Objective Shoulder dislocations,most of which are anterior dislocations,account for over 40% of joint dislocations.The main pathological mechanism is the dysfunction of the anteroinferior glenolabral articular ligamental complex,namely theBankart injury.Failure of the repair can cause the recurrent dislocation.Some cases are accompanied with the glenoidavulsion fracture or the bony defect,even with the inverted pear glenoid.Open or arthroscopic reconstruction can achieve excellent clinical results for the Bankart injury which bone defect is less than 25%.But if bony defect of glenoid is over 25%-30% or associtaed with Hill-Sachs injury,the re-dislocation rate is up to 67% after the simple Bankart reconstruction.The Latarjet procedure is able to reduce the recurrent dislocation significantly.This study is to retrospectively evaluate the three-to-five years' follow-up results of the Latarjet coracoid bone block procedure for the recurrent anterior dislocation of the shoulder associated with the severe bony defects.Methods Thirty-seven patients (23 men and 14 women) underwent the Latarjet procedure for the anterior glenohumeral instability between April 2006 and October 2009.All the shoulders had the severe osseous deficiency of the anterior glenoid rim,which was more than 25% of the glenoid width according to 3-dimensional CT scan and arthroscopic findings.The patients were associtated with Engaging Hill-Sachs lesion.21 patients were treated by the parallel coracoid transposition bone block from January 2008 to October 2009,and 16 patients were performed with the intorted coracoid transposition method from April 2006 to December 2007.Apprenhension sign was positive in all of the 37 patients before operation.And the mean time of their dislocations was 13.5 (ranged from 8 to 28 times).We evaluated the preoperative and postoperative pain,the daily living activities,the range of motion,stability of the shoulders,and function of the shoulder using the American Shoulder and Elbow Surgeons Assessment (ASES),the Constant-Murley Score and the VAS score.Results The follow-up period ranged from 37 to 61 months (mean,48.3 months).All the patients got bony union in the coracoid parallel transposition group while three got a nonunion in the intorted group according to the 3 dimensional CT scan taken at 6 months' follow-up.For the parallel transposition group,most of the patients had a satisfactory pain relief and daily living activities postoperatively at the final follow-up.The forward elevation improved from (152.5±22.6)° preoperatively to (168.0±7.8)° postoperatively,the average external rotational limitation measured in the neutral position of the arm improved from (52.6±18.4)° to (44.9±15.0)°(t=1.486,P＞0.05),the ASES scores increased from 80.7±16.7 to 92.2±6.4(t=2.947,P＜0.05),the Constant-Murley scores increased from 78.6±10.1 to 91.6±13.2(t=3.584,P＜0.05),and the VAS scores increased from 6.0±1.4 to 4.3±1.6(t=3.664,P＜0.05).However,for the intorted transposition group,the forward elevation improved from (148.5±19.2)° to (170.0±10.5)°(t=3.930,P＜0.05),the mean external rotation improved from (55.8±16.9)° to (40.6±13.6)°(t=2.803,P＜0.05),the ASES score increased from 81.4±14.7 to 92.4±7.0(t=2.702,P＜0.05),the Constant-Murley score increased from 80.2±12.6 to 92.8±5.1(t=3.708,P＜0.05),the VAS score increased from 6.4±1.5 to 4.2±2.1(t=3.410,P＜0.05),and one patient had a residual positive Apprehension sign postoperatively,two had mild pain at the position of the maximal abduction or the external rotation.Only one got mild pain at this position in the parallel group.Secondary mild to moderate osteoarthritic changes of the glenohumeral joint were observed in six shoulders postoperatively in the final follow-up.Discussion Glenohumeral stability depends on the structure of the muscle,the ligament and the bone,which can maintain the rotation center of the humeral head and the glenoid.The incidence of shoulder dislocation in US is 11.2/10million,90% of which is areanterior dislocation.The recurrent dislocation will further change the glenohumeral joint contact area and the static stability,which reduces the stability of glenohumeral.Through the MRI examination for patients with the acute anterior shoulder dislocation,Widjaja and colleagues found that 73% of the initial dislocation were associated with Bankart injury and 67% with Hill-Sachs injury.Yiannakopoulos et al.demonstrated that the rates of Bankart and ALPSA injury were up to 97% after the repeated anterior dislocation,howerer,the rates of Hill-Sachsinjury and inverted pearglenoid were 93% and 15%,respectively.Robinson et al.reported a prospective clinical study of patients (aged from 15-35 years old) after the conservative treatment for the anterior shoulder dislocation,56% of which were re-dislocated.The instability rate of those 20-year-old males was as high as 72%-86%.The open Bankart reconstruction could restore the anterior glenoid anatomy,and had been considered as the gold standard with the 3% recurrence rate.With the development of the arthroscopic techniqueand instruments,many authors have reported the arthroscopic Bankart reconstruction with excellent results,even 