In vitro performance of a biodegradable zinc alloy adjustable-loop cortical suspension fixation for anterior cruciate ligament reconstruction

Anterior cruciate ligament(ACL)injuries of the knee are one of the most common and serious athletic injuries.The widely used cortical suspension fixation buttons for ligament reconstruction are permanent implants,particularly those made from conventional steel or titanium alloys.In this study,a biodegradable Zn-0.45Mn-0.2Mg(ZMM42)alloy with the yield strength of 300.4 MPa and tensile strength of 329.8 MPa was prepared through hot extrusion.The use of zinc alloys in the preparation of cortical suspension fixation buttons was proposed for the first time.After 35 d of immersion in simulated body fluids,the ZMM42 alloy fixation buttons were degraded at a rate of 44μm/a,and the fixation strength was retained(379.55 N)in the traction loops.Simultaneously,the ZMM42 alloy fixation buttons exhibited an increase in MC3T3-E1 cell viability and high antibacterial activity against Escherichia coli and Staphylococcus aureus.These results reveal the potential of biodegradable zinc alloys for use as ligament reconstruction materials and for developing diverse zinc alloy cortical suspension fixation devices.

Lateral femoral tunnel preparation and graft fixation for anterior cruciate ligament reconstruction–A discussion

This article provides a discussion and commentary around the recent advances in arthroscopic anterior cruciate ligament reconstruction(ACLR),with a focus on the aspects of lateral femoral tunnel preparation and graft fixation techniques.The paper explores and comments on a recently published review by Dai et al,titled"Research progress on preparation of lateral femoral tunnel and graft fixation in ACLR",while providing insight into its relevance within the field of ACLR,and recommendations for future research.

Recurrent cyclops lesion after primary resection of fibroreactive nodule following anterior cruciate ligament reconstruction

In this case report featured in World Journal of Orthopedics,Kelmer et al describe a rare finding of a 28-year-old female patient who presented with a recurrent fibroreactive nodule 7 months following the resection of a primary cyclops lesion,suggesting recurrent cyclops syndrome.The patient had undergone an initial anterior cruciate ligament reconstruction for a non-contact right knee injury and reported successful recovery.Two years later,the patient sustained a repeat right knee injury followed by a positive McMurray test and acute pain with terminal extension.Arthroscopic synovectomy confirmed magnetic resonance imaging(MRI)finding of a cyclops lesion,which was surgically removed.Seven months postoperatively,the patient reported stiffness and difficulty with terminal extension.Repeat MRI indicated a recurrent cyclops lesion,which was surgically resected.Following resection of the second lesion,the patient underwent physical therapy and achieved full range of motion,maintaining complete recovery 19 months postoperatively.Recurrent cyclops lesions have rarely been reported in the literature,and this article is novel in its report of recurrent cyclops syndrome following a bone-patellar tendon-bone allograft.The presentation of this unusual finding exposes a need for further investigation of cyclops lesion pathology,which will aid its prevention and treatment.

Comparative study of the clinical efficacy of all-inside and traditional techniques in anterior cruciate ligament reconstruction

