Dedicated Knee Coil Research Articles

Increased signal of the fibular collateral ligament of the knee on MRI, clinically significant?

IntroductionThe purpose of this study was to determine the clinical significance of signal hyperintensity in the proximal fibular collateral ligament (FCL) on coronal proton density (PD) fat-saturated (FS) MRI of the knee, a common finding. This study is unique in that it characterizes the FCL of a comprehensive, large cohort of both symptomatic and asymptomatic patients, which to our knowledge represents the first study with such broad inclusion criteria. MethodsA large case series was performed analyzing MRI of the knee of 250 patients from July 2021 through September 2021 and retrospectively reviewed. All studies were performed on 3-Tesla MRI scanners with a dedicated knee coil and in accordance with standard institutional knee MRI protocol. Signal in the proximal fibular collateral ligament was assessed on coronal PDFS and axial T2-weighted FS images. Increased signal was classified as none, mild, moderate, or severe. A corresponding chart review of clinic notes was performed to determine the presence or absence of lateral knee pain. An FCL sprain or injury was considered present if the medical record described tenderness on palpation of the lateral knee, positive finding against resistance to the leg (varus stress test) or reverse pivot shift, or any clinical suspicion for lateral complex sprain or posterolateral corner injury. ResultsThe majority (74%) of knee MRIs demonstrated the presence of increased signal in the proximal fibular collateral ligament on coronal PD FS images. <5% of these patients had associated clinical findings of fibular collateral ligament and/or lateral supporting structure injury. DiscussionAlthough increased signal in the proximal FCL of the knee is a common finding on coronal PDFS images, the majority are not associated with clinical symptoms. Thus, this increased signal is likely not a pathological finding in the absence of clinical findings of fibular collateral ligament sprain/injury. Our study emphasizes the importance of clinical correlation in identifying increased signal in the proximal FCL as pathologic.

The ACL can hypertrophy in response to mechanical loading: an MRI study in elite athletes (157)

The ACL can hypertrophy in response to mechanical loading: an MRI study in elite athletes (157)

Effect of Time on MRI Appearance of Graft After ACL Reconstruction: A Comparison of Autologous Hamstring and Quadriceps Tendon Grafts

Background:After anterior cruciate ligament (ACL) reconstruction (ACLR), changes in the appearance of the ACL graft can be monitored using magnetic resonance imaging (MRI).Purpose:The purpose of this study was to evaluate and compare the MRI signal intensity (SI) of hamstring and quadriceps tendon grafts during the first postoperative year after ACLR. As a secondary aim, the relationship of SI to clinical and anatomic measurements was analyzed.Study Design:Cohort study; Level of evidence, 2.Methods:A total of 78 patients who underwent ACLR with an autologous graft were reviewed; 55 received hamstring grafts and 23 received quadriceps tendon grafts. At 3 and 9 months postoperatively, 3-T MRI was performed using a dedicated knee coil, and the median SI of the intra-articular ACL graft was measured on sagittal-plane images. Postoperative lateral radiographs were analyzed to determine medial and lateral posterior tibial slope (PTS). Side-to-side difference in anterior knee laxity between injured and uninjured limbs was measured at 6 and 12 months postoperatively.Results:The median SI of quadriceps grafts was significantly greater than hamstring grafts at 3 months after ACLR (P = .02). Between 3 and 9 months, the median SI of quadriceps grafts decreased (P < .001), while that of hamstring grafts did not significantly change (P = .55). The lateral PTS was significantly correlated with median SI measurements at 3 and 9 months such that greater lateral PTS values were associated with greater median SI. The side-to-side difference in anterior knee laxity decreased for the quadriceps group (P = .04) between 6 and 12 months but did not change for the hamstring group (P = .88).Conclusion:The median SI of quadriceps grafts significantly decreased on MRI between 3 and 9 months after ACLR, while the median SI of hamstring grafts did not significantly change. The change in MRI appearance of the quadriceps grafts was paralleled by a reduction in anterior knee laxity between 6 and 12 months after surgery. In the absence of standardized imaging techniques and imaging analysis methods, the role of MRI in determining graft maturation, and the implications for progression through rehabilitation to return to sport, remain uncertain.

