Imaging in groin pain:
Radiological investigation using ultrasound (US) or magnetic resonance imaging (MRI) is usually required to delineate the cause of groin pain.
MRI,
in particular,
plays a pivotal role in identifying the source of the groin pain and gives optimal soft tissue resolution and anatomical detail of the key groin anatomy and good visualisation of bones,
joints and soft tissue structures in the area of interest [1].
The imaging protocol for groin pain in our institution includes axial and coronal T1 weighted imaging & axial,
coronal and sagittal PD FS weighted sequences of the pelvis.
Groin pain - differential diagnosis:
In athletes,
groin pain is typically thought to represent an overuse injury in the setting of excessive or repetitive activity and accounts for approximately 2-18% of all sports injuries [2].
Groin pain in athletes can be acute (for example,
acute muscle tear) or chronic in the setting of repetitive micro-trauma [3].
Athletes involved in kicking sports such as rugby and football are particularly susceptible to groin pain [4].
The differential diagnosis for groin pain is broad and includes injuries of the adductor/abdominal wall musculature and the common adductor-rectus abdominis aponeurosis,
osteitis pubis, stress fractures and hernias.
Groin pain may also be referred secondary to pathology in the hip,
spine and pelvis and referred pain should be considered in the differential diagnosis [5].
Common causes of groin pain identified in our department:
1. Muscle/tendon injuries: (Fig.
8-10)
The commonest cause of acute groin pain are strains of the adductor muscles.
These injuries occur in the setting of excessive loading of the musculotendinous unit beyond its normal limit.
The musculotendinous junction is especially prone to injuries as it is the weakest point of the muscle-tendon complex [6].
MRI aids in the diagnosis by confirming the site of injury and associated tendon involvement by identifying the presence of oedema or a focal tear the site of injury [7].
The adductor longus muscle is the most anterior adductor muscle and the most susceptible to injuries.
On MRI,
fluid extends from within the pubic symphysis and inferolateral to the adductor longus tendon producing a secondary cleft of fluid,
the 'secondary cleft sign'.
2.
Common adductor-rectus abdominis aponeurosis injuries:
Tears can occur anywhere within the aponeurosis complex from the rectus abdominis or adductor tendon to the aponeurosis itself or the aponeurosis can be pulled off the anterior surface of the pubic symphysis (to which it normally attached).
3.
Osteitis pubis: (Fig.
11&12)
Osteitis pubis is a self-limiting,
non-infectious,
inflammatory condition of the pubic symphysis caused by repetitive shearing/motion injury and asymmetry of muscle development.
It commonly occurs in runners,
footballers and hockey players but other risk factors include previous trauma,
overuse and vaginal delivery [8].
Osteitis pubis can be divided into three zones: suprapubic,
intrapubic and infrapubic according to the source of the injury,
for example - suprapubic osteitis is caused by injury to the rectus muscle/tendon,
intrapubic is due to injury to the central fibrocartilaginous disc and infrapubic osteitis is due to injury/strain to the adductor tendons/muscles [8].
On MRI,
bone marrow oedema is seen in the parasymphyseal pubic bodies indicating stress response/trabecular microtrauma [9].
In chronic cases,
degenerative changes with osteophyte formation,
subchondral cystic change and articular surface irregularity may also be identified.
Bone resorption with widening of the joint space >7mm may also be seen [2].
It is important to note that parasymphyseal bone marrow oedema can be seen on MRI in asymptomatic athletes and clinical correlation is advised when interpreting this finding [10].
4.
Apophyseal Injury - avulsion and apophysitis: (Fig.
13-15)
The apophyses are non-weight-bearing secondary ossification centres and are crucial components of the developing musculoskeletal system,
acting as musculotendinous attachment sites.
They are seen at a number of different sites in the bony pelvis and can be a source of groin pain.
They usually fuse by the age of 20 but fusion may take longer around the pelvis [11].
Unfused apophyses are prone to traction and avulsion (Salter Harris type 1) injuries as the physis is weaker than the adjacent bone/tendon [12].
The apophysis is also prone to chronic overuse stress with healing response in athletes termed 'apophysitis'.
Sudden forceful muscular contraction in physically active adolescents and young adults causes avulsion of the apophysis to which the tendon attaches.
Kicking sports are usually implicated.
5.
Stress response & stress fractures of the proximal femur: (Fig.
16)
Osseous stress related injuries of the proximal femur are a relatively common cause of groin pain.
A stress injury is termed 'stress response' when marrow oedema is evident,
but an underlying fracture line is not seen.
Stress injuries usually result from abnormal stress on normal bone or normal stress on abnormal bone.
Long distance runners,
female athletes and patients with anorexia are particularly susceptible to these injuries [13].
Proximal femoral stress fractures in athletes arise most frequently in the medial aspect of the femoral neck where compressive forces are greatest.
Stress fractures may also occur in the trochanteric or subtrochanteric regions,
in the pubic rami or in the distal femoral shaft [14].
6.
Sportsman hernia:
A sportsman hernia,
also termed 'sports hernia',
'athletic pubalgia' or 'Gilmore hernia',
is a relatively common cause of groin pain in athletes and accounts for up to 13% of cases of groin pain [15].
Soccer players are particularly susceptible.
It is not a true hernia but an acquired deficiency of the anterior (external oblique muscle & aponeurosis) or posterior (internal oblique or transverse abdominis muscles) inguinal walls and is caused by a weakness or tear [16].
7.
Referred groin pain secondary to spinal pathology:(Fig 17)
Degeneration changes of the spine with disc herniation can cause groin pain.
The groin is innervated by the ilioinguinal and genitofemoral nerves (S1-S3 nerve roots).
Impingement of these nerves roots can result in groin pain [17].