Cartilage Repair with Microfracture: What Surgeons Need to Know

Introduction

Microfracture surgery has emerged as a pivotal procedure in the management of articular cartilage injuries, particularly in the knee joint. This surgical technique aims to stimulate the body’s natural repair mechanisms to regenerate hyaline-like cartilage, providing relief from pain and improving joint function. Despite the simplicity of the procedure, the outcomes can be influenced by various factors, including patient selection, surgical technique, and postoperative care. This comprehensive guide will delve into every aspect of microfracture surgery, providing surgeons with a detailed understanding of the procedure, from indications to long-term outcomes.

Indications for Microfracture Surgery

Microfracture surgery is primarily indicated for patients with full-thickness cartilage lesions in the weight-bearing areas of the knee. These defects are often the result of trauma, sports injuries, or degenerative conditions like osteoarthritis. The ideal candidate for microfracture surgery is typically younger, active, and has a single, well-defined lesion. The size of the lesion plays a critical role in the success of the surgery; generally, defects less than 2-3 cm² are most suitable for this procedure.

Common Indications:

• Focal chondral defects in the knee joint
• Symptomatic osteochondritis dissecans (OCD)
• Post-traumatic chondral lesions
• Early-stage osteoarthritis with localized cartilage damage

Preoperative Evaluation

A thorough preoperative evaluation is crucial to identify the suitability of the patient for microfracture surgery. This involves a detailed history, physical examination, and imaging studies.

History and Physical Examination:

• Assess the duration, location, and severity of symptoms.
• Evaluate the patient’s activity level and overall joint health.
• Conduct a physical examination to determine the extent of joint swelling, range of motion, and mechanical symptoms like locking or catching.

Imaging Studies:

• MRI: Magnetic Resonance Imaging is the gold standard for assessing cartilage lesions. It helps in evaluating the size, depth, and location of the defect.
• X-rays: Useful for ruling out other conditions such as fractures or advanced osteoarthritis.
• Arthroscopy: In some cases, diagnostic arthroscopy is performed to confirm the extent and location of the cartilage damage.

Contraindications

Not all patients with cartilage defects are suitable candidates for microfracture surgery. Contraindications must be carefully considered to avoid poor outcomes.

Absolute Contraindications:

• Advanced osteoarthritis with diffuse cartilage loss
• Large, multifocal cartilage lesions
• Severe joint malalignment or instability
• Obesity, as it increases the load on the affected joint

Relative Contraindications:

• Age over 50 years, as the healing potential decreases with age
• Smoking, which can impair cartilage healing
• High-impact sports participation, which may overload the repair site

Surgical Techniques and Steps

Microfracture surgery is a minimally invasive procedure that can be performed arthroscopically. The primary goal is to create a controlled environment that stimulates the formation of a fibrocartilage repair tissue.

Step-by-Step Procedure:

1. Patient Positioning and Anesthesia:
   • The patient is positioned supine with the affected knee placed in a leg holder.
   • General or regional anesthesia is administered.
2. Arthroscopic Access:
   • Standard anterolateral and anteromedial portals are created to access the knee joint.
   • The joint is thoroughly examined, and any loose bodies or meniscal tears are addressed.
3. Preparation of the Lesion:
   • The cartilage defect is debrided to create stable, perpendicular edges.
   • The subchondral bone is exposed by removing any calcified cartilage layer, ensuring a well-defined defect.
4. Microfracture Technique:
   • A microfracture awl is used to create small holes in the exposed subchondral bone.
   • The holes should be 3-4 mm apart and 2-4 mm deep to penetrate the subchondral bone without causing excessive damage.
   • This technique allows the bone marrow to leak into the defect, forming a blood clot that contains mesenchymal stem cells.
5. Postoperative Hemostasis:
   • The knee is thoroughly irrigated to remove any debris, and hemostasis is achieved.
   • The portals are closed, and a sterile dressing is applied.

Postoperative Care

The success of microfracture surgery is highly dependent on the postoperative rehabilitation protocol. The primary goals are to protect the repair site while promoting the formation of stable fibrocartilage.

Immediate Postoperative Phase:

• Weight-Bearing: Patients are typically non-weight-bearing for 6-8 weeks to protect the repair site.
• Cryotherapy: Ice application is recommended to reduce pain and swelling.
• Continuous Passive Motion (CPM): Early initiation of CPM is crucial to promote cartilage healing and prevent joint stiffness.