Increased signal in the proximal patellar tendon: normal or pathologic?

To determine the clinical significance of T2 signal hyperintensity in the proximal patellar tendon seen on MRI of the knee. MRIs of 100 patients who underwent MRI of the knee between 1 May 2018 and 15 July 2018 were retrospectively evaluated. All examinations were performed on 3-Tesla MRI scannerswith a dedicated knee coil and in accordance with our institution's standard knee MRI protocol. The presence of increased T2 signal was assessed on both sagittal and axial T2-weighted fat-saturated images. The amount of increased signal in the proximal patellar tendon on T2-weighted images was characterized as: none, mild, moderate, or severe. A corresponding chart review of the referring physicians' notes was performed to determine the presence of clinical symptoms of patellar tendinopathy. Patellar tendinopathy was considered present if the clinical notes described tenderness on palpation of the inferior patellar pole, infrapatellar tenderness, or patellar tendinosis/tendinitis. The majority(66%) of knee MRIs demonstrated the presence of increased T2 signal in the proximal patellar tendon. Only 4.5% of these patients had associated clinical findings of patellar tendinopathy. Although increased T2 signal in the proximal patellar tendon is a common finding, only in rare cases are there associated clinical symptoms. Thus, increased T2 signal in the proximal patellar tendon may not be a pathological finding in the absence of clinical findings of patellar tendinopathy.

Imaging of Individual Anatomical Risk Factors for Patellar Instability.

This review article presents several pitfalls and limitations of image interpretation of anatomical risk factors for patellar instability. The most important imaging examinations for the work-up of patients with patellar instability are the true lateral radiograph and transverse computed tomography (CT) or MR images of the knee. Primary anatomical risk factors are an insufficient medial patellofemoral ligament (MPFL), patella alta, trochlear dysplasia, increased distance from the tibial tuberosity to the trochlear groove (TTTG), and torsional limb parameters. Limitations of the Caton-Deschamps index are related to the clear identification of the patellar and tibial articular margin. Classification of trochlear dysplasia according to the Dejour system on radiographs and MR images revealed a weak reliability. The comparability of TTTG values obtained on CT and MR images at various flexion angles and different varus alignments of the knee is limited. Thus MRI performed with a dedicated knee coil may underestimate the TTTG distance compared with CT images. Increased lateral patellar tilt is a consequence of primary anatomical risk factors rather than an independent anatomical risk factor for patellar instability. The pretest likelihood of a torn MPFL on MR images is very high after an acute episode of lateral patellar dislocation. Surgical restoration of the patellofemoral joint stability addresses the complex multifactorial biomechanics by a custom-made management such as MPFL reconstruction, sulcus-deepening trochleoplasty, as well as medialization and distalization of the tibial tubercle. Quantification of anatomical risk factors for patellar instability in each person is important for highly individual treatment.

MRI performed on dedicated knee coils is inaccurate for the measurement of tibial tubercle trochlear groove distance

Tibial tubercle trochlear groove distance (TTD) is a significant factor in patello-femoral instability. Initially described on CT scans with the knee in full extension, the measurement has been validated on MR scans. Dedicated knee MRI coils have subsequently superseded both CT and MRI body coils for knee imaging. However, the knee rests in partial flexion within the dedicated knee coil. The objective of this study is to investigate whether images from dedicated knee MRI coils produce different TTD measurements from MR body coils. Thirty-two symptomatic knees (27 patients) had simultaneous knee MR scans performed in both a dedicated knee coil and a body coil. TTD measurements were independently compared to assess whether the coil type used affected TTD. Patients' ages ranged from 10 to 27 years (mean 15 years). Mean TTD in the dedicated knee coil (partially flexed knee) was 11.3 mm compared with 19.9 mm in the body coil (that permits full knee extension). The mean difference was 8.6 mm, which was highly significant (p < 0.0001, unpaired t test). Inter-rater correlation co-efficient was 96 %. Of the knees that recorded a "normal" TTD on the dedicated knee coil, 60-100 % recorded a "pathological" TTD on body coil images, depending on which diagnostic value for "normal" cut-off was used. This study has identified a highly significant difference in TTD measurement when knees are scanned in a dedicated knee coil with the knee partially flexed, compared with an MR body coil. It is critical for surgeons and radiologists managing patello-femoral instability to appreciate this profound difference. TTD measurement taken from knees scanned in dedicated knee coils may lead to patients being falsely re-assured or erroneously denied surgery.

