Study procedures and variables

The demographics, body mass index (BMI), current and former smoking, presence of diabetes mellitus, laterality of rib fractures, number of rib fractures, AO classification of the fractured clavicles, and associated injuries were abstracted from the medical record. The presence of an associated injury except for chest wall injuries was defined as a concurrent injury with an Abbreviated Injury Scale ≧3 [21].

The initial chest radiograph and/or CT scan of the chest were reviewed, and diagnoses of rib fractures and associated thoracic injuries were confirmed by a thoracic and a trauma surgeon. The postoperative radiographs of the clavicle were reviewed blindly by two board-certified orthopedic surgeons (W.T.T. and Y.H.S.). Any objective radiographic complications, including fracture malunion, nonunion, implant loosening, implant breakage, implant malposition, and osteolysis, were recorded. Malunion was defined as shortening > 2 cm, angulation > 30 degree, and translation > 1 cm [22]. Nonunion was defined as no bridging callus by 6 months post-injury. Loosening was defined as presence of halo sign around implants or migration of implant compared with postoperative X-rays. Implant malposition was defined as screw violation to the acromioclavicular joint [23].

The patients were divided into a CWI group, and a no-CWI group. The CWI group was further subdivided into a minor-CWI group comprising patients who sustained one to three rib fractures but no flail chest, and a complex-CWI group comprising patients who suffered four or more rib fracture or a flail chest [24]. Flail chest was defined as at least 3 consecutive rib segmental fractures.

Dependent variables in this study included the overall complication rate, surgery-related complications, and any unplanned 30- and 90-day hospital readmissions [25]. Surgery-related complications included bone union, delayed union, implant-related, and wound complications. Wound complications comprised postoperative surgical site infections and wound dehiscence. Implant-related complications included implant breakage and malposition, loss of reduction, peri-implant fractures, delayed union and malunion, and osteolysis [26, 27]. Data on unplanned hospital readmissions were also extracted from the hospital medical records.