Heterotopic Ossification

Author: Colin Woon

Topic updated on 05/17/13 7:25pm

Introduction

Formation of bone in atypical, extraskeletal tissues
- usually occurs
  - spontaneously or following trauma
  - within 2 months of neurologic injury (brain or spinal cord)
- most common location is between muscle and joint capsule
Epidemiology
- incidence
  - (see table below)
- location
  - traumatic brain injury or stroke
    - hip > elbow > shoulder > knee
    - elbow HO more common following brain trauma
    - occurs on affected (spastic) side
    - rarely in the knee (TBI)
  - spinal cord injury
    - hip > knee > elbow > shoulder
    - hip flexors and abductors > extensors or adductors
    - medial aspect of the knee
- risk factors
  - (see table below)
Pathophysiology
- exact cause of HO is not known but there appears to be a genetic disposition
- experimental HO associated with
  - tissue expression of BMP
Associated conditions
- orthopaedic manifestations
  - pathologic fractures
    - from decreased joint ROM and osteoporotic bone
  - nerve impingement
  - soft tissue contractures, contributing to the formation of decubitus ulcers
  - CRPS (more common in patients with HO)
  - joint ankylosis
  - HO after THA adversely affects outcome of THA
- nonorthopaedic conditions
  - skin maceration and hygiene problems

Risk Factors for Heterotopic Ossification
Injury severity score (ISS)		11%
Traumatic brain injury (TBI)	Higher incidence in the spastic limbs of the patient	11%
Spinal cord injury	Completeness of SCI (complete SCI produces more HO than incomplete SCI). Cervical and thoracic SCI produces more HO than lumbar SCI. Younger age produces more HO (20-30yo). Higher incidence in the spastic limbs of the patient.	20%
Neurologic compromise	Prolonged coma in young patient (20-30yo)
Decubitus ulcers	Worse with concomitant decubitus ulcers and SCI or TBI	70% (with concomitant SCI)
Antegrade femoral nail entry site	Worse with piriformis fossa entry point.	25%
Distal femur traction pins	HO in distal quadriceps. Higher incidence in patients with other concomitant injuries, use of large diameter Steinmann pins (5mm). Thought to be because of local hematoma, soft tissue injury from percutaneous insertion.	rare
Amputation thru zone of injury	Worse with blast mechanism	63%
Surgical approaches	Extended iliofemoral > Kocher-Langenbeck > ilioinguinal approach (acetabular fracture). Direct lateral Hardinge approach for total hip arthroplasty. Anterior approach > posterior approach for femoral head fracture fixation.	25% (acetabular fracture fixation)
Total hip arthroplasty	THA Complications	53% (significant in only 5%)
Total knee arthroplasty	TKA complications

Classification

Subtypes
- neurogenic HO (discussed here)
- traumatic myositis ossificans
- fibrodysplasia ossificans progressiva (Muchmeyer's disease)

Presentation

Symptoms
- painless loss of ROM
- interferes with ADL
- CRPS symptoms
- fever
Physical exam
- inspection
  - warm, painful, swollen joint
  - may have effusion
  - skin problems
    - decubitus ulcers
      - from contractures around skin, muscles, ligaments
    - skin maceration and hygiene problems
- motion
  - decreased joint ROM
  - joint ankylosis
- neurovascular
  - peripheral neuropathy
    - HO often impinges on adjacent NV structures

Imaging

Radiographs
- recommended views
  - Judet view valuable for evaluation of hip HO
- findings
  - ossification usually easy to visualize
  - maturity of HO
    - the appearance of a bony cortex suggests mature HO
    - sharp demarcation from surrounding tissue
    - trabecular pattern
- sensitivity and specificity
  - not useful for early diagnosis
  - only useful at 1 week after onset of symptoms
    - calcium is deposited 7-10 days later than symptom onset
  - demarcation at 2-3 months
    - not useful to assess maturity of HO
    - mature areas of HO may hide immature areas
Ultrasound
- indications
  - for early diagnosis of hip HO
- findings
  - echogenic surfaces with posterior acoustic shadowing
CT
- indications
  - useful for preoperative planning
Triphasic bone scan
- indications
  - best for early diagnosis
  - most commonly used diagnostic study