Analysis of Low-Field Magnetic Resonance Imaging Scanners for Evaluation of Knee Pathology Based on Arthroscopy.

Background:In recent years, few studies have evaluated low-field magnetic resonance imaging (MRI) diagnoses compared with intraoperative findings of the knee.Purpose:To determine the accuracy and sensitivity of low-field MRI scanners in diagnosing pathology of the menisci, cruciate ligaments, and osteochondral surfaces.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:MRI examinations without intra-articular contrast were performed on 379 patients for knee pathologies over a 4-year period. The MRI examinations were done using a 0.2-tesla scanner utilizing a dedicated knee coil and read by 1 of 3 board-certified, musculoskeletal fellowship–trained radiologists. Within a mean time of 50 days after MRI, all patients underwent knee arthroscopy performed by 1 of 2 sports fellowship–trained orthopaedic surgeons. Operative notes from the knee arthroscopies were then reviewed by a single independent observer, and the intraoperative findings were compared with the MRI reports.Results:For medial meniscus tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 83%, 81%, 89%, and 71%, respectively. For lateral meniscus tears, the values were 51%, 93%, 84%, and 73%, respectively. For anterior cruciate ligament (ACL) tears, the values were 85%, 94%, 69%, and 97%, respectively. For osteochondral lesions, the values were 8%, 99%, 29%, and 94%, respectively. For posterior cruciate ligament (PCL) tears, the specificity and negative predictive value were 99% and 100%, respectively.Conclusion:Low-field MRI was an accurate tool for evaluation of medial meniscus and ACL tears. However, within the study population, it is not as effective in diagnosing lateral meniscus tears and showed a poor ability to detect osteochondral lesions. More information is needed to properly assess its ability to diagnose PCL tears.

Assessment of perfusion in osteoarthritis induced bone marrow lesions using dynamic contrast enhanced magnetic resonance imaging

Assessment of perfusion in osteoarthritis induced bone marrow lesions using dynamic contrast enhanced magnetic resonance imaging

Cartilage loss, measured with mri, predicts knee replacement - data from the osteoarthritis initiative

Cartilage loss, measured with mri, predicts knee replacement - data from the osteoarthritis initiative

Magnetic resonance imaging features of asymptomatic bipartite patella

Objective The purpose of our study was to describe the magnetic resonance imaging (MRI) features of bipartite patella in asymptomatic patients. Materials and methods The study was prospective in type and performed following institutional ethical committees approval. In total, 25 subjects were recruited into the study and informed consent obtained in each case. The local radiology database was utilised in conjunction with a clinical questionnaire to identify patients who had asymptomatic bipartite patella. Any patient with a history of trauma or symptomatic disease was excluded from the study. MRI imaging was performed in each case on a 1.5 T system using a dedicated knee coil and a standardised knee protocol. The images obtained were then analysed by two musculoskeletal radiologists in consensus. Results Of the 25 subjects, there were 8 females and 17 males. The mean age was 34.6 years. All but one of the bipartite fragments were located on the superolateral aspect of the patella. In 23 cases, one fragment was identified. The average transverse diameter of the fragment was 12.8 mm. The average distance between the fragment and the adjacent patella in the axial plane was 1.46 mm. In addition, the cartilage overlying the patella and accessory fragment was intact in all cases. The average thickness of the patella cartilage at its border to the fragment was 2.4 mm with an average ratio of the cartilage thickness of the fragment as compared with the cartilage thickness of the patella of 0.72. There was no evidence of high signal or bone marrow oedema on fluid sensitive sequences within either the patella or the fragment in any of the patients. Fluid was identified in the cleft between the patella and the fragment in the majority of cases. Conclusions Asymptomatic bipartite patella is characterised by intact but thinned cartilage along the border between the patella and the fragment, fluid between the cleft and a lack of any bone marrow oedema or high signal within the patella or its fragment.