BACKGROUND Many studies have focused on the femoral tunnel technique and fixation method,but few studies have involved the tibial tunnel technique and fixation method.The all-inside technique is one of the new techniques that has been described in recent years.All-inside anterior cruciate ligament(ACL)reconstruction is based on a tibial socket instead of a full tunnel.This method has many potential advantages.AIM To compare clinical outcomes of knee ACL autograft reconstruction using allinside quadrupled semitendinosus(AIST)and traditional hamstring tendon(TBT)techniques.METHODS From January 2017 to October 2019,the clinical data of 80 patients with ACL reconstruction were retrospectively analyzed,including 67 males and 13 females.The patients had an average age of 24.3±3.1 years(age range:18-33 years).The AIST technique was used in 42 patients and the TBT technique was used in 38 patients.The time between operation and injury,operative duration,postoperative visual analogue scale(VAS)score and knee functional recovery were recorded and compared between the two groups.The International Knee Documentation Committee(IKDC)and Lysholm scoring system were used to comprehensively evaluate clinical efficacy.RESULTS Eighty patients were followed for 24-36 mo,with an average follow-up duration of 27.5±1.8 mo.There were no significant differences in the time between surgery and injury,operative duration,IKDC and Lysholm scores of the affected knee at the last follow-up evaluation between the two groups.There were significant differences in VAS scores 1 d,3 d,7 d,2 wk and 1 mo after surgery(P<0.05).There was no significant difference in VAS score at 3 mo,6 mo and 1 year after operation.CONCLUSION The efficacy of the AIST ACL reconstruction technique was comparable to the TBT technique,but the postoperative pain was less with the AIST technique.Thus,the AIST technique is an ideal treatment choice for ACL reconstruction.

Recurrent cyclops lesion after primary anterior cruciate ligament reconstruction using bone tendon bone allograft:A case report

BACKGROUND Cyclops lesions are a known complication of anterior cruciate ligament(ACL)reconstruction,with symptomatic cyclops syndrome occurring in up to 11%of surgeries.Recurrent cyclops lesions have been rarely documented;this case study documents the successful treatment of a recurrent cyclops lesion.CASE SUMMARY A 28-year-old female presented following a non-contact injury to the right knee.Workup and clinical exam revealed an ACL tear,and arthroscopic reconstruction was performed.Two years later a cyclops lesion was discovered and removed via arthroscopic synovectomy.Seven months postoperatively,the patient presented with pain,stiffness,and difficulty achieving terminal extension.A smaller recurrent cyclops lesion was diagnosed,and a repeat synovectomy was performed.The patient recovered fully.CONCLUSION To the best of our knowledge,this is the first documented case of recurrent cyclops lesion after bone-patellar tendon-bone allograft ACL reconstruction presenting as cyclops syndrome.

Research progress on preparation of lateral femoral tunnel and graft fixation in anterior cruciate ligament reconstruction

Anterior cruciate ligament(ACL)injury is one of the most common types of sports injuries.People’s need to participate in sports and desire for a high quality of life promotes the continuous development of ACL reconstruction technology.Arthroscopic ACL reconstruction has been recognized as an effective method for the treatment of ACL injuries.This review analyses and summarizes the advantages and limitations of each surgical procedure for arthroscopic ACL reconstruction reported in the relevant literature so as to promote the future development of more relevant techniques.

Assessment of functional prognosis of anterior cruciate ligament reconstruction in athletes based on a body shape index

