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Introduction
  • Spectrum of disease entities from single, focal defects to advanced degenerative disease of articular (hyaline) cartilage
  • Epidemiology
    • incidence
      • 5-10% of people > 40 years old have high grade chondral lesions
    • location
      • chronic ACL tear
        • anterior aspect of lateral femoral chondyle and posterolateral tibial plateau
      • osteochondritis dissecans topic
        • 70% of lesions found in posterolateral aspect of medial femoral condyle
  • Pathophysiology
    • mechanism of injury
      • acute trauma or chronic repetitive overload
        • impaction resulting in cartilage softening; fissuring; flap tears; or delamination
      • the cause of OCD is unknown
    • pathomechanics
      • impaction forces greater than 24 MPa will disrupt normal cartilage
    • cellular biology
      • cartilage injuries have limited spontaneous healing and propensity to worsen over time
Anatomy
  • See Articular Cartilage Basic Science topic
Classification
 
 Outerbridge Arthroscopic Grading System
Grade 0 Normal cartilage
Grade I Softening and swelling
Grade II Superficial fissures
Grade III Deep fissures, without exposed bone               
Grade IV Exposed subchondral bone
 
ICRS (International Cartilage Repair Society) Grading System
Grade 0 Normal cartilage
Grade 1 Nearly normal (superficial lesions)
Grade 2 Abnormal (lesions extend < 50% of cartilage depth)
Grade 3 Severely abnormal (>50% of cartilage depth)
Grade 4 Severely abnormal (through the subchondral bone)
 
