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The Microfracture Technique for the Treatment of Articular Cartilage Lesions in the Knee. a Prospective Cohort Study.

·J Bone Joint Surg Am·2005·591 citations·Sports Medicine
DOI·PubMed
SummaryAbstract on PubMed →

Prospective cohort of 48 patients with isolated full-thickness femoral cartilage defects treated by microfracture. The study used validated outcome scores and cartilage-sensitive MRI to identify which factors predict functional success at minimum 2-year follow-up.

Study Snapshot

Design
Prospective cohort
Blinding: Single-blind
Setting: Single center (Hospital for Special Surgery)
Funding: None
Objective
Whether microfracture improves 2-year function and whether outcome correlates with percentage of lesion filled
Outcome(s)
Validated knee function scores (ADL, IKDC, SF-36 PCS) at minimum 24 months
Subjects
48 patients with isolated femoral cartilage defects
  • Microfracture per Steadman technique
Inclusion
  • Single Outerbridge grade-3/4 femoral lesion
  • Stable, well-aligned knee
  • Minimum 24-month follow-up
Exclusion
  • Ligamentous instability or malalignment
  • Generalized osteoarthritis or multiple lesions
  • Patellar/tibial lesions or concomitant ligament surgery
Follow-up
Minimum 24 months (mean 41)
Statistics
Paired t testChi-squareLinear regressionCorrelation analysis

Key Findings

  • Knee function was good to excellent in 67% of patients (32 of 48), fair in 25%, and poor in only 8% at a mean 41-month follow-up. ADL, SF-36 physical, and IKDC scores all rose significantly (p < 0.05) within the first two years.
  • Function deteriorated after 24 months in many patients: IKDC scores declined in 69% (33 patients) after the two-year mark. This signals that early gains from microfracture are not always durable.
  • MRI repair fill grade tracked outcome directly:
    –Good fill (67-100%): all 13 improved ADL
    –Moderate fill (34-66%): only 3 of 7 improved
    –Poor fill (0-33%): only 1 of 4 improved
  • Fill grade is the strongest predictor of durable benefit.
  • Poor fill predicted decline: every poor-fill knee lost function after two years versus only 3 of 13 good-fill knees (p < 0.05). This is the first clinical evidence linking repair volume to durability.
  • A high BMI hurt outcomes. BMI inversely correlated with ADL (r = -0.330) and SF-36 (r = -0.343), and patients with BMI >30 kg/m2 had the worst scores, making obesity a relative contraindication.
  • Symptom duration mattered. 76% of patients with symptoms under 12 months improved ADL versus only 7 of 19 with longer duration (p < 0.05), supporting early surgery.
  • MRI showed the repair is fibrocartilage, not hyaline:
    –Hyperintense signal in 92%
    –Depressed morphology in 54%
    –Persistent peripheral gaps in 92%
    –Osseous overgrowth in 25%.
Board PearlMicrofracture produces fibrocartilage, not hyaline cartilage; outcomes are best with good MRI fill, BMI under 30, and symptoms under 12 months.

Clinical Relevance

Microfracture is the first-line marrow-stimulation procedure for small symptomatic femoral cartilage defects, and this paper defines who actually benefits. The decision rule: a young, lean patient (BMI under 30) with symptoms under 12 months and an isolated grade-3 or 4 femoral lesion in a stable, well-aligned knee is the ideal candidate.

Remember the mechanism for boards. Penetrating the subchondral plate recruits marrow stem cells that form fibrocartilage with type-II collagen, not durable hyaline cartilage. That explains the depressed morphology, peripheral gaps, and the late functional decline seen here.

The most testable concept is that MRI repair fill grade predicts durability. Good fill (>two-thirds) means lasting improvement; poor fill predicts decline after two years. Clinically, counsel obese patients that BMI over 30 is a relative contraindication, and do not let cartilage symptoms linger past a year before considering surgery.

