Abstract
BackgroundThe medial patellofemoral ligament (MPFL) is the main stabiliser of the patella and thus mostly reconstructed in the surgical treatment of patellofemoral dislocation. The aims of this study were to gain a better understanding of the influence of altered MPFL graft-fixation locations and different graft pre-tensions on patellofemoral contact pressure.MethodsSix human cadaveric knee joints were placed in a six-degree-of-freedom knee simulator. Mean PFCP (mPFCP) was evaluated in knee flexion of 0, 30 and 90° using a calibrated pressure-measurement system. After data assessment of the native knee joint, five MPFL reconstruction conditions were conducted: Anatomical double bundle; non-anatomical proximal patellar; non-anatomical distal patellar; non-anatomical proximal femoral; non-anatomical ventral femoral. The gracilis graft was fixed at a defined knee flexion of 30° and pre-tensioned to 2, 10 and 20 N.ResultsKruskal-Wallis testing resulted in no mPFCP differences between the native and anatomical reconstruction states.Comparing the native and anatomical reconstruction states with the non-anatomical reconstruction states, no difference in the mPFCP both in knee extension (0°) (p>0.366) and in 30° knee flexion (p>0.349) was found. At 90° knee flexion, the following differences were identified: compared to the native knee state, the mPFCP increased after non-anatomical proximal femoral and non-anatomical ventral femoral reconstruction by 257% (p=0.04) and 292% (p=0.016), respectively. Compared to the anatomical reconstruction state, the mPFCP increased after non-anatomical proximal femoral reconstruction by 199% (p=0.042).Discussion and ConclusionsWith respect to all study findings and to restore a physiological PFCP, we recommend using the anatomical footprints for MPFL reconstruction and a moderate graft pretensioning of 2-10 N.
Highlights
The medial patellofemoral ligament (MPFL) is the main stabiliser of the patella and mostly reconstructed in the surgical treatment of patellofemoral dislocation
The same pattern was detected at 30° knee flexion and after anatomical reconstruction (Pa), where the Mean patellofemoral contact pressure (PFCP) (mPFCP) significantly decreased (p = 0.04) under a pre-tensioning of 10 N (0.71 MPa) compared to 2 N (0.77 MPa) pre-tensioning (Fig. 5)
The median mPFCP decreased under a higher pre-tension from 1.12 to 0.87 MPa and from 1.12 to 1.04 MPa, respectively (Fig. 6)
Summary
The medial patellofemoral ligament (MPFL) is the main stabiliser of the patella and mostly reconstructed in the surgical treatment of patellofemoral dislocation. The footprints of the MPFL have been characterised by several cadaveric examinations (Baldwin 2009; Desio et al 1998; Feller et al 1993; LaPrade et al 2007; Nomura et al 2002; Philippot et al 2009; Smirk and Morris 2003; Tuxoe et al 2002). It originates between the adductor tubercle and the medial epicondyle. Other previous examinations focused rather on length-change patterns and isometry of the graft than on the PFCP after alteration of the patellar fixation (Steensen et al 2004; Stephen et al 2012)
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