Presentation
  • History
    • commonly present with history of precipitating trauma
    • some defects found incidentally on MRI or arthroscopy
  • Symptoms
    • asymptomatic vs. localized knee pain
    • may complain of effusion, motion deficits, mechanical symptoms (e.g., catching, instability)
  • Physical exam
    • inspection
      • look for background factors that predispose to the formation of articular defects
        • joint laxity
        • malalignment
        • compartment overload
    • motion
      • assess range of motion, ligamentous stability, gait
Imaging
  • Radiographs
    • indications
      • used to rule out arthritis, bony defects, and check alignment
    • recommended views
      • standing AP, lateral, merchant views 
    • optional views
      • semiflexed 45 deg PA views
        • most sensitive for early joint space narrowing 
      • long-leg alignment views 
        • determine the mechanical axis 
  • CT scan
    • indications
      • better evaluation of bone loss
    • findings
      • used to measure TT-TG when evaluating the patello-femoral joint
  • MRI
    • indication
      • most sensitive for evaluating focal defects
    • views
      • Fat-suppressed T2, proton density, T2 fast spin-echo (FSE) offer improved sensitivity and specificity over standard sequences
      • dGEMRIC (delayed gadolinium-enhanced MRI for cartilage) and T2-mapping are evolving techniques to evaluate cartilage defects and repair 
Studies
  • Laboratory
    • may be used to rule out inflammatory disease 
Treatment
  • Nonoperative
    • rest, NSAIDs, physiotherapy, weight loss
      • indications
        • first line of treatment when symptoms are mild
    • viscosupplementatoin, corticosteroid injections, unloader brace
      • indications
        • controversial 
        • may provide symptomatic relief but healing of defect is unlikely
  • Operative
    • debridement/chondroplasty vs. reconstruction techniques 
      • indications
        • failure of nonoperative management 
        • acute osteochondral fractures resulting in full-thickness loss of cartilage
      • technique
        • treatment is individualized, there is no one best technique for all defects
        • decision-making algorithm is based on several factors
          • patient factors
            • age
            • skeletal maturity
            • low vs. high demand activities
            • ability to tolerate extended rehabilitation
          • defect factors
            • size of defect
            • location
            • contained vs. uncontained
            • presence or absence of subchondral bone involvement
      • basic algorithm (may vary depending on published data)
        • femoral condyle defect
          • correct malaligment, ligament instability, meniscal deficiency
          • measure size 
            • < 4 cm2 = microfracture or osteochondral autograft transfer (pallative if older/low demand)
            • > 4 cm2 = osteochondral allograft transplantation or autologous chondrocyte implantation
        • patellofemoral defect
          • address patellofemoral maltracking and malalignment
          • measure size 
            • < 4 cm2 = microfracture or osteochondral autograft transfer
            • > 4 cm2 =  autologous chondrocyte implantation (microfracture if older/low demand)
Surgical Techniques
  • Debridement / Chondroplasty
    • overview
      • goal is to debride loose flaps of cartilage
      • removal of loose chondral fragments may relieve mechanical symptoms
      • short-term benefit in 50-70% of patients
    • benefits 
      • include simple arthroscopic procedure, faster rehabilitation
    • limitations
      • problem is exposed subchondral bone or layers of injured cartilage
      • unknown natural history of progression after treatment
  • Fixation of Unstable Fragments
    • overview
      • need osteochondral fragment with adequate subchondral bone
    • technique
      • debride underlying nonviable tissue
      • consider drilling subchondral bone or adding local bone graft
      • fix with absorbable or nonabsorbable screws or devices
    • benefits
      • best results for unstable osteochondritis dissecans (OCD) fragments in patients with open physis
    • limitations
      • lower healing rates in skeletally mature patients
      • nonabsorbable fixation (headless screws) should be removed at 3-6 months 
  • Marrow Stimulation Techniques 
    • overview
      • goal is to allow access of marrow elements into defect to stimulate the formation of reparative tissue
      • includes microfracture, abrasion chondroplasty, osteochondral drilling
    • microfracture technique 
      • defect is prepared with stable vertical walls and the calcified cartilage layer is removed
      • awls are used to make multiple perforations through the subchondral bone 3 - 4 mm apart 
      • protected weight bearing and continuous passive motion (CPM) are used while mesenchymal stem cells mature into mainly fibrocartilage  
    • benefits
      • include cost-effectiveness, single-stage, arthroscopic
      • best results for acute, contained cartilage lesions less than 2 cm x 2cm
    • limitations
      • poor results for larger defects >2 cm x 2cm
      • does not address bone defects
      • requires limitation of weight bearing for 6 - 8 weeks
  • Osteochondral autograft / Mosaicplasty
    • overview
      • goal is to replace a cartilage defect in a high weight bearing area with normal autologous cartilage and bone plug(s) from a lower weight bearing area
      • chondrocytes remain viable, bone graft is incorporated into subchondral bone and overlying cartilage layer heals. 
    • technique
      • a recipient socket is drilled at the site of the defect
      • a single or multiple small cylinders of normal articular cartilage with underlying bone are cored out from lesser weight bearing areas (periphery of trochlea or notch)
      • plugs are then press-fit into the defect
    • limitations
      • size constraints and donor site morbidity limit usage of this technique
      • matching the size and radius of curvature of cartilage defect is difficult
      • fixation strength of graft initially decreases with initial healing response
        • weight bearing should be delayed 3 months 
    • benefits 
      • include autologous tissue, cost-effectiveness, single-stage, may be performed arthroscopically
  • Osteochondral allograft transplantation 
    • overview 
      • goal is to replace cartilage defect with live chondrocytes in mature matrix along with underlying bone
      • fresh, refrigerated grafts are used which retain chondrocyte viability
      • may be performed as a bulk graft (fixed with screws) or shell (dowels) grafts
    • technique
      • match the size and radius of curvature of articular cartilage with donor tissue
      • a recipient socket is drilled at the site of the defect 
      • an osteochondral dowel of the appropriate size is cored out of the donor 
      • the dowel is press-fit into place
    • benefits 
      • include ability to address larger defects, can correct significant bone loss, useful in revision of other techniques
    • limitations
      • limited availability and high cost of donor tissue
      • live allograft tissue carries potential risk of infection 
  • Autologous chondrocyte implantation (ACI) 
    • overview
      • cell therapy with goal of forming autologous "hyaline-like" cartilage
    • technique 
      • arthroscopic harvest of cartilage from a lesser weight bearing area
      • in the lab, chondrocytes are released from matrix and are expanded in culture
      • defect is prepared, and chondrocytes are then injected under a periosteal patch sewn over the defect during a second surgery
    • benefits 
      • may provide better histologic tissue than marrow stimulation
      • long term results comparable to microfracture in most series
      • include regeneration of autologous tissue, can address larger defects
    • limitations 
      • must have full-thickness cartilage margins around the defect
      • open surgery
      • 2-stage procedure
      • prolonged protection necessary to allow for maturation
  • Patellar cartilage unloading procedures
    • Maquet (tibia tubercle anteriorization)
      • indicated only for distal pole lesions
      • only elevate 1 cm or else risk of skin necrosis
      • contraindications
        • superior patellar arthrosis (scope before you perform the surgery)
    • Fulkerson alignment surgery (tibia tubercle anteriorization and medialization  post 
      • indications (controversial)
        • lateral and distal pole lesions 
        • increased Q angle
      • contraindications
        • superior medial patellar arthrosis (scope before you perform the surgery) 
        • skeletal immaturity
  • Matrix-associated autologous chondrocyte implantation
    • overview
      • example is "MACI" 
      • cells are cultured and embedded in a matrix or scaffold
      • matrix is secured with fibrin glue or sutures
    • benefits
      • include ability to perform without suturing, may be performed arthroscopically
    • limitations
      • 2-stage procedure
      • in worldwide use/evaluation- not available in the USA
 

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