BACKGROUND A healthy body shape is essential to maintain athletes’sports level.At present,little is known about the effect of athletes’body shape on anterior cruciate ligament reconstruction(ACLR).Moreover,the relationship between body shape and variables such as knee joint function after operation and return to the field has not been well studied.AIM To verify the relationship between a body shape index(ABSI)and the functional prognosis of the knee after ACLR in athletes with ACL injuries.METHODS We reviewed 76 athletes with unilateral ACL ruptures who underwent ACLR surgery in the First Hospital of Shanxi Medical University between 2017 and 2020,with a follow-up period of more than 24 mo.First,all populations were divided into a High-ABSI group(ABSI>0.835,n=38)and a Low-ABSI group(ABSI<0.835,n=38)based on the arithmetic median(0.835)of ABSI values.The primary exposure factor was ABSI,and the outcome indicators were knee function scores as well as postoperative complications.The correlation between ABSI and postoperative knee function scores and postoperative complications after ACLR were analyzed using multifactorial logistic regression.RESULTS The preoperative knee function scores of the two groups were similar.The surgery and postoperative rehabilitation exercises,range of motion(ROM)compliance rate,Lysholm score,and Knee Injury and Osteoarthritis Outcome Score of the two groups gradually increased,whereas the quadriceps atrophy index gradually decreased.The knee function scores were higher in the Low-ABSI group than in the High-ABSI group at the 24-mo postoperative follow-up(P<0.05).In multifactorial logistic regression,ABSI was a risk factor of low knee joint function score after surgery,specifically low ROM scores(odds ratio[OR]=1.31,95%confidence interval[CI][1.10-1.44];P<0.001),low quadriceps atrophy index(OR=1.11,95%CI[0.97-1.29];P<0.05),low Lysholm scores(OR=2.34,95%CI[1.78-2.94];P<0.001),low symptoms(OR=1.14,95%CI[1.02-1.34];P<0.05),low activity of daily living(OR=1.34,95%CI[1.18-1.65];P<0.05),low sports(OR=2.47,95%CI[1.78-2.84];P<0.001),and low quality of life(OR=3.34,95%CI[2.88-3.94];P<0.001).ABSI was also a risk factor for deep vein thrombosis of the lower limb(OR=2.14,95%CI[1.88-2.36],P<0.05]and ACL recurrent rupture(OR=1.24,95%CI[0.98-1.44],P<0.05)after ACLR.CONCLUSION ABSI is a risk factor for the poor prognosis of knee function in ACL athletes after ACLR,and the risk of poor knee function after ACLR,deep vein thrombosis of lower limb,and ACL recurrent rupture gradually increases with the rise of ABSI.

Effect of suspension training on neuromuscular function, postural control, and knee kinematics in anterior cruciate ligament reconstruction patients

BACKGROUND Suspension training(SET)is a method of neuromuscular training that enables the body to carry out active training under unstable support through a suspension therapy system.However,there have been few reports in the literature on the application of SET to anterior cruciate ligament reconstruction(ACLR)patients.It is not clear what aspects of the patient's function are improved after SET.AIM To investigate the effect of SET on the neuromuscular function,postural control,and knee kinematics of patients after ACLR surgery.METHODS Forty participants were randomized to an SET group or a control group.The SET group subjects participated in a SET protocol over 6 wk.The control group subjects participated in a traditional training protocol over 6 wk.Isokinetic muscle strength of the quadriceps and hamstrings,static and dynamic posture stability test,and relative translation of the injured knee were assessed before and after training.RESULTS The relative peak torque of the quadriceps and hamstrings in both groups increased significantly(P<0.001),and the SET group increased by a higher percentage than those in the control group(quadriceps:P=0.004;hamstrings:P=0.011).After training,both groups showed significant improvements in static and dynamic posture stability(P<0.01),and the SET group had a greater change than the control group(P<0.05).No significant improvement on the relative translation of the injured knee was observed after training in either group(P>0.05).CONCLUSION Our findings show that SET promotes great responses in quadriceps and hamstring muscle strength and balance function in ACLR patients.

Current and future of anterior cruciate ligament reconstruction techniques

In recent years,anterior cruciate ligament(ACL)reconstruction has generally yielded favorable outcomes.However,ACL reconstruction has not provided satisfactory results in terms of the rate of returning to sports and prevention of osteoarthritis(OA)progression.In this paper,we outline current techniques for ACL reconstruction such as graft materials,double-bundle or single-bundle reconstruction,femoral tunnel drilling,all-inside technique,graft fixation,preservation of remnant,anterolateral ligament reconstruction,ACL repair,revision surgery,treatment for ACL injury with OA and problems,and discuss expected future trends.To enable many more orthopedic surgeons to achieve excellent ACL reconstruction outcomes with less invasive surgery,further studies aimed at improving surgical techniques are warranted.Further development of biological augmentation and robotic surgery technologies for ACL reconstruction is also required.

Degradability of absorbable sutures in tendon grafts following anterior cruciate ligament reconstruction

Objective To observe the degradability of absorbable sutures in tendon grafts and the histology of tendon healing in a rabbit model.Methods Semitendinosus tendons were harvested from 15 healthy adult New Zealand rabbits in this study.

