Microfracture Technique in the Knee

Microfracture Technique in the Knee

Chapter Synopsis

• Microfracture is a safe, minimally invasive, technically simple, and cost-effective marrow stimulation technique that provides effective short-term functional improvement of small to medium cartilage defects. Appropriate indications, attention to surgical detail, and well-structured rehabilitation help to optimize the outcome from this cartilage repair technique. Shortcomings include limited hyaline repair tissue, variable repair cartilage volume, subchondral bone changes, functional deterioration in some patients, and unclear long-term efficacy. Despite its limitations, microfracture is still the most frequently used cartilage repair technique.

Important Points

• Indication: Symptomatic cartilage lesions of femur, patella, and tibia smaller than 4 cm².

• Technical steps: Debridement, calcified cartilage removal, systematic microfracture from periphery with use of a spiral pattern, leaving 3 to 4 mm between individual microfracture holes.

• Individualized rehabilitation addresses unique defect characteristics and associated pathology.

Clinical and Surgical Pearls

• Preoperative patient counseling and close cooperation with well-trained physical therapists improves postoperative rehabilitation.

• Gentle but thorough removal of calcified cartilage improves repair tissue volume and adherence.

• Systematic placement of microfracture holes optimizes clot adherence and mesenchymal stem cell distribution and reduces risk for subchondral bone collapse and bony overgrowth.

• Criteria-based progression during postoperative rehabilitation avoids activity-related pain and swelling.

Clinical and Surgical Pitfalls

• Insufficient debridement to a stable peripheral cartilage margin and failure to remove the calcified cartilage layer limit peripheral and basilar integration.

• Compromised subchondral bone plate integrity can occur with inappropriate microfracture technique.

• Insufficient subchondral bone penetration with limited access to mesenchymal stem cells may reduce the quality and quantity of the repair cartilage tissue.

• Clot displacement or limited integration of repair tissue may occur from premature weight bearing.

• Video 64-1: Anterior cruciate ligament tunnel preparation and graft passage

Articular cartilage injuries affect an estimated 900,000 individuals in the United States every year, resulting in considerable morbidity and disability for affected individuals with a substantial associated burden on the healthcare system.¹ Treatment of articular cartilage injury in the knee still presents a great therapeutic challenge owing to the limited regenerative capacity of articular cartilage. Although no validated treatment algorithm exists for treating articular cartilage lesions in the knee, the arthroscopic microfracture technique is commonly used as a first-line option and frequently serves as the standard technique against which other cartilage repair procedures are compared.^2–4 Developed by Steadman in the 1980s, this widely used marrow stimulation procedure is generally regarded as safe and cost-effective.⁵ Histologic studies have demonstrated that microfracture results in a fibrocartilage or hybrid fibrohyaline repair tissue with variable proteoglycan and type II collagen content.^3,6 Microfracture is a minimally invasive and technically simple procedure clinically, and current scientific data demonstrate that close adherence to the indications for, technical details of, and postoperative rehabilitation after this technique will help to optimize the outcomes from this cartilage repair procedure in the knee.

Preoperative Considerations

Obtaining a thorough history in patients with knee cartilage defects is a critical first step in the selection of patients who are appropriate candidates for microfracture. Symptoms from cartilage defects are usually nonspecific and can mimic other knee pathology such as meniscal tears. Pain on weight bearing is frequent and is often present during impact activities. Catching and locking sensations can occur from cartilage flaps or larger defects. Joint effusion is frequently reported, particularly after demanding impact activities. Defects of the femoral condyles often produce focal tenderness over the condyle rather than the joint line. Patellar or trochlear lesions usually lead to pain when ambulating up and down stairs, driving a car, or rising from a seated or squatting position. Symptoms of patellar instability may be reported. Articular cartilage defects may manifest acutely, such as after joint trauma including knee ligament tears, or they may be a chronic issue. Any history of previous knee surgeries should be noted, because microfracture is most effective as a first-line treatment.

