The current indications for primary hemiarthroplasty include a displaced and translated four-part fracture, with or without associated dislocation of the humeral head, and a head-splitting fracture with involvement of > 40% of the articular surface. . There are many factors associated with the treatment of humeral head replacement. In order to avoid mutual interference between the various factors, the current study used univariate analysis combined with multivariate Logistic regression analysis to investigate the risk factors for the treatment of humeral head replacement [19–21]. Currently, the insufficient bony healing of displaced tuberosities after intra-operative fixation at the stem of the prosthesis, malpositioning of the tuberosity fragments, and incorrect positioning of the prosthesis are probably the most important factors determining the outcomes of this treatment modality[22–24]. In this study, the same team made the surgeries, it can effectively reduce the error caused by surgical operations, especially tuberosity fragments and positioning of the prosthesis. This study confirmed patient factors that age (P = 0.018, OR = 51.120), time from injury to surgery (P = 0.037, OR = 18.411), whether with shoulder dislocation (P = 0.048, OR = 12.972), time to start exercising after surgery (P = 0.025, OR = 16.772)), and whether the patient regular follow-up (P = 0.041, OR = 0.088) were risk factors for treatment of humeral head replacement.
This study showed that age was the first risk factor for treatment of humeral head replacement, with OR = 51.120, P<0.05. Robinson et al. performed a thirteen-year observational cohort study of 163 consecutive patients treated with hemiarthroplasty for a proximal humeral fracture. They found that the results are poorer in the larger group of elderly patients who undergo this procedure, especially if they have a neurological deficit, a postoperative complication requiring a reoperation, or an eccentrically located prosthesis with retracted tuberosities. While a good functional outcome can be anticipated for a younger individual. In our study, age was a risk factor for the surgery. The influence of age on the predicted outcome is likely to reflect many factors that adversely affect outcome, including degenerative change within the rotator cuff, osteoporosis, and the lack of motivation to achieve a range of motion beyond the limited functional needs of an elderly patient. In another, the elder patients’ expectation for postoperative functional recovery of shoulder joint are lower than young patients’. Thus, the postoperative functional exercise is not active as young patients. Therefore, some experts suggest conservative treatment should be considered for the elderly patients with lower functional requirements and who can accept the painless and function limited shoulder joint.
The results of this study showed that time from injury to surgery was the second risk factor to affect the treatment of humeral head replacement, with OR = 18.411, P<0.05. Bosch, et al. compared patients in whom hemiarthroplasty was performed < 4 weeks after injury with patients in whom hemiarthroplasty was performed > 4 weeks after injury. They found the outcome after early (< 4 weeks) humeral head replacement was significantly better than after late (> or = 4 weeks) humeral head replacement with California-Los Angeles scale, Constant-Murley scale and active forward flexion. Gronhagen et al believed that surgery should be performed as soon as possible after injury. Maybe the soft tissue adhesion will widely formed with the late surgery, which will influence the shoulder activity range and rotator cuff reconstruction. What’s more, muscle atrophy and extensive adhesions around the shoulder will seriously affect the shoulder joint postoperative functional exercise. Thus, the decision to perform prosthetic humeral head replacement should be made as early as possible after trauma.
This study showed that early exercise was the third risk factor to affect the treatment of humeral head replacement, with OR = 16.772, P<0.05. Field et al.  believes that the time to start exercising after surgery depend on the patient's actual condition. Handoll, et al. made a system review to investigate interventions for treating proximal humeral fractures in adults. In the results, 4 trials compared early (usually one week) versus delayed (three or four weeks) mobilisation after fracture but only limited pooling was possible and most of the data were from one trial (86 participants). This found some evidence that early mobilisation resulted in better recovery and less pain in people with mainly minimally displaced fractures. In our opinion, early shoulder joint exercise can be effective to reduce the adhesion of soft tissue around the shoulder joint. So, we recommend that the appropriate strength of functional exercise should be performed as soon as possible after humeral head replacement surgery.
This study also found that regular outpatient follow-up was a protective factor to affect the treatment of humeral head replacement, with OR = 0.088, P<0.05. Grönhagen et al. performed a study of medium-term results after primary hemiarthroplasty for comminute proximal humerus fractures with regular outpatient follow-up. The mean time for physiotherapy was 27 weeks in 58 patients, working with a physiotherapist 1 to 2 times a week. Most of the patients still did at follow-up. Their results showed hemiarthroplasty usually prevented shoulder pain with moderate function. In our experience, with regular follow-up, a lot of problems can be solved timely. Therefore, we suggested that the time of regular outpatient follow-up should not less than 2 years.
Our study could not find osteoporosis was a risk factor to affect the treatment of humeral head replacement. Hemiarthroplasty is frequently used in situations of severe comminution, concern for humeral head ischemia, and poor bone quality. The tenuous fixation of fracture fragments in osteoporotic bone have led most surgeons to advocate hemiarthroplasty as the preferred option over internal fixation. Beaudreuil et al hold that when proximal humeral fracture patients with osteoporosis, even if the fracture fragment is reduced effectively, it is still hard to fix it steadily, and patient with osteoporosis will increase the difficulty of rotator cuff reconstruction and the risk of the postoperative reinjury of rotator cuff and intra-articular loose. However, our result found that osteoporosis was not a significant for the functional outcome. Maybe we used the cement in the operation, so there were few complications of intra-articular loose in our study. Or the sample population was to small to draw the conclusion about the osteoporosis affecting the outcomes.
Several limitations associated with this study warrant mention. Firstly, the sample population was small, which may increase the occurrence of standard errors and type II errors, and the population of patients was heterogeneous, and the results of our study may be affected by confounding variables. Secondly, this study was retrospective with certain selection biases and missing data. A prospective study with more patients should be performed to confirm the results in the future.