Effects of higher femoral tunnels on clinical outcomes,MRI,and second-look findings in double-bundle anterior cruciate ligament reconstruction with a minimal 5-year follow-up

Background:To perform anatomical anterior cruciate ligament reconstruction(ACLR),tunnels should be placed relatively higher in the femoral anterior cruciate ligament(ACL)footprint based on the findings of direct and indirect femoral insertion.But the clinical results of higher femoral tunnels(HFT)in double-bundle ACLR(DB-ACLR)remain unclear.The purpose was to investigate the clinical results of HFT and lower femoral tunnels(LFT)in DB-ACLR.Methods:From September 2014 to February 2016,83 patients who underwent DB-ACLR and met the inclusion and exclusion criteria were divided into HFT-ACLR(group 1,n=37)and LFT-ACLR(group 2,n=46)according to the position of femoral tunnels.Preoperatively and at the final follow-up,clinical scores were evaluated with International Knee Documentation Committee(IKDC),Tegner activity,and Lysholm score.The stability of the knee was evaluated with KT-2000,Lachman test,and pivot-shift test.Cartilage degeneration grades of the International Cartilage Repair Society(ICRS)were evaluated on magnetic resonance imaging(MRI).Graft tension,continuity,and synovialization were evaluated by second-look arthroscopy.Return-to-sports was assessed at the final follow-up.Results:Significantly better improvement were found for KT-2000,Lachman test,and pivot-shift test postoperatively in group 1(P>0.05).Posterolateral bundles(PL)showed significantly better results in second-look arthroscopy regarding graft tension,continuity,and synovialization(P<0.05),but not in anteromedial bundles in group 1.At the final follow-up,cartilage worsening was observed in groups 1 and 2,but it did not reach a stastistically significant difference(P>0.05).No statistically significant differences were found in IKDC subjective score,Tegner activity,and Lysholm score between the two groups.Higher return-to-sports rate was found in group 1 with 86.8%(32/37)vs.65.2%(30/46)in group 2(P=0.027).Conclusion:The HFT-ACLR group showed better stability results,better PL,and higher return-to-sports rate compared to the LFT-ACLR group.

Are failures of anterior cruciate ligament reconstruction associated with steep posterior tibial slopes？ A case control study

Background Recently, increasing number of literature has identified the posterior tibial slope （PTS） as one of the risk factors of primary anterior cruciate ligament （ACL） injury. However, few studies concerning the association between failure of ACL reconstruction （ACLR） and PTS have been published. The objective of this study was to explore the association between the failure of ACLR and PTS at a minimum of two years follow-up. Methods Two hundred and thirty eight eligible patients from June 2009 to October 2010 were identified from our database. A total of 20 failure cases of ACLR and 20 randomly selected controls were included in this retrospective study. The demographic data and the results of manual maximum side-to-side difference with KT-1000 arthrometer at 30°of knee flexion and pivot-shift test before the ACLR and at the final follow-up were collected. The medial and lateral PTSs were measured using the magnetic resonance imaging （MRI） scan, based on Hudek＇s measurement. A comparison of PTS between the two groups was performed. Results The overall failure rate of the present study was 8.4%. Of the 40 participants, the mean medial PTS was 4.1°±3.2°and the mean lateral PTS was 4.6°±2.6°. The medial PTS of the ACLR failure group was significantly steeper than the control group （3.5°±2.5° vs. 6.1°±2.1°, P=0.000）. Similarly, the lateral PTS of the ACLR failure group was significantly steeper than the control group （2.9°±2.1 °vs. 5.5°±3.0°, P=0.006）. For medial PTS ≥5°, the odds ratio of ACLR failure was 6.8 （P=0.007）; for lateral PTS ≥5°, the odds ratio of ACLR failure was 10.8 （P=0.000）. Conclusion Both medial and lateral PTS were significantly steeper in failures of ACLR than the control group. Medial or lateral PTS ≥5° was a new risk factor of ACLR failure.

