The biomechanics of locked plating for repairing proximal humerus fractures with or without medial cortical support

Risk of Axillary Nerve Injury With Medial Support Screws in Intramedullary Nails: An Anatomical Study

BACKGROUND

In recent years, intramedullary nails with medial support screws for proximal humeral fractures have become available. Although these devices have a potential risk of iatrogenic axillary nerve injury, no studies have investigated the anatomical relationship between the medial support screws in the modern intramedullary nail and the axillary nerve. This study aimed to clarify the anatomical relationship between the medial support screws in the intramedullary nail and the axillary nerve.

MATERIALS AND METHODS

In total, 29 cadaveric shoulders (mean age: 82.6 years old (range: 61-105); 15 males and 14 females) were included in this study. Shoulders within whole-body cadavers were used in all cases. A single proximal humeral nail with medial support screws (ARISTO Proximal Humeral Nail; MDM, Tokyo, Japan) was used. The distance of each medial support screw from the axillary nerve and its branches was measured.

RESULTS

In two (6.90%) of 29 shoulders, the axillary nerves came into contact with the medial support screws. In the remaining 27 of 29 shoulders (93.1%), the nerves were located proximal to the medial support screws.

CONCLUSION

Medial support screws in proximal humeral fracture nails had the potential to injure the axillary nerve and its branches.

Plate Fixation of Proximal Humerus Fractures: How to Get It Right and Future Directions for Improvement

PURPOSE OF REVIEW

Open reduction and internal fixation with locking plates (ORIF-LP) has been used for decades for the surgical management of proximal humerus fractures. Despite good outcomes have been widely published in the literature, unacceptably high rates of complications (up to 40%), many of them yielding poor outcomes and requiring reoperation (up to 25%), have also been reported, especially in elderly patients. Most common complications are related to implant failure, with intra-articular screw penetration as the most frequent and devastating.

RECENT FINDINGS

Advances in patient selection and surgical technique, and implementation of bone or cement augmentation, have been developed to hopefully decrease complication rates. Mayo-FJD Classification offers prognostic information that can aid in the decision-making process for proximal humeral fractures. Displaced valgus impacted fractures seem to be associated with well over a 10% rate of avascular necrosis after ORIF-LP. A principle-based and stepwise surgical technique combining anatomic reduction and a short screw configuration can provide good outcome in most patients, even the elderly, decreasing implant failures to less than 10%. Acrylic cement augmentation has the potential to further decrease implant failure rate to 1%. Reoperation rates are higher partly due to the need to remove hardware for painful subacromial conflict. However, no studies to date definitively demonstrated the superiority of ORIF-LP compared to non-operative treatment, intramedullary nailing, or reverse shoulder arthroplasty. ORIF-LP can provide good results for the surgical management of displaced proximal humerus fractures even in elderly patients provided adequate patient selection and a principle based and stepwise surgical technique, supplemented with bone graft or acrylic cement when needed. Poor outcomes and high complication and reoperation rates should be expected when these recommendations are not followed.

Intramedullary Nail for Treatment of Proximal Humeral Fracture: A Credible Fixation in Comminuted Calcar

OBJECTIVE

Restoration of the medial support is especially important for the treatment of proximal humeral fractures. The objective of this study was to investigate the radiographic and clinical outcomes of intramedullary nail fixation with a special focus on the presence of calcar comminution.

METHODS

In this retrospective study of patients with displaced proximal humeral fractures that were treated by intramedullary nail between January 2018 and July 2021, fracture morphology and the calcar integrity were noted on preoperative radiographs. Patients were divided into two groups according to calcar integrity. During follow-up, radiological assessment and functional outcome, including the deltoid tuberosity index (DTI), neck shaft angle (NSA), visual analog scale (VAS), the American Shoulder and Elbow Surgeons (ASES) score, the Simple Shoulder Test (SST) score, active and passive range of motion, were performed. A Student t-test and univariate logistic regression analysis was used.

RESULTS

A total of 83 patients (54 female, 29 male) had complete follow-up (average, 12.8 months; range, 10 to 33 months) and functional assessment in our study. The average age was 58.6 years (range, 20 to 89 years). The mean loss of NSA was 4° (range, 0°-12°) and no significant difference was found between two groups (p = 0.27). DTI had an average of 1.50 ± 0.19 (range 1.13-2.04). Patients with intact calcar achieved greater range of forward elevation (129.06 ± 11.91 vs. 121.05 ± 11.97, p = 0.01), and higher SST scores (8.61 ± 1.85 vs. 7.37 ± 2.22, p = 0.02). Two groups showed similar outcomes in VAS, ASES score, and range of abduction. One patient demonstrated a proximal interlocking screw cutting through and osteonecrosis of the humeral head, who underwent a second surgery for screw removal. There were no cases of infection, malunion, nonunion, nerve injury, subacromial impingement, or rotator cuff tear during the study period.

CONCLUSION

Intramedullary nail can favorably be used to manage proximal humeral fractures with good early radiographic and functional outcomes, even for those with comminuted calcar.

The effect of long calcar screws on the primary stability of 3-part, varus impacted proximal humeral fractures compared to short calcar screws: a real fracture simulation study

BACKGROUND

Complex proximal humeral fracture ranks among the most common fracture types, especially in elderly patients. In locked plate fixation of proximal humerus fractures, the calcar is deciding for screws providing further medial column support. To date, the biomechanical effect of the length of these calcar screws is not well known. The purpose of this study was to analyze the effect of long calcar screws on fresh frozen prefractured cadaveric specimens.

METHODS

In the present biomechanical study, 8 pairs of cadaveric proximal humeri were fractured identically using a custom-made fracture simulator. ORIF was performed using a locking plate (PHILOS; Fa. Synthes). The specimens were tested in a biomechanical setup under increased axial load without any calcar screws installed, with short calcar screws and long calcar screws installed. Strain gages (4-wire-120 Ohm, Fa. Vishay) mounted on the locking plate were used to evaluate the fixation strain and to give an estimate for primary stability..

RESULTS

The measured strain of the locking plate without calcar screws (804,64 µm/m) at maximum load (200 N) was significantly higher than with short (619,07 µm/m; p = 0.02) or long calcar screws (527,31 µm/m; p = 0.007). Additionally, strain with short calcar screws was noticeably higher in comparison to long calcar screws (619,07 µm/m vs. 527,31 µm/m; p = 0.03).

CONCLUSION

Use of calcar screws improves the stability of realistically impacted 3-part varus humeral fractures. Long calcar screws that are positioned as close as possible to the joint provide further primary stability compared to short calcar screws.

LEVEL OF EVIDENCE

Basic science study.

Expert consensus on the bone repair strategy for osteoporotic fractures in China

Osteoporotic fractures, also known as fragility fractures, are prevalent in the elderly and bring tremendous social burdens. Poor bone quality, weak repair capacity, instability, and high failure rate of internal fixation are main characteristics of osteoporotic fractures. Osteoporotic bone defects are common and need to be repaired by appropriate materials. Proximal humerus, distal radius, tibia plateau, calcaneus, and spine are common osteoporotic fractures with bone defect. Here, the consensus from the Osteoporosis Group of Chinese Orthopaedic Association concentrates on the epidemiology, characters, and management strategies of common osteoporotic fractures with bone defect to standardize clinical practice in bone repair of osteoporotic fractures.

Evaluation of mushroom-shaped allograft for unstable proximal humerus fractures

INTRODUCTION

Proximal humerus fractures are common injuries of the elderly. Different treatment options, depending on fracture complexity and stability, have been recommended in the literature. Particularly for varus displaced fractures with a lack of medial support, and patients suffering from osteoporosis, structural allografts can be used to enhance the stability of the construct. An individually shaped allograft has been suggested in the literature and investigated in a clinical setting. However, biomechanical properties have yet to be evaluated.

MATERIALS AND METHODS

Twenty-four fresh-frozen humeri and 12 femoral heads were obtained, and an unstable three-part fracture of the humeral head was simulated. Fracture fixation was achieved by using a locking plate in both groups. In the test group, a mushroom-shaped allograft was tailored out of a femoral head to individually fit the void inside the humeral head. Specimens were fitted with a 3D motion analysis system and cyclically loaded with a stepwise increasing load magnitude in a varus-valgus bending test until failure or up to a maximum of 10,000 load cycles.

RESULTS

The mushroom group reached a significantly higher number of load cycles (8342; SD 1,902; CI 7133-9550) compared to the control group (3475; SD 1488; CI 2530-4420; p < 0.001). Additionally, the test group showed significantly higher stiffness values concerning all observational points (p < 0.001).

CONCLUSION

This mushroom-shaped allograft in combination with a locking plate significantly increased load to failure as well as stiffness of the construct when exposed to varus-valgus bending forces. Therefore, it might be a viable option for surgical treatment of unstable and varus displaced proximal humerus fractures to superiorly prevent loss of reduction and varus collapse.

