| The medial patellofemoral complex, consisting of the medialpatellofemoral ligament (MPFL), the medial patellotibial ligament, and thevastus medialis obliquus, is the main passive stabilizer of the patellofemoraljoint. Recently, it has been shown that the medial patellofemoral complex is themain pathoanatomy after patellar dislocation. In addition, biomechanical studieshave demonstrated that the MPFL is the main restraint against lateral patellardisplacement and that repair or reconstruction of the MPFL restores normalpatellar tracking. MPFL reconstruction is widely accepted to treat lateral patellarinstability. An isometric reconstruction of MPFL is considered to an ideal target.Failure to restore proper isometric MPFL may ultimately bring abnormalpatellar tracking, patellofemoral pain and arthritis, knee flexion stiffness andredislocation. Numerous studies have declared that the peak strain of the MPFLoccurs at the early flexion of knee from0°to60°. In addition, it was believedthat the MPFL relaxes with decrease of length, and the femoral groove is deepenough to avoid patella dislocation at a flexion angle exceeding60. Clarificationof the femoral origin of MPFL would be crucial to achieve MPFL isometricreconstruction for a good clinical outcome. while there has not been a consensuson its exact location. The anatomic studies described particularly in anatomy andmorphology, and measured the pattern of the ligament changes during themovement, which failed to reflect the actual conditions in the living body whennot considering the interaction between MPFL and the soft tissues around theknee. The purpose of this study is to characterize the functional length changesof various patellar and femoral fixation sites during the knee flexion using in vivo three dimension (3D) movement patterns. We sought to determine the idealgraft fixation sites at which the graft remains almost isometric or constant lengthat early flexion, which will be expected to guide the MPFL reconstruction.Materials and methods: Twelve right knees of healthy male volunteers(22-26years; average age,24.1years) were involved. None of them has anyhistory of traumatic injuries of the knee ligament, history of congenital diseases,knee osteoarthritis, or the like, or any symptoms related thereto. The right kneeof each volunteer was examined at different flexion angles (0°,10°,20°,30°,40°,50°, and60°) using a horizontal-type open MR scanner with thickness1mm.The subjects were asked to take the lateral decubitus position, while the legswere retained in a custom-made leg holder during magnetic resonance scanning.After which,3D surface models were constructed with extracted data by usingthe marching cubes algorithm. According to previous studies, MPFL origin wereselected at adductor tubercle (D), medial epicondyle (E),5mm posterior to themedial epicondyle (F), dome of the Blumensaat line (G),10mm inferior to theadductor tubercle (H), and midpoint between the adductor tubercle and themedial epicondyle (I). As for the patella, we allocated MPFL insertion to threepoints equidistantly on the medial aspect of the patella: superior pole (A),midpoint (B) and inferior pole (C). Virtual ligaments that connect each possiblegraft fixation sites were created as the shortest paths in3D space, which weredetoured by the3D surface of the bone models. The lengths of the virtualligaments were calculated at different knee flexion degrees. All data wereexpressed as the mean±standard deviation. Statistical analysis of the lengthchanges data for all sequential flexion was analyzed using a single-factorANOVA test, and the comparison between the two groups were analyzed usingLSD test. The statistical analysis was performed using SPSS19.0. p <.05wasconsidered statistically significant. Results: AH showed the smallest lengthchanges among the virtual ligaments. However, there are no statistically significant differences between each two of AH, BH, CH, AI, BI, CI, AG, BG,CG, AF, BF, CF, AE, BE, and CE (all p>0.05). For3patellar points, there wereno statistically significant differences in length changes of these ligaments. TheAI, BI, CI and BG, CG, AH, BH, lengths did not show significant decrease orincrease during0–60°of knee flexion (p>0.05). AG increased slightly duringflexion from0°to10°(p>0.05) and decreased between10°and60°of flexion (p<0.05). The CH length decreased slightly during flexion from0°to20°(p>0.05)and increased between20°and60°of flexion (p=0.040).Conclusion: The virtual ligaments including G, H, I were more isometricthan those including D, which indicateding that the length changes ofreconstructed MPFL depended mainly on the femoral attachment sitedominantly. The patellar fixation sites had no play a slight role significantinfluence on in the length changes. The adductor tubercle (D), medialepicondyle (E),5mm posterior to the medial epicondyle (F) were not idealfemoral fixation sites, while a better choice reside in a triangler zone formedwith dome of the Blumensaat line (G),10mm inferior to the adductor tubercle(H), and midpoint between the adductor tubercle and the medial epicondyle (I)were the best sites. The femoral insertion within this triangler zone will providea relative isometric reconstruction, which is essential for the kinematic functionof the MPFL. Dome of the Blumensaat line (G) is not an ideal femoral fixationsite during the MPFL reconstruction using the superficial quad technique. Ourcurrent data suggest that any angle from0°to60°of knee flexion is acceptablefor fixation. |
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