Are locking screws advantageous with plate fixation of humeral shaft fractures? A biomechanical analysis of synthetic and cadaveric bone

Influence of physical fitness components on personality factors and risk perception of children and adolescents: a cross-sectional study

OBJECTIVES

To examine the associations of cardiorespiratory fitness (VO2 max) and muscular strength with indicators related to the risk scale, such as perceived competence, sensation seeking, competitiveness, risk taking and risk perception in sports.

DESIGN

Cross-sectional study.

SETTING

High schools from the Region of Murcia (Spain).

PARTICIPANTS

Three-hundred-and-seventeen adolescents participated (mean age: 13.69±1.2 years old).

PRIMARY AND SECONDARY OUTCOME MEASURES

Body mass, body height, Course-Navette test, upper limb strength and psychoeducational factors that determine the propensity towards sports accidents in school children, the Sports Accident Propensity Scale were evaluated. It was performance t-test for independent samples, stepwise multiple linear regression models and a multiple mediation analysis.

RESULTS

The analysis showed significant differences with respect to sex in height, VO2 max, handgrip strength and in all factors of the questionnaire (p=0.02-<0.01). Adolescents who presented greater VO2 max, strength in the handgrip test and age showed a higher score in factors 1 and 3. Higher scores in factor 2 were associated with better VO2 max and strength in handgrip test. Youngers and better values of strength in the handgrip showed higher score in factors 4 and 5. The mediation analysis with two mediating variables (handgrip strength and VO2 max) showed a significant indirect effect. When handgrip strength and VO2 max were included in the equations, the association between sex and each factor ceased to be significant.

CONCLUSION

This study highlights the potential benefits of muscular strength (handgrip) and VO2 max in the perceived risk scale, and the variable of age on this.

TRIAL REGISTRATION NUMBER

Clinical trial: NCT05544370 (pre-results).

Failure of humeral shaft fixation: construct characteristics

PURPOSE

Fixation failure following open reduction and internal fixation (ORIF) of humeral shaft fractures can be a challenging complication. We aimed to identify the modes of failure and characteristics of failed fixation constructs.

METHODS

We queried our institutional database for patients > 18 years old with fixation failure after ORIF with single plate and screw constructs of humeral shaft fractures from 2006 to 2017. Demographics, fracture characteristics, fixation construct design and mode of failure were recorded.

RESULTS

Twenty-three failures were identified. Mean age was 55.9 years (SD 19.2 years) with 15 (65%) women. Twelve patients (52%) had midshaft fractures; the remainder had distal-third shaft (8 pts, 35%) or proximal-third shaft (3 pts, 13%) fractures. Midshaft fractures were most commonly fixed through an anterolateral approach with plates and all non-locking screws (83%), while distal-third shaft fractures were fixed with a combination of locking and non-locking screws from a posterior approach. Distal-third shaft fractures failed by plate breakage (63%) or screw pullout (38%) and all midshaft failures occurred by screw pullout proximal (92%) or distal (8%) to the fracture. Resultant varus deformity occurred in 20 (87%) fractures.

CONCLUSION

Screw pullout in midshaft fractures suggests that fixation to bone was insufficient or biomechanically disadvantageous. Varus moments contribute significantly to the failure of humeral shaft fracture ORIF. Plate breakage in distal fractures suggests high concentrations of stress over a narrow working length of constructs with inadequate plate strength. Recognizing how these constructs fail can aid proper implant selection and application for humeral shaft fracture.

LEVEL OF EVIDENCE

Treatment level IV.

Small-Fragment Plate Fixation of Humeral Shaft Fractures

Fixation of humeral shaft fractures is frequently performed with large-fragment (4.5 mm) plates to accommodate immediate weight bearing. Use of small-fragment (3.5 mm) plates as an alternative carries theoretical benefits. We examined nonunion rates and postoperative radial nerve palsy (RNP) rates in a retrospective cohort of patients undergoing open reduction and internal fixation of humeral shaft fractures with 3.5-mm or 4.5-mm plates. Two hundred thirty-six patients with 241 humeral shaft fractures were included. Small 3.5-mm plates were used in 83% of the patients, and large 4.5-mm plates were used in 17% of the patients. Fifty-three percent were made weight bearing as tolerated following surgical fixation. There was a 7% incidence of nonunion and a 10% incidence of RNP in the 3.5-mm plate group. There was a 7% incidence of nonunion and a 15% incidence of RNP in the 4.5-mm plate group. No statistically significant relationship was shown between nonunion or RNP and plate size (P=.74 and P=.39). No relationship was shown between nonunion and postoperative weight-bearing status (P=.45). Subgroup analysis according to plate size additionally showed no association of nonunion with postoperative weight bearing in both the 4.5-mm (P=.55) and the 3.5-mm (P=.25) cohorts. Small-fragment and large-fragment plating of humeral shaft fractures resulted in comparable union and RNP rates, regardless of postoperative weight-bearing status. Our findings suggest that 3.5-mm plate fixation of humeral shaft fractures is a safe alternative to 4.5-mm plate fixation. [Orthopedics. 2023;46(4):198-204.].

Implant cost variation in surgically treated distal radius fractures

Aims & objectives

The purpose of this study was to evaluate for cost variation in distal radius fractures (DRFs) treated with a volar locking plate (VLP) and to identify key factors that affect the total construct cost.

Materials & methods

A retrospective case series was conducted for a single healthcare system. A total of 140 patients with a DRF treated with a VLP from May 2014 to December 2021 were identified. Patients were excluded for polytrauma, open fractures, and skeletal immaturity.

Results

Most patients were female (n = 120, 85.7%) and were on average 59 ± 13.7 years old. Patients most often injured their dominant hand (n = 75, 53.6%) and presented with an AO/OTA 23C fracture (n = 93, 66.4%). Twenty-two surgeons were included with fellowship training in hand or trauma and orthopaedic or plastic surgery residency. Orthopaedic hand-trained surgeons treated the highest proportion of 23C fractures (69.8%). Ninety patients (64.3%) were treated at a surgery center. The average cost was $1289.67 ± $215.32 (range: $857.83-$2156.95). The most expensive fixation constructs used a variable angle locking screw ($1316.75 ± $264.99) or a multidirectional threaded peg ($1321.67 ± $192.94). Multivariable regression analysis revealed none of the study variables to be significant contributors to construct cost (all p-values >0.27).

Conclusions

Surgically treated DRFs with a VLP demonstrated similar total implant costs regardless of fracture pattern, surgeon specialty, or treatment facility. Contrary to previous literature, VLPs showed minimal cost variation, although some surgeons were able to decrease the overall cost by reducing the number of screws used.

