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February 2010 Case of the Month



Compiled by: Masood A. Siddiqui, D.O.                                                                                                         


History:
17-year-old male who felt a pop in right groin on 09/13/2009 while playing football. Continuouspain in the right groin. No swelling or lump. Evaluated for a muscle tear.

Exam: Figs 1 and 2 are axial and coronal STIR images obtained on a 0.7 T open magnet.


Findings: Inflammation at the pubic symphysis with tenoosseous pealing of the right adductorlongus/pectineus (Figs 1 and 2). No evidence of osseous or ligamentous injury.

Images:

Figure 1

Figure 2

Diagnosis
Pubic symphysitiswithtenoosseouspealingof the right adductorlongus/pectineus. Findings are within the spectrum of the sports hernia complex
 

Discussion: Groin pain is a common result of athletic injury, but it poses a diagnostic challenge for radiologists, athletic trainers, team physicians, and consulting surgeons. Athletes in sports that rely on quick acceleration, rapid changes in direction, kicking, and frequent side-to-side motions (eg, soccer, ice hockey, American- and Australian rules football, fencing, track and field events such as high jumping, and baseball) may be subject to injuries that lead to groin pain. Between 2 and 8 percent of all athletic injuries involve the groin, and up to 13 percent of soccer injuries are groin related. According to one report, 58 percent of soccer players have a history of groin injury. 


Clinically, athletes frequently present pain in the inguinal region, which may radiate to the thigh adductor muscle origins or to the scrotum and testicles. At physical examination, point tenderness is often localized to the external ring of the inguinal canal and the pubic tubercle, the lower rectus abdominis musculature, or the pubic symphysis, but there is no palpable hernia. Although groin injuries may be acute, they more often have an insidious onset and progress over a period of weeks or months. They are a significant cause of missed practice and playing time. Although many acute groin injuries are successfully treated with a conservative regimen including rest and a nonsteroidal anti-inflammatory drug (NSAID), groin injuries often reoccur and may lead to the premature termination of athletic careers. 

 

The pathophysiologic causes of groin pain are complicated and poorly understood. First, the anatomy of the pubic symphyseal region includes a number of interrelated muscle attachments that are located in close proximity. The interrelation of these muscle attachments causes complex interactions between the forces exerted across the pubic symphysis. Second, the differential diagnosis of groin pain in athletes is extensive because various pathologic entities may cause similar clinical signs and symptoms (Table 1). Third, patients may be unable to precisely locate their pain or recall the mechanism of injury. They may also present with multiple coexisting injuries, making it difficult to establish which injury is the major contributor. 

 

Given these complexities, both conservative management and numerous invasive therapies, including herniorrhaphy, adductor tenotomy, pelvic floor relaxation, and surgical repair of the posterior wall of the inguinal ring, have been applied with variable success to treat refractory groin pain. The terms used in the literature to describe this condition include sports hernia, sportsman’s hernia, athletic pubalgia, Gilmore groin, hockey goalie syndrome, adductor dysfunction, and osteitis pubis—likely adding to confusion in the diagnosis and treatment of groin pain. 

 

Normal Anatomy of the Pubic Symphysis

The pubic symphysis is an amphiarthrodial joint composed of the paired pubic bones and an intervening articular disk. The pubic bone forms the anterior portion of the innominate bone and is divided into the body, which is located medially and the superior and inferior pubic rami. The medial border of the body forms the articular surface of the pubic symphysis. This surface is ovoid, covered by a thin layer of hyaline cartilage, and composed of transversely oriented alternating ridges and grooves that may help protect the joint from shear forces. From the upper margin of the body arises the pubic crest, which projects over the anterior surface of the body. The pubic tubercle, on which the inguinal ligament attaches, is an osseous process emerging from the lateral margin of the pubic crest. The rami are osseous struts radiating laterally from the pubic body. The superior pubic ramus contributes the anterosuperior one-fifth of the acetabular fossa as well as a portion of the obturator foramen, while the inferior pubic ramus bridges the pubic body and ischium.

 

There is no true joint capsule, although the articular disk and four ligaments provide soft tissue support to the osseous structures of the pubic symphysis. The interpubic disk is a fibrocartilaginous structure that is critical to the function of the pubic symphysis. It is interposed between the ridges and grooves of the pubic symphyseal articular surfaces, and its main function during normal motion is to absorb and dissipate axial and shear forces experienced at the joint. Approximately 10 percent of adults have a fluid-filled posterosuperior cleft located in the central portion of the disk. This cleft is not seen in children younger than two years and is believed to be developmental.

