***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: In a prospect i ve study of 321 consecutive cases of dislocation ankle fractures , operatively treated according to the AO ( ASIF ) principles , 306 cases ( 95 % ) were followed up two to six years after surgery . The infection rate was 1.8 % with no septic arthritis . The clinical results were " excellent and good " in 82 % , " acceptable " in 8 % , and " poor " in 10 % . Posttraumatic arthritis occurred in 14 % and was significantly more common among middle-aged women . There was a strong correlation between the degree of arthritis and the clinical result . A computer analysis ( AID ) revealed that the most decisive factors influencing the clinical result were the type of fracture , the accuracy of the reduction , and the sex of the patient . Exact reduction , rigid internal fixation  , early postoperative joint exercises  , and subsequent full weight-bearing  in a below-the-knee walking plaster are essential for a good end result of fracture-dislocations of the ankle joint Objectives : To compare radiographic and clinical midterm outcomes of posterior malleolar fractures treated with posterior buttress plating versus anterior to posterior lag screw fixation . Design : Retrospective case series . Setting : Level I trauma center . Patients / Participants : Between January 2002 and December 2010 , patients with posterior malleolar fractures were identified by Current Procedural Terminology code and their charts review ed for eligibility . Intervention : Posterior malleolar fixation using either anterior to posterior ( AP ) lag screws or posterior buttress plating . Main Outcome Measurements : Demographic data , length of follow-up , range of motion , and postoperative Short Musculoskeletal Function Assessment ( SMFA ) scores were the main outcome measurements . Immediate postoperative radiographs for residual gap/step-off and final follow-up radiographs for the degree of arthritis that developed were evaluated . Results : Thirty-seven patients were eligible for the study , and 27 chose to participate . Sixteen patients underwent posterior buttress plating , and 11 underwent AP screw fixation with mean follow-up times of 54.9 and 32 months , respectively . Demographic data were similar between groups . The posterolateral plating group demonstrated superior postoperative SMFA scores compared with the AP screw group with statistically significant differences in the SMFA bother index ( 26.7 vs. 9.2 , P = 0.03 ) and trends toward improvement in the mobility ( 28.3 vs. 12.9 , P = 0.08 ) and functional indices ( 20.2 vs. 9.4 , P = 0.08 ) . There were no significant differences in the range of motion or the development of ankle arthritis over time . Conclusions : Patients with trimalleolar ankle fractures in whom the posterior malleolus was treated with posterolateral buttress plating had superior clinical outcomes at follow-up compared with those treated with AP screws . Level of Evidence : Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence Purpose In this retrospective study , we evaluated the treatment effect of  ankle joint fracture surgery involving the posterior malleolus , and discuss relevant factors influencing the occurrence of traumatic arthritis of the ankle joint . Methods A total of 102 cases of ankle joint fractures involving the posterior malleolus in five large-scale skeletal trauma centres in China , from January 2000 to July 2009 , were retrospectively analysed in terms of surgical treatment and complete follow-up . Ankle joint mobility , posterior malleolus fragment size , articular surface evenness , Ankle-Hindfoot Scale of the American Orthopedic Foot and Ankle Society ( AOFAS ) score , and imaging scale score for arthritis were recorded . The degree of fracture pain during rest , active movement , and weight-bearing walking , and satisfaction with treatment were evaluated using a visual analogue scale ( VAS ) . Results The average AOFAS score was 95.9 , excellence rate was 92.2 % , and average VAS scores for degree of fracture pain during rest , active movement , and weight-bearing walking were 0.15 , 0.31 , and 0.68 , respectively . Thirty-six cases showed arthritic manifestations . Ankle joint mobility along all directions on the injured side was lower than that on the unaffected side . There was no obvious difference in treatment effect between the fixed and unfixed posterior malleolus fragment groups for all and for fragment size of < 25 % ; between fixing the posterior malleolus fragment from front to back or from back to front ; or between elderly patients ( ≥60 years old ) and young patients ( < 60 years old ) . There was a distinct difference in the treatment effect between articular surface evenness and unevenness for all and for fragment size of ≥25 % . Conclusions For all 102 cases of ankle joint fracture involving the posterior malleolus , the treatment effect was satisfactory . Restoration of an even articular surface , especially when fragment size ≥25 % , should be attempted during treatment Background : The goal of this study was to report the results of selective open reduction and internal fixation of fractures of the posterior malleolus with a posterolateral approach and to compare the results of the 2 techniques . Methods : We prospect ively evaluated 40 patients who underwent posterior malleolar fracture fixation between 2008 and 2012 . The patients were treated with a posterolateral approach . We assigned alternating patients to receive plate fixation and the next screw fixation , consecutively , based on the order in which they presented to our institution . Fixation of the posterior malleolus was made with lag screws in 20 patients and a buttress plate in 20 patients . We used American Orthopaedic Foot and Ankle Society ( AOFAS ) scores , range of motion ( ROM ) of the ankle , and radiographic evaluations as the main outcome measurements . The mean follow-up was 38.2 ( range , 24 - 51 ) months . Results : Full union without any loss of reduction was obtained in 38 of the 40 patients . We detected a union with a step-off of 3 mm in 1 patient in the screw group and a step-off of 2 mm in 1 patient in the plate group . At the final follow-up , the mean AOFAS score of the patients regardless of fixation type was 94.1 ( range , 85 - 100 ) . The statistical results showed no significant difference between the patients regardless of the fixation type of the posterior malleolus in terms of AOFAS scores and ROM of the ankle ( P > .05 ) . Conclusions : Good ( AOFAS score of 94/100 ) and equivalent ( within 3 points ) results were obtained using the 2 techniques ( screws or plate ) for fixation after open reduction of posterior malleolar fragments . Level of Evidence : Level II , prospect i ve case series Objectives : To evaluate the lateral transmalleolar ( LTM ) approach for a displaced posterolateral fragments of a posterior malleolus fracture . Design : Prospect i ve , consecutive . Setting : Level 1 trauma center . Patients : Thirty-six patients . Outcome Measures : The x-rays , evaluation of arthritic changes of the ankle joint , range of motion , and Short Musculoskeletal Function Assessment question naire ( SMFA ) . Intervention : The LTM approach followed by multiple interfragmentary miniscrew-only fixation . Results : No patients experienced intraoperative or postoperative complications that required a revision operation . All fractures healed . There were no infections , and no patient required implant removal . The median range of motion showed no significant difference as compared with the uninjured side . Patients achieved a mean SMFA dysfunction index of 8.2 ± 2.4 points and a mean SMFA bother index of 3.2 ± 1.2 points . All patients performed normal daily life activities at averagely 3 ( range , 2–5 ) months postoperatively . Conclusions : Direct visualization with the LTM approach followed by fixation with multiple miniscrews may be an alternative option for the treatment of ankle fractures with a posterolateral fragment associated with a posterior malleolar fracture . Level of Evidence : Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence 
    Output:
    
There was no clear association between posterior fragment size and functional outcome or development of osteoarthritis .
The non-anatomical reduction of the fragment was of more influence on outcome .
Radiological and functional outcome was better after open reduction and internal fixation via the posterolateral approach than after percutaneous anterior-to-posterior screw fixation .
Conclusion The posterior fragment size is not a clear indication for its fixation .
A step-off , however , seems an important indicator for developing posttraumatic osteoarthritis and worse functional outcome .
Posterior fragments involving the intra-articular surface need to be reduced and fixated to prevent postoperative persisting step-off .
Furthermore , fixation of the posterior malleolus via an open posterolateral approach seems superior to percutaneous anterior-to-posterior fixation .