Aims. Though most humeral shaft fractures heal nonoperatively, up to one-third may lead to nonunion with inferior outcomes. The Radiographic Union Score for
Introduction: The treatment of Complex Proximal
Lateral-entry wiring (LEW) for displaced supracondylar humeral fractures (SHFs) has been popularised internationally. BOAST guidance suggests either LEW or crossed wires; the latter has reported lower risk of loss of fracture reduction –we explore technical reasons why. We reviewed 8 years of displaced SHFs in two regional centres. Injuries were grouped using the Gartland Classification, with posterolateral or posteromedial displacement assessment for Gartland 3 injuries. We identified any loss of fracture reduction, and reviewed intra-operative imaging to identify learning points that may contribute to early rotational displacement (ERD). 345 SHFs were included, between 2012 and 2020. Gartland 2 (n=117) injuries had a 3.42% risk. ERD. Gartland 3 crossed wirings (n=114) had a 6.14% risk of ERD, with those moving all being posterolaterally displaced. Gartland 3, posterolaterally displaced LEW (n=56) had a 35.7% risk of ERD. Gartland 3, posteromedially displaced LEW (n=58) had a 22.4% risk of ERD. All injuries with ERD except 3 had identifiable learning points, the commonest being non-divergence of wires, or wires not passing through both fracture fragments. LEW requires divergent spread and bicolumnar fixation. Achieving a solid construct through this method appears more challenging than crossed wiring, with rates of ERD 3–5× higher. Low-volume surgeons should adhere to BOAST guidelines and choose a wiring construct that works best in their hands. They can also be reassured that should a loss of position occur, the risk of requirement for revision surgery is extremely low in our study (0.3%), and it is unlikely to affect long term outcomes.
There is little literature exploring clinical outcomes of secondarily displaced proximal humerus fractures. The aim of this study was to assess the rate of secondary displacement in undisplaced proximal humeral fractures (PHF) and their clinical outcomes. This was a retrospective cohort study of undisplaced PHFs at Royal Derby Hospital, UK, between January 2018-December 2019. Radiographs were reviewed for displacement and classified according to Neer's classification. Displacement was defined as translation of fracture fragments by greater than 1cm or 20° of angulation. Patients with pathological, periprosthetic, bilateral, fracture dislocations and head-split fractures were excluded along with those without adequate radiological follow-up.Abstract
Introduction
Methods
The Gartland extension-type supracondylar humerus fracture is the most common elbow fracture in the paediatric population. Depending on fracture classification, treatment options range from nonoperative treatment such as taping, splinting or casting to operative treatments such as closed reduction and percutaneous pinning or open reduction. Classification variability between surgeons is a potential contributing factor to existing controversy over nonoperative versus operative treatment for Type II supracondylar fractures. The purpose of this study was to investigate levels of agreement in classification of extension-type supracondylar humerus fractures using the Gartland classification system. A retrospective chart review was conducted on patients aged 2–12 years who had sustained an extension-type supracondylar fracture and received either operative or nonoperative treatment at a tertiary children's hospital. De-identified baseline anteroposterior (AP) and lateral plain elbow radiographs were provided along with a brief summary of the modified Gartland classification system to surgeons across Canada, United States, Australia, United Kingdom and India. Each surgeon was blinded to patient treatment and asked to classify the fractures as Type I, IIA, IIB or III according to the classification system provided. A total of 21 paediatric orthopaedic surgeons completed one round of classification, of these, 15 completed a second round using the same radiographs in a reshuffled order. Kappa values using pre-determined weighted kappa coefficients were calculated to assess interobserver and intraobserver levels of agreement. In total, 60 sets of baseline elbow radiographs were provided to survey respondents. Interobserver agreement for classification based on the Gartland criteria between surgeons was a mean of 0.68, 95% CI [0.67, 0.69] (0.61–0.80 considered substantial agreement). Intraobserver agreement was a mean of 0.80 [0.75, 0.84]. (0.61–0.80 substantial agreement, 0.81–1 almost perfect agreement). Radiographic classification of extension-type supracondylar humerus fractures at baseline demonstrated substantial agreement both between and within surgeon raters. Levels of agreement are substantial enough to suggest that classification variability is not a major contributing factor to variability in treatment between surgeons for Type II supracondylar fractures. Further research is needed to compare patient outcomes between nonoperative and operative treatment for these fractures, so as to establish consensus and a standardized treatment protocol for optimal patient care across centres.
