Myopectineal Orifice in Hernia Repair
Anatomical Definition and Clinical Significance
The myopectineal orifice (MPO) represents the critical anatomical weak area of the abdominal wall where all groin hernias occur, and adequate mesh coverage of this entire space is essential to prevent hernia recurrence. 1, 2
The MPO is bounded by:
- Superiorly: Transversus abdominis arch and internal oblique muscle 3
- Inferiorly: Iliopubic tract and Cooper's ligament 3
- Medially: Rectus abdominis muscle 3
- Laterally: Iliopsoas muscle 3
MPO Dimensions and Mesh Sizing
Standard MPO Measurements
The MPO dimensions vary by gender and hernia size 4:
- Males: Average 7.6 cm × 7.6 cm (width × height) 4
- Females: Average 8.1 cm × 5.3 cm (width × height, with greater width than height) 4
- Overall average: 7.8 cm (±3.0) width × 6.5 cm (±1.9) height 4
Evidence-Based Mesh Size Recommendations
For totally extraperitoneal (TEP) repair, mesh size should be determined by the hernia orifice size to ensure adequate MPO coverage 1:
- Small hernias (<3 cm orifice): Use 13.2 cm × 10.4 cm mesh 1
- Large hernias (≥3 cm orifice): Use 15.6 cm × 13.0 cm mesh 1
These dimensions are calculated by adding 2-3 cm overlap beyond the 95th percentile MPO measurements to ensure complete coverage 1. This approach achieved a recurrence rate of only 0.2% in 406 patients 1.
Alternative Sizing Approach
A simpler universal mesh of 10 cm × 8 cm can be used for both genders 4:
- In females: Covers the entire MPO including infraligamental area 4
- In males: Preferentially covers the weak inguinal area 4
Critical View of the MPO Concept
Achieving a "critical view of the MPO" during minimally invasive surgery (MIS) is analogous to the critical view of safety in cholecystectomy and is essential for safe hernia repair 3. This involves:
- Complete visualization of all MPO boundaries 3
- Identification of the "inverted Y" formed by the iliopubic tract and Cooper's ligament 3
- Recognition of five anatomical triangles within the MPO 3
- Ensuring mesh placement covers all potential hernia sites (lateral/indirect, medial/direct, and femoral) 3
Clinical Implications for Hernia Repair
Why MPO Coverage Matters
All groin hernia recurrences occur within the MPO area, making complete coverage with mesh the fundamental principle of successful repair 2. A study using small meshes covering only the MPO achieved:
Mesh Placement Techniques
For clean surgical fields (CDC Class I), synthetic mesh repair covering the entire MPO is recommended 5:
- Laparoscopic approaches (TAPP, TEP): Lower wound infection rates and shorter hospital stays 6, 7
- Mesh positioning: Preperitoneal space without fixation or minimal fixation 2
- Coverage principle: Mesh must extend beyond MPO boundaries by at least 2-3 cm 1
Combined Repair Approach
Combining mesh coverage of the MPO with tissue reinforcement of the weak area between the transversus abdominis arch and iliopubic tract (TMC repair) can achieve recurrence rates as low as 0.68% 8. This addresses the limitation of mesh-only repair, which covers the MPO but doesn't reinforce the naturally weak superior boundary 8.
Common Pitfalls to Avoid
- Insufficient mesh size: Using mesh smaller than MPO dimensions is a major risk factor for recurrence 1
- Inadequate lateral coverage: Failing to extend mesh sufficiently lateral to cover indirect hernia sites 3
- Missing femoral hernias: Not covering the femoral space (inferior MPO) 3
- Mesh misplacement: The single recurrence in one series was due to incorrect mesh positioning 2
- Oversized mesh complications: While adequate coverage is essential, excessively large meshes spread over iliac vessels and bladder can cause future difficulties with urogenital or vascular procedures 2
Special Considerations for Contaminated Fields
In contaminated/dirty surgical fields (CDC Class III/IV), the MPO repair strategy changes 6, 9: