The comminuted midshaft clavicle fracture: a biomechanical evaluation of plating methods

Great debates in trauma biomechanics

At the 2021 annual meeting of the Orthopaedic Trauma Association, the Basic Science Focus Forum hosted its first ever debate-style symposium focused on biomechanics and fracture repair. The 3 subjects of debate were "Mechanics versus Biology-Which is 'More Important' to Consider?" "Locked Plate versus Forward Dynamization versus Reverse Dynamization-Which Way Should I Go?" and "Sawbones versus Cadaver Models-What Should I Believe Most?" These debates were held because fracture healing is a highly organized synergistic response between biological factors and the local mechanical environment. Multiple studies have demonstrated that both factors play roles in governing bone healing responses, and the causal relationships between the 2 remain unclear. The lack of clarity in this space has led to a spectrum of research with the common goal of helping surgeons make good decisions. Before reading further, the reader should understand that the questions posed in the debate titles are unanswerable and might represent a false choice. Instead, the reader should appreciate that the debates were held to gain a more thorough understanding of these topics based on the current state of the art of experimental and clinical studies, by using an engaging and thought-provoking format.

Examining the novel use of continuous compression implants in clavicle reconstruction: A biomechanical study

BACKGROUND

Current implants for clavicle fractures are known to cause poor cosmesis and irritation, which may require implant removal. Low-profile shape-memory staples provide an attractive alternative, but their biomechanical utility in clavicle reconstruction is unknown. We hypothesized that shape-memory reconstructions would be more compliant compared to traditional constructs but would also outperform conventional plates during cyclic loading to failure.

METHODS

This study was performed with 36 synthetic clavicles and 12 matched pairs of cadaveric specimens. The synthetic study tested four reconstructions: a single superiorly placed staple (n = 6), a single anteroinferiorly-placed staple (n = 6), a 3.5 mm reconstruction plate (n = 12), and two orthogonally placed staples (n = 12). The cadaveric study tested three constructs: reconstruction plate (n = 8), two orthogonal staples (n = 8), and a 2.7 mm reconstruction plate combined with a superior staple (n = 8). Non-destructive 4-point bending, compression, and torsion assays were performed prior to destructive cantilever bending and cyclic torsion tests.

FINDINGS

The single staple and double staple groups demonstrated significantly decreased resistance to bending (p < 0.001) and torsion (p ≤ 0.027) when compared to reconstruction plate groups. The double staple group sustained significantly fewer cycles to failure than the reconstruction plate group in cyclic torsional tests (p = 0.012). The synthetic models produced higher stiffness and failure mechanisms that were completely different from cadaveric specimens.

INTERPRETATION

Shape memory alloy implants provided inadequate stiffness for clavicle fixation but may have utility in other orthopaedic applications when used as a supplementary compression device in conjunction with traditional plated constructs. Synthetic bones have limited capacity for modeling fragility fractures.

Mechanical Evaluation of 2.7- Versus 3.5-mm Plating Constructs for Midshaft Clavicle Fractures

OBJECTIVES

This study compares the mechanical performance of 2.7- and 3.5-mm plating constructs for the treatment of midshaft clavicle fractures.

METHODS

Twenty-four synthetic clavicles were randomly divided into four treatment groups-Synthes 2.7-mm cold-worked calcaneal reconstruction plate with 6 (CRP6) or 8 bicortical screws (CRP8); Synthes 3.5-mm LCP reconstruction plate (RP; and Synthes 3.5-mm LCP precontoured superior-anterior clavicle plate (PCRP). All clavicles were plated, a wedge-shaped inferior cortical defect was created, and testing was performed using a cantilever bending model to determine bending stiffness and yield point for each construct.

RESULTS

Bending stiffness for the 3.5-mm PCRP construct was markedly higher when compared with the other three constructs, whereas the 3.5-mm RP construct was markedly stiffer than both of the 2.7-mm CR constructs. The yield point for the 3.5-mm PCRP construct was greater than the other three constructs; however, the yield point for the 2.7-mm CRP with six screws and with eight screws was higher than the 3.5-mm RP construct. The amount of displacement required to reach the yield point was highest for the 2.7-mm CRP with six screws. and this was markedly higher than the values for the other three constructs.

DISCUSSION

The 3.5-mm plates demonstrated increased bending stiffness compared with the 2.7-mm plates. Despite the lower resistance to bending forces, the cold-worked 2.7-mm plate exhibited a markedly higher yield point and required markedly more superior to inferior displacement to initiate plastic deformation when compared with the 3.5-mm LCP RP.

LEVEL OF EVIDENCE

Level IV.

Comparing internal fixation constructs for scapular spine insufficiency fractures following reverse shoulder arthroplasty

INTRODUCTION

There is limited research on the surgical management techniques for scapular spine fractures after reverse shoulder arthroplasty (RTSA). As such, the purpose of this in vitro biomechanical study was to compare 4 fixation constructs to stabilize scapular spine insufficiency fractures.

METHODS

Twelve paired fresh-frozen cadaveric scapulae (N = 24) were randomized into 4 fixation groups: subcutaneous border plating (± hook) and supraspinatus fossa plating (± hook). A Levy type II fracture was simulated. Each specimen was cyclically loaded incrementally up to 700 N in 50 N steps or until failure. Between 50 and 200 N construct stiffness was measured, and stability failure was defined as displacement greater than 2.5 mm.

RESULTS

Seventy-nine percent (19 of 24) of the specimens failed before the maximum load of 700 N. The average survival force with subcutaneous border plating was 480 ± 80 N compared with 380 ± 30 N for supraspinatus fossa plating (P = .3). Fixation construct failure was significantly more likely with fossa plating over subcutaneous plating (P = .012). The presence of the lateral plate hook was beneficial in preventing failure of the lateral acromion (P = .016).

CONCLUSION

When appropriately surgically indicated, a dorsally applied plate to the subcutaneous border of the scapular spine with a lateral inferior supporting hook may be advantageous for internal fixation of type II scapular spine insufficiency fractures after RTSA.

Two reconstruction plates provide superior stability of displaced midshaft clavicle fractures in comparison to single plating - A biomechanical study

BACKGROUND

Displaced midshaft fractures are the most common surgically treated clavicle fractures. However, they are associated with high complication rates following plating due to fixation failure in terms of plate breakage, screw breakage and/or screw loosening. The aim of this study was to compare the biomechanical competence of three different plating techniques for fixation of displaced midshaft clavicle fractures.

METHODS

Displaced midshaft fractures type 2B according to the Robinson classification were simulated by standardized osteotomy gap in 18 synthetic clavicles, assigned to three groups (n = 6) for plating with either superiorly placed Dynamic Compression Plate (width/thickness 11.0/4.0 mm), locked Superior Anterior Clavicle Locking Compression Plate (width/thickness 10.2/2.0 mm), or two non-locked Reconstruction Plates placed superiorly and anteriorly (width/thickness 10.0/2.8 mm). Each specimen was cyclically tested at 3 Hz under craniocaudal cantilever bending, superimposed with torsion around the shaft axis over 720'000 cycles or until failure occurred. The latter was defined by plate breakage, screw breakage or screw loosening.

FINDINGS

Initial construct stiffness (N/mm) and cycles to failure in group Reconstruction Plates (22.30 ± 4.07; 712'778 ± 17'691) were significantly higher compared with both groups Compression Plate (12.53 ± 2.09; 348'541 ± 212'941) and Locking Plate (4.19 ± 0.46; 19'536 ± 3'586), p ≤ 0.019. In addition, these two outcomes were significantly higher in group Compression Plate versus Locking Plate, p ≤ 0.029.

INTERPRETATION

Double plating of unstable midshaft clavicle fractures with reconstruction plates seems to provide superior fixation stability under dynamic loading, when compared to single compression or locked plating, whereas the latter is associated with inferior performance.

Plate osteosynthesis for mid-shaft clavicle fractures: An update

INTRODUCTION

Over the last few years, treatment of mid-shaft clavicle fractures seems to have shifted from conservative to surgical. Our study reports the results of plate osteosynthesis of mid-shaft clavicle fractures and compares them with literature.

