***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: Background and purpose No prospect i ve surveillance systems have been available for monitoring the outcome of  cruciate ligament surgery in Sc and inavia ( Denmark , Norway , and Sweden ) . In the present paper we describe the Sc and inavian ACL registries including their main function , similarities , and preliminary baseline results . Methods The Sc and inavian registries were established in 2004 ( Norway ) and 2005 ( Denmark and Sweden ) . The Danish and Swedish registries were originally based on the Norwegian registry , and there is no overriding difference between the three . In Denmark , all hospitals and clinics are legally bound to report to an approved national data base . In Norway and Sweden , the registries are based on voluntarily reporting by surgeons . Results The annual incidence of primary ACL reconstructions  is higher in Denmark than in Norway , except in females younger than 20 years . Among Sc and inavian surgeons , there is a similar approach to the patients . Differences do , however , exist regarding choice of grafts , choice of implants , and choice of treatment of simultaneous meniscal and cartilage injuries ; the proportion of ACL reconstructions performed as outpatient surgery ; and the use of prophylactic anticoagulation . Clinical ly , the preoperative KOOS scores are not significantly different between the Sc and inavian registries , except that Denmark reports more symptoms both pre- and postoperatively . Interpretation The Sc and inavian national ACL registries will generate new data about ACL reconstructions . They will contribute important knowledge regarding ACL epidemiology . They will be the only source of data on the performance of a wide range of different implants and techniques . In addition , they will hopefully have an impact on the selection of methods for ACL reconstructions in Sc and inavia and elsewhere Background The choice of different graft types and surgical techniques used when reconstructing a torn anterior cruciate ligament may influence the long-term prevalence of osteoarthritis and functional outcomes . Hypothesis There are no differences in the prevalence of knee osteoarthritis or  knee function in patients undergoing reconstruction of a torn anterior cruciate ligament with 4-str and hamstring autograft versus patellar tendon — bone autograft .  Study Design R and omized controlled trial ; Level of evidence , 1 . Methods Seventy-two patients with subacute or chronic rupture of the anterior cruciate ligament were r and omly assigned to autograft reconstruction with 4-str and gracilis and semitendinosus tendon ( HAM ) ( N = 37 ) or with patellar tendon — bone ( PTB ) ( N = 35 ) from the ipsilateral side . Outcome measurements were the Cincinnati knee score , single-legged hop tests , isokinetic muscle strength tests , pain , knee joint laxity test ( KT-1000 arthrometer ) , and a radiologic evaluation ( Kellgren and Lawrence ) at 10-year follow-up . Results At 10 years , 57 patients ( 79 % ) were eligible for evaluation—29 in the HAM group and 28 in the PTB group . No differences were found between the 2 graft groups with respect to the Cincinnati knee score , the single-legged hop tests , pain , muscle strength measurements , or knee joint laxity . Fifty-five percent and 64 % of the patients had osteoarthritis corresponding to Kellgren and Lawrence grade 2 or more in the HAM and the PTB groups , respectively ( P = .27 ) . For the uninvolved knee , the corresponding numbers were 28 % and 22 % ( P = .62 ) . Conclusion At 10 years postoperatively , no statistically significant differences in clinical outcome between the 2 graft types were found . The prevalence of osteoarthritis was significantly higher in the operated leg than in the contralateral leg , but there were no significant differences between the 2 groups . The results indicate that the choice of graft type after an anterior cruciate ligament injury has minimal influence on the prevalence of osteoarthritis 10 years after surgery Seventy-two patients with subacute or chronic rupture of the anterior cruciate ligament were r and omly assigned to autograft reconstruction with four-str and gracilis and semitendinosus tendon ( N = 37 ) or with patellar tendon-bone ( N = 35 ) from the ipsilateral side . The groups were similar in terms of age , sex , level of activity , degree of laxity , meniscal lesions found surgically , and rehabilitation program . The follow-up was performed at another hospital by independent observers after 6 , 12 , and 24 months . Sixty-one patients ( 32 with hamstring tendon grafts and 29 with patellar tendon grafts ) complied with the follow-up routine for the full 24 months . No differences were found between the groups with respect to Cincinnati functional score , KT-1000 arthrometer measurements , or stairs hopple test results . The subjective result and the single-legged hop test result were better for the hamstring