Abstract: BACKGROUND: Although materials and technologies of internal fixation have been improved significantly, the treatment of Pauwels III fractures of femoral neck in young adults remains a challenging and controversial issue.  
OBJECTIVE: To explore the early effect of percutaneous hollow compression screw combined with medial buttress plate via direct anterior approach for modified Pauwels type III femoral neck fractures in young adults, causes of main complications and problems in perioperative period need to be paid attention to.
METHODS:  Clinical data of 18 young adults of modified Pauwels type III femoral neck fractures in young adults treated with percutaneous hollow compression screw combined with medial buttress plate via direct anterior approach in Affiliated Hospital of Yangzhou University from November 2016 to November 2018 were retrospectively analyzed in this retrospective study. The data, including time from injury to admission, time from injury to operation, operation time, postoperative partial-weight bearing time and full-weight bearing time, imaging bone healing time and clinical bone healing time, were all required to be carefully recorded. According to the results of X-ray and CT examination, the failure of internal fixation, bone non-unions, femoral neck shortening, and aseptic necrosis of the femoral head were assessed. It was necessary to further perform MRI if having suspected the occurrence of aseptic necrosis of the femoral head. Meanwhile, the reduction quality and functional recovery of the affected hips, at immediately, 3, 6, 12, and 24 months after surgery, were evaluated respectively by Garden's alignment index and the Harris score.  
RESULTS AND CONCLUSION: (1) In all 18 patients, the average follow-up time was 24-36 months. The average image bone healing time and clinical bone healing time were (4.3±1.1) months (3.8-6.1 months) and (5.8±0.9) months (4.9-8.2 months), respectively. (2) There was no significant difference in Garden’s alignment index on the anteroposterior and lateral X-rays of the affected hip immediately, 3, 6, 12, and 24 months after surgery (P > 0.05). (3) At 3, 6, 12, and 24 months after surgery, the Harris scores and total scores of the affected hip were all significantly higher than those before surgery (P < 0.05). Compared with 3 months after surgery, the Harris scores and total scores of the affected hip were all significantly improved at 6, 12, and 24 months after surgery (P < 0.05). Compared with 6 months after surgery, the hip function, range of motion and total Harris score were all significantly improved at 12 and 24 months after surgery (P < 0.05). (4) The wounds of all patients healed at the first level, and there were no complications such as nonunion, deep venous thrombosis, hypostatic pneumonia, or bed sore. Two cases of patients had withdrawals of hollow compression screw accompanied with shortening of the femoral neck after surgery (about 8 mm), but the clinical bone healing was successfully completed. Aseptic necrosis of the femoral head occurred in one patient concomitant with hip dysfunction 2 years postoperatively, who was revised subsequently by total hip arthroplasty via original direct anterior approach. One patient experienced obvious pain during the hyperflexion of the hip joint, and the symptoms were relieved 3 months after the primary operation without special treatment. 
(5) The all outcomes indicated that fixation of percutaneous hollow compression screw combined with medial buttress plate via direct anterior approach in young adults with modified Pauwels type III femoral neck fractures can achieve the anatomical reduction and fixation of the fractures under direct vision, and its early effect is satisfactory. However, it is required to control surgical indications and strengthen perioperative management strictly so as to prevent the occurrence of major complications, such as nonunion and aseptic necrosis of the femoral head.

Key words: femoral neck fracture, modified Pauwels type III, young adults, direct anterior approach, hollow compression screw, medial buttress plate, complications