Core muscle injury is a common but difficult problem to treat. Although it can affect all individuals, it is most commonly seen in male athletes in cutting, twisting, pivoting, and explosive sports. Owing to the high association of femoroacetabular impingement, we believe these individuals are best treated with a multidisciplinary approach involving both orthopedic and general surgeons. Conservative treatment should be the first step in management. When conservative means are unsuccessful, operative intervention to correct all the pathologic issues around the pubis can have extremely high success rates.
Key points
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Core muscle injury is a difficult problem to diagnose and treat with an expansive differential diagnosis.
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Core muscle injury is best treated with a multidisciplinary approach involving physical therapists, athletic trainers, radiologists, and both orthopedic and general surgeons.
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Nonoperative management, including rest, a core strengthening physical therapy regimen, nonsteroidal anti-inflammatories, and oral or injectable corticosteroids are the first line in management.
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Upon failure of conservative treatment, operative intervention to treat all pathology around the pubis using several techniques has been shown to be extremely successful.
Introduction
Groin pain can be a difficult problem for patients as well as practitioners. Lower abdominal and groin injuries are among the most common causes of both pain and lost playing time in sports. These injuries affect athletes and nonathletes alike. Most lower abdominal and groin injuries are self-limited and only a small percentage cause symptoms for more than 3 weeks. However, there are still many that do not improve despite conservative management. The majority of symptomatic core muscle injuries requiring surgical management occur in male athletes who play soccer, hockey, football, basketball, skiing, or rugby. Core muscle injuries are also becoming increasingly recognized in the female athlete with women comprising about 5% to 15% of the injured population. The differential diagnosis is expansive, including musculoskeletal, genitourinary, and intra-abdominal pathologies. We believe that a multidisciplinary team approach to assess all patients with possible core muscle injury is important. This team involves athletic trainers, physical therapists, radiologists, operative and nonoperative sports medicine specialists, and a general surgeon with a special interest in abdominal wall disorders.
Terminology
Athletic pubalgia is an ill-defined term used in the literature. It is used to detail a constellation of symptoms that involve the inguinal region and core. Core muscle injury refers to damage to any skeletal muscle within the area between the chest and midthigh. One of the difficulties with diagnosing athletic pubalgia is an inconclusive agreed upon nomenclature. Nonspecific terms including sports hernia, sportsman’s hernia, sportsman’s groin, athletic pubalgia, sports pubalgia, incipient hernia, Gilmore groin, hockey groin, and core muscle injury have been used, among others. At our institution we have chosen to use the term core muscle injury. This terminology does not correlate with any anatomic structures, creating potential confusion for practitioners. Although none of these terms are perfect, they all seek to describe a poorly understood disease. Historically, much of the literature on core muscle injury has been outside of the orthopedic arena. More recently, there has been an increasing awareness for core muscle injury among orthopedists owing to the growing number of diagnoses among high-profile athletes.
History
Athletes presenting with a core muscle injury often report worsening groin pain located about the pubic symphysis, which may radiate into the lower abdomen or proximal adductors. Most patients describe an insidious onset of symptoms, but some recall a traumatic event involving a trunk hyperextension, hip hyperabduction mechanism. Activities that involve repetitive cutting, pivoting, kicking, sprinting, or sudden acceleration–deceleration movements typically incite the pain. Sports such as soccer, ice hockey, basketball, football, skiing, and rugby have been implicated as having a higher incidence of core muscle injury compared with other sports. The cessation of rigorous activity may temporarily alleviate the pain, but symptoms often return once the athlete returns to sport without treatment. The pain may also be aggravated by coughing, sneezing, or sit-ups, and it is not uncommon for the pain to radiate into the perineum, inner thigh, or testicles.
Anatomy and pathophysiology
A detailed understanding of inguinal anatomy is essential when evaluating the athlete presenting with a core muscle injury. Multiple musculotendinous, ligamentous, neurovascular, and bony structures converge in the inguinal region, which can make determining the specific underlying etiology a diagnostic challenge.
