Clinical History: A 20 year-old skater complains of chronic pubic pain radiating to the left groin. (1a) Fat-suppressed T2-weighted coronal, (1b) proton density-weighted axial, and (1c) proton density-weighted sagittal images are provided. What are the findings? What is your diagnosis?
Moderate osteitis pubis with an associated chronic partial avulsion of the left common adductor-rectus abdominis aponeurosis and adductor longus tendon origin.
Groin injuries are common in athletes that require rapid changes of direction, repetitive side-to-side ambulation, frequent forceful twisting of the trunk, and kicking. Soccer, ice hockey, and American and Australian rules football are among the sports with the highest incidence of groin injuries. Groin injuries tend to recur and can lead to significantly reduced playing time and a shortened career. Generally defined, “groin injuries” involve the anatomy at or arising from the symphysis pubis region and encompass both inguinal regions, extending inferiorly to involve the proximal aspect of the adductor compartment of both thighs1. The anatomy centered at the pubis is complex and very closely integrated with multiple tendinous and ligamentous insertions which contribute to anterior pelvic stability. Because of the complex anatomy in this region, multiple varied treatment options have been employed for athletic-related groin pain, often with little understanding of the underlying anatomic defect. Not surprisingly, these differing approaches have resulted in a broad range of outcomes. An improved understanding of the anatomy at the symphysis pubis and the underlying pathophysiology has allowed more focused therapy and has resulted in improved outcomes.
Anatomy and Biomechanics
The symphysis pubis is stabilized by the underlying articular surface anatomy, pubic ligaments, and by the dynamically balanced musculotendinous insertions from the adductor muscle group and abdominal wall muscles. These structures merge as they insert anterior to the pubis. In turn, this anatomic region provides an anchor for motion of the trunk and adduction of the thigh.
The pubic bone is divided into the body, located medially, and the superior and inferior pubic rami. The bodies vary in appearance depending on the patient’s age. In athletes under 21 years of age, anteromedial foci of enchondral ossification are common (3a) and enhance after gadolinium administration1. The pubic crest arises from the anterosuperior body and projects anteriorly. The pubic tubercle is found at the lateral extent of the pubic crest. At the symphysis pubis, the articular surfaces of the pubic bones have alternating ridges and grooves providing added resistance to vertical shearing forces across the symphysis pubis. The medial portions of the paired pubic bodies are hyaline covered and articulate with a fibrocartilaginous disc at the symphysis pubis. This fibrocartilaginous disc blends with the overlying ligamentous structures as well as the aponeurosis of the adductor longus and rectus abdominis2, and serves to dissipate compressive and shearing forces at the symphysis pubis to the more posterior portions of the pelvis. In approximately 10% of adults, a small fluid-filled cleft is present in the posterosuperior portion of the fibrocartilaginous disk and is believed to be a developmental variation3.
The inferior pubic (arcuate) ligament is the most important ligament providing stability across the symphysis4. It extends along the inferior margin of the symphysis pubis and blends with the articular disc as well as the aponeurosis of the adductor longus and gracilis muscles. The superior pubic ligament extends between the pubic tubercles and provides stability against shearing forces at the symphysis pubis. The anterior pubic ligament blends with the fibrocartilaginous disc and also blends with the aponeurosis of the external oblique and rectus abdominis muscles, as well as fibers from the adductor longus and brevis2. The posterior pubic ligament is poorly defined and provides little functional support.
The muscle groups that attach to the symphysis pubis include the anterior and anterolateral abdominal muscles and the thigh adductor muscle group. The abdominal muscles attaching at the symphysis are the external and internal oblique muscles, the transversus abdominis, and the rectus abdominis. The adductor muscles arising from the symphysis are the pectineus, gracilis, adductor longus, adductor brevis, and adductor magnus. Of these muscles, the rectus adbdominis and the adductor longus are most important for maintaining anterior pelvic stability5. The rectus abdominis is covered by the anterior rectus sheath which attaches to the periosteum of the pubic bone anterior and adjacent to the rectus abdominis muscle. The rectus abdominis arises as a medial and lateral head. The medial heads blend inferiorly, merging with the anterior pubic ligament4. The lateral head is broader, arising from the pubic crest and pubic tubercle and blends with adductor longus tendon and ligamentous tissue anterior to the pubic body (E,F). At the craniad extent, the rectus abdominis attaches to the 5th through 7th costal cartilages and xiphoid process. The rectus abdominis assists in flexing the trunk, supplies muscle tone to the ventral abdominal wall, and acts as an anatagonist to the diaphragm6. The adductor longus lies posterior and medial to the pectineus muscle and is the most anterior of the adductor muscles. The adductor longus arises from the anterior pubic body below the pubic crest via a consistently seen tendon and a deeper, more variable muscular attachment 7(4a,5a). The adductor tendinous and muscular origins demonstrate variable attachment to the parasymphyseal ligamentous tissues1. The paired adductor longus tendons merge across the midline, giving rise to the so-called “moustache” configuration1(4a). The adductor longus assists in adduction of the thigh, hip flexion, and medial rotation of the hip8. It also helps stabilize the anterior pelvis during the swing phase of gait7.
