Locked plating in orthopaedic trauma: a clinical update

IFM calculator: An algorithm for interfragmentary motion calculation in finite element analysis

BACKGROUND

Interfragmentary motion (IFM) is a complex state that significantly impacts the healing process of fractures following implant placement. It is crucial to fully consider the IFM state after implantation in the design and biomechanical testing of implants. However, current finite element analysis software lacks direct tools for calculating IFM, and existing IFM tools do not offer a comprehensive solution in terms of accuracy, functionality, and visualization.

METHODS

In our study, we developed a Python-based algorithm for calculating IFM that addresses limitations. Our algorithm automatically calculated IFM distances, sliding distances, gaps, as well as the angles and rotation of the two fracture surfaces using all nodes on both sides of the fracture ends. Researchers could input data and selected desired parameters in the interface. The algorithm then performed the necessary calculations and presented the results in a clear and concise manner. The algorithm also provided comprehensive data export capabilities, allowing researchers to customize analyses based on specific needs.To provide a more intuitive demonstration of the calculation process and usage of IFM-Cal, we conducted simulations in Ansys using two rectangular blocks to compare the accuracy and function of three different methods (Point based method, contact tool and IFM-Cal).

RESULTS

The point-based method and the contact tool could not accurately calculate IFA, while IFM-Cal could provide a comprehensive evaluation of IFA. In simulation 1, the IFM distances calculated using the point sampling method, contact tool, and IFM-Cal were 2.00 mm, 3.15 mm, and 2.00 mm, respectively. In simulation 2, both the point sampling method and contact tool failed to calculate the interfragmentary angle (IFA), while the IFM-Cal algorithm estimated an angle of -7.87°, which had a small error compared to the ground-truth value of 7.9°.

CONCLUSION

We have developed an algorithm for computing IFM which can be utilized in finite element analysis and biomechanical experiments. By conducting comparative simulations with other existing algorithms, we have demonstrated the superior accuracy and expanded evaluation capabilities of our algorithm.

Retrospective analysis of locked versus non-locked plating of distal fibula fractures

INTRODUCTION

Unstable distal fibular fractures have traditionally been treated with open reduction internal fixation using a 1/3 tubular non-locked plate (compression plating). Locked plating is a newer technique that has become more popular despite the lack of clinical data supporting improved outcomes. The cost of locked plating is almost four times that of compression plating. We compared rates of reoperation due to implant failure, infection, and symptomatic device between compression and locked plating in open reduction internal fixation of distal fibular fractures METHODS: A retrospective study was performed at a level one trauma center over a ten-year period (2008-2017). Patients who were 18 and older and treated for unstable ankle fractures with locking or non-locking plate were included in this study. Patient charts were reviewed by orthopedic trauma surgeons to identify whether patients were treated with a 1/3 tubular non-locking or pre-contoured locked plate and to determine the cause of reoperation.

RESULTS

In total, 442 patients were identified with 203 in the non-locked 1/3 tubular plate group and 239 in the pre-contoured locked plate group. A total of 38 patients (8.6%) underwent device removal with a higher proportion of patients in the non-locked 1/3 tubular plate cohort (11.3% vs. 6.3%, p = 0.059). Statistically significant differences in reasons for reoperation were found for symptomatic implant (78.3% vs. 46.7%, p = 0.045) and infection (8.7% vs 53.3%., p < 0.01). Of patients who had device removal for symptomatic implant in the compression plating cohort, 13 (72.2%) had lateral positioning and 5 (27.8%) had posterior positioning (p < 0.01) whereas there was no statistical difference in plate positioning in the locked cohort. Of all medical comorbidities identified, only diabetes was associated with a higher rate of infection-related reoperations (83.3% vs. 15.6%, p < 0.01).

CONCLUSIONS

Both compression and locked plate techniques demonstrated low reoperation rates. Compression plating with 1/3 tubular plates placed laterally more often resulted in reoperation due to symptomatic implant but had fewer complications of infection. Given that the cost is significantly less, 1/3 tubular plating placed posteriorly may be preferred to decrease the risks of symptomatic implant and infection.

