to the infrequency of these injuries and because most of the available literature is limited to small case series. Balancing the risks and benefits of each treatment compared to another based on the fracture pattern, associated injuries, patient demographics and fragment size is key (Fig. 3).

Conservative management

In a select number of femoral head fracture cases, conservative management may be considered. These are classified as Pipkin type I or II fractures, of whom following closed reduction, fracture displacement is 1 mm or less, the hip joint is anatomically congruent, and no loose bodies remain within the joint space (18, 19). Non-operative management may also be considered for Pipkin type IV fractures, where the femoral head and acetabular fractures are non-displaced (1). Historically, conservative management involved prolonged bed rest, axial traction and closed reduction (20). However, this is no longer justified due to the increased risk of chondrolysis (21). Partial weight-bearing is now recommended, with the limb restricted in adduction and internal rotation above neutral for four to six weeks (1, 14). Serial radiographs are required to obtain satisfactory results to document maintained joint reduction (1, 22).

Surgical management

Surgical management of Pipkin type I and II femoral head fractures is recommended if the criteria mentioned above are not fulfilled (1). A meta-analysis of 15 studies containing 274 cases of Pipkin type I and II femoral head fractures found evidence of significantly better outcomes with open reduction internal fixation when compared to fragment excision techniques (23). The fragment is commonly fixed with countersunk or headless compression screws. An alternative may be the use of Herbert screws or bio-absorbable pins (1). It should be noted that poorer functional outcomes have been recorded in patients whose fractures were stabilised with 3 mm cannulated screws with threaded washers due to back-out and dissociation between screw and washer (24). Regardless, screws can be utilised synergistically with Tisseel, a fibrin sealant that promotes tissue adhesion (25). This would enable further stabilisation of the implants and thus support better healing and integration, especially in cases with complex fractures where screw fixation alone might be less stable due to poor bone quality and/or comminuted fracture patterns. Furthermore, Tisseel has a concomitant ability to enhance haemostasis and promote healing without significant undue inflammatory reactions, contributing to shorter surgical times and fewer post-operative complications. These advantages have led to a growing preference for the use of Tisseel in fracture fixation (25, 26). However, literature regarding their use in open reduction internal fixation of the hip is currently limited, and as such, there is uncertainty about their benefit in this field.

The main fragment in Pipkin type I and II fractures is usually located in the anteromedial area of the femoral head. Therefore, the anterior Smith-Petersen approach allows adequate exposure to fixate the fragment while avoiding the need to fully dislocate the hip (27). The incision for this approach is centred over the tensor fascia latae, starting between the iliac crest and anterior superior iliac spine and then extending distally for about ten centimetres. Deep dissection and retraction of the rectus femoris medially and gluteus medius laterally reveal the hip joint capsule, allowing for direct visualisation and internal fixation of femoral head fragments (27). Studies have demonstrated that this approach reduces operation time and estimated blood loss alongside reduced rates of avascular necrosis of the femoral head compared to posterior approaches. However, the risk of heterotopic ossification is much higher (28, 29).

Pipkin type III fractures are much less common than type I and II fractures and tend to have poorer outcomes, including high rates of fixation failure and avascular necrosis of the femoral head. A systematic review conducted by Giannoudis et al. reported a poor and fair outcome in 50% of Pipkin type III fractures compared to 12, 15 and 27% for Pipkin types I, II and IV, respectively (30). The femoral neck fracture makes closed reduction of the dislocated hip almost always impossible. Therefore, open reduction must be undertaken as soon as possible (31). Management options for these fractures include open reduction internal fixation via either the anterior Smith-Petersen or the anterolateral Watson-Jones approach or total hip arthroplasty. However, the outcome of these treatments highly depends on patient age, time to surgery and amount of comminution (19). Open reduction internal fixation is generally recommended for younger, more active patients, while total hip arthroplasty is reserved for older and frailer patients. The risk of hip dislocation in total hip arthroplasty for treating Pipkin type III fractures is more significant compared to total hip arthroplasty for treating hip joint osteoarthritis (13, 32).

The anterolateral Watson-Jones approach is particularly useful in the open reduction internal fixation of Pipkin type III fractures. Dissection between the intermuscular plane between the tensor fascia latae and gluteus medius provides optimum exposure of the femoral neck, allowing the surgeon to address this fracture at the same time as the femoral head fracture. However, this approach offers limited exposure to the acetabulum and any posterior injuries, making it inappropriate if these areas need addressing (27).