The inguinal canal is an obliquely oriented tunnel traversing the inferior abdominal wall, containing the spermatic cord and vessels in males. The floor of the inguinal canal is formed by the inguinal ligament, which extends from the anterosuperior iliac spine to the pubic tubercle and is formed by the condensation of fibers from the external oblique aponeurosis. The anterior wall of the inguinal canal is formed by the external oblique aponeurosis, which splits distally and medially near its insertion at the pubic tubercle to form the external inguinal ring. The medial crus of the external inguinal ring inserts at the pubic tubercle and merges with the adjacent aponeurotic and ligamentous complex anterior to the pubis. The posterior wall of the inguinal canal is formed by the transversalis fascia. A defect in this fascia forms the internal inguinal ring. Medially the posterior wall of the inguinal canal receives additional support from the lowermost fibers of the internal oblique and transversus abdominis muscles, which primarily insert onto the anterolateral aspect of the rectus sheath1( 5a). Components of the inguinal canal are thus stabilized by the inserting complex of tendons and ligaments at the pubis9.
The common adductor-rectus abdominis aponeurosis (CA-RA) is of critical biomechanical and pathophysiologic importance. This aponeurosis is composed of the tendons of the adductor longus and rectus abdominis muscles, which blend and insert on the anterior pubis10 (5a,6a). In addition, cadaver and MRI studies demonstrate that the CA-RA interweaves with ligamentous tissue at the symphysis pubis and subjacent fibrocartilaginous disk1. This interrelated anatomy allows several patterns of injury. Because the adductor longus and rectus abdominis muscles act as antagonists across the pubis, injury to one of these tendons alters the biomechanical stability at the anterior pelvis and may also compromise the integrity of the common aponeurosis, thus predisposing the opposing tendon to injury. Tears of the rectus abdominis or adductor longus attachment most commonly extend to involve the aponeurosis. The unopposed tendon weakens through degeneration and tearing, eventually leading to confluent tears extending across the aponeurosis and both tendon attachments. Tears of the aponeurosis may extend into other adductor tendon origins, most commonly undermining the pectineus and adductor brevis origins, or they may cross the midline affecting the contralateral aponeurosis5. Ultimately, such a series of injuries may lead to instability of the pubic symphysis4.
“Athletic pubalgia” is a general term that encompasses a wide range of injuries at the symphysis pubis that share a similar injury mechanism and clinical presentation of exertional pubic and groin pain5. Groin pain most commonly develops insidiously, but may present acutely with a clinical history of a sudden tearing sensation. Symptoms are most often unilateral but may be bilateral. The patient typically experiences pain during exercise, complaining of discomfort in the inguinal region over the distal rectus abdominis, in the perineum, or radiating to the testicles. On physical examination, the patient may experience pain with resisted hip adduction or resisted sit-ups4. Local tenderness may be elicited at the attachments of the adductor longus or rectus abdominis or over the external inguinal ring, and Valsalva maneuver may cause pain.
Because of the complex anatomy in the pubic region and the variety of injuries that may be encountered, MR imaging is recommended in 3 planes. Water-sensitive STIR or fat-suppressed T2-weighted images optimally display recent muscle and tendon injuries. In particular, sagittal images are most helpful in depicting the CA-RA aponeurosis (6a). Water-sensitive sequences detect increased marrow signal abnormalities within the pubis associated with stress-related changes, avulsive marrow edema, bone bruise or fracture. T1-weighted images are most helpful in depicting anatomy.
A wide range injuries may be encountered involving the symphysis pubis and inserting structures. Strains or small tears of the muscles and tendons are most common and demonstrate increased intramuscular and intratendinous signal on water-sensitive sequences (7a).
Isolated tears of the adductor longus or rectus abdominis tendons are evident as fluid-signal filled defects in the tendons. In the acute phase surrounding hemorrhage and edema and coexisting muscle strains are present. Musculotendinous injuries at the pubis most commonly involve the adductor muscle group, with the adductor longus being the most commonly injured5. Proximal adductor longus tendon tears at the pubis frequently extends to involve the aponeurosis (8a).
In the distal rectus abdominis, the lateral attachment is most frequently injured4. Axial images best demonstrate interruption of the distal rectus abdominis tendon just cephalad to its attachment to the pubis (9a). Chronic injuries of the rectus abdominis muscle or tendon may result in muscle asymmetry (10a).
