Hip traumatic injuries occur due to high energy transmission across the joint often conducted through the knee joint via the femoral shaft. Hip fracture dislocation has been widely reported to be associated with knee injuries. Such knee injuries often go undiagnosed in view of more severe hip trauma. Acetabulum fractures have been found to be associated with knee ligament injuries1-4.
Posterior cruciate ligament (PCL) avulsion injuries occur by different mechanisms5. Dashboard injuries, where the knee in the flexed position is pushed backward when it hits the dashboard, is a common mechanism. This force often gets transmitted upward via the shaft of the femur and could cause an acetabulum fracture with or without femoral head dislocation. Displaced fractures of the head of the femur are rare injuries6,7. Dashboard injuries may cause such a fracture depending on the amount of knee flexion; less than 60° causing impingement of the head of the femur against the posteriosuperior acetabular rim8,9.
Since the mechanisms causing PCL avulsions and ipsilateral femoral head fractures are the same and sequential, a coexistent injury is theoretically possible. To the best of our knowledge, there is no published work on PCL avulsion with femoral head fracture. We present such a case of PCL avulsion along with ipsilateral fracture femoral head, who was managed surgically for both the injuries.
The femoral head fragment was displaced out of the hip joint, but the remainder of the femoral head was not dislocated on presentation. However, it could have spontaneously reduced. There were no other fractures.
The patient was informed that data concerning the case would be submitted for publication, and he provided consent.
A 25-year-old male presented to the Advanced Trauma Centre of our institute, with a history of road traffic accident, when the car he was driving collided head on with a bus. The patient was not wearing the seat belt, and the vehicle was not equipped with air bags. He sustained injuries to his right knee and hip. He was brought to our center within 4 hours of the injury and had complaints of pain in the right hip, with inability to stand. He had no head, chest, or abdominal injuries. The distal neuromuscular status of the limb was intact. There were no other long bone injuries. Physical examination of his right knee revealed good alignment with marked swelling and intact skin. A passive knee range of motion of 20° to 60° was painful. Ligamentous examination was limited by patient's guarding but suggested posterior sag with poor endpoint to posterior drawer. Forty cubic centimeters of blood was aspirated from the knee, which provided some temporary pain relief.
Radiographs of bilateral hips with pelvis and right knee were taken. Radiograph of the right knee showed a large ∼3 cm bony fragment from the posterior tibial intercondylar area with a 1 cm displacement, suggestive of avulsion of the PCL (Figs. 1 and 2). The hip computed tomography showed fracture of the head of the femur that was inferior to the fovea with no injury to acetabulum (Figs. 3 and 4). The fragment was displaced inferomedially, while the remaining part of the head was congruous. However, spontaneous reduction post trauma could not be ruled out.
The patient was taken up for the 1st surgery after 8 hours of presentation, as soon as the anesthetic clearance was given and the operating table was available, where the femoral head fracture was operated upon in a lateral position with Ganz safe surgical dislocation of hip, which is a posterior approach without the release of the external rotators10. We performed the trochanteric flip osteotomy for the exposure. The capsule was stretched, and the fragment could be palpated underneath. There was no cartilage damage or impaction; however, the fragment was devoid of any soft tissue attachment. Fixation was performed with two 4.0 mm small-fragment partially threaded cannulated screws (PTCS), and the screw heads were countersunk (Fig. 5). He was subsequently operated for PCL avulsion via a posteromedial approach after making him lie prone on the table in the same setting, with a 4.0 mm PTCS along with a washer5 (Figs. 6 and 7). Preoperatively, the knee was examined under anesthesia and there were no associated ligamentous injuries.
His knee was immobilized for 3 weeks with a knee immobilizer followed by knee physiotherapy and rehabilitation as per our institute protocol. After the epidural catheter was removed on the post-operative day 2, deep vein thrombosis chemoprophylaxis was initiated in the form of oral apixaban 2.5 milligram twice a day until patient was allowed to walk with support. Initially the patient was allowed to sit upright on the bed with back support, and side sitting on the bed was allowed after pain relief. Non-weight-bearing ambulation began at 3 weeks, whereas we allowed weight bearing only after 12 weeks of surgery. The patient was doing well at the last follow-up of 15 months in his activities of daily living (Figs. 8 and 9). Active knee range of motion was 0 to 120, and his knee was stable with negative posterior drawer, dial, reverse pivot shift, valgus and varus stress, Lachman, and pivot test. Hip range of motion was 90% of normal, and he walked normally with a negative Trendelenburg sign. The patient was able to run and returned to all previous activities.