 

Functionally, the superior and arcuate (or inferior) pubic ligaments are more important, particularly for resisting shear forces, than the anterior and posterior pubic ligaments. The superior pubic ligament bridges the pubic tubercles. The arcuate ligament forms a fibrous arch along the inferior margin of the joint and blends with the articular disk. The arcuate ligament also merges inferiorly with the aponeuroses of the gracilis and adductor longus muscles. The anterior pubic ligament is composed of a deep layer that merges with the articular disk and a superficial layer that blends with the aponeurosis of the external oblique and rectus abdominis muscles. The least developed ligament is the posterior pubic ligament, which is formed by relatively few transversely oriented fibers. 

 

The pubic symphysis has a number of important functions. First, it stabilizes the anterior pelvis, while allowing a small degree of movement (up to 2 mm in the craniocaudal direction and up to 3.0° of rotation during walking). The large contact area of the joint allows an even distribution of the superior and inferior shear forces generated during walking and running, helping protect the joint from injury. The rami also help perform this function by transmitting compressive forces generated at the symphysis to the remainder of the innominate bone. In women, laxity of the pubic symphysis under hormonal influences plays an important role in childbirth, allowing passage of the neonate through the birth canal.

 

Muscle Anatomy and Biomechanics of the Pubic Symphysis

The pubic symphysis is the centerpoint of numerous musculotendinous attachments that act to dynamically stabilize the position of the anterior innominate bone. The muscles that attach to the symphysis include the anterolateral abdominal muscles (external and internal oblique muscles, transversus abdominis, and rectus abdominis) and the thigh adductor muscles (pectineus, gracilis, adductor longus, adductor brevis, and adductor magnus). Of these, the most robust and critical for maintaining the stability of the anterior pelvis are the rectus abdominis and the adductor longus (Diagram).

 

Athletic Pubalgia

Groin pain and pubalgia have long been recognized as significant causes of injury in high-level athletes. Most patients report an insidious onset of pubic and deep groin pain that is exacerbated by physical activity and that may radiate to the inguinal ligament, rectus abdominis, and perineum. Symptoms are most often unilateral but are not uncommonly bilateral. Patients may experience alternating episodic exacerbations and periods of improvement, or they may have gradually progressive symptoms. Most patients have symptoms for months or years before a clinical diagnosis is obtained. Physical examination frequently reveals pain with resisted hip adduction or sit-ups, as well as focal tenderness at the pubic attachment of the rectus abdominis or adductor longus muscle or at the external inguinal ring. 

 

The terms sports hernia and sportsman’s hernia were first used to describe inguinal pain experienced by athletes without evidence of an actual hernia at physical examination. Many authors initially used the term to refer to a weakness in the posterior wall of the inguinal canal, believing that this represented an incipient inguinal hernia. The exact location of this weakness or tear was disputed; some authors favored the external oblique muscle aponeurosis and conjoined tendon, while others believed it was in the transversalis fascia. In an effort to strengthen the posterior wall of the inguinal canal, several authors performed herniorrhaphies with various surgical techniques in their patients. Although many patients improved after this surgical treatment, the overall results were mixed. Other authors proposed nerve entrapment, particularly of the cutaneous branches of the ilioinguinal nerve and the genital branch of the genitofemoral nerve, as the causal mechanism of pain in sports hernias. These authors suggested that surgical manipulation of this area during hernia repair might release the entrapped nerve and thus bring about a resolution of symptoms. 

 

Although some patients experience pain relief after herniorrhaphy with standard techniques, many others either experience little or no improvement in groin pain or develop recurrent symptoms that are detected at long-term followup. Because of this, other authors have suggested that the fundamental pathologic process in athletic pubalgia is unrelated or only marginally related to inguinal herniation. The association of this process with herniation may be misleading, and surgery performed to repair an inguinal hernia may not necessarily address the cause of groin pain.

 

Several articles have proposed the use of the term athletic pubalgia rather than sports hernia to refer to a group of musculoskeletal processes that occur in and around the pubic symphysis and that share similar mechanisms of injury and common clinical manifestations. These authors have attributed the findings to chronic repetitive torque on the pubic symphysis during aggressive abduction of the thigh and hyperextension of the trunk. Most commonly, such movements injure the common aponeurosis of the rectus abdominis and adductor longus tendons, which is located along the anterior aspect of the pubic symphysis, and may lead to eventual avulsion of the tendon and a tear in the aponeurosis. 

