Adductor Muscles Injuries

Fig. 14.1

A 28-year-old male athlete with an injury to the myotendinous junction of the left adductor longus (AL). (a) Coronal and (b) axial short tau inversion recovery MRI show intrasubstance high signal intensity (arrow) at the proximal portion of the left AL, distant from its osseous attachment, consistent with an injury to the myotendinous junction

Fig. 14.2

A 20-year-old male athlete with a tear of the right adductor longus at the proximal myotendinous junction. (a) Coronal and (b) sagittal short tau inversion recovery MRI show a tear at the myotendinous junction with retraction of the proximal fibers (arrow). Note the presence of hemorrhage delineating the torn muscle (asterisk)

Fig. 14.3

A 24-year-old male athlete with an intrasubstance tear of the right pectineus muscle. (a) Axial, and (b) coronal short tau inversion recovery MRI show right pectineus muscle is enlarged and displays intra-substance high signal intensity interspersed within muscle fibers (arrow), in keeping with muscle strain. The proximal attachment of the right pectineus is intact

MR findings of acute muscle strain include enlargement and increased signal intensity in fluid-sensitive sequences dissecting muscle fibers, resulting in “feathery edema” appearance. Perifascial edema can also be seen. These abnormalities may outline adjacent femoral neurovascular structures, given the proximity of the adductor canal [24].

Associated hemorrhage may appear as fluid-like intensity tracking along fascia and muscle fibers. Hematoma appears as a homogeneous fluid collection in the early phase. Long-standing organized hematomas tend to be more heterogeneous. Chronic injuries may show fibrous scarring, which appears as hypointense fascial thickening in fluid sensitive images. In ultrasound, there is loss of the normal pennate appearance of the muscle, with areas of altered echogenicity, and loss of perimysial striation adjacent to the myotendinous junction. In complete tears, interruption and retraction of muscle fibers can be seen usually with surrounding fluid collection corresponding to hematoma [25].

Recurrent and chronic adductor muscle strain, extensive intermuscular fluid and intramuscular edema can cause an “exercise-induced compartment syndrome” [12]. If suspected, axial T2-weighted images should be acquired before and after exercise to compare the degree of mass effect [12].

14.4.1.1 Baseball Pitcher-Hockey Goalie Syndrome

Rarely the AL can be herniated through its epimysium, causing a prolonged course of pain. This entity called “baseball pitcher-hockey goalie syndrome” may be seen along with a chronic or repaired injury to the RA-AL aponeurosis [12, 14]. It is thought that an epimysial defect may result from chronic repetitive stress at the sites of relative weakness, such as entry points of neurovascular structures [14, 26]. Although this injury occurs distal to the tendon insertion, patients often report groin pain [6] – likely because of associated RA-AL injury. A detailed medical history (acute onset of pain worse after stretching) and careful physical examination (site of pain distal to the pubic symphysis, over the herniated area) may suggest this diagnosis [6]. MRI findings are not well described although one may see focal edema in the AL muscle belly, with a focal bulge at the site of herniation [27]. “Baseball pitcher-hockey goalie syndrome” is reported to respond poorly to conservative management and treatment of recalcitrant pain requires surgical epimysiotomy and debridement [6].

14.4.2 Adductor Injury of the Tendon and Enthesis

Because of the anatomic complexity of the groin region, and intimate relationships of tendons from different muscle groups at this level (such as the iliacus and adductor), there is much confusion about the terminology used to designate the clinical entity related to adductor tendon and insertion injuries. Terms such as athletic pubalgia, osteitis pubis, and sports hernia have been used [28]. To overcome this confusion, a group of experts in sports medicine met in Doha in 2014 to reach an agreement on the definitions and classifications of different entities that cause groin pain [29]. They concluded by suggesting the term “adductor-related groin pain”, defined as tenderness and pain on resisted adduction testing at the insertion sites of adductor muscles [29].

Two prospective studies have used clinical examination and imaging for diagnostic confirmation of diagnosis of acute adductor-related groin pain [3, 30]. Only the more recent study by Serner et al. included MRI findings [3]. Among 110 athletes with acute groin injuries, Holmich et al. found a high prevalence of clinically defined adductor injuries (73 individuals, 66 %) [3]. However, only 54 of the 73 (73 %) were examined with MRI, which showed the AL to be most commonly affected (50 cases, 93 %), followed by the pectineus (10 cases, 19 %), and adductor brevis (9 cases, 17 %). One gracilis and one adductor magnus were affected (2 %) [3]. The same study showed a better correlation between clinical and radiological findings for clinically diagnosed adductor-related groin pain when compared with injuries to the iliopsoas, rectus femoris and sartorius. When multiple adductor muscles are involved, injuries of the AL, adductor brevis and pectineus are often combined [3]. Avulsion and retraction of the AL should prompt assessment of the caudal RA, as these injuries are often seen concurrently [14]. Unfortunately very little is known about diagnostic reliability of cross-sectional imaging for adductor injuries [4].

A recent review of the literature reported four main consistent radiological findings for long-standing symphyseal and adductor-related groin pain across studies: pathology of the adductor muscle insertions, pubic bone marrow edema, the “secondary cleft sign”, and degenerative changes of the symphyseal joint [4].

