http://upload.orthobullets.com/topic/8044/images/53a_moved.jpg
http://upload.orthobullets.com/topic/8044/images/53c_moved.jpg
http://upload.orthobullets.com/topic/8044/images/53d_moved.jpg
http://upload.orthobullets.com/topic/8044/images/elbow.jpg
http://upload.orthobullets.com/topic/8044/images/xr ho knee medial.jpg
http://upload.orthobullets.com/topic/8044/images/ultrasound ho.jpg

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)
    • demographics
      • male:female = 2:1
      • especially men with hypertrophic osteoarthritis, and women >65y
    • 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) q   High ISS is a risk 11%
Traumatic brain injury (TBI) Higher incidence in the spastic limbs of the patient      11%
Spinal cord injury 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), and prolonged ventilator use  
Other diseases
DISH, ankylosing spondylitis, hypertrophic osteoarthritis (prominent osteophytes)
 
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) because of hematoma, soft tissue injury from percutaneous insertion. rare
Amputation through zone of injury   Worse with blast mechanism  63%
Surgical approaches Extended iliofemoral > Kocher-Langenbeck > ilioinguinal approach (acetabular fracture). Anterior approach > posterior approach for femoral head fracture fixation.  25% (acetabular fracture fixation)
Total hip arthroplasty THA Complications  Increased risk with psoas tenotomy and cementless components (more particulate debris and marrow spillage, muscle trauma from difficult broaching). Smith-Petersen and Hardinge > transtrochanteric > posterior (posterior has lowest risk of HO). 53% (significant in only 5%)
Total knee arthroplasty 

TKA complications  Increased risk with notching anterior femur, surgical trauma to quadriceps, distal femur exposure and periosteal stripping, and postop manipulation under anesthesia, and high lumbar BMD

 
 
Classification
  • Subtypes
    • neurogenic HO (discussed here)
    • traumatic myositis ossificans 
    • fibrodysplasia ossificans progressiva (Munchmeyer'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
      • with HO after TKA, might develop quad muscle snapping or patella instability
    • 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
  • 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 (>250IU/L)
      • ALP removes inhibitors of mineralization
      • nonspecific, may be elevated with skeletal trauma
      • cannot determine maturity of HO
      • elevated 12wks after surgery is predictor
    • elevated CRP
      • correlates with inflammatory activity of HO better than ESR
      • normalization of CRP may correlate with maturity of HO
    • elevated ESR (>35mm/h)
      • 12wks after THA is predictor
    • 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 10days to 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 700cGy can be given either 4 hours preop or within 72 hours postoperatively 
        • <550cGy not effective
  • 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 (controversial)
        • marked decrease in bone scan activity AND normalization of ALP
        • 6 months following general trauma
        • 1 year following SCI
        • 1.5 years following TBI
          • some data suggests equivalent results when comparing early versus late resection
      • 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


 

Please rate topic.

Average 4.2 of 19 Ratings

Questions (6)

(OBQ12.125) A 24-year-old male presents with a painful, stiff elbow after sustaining an injury 4 months ago. A radiograph is shown in Figure A. Which of the following statements is true about his condition? Review Topic

QID:4485
FIGURES:
1

Early excision has been found to decrease rate of recurrence compared to excision after maturity

5%

(136/2879)

2

Radiographs may be used to assess maturity of the lesion

46%

(1331/2879)

3

Bone scan will always be negative once the lesion is considered mature

19%

(545/2879)

4

The lesion is considered mature 12 months after initial radiographic findings are seen

19%

(534/2879)

5

Alkaline phosphatase level measurements are used to determine the maturity of the lesion

11%

(306/2879)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Radiographs are extremely useful in the staging of heterotopic ossification, and will show the development of sharp cortical margins once the lesion has reached maturity.

Heterotopic bone is a condition in which lamellar bone forms in non-ossified soft tissues. In the early stages, studies such as MRI and bone scan are more sensitive for diagnosis, as radiographs may appear normal for the first three weeks. After the appropriate diagnosis is made, sequential radiographs are useful for monitoring the progression of the ossification. Once it has reached the mature stage, sharp cortical margins will appear, and surgical resection may be considered.