Controversy remains regarding the surgical approach required for managing Pipkin type IV fractures. The coexisting acetabulum and femoral head fractures require careful evaluation when deciding the appropriate surgical approach. Combined approaches are often helpful when adequate visualisation of both fractures is not possible with a single approach. Surgical approaches include the anterior Smith-Petersen or Watson-Jones approach versus the posterior Kocher–Langenbeck approach with a trochanteric flip osteotomy and anterior hip dislocation (33). Other approaches have also been described, such as the Gibson (33, 34), Stoppa (1, 22) and Heuter approaches (35).

The Kocher–Langenbeck approach is recommended for posterior hip dislocations alongside acetabular fractures of the posterior column and wall (1). This approach extends from the posterior superior iliac spine laterally and distally towards the greater trochanter. The gluteus maximums fibres are dissected into proximal and distal halves, revealing the posterior wall of the acetabulum (27). If the fracture fragment is orientated more anteromedially, this approach makes direct screw fixation more difficult. In this situation, an additional anterior ilioinguinal or intrapelvic approach is required to fixate the fragments or an extension of the posterior approach via trochanteric flip osteotomy. The Kocher–Langenbeck approach with trochanteric flip osteotomy improves the exposure of the femoral head while preserving its vasculature and reducing the operation time and estimated blood loss (36, 37). Occasional complications, such as non-union, trochanter migration and trochanteric bursitis, have been described (33).

The removal of fracture fragments is a consideration that individual surgeons need to make based on the fragment size, degree of comminution and location of the fragment in relation to the weight-bearing surface. Generally, this should be performed if the fracture fragment is sufficiently large (>2 cm) to allow for stable internal fixation. Small or comminuted fragments, or fragments outside the weight-bearing portion of the head, can be removed from the joint (22). Intra-articular fragments can prevent congruent joint reduction and, if left, may damage the articular surface via wear and tear. More recently, many have advocated for the use of hip arthroscopy as a method to evaluate a hip dislocation and remove any loose bodies (38). Advantages of this technique include faster recovery time, reduced blood loss and less capsuloligamentous structure disruption. Complications include sciatic, femoral and pudendal nerve damage or damage to the lateral cutaneous nerve to the thigh. Further complications, such as bruising and bleeding, osteonecrosis of the femoral head, scrotal swelling and abdominal compartment syndrome, have been reported. However, the rate of complications is very low, ranging from 1 to 6% (38).

Post-operative protocol should optimise touch weight-bearing and early mobilisation to restore the range of motion of the hip joint. Immediate 20 kg partial weight-bearing with crutches is recommended for six to eight weeks following the operation, assuming the fracture is stable. Following this, radiographic evidence is required to identify fracture healing and any signs of avascular necrosis and osteoarthritis. If the fracture is healing well at six to eight weeks, the patient can be weaned off crutches. Full weight-bearing is usually achieved within three months (1).

Outcomes and complications

Femoral head fractures are severe injuries mainly resulting from high-energy trauma, often occurring with life-threatening injuries. Prognosis is variable, with outcomes depending on the severity of the fracture, associated injuries and management. A systematic review by Giannoudis et al. analysed the outcome of femoral head fractures using Thompson and Epstein’s criteria. The review demonstrated excellent results in 14.3%, good results in 39.8%, fair results in 19.3% and poor results in 26.5% of all cases, regardless of Pipkin classification (30). Despite no significant differences, the review demonstrated superior outcomes in Pipkin type I and II fractures compared to types III and IV. However, this review was limited to a small number of cases enrolled in the subgroups when the statistical analysis was performed. Furthermore, no validated outcome instrument or high-quality randomised control studies were included (30). In a retrospective review by Scolaro et al., 69 femoral head fractures in 68 patients were followed for over 6 months across a 13-year period. Of these, 62 fractures (89.9%) achieved uneventful union, although all Pipkin III fractures failed operative fixation (39).

Patient-reported outcomes also vary, evidenced by Koerner et al. in their 10-year follow-up of femoral head fractures (40). This retrospective PROMs study demonstrated variable satisfaction, with the Oxford hip score ranging between 27 and 41. Again, this study was limited by the small cohort of 28 cases (40).

Following the surgical intervention of femoral head fractures, the most frequent early complication is wound infection at a rate of 3.2%. In fracture-dislocations, 3.95% of injuries are complicated by sciatic nerve palsy, often in the peroneal division (30), with 60–70% showing spontaneous recovery (21).