Surgeries for reverse total shoulder arthroplasty (RTSA) significantly increased in the last ten years. Initially developed to treat patients with cuff tear arthropathy (CTA) and pseudoparalysis, wider indications for RTSA were described, especially complex proximal humerus fractures. We previously demonstrated in patients with CTA a different sequence of muscular activation than in normal shoulder, with a decrease in deltoid activation, a significant increase of upper trapezius activation and slight utility of the latissimus dorsi. There is no biomechanical study describing the muscular activity in patients with RTSA for fractures. The aim of this work is to describe the in vivo action of RTSA in patients with complex fractures of the proximal humerus. We conducted an observational prospective cohort study comparing 9 patients with RTSA for complex humerus fracture (surgery more than 6 months, healed tuberosities and rehabilitation process achieved) and 10 controls with normal shoulder function. Assessment consisted in a synchronized analysis of range of motion (ROM) and muscular activity on electromyography (EMG) with the use of 7 bipolar cutaneous electrodes, 38 reflective markers and 8 motion-recording cameras. Electromyographic results were standardized and presented in muscular activity (RMS) adjusted with maximal isometric contractions according to the direction tested. Five basic movements were evaluated (flexion, abduction, neutral external rotation, external rotation in 90° of abduction and internal rotation in 90° of abduction). Student t-test were used for comparative descriptive analysis (p < 0,05). The overall range of motion with RTSA is very good, but lower than the control group: flexion 155.6 ± 10 vs 172.2 ± 13.9, p<0.05, external rotation at 90° 55.6 ± 25 vs 85.6 ± 8.8, p<0,05, internal rotation at 90° 37.8 ± 15.6 vs 52.2 ± 12, p<0,05. The three heads of the deltoid are more stressed during flexion and abduction in the RTSA group (p The increased use of the 3 deltoid chiefs does not support the hypothesis proposed by Grammont when the RTSA is performed for a complex proximal humerus fracture. This can be explained by the reduced dispalcement of the rotation center of the shoulder in these patients compared to those with CTA. These patients also didn't present shoulder stiffness before the fracture. The maximal muscle activity of the trapezius in flexion and of the latissimus dorsi in flexion and abduction had not been described to date. These new findings will help develop better targeted rehabilitation programs. In addition, the significant role of the latissimus dorsi must question the risks of its transfer (L'Episcopo procedure) to compensate for external rotation deficits.
Proximal humerus fractures (PHF) are the third most common fractures in the elderly. Treatment of complex PHF has remained challenging with mechanical failure rates ranging up to 35% even when state-of-the-art locked plates are used. Secondary (post-operative) screw perforation through the articular surface of the humeral head is the most frequent mechanical failure mode, with rates up to 23%. Besides other known risk factors, such as non-anatomical reduction and lack of medial cortical support, in-adverse intraoperative perforation of the articular surfaces during pilot hole drilling (overdrilling) may increase the risk of secondary screw perforation. Overdrilling often occurs during surgical treatment of osteoporotic PHF due to minimal tactile feedback; however, the awareness in the surgical community is low and the consequences on the fixation stability have remained unproved. Therefore, the aim of this study was to evaluate biomechanically whether overdrilling would increase the risk of cyclic screw perforation failure in unstable PHF. A highly unstable malreduced 3-part fracture was simulated by osteotomizing 9 pairs of fresh-frozen human cadaveric proximal humeri from elderly donors (73.7 ± 13.0 ys, f/m: 3/6). The fragments were fixed with a locking plate (PHILOS, DePuy Synthes, Switzerland) using six proximal screws, with their lengths selected to ensure 6 mm tip-to-joint distance. The pairs were randomized into two treatment groups, one with all pilot holes accurately predrilled (APD) and another one with the boreholes of the two calcar screws overdrilled (COD). The constructs were tested under progressively increasing cyclic loading to failure at 4 Hz using a previously developed setup and protocol. Starting from 50 N, the peak load was increased by 0.05 N/cycle. The event of initial screw loosening was defined by the abrupt increase of the displacement at valley load, following its initial linear behavior. Perforation failure was defined by the first screw penetrating the joint surface, touching the artificial glenoid component and stopping the test via electrical contact. Bone mineral density (range: 63.8 – 196.2 mgHA/cm3) was not significantly different between the groups. Initial screw loosening occurred at a significantly lower number of cycles in the COD group (10,310 ± 3,575) compared to the APD group (12,409 ± 4,569), p = 0.006. Number of cycles to screw perforation was significantly lower for the COD versus APD specimens (20,173 ± 5,851 and 24,311 ± 6,318, respectively), p = 0.019. Failure mode was varus collapse combined with lateral-inferior translation of the humeral head. The first screw perforating the articular surface was one of the calcar screws in all but one specimen. Besides risk factors such as fracture complexity and osteoporosis, inadequate surgical technique is a crucial contributor to high failure rates in locked plating of complex PHF. This study shows for the first time that overdrilling of pilot holes can significantly increase the risk of secondary screw perforation. Study limitations include the fracture model and loading method. While the findings require clinical corroboration, raising the awareness of the surgical community towards this largely neglected risk source, together with development of devices to avoid overdrilling, are expected to help improve the treatment outcomes.
