Accounting for 5% of all fractures, proximal humerus fracture is one of the most common fractures for osteoporotic group with an incidence of 90.9/100 000 per year. Its incidence rate increases with age, and approximately 70% of proximal humeral fractures occur in patients over 60 years old. Female accounts for the majority of the affected elderly over 80 years old, as the ratio between men and women is 3:7. With obvious displacement and osteoporosis, bone compression and loss are easily formed after fracture, which result in the loss of the unique anatomical mark of humeral neck. The therapeutic effect of conservative treatment for displaced fracture is unsatisfactory. The displacement even causes great difficulty in plate fixation during surgery, which easily triggers complications such as loss of reduction, ischemic necrosis, screw piercing, etc. For osteoporotic proximal humeral fracture, locking plate fixation has the advantages of multi-angle and stable fixation, which can significantly improve postoperative function and reduce complications. However, the complications caused by locking plate still happen. According to the literature, the rate of humeral head bone loss and screw piercing is still as high as 29% with the bone loss of about 6 mm. Allograft bone transplantation can provide good support for humeral head and promote fracture healing, and the clinical effect is satisfactory. Although locking plate fixation with allogeneic bone graft has been applied for the treatment of senile osteoporotic proximal humeral fracture, the clinical efficacy evaluation and imaging data analysis of different types have been barely reported. Therefore, this article aims to explore the application value of allograft bone transplantation in different types of osteoporotic proximal humerus fracture.

(1) General information. A total of 36 patients (17 males and 19 females) were included in this study, and the age ranged from 65 to 82 years with an average of (71.5±5.5) years. The causes of injury include 25 cases of fall damage, 7 cases of traffic accident and 4 cases of sports injury. According to Neer classification, there were 14 cases of surgical neck or anatomic neck part-2 fracture, 13 cases of part-3 fracture and 9 cases of part-4 fracture. Furthermore, there were 4 cases combined with shoulder joint dislocation, 3 cases combined with rib fracture and 1 case combined with clavicular fracture. All patients were treated with open reduction and locking plate internal fixation. (2) Inclusive and exclusive criteria. Inclusive criteria: ① osteoporosis with dual energy x-ray absorptiometry (DXA) T value <-2.5 SD (according to the diagnostic criteria of WHO, DXA T value <-2.5 SD is regarded as osteoporosis) ;② unilateral proximal fracture with displacement > 1 cm and angulation> 45o; ③ Neer part-2, part-3 and part-4 impacted fracture, s with humeral head bone loss; ④ age over 60 years; ⑤ follow-up time ≥1 year. Exclusive criteria: ① pathological fracture or open fracture; ② combined with neurovascular injury ; ③history of diseases that affects limb function, such as previous operation, chronic arthritis, etc. (3) Surgical procedures. The patients were operated under brachial plexus block or general anesthesia. Deltoid-pectoralis approach was used in 26 cases, while deltoid-splitting approach was used in 10 cases. The removal of periosteum and surrounding soft tissue was minimized during the operation. For simple fracture, the intraoperative traction of affected limb should be conducted appropriately by assistants based on the specific conditions. Meanwhile, the affected limb was operated with internal or external rotation if necessary. The humeral head was raised and applied with 2 Kirschner wires of 2.5 mm above the greater tuberosity. The rotation and displacement of humeral head were controlled by Kirschner manipulation lever to assist with reduction. For complex fracture (especially the comminuted fracture with split greater tuberosity and displaced lesser tuberosity) , the insertions of subscapularis, supraspinatus and infraspinatus were penetrated respectively with 2 non-absorbable sutures, and the fragments of greater or lesser tuberosities were indirectly reduced by the traction of these sutures. According to the displacement direction of humeral head, the reduction was achieved through proper pulling, internal or external rotation of humeral shaft and simultaneous poking of humeral head. When the fracture was reduced with satisfactory shape of humeral head, the sutures could be intersected and knotted temporarily to fix the fracture fragments, and the humeral head was percutaneously placed with 2 Kirschner wires above greater tuberosity. With satisfactory reduction of the inferomedial area of bone cortex, 2 Kirschner wires were inserted percutaneously and obliquely upward from the posterior humeral shaft to the inferomedial area of humeral head for temporary fixation. With satisfactory reduction of fracture under fluoroscopy, the metaphysis defect was evaluated under direct vision. The defect over 5 mm was regarded as the standard for bone graft. A moderate amount of allograft bone was transplanted into the gap between fracture end and humeral head. As satisfactory reduction was confirmed under fluoroscopy once again, the fracture was ultimately fixed with locking plate that was placed 5 mm lateral to the intertubercular sulcus and 5-8 mm inferior to the apex of greater tuberosity. When locking screws were pierced proximally, the depth of drilling was controlled carefully. The screws of proper length were selected based on fluoroscopy, that was, the screws reached to the subchondral bone of humeral head (approximately 6 mm from the articular surface) . The inferomedial area of humeral head was inserted with another oblique screw to protect the humeral head from collapse. The suture holes on plate were penetrated with 3 No.2 non-absorbable sutures before placement. After the plate and screws were fixed, the insertions of subscapularis, supraspinatus, infraspinatus and teres minor were penetrated with non-absorbable suture with the knot tightened. For combined lesser tuberosity fracture, one hollow screw of 3.5 mm was used for fixation. After internal fixation, radiographic examination was performed in multiple perspectives including anteroposterior view and auxiliary view to confirm that the screw was not in joint cavity. Afterward, the incision was irrigated and closed. In this study, proximal humeral internal locking system (PHILOS plate, Synthes, Switzerland) was used in 16 cases; locking proximal humeral plate (LPHP, Zimmer, USA) was used in 14 cases; proximal humeral locking plate (Double medical technology Inc., Xiamen) was used in 6 cases. The drainage tube was routinely placed and removed within 24 hours after operation. (4) Postoperative rehabilitation.The active movements of interphalangeal joints and wrist were encouraged on the 1st postoperative day. The flexion and extension of elbow joint and the shoulder abduction of < 90o were conducted 1 week later. The climbing exercises of upper limb was carried out 2 weeks after operation. The shoulder joint was suspended for immobilization at the position of internal rotation and slight anteflexion and abduction within 4 weeks. The isometric exercises of the rotator cuff started at the 6th week, and gradually transferred to the active exercises. (5) Follow-up evaluation. The postoperative follow ups were conducted at the 2nd week, 1st, 2nd, and 3rd months. The radiographic examination was performed every 2 months in the outpatient visit till the fracture was healed. According to the imaging assessment of fracture healing, the neck-shaft angle and the height of humeral head (the distance between the two parallel lines that were respectively over the superior edge of plate and the top of humeral head and vertical to the humeral shaft) were recorded. One year after operation, the curative effect was evaluated by Constant score, UCLA scoring system and visual ana1ogue scale (VAS) . In the meanwhile, the shoulder joint function and postoperative complications in the last follow up were recorded as well, including internal fixation failure, screw cutting-out, humeral head necrosis, infection, etc.

