Chapter 27 Heterotopic Ossification (HO) Flashcards
Heterotopic ossification (HO) is the formation of bone at an abnormal anatomical site, usually in _______, due to the metaplasia of mesenchymal cells into osteoblasts. There are two forms: _______ form, which is precipitated by a musculoskeletal trauma such as fracture, thermal injury, or THA, and _______ form, examples of which are SCI, stroke, and TBI.
Heterotopic ossification (HO) is the formation of bone at an abnormal anatomical site, usually in soft tissue, due to the metaplasia of mesenchymal cells into osteoblasts. There are two forms: acquired form, which is precipitated by a musculoskeletal trauma such as fracture, thermal injury, or THA, and neurogenic form, examples of which are SCI, stroke, and TBI.
HO is typically seen near _______ and below levels of neurologic injury.
HO is typically seen near large joints and below levels of neurologic injury.
The differential diagnosis of HO can include ________, ________, ________, thrombophlebitis, osteomyelitis, hematoma, osteosarcoma, hemarthrosis, or CRPS.
The differential diagnosis of HO can include DVT, septic arthritis, cellulitis, thrombophlebitis, osteomyelitis, hematoma, osteosarcoma, hemarthrosis, or CRPS.
If HO is suspected, a ________ or ________ may be obtained. The ________ may be positive at least 1 week before ________ is positive; phases ________ of the ________ are highly sensitive.
If HO is suspected, a plain x-ray or three-phase bone scan may be obtained. The bone scan may be positive at least 1 week before x-ray is positive; phases 1 and 2 of the bone scan are highly sensitive.
In burns, common sites of HO include _______ (posterior > anterior) > _______ (adult) or _______ (children). HO location may not coincide with the area of the burn.
In burns, common sites of HO include elbow (posterior > anterior) > shoulder (adult) or hip (children). HO location may not coincide with the area of the burn.
In SCI, HO is seen at the _______ (anterior > posterior) > _______ > _______ > _______ > _______.
In SCI, HO is seen at the hip (anterior > posterior) > knee > shoulder > elbow > feet.
With TBI, location of HO: _______ equals _______; shoulder ≃ elbow ≃ hip. _______ HO is commonly seen following THA.
With TBI, location of HO: UEx equals LEx; shoulder ≃ elbow ≃ hip. Hip HO is commonly seen following THA.
HO may occur at the distal end of _______ limbs.
HO may occur at the distal end of amputated limbs.
Some complications of HO include _______, pressure ulcers, and functional impairment if _______ _______ develops.
Some complications of HO include peripheral nerve entrapment, pressure ulcers, and functional impairment if joint ankylosis develops.
Treatment – _______ the acutely involved joint for ≤ _______ weeks is acceptable to ↓ _______ and microscopic hemorrhages. Ice may also be helpful. While still an area of controversy, gentle ROM exercises, such as painless passive ROM or active ROM, are recommended to maintain joint mobility. More aggressive ROM may be initiated after the first 2 weeks, but must be curtailed if erythema or swelling increases. Immobilization in a functional position is prudent if ankylosis is inevitable.
Treatment – Resting the acutely involved joint for ≤2 weeks is acceptable to ↓ inflammation and microscopic hemorrhages. Ice may also be helpful. While still an area of controversy, gentle ROM exercises, such as painless passive ROM or active ROM, are recommended to maintain joint mobility. More aggressive ROM may be initiated after the first 2 weeks, but must be curtailed if erythema or swelling increases. Immobilization in a functional position is prudent if ankylosis is inevitable.
Medical options include _______ (e.g., _______, 25 mg po tid × ≥6 weeks) or _______ (e.g., 20 mg/kg po qd × 2 weeks, then 10 mg/kg po qd × 10 weeks; other regimens exist). _______ is thought to reduce further HO formation by reducing osteoblastic/clastic activity and _______ _______ precipitation. It _______ _______, however, treat HO that has already formed.
Medical options include NSAIDs (e.g., indomethacin, 25 mg po tid × ≥6 weeks) or etidronate (e.g., 20 mg/kg po qd × 2 weeks, then 10 mg/kg po qd × 10 weeks; other regimens exist). Etidronate is thought to reduce further HO formation by reducing osteoblastic/clastic activity and calcium phosphate precipitation. It does not, however, treat HO that has already formed.
_______ therapy has been used with success to prevent and/or treat HO in post-_______ patients, although it is rarely used.
Radiation therapy has been used with success to prevent and/or treat HO in post-THA patients, although it is rarely used.
Surgical resection may be indicated to address significant functional limitations. An ideal surgical candidate would have three factors: no joint _______ or swelling, a normal _______ level (which tends to normalize with maturity), and a three-phase bone scan indicating _______ HO.
Surgical resection may be indicated to address significant functional limitations. An ideal surgical candidate would have three factors: no joint pain or swelling, a normal alkaline phosphatase level (which tends to normalize with maturity), and a three-phase bone scan indicating mature HO. It is important to ensure that the HO has reached maturity before resection, because resection of immature HO leads to recurrence rates of nearly 100%. Gentle, early (within 48 hours) postoperative ROM is recommended.
