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Changes in the length of the medial patellofemoral ligament: an in vivo analysis using 3-dimensional computed
Yon-Sik Yoo1, Ho Geun Chang, Young-Jin Seo
1Department of Orthopaedic Surgery, Hangang Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Republic of Korea.
Background:
The ideal points for medial patellofemoral ligament (MPFL) reconstruction have not been precisely defined.
Purpose:
To determine at which flexion angles the grafts should be fixed to best restore patellar stability as well as to compare the length change of various femoral and patellar fixation sites for current MPFL reconstruction during knee flexion in vivo.
Study Design:
Descriptive laboratory study.
Methods:
The right knees of 10 living patients were scanned with a high-resolution computed tomography scanner at 0°, 30°, 60°, 90°, and 120° of knee flexion, and 3-dimensional knee models were constructed using customized software. Based on recent anatomic studies and current surgical techniques, 4 femoral points (A: adductor tubercle; B: midpoint between the medial epicondyle and the adductor tubercle; C: medial epicondyle; and D: 10 mm inferior to the adductor tubercle) and 2 patellar points (30% [point 1] and 45% [point 2] from the proximal pole of the patella) were marked. The lengths of the 8 ligaments were digitally measured, and the length changes of these ligaments at the 5 different knee flexion angles were calculated.
Results:
Two ligaments including the adductor tubercle (A1, A2) showed an increase while the knee was flexed over 60°. Four ligaments (B1, B2, D1, D2) showed a slight increase as the knee flexed from 0° to 30° and a decrease as the flexion angle exceeded 30°. Length changes in these 6 ligaments were not significantly different. There was no significant difference between 2 patellar points in the length changes of these 6 ligaments. Two ligaments including the medial epicondyle (C1, C2) showed an excessive decrease during knee flexion and showed greatest length changes.
Conclusion:
The femoral fixation sites should be located at point B or point D. Point A and point C are not ideal femoral fixation sites. The best angle for graft fixation would be near 30° of knee flexion.
Clinical Relevance:
The data obtained for length and length change pattern in each virtual ligament will serve as a useful basis for improved MPFL reconstruction.
