Fixed-angle plate fixation in simulated fractures of the proximal humerus: a biomechanical study of a new device

Biomechanical effects of different loads and constraints on finite element modeling of the humerus

Currently, there is no established finite element (FE) method to apply physiologically realistic loads and constraints to the humerus. This FE study showed that 2 'simple' methods involving direct head loads, no head constraints, and rigid elbow or mid-length constraints created excessive stresses and bending. However, 2 'intermediate' methods involving direct head loads, but flexible head and elbow constraints, produced lower stresses and bending. Also, 2 'complex' methods involving muscles to generate head loads, plus flexible head and elbow constraints, generated the lowest stresses and moderate bending. This has implications for FE modeling research on intact and implanted humeri.

Biomechanical Analysis of Combined Medial Calcar and Lateral Locked Plating Versus Isolated Lateral Locked Plating of Proximal Humerus Fractures

OBJECTIVE

Medial calcar buttress plating combined with lateral locked plating is biomechanically tested against isolated lateral locked plating in synthetic humeri models for the treatment of proximal humerus fractures.

METHODS

Proximal humerus fractures (OTA/AO type 11-A2.1) were manufactured in 10 pairs of Sawbones humeri models (Sawbones, Pacific Research Laboratories, Vashon Island, WA). Specimen were randomly assigned and instrumented with either medial calcar buttress plating combined with lateral locked plating (CP) or isolated lateral locked plating (LP). Nondestructive torsional and axial load tests were performed to evaluate construct stiffness. Large-cycle axial tests were conducted followed by destructive ramp-to-failure tests. Cyclic stiffness was compared in both nondestructive and ultimate failure loads. Failure displacement was recorded and compared between groups.

RESULTS

The addition of medial calcar buttress plating to lateral locked plating constructs significantly increased the axial ( P < 0.01) and torsional ( P < 0.01) stiffness of the construct compared with isolated lateral locked plating by 95.56% and 37.46%, respectively. All models demonstrated greater axial stiffness ( P < 0.01) after 5000 cycles of axial compression, not dependent on the fixation method. During destructive testing, the CP construct withstood 45.35% larger load ( P < 0.01) and congruently exhibited 58% less humeral head displacement ( P = 0.02) before failure when compared with the LP construct.

CONCLUSION

This study demonstrates the biomechanical superiority of medial calcar buttress plating when combined with lateral locked plating as compared with isolated lateral locked plating of OTA/AO type 11-A2.1 proximal humerus in synthetic humeri models.

A Standardized Operative Protocol for Fixation of Proximal Humeral Fractures Using a Locking Plate to Minimize Surgery-Related Complications

The current literature suggests that up to 55% of complications after plate osteosynthesis treatment for patients with proximal humerus fractures are attributed to the surgical procedure. The hypothesis of this study was that a standardized surgical protocol would minimize surgery-related adverse events. This prospective cohort study included 50 patients with a mean age of 63.2 (range 28-92) years treated by one single surgeon using a previously published standardized surgical protocol. Clinical and radiological follow-up examinations were conducted for up to 24 months using Constant-Murley Score (CS), Subjective Shoulder Value (SSV) and radiographs in true anteroposterior, axial and y-view. Finally, CS was 73.9 (standard deviation [SD]: 14.0) points (89% compared to the uninjured shoulder), and SSV was 83.3% (SD: 16.7) at two years of follow-up. Postoperative radiologic evaluation revealed no primary surgical-related or soft-tissue-related complications (0%). The main complications were secondary, biological complications (20%), largely represented by avascular necrosis (8%). Eight patients underwent revision surgery, mainly for implant removal. In addition, a total of four patients were revised using a hemiarthroplasty (n = 2), reverse shoulder arthroplasty (n = 1) or re-osteosynthesis. The use of our standardized surgical technique on proximal humerus fractures improves fixation with regard to primary stability and prevents primary, surgical-technique-related complications. The subjective grading of a high level of difficulty surgery was associated with more complications.

Effect of Calcar Screw in Locking Compression Plate System for Osteoporotic Proximal Humerus Fracture: A Finite Element Analysis Study

This study proposes a finite element analysis (FEA) model for complex fractures at the osteoporotic proximal humerus and investigates the relevance of using a calcar screw in surgical treatments using this model. Two types of three-dimensional (3D) fracture models of patients with osteoporotic humerus were constructed reflecting the mechanical properties of the osteoporotic humerus, such as the Young’s modulus and Poisson’s ratio, and two load conditions mimicking the clinical environment were applied for simulation. Using the 3D models and the conditions, the FEA software calculated the concentration and distribution of stresses developing in the humerus, locking compression plate (LCP), and screws. Then, we evaluated and predicted the fixed state of a LCP system depending on whether the maximum stress value exceeded tensile strength. When axial force was applied, insertion of the calcar screw led to significant reduction of stress applied on screws in the fracture model having a medial gap by approximately 61%, from 913.20 MPa to 351.84 MPa. Based on the results, it was clearly confirmed that using of calcar screws improved the stability of a three-part fractures and simultaneously reinforced medial support.

Biomechanical study of Proximal humeral fracture fixation: Locking plate with medial support screw vs. locking plate with intramedullary fibular graft

BACKGROUND

The purpose of this study was to evaluate the biomechanical properties of two different fixation constructs in varus collapse proximal humerus fracture, locking plate with medial support screw and locking plate with intramedullary fibular graft.

METHODS

We used 8 pairs of undamaged fresh-frozen humen cadaveric humeri and fibula from patients ranging in age from 62 to 81 years. We simulated a proximal humerus fracture with medial comminution using wedge shaped osteotomy. One group was fixed with locking plate with medial support screws, the other group with locking plate with intramedullary fibular graft. Biomechanical test was carried out using servohydraulic material testing system. We measured displacement of specimens under cyclic load test, maximum failure load, initial stiffness, and mode of failure under increasing load test.

FINDINGS

Under cyclic loading, the displacement of the specimen was significantly less in the locking plate with fibular strut graft group than in the locking plate with medial support screws group. (p = 0.012) Under increasing load test, the Locking plate with fibular strut graft group showed higher values in both maximum failure load and initial stiffness than the Locking plate with medial support screws group, and this was statistically significant. (p = 0.012, p = 0.001).

INTERPRETATION

In biomechanical study, the locking plate with fibular strut graft showed significantly better results in all of the maximum failure load, initial stiffness, and gap depletion compared to the locking plate with medial support screws.

LEVEL OF EVIDENCE

Level IV.