Traditionally, open reduction and internal fixation (ORIF) and hemiarthroplasty (HA) have been the surgical treatments of choice for displaced proximal humerus fractures (PHF) despite high rates of fixation failure and tuberosity nonunion, especially in the elderly population with poor bone quality. Recently, there has been a significant increase in the use of reverse total shoulder arthroplasty (RTSA) as a treatment option in both acute fractures, as well as a salvage procedure for fracture sequelae (i.e., malunion, nonunion, fixation failure, tuberosity non-union). Despite the growing enthusiasm it remains unknown whether functional outcomes after RTSA as a salvage procedure are similar to those following acute RTSA. As a result, the purpose of this systematic review was to compare functional outcomes after RTSA as a primary versus salvage procedure for displaced PHF in the elderly. A literature search of the electronic databases EMBASE, MEDLINE, and PubMed was conducted to identify all studies comparing RTSA as a primary treatment for displaced PHF and as a salvage procedure for failed initial management. Only studies with a minimum follow-up of two years were included. Data pertaining to range of motion, patient reported outcome measures and complications were extracted from eligible studies and entered into a meta-analysis software package (RevMan version 5.1, The Cochrane Collaboration) for pooled analysis. The Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of eligible studies. The search identified four studies consisting of 200 patients with a mean age of 73.3 years and a mean follow-up of 3.2 years. There were a total of 76 patients (75% female) who underwent acute RTSA following displaced PHF, while 124 patients (77% female) required salvage RTSA for failure of initial treatment. Primary RTSA was found to have significantly higher American Shoulder and Elbow (ASES) (P = 0.04), Constant (P = 0.01) and University of California at Los Angeles (UCLA) (P = 0.0004) scores compared to salvage RTSA. Forward flexion (P = 0.001) and external rotation (P< 0.0001) were significantly greater amongst those undergoing RTSA acutely versus as a salvage procedure. The odds of having a complication (e.g., infection, dislocation, fracture) were 76% lower amongst those who had primary RTSA compared to salvage RTSA (P = 0.02). The overall quality of eligible studies was moderate to high. Based on the current available evidence, elderly patients with displaced PHF have significantly greater range of motion, higher patient reported outcomes and lower risk of complications with primary RTSA compared to those undergoing RTSA as a salvage procedure. Additional prospective studies are warranted to confirm these findings.
Proximal humeral fractures account for approximately 4–5% of all fractures seen in the emergency departments. Of all shoulder injuries they account for aproximatelly 53%. In 1970 Neer published his classic study, in which he described a new method of classification, and gave recommendations for treatment. Neer recommended ORIF for three-part fractures, and prosthetic replacement for four-part fractures and fracture-dislocations. However there is still disagreement on the management of the displaced humeral fractures.
Accurate radiographic evaluation, is essential in order to make a correct classification of the proximal humeral fractures. The radiographic examination consists of films from three different views. The anterio-posterior (AP), lateral (Y view of the scapula), and the axillary one. The AP view will assess the fracture position, and by centring it 30 degrees posteriorly and obliquely, clearly image the glenohumeral joint space. The lateral view is taken perpendicular to the scapular plain. The head overlaps the glenoid, and projects on the centre of a “Y“, formed by acromion, the coracoid superiorly, and the scapular body inferiorly. In this projection any large avulsed greater tuberosity fragments are usually easy to visualise posteriorly, and the lesser tuberosity is visualised medialy. The axillary view is the most useful in assessing the relationship between the humeral head and the glenoid. Fracture dislocations, and true posterior dislocations can be easily distinguished in the axial view. Computer tomography, plain or with three dimensional reconstruction-views might also help the surgeon to make an accurate diagnosis and in preoperative planning.