MATERIALS AND METHODS

A retrospective cohort study was conducted on 32 patients with mid-shaft clavicle fractures treated with plate and screws between January 2009 and December 2014. All the patients followed the same post-operative rehabilitation program with radiographic and clinical evaluation (DASH score and Constant score) at a minimum follow-up of 24 months.

RESULTS

All the patients healed clinically and radiographically, without deformities or non-unions, with complete and early functional recovery and return to their pre-injury sport activities. At one year follow-up the mean Constant Score was 93.8 (SD 4.8) and the mean DASH score was 42 (SD 5.0).

CONCLUSIONS

Osteosynthesis with plate and screws of mid-shaft clavicle fractures allows not only restoration of the anatomy, but also early recovery of shoulder function. For this reason, such surgical treatment should always be considered when facing this particular fracture group, also in accordance with recent literature.

Single versus dual orthogonal plating for comminuted midshaft clavicle fractures: a biomechanics study

BACKGROUND

Dual orthogonal plating of clavicle fractures may provide greater stiffness and strength than unilateral plate constructs and allow the use of lower-profile plates. We aim to biomechanically compare three clavicle plating constructs in a comminuted clavicle fracture model.

METHOD

Fifteen clavicle sawbones were osteotomised, simulating a comminuted midshaft fracture and allocated to either: group 1, single superior plate (3.5 mm superior plate); group 2, combination plating (3.5 mm superior plate, 2.8 mm anterior plate) and group 3, dual mini-plates (two 2.8-mm orthogonal mini-plates). Specimens were biomechanically tested under torsion and cantilever bending. Construct stiffness (Nm/degree) and load to failure (Nm) were measured.

RESULTS

Group 2 had higher torsional (0.70 vs. 0.60 Nm/deg, p = 0.017) and cantilever bending stiffness (0.61 vs. 0.51 Nm/deg, p = 0.025) than group 1. Group 3 had lower cantilever bending stiffness (0.39 vs. 0.51 Nm/deg, p < 0.004) and load to failure (40.87 vs. 54.84 Nm, p < 0.01) than group 1. All dual plate constructs that catastrophically failed did so from fracture at the lateral ends of the plates. Single plate constructs failed due to plate bending.

CONCLUSION

Dual orthogonal fixation with mini-plates demonstrated lower stiffness and strength than traditional superior plating. The addition of an anterior mini-plate to a traditional superior plating improved construct stiffness and may have a role in patients seeking early return to activity.

LEVEL OF EVIDENCE

Basic science biomechanical study.

Comparison of radiological and clinical outcomes, complications, and implant removals in anatomically pre-contoured clavicle plates versus reconstruction plates - a propensity score matched retrospective cohort study of 106 patients

Background

Plate fixation is frequently used to treat displaced midshaft clavicular fractures, however the ideal plate choice remains subject to discussion; reconstruction locking compression plates (RLCPs) are cheaper and can be easily contoured, whereas anatomically pre-contoured locking compression plates (ALCPs) are thought to provide better stability and therefore lower rates of mechanical failure.

To compare the incidence of mechanical failures, functional and radiological outcomes in patients with midshaft clavicular fractures treated with ALCPs versus RLCPs.

Methods

A propensity score matched retrospective cohort study was conducted across two centers. One hundred and six consecutively recruited patients with displaced midshaft clavicular fractures, who were treated with plate fixation and had a minimum follow-up of 6 months, were matched on gender, age, fracture grading, energy of injury, and fracture location. The resulting groups included 53 ALCP-treated fractures and 53 matched controls treated with RLCPs.

Results

During a mean follow-up of 20.5 months, there were no implant deformities in the ALCP group whereas the RLCP group had 6 patients (11.3%, p = 0.012) with implant deformities (5 occurrences of plate bending with fracture union, and 1 plate breakage with nonunion). Despite the higher rate of plate deformities in the RLCP group, there were no statistically significant differences in number of patients recovering full shoulder range of motion (ALCP 90.6%, RLCP 88.7%, p = 0.751), incidence of rest pain (ALCP 13.2%, RLCP 9.4%, p = 0.542), or implant removals (ALCP 49.1%, RLCP 56.6%, p = 0.439).