Medial cortical positive support: A key factor for the postoperative stability of proximal humerus fractures

Treatments for proximal humerus fractures (PHFs) often fail to achieve anatomical reduction. The purpose of this study was to evaluate the role of positive medial cortical support (PMCS) in the nonanatomical reduction of PHFs.A retrospective analysis was performed of 78 patients with PHFs who underwent surgery from August 2014 to September 2017 and whose treatments did not achieve anatomical reduction. Based on the results of standard AP radiographs of the shoulders 3, 6, and 12 months after surgery, the patients were divided into PMCS or negative medial cortical support (NMCS) groups. The postsurgical change in head-shaft angle (HSA) between the 2 groups was compared. Shoulder joint function and visual analog scale (VAS) scores of the 2 groups were also compared at the same time.Of the 78 patients analyzed, 37 were in the PMCS group and, 41 in the NMCS group. There was no statistically significant difference in any of the characteristics of the 2 groups (P > .05), or in postsurgical HSA. However, the HSA of the 2 groups had become significantly different (P < .05) 3, 6, and 12 months following surgery. The changes in HSA of the 2 groups were different at various time points (P < .05). One year after surgery, the shoulder function score of the PMCS group was significantly better than that of the NMCS group, as was the VAS score (both P < .05).Patients whose surgery for PHF does not achieve anatomical reduction during surgery can undergo PMCS to achieve improved results, postoperatively. NMCS should be avoided as far as possible.

Arthroscopic-Assisted Removal of Proximal Humerus Locking Plates With Capsular Release Significantly Improves Range of Motion and Function

Purpose

To investigate the clinical outcomes following the arthroscopic removal of proximal humerus locking plates for symptomatic hardware after open reduction and internal fixation (ORIF) of proximal humerus fractures.

Methods

Patients who underwent arthroscopic removal of hardware (ROH) with capsular release due to pain and/or immobility after receiving locking plates to treat proximal humerus fractures from 2009 to 2016 were identified. Operative and clinic records were reviewed to obtain demographic information, concomitant procedures during ROH, and pre- and postoperative active shoulder range of motion. Postoperative patient-reported outcomes included the QuickDASH, PROMIS Pain Intensity, Constant, and University of California, Los Angeles shoulder rating scale.

Results

In total, 88 patients were included. Patients were evaluated at a minimum of 6 weeks postoperatively after ROH. Patients with pre- and postoperative active range of motion values demonstrated significant improvements in mean forward elevation (n = 69; 78.4%; 115.1° to 152.1°, P < .001), abduction (n = 29; 33.0%; 70.9° to 138.7°, P < .001), external rotation (n = 49; 55.7%; 43.7° to 58.6°, P = .012), and internal rotation (n = 45; 51.1%; 25.7° to 61.9°, P < .001). Patients also reported positive patient-reported scores, including the QuickDASH (4.1 ± 7.8), PROMIS Pain Intensity (3.5 ± 0.9), Constant (84.6 ± 10.7), and University of California, Los Angeles shoulder rating scale (33 ± 2.9), which were measured 70.6 ± 26.6 months postoperatively. There were no surgical complications, no arthroscopic cases were converted to open, but 2 reported refractures (2.3%).

Conclusions

Arthroscopic-assisted removal of proximal humerus locking plates significantly improves motion and function while allowing for management of concomitant shoulder pathology and potentially avoiding open surgery complications. Given that patients undergoing this procedure frequently have multiple comorbidities, arthroscopic-assisted removal with smaller incisions may minimize risks while restoring shoulder mobility. Therefore, arthroscopic ROH for patients experiencing symptomatic hardware after ORIF is recommended.

Level of Evidence

Level IV, therapeutic case series.

Recent Trends, Technical Concepts and Components of Computer-Assisted Orthopedic Surgery Systems: A Comprehensive Review

Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.

Low complication rates in Minimally Invasive Plate Osteosynthesis (MIPO) for proximal humeral fractures at 5 years of follow-up

INTRODUCTION

Purpose of this study was to analyse the medium term follow-up of minimally invasive plate osteosynthesis (MIPO) for proximal humeral fractures in terms of postoperative shoulder function, radiological outcome and complications.

METHODS

76 consecutive patients with unstable proximal humeral fractures were treated using locking plate with a minimally invasive antero-lateral approach in two surgical centers. Constant score and radiographic evaluation of 74 patients were available at mean follow up of 5 years (minimum 4 years).

RESULTS

Mean Constant score was 74 (range to 28-100). Results were comparable in the two centers. Younger patients registered significantly higher scores (p < 0.05). 20 patients (27%) developed complications. Subacromial impingement occurred in 16,2% of cases for varus malreduction (6,7%) and for too proximal plate positioning (9,5%). Primary screws perforation (2,7%), secondary perforation due to cut-out (1,4%), avascular necrosis (AVN) of humeral head (1,4%), partial resorption of greater tuberosity (2,7%), secondary displacement of the greater tuberosity (2,7%) and stiffness (2,7%) were observed.

DISCUSSION AND CONCLUSIONS

Even at a medium term follow-up, MIPO for proximal humeral fractures ensured good and reproducible results for most common pattern of fractures. Major complications were lower respect to open procedures, because of soft tissue, deltoid muscle and circumflex vessels sparing.

The elderly have similar outcomes compared to younger patients after ORIF with locking plate for comminuted proximal humerus fracture

Objective

The aim of this study was to compare clinical and radiological outcomes of elder and younger patients with comminuted proximal humerus fracture treated with osteosynthesis with locking plate.

Methods

A total of 70 patients (30 males and 40 females; mean age 65.4 years) operated on for Neer 3- or 4-part proximal humeral fractures between 2010 and 2016 and followed for at least one-year were included in the study. The reduction was achieved through intraosseous window to minimize soft tissue stripping in all patients and structural allograft at metaphyseal diaphyseal junction was used aggressively to resist varus force. Group 1 consisted of 32 patients aged 70 or older (14 males and 18 females; mean age: 77.8 ± 5.1), while Group 2 consisted of 38 patients younger than 70 (16 males and 22 females; mean age: 58.2 ± 9.3). The groups were compared for their clinical and radiological outcomes.

Results

There was no significant difference in clinical outcomes by Oxford score (54.8 ± 2.7 vs 56.6 ± 3.4, p = 0.13) and ASES score (89.7 ± 5.7 vs 90.8 ± 8.2, p = 0.68). Two groups had similar radiological outcomes regarding neck shaft angle, greater tip height and offset. However, group 2 had better final shoulder forward elevation (162.6 ± 8.7 vs 135.4 ± 14.7ß, p < 0.05) and shorter duration to achieve maximal range of motion (4.37 ± 2.37 vs 8.14 ± 3.25 months, p < 0.05) than group 1. Two groups had similar complication rates (9.4% vs 7.9%). All the complications were related to greater tuberosity including mal-reduction and avulsion.