A valid classification system can be useful as a tool to select the optimal treatment. The system should be comprehensive enough to reflect the complex fracture pattern, and specific enough to allow an accurate diagnosis. The classification should be useful as a tool for identifying those fractures which should be operated upon. In 1935, Codman proposed a new classification system based on four different anatomical fragments of the proximal humerus. The anatomical head, the greater tuberosity, the lesser tuberosity and the humeral shaft. Codman stressed that the musculotendinous cuff attachment to each fragment was of major significance to the fracture pattern. In 1970 Neer further developed Codmans classification, stressing the importance of the biomechanical forces, and the degree of displacement for more complex fractures. When any of the four major segments is displaced over 1 cm or angulated more than 45 degrees, the fracture is considered to be displaced: In the 1970’s the AO group from Switzerland, emphasised the importance of the blood supply to the articular surface of the humeral head. Since the risk for avascular necrosis was high, they based their classification on the vascular anatomy of the proximal humerus. The system classified the fractures into three different categories:
Each group is sub-divided into three categories, from less to more serious lesions. This gave us 27 different sub-groups to analyse and interpret. The AO system is easy to use for the diaphyseal segments of the femur, tibia and humeral shaft, but applying it to the proximal humerus is confusing, and makes it more difficult to use than the Neer system. Consequently the AO classification system has not gained general acceptance among shoulder surgeons. The reliability and the reproducibility of these classifications have been questioned Unfortunately, we do not have a better classification system on hand and therefore the Neer system is still widely used.
Many methods of treatment of proximal humeral fractures have been proposed during the past 50 years, creating a great deal of controversy and confusion. There are two main treatment options: Non-operative treatment and operative.
Approximately 80% of all proximal humeral fractures are non-displaced, or only minimally displaced, and the clinical outcome is satisfactory after conservative treatment. After some days of rest, early mobilisation with gentle physiotherapy is of great importance.
Various types of osteosynthesis have been suggested. Semitubular straight or angulated plates, screws, Rush pins, external fixators, cerclage wires, tension band technique or K-wires with bone grafting have been used. The results reported range from excellent to poor. In cases of three- and four- part fractures, most authors have used open reduction with internal fixation. Because of poor bone quality, and a torn cuff, especially in elderly patients, osteosynthesis is not always the best choice. Hemiarthroplasty is reported to give an excellent outcome in many studies. In fracture dislocations, when closed reduction is not possible, the only way to restore the dislocated shoulder joint is to perform an open reduction and stabilise the fracture with an osteosynthesis implant, or replace the humeral head with a hemiarthroplasty.
There are two rating systems generally used. The Neer system from 1970 has been widely used in a number of studies, all over the world, and the Constant-Murley system from 1987 has been recommended for use in Europe. Neer’s rating system from 1970 is used to assess shoulder function, after fractures, arthroplasty and dislocations. It is based on a 100 units scale, with points for pain (35), function (30), range of motion (25), and anatomy (10). In 1987 Constant and Murley designed a European scoring system, claiming it to be applicable for measuring shoulder function regardless of diagnosis. This system is also based on a 100 point scale. The degree of pain, activities of daily living, strength, and active range of movement are assessed. The results are then related to gender, age and activity level of the patient. Both systems has recently been questioned because of its low reliability. Confusion remains because different authors from the USA and Europe continue to use their own criteria for evaluation. Consequently, it is not unusual that the reported results after fracture treatment vary, depending on which rating system was used.
A reverse shoulder arthroplasty has become increasingly common for the treatment of proximal humerus fractures. A reverse shoulder arthroplasty is indicated especially in older and osteopenic individuals in whom the osteopenia, fracture type or comminution precludes fixation. However, there are many other ways to treat proximal humerus fractures and many of these are appropriate for different indications. Percutaneous pinning remains an option in certain surgical neck or valgus impacted proximal humerus fractures with minimal or no comminution at the medial calcar. In general, a fracture that is amenable to open reduction and fixation should be fixed. Open reduction and internal fixation should be the gold standard treatment for three-part fractures in younger and middle-aged patients. Four-part fractures should also be fixed in younger patients. Hemiarthroplasty results are less predictable as they are very dependent on tuberosity healing. While a reverse shoulder replacement may be considered in patients with severe comorbidities, patients always have better outcomes in the setting of an appropriately reduced and stably fixed proximal humerus fracture.