14.4.2.1 Pathology of the Adductor Tendons

On MRI the affected tendons, mostly the AL, may show several findings including edema, contrast enhancement following gadolinium injection [31–33], and partial or total disruption, i.e. avulsion. In this case there is retraction of the distal portion of the tendon with associated fluid signal collection at the site of rupture, related to hematoma (Figs. 14.4, 14.5, and 14.6). Robinson et al. reported that abnormal enhancement at the site of enthesis shows good correlation with the site of pain [32]. In chronic injuries, tendon thickening can be seen [6, 34]. In this case, there is enlargement and hypointense signal of the tendon on fluid-sensitive images with possible focal rounded hypointensity representing hydroxyapatite deposition tendinosis [6, 14].

Fig. 14.4

A 21-year-old male athlete with avulsion tears to the right adductor longus (AL) and brevis muscles. (a) Coronal and (b) axial short tau inversion recovery MRI show complete discontinuity with retraction of the proximal attachment of the right AL (blue arrow) surrounded by fluid, consistent with hemorrhage (asterisk). In the axial image, the tendon rupture appears to involve the adductor brevis (b), as suggested by the irregularity of its anterior surface (red arrow)

Fig. 14.5

A 19-year-old male athlete with tenoperiosteal detachment of the rectus abdominis-adductor longus (RA-AL) aponeurosis. (a) Axial and (b) coronal short tau inversion recovery MRI show avulsion of the proximal tendon of the left adductor longus (AL) with tenoperiosteal detachment of the RA-AL aponeurosis (red arrow) from the pubic tubercle (P). The tear extends to the distal rectus abdominis attachment (blue arrow). Note fluid signals tracking along the torn AL muscle (asterisk), consistent with hemorrhage

Fig. 14.6

A 31-year-old male athlete with adductor longus (AL) proximal tendon avulsion and detachment of the rectus abdominis-adductor longus (RA-AL) aponeurosis. (a) Coronal and (b) sagittal short tau inversion recovery MRI show avulsion of the proximal tendon of the left AL with an osseous defect at the left pubic tubercle (red arrow). Sagittal image shows tenoperiosteal detachment of RA-AL aponeurosis (blue arrow)

On ultrasound, detection of tendon changes is made easier by comparing the contralateral side. Unfortunately changes appreciated by ultrasound in adductor injuries are not always distinguishable from uncomplicated tendinosis or normal variations in athletes. Color Doppler imaging may show hyperemia, but it is not a consistent finding [13].

RA-AL Aponeurosis Injury

Adductor tendon avulsion is most commonly associated with injury to the RA-AL aponeurosis, which in turn can predispose to large multitendon adductor tears. For this reason, careful assessment of any small detachment of the RA-AL aponeurosis is necessary in case of injury to the AL tendon [12]. This occurs lateral to midline, at the attachment site to the pubic tubercle. This tenoperiosteal disruption may be most visible on axial and sagittal fluid-sensitive images acquired approximately 1–2 cm lateral to the pubic symphysis, where it appears as irregular areas of fluid signal intensity undermining the aponeurosis (Figs. 14.5 and 14.6) [6]. Unilateral RA-AL aponeurosis lesions can range in severity from very small lateral edge detachments to severe distractive tears with the RA retracted cephalad and AL retracted distally into the medial thigh. Chronic unilateral RA-AL lesions may manifest on MRI as atrophy of the RA in cross section just above the pubis, or as mild asymmetric bone marrow edema at the pubic tubercle in the smaller field of view sequences. When a tear to the proximal adductor insertion is diagnosed, it is crucial to look for an associated RA injury, as treatment of the adductor injury without addressing the RA can lead to recurrence and protracted pain [12].

Recently, Coker and Zoga described a subset of severe RA-AL aponeurosis tears that combines pectineus and AL avulsion, termed “combined anterior adductor avulsion lesion” [12]. Although the MRI appearance is dramatic, the combined avulsed tendon group can be reduced and fixed with relative ease with surgery, and athletes often return to play within 8 weeks [12]. In contrast, organized soft tissue hematoma in the setting of high grade RA-AL aponeurosis lesions can serve as a harbinger of delayed return to activity, and collections can localize superficial to the pubis, insinuate into the inguinal canal, or even extend into the peritoneal cavity. Coronal oblique images are often very useful in localizing fluid collection with regard to the inguinal canal.

Midline Pubic Plate Lesion

In addition to the RA-AL aponeurosis detachment, there is another dominant pattern of injury, which occurs at the midline anterior to the pubic tubercle. This injury pattern is termed “midline pubic plate lesion”, and often extends through the lateral edge of RA-AL aponeurosis, unilaterally or bilaterally [12]. Other associated injuries are also often asymmetric, including secondary cleft, bone marrow edema and osseous resorption. This asymmetry correlates with clinical findings with pain usually predominant on the side of greater bone marrow edema or osseous resorption [12].

Incipient Breach

Another MR feature was recently described by Coker and Zoga, the “incipient breach”, which is thought to occur at the early stage of midline pubic plate lesions. Sagittal fluid-sensitive MRIs reveal a very small detachment of the fibrous plate at midline from the anterior aspect of the symphyseal capsule with disruption of the antero-inferior pubic symphysis. It is hypothesized that the incipient breach may indicate the site of initial injury, which is potentially helpful for repair [12].

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