Inadequate proximal screw fixation increases risk of failure following plate fixation of diaphyseal humerus fractures

BACKGROUND

Operative treatment of humeral shaft fractures (AO/OTA 12) is being performed more frequently. Accordingly, it is important to understand the complications associated with plate fixation. This study analyzes risk factors associated with mechanical failure following plate fixation of humeral shaft fractures in order to further elucidate the mode and location of failure.

METHODS

A retrospective review of 351 humeral shaft fractures was completed at a single level I trauma center. Eleven of eighty-five humeral shaft fractures had aseptic mechanical failure requiring revision (12.9%), following initial plate fixation. Fracture characteristics (AO type, comminution, location) and fracture fixation (plate type, multiplanar, number of screws proximal and distal to the fracture) were compared between aseptic mechanical failure and those without failure. A forward stepwise logistic regression analysis was performed to determine any significant predictors of aseptic mechanical failure.

RESULTS

There was significant differences in fixation between the aseptic mechanical failure group and those without failure, specifically in the number of screws for proximal fixation (p = 0.008) and distal fixation (p = 0.040). In the aseptic mechanical failure group, patients tended to have less than < 8 cortices of proximal fixation (82%) and less than < 8 cortices of distal fixation (64%). Conversely, in patients without mechanical failure there was a tendency to have greater than > 8 cortices in both the proximal (62%) and distal fixation (70%). A forward stepwise logistic regression analysis found that less than < 8 cortices of proximal fixation was a significant predictor of aseptic failure, OR 7.96 (p = 0.011). We think this can be accounted for due to the variable bone quality, thinner cortices and multiple torsional forces in the proximal shaft that may warrant special consideration for fixation.

CONCLUSION

The current dogma of humeral shaft fracture stabilization is to use a minimum of 3 screws proximal and distal to the fracture, however the current study demonstrates this is associated with higher rates of mechanical failure. In contrast, 4 bicortical screws or more of fixation on either side of the fracture had lower failure rates and may help to reduce the risk of mechanical failure. Level of Evidence Level III.

A new design for the humerus fixation plate using a novel reliability-based topology optimization approach to mitigate the stress shielding effect

BACKGROUND

Due to high stiffness, metal fixation plates are prone to stress shielding of the peri-prosthetic bones, leading to bone loss. Therefore, it has become important to design implants with reduced rigidity but increased load-carrying capacity. Considering the uncertainties in the parameters affecting the implant-bone structure is critical in making more reliable implant designs. In this study, a Response Surface Method based Reliability-based Topology Optimization approach was proposed to design a fixation plate for humerus fracture having less stiffness than the conventional plate.

METHODS

The design of the fixation plate was described as an Reliability-based Topology Optimization problem in which the probabilistic constraint was replaced with a meta-model generated using the Kriging method. The artificial humerus bone model was scanned, and the 3D simulation model was used in the finite element analysis required in the solution. The optimum plate was manufactured using Selective Laser Melting. Both designs were experimentally compared in terms of rigidity.

FINDINGS

The volume of the conventional plate was reduced from 2512.5 mm³ to 1667.3 mm³; nevertheless, the optimum plate had almost one-third less rigidity than the conventional plate. The probability of failure of the conventional plate was computed as 0.994. However, this value was almost half for the optimum fixation plate. Interpretation The studies showed that the new fixation plate design was less rigid but more reliable than the conventional one. The computation time required to have the optimum plate was reduced by one-tenth by applying the Response Surface Method for the Reliability-based Topology Optimization problem.

Risk of Radial Nerve Injury in Anterolateral Humeral Shaft Plating

PURPOSE

The purpose of this study was to evaluate and compare the risk of iatrogenic radial nerve injury between arm positionings of 45° and 60° abduction in anterolateral humeral plating using a 4.5-mm narrow dynamic compression plate.

METHODS

Fifty-six humeri of cadavers in the supine position with 45° of arm abduction were exposed through the anterolateral approach. A hypothetical fracture line was marked at the middle of the humerus, and a precontoured ten-hole 4.5-mm narrow dynamic compression plate was applied and fixed to the anterolateral surface. After the fixation, the radial nerve was exposed through a triceps-splitting approach. Screws in contact with or which had penetrated the radial nerve were deemed to be injuries. Then, the screws and plate were removed, the arm changed to the 60° arm abduction position, and the steps of applying the plate and inserting the screws were followed as in the 45° arm abduction step.

RESULTS

The screws which could potentially injure the radial nerve were those of the second to sixth screw holes in both the 45° and 60° of arm abduction positions. The incidences of iatrogenic radial nerve injury of the second to sixth screw holes in the 45° position were 5.36%, 39.29%, 80.36%, 60.71%, and 10.71%, respectively, and at the 60° position were 5.36%, 53.57%, 83.93%, 60.71%, and 7.14%, respectively. There were no statistically significant differences in risk of injury between the two positions in all screw holes (all P-values > 0.05).

DISCUSSION

In anterolateral humeral shaft fixation, arm abduction position did not affect the risk of iatrogenic radial nerve injury, with the main risk from certain screw holes. The surgeon should be careful in screw insertion, especially at the fourth and fifth screw holes.

LEVEL OF EVIDENCE

IV; cadaveric study.

The risk of iatrogenic radial nerve and/or profunda brachii artery injury in anterolateral humeral plating using a 4.5 mm narrow DCP: A cadaveric study

INTRODUCTION

Fixation of humeral shaft fractures with a plate and screws can endanger the neurovascular structure if proper care is not taken. No studies to our knowledge have studied the risk of iatrogenic radial nerve and/or profunda brachii artery (RNPBA) injury from each screw hole of a 4.5 mm narrow dynamic compression plate (narrow DCP). The purpose of this study is to evaluate the risk of RNPBA injury in anterolateral humeral plating with a 4.5 mm narrow DCP.

MATERIAL AND METHODS

18 humeri of 9 fresh-frozen cadavers in the supine position were exposed via the anterolateral approach with 45 degrees of arm abduction. A hypothetical fracture line was marked at the midpoint of each humerus. A precontoured ten-hole 4.5mm narrow DCP was applied to the anterolateral surface of the humerus using the fracture line to position the center of the plate. All screw holes were drilled and screws inserted. The cadaver was then turned over to the prone position with 45 degrees of arm abduction, and the RNPBA exposed. The holes through in which 100% of the screw had contact with or penetrated the RNPBA were identified as dangerous screw holes, while lesser percentages of contact were defined as risky.