Successful ORIF of proximal humeral fractures requires a careful assessment of the patient factors (age/osteoporosis/functional expectations), accurate identification the fracture segments (head/shaft/tuberosities) and accessory factors which are of vascular and surgical relevance (length of posteromedial metaphyseal head extension, integrity of medial soft tissue hinge, head split segments, tuberosity/head segments impacted to-gether or distracted apart). Fixation of the fracture can be achieved by a number of techniques because of the multiple factors that often apply—numerous techniques are usually required of the surgeon. The principles of fixation require accurate restoration of the head and tuberosity orientation, fixation of the metaphyseal segments (tuberosities) results in a stable circular platform on which the head segment rests. Thus, the fixation of choice acts as a load sharing device not a load bearing device. This fixation is often augmented with tension band and circlage suture fixation. These concepts are especially applicable to the osteoporotic patient. The order of fixation requires that the medial hinge not be disrupted. If it is disrupted in the younger patient it requires fixation first. All tuberosity segments are tagged with ethibond sutures. The head and the largest tuberosity segment are reduced and held with k-wire or canulated scews, avoiding the central medullary canal entry point. If the head tuberosity segment is unstable in relation to the shaft, the fixation implant of choice (plate/intramedullary) is chosen and the head/tuberosity complex is reduced to the shaft. Depending on the fracture segments and the degree of comminution this may require compression of distraction. Post-op the patient is immobilised in external rotation to balance the cuff forces. If very rigid fixation is achieved then early mobilisation is undertaken to minimise the adhesions due to opening of the subdeltoid space. If fixation is tenuous movement is commenced a 3–4 weeks. AVN of the humeral head with good tuberosity head architecure can be salvaged. The diagnosis of AVN is determned at three months with a MRI and consideration given to Zolidronate therapy. Post-traumatic stiffness with good architecture can be salvaged with an arthroscopic capsular release.
Osteoporotic fracture fixation in the proximal humerus remains a critical challenge. While the biomechanical benefits of screw augmentation with bone cement are established, minimising the cement volume may help control any risk of extravasation and reduce surgical procedure time. Previous experimental studies suggest that it may be sufficient to only augment the screws at the sites of the lowest bone quality. However, adequately testing this hypothesis in vitro is not feasible. This study systematically evaluated the 64 possible strategies for augmenting six screws in the humeral head through finite element simulations to determine the relative biomechanical benefits of each augmentation strategy. Two subjects with varying levels of local bone mineral density were each modeled with a 2-part and 3-part fracture that was stabilised with a PHILOS plate. The biomechanical fixation was evaluated under physiological loads (muscle and joint reaction forces) that correspond to three different motions: 45 degrees abduction, 45 degrees abduction with 45 degrees internal rotation, and 45 degrees flexion.Background
Methods
We aimed to assess the functional outcomes of elderly patients with isolated comminuted distal humerus fractures that were managed non-operatively. Retrospective analysis of patients over 65 years presenting to our unit between 2005–2015 was undertaken. 67 patients were identified, 7 had immediate TEA, 41 died and 5 were lost to follow-up leaving 14 available for review. Mean Follow-up was 55 months(range 17–131) Patient functional outcomes were measured using VAS scores for pain at rest and during activity, and the Oxford Elbow Score (OES). Need for conversion to TEA and complications were recorded. The mean age at injury was 76 years(range 65–90) of which 79%(11/14) were females. The mean score on the OES was 46(range 29 – 48). The mean VAS score at rest was 0.4(range 0–6) and the mean VAS score during activity was 1.3(range 0–9). 93%(13/14) of patients reported no pain (0 out of 10 on the numeric scale for pain) in their injured elbow at rest and 79%(11/14) reported no pain during activity. No patients converted to TEA and there were no complications. Non-operative management of comminuted distal humerus fractures should be considered for elderly patients, avoiding surgical risks whilst giving satisfactory functional outcomes in this low demand group.