Role of inferomedial supporting screws for secondary varus deformity in non-osteoporotic proximal humerus fracture: A biomechanical study

INTRODUCTION

The purpose of this study was to evaluate the effect of a medial support screw through a proximal humerus fracture. For this purpose, we verified whether the biomechanics are different according to the position of the screw while using the same number of screws. In addition, we tried to verify whether the insertion of additional inferomedial screws would make a difference in stability.

MATERIALS AND METHODS

Twenty-four proximal humerus bones were included in the study. A two-part fracture was created and fixed using a locking plate. Cyclic loading and load-to-failure test were applied to three groups: group A (proximal 6 screws + calcar screws), group B (proximal 6 screws), and group C (proximal 4 screws + calcar screws). Interfragmentary gaps were measured following cyclic loading and compared. The failure was defined when the bone breakage or medial gap closing was observed during ultimate failure load applied. The load-to-failure, maximum displacement, stiffness, and yield load were recorded and compared.

RESULTS

The interfragmentary gap was differently reduced by 0.29 ± 0.14 mm, 0.73 ± 0.25 mm, and 0.53 ± 0.09 mm following 1000 cyclic loading for groups A, B, and C, respectively. The load-to-failure was 945.22 ± 101.02 N, 941.40 ± 148.90 N, and 940.58 ± 91.78 N in groups A, B, and C, respectively. The stiffness of group A (214.76 ± 34.0 N/mm) was superior when compared to that of group C (171.12 ± 23.0 N/mm; p = 0.025). The maximum displacement prior to failure, yield load, showed no significant difference between comparative groups.

CONCLUSION

Our study did not show any additional biomechanical effects with the use of inferomedial supporting screws in non-osteoporotic proximal humerus fracture, besides making the fracture-plate construct stiff. The role of the inferomedial supporting screw was also unclear. However, the groups that used increased screw fixation and inferomedial screw insertion seemed to be more resistant to cyclic loading.

Additively manufactured patient-specific prosthesis for tumor reconstruction: Design, process, and properties

Design and processing capabilities of additive manufacturing (AM) to fabricate complex geometries continues to drive the adoption of AM for biomedical applications. In this study, a validated design methodology is presented to evaluate AM as an effective fabrication technique for reconstruction of large bone defects after tumor resection in pediatric oncology patients. Implanting off-the-shelf components in pediatric patients is especially challenging because most standard components are sized and shaped for more common adult cases. While currently reported efforts on AM implants are focused on maxillofacial, hip and knee reconstructions, there have been no reported studies on reconstruction of proximal humerus tumors. A case study of a 9-year-old diagnosed with proximal humerus osteosarcoma was used to develop a patient-specific AM prosthesis for the humerus following tumor resection. Commonly used body-centered cubic (BCC) structures were incorporated at the surgical neck and distal interface in order to increase the effective surface area, promote osseointegration, and reduce the implant weight. A patient-specific prosthesis was fabricated using electron beam melting method from biocompatible Ti-6Al-4V. Both computational and biomechanical tests were performed on the prosthesis to evaluate its biomechanical behavior under varying loading conditions. Morphological analysis of the construct using micro-computed tomography was used to compare the as-designed and as-built prosthesis. It was found that the patient-specific prosthesis could withstand physiologically-relevant loading conditions with minimal permanent deformation (82 μm after 105 cycles) at the medial aspect of the porous surgical neck. These outcomes support potential translation of the patient-specific AM prostheses to reconstruct large bone defects following tumor resection.

Supporting the medial hinge in proximal humerus fractures with an intramedullary plate

Proximal humerus fractures are common and approximately 20% of displaced fractures may benefit from surgery. A lack of medial support is found to be a predictor of failure after surgical fixation of proximal humerus fractures. The optimal technique for restoring the medial hinge is unclear. We describe two cases of patients with a dislocated 4-part humerus fracture treated with a locking plate and an additional small intramedullary plate to support the medial hinge. This technique is simple and allows for an enhanced stability of the medial hinge during and after surgery.

How Many Proximal Screws Are Needed for a Stable Proximal Humerus Fracture Fixation?

Purpose

This biomechanical study investigates the optimal number of proximal screws for stable fixation of a 2-part proximal humerus fracture model with a locking plate.

Methods

Twenty-four proximal humerus fracture models were included in the study. An unstable 2-part fracture was created and fixed by a locking plate. Cyclic loading and load-to-failure tests were used for the following 4 groups based on the number of screws used: 4-screw, 6-screw, 7-screw, and 9-screw groups. Interfragmentary gaps were measured following cyclic loading and compared. Consequently, the load to failure, maximum displacement, stiffness, and mode of failure at failure point were compared.

Results

The interfragmentary gaps for the 4-screw, 6-screw, 7-screw, and 9-screw groups were significantly reduced by 0.24 ± 0.09 mm, 0.08 ± 0.06 mm, 0.05 ± 0.01 mm, and 0.03 ± 0.01 mm following 1000 cyclic loading, respectively. The loads to failure were significantly different between the groups with the 7-screw group showing the highest load to failure. The stiffness of the 7-screw group was superior compared with the 6-screw, 9-screw, and 4-screw groups. The maximum displacement before failure showed a significant difference between the comparative groups with the 4-screw group having the lowest value. The 7-screw group had the least structural failure rate (33.3%).

Conclusion

At least 7 screws would be optimal for proximal fragment fixation of proximal humerus fractures with medial comminution to minimize secondary varus collapse or fixation failure.

Level of Evidence

Basic science study.

Reconstruction of proximal humeral fractures without screws using a reinforced bone substitute

Multi-fragment fractures are still a challenge: current clinical practice relies on plates and screws. Treatment of fractures of the proximal humerus has the intra-operative risk of articular damage when inserting multiple screws. Distal-varus collapse of the head is a frequent complication in osteoporotic patients. The aim of this biomechanical study was to investigate if an Innovative-cement-technique (the screws are replaced by injection of cement) provides the same or better stability of the reconstructed head compared to the Standard-technique (locking screws). A four-fragment fracture was simulated in twelve pairs of humeri, with removal of part of the cancellous bone to simulate osteoporotic "eggshell" defect. One humerus of each pair was repaired either with a Standard-technique (locking plate, 2 cortical and 6 locking screws), or with the Innovative-cement-technique (injection of a partially-resorbable reinforced bone substitute consisting of PMMA additivated with 26% beta-TCP). Cement injection was performed both in the lab and under fluoroscopic monitoring. The reconstructed specimens were tested to failure with a cyclic force of increasing amplitude. The Innovative-cement-technique withstood a force 3.57 times larger than the contralateral Standard reconstructions before failure started. The maximum force before final collapse for the Innovative-cement-technique was 3.56 times larger than the contralateral Standard-technique. These differences were statistically significant. The Innovative-cement-technique, based on the reinforced bone substitute, demonstrated better biomechanical properties compared to the Standard-technique. These findings, along with the advantage of avoiding the possible complications associated with the locking screws, may help safer and more effective treatment in case of osteoporotic multi-fragment humeral fractures.

A new classification of impacted proximal humerus fractures based on the morpho-volumetric evaluation of humeral head bone loss with a 3D model

BACKGROUND

This study aimed to classify the pathomorphology of impacted proximal humeral fractures according to the control volume theory, with the intention to introduce a severity index to support surgeons in decision making.

METHODS

In total, 50 proximal humeral fractures were randomly selected from 200 medical records of adult patients treated from 2009 to 2016. Four nonindependent observers used 2 different imaging modalities (computed tomography scans plus volume rendering; 3D model) to test the classification reliability. A fracture classification system was created according to the control volume theory to provide simple and understandable patterns that would help surgeons make quick assessments. The impacted fractures table was generated based on an evaluation of the calcar condition, determined by the impairment of a defined volumetric area under the cephalic cup and the humeral head malposition. In addition to the main fracture pattern, the comminution degree (low, medium, high), providing important information on fracture severity, could also be evaluated.

RESULTS

From 3D imaging, the inter- and intraobserver reliability revealed a k value (95% confidence interval) of 0.55 (0.50-0.60) and 0.91 (0.79-1.00), respectively, for the pattern code, and 0.52 (0.43-0.76) and 0.91 (0.56-0.96), respectively, for the comminution degree.

CONCLUSIONS

The new classification provides a useful synoptic framework for identifying complex fracture patterns. It can provide the surgeon with useful information for fracture analysis and may represent a good starting point for an automated system.

Correlation of radiological parameters to functional outcome in complex proximal humerus fracture fixation: A study of 127 cases

OBJECTIVE

The purpose of this study is to analyze the radiological and functional outcome of complex proximal humerus fractures treated by open reduction and plate fixation, and how radiological parameters correlate with functional outcome.