RESULTS

The relative distance ratios of the entire humeral length from the lateral epicondyle of the humerus to the 4th, 3rd, 2nd and 1st proximal holes were 0.64, 0.60, 0.56 and 0.52, respectively. The most dangerous screw hole was the 2nd proximal, in which all 18 screws had contacted or penetrated the nerve, followed by the risky 1st (12/18), 3rd (8/18) and 4th (2/18) holes.

CONCLUSION

In humeral shaft plating with the 4.5mm narrow DCP using the anterolateral approach, the 2nd proximal screw hole carries the highest risk of iatrogenic radial nerve and/or profunda brachii artery injury.

Is Bridge Plating of Comminuted Humeral Shaft Fractures Advantageous When Using Compression Plates with Three versus Two Screws per Fragment? A Biomechanical Cadaveric Study

Background

Minimally invasive plate osteosynthesis (MIPO) is one of the generally accepted surgical techniques for the treatment of humeral shaft fractures. However, despite the high bone union rate, a variety of complications are still prevailing. Moreover, the current literature lacks data comparing the anterolateral MIPO approach using dynamic compression plates accommodating different numbers of screws. The aim of this study was to analyze the biomechanical performance of comminuted humeral shaft fractures fixed with dynamic compression plates using either two or three screws per fragment.

Methods

Six pairs of fresh-frozen human cadaveric humeri from donors aged 66.8 ± 5.2 years were randomized to two paired study groups for simulation of bridge-plated comminuted shaft fracture type AO/OTA 12-C1/2/3 without interfragmentary bony support, using a dynamic compression plate positioned on the anterolateral surface and fixed with two (group 1) or three (group 2) screws per fragment. All specimens underwent nondestructive quasistatic biomechanical testing under lateral bending, anterior bending, axial bending, and torsion in internal rotation, followed by progressively increasing cyclic torsional loading in internal rotation until failure.

Results

Initial stiffness of the plated specimens in lateral bending, anterior bending, axial bending, and torsion was not significantly different between the groups (P ≥ 0.22). However, cycles to 10°, 15°, and 20° torsional deformation and cycles to construct failure were significantly higher in group 2 compared with group 1 (P ≤ 0.03).

Conclusions

From a biomechanical perspective, no significant superiority is identified in terms of primary stability when using two or three screws per fragment for bridge compression plating of comminuted humeral shaft fractures. However, three-screw configurations provide better secondary stability and maintain it with a higher resistance towards loss of reduction under dynamic loading. Therefore, the use of a third screw may be justified when such better secondary stability is required.

Humeral shaft fractures

Humeral shaft fractures are relatively common, representing approximately 1% to 5% of all fractures.

Conservative management is the treatment of choice for most humeral shaft fractures and offers functional results and union rates that are not inferior to surgical management.

Age and oblique fractures of the proximal third are risk factors for nonunion. Surgical indication threshold should be lower in patients older than 55 years presenting with this type of fracture.

Functional outcomes and union rates after plating and intramedullary nailing are comparable, but the likelihood of shoulder complications is higher with intramedullary nailing.

There is no advantage to early exploration of the radial nerve even in secondary radial nerve palsy.

Cite this article: EFORT Open Rev 2021;6:24-34. DOI: 10.1302/2058-5241.6.200033

Locking Screws With a Threaded Degradable Polymer Collar Reduce Construct Stiffness Over Time

OBJECTIVES

The stiffness of locking plates provide increased stability for early fracture healing but may limit late interfragmentary motion (IFM) necessary for secondary bone healing. An ideal plating construct would provide early rigidity and late flexibility to optimize bone healing. A novel screw plate construct utilizing locking screws with a degradable polymer locking mechanism is a dynamic option.

METHODS

Conventional locked plating constructs (group A) were compared with locking screws with a threaded degradable polymer collar before (group B) and after polymer dissolution (group C). Monotonic axial compression, monotonic torsion, cyclic axial load to failure, and IFM at the near and far cortices were tested on synthetic bone models.

RESULTS

One-way analysis of variance and post hoc Tukey-Kramer testing demonstrated similar axial stiffness in group A (873 ± 146 N/mm) and B (694 ± 314 N/mm) but significantly less stiffness in group C (379 ± 59 N/mm; F(2,15) = 9.12, P = 0.003). Groups A and B also had similar IFM, but group C had significantly increased IFM at both the near (F(2, 15) = 48.66, P = 2.76E-07) and far (F(2, 15) = 11.78, P = 0.0008) cortices. In cyclic axial load to failure, group A (1593 ± 233 N) and B (1277 ± 141 N) were again similar, but group C was significantly less (912 ± 256 N; F(2, 15) = 15.00, P = 0.0003). All failures were above the 500-N threshold seen in typical weight-bearing restrictions for fracture care. Torsional stiffness demonstrated significant differences between all groups (F(2, 15) = 106.64, P = 1.4E-09).

CONCLUSIONS

Use of locking plates with a degradable polymer collar show potential for in vitro construct dynamization. Future in vivo studies are warranted to assess performance under combined loading and the effects of decreasing construct stiffness during the course of bony healing.

Biomechanical comparison of humeral nails with different distal locking mechanisms: Insafelock nails versus conventional locking nails

Objective

The aim of this study was to compare the biomechanical resistance to rotational and axial forces of a conventional locking nail with a newly designed intramedullary humeral nail developed for humeral shaft fractures with a secure locking mechanism through the distal part of the nail.

Methods

InSafeLOCK humeral nail system (group 1, TST, Istanbul, Turkey) and Expert humeral nail system (group 2, DePuy Synthes, Bettlach, Switzerland) of the same size (9 × 300 mm) were examined. In total, 24 fourth-generation humerus sawbones were used in the experiment. Osteotomy was performed at the humerus shaft, and a defect was created by removing 1 cm of bone. After pre-loading 5000 cycles at a frequency of 2 Hz and a force of 50–250 N for axial loading and 5000 torsion torques between 0.5 Nm and 6.5 Nm at a 2 Hz frequency for torsional loading, the failure load values of each load were recorded. Distal interlocking was performed with an endopin in group 1, while a double cortex screw was used in group 2.

Results

All samples successfully passed the cyclic loading. The initial and final stiffness values were similar between the groups after axial loading (p = 0.873 and p = 0.522, respectively). The mean axial failure load values in groups 1 and 2 were 2627 ± 164 N and 7141 ± 1491 N, respectively. A significant difference was found in the axial failure load values (p = 0.004). Significant differences were observed between the initial and final torsional stiffness between the two groups (p = 0.004 and p = 0.004, respectively). No significant difference was found in the failure load values after torsional loading (11791 ± 2055 N.mm and 16997 ± 5440 N.mm) (p = 0.055).