The femoral head fragment healed and joint space remained intact (Fig. 10). The PCL fragment had united (Fig. 11).
Dashboard injury patterns where the knee strikes the dashboard in a decelerating car wreck commonly include PCL injuries and posterior hip dislocations. This case reports the specific unusual combination of a PCL avulsion fracture of the proximal tibia and a femoral head fracture with displaced fragment. The avulsion fracture facilitated the recognition of the PCL injury, which can otherwise be subtle and can be missed in acute injuries11. The avulsion fracture also facilitated the treatment of the PCL injury (open reduction and internal fixation, ORIF), which can otherwise be much more complicated12. Intrasubstance PCL injuries are more common, and operative stabilization usually requires graft reconstruction. The displaced (and dislocated) femoral head fracture required ORIF, which was accomplished by a trans-trochanteric surgical dislocation approach and ORIF of the head fragments.
Head of the femur fracture dislocation is a rare entity first described by Birkett13. It is a surgical emergency with early fixation and reduction, creating better chances of cartilage preservation. Dashboard injuries are the most common reason for these fractures8,9. Concomitant injuries such as fractures of proximal femur, acetabulum, and knee injuries are documented possibilities. Surgical treatment for displaced fractures are indicated. There should not be any intra-articular loose fragments. ORIF with Herbert headless screws or small-fragment PTCS is performed for noncomminuted fragments. Comminuted fragments can be sutured with nonabsorbable sutures such as polyester (Ethibond Excel/Ethicon)14.
Knee and hip injuries often occur together. There have been documented reports and studies on PCL avulsion-associated injuries. Fractures of acetabulum, patellae, neck of femur and femoral shaft, with or without hip dislocation have been reported widely1-4.
The mechanism by which the coexistent injuries occur is difficult to assess. Knee can be injured by a direct traumatic impact, while being in some degree of sagittal plane displacement, with or without associated rotational stress. This force can be transmitted to the hip via the femur shaft, and this explains the injury around the hip joint with fracture and/or dislocation. It can also be due to the indirect mechanism when the foot locked in its position bears the first hit and the force gets transmitted upward to the extended knee and then via the femur shaft to the hip. Either could have been the mechanism in the present case, although we cannot be sure whether it was a direct or indirect mechanism. Since avulsions of PCL require higher injury force, we theorize that the probable mechanism was direct, with knee bearing the maximum brunt of the trauma. The transmitted force to the hip can lead to the abutment of femoral head to the acetabulum causing rim fractures, head fractures, or both8,9. Dislocations are often co-existent. In this case, it was the head that sustained a fracture and the acetabulum escaped injury. There was no dislocation when the patient presented to us, but spontaneous reduction in the field cannot be ruled out. This makes the present case typically rare, and such a traumatic event has never been reported before, which adds to the novelty of our report.
We were able to diagnose both the injuries at the initial presentation, although knee ligament injuries could be missed when hip fracture dislocation co-exists because of the other associated bony injuries, especially at knee, such as tibial plateau or distal femur fractures, that can make knee examination for instability close to impossible15.
There is an increasing frequency of co-existent hip fracture dislocation with ligament injuries of knee, especially PCL avulsion. Although knee ligament injuries are more common, bony avulsions are typically a result of very high traumatic force, as in the present case. So, one should be vigilant when either one is diagnosed. Association of isolated femoral head fracture as the hip injury with PCL injury is a much rarer subset and requires proper early surgical management for the prevention of long-term complications such as avascular necrosis of hip or chronic knee instability.
The take-home message of the present case is the rare event in itself, its increased novelty because such a case has never been reported before, and the fact that early diagnosis and efficient intervention is the keystone for minimizing long-term complications.
Co-existent femoral head fracture and PCL avulsion in the same limb is a very rare but high velocity injury that requires prompt diagnosis and surgical management to prevent long-term complications. Dashboard injuries could result in this combination with or without hip dislocation. We report a case where the unusual pattern was a fracture of the proximal tibia (large PCL avulsion fragment) combined with a displaced femoral head fracture. ORIF of both fractures resulted in a good outcome at 15 months. Orthopedists should be aware of this particular combination of injuries and the potential for good results with ORIF.
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