Conclusion

ALCPs may be superior to RLCPs in terms of implant stability but appear to produce similar clinical results.

Low-Profile Dual Small Plate Fixation Is Biomechanically Similar to Larger Superior or Anteroinferior Single Plate Fixation of Midshaft Clavicle Fractures

BACKGROUND

Limited biomechanical data exist for dual small plate fixation of midshaft clavicle fractures, and no prior study has concurrently compared dual small plating to larger superior or anteroinferior single plate and screw constructs.

PURPOSE

To biomechanically compare dual small orthogonal plating, superior plating, and anteroinferior plating of midshaft clavicle fractures by use of a cadaveric model.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The study used 18 cadaveric clavicle specimens (9 pairs total), and 3 plating techniques were studied: anteroinferior, superior, and dual. The dual plating technique used smaller diameter plates and screws (1.6-mm thickness) than the other, single plate techniques (3.3-mm thickness). Each of the 9 clavicle pairs was randomly assigned a combination of 2 plating techniques, and randomization was used to determine which techniques were used for the right and left specimens. Clavicles were plated and then osteotomized to create an inferior butterfly fracture model, which was then fixed with a single interfragmentary screw. Clavicle specimens were then potted for mechanical testing. Initial bending, axial, and torsional stiffness of each construct was determined through use of a randomized nondestructive cyclic testing protocol followed by load to failure.

RESULTS

No significant differences were found in cyclical axial (P = .667) or torsional (P = .526) stiffness between plating groups. Anteroinferior plating demonstrated significantly higher cyclical bending stiffness than superior plating (P = .005). No significant difference was found in bending stiffness between dual plating and either anteroinferior (P = .129) or superior plating (P = .067). No significant difference was noted in load to failure among plating methods (P = .353).

CONCLUSION

Dual plating with a smaller plate-screw construct is biomechanically similar to superior and anteroinferior single plate fixation that uses larger plate-screw constructs. No significant differences were found between dual plating and either superior or anteroinferior single plating in axial, bending, or torsional stiffness or in bending load to failure. Dual small plating is a viable option for fixing midshaft clavicle fractures and may be a useful low-profile technique that avoids a larger and more prominent plate-screw construct.

CLINICAL RELEVANCE

Plate prominence and hardware irritation are commonly reported complaints and reasons for revision surgery after plate fixation of midshaft clavicle fractures. Dual small plate fixation has been used to improve cosmetic acceptability, minimize hardware irritation, and decrease reoperation rate. Biomechanically, dual small plate fixation performed similarly to larger single plate fixation in this cadaveric model of butterfly fracture.

Biomechanical Analysis of Superior and Anterior Precontoured Plate Fixation Techniques for Neer Type II-A Clavicle Fractures

OBJECTIVE

There are limited biomechanical data supporting the use of anterior or superior-lateral precontoured clavicle plates for the treatment of displaced Neer type II-A clavicle fractures. The objectives of this study were as follows: (a) compare noncontoured versus precontoured superior plating; (b) compare use of locking versus nonlocking screws in the lateral fragment for superior precontoured plates; and (c) compare superior versus anterior precontoured plates with locking lateral fragment screws.

METHODS

The following constructs were tested on a synthetic clavicle model simulating a Neer type II-A fracture: (a) superior precontoured plate with locking (SUP-L, n = 6); (b) superior precontoured plate with nonlocking (SUP-NL, n = 8); (c) anterior precontoured plate with locking (ANT-L, n = 7); and (d) superior noncontoured locking compression plate (SUP-LCP, n = 6). Constructs were subjected to cyclical cantilever loads. Construct stiffness and survival (cycles to failure) were documented. Mann-Whitney U tests were performed for group-wise statistical comparison (α = 0.05) of data.

RESULTS

The SUP-L construct was significantly stiffer than both SUP-LCP and ANT-L constructs (P < 0.02). The SUP-NL construct was stiffer than the SUP-L (P = 0.03) construct. Both SUP-L and ANT-L precontoured constructs survived longer than the noncontoured SUP-LCP construct (P < 0.022). The SUP-L construct survived longer than the SUP-NL (P = 0.013) and the ANT-L (P = 0.008) constructs.