Conclusion

These results provide a biomechanical demonstration of the adequate stability of both nails after axial and rotational loading. The reliability of the newly developed InSafeLOCK humeral nail system, which does not require fluoroscopic control and an additional incision for distal locking, supports its use in the clinic.

Biomechanical analysis of a novel plating for intra-articular distal humerus fractures: combined anteromedial and anterolateral plating

Purpose

The traditional strategy for fixing intra-articular distal humerus fractures is double plating placed in an orthogonal or parallel configuration, based on posterior approach. With a combined medial and lateral approach, a novel configuration of plating (combined anteromedial and anterolateral plating) has been used. In this study, we investigated the biomechanical properties of the novel plating by comparing it with orthogonal plating.

Methods

Based on the 3D morphology of a healthy subject’s humerus, the models of simple intra-articular distal humerus fractures were simulated. Two configurations of plating were applied to fix the models: the novel plating (with one plate anteromedially and the other anterolaterally on distal humerus), and orthogonal plating. Stresses, displacement, and stiffness were simulated and calculated under the conditions of axial compression, rotation torsion, bending torsion, and valgus torsion by using finite element analysis.

Results

In all the conditions, the maximal von Mises stresses of the novel plating are similar to those of orthogonal plating, and the patterns of stress distribution are similar between these two configurations. However, the impact of high stresses was weaker on the novel plating. The maximal displacement of the novel plating is smaller than that of orthogonal plating. The stiffness of the novel plating is superior to that of orthogonal plating, with the improvements of 19.4%, 122.7%, 25.0%, and 54.2% in axial compression, rotation torsion, bending torsion, and valgus torsion, respectively.

Conclusions

The novel plating is stronger than orthogonal plating without increasing stress magnitude when fixing simple intra-articular distal humerus fractures, which makes it a feasible alternative. Further biomechanical and clinical studies are needed for a decisive conclusion.

Humeral shaft fractures

Fractures of the humeral shaft are common injuries with multiple management strategies. Many still regard nonoperative management as the standard of care; however, as the understanding of these injuries increases, treatment recommendations are also evolving. Fracture pattern, fracture location, and identifiable patient risk factors may predict poor outcome with nonoperative management, and earlier operative intervention may be recommended. Operative management includes open reduction and internal fixation through a variety of exposures, intramedullary nail fixation, and external fixation. With increasing rates of shoulder arthroplasty, periprosthetic humeral shaft fractures also deserve special consideration.

Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model

Objectives: To compare the mechanical properties of locking compression plate (LCP) and limited contact dynamic compression plate (LC-DCP) constructs in an experimental model of comminuted fracture of the canine femur during eccentric cyclic loading.

Methods: A 20 mm mid-diaphyseal gap was created in eighteen canine femora. A 10-hole, 2.4 mm stainless steel plate (LCP or LC-DCP) was applied with three bicortical screws in each bone fragment. Eccentric cyclic loadings were applied at 10 Hertz for 610,000 cycles. Quasistatic loading / unloading cycles were applied at 0 and 10,000 cycles, and then every 50,000 cycles. Structural stiffness was calculated as the slope of the linear portion of the load-displacement curves during quasistatic loading / unloading cycles.

Results: No bone failure or screw loosening occurred. Two of the nine LCP constructs failed by plate breakage during fatigue testing, whereas no gross failure occurred with the LC-DCP constructs. The mean first stiffness of the LCP constructs over the course of testing was 24.0% lower than that of constructs stabilized by LC-DCP. Construct stiffness increased in some specimens during testing, presumably due to changes in boneplate contact. The first stiffness of LC-DCP constructs decreased by 19.4% and that of locked constructs by 34.3% during the cycling period. A biphasic stiffness profile was observed: the second stiffness was significantly greater than the first stiffness in both groups, which allowed progressive stabilization at elevated load levels.

Clinical significance: Because LCP are not compressed to the bone, they may have a longer working length across a fracture, and thus be less stiff. However, this may cause them to be more susceptible to fatigue failure if healing is delayed.

In vitro biomechanical testing of the 3.5 mm LCP in torsion: a comparison of unicortical locking to bicortical nonlocking screws placed nearest the fracture gap

Objective

This biomechanical study compared the torsional strength and stiffness of a locking compression plate with all locking versus nonlocking screws and examined the effect of placing a locking unicortical or nonlocking bicortical screw nearest the fracture gap in a synthetic bone model.

Results

Synthetic bone models simulating a diaphyseal fracture without anatomic reduction were tested using four screw configurations: all bicortical locking (ABL), all bicortical nonlocking (ABN), a hybrid construct with a bicortical nonlocking screw nearest the fracture gap (BN), and a unicortical locking screw placed nearest the fracture gap (UL). Torsional stiffness, rotation and torque at failure were compared via ANOVA and post hoc pairwise comparisons (p < 0.05). ABN and BN had the highest stiffness (p < 0.01) with ABL greater than UL (p < 0.01). Rotation at failure was greatest for ABL (p < 0.01) with UL greater than ABN (p < 0.05). Unicortical locking screws nearest the fracture gap decreased stiffness, without significantly affecting torque or rotation at failure. Construct stiffness was found to exist in a very narrow range of 0.9–1.2 N m/deg with standard deviations of 0.1 N m/deg in all cases. The results of this study support the use of nonlocking screws in a hybrid construct to increase torsional stiffness.

Electronic supplementary material

The online version of this article (10.1186/s13104-017-3102-y) contains supplementary material, which is available to authorized users.

Biomechanical Study of the Fixation Strength of Anteromedial Plating for Humeral Shaft Fractures

Background:

Open reduction and internal fixation with plate and screws are the gold standard for the surgical treatment of humeral shaft fractures, this study was to compare the mechanical properties of anteromedial, anterolateral, and posterior plating for humeral shaft fractures.

Methods:

A distal third humeral shaft fracture model was constructed using fourth-generation sawbones (#3404, composite bone). A total of 24 sawbones with a distal third humeral shaft fracture was randomly divided into three Groups: A, B, and C (n = 8 in each group) for anteromedial, anterolateral, and posterior plating, respectively. All sawbones were subjected to horizontal torsional fatigue tests, horizontal torsional and axial compressive fatigue tests, four-point bending fatigue tests in anteroposterior (AP) and mediolateral (ML) directions and horizontal torsional destructive tests.