Studies

Labs
- elevated serum alkaline phosphatase
  - AlkP removes inhibitors of mineralization
  - nonspecific, may be elevated with skeletal trauma
  - cannot determine maturity of HO
- elevated CRP
  - correlates with inflammatory activity of HO better than ESR
  - normalization of CRP may correlate with maturity of HO
- elevated CK
  - correlates with involvement of muscle, extent of muscle involvement
Histology
- mature fatty bone marrow
- mature trabecular bone

Treatment

Prophylaxis
- bisphosphonates & NSAIDS
  - indications
    - although no literature supports, are commonly used
  - technique
    - indomethacin is most commonly used
      - dose is 75mg/day for 6 weeks
- perioperative radiation
  - indications
    - although no literature supports, commonly used
    - is thought to be effective by blocking osteoblast differentiation
  - technique
    - a single perioperative dose of 700 rad can be given either 4 hours preop or within 72 hours postoperatively
Posttraumatic
- wide exposure and surgical resection
  - indications
    - severe loss of motion and decreased function
  - technique
    - wide exposure required to identify all neurovascular structures that may be involved
  - timing of resection
    - 6 months following general trauma
    - 1 year following SCI
    - 1.5 years following TBI
  - postop
    - follow with 5 day course of indomethacin
    - early gentle joint mobilization
Arthroplasty
- treatment for HO following THA
- treatment for HO following TKA

Complications

Hematoma and intraoperative bleeding
Infection
- higher rate of infection following joint arthroplasty if HO is present
Fractures of osteoporotic bone
- osteopenic from disuse
- during surgery or physiotherapy
Recurrence
- recurrence rate correlates with neurological injury
  - greater recurrence if severe neurological compromise
AVN
- if extensive dissection or stripping is required

IBank

	Location	Xray	Xray	CT	B. Scan	MRI	MRI	Histo(1)
Case A	tibia
Case B	hip

(1) - histology does not always correspond to case

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Qbank (6 Questions)

TAG

(OBQ09.135) A 27-year-old man is involved in a motor vehicle crash and sustains a closed head injury and right intertrochanteric hip fracture with ipsilateral femoral head fracture. He undergoes operative stabilization of his right hip. At 1 year follow-up he has limited rotation and abduction of the hip. Radiographs are shown in Figures A and B. What intervention during his initial treatment could have potentially prevented this outcome? Topic

Review Topic

FIGURES: A

1. 700 cGy of radiation within 72 hours of surgery
2. Pulsed administration of recombinant PTH 1,34 postoperatively for 1 year
3. 3 cycles of VAC (Vincristine, Actinomycin D, and Cyclophosphamide)
4. 700 cGy of radiation 2 weeks prior to surgery
5. 3 treatments of 700 cGy of radiation divided over 1 week after surgery

PREFERRED RESPONSE ▶

DISCUSSION: The patient has post-traumatic heterotopic ossification (HO). HO can occur about the hip following acetabular and hip fractures as well total hip arthroplasties (THA). Comprehensive Orthopaedic Review puts the incidence as high as 80% in THA patients and Miller's states that it is seen most with the direct lateral approach in THA and extensile approaches for acetabular fractures. The presence of a head injury makes an orthopedic trauma patient high risk for HO. Board et al conducted a review of HO following THA and found that in high risk individuals 700-800 cGY delivered less than 4 hours preoperatively or within 72 hours postoperatively appeared to be more effective than indomethacin 75mg daily for 6 weeks. Ayers et al also conducted a review of the literature and concluded that localized radiation was the treatment of choice to prevent heterotopic ossification following cementless total hip arthroplasty in high risk individuals. Irradiation prevents proliferation and differentiation of primordial mesenchymal cells into osteoprogenitor cells that can form osteoblastic tissue. Oral diphosphonates are not effective for prophylaxis as they inhibit mineralization of osteoid, but do not prevent the formation of osteoid matrix and when diphosphonate therapy is discontinued, mineralization with formation of HO may occur. VAC (Answer 3) is a chemotherapy regimen used in Ewings sarcoma treatment. Recombinant PTH 1,34 (Answer 2) has been shown to increase bone mineral density.

