Medial Tibial Stress Syndrome

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Media tibial stress syndrome (MTSS), also known as "Shin Splints" is a spectrum of exercise-induced stress injury of the medial to distal tibia.

Classification

There are two types

  • Medial (posteromedial) tibial stress syndrome: the most common
  • Anterior (anterolateral) tibial stress syndrome

Epidemiology

It is found in 10-15% of running injuries, and 60% of leg pain syndromes.

Risk factors are

  • Runners without enough shock absorption (running on hard or uneven surfaces, improper running shoes)
  • Training errors (sudden increase in training intensity and duration)
  • Running >20 miles/week
  • Hill training early in the season
  • History of previous lower extremity injuries
  • Over-pronation or increased internal tibial rotation, increased external rotation of the hip, particularly in females
  • Female runner
  • Recreational runner (<5 years)
  • Orthotic use

Pathophysiology

It is caused by a traction periostitis due to muscle imbalance, overuse, and improper biomechanical alignment.

  • Anterior (anterolateral): traction periostitis of tibialis anterior on the tibia and interosseous membrane
  • Medial (posteromedial): traction periostitis of tibialis posterior and soleus

It is not related to anthropomorphic features. There is greater PT excursion, peak hip internal rotation, and decreased flexion.

It is associated with RED-S. Females have a 1.5-3.5 times increased risk of progression to stress fracture.

Clinical Features

The pain is vague and diffuse that spreads along the middle to distal tibia that decreases with running in the early stage. This is differentiated from exertional compartment syndrome where the pain increases as running continues. There is an earlier onset of pain with more frequent training in latera stages.

On physical examination there is tenderness along the posteromedial border of the tibia. This is typically 4cm proximal to the medial malleolus, and extends proximally up to 12cm. There is often foot pronation and a tight Achilles tendon. The core muscles may be weak. Pain may be reproduced with the provocation test which is pain on resisted plantar flexion. With the "one-leg hop test" the patient can hop at least 10 times on the affected leg, while the patient with a stress fracture cannot without severe pain.

Imaging

Fredericson grading system

Plain Radiographs: Plain films are indicated to exclude stress fracture. They are insensitive and often normal, especially in the early phase. Long-term changes may occur with subtle periosteal exostoses around the cortex of the tibia medially. This is differentiated from stress fracture which shows the "dreaded black line."

CT: CT is not very sensitive, but may show mild osteopenia as an early sign of fatigue injury of the cortical bone in the tibial diaphysis.

Ultrasound: On ultrasound there may be focal hyperechoic elevation of the periosteum with irregularity over the distal tibial and increased flow on Doppler.

Bone Scan: 3-phase bone scan is fairly sensitive. Findings are a diffuse longitudinal increased uptake along the posteromedial border of the tibia in the delayed phase (phase 3). There are normal findings on the flow phase (phase 1), and blood pool phase (phase 2). Stress fractures on bone scan show a focal intense hyperperfusion and hyperaemia in phase 1 and 2, and focal fusiform uptake in phase 3.

MRI: MRI is the most sensitive examination. There are a spectrum of findings ranging from normal, to periosteal and marrow oedema, to stress fracture. Findings are most often seen in the medial cortex with or without posterior cortex involvement. The most useful sequences are the axial fluid sensitive and fat saturated sequences. Periosteal oedema can be very subtle. Bone marrow oedema usually occurs at similar levels to the periosteal oedema.

In late stages there may be bone remodelling caused by osteoclast mediated resorption and osteoblast replacement. Normal cortex has low signal intensity on T1 and T2. In osteopenia there is a loss of cortical signal void, the resorption cavity is a round or focal intracortical area with increased signal intensity. Striation may be seen as a subtle intracortical linear hyperintensity.

The Fredericson grading system can be used to grade the MRI findings and is correlated with clinical severity and prognosis.

Bone scan compared with MRI for grading tibial stress injuries
Grade Bone Scan MRI
1 Small ill-defined cortical area of mildly increased activity Periosteal oedema is mild to moderate on T2 weighted images with no associated bone marrow abnormalities
2 Better-defined cortical area of moderately increased activity Periosteal oedema is moderate to severe with mild bone marrow oedema visible only on fat-suppressed T2 weighted images.
3 Wide to fusiform, cortical-medullary area of highly increased activity Periosteal oedema and extensive bone marrow oedema visible on T1 and fat-suppressed T2WI
4 Transcortical area of intensely increased activity Grade 4a: Periosteal oedema, extensive bone marrow oedema visible on T1WI and fat-suppressed T2WI and multiple focal areas of intracortical signal changes

Grade 4b: Periosteal oedema, extensive bone marrow oedema visible on T1WI and fat-suppressed T2WI and linear region of intracortical signal change (i.e. a fracture line)

Differential Diagnosis

Differential Diagnosis
  • Tibial or fibular stress fracture
  • Compartment syndrome
  • Nerve entrapment (sural or superficial peroneal nerves)
  • Popliteal artery entrapment
  • Lumbar Radicular Pain
  • Tendinopathy (Achilles, peroneal, tibialis posterior)
  • Bone tumours (osteosarcoma in younger patients)

Treatment

Rest, ice and analgesia may be helpful.

Physiotherapy: iontophoresis, phonophoresis, ice massage, ultrasound, acupuncture in particular the periosteal pecking method.

Activity modification: Decrease intensity, running distance and frequency. Look for alternative exercises that are low impact and do cross training. Run on soft tracks, avoid hard and uneven surfaces. Avoid hills

Strengthening and stretching, however there is no difference with graded exercises versus graded with stretching versus graded with stretching and compression stockings.

Attention to footwear is important. Footwear can be professional fitted and replaced regularly. Consider orthotics if pronated.

ESWT may provide a faster recovery.

Surgery can be considered in refractory cases

Prognosis

Relapse is very common. Treatment studies show 60-100 days to "recovery." Women tend to have a more chronic course. Progression to stress fracture may occur.

References

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Literature Review