| Posterior cruciate ligament(PCL) arises from the lateral surface of the medial femoral condyle and extends posterolaterally to the posterior tibia 10mm below the joint line. It bears the weight of 85～100% retroposition strength and is considerded to be the key factor providing stability to the posterior directed aspect of the knee. The fibers of the PCL are usually reported as two separate bundles: the anterolateral(AL) and the posteromedial(PM) bundles. The distinct insertion sites of the two bundles on the tibia and femur are approximately equal in size. The ALbundle is two times larger in cross-sectional area than the PM bundle. During passive flexion and extension of the knee the AL bundle is more taught in flexion and lax in extension, conversely, the PM bundle is more taught in extension and lax in flexion. The distance between the femur and the tibia and the activity centre change unceasingly during flexion and extension of the knee. According to the different duty, the fibers twist correspondingly, making PCL adjust length and tension, so as to provide stability to the knee in all flexion angle. The intensity of PCL is 1.5～2 times higher than that of ACL, which hint that the PCL injuris mostly caused by high intensity, high opposability sports injuries and traffic accident. The most common trauma mechanism of PCL injury in sports is hyperflexion injuries which it more easily resulted in isolated PCL injuries. When posteriorly directed force applied to the proximal tibia, the tibia suddenly subluxates posteriorly and the posterior edge of the tibia platform stikes on the hanging wall of the intercondylar fossa, which can cut PCL off. Because of the substance of PCL tapering from the femur to the tibia, the PCL bony avulsion of tibia insertion is more common than that of femur insertion. The diagnosis of PCL injury depends on the detailed initial injury history collection and physical examination, combined with X ray, CT and MRI imageological examination. The knee′s position, weight loading state, strength laod, direct or indirect injury, patient′s momentum, and the limb′s position after injury are all important. The most accurate tests for detecting PCL injury include: posterior drawer tests, Lachman tests, quadriceps active tests , reverse pivot shift tests and Dial tests. Stress radiographs has diagnostic value on PCL tibial bony avulsion, especially when posterior subluxation of the tibial plateau and microscleres were found on the posterior edge of the tibia, higher than the joint line. If no fracture signs were found on the X ray, magnetic resonance imaging(MRI) should be executed, which has been shown to be extremely effective in confirming the diagnosis of PCL injury. If the diagnosis of PCL injury were missed, the treatment would be delayed.The treatment of PCL injuries may be the most disputed topic of knee surgery. The main reason is the deficient understanding of the natural history of PCL injuries. Traditionally most experts suggest isolated PCL injuries have good outcomes with a conservative treatment, such as bed rest, plaster or orthosis fixation. Recently more and more studies support early surgical treatment on PCL tibial bony avulsion and other associated ligament injuries. Because the proprioceptive sense lies in the femur insertion and the substance is complete, good healing capability and long-term effects can be gained after reduction. The most appropriate timing of surgical treatment is 1～2 weeks after injury when the intraarticular painful reaction has fade away and all the move range and partial strengh of the knee have recovered. The traditional surgical fixation of the avulsed PCL is usually performed through an open posterior approach with the patient in the prone position. It needs reveal the nerves and blood vessels behind the joint. The surgical trauma is serious, the operation is compicated, and the recovery postoperation is slow. Recently more and more surgeons tried to fix the cruciate ligaments bony avulsion through the arthroscope. The suture of ACL tibial bony avulsion has received good effects and was applied generally. But the PCL tibial insertion site lies in the tibial grooves and associates with the posterior articular capsule tightly, which makes the reduction extremely difficult after displacement. It often leads to insufficient repositon and PCL looseness. We treated 23 cases of PCL tibial bony avulsion via an open posteromedial approach through the space between the medial head of gastrocnemius and semitendinosus in reverse L shaped incisions, getting out of the way of all important nerves and blood vessels, revealing the PCL tibial insertion site. After accurate reduction, fix the bony avulsion firmly with screw, adsorbable screw or wire lock. Plaster cast fixed the knee in 30°-flexion position after operation. Quadriceps isometric contraction training should be taken the next day. The plaster fixation were removed after 6 weeks and performed joint active monement and CPM functional exercise. Began to gradually weigh-loading walk from 8th week. All the cases gained bone union after 2.5～6 months(average 4 months). The joint function greatly improved. No compications such as joint infection, non-union, fracture displacement and injury of nerves or blood vessels. We concluded that the posteromedial approach has the following advantage: convenient, reliable,and minimally invasive. The knee′s stability can be regained.The restricted exploration of the knee joint is the disadvantage through this approach. It should be accurately judged that the injury of PCL is isolated or complex before operation. So the overall and careful physical examination and MRI examination are quite necessary. |
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