20% of the patients with the glenoid bone defect had satisfactory outcomes for the reconstruction of the arthroscopic soft tissue.However,a growing number of researches show that the structural integrity of the glenoid bone is one of the key factors for the successful surgical repair.Burkhart et al.demonstrated the rate of the failure repair was as high as 67% in the soft tissue Bankart reconstruction for the obpyriform glenoid.Therefore,the bony reconstruction was recommended for the obpyriform glenoid associated with the Engaging Hill-Sachs injury.Latarjet and Helfet reported the treatment of the recurrent anterior shoulder dislocation with the coracoid process transposition had achieved satisfactory results in 1954 and 1958,respectively.The principle of latarjet procedure is to make the coracoid fragment become a platform to attain the extra-articular extension of the articular surface.Its role in stabilizing the shoulder are: 1 the fragment increases the security area of glenoid before the humeral head is dislocated; 2 the conjoined tendon acts to prevent the huemral head to move forward while the external rotation of the arm; 3 the anteroinferior capsule can be reinforced by the translocated coracoid process and the conjoined tendon strided across the lower 1/3 position of the subscapularis tendon.This study demonstrated that the Latarjet procedure had good results to treat recurrent anterior dislocation associated with severe bone defects,and significantly increased the anterior stability and the flexion of the shoulder as well as a variety of functional scores.The traditional Latarjet procedure needs to cut off the proximal subscapularis tendon,which declines the muscle strength of subscapularis and reduces the restriction of the humeral head moving forward.The overlapping suture of subscapularis and the shoulder immobilization in internal rotation cause a significant loss of the external rotation of shoulder.Osteotomy in the classic Latarjet surgery is between the origins of the pectoralis minor and the coracoclavicular ligaments.The coracoid fragment is shifted laterally to anteroinferior rim of glenoid,and its lateral edge is surfaced.In the latarjet procedure modified by de Beer,the coracoid fragment is pronated 90° along its long axis,so that the lower edge of the coracoid processis is surfaced.The width of the coracoid fragment is greater than its thickness,so the coracoid fragment has a larger contact area with the glenoidin classic transposition,and can be fixed with two 3.5 mm cortical screws with more stability.On the contrary,the fragment has a smaller contact area with the glenoid in the modified transposition,and can be fixed with only two 3.0 mm cannulated screws.Therefore,the classic transposition has a better biomechanical advantage and improves the union of bones.However,the modified transposition provides a greater articular surface,and are advised for the patients with the massive bone defect.In this study,the first three patients from the intorted coracoid transposition group suffered the nonunion which reduced the stabilization offered by Latarjet procedure,therefore,Apprehension sign of one case was positive,and the mild pain existed while the maximum of abduction and external rotation in the remaining two cases.In order to decrease the risk of the nonunion,we performed the autograft between the glenoid and the fragment with the cancellous bone obtained from the base of the corocoid process.There was no significant statistical differences between the parallel group and the intorted group on the forward elevation,the external rotation in the neutral position of the arm,the ASES scores,the Constant-Murley scores,and the VAS instability scores.The loss of the external rotation was obviously greater than that in intorted group,for the rehabilitation physicians were unwilling to strictly carry out the postoperative rehabilitation program due to their anxiety about the bone union.The roughness of the articualr surface is closely related with the occurrence of the postoperative arthritis.So we adjusted the curvature of the fragment to make it consistent with articular surface.The fragment was first fixed with two 1.0mm K-wires for the temporary fixation,and then screws were used for the fixation.Postoperative CT scans confirmed that the glenoid surface was relatively smooth and the step was less than 3mm.According to the Samilson and Prieto osteoarthritis classification,6 patients had OA in X-ray films in the final follow-up of this study,which might be related with the intraoperative fragment reduction and the short follow-up period.Compared with the modified transposition,the classic procedure had more stability of fixation,so the bone heeled in all cases and OA only appeared in one case.Conclusions The Latarjet coracoid bone block procedure has proved effective with a lower redislocation rate for most of the patients with the complex recurrent anterior dislocation of the shoulder accompanied by the severe glenoid bony defect.The parallel coracoid transposition group with more contact area and more stable fixation strength had a higher union rate compared with the coracoid intorted group.