***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : Acromioclavicular joint dislocations are common orthopaedic injuries . Numerous operative techniques have been described , but the gold st and ard has yet to be defined . The goal of fixation is to create a stiff and strong reconstruction of the coracoclavicular ligaments to provide optimal stability . The modified Weaver-Dunn is the traditional surgical procedure . However , due to the high rate of recurrent instability with this technique , a shift toward a more anatomic repair has occurred . Purpose : To evaluate the biomechanical performance of multiple types of coracoclavicular ligament reconstruction . Study Design : Controlled laboratory study . Methods : Thirty fresh-frozen human cadaveric shoulders were assigned to 1 of 5 reconstruction groups or a control group : modified Weaver-Dunn , nonanatomic allograft , anatomic allograft , anatomic suture , and GraftRope .  A type III acromioclavicular joint dislocation was simulated in all specimens . The 5 techniques were completed , and a cyclic preload and a load-to-failure protocol were performed . Results : The control had an average load to failure of 1330.6 ± 447.0 N. Compared with all techniques , the anatomic allograft had the highest load to failure , 948 ± 148 N. It had a significantly higher load to failure than the modified Weaver-Dunn ( 523.2 ± 98.6 N , P = .001 ) , the anatomic suture ( 578.2 ± 195.3 N , P = .01 ) , the nonanatomic allograft ( 591.2 ± 65.6 N , P = .003 ) , and the GraftRope ( 646 ± 167.4 , P = .016 ) . No significant difference in load to failure was found between the remaining techniques . Conclusion : The anatomic allograft reconstruction has superior initial biomechanical properties compared with the modified Weaver-Dunn , nonanatomic allograft , anatomic suture , and GraftRope techniques . Clinical Relevance : Anatomic reconstruction of the coracoclavicular ligaments with allograft may provide a stronger biological solution for acromioclavicular joint dislocations . This reconstruction may minimize recurrent subluxation and pain and permit earlier rehabilitation when compared with current techniques Purpose To compare outcomes of acromioclavicular ( AC ) joint reconstruction with ligament augmentation and reconstruction system ( LARS ) ligament in professional and non-professional athletes at 2-year minimum follow-up . Methods Forty-three patients ( men ; mean age 30 , range 19–54 years ) with Rockwood type III to V chronic AC joint dislocations underwent AC joint reconstruction with LARS ligament and st and ardized rehabilitation .  Patients were divided into two groups : professionals ( 22 ) and non-professionals ( 21 ) . Clinical and radiological evaluations were performed preoperatively , at 3- and 24-month follow-up . Results All clinical ( Oxford and Constant ) scores and patient satisfaction improved significantly from preoperative to follow-up intervals ( p < 0.00001 ) . However , professionals showed nonsignificant improvements from 3- to 24-month follow-up in Constant . Although groups differed preoperatively in Constant ( p = 0.037 ) , they were not different in preoperative-to-postoperative differences in clinical scores , postoperative final satisfaction and median time to return to unrestricted activity [ 4 ( interquartiler range 3–5 ) months to return to full sport in professionals ] . Follow-up radiographs revealed an AC joint ratio ( clavicle inferior-to-superior translation as ratio of AC joint height ) of 0.09 and 0.16 in 8/22 professionals , 0.19 and 0.31 in 9/21 non-professionals , 0.14 and 0.24 in 17/43 overall patients at 3- and 24-month follow-up , respectively . Slight loss of reduction ( 0.25 < AC joint ratio < 0.50 ) : 21 % . There were no significant clinical –radiographic correlations . Complication : one coracoid fracture at follow-up and one wound infection . Conclusions AC joint reconstruction with LARS ligament did not reveal differences in clinical outcomes between groups , with 2 % of failures ( re-dislocations ) at 2-year minimum follow-up . Superior radiological outcomes in professionals were not correlated to clinical results .Level of evidence Therapeutic study – prospect i ve comparative study , Level II Background Despite numerous surgical techniques described , there have been few studies evaluating the biomechanical performance of acromioclavicular joint reconstructions . Purpose To compare a