Surgical treatment of 4-part proximal humerus fractures and fracture dislocations remain challenging because of difficulties in exposure, reduction, and achieving a stable internal fixation. We have treated these injuries using extended deltoid-splitting approach with internal fixation using locking plates, calcium sulfate graft, and tuberosity repair with polyethylene sutures. We have used this technique in 21 cases (20 patients) 7 male, 13 female with displaced 4-part fractures or fracture dislocations. The average age was 59 years (range, 27 to 74 y) and average length of follow-up 5 years (range, 3 to 7 y). Overall 19 cases (90%) achieved good or excellent results. All cases united without any serious complications such as loss of tuberosity fixation, humeral head perforation, avascular necrosis, or axillary nerve palsy. In 1 case there was varus malunion. In another varus malunion and infection, but this resolved satisfactorily with 1 episode of debridement and insertion of gentamicin-impregnated collagen sheets. The clinical result of both varus malunited cases was good as the tuberosity reconstruction remained anatomic. We have found the extended deltoid-splitting approach to ease exposure, especially in posterior fracture dislocations and enhance accuracy of tuberosity reduction. The use of locking plates, calcium sulfate graft, and tuberosity repair with polyethylene sutures has also given us a reliable means of achieving a stable fixation in these difficult cases, allowing early postoperative rehabilitation.