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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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Questions (6)

(OBQ13.203) What type of tissue is formed by the activation of marrow mesenchymal cells following subchondral drilling of an 8x7 mm osteochondral defect? Review Topic

QID:4838
1

Elastic cartilage

0%

(4/2679)

2

Fibrocartilage

96%

(2572/2679)

3

Hyaline cartilage

1%

(40/2679)

4

Trabecular bone

1%

(20/2679)

5

Hypertrophic chondrocytes

1%

(32/2679)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Subchondral drilling of an osteochondral defect will create fibrocartilage tissue.

The premise of subchondral drilling is to utilize the marrow stimulating effects of subchondral bone to create fibrocartilage in place of hyaline cartilage defects. Penetrating the subchondral plate will expose the damaged area to progenitor cells that reside in the subchondral bone. Activating of progenitor cells will create fibrocartilaginous scarring. Fibrocartilage is biologically and biomechanically inferior to native hyaline cartilage. However, this repair process will create a congruent joint surface and prevent further deterioration of the adjacent cartilaginous tissue.

Mithoefer et al. examined forty-eight patients with isolated full-thickness articular cartilage defects of the femur that were treated with a microfracture technique. MRI imaging showed good or moderate tissue repair and filling in 83% of patients. These patients showed greater improvements in their SF-36 score after treatment compared to the other 17% of patients with low tissue repair and filling.

Illustration A shows a diagram of bone-marrow stimulating technique of an osteochondral defect. The steps of this technique include (from A-D): debriding the sclerotic bone, trimming the edges of unstable articular cartilage, drilling past the subchondral plate (~4mm), and obtaining sufficient converge between holes to allow for a mesenchymal clot.

Incorrect Answers:
Answer 1: Elastic cartilage is mostly found in the external ear, epiglottis and larynx.
Answer 3: Hyaline cartilage is mostly found in in the ribs, nose, larynx, trachea.
Answer 4: Subchondral drilling has been shown to alter the subchondral bone plate and trabecular bone composition by causing micro cysts and intralesional osteophytes that later fill in with cancellous bone.
Answer 5: Hypertrophic chondrocytes are cells not tissue. Subchondral drilling has no effect on their activity.

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(OBQ11.1) A 24-year-old female has moderate arthrosis of the medial facet of the patella and the medial femoral condyle. Which of the following procedures is contraindicated? Review Topic

QID:3424
1

Anterior (Maquet) tibial tubercle osteotomy

3%

(87/2525)

2

Anteromedial (Fulkerson) tibial tubercle osteotomy

78%

(1960/2525)

3

Anterolateral tibial tubercle osteotomy

9%

(235/2525)

4

Medial opening wedge high tibial osteotomy

6%

(141/2525)

5

Lateral closing wedge high tibial osteotomy

4%

(92/2525)

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PREFERRED RESPONSE 2

Anteromedial (Fulkerson) tibial tubercle osteotomy is contraindicated in patients with significant arthrosis of the medial facet of the patella and the medial femoral condyle.

Anteromedial tibial tubercle osteotomy (Fulkerson procedure) involves the transfer of the tubercle to a more anterior and medial location. Changing the vector of the extensor mechanism can help reduce lateral patellar subluxation/dislocation and concomitantly unload areas of arthrosis on the distal and lateral aspects of the patella. When performing a tibial tubercle transfer, the surgeon should beware of proximal lesions or medial facet or condylar lesions. Thus, intact proximal and medial cartilage is required to obtain the maximum benefit from this procedure.

Pascual-Garrido et al, in a Level 4 study, reviewed 62 patients who underwent autologous chondrocyte implantation of the patellofemoral joint for defects an average size of 4cm(2). Those that underwent anteromedialization tended to have better clinical outcomes than those without realignment, however 44% of the patients still required a subsequent procedure.

Paulos et al, in a Level 3 study, prospectively followed 25 patients with a dislocating patella that underwent a derotational high tibial osteotomy, medial, or anteromedial tibial tubercle osteotomy. There were no dislocation recurrences in either group and 92% of the patients stated that they were happy with the results of their surgery and would undergo the procedure again.

Illustration A shows a video of a Fulkerson osteotomy being performed on a cadaveric specimen.

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(OBQ10.257) Following a medial femoral condyle osteochondral autograft mosaicplasty, which of the following statements best describes the fixation of the graft? Review Topic

QID:3353
1

Graft fixation strength increases linearly with time until subchondral union at 3 months

4%

(17/390)

2

Graft fixation strength initially decreases during the early healing phase, and then increases with subchondral bone healing

85%

(332/390)

3

Graft fixation strength does not change during the first 3 months following surgery

2%

(6/390)

4

Graft fixation strength is enhanced by early weight bearing

5%

(20/390)

5

Graft fixation strength initially increases over the first 6 weeks, then recedes with bony remodeling

4%

(15/390)

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PREFERRED RESPONSE 2

Studies have shown graft fixation strength initially decreases during the early healing phase, and then increases with subchondral bone healing.

Following mosaicplasty, appropriate post-operative rehabilitation and weight-bearing status must be based upon the fixation of the osteochondral autograft plugs. In addition, early non-weight bearing motion is important to prevent stiffness and protect the joint surfaces with synovial fluid.