newly developed anatomical coracoclavicular ligament reconstruction with a modified Weaver-Dunn procedure and a recently described arthroscopic method using ultrastrong nonabsorbable suture material . Study Design Controlled laboratory study . Methods Forty-two fresh-frozen cadaveric shoulders ( 72.8 ± 13.4 years ) were r and omly assigned to 3 groups : arthroscopic reconstruction , anatomical coracoclavicular reconstruction , and a modified Weaver-Dunn procedure . Bone mineral density was obtained on all specimens . Specimens were tested to 70 N in 3 directions , anterior , posterior , and superior , comparing the intact to the reconstructed states . Superior cyclic loading at 70 N for 3000 cycles was then performed at a rate of 1 Hz , followed by a load to failure test ( 120 mm/min ) to simulate physiologic states at the acromioclavicular joint . Results In comparison to the intact state , the modified Weaver-Dunn procedure had significantly ( P < . 05 ) greater laxity than the anatomical coracoclavicular reconstruction or the arthroscopic reconstruction . There were no significant differences in bone mineral density ( g/cm2 ) , load to failure , superior migration over 3000 cycles , or superior displacement . The anatomical coracoclavicular reconstruction had significantly less ( P < . 05 ) anterior and posterior translation than the modified Weaver-Dunn procedure . The arthroscopic reconstruction yielded significantly less anterior displacement ( P < . 05 ) than the modified Weaver-Dunn procedure . Conclusion The anatomical coracoclavicular reconstruction has less anterior and posterior translation and more closely approximates the intact state , restoring function of the acromioclavicular and coracoclavicular ligaments . Clinical Relevance A more anatomical reconstruction using a free tendon graft of both the trapezoid and conoid ligaments may provide a stronger , permanent biologic solution for dislocation of the acromioclavicular joint . This reconstruction may minimize recurrent subluxation and residual pain and permit earlier rehabilitation HYPOTHESIS Despite a statistically significant improvement in functional scores after receiving a reverse shoulder arthroplasty ( RSA ) in a cuff-deficient shoulder , not all patients perceive a minimal clinical ly important difference ( MCID ) in every functional domain of the score . METHODS This was a prospect i ve longitudinal study including 60 consecutive patients with a cuff-deficient shoulder treated with a RSA .  The Constant score was recorded before surgery and at a 1-year follow-up assessment . At the 1-year follow-up , all patients also filled out a 15-item anchor question naire to assess their perception of change in their overall function , forward elevation , lateral rotation , internal rotation , and strength to determine the MCID . RESULTS The mean Constant score was 30.1 ( st and ard deviation , 10.7 ) before surgery and was 58.4 ( st and ard deviation , 16.2 ) at the 1-year follow-up , with statistically significant improvement ( P < .001 ) . A statistically significant improvement was found in the domains of forward elevation ( P < .001 ) , lateral rotation ( P < .001 ) , and strength ( P < .001 ) except for internal rotation ( P = .15 ) . The MCID for overall function , forward elevation , lateral rotation , internal rotation , and strength in the Constant score increased by 8 , 6 , 2 , 2 , and 11.5 points , respectively ; only 46.7 % , 20 % , 50 % , 45.8 % , and 33.3 % of the patients , respectively , exceeded the MCID on each domain after surgery . CONCLUSIONS A statistically significant improvement in the Constant score is expected after receiving an RSA in a cuff-deficient shoulder , but a considerable number of patients do not reach the MCID in the function and strength domains . A small improvement in rotation is perceived to be beneficial by patients , whereas large improvements in forward elevation are required for the improvement to be perceived to be beneficial BACKGROUND The minimal clinical ly important difference ( MCID ) is increasingly used to evaluate treatment effectiveness . The MCID for the Constant score has not been previously reported . MATERIAL S AND METHODS A prospect ively collected cohort of 802 consecutive shoulders with arthroscopically treated partial- or full-thickness rotator cuff tears was analyzed . The Constant score was measured preoperatively and at 3 months and 1 year