DESIGN

Retrospective study.

SETTING

Level-1 trauma center.

PATIENTS/METHODS

One hundred twenty-seven patients were analyzed, with a mean follow-up of 5 (3-7) years.

OUTCOME MEASUREMENTS

Radiological parameters studied were neck-shaft angle (NSA), greater tuberosity (GT) to articular surface (AS) distance, medial hinge reduction, and presence (or absence) of calcar screw. Functional outcome evaluated by DASH and Constant-Murley (C-M) score.

RESULTS

The mean age is 53.8 years. All patients had a union in 14 (12-18) weeks. The mean NSA is 135° (112-155°). One hundred and thirteen patients with an NSA of >120° had a good functional outcome. Fourteen patients with NSA ≤120° had shoulder abduction <90°. The mean GT to AS distance is 7.2 mm (-2 to 16). The superior displacement of GT above AS is associated with abduction of <90° (16 patients). The mean medial gap is 3 mm (0-17). In 14 patients with a medial gap of >4 mm and without calcar screw, varus collapse is observed. All patients had a good outcome on DASH score and 122 patients had good to excellent outcome on C-M score. Five patients with poor outcome on C-M score had NSA <120° and displacement of GT above AS.

CONCLUSION

Radiographic indicators for poor outcome are varus angulation with NSA <120°, superior displacement of GT above AS, the presence of medial gap >4 mm, and absence of calcar specific screw. This "terrible triad" of proximal humerus fracture should be avoided during operative fixation.

[Research progress in treatment of proximal humeral fracture with fibular allograft and locking plate]

OBJECTIVE

To review the research progress in the treatment of proximal humeral fractures with fibular allograft and locking plate.

METHODS

The literature about the treatment of proximal humeral fractures with fibular allograft and locking plate was reviewed and analyzed from the aspects such as the biomechanics, imaging prognosis, and clinical prognosis.

RESULTS

Fibular allograft and locking plate can provide effective medial support for proximal humeral fracture and increase the strength of internal fixation system. Compared with locking plate, fibular allograft combined with locking plate can maintain better humeral neck-shaft angle and the humeral head height after operation in the treatment of proximal humeral fractures, and has better shoulder mobility and shoulder joint function, and does not increase the risk of complications.

CONCLUSION

Fibular allograft combined with locking plate may be a new and effective treatment for proximal humeral fractures. However, the long-term follow-up results are insufficient, the final outcome of fibula is uncertain, and the long-term potential adverse reactions caused by this treatment are still indefinite.

Failure to restore the calcar and locking screw cross-threading predicts varus collapse in proximal humerus fracture fixation

BACKGROUND

Varus collapse is a common failure mode of proximal humerus fracture (PHF) fixation. The purpose of this study was to analyze predictors of varus collapse of PHF after open reduction, internal fixation (ORIF).

METHODS

All patients who underwent ORIF of a PHF from January 2008 to July 2018 were identified. Known predictors of fixation failure were assessed, including calcar distance, calcar ratio, and calcar restoration. Additionally, the presence of cross-threaded screws was determined. The primary outcome analyzed was varus collapse of the fracture defined as a change in neck shaft angulation to less than 120°.

RESULTS

There were 112 patients identified who underwent ORIF of a PHF that met inclusion criteria. The population was 75.0% female (84/112), average age was 62.5 ± 10.4 years (range 40.0-87.9), and average body mass index was 28.0 ± 5.5 (17.5-46.4). There were 17 with varus collapse. In 11 of the 17 patients (64.7%), there was screw cross-threading (vs. 31/95 [32.6%] in those that did not collapse); P = .012. In addition, 8 of the 17 (47.1%) did not have restoration of the calcar (vs. 16/95 [16.8%]; P = .005).

CONCLUSION

This study identifies 2 surgeon-controlled variables that can contribute to varus collapse after ORIF of PHFs. Cross-threading of locking screws and failure to restore the medial calcar can be a function of implant design, surgeon technical skill, and/or bone quality.

Finite element analysis of an intramedulary anatomical strut for proximal humeral fractures with disrupted medial column instability: A cohort study

BACKGROUND

Lateral locking plate (LLP) fixation has gained popularity for the treatment of proximal humeral fractures (PHFs); however, complications can occur due to loss of the medial cortical buttress from fracture comminution.

MATERIALS AND METHODS

We designed a novel intramedullary anatomical medial strut with allograft bone (IAMSAB) using MIMICS software to specifically fill the intramedullary canal of the proximal humeral bone. We used finite element analysis to evaluate the biomechanical characteristics of a LLP, LLP-intramedullary fixation system (IFS), LLP-anatomical medial locking plate (AMLP), or the combined application of a LLP and IAMSAB (LLP-IAMSAB) fixation construct in patients with a PHF and an unstable medial column.

RESULTS

For axial or rotational loads, under (normal) Nor or osteoporotic (Ost) bone conditions, the LLP-IAMSAB fixation construct was significantly stiffer than the LLP-IFS fixation construct, and displacement at the fracture site after LLP-IAMSAB fixation was significantly less than after LLP or LLP-IFS fixation (P < 0.05). Stiffness of the LLP-IAMSAB and LLP-AMLP fixation constructs and displacement at the fracture site after LLP-IAMSAB and LLP-AMLP fixation were not significantly different. The IFS, AMLP, and IAMSAB shared the load in the LLP and decreased the risk of implant failure. There were no significant differences in von Mises stress and stress distribution after fixation with the LLP-IFS, LLP-AMLP, and LLP-IAMSAB constructs.

CONCLUSION

These data suggest that the IAMSAB can provide direct medial support or resistance to rotation and augment the biomechanics of the LLP. The combined application of the IAMSAB and LLP may achieve functional outcomes that are similar to the LLP-AMLP fixation construct.

Comparison of the Effects of Proximal Humeral Internal Locking System (PHILOS) Alone and PHILOS Combined with Fibular Allograft in the Treatment of Neer Three- or Four-part Proximal Humerus Fractures in the Elderly

Objective

To compare and analyze the clinical outcomes of the proximal humeral internal locking system (PHILOS) alone and the PHILOS combined with fibular allograft in the treatment of Neer three‐ and four‐part proximal humerus fractures (PHF) in the elderly.

Methods

From January 2014 to January 2018, a total of 42 elderly patients with Neer three‐ or four‐part PHF admitted to our hospital were randomly divided into observation group and control group, with 21 patients in each group. The observation group was treated with the PHILOS combined with fibular allograft. The control group was treated with the PHILOS alone. Perioperative parameters and fracture classification were recorded in the two groups. Function results were assessed by Visual Analog Scale (VAS), Constant‐Murley score (CMS), American Shoulder and Elbow Surgeons (ASES) score, and the Disability of Arm‐Shoulder‐Hand (DASH) score. Radiological results were evaluated using the neck‐shaft angle (NSA) and humeral head height (HHH), and complications were also recorded in each group.

Results

There were no significant differences between the two groups in terms of preoperative status, age, gender, cause of trauma, fracture site, and fracture classification. The average follow‐up time was 12 months. At the last follow‐up, the VAS and DASH observation groups were lower than the control group, and there was significant difference between the two groups (P < 0.05). The CMS and ASES were higher in the observation group than the control group, and there was significant difference between the two groups (P < 0.05). The mean difference in the NSA and HHH were lower in the observation group than the control group, and there was a significant difference between the two groups (P < 0.05). There was one postoperative complication in the observation group, which was humeral head avascular necrosis (AVN). There were seven postoperative complications in the control group, including three cases of humeral head collapse and three cases of screw cutout and one case of humeral head AVN. The incidence of postoperative complications in the observation group was significantly lower than the control group (P < 0.05), there was a significant difference between the two groups.

Conclusions

For Neer three‐ or four‐part PHF in the elderly patients, PHILOS fixation with fibular allograft shows satisfactory short‐term results with respect to humeral head support and maintenance of reduction, and may reduce the incidence of complications associated with fixation using a PHILOS alone.

Effects of medial support screws on locking plating of proximal humerus fractures in elderly patients: a retrospective study

Background

This study aimed to explore the effects of medial support screws (MSS) on the locking proximal humeral plate in elderly patients who suffered from proximal humeral fractures.

Methods

From December 2016 to December 2018, eighty-five elderly patients who suffered from proximal humeral fracture and received standard plate or locking plate with or without MSS were selected. The patients were allocated into 3 groups: Standard plate group (n=23), Locking plate without MSS group (n=34) and Locking plate with MSS group (n=28). Clinical data from all these 3 groups were collected and analyzed.

Results

These eighty-five elder patients (ranging 60-78 years) accomplished a follow-up with an average of 16.3 months. The outcome data showed that significant difference was found on the Constant score, humeral internal rotation angle and humeral height ratio (all the P<0.05) among 3 groups, and a highest Constant score and a lowest humeral internal rotation angle and humeral height ratio loss was revealed in Locking platelet with MSS group. Furthermore, the lowest incidence of post-operation complication events (7.1%, P=0.051) and an evident reduction of secondary surgery incidence (P=0.021) was also presented in Locking plate with MSS among these 3 groups.