Results:

In the horizontal torsional fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 6.12°, 6.53°, and 6.81°. In horizontal torsional and axial compressive fatigue tests, the mean torsional angle amplitude in Groups A, B, and C were 5.66°, 5.67°, and 6.36°. The mean plate displacement amplitude was 0.05 mm, 0.08 mm, and 0.10 mm. Group A was smaller than Group C (P < 0.05). In AP four-point bending fatigue tests, the mean plate displacement amplitude was 0.16 mm, 0.13 mm, and 0.20 mm. Group B was smaller than Group C (P < 0.05). In ML four-point bending fatigue tests, the mean plate displacement amplitude were 0.16 mm, 0.19 mm, and 0.17 mm. In horizontal torsional destructive tests, the mean torsional rigidity in Groups A, B, and C was 0.82, 0.75, and 0.76 N·m/deg. The yielding torsional angle was 24.50°, 25.70°, and 23.86°. The mean yielding torque was 18.46, 18.05, and 16.83 N·m, respectively.

Conclusions:

Anteromedial plating was superior to anterolateral or posterior plating in all mechanical tests except in AP four-point bending fatigue tests compared to the anterolateral plating group. We can suggest that anteromedial plating is a clinically safe and effective way for humeral shaft fractures.

Is Anterior Bridge Plating for Mid-Shaft Humeral Fractures a Suitable Option for Patients Predominantly Involved in Overhead Activities? A Functional Outcome Study in Athletes and Manual Laborers

BACKGROUND

To assess the functional and radiological outcomes of minimally invasive anterior bridge plating (ABP) for mid-shaft humerus fractures in patients predominantly involved in overhead activities (athletes and manual laborers).

METHODS

Forty-eight patients fulfilling inclusion criteria were treated with ABP at a level-I trauma center using a 4.5-mm dynamic/locking compression plate and followed for a period of 1 year. Functional outcome was assessed using the Constant, Mayo elbow, and Disabilities of the Arm, Shoulder and Hand (DASH) scores. Range of motion (ROM), subjective strength, and radiographic union were assessed. A general satisfaction questionnaire was also administered.

RESULTS

Most patients achieved excellent functional and radiological outcomes. ROM and strength of the shoulder girdle exhibited clinically nonsignificant loss as compared to the opposite side. The mean time for return to the original activities was 64 days (range, 36 to 182 days) and the mean time for confirmed radiographic union was 45 days (range, 34 to 180 days). The mean Constant, Mayo elbow, DASH scores were 95.73 ± 5.76 (range, 79 to 100), 95.94 ± 6.74 (range, 85 to 100), and 1.56 ± 3.15 (range, 0.0 to 14.0), respectively. The majority of patients (43 patients, 89.6%) who fell in the excellent or very good category according to our questionnaire were extremely satisfied. There were 2 cases (4.17%) of nonunion and 3 patients (6.25%) had to change/modify their original occupation.

CONCLUSIONS

ABP is fundamentally different from traditional open posterior plating or conventional intramedullary nailing. It gives relative stability with union taking place by callus formation, and a longer plate on the tensile surface ensures that the humerus can withstand greater amount of rotational and bending stresses. The minimally invasive nature causes minimal soft tissue damage and, if done correctly, causes no damage to the vital structures in proximity. ABP for mid-shaft humerus fractures in patients predominantly engaged in overhead activities is a safe and effective treatment modality yielding high rates of union, excellent functional recovery, minimal biological disruption, better cosmesis, and superior satisfaction rates.

Comparison of the effect on bone healing process of different implants used in minimally invasive plate osteosynthesis: limited contact dynamic compression plate versus locking compression plate

Minimally invasive plate osteosynthesis (MIPO) has been widely accepted because of its satisfactory clinical outcomes. However, the implant construct that works best for MIPO remains controversial. Different plate designs result in different influence mechanisms to blood flow. In this study, we created ulnar fractures in 42 beagle dogs and fixed the fractures using MIPO. The dogs were randomly divided into two groups and were fixed with a limited contact dynamic compression plate (LC-DCP) or a locking compression plate (LCP). Our study showed that with MIPO, there was no significant difference between the LCP and the LC-DCP in terms of fracture fixation, bone formation, or mineralization. Combined with the previous literature, we inferred that the healing process is affected by the quality of fracture reduction more than plate selection.

Dual plating for fixation of humeral shaft fractures: A mechanical comparison of various combinations of plate lengths

Objective

The role of plate configuration was found inconclusive on the biomechanical effects of the plate size and hole number for dual plate constructions in humeral shaft fractures. The purpose of this study was to test the biomechanical stability of various dual plate constructions.

Methods

Twenty-four left humeri (4th Generation Composite Humerus, Sawbones, Malmö, Sweden) with comminuted midshaft humeral fracture were used. Four groups of plate constructs were tested: laterally fixed 8-hole locking plate and screws were combined with anteriorly locking plates containing 0, 4, 6, or 8 holes in groups I, II, III, and IV, respectively. The alterations in axial, bending, and torsional angles were recorded.

Results

There were no fixation failures during axial, bending, or torsional stiffness testing within the elastic behavior limits. Axial stiffness was highest in Group IV. Torsional stiffness, posterior-to-anterior bending stiffness, lateral-to-medial bending stiffness, and medial-to-lateral bending stiffness were lowest in Group I.

Conclusion

The similar stiffness values for the 8-to-4 hole and 8-to-6 hole plate constructions indicate that the 8-to-4 hole construction is an option in young adults, while the stiffest 8-to-8 hole combination may be an option for osteoporotic patients.

Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs

OBJECTIVE

To compare the bending properties of String-of-Pearls® (SOP) and Limited Contact Dynamic Compression Plate® (LC-DCP) constructs in orthogonal bending directions.

METHODS

3.5 mm SOP and LC-DCP plates were fixed to a bone model simulating a comminuted tibial fracture. Specimens were non-destructively tested in both mediolateral and craniocaudal bending for 10 cycles. Bending stiffness and total angular deformation were compared using parametric analyses (p <0.05).

RESULTS

For both constructs, stiffness was significantly less when bending moments were applied against the thickness of the plates (mediolateral bending) than against the width (craniocaudal bending). When compared to the mediolateral plane, bending constructs in the craniocaudal plane resulted in a 49% (SOP group) and 370% (LC-DCP group) increase in stiffness (p <0.001). Mediolateral bending stiffness was significantly greater in the SOP than the LC-DCP constructs. Conversely, in craniocaudal bending, SOP constructs stiffness was significantly less than that of the LC-DCP constructs. The differences between the two constructs in total angular deformation had an identical pattern of significance.

