Evaluation of Patellar Contact Pressure Changes after Static versus Dynamic Medial Patellofemoral Ligament Reconstructions Using a Finite Element Model

Abstract

Objectives: To evaluate the effect of various medial patellofemoral ligament (MPFL) fixation techniques on patellar pressure compared with the native knee. Methods: A finite element model of the patellofemoral joint consisting of approximately 30,700 nodes and 22,200 elements was created from computed tomography scans of 24 knees with chronic lateral patellar instability. Patellar contact pressures and maximum MPFL graft stress at five positions of flexion (0°, 30°, 60°, 90°, and 120°) were analyzed in three types of MPFL reconstruction (MPFLr): (1) static/anatomic, (2) dynamic, using the adductor magnus tendon (AMT) as the femoral fixation, and (3) dynamic, using the quadriceps tendon as the attachment (medial quadriceps tendon-femoral ligament (MQTFL) reconstruction). Results: In the static/anatomic technique, the patellar contact pressures at 0° and 30° were greater than in the native knee. As in a native knee, the contact pressures at 60°, 90°, and 120° were very low. The maximum MPFL graft stress at 0° and 30° was greater than in a native knee. However, the MPFL graft was loose at 60°, 90°, and 120°, meaning it had no tension. In the dynamic MPFLr using the AMT as a pulley, the patellar contact pressures were like those of a native knee throughout the entire range of motion. However, the maximum stress of the MPFL graft at 0° was less than that of a native ligament. Yet, the maximum MPFL graft stress was greater at 30° than in a native ligament. After 30° of flexion, the MPFL graft loosened, similarly to a native knee. In the dynamic MQTFL reconstruction, the maximum patellar contact pressure was slightly greater than in a normal knee. The maximum stress of the MPFL graft was much greater at 0° and 30° than that of a native MPFL. After 30° of flexion, the MQPFL graft loosened just as in the native knee. Conclusions: The patellar contact pressures after the dynamic MPFLr were like those of the native knee, whereas a static reconstruction resulted in greater pressures, potentially increasing the risk of patellofemoral osteoarthritis in the long term. Therefore, the dynamic MPFLr might be a safer option than a static reconstruction from a biomechanical perspective.

The quantitative influence of current treatment options on patellofemoral stability in patients with trochlear dysplasia and symptomatic patellofemoral instability - a finite element simulation

“…1). The stabilizing effect diminishes in greater flexion in accordance with the effect of the native MPFL (Amis et al, 2003) and other FE simulations (Sanchis-Alfonso et al, 2019a;Sanchis-Alfonso et al, 2019b). We believe the pronounced increase of patellofemoral stability is mostly due to the greater stiffness of the gracilis tendon loop of approx.…”

Dynamic–Anatomical Reconstruction of Medial Patellofemoral Ligament in Open Physis

“…Discrepancies at the 5-mm insertion site increase graft elongation by up to 12 mm during flexion extension, 12,16 which is reflected in increased patellofemoral contact pressures 13,17 and clinically in pain, joint cartilage wear and eventually future repeated surgical intervention of the patient. If the graft is fixed in a more proximal position it will lead to an increase in the distance between the femoral anchor point and the patella during knee flexion, increasing tension and with it the pressure on the medial aspect of the patellofemoral joint.…”

“…In contrast, our technique differs from those described by Monllau et al 20 and Lind et al 21 because we reconstruct the MQFL, replicating anatomy and associating a new point of dynamism with the construct. 12 In addition, the most distal arm of the graft is fixed to the femoral periosteum with VICRYL replicating the insertion in the anatomical site (Tables 1 and 2).…”

“…Then, with the knee in 60° flexion, pulling and joining both ends, the fixation is decided, while allowing a +1 or +2 glide of the patella. 3 , 12 , 13 , 14 The proximal end is sutured with the distal end, anterior to the patella with the VICRYL 1.0 suture and passing the stitches over the remaining tissue of the retinaculum and anterior fibers of the quadricipital tendon ( Fig 6 ).

Fig 6 Final anterior view of the dynamic fixation of the MPFL.

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Diz çevresi osteotomilerinde kıkırdak rejenerasyonunu artırıcı uygulamalar

“…Patellofemoral uyumsuzluk, geniş bir klinik görünüm yelpazesine sahip karmaşık bir patolojidir. [5] Çeşitli özellikler Q açısını ve sonuç olarak PF reaksiyon kuvvetlerini etkileyebilir. PF uyumsuzluğun en sık anatomik anormalliklerin birleşmesinin bir sonucu olması nedeniyle tek tanımlayıcı etiyolojik faktör olamaz.…”