Management of Canine Y-T Humeral Fractures Using Titanium Polyaxial Locking Plates in 17 Dogs

The objective of this study was to document the short- and medium-to-long-term outcomes and complication rates of Y-T humeral condylar fractures fixed using titanium polyaxial locking plate (T-PLP). A retrospective review was performed of the medical records and radiographs of dogs with a Y-T humeral condylar fracture treated with T-PLP at a single veterinary referral center (2012–2018). Seventeen cases met the inclusion criteria. Medium- to long-term follow-up (.6 mo) information was derived using the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire. Recorded complications were catastrophic (1/17) and minor (2/17). Gait at 10–12 wk following surgery was subjectively assessed as good or excellent for 13 cases. Radiographic bone union was achieved in 7/12 cases at 4–6 wk. LOAD scores obtained a mean of 15 mo (range 6–29 mo) following surgery and indicated no or mild impairment in 15/16 and moderate functional impairment in 1. The application of T-PLP for the treatment of Y-T humeral condylar fractures resulted in adequate stabilization allowing successful fracture healing and medium- to long-term outcomes comparable to previous reports. According to results of LOAD testing, the medium- to long-term follow-up suggests that clients were aware of mild to moderate functional impairment in all cases.

High Tibial Osteotomy: An Update for Radiologists

High tibial osteotomy (HTO) is a surgical procedure to treat symptomatic unicompartmental osteoarthritis (OA) associated with knee malalignment. There has been a recent resurgence of interest in HTO in patients who prefer joint-preserving surgery, as HTO shifts the knee's mechanical axis from the arthritic compartment to a neutral position, thereby reducing knee pain, slowing progression of OA, and delaying the need for a total knee arthroplasty. The ideal candidates for HTO are young, active, nonobese patients with isolated varus deformity of the knee due to medial compartment OA. Radiography is critical in the preoperative evaluation for HTO and can help expand surgical indications to include a wider variety of patients. Radiography is also routinely obtained in postoperative assessment and is typically the first test to suspect complications. This review describes the radiologic aspects of HTO, including preoperative imaging assessment, as well as normal and abnormal postoperative imaging appearances. Surgical techniques and osteotomy fixation devices are described, with a focus on the medial opening wedge approach. Given the growing interest in HTO, radiologists should become familiar with the basics of the procedure and the role of imaging in preoperative and postoperative evaluation.

Minimally Invasive Internal Fixation of Femoral Shaft Fractures-A Biomechanical Study with a Disruptive Technique

(1) Background: In polytrauma patients, femur fractures are usually stabilised by external fixation for damage control, later being treated with definitive plate or nail osteosynthesis. Screw/rod systems established in spinal surgery might be inserted for internal fixation, providing sufficient fracture stability that subsequent intervention is unnecessary. This was to be investigated biomechanically. (2) Methods: The unilaterally applied spinal internal fixator (IF) was subjected to load and deformation analysis on artificial femurs with 32-A3 fracture according to AO classification. Distance of screws to fracture and rod to cortical bone were analysed as parameters influenced surgically as stiffness and deformation of the treated fracture. In addition, the stability of another construct with a second screw/rod system was determined. The axial load in stance phase during walking was simulated. The results were compared against an established fixed-angle plate osteosynthesis (IP). (3) Results: There were no implant failures in the form of fractures, avulsions or deformations. All unilateral IF combinations were inferior to IP in terms of stability and stiffness. The bilateral construct with two screw/rod systems achieved biomechanical properties comparable to IP. 4) Conclusion: Biomechanically, a biplanar screw/rod system is suitable for definitive fracture stabilisation of the femur, despite a damage control approach.

Salvaging Pull-Out Strength in a Previously Stripped Screw Site: A Comparison of Three Rescue Techniques

Screw stripping during bone fixation is a common occurrence during operations that results in decreased holding capacity and bone healing. We aimed to evaluate the rescue of the stripped screw site using screws of different dimensions. Five screw configurations were tested on cadaveric specimens for pull-out strength (POS). The configurations included a control screw tightened without stripping, a configuration voluntarily stripped and left in place, and three more configurations in which the stripped screws were replaced by a different screw with either increased overall length, diameter, or thread length. Each configuration was tested five times, with each screw tested once. The POS of the control screw, measured to be 153.6 ± 27 N, was higher than the POS measured after stripping and leaving the screw in place (57.1 ± 18 N, p = 0.001). The replacement of the stripped screw resulted in a POS of 158.4 ± 64 N for the screw of larger diameter, while the screws of the same diameter but increased length or those with extended thread length yielded POS values of 138.4 ± 42 and 185.7 ± 48 N, respectively. Screw stripping is a frequent intraoperative complication that, according to our findings, cannot be addressed by leaving the screw in place. The holding capacity of a stripped screw implanted in cancellous bone can successfully be restored with a different screw of either larger diameter, longer length, or extended thread length.