CONCLUSIONS

Superior precontoured plates yielded biomechanically superior constructs compared with anterior precontoured and superior noncontoured plates. Using locking screws in the lateral fragment over nonlocking screws may improve overall superior precontoured plate construct survivability. However, our results were limited to a synthetic biomechanical model and require further investigation to establish a clinical correlation.

Immediate Weight-bearing as Tolerated has Improved Outcomes Compared to Non–weight-bearing after Surgical Stabilisation of Midshaft Clavicle Fractures in Polytrauma Patients

Background

Clavicle fractures are common injuries in the polytrauma population and frequently limit early mobilisation. This study evaluates the effect of immediate crutch weight-bearing (WB) in polytrauma patients after surgical stabilisation of a displaced midshaft clavicle fracture.

Methods

A retrospective review identified 26 polytrauma patients with operatively managed displaced midshaft clavicle fractures and a non–weight-bearing (NWB) lower extremity injury. Patients were allowed immediate WB after surgery or NWB. The primary outcome was total hospital length of stay. Statistical analysis was done using Mann–Whitney U test.

Results

The WB group had decreased total hospital length of stay (10.4 vs. 17.0 days, p = 0.012) and improved physical therapy score (3.9 vs. 2.9, p = 0.054) and postoperative length of stay (6.8 vs. 12.7 days, p = 0.006) compared with the NWB group.

Conclusions

Our data suggest that an immediate WB as tolerated protocol for polytrauma patients after surgical fixation of displaced clavicle fractures may decrease the overall length of stay.

Surgical fixation of midshaft clavicle fractures: A systematic review of biomechanical studies

PURPOSE

Surgical treatment of displaced midshaft clavicle fractures requires a decision between plate fixation and intramedullary (IM) fixation. Numerous studies report on the biomechanical properties of various repair constructs. The goal of this systematic review was to provide an overview of studies describing the biomechanical properties of the most commonly used surgical fixations of midshaft clavicle fractures. Additionally, we aimed to translate these biomechanical results into clinically relevant conclusions.

METHODS

A computer-aided search of the EMBASE and PudMed/MEDLINE databases was conducted. Studies included for review compared biomechanical properties of plate fixation with IM fixation and superiorly positioned plates with anteroinferiorly positioned plates for midshaft clavicle fractures.

RESULTS

Fifteen studies were eligible for inclusion. Plate fixation seemed to form a more robust construct than IM fixation in terms of stiffness and failure loading. The remaining clavicle was stronger after removal of the IM device than after removal of the plate. Superior plating of transverse fractures generally seemed to provide greater stiffness and strength during bending loads than anteroinferior plating did. The absence of cortical alignment in wedge and comminuted fractures directly influenced the fixation stability for both IM fixation and plate fixation, regardless of location.

CONCLUSION

Each type of fracture fixation has biomechanical advantages and disadvantages. However, exact thresholds of stiffness for inducing healing and failure strength to withstand refractures are unknown. The clinical relevance of the biomechanical studies may be arguable. Since none of the studies investigate the effect of tissue adaptation over time they should be interpreted with caution.

A Biomechanical and Clinical Comparison of Midshaft Clavicle Plate Fixation: Are 2 Screws as Good as 3 on Each Side of the Fracture?

Background:

The standard of care for plating displaced midshaft clavicle fractures has been 6 cortices of purchase on each side of the fracture. The use of locking plates and screws may afford equivalent biomechanical strength with fewer cortices of purchase on each side of the fracture.

Purpose:

To compare the biomechanical and clinical performance of 3- versus 2-screw constructs for plating displaced midshaft clavicle fractures.

Study Design:

Controlled laboratory study/cohort study; Level of evidence, 3.

Methods:

Lateral fragments of simulated midshaft fractures in 10 pairs of cadaveric clavicles were randomly assigned to plate fixation with either 3 nonlocking screws or 2 locking screws. Cyclic tensile loads were applied along the long axis of the clavicle. The constructs were then loaded to failure with pullout forces applied parallel to the long axis of the screws. Additionally, clinical outcomes of patients who had midshaft clavicle fractures that were surgically repaired were retrospectively identified and compared; 21 patients were treated with 3-screw constructs and 20 with 2-screw constructs.