We present the results of surgical treatment of proximal humeral fractures in a group of 40 patients. The fractures were treated with the angular stable Lockin Proximal Humeral Plate, which is based on the LCP-principle (Locking Compression Plate). The upper part of the plate contains small suture holes for fixation of the tuberosities. Between january 2002 and december 2005, 40 patients were operated using this technique. There were 24 women and 16 men and the mean age of our population was 56.5 years. Clinical and radiological evolution was followed until fracture fracture healing and functional recovery and a Constant-score was taken on a retrospective basis with a mean follow-up of 23.6 months. During follow-up 2 patients died of unrelated causes with their fractures healed and 2 patients were lost because they were living abroad. Fracture healing was uncomplicated in 34 patients (89 %). In 4 patients there was secondary displacement of the fracture: varus displacement in 3 cases and complete loosening of the osteosynthesis in a patient who fell again a few weeks after the first intervention. In this patient a new osteosynthesis with the same device was realised and the fracture healed correctly. In the other 3 cases the fracture healed with some varus alignment and in 1 of these the hardware had to be removed because of intra-articular positioning of some screws after varisation of the humeral head. No secondary displacement of the tuberosities was seen. In one case we had an aseptic necrosis of the humeral head 6 months after the osteosynthesis and this patient needed a shoulder arthroplasty. Another patient had severe chondral lesions of the humeral head but symptoms respond well to medical treatment. Hardware removal was necessary in 8 patients because of subacromial impingement or local tenderness. Reflex sympathetic dystrophy occured in 4 cases. The mean Constant-score was 57.6; when correction was made for age and gender the mean score was 73.0.
Proximal humeral fractures are common and a minority develop non-union, which can result in pain and disability. We aimed to identify the risk factors and quantify the prevalence of non-union. A thirteen-year retrospective study of 7039 patients with proximal humeral fractures was performed and a database created. 246 patients with non-union were compared to a control group to identify risk factors. Logistic regression analyses were performed to identify significant variables obtained at presentation to predict non-union.Background
Methods
Two-part surgical neck fractures, two-part greater tuberosity fractures and three- and four-part fractures of the proximal humerus represent a frequently encountered clinical problem. Many types of conservative treatments have been proposed, with a poor functional outcome, however; when the fracture fragments are displaced, surgery is required. Because the open reduction and the internal fixation disrupts soft tissue and increases the risk of avascular necrosis of the humeral head, closed or minimally open reduction and percutaneous pin fixation should represent an advantage. We report on 31 patients affected by fractures of the proximal humerus (n=6, two-part surgical neck fractures; n=5, with two-part greater tuberosity fractures; n=10, three-part fractures; and n=11, four- part fractures) treated with minimally open reduction and percutaneous fixation. The average age was 57 years. Most of the four-part fractures were of the valgus type with no significant lateral displacement of the articular segment. A small skin incision was performed laterally at the shoulder and a rounded-tipped instrument was introduced to obtain the fracture reduction; this latter was stabilised by percutaneous pins and cannulate screws. A satisfactory reduction was achieved in most cases. The average follow-up was 24 months (range 18–47). Only one patient, with four-part fractures associated with lateral displacement of the humeral head, showed avascular necrosis and received a prosthetic implant. Minimally open reduction and percutaneous fixation is a non-invasive technique with a low risk of avascular necrosis and infection. This surgical technique allows a stable reduction with minimal soft tissue disruption and facilitates postoperative mobilisation.
Locking plates can provide greater stability than conventional plates; however, reports revealed that fractures had a high incidence of failure without medial column support; the mechanical support of medial column could play a significant role in humeral fractures. Recent studies have demonstrated the importance of intramedullary strut in proximal humeral fracture fixation, the relationship to mechanical stability and supporting position of the strut remain unclear. The purpose of this study was to evaluate the influence of position of the intramedullary strut on the stability of proximal humeral fractures using a locking plate. Ten humeral sawbone (Synbone) and locked plates (Synthes, cloverleaf plate), with and without augmented intramedullary strut (five in each group) for proximal humerus fractures, were tested using material testing machine to validate the finite element model. A 10 mm osteotomy was performed at surgical neck and a strut graft (10 cm in length) was inserted into the fracture region to lift the head superiorly. Each specimen was statically tested at a rate of 5 mm/min until failure. To build the finite element (FE) model, 64-slices CT images were converted to create a 3D solid model. The material properties of screws and plates were modeled as isotropic and linear elastic, with an elastic modulus of 110 GPa, (Poisson's ratio, n=0.3). The Young's moduli of cortical and cancellous bones were 17 GPa and 500 MPa (n=0.4), respectively. Three alter shifting toward far cortex by 1, 2, and 3 mm in humeral canal were installed in the simulating model.Introduction
Materials and methods