N°276 - August/September 2018
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Is there a place for MPFL reconstruction after total knee prosthesis?
By R. Canetti, G. Demey, S. Lustig, E. Servien in category FOLLOW-UP
Hôpital Lyon Croix-Rousse, 3 Grande rue de la Croix Rousse, 69004 Lyon, France
Patellofemoral instability (PFI) is one of the causes of total knee prosthesis (TKP) failure. It may be responsible for most patellar complications, such as anterior pain, abnormal wear or loosening of the patellar component, and can even extend to dislocation of the patella.
Patellar instability is not exclusively due to patellofemoral technical errors, but also results from a balancing error, especially in the axial plane with a rotational deformity. Any intervention that increases the tension of the lateral retinaculum, decreasing that of the medial retinaculum or increasing the Q angle, modifies patellar balance and causes this instability. The technical causes of PFI can be divided into four broad categories:
1) poor positioning of the implants, particularly in the axial plane (rotation), the frontal plane (alignment of the limb in valgus) or the sagittal plane (increase or decrease of the anterior space);
2) inappropriate design of the prosthetic trochlea ;
3) incorrect or incomplete patellar preparation;
4) poor peripatellar soft tissue balance.
Prevention of PFI thus requires the use of suitable implants and observance of the well-known major principles of knee arthroplasty:
- a natural limb axis, avoiding valgus;
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