A seventy-seven-year-old man presented with left knee pain. He had previously been diagnosed with primary osteoarthritis and had had unsuccessful nonoperative management. Physical examination revealed an antalgic gait, with the patient favoring the left lower extremity; he also had a partially correctable varus deformity. The left knee ligaments were stable. Active knee motion was −5° of extension to 115° of flexion. Radiographs showed tricompartmental osteoarthrosis (Fig. 1).
The patient underwent a left total knee arthroplasty. At the time of surgery, the posterior cruciate ligament (PCL) was competent, so a cruciate-retaining implant was utilized (Duracon; Stryker, Mahwah, New Jersey). A 15-mm patellar osteotomy was performed (Fig. 2). The knee ligaments remained stable and the patient had matched flexion-extension gaps. The patient was rehabilitated and recovered uneventfully. After two years of follow-up, he had no symptoms. He was able to return to work and perform all desired recreational activities.
The patient presented to the emergency department twenty-seven months following the total knee arthroplasty. An obese relative had fallen onto the anterior aspect of the patient’s left thigh. He noted immediate pain, deformity, and the inability to flex and extend the knee. The elapsed time between injury and arrival to the hospital was unknown. Radiographs revealed a direct anterior dislocation of the prosthesis (Fig. 3). The orthopaedic service was notified at 7:20 a.m. The patient’s leg remained neurologically intact but did not have tibialis posterior or dorsalis pedis pulses on Doppler ultrasound examination. He underwent successful closed reduction of the knee under conscious sedation at 7:50 a.m.; reduction was confirmed with radiography. The distal pulses did not return after reduction. Vascular surgery consultation was obtained, and an arteriogram performed at 8:50 a.m. showed interruption of the blood flow at the popliteal artery (Fig. 4).
The patient was taken to the operating room by the vascular surgery team at 12:05 p.m. Exploration of the popliteal artery revealed a large hematoma and complete transection of the artery. He successfully underwent femoral-popliteal artery bypass with a reverse saphenous vein graft, which was harvested from the right thigh. At the end of the procedure (approximately 4:00 p.m.), he had decreased left foot pulses on Doppler examination. A balloon embolectomy of the newly placed graft was performed. Because of clinical suspicion and prolonged warm ischemia time, lower-leg compartment fasciotomies were performed, and Wound V.A.C.s (Kinetic Concepts, San Antonio, Texas) were placed on the open fasciotomy wounds. No compartment pressure measurements were taken.
The patient was transferred to the surgical intensive care unit while still intubated. Intraoperatively, he had had hypotension and an abnormal electrocardiogram. He did well postoperatively, was extubated on postoperative day one, and was transferred to the floor. On postoperative day three, he was returned to the operating room for irrigation and debridement of the fasciotomy wounds as well as reapplication of the Wound V.A.C.s. On postoperative day five, he was again returned to the operating room for closure of the medial wound and split-thickness skin graft to the lateral wound. A Wound V.A.C. was placed on the skin graft at this time. He was then allowed to walk with the knee in an immobilizer and was functioning well.
Instability of the knee required that the patient walk with the knee in an immobilizer. Without the immobilizer, he felt unstable, especially with the knee flexed to 30°. On clinical examination, the medial and lateral collateral ligaments and the PCL were grossly incompetent. Two months after the dislocation, he underwent revision total knee arthroplasty. A tourniquet was not utilized, and a vascular surgeon was available during the case. A hinged-knee prosthesis (Monogram Modular Rotating Hinge Knee System; Stryker) was implanted (Fig. 5). The patient had an uneventful postoperative course. At three years following revision arthroplasty, he had a well-functioning knee and was able to do all desired activities.
Dislocation of a total knee prosthesis is an infrequent but potentially disastrous complication. Lebel and Lewallen reported the incidence as 0.093% for primary total knee arthroplasties and 0.661% for revision cases2. Dawson-Bowling et al. reported a much higher incidence at 0.15% to 0.5% for fixed-bearing knee implants3. Lombardi et al. reported fifteen posterior dislocations in 3032 cases (0.50%)4. Hossain et al. reported three dislocations with use of the Insall-Burstein II modified prosthesis in 1500 cases (0.2%)5. PCL-retaining implants and mobile-bearing implants are more commonly involved in dislocations6. Most dislocations can be attributed to a definite cause5-8. Our literature search identified eight anterior total knee prosthesis dislocations, one of which resulted in vascular compromise1,6,9-14; three of these dislocations were the result of a traumatic event1,11,12.
The majority of reported anterior total knee prosthesis dislocations were not the result of a single traumatic incident. Tuoheti et al. reported an anterior dislocation attributed to massive polyethylene wear, injury to the medial collateral ligament and patella tendon, and stress fracture of the fibula. This occurred secondary to a severe posterior slope of the tibial component (18°)9. Villanueva et al. reported one anterior dislocation that was caused by excessive internal rotation and varus angulation (>5°) of the tibial component and flexion-extension imbalance6. Wang and Wang reported two anterior dislocations. Both of these cases were clinically documented to be unstable prior to frank dislocation. This instability was manifested as gradual lengthening and incompetence of the PCL and posterior capsule10.
We found three cases of traumatic anterior total knee prosthesis dislocation in the literature. One was after a fall on a hyperextended knee from standing height. A closed reduction was performed, and no additional treatment was necessary11. The second occurred after a fall on an icy road. Because of instability, revision surgery was recommended, but was refused by the patient12. The third resulted in an above-the-knee amputation1.
Vascular compromise is an uncommon result of total knee prosthesis dislocation, and the true incidence is unknown. It is believed to be more common with anterior dislocations, similar to native knee dislocations, with which there is a 35% to 42% incidence of vascular injury caused by the relatively high-energy mechanism of injury15. Pao and Jiang attributed the low occurrence of vascular injury in total knee prosthesis dislocations to the typically low-energy mechanism of injury1. They described a recurrent anterior dislocation (which occurred after a fall from standing height) that caused vascular injury and resulted in an above-the-knee amputation as a result of patient apprehension and the resultant delay in treatment1.
Aderinto et al. described an anterior total knee prosthesis dislocation that resulted in neurovascular compromise13. They attributed the nontraumatic dislocation of a posterior-stabilized knee to the patient’s morbid obesity. She had no symptoms of instability prior to frank dislocation, which occurred while bending forward to open an oven. At the time of injury and closed reduction, there was no vascular insult detected, but she had lost sensory and motor function below the knee. On day three of hospitalization, the leg became acutely ischemic, and angiography detected thrombosis of the popliteal artery. A femoral-popliteal artery bypass was performed, and an external fixator was applied to protect the vascular repair. Six months after the dislocation, the external fixator had been removed, but the patient had no return of neurological function to the lower leg and could not walk independently.
Our report represents a case of traumatic anterior total knee prosthesis dislocation causing vascular compromise, which was successfully treated by closed reduction, vascular graft, and delayed revision to a hinged prosthesis. Recognition of the vascular injury by the emergency department physicians and orthopaedic team and repair by the vascular surgery team was paramount to the successful treatment of this uncommon injury.