Conclusions

The medial support screws in the locking proximal humeral plate in treating proximal humeral fractures could reduce humerus restoration loss and humeral internal rotation angle.

Biomechanical Testing of Additive Manufactured Proximal Humerus Fracture Fixation Plates

Achieving satisfactory fracture fixation in osteoporotic patients with unstable proximal humerus fractures remains a major clinical challenge. Varus collapse is one of the more prominent complications that may lead to screw cutout. This aim of this study was to compare the fixation provided by conventional locking plates with novel design concepts that are only feasible through additive manufacturing (AM) techniques. In addition to reversed engineered implants, two novel implant designs with integrated struts were included in the study to provide medial support to humeral head. The medial strut was either solid or included a porous lattice structure intended to promote bone ingrowth. Biomechanical tests were performed using low density synthetic bones with simulated 3-part comminuted fractures. Nondestructive torsion and compression were performed, followed by increasing cyclic loading. The relative displacements between the bone fragments were determined using a 3D motion capture system. The AM manufactured implants with medial strut showed significant reduction of varus displacement during the increasing cyclic loading when compared to conventional designs. AM reversed-engineered locking plates showed similar mechanical behavior to conventional plates with identical geometry. This study demonstrates the feasibility and potential of employing alternative design via AM for fixation of unstable comminuted proximal humerus fractures to reduce fragment displacement.

"90/90" Plating of proximal humerus fracture-a technical note

INTRODUCTION

While locking plates have markedly improved fixation of proximal humerus fractures, a cohort of fractures remains difficult to treat. This cohort has been identified as fractures with marked medial comminution and varus deformity. Loss of reduction and fixation failure are the most frequently reported complications for this cohort. We report the use of an orthogonal 1/3 tubular plate to augment the proximal humerus locking plate.

METHODS

The subject underwent osteosynthesis for a four-part proximal humerus fracture with medial comminution. Fixation was performed within 24 h of injury. Standard deltopectoral approach exposed the fracture. Sutures were sited to control the tuberosities and cuff. Initial reduction was held with a K-wire and augmented with a three-hole 1/3 tubular plate. Proximal humerus locking plate was sited in standard fashion including locked medial support screws. Reduction was confirmed both clinically and with intra-operative radiography.

RESULTS

The technique provided satisfactory results. At 6 months, the fracture had fully united with no loss of reduction. At 1 year, the patient had excellent range of motion.

CONCLUSION

The use of a 1/3 tubular plate to augment fixation of proximal humerus fractures with medial comminution may provide a simple, reproducible, and cost-effective method to decrease loss of reduction and subsequent malunion.

Biomechanical comparison of screw-based zones of a spatial subchondral support plate for proximal humerus fractures

Stabilisation of proximal humerus fractures remains a surgical challenge. Spatial subchondral support (S3) plate promises to overcome common complications associated with conventional proximal humerus plates. This study compared the biomechanical performance of S3 plate with a fixed-angle hybrid blade (Equinoxe Fx) plate and a conventional fixed-angle locking plate (PHILOS). The effects of removal of different S3 plate screws on the humeral stability were also investigated. A total of 20 synthetic left humeri were osteotomised transversely at the surgical neck to simulate a two-part fracture and were each treated with an S3 plate. Head screws were divided into three zones based on their distance from the fracture site. Specimens were divided into four equal groups where one group acted as a control with all screws and three groups had one of the screw zones missing. With humeral head fixed, humeral shaft was first displaced 5 mm in extension, flexion, valgus and varus direction (elastic testing) and then until 30 mm varus displacement (plastic testing). Load-displacement data were recorded to determine construct stiffness in elastic tests and assess specimens' varus stability under plastic testing. Removal of the screw nearest to the fracture site led to a 20.71% drop in mean elastic varus bending stiffness. Removal of the two inferomedial screw above it resulted in a larger drop. The proximal screw pair had the largest contribution to extension and flexion bending stiffness. Varus stiffness of S3 plate constructs was higher than PHILOS and Fx plate constructs. Stability of humeri treated with S3 plate depends on screws' number, orientation and location. Varus stiffness of S3 plate construct (10.54 N/mm) was higher than that of PHILOS (6.61 N/mm) and Fx (7.59 N/mm) plate constructs. We attribute this to S3 plates' thicker cross section, the 135° inclination of its screws with respect to the humeral shaft and the availability of pegs for subchondral support.

Biomechanical evaluation of hybrid double plate osteosynthesis using a locking plate and an inverted third tubular plate for the treatment of proximal humeral fractures

Background

Treating proximal humerus fractures can be challenging because of large metaphyseal defects that conceal anatomical landmarks. In such cases, medial cortical support with, for example, calcar screws, is mandatory. Nevertheless, varus dislocations and implant failures in patients with impaired bone quality persist. Thus, the need for effective treatment of these patients exists. Hybrid double plate osteosynthesis was introduced as an alternative, yielding similar results as calcar screws. However, a biomechanical comparison of the stability of these two techniques is pending.

Methods

Cadaveric humeral specimens were treated with plate osteosynthesis and calcar screws (group 1, n = 9) or hybrid double plate osteosynthesis (group 2, n = 9) using a proximal humerus fracture model with a two-part fracture. Displacement, stiffness, failure mode, and ultimate load were examined biomechanically in a cyclic compressive-loading scenario.

Results

Although the hybrid double plate osteosynthesis (group 2) tended to confer higher stiffnesses than the medial support screws at higher cycles (group 1), this trend was below the level of significance. The displacement revealed non-significantly lower values for group 1 as compared with group 2 for cycles 50 and 2000, but at 5000 cycles, group 2 offered non-significantly lower displacement values than group 1. The ultimate load tended to be non-significantly higher in the hybrid double plate osteosynthesis group (group 2: 1342±369 N, group 1: 855±408 N). Both groups yielded similar failure rates, with the majority of failures in group 2 being gap closures (n = 8), whereas those in group 1 being plate dislocations (n = 4).

Conclusions

The use of an additive plate osteosynthesis in the region of the bicipital groove may be a potential alternative to the previously-established method of using calcar screws. The biomechanical data obtained in this study suggests that hybrid double plate osteosynthesis is as rigid and robust as calcar screws.

Proximal Humeral Locking Plates: A Cadaveric Study of 5 Versus 7 Metaphyseal Locking Screws

The most common operative treatment of proximal humerus fractures is internal fixation with fixed-angle locking plates. Although this surgical technique has been refined, a significant failure rate remains. This study aimed to determine whether the number of locking screws in the humeral head affects the biomechanical strength and stability of the construct in bone from elderly individuals. Ten pairs of embalmed cadaveric humeri were osteotomized in a gap model and fixed with periarticular locking plates placed in the standard position. Five or 7 proximal locking screws were inserted. Mechanical testing was performed, and cyclic displacements and maximum force to failure were recorded. No significant difference was found between 5 and 7 locking screws in mean cyclic displacement on the medial (1.09 mm vs 1.12 mm, P=.834) or posterior (0.45 mm vs 0.42 mm, P=.791) sides of the fracture model. On testing to failure, 7 and 5 screws showed similar stiffness (336 N/mm vs 292 N/mm, P=.176), force at ultimate load (745 N vs 662 N, P=.309), and displacement at ultimate load (5.90 mm vs 4.36 mm, P=.080). All samples failed at diaphyseal fixation, and no screw cutout or varus collapse was observed. Results from this study suggest that there is no significant difference between 5 and 7 metaphyseal locking screws for stiffness of fixation of proximal humeral fractures in elderly patients. With the inherent possibility of screw penetration of the humeral head, fewer screws may lead to fewer complications. [Orthopedics. 2018; 41(5):306-311.].

Influence of Medial Support Screws on the Maintenance of Fracture Reduction after Locked Plating of Proximal Humerus Fractures

Background

Technical aspects of the correct placement of medial support locking screws in the locking plate for proximal humerus fractures remain incompletely understood. This study was to evaluate the clinical relationship between the number of medial support screws and the maintenance of fracture reduction after locked plating of proximal humerus fractures.

Methods

We retrospectively evaluated 181 patients who had been surgically treated for proximal humeral fractures (PHFs) with a locking plate between September 2007 and June 2013. All cases were then subdivided into one of four groups as follows: 75 patients in the medial cortical support (MCS) group, 26 patients in the medial multiscrew support (MMSS) group, 29 patients in the medial single screw support (MSSS) group, and 51 patients in the no medial support (NMS) group. Clinical and radiographic evaluations included the Constant-Murley score (CM), visual analogue scale (VAS), complications, and revision surgeries. The neck-shaft angle (NSA) was measured in a true anteroposterior radiograph immediately postoperation and at final follow-up. One-way analysis of variance or Kruskal-Wallis test was used for statistical analysis of measurement data, and Chi-square test or Fisher's exact test was used for categorical data.