postoperatively . At follow-up visits , the patients were asked a simple 2-stage question : Is the shoulder better or worse after the operation compared with the preoperative state ? This single 2-level question was used as an indicator of patient satisfaction and as an anchor to calculate the  MCID  for the Constant score . RESULTS At 1 year , 781 ( 97.4 % ) patients ( 474 men , 307 women ) were available for follow-up . The preoperative Constant score was 53.1 ( SD 17.2 ) in all patients , 56.2 ( SD 17.4 ) in male patients , and 48.2 ( SD 15.6 ) in female patients . Postoperatively at 3 months , the scores were 61.7 ( SD 16.4 ) in all patients , 65.1 ( SD 16.1 ) in male patients , and 56.8 ( SD 15.5 ) in female patients . At 1 year , the scores were 75.9 ( SD 15.2 ) in all patients , 79.0 ( SD 14.9 ) in male patients , and 71.0 ( SD 14.3 ) in female patients . At 3 months postoperatively , 92.2 % of male patients and 87.2 % of female patients were satisfied with the outcome ( P = .027 ) ; at 1 year , the satisfaction was 93.2 % and 89.5 % , respectively ( P = .067 ) . Five different statistical approaches yielded 5 different MCID estimates ( range , 2 - 16 ) . The 3-month mean change estimate of MCID was 10.4 points . CONCLUSION Our study demonstrates an MCID estimate of 10.4 points as the threshold for the Constant score in patients with rotator cuff tear . LEVEL OF EVIDENCE Basic science study , validation of outcomes instruments/classification systems Background Biomechanical studies comparing various surgical techniques for acromioclavicular joint reconstruction have reported that semitendinosus tendon graft for coracoclavicular ligament reconstruction provides a substantial improvement in initial stability and a load-to-failure equivalent to the intact coracoclavicular ligaments . Although it represents a biomechanical improvement compared with coracoacromial ligament transfer , there is still a lack of prospect i ve comparative studies confirming the clinical relevance of these biomechanical findings . Hypothesis Semitendinosus tendon graft for coracoclavicular ligament reconstruction is associated with superior clinical results compared with a modified Weaver-Dunn procedure in chronic complete acromioclavicular joint dislocation . Study Design Cohort study ; Level of evidence , 2 . Methods Twenty-four patients ( mean age , 42 years ) with painful , chronic Rockwood type III through V acromioclavicular joint dislocations were subjected to surgical reconstruction . In 12 patients , a modified Weaver-Dunn procedure was performed ; in the other 12 patients , autogenous semitendinosus tendon graft was used . Clinical evaluation was performed using the American Shoulder and Elbow Surgeons shoulder score and the Constant score after a mean follow-up time of 37 months . Preoperative and postoperative radiographs were compared . Results The mean American Shoulder and Elbow Surgeons shoulder score improved from 74 ± 7 points preoperatively to 86 ± 8 points postoperatively in the Weaver-Dunn group , and from 74 ± 4 points to 96 ± 5 points in the semitendinosus tendon group ( P < .001 for both techniques ) . The mean Constant score improved from 70 ± 8 points to 81 ± 8 points in the Weaver-Dunn group , and from 71 ± 5 points to 93 ± 7 points in the semitendinosus tendon group ( P < .001 ) . The results in the semitendinosus tendon group were significantly better than in the Weaver-Dunn group ( P < .001 ) . The radiologic measurements showed a mean coracoclavicular distance of 12.3 ± 4 mm in the Weaver-Dunn group increasing to 14.9 ± 6 mm under stress loading , compared with 11.4 ± 3 mm increasing to 11.8 ± 3 mm under stress in the semitendinosus tendon group . The difference during stress loading was statistically significant ( P = .027 ) . In the semitendinosus tendon group , horizontal displacement of the lateral clavicle end could be reduced in all cases with type IV dislocation . Conclusion Semitendinosus tendon graft for coracoclavicular ligament reconstruction result ed in significantly superior clinical and radiologic outcomes compared to the modified Weaver-Dunn procedure 
    Output:
    
Conclusion Both anatomic and non-anatomic ACJ reconstructions provide significant post-operative improvements , but definitive conclusions on optimal technique remain elusive .
Notwithst and ing , comparative studies support the use of anatomic ACJ reconstruction which should be preferably used .