Results:

Biomechanically, there were no significant differences for cyclic displacement, stiffness, yield load, or ultimate load between groups. Forces required for screw pullout were considerably higher than physiologic forces experienced by a healing clavicle in vivo. Clinically, there were no significant differences in American Shoulder and Elbow Surgeons, Constant, visual analog scale, and Single Assessment Numeric Evaluation scores; complications; or mean time to union. Additionally, we found that the plates used in the 2-screw group were consistently shorter.

Conclusion:

Plate fixation of displaced midshaft clavicle fractures with 4 cortices of purchase with 2 locking screws demonstrated no significant differences biomechanically when compared with fixation with 6 cortices of purchase and 3 nonlocking screws. Clinically, there were no significant differences in outcomes or complications seen in patients receiving 2- or 3-screw constructs.

Clinical Relevance:

Clinical benefits of using the 3-screw construct for plate fixation include decreased surgical exposure, morbidity, and cost, and the use of shorter and noncontoured straight plates eliminates the extra time and technical difficulty associated with matching longer contoured plates to the complex morphology of the clavicle.

Strength analysis of clavicle fracture fixation devices and fixation techniques using finite element analysis with musculoskeletal force input

In the cases, when clavicle fractures are treated with a fixation plate, opinions are divided about the best position of the plate, type of plate and type of screw units. Results from biomechanical studies of clavicle fixation devices are contradictory, probably partly because of simplified and varying load cases used in different studies. The anatomy of the shoulder region is complex, which makes it difficult and expensive to perform realistic experimental tests; hence, reliable simulation is an important complement to experimental tests. In this study, a method for finite element simulations of stresses in the clavicle plate and bone is used, in which muscle and ligament force data are imported from a multibody musculoskeletal model. The stress distribution in two different commercial plates, superior and anterior plating position and fixation including using a lag screw in the fracture gap or not, was compared. Looking at the clavicle fixation from a mechanical point of view, the results indicate that it is a major benefit to use a lag screw to fixate the fracture. The anterior plating position resulted in lower stresses in the plate, and the anatomically shaped plate is more stress resistant and stable than a regular reconstruction plate.

VA-LCP anterior clavicle plate: the anatomically precontoured fixation system with angular stability for clavicle shaft

INTRODUCTION

The aim of this investigation was to evaluate the introduction of the VA-LCP anterior clavicle plate in the treatment of clavicle fractures.

MATERIAL AND METHODS

From March 2011 to March 2013, 42 clavicle fractures were treated; 40 were middle-third and 2 lateral-third, and 13/42 (31 %) patients were treated due to painful nonunion. Patient age ranged from 16 to 81 years.

RESULTS

Complications were screw placement through the AC-joint, one superficial wound infection and one neuropraxia of the nervus radialis with dropping hand. We had some difficulties prebending both lateral to low and lateral to high but without clinical consequences. In all cases, the fracture healed with full functionality. After 1 year, 4 patients underwent a removal of the hardware.

CONCLUSION

The VA-LCP anterior plate showed good reliability and sufficient stability with both middle-third, lateral and nonunion fractures of the clavicle.

Minimally invasive plating for fresh displaced midshaft fractures of the clavicle

The authors retrospectively reviewed 269 patients treated from September 2006 to August 2011 with the minimally invasive plate osteosynthesis (MIPO) technique using a universal reconstruction ribbon plate for fresh displaced midshaft fracture of the clavicle. Mean follow-up was 40.6 months. All had bony union (average healing time, 14.6 weeks). At 2-month postoperative follow-up, the mean Constant-Murley score was 92 points and the mean Disabilities of the Arm, Shoulder and Hand (DASH) score was 4.6 points. A total of 166 patients underwent hardware removal at an average of 15 months. A total of 258 patients were satisfied with the results of this surgery. This technique appears to be safe, simple, effective, and practical and to lead to rapid recovery, a high rate of union, a favorable cosmetic effect, and excellent function restoration. Thus, it can be considered an alternative to conventional plate osteosynthesis, intramedullary fixation, or non-operative treatment for fresh displaced midshaft clavicle fractures.

