A Biomechanical Study Of 3 Different Techniques In Medial Patellofemoral Ligament Reconstruction

Background: Patellar dislocation is a common disease in clinical orthopaedics.Patellar dislocation will cause damage and degeneration of the patellofemoral joint surface.The medial patellofemoral ligament is the most frequently injured soft tissue structure following acute lateral patellar dislocation.The role of the medial patellofemoral ligament is to maintain the stability of the patella.Biomechanics studys show that the medial patellofemoral ligament is the main medial soft-tissue to keep patella stability.So the medial patellofemoral ligament reconstruction in the treatment of patients with patellar dislocation has become the main treatment.At present,multiple techniques for reconstruction of the medial patellofemoral ligament have been described;however,little is known about the biomechanical properties of these techniques.The author will show different biomechanical properties of different techniques.Purpose: This experiment used fresh vitro knee joint specimens,to reconstructed medial patellofemoral ligament.The purpose of this study was to compare the ultimate failure load,stiffness of 3 different medial patellofemoral ligament patellar fixation techniques(suture anchor,sutured tendon and folio tendon).To provide theoretical basis for clinical medial patellofemoral ligament reconstruction.Materials and Methods: Six fresh frozen cadaver specimens(4 men and 2 women;range from 57-69 years old)were obtained for this study,they were cut 20 cm from the joint line.Specimens were stored at-20° C prior to thawing at room temperature for a period of 48 hours.None of the cadaveric specimens had a history of knee surgery or trauma and there was no medical history of osteoporosis in any of the cadaveric specimens.The six specimens were performed in turn by suture anchor,sutured tendon and folio tendon fixation.Suture anchor reconstruction was completed with 2 parallel 5.0-mm biocomposite suture anchors.The sutures on the anchors were then tied around the graft,securing the graft to the medial patella.Sutured tendon group: A 2.4-mm guide pin with an eyelet was transversely inserted from the medial edge of the patella to the lateral border,and then a tunnel was drilled over the guide pin to a depth of 20 mm with a 5.0-mm cannulated reamer.Then,the 2.4-mm guide pin with an eyelet was inserted from upper inner corner of the patella to the lateral border.An oblique tunnel of 20 mm depth was drilled under the guidance of guide pin with a 5.0-mm diameter cannulated reamer.The free ends of the tendon were sutured by Ethicon non-absorbable sutures and pulled into patellar semi-tunnels.The two Ethicon non-absorbable sutures over the lateral bone bridge were fasten for fixation.Folio tendon group: Production of tunnels method as above.Two Ethicon non-absorbable sutures were passed through the two folded ends and pulled separately into the patellar semi-tunnels.The two Ethicon non-absorbable sutures over the lateral bone bridge were fasten for fixation.In all groups,after fixation of the tendon grafts to the patella,the other ends of the tendons were fixed to the up side of the testing machine.The patella was fixed to the bottom of the testing machine.We recorded maximum load,stiffness,and elongation.Results:1 Maximum Load to Failure and elongationThe suture anchor group's maximum load to failure was 222.17±5.19 N,which was significantly less than the sutured tendon group(364.5±2.42N)and folio tendon group(367.83±5N).The elongation of suture anchor group was 8.08±0.37mm;the elongation of the sutured tendon group was 9.60±0.10mm;the elongation of the folio tendon group was 8.00±0.20 mm.2 StiffnessThe suture anchor group resulted in a mean stiffness of 27.95±2.87N/mm.The sutured tendon group resulted in a mean stiffness of 28.68±6.92N/mm.The folio tendon group presented with a stiffness of 43.73±2.62N/mm.The sutured tendon group had significantly less stiffness than did the folio tendon group(P<0.05).Conclusions: In the reconstruction of medial patellofemoral ligament,the suture anchor technique has some advantages,such as the simple operation and not easy to damage the patellar cortex.But the suture anchor group was found to be weaker than the sutured tendon and folio tendon group when comparing the ultimate failure load and stiffness.The suture anchors were easily pulled out when given a smaller force.For the two semi-tunnel technique: sutured tendon and folio tendon group,they provided enough force to ensure the graft could not be pulled out.But there is a relative motivation between the tendon and the suture.Because the tendon slid relatively to the suture,in the initial phase of the test,the sutured tendon was pulled smoothly.After that,there was no more space between the suture and tendon,the sutured tendon was pulled roughly.Comprehensive view,the folio tendon could provide enough force and stability compared with the other two techniques.There are still many limitations in our biomechanical test,but it may provide theoretical basis for clinical medial patellofemoral ligament reconstruction and to avoid the associated complications.