The rectus abdominis is a long, flat, paired muscle that spans the entire length of the anterior abdominal wall. It originates from the pubic symphysis, pubic crests, and pubic tubercles and it inserts onto the xiphoid process and costal cartilages of ribs V through VII.
The lower abdomen is organized into several distinct layers on either side of the rectus muscle ( Fig. 1 ). The most superficial layer beneath the skin and subcutaneous tissue is formed by the external oblique muscle and fascia. The external oblique muscle originates from the lower 8 ribs and inserts onto the iliac crest, anterior superior iliac spine, and pubic tubercle. Inferiorly, the external oblique aponeurosis is contiguous with the inguinal ligament. The inguinal ligament originates from the anterior superior iliac spine and inserts onto the pubic tubercle, forming the base of the inguinal canal. Together, the external oblique aponeurosis and inguinal ligament form the external inguinal ring that lies superficial and lateral to the pubic tubercle.
The next layer deep to the external oblique muscle is formed by the internal oblique muscle and fascia. The internal oblique muscle originates from the iliac crest, thoracolumbar fascia, and lateral inguinal ligament. The internal oblique muscle forms the superior portion of the inguinal canal and envelopes the spermatic cord (or round ligament in females), the genital branch of the genitofemoral nerve, and the ilioinguinal nerve.
The deepest structures of the abdominal wall are the transversus abdominis muscle and transversalis fascia. The transversus abdominis muscle originates from the thoracolumbar fascia, iliac crest, lateral inguinal ligament, and the costal cartilages of ribs VII through XII. The transversalis fascia forms the internal inguinal ring, which marks the entryway for the spermatic cord (or round ligament) into the inguinal canal. Distally, the transversus abdominus and internal oblique muscles merge to form the conjoint tendon. The conjoint tendon blends with fibers of the rectus sheath and external oblique aponeurosis as they attach to the pubic tubercle. These fibers in turn coalesce with the origins of the adductor longus and gracilis tendons forming the “aponeurotic plate” anterior to the pubic symphysis ( Fig. 2 ). ,
Thus, the pubic symphysis is the focal point of the complex muscular anatomy of the lower abdomen. A nonsynovial amphiarthroidal joint, the pubic symphysis marks the convergence of the 2 pubic bones at the center of the anterior pelvis. The pubic bones are separated by a fibrocartilaginous disk and are rigidly connected by anterior, posterior, superior, and inferior ligaments. The inferior ligament, or arcuate ligament, spans both inferior pubic rami and confers the greatest stability to the joint. The rigidity of the pubic symphysis limits shear and tensile stresses, allowing it to act as a fulcrum for the muscular and ligamentous structures that attach to the aponeurotic plate. , ,
Given this complex anatomy, 3 prevailing theories exist with regard to the pathophysiologic causes of core muscle injury. , The first theory is that muscular imbalance between the rectus abdominis and the adductors leads to injury about the aponeurotic plate ( Fig. 3 ). A second theory suggests that pain related to core muscle injury stems from either a defect or weakness within the posterior inguinal canal. , , Last, a third theory proposes that weakness of the posterior inguinal canal leads to dynamic compression of the genital branch of the genitofemoral nerve resulting in neuropathic pain. Therefore, the management of core muscle injuries is aimed at identifying and treating the underlying anatomic etiology of the patient’s pain.
Physical examination
Physical examination of an athlete presenting with a suspected core muscle injury should begin with direct visualization of the inguinal region. The patient’s skin must be examined for any signs of ecchymosis or swelling that could indicate an acute injury, and any scars or previous surgical incisions should be documented.