Cipriano et al. review heterotopic ossification following traumatic brain and spinal cord injuries. They discuss that the rate of radiographic recurrence is high (82-100%), but that that the rate of clinically significant recurrence is much lower (17-52%).

Figure A is a lateral radiograph of an elbow showing extensive heterotopic ossification with sharp cortical margins. This is consistent with heterotopic ossification in the mature stage.

Incorrect Answers:
Answer 1: Waiting for maturity has been found by some studies to decrease the chance of recurrence when compared to early excision.
Answer 3: Bone scans may still be positive after the lesion has reached maturity.
Answer 4: Duration from initial injury does not always correlate with level of maturity.
Answer 5: Alkaline phosphatase levels may aid in the diagnosis of heterotopic ossification, but are not used to assess the level of maturity of the lesion.


Please rate question.

Average 3.0 of 23 Ratings

Question COMMENTS (7)

(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? Review Topic

QID:2948
FIGURES:
1

700 cGy of radiation within 72 hours of surgery

92%

(982/1069)

2

Pulsed administration of recombinant PTH 1,34 postoperatively for 1 year

1%

(10/1069)

3

3 cycles of VAC (Vincristine, Actinomycin D, and Cyclophosphamide)

1%

(10/1069)

4

700 cGy of radiation 2 weeks prior to surgery

1%

(11/1069)

5

3 treatments of 700 cGy of radiation divided over 1 week after surgery

5%

(52/1069)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

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 bisphosphonates are not effective for prophylaxis as they inhibit mineralization of osteoid, but do not prevent the formation of osteoid matrix and when bisphosphonate 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.


Please rate question.

Average 4.0 of 20 Ratings

Question COMMENTS (5)

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

QID:729
1

75-year-old diabetic with an ischemic limb undergoing a transtibial amputation

3%

(13/492)

2

45-year-old woman that had a propane tank explode near her thigh undergoing a transfemoral amputation

66%

(324/492)

3

25-year-old army captain with a complex blast injury to his shin undergoing transfemoral amputation

25%

(125/492)

4

65-year-old with necrotizing fasciitis of his lower leg undergoing knee transfemoral amputation

2%

(8/492)

5

35-year-old woman with a grade IIIC open distal tibia fracture who elects for a below the knee amputation

4%

(20/492)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

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.


Please rate question.

Average 3.0 of 29 Ratings

Question COMMENTS (2)

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

QID:820
1

distal femur

81%

(770/950)

2

proximal tibia

4%

(42/950)

3

calcaneus

5%

(45/950)

4

radius shaft

8%

(80/950)

5

metacarpal shaft

1%

(10/950)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

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.


Please rate question.

Average 2.0 of 32 Ratings

Question COMMENTS (2)

(OBQ05.61) Which of the following has not been shown in the literature to increase the risk of heterotopic ossification? Review Topic

QID:947
1

Prolonged ventilator time in multiply traumatized patients

14%

(177/1261)

2

Spinal cord injury

13%

(168/1261)

3

Amputation through the zone of injury in patients injured in blasts

4%

(54/1261)

4

Open fractures

50%

(636/1261)

5

Severe burns

18%

(223/1261)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

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:

Please rate question.

Average 3.0 of 22 Ratings

Question COMMENTS (2)

(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? Review Topic

QID:119
FIGURES:
1

Injury Severity Score (ISS)

41%

(524/1271)

2

Glascow Coma Scale (GCS)

46%

(585/1271)

3

Timing of knee reconstruction

4%

(57/1271)

4

Number of ligaments reconstructed

4%

(45/1271)

5

Open ligament reconstruction

4%

(52/1271)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

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.


Please rate question.

Average 1.0 of 78 Ratings

Question COMMENTS (5)
Sorry, this question is available to Virtual Curriculum members only.

Click HERE to learn more and purchase the Virtual Curriculum today!


GROUPS (1)
EVIDENCE & REFERENCES (23)
Topic COMMENTS (27)