Avascular Necrosis of Femoral Head

Abstract

Avascular necrosis (AVN) of the femoral head is a relatively uncommon complication following an extracapsular hip fracture. Although it can occur following fixation of unstable 3-part or 4-part intertrochanteric fractures with significant posteromedial and posterolateral comminution, it remains a rare complication. We present a case of AVN of the femoral head following fixation of a stable 2-part intertrochanteric fracture in spite of good healing at the hip fracture site. This is a rare but eminently treatable cause of persisting hip pain after hip fracture surgery, and primary or secondary care physicians should be aware of this possibility.

Introduction

Avascular necrosis (AVN) of the femoral head following a stable extracapsular hip fracture is a rare complication, with isolated case reports in the English literature. We describe an unusual case of AVN of the femoral head in an octogenarian following dynamic hip screw (DHS) fixation for a stable 2-part intertrochanteric fracture.

Case Report

An 80-year-old female presented with a left hip fracture following a fall. She had no significant medical comorbidities. Radiological examination confirmed a simple extracapsular hip fracture (type 31 A1 fracture) devoid of any posteromedial and posterolateral comminution (Figure 1). The fracture was stabilized with DHS fixation within 24 hours of admission. Intraoperative images confirmed accurate fracture reduction and hardware placement (Figure 2).

Figure 1.

A and B, The anterior–posterior (AP) and lateral radiograph of the left hip showing extracapsular fracture.

Figure 2.

A and B, Intraoperative radiographs displaying optimal position of lag screw and neck shaft angle.

There were no intraoperative complications, and the patient made an uneventful recovery. She was discharged home 8 days after the surgery.

Two years later, the patient was referred to the orthopedic service with increasing left groin and knee pain and difficulty mobilizing. Clinically, the patient had groin tenderness, painful restricted range of hip movements, particularly internal rotation of the hip. Although knee radiographs were normal, sequential radiographs of the left hip confirmed superolateral AVN of the femoral head (Figure 3A and B). The patient was therefore offered a total hip replacement (THR), which she agreed to. Intraoperatively, there was no evidence of posttraumatic osteoarthritis. However, there was softening and destruction of the femoral head cartilage and underlying bone suggestive of AVN. Following removal of the DHS, an uncemented THR with metal-on-polyethylene bearing was implanted. After appropriate rehabilitation, the patient was discharged without any postoperative complications. At the last clinical review, 6 months following the THR, the patient remained pain free and independently mobile, with check radiographs confirming a well-seated uncemented THR (Figure 4).

Figure 3.

A and B, The anterior–posterior (AP) left hip showing early and late superolateral avascular necrosis (AVN) of the left femoral head.

Figure 4.

The anterior–posterior (AP) pelvis demonstrating uncemented total hip replacement (THR).

Discussion

A detailed review of the English literature puts the incidence of AVN following fixation of extracapsular intertrochanteric fractures at 0.3% to 1.16%. ^{1 –6} Although 48 cases of AVN of the femoral head were reported in 9725 patients with intertrochanteric fractures, this rare complication was more prevalent in unstable extracapsular hip fractures (type 31 A2 and 31 A3 fractures). In patients with stable fractures (type 31 A1), AVN was reported only sporadically: the 48 cases of AVN identified, consisted of only 3 cases of stable 2-part intertrochanteric fractures. In our patient, the fracture was only minimally displaced, was reduced satisfactorily by closed method, and was stabilized by an experienced surgeon within 24 hours of admission to the hospital. There were thus no risk factors for AVN of the femoral head.

Anatomical variations in extracapsular and intraosseous vascular anastomoses have been extensively debated in the literature. ⁷ This suggests that disruption of blood supply to the femoral head via posterior retinacular branches of profunda medial circumflex artery may still appear to be the primary etiology of the present complication. Some authors have postulated that with advancing age blood vessels are less resistant to overstretching during fracture reduction maneuvers, which may jeopardize the already precarious blood supply to the femoral head. The AVN of the femoral head has been reported to occur in patients treated with antegrade intramedullary nail when the entry point of the nail is medial to the greater trochanter around the piriform fossa, thereby causing iatrogenic injury to the deep branch of medial circumflex artery. ⁸ Inadvertent placement of guide wire or multiple attempts of passing the guide wire across the femoral neck are theoretical risk factors for AVN of the femoral head. However, none of these is thought to be responsible for AVN in our patient.

Several studies have been reported in the literature on the management of complications of proximal femoral fracture by hip arthroplasty. ^{9 –12} The majority of the complications are mechanical in nature and related to hardware failure. Cut out and migration of the lag screw are the commonest, followed by plate failure and intramedullary nail or lag screw fracture. Posttraumatic osteoarthritis, nonunion, and AVN of the femoral head, although infrequent, can be successfully managed by THR even in the elderly patients. In a recent large series of 102 THRs performed for complications of internal fixation of proximal femoral fractures, 39 of them were for failed intertrochanteric hip fractures. ⁹ Of these 39 cases (33 treated with a DHS and 3 with an intramedullary nail), the authors reported AVN of the femoral head in 11 cases. However, the review does not mention the AVN rates in stable 2-part intertrochanteric fractures. A review focussing on THR (n = 32) following failure of DHS fixation of fractures of the proximal femur does not report the clear incidence of AVN of the femoral head. ¹¹

The THR performed for reasons other than primary osteoarthritis is associated with higher complication rates, and THR secondary to failed intertrochanteric fractures is no exception. In the most recent reviews, a dislocation rate of 2% to 5% and a periprosthetic fracture rate of 3% to 6% are quoted when a THR is performed for complications of intertrochanteric hip fracture. ^{9 –12} Elderly patients should be adequately counseled about this when offered a major procedure such as THR.

The current case highlights the possibility of AVN of the femoral head after fixation and healing of a stable 2-part intertrochanteric hip fracture. As most elderly patients with osteoporotic proximal femoral fractures are not followed up on discharge and do not seek medical attention, this complication may perhaps be underestimated. Once diagnosed appropriately, with the help of multidisciplinary support, we were able to offer our patient an uncemented THR thereby improving her quality of life. Although AVN is a rare occurrence after extracapsular hip fractures, persisting hip or leg pain should alert the treating physician or surgeon to this unusual complication, which can be easily treated to improve the patient’s pain, mobility, and quality of life.