Computational Biomechanical Analysis of Postoperative Calcaneal Fractures with Different Placement of the Sustentaculum Screw

OBJECTIVE

To evaluate the computational biomechanical analysis of intra-articular calcaneal fractures with different fixation status of the sustentaculum plate screw, when the finite element modeling of calcaneal fractures were fixed by the lateral locking plate.

METHODS

The normal right foot of a male (age: 36 years; height: 174 cm; body weight: 65 kg) was scanned by the CT scanner. As the computational biomechanical study, the three-dimensional finite element model of the simplified Sanders type-II calcaneal fracture was built. Fixation with the lateral calcaneal locking plate and screws was simulated using a finite element software package according to clinical operation. According to the different placement of the sustentaculum plate screw, the models were categorized as the accurate fixation group, marginal fixation group, and non-fixation group. The loading of 650 N with the vertical axial compression was applied to simulate the standing phase with single foot. The Von Mises stress distribution, maximal displacement, and contact area of the subtalar joint were analyzed among three groups.

RESULTS

The pressure distribution of the subtalar joint facet was inhomogeneous. The stress concentration of the calcaneus was located at the medial zone of the posterior subtalar joint facet. The peak Von Mises stress distribution in three groups was similar at the subtalar joint facet of 4.9 MPa, 5.1 MPa, and 5.4 MPa. In the accurate fixation group, the contact area on the posterior articular facet was 277.1 mm² ; the maximal displacement was 0.18 mm. The contact area of the marginal fixation group was 265.3 mm² on the posterior facet, where the maximal displacement was 0.23 mm. In the non-fixation group, the contact area was 253.8 mm² ; the maximal displacement was 0.25 mm. There was a slight change in the contact area of the subtalar joint and no prominent displacement of the calcaneus could be detected among the three groups.

CONCLUSIONS

The biomechanical results, including the peak stress distribution, contact area, and maximal displacement of subtalar joint, were similar whether the screw is placed exactly within the sustentaculum tali or not, when the calcaneal fractures were fixed by the lateral locking plate. The sustentaculum plate screw had less effect on the biomechanical performance of the calcaneus.

A comparison of bone union and complication rates between locking and non-locking plates in distal fibular fracture: Retrospective study of 106 cases

BACKGROUND

Ankle fractures represents the third most frequent fracture in elderly patients. There is a current tendency to fix long bones fractures with locking plates. However, we rarely find published accounts about the use of locking plates in distal fibula fractures, except for biomechanical ones, studying human cadaveric fibula.

OBJECTIVES

The main objective was to compare radiographic bone union rates at 6 and 12 weeks of follow up, then wound complications and hardware removal rates, and construct cost.

STUDY DESIGN & METHODS

We retrospectively analyzed 105 patients who underwent surgery with locking plates or non-locking plates over a two-year period, out of which 42 patients were treated with non-locking plates (VIVES™ - Stryker^Ⓡ) and 63 with locking plates (VariAx™ - Stryker^Ⓡ,). We analyzed bone union on anterior posterior and lateral X-rays of the ankle. We collected data of wound complications and hardware removal from patient records. Multiple linear regression techniques were performed after identifying dependent variables.

RESULTS

There was no significant difference between non-locking and locking plates in the radiographic bone union rate of distal fibula, respectively at 6 and 12 post-operative weeks (85.71% vs. 81%; p = 0.525 and 97.62% vs. 96.83%; p = 1). No significant difference was found in the wound complication rate between the two groups (11.9% vs. 11.12%; p = 0.9). No significant differences were found in the hardware removal rate, either with or without operative site's infection (respectively: 30.95% vs. 39.68%; p = 0.361 and 21.42% vs. 38.09%; p = 0.071). Cost efficiency is in the favor of non-locking plates.

CONCLUSION

Non-locking constructs are as effective as locking constructs in the treatment of displaced distal fibula fractures at a substantially lower cost. High-quality randomized controlled trials are needed in the future to verify the finding of this study.

Reverse distal femoral locking plate for subtrochanter femur fracture

In these case series, we used titanium locking compression plate-distal femur (LCP-DF) plate (Synthes) 9–11 hole using less invasive stabilization system or open reduction technique. This case series aims to determine the functional scores on reverse distal femoral locking plate for subtrochanteric femur fracture. A 34-year-old male with closed subtrochanteric fracture of the right femur (Seinsheimer 2B) with Harris hip scores (HHