An unusual presentation of isolated fracture of femoral head with acetabular rim fracture: ‘A case report’

INTRODUCTION

The femoral head fracture was first described by Birkett in 1869 while performing a postmortem on a 35-year-old female who died from falling from the 2^nd floor.¹ These fractures are rare and associated with high-velocity injuries. They are associated with 5-15 % of posterior hip dislocation.² Pipkin, in 1957, classified femoral head fractures into four types, and it is still the most common classification system used.^3,4 All its variants are associated with hip dislocation. Pipkin type IV fractures include fractures of the femoral head with an acetabulum fracture after hip dislocation. Posterior acetabular wall fractures are most commonly seen in association.⁴ Femoral head fractures, especially Pipkin type IV, are associated with complications like nerve palsy, avascular necrosis of the head of the femur, post-traumatic arthritis and heterotopic ossification.⁵ There has not been a described case of the Pipkin IV variant involving the supra-foveal weight-bearing part without hip dislocation. We describe the first such case.

CASE REPORT

A 38-year-old male presented to the emergency department with a history of a road traffic accident followed by pain in his right hip and knee. He was allegedly hit by a four-wheeler while driving a two-wheeler, leading to a fall on his right knee. He presented with a history of pain associated with swelling in the right knee, with difficulty in bearing weight on the right lower limb. He also had a history of mild pain in his right hip. On examination of the right knee and hip, he had an abrasion and ecchymosis over the medial aspect of the right knee. Palpation revealed swelling over the right knee with tenderness over the joint line. Tenderness was also found to be present over Scarpa’s triangle of the right hip joint. The range of movement (ROM) of the hip was found to be full with terminal restriction of external rotation and abduction. ROM of the right knee joint was full and free. Neurovascular status of the limb was found to be intact.

The patient was initially evaluated radiologically with a plain radiograph of the pelvis with Bilateral hips Antero-Posterior (AP) view [Figure 1a] and radiograph of right knee joint AP and lateral view. The initial radiograph was found to be within normal limits and hence the patient was managed conservatively with rest, ice-pack, analgesics, and physiotherapy in the form of ROM exercises of the hip and knee. He showed symptomatic improvement in his symptoms with conservative management. However, he continued to have difficulty in bearing weight on his right lower limb with mild pain in his right hip joint.

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Figure 1:

(a) Plain radiograph of pelvis with bilateral hips antero-posterior (AP) view, (b & c) pelvis with bilateral hips, inlet and outlet views. femoral head was found to be deformed in inlet view (red arrow).

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Given the persistence of symptoms, he was subjected to a repeat radiograph of the Pelvis with bilateral hips with AP, inlet and outlet views. On inlet view, the femoral head was found to be deformed. (Figure 1b and c) Subsequently, he underwent CE-MRI with NCCT of both hip joints to rule out any occult pathology of the hip joint. (Figure 2 and 3) On CE-MRI with NCCT correlation, he was found to have a displaced fracture head of the femur involving posterosuperior articular surface with associated displaced posterosuperior acetabular rim fracture. It was a 3 cm x 1.5 cm and 0.5 cm piece and volume was 2.25 cm3 volume of acetabular rim The displaced fracture fragment involved 30% of the articular surface with the normal contour of the articular head. The superior labral tear was noted at the posterior aspect of the hip joint.

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Figure 2:

(a-c) Contrast enhanced (CE)-MR images of hip suggesting of displaced fracture head of femur involving posterosuperior articular surface with associated posterosuperior ace-tabular rim fracture (red arrow).

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Figure 3:

(a and b) Non-contrast computed tomography pelvis with 3D reconstruction confirming displaced fracture head of femur involving posterosuperior articular surface with associated posterosuperi-or acetabular rim fracture (red arrow).

