| Objective:The injury of anterior curciate ligament as one of kneeimportant static stable structure can lead to significant knee anterior androtational instability and then followed by the degeneration of articularcartilage,what seriously effect the function of knee.So early ACLreconstruction can avoid the damage of articular cartilage.The method ofsingle-bundle anterior cruciate ligament reconstruction is the most widely usedcurrently.However,a recent Meta-analysis results shows that only41%and33%patients’knee function score return to normal level after anterior cruciateligament reconstruction using patellar tendon and hamstringrespectively.Furthermore,the incidence of anterior knee pain after usingbone-tendon-bone and hamstring tendon reconstruction is43%and33%respectively.The biomechanical properties change of patellofemoral joint afteranterior cruciate ligament injury is one of the reasons that lead topatellofemoral cartilage degeneration.In recent years,many scholars,whofocus on the pressure and the contact area changes of patellofemoral joint afteranterior cruciate ligament injury and single-bundle reconstruction,think thatthe anterior cruciate ligament injuy will cause patellar lateral tilt and shift, butwhen mention the single-bundle reconstruction,various result wasreported.Report of the change after double-bundle anatomic reconstructionis rare.In this study,the patellofemoral biomechanic changes afterdouble-bundle anatomical and single-bundle reconstruction is being discussedafter biomechanical erperiments in order to provide a theoretical basis andguidance for clinical practices. This experiment was to investigate a better protection of thepatellofemoral joint cartilage after anterior cruciate ligament reconstructionand provide a theoretical basis and guidance for clinical practices throughcomparing the impact on the biomechanics charateristics of patellofemoral andexploring the changes of contact area、contact pressure and movement patternof patellofemoral after anterior cruciate ligament injury、single-bundle andanatomic double-bundle reconstruction.Methods:We randomly select eight cases of normal anticorrosional adultcadavers as the anterior cruciate ligament intact group,using thebio-mechanical testing machine with a axial force of125N,5mm/minspeed.Test the medial and lateral patellofemoral articular surface contact areaand pressure through Prescale pressure-sensitive paper as knee knees30°,60°,90°.The contact areas of patellofemoral joint were calculated by AutoCAD software,what can measure irregular area through line delineation.Thecontact pressures of patellofemoral joint were read by Fuji pressurereader.After the intact group was estimated,transect the anterior cruciateligament of eight specimens in the lower1/3as ACL deficient group.And thencontact pressures and areas were measured at different angles.Randomly selectfour cases of specimen as single-bundle reconstruction group,and the others asdouble-bundle anatomical reconstruction group.The tibial and femoral tunnelsof single-bundle reconstruction group were used9mm bone tunnel,thus thetibial and femoral tunnels of double-bundle anatomical reconstruction wereused5~7mm of anteromedial and posterolateral bone marrows which may beadjusted according to the ligament.All of reonstruction methods were usedallograft hamstrings and braided pre-sheets to implant into specimens.All offixation methods were Endo-Button suspension.Results:The total patellofemoral contact area of ACL-deficient group(148.9±9.29mm2) and ACL single-bundle reconstruction group(156.9±13.3mm2) significantly decreased when compared with thoseACL-intact group (195.7±14.71mm2) at30°of knee flexion,P＜0.05.Thus,double-anatomic reconstruction group (193.1±12.04mm2) was no significant differences when compared with ACL-intact group.The lateralpatellofemoral contact area of ACL-deficient group and ACL single-bundlereconstruction group (205.9±5.65mm2and207.1±8.12mm2,respectively) wassignificantly greater than ACL-intact group (162.8±8.87mm2) at90°of kneeflexion,P＜0.05.But the lateral and medial patellofemoral contact area of ACLdouble-bundle anatomic reconstruction group (144.2±6.80mm2and287.0±8.09mm2) was significantly decreased while compared withACL-intact group,P＜0.05.The lateral average pressure of ACL-deficient group (1.01±0.28MPa)was significantly higher when compared with ACL-intact group (0.86±0.28MPa) at60°of knee flexion,P＜0.05.The medial and lateral average pressureof ACL single-bundle reconstruction group (1.18±0.24MPa and0.91±0.23MPa,respectively) was significant lower than ACL-intact group(1.72±0.55MPa and1.36±0.45MPa,respectively),P＜0.05.The contact pressure ofanatomic double-bundle ACL reconstruction group was similar to those ofACL-intact group,P＞0.05，no statistically difference.Conclusion:1、ACL deficiency resulted in a significant decrease inpatellofemoral contact areas,espectively in the medial patellofemoral joint,thusthe lateral contact areas were improved at60°and90°of knee flexion. Also,ACL deficiency resulted in a decrease in medial contact pressure and aincrease in lateral contact pressure,espectively at60°of knee flexion.2、Anatomic double-bundle ACL reconstruction restored the patellofemralcontact area and pressure more closely to normal when compared withsingle-bundle ACL reconstruction,but the contact area is still less than normalat90°of knee flexion.Clinical Relevance:Our experiment suggest that the changes of medialand lateral contact area and contact pressure after ACL injury andsingle-bundle ACL reconstruction is one of causes of patellofemal pain afterACL reconstruction.The patellofemoral biomechanical properties was moreclosely to normal after anatomic double-bundle ACL reconstruction whencompared with single-bundle ACL reconstruction. |
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