 

At MR imaging and surgery in patients with clinical athletic pubalgia, injury is most commonly observed along the lateral border of the rectus abdominis, just cephalad to its pubic attachment, or at the origin of the adductor longus. After an injury to either the rectus abdominis muscle or the adductor muscle, there is a repetitive unbalanced contraction in the other muscle. It is postulated that the lack of opposing force leads to degeneration and tearing of the tendon not initially torn. Ultimately, the lesion extends confluently through the aponeurosis into both the rectus abdominis and the adductor longus. Most commonly, the extension of the lesion under the pubic periosteum causes frank disruption of the rectus abdominis-adductor longus aponeurosis from its pubic attachment. In other cases, the injury may extend into the adductor tendon origins, particularly the pectineus and adductor brevis, or may extend along the anterior pubic symphysis and across the midline to involve the contralateral rectus abdominis-adductor longus aponeurosis.

In a severe injury, the tendons may be completely avulsed from the pubis. In most patients with clinical athletic pubalgia who are
referred for MR imaging, changes are detected in the area of the pubic symphysis that represent pathologic processes that often have similar clinical manifestations; however, the detection of a true hernia is rare. Groin pain in patients with clinical athletic pubalgia may result from the initial injury to the tendon or aponeurosis as well as chronic repetitive injury to the opposing, adjacent, or contralateral tendons or the destabilized pubic symphysis. Hernia-like symptoms may be related to the proximity of the injury site to the medial margin of the superficial ring of the inguinal canal or to lesion extension through the superficial ring and resultant weakening of the posterior wall of the inguinal canal.

 

Patients with MR imaging findings and surgical findings of athletic pubalgia are predominantly male and generally under the age of 40 years. It has been suggested that the male predominance of athletic pubalgia is related to a disparity between the sexes in athletic participation or to the generation of stronger forces around the pubic symphysis in male athletes. An increasing number of female athletes around the world participate in professional and amateur sports that require quick acceleration and deceleration and side-to-side movements, yet the disparity between the numbers of male and female athletes with clinical athletic pubalgia persists. Informally, we have observed that female patients generally have larger and more robust caudal rectus abdominis attachments, with a convergence of aponeurotic fibers from both sides as they cross the midline along the anteroinferior pubic symphysis, a situation not seen in most male patients. In addition, the female pelvis is wider and has a larger subpubic angle than the male pelvis, properties that may aid the transference of forces away from the pubic region to the rest of the innominate bones or the lower extremities. The anatomic and biomechanical differences in the female pelvic structure may help stabilize the pubic region and contribute to the relative infrequency of athletic pubalgia injuries in female patients

 

MR Imaging Technique and Findings of Athletic Pubalgia

Until recently, imaging was thought to be unreliable or of little use for the diagnosis of athletic pubalgia, and MR imaging was used mainly to exclude other possible causes of groin pain, such as stress fracture or acetabular labral tear. However, improved knowledge about anatomic structures, pathophysiologic changes, and clinical findings associated with athletic pubalgia has allowed improved imaging techniques. Centering the MR imaging on the pubic symphysis and the use of a phased-array pelvic surface coil help greatly improve the signal-to-noise ratio in the anterior pubic region. Patients should empty their bladders before the exam. Imaging usually can be performed with the patient supine. Prone positioning may be necessary to eliminate significant respiratory artifacts, but such instances are rare in our experience.

 

Since it may be difficult to clinically distinguish between the causes of groin pain (eg, an acetabular labral tear or athletic pubalgia), an MR imaging survey of the pelvis is recommended during the initial evaluation. Immediate review of the large-field-of-view images as they are acquired may reveal particular regions of suspected pathologic change and help direct further high-resolution small-field-of-view imaging. 

 

The combined use of non-fat-suppressed T1-weighted and fat-suppressed fluid-sensitive sequences is recommended. Because a number of relevant muscles are attached to a small area on the anterior pubic symphysis, fluid-sensitive sequences in the three standard orthogonal planes may be helpful. An axial oblique sequence has been described that allows visualization of the adductor tendon origins along their long axes; images are obtained in off-midline sagittal planes parallel to the arcuate line of the pelvic inlet.

 

While frequently the diagnosis is achieved with conventinal imaging planes, axial oblique images may help improve diagnostic certainty about symphyseal changes and may better depict pathologic processes such as true inguinal herniation. 