CLINICAL SIGNIFICANCE

This study found that SOP showed less variability between the orthogonal bending directions than LC-DCP in a comminuted fracture model, and also described the bi-planar bending behaviour of both constructs. Although not exhibiting identical bending properties in both planes, SOP constructs had a more homogenous bending behaviour in orthogonal loading directions. The difference between the SOP with a circular cross sectional shape compared to the rectangular shape of standard plates is probably responsible for this difference.

Internal fixation of osteoporotic fractures

Osteoporosis leads to bone fragility and increased risk of fracture. Despite advances in diagnosis and treatment, the prevalence continues to rise. Osteoporotic fracture treatment has a unique set of difficulties related to poor bone quality and traditional approaches, and implants may not perform well. Fixation failure and repeat surgery are poorly tolerated and highly undesirable in this patient population. This review illustrates the most recent updates in internal fixation, implant design, and surgical theory regarding treatment of patients with osteoporotic fractures.

Experimental analysis of the minimally invasive plate osteosynthesis technique applied with non-locking screws and screw locking elements

Minimally invasive plate osteosynthesis (MIPO) is an effective surgical technique in the repair of humeral and tibial shaft fractures. There is some controversy as to the minimum number of screws required to ensure correct stability to promote healing, especially when dealing with low quality bones. This work compared different systems assembled on synthetic models simulating a comminuted fracture. Group 1 comprised a locking compression plate with four non-locking screws placed at the holes furthest from the fracture. Group 2 differed from group 1 only in the additional use of two screw locking elements (SLE). Group 3 had four rather than two SLE and, finally, Group 4 used 4 locking screws. The compression and torsion tests with static and cyclic loads showed that, in MIPO, two locking screws or two non-locking screws with SLE could be used per segment without any significant loss in stiffness after 1000 cycles, with system stability guaranteed in both cases. However, lower strength and significant loss of stiffness were observed when non-locking screws were used alone.

Comparison of lateral and posterior surgical approach in management of extra-articular distal humeral shaft fractures

OBJECTIVE

The objective of this study was to compare treatment results and complication rates between lateral and posterior approaches in surgical treatment of extra-articular distal humeral shaft fractures.

MATERIAL AND METHODS

Between June 2008 and May 2012, a total of 68 patients with extra-articular distal humeral shaft fractures were treated by lateral and posterior approaches. Of the patients, 30 were operated by a lateral approach (group I) and 26 patients were operated by a posterior approach (group II). There was no statistical significance between the two groups in sex distribution, age, the mechanism of the injury, injured arms, AO/ASIF (Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation) classification, and the time from injury to surgery (P>0.05). Operation time, intraoperative bleeding volume, hospitalisation, clinical outcomes, and complications were compared between the two groups. The elbow functional results were evaluated by the Mayo Elbow Performance Score (MEPS).

RESULTS

All patients were followed up. The average of follow-up in group I was 15.53±2.636 months (range, 12-22 months), and was 16.12±2.889 months (range, 12-22 months) in group II. There was no significant difference in the operation time, intraoperative bleeding time, and hospitalisation between the two groups (P>0.05). In group I, the mean time of bone union was 12.87±1.852 weeks (range, 10-16 weeks), the mean degrees of elbow flexion was 139.20°±3.274° (range, 134-146°), the mean degrees of elbow extension was 4.77°±1.906° (range, 0-8°), and the mean points of MEPS was 87.00±7.724 (range, 70-100 points). In group II, the mean time of bone union was 12.96±2.218 weeks (range, 10-16 weeks), the mean degrees of elbow flexion was 137.85°±4.076° (range, 130-145°), the mean degrees of elbow extension was 5.15°±2.327° (range, 0-9°), and the mean points of MEPS was 86.15±7.656 (range, 70-100 points). There was no significant difference in the bone union, range of elbow flexion, range of elbow extension and MEPS between the two groups (P>0.05). The overall complication rate in group I was lower than that in group II (P=0.041).

CONCLUSIONS

Both lateral and posterior surgical approaches acquired satisfied treatment results in the management of extra-articular distal humeral shaft fractures, and there was a lower complication rate using the lateral approach.

Do locking screws work in plates bent at holes?

OBJECTIVES

To assess whether plate bending at a hole significantly changes the biomechanical properties of a locked screw.

METHODS

Coronal plane bends of 5-, 15-, or 45-degree angles were placed in 3.5-mm locking compression plates with the apex at a locking hole. An additional 45-degree angle test group was created in which a threaded screw head insert was placed before bending. Ten plates were tested in each group and compared with nonbent controls in a stepwise cyclic loading protocol.

RESULTS

Statistically significant differences in protocol survival were shown between the control group and the 15-degree angle (P = 0.006) and 45-degree angle (P = 0.0007) groups. An apparent decrease in protocol survival in the 5-degree angle group did not reach statistical significance (P = 0.17). The average number of cycles survived was significantly different between the control group and the 15-degree angle (P = 0.027) and 45-degree angle (P = 0.0002) groups. The mean cycles to failure for the 5-degree angle group was 16% lower than for controls but did not reach statistical significance (P = 0.37). The test group bent to an angle of 45 degrees after placement of a threaded screw head insert showed no difference in protocol survival or in mean number of cycles survived compared with the regular 45-degree angle group.

CONCLUSION

Bending of a 3.5-mm locking compression plate by more than 5 degrees at a locking hole results in a statistically significant decrease in survival of the corresponding locked screw. This effect cannot be prevented by the placement of a threaded screw head insert before bending.

Dual plating of humeral shaft fractures: orthogonal plates biomechanically outperform side-by-side plates

BACKGROUND

Single large-fragment plate constructs currently are the norm for internal fixation of middiaphyseal humerus fractures. In cases where humeral size is limited, however, dual small-fragment locking plate constructs may serve as an alternative. The mechanical effects of different possible plate configurations around the humeral diaphysis may be important, but to our knowledge, have yet to be investigated.

QUESTIONS/PURPOSES

We used finite element analysis to compare the simulated mechanical performance of five different dual small-fragment locking plate construct configurations for humeral middiaphyseal fracture fixation in terms of (1) stiffness, (2) stress shielding of bone, (3) hardware stresses, and (4) interfragmentary strain.

