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Ischiofemoral impingement refers to the impingement of soft tissues between the ischial tuberosity and lesser trochanter of the femur.
Patients with ischiofemoral impingement present with chronic pain in the groin and/or buttock, without a history of traumatic injury. Pain may radiate into the lower extremity, with thigh and/or knee pain, because the quadratus femoris muscle is in close proximity to the sciatic nerve, and pressure effects may produce nerve-related symptoms ref. Patients may also suffer from snapping sensation, crepitation, or locking in the joint 6,7.
Internal/external rotation, adduction/abduction, and flexion/ extension can provoke symptoms ref.
Females are more affected than males. Ischiofemoral narrowing may be bilateral but symptoms may only be unilateral 3,9.
Narrowing of ischiofemoral space and quadratus femoris space or the distance between the ischial tuberosity and lesser trochanter of the femur predisposes to symptomatic ischiofemoral impingement, primarily affecting the quadratus femoris muscle manifesting with muscle belly edema in the acute setting and fatty degeneration in chronic cases. It can also lead to tears of the common hamstring tendon.
There are numerous causes for narrowing of the ischiofemoral and quadratus femoris space including 2,4,9,10:
medial implant offset after total hip arthroplasty
Radiographs are typically normal, although cystic change and sclerosis may be seen within the lesser trochanter or ischial tuberosity.
A recent study suggested ischiofemoral impingement is likely in patients with chronic pelvic pain if the ischiofemoral space is <2 cm or <1.9 cm on supine and standing pelvic x-rays, respectively. It warrants further investigation by pelvic MRI 5.
The main finding in the acute case is muscle edema of the quadratus femoris muscle, in some cases with concomitant adventitious bursitis / bursa-like fluid collection at the lesser trochanter 3,10. Bone marrow edema or cystic change of the ischium/lesser trochanter may also be apparent.
In addition, the ischiofemoral and quadratus femoris spaces can be measured, they are, however difficult to standardize due to leg positioning 10:
ischiofemoral space is measured on an axial T1 sequence
shortest distance between medial cortex lesser trochanter and lateral cortex ischial tuberosity 8
cut-off: ≤15 mm (sensitivity 77%, specificity 81%, accuracy 74%) 1
quadratus femoris space is measured on an axial T1 sequence
smallest distance for the passage of quadratus femoris between the posteromedial iliopsoas tendon or ischial tuberosity and the superolateral hamstring tendons 8
cut-off: ≤10 mm (sensitivity 79%, specificity 74%, accuracy 77%) 1,9
fatty atrophy of quadratus femoris may be present 9
quadratus femoris muscle belly edema and/or tears 9
muscle belly edema may extend to the hamstrings and/or iliopsoas muscles 9
In chronic situations of impingement, there will be fatty infiltration and atrophy of the quadratus femoris muscle and sometimes tears of the hamstring musculature at their common insertion site 10.
Treatment and prognosis
Conservative therapy is the treatment of choice, while surgical option with treatment of underlying comorbidities just in cases where conservative therapy falls short.
History and etymology
Ischiofemoral impingement was first described as a cause for hip pain by K A Johnson in 1977 4.
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