All patients were followed up for 6 to 36 months with an average of 31.6 months, and 34 patients acquired bone healing. The healing time was (5.5±0.7) months (3-9 months) , and no allograft rejection occurred. Follow up was carried out 1 year after operation. During the last follow up, the neck-shaft angles of part-2, part-3 and part-4 fractures were 129°±5° (121-135°) , 128°±3° (111-140°) and 121°±4° (110-134°) respectively. The neck-shaft angle of part-4 fracture was remarkably lower than those of part-2 and part-3 fractures, and the difference is statistical significant (P <0.01) . The humeral head height losses of part-2, part-3 and part-4 fractures were (1.7±0.4) mm (1.2-2.7 mm) , (1.8±0.3) mm (1.3-3.1 mm) and (1.9±0.5) mm (1.4-3.5 mm) respectively, and no significant difference was observed among three groups (P>0.05) . The VAS scores of part-2, part-3 and part-4 fractures were (1.7±0.8) points (1-3 points) , (1.5±0.5) points (1-3 points) and (1.4±0.3) points (1-3 points) respectively, and the difference between groups did not show statistical significance (P>0.05) . On the other hand , the Constant scores of part-2, part-3 and part-4 fractures were (82.0±4.2) points (52-90 points) , (78.0±3.6) points (57-91 points) and (63.0±3.8) points (55-89 points) respectively, and the UCLA scores were (31.3±2.1) points (27-35 points) , (30.2±1.5) points (26-33 points) and (27.6±1.6) points (23-31 points) respectively. The shoulder joint functions of part-2 and part-3 fractures were remarkably superior to that of part-4 fracture, and the difference had statistical significance (P <0.01) . Seven cases had complications, and the complication rate was 19.4%. The complication rate of part-4 fracture was up to 44%, which was obviously higher than those of part-2 fracture (7.6%) and part-3 fracture (14.2%) . One patient of part-2 fracture had subacromial impingement syndrome, and the function was acceptable. One patient of part-3 fracture had subacromial impingement syndrome as well, and the pain was still tolerable. Another case had the loss of reduction, and the fracture healed 3 months after revision surgery. One case of part-4 fracture was discovered with the penetration of screw into joint cavity, and the screw was removed later. Two cases underwent hemiarthroplasty due to humeral head necrosis. Humeral head collapse occurred in 1 patient, and his family refused reoperation because of the advanced age.

The treatment of osteoporotic proximal humeral fracture with allograft bone transplantation can provide effective support to humeral head, reduce loss of humeral head height and lower related complications. Therefore, the patient can carry out training early and thus acquire the function level closed to preinjury. For part-4 fracture, however, the clinical effect was poor with high rate of complication. The defect of this article is that this research is a simple retrospective study with limited cases. Expansion of sample size, prolonged follow-up and randomized trial are required for further validation of our conclusion.