MPFL Repair-Graft Position

Courtesy: Dr B Sabnis, Ashok Shyam TV, Ortho

MPFL Anatomy Overview

• The medial patellofemoral ligament (MPFL) is a fan-shaped structure.

• Length varies with body habitus:

  • Approximately 46–49 mm in smaller Asian populations.

  • Approximately 50–56 mm in Caucasian populations.

  • Indian population typically in between.

• Width ranges widely (3–30 mm), consistent with its fan-shaped configuration.

Patellar Attachment

• Located on the proximal half of the patella.

• Rarely extends beyond the equator.

• Positioned more toward the dorsal aspect of the medial patella.

• Lies between layer II and layer III.

Femoral Attachment

• Not a single point.

• More accurately described as a “cloud” of attachment.

• Located between:

  • Medial epicondyle

  • Adductor tubercle

Anatomic landmarks are generally reliable but vary in dysplastic knees.

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Anatomy vs Isometry: The Core Debate

Important Principle

The MPFL is a non-isometric ligament.

• Its length changes during knee motion.

• Therefore, it cannot behave like a perfectly isometric structure.

• The knee is not a simple hinge of two perfect circles.

Definition of Isometry

• A truly isometric ligament would not change length through flexion-extension.

• The MPFL does change length.

• Therefore, strict isometric reconstruction is not anatomically correct.

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Radiographic Landmarks and Schöttle’s Point

• Schöttle’s point is widely described for femoral tunnel placement.

• However:

  • Radiographic landmarks are not perfectly reproducible.

  • Trochlear dysplasia alters anatomy.

  • Fluoroscopy alone may not guarantee accuracy.

• Studies show variability in tunnel placement even among expert surgeons.

Conclusion:
Radiographic landmarks should guide but not dictate tunnel placement.

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Anatomic Reconstruction Approach

Surgical Steps (Anatomic Philosophy)

1. Identify proximal patellar border.

2. Create medial patellar trough.

3. Insert two anchors in proximal half of patella.

4. Identify femoral landmarks:

   • Medial epicondyle

   • Adductor tubercle

   • Approximately 1 cm posterior to medial epicondyle (flexed knee view)

   • Approximately 5 mm anterior and distal to adductor tubercle

5. Pass graft between layer II and layer III.

6. Fix femoral side after confirming position.

Short-term results:

• Good stability.

• Low early failure rates.

• Long-term data still evolving.

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Counterpoint: Functional Isometry Matters

Although MPFL is non-isometric:

• It should behave nearly isometric between 0° and 60° of flexion.

• It should loosen beyond 60–90° of flexion.

• It must never tighten in deep flexion.

Why This Matters

Improper femoral tunnel placement can cause:

• Overconstraint.

• Increased patellofemoral contact pressure.

• Pain.

• Cartilage damage.

• Graft failure.

Most MPFL failures are due to incorrect femoral tunnel placement.

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Practical Approach: Blended Strategy

Stepwise Method

1. Palpate anatomic landmarks.

2. Insert guide pin.

3. Check graft behavior through range of motion.

4. Confirm with fluoroscopy if needed.

Isometric Check Technique

• Mark graft at two points.

• Flex knee from 0° to 90°.

• Desired behavior:

  • Minimal length change from 0°–60°.

  • Slight loosening beyond 60°.

  • Never tightening in flexion.

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Challenges in Abnormal Anatomy

In patients with:

• Trochlear dysplasia

• Patella alta

• Severe maltracking

• Significant tibial tubercle lateralization

Anatomic landmarks may not correspond to ideal functional positioning.

In these cases:

• Isometric behavior check becomes critical.

• Purely fluoroscopic placement may be unreliable.

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Pediatric Considerations

• Open distal femoral physis must be protected.

• Avoid physeal violation.

• Options:

  • Distal and anterior angulation of tunnel.

  • Soft tissue techniques.

  • Adductor sling techniques.

• Anatomic location may need modification to preserve physis.

Important:
Some skeletally immature patients with severe deformity may require staged procedures once skeletal maturity is reached.

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MQTFL vs MPFL Discussion

• Medial quadriceps tendon femoral ligament (MQTFL) avoids patellar drilling.

• Reduces risk of patellar fracture.

• Some surgeons have transitioned entirely to this technique.

• Avoid overtensioning in all techniques.

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Key Shared Principles

Both perspectives agree on critical points:

• Avoid overtightening.

• Avoid overconstraint.

• Confirm graft behavior dynamically.

• Do not rely solely on fluoroscopy.

• Do not rely solely on palpation.

• Individualize based on patient anatomy.

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When to Be Especially Careful

• Severe trochlear dysplasia.

• Significant patella alta.

• Large J-sign.

• Pediatric open physis.

• Complex deformity where osteotomy may eventually be required.

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Take-Home Messages

1. MPFL is anatomically well described but functionally complex.

2. It is non-isometric by nature.

3. Femoral tunnel malposition is the most common cause of failure.

4. Functional behavior through early flexion arc is critical.

5. Anatomy should guide placement.

6. Isometric testing should validate placement.

7. Avoid overtightening at all costs.

8. Pediatric patients require additional caution regarding physeal safety.

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Conclusion

The debate is not anatomy versus isometry.

The correct approach is:

• Anatomic landmark identification

• Followed by functional isometric validation

• With fluoroscopic confirmation when necessary

Successful MPFL reconstruction depends less on philosophy and more on precise femoral positioning and avoidance of overconstraint.