Does plate type influence the clinical outcomes and implant removal in midclavicular fractures fixed with 2.7-mm anteroinferior plates? A retrospective cohort study

BACKGROUND

The purpose of this study was to evaluate surgical healing rates, implant failure, implant removal, and the need for surgical revision with regards to plate type in midshaft clavicle fractures fixed with 2.7-mm anteroinferior plates utilizing modern plating techniques.

METHODS

This retrospective exploratory cohort review took place at a level I teaching trauma center and a single large private practice office. A total of 155 skeletally mature individuals with 156 midshaft clavicle fractures between March 2002 and March 2012 were included in the final results. Fractures were identified by mechanism of injury and classified based on OTA/AO criteria. All fractures were fixed with 2.7-mm anteroinferior plates. Primary outcome measurements included implant failure, malunion, nonunion, and implant removal. Secondary outcome measurements included pain with the visual analog scale and range of motion. Statistically significant testing was set at 0.05, and testing was performed using chi-square, Fisher's exact, Mann-Whitney U, and Kruskall-Wallis.

RESULTS

Implant failure occurred more often in reconstruction plates as compared to dynamic compression plates (p = 0.029). Malunions and nonunions occurred more often in fractures fixed with reconstruction plates as compared to dynamic compression plates, but it was not statistically significant. Implant removal attributed to irritation or implant prominence was observed in 14 patients. Statistically significant levels of pain were seen in patients requiring implant removal (p = 0.001) but were not associated with the plate type.

CONCLUSIONS

Anteroinferior clavicular fracture fixation with 2.7-mm dynamic compression plates results in excellent healing rates with low removal rates in accordance with the published literature. Given higher rates of failure, 2.7-mm reconstruction plates should be discouraged in comparison to stiffer and more reliable 2.7-mm dynamic compression plates.

Effectiveness of Selected Fitness Exercises on Stress of Femoral Neck using Musculoskeletal Dynamics Simulations and Finite Element Model

The purpose of the study was to establish a dynamics model and a three-dimensional (3D) finite element model to analyze loading characteristics of femoral neck during walking, squat, single-leg standing, and forward and lateral lunges. One male volunteer performed three trials of the five movements. The 3D kinematic data were captured and imported into the LifeMOD to establish a musculoskeletal dynamics model to obtain joint reaction and muscle forces of iliacus, gluteus medius, gluteus maximus, psoas major and adductor magnus. The loading data LfeMOD were imported and transformed into a hip finite-element model. The results of the finite element femur model showed that stress was localized along the compression arc and the tension arc. In addition, the trabecular bone and tension lines of the Ward's triangle also demonstrated high stress. The compact bone received the greatest peak stress in the forward lunge and the least stress in the squat. However, the spongy bone in the femoral neck region had the greatest stress during the walk and the least stress in the squat. The results from this study indicate that the forward lunge may be an effective method to prevent femoral neck fractures. Walking is another effective and simple method that may improve bone mass of the Ward's triangle and prevent osteoporosis and femoral neck fracture.

Early postoperative failure of a new intramedullary fixation device for midshaft clavicle fractures

The Sonoma CRx device (Sonoma Orthopedic Products, Santa Rosa, California) is a recently introduced intramedullary device with a flexible shaft that becomes rigid once actuated to allow deployment within the sigmoidal contour of the clavicular shaft. Medial intramedullary cortical purchase is obtained by grippers and lateral purchase through a locking bicortical buttressing screw. This article describes 2 cases of early hardware failure using this device. In both cases, early postoperative radiographs demonstrate adequate initial fracture reduction and implant position. Both patients sustained repeat injuries, one under low physiologic load and the other after returning to mixed martial arts 4 months postoperatively. Implant failure was noted after reinjury in both cases. Complete healing and full return to function was documented for both patients at 2 years. Proper patient selection and counseling regarding the limitations of this intramedullary fixation device are important. Biomechanical comparison of this implant to plate fixation under physiologic loads of combined axial compression and torsion may shed light on differences in fixation stability.

