The accuracy of routine knee MR imaging in detection of acute neurovascular injury following multiligamentous knee injury.

OBJECTIVE: To assess the accuracy of routine knee MRI in detecting acute popliteal artery and/or common peroneal nerve (CPN) dysfunction following multiligamentous knee injury (MLKI), with correlation of MRI findings to clinical outcome. MATERIALS AND METHODS: Routine MRI knee examinations in 115 MLKI patients (54/115 with acute neurovascular injury, 61/115 without neurovascular injury) were retrospectively reviewed. Cases were classified by injury mechanism and ligamentous injuries sustained. MRI examinations were reviewed by two readers for vascular (arterial flow void, arterial calibre, intimal flap, perivascular hematoma) and CPN (intraneural T2-hyperintensity, calibre, discontinuity, perineural hematoma) injuries. Accuracy of routine knee MRI in the diagnosis of acute neurovascular injury and correlation of MRI findings to clinical outcome were evaluated. RESULTS: Patients included 86/115 males, mean age 33 years. The accuracy of MRI in diagnosis of acute CPN injury was 80.6%, 83.6% (readers 1 and 2): sensitivity (78%, 79.7%), specificity (80%, 86.7%), PPV (78%, 82.5%), and NPV (82.7%, 84.4%). Increased intraneural T2 signal showed a significant correlation to acute CPN dysfunction (p < 0.05). MRI was 75%, 69.8% (readers 1 and 2) accurate in detecting acute vascular injury: sensitivity (73.3%, 86.7%), specificity (75.2%, 67.3%), PPV (30.5%, 36.1%), and NPV (95%, 97.1%). No MRI features of vascular injury showed a statistical correlation with clinical outcome. Neurovascular complications were more common in ultra-low-energy injuries and KD-V3L pattern of ligament disruption. CONCLUSION: Routine MRI is of limited accuracy in assessing vascular complication, but higher accuracy in assessing CPN injury following MLKI. Increased intraneural T2 signal on conventional knee MR imaging shows statistically significant association with clinically documented acute CPN dysfunction following MLKI.

Imaging of the Postoperative Condition of Posterolateral Corner Injuries.

Posterolateral corner (PLC) injuries of the knee are often sustained in combination with anterior or posterior cruciate ligament injuries. A variety of surgical techniques including acute repair, nonanatomical reconstructions, and anatomical reconstructions have been used to treat grade III PLC injuries. Scant literature is available on postoperative imaging of the PLC. This article reviews the more commonly used surgical techniques and the postoperative imaging assessment of the PLC of the knee.

Imaging of postoperative avascular necrosis of the ankle and foot.

Avascular necrosis (AVN) of the ankle and foot is an uncommon and often unexpected postoperative complication in patients with persistent pain and disability postprocedure. Artifacts from metallic implants may obscure characteristic imaging signs of AVN, and radiography and computer tomography are the mainstay imaging modalities of the postoperative ankle and foot. MRI and nuclear medicine imaging play an important complementary role in problem solving and excluding differential diagnostic considerations including infection, nonunion, occult fracture, and secondary osteoarthritis.This review article evaluates different imaging modalities and discusses characteristic sites of AVN of the ankle and foot in the postoperative setting including the distal tibia, talus, navicular, and first and lesser metatarsals. Radiologists play a key role in the initial diagnosis of postoperative AVN and the surveillance of temporal evolution and complications including articular collapse and fragmentation, thus influencing orthopedic management.

Avascular necrosis of the talus: a pictorial essay.

The talus is predisposed to avascular necrosis (AVN), or bone death due to ischemia, owing to its unique structure, characteristic extraosseous arterial sources, and variable intraosseous blood supply. Both traumatic and atraumatic causes have been implicated in talar AVN. The risk of posttraumatic AVN can be predicted using the Hawkins classification system. In addition, the "Hawkins sign" can be used as a radiographic marker that excludes the development of AVN. At radiography, talar AVN typically manifests as an increase in talar dome opacity (sclerosis), followed by deformity and, in severe cases, articular collapse and bone fragmentation. At any stage of this sequence, the radiographic findings can vary depending on differences in the vascular status of the talus and the degree of bone repair. Magnetic resonance imaging is the most sensitive technique for detecting talar AVN and can be used when AVN is strongly suspected clinically despite normal radiographic findings. Computed tomography (CT) also demonstrates typical patterns and can be used to confirm radiographic findings. Coronal CT is required for viewing the articular surface of the talar dome to rule out subtle depression, collapse, and fragmentation. Nevertheless, radiography remains the mainstay of the diagnosis and temporal observation of talar AVN.