Posterolateral and Posteromedial Corner Injuries of the Knee
Department of Radiological, Oncological and Pathological Sciences, Sapienza University of Rome, Viale Regina Elena 324, Rome 00161, Italy. Radiologic Clinics of North America
(Impact Factor: 1.98).
05/2013; 51(3):413-32. DOI: 10.1016/j.rcl.2012.10.004
Posterolateral (PLC) and posteromedial (PMC) corners of the knee represent complex anatomic regions because of intricate soft tissue and osseous relationships in small areas. Concise knowledge of these relationships is necessary before approaching their evaluation at imaging. Magnetic resonance imaging offers an accurate imaging diagnostic tool to establish normal anatomy and diagnose and characterize soft tissue and osseous injury. It is important to carefully evaluate the PLC and PMC structures on magnetic resonance imaging before planned surgical intervention to avoid potential complications resulting from occult injury.
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ABSTRACT: Meniscal resection decreases the ability of the meniscus to evenly distribute forces placed on it. These forces are oriented centrifugally on the meniscus by normal weight-bearing and are distributed by circumferentially oriented fibers. This alteration may predispose the knee to radial tears after surgery.
One of three musculoskeletal radiologists prospectively interpreted 100 consecutive postoperative MRI examinations of the knee. A prospective MRI report was generated for the referring orthopedic surgeon, and prospective MRI interpretations were correlated with arthroscopic findings (n = 63). MRI examinations on those patients who underwent second-look arthroscopy were retrospectively reviewed by three musculoskeletal radiologists who reached a consensus on the prevalence of new postoperative meniscal radial tears. MRI criteria for radial tear diagnosis were used as outlined by Tuckman et al.: truncation, abnormal morphology, lack of continuity, absence of the meniscus, or any combination of those criteria on one or more MR images. An additional criterion used was abnormal increased signal in that area on T2-weighted images.
Thirty-two of the 100 patients had meniscal radial tears on prospective MRI interpretations. In 29 of these 32 patients, second-look arthroscopy confirmed meniscal radial tears in the areas described on the MRI examinations. Five additional radial tears were shown on second-look arthroscopy that were not seen on prospective MRI interpretations. Two of those additional five radial tears were seen on consensus retrospective MRI review.
In this study, a 32% prevalence of meniscal radial tears in the postoperative knee was present on prospective MRI interpretations as opposed to a reported 14% prevalence in the nonoperated knee. Meniscal resection decreases the ability of the meniscus to evenly distribute forces placed on it. This circumstance may increase the prevalence of meniscal radial tears in the postoperative knee. New meniscal radial tears are common in patients presenting with pain after knee surgery.
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ABSTRACT: The purpose of this study was to identify differences in the MRI findings of septic arthritis and transient synovitis in patients with nontraumatic acute hip pain and hip effusion.
The MRI findings in nine patients with septic arthritis and 11 with transient synovitis were reviewed retrospectively. This study was approved by our institutional review board. The diagnoses were based on findings at physical examination, laboratory studies, and joint aspiration and bacteriologic study. The MRI findings were analyzed with emphasis on the grade of joint effusion, alterations in signal intensity in the soft tissues and bone marrow, and the presence of decreased perfusion at the femoral head.
Low signal intensity on fat-suppressed gadolinium-enhanced T1-weighted coronal MRI suggesting decreased perfusion at the femoral head of the affected hip joint was seen in eight of nine patients with septic arthritis and in two of 11 patients with transient synovitis. Statistically reliable differences (p = 0.005) were found between the two groups. Alterations in signal intensity in the bone marrow were seen in three patients with septic arthritis but in none of the patients with transient synovitis. Decreased perfusion on fat-suppressed gadolinium-enhanced coronal T1-weighted MRI was seen in the six patients with septic arthritis who did not have alterations in signal intensity involving the bone marrow.
Decreased perfusion at the femoral epiphysis on fat-suppressed gadolinium-enhanced coronal T1-weighted MRI is useful for differentiating septic arthritis from transient synovitis.
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ABSTRACT: The purpose of this study is to investigate the distal insertions of the semimembranosus tendon with MR imaging, correlated with findings in cadavers.
Four fresh cadaveric specimens were studied with 3-T MR imaging. Sequences included proton density (PD) sequences (TE, 13; TR, 4957; FOV, 170 × 170; matrix, 424 × 413; NA, 2; slice thickness, 2.5 mm) in the axial, coronal, and sagittal planes and 3D fast field echo (FFE) sequences (TR 9.4; TE 6.9; FOV, 159 × 105; matrix, 200 × 211; NA, 2; slice thickness, 0.57 mm). One specimen was dissected and three specimens were sectioned with a bandsaw in the axial, coronal, and sagittal plane. The sections were photographed and correlated with MR images. To standardize the analysis, the semimembranosus muscle and tendon were assessed at seven levels for the axial sections, and at three levels for the coronal and sagittal sections.
Anatomic dissection revealed six insertions of the distal semimembranosus tendon: direct arm, anterior arm, posterior oblique ligament extension, oblique popliteal ligament extension, distal tibial expansion (popliteus aponeurosis), and meniscal arm. Axial MR images showed five of six insertions: direct arm, anterior arm, oblique popliteal ligament extension, posterior oblique ligament extension, and distal tibial expansion. Sagittal MR images showed four of six insertions: direct arm, anterior arm, oblique popliteal ligament arm, and distal tibial expansion. Sagittal MR images were ideal for showing the direct arm insertion, but were less optimal than the axial images for showing the other insertions. The anterior arm was seen but volume averaging was present with the gracilis tendon. Coronal MR images optimally revealed the anterior arm, although magic angle artifact was present at its posterior aspect. The common semimembranosus tendon and meniscal arm were also well depicted. The division in anterior arm, direct arm, and oblique popliteal ligament arm was poorly seen on coronal images due to volume averaging.
Although the anatomy of the distal semimembranosus tendon is complex, six different semimembranosus insertions can be identified on routine proton density and FFE sequences at 3 T. Analysis of images at defined levels in the three imaging planes simplifies MR interpretation of the anatomy of the distal semimembranosus tendon.
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