 

Once injury to the pubic region is confirmed or pathologic change in more remote areas is excluded on large-field-of-view images, dedicated imaging of the anterior pubic musculoskeletal structures is recommended to better characterize the location and severity of injuries. Frequently, images obtained with fluid-sensitive sequences allow direct visualization of tears involving the rectus abdominis-adductor aponeurosis, which appear as irregular areas with fluid signal intensity undermining the aponeurosis. This tenoperiosteal disruption may be most visible on axial and sagittal fluid-sensitive images acquired 1 – 2 cm lateral to the pubic symphysis.

 

Other findings that are commonly associated with an aponeurotic lesion are abnormal marrow signal isolated to the anterior-inferior pubic body and deep to the rectus abdominis-adductor aponeurotic attachment and the so-called "secondary cleft sign," an apparent inferior extension of the central symphyseal fibrocartilaginous cleft along the anteroinferior margin of the pubic body. The secondary cleft sign, which commonly appears on the side ipsilateral to the side of groin pain, is believed to reflect a microtear in the origin of the adductor longus and gracilis tendons. Although it was initially described at arthrography of the pubic symphysis, the secondary cleft sign is also visible on unenhanced MR images obtained with fluid-sensitive pulse sequences, where it appears as a curvilinear high signal intensity adjoining the pubic symphysis.

 

An aponeurotic lesion may appear as an edematous or atrophic rectus abdominis near its pubic tendinous attachment. Alternatively, there may be frank disruption of the tendon, particularly at the pubic attachment of its lateral head. The adductor tendons, most commonly those of the adductor longus, may be disrupted or thickened, with intermediate or high signal intensity indicative of tendinosis, and the myotendinous junctions may appear edematous. This constellation of MR imaging findings is sometimes observed in conjunction with osseous productive changes and subchondral cysts in the pubic symphysis. In some patients, the initial tendinous injury precedes clinical symptoms and MR imaging findings of osteitis pubis. In these patients, it is likely that the symphysis was destabilized after the initial aponeurotic injury, producing conditions that led to a secondary and potentially more symptomatic pubic symphyseal arthropathy. 

 

Although athletic pubalgia is uncommon in women, aponeurotic injuries in female patients tend to be more severe than those in male patients. In many male patients, aponeurotic injuries remain unilateral, whereas in female patients they frequently start from the midline and propagate to both sides.


Conclusion: A pelvic MRI, combined with high-resolution MR imaging of the pubic symphysis, affords an assessment for various causes of athletic pubalgia. MRI may demonstrate the location of injury and delineate its severity. Familiarity with the pubic anatomy, and with the MR imaging findings in athletic pubalgia and other causes of groin pain, allows accurate diagnosis and treatment.

Table 1: Differential Diagnosis of Groin Pain in Athletes

Visceral causes

Inguinal hernia

Other abdominal hernias

Testicular torsion

Hip-associated causes

Acetabular labral tear and femoroacetabular impingement

Osteoarthritis

Snapping hip syndrome and iliopsoas tendonitis

Avascular necrosis

Iliotibial band syndrome

Pubic symphyseal causes

Rectus abdominis strain

Adductor muscle-tendon dysfunction

Rectus abdominis–adductor longus aponeurosis tear

Osteitis pubis

Infectious causes

Septic arthritis

Osteomyelitis

Pelvic inflammatory disease

Prostatitis

Epididymitis and orchitis

Herpes infection

Inflammatory causes

Endometriosis

Inflammatory bowel disease

Pelvic inflammatory disease

Traumatic causes

Stress fracture

Tendon avulsion

Muscle contusion

Baseball pitcher–hockey goalie syndrome

Developmental causes

Apophysitis

Growth plate stress injury or fracture

Legg-Calvé-Perthes disease

Developmental dysplasia

Slipped capital femoral epiphysis

Neurologic causes

Nerve entrapment syndromes (eg, ilioinguinal nerve)

Referred pain

Sacroiliitis

Sciatic entrapment (piriformis syndrome)

Hamstring strain

Knee pain

Neoplastic causes

Testicular carcinoma

Osteoid osteoma




Diagram: Lateral schematic of the pubic soft-tissue anatomy shows the superficial ring of the inguinal ligament, located a few millimeters from the lateral margin of the rectus abdominis–adductor longus aponeurosis.  Yellow arrowheads indicate the directions of major force vectors to which the pubic bone is commonly subjected during sports.


References:

1. Omar et al. "Athletic Pubalgia and "Sports Hernia": Optimal MR Imaging Technique and Findings."RadioGraphics 2008; 28:1415–1438.

  

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