After a careful visual inspection, palpation of several key anatomic landmarks should occur. The pubic symphysis, pubic tubercles, rectus abdominis tendon, conjoint tendons, and adductor longus tendons should all be palpated, and any localized tenderness or palpable defects should be noted. The external inguinal ring must also be assessed to rule out the possibility of an inguinal hernia ( Fig. 4 ). According to the British Hernia Society’s position statement from 2014, a diagnosis of a sports hernia can be made if 3 of the following 5 criteria are confirmed on clinical examination :
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Pinpoint tenderness over the pubic tubercle at the point of insertion of the conjoint tendon.
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Palpable tenderness over the deep inguinal ring.
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Pain and/or dilation of the external ring with no obvious hernia evident.
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Pain at the origin of the adductor longus tendon.
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Dull, diffuse pain in the groin, often radiating to the perineum and inner thigh or across the midline.
Further provocative testing is also helpful in determining the underlying etiology. Having the patient cough or perform a Valsalva maneuver classically reproduces groin pain in patients with a core muscle injury. Pain with resisted sit-ups can be indicative of rectus abdominis or conjoint tendon pathology ( Fig. 5 ). Sit-ups can be performed with the patient’s hips straight, at 45° flexion, and 90° of flexion to stress the rectus muscle in several different planes. The oblique muscles can be further isolated by asking the patient to perform a lateral bend against resistance toward the affected side. Pain with passive hip abduction or resisted hip adduction are suggestive of adductor longus tendon pathology.
Last, careful consideration must be given to the patient’s hip joint owing to the high association between core muscle injuries and femoroacetabular impingement (FAI). Hip range of motion bilaterally should be evaluated in flexion/extension, abduction/adduction, and internal/external rotation. Provocative tests such as flexion, abduction, and external rotation; flexion, adduction, and internal rotation; and McCarthy’s sign should also be performed to rule out a concomitant diagnosis of FAI.
In patients who exhibit a mixed clinical examination, injections can be used for both diagnostic and therapeutic purposes. The resolution of symptoms after the administration of a local anesthetic with or without a corticosteroid to either the rectus attachment, adductor longus origin, or pubic symphysis are more consistent with a diagnosis of core muscle injury. Pain relief with an intra-articular hip injection suggests a pathology related to FAI.
Imaging
Diagnostic imaging is valuable for both confirming the presence of a core muscle injury and excluding other causes from the differential. Radiographs of the pelvis and hip are the initial imaging modality of choice in all patients presenting with groin pain.
A standard anteroposterior view of the pelvis can be used to evaluate the pubic symphysis for any abnormal widening or erosive changes. Dedicated hip radiographs including an anteroposterior, frog-leg lateral, cross-table lateral, false profile view, and modified 45° Dunn view are all useful for evaluating FAI. Other pathologies that should always be considered include pelvic avulsion fractures, stress fractures, apophyseal injuries, apophysitis, degenerative joint disease, and hip dysplasia. ,
Although radiographs are a useful screening tool, MRI is the imaging modality of choice for evaluating a core muscle injury. A dedicated sports hernia MRI protocol is recommended to enhance visualization of the affected area. Standard coronal, sagittal, and axial sequences with a large field of view should be obtained first. These images are useful for evaluating the entire pelvis and ruling out other concomitant pathology such as osteitis pubis, osteonecrosis, stress fractures, tumors, myotendinous injuries, and intra-articular disorders. A smaller field of view with a higher resolution is necessary to focus on the pubic symphysis and aponeurotic plate. Coronal oblique and axial oblique sequences through the rectus abdominis insertion and pubic symphysis give the most accurate representation of the anatomy. Tears of the aponeurotic plate, fluid undermining the aponeurosis, and abnormal marrow signal in 1 or both pubic bones are best visualized on the axial oblique and sagittal sequences. Partial or complete tears of the adductor musculature are better appreciated on coronal oblique sequences. Overall, MRI has been found to be 68% sensitive and 100% specific for rectus abdominis pathology and 86% sensitive and 89% specific for adductor longus pathology. ( Figs. 6 and 7 )