Late complications include heterotopic ossification in 15.4%, avascular necrosis in 8.8%, fracture-related infection in 0.7% and post-traumatic arthritis in 8.9% of patients (41). The surgical approach and Pipkin classification influence the rate of late complications (Tables 2 and 3) and should be considered for informing patient expectations and anticipating patient requirements for further treatment. These complications interrupt post-operative healing and rehabilitation, resulting in restricted hip function and varying degrees of resultant disability. The risk of avascular necrosis of the femoral head increases significantly if the initial hip reduction is delayed for more than six hours or if reduced incongruently (2). Furthermore, the risk of avascular necrosis increases when a posterior approach is used compared to an anterior or trochanteric-flip osteotomy approach (30). However, the anterior approach increases the risk of heterotopic ossification compared to the posterior, potentially due to extensive disruption of the soft tissues (42). When there is concern for heterotopic ossification development, radiotherapy has been suggested as treatment and, in some cases, prophylaxis (43).

Future perspectives

Current studies regarding femoral head fractures have greatly transformed the field in terms of approaches to treating these injuries, resulting in enhanced patient outcomes (19, 46). Despite this, several prospective strategies could be implemented to further enhance treatment. First, innovative technological advancements could be utilised to improve the precision of fracture repair. 3D printing technologies have gained popularity in the pre-operative planning of femoral fractures due to their ability to provide detailed viewpoints of the fracture characteristics compared to two-dimensional CT and MRI data, enabling better visualisation and fixation (47). In a study by Wang et al. (48), who treated 17 patients with a variety of Pipkin fractures, this was found to substantially reduce operative times and blood loss compared to previous studies. This makes it an attractive approach for future femoral head fracture repair, especially as the cost of manufacturing decreases gradually in health care, facilitating wider adoption of this technology.

Clinical studies thus far have provided greater clarity regarding treatment outcomes based on Pipkin classification and/or surgical approach to femoral head fracture repair. However, improvements can be made to clinical study design to enhance our understanding further. Currently, the majority of the clinical studies have been retrospective, which may result in the utilisation of patient data that may be incomplete, poorly documented or inaccurate, hindering our ability to draw definitive conclusions about the effects of specific interventions. Furthermore, these studies were often uncontrolled, making identifying and controlling for confounding variables that may influence treatment outcomes difficult. Future studies should use randomised control trials to study different approaches towards the femoral head in patients with different Pipkin-graded fractures, allowing us to identify optimal approaches with greater accuracy and enhance overall treatment outcomes. Furthermore, most individual case studies have involved a small number of patients. Although femoral head fractures are not common, more consistent reporting and greater documentation of these fractures are needed in major trauma centres. This will enable analysis of larger sample sizes, enhancing the statistical power and generalisability of any findings. In addition, this will permit prospective analysis of these femoral head fractures, allowing greater control of confounding variables, reducing bias and providing greater insight into future outcomes.

Beyond clinical study, the reported results from these clinical studies should be used to establish guidelines for managing femoral head fractures. This is lacking from the British Orthopaedic Association Standards for Trauma and Orthopaedics (BOASts) guidance, which currently has a set of guidelines for several other trauma-related musculoskeletal conditions (49). Establishing a set of guidelines with BOASts would be of great benefit, improving patient outcomes and minimising variation in practice. This would facilitate greater standardisation of the data collected from patients, allowing us to evaluate the effectiveness of treatments over time and identify trends in outcomes and complications. This information could refine protocols, optimising patient care regarding femoral head fracture treatment.

Conclusion

Femoral head fractures are relatively rare and typically occur due to high-energy trauma and are frequently associated with hip dislocations, making them an orthopaedic emergency. Prompt closed reduction of the hip is essential to optimise patient outcomes. Treatment depends on fracture displacement and joint conservative management may be appropriate for non-displaced fractures with preserved alignment, while displaced fractures typically require surgical intervention. Operative options include open reduction internal fixation of the fracture fragment, fragment excision for smaller fragments or hip arthroscopy. The choice of surgical approach is guided by the fracture pattern, associated injuries and the surgeon’s expertise. Early complications associated with surgical management include infection and sciatic nerve injury, while late complications include avascular necrosis, heterotopic ossification and post-traumatic arthritis. Further research is needed to compare surgical techniques and establish an evidence-based gold standard for management.

ICMJE Statement of Interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the work reported.

Funding Statement

This work did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.