US revealed 48 minor and 66 major traumas.
The concordance with MRI was in 99 patients (but the extent of the lesions was generally higher with MRI).
Minor traumas
US demonstrated low sensitivity in detection of minor traumas because US findings were vague and indistinct with poor oedema and without evident fiber disruption (89% mild contusions,
76% lengthenings,
59% DOMS).
In mild contusions,
a blunt external force caused a direct trauma.
The athlete experienced a dull,
diffuse pain but it was able to continue sport activity.
MRI showed focal hyperintensity both in T1-w,
T2-w and STIR sequences due to the presence of small hematoma and oedema.
Mild contusions were not accompanied by a gross structural damage of muscle tissue and US might show only the presence of small hematoma as a focal hypoechogenic area at the injury site,
with surrounding inhomogeneous hyperechogenicity due to haemorrhagic infarction.
Lengthenings were characterized by acute localized muscle pain during exercise,
exacerbated by contraction or stretching.
All patients recalled the precise time of pain onset.
Delayed onset muscle soreness (DOMS) describes a clinical entity characterized by muscular pain,
soreness,
and swelling that occurs several hours after unaccustomed physical exercise.
Delayed soreness typically begins to develop 12-24 hours after the exercise and can increase until 24-72 hours after the exercise has been performed.
It resolves spontaneously usually within a week,
but if unrecognised and untreated,
it may causestructuralinjuries such as partial tears.
Typically,
in DOMS several muscles across compartments are affected with a typical geographical distribution.
[2]
In lengthenings and DOMS,
MRI showed signal hyperintensity on fluid-sensitive sequences (T2-w and STIR) due exclusively to the presence of muscular oedema,
without signal alterations in T1-w sequences in absence of evident muscular damage.
In comparison US examination was often normal and referred false negative results because there were only slight muscle alterations without significant fiber disruption.
In all these cases the discordant findings between US and MRI scans typically consisted in subtle hyperintensity on T2-w images without muscle fiber tearing in T1-w sequences.
Major traumas
US demonstrated high sensitivity for major traumas (95% strains,
100% severe contusions).
Strains were caused by indirect injury and the lesion was typically sited along the musculotendinous junction with the presence of hematoma and oedema.
Muscles frequently involved crossed two joints and were stretched in eccentric contractions during strenuous activity.
In moderate-severe contusions,
the athletes referred a sudden onset of pain localized in the site of injury; extensive subcutaneous ecchymosis was present distal to the lesion due to intermuscular hematomas.
In these cases both US and MRI correctly detected muscular lesions with grossly interrupted muscle fibers (including muscular retractions),
extensive intermuscular hematoma secondary to fascial injury and extensive edema in the surrounding soft tissues.
In severe contusions,
there was complete agreement (100%) between MRI and US as regard the lesion site and type,
whereas the extent of the lesions was generally higher with MRI.