Results

The mean postoperative NSAs were 133.46° ± 6.01°, 132.39° ± 7.77°, 135.17° ± 10.15°, and 132.41° ± 7.16° in the MCS, MMSS, MSSS, and NMS groups, respectively, and no significant differences were found (F = 1.02, P = 0.387). In the final follow-up, the NSAs were 132.79° ± 6.02°, 130.19° ± 9.25°, 131.28° ± 12.85°, and 127.35° ± 8.50° in the MCS, MMSS, MSSS, and NMS groups, respectively (F = 4.40, P = 0.008). There were marked differences in the NSA at the final follow-up between the MCS and NMS groups (P = 0.004). The median (interquartile range [IQR]) NSA losses were 0.0° (0.0-1.0)°, 1.3° (0.0-3.1)°, 1.5° (1.0-5.2)°, and 4.0° (1.2-7.1)° in the MCS, MMSS, MSSS, and NMS groups, respectively (H = 60.66, P < 0.001). There were marked differences in NSA loss between the MCS and the other three groups (MCS vs. MMSS, Z = 3.16, P = 0.002; MCS vs. MSSS, Z = 4.78, P < 0.001; and MCS vs. NMS, Z = 7.34, P < 0.001). There was also significantly less NSA loss observed in the MMSS group compared to the NMS group (Z = -3.16, P = 0.002). However, there were no significant differences between the MMSS and MSSS groups (Z = -1.65, P = 0.225) or the MSSS and NMS groups (Z = -1.21, P = 0.099). The average CM scores were 81.35 ± 9.79, 78.04 ± 8.97, 72.76 ± 10.98, and 67.33 ± 12.31 points in the MCS, MMSS, MSSS, and NMS groups, respectively (F = 18.68, P < 0.001). The rates of excellent and good CM scores were 86.67%, 80.77%, 65.52%, and 43.14% in the MCS, MMSS, MSSS, and NMS groups, respectively (χ² = 29.25, P < 0.001). The median (IQR) VAS scores were 1 (0-2), 1 (0-2), 2 (1-3), and 3 (1-5) points in the MCS, MMSS, MSSS, and NMS groups, respectively (H = 27.80, P < 0.001). Functional recovery was markedly better and VAS values were lower in the MCS and MMSS groups (for CM scores: MCS vs. MSSS, P < 0.001; MCS vs. NMS, P < 0.001; MMSS vs. MSSS, P = 0.031; and MMSS vs. NMS, P < 0.001 and for VAS values: MCS vs. MSSS, Z = 3.31, P = 0.001; MCS vs. NMS, Z = 4.64, P < 0.001; MMSS vs. MSSS, Z = -2.09, P = 0.037; and MMSS vs. NMS, Z = -3.16, P = 0.003).

Conclusions

Medial support screws might help enhance mechanical stability and maintain fracture reduction when used to treat PHFs with medial metaphyseal comminution or malreduction.

Biomechanical comparison of screw-based zoning of PHILOS and Fx proximal humerus plates

Background

Treatment of proximal humerus fractures with locking plates is associated with complications. We aimed to compare the biomechanical effects of removing screws and blade of a fixed angle locking plate and hybrid blade plate, on a two-part fracture model.

Methods

Forty-five synthetic humeri were divided into nine groups where four were implanted with a hybrid blade plate and the remaining with locking plate, to treat a two-part surgical neck fracture. Plates’ head screws and blades were divided into zones based on their distance from fracture site. Two groups acted as a control for each plate and the remaining seven had either a vacant zone or blade swapped with screws. For elastic cantilever bending, humeral head was fixed and the shaft was displaced 5 mm in extension, flexion, valgus and varus direction. Specimens were further loaded in varus direction to investigate their plastic behaviour.

Results

In both plates, removal of inferomedial screws or blade led to a significantly larger drop in varus construct stiffness than other zones. In blade plate, insertion of screws in place of blade significantly increased the mean extension, flexion valgus and varus bending stiffness (24.458%/16.623%/19.493%/14.137%). In locking plate, removal of screw zones proximal to the inferomedial screws reduced extension and flexion bending stiffness by 26–33%.

Conclusions

Although medial support improved varus stability, two inferomedial screws were more effective than blade. Proximal screws are important for extension and flexion. Mechanical consequences of screw removal should be considered when deciding the number and choice of screws and blade in clinic.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2185-5) contains supplementary material, which is available to authorized users.

Biomechanical analysis of plate systems for proximal humerus fractures: a systematic literature review

BACKGROUND

Proximal humerus fractures are the third most common in the human body but their management remains controversial. Open reduction and internal fixation with plates is one of the leading modes of operative treatment for these fractures. The development of technologies and techniques for these plates, during the recent decades, promise a bright future for their clinical use. A comprehensive review of in vitro biomechanical studies is needed for the comparison of plates' mechanical performance and the testing methodologies. This will not only guide clinicians with plate selection but also with the design of future in vitro biomechanical studies. This review was aimed to systematically categorise and review the in vitro biomechanical studies of these plates based on their protocols and discuss their results. The technologies and techniques investigated in these studies were categorised and compared to reach a census where possible.

METHODS AND RESULTS

Web of Science and Scopus database search yielded 62 studies. Out of these, 51 performed axial loading, torsion, bending and/or combined bending and axial loading while 11 simulated complex glenohumeral movements by using tendons. Loading conditions and set-up, failure criteria and performance parameters, as well as results for each study, were reviewed. Only two studies tested four-part fracture model while the rest investigated two- and three-part fractures. In ten studies, synthetic humeri were tested instead of cadaveric ones. In addition to load-displacement data, three-dimensional motion analysis systems, digital image correlation and acoustic emission testing have been used for measurement.

CONCLUSIONS

Overall, PHILOS was the most tested plate and locking plates demonstrated better mechanical performance than non-locking ones. Conflicting results have been published for their comparison with non-locking blade plates and polyaxial locking screws. Augmentation with cement [calcium phosphate or poly(methyl methacrylate)] or allografts (fibular and femoral head) was found to improve bone-plate constructs' mechanical performance. Controversy still lies over the use of rigid and semi-rigid implants and the insertion of inferomedial screws for calcar region support. This review will guide the design of in vitro and in silico biomechanical tests and also supplement the study of clinical literature.

Calcar screw position in proximal humerus fracture fixation: Don't miss high!

INTRODUCTION

In locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of "missing" the calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model.

MATERIALS AND METHODS

This experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups.

RESULTS

Cadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p = 0.003, p = 0.034) and axial stiffness (p = 0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p = 0.020), increased axial stiffness (p = 0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement.

DISCUSSION

The distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness.

RESULTS

from the Sawbones model were more definitive and provided further evidence that proximal calcar screw placements are undesirable and distal implant placement may provide improved construct stability.

CONCLUSION

Successful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.

Assessment of Screw Length of Proximal Humerus Internal Locking System (PHILOS) Plate for Proximal Humeral Fractures Using Three-Dimensional Computed Tomography Scan

Background

Screw perforation and varus collapse are common complications of treatment with a PHILOS (proximal humerus internal locking system) plate for proximal humerus fractures, which are associated with improper screw length selection and lack of medial column support. The purposes of this study were: (1) to measure the proper length of periarticular screws of the PHILOS plate in the humeral head, and (2) to determine what factors influence the screw length and implantation of the inferomedial support screw.

Material/Methods

Computed tomography (CT) images of the normal proximal humerus in 134 cases were retrospectively reviewed. The length of periarticular screws was measured using three-dimensional (3D) techniques. Intraobserver and interobserver reliability of measurement were evaluated using intraclass correlation coefficients (ICCs). Sex and body height influences on screw length and implantation of the inferomedial screw were analyzed.

Results

All measurements had excellent agreement (ICC>0.75). The screw length and implantation rate of the inferomedial screw were greater in males than in females. Positive correlations were observed between body height and screw length and implantation of the inferomedial screw (all P<0.001).

Conclusions

The screws were longer and the implantation rate was higher for inferomedial screws in males than in females, and were positively correlated with body height. Our data can be used as a reference for surgeons to reduce the number of times screws are changed intraoperatively and to reduce operation duration and minimize use of intraoperative fluoroscopy for proximal humerus fractures treated with the PHILOS plate.

Establishing the appropriate position of proximal humerus locking plates: a cadaveric study of five plating systems and their anatomic reference measurements

BACKGROUND

The present study aimed to determine anatomic references for the placement of five proximal humerus locking plates.

