Original Article
The synergistic effect of medial and lateral patellar retinaculum on the stability of patella in full extension
Abstract
Background: Patellar instability is a common problem. It is unclear that the medial and lateral patellar retinaculum respective effect on patella. The purpose of this study was to evaluate the synergistic effect of medial and lateral patellar retinaculum on the stability of patella.
Methods: Eight cadaveric knees were collected. Each of them was performed on patellofemoral joints under five conditions, including normal condition (Group N) and experimental conditions (Group M1, L1, L2, and M2). In Group M1, 2 kg was forced on the normal medial patellofemoral joint using a homemade knee joint immobilization apparatus. In Group L1, 2 kg was forced on the normal lateral patellofemoral joint. In Group L2, the medial retinaculum and the capsule were separated, and the lateral patellar border endured a force of 2 kg. In Group M2, the dissected medial soft tissues were sutured in-situ, and then the lateral retinaculum and the capsule were separated, and the medial patellar border endured a force of 2 kg. Evaluations included CT scan, and the scanned images of these five groups were analyzed for patellar tilt angle (PTA) and the lateral patellar displacement (LPD) values.
Results: PTA (°) and LPD (mm) of Group M1 and Group L1 were not significantly different compared to Group N (P≥0.01). PTA values and LPD values of Group L2 and Group M2 increased significantly compared to Group N (P≤0.01). PTA and LPD values of Group L2 showed significant differences compared to Group M2 (P≤0.01).
Conclusions: Medial patellar retinaculum prevents LPD and lateral patellar tilt. Lateral patellar retinaculum plays an important role to prevent medial patellar tilt. Medial and lateral retinaculum show synergistic effect to stabilize the patella.
Methods: Eight cadaveric knees were collected. Each of them was performed on patellofemoral joints under five conditions, including normal condition (Group N) and experimental conditions (Group M1, L1, L2, and M2). In Group M1, 2 kg was forced on the normal medial patellofemoral joint using a homemade knee joint immobilization apparatus. In Group L1, 2 kg was forced on the normal lateral patellofemoral joint. In Group L2, the medial retinaculum and the capsule were separated, and the lateral patellar border endured a force of 2 kg. In Group M2, the dissected medial soft tissues were sutured in-situ, and then the lateral retinaculum and the capsule were separated, and the medial patellar border endured a force of 2 kg. Evaluations included CT scan, and the scanned images of these five groups were analyzed for patellar tilt angle (PTA) and the lateral patellar displacement (LPD) values.
Results: PTA (°) and LPD (mm) of Group M1 and Group L1 were not significantly different compared to Group N (P≥0.01). PTA values and LPD values of Group L2 and Group M2 increased significantly compared to Group N (P≤0.01). PTA and LPD values of Group L2 showed significant differences compared to Group M2 (P≤0.01).
Conclusions: Medial patellar retinaculum prevents LPD and lateral patellar tilt. Lateral patellar retinaculum plays an important role to prevent medial patellar tilt. Medial and lateral retinaculum show synergistic effect to stabilize the patella.
