Duke Orthopaedics
Wheeless' Textbook of Orthopaedics

Heterotopic Ossification

- See: Ossification of Soft Tissues: and Myositis Ossificans

- Discussion:
    - occurence and formation of mature bone in non-osseous tissue; 
    - may present w/ signs of localized inflammation or pain, elevated skin temp, ect.
    - tends to occur after thr, spinal injury, head injury (11%), burns, bruises, elbow trauma, total hip replacement;
           - ref: Osteoblasts Have a Neural Origin in Heterotopic Ossification..
    - Events leading to HO;
           - mesenchymal cell (XRT prevents induced differentiation)
           - osteoblast
           - matrix (EHDP)
           - osteocyte
    - HO following THR:
    - HO following acetabular fracture  (acetabular frx)
           - Heterotopic ossification as a complication of acetabular fracture. Prophylaxis with low-dose irradiation.
           - Heterotopic ossification following operative treatment of acetabular fracture. An analysis of risk factors.
           - Heterotopic ossification prophylaxis following operative treatment of acetabular fracture.
           - Extended iliofemoral versus triradiate approaches in management of associated acetabular fractures.
           - Prophylaxis with indomethacin for heterotopic bone. After open reduction of fractures of the acetabulum.

    - HO of the elbow:
           - Early excision of heterotopic ossification about the elbow followed by radiation therapy.
    - HO following spinal cord trauma:
           - radiographically develops in 3-5% of patients, 1-4 mo (or upto 18 mo) after injury;
           - it occurs below the level of the injury, usually at major joints;
           - incidence is 40% (1/2 of these are clinically significant);
           - after transection of spinal cord, ossification often takes place in soft tissues adjacent to large joints;
           - lower extremities are particularly suseptible & most dramatic changes are seen in Knee > Pelvis > Hip;
           - characteristic finding is a bilateral accretion of well defined bone which encircle the joints;
                    - Resection of heterotopic ossification in patients with spinal cord injuries.
                    - Resection of heterotopic ossification in the adult with head trauma.
                    - Clinical observations on fractures and heterotopic ossification in the spinal cord and traumatic brain injured populations.
                    - Surgical approaches for resection of heterotopic ossification in traumatic brain-injured adults.
                    - Periarticular heterotopic ossification in head-injured adults. Incidence and location.
                    - Heterotopic ossification around the hip in spinal cord-injured patients. A long-term follow-up study.

- Radiographic Studies:
     - x-rays: soft tissue ossification usually does not appear in 1st mo
     - bone scans may reveal incr isotopic intake by the second weak;

- Labs:
     - alkaline phosphatase activity correlates w/ bone scans;

- Non Operative Treatment:
    - NSAIA
          - Indomethacin 25 mg PO tid for 3-6 months;
    - Etidronate
          - theoretically works by delaying mineralization of osteoid
          - diphosphonates do not prevent heterotopic bone formation in lab animals but they do delay of mineralization of osteoid.
          - delay in mineralization caused by diphosphanates are reversed when the disphosphonates are discontinued;
    - Radiation Therapy:
          - single does of 600 to 800 centgray of radiation given within 24 hours of surgery preoperatively or 72 hours postoperatively;
          - a relative contra-indication of XRT may be posterior hip dislocation w/ femoral head frx, since there is a theoretical risk of
                    contributing to AVN or non-union;
          - cost: $ 2,000 to 2,500;
          - references:
                 - Preoperative irradiation versus the use of nonsteroidal anti-inflammatory drugs for prevention of heterotopic ossification following total hip replacement: the results of a randomized trial.
                 -  Radiotherapy vs. nonsteroidal anti-inflammatory drugs for the prevention of heterotopic ossification after major hip procedures: a meta-analysis of randomized trials.

- Operative Resection:
    - main disadvantage is risk of recurrence heterotopic ossification;
    - operative timing:
            - if HO has caused the loss of motion, some recommend allowing process to mature (sharp cortical and trabecular markings)
                    before operative resection;
           - some recommend waiting 12 months before operative resection;
           - once serial radiographs have shown that the ossification is mature w/ sharp peripheral edges and no indication of expansion,
                    resection is considered;
           - bone scans and alkaline phosphatase may not be helpful in predicting maturity of the ossification;
    - references:
           - What Risk Factors Predict Recurrence of Heterotopic Ossification After Excision in Combat-related Amputations?
    - in the study by Genet, et al., a consecutive series of 143 patients w/ traumatic brain injury and spinal cord injury;
           - some patients had complete ankylosis, and some had severe limitation of motion;
           - patients with ankylosis had improvement from an average of 0° to 90° of hip flexion but had only 63° of motion;
           - patients without ankylosis had improvement from an average of 38° to 95° of motion, with 83° of motion;
           - authors noted the importance of estimating bone mineral density prior to surgery to assess the risk of intraoperative fracture;
           - delayed surgery can increase in intra-articular pathology and osteoporosis;
           - Impact of late surgical intervention on heterotopic ossification of the hip after traumatic neurological injury.

Botulinum Toxin-induced Muscle Paralysis Inhibits Heterotopic Bone Formation.

Heterotopic ossification about the hip after intramedullary nailing for fractures of the femur.

Heterotopic ossification around the hip with intramedullary nailing of the femur.

Prevention of heterotopic ossification in high-risk patients by radiation therapy.

A clinical perspective on common forms of acquired heterotopic ossification.

The use of radiation to discourage ectopic bone. A nine-year study in surgery about the hip.

Prophylaxis with indomethacin for heterotopic ossification after Chiari osteotomy of the pelvis.

Keeping Bugs Bunny on the Move 

Heterotopic ossification in complex orthopaedic combat wounds: quantification and characterization of osteogenic precursor cell activity in traumatized muscle.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, August 16, 2016 6:21 pm

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