Factors affecting proprioceptive recovery after anterior cruciate ligament reconstruction

Background Proprioception plays an important role in knee movements. Since there are controversies surrounding the overall recovery time of proprioception following surgery, it is necessary to define the factors affecting proprioceptive recovery after anterior cruciate ligament （ACL） reconstruction and to investigate the relationship between proprioception and muscle strength. Methods A total of 36 patients who had their ACL reconstructed with a semitendinosus/gracilis graft （reconstructed group： 6 months post-surgery） and 13 healthy adults without any knee injury （control group） were included in the study. Knee proprioception was evaluated with a passive reproduction test. Isokinetic strength was measured using the Biodex System. Statistical analysis was used to compare proprioception of the reconstructed group versus the control group, and to define causal factors, including sex, hamstring/quadriceps ratio, and the course of injury before reconstruction, We also investigated the correlation between the passive reproduction error and quadriceps index. Results There was a significant difference in proprioception between the reconstructed and control groups （P 〈0.05）. When the course of injury before reconstruction was less than 4 months, there was a linear correlation with proprioception 6 months after the operation （r=0.713, P 〈0.05）. There was a positive correlation between post-surgery proprioception and the quadriceps index at 6 months post-surgery. Conclusions Impaired knee proprioception is observed 6 months after ACL reconstruction. Within 4 months of injury, early undertaking of reconstruction is associated with better proprioception outcome. Patients with enhanced proprioception have a better quadriceps index.

Knee function after anterior cruciate ligament reconstruction with patellar or hamstring tendon： a meta-analysis

Background There is currently no consensus regarding the best graft type for anterior cruciate ligament reconstruction. Therefore, the aim of this study was to investigate the effects of patellar and hamstring tendon grafts on long-term knee function after anterior cruciate ligament reconstruction. Methods This meta-analysis was conducted according to the methodological guidelines outlined by the Cochrane Collaboration. An electronic search of the literature was performed and all trials published between January 1966 and August 2011 comparing knee function after anterior cruciate ligament reconstruction using patellar tendon grafts with knee function after reconstruction with hamstring tendon grafts were pooled. Six studies were included in the final meta-analysis. Results Anterior cruciate ligament reconstruction using hamstring tendon grafts resulted in greater pain upon kneeling than reconstruction using patellar tendon grafts （P=0.001）. However, both grafts resulted in similar levels of anterior tibial translation, and similar results regarding isokinetic extension/flexion tests, Lysholm scores, and the stair-hop test （P 〉0.05）. Conclusion Anterior cruciate ligament reconstruction using patellar or hamstring tendon grafts results in similar long-term knee function.

High-purity magnesium screws modulate macrophage polarization during the tendon–bone healing process in the anterior cruciate ligament reconstruction rabbit model

Magnesium(Mg)screws perform clinical potential in anterior cruciate ligament(ACL)reconstruction,and promote fibrocartilaginous entheses regeneration at the femoral entrance.We aim to prove that high-purity Magnesium(HP Mg)screws modulate macrophage polarization in fibrocartilage interface regeneration both in vitro and in vivo.HP Mg extracts performed good cytocompatibility and significantly promoted M2 macrophage polarization in the flow cytometry and ELISA assays.M2 macrophages stimulated fibrochondrocyte differentiation of cocultured hBMSCs,and HP Mg extracts had synergistic effect on the process.Then we applied HP Mg screws,with Ti screws as control,in the ACL reconstruction rabbit model.In the histological and immunofluorescence analysis,HP Mg screws inhibited M1 polarization at 2 weeks and highly promoted M2 polarization at 2 and 4 weeks at the tendon–bone interface.Furthermore,regeneration of fibrocartilaginous entheses,rather than the fibrovascular scar interface,was detected in the HP Mg group at 12 weeks.For further mechanism study via RNA-seq detection and WB assays,we found that AKT1 was highly activated in M2 polarization,and HP Mg could stimulate AKT1 expression,rather than AKT2,in the early phase of tendon–bone healing.Our study elucidated macrophage polarization during tendon–bone healing process and emphasized HP Mg on M2 polarization and fibrocartilage interface regeneration via the selective activation of AKT1 and PI3K/AKT pathway.