REFERENCES:

1. Board TN, Karva A, Board RE, Gambhir AK, Porter ML. The prophylaxis and treatment of heterotopic ossification following lower limb arthroplasty. J Bone Joint Surg Br. 2007 Apr;89(4):434-40. PMID:17463108 (Link to Abstract)

2. Ayers DC, Pellegrini VD Jr, Evarts CM. Prevention of heterotopic ossification in high-risk patients by radiation therapy. Clin Orthop Relat Res. 1991 Feb;(263):87-93. PMID:1899641 (Link to Abstract)

Question Authors:

Michael Hughes MD, Patrick McCulloch MD,

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(OBQ07.68) Which amputation patient would have the highest risk of developing heterotopic ossification at the amputation site? Topic

Review Topic

1. 75-year-old diabetic with an ischemic limb undergoing a transtibial amputation
2. 45-year-old woman that had a propane tank explode near her thigh undergoing a transfemoral amputation
3. 25-year-old army captain with a complex blast injury to his shin undergoing transfemoral amputation
4. 65-year-old with necrotizing fasciitis of his lower leg undergoing knee transfemoral amputation
5. 35-year-old woman with a grade IIIC open distal tibia fracture who elects for a below the knee amputation

PREFERRED RESPONSE ▶

DISCUSSION: Heterotopic ossification (HO) most commonly occurs at the amputation site if the amputation was performed thru the zone of injury, especially if the injury was a blast mechanism. Potter et al reviewed 213 military amputations and found heterotopic ossification was present in 63% of the residual limbs. A final amputation level within the zone of injury and a blast mechanism were risk factors for the development of heterotopic ossification. Symptomatic HO was removed successfully with a low recurrence rate (<10%). Other answers listed describe amputations at a level above the zone of injury.

REFERENCES:

1. Potter BK, Burns TC, Lacap AP, Granville RR, Gajewski DA. Heterotopic ossification following traumatic and combat-related amputations. Prevalence, risk factors, and preliminary results of excision. J Bone Joint Surg Am. 2007 Mar;89(3):476-86. PMID:17332095 (Link to Abstract)

Question Authors:

Charles Jobin MD,

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(OBQ07.159) Heterotopic ossification has been recognized as a rare complication from Steinmann pins placed in which location for traction purposes? Topic

Review Topic

1. distal femur
2. proximal tibia
3. calcaneus
4. radius shaft
5. metacarpal shaft

PREFERRED RESPONSE ▶

DISCUSSION: Symptomatic heterotopic ossification of the quadriceps may occur following placement of a large-diameter Steinmann pin for the purpose of temporary skeletal traction. This potential complication should be considered when using a large-diameter Steinmann pin in the distal femur for skeletal traction. The other locations have not been recognized as areas for heterotopic ossification.

The referenced study reported on a case series of symptomatic quadriceps heterotopic ossification as a result of large diameter traction pin placement into the distal femur.

REFERENCES:

1. Specht LM, Gupta S, Egol KA, Koval KJ. Heterotopic ossification of the quadriceps following distal femoral traction: a report of three cases and a review of the literature. J Orthop Trauma. 2004 Apr;18(4):241-6 PMID:15087970 (Link to Abstract)

Question Authors:

Greg Galano MD, Guillem Lomas MD, Ben Taylor MD,

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(OBQ05.61) All of the following have been shown in the literature to increase the risk of heterotopic ossification EXCEPT? Topic

Review Topic

1. Prolonged ventilator time in multiply traumatized patients
2. Spinal cord injury
3. Amputation through the zone of injury in patients injured in blasts
4. Open fractures
5. Severe burns

PREFERRED RESPONSE ▶

DISCUSSION: Heterotopic ossification is the formation of bone outside of the skeleton - often occuring within skeletal muscles. Illustrations A and B are representative examples of heterotopic ossification around the elbow and following a total hip arthroplasty. Around the hip, heterotopic ossification is classified via the Brooker classification (Illustration C). It is caused by activation and proliferation of mesenchymal stem cells and is an active research area in trauma and rehabilitation. Prolonged ventilator time, brain injury, spinal cord injury, burns, neurologic compromise (measured via GCS), and amputation thru the zone of injury in a patient injured in a blast are all literature proven risk factors for development of heterotopic ossification. Pape et al retrospectively studied heterotopic ossifications in patients with blunt multiple trauma with and without associated head injury. They evaluated two cohorts of patients at risk for development of heterotopic ossification and found prolonged ventilation times in multiply traumatized patients was associated with an increased risk of development of heterotopic ossification.

