The Shins: Shin Splints and Fractures James DuRant – Radiology Elective – October 22, 2009 University of South Carolina School of Medicine

2 The shins - Clinical Vignette A 16 year old male complains of bilateral lower leg pain over the past 2 weeks. He describes a gradual pain on both sides while pointing to the posteromedial surface of the tibia and has progressively gotten worse. He is an athlete who recently finished his cross country running season and now beginning basketball season. He wants to know if these are just shin splints and how long until he will be at full speed on the court because right now “both legs are killing him.”

3 The shins – Clinical vignette Getting more of a history he says that the pain has been gradual over the past 2 weeks, but the past week has been the worst with him barely able to bear any weight on his right foot. He did “turn his ankle” during the past week which has causes him to not be able to put pressure on his right leg, though the pain and swelling in his ankle has subsided. Physical exam shows tenderness to palpation along the posterior medial portion of both legs, no erythema or induration, and the right leg has increased point tenderness on his medial tibial bone.

4 Illustration What is “shin splints syndrome”? Medial tibial stress syndrome What is the pathophysiology? Periosteal edema leads to marrow involvement which leads to cortical stress fracture. Who gets them? Frequently athletes from repetitive stress injuries and high impact.

5 Differential Diagnosis Stress injury versus Tibial Stress Fracture Stress injury - wide spectrum musculoskeletal injuries that occur in response to changes in the mechanical environment Develop when bone is subjected to repeated cyclic loading or skeleton is weakened Edema of the periosteum, muscle or bone marrow are earliest changes of stress reaction Stress fractures seen as band-like areas of low signal intensity in intramedullary space that may be continuous with cortex Much later, linear areas of low signal intensity on all sequences which represent callus and new bone formation at fracture site is seen

6 Imaging - Radiography Initial imaging used to confirm diagnosis at relatively low cost Low sensitivity for early fracture - lag time of 1 week to several months Compare to contralateral side

7 Radiography Horizontal and transverse lucency through the anterior cortex Cortical thickening (arrow).

8 Imaging - MRI Fracture is seen as low signal intensity with surrounding marrow edema (Fig. 5, Fig. 6, Fig. 7) In shin splints increased cortical signal intensity on T2- weighted MR images may signify overt stress fracture (Fig. 8) Periosteal edema at origins of tibialis posterior, flexor digitorum longus, soleus muscles of runners with tibial stress injuries

9 T2 MR Shin splint Marrow edema (arrow) high signal intensity of the periosteum (arrowhead), suggesting a shin splint.

10 T1-weigted coronal MR tibial fracture Decreased marrow signal intensity (arrow) Focal low signal intensity (arrowhead) in the right proximal tibia

11 Imaging - Nuclear Medicine Very high sensitivity but lacks specificity in differentiating stress injuries from tumors, infection, infarction Investigation of choice is bone scintigraphy in classic horizontal tibial stress fracture

12 Imaging – Nuclear Medicine Bone scan showing increased focal radiotracer in bilateral anterior tibiae. Right tibia uptake greater than left.

13 Imaging - CT Helpful in defining extent of suspected stress fracture CT has inferior sensitivity to bone scintigraphy, MR imaging Helpful in differentiation from osteoid osteoma CT may also help detect discrete fracture line, periosteal reaction when findings are equivocal on other modalities

14 CT Curvilinear lucencies (arrowhead) and cortical thickening (arrow) secondary to callus formation in the posterior cortex of the right tibia.

15 CT Radiolucent fracture line (arrowhead) Cortical thickening (arrow) of the anterior tibial cortex.

16 Treatment Treatment consists of activity restriction to minimize symptoms (ie, a period of non weight bearing may be necessary) before engaging in strengthening and conditioning. Eventual return to play in 8-12 weeks. pneumatic leg brace allowed athletes to recover more quickly than athletes treated with activity restriction alone.

17 References Fredericson M, Jennings F, Beaulieu C, Matheson GO. Stress fractures in athletes [review]. Top Magn Reson Imaging. 2006;17:309–325. Tibial Stress Fracture, imaging.consult.com Stress Injury, imagining.consult.com