tendon group after 6 and 12 months , but no differences were found after 24 months . The hamstring tendon group showed better isokinetic knee extension strength than did the patellar tendon group after 6 months , but not after 12 and 24 months . There was a significant weakness in isokinetic knee flexion strength among the hamstring tendon group . Anterior knee pain was not significantly different between the groups , but kneeling pain was significantly less common in the hamstring tendon group after 24 months Background : R and omized controlled trials after anterior cruciate ligament reconstructions with long-term follow-up including assessment of health-related quality of life are rare . Purpose : To compare clinical outcome and health-related quality of life 8 years after  anterior cruciate ligament reconstruction  using 2 types of graft . Study Design : R and omized controlled trial ; Level of evidence , 1 . Methods : Long-term follow-up of 164 patients with anterior cruciate ligament injury r and omized to arthroscopic reconstruction with a quadrupled semitendinosus graft or a bone – patellar tendon – bone graft was undertaken . After a mean 8 years , 153 patients were available for follow-up , including instrumented laxity , 1-legged hop test , a knee-walking test , and assessment with International Knee Documentation Committee , Lysholm , Tegner , and patellofemoral pain score . Health-related quality of life was assessed with Knee Osteoarthritis Outcome Score and Short Form–36 . Results : Patients in both graft groups retained the same stability , knee function , and health-related quality of life . The patellofemoral pain score was similar for both groups ; the bone – patellar tendon – bone group had more donor site morbidity from kneeling and knee walking . In the bone – patellar tendon – bone group , 19 patients had no kneeling problems , 23 slight problems , 31 moderate problems , and 5 unable to kneel . Corresponding figures for the semitendinosus group were 25 , 32 , 16 , and 2 ( P < .001 ) . Patients with early reconstructions ( < 5 months ) had a lower risk for meniscal injuries ( 37 % ) than did later reconstructed ( 62 % , P = .008 ) . Health-related quality of life regarding physical functioning in Short Form–36 was better for the early-reconstructed patients than for the later reconstructed ( 92 vs 85 ; P = .014 ) . Patients without medial meniscal surgery had higher Knee Osteoarthritis Outcome Scores for all subscales than did patients with medial meniscal surgery , with most significant difference for sport and recreation ( 63 vs 75 , P = .008 ) . Conclusion : In the long term , the semitendinosus graft provided similar stability , knee function , and health-related quality of life but with less kneeling morbidity than did the bone – patellar tendon – bone graft Background No prospect i ve surveillance system exists for monitoring the outcome of cruciate ligament surgery . Purpose This article is intended to describe the development and procedures of the Norwegian National Knee Ligament Registry ( NKLR ) , including baseline results from the first 2 years of operation . Study Design Cohort study ( prevalence ) ; Level of evidence , 1 . Methods The NKLR was established on June 7 , 2004 to collect information prospect ively on all cases of cruciate ligament reconstruction surgery in Norway . Information on the details of surgery is gathered through a registration form completed by the surgeon postoperatively , and a vali date d knee outcome score form is completed by the patients preoperatively and at follow-ups on all patients at 2 , 5 , and 10 years postoperatively . Hospital compliance was examined in 2005 and 2006 . Results A total of 2793 primary cruciate ligament reconstruction surgeries were registered by 57 hospitals . This corresponds to an annual population incidence of primary anterior cruciate ligament reconstruction surgeries of 34 per 100 000 citizens ( 85 per 100 000 citizens in the main at-risk age group of 16–39 years ) . After 21 months of operation , the NKLR had an overall compliance of 97 % when compared with the hospital records . Conclusions A national population -based cruciate ligament registry has been developed , implemented , and maintained in Norway . The registry will each year enroll approximately 1500 primary cruciate ligament reconstruction cases . It is expected that inadequate procedures and devices can be identified , as well as prognostic factors associated with good and poor outcomes , at least for the most frequent categories In a two-centre study , 164 patients with unilateral instability of the anterior cruciate ligament were prospect ively r and omised to arthroscopic reconstruction with either a patellar tendon graft using interference screw fixation or a quadruple semitendinosus graft using an endobutton fixation technique . The same postoperative rehabilitation protocol was used for all patients and follow-up at a median of 31 months ( 24 to 59 ) was carried out by independent observers . Four patients ( 2 % ) were lost to follow-up . No significant differences were found between the groups regarding the Stryker laxity test , one-leg hop test , Tegner activity level , Lysholm score , patellofemoral pain score , International Knee Documentation Committee ( IKDC ) score or visual analogue scale , reflecting patient satisfaction and knee function . Slightly decreased extension , compared with the non-operated side , was found in the patellar tendon group ( p < 0.05 ) . Patients with associated meniscal injuries had lower IKDC , visual analogue ( p < 0.01 ) and Lysholm scores ( p < 0.05 ) than those without such injuries . Patients in whom reconstruction had been carried out less than five months after the injury had better final IKDC scores than the more chronic cases ( p < 0.05 ) . We conclude that patellar tendon and quadruple semitendinous tendon grafts have similar outcomes in the medium term . Associated meniscal pathology significantly affects the final outcome and early reconstruction seems to be beneficial Objective the aim of this study was to radiologically evaluate the femoral tunnel position in anterior cruciate ligament ( ACL ) reconstructions using the isometric and anatomical techniques . Methods a prospect i ve analytical study was conducted on patients undergoing ACL reconstruction by means of the isometric and anatomical techniques , using grafts from the knee flexor tendons or patellar tendon . Twenty-eight patients were recruited during the immediate postoperative period , at the knee surgery outpatient clinic of FCMMG-HUSJ .  Radiographs of the operated knee were produced in anteroposterior ( AP ) view with the patient st and ing on both feet and in lateral view with 30 ° of flexion . The lines were traced out and the distances and angles were measured on the lateral radiograph to evaluate the sagittal plane . The distance from the center of the screw to the posterior cortical bone of the lateral condyle was measured and divided by the Blumensaat line . In relation to the height of the screw , the distance from the center of the screw to the joint surface of the lateral condyle of the knee was measured . On the AP radiograph , evaluating the coronal plane , the angle between the anatomical axis of the femur and a line traced at the center of the screw was measured . Results with regard to the p measurement ( posteriorization of the interference screw ) , the tests showed that the p-value ( 0.4213 ) was greater than the significance level used ( 0.05 ) ; the null hypothesis was not rejected and it could be stated that there was no statistically significant difference between the anatomical and isometric techniques . With regard to the H measurement ( height of the screw in relation to the lower cortical bone of the knee ) , the p-value observed ( 0.0006 ) was less than the significance level used ( 0.05 ) ; the null hypothesis was rejected and it could be stated that there was a statistically significant difference between the anatomical and isometric techniques . It can be concluded that the latter difference occurred because the isometric technique generated greater values for the H measurement than the anatomical technique . With regard to the MED variable ( position of the screw on the AP radiograph ) , the observed p-value ( 0.000 ) was less than the significance level ( 5 % ) ; the null hypothesis was rejected and it could be stated with 95 % confidence that there was a significant difference between the anatomical and isometric techniques . Conclusions there were statistically significant differences in the radiological evaluations of the femoral tunnel , both in the sagittal and in the coronal plane , between the ACL reconstruction techniques Radiographic tibial and femoral bone tunnel enlargement has been demonstrated following anterior cruciate ligament ( ACL ) reconstruction . This study investigated whether bone tunnel enlargement differs between  four-str and hamstring 
    Output:
    
We found significant differences in favor of the HT technique in the domains of anterior knee pain , kneeling pain , and restriction in the range of active extension ( " extension deficit " ) .
We found no differences between the PT and HT technique in terms of rerupture rate .
There were no clinical ly significant differences for the outcomes of Lysholm score and Tegner Activity Scale as well as the KT-1000 side-to-side at maximum manual force .
Contemporary 4-str and HT ACL reconstruction is comparable with the PT technique in terms of clinical stability and postoperative functional status across most parameters studied .
The HT technique carries lower risk of postoperative complications such as anterior knee pain , kneeling discomfort , and extension deficit .
Primary ACL reconstruction using the 4-str and HT technique achieves clinical results that are comparable with the PT technique with significantly less postoperative complications .