Analysis of modified double-bundle anterior cruciate ligament reconstruction with implantless fixation on tibial side

Purpose To avoid potential problems of double-bundle anterior cruciate ligament reconstruction(ACLR),various modifications have been reported.This study analyzed a novel technique of modified double-bundle(MDB)ACLR without implant on tibial side in comparison to single-bundle(SB)ACLR.Methods Eighty cases of isolated anterior cruciate ligament tear(40 each in SB group or MDB group)were included.SB ACLR was performed by outside in technique with quadrupled hamstring graft fixed with interference screws.In MDB group,ACLR harvested tendons were looped over each other at the center and free ends whipstitched.Femoral tunnel was created by outside in technique.Anteromedial tibial tunnel was created with tibial guide at 55°.The anatomic posterolateral aiming guide(Smith-Nephew)was used to create posterolateral tunnel.With the help of shuttle sutures,the free end of gracillis was passed through posterolateral tunnel to femoral tunnel followed by semitendinosus graft through anteromedial tunnel to femoral tunnel.On tibial side the graft was looped over bone-bridge between external apertures of anteromedial and posterolateral tunnel.Graft was fixed with interference screw on femoral side in 10°knee flexion.International Knee Documentation Committee(IKDC),Tegner score,Pivot shift and knee laxity test(KLT,Karl-Storz)were recorded pre-and post-surgery.At one year magnetic resonance imaging(MRI)was done.Statistical analysis was done by SPSS software.Results Mean preoperative KLT reading of(10.00±1.17)mm in MDB group improved to(4.10±0.56)mm and in SB group it improved from(10.00±0.91)mm to(4.80±0.46)mm.The mean preoperative IKDC score in MDB group improved from(49.49±8.00)to(92.5±1.5)at one year and that in SB group improved from(52.5±6.9)to(88.4±2.6).At one-year 92.5%cases in MDB group achieved their preinjury Tegner activity level as compared to 60%in SB group.The improvement in IKDC,KLT and Tegner scale of MDB group was superior to SB group.MRI confirmed graft integrity at one year and clinically at 2 years.Conclusion MDB ACLR has shown better outcome than SB ACLR.It is a simple technique that does not require fixation on tibial side and resultant graft is close to native ACL.

Meniscus repair with simultaneous anterior cruciate ligament reconstruction: Clinical outcomes, failure rates and subsequent processing

Purpose::To retrospectively analyze the clinical outcomes of meniscus repair with simultaneous anterior cruciate ligament(ACL)reconstruction and explore the causes of failure of meniscus repair.Methods::From May 2013 to July 2018,the clinical data of 165 patients who were treated with meniscus surgery and simultaneous ACL reconstruction,including 69 cases of meniscus repair(repair group)and 96 cases of partial meniscectomy(partial meniscectomy group)were retrospectively analyzed.The exclusion criteria were as follows:(1)ACL rupture associated with fracture,collateral ligament injury,or complex ligament injury;(2)a history of knee surgery;or(3)a significant degree of osteoarthritis.The 69 patients in the repair group were divided into the non-failure group(62 cases)and the failure group(7 cases)depending on the repair effect.Postoperative outcomes of the repair group and the partial meniscectomy group were compared.General conditions and postoperative outcomes of the failure group and the non-failure group were compared.During the median follow-up period of 28 months(range,4-65 months)after the second arthroscopy,postoperative outcomes of seven patients in the failure group were summarized.SPSS 25.0 statistical software was used for statistical analysis.A p value less than 0.05 was considered statistically significant.Results::Seven patients in the failure group who underwent the second arthroscopy were followed up for(30±17.4)months and their postoperative outcomes were summarized.Compared with the partial meniscectomy group,the International Knee Documentation Committee scores of patients in the repair group improved significantly(p=0.031).Compared with the non-failure group,more patients in the failure group were younger than 24 years(p=0.030).The median follow-up period was 39.5 months.All patients recovered well after subsequent partial meniscectomy and relieved clinical symptoms.Visual analog scale scores decreased significantly(p=0.026),and the International Knee Documentation Committee and Lysholm scores improved significantly(p=0.046 for both).Conclusion::The failure rate of meniscus repair in this study was 10.1%(7/69),all of which were medial meniscus tears.However,the surgical outcomes of ACL reconstruction were not affected,and there might be a role for graft protection.Therefore,meniscus retears can be successful treated by performing subsequent partial meniscectomy in patients with repair failure.