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He was diagnosed with a case of Pipkin type IV fracture of the femoral head. For managing his injury, we had to resort to the operative option as it was a significantly large superior sectoral fracture of the femoral head under the weight-bearing dome of the acetabulum. The fracture line ran from anterosuperior to posteroinferior, involving almost 30% of the head. The acetabular lip fragment was small with an attached labrum. Since there was no hip dislocation, there was no posterior capsular rent or tear in the short external rotators. However, there was a bony capsulo-labral avulsion from the posterior acetabular rim from 9 O’clock to 2 O’clock position. There was preoperative debate regarding the selection of the approach. However, given the existing posterior injury and the need to fix the posterior acetabular lip, we selected a posterior approach to the hip but used a posterior horizontal arthrotomy starting from the 11 O’clock position on the acetabular face just below the piriformis without detaching any of the rotators from the femoral side. This allowed us to raise the T flaps of the capsule, and with careful hip positioning and traction, we could reduce the femoral head fracture without dislocating the hip and fix it [Figure 4a] with three multidirectional countersunk differential pitch compression screws. There was some articular surface indentation at the fracture edges which could not be elevated. Following this, the acetabular bony lip (1 to 1.5 cm in width), which was from 8 O’clock to 02 O’clock with little comminution, was reattached using a 2.4 mm headless compression screw and neutralized with two spring plates, which were clawing onto the labrum and compressing it onto the acetabular lip [Figure 4b]. Post-operative check radiographs showed adequate reduction and fracture fixations with a congruous hip joint confirmed [Figure 5a]. He underwent post-op rehabilitation in the form of ROM exercises of the hip and non-weight-bearing ambulation for 8 weeks. Only simulated weight-bearing exercises were allowed. At 6 months on check radiography, he had a congruous hip with a healing femoral head and acetabular lip fractures [Figure 5b].

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Figure 4:

(a) Line diagram showing the posterior approach used to fix the head and pelvis (red arrow). (b) Fixation of the head and the acetabular lip (red arrow).

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Figure 5:

(a and b) Plain radiograph of pelvis with bilateral hips antero-posterior (AP) view post-operatively and at follow-up of 6 months.

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DISCUSSION

Isolated femoral head fracture without hip dislocation is an extremely rare entity first described by Werken et al in 1987.⁶ Since then, there have been eleven published case reports of isolated femoral head fractures without hip dislocation.^6-15 They have described the detection, evaluation, and management of 12 such cases with different associated lesions [Table 1]. None of the cases had a fracture pattern as described in our case, wherein there was a large supra-foveal femoral head fracture associated with a posterior acetabular lip fracture without hip dislocation. Since there was no hip dislocation patient had minimal complaints in the hip, and the knee injury distracted the patient’s attention away from trivial hip symptoms. There was only a terminal restriction of ROM of the hip in external rotation and abduction. Due to minimal fracture displacement, the initial radiograph of the Pelvis with bilateral hip was found to be normal.

When we interrogated the patient with leading questions regarding the mechanism of injury, it seemed that he had loading and impact on the hip in mid-range of flexion, abduction, and external rotation when the acetabular rim impaled the femoral head and resulting in the fracture of the femoral head and reciprocal acetabular rim injury. The high degree of suspicion ensured advanced radiology and detection of the lesion. Although most studies have mentioned safe surgical dislocation in the management of isolated femoral head fractures, in our case, with the associated posterior acetabular lip fracture, we chose a posterior approach and a simple transverse arthrotomy in the avulsed bony capsulo-labral structure allowed minimal stripping of soft tissue and preservation of femoral head vascularity. However, the indentation along the posterosuperior fractured edge of the femoral head predisposes it to focal incongruity and risk of arthritis with time. As we follow up on this patient, we also remain acutely aware that there is a risk of Avascular Necrosis of the femoral head fragment. Reducing both the femoral head and acetabular lip fractures and fixing them adequately ensured hip stability and allowed early non-weight bearing mobilization, which has offered good early recovery.

Being the first description of Pipkin Type IV femoral head fracture without hip dislocation, it has elucidated the challenges faced in its detection and choosing appropriate management regarding the approach, sequence, and option of fracture fixation. A successful early outcome makes it a useful literature to help surgeons manage this unusual variant of isolated femoral head fracture.

CONCLUSION

Complex fractures like Pipkin Type IV fracture head of the femur can even present without hip dislocation, with subtle clinical signs and symptoms. These fractures can be missed on plain radiographs. It is important to get orthogonal views to diagnose such fractures. In case of dilemmas, it is advisable to subject the patient to advanced imaging like CT & MRI to avoid missing such fractures. Management remains open reduction and fixation, which can be achieved effectively using acetabular lip fracture and horizontal extension of capsular avulsion in the least traumatic manner.