An Exceptionally Uncommon Hip Injury: Femoral Neck Fracture Dislocation with Abductor Avulsion

Abstract

Case:

This report presents an extremely rare case of a femoral neck fracture dislocation with associated complete hip abductor avulsion. The patient was treated with open reduction of the dislocation, open reduction internal fixation (ORIF) of the femoral neck, and repair of the hip abductors. The patient initially healed but developed avascular necrosis (AVN) requiring conversion to total hip arthroplasty at 3 years. A Harris Hip Score was 92 eleven years after injury.

Conclusion:

We recommend prompt, anatomic ORIF of the femoral neck fracture dislocation, direct repair of the hip abductor complex, and long-term follow-up given the high risk of AVN.

Femoral neck fractures in young patients are high energy injuries with complications including avascular necrosis (AVN), malunion, nonunion, and posttraumatic arthritis^1,2. Recent studies have reported a more than 40% incidence of major complications with nearly one-third of patients requiring major reconstructive surgery¹. Femoral neck fracture dislocations are a rare subset of these injuries with similar complication profiles^2-5. Associated posterior, anterior, and direct inferior dislocations have been described with varying nomenclature and classification systems^2,3,6. Treatment options include open reduction internal fixation (ORIF) and arthroplasty^2,3,7.

Described associated injuries include femoral head impaction and fractures of the pubic rami and acetabulum^3,4,8,9. To the authors' knowledge, this is the first described case of a femoral neck fracture dislocation with a complete tear of the hip abductors.

The patient was informed that data concerning the case would be submitted for publication, and he provided consent.

Case Presentation

A 21-year-old man was ejected from a motorcycle and presented to the emergency department with a right femoral neck fracture dislocation (Figs. 1-A, 1-B, 1-C), an ipsilateral lateral compression pelvic ring fracture, and an ipsilateral ligamentous knee injury. He was taken emergently to the operating room (OR) for other life-threatening injuries, including a severe splenic laceration.

Fig. 1-A.

Displaced right femoral neck fracture dislocation on AP pelvis radiograph. The femoral head sits directly inferior to the acetabulum, and the obturator foramen is unobscured, consistent with a direct inferior type fracture dislocation.

Fig. 1-B.

Axial CT pelvis image showing inferior, but no anterior or posterior, displacement of the dislocated femoral head.

Fig. 1-C.

Coronal and corresponding sagittal CT image confirming the direction of dislocation and associated femoral neck fracture. AP = anteroposterior, and CT = computed tomography.

The patient remained intubated and did not clear for orthopaedic intervention until 16 hours after injury. He was taken to the OR at that time and positioned in the left lateral decubitus position. A 15 cm incision was made laterally centered on the greater trochanter for an anticipated Watson-Jones approach. After incising the iliotibial band, however, a large hematoma was encountered and evacuated. The greater trochanter was visualized and noted to be stripped of all soft tissue attachments with a large exposed bare area. Further inspection showed complete avulsion of the gluteus minimus, medius, and maximus tendons.

The femoral head was rotated 180° and buttonholed through the inferior capsule. The traumatic rent through the capsulotomy was extended to allow the head to be retrieved using terminally threaded wires to control the fragment and to reduce it to the femoral shaft. Additional wires were used to provisionally hold the reduction after confirming the fracture was anatomic via palpation and direct visualization. A 7.0 mm partially threaded screw was placed superiorly as an antirotational device. Definitive fixation was achieved using a sliding hip screw (Figs. 2-A and 2-B).

Fig. 2-A.

AP and lateral intraoperative fluoroscopy images showing reduction of the hip dislocation and associated femoral neck fracture as well as fixation of the fracture with a sliding hip screw and a partially threaded antirotational screw.

Fig. 2-B.

Postoperative AP radiograph and postoperative CT coronal image showing vertical, Pauwels III type orientation of femoral neck fracture, and acceptable fracture reduction. Endovascular coiling of the inferior gluteal artery and gelfoam embolization of the superior gluteal artery were performed preoperatively for active bleeding. AP = anteroposterior, and CT = computed tomography.

Next, attention was turned to the hip abductors. The posterior gluteus medius tendon was reattached to the posterosuperior greater trochanter using 2 drill tunnels and a running Krackow nonabsorbable (FiberWire) suture. The anterior gluteus medius and minimus tendons were secured to the lateral greater trochanter using 2 suture anchors with a similar running suture. The hip was then taken through a physiologic range of motion, confirming the integrity of the repair. Finally, the gluteus maximus was fixed to the gluteal tuberosity using bone tunnels and a similar suture repair.

The patient's pelvic fracture was treated conservatively with close radiographic and clinical follow-up after undergoing initial embolization for active bleeding from the superior and inferior gluteal arteries (Fig. 2-B). His ligamentous knee injury was treated outpatient. He was kept non–weight bearing for 12 weeks for his right hip injury, without bracing or hip precautions.

At 1 year postoperatively, the patient reported no functional limitations. He was able to abduct against resistance and had a nonantalgic gait. However, radiographs at that time showed early signs of AVN (Fig. 3). At 3 years postoperatively, he reported progressively increasing hip pain and difficulty with ambulation. Imaging showed severe AVN (Fig. 4). He was referred for total hip arthroplasty (THA). A direct lateral approach was used for removal of hardware and simultaneous THA (Fig. 5). Hip abductors were noted to be intact intraoperatively. At follow-up 11 years after injury, the patient reported regular walking and biking without limitations in activities of daily living. On examination, he had no hip abductor weakness or Trendelenburg gait despite resorption of a portion of the greater trochanter on imaging (Fig. 6). A Harris Hip Score was 92.

Fig. 3.

