When Groin Pain Signals an Adductor Strain

Adductor strains typically occur brief with forceful abduction of the thigh during adduction or with hyperabduction. The history and physical exam are usually diagnostic; however, other causes of acute groin pain must always be ruled out. Using CT, MRI, or ultrasound can facilitate diagnosis of difficult or unusual cases. Management of acute partial strains usually requires nonsteroidal anti-inflammatory drugs, ice, compression, physical therapy, and rest. The mainstay of treatment is early active rehabilitation and returq to competition. Surgery is often required for complete ruptures, but the treatment for such injuries remains under discussion

A Threshold and Continuum of Injury During Active Stretch of Rabbit Skeletal Muscle

Previous studies of acute muscle injury with active stretch used cyclic stretching or stretching the muscle to complete muscle-tendon dissociation. This study tried to determine minimal force required for skeletal muscle injury with one active stretch to establish an in jury "threshold." Tibialis anterior and extensor digitorum longus rabbit muscles were actively stretched at 10 cm/ sec to 60%, 70%, 80%, or 90% of the force required to passively fail tibialis anterior and extensor digitorum lon gus muscles of the control (contralateral) limb. Maximal isometric contractile force, tensile properties, histology, and electromyography were measures of injury. Both muscles of the 60% group showed no abnormalities in maximal isometric contractile force, tensile properties, histology, or electromyographic activity; 70%, 80%, and 90% groups showed diminished maximal isometric con tractile force, muscle fiber disruption, edema, hemor rhage, and decreased electromyographic maximal volt age amplitude. The 90% group also showed alterations in tensile properties at failure along with connective tis sue damage. Injury site included fiber disruption both at the distal myotendinous junction and muscle belly, with injury noted initially at the distal myotendinous junction in the 70% group. Electromyographic studies showed maximal isometric contractile force and maximal volt age correlated well as indices of damage. This study shows that a threshold and continuum for active stretch- induced injury exist, with muscle fiber disruption occur ring initially and connective tissue disruption occurring only with larger muscle displacements

An Explanation for Various Rectus Femoris Strain Injuries Using Previously Undescribed Muscle Architecture

We performed cadaveric dissection of the rectus femo ris muscle to correlate the various lesions of strain injury seen with imaging studies to the muscular anatomy. The proximal tendon is composed of a superficial, an terior portion from the direct head, and a deep intra muscular portion from the indirect head. The muscle fibers arising from the anterior superficial tendon of the direct head travel in a posterior and distal direction to insert on the posterior tendon of insertion, giving the proximal muscle a unipennate architecture. Muscle fi bers from the intramuscular tendon of the indirect head originate on both the medial and lateral sides of the tendon and insert on the distal posterior tendon to cre ate its bipennate structure. Three chronic strain injuries involving the midmuscle belly substance were explored grossly and microscopically. It appears that one type of acute strain injury occurs in the midmuscle belly with disruption of the muscle-tendon junction of the intra muscular tendon resulting in local hemorrhage and edema. More chronically, this hematoma organizes into a fatty, loose connective tissue encasement of the deep intramuscular proximal tendon. Serous fluid from the hematoma may remain within the connective tissue sheath, creating a pseudocyst with the deep intra muscular tendon of the indirect head at its center. The muscle's anatomy helps to explain a different rectus femoris strain injury

Incomplete, Intrasubstance Strain Injuries of the Rectus Femoris Muscle

Rectus femoris muscle strain injuries commonly occur at the distal muscle-tendon junction of the quadriceps tendon. However, we have recently recognized a pat tern of strain injury that consists of an incomplete in trasubstance tear at the muscle-tendon junction formed by the deep tendon of the muscle's indirect head and those muscle fibers originating from this tendon. These injuries are found more proximally within the thigh than the "classic" distal rectus femoris muscle strain. We re viewed 10 athletes with these intrasubstance tears, all of whom had diagnostic imaging performed using com puted tomography or magnetic resonance imaging or both. Two of these patients required surgical interven tion. The mechanism of injury usually involved kicking or sprinting. All patients had chronic thigh pain or an anterior thigh mass or both. Physical examination re vealed thigh asymmetry and a nontender to mildly ten der intrasubstance muscle mass. Magnetic resonance imaging demonstrated abnormal signal intensity cen tered about the intramuscular tendon of the indirect head of the muscle. Surgical findings included a mass of fibrous scar and fatty tissue encasing the deep ten don. Surgical removal of this fibrous mass appears curative. We contrast this injury from distal strains of the rectus femoris muscle, as well as from soft tissue neoplasms