Osteochondritis Dissecans - Knee & Sports

Summary
- Osteochondritis Dissecans is a pathologic lesion affecting articular cartilage and subchondral bone with variable clinical patterns.
- Diagnosis may be made radiographically (notch view) but MRI usually required to determine size and stability of lesion, and to document the degree of cartilage injury.
- Treatment may be nonoperative with restricted weight bearing in children with open physis. Surgical treatment may be indicated in older patients (closed physis), lesions that are unstable and patients who have failed conservative management.

Epidemiology
- Demographics
  - juvenile form (open physes)
    
    occurs at age 10-15 while the physis is still open
  - adult form (skeletal maturity)
- Anatomic location
  - knee (most common)
    
    posterolateral aspect of medial femoral condyle (70% of lesions in knee)
  - capitellum of humerus
  - talus

Etiology
- Pathophysiology
  - mechanism/etiology may be
    
    hereditary
    
    traumatic
    
    vascular
    
    cause of adult form is thought to be vascular
  - pathoanatomic cascade
    
    softening of the overlying articular cartilage with intact articular surface
    
    early articular cartilage separation
    
    partial detachment of lesion
    
    osteochondral separation with loose bodies

                        Classification
                    
                        Clanton Classification of Osteochondritis (Clanton and DeLee)
                    
                        Type I
                    
                        Depressed osteochondral fracture
                    
                        Type II
                    
                        Fragment attached by osseous bridge
                    
                        Type III
                    
                        Detached non-displaced fragment
                    
                        Type IV
                    
                        Displaced fragment

Presentation
- Symptoms
  - pain
    
    activity related pain that is vague and poorly localized
  - mechanical symptoms
    
    indicates advanced disease
  - recurrent effusions of the knee
- Physical exam
  - localized tenderness
  - stiffness
  - swelling
  - Wilson’s test
    
    pain with internally rotating the tibia during extension of the knee between 90° and 30°, then relieving the pain with tibial external rotation

Imaging
- Radiographs
  - recommended views
    
    weight-bearing anteroposterior, lateral radiographs
    
    obtain tunnel (notch) view
    
    knee bent between 30 and 50 degrees
- MRI
  - useful for characterizing
    
    size of lesion
    
    status of subchondral bone and cartilage
    
    signal intensity surrounding lesion
    
    presence of loose bodies

Treatment
- Nonoperative
  - restricted weight bearing and bracing
    
    indications
    
    stable lesions in children with open physes
    
    asymptomatic lesions in adults
    
    outcomes
    
    50-75% will heal without fragmentation
- Operative
  - diagnostic arthroscopy
    
    indications
    
    impending physeal closure
    
    clinical signs of instability
    
    expanding lesions on plain films
    
    failed non-operative management
  - subchondral drilling with K-wire or drill
    
    indications
    
    stable lesion seen on arthroscopy
    
    performed either transchondral or retrograde
    
    outcomes
    
    leads to formation of fibrocartilagenous tissue
    
    improved outcomes in skeletally immature patients
  - fixation of unstable lesion
    
    indications
    
    unstable lesion seen on arthroscopy or MRI >2cm in size
    
    outcomes
    
    85% healing rates in juvenile OCD
  - chondral resurfacing
    
    indications
    
    large lesions, >2cm x 2cm
  - knee arthroplasty
    
    indications
    
    patients > 60 years

Techniques
- Microfracture
  - technique
    
    tap awl to a depth of 1-1.5cm below articular surface
  - post-operative
    
    NWB for 4-6 weeks with CPM
- Internal fixation
  - technique
    
    options for fixation
    
    cannulated screws
    
    Herbert screws
    
    bone pegs
    
    Kirschner wires
  - cons
    
    may require hardware removal
- Osteochondral grafting
  - arthrotomy (vs. arthroscopy) indicated in lesions > 3cm
    
    technique
    
    open vs. arthroscopic
    
    arthroscopy generally used for lesions <3cm
    
    arthrotomy used for lesions > 3cm
    
    allograft plugs
    
    autograft OATS
- Periosteal patches

Prognosis
- Juvenile form
  - prognosis correlates with
    
    age
    
    younger age correlates with better prognosis
    
    open distal femoral physes are the best predictor of successful non-operative management
    
    location
    
    lesions in lateral femoral condyle and patella have poorer prognosis
    
    appearance
    
    sclerosis on xrays correlates with poor prognosis
    
    synovial fluid behind the lesion on MRI correlates with a worse prognosis
- Adult form
  - worse prognosis
  - usually symptomatic and leads to DJD if untreated

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T

Clanton Classification of Osteochondritis (Clanton and DeLee)
Type I	Depressed osteochondral fracture
Type II	Fragment attached by osseous bridge
Type III	Detached non-displaced fragment
Type IV	Displaced fragment