Conclusion

With the prerequisite of good alignment with robust medial cortical support and untouched soft tissue over medial metaphysis area via intra-osseous reduction, comminution of proximal humeral fracture can achieve satisfactory result and low complication rate by osteosynthesis with locking plate system, regardless of age. In addition, we suggested to use structural bone graft for comminuted medial cortex fracture with multiple fragments or bony defect more than 2 cm.

Level of evidence

Level III Therapeutic study.

Effect of screw thread length on stiffness of proximal humerus locking plate constructs: A finite element study

Plate-based treatment of proximal humerus fractures is associated with a high risk of complications such as screw perforation into glenohumeral joint. Smooth and threaded pegs were developed with the hope of minimising these risks. No consensus exists onto which threading profile achieves stiffest bone-plate construct. This study investigated the biomechanical effect of five percentages of threading on individual humeral head screws on a bone-plate construct. A finite element model simulating a two-part proximal humerus fracture treated with a Spatial Subchondral Support plate was developed and validated against in vitro biomechanical tests. The proportion of the humeral head screw length that was threaded was varied between 0%-100% in 25% increments. A 5-mm cantilever varus displacement was applied and the required load (F₅) was calculated. Full (100%) threading achieved the stiffest construct for all six screws. Fully threading all smooth pegs at once increased F₅ by 18%. Threading did not increase F₅ equally in all screws. Inferior three plate screws exhibited a larger increase in stiffness than superior three. Most of the mechanical benefits of threading in inferior three screws can be achieved by using threaded pegs (50% threading) while the superior three screws need to be fully threaded. In practice, the smooth surface profile may also offer additional mechanical benefits if implanted with longer lengths and larger diameters. Threading is an effective way of increasing the varus bending stiffness of proximal humerus plates constructs.

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.].

Complex Proximal Humeral Fracture Fixation with PHILOS Plate using Minimal Invasive Percutaneous Plate Osteosynthesis (MIPPO) Technique: A Series of 30 Patients

Introduction: Proximal humerus fracture fixation using plate osteosynthesis depends on the quality of the bone, design of the fixation devices and intra-operative soft tissue dissection. This study evaluates the functional outcome of minimally invasive percutaneous plate osteosynthesis using locking compression plate in proximal humerus fracture treatment.

Materials and Methods: The study was conducted on 30 patients with complex proximal humerus fractures treated by minimally invasive percutaneous plate osteosynthesis using locking compression plate (PHILOS). There were 21 males and 9 females. The average age of our study group was 58.8 years. All the patients were evaluated at six weeks, three months, four months, six months and 12 months following surgery.

Results: All patients had fracture union at an average of 13.2 weeks. The mean DASH score at the follow-up was 8.69 (2.5 to 17.16), the average range of flexion was 143.83 degrees (100 to 170 degrees) and abduction was 121.49 degrees (90 to 160 degrees). We had superficial infection in three patients which resolved with a short course of antibiotics. There was excellent outcome in 26 patients, good and fair in two patients each.

Conclusion: Proximal humerus fractures treated with minimally invasive percutaneous plate osteosynthesis using locking compression plate with minimal soft tissue dissection, provides good functional outcome and early return of shoulder function.

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.

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.

Comparison of intramedullary fibular allograft with locking compression plate versus shoulder hemi-arthroplasty for repair of osteoporotic four-part proximal humerus fracture: Consecutive, prospective, controlled, and comparative study

OBJECTIVES

To compare the outcomes of intramedullary fibular allograft (IFA) with locking compression plates (LCPs) versus shoulder hemi-arthroplasty (HA) in osteoporotic four-part proximal humeral fracture (PHF).

METHODS

Between January 2010 and December 2012, totally 60 cases with osteoporotic four-part PHF were enrolled in this study and were randomly separated into IFA and LCPs group and HA group (n=30). Additionally, surgery indexes for patients in the two groups, such as Constant-Murley score (CMS), the Disability of Arm, Shoulder and Hand (DASH) score, individual subject evaluation of the outcomes, plain X-ray, and computer tomography (CT) scanning were evaluated and compared.

RESULTS

CMS, DASH score, activities of daily living (ADL), and range of motion (ROM) were statistically higher in the IFA and LCPs group than those in the HA group at the last follow-up, whereas the pain were obviously lower than that in the HA group. Besides, patients in the IFA and LCPs group had higher abduction, external rotation with elbow, strength, and satisfactory rating compared with HA group at the last follow-up. However, one case developed avascular necrosis (AVN), one case encountered screw perforation, and one case experienced varus displacement in the IFA and LCPs group, while there were 2, 4, and 2 cases suffered from superficial infection, shoulder stiffness, tuberosity migration in the HA group, respectively.

CONCLUSION

IFA with LCP have an advantage in functional outcomes than shoulder HA.

LEVEL OF EVIDENCE

Level II. Prospective cohort study.

Minimally invasive plate osteosynthesis for proximal humeral fractures

PURPOSE

To report the outcome after minimally invasive plate osteosynthesis (MIPO) through the deltoid-splitting approach for proximal humeral fractures.

METHODS

10 men and 30 women aged 37 to 88 years underwent MIPO through the deltoid-splitting approach using the Proximal Humerus Internal Locking System or the Locking Proximal Humerus Plate for 2-part (n=18), 3-part (n=20), and 4-part (n=2) proximal humeral fractures. The rehabilitation protocol was standardised.

RESULTS

All 40 patients were followed up at 3 months, 34 (85%) at 6 months, 30 (75%) at one year, and 13 (33%) at 2 years. Two patients had malunion. No patient had avascular necrosis, infection, nerve palsy, or nonunion. The mean Constant score at one year and 2 years was 75 and 87.5, respectively. The Constant score at 6 months correlated to that at one year (r=0.926, p<0.0001) and at 2 years (r=0.874, p=0.0001). In younger patients, improvement in the range of motion was faster. The early plateau group (those with no further improvement after 6 months) and the late plateau group (those with no further improvement after one year) did not differ significantly in age, fracture grade, or hand dominance.

CONCLUSION

MIPO for fixation of proximal humeral fractures using a locking plate is safe and effective in enabling an early return of shoulder function.

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.