Rehabilitation Protocol:

• Phase 1 (0-6 Weeks): Focus on pain management, swelling reduction, and gentle range-of-motion exercises.
• Phase 2 (6-12 Weeks): Gradual introduction of weight-bearing activities, closed-chain strengthening exercises, and stationary biking.
• Phase 3 (3-6 Months): Progressive strengthening, balance training, and low-impact cardiovascular exercises.
• Phase 4 (6-12 Months): Return to sport-specific activities, with careful monitoring of the patient’s symptoms.

Possible Complications

While microfracture surgery is generally safe, like any surgical procedure, it carries potential risks.

Short-Term Complications:

• Infection: Though rare, infection can occur and may require surgical intervention.
• Hemarthrosis: Accumulation of blood in the joint, leading to pain and swelling.
• Deep Vein Thrombosis (DVT): A rare but serious complication that can be mitigated with prophylactic measures.

Long-Term Complications:

• Incomplete Healing: The formation of fibrocartilage instead of hyaline cartilage, leading to less durable repair.
• Joint Stiffness: Can result from inadequate postoperative rehabilitation or prolonged immobilization.
• Recurrent Symptoms: Some patients may experience persistent pain or functional limitations despite surgery.

Different Techniques

Several modifications of the traditional microfracture technique have been developed to improve outcomes.

NanoFracture:

• A newer technique that uses smaller, more precise instruments to create microfractures, potentially leading to better quality repair tissue.

Augmented Microfracture:

• The addition of biological agents such as platelet-rich plasma (PRP) or stem cells to enhance cartilage regeneration.

Autologous Matrix-Induced Chondrogenesis (AMIC):

• Combines microfracture with a collagen membrane to stabilize the clot and improve cartilage repair.

Prognosis and Outcome

The prognosis of microfracture surgery varies depending on several factors, including the size and location of the lesion, the patient’s age, and adherence to postoperative rehabilitation.

Positive Outcomes:

• Many patients experience significant pain relief and improved joint function, especially in the short to medium term.
• Younger patients with small, isolated lesions tend to have the best outcomes.

Limitations:

• The repaired cartilage is fibrocartilage, which is less durable than the original hyaline cartilage.
• Long-term outcomes may include a gradual deterioration of the repair site, leading to the need for additional interventions.

Alternative Options

For patients who are not ideal candidates for microfracture surgery, or when the procedure fails, several alternative treatments are available.

Autologous Chondrocyte Implantation (ACI):

• A two-stage procedure that involves harvesting and culturing the patient’s chondrocytes, followed by implantation into the defect.

Osteochondral Autograft Transfer System (OATS):

• Involves the transfer of cartilage and subchondral bone from a non-weight-bearing area to the defect site.

Mosaicplasty:

• Similar to OATS, but involves the use of multiple small plugs to fill the cartilage defect.

Recent Advances

Recent advances in cartilage repair have focused on enhancing the microfracture technique and improving the quality of the repair tissue.

Gene Therapy:

• Experimental approaches are being developed to deliver specific genes to the repair site, promoting the formation of hyaline-like cartilage.

Scaffold-Based Therapies:

• The use of scaffolds impregnated with growth factors or stem cells to provide structural support and enhance tissue regeneration.

Biological Augmentation:

• The use of biological agents such as bone marrow aspirate concentrate (BMAC) or adipose-derived stem cells to improve the healing process.

Cost Considerations

The cost of microfracture surgery can vary widely depending on geographic location, the complexity of the case, and the surgeon’s expertise.

Average Cost:

• In the United States, the cost of microfracture surgery typically ranges from $5,000 to $15,000, including surgeon’s fees, hospital charges, and postoperative care.
• In other countries, the cost may be lower, but it’s important to consider the quality of care and available rehabilitation services.

Conclusion

Microfracture surgery remains a valuable option for the treatment of cartilage defects, particularly in younger, active patients with well-defined lesions. While the procedure has its limitations, advancements in technique and postoperative care continue to improve outcomes. As with any surgical intervention, careful patient selection, meticulous surgical technique, and adherence to a structured rehabilitation program are critical to achieving the best possible results.