Anatomical and Biomechanical properties of MPFL reconstruction technique using Adductor Magnus tendon graft

Abstract

Aims and Objectives:The main goal of the presented study was to evaluate the anatomical and biomechanical properties of the proposed surgical technique for anatomical Medial Patellofemoral ligament (MPFL) reconstruction using the flat Adductor tendon (AT) graft in order to primarily determine its overall plausibility and application potential, as well as to reveal the main risks and pitfalls of the technique.Materials and Methods:Anatomical descriptive evaluation, followed by biomechanical testing of the proposed AT- MPFL reconstruction was conducted on 12 fresh frozen human cadaveric knees. The morphological and topographical features of the AT and native MPFL were reported. The biomechanical tests were performed in order to determine the strength and resistance to maximum loading force of the reconstruction. The construct was placed in an uniaxial testing machine and cyclically loaded 500 times between 5 and 50N, followed by load to failure, measuring the maximum elongation, stiffness and maximum load respectively.Results:Regarding the anatomical evaluation of the structures in focus, several findings have been reported. The mean length of the tendon was found to be 12,59±1,54cm, the mean distance between the insertion on the Adductor tubercule and Hiatus was measured at 10,83±1,27cm, exceeding the mean desired length of the graft, found at 7,54±0,45cm by 2,43±0,56cm. The desired length of the graft was based on the measured length of the native MPFL with additional ±25-30mm of the tendon that allows for intraoperative length changes and different means of patellar fixation depending on the surgeons preference. The insertion of the Adductor tendon on the Adductor tubercule was found to be superior and posterior to the insertion of the native MPFL. The distal portion of AT was found to be consisted of two distinct parts with varying fiber orientation, the tendinous and the membranous part. After cyclic load, the maximum elongation was reported at 1,9 ± 0,4mm. The mean stiffness and load to failure of the construct were measured at 26,2±7,6N/mm and 148,74±22,01N. The graft failed at the patellar insertion site in two of the tested specimens and at the femoral insertion site in the remaining 10.Conclusion:Due to its advantageous anatomical and topographical aspects, as well as adequate biomechanical properties, the Adductor tendon graft caries a high utilization potential for MPFL reconstruction. Application that allows for primarily soft tissue fixation on the patella, in addition to absence of femoral drill holes with consequently no risk of injury to the physis, makes the AT graft choice a preferable option when considering MPFL reconstruction in patients with open growth plates. Even though it includes graft and methods of fixation alternative to the traditionally used techniques, this reconstruction is not exclusively predetermined for the skeletally immature patients and has a high application potential for the older patient population as well.