A comprehensive update on current fixation options for two-part proximal humerus fractures: a biomechanical investigation

BACKGROUND

Recent advancements in implant technology offer updated options for surgical management that have been rapidly adopted into clinical practice. The objective of this study is to biomechanically test and compare the current fixation options available for surgical fixation of two-part proximal humerus fractures and establish load to failure and stiffness values.

METHODS

Sixteen match-paired (32 total) fresh-frozen, cadaveric specimens were randomized to receive 1 of 4 fixation constructs following creation of an AO/OTA Type 11A3 (two-part) proximal humerus fractures. Fixation constructs tested consisted of 3.5 mm fixed angle plate (3.5-FAP), 4.5 mm fixed angle plate (4.5-FAP), humeral intramedullary nail (IMN), and a humeral intramedullary nail with a fixed angle blade (IMN-FAB). Specimen bone density was measured to ensure no adequate, non-osteoporotic bone. Constructs were tested for stiffness and ultimate load to failure and compared via one-way ANOVA analysis with subsequent post hoc Tukey HSD multiple group comparison statistical analysis.

RESULTS

The IMN-FAB construct was significantly stiffer than the 3.5-FAP construct (123.8 vs. 23.9, p<0.0001), the 4.5-FAP construct (123.8 vs. 33.3, p<0.0001) and the IMN construct (123.8 vs. 60.1, p=0.005). The IMN-FAB construct reported a significantly higher load to failure than the 3.5-FAB construct (4667.3 N vs. 1756.9 N, p<0.0001), and the 4.5-FAP construct (4667.3 N vs. 2829.4 N, p=0.019, Table 2). The IMN construct had a significantly higher load to failure than the 3.5-FAP construct (3946.8 vs. 1756.9, p=0.001, Table 2).

CONCLUSION

Biomechanical testing of modern fixation options for two-part proximal humerus fracture exhibited that the stiffest and highest load to failure construct was the IMN-FAB followed by the IMN, 3.5-FAP and then the 4.5-FAP constructs. However, prospective clinical trials with longer-term follow-up are required for definitive assessment of the ideal fixation construct for surgical management of two-part proximal humerus fractures.

Outcomes evaluation of locking plate osteosynthesis in displaced fractures of the proximal humerus

Objective

To evaluate functional outcomes, radiographic findings and complications of proximal humeral fractures treated with locking plates and to determine prognostic factors for successful clinical outcomes.

Methods

Forty patients undergoing internal fixation of fractures of the proximal humerus with the Philos^® plate were included in the study. The surgeries were performed between 2004 and 2011 and the patients underwent radiographic and clinical evaluation, by Constant–Murley and Dash score. Outcomes were analyzed by use of multivariate regression with several different variables.

Results

Patients were on average of 61.8 ± 16.28 years, and most were female (70%). The Constant–Murley score was 72.03 ± 14.01 and Dash score was 24.96 ± 19.99. The postoperative radiographs showed a head-shaft angle of 135.43° ± 11.82. Regression analysis showed that the patient's age and the Hertel classification influenced the Constant–Murley scale (p = 0.0049 and 0.012, respectively). Other prognostic criteria such as Neer and AO classification, head-shaft angle, the presence of metaphyseal comminution and extension of the humeral metaphyseal fragment showed no effect on prognosis. Complications occurred in four patients (10%).

Conclusion

The fixation with the Philos^® plate provided good clinical and radiographic results in fractures of the proximal humerus, with a low complication rate. Patient's age and Hertel classification were defined as prognostic factors that led to worse functional outcomes.

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.

Effect of calcium triphosphate cement on proximal humeral fracture osteosynthesis: a cadaveric biomechanical study

PURPOSE. To evaluate the effect of filling a central humeral bone void with calcium triphosphate cement on the strength and stability of an osteosynthesis in elderly cadavers. METHODS. 14 fresh cadaveric shoulder specimens obtained from 11 donors (mean age, 91.5 years; mean body weight, 61 kg) were divided into 2 age- and sex-matched groups. A standardised 3-part proximal humeral fracture with a central bone void was created in each specimen. Each specimen was reduced and fixed with a locking plate. In half the specimens the central bone void was packed with calcium triphosphate cement. The intra-fragmentary motion and the load and mode of failure were recorded. RESULTS. Respectively in the test group and controls, the intra-fragmentary motion was 1.0 and 6.4 mm, and the peak displacement at the 500 N load was 1.8 and 9.1 mm. The Cohen's d was 1.6 to 2.7 for all load steps, indicating a large effect of the calcium triphosphate cement on strength and stability. The mean difference in the failure load was 300 N (p<0.05). CONCLUSION. Construct stability and failure load improved significantly when the central humeral bone void was filled with calcium triphosphate cement.

Biomechanical analysis of a novel locking plate with smooth pegs versus a conventional locking plate with threaded screws for proximal humerus fractures

BACKGROUND

Repair of proximal humeral fractures with locking plates has greatly improved outcomes. However, an alarming rate of complications including screw cutout and impingement under the acromion has recently been reported. A novel locking plate with smooth pegs was developed to reduce these risks. The purpose of this study was to compare these 2 fixation methods with a cadaveric biomechanical study.

MATERIALS AND METHODS

Fourteen pairs of cadaveric proximal humeri (mean age, 77 years) were harvested, and bone density was measured. Osteosynthesis was performed on each pair using either a locking plate with threaded screws (TS group) or smooth pegs (SP group) on the contralateral side. Seven pairs of humeri were tested for cyclic bending, and 7 pairs for cyclic torsional evaluation: TS bending, SP bending, TS torsion, and SP torsion. The bending protocol consisted of cyclically loading to a maximum of 7.5 Nm bending moment for 10,000 cycles. The torsion protocol consisted of ±2 Nm of axial torque for 10,000 cycles. Surgical neck fractures were simulated by excising a 10-mm wedge of bone.

RESULTS

No implant failure or screw cutout was observed in any of the groups tested. Under bending loads, mean displacement of the distal fragment was significantly less for the SP group than that for the TS group over 5,000 cycles. In torsion tests, no significant differences were observed between the 2 fixation methods.

DISCUSSION

The SP group demonstrated superior biomechanical characteristics to the TS group in regards to cyclic bending.

Locking plate fixation of fractures of the proximal humerus: analysis of complications, revision strategies and outcome

BACKGROUND

Locking plates for open reduction-internal fixation (ORIF) of proximal humeral fractures are widely used. We observed an unusually high number of patients with complications referred to our institution. It was the purpose of this study to report these complications, as well as their treatment and outcome.