METHODS

Middiaphyseal humeral fracture fixation was simulated using the finite element method. Three 90° and two side-by-side seven-hole and nine-hole small-fragment dual locking plate configurations were tested in compression, torsion, and combined loading. The configurations chosen are based on implantation using either a posterior or anterolateral approach.

RESULTS

All three of the 90° configurations were more effective in restoring the intact compressive and torsional stiffness as compared with the side-by-side configurations, resulted in less stress shielding and stressed hardware, and showed interfragmentary strains between 5% to 10% in torsion and combined loading.

CONCLUSIONS

The nine-hole plate anterior and seven-hole plate lateral (90° apart) configuration provided the best fixation. Our findings show the mechanical importance of plate placement with relation to loading in dual-plate fracture-fixation constructs.

CLINICAL RELEVANCE

The results presented provide novel biomechanical information for the orthopaedic surgeon considering different treatment options for middiaphyseal humeral fractures.

Biomechanical considerations for surgical stabilization of osteoporotic fractures

The incidence of osteoporotic fractures has been steadily rising along with the aging of the population. Surgical management of these fractures can be a challenge to orthopedic surgeons. Diminished bone mass and frequent comminution make fixation difficult. Advancements in implant design and fixation techniques have served to address these challenges and when properly applied, can improve overall outcome. The purpose of this review is to describe fixation challenges of common osteoporotic fractures and provide options for successful treatment.

Designing a biomechanics investigation: choosing the right model

Physical testing is commonly performed to answer important biomechanical questions in the treatment of patients with fractures and other orthopaedic conditions. However, a variety of mistakes that are made in performing such investigations can severely limit their impact. The goal of this article is to discuss important aspects of study design to consider when planning for biomechanical investigations so that the studies can provide maximal benefit to the field. The best mechanical investigations begin with a good research question, one that comes out of patient care experience, is clearly defined, and can be stated concisely. The first practical issue to be considered is often choosing the type of physical specimens to be tested to address the research question. A related issue involves determining how many specimens will be needed to answer the posed mechanical question. Cadavers are generally still the closest to the actual clinical situation, but they are limited by interspecimen variability, which often requires a matched pair design that can address only one question. Simulated bone specimens limit variability and can replicate normal and osteoporotic bone. In planning the physical testing, the critical mechanical variables involved in answering the research question must be identified and due consideration given to deciding how best to measure them. Another important issue that arises relates to whether or not single static loadings will suffice in the testing (eg, to study construct stiffness) or whether cyclic dynamic testing is necessary (eg, to study late failure likely attributable to fatigue). To summarize, experimental design should be carefully planned before initiating mechanical testing. Sample size calculations should be performed to ensure adequate power and that clinically relevant differences can be detected. This pregame analysis can save significant time and cost and greatly increase the likelihood that the results will advance knowledge.

Subbrachial approach to humeral shaft fractures: new surgical technique and retrospective case series study

BACKGROUND

There are few surgical approaches for treating humeral shaft fractures. Here we present our results using a subbrachial approach.

METHODS

We conducted a retrospective case series involving patients who had surgery for a humeral shaft fracture between January 1994 and January 2008. We divided patients into 4 groups based on the surgical approach (anterior, anterolateral, posterior, subbrachial). In all patients, an AO 4.5 mm dynamic compression plate was used.

RESULTS

During our study period, 280 patients aged 30-36 years underwent surgery for a humeral shaft fracture. The average duration of surgery was shortest using the subbrachial approach (40 min). The average loss of muscle strength was 40% for the anterolateral, 48% for the posterior, 42% for the anterior and 20% for the subbrachial approaches. The average loss of tension in the brachialis muscle after 4 months was 61% for the anterolateral, 48% for the anterior and 11% for the subbrachial approaches. Sixteen patients in the anterolateral and anterior groups and 6 patients in the posterior group experienced intraoperative lesions of the radial nerve. No postoperative complications were observed in the subbrachial group.

CONCLUSION

The subbrachial approach is practical and effective. The average duration of the surgery is shortened by half, loss of the muscle strength is minimal, and patients can resume everyday activities within 4 months. No patients in the subbrachial group experienced injuries to the radial or musculocutaneous nerves.

Locking plates in osteoporosis: a biomechanical cadaveric study of diaphyseal humerus fractures

OBJECTIVE

To determine whether locking plates offer an advantage in fixation of fractures in osteoporotic humeral bone.

DESIGN

Biomechanical testing of 18 matched pairs of osteoporotic human cadaver humeri plated posteriorly with either all locked or all nonlocked screws. An established protocol was used to test the constructs with torque applied to a peak of ±10 Nm for 1000 cycles at 0.3 Hz or until failure. Eighteen pairs were tested for failure, 11 pairs were tested for cycles survived, and 10 pairs were tested for stiffness.

SETTING

University biomechanical laboratory.

MAIN OUTCOME MEASUREMENTS

Percentage surviving testing, mean cycles survived, and stiffness.

RESULTS

We observed catastrophic failure of the constructs in 47% of the samples. Humeri plated with nonlocking plates failed at a higher rate than those with locking plates (67% nonlocking vs 28% locking, n = 18 pairs, P = 0.008). Locking constructs also outperformed nonlocking constructs in mean cycles survived (707 cycles locking, 345 cycles nonlocking, n = 11 pairs, P < 0.05) and stiffness at 10 cycles (0.853 Nm/degree locking vs 0.416 Nm/degree nonlocking, n = 10 pairs, P < 0.001).

CONCLUSIONS

Locking plates were shown to provide improved mechanical performance over nonlocking plates in torsional cyclic loading in a osteoporotic cadaveric fracture model. Our results confirm general conclusions of previous work that used a synthetic bone model of osteoporosis, but we found a high rate of catastrophic failure, questioning the validity of the previously published synthetic model of osteoporosis (overdrilling of synthetic bone) for this application.

[Therapy of humeral shaft fractures]

Fractures of the humeral shaft are less frequent than those of the proximal humerus. The formerly recommended treatment of humeral shaft fractures was conservative according to Böhler. This still remains an adequate concept of treatment but according to a change in the technical possibilities and the demands of patients and physicians on fast restoration of function and low pain, there is a trend towards surgical stabilization of humeral shaft fractures. The implant of choice is discussed controversially and consists of various types of nails versus plating. The technique of nailing is antegrade or retrograde and depends on the localization of the fracture. In our opinion good indications for plating are combined fractures of the proximal humerus and the shaft as well as very distal humeral shaft fractures. A primary lesion of the radial nerve is no imperative indication for exploration and different studies have shown the same results for exploration after 2 or 3 months if there is no spontaneous remission.