METHODS

Five proximal humerus locking-plate systems were placed on six human shoulder cadavers. Plates were positioned by fluoroscopic confirmation so that the inferior oblique screw was within 5 mm of the inferomedial cortex. Plate position was measured using the superior border of the pectoralis major tendon (PMT) to the bottom of the first slotted or nonlocking hole and top of the plate to the top of the greater tuberosity. The distance from the PMT insertion to the top of the humeral head was measured as a control.

RESULTS

There was consistency within each plating system for both the distance from the PMT insertion to the first hole and the top of the plate to the greater tuberosity: Synthes first-generation [mean (SD) 13.7 mm (3.1 mm); 10 mm (1.3) mm], Synthes second-generation [28.2 mm (2.2 mm); 18.5 mm (2.7 mm)], Biomet OptiLock® [25.5 mm (2.7 mm); 18.7 mm (2 mm)], Stryker AxSOS® [5 mm (2.8 mm); 12.3 mm (3.3 mm)] and Acumed Polarus® [9.5 mm (1.8 mm); 14.8 mm (1.6 mm)].

CONCLUSIONS

The present study provides measurements that improve the accuracy of plate positioning for five plating systems.

Grafting and fixation of proximal humeral aseptic non union: a prospective case series

Background

Fractures of the proximal part of the humerus represent almost 4-5% of all fractures. The rate of non union is estimated to be 1.1 to 10%. Non union, displacement, and fixation failure can be hazardous complications for these injuries. The purpose of our study was to evaluate the outcomes of plate and bone strut allograft with bone chips grafting augmentation in the management of proximal humeral aseptic non union.

Methods

We treated 16 aseptic non union proximal humeral fractures by the medial humeral shaft bone strut allograft and lateral plate and screws with bone chips grafting. The patients' ages were between 55 and 70 years. The chosen criteria to evaluate the group during the clinical and radiological follow-up were the quality of life measured by The Short Form (12) Health Survey (SF-12), shoulder function and related quality of life measured by the Constant Shoulder Score (CSS) compared with healthy side, bone healing measured by X-rays, and postoperative complications. The follow-up was perfor med with clinical and radiographic controls at 1, 3, 6 and 12 months. Surgical time and international units of red blood cells transfused were also calculated. The evaluation endpoint was set at 12 months.

Results

The X-rays bone healing occurred in our group on average of 126.4 days after surgery. The surgical time and blood loss were consistent with standard surgical procedures. The quality of life and functional recovery were excellent after plate and bone strut allograft.

Conclusions

Surgical techniques that increase mechanical stability, while incorporating bone biology, are effective aids for treating problematic fractural patterns.

Current concepts in locking plate fixation of proximal humerus fractures

Despite numerous available treatment strategies, the management of complex proximal humeral fractures remains demanding. Impaired bone quality and considerable comorbidities pose special challenges in the growing aging population. Complications after operative treatment are frequent, in particular loss of reduction with varus malalignment and subsequent screw cutout. Locking plate fixation has become a standard in stabilizing these fractures, but surgical revision rates of up to 25% stagnate at high levels. Therefore, it seems of utmost importance to select the right treatment for the right patient. This article provides an overview of available classification systems, indications for operative treatment, important pathoanatomic principles, and latest surgical strategies in locking plate fixation. The importance of correct reduction of the medial cortices, the use of calcar screws, augmentation with bone cement, double-plate fixation, and auxiliary intramedullary bone graft stabilization are discussed in detail.

The Applications of Finite Element Analysis in Proximal Humeral Fractures

Proximal humeral fractures are common and most challenging, due to the complexity of the glenohumeral joint, especially in the geriatric population with impacted fractures, that the development of implants continues because currently the problems with their fixation are not solved. Pre-, intra-, and postoperative assessments are crucial in management of those patients. Finite element analysis, as one of the valuable tools, has been implemented as an effective and noninvasive method to analyze proximal humeral fractures, providing solid evidence for management of troublesome patients. However, no review article about the applications and effects of finite element analysis in assessing proximal humeral fractures has been reported yet. This review article summarized the applications, contribution, and clinical significance of finite element analysis in assessing proximal humeral fractures. Furthermore, the limitations of finite element analysis, the difficulties of more realistic simulation, and the validation and also the creation of validated FE models were discussed. We concluded that although some advancements in proximal humeral fractures researches have been made by using finite element analysis, utility of this powerful tool for routine clinical management and adequate simulation requires more state-of-the-art studies to provide evidence and bases.

Biomechanical evaluation of a novel dualplate fixation method for proximal humeral fractures without medial support

Background

Comminuted fractures of the proximal humerus are generally treated with the locking plate system, and clinical results are satisfactory. However, unstable support of the medial column results in varus malunion and screw perforation. We designed a novel medial anatomical locking plate (MLP) to directly support the medial column. Theoretically, the combined application of locking plate and MLP (LPMP) would directly provide strong dual-column stability. We hypothesized that the LPMP could provide greater construct stability than the locking plate alone (LP), locking plate combined with a fibular graft (LPSG), and locking plate combined with a distal radius plate (LPDP).

Methods

LP, LPMP, LPSG, and LPDP implants were instrumented into the finite element model of a proximal humeral fracture. Axial, shear, and rotational loads were applied to the models under normal and osteoporotic bone conditions. The whole simulation was repeated five times for each fixator. To assess the biomechanical characteristics, the construct stiffness, fracture micromotion, stress distribution, and neck-shaft angle (NSA) were compared.

Results

The LPMP group showed significantly greater integral and regional construct stiffness, and endured less von Mises stresses, than the other three fixation methods. The stresses on the lateral locking plate were dispersed by the MLP. The LPMP group showed the least change in NSA.

Conclusions

From the finite element viewpoint, the LPMP method provided both lateral and medial direct support. The LPMP system was effective in treating proximal humeral fracture with an unstable medial column.

Intramedullary cortical bone strut improves the cyclic stability of osteoporotic proximal humeral fractures

Background

Proximal humeral fractures treated with locking plate can fail due to varus collapse, especially in osteoporotic bone with medial cortex comminution. The use of an intramedullary strut together with locking plate fixation may strengthen fixation and provide additional medial support to prevent the varus malalignment. This study biomechanically investigates the influence of an intramedullary cortical bone strut on the cyclic stability of proximal humeral fractures stabilized by locking plate fixation in a cadaver model.

Methods

Ten cadaveric humeri were divided into two groups statistically matched for bone density. Each specimen was osteotomized with 10 mm gap at the surgical neck. The non-augmented group stabilized with locking plate alone; in the augmented group, a locking plate was used combined with an intramedullary cortical bone strut. The strut was retrograded into the subchondral bone, and three humeral head screws were inserted into the strut to form a plate-screw-strut mechanism. The cyclic axial load was performed to 450 N for 6000 cycles and then loaded to failure. Construct stiffness, cyclic loading behavior and failure strength were analyzed to identify differences between groups.

Results

The augmented constructs were significantly stiffer than the non-augmented constructs during cycling. On average, the maximum displacements at 6000 cycles for non-augmented and augmented groups were 3.10 ± 0.75 mm and 1.7 ± 0.65 mm (p = 0.01), respectively. The mean peak-to-peak (inter cycle) displacement at 6000 cycles was about 2 times lower for the augmented group (1.36 ± 0.68 mm vs. 2.86 ± 0.51 mm). All specimens showed varus collapse combined with loss of screw fixation of the humeral head. The failure load of the augmented group was increased by 2.0 (SD = 0.41) times compared with the non-augmented group (p < 0.001).

Conclusions

The stability and strength of the locking plate augmented with an intramedullary strut were significantly increased. For bone with poor quality, the subsidence of the locked screws led larger displacement, decreased the stability of the constructs, however, the plate-screw-strut mechanism provided more rigidity to stabilize the fixation. This study emphasized the importance of intramedullary support for the proximal humeral fractures fixed with a locked plate under cyclic loading, especially in bone with poor quality. This work is based on the results of cadaver model, further in vivo analysis is necessary to determine if the clinical results can be extrapolated from this data.

Minimally invasive plate osteosynthesis with PHILOS plate for proximal humerus fractures

OBJECTIVES

The aim of the present study was to evaluate results, including clinical and radiological outcomes and number of complications, following minimally invasive plate osteosynthesis (MIPO) of proximal humerus fractures, using the PHILOS® proximal humerus internal locking system (Synthes Holding AG, Solothurn, Switzerland).

METHODS

Retrospectively evaluated were 31 patients treated with MIPO (12 male, 19 female; average age: 58.4 years). Four patients had 2-part fractures, 14 patients had 3-part fractures, and 13 patients had 4-part fractures, according to Neer classification. Healing, complications, and head-shaft angle (HSA) were radiographically evaluated. Clinical outcomes were assessed at 1-year follow-up with Constant score.