Three-tesla imaging of the knee: initial experience

To assess 3-T imaging of the knee. We reviewed 357 3-T magnetic resonance images of the knee obtained using a dedicated knee coil. From 58 patients who had arthroscopy we determined the sensitivity and specificity for anterior cruciate ligament (ACL) tear and medial and lateral meniscal tear. A chemical shift artifact showed prominently at 3 T even after improvements had been made by increasing the bandwidth. For complete ACL tear the sensitivity was 100% (95% confidence interval, CI, 75.30-100.00), and the specificity was 97.9% (95% CI 87.7-99.9). For the medial meniscus the sensitivity was 100.00% (95% CI 90.0-100.00), and the specificity was 83.3%(95% CI 66.6-95.3). For the lateral meniscus the sensitivity was 66.7% (95% CI 38.4-88.2), and the specificity was 97.6% (95% CI 87.1-99.9). In general 3-T imaging allows a favorable display of anatomy and pathology. The lateral meniscus was assessed to be weaker than the other anatomic structures. Three-tesla imaging allows increased signal-to-noise ratio, increased resolution, and faster scanning times.

Perinatal Mortality: Clinical Value of Postmortem Magnetic Resonance Imaging Compared With Autopsy in Routine Obstetric Practice

Although perinatal autopsy is accepted as having diagnostic value, studies from both the United States and Europe indicate that as many as 40% of all perinatal deaths are not followed by autopsy. This cohort study from a large teaching hospital compared the results of postmortem magnetic resonance imaging (MRI) with the autopsy findings in fetuses at 16 weeks or more gestational age and neonates up to 28 days after birth. MRI was performed as soon as possible after obtaining parental consent. Infants up to 500 g were imaged using a dedicated knee coil and larger children with a wrap-around surface coil. Sagittal and transverse T1-weighted sequences were used to image the head, whereas the body was imaged in the coronal and sagittal planes. Good-quality MR images were consistently obtained in this study. Twenty-six parents agreed to both MRI and autopsy. Acceptance rates for both examinations were higher for early-gestational-age fetuses. Autopsies disclosed 18 major and 8 minor malformations. MRI detected more than half of the major malformations (56%). MRI also detected umbilical hernia and lung lesions, considered to be minor malformations. Four pregnancies were electively terminated because of congenital malformations. In 84% of cases it was possible to perform MRI within 48 hours. MRI had a positive predictive value of 80% and a negative predictive value of 65%. MRI was less accurate than hoped for when performed postmortem, and it cannot at present be recommended in place of a full autopsy. MRI does have value if autopsy is refused, and it is more readily accepted by parents than autopsy. When autopsy is permitted, MRI offers no added diagnostic value. The option of postmortem MRI probably should be raised only when autopsy is refused, unless an abnormality known to be detected by MRI is suspected.

Patellar tendon defect during the first year after anterior cruciate ligament reconstruction: Appearance on serial magnetic resonance imaging

The purpose of this study was to use magnetic resonance imaging to evaluate various parameters of the patellar tendon during the first year after harvest for anterior cruciate ligament (ACL) reconstruction. Twelve consecutive patients were serially imaged on a 1.5 Tesla GE magnet (GE Medical Systems, Milwaukee, WI) with a dedicated knee coil at 3 weeks, 3 months, 6 months, and 1 year after undergoing ACL reconstruction using a central one-third patellar tendon autograft. The tendon defect was not closed primarily, but the paratenon was approximated. The following measurements were performed: tendon width, defect width, cross-sectional area of the tendon, and tendon length. In addition, the patellar bone harvest site was evaluated for healing. The width of the tendon defect decreased by 62% over 12 months (P < .05). Only two patients showed complete closure of the defect. Tendon width was noted to decrease by 6.5% (P=.017). The ratio of defect width to overall tendon width (designated R) decreased by 58% (P < .05). Tendon length was noted to decrease during this by 8% (P=.037). The tendon cross-sectional area was noted to increase by 9% at 1 year, but this was not found to be statistically significant (P=.39). One year after ACL reconstruction using a central one-third patellar tendon, the tendon defect has begun to reconstitute itself but there is still a significant gap. This persistent defect must be taken into consideration when planning revision ACL surgery using reharvest of the central one third of the patellar tendon. The entire tendon also exhibits a reduction in width and length, while cross-sectional area increases slightly. Complete healing of the graft defect can not be assumed at 12 months post-ACL reconstruction. (Arthroscopy 1998 Nov-Dec;14(8):804-9.)

Tear of the anterior cruciate ligament: evaluation with MR imaging.

Sixteen patients with traumatic injury to the knees were surveyed with magnetic resonance (MR) machines with field strength of either 0.5 Tesla (T) using head coil (10 cases) or 1.5 T using dedicated knee coil (6 cases). Tears of the anterior cruciate ligament (ACL) were found in eight cases. The other eight cases had injuries of the other ligaments, meniscus or bone with intact ACL. All cases were proved by arthroscopy. Primary and secondary signs of the ACL tears were evaluated by MR imaging. Primary signs included the status of ACL. Secondary signs consisted of bone bruise in the posterolateral tibial plateau, in the lateral femoral condyle, or both (so-called kissing bone bruise), fracture at the posterolateral tibial plateau, Segond fracture, anterior dislocation of the tibia (> 5 mm), buckled posterior cruciate ligament (PCL), positive PCL line and the deep lateral femoral notch (> 1.5 mm). Of the eight cases of the ACL tears, 5 cases (62.5%) revealed thickening and edema of the ACL, 3 cases (37.5%) kissing bone bruise, 1 case (12.5%) Segond fracture, 2 cases (25%) buckled PCL, 2 cases (25%) deep lateral femoral notch, 2 cases (25%) anterior dislocation of the tibia and 0 case (0%) positive PCL line. The ACL had normal thickness of low signal intensity in 3 cases of chronic ACL tears (50%). Lateral meniscal tears were found in seven of the eight cases of ACL tears (87.5%). For the eight cases with intact ACL, the ACL was normal in thickness and of low signal intensity. Other findings were bone bruise in the lateral femoral condyle (1 case, 12.5%), fracture at the posterolateral tibial plateau (1 case, 12.5%), buckled PCL (1 case, 12.5%) and positive PCL line (1 case, 12.5%). It is concluded that primary sign is important in the MR diagnosis of the ACL tears. Secondary signs are helpful but may be present in lesions with intact ACL.

Magnetic resonance imaging of injury to the lateral ankle ligaments.

To establish the value of magnetic resonance imaging in determining which patients with ankle sprains will benefit from surgical treatment, 1 uninjured volunteer and 15 patients with acute, subacute, and chronic injuries of the lateral ankle ligaments were imaged at 1.0 tesla using a fast imaging with steady-state precision three-dimensional technique and 1.5-mm slice thickness. A dedicated knee coil was used to hold the foot in a neutral or plantar-flexed position. In cases of acute, low-grade injuries, fraying of the anterior talofibular ligaments with intact calcaneofibular ligaments was observed in the presence of edema and hemorrhagic fluid. In cases of acute, high-grade sprains, the calcaneofibular ligament appeared wavy or was visualized only partially or not at all. Subacute injuries showed ligament disruption; chronic lesions, on occasion, showed atrophy of the calcaneofibular ligament but no edema or hemorrhagic fluid. These findings showed a good qualitative correlation with the results of graded stress radiography. Magnetic resonance imaging can definitely determine the ligaments involved in lateral ankle sprains and provide useful anatomic information in cases in which acute or reconstructive surgery is contemplated. However, the magnetic resonance imaging findings do not directly correlate with degree of instability and do not replace those of physical examination or routine radiographic studies.