Physical Examination

Physical examination includes evaluation of gait pattern as well as hip, knee, and ankle range of motion. The knee should be routinely evaluated for ligamentous instability, patellar maltracking or instability, and lower extremity malalignment. Any joint effusion should be noted. Depending on defect location and size, mechanical symptoms may or may not be present and may overlap with meniscal test findings. The patient’s body mass index (BMI) should be assessed because it has been shown to correlate with functional outcome after microfracture.1,7–9

Preoperative Imaging

Plain radiographs including weight-bearing anteroposterior (AP), lateral, and Merchant views are obtained. In addition, a 45-degree flexion posteroanterior (PA) or Rosenberg view and long-leg films can help to identify the presence of osteochondral lesions, joint space narrowing, patellar maltracking, and overall lower extremity malalignment. Cartilage-sensitive magnetic resonance imaging (MRI) is a sensitive, specific, and accurate tool for noninvasive diagnosis of articular cartilage injury.⁸ It provides useful information about the status of the menisci, ligaments, and subchondral bone, as well as the size and depth of the lesion. Owing to the pathologic changes in the surrounding cartilage the final size of the defect usually is larger than defect size measured on preoperative MRI.¹

Indications and Contraindications

Microfracture is indicated for symptomatic, high-grade (grade III or IV) chondral defects of the knee in active patients who are physiologically too young for arthroplasty. This technique is most successful as a first-line treatment for isolated chondral lesions up to 4 cm² that involve the femoral condyles, trochlea, and patella. Prerequisites for successful microfracture include adequate range of motion, appropriate axial alignment or patellar tracking, ligamentous stability, and the ability to comply with the postoperative rehabilitation. Adjuvant procedures can be performed simultaneously to address coexisting pathology without negative effects on the postoperative functional outcome and activity level. Detailed indications and contraindications for microfracture are listed below.

Indications

• Symptomatic cartilage lesions of femur, patella, tibia (including incidental defects)

• Defect size less than 4 cm²

• Short preoperative duration of symptoms (optimally <12 months)

• Patient age (optimally <45 years)

Contraindications

Absolute Contraindications:

• Generalized degenerative joint changes

• Limited patient compliance

• Uncontained chondral lesions

• Severe axial malalignment of greater than 5 degrees for femoral condyle lesions (surgical realignment required)

• Patellar maltracking or instability for patellofemoral lesions

• High-grade ligamentous instability (surgical stabilization required for translation >10 mm)

• Inflammatory arthropathy

• Systemic cartilage disorder

Relative Contraindications:

• Preoperative duration of symptoms longer 12 months

• Body mass index greater than 30

• Meniscal deficiency

• Moderate to advanced chondropenia

• Defect size greater than 4 cm²

• Patient age greater than 60 years

Preoperative Planning and Counseling

Based on the history, physical examination findings, and radiologic information, the indication for microfracture or adjuvant procedures is discussed with the patient preoperatively. In-depth preoperative patient counseling is critically important to determine the patient’s demands, to assess his or her ability to comply with the postoperative rehabilitation, and to create realistic expectations and goals for postoperative knee function and activity level.

Surgical Technique

Positioning of the extremity must allow knee motion without limitation. A tourniquet is placed on the proximal thigh but not routinely inflated. Portals are positioned according to the location of the cartilage lesion to provide optimal access to the articular cartilage defect. Standard anterolateral and anteromedial portals can be used for lesions of the central femoral condyles. For defects of the posterior condyles, portals should be placed lower to facilitate access to and visualization of the defects. Far medial or lateral portals can be added if necessary. Superolateral portals can be helpful for patellar and trochlear lesions. Thorough diagnostic arthroscopy is performed to identify any additional intra-articular pathology such as meniscal tears, ligamentous disruption, patellar maltracking, or multiple cartilage defects.

Specific Steps

The specific steps of this procedure are outlined in Box 64-1.

Box 64-1 Surgical Steps

1. Complete arthroscopic joint survey to identify associated pathology and assess joint cartilage status.

2. Debride chondral defect to stable and healthy surrounding cartilage margins, and determine final defect size.

3. Gently but thoroughly remove calcified cartilage layer, avoiding bleeding from subchondral bone.

4. Start microfracture in periphery of defect with perpendicular access of the awl tip to the defect base.

5. Systematically penetrate the subchondral bone plate with use of a spiral pattern, leaving 3 to 4 mm between individual microfracture holes.

6. Ensure appropriate depth of the penetration to subchondral bone marrow by visualization of fat droplets or bleeding from the individual microfracture holes.

7. Close portal incisions tightly and avoid drain placement.

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Sep 11, 2016 | Posted by admin in SPORT MEDICINE | Comments Off

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