Avulsion injuries or tears of the CA-RA aponeurosis are seen as fluid signal interposed between the aponeurosis and subjacent bone. These may be detected as small microtears on sagittal imaging. These injuries are often chronic, associated with repetitive trauma and are often of uncertain clinical significance. When there is associated subjacent localized marrow edema, these small tears are more likely to be symptomatic (11a). More extensive injuries at the aponeurosis may be encountered with complete avulsion in severe cases (12a,13a).
The secondary cleft sign was originally described as an arthrographic finding following injection of the symphysis pubis, with abnormal inferior extension of contrast from the central symphyseal fibrocartilaginous cleft, and was felt to represent a microtear of the adductor longus and gracilis tendon origins. An MRI equivalent of the secondary cleft is visible on fluid-sensitive sequences as a curvilinear fluid-signal interface that is continuous with the symphysis pubis and undermines the inserting structures at the pubis9. Although the exact etiology of the secondary cleft remains to be elucidated, this most likely represents a tear of the adductor longus origin and CA-RA aponeurosis11 and because of the interrelated anatomy may extend bilaterally (14a).
Osteitis pubis is most commonly seen in athletes participating in kicking sports such as soccer or Australian rules football. It is believed to result from instability of the pubic symphysis associated with repetitive shear and distraction injuries and an imbalance of the forces applied by the inserting abdominal wall and adductor muscle groups4. Indeed, osseous changes at the symphysis pubis frequently accompany injuries of the tendons and aponeurosis of the adductor longus and rectus abdominis (as in the test case), and in some cases these tendinous and aponeurotic injuries precede the clinical and MR findings of osteitis pubis4. The earliest sign of osteitis pubis is diffuse subarticular marrow edema bordering the symphysis pubis, which is typically bilateral and generalized (15a). Periostitis, bony resorption, subchondral cysts and osteophytes are seen in more advanced conditions (16a).
Sportsman’s Hernia is a popular but nonspecific term generally applied to conditions which present with pain in the medial inguinal region in the athlete. Initially, these symptoms were felt to represent injury along the inguinal canal with injuries of the superficial inguinal ring, posterior inguinal wall, and even discrete hernia formation. Although these injuries may in fact be the result of direct injury to the structures forming the inguinal canal, more commonly they are the result of injury at the adductor longus-rectus abdominis aponeurosis. Given the close proximity and interrelated nature of these structures, tears of the lateral rectus abdominis or rectus sheath, in some cases, may weaken the internal oblique and transversus abdominis components of the posterior inguinal wall, or of the external oblique aponeurosis at the superficial inguinal ring. True inguinal hernia is a rare cause of pain in the athletic population. Herniation of bowel or peritoneal fat as indirect or direct hernia expands the inguinal canal and is readily depicted on MRI (17a). Injuries of the posterior inguinal wall or inguinal ring without hernia are rarely detected by MRI except in the acute setting when hemorrhage and edema may be present (18a). Occasionally anterior displacement of the posterior inguinal wall and spermatic cord may be detected1, but dynamic sonography is the preferred method of detecting posterior wall deficiency12.
Treatment strategies for patients with groin pain are evolving, guided by an improved understanding of the biomechanics of the anterior pelvis and a more focused imaging approach. Non-operative treatment is often successful with isolated tendon or musculotendinous strains. In more severe injuries, steroid injections of the symphysis pubis or adductor tendons may be utilized, but since the steroid injection does not address the underlying injury, symptoms frequently recur with resumption of athletic activities. Surgery is considered if non-operative treatment fails after 6-8 weeks. Hernia repair without a detectable hernia has reported variable success rates with either a conventional or laparoscopic approach, commonly using mesh to repair and reinforce the abdominal wall. Some authors suggest that success in these patients may result from scarring of the inserting structures in the pubic region that secondarily stabilizes the unrecognized symptomatic anatomic defect13. Current surgical treatment is focused on correcting the underlying anatomic defect and stabilizing the anterior pelvis. These targeted repairs have resulted in improved outcomes13,14. Pelvic floor repair with reattachment of the lateral margin of the rectus abdominis tendon at the pubis has been associated with some of the highest success rates. Depending on associated injuries, adductor tendon release or tenotomy may also be performed. Isolated full-thickness adductor tendon avulsions are typically surgically reattached.
Osteitis pubis is initially managed by NSAID therapy and physical rehabilitation. Steroid injections are considered as the next line of therapy15. Symphyseal arthrodesis is reserved for patients failing conservative measures5.
Athletic pubalgia comprises a common group of injuries which potentially affect multiple musculotendinous and ligamentous structures of the pubic region. The complex, interrelated anatomy and the similarity of clinical symptoms often lead to diagnostic confusion. MRI allows direct visualization and assessment of the key anatomic structures in the pubic region, enabling a more focused treatment approach and improved outcomes for the affected athlete.
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