RESULTS

Average Constant scores for fractured and normal shoulders were 73.2 ± 10.9 and 84.8 ± 5.1, respectively. Varus progression, fracture type, and age had no significant effect on functional outcome. Average postoperative and follow-up HSA's were 130.80 ± 7.70 and 128.80 ± 10.00, respectively. Significant varus progression was observed during follow-up (p = 0.01). Varus progression was more prominent in patients with postoperative HSA < 130° (p < 0.001). Inferomedial calcar screw usage, fracture type, and age had no significant effect on varus progression. Complications included 2 implant failures, 1 case of avascular necrosis (AVN), 1 primary screw cut-out, 1 axillary nerve injury, and 1 radial nerve injury (22.6% overall).

CONCLUSION

MIPO is a safe and effective option for the treatment of proximal humerus fractures, with good functional recovery and fewer complications, which are typically technique dependent. Reduction may be difficult, resulting in varus progression. Another disadvantage is risk of axillary nerve injury. Careful surgical technique and correct implant selection is important in the prevention of nerve injury.

LEVEL OF EVIDENCE

Level IV, Therapeutic study.

Influence of plate material and screw design on stiffness and ultimate load of locked plating in osteoporotic proximal humeral fractures

INTRODUCTION

The main purpose was to compare the biomechanical properties of a carbon-fibre reinforced polyetheretherketone (CF-PEEK) composite locking plate with pre-existing data of a titanium-alloy plate when used for fixation of an unstable 2-part fracture of the surgical neck of the humerus. The secondary purpose was to compare the mechanical behaviour of locking bolts and conventional locking cancellous screws.

METHODS

7 pairs of fresh frozen human humeri were allocated to two equal groups. All specimens were fixed with the CF-PEEK plate. Cancellous screws (PEEK/screw) were compared to locking bolts (PEEK/bolt) for humeral head fixation. Stiffness, fracture gap deflection and ultimate load as well as load before screw perforation of the articular surface were assessed. Results were compared between groups and with pre-existing biomechanical data of a titanium-alloy plate.

RESULTS

The CF-PEEK plate featured significantly lower stiffness compared to the titanium-alloy plate (P<0.001). In ultimate load testing, 6 out of 14 CF-PEEK plates failed due to irreversible deformation and cracking. No significant difference was observed between results of groups PEEK/screw and PEEK/bolt (P>0.05).

DISCUSSION

The CF-PEEK plate has more elastic properties and significantly increases movement at the fracture site of an unstable proximal humeral fracture model compared to the commonly used titanium-alloy plate. The screw design however does neither affect the constructs primary mechanical behaviour in the constellation tested nor the load before screw perforation.

Clinical and radiological outcomes of unstable proximal humeral fractures treated with a locking plate and fibular strut allograft

PURPOSE

To evaluate the clinical and radiological outcomes of unstable proximal humeral fractures (PHFs) treated with a locking plate and fibular strut allograft.

METHODS

This study included 36 patients [7 men, 29 women; mean age, 68 years (range, 22-94 years)] with unstable PHFs with medial column disruption. All patients were treated with open reduction and internal fixation using a locking plate and fibular strut allograft. Post-operative assessment included clinical outcomes, shoulder range of motion, radiographic examination, and any complications. Post-operative radiological assessment including the humerus neck-shaft angle (NSA) and the humeral head height was performed.

RESULTS

At the mean two year follow-up visit, the mean American Shoulder and Elbow Society (ASES) and University of California, Los Angeles (UCLA) scores were 77 and 28, respectively. According to the UCLA rating scale, the result was excellent in six, good in 20, fair in six, and poor in four cases. According to the Paavolainen method, 31 patients had good results with an NSA of 130 ± 10°; three patients showed fair results with an NSA of 100-120°, and two patients experienced a poor result with an NSA of <100°. When calculating the humeral head height, the mean loss of reduction was measured as 1.6 mm (from 10.8 or 9.2 mm). Varus collapse and avascular necrosis of the humeral head was noted in two patients for each condition.

CONCLUSIONS

For unstable proximal humerus fractures, particularly in elderly patients with severe osteoporosis or in younger patients with a four-part fracture, locking plate fixation with a fibular strut allograft provided rigid medial support and showed satisfactory clinical and radiological outcomes.

Is there any advantage in placing an additional calcar screw in locked nailing of proximal humeral fractures?

BACKGROUND

The objective of this study was to evaluate the biomechanical effect of an additional unlocked calcar screw compared to a standard setting with three proximal humeral head screws alone for fixation of an unstable 2-part fracture of the surgical neck.

HYPOTHESIS

The additional calcar screw improves stiffness and failure load.

METHODS

Fourteen fresh frozen humeri were randomized into two equal sized groups. An unstable 2-part fracture of the surgical neck was simulated and all specimens were fixed with the MultiLoc(®)-nail. Group I represented a basic screw setup, with three locked head screws and two unlocked shaft screws. Group II was identical with a supplemental unlocked calcar screw (CS). Stiffness tests were performed in torsional loading, as well as in axial and in 20° abduction/20° adduction modes. Subsequently cyclic loading and load-to-failure tests were performed. Resulting stiffness, displacement under cyclic load and ultimate load were compared between groups using the t-test for independent variables (α=0.05).

RESULTS

No significant differences were observed between the groups in any of the biomechanical parameters. Backing out of the CS was observed in three cases.

DISCUSSION

The use of an additional unlocked calcar screw does not provide mechanical benefit in locked nailing of an unstable 2-part fracture of the surgical neck.

Medial calcar support and radiographic outcomes of plate fixation for proximal humeral fractures

Plate fixation remains one of the most popular surgical procedures for treating proximal humeral fractures (PHFx); however, substantial rates of complications have been reported in the literature. The objectives of the study were to examine how medial calcar support (MCS) affects the radiographic outcomes and to determine the prognostic factors predicting treatment failure. We performed a retrospective cohort study of 89 adult patients who had PHFx and were treated with plate fixation at our institution in 2007–2011. The enrolled patients were separated into two groups according to disruption of medial calcar. Our results revealed an increased rate of poor radiographic outcomes in patients with disrupted medial calcar. Osteonecrosis of the humeral head and redisplacement were the two radiographic outcomes which had a positive causality with disruption of medial calcar (P = 0.008 and 0.050, resp.). Deficient medial calcar, inadequate reduction, diabetes mellitus, chronic kidney disease, and chronic liver disease were all significant predictors for the development of osteonecrosis in patients after PHFx surgery. Inadequate reduction was also a predictor for redisplacement. We confirmed that the restoration of medial calcar as well as comorbid conditions plays key roles in treatment of patients having PHFx with disrupted medial calcar.

Minimally invasive plate osteosynthesis for proximal humeral fractures: clinical and radiologic outcomes according to fracture type

BACKGROUND

This study evaluated the clinical and radiologic outcomes, according to fracture type, of proximal humeral fractures treated by the minimally invasive plate osteosynthesis (MIPO) technique.

MATERIALS AND METHODS

Of 85 patients with proximal humeral fractures who were treated by the MIPO technique, 62 were evaluated: 27 with 2-part fractures, 24 with 3-part fractures, and 11 with 4-part fractures. An additional inferomedial screw or fibular allograft was used when severe medial cortical comminution was found in the proximal humerus. Clinical and radiographic outcomes were evaluated during the follow-up of 37 months.

RESULTS

There was a significant difference in the Constant scores of patients with 4-part fractures compared with those with 3-part fractures (P = .039). The neck-shaft angle in 4-part fractures (121° ± 3°) at final follow-up was significantly lower compared with other fracture types (2-part: 129° ± 9°, P = .036; 3-part: 129° ± 2°, P = .031). Complication rates (72.7%) of 4-part fractures were significantly higher than with other fracture types (2-part, 7.4%; 3-part, 20.8%; P = .001). Sixteen fractures were fixed with an additional inferomedial screw, and 3 patients had insertion of a fibular allograft.

CONCLUSION

Satisfactory clinical and radiologic outcomes were obtained by the MIPO technique in proximal humeral fractures. In addition, medial cortical support can be performed with an inferomedial screw or fibular allograft in the MIPO technique. However, the MIPO technique for 4-part fractures showed relatively inferior outcomes compared with 2- and 3-part fractures. Conversion to open plating is also considered if adequate reduction, that is, a neck-shaft angle >120°, is not able to be obtained in the MIPO technique for 4-part fractures of the proximal humerus.

The mechanical benefit of medial support screws in locking plating of proximal humerus fractures

Background

The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs) in the locking proximal humeral plate for treating proximal humerus fractures.

Methods

Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed.

Results

Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001). When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P≤0.0207). Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture.

Conclusions

Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure.

