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Ischial Tuberosity Avulsion Fracture

synonyms: ischial tuberosity fracture, ischial tuberosity avulsion fracture

Ischial Tuberosity Avulsion Fracture ICD-9

  • 808.42 (Fracture of Pelvis; ischium; closed)
  • 808.52 (Fracture of Pelvis; ischium; open)

Ischial Tuberosity Avulsion Fracture Etiology / Epidemiology / Natural History

  • Ischial avulsion fractures generally occur from forced hyperflexion (eccentric contraction) of the hip while the knee is fully extended.
  • Commonly occurs in: sprinters, hurdlers, gymnasts, soccer.

Ischial Tuberosity Avulsion Fracture Anatomy

  • Hamstrings = Biceps(long head)[tibial n] and Biceps(short head[peroneal n]), Semitendinosus[tibial n], Semimembranosus[tibial n]. 
  • All except short head originate from ischial tuberosity. 
  • Separate muscle become distinguishable 5-10cm form tuberosity. 
  • Complete avulsions generaly occur at the ishial tuberosity.
  • Ischial apophysis is relatively weak in adolescences making ischail apophyseal avulsion fractures more common in adolescences.
  • Ischail apophyseal secondary ossification center appears in early puberty and does not fuse until late adolescences. (Gidwani S, BMJ 2004;329:99).

Ischial Tuberosity Avulsion Fracture Clinical Evaluation

  • Acute posterior thigh pain (buttock ot mid-thigh). Antalgic gait.
  • May have thigh swelling / ecchymosis.
  • Examine posterior thigh for asymmetry / contracted hamstring muscle belly. may have hamstring weakness.
  • Ischial tuberosity tenderness / palpable gap in hamstring origin.
  • Chronic avulsions: buttock / thigh pain with sitting and walking. Inability to return to sport.
  • May present with sciatica (sciatic nerve may be compressed by avulsion fragment or extensive scare/callus)

Ischial Tuberosity Avulsion Fracture Xray / Diagnositc Tests

  • A/P pelvis, A/P and lateral of affected hip. Evaluate for cortical irregularity at the inferior margin of the ischial tuberosity and inferiorly displaced fragment in acute cases. Chronic cases may demonstrate exuberant callus formation around an enlarged ischial tuberosity. May have proliferative callus and osteolysis mimicing osteomyelitis or neoplasm (Ewing's sarcoma).
  • CT: better delineates fragments. Evaluate for asymmetry of ischial apophyses, periosteal new bone, callus formation, cortical disruption. (Brandser EA, Radiology 1995;197:257).
  • MRI: most sensitive and specific. Proximal hamstring tendon should seen as a linear homogeneous low signal originating from the posterolateral margin of the ischial tuberosity on a sequences. Fractures will demonstrate edema like signal in the ischial tuberosity. May see fluid or hemorrhage around the tendon. Feathery increased signal on T2 images indicates musculotendinous injury or muscular stain (Hamstring). Fatty infiltrate in the muscle indicates chronic injury.

Ischial Tuberosity Avulsion Fracture Classification / Treatment

  • >2cm displacement of fracture fragments or tendon = ORIF +/- tendon repair. (Wood DG, JBJS 2009;90:2365).
    -27215 (Open treatment of iliac spine, tuberosity avulsion, or iliac wing fracture)
  • Nondisplaced: rest, activity limitations, sport specific rehab when painfree

Ischial Tuberosity Avulsion Fracture Associated Injuries / Differential Diagnosis

Ischial Tuberosity Avulsion Fracture Complications

  • Nonunion / fibrous nonunion
  • Chronic pain
  • Weakness
  • Inability to return to sport
  • Sciatica / Sciatic nerve palsy

Ischial Tuberosity Avulsion Fracture Follow-up Care

Ischial Tuberosity Avulsion Fracture Review References

  • Wood DG, JBJS 2009;90:2365
  • Gidwani S, BMJ 2004;329:99

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