Illustrations: A

REFERENCES:

1. Pape HC, Lehmann U, van Griensven M, Gänsslen A, von Glinski S, Krettek C. Heterotopic ossifications in patients after severe blunt trauma with and without head trauma: incidence and patterns of distribution. J Orthop Trauma. 2001 May;15(4):229-37. PMID:11371787 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD,

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(OBQ04.8) A 32-year-old male sustains a the injury shown in Figure A after a high-speed motor vehicle collision. Which factor has been found to have the highest direct correlation with severe heterotopic ossification after traumatic knee dislocation? Topic

Review Topic

FIGURES: A

1. Injury Severity Score (ISS)
2. Glascow Coma Scale (GCS)
3. Timing of knee reconstruction
4. Number of ligaments reconstructed
5. Open ligament reconstruction

PREFERRED RESPONSE ▶

DISCUSSION: Figure A shows a knee dislocation with cruciate ligament avulsion injuries. Development of significant heterotopic ossification (HO) formation has been shown to be most directly correlated to the ISS score.

Mills and Tejwani looked at multiple variables including injury severity score (ISS), Glascow coma scale (GCS), closed head injury (CHI), timing of surgery (> or < 3 weeks) and type of surgery (open vs. arthroscopic, number of ligaments reconstructed) in its relation to the formation of HO following knee dislocation. In the final group the sensitivity and specificity of the ISS in relation to HO formation was 100%, while presence of CHI had a specificity of 97%. Timing, type of surgery and approach did not influence HO formation.

REFERENCES:

1. Mills WJ and Tejwani N. Heterotopic ossification after knee dislocation: The predictive value of the injury severity score. J Orthop Trauma, 17:338-45. 2003 PMID:12759638 (Link to Abstract)

Question Authors:

Ben Taylor MD, John Badylak MD, Michael Hughes MD,

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Groups

ABOS II: Heterotopic Ossification

General - Oral Boards Review

7/29/2011

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Evidence & References Show References

Level of Evidence 3 (Retrospective Cohort Study or Case-Control Study)

Pape HC, Lehmann U, van Griensven M, Gänsslen A, von Glinski S, Krettek C. Heterotopic ossifications in patients after severe blunt trauma with and without head trauma: incidence and patterns of distribution. J Orthop Trauma. 2001 May;15(4):229-37. PMID:11371787 (Link to Abstract)

Level of Evidence 4 (Case Series)

Mills WJ and Tejwani N. Heterotopic ossification after knee dislocation: The predictive value of the injury severity score. J Orthop Trauma, 17:338-45. 2003 PMID:12759638 (Link to Abstract)

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Board TN, Karva A, Board RE, Gambhir AK, Porter ML. The prophylaxis and treatment of heterotopic ossification following lower limb arthroplasty. J Bone Joint Surg Br. 2007 Apr;89(4):434-40. PMID:17463108 (Link to Abstract)
Ayers DC, Pellegrini VD Jr, Evarts CM. Prevention of heterotopic ossification in high-risk patients by radiation therapy. Clin Orthop Relat Res. 1991 Feb;(263):87-93. PMID:1899641 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012

Undefined

Potter BK, Burns TC, Lacap AP, Granville RR, Gajewski DA. Heterotopic ossification following traumatic and combat-related amputations. Prevalence, risk factors, and preliminary results of excision. J Bone Joint Surg Am. 2007 Mar;89(3):476-86. PMID:17332095 (Link to Abstract)
Specht LM, Gupta S, Egol KA, Koval KJ. Heterotopic ossification of the quadriceps following distal femoral traction: a report of three cases and a review of the literature. J Orthop Trauma. 2004 Apr;18(4):241-6 PMID:15087970 (Link to Abstract)

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Heterotopic Ossification

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