Combined finite element and multibody musculoskeletal investigation of a fractured clavicle with reconstruction plate

This paper addresses the evaluation of clavicle fixation devices, by means of computational models. The aim was to develop a method for comparison of stress distribution in various fixation devices, to determine whether the use of multibody musculoskeletal input in such model is applicable and to report the approach. The focus was on realistic loading and the motivation for the work is that the treatment can be enhanced by a better understanding of the loading of the clavicle and fixation device. The method can be used to confirm the strength of customised plates, for optimisation of new plates and to complement experimental studies. A finite element (FE) mesh of the clavicle geometry was created from computed tomography data and imported into the FE solver where the model was subjected to muscle forces and other boundary conditions from a multibody musculoskeletal model performing a typical activity of daily life. A reconstruction plate and screws were also imported into the model. The combination models returned stresses and displacements of plausible magnitudes in all included parts and the result, upon further development and validation, may serve as a design guideline for improved clavicle fixation.

Biomechanical analysis of locked and non-locked plate fixation of the clavicle

INTRODUCTION

During plate fixation of clavicular fractures the brachial plexus and subclavian vessels are vulnerable to injury beneath the clavicle. Locking plate fixation allows for mono-cortical fixation, theoretically reducing the risk of injury to these structures. Biomechanical analysis of the performance of such fixation is limited, and this study was designed to explore this further as a treatment option in clavicle fractures.

MATERIALS AND METHODS

Fixation of fifteen simulated mid-shaft fractures was undertaken using a combination of mono-cortical locked, bicortical locked and bicortical non-locked plating methods in cadaveric clavicles. Samples were then tested via three-point bending to destruction, and the performance of each with respect to failure load, bending stress, bending stiffness and Young's modulus was then analysed. The influence of the number of cortices engaged and locking was also assessed.

RESULTS

Clavicles fixed with monocortical locking plates displayed a significantly lower bending stress (12±1 MPa) than both the bicortical locking (28±3 MPa, p=0.015) and non-locking specimens (24±3 MPa, p=0.002). Engaging two cortices with the fixation produced a significant increase in failure load (291±28 N vs 138±48 N, p=0.018) and bending stress (26±2 MPa vs 9.9±3.5 MPa, p=0.002) compared to single cortex fixation.

DISCUSSION

The greatest influence upon the performance of the fixation was the number of cortices engaged, with bicortical fixation performing significantly better than mono-cortical. Whether or not the fixation device was a locking one did not have a significant bearing upon the performance.

CONCLUSION

This in vitro biomechanical analysis demonstrates that mono-cortical locked plating fails at significantly lower levels of load and stress than bicortical locked and non-locked plating in mid-shaft fractures of the clavicle, and caution would therefore be advised in its use as a fixation modality for these injuries.

Comparison of dynamic and locked compression plates for treating midshaft clavicle fractures

The purpose of this study was to compare the parameters of perioperative course and cost-effectiveness for patients with midshaft clavicle fractures treated by dynamic compression plates or locked compression plates.This retrospective, case-controlled study involved 54 patients with midshaft clavicle fractures who received dynamic compression plates (n=21) or locked compression plates (n=33) between January 2002 and December 2008. Indications for surgery included displacement or shortening >2 cm, comminuted fractures, and skin tenting. Patients with previous malunion, nonunion, multiple injuries of the shoulder girdle, or open fractures were excluded. Preoperative demographics showed no statistically significant differences between the 2 groups. Eighteen patients with dynamic compression plates and 28 patients with locked compression plates with postoperative follow-up >1 year were included for comparison. Statistical analyses for operative time, blood loss, complication rate, hospital stay, and union rate demonstrated no statistically significant difference between the 2 groups. The only statistically significant difference was a higher rate of plate removal requests in the dynamic compression plate group. Considering medical expenditure, locked compression plates cost 6 times more than dynamic compression plates in the authors' institution (US $600 vs $100, respectively).Other than more plate removal requests in the dynamic compression plate group and greater expense in the locked compression plate group, dynamic compression plates and locked compression plates achieved satisfactory operative outcomes in treating midshaft clavicle fractures, with no statistically significant difference between perioperative course and eventual fracture union observed between the 2 groups.