MATERIALS AND METHODS

From 2003 to 2010, all patients treated for complications after ORIF with locking plates for proximal humeral fractures were prospectively collected and retrospectively analyzed. Patients were followed up clinically and radiographically.

RESULTS

In total, 121 patients (67 women and 54 men; mean age, 59 years) were referred after primary locking plate ORIF; 80% had a 3- or 4-part fracture. A mean of 3 complications occurred per patient, including malreduction, primary screw cutout, malunion, nonunion, avascular necrosis, and infection. Secondary screw cutout was found in 57% of patients, causing glenoid destruction in 33% of patients. A mean of 1.5 revision surgeries were needed. Hemiarthroplasty, total shoulder arthroplasty, and reverse shoulder arthroplasty improved the mean Constant score (24 to 55 points, P < .05; 29 to 54 points, P = .3; and 25 to 48 points, P < .05, respectively) after a mean of 24 months. In 6 patients, glenoid implantation was no longer possible because of the destruction by perforated head screws.

CONCLUSION

In this negatively selected series, complications resulted in secondary arthroplasties in over 50% of the patients. Shoulder function, though improved, remained substantially restricted even after revision surgery. Glenoid destruction by locking screws was the most devastating and previously almost unseen complication, which limited the options of treatment.

Short, locked humeral nailing via Neviaser portal: an anatomic study

OBJECTIVE

Supraspinatus tendon trauma may contribute to residual shoulder pain after nail fixation for proximal humeral fractures. Some have proposed a more medial starting point for humeral nail insertion to avoid cuff tendon footprint damage. We hypothesized that percutaneous nail insertion via Neviaser portal would not only be possible, but would avoid tendon trauma, while sacrificing articular cartilage.

MATERIALS AND METHODS

Under c-arm guidance and in percutaneous fashion, we nailed 16 consecutive complete (head and neck, etc, intact) specimen right proximal humeri with locked short humeral nails (Aequalis) via Neviaser portal. Each shoulder was dissected to study the damage to the rotator cuff and long head of the biceps tendons as well as to the articular surfaces. We measured the humeral-thoracic abduction arc before the damaged articular surface contacted the superior glenoid. There were 5 male specimens and 11 female specimens with a mean age of 83 years at the time of death.

RESULTS

We successfully inserted 15 of 16 humeral nails through this percutaneous approach. No supraspinatus tendon or long head of the biceps tendon was damaged. All nails passed entirely through supraspinatus muscle belly. Thirteen of 15 starting points were entirely on articular surface. Mean arc of abduction before superior glenoid contact was 76 degrees (range, 50 degrees-130 degrees). Mean distance from the edge of the articular surface to the most lateral part of the nail insertion was 11 mm (0-25 mm).

CONCLUSIONS

Short, locked humeral nail insertion is possible in percutaneous fashion via Neviaser portal without tendon injury. However, successful insertion comes at the cost of articular cartilage damage.

Biomechanics of four techniques for fixation of the four-part humeral head fracture

OBJECTIVE:

To carry out a biomechanical study of four techniques for fixation of four-part humeral head fractures.

METHODS:

The fracture was reproduced in 40 plastic humeri, divided into groups of ten according to the fixation technique, each one employing different fixation resources, in different configurations. The humeral models were mounted on an aluminum scapula, with leather straps simulating the rotator cuff tendons, and submitted to bending and torsion tests in a universal testing machine, using relative stiffness as an evaluation parameter. Assemblies with intact humeri were analyzed for comparison.

RESULTS:

The biomechanical behavior of the fixation techniques varied within a wide range, where the assemblies including the DCP plate and the 4.5mm diameter screws were significantly more rigid than the assemblies with the Kirschner wires and the 3.5mm diameter screws.

CONCLUSION:

The four fixation techniques were able to bear loads compatible with the physiological demand, but those with higher relative stiffness should be preferred for clinical application.

Laboratory investigation

.

Plating of proximal humeral fractures

The optimal treatment for proximal humeral fractures is controversial. Few data exist concerning the influence of the surgical approach on the outcome. The purpose of this study was to evaluate the clinical and radiological outcomes of proximal humeral fractures treated with locking plate fixation through a deltopectoral vs an anterolateral deltoid-splitting approach. Of 86 patients who met the inclusion criteria, 70 were available for follow-up examination. Thirty-three patients were treated through a deltopectoral approach and 37 through an anterolateral deltoid-splitting approach. In all cases, open reduction and internal fixation with a PHILOS locking plate (Synthes, Umkirch, Germany) was performed. Clinical follow-up included evaluation of pain, shoulder mobility, and strength. Constant score and Disabilities of the Arm, Shoulder and Hand (DASH) score were assessed. A clinical neurological examination of the axillary nerve was also performed. Consolidation, reduction, and appearance of head necrosis were evaluated radiographically. After a mean follow-up of 33 months, Constant scores, DASH scores, and American Shoulder and Elbow Surgeons scores showed no significant differences between the groups. Clinical neurologic examination of the axillary nerve revealed no obvious damage to the nerve in either group. Deltopectoral and anterolateral detoid-splitting approaches for plate fixation of proximal humeral fractures are safe and provide similar clinical outcomes. The results of this study suggest that the approach can be chosen according to surgeon preference.

Retrograde nailing versus locking plate osteosynthesis of proximal humeral fractures: a biomechanical study

BACKGROUND

In locking plate osteosynthesis of proximal humeral fractures, secondary varus malalignment is a specific complication. Retron nails (Tantum AG, Neumunster, Germany), among others, have been designed to improve medial support of the calcar humeri. The aim of our biomechanical study was to examine whether Retron nails provide increased stiffness for axial loads and adequate stiffness for torsional loads when compared with Philos plates (Synthes AG, Umkirch, Germany).

MATERIALS AND METHODS

Twenty-two fresh-frozen paired humeri were collected. After potting the specimens, intact bones were exposed to sinusoidal axial (10-120 N) and torsional (±2.5 Nm) loading for 8 cycles to calculate the initial stiffness and exclude pairs with differences. Afterward, an unstable proximal humeral fracture (AO 11-A3) was created by means of an oscillating saw, and the respective osteosynthesis devices were implanted. After another 4 cycles, initial changes in stiffness were measured. Subsequently, all specimens were tested for 1,000 cycles of loading before final stiffness was assessed.

RESULTS

We found no statistically significant differences between Retron and Philos specimens after 4 or 1,000 cycles of loading.

CONCLUSION

Our study suggests that retrograde nailing provides sufficient stability for axial and torsional loading in 2-part fractures of proximal humeri.