AP and lateral hip radiographs 1 year postoperatively showing a healed femoral neck fracture, maintained joint space, and femoral head sclerosis consistent with early AVN. AP = anteroposterior, and AVN = avascular necrosis.

Fig. 4.

AP and lateral hip radiographs 3 years postoperatively showing healed fracture with femoral head collapse and arthritis consistent with severe AVN. AP = anteroposterior, and AVN = avascular necrosis.

Fig. 5.

Initial AP pelvis radiograph after total hip arthroplasty. AP = anteroposterior.

Fig. 6.

Final AP pelvis radiograph 8 years after THA, 11 years after injury, with no signs of implant loosening or subsidence. Resorption of a portion of the greater trochanter is noted. AP = anteroposterior, and THA = total hip arthroplasty.

Discussion

Fracture dislocation of the femoral neck is an uncommon but severe condition. Associated acetabulum, pelvic ring, and femoral head injuries have all been reported^4,9-11. The presented patient had a displaced transcervical femoral neck fracture with a direct inferior dislocation of the femoral head and associated complete traumatic avulsion of the hip abductors.

As with other hip dislocations, correctly identifying the direction of displacement is essential for treatment. Fracture dislocations of the femoral neck can be categorized as posterior, anterior, and direct inferior^2,3,6,12. Posterior injuries show superior displacement of the femoral head². Anterior injuries include pubic and obturator variants, with the obturator type more commonly associated with femoral neck fractures³. Although direct inferior fracture dislocations are described, they are often grouped with anterior-obturator injuries, and the terms “anterior,” “obturator,” and “inferior” are frequently used interchangeably^3,6,12. However, true direct inferior fracture dislocations, such as in the presented case, are distinguished by the femoral head lying directly inferior to the acetabular ring rather than anterior to it, with the obturator ring remaining unobscured^13-15 (Fig. 1-A).

A recent review by Liu et al. of femoral neck fractures with either anterior or inferior dislocations found 11 of 18 cases treated with ORIF, with the remaining 7 undergoing primary arthroplasty³. While there is no consensus on fixation vs. arthroplasty, many have suggested younger age may favor fixation^2,3,7,10. Advocates for ORIF cite the benefit of preserving native bone stock and the risk that primary arthroplasty may require complex revision(s) through the patient's lifetime^2,3,10. Still, caution should be exercised when interpreting reported ORIF outcomes; the majority of reports have radiographic AVN changes^2,16,17 or included no more than 2 years follow-up^3,8; few have shown no AVN with long-term follow-up^6,18. Regarding associated injuries, Jain et al. reported a more than 60% incidence of osteochondral lesions in anterior dislocations with associated femoral neck fractures⁴. The importance of recognizing and addressing articular cartilage injuries when attempting ORIF has been stressed in the literature^4,19,20. Associated pelvic ring and acetabular injuries are generally treated as they would be in isolation^7,10.

The most commonly used approaches for anterior or inferior femoral neck fracture dislocations are the lateral (Hardinge) and anterolateral (Watson-Jones) approaches⁴. An anterior (Smith-Petersen) approach has also been described. This may provide improved visualization of the femoral head³, though this should be weighed against the need for a second lateral approach if a sliding hip screw is used or if access to the lateral soft tissues, including the hip abductors, is needed. In the present case, the large traumatic injury zone allowed adequate visualization of the fracture site through the Watson-Jones approach alone. A trochanteric flip osteotomy has also been described to facilitate simultaneous treatment of femoral head, neck, and acetabular injuries⁷. When selecting the operative approach, anticipated fixation strategy and associated injuries should be considered. While sliding hip screws may have shown improved outcomes for displaced fractures^2,21, cannulated screws have also been successfully used in treating this injury². In this particular case, a partially threaded superior screw was initially placed in the femoral neck to control rotation of the fragment^22,23. A sliding hip screw was then placed to further resist the shear forces given the vertical nature of the fracture (Fig. 2-B).

Few mechanisms have been proposed to explain combined femoral neck fracture dislocations. For anterior fracture dislocations, Liu et al. described extension and external rotation resulting in anterior dislocation of the femoral head, followed by a secondary force to the femoral shaft that drives the femoral head into the obturator foramen. Impact against the inferior pubic ramus may subsequently result in fracture of the ramus³. In the presented injury, we hypothesized the mechanism to be a combination of forces. Hyperabduction, flexion, and external rotation may initially result in inferior dislocation of the femoral head as has been described²⁴, followed by a secondary medial force to the femoral shaft that drives the femoral head against the acetabular rim, resulting in fracture of the femoral neck³. The associated tear of the hip abductor complex may be attributable to the initial forced external rotation, consistent with a described mechanism for acute gluteus medius injury²⁵. Reports of acute traumatic tears of the hip abductors are very rare with most noted to be degenerative in nature^25,26. The gluteus medius tendon has posterosuperior and lateral attachments to the greater trochanter, while the gluteus minimus tendon attaches more anteriorly and deep to the medius²⁷. This native anatomy should be considered when repairing these structures. Like with rotator cuff tears, there is debate regarding optimal repair techniques including single-row vs. double-row anchors and use of drill tunnels vs. suture anchors with no clear clinical differences found^25,26,28-30. A combination of bony tunnels and suture anchors were used in this case.

The treatment and long-term outcomes of this combination of injuries have not been previously reported. In younger patients, we recommend urgent open reduction of the dislocation and ORIF of the femoral neck to attempt to salvage the femoral head, as well as repair of the hip abductors to restore function. Lateral approaches should be considered to assess the integrity of the hip abductor complex. Finally, patients should be followed for several years given the significant risk of developing AVN.