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|

The Microfracture Technique for the Treatment of Articular Cartilage Lesions in the Knee. a Prospective Cohort Study.

·J Bone Joint Surg Am·2005·591 citations·Sports Medicine
DOI·PubMed
SummaryAbstract on PubMed →

Prospective cohort of 48 patients with isolated full-thickness femoral cartilage defects treated by microfracture. The study used validated outcome scores and cartilage-sensitive MRI to identify which factors predict functional success at minimum 2-year follow-up.

Study Snapshot

Design
Prospective cohort
Blinding: Single-blind
Setting: Single center (Hospital for Special Surgery)
Funding: None
Objective
Whether microfracture improves 2-year function and whether outcome correlates with percentage of lesion filled
Outcome(s)
Validated knee function scores (ADL, IKDC, SF-36 PCS) at minimum 24 months
Subjects
48 patients with isolated femoral cartilage defects
  • Microfracture per Steadman technique
Inclusion
  • Single Outerbridge grade-3/4 femoral lesion
  • Stable, well-aligned knee
  • Minimum 24-month follow-up
Exclusion
  • Ligamentous instability or malalignment
  • Generalized osteoarthritis or multiple lesions
  • Patellar/tibial lesions or concomitant ligament surgery
Follow-up
Minimum 24 months (mean 41)
Statistics
Paired t testChi-squareLinear regressionCorrelation analysis

Key Findings

  • Knee function was good to excellent in 67% of patients (32 of 48), fair in 25%, and poor in only 8% at a mean 41-month follow-up. ADL, SF-36 physical, and IKDC scores all rose significantly (p < 0.05) within the first two years.
  • Function deteriorated after 24 months in many patients: IKDC scores declined in 69% (33 patients) after the two-year mark. This signals that early gains from microfracture are not always durable.
  • MRI repair fill grade tracked outcome directly:
    –Good fill (67-100%): all 13 improved ADL
    –Moderate fill (34-66%): only 3 of 7 improved
    –Poor fill (0-33%): only 1 of 4 improved
  • Fill grade is the strongest predictor of durable benefit.
  • Poor fill predicted decline: every poor-fill knee lost function after two years versus only 3 of 13 good-fill knees (p < 0.05). This is the first clinical evidence linking repair volume to durability.
  • A high BMI hurt outcomes. BMI inversely correlated with ADL (r = -0.330) and SF-36 (r = -0.343), and patients with BMI >30 kg/m2 had the worst scores, making obesity a relative contraindication.
  • Symptom duration mattered. 76% of patients with symptoms under 12 months improved ADL versus only 7 of 19 with longer duration (p < 0.05), supporting early surgery.
  • MRI showed the repair is fibrocartilage, not hyaline:
    –Hyperintense signal in 92%
    –Depressed morphology in 54%
    –Persistent peripheral gaps in 92%
    –Osseous overgrowth in 25%.
Board PearlMicrofracture produces fibrocartilage, not hyaline cartilage; outcomes are best with good MRI fill, BMI under 30, and symptoms under 12 months.

Clinical Relevance

Microfracture is the first-line marrow-stimulation procedure for small symptomatic femoral cartilage defects, and this paper defines who actually benefits. The decision rule: a young, lean patient (BMI under 30) with symptoms under 12 months and an isolated grade-3 or 4 femoral lesion in a stable, well-aligned knee is the ideal candidate.

Remember the mechanism for boards. Penetrating the subchondral plate recruits marrow stem cells that form fibrocartilage with type-II collagen, not durable hyaline cartilage. That explains the depressed morphology, peripheral gaps, and the late functional decline seen here.

The most testable concept is that MRI repair fill grade predicts durability. Good fill (>two-thirds) means lasting improvement; poor fill predicts decline after two years. Clinically, counsel obese patients that BMI over 30 is a relative contraindication, and do not let cartilage symptoms linger past a year before considering surgery.

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