Clinical outcome and complications using a polyaxial locking plate in the treatment of displaced proximal humerus fractures. A reliable system?

INTRODUCTION

The surgical treatment of displaced proximal humeral fractures (ORIF) is a perpetual challenge to the surgeon. For this reason, the principle of polyaxiality was developed to provide an improved primary stability of the fracture through better anchorage of the screws, especially in osteoporotic bone. The aim of this study was to present clinical results with the polyaxial locking plate in the operative treatment of proximal humerus fractures in order to determine whether the technique of polyaxiality leads to better functional outcome and lower complication rates in comparison to monoaxial plates in the literature.

PATIENTS AND METHODS

Seventy-three patients with displaced proximal humeral fractures were treated surgically with the polyaxial locking Suture Plate™ (Arthrex(®)) between 03/2007 and 06/2009. Fifty-two of the patients (mean age, 69.9 ± 12.1) were included in a radiographical and clinical examination using the Constant score (CS) and the Disabilities of the Arm, Shoulder and Hand score (DASH).

RESULTS

The follow-up examinations were on average 13.9 ± 4.5 months (10-27 months) after surgical treatment. The mean CS of the patients was 66.0 ± 13.7 points, the age- and gender-related CS was 90.9% ± 20.0% and the mean DASH score was 23.8 ± 19.8 points for the injured side. The patients with a nearly anatomical reduction of their fracture (n = 13) reached a significantly higher CS (75.1 ± 8.5; p = 0.004) and DASH-score (13.6 ± 11.6; p = 0.043) and none of these patients had a complication. The complications were identified in 12 (23.1%) cases, 5 of which involved loss of reduction. All of these 5 cases were lacking of initial medial column support and 4 of which were type C2.3 AO-Classification.

CONCLUSION

The data show that the combination of angular stability with the possibility of variable polyaxial screw direction is a good concept for reduction and fixation of displaced proximal humeral fractures, but anatomical reduction and medial support remain important preconditions for a good outcome. However, a significantly lower rate of complications or better clinical outcome than that reported in the literature could not be found.

The biomechanical performance of locking plate fixation with intramedullary fibular strut graft augmentation in the treatment of unstable fractures of the proximal humerus

We evaluated the biomechanical properties of two different methods of fixation for unstable fractures of the proximal humerus. Biomechanical testing of the two groups, locking plate alone (LP), and locking plate with a fibular strut graft (LPSG), was performed using seven pairs of human cadaveric humeri. Cyclical loads between 10 N and 80 N at 5 Hz were applied for 1 000 000 cycles. Immediately after cycling, an increasing axial load was applied at a rate of displacement of 5 mm/min. The displacement of the construct, maximum failure load, stiffness and mode of failure were compared.

The displacement was significantly less in the LPSG group than in the LP group (p = 0.031). All maximum failure loads and measures of stiffness in the LPSG group were significantly higher than those in the LP group (p = 0.024 and p = 0.035, respectively). In the LP group, varus collapse and plate bending were seen. In the LPSG group, the humeral head cut out and the fibular strut grafts fractured. No broken plates or screws were seen in either group.

We conclude that strut graft augmentation significantly increases both the maximum failure load and the initial stiffness of this construct compared with a locking plate alone.

Avascular necrosis following fracture-dislocation of the hip and spontaneous relocation

Injuries occurring during soccer tend to occur with lower energy transfer than in some other contact sports. Tibial and femoral shaft fractures occasionally occur, but pelvic fractures are rare. We report a case of a missed posterior acetabular rim fracture, caused by a low energy trauma playing soccer, complicated by the development of avascular necrosis (AVN) of the femoral head and subsequent osteoarthritis.

Resultados do tratamento das fraturas do terço proximal do úmero com placas de bloqueio

OBJETIVO: Avaliação dos resultados do tratamento das fraturas do terço proximal do úmero com placa de bloqueio proximal. MÉTODOS: No período de novembro de 2003 a janeiro de 2008, os autores realizaram 34 osteossínteses em 33 pacientes com fratura do úmero proximal, sendo 17 fraturas tipo II de Neer, 13 do tipo III e quatro do tipo IV. A média de idade foi de 57 anos (33 a 86), sendo 14 pacientes do sexo masculino e 19 do sexo feminino. Todos os pacientes foram operados na fase aguda da fratura, até uma semana após o trauma. Os pacientes foram tratados com redução aberta e fixação interna utilizando placas de bloqueio. A técnica utilizada, o implante, o tempo de imobilização e protocolo de reabilitação foram os mesmos para todos os pacientes. O seguimento médio foi de 24 meses (8 a 60 meses). RESULTADOS: A avaliação funcional foi realizada através do escore da Universidade da Califórnia em Los Angeles (UCLA). Foram obtidos 31 (91,2%) excelentes e bons resultados, e 3(8,8%) maus resultados. CONCLUSÃO: Observamos ser eficaz este método de fixação interna para fraturas do terço proximal do úmero.

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

BACKGROUND

Comminuted proximal humerus fracture fixation is controversial. Locked plate complications have been addressed by anatomic reduction or medial cortical support. The relative mechanical contributions of varus malalignment and lack of medial cortical support are presently assessed.

METHODS

Forty synthetic humeri divided into three subgroups were osteotomized and fixed at 0 degrees, 10 degrees, and 20 degrees of varus malreduction with a locking proximal humerus plate (AxSOS, Global model; Stryker, Mahwah, NJ) to simulate mechanical medial support with cortical contact retained. Axial, torsional, and shear stiffness were measured. Half of the specimens in each of the three subgroups underwent a second osteotomy to create a segmental defect simulating loss of medial support with cortex removed. Axial, torsional, and shear stiffness tests were repeated, followed by shear load to failure in 20 degrees of abduction.

RESULTS

For isolated malreduction with cortical contact, the construct at 0 degrees showed statistically equivalent or higher axial, torsional, and shear stiffness than other subgroups examined. Subsequent removal of cortical support in half the specimens showed a drastic effect on axial, torsional, and shear stiffness at all varus angulations. Constructs with cortical contact at 0 degrees and 10 degrees yielded mean shear failure forces of 12965.4 N and 9341.1 N, respectively, being statistically higher (p < 0.05) compared with most other subgroups tested. Specimens failed primarily by plate bending as the humeral head was pushed down medially and distally.

CONCLUSIONS

Anatomic reduction with the medial cortical contact was the stiffest construct after a simulated two-part fracture. This study affirms the concept of medial cortical support by fixing proximal humeral fractures in varus, if absolutely necessary. This may be preferable to fixing the fracture in anatomic alignment when there is a medial fracture gap.