Biomechanical effects of calcar screws and bone block augmentation on medial support in locked plating of proximal humeral fractures

BACKGROUND

The objective of this study was to investigate the biomechanical effects of medial fracture gap augmentation in locked plating of an unstable 2-part proximal humeral fracture with calcar screws and insertion of a corticocancellous bone block. Furthermore the mechanical behavior of dynamic locking screws in the non-parallel arrangement of a proximal humeral plate was of interest.

METHODS

Thirty-two fresh frozen humeri were randomized in four equal groups. An unstable 2-part fracture was fixed by locked plating in all specimens. The basic screw setup was supplemented by additional calcar screws in one group. Humeral head screws were replaced by dynamic locking screws in a second group. The third group featured an additional corticocancellous femoral head allograft. Assessment of stiffness was followed by cyclic loading and load to failure tests. Resulting stiffness, fracture gap deflection and ultimate load were compared utilizing Bonferroni corrected t-test for independent samples.

FINDINGS

The mechanical effect of additional calcar screws was non-significant as compared to the basic screw configuration whereas bone block insertion significantly increased construct stiffness and failure load. The use of dynamic locking screws did not significantly reduce construct stiffness when compared to conventional locking screws.

INTERPRETATION

Additional calcar screws alone did not improve the initial biomechanical properties of an unstable 2-part proximal humeral fracture model. However bone block augmentation appeared to be a reliable alternative of additional bony support by raising stiffness and failure load. Dynamic locking screws did not show their expected dynamic component when used in a non-parallel arrangement.

Bone properties of the humeral head and resistance to screw cutout

Surgical treatment of fractures involving the proximal humeral head is hampered by complications. Screw cutout is the major pitfall seen in connection with rigid plating. We have exploited a bony explanation for this phenomenon.

Radiological evaluation of reduction loss in unstable proximal humeral fractures treated with locking plates

PURPOSE

The aim of this study was to radiologically evaluate the risk of reduction loss after locking plate fixation of proximal humerus fractures.

METHODS

From September 2007 to April 2009, 71 patients (28 males, 43 females) with unstable proximal humeral fracture were treated with open reduction and internal fixation by locking plate. The mean follow-up time was 31.2 months (range: 26-47). The head-shaft angulation (HSA) and the humeral head height (HHH) in true anteroposterior (AP) were recorded and compared over time. All complications were noted. Shoulder function was measured by the Constant score.

RESULTS

Patients with ΔHSA >10° (t=2.740, P=0.008) and ΔHHH >5mm (t=2.55, P=0.019) were more likely to have impaired shoulder function. Varus collapse occurred most frequently in patients with initial reduction of HSA <125° (χ(2)=19.17, P<0.001, Fisher's exact test F<0.001). Patients with >5mm HHH decrease were strongly associated with loss of reduction (χ(2)=24.23, P<0.001, F<0.001).

CONCLUSIONS

Dynamic change of HSA >10° and HHH >5mm were radiological factors that indicated poor shoulder function. Intra-operative HSA >125° should be achieved to avoid reduction loss following locking plate fixation of proximal humerus fracture.

LEVEL OF EVIDENCE

level IV.

Biomechanical Measurements of Stiffness and Strength for Five Types of Whole Human and Artificial Humeri

The human humerus is the third largest longbone and experiences 2–3% of all fractures. Yet, almost no data exist on its intact biomechanical properties, thus preventing researchers from obtaining a full understanding of humerus behavior during injury and after being repaired with fracture plates and nails. The aim of this experimental study was to compare the biomechanical stiffness and strength of “gold standard” fresh-frozen humeri to a variety of humerus models. A series of five types of intact whole humeri were obtained: human fresh-frozen (n = 19); human embalmed (n = 18); human dried (n = 15); artificial “normal” (n = 12); and artificial “osteoporotic” (n = 12). Humeri were tested under “real world” clinical loading modes for shear stiffness, torsional stiffness, cantilever bending stiffness, and cantilever bending strength. After removing geometric effects, fresh-frozen results were 585.8 ± 181.5 N/mm2 (normalized shear stiffness); 3.1 ± 1.1 N/(mm2 deg) (normalized torsional stiffness); 850.8 ± 347.9 N/mm2 (normalized cantilever stiffness); and 8.3 ± 2.7 N/mm2 (normalized cantilever strength). Compared to fresh-frozen values, statistical equivalence (p ≥ 0.05) was obtained for all four test modes (embalmed humeri), 1 of 4 test modes (dried humeri), 1 of 4 test modes (artificial “normal” humeri), and 1 of 4 test modes (artificial “osteoporotic” humeri). Age and bone mineral density versus experimental results had Pearson linear correlations ranging from R = −0.57 to 0.80. About 77% of human humeri failed via a transverse or oblique distal shaft fracture, whilst 88% of artificial humeri failed with a mixed transverse + oblique fracture. To date, this is the most comprehensive study on the biomechanics of intact human and artificial humeri and can assist researchers to choose an alternate humerus model that can substitute for fresh-frozen humeri.

Biomechanical measurements of stopping and stripping torques during screw insertion in five types of human and artificial humeri

During orthopedic surgery, screws are inserted by “subjective feel” in humeri for fracture fixation, that is, stopping torque, while trying to prevent accidental over-tightening that causes screw–bone interface failure, that is, stripping torque. However, no studies exist on stopping torque, stripping torque, or stopping/stripping torque ratio in human or artificial humeri. This study evaluated five types of humeri, namely, human fresh-frozen (n = 19), human embalmed (n = 18), human dried (n = 15), artificial “normal” (n = 13), and artificial “osteoporotic” (n = 13). An orthopedic surgeon used a torque screwdriver to insert 3.5-mm-diameter cortical screws into humeral shafts and 6.5-mm-diameter cancellous screws into humeral heads by “subjective feel” to obtain stopping and stripping torques. The five outcome measures were raw and normalized stopping torque, raw and normalized stripping torque, and stopping/stripping torque ratio. Normalization was done as raw torque/screw–bone interface area. For “gold standard” fresh-frozen humeri, cortical screw tests yielded averages of 1312 N mm (raw stopping torque), 30.4 N/mm (normalized stopping torque), 1721 N mm (raw stripping torque), 39.0 N/mm (normalized stripping torque), and 82% (stopping/stripping torque ratio). Similarly, fresh-frozen humeri gave cancellous screw average results of 307 N mm (raw stopping torque), 0.9 N/mm (normalized stopping torque), 392 N mm (raw stripping torque), 1.2 N/mm (normalized stripping torque), and 79% (stopping/stripping torque ratio). Of the five cortical screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in four cases (embalmed), three cases (dried), four cases (artificial “normal”), and four cases (artificial “osteoporotic”). Of the five cancellous screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in five cases (embalmed), one case (dried), one case (artificial “normal”), and zero cases (artificial “osteoporotic”). Stopping/stripping torque ratios were relatively constant for all groups at 77%–88% (cortical screws) and 79%–92% (cancellous screws).

The role of medial comminution and calcar restoration in varus collapse of proximal humeral fractures treated with locking plates

BACKGROUND

Proximal humeral fractures that are treated with locked plate constructs remain susceptible to collapse into a varus position. The objectives of the present study were to examine how medial comminution affects fracture stability and to determine the effect of calcar fixation on osteosynthesis stability.

METHODS

Eleven matched pairs of cadaveric humeri were osteotomized to create standard three-part fractures involving the surgical neck and the greater tuberosity. Five matched pairs were randomly assigned to have the medial calcar region remain intact. Six matched pairs had removal of a 10-mm medially based wedge of bone to simulate medial comminution. All fractures were stabilized in a uniform fashion with a proximal humeral locking plate. The constructs were secured, and the superior portion of the humeral head was subjected to compressive loading to induce varus collapse. Load-to-failure and energy-to-failure values along with stiffness and displacement at the time of failure were determined.

RESULTS

Medial comminution decreased the mean load to failure by 48% (523 N) (p = 0.015) and the mean energy to failure by 44% (2009 Nmm) (p = 0.013). The use of calcar screw fixation increased the mean load to failure by 31% (219 N) (p = 0.002) and the mean energy to failure by 44% (1279 Nmm) (p = 0.006).

CONCLUSIONS

Medial comminution significantly decreased the stability of proximal humeral fracture fixation constructs. Calcar restoration with screw fixation significantly improved the stability of repaired fractures in cadaveric specimens.

CLINICAL RELEVANCE

The data suggest that medial comminution is a predictor of poor stability of proximal humeral fractures and that stability may be improved through calcar restoration.

Open reduction internal fixation of proximal humerus fractures

The treatment of proximal humerus fractures continues to evolve. While the many of these injuries can be managed nonoperatively, a certain percentage require operative treatment. Open reduction internal fixation can offer excellent outcomes when performed in the appropriate patient and utilizing proper techniques. This article reviews the most up-to-date literature regarding all phases of proximal humerus fracture osteosynthesis, including diagnosis, imaging, anatomic considerations, surgical indications, fixation, and surgical outcomes.