Radiologic Imaging of Pelvis, Groin, Hip, and Thigh Injuries
Radiography, CT(A), and MRI(A) are the major radiological techniques to evaluate pelvic and hip sports injury. Intra-articular pathology of the hip is ideally assessed with magnetic resonance arthrography (MRA). Typical diagnoses are labral lesions in femoroacetabular impingement. Hyaline articular cartilage abnormalities are identified with lower sensitivity. Intra-articular loose bodies are well demonstrated on MRA (direct or indirect) (D-MRA or I-MRA). Avascular necrosis (AVN) may occur in athletes especially after subcapital fracture or hip dislocation. MRI is very sensitive and specific in the diagnosis of AVN of the hip. Based on the shape of the lesion, AVN can be differentiated from subchondral insufficiency fractures (SIF) in osteoporotic women. Subchondral fatigue fractures in young athletes show identical imaging findings as the insufficiency fractures and may be located either in the femoral head or in the acetabulum.
MRI and CT detect a reduced distance between the ischial tuberosity and lesser trochanter in ischiofemoral impingement syndrome, on fluid-sensitive sequences on MRI increased signal intensity of the quadratus femoris muscle is detected.
Iliopsoas impingement is a recently described entity in the orthopedic literature. The only reliable MR feature seems to be the visualization of a labral tear at the 3-o’clock position on MR arthrography.
A specific but not sensitive examination to evaluate snapping iliopsoas tendon is dynamic ultrasound performed by an experienced ultrasonographist. Lateral snapping hip is caused by snapping of the iliotibial tract or gluteus maximus relative to the greater trochanter. Intra-articular processes may produce a snapping hip sensation, such as intra-articular bodies.
US is sensitive to demonstrate the superficially located iliopsoas bursa. MRI is the modality of choice for deeper located bursitis like obturator externus bursitis and ischiogluteal bursitis. Trochanteric bursitis can be found in case of trochanteric pain syndrome, especially in case of tendinopathy of the gluteus medius and minimus. Fluid in the bursae is often not prominent and secondary to tendinopathy. The gluteal tendons may be evaluated with MRI and ultrasound. US-guided treatment is performed in therapy-resistant tendinopathy.
Morel-Lavallée lesion at the hip region is typically located at the level of the greater trochanter and can well be evaluated with US because of its superficial localization.
Muscle contusions are very frequent around the hip and thigh in sports. The damage with contusion usually occurs in the layer closest to the bone (intermediate vastus muscle of the quadriceps) or tendon. MR images reveal edema at the injured site, frequently due to interstitial hemorrhage as well as edema. In more severe contusions, hematomas can be seen as mass-like lesions surrounded by edema. The signal intensity of a hematoma on T1W and T2W images depends on the degradation of hemoglobin. The major complications of muscle contusion are myositis ossificans and seroma.
Myositis ossificans (MO) or focal myositis is a noninfectious myositis often with heterotopic ossification. Imaging plays an important role in identifying myositis ossificans and focal myositis to prevent biopsy with misleading histology and wide resection. CT and ultrasound are more sensitive than radiography for detecting ossification. MRI may show the so-called zone phenomenon before ossification appears. US may be the most sensitive imaging modality to early depict the calcified area at the peripheral zone in MO. The aspect of adult bone in the later stages characterized by central spongious bone containing fat and at the periphery cortical bone, that is easily recognized on radiographs, CT, or MRI.
Muscle strains in adults at the level of the quadriceps (rectus femoris) are typically located at the level of the proximal or distal musculotendinous junction (MTJ).
In superficial and low-grade MTJ lesions even at the hamstrings, ultrasound has the advantage to better differentiate grade II lesions with elongation or grade I lesions. Generally in acute lesions US is as useful as MRI in depicting hamstring MTJ injuries. Strains at the hamstring enthesis are examined with MRI.
On MRI ruptures of the rectus abdominis–common adductor origin (RA-CAO) will show the shearing of the RA-CAO aponeurosis with surrounding soft tissue edema, widening the distance between the aponeurosis and the pubis; arcuate ligament tear is only demonstrated on MRI. RA-CAO lesions may predispose to a direct inguinal hernia or a “sportsman’s hernia” that is demonstrated on dynamic US.
MRI is the imaging modality of choice to evaluate osteitis pubis; radiographs and CT only demonstrate chronic advanced disease.
In patients with bone marrow edema (BME) on MRI at the SI joints, the major differential with sacroiliitis is stress reaction. Specific radiological diagnosis is not possible in early cases of sacroiliitis without demonstration of erosions. A specific diagnosis of sacroiliitis is made in bilateral and symmetrical presentations in SpA and is typical asymmetric in psoriasis and reactive arthritis.
Nerve lesions around the hip involve especially the ischial nerve, the femoral nerve, and the lateral femoral cutaneous nerve. Entrapment of the lateral femoral cutaneous nerve can best be evaluated with high-frequency US. US-guided treatment with injection of corticoids in the perineurium shows promising results.
Because of its deeper location, the best modality to evaluate the sciatic nerve is MRI.
US is particularly well suited to examine the pediatric musculoskeletal system, especially of the hip and pelvis. It is a well-tolerated and noninvasive way without using ionizing radiation or sedation. In transient synovitis, fluid is seen between the 2 layers of the hip capsule.
In recurrent stress on the apophysis with apophysitis in children, apparent physeal widening, apophyseal edema, and adjacent muscle and bone edema can be seen on MRI. On ultrasound the physeal widening and the apophyseal hypertrophy and angiogenesis can be depicted.
More severe acute trauma may result in an avulsion of the apophysis or apophysiolysis. In these a distraction of the apophysis is demonstrated without signs of inflammation and angiogenesis in the acute phase on US. There can be a hematoma and bone marrow edema in the apophysis and adjacent bone.
Fractures of the hip and the pelvis are initially evaluated with radiographs. In the second stage CT with three-dimensional reconstruction is used.
KeywordsBone Marrow Edema Slip Capital Femoral Epiphysis Magnetic Resonance Arthrography Myositis Ossificans Lateral Femoral Cutaneous Nerve
Association Research Circulation Osseous
Bone marrow edema
Computed tomographic arthrography
Developmental hip dysplasia
Direct magnetic resonance imaging arthrography
Diethylene triamine pentaacetic acid
Flexion, adduction, and internal rotation of the hip: impingement test
Femoral head avascular necrosis
Greater trochanter pain syndrome
Indirect magnetic resonance imaging arthrography
US high-frequency ultrasound
Magnetic resonance imaging
Magnetic resonance imaging arthrography
Magnetic resonance imaging
Nervus cutaneus femoris lateralis
Positron emission tomography
Power Doppler ultrasound
Rectus abdominis and the common adductor origin
Slipped capital femoral epiphysis
Subchondral insufficiency fracture
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