Clinical results for minimally invasive locked plating of proximal humerus fractures

OBJECTIVES

To describe the minimally invasive treatment of fractures of the proximal humerus using the Non-Contact-Bridging (NCB) plate. The system allows secondary locking of screws to the plate with a locking cap and polyaxial (30 degrees radius) screw placement.

DESIGN

Prospective cohort study.

SETTING

University Level I trauma center.

PATIENTS

Fifty-four patients with unstable fractures of the proximal humerus.

INTERVENTION

Minimal anterolateral acromial approach to the proximal humerus, percutaneous fracture reduction, and minimally invasive application of the NCB plate.

MAIN OUTCOME MEASUREMENTS

Constant Score and radiologic follow-up (anteroposterior and transscapular). Visual Analog Scale for subjective evaluation of pain and function.

RESULTS

After 17 months, the average Constant Score was 66.8 points (87% of the age- and sex-related normal values). Implant-related complications (plate impingement, screw perforation into the glenohumeral joint, loosening of screws) occurred in nine cases (17%). The rate of avascular necrosis was low (5.5%) and no cases of nonunion were seen.

CONCLUSIONS

The effectiveness of the NCB is similar to other published methods of treatment for fractures of the proximal humerus and potentially provides a less invasive option for this problem. Complication rates and functional outcome in this series are comparable to the literature. An important factor in this technique is the process of percutaneous fracture reduction. The NCB plate is suitable for both a minimally invasive technique or standard open reduction and internal fixation through a deltopectoral approach; the surgeon must decide which approach is best for each particular fracture pattern and should be comfortable with both techniques.

[Biomechanical investigation of fixed-angle plate osteosynthesis of the proximal humerus]

INTRODUCTION

Proximal humeral fractures are common in the elderly population and are often associated with osteoporosis. Fixation of unstable proximal humeral fractures is problematic due to loss of fixation in osteoporotic bone. Fixed-angle devices are intended to provide superior mechanical stability due to the principle of an internal fixator. The NCB(R)-PH (non-contact-bridging proximal humerus) plate is a new fixed-angle device that locks the screws to the plate by secondary insertion of a locking cap. The aim of this study was to investigate if and to what extent NCB-PH plates applied in the locked mode provide higher mechanical stability in a proximal humerus fracture model.

METHODS

For this investigation 16 (8 pairs) fresh frozen cadaveric humeri were used. An AO/ASIF 11-B 1 fracture of the proximal humerus was created in each bone and fixed with the NCB-PH plate. In a paired setting one bone was fixed with the plate in the locked mode and the other with the plate in the non-locked mode. The bones were then subjected to 100 cycles of axial loading and interfragmentary motion was measured. Bones surviving this test were subjected to load-to-failure testing and the force at which failure occurred was recorded.

RESULTS

Bones fixed with the plate in the locked mode showed a statistically significant lower (51%) interfragmentary rotation compared to bones fixed with the plate in the non-locked mode. There was also a tendency for the bones fixed with the plate in the locked mode to fail first under higher forces (16%) during load-to-failure testing.

CONCLUSION

The NCB-PH plate provides superior interfragmentary stability when used in the locked mode in a human cadaveric proximal humerus fracture model. Therefore, we recommend that all screws should be inserted in the locked mode. The results suggest that the NCB-PH plate in the locked mode provides higher primary postoperative stability thus permitting early functional treatment of the patient.

Biomechanical comparison of a proximal humeral locking plate using two methods of head fixation

HYPOTHESIS

Locking plates have emerged as the implant of choice for stabilization of proximal humeral fractures. The biomechanical properties of a locked plating system using smooth pegs vs threaded screws for fixation of the humeral head were compared to test the hypothesis that there would be no biomechanical difference between pegs and threaded screws.

MATERIALS AND METHODS

Sixteen pairs of fresh frozen cadaveric humeri were randomized to have a surgical neck gap osteotomy stabilized with a locked plate using threaded screws (n=8) or smooth pegs (n=8). The intact contralateral humerus served as a control. Each specimen was tested with simultaneous cyclic axial compression (40 Nm) and torsion (both +/-2 Nm and +/-5 Nm) for 6000 cycles. All specimens were loaded to failure. Interfragmentary motion and load-displacement curves were analyzed to identify differences between the groups. Our data were then compared to previously published forces across the glenohumeral joint to provide evidence based recommendations for postoperative use of the shoulder.

RESULTS

There was a statistically significant difference between test specimens and their paired control (P < .001) in cyclic testing and load to failure. Differences between the smooth pegs and threaded screws were not statistically significant.

DISCUSSION

There is no biomechanical difference between locked smooth pegs and locked threaded screws for proximal fragment fixation in an unstable 2-part proximal humeral fracture model.

CONCLUSION

Our study contributes to the published evidence evaluating forces across the glenohumeral joint and suggests that early use of the affected extremity for simple activities of daily living may be safe. Use of the arm for assisted ambulation requiring a crutch, cane, walker, or wheelchair should be determined on a case-by-case basis.

The results of ORIF of displaced unstable proximal humeral fractures using a locking plate

BACKGROUND/HYPOTHESIS

Surgical management of displaced unstable proximal humerus fracture remains a challenge due to poor proximal bone quality and significant deforming forces. We hypothesized that the technique of application and mechanical properties of the proximal humeral locking plate would allow successful treatment of unstable and displaced proximal humeral fractures even in the face of osteoporotic bone.

METHOD

We evaluated prospectively the results of open reduction internal fixation of 22 displaced unstable proximal humerus fractures in 22 patients utilizing a proximal humeral locking plate.

RESULTS

Results according to the ASES scoring system at a minimum of 2 years were excellent in 13, good in 4, fair in 1, and poor in 3. One patient was lost to follow-up. All fractures healed. Anatomic alignment was obtained in 72%. Two patients developed avascular necrosis of the humeral head. There were no cases of hardware failure, infection, or loss of reduction. Three separate reduction maneuvers were employed in this series depending on fracture type.

CONCLUSION

The locking plate is an excellent device in the management of displaced unstable proximal humeral fractures and is expanding the indications for ORIF in these fractures.

Biological osteosynthesis of complex proximal humerus fractures: surgical technique and results from a prospective single center trial

INTRODUCTION

Locked plating for complex proximal humerus fractures through a deltopectoral incision can be difficult due to the fracture morphology and need for fixed angle screws. Although good results have been reported with the deltopectoral approach; technical difficulties, excessive soft tissue stripping and fears of avascular necrosis have lead to the use of minimal access techniques.

