How should a 15-year-old male with a near full‑thickness cartilage lesion of the patellar apex after an acute hyperextension knee injury, without subchondral bone disruption, be managed?

Management of Acute Traumatic Near Full-Thickness Patellar Apex Cartilage Lesion in a 15-Year-Old

This 15-year-old should undergo urgent arthroscopic evaluation with strong consideration for primary fixation of the cartilage fragment if it can be identified and is of adequate quality, as acute traumatic chondral-only injuries in adolescents demonstrate excellent healing potential when surgically repaired within the first few weeks after injury.

Initial Management Approach

The critical window for optimal intervention is within 3 weeks of injury 1. Beyond this timeframe, fibrous healing begins and the cartilage fragment deforms, significantly reducing the likelihood of successful repair 1. Given that this is an acute injury with a near full-thickness lesion and intact subchondral bone plate, this patient falls into the ideal category for cartilage preservation surgery.

Diagnostic Arthroscopy and Fragment Assessment

Proceed with diagnostic arthroscopy to:

• Locate any displaced cartilage fragment (may be free-floating or partially attached)
• Assess fragment quality and size - viable fragments typically maintain their structural integrity
• Evaluate the donor site for delamination at the lesion shoulders, which is common in these acute stress-related injuries 1
• Measure defect size precisely to guide treatment selection

Treatment Algorithm Based on Findings

If Cartilage Fragment is Salvageable (Preferred Option)

Primary fixation should be performed using bioabsorbable fixation devices such as poly-L-lactic acid chondral darts 2, 1. This approach has demonstrated:

• 93.75% success rate (15/16 patients) in skeletally immature patients 2
• Mean defect size treated: 3.2 cm² 2
• Excellent functional outcomes at mean 3.5-year follow-up: IKDC scores of 95.2, with all but one patient returning to same or higher level of sports competition 2
• MRI-confirmed cartilage reintegration in successful cases 2

Technical considerations for fixation:

• The fragment can be chondral-only (no attached bone) and still heal successfully 2, 1
• Debride any delaminated cartilage at the lesion shoulders 1
• Ensure stable fixation with multiple points of contact
• The subchondral bone bed should be prepared but not violated (no microfracture needed for acute repairs)

If Fragment is Not Salvageable or Cannot Be Located

For a near full-thickness defect at the patellar apex in this age group, treatment depends on the exact defect size once measured arthroscopically:

For defects <2.5 cm²:

• Chondroplasty alone (debridement to stable cartilage margins) 3
• Avoid microfracture - it has not shown superiority over chondroplasty and carries risks of cyst formation and intralesional osteophytes 3

For defects ≥2.5 cm²:

• Single-stage autologous minced cartilage with PRP scaffold is an emerging option specifically validated in adolescent patellar defects 4

  • Harvest healthy cartilage arthroscopically from non-weight-bearing areas
  • Mix with PRP and biologic scaffold
  • If bone involvement develops, add cancellous bone graft 4
  • Advantage: Single-stage procedure avoiding the burden of two-stage techniques in young patients 4

• Alternative: Osteochondral autograft transplantation (OAT) if the lesion progresses to involve subchondral bone

  • Superior ICRS scores and fewer failures compared to microfracture in the 12-15 age group 5
  • Higher return to preinjury activity levels 5

Critical Pitfalls to Avoid

1. Delaying surgery beyond 3 weeks - The cartilage fragment will undergo fibrous healing and deformation, making successful repair impossible 1

2. Performing microfracture in this acute setting - This violates the intact subchondral bone plate unnecessarily and has inferior outcomes compared to fragment fixation or other techniques 3

3. Assuming the fragment is lost - Even if not immediately visible, thorough arthroscopic examination often locates displaced chondral fragments that can be salvaged 2

4. Ignoring the risk of early osteoarthritis - Untreated full-thickness cartilage lesions in adolescents carry significant risk of irreversible osteoarthritis, for which treatment options are extremely limited in young patients 5

Post-Operative Protocol

• Knee locked in extension for 6 weeks if fixation performed 6
• Continuous passive motion initiated immediately, progressing to full ROM by week 6 6
• Weight-bearing as tolerated with knee in extension 6
• MRI at 3 months to assess healing 1, 4
• Return to sports typically 6-12 months depending on healing confirmation 2

Shared Decision-Making Considerations

While surgery is strongly recommended given the acute nature, size, and location of this lesion in a young patient, the decision requires informed consent discussing 5:

• Surgical risks: infection, fixation failure (6.25% in published series), need for revision
• Non-surgical risks: progression to irreversible osteoarthritis with very limited treatment options at this age
• Benefits: prevention/delay of osteoarthritis, symptom relief, return to activities

The evidence strongly favors intervention in this acute traumatic setting with a salvageable lesion in a skeletally immature patient, as opposed to the more conservative approach sometimes appropriate for incidentally discovered, minimally symptomatic OCD lesions 5.