Plating of acute humeral diaphyseal fractures through an anterior approach in multiple trauma patients

OBJECTIVE

We evaluated the clinical and long-term functional outcomes of humeral diaphyseal fractures treated with acute anterior plating in a trauma population.

DESIGN

Single-center, retrospective cohort analysis with long-term prospective follow-up.

SETTING

Urban, Level I trauma center.

PATIENTS

Ninety-six patients with high-energy fractures of the humeral shaft were treated over a 10-year period.

INTERVENTION

All patients were treated by a standard surgical protocol of open reduction through an anterior approach with small or large fragment fixation in the supine position.

MAIN OUTCOME MEASUREMENTS

Mechanism of injury, time to union, complications, and range of motion during clinical follow-up were obtained. We also prospectively assessed long-term strength, range of motion, and perceptions of disability using the Disabilities of the Arm, Shoulder and Hand questionnaire.

RESULTS

Mean time to surgery was 5 days (standard deviation, 11 days); 97.5% of patients achieved union in an average of 16.9 weeks (range, 6-56 weeks). Complications included two postoperative infections, two nonunions, and three implant failures. Long-term follow-up (n = 34) averaged 4.75 years (range, 1.4-10.8 years). On average, no significant differences between the injured and uninjured extremities were seen in range of motion at the shoulder and elbow with the exception of shoulder flexion. A modest loss of upper extremity strength in the injured arm was appreciated. The mean Disabilities of the Arm, Shoulder and Hand score was 25.9 (range, 0-79).

CONCLUSIONS

A standard anterior surgical approach with small fragment fixation is a safe and effective treatment for humeral shaft fractures in multiple trauma patients. We show a high union rate and few complications, although a modest loss of function and some perceived disability exists in the long-term.

Crutch weightbearing on comminuted humeral shaft fractures: a biomechanical comparison of large versus small fragment fixation for humeral shaft fractures

PURPOSE

This study evaluated the failure properties of length unstable humerii secured with small or large fragment plates.

METHODS

Two nonlocking plate constructs were examined, a nine-hole 4.5-mm limited contact dynamic compression plate (large fragment group) and a 12-hole 3.5-mm limited contact dynamic compression plate (small fragment group), both on composite humerii with a 1-cm defect to simulate comminution (n = 12 for each group). Each plate construct had similar working lengths and number of fixation points. Mechanical testing was first randomized for stiffness measurements in axial and torsional loads. All constructs were then tested in cyclic axial loads to failure.

RESULTS

For axial testing, the large fragment group had a mean stiffness of 1020 ± 195 N/mm compared with 268 ± 67 N/mm in the small fragment group (P < 0.0001). For torsional testing, the large fragment group had a mean stiffness of 1.5 ± 0.05 Nm/degree compared with 0.9 ± 0.04 Nm/degree in the small fragment group (P < 0.0001). Plastic deformation in the large fragment and small fragment groups were 0.09 ± 0.07 mm and 0.20 ± 0.24 mm, respectively (P = 0.1) assessed during cyclic testing up to 300 N. The postcyclic yield force in the large fragment group was 227 ± 30 N and in the small fragment group was 153 ± 5 N (P < 0.0001). The ultimate load in the large fragment and small fragment groups were 800 ± 87 N and 307 ± 15 N, respectively.

CONCLUSION

The results corroborate anticipated plate mechanical behavior with plate stiffness increasing as both plate width and thickness increase. The calculated yield force data suggest that both small and large fragment constructs would experience plastic deformation during bilateral crutch ambulation in a patient weighing 50 kg or more. The large fragment construct is not expected to catastrophically fail when subjected to loads in a patient 90 kg or less. The small fragment construct is predicted to catastrophically fail in patients weighing 70 kg or more.

Biomechanical investigation of an alternative concept to angular stable plating using conventional fixation hardware

Background

Angle-stable locking plates have improved the surgical management of fractures. However, locking implants are costly and removal can be difficult. The aim of this in vitro study was to evaluate the biomechanical performance of a newly proposed crossed-screw concept ("Fence") utilizing conventional (non-locked) implants in comparison to conventional LC-DCP (limited contact dynamic compression plate) and LCP (locking compression plate) stabilization, in a human cadaveric diaphyseal gap model.

Methods

In eight pairs of human cadaveric femora, one femur per pair was randomly assigned to receive a Fence construct with either elevated or non-elevated plate, while the contralateral femur received either an LCP or LC-DCP instrumentation. Fracture gap motion and fatigue performance under cyclic loading was evaluated successively in axial compression and in torsion. Results were statistically compared in a pairwise setting.

Results

The elevated Fence constructs allowed significantly higher gap motion compared to the LCP instrumentations (axial compression: p ≤ 0.011, torsion p ≤ 0.015) but revealed similar performance under cyclic loading (p = 0.43). The Fence instrumentation with established bone-plate contact revealed larger fracture gap motion under axial compression compared to the conventional LC-DCP osteosynthesis (p ≤ 0.017). However, all contact Fence specimens survived the cyclic test, whereas all LC-DCP constructs failed early during torsion testing (p < 0.001). All failures occurred due to breakage of the screw heads.

Conclusions

Even though accentuated fracture gap motion became obvious, the "Fence" technique is considered an alternative to cost-intensive locking-head devices. The concept can be of interest in cases were angle-stable implants are unavailable and can lead to new strategies in implant design.

Pathological fractures of the proximal humerus treated with a proximal humeral locking plate and bone cement

Bone loss secondary to primary or metastatic lesions of the proximal humerus remains a challenging surgical problem. Options include preservation of the joint with stabilisation using internal fixation or resection of the tumour with prosthetic replacement. Resection of the proximal humerus often includes the greater tuberosity and adjacent diaphysis, which may result in poor function secondary to loss of the rotator cuff and/or deltoid function. Preservation of the joint with internal fixation may reduce the time in hospital and peri-operative morbidity compared with joint replacement, and result in a better functional outcome. We included 32 patients with pathological fractures of the proximal humerus in this study. Functional and radiological assessments were performed. At a mean follow-up of 17.6 months (8 to 61) there was no radiological evidence of failure of fixation. The mean revised musculoskeletal Tumour Society functional score was 94.6% (86% to 99%). There was recurrent tumour requiring further surgery in four patients (12.5%). Of the 22 patients who were employed prior to presentation all returned to work without restrictions.

The use of a locking plate combined with augmentation with cement extends the indications for salvage of the proximal humerus with good function in patients with pathological and impending pathological fractures.