METHOD

Fifteen patients with three or four part fractures were treated by locked plating through a mini-invasive lateral trans-deltoid approach. All patients were relatively young with good bone quality and had sustained a high-velocity injury. Initial closed reduction was attempted in all patients, but majority of the patients (9/15) required open reduction to achieve a satisfactory reduction.

RESULTS

Union was achieved in all patients. All fractures united with an acceptable alignment. There were no incidences of axillary nerve palsy. There were no incidences of hardware failure or loss of reduction. There were no incidences of avascular necrosis at 1-year follow-up. The mean normalized constant score at last follow-up was 85.24.

CONCLUSION

Locked plating through lateral trans-deltoid incision may offer a better alternative to the deltopectoral approach in these complex fractures where locked plating is contemplated. It respects the fracture biology, allows ease in placement of the locking plate and angle stable screws and offers a stable construct with less surgical morbidity.

Biomechanical in vitro assessment of fixed angle plating using a new concept of locking for the treatment of osteoporotic proximal humerus fractures

Locked plating attempts to improve mechanical stability via better anchorage of the screws in the bone. In 22 paired osteoporotic humeri an AO/ASIF 11-B 1 fracture was created. Locked and conventional plating using the same device of the latest generation was performed. Torsional loading around three axes (x = varus/valgus, y = flexion/extension, z = axial rotation) with an increasing moment (2, 3.5, 5 and 7.5 N·m) was applied. Interfragmentary motion within the locked group was lower for all three axes with higher cumulative survival rates (p < 0.05). The typical mode of failure was loss of fixation in the humeral head occurring earlier in the conventional group. The locking mechanism investigated provides more ultimate strength in an osteoporotic proximal humerus fracture model. Correlation with BMD suggests that this device may especially be suitable for use in osteoporotic bone.

Second generation locked plating of proximal humerus fractures--a prospective multicentre observational study

Surgical treatment of most displaced proximal humerus fractures is challenging due to osteoporosis. Locking plates are intended to provide superior mechanical stability. In a prospective multicentre study 131 patients were treated with second generation locked plating (NCB-PH, Zimmer, Inc.). The open procedure (n = 78) was performed using a deltopectoral approach; the minimally invasive technique (n = 53) involved percutaneous reduction and an anterolateral deltoid split approach. Clinical and radiological follow-up was obtained. Improvement in function (ROM) was statistically significant. Fracture type (AO) had the most significant impact on the incidence of complications. The most frequent complications detected were intra-articular screw perforation (15%) and secondary displacement (8%). Complication rate and functional outcome of the NCB-PH are comparable to reports in the literature. Not all problems are likely to be solved by this new generation of implants, i.e. secondary dislocation still occurred in 8% of our patients.

Biomechanical evaluation of 3-part proximal humerus fractures: a cadaveric study

Proximal humerus fractures occur frequently, and treatment remains controversial. This study compares stiffness in axial loading for 3 methods of fixation (locking compression plate, standard (nonlocking) proximal humerus plate, and blade plate) in a 3-part proximal humerus fracture model. Twelve paired proximal humeri were obtained from embalmed human cadavers and separated into 3 groups. Osteotomies of the surgical neck and greater tuberosity were created to simulate a 3-part proximal humerus fracture. After fixation, constructs were axially loaded in 20 degrees of abduction for 200 cycles in an Instron materials testing machine (Norwood, Massachusetts). The blade plate (mean, 146.87+/-28.9 N/mm) demonstrated 29% more mean stiffness than the standard plate (mean, 113.0+/-22.3 N/mm; P=.19). The locking compression plate (mean, 130.71+/-39.2 N/mm) exhibited 15% greater stiffness compared to the standard plate in our 3-part model (P=.58). The blade plate demonstrated 12% greater stiffness than the locking compression plate (P=.64). There was no significant difference in mean stiffness between the fixed-angle devices and the standard plate. Future in vitro and clinical studies of plate devices for proximal humerus fractures would be worthwhile to determine the benefits and limitations of various implants for specific types of fractures, including clinical performance and cost of care.

Analysis of early failure of the locking compression plate in osteoporotic proximal humerus fractures

BACKGROUND

Although there has been continuous evolution in the management of fracture fixation, treatment for osteoporotic proximal humerus fractures is still challenging to trauma surgeons. The purpose of this study was to report early failure of the locking compression plate (LCP) in the treatment of osteoporotic proximal humerus fracture and characterize the mode of failure.

METHODS

Nine patients, older than 65 years, underwent internal fixation with the use of a locking compression plate and had early failure within 4 weeks postoperatively. According to Neer's classification, five were included in a two-part surgical neck fracture, three in a three-part fracture, and one in a four-part fracture.

RESULTS

All failures occurred with back-out of the plate-screw construct, leading to varus displacement in eight patients and plate breakage in one. Revision surgery was performed in six patients using replating and tension band wiring with a bone graft, and three patients underwent hemiarthroplasty. The average UCLA score was 25 points for the hemiarthroplasty group and 30 points for the reconstruction group.

CONCLUSIONS

Early postoperative failure of the LCP developed within 4 weeks with a presentation of en bloc back-out of the plate-screw construct and plate breakage. Possible risk factors included malreduction, loss of medial support, and negligence of tension band sutures on the tuberosities.

A mechanical comparison between conventional and modified angular plates for proximal humeral fractures

The objective of this study is to present a modified angular blade plate for fixing 2-part and even 3-part fractures of the proximal humerus, as well as the results of the comparative mechanical test between the conventional angular blade plate and this new modified plate. The plates were tested in flexion and rotational trials in a wooden model that simulated a 2-part humeral fracture of the proximal extremity. The results (mean +/- SD) of bending strength and stiffness obtained after testing showed findings of 601 +/- 349 N and 0.5 +/- 0.2 N/mm, respectively, for the conventional plate and 4005 +/- 164 N and 3.9 +/- 0.7 N/mm, respectively, for the modified plate. The torsional stiffness test showed findings of 1.26 +/- 0.09 KN.mm degrees for the conventional plate and 1.74 +/- 0.21 KN.mm degrees for the modified plate. The test of torsional moment showed findings of 57.0 +/- 7.6 KN.mm for the conventional plate and 115.2 +/- 9.3 KN.mm for the modified plate. The test of angular displacement at the torsional moment showed findings of 50.8 degrees +/- 7.2 degrees for the conventional plate and 70.2 degrees +/- 2.6 degrees for the modified plate. The results of the mechanical trials of flexion and rotation were superior for the modified angular blade plate compared with the conventional angular blade plate.