Whiteside et al. performed a porcine study evaluating the fixation strength of osteochondral autograft mosaicplasty during the first week following implantation. The graft fixation was notably weaker one week following surgery due to the post-operative response and host remodeling. These results suggest that protected weight bearing should be used until the osteochondral plugs have healed into the subchondral bone, generally by 3 months.


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(OBQ08.94) A 32-year-old female is referred to you for definitive treatment of a symptomatic focal chondral defect on her medial femoral condyle. A photograph from a recent diagnostic arthroscopy shows the defect (Figure A), which measured 25 x 25mm after debridement. What surgical treatment would you recommend? Review Topic

QID:480
FIGURES:
1

Osteochondral autograft with 1-2 plugs

30%

(44/149)

2

Osteochondral allograft

42%

(63/149)

3

Microfracture

22%

(33/149)

4

Unicompartment arthoplasty

5%

(8/149)

5

Abrasion arthroplasty

1%

(1/149)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Based on the age of this patient and the size of this lesion (2 x 2.5 = approx 5cm square) an osteochondral allograft plug is the best choice. The results of microfracture are better for contained defects less than 2cm square. Autografts are generally reserved for smaller defects as well because harvesting enough plugs to fill this defect may lead to significant donor site morbidity. Chondroplasty and abrasion arthroplasty are not good solutions to this chondral defect in a young symptomatic patient. Autologous chondrocyte implantation (ACI) would also be a correct response, but it was not listed.

Bert discusses the science, histology, history, and clinical results of abrasion arthroplasty for treatment of osteoarthritis of the knee.

Alford et al. review the indications for treatment of chondral defects and describe the various treatment options. In addition, they discuss clinical scenarios regarding comorbid conditions including ligament instability, meniscal deficiency, and malalignment by developing a treatment algorithm (Illustration A).

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(SBQ07.32) A patient with a symptomatic chondral defect undergoes the arthroscopic procedure seen in Figure A. The reparative tissue would best be described as which of the following? Review Topic

QID:1417
FIGURES:
1

Fibrocartilage

94%

(700/741)

2

Fibrous tissue

2%

(15/741)

3

Elastofibroma

0%

(2/741)

4

Hyaline cartilage

3%

(20/741)

5

Chondromalacia

0%

(3/741)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

The figure is an arthroscopic photo of a microfracture procedure, which creates a reparative tissue best described as fibrocartilage. Microfracture is a marrow stimulation technique where stem cells from the medullary canal are given access to the base of the lesion by making small perforations in the subchondral bone. The rationale for this technique is based on these stem cells differentiating into cells that will produce an articular cartilage repair. However, biopsy findings in animals and humans have demonstrated primarily a fibrocartilagenous repair tissue and not true articular cartilage regeneration. The collagen type found in hyaline or articular cartilage is of the type II variety. Fibrocartilage possesses some type II, but is mostly type I and III cartilage.

Both the Intructional Course Lecture and the textbook by Buckwalter provide an in-depth review of articular cartilage biology and the background for chondral resurfacing techniques.

Incrorrect Responses:
2. Fibrous tissue is created by fibrocytes and lacks type II collagen.
3. Elastofibroma is a distractor (elastofibroma dorsi is a fibrous tumor with a predeliction for the scapulothoracic joint).
4. Hyaline cartilage is true articular cartilage with predominantly type II collagen. It also has columnar organization and a lamina splendens (which differentiates it from what has been called hyaline-like tissue).
5. Chondromalacia refers abnormal softening of the cartilage and is a common pathologic condition of the the knee.


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(OBQ06.186) All of the following are acceptable scenarios for the use of autologous chondrocyte implantation (ACI) in the patellofemoral joint EXCEPT: Review Topic

QID:372
1

Grade 4 lesion of the medial femoral condyle

11%

(91/833)

2

Grade 4 lesion of the trochlea

6%

(47/833)

3

Joint space narrowing on Merchant view

54%

(447/833)

4

Varus mechanical axis on standing full length radiograph

25%

(207/833)

5

Concomitant anteromedial tibial tubercle transfer osteotomy (Fulkerson's)

5%

(40/833)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

Joint space narrowing on a merchant view is a contraindication for autologous chondrocyte implantation for patellofemoral arthritis.

Saleh et al states ACI relies on intact, full-thickness cartilage margins to maintain the joint space so that the growing cartilage repair tissue may fill the defect. Cartilage loss seen with diffuse arthritis is not amenable to ACI. It is critical that there is a preserved patellofemoral joint space as seen on a Merchant or skyline view. The article states that ACI can be used for grade 3 or 4 defects on the patella or trochlea. Concomitant realigment procedures of the patellofemoral joint (such as lateral release, medial tubercle transfer, or anteromedial tubercle transfer) and the tibiofemoral joint (high tibial osteotomy) are indicated in the presence of mechanical malalignment.

The article by Peterson et al followed 94 patients for 2-9 years and found graft failure in only seven patients. Histologic analysis of 37 "second-look" arthroscopy biopsy specimens showed a correlation between hyaline-like tissue and good to excellent clinical results.

NOTICE: ACI is not FDA approved for use on the patella and the use of ACI "off-label" should be discussed with patients preoperatively.



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