Biomechanical comparison of single-tunnel double-bundle and single-bundle reconstruction of anterior cruciate ligament

Objective To compare the difference in stability of the knee joint after single-tunnel double-bundle and single-bundle anterior cruciate ligament (ACL) reconstruction.Methods Six formalin-soaked specimens of the human knee with retained

Hamstring autograft utilization in reconstructing anterior cruciate ligament:Review of harvesting techniques,graft preparation,and different fixation methods

Rupture of the anterior cruciate ligament(ACL)is a common orthopedic injury.Various graft options are available for the reconstruction of ruptured ACL.Using the hamstring muscle as an autograft was first described in 1934,and it remains a commonly harvested graft for ACL reconstruction.Hamstring autografts can be harvested using the traditional anteromedial approach or the newer posteromedial technique.An isolated semitendinosus tendon can be used or combined with the gracilis tendon.There are numerous methods for graft fixation,such as intra-tunnel or extra-tunnel fixation.This comprehensive review discusses the different hamstring muscle harvesting techniques and graft preparation options and fixation methods.It provides a comprehensive overview for choosing the optimal surgical technique when treating patients.

Patellofemoral MRI Alterations Following Single Bundle ACL Reconstruction with Hamstring Autografts Are Associated with Quadriceps Femoris Atrophy

High incidence of patellofemoral pain and patellofemoral joint osteoarthritis was found following anterior cruciate ligament(ACL)reconstruction.The unstability of patellofemoral joint might be an important contribution factor.This study was designed to define the relationship between the unstability of patellofemoral joint and quadriceps femoris atrophy.Twenty patients underwent MRI scan before ACL reconstruction and every two weeks after surgery,until 12 weeks.The merchant’s patellar congruence angle,lateral inclination angle,and quadriceps femoris muscle cross-sectional area were measured and the relationship between the changes of angles and the ratio of quadriceps femoris atrophy was studied by multiple regression analysis.Significant quadriceps femoris atrophy was observed after ACL reconstruction during the follow-up period of 12 weeks.The merchant’s patellar congruence angle and lateral inclination angle significantly changed after surgery.The alterations of the merchant’s patellar congruence angle were significantly correlated with the atrophy ratio of vastus medialis(coefficient=-5.76)and vastus lateralis(coefficient=8.35)during the follow-up period of 12 weeks.The alterations of lateral inclination angle were significantly correlated with the atrophy ratio of vastus medialis(coefficient=20.62),vastus lateralis(coefficient=-11.38)and rectus femoris(coefficient=-0.469)during the follow-up period 12 weeks.To sum up,ACL reconstruction can alleviate the dysfunction of patellofemoral joint to a certain extent.But,the unbalanced atrophy of quadriceps femoris once again destroyed the stability of patellofemoral joint following the operation,which might be one cause of patellofemoral joint pain and early onset of osteoarthritis after ACL reconstruction.So,rehabilitation training that focuses on quadriceps femoris especially the vastus medialis shortly following operation is suggested.