Use of Fat-Suppressed T2-Weighted MRI Images to Reduce the Magic Angle Effect in Peroneal Tendons

MRI findings of peroneal tendon tears do not necessarily correlate to clinical findings in paediatric and adolescent patients

PURPOSE

Pathologic abnormality of the peroneal tendons are thought to be an under-appreciated source of vague ankle and hindfoot pain in paediatric patients, partly because they can be difficult to diagnose and differentiate from lateral ankle ligament injuries. While magnetic resonance imaging (MRI) is the primary imaging modality used to detect peroneal tendon pathology, previous studies in adults have found that positive MRIs demonstrate a positive predictive value (PPV) of associated clinical findings around 48%. There are no similar known published studies in the paediatric population. Our objective was to determine the positive predictive value of peroneal tendon pathology as diagnosed by MRI as related to positive clinical exam findings in the paediatric and adolescent population.

METHODS

This IRB approved retrospective study was conducted at a tertiary children's hospital. Inclusion criteria included patients under 18 years from our tertiary care institution with (a) ankle MRI findings indicating pathology of the peroneus brevis/longus tendons confirmed by a board certified paediatric musculoskeletal radiologist and (b) formal review of the clinical examination by a fellowship trained paediatric orthopaedic surgeon. Patients with congenital deformities or previous surgical intervention of the lateral ankle were excluded.

RESULTS

Forty-seven patients (with 48 MRIs) met inclusion criteria over a ten year period. The majority of the positive MRI scans (70%) demonstrated a peroneus brevis split tear. Of the patients with positive findings on MRI, 17 patients had an associated positive clinical exam. The positive predictive value of MRI for peroneal tendon tears with positive clinical findings was 35.41% (95% confidence interval = 31.1% to 41.6%). There were 31 patients with MRI positive findings with a negative clinical exam.

CONCLUSION

Despite having a negative clinical exam, a high percentage of patients had positive MRI findings suggestive of peroneal tendon pathology which confirms findings of adult populations demonstrating a high rate of incidental finding of peroneal tendon pathology on MRI in paediatric patients.

Postsurgical Evaluation of the Pediatric Foot and Ankle

This article reviews situations in which surgical treatment is required in the context of different types of pathology in the foot and ankle of children, focusing on the role of imaging in surgical planning and postsurgical assessment. The types of pathology analyzed from this perspective are congenital pathology, neuromuscular disorders, osteochondral lesions, fractures and infection, ligament injuries, and tumors.We address the most common pitfalls of postsurgical imaging of the ankle and foot in children. With some exceptions, postsurgical follow-up focuses on clinical assessment, with imaging follow-up only needed in patients where complications are suspected or symptoms recur. Postoperative assessment of the foot and ankle in children and adolescents requires knowing the indications for surgery and the most common types of interventions, along with their imaging characteristics. The radiologist needs to be aware of the normal sequence of development of structures and how to select adequate imaging techniques to assess anatomy at various stages or in different postsurgical scenarios.

Peroneal Tendinosis and Subluxation

Peroneal tendinosis and subluxation are lifestyle-limiting conditions that can worsen if not properly diagnosed and treated. Adequate knowledge of ankle anatomy and detailed history and comprehensive physical examination is essential for diagnosis. Peroneal tendinopathy is likely to result from overuse, whereas subluxation often precipitates from forceful contraction of peroneals during sudden dorsiflexion while landing or abruptly stopping. In athletes, conservative measures remain first-line treatment of tendinopathy, but surgery is often immediately indicated in cases of recurrent symptomatic subluxation or dislocation. Surgical technique varies on the type, mechanism, and severity of injury, but most procedures have a high success rate.

Risk of intra-articular injection with longitudinal ultrasound-guided injection of collateral ligaments of the equine distal interphalangeal joint

Desmopathy of the collateral ligaments of the distal interphalangeal joint is a common cause of equine foot lameness and carries a poor prognosis with conservative management. Intralesional injections may improve healing, although accuracy of radiographically guided injections is significantly less than when guided by MRI, which requires special needles. Longitudinal ultrasound-guided injection of the distal collateral ligament has not been evaluated objectively. In this prospective, anatomic study, seven equine cadaver limbs (14 collateral ligaments) were injected with methylene blue dye and radiographic contrast medium using ultrasound to guide the needle longitudinally into the collateral ligaments until contacting bone. The insertion site of the needle proximal to the coronary band was measured on the limb and the needles left in place for radiography and CT to evaluate the needle angulation, location of the contrast medium, and whether the contrast entered the distal interphalangeal joint. The limbs were frozen and sectioned with a band saw to identify the location of the dye. Fifty percentage of injections were in or around the collateral ligaments. However, the percentage of "successful" injections, defined as in the collateral ligament but not in the joint, was only 36%. All legs had dye and contrast in the joint after both ligaments had been injected. There were no significant differences between the needle angle and entry site for "successful" and "unsuccessful" injections. Findings from this study indicates that the success rate is low for injecting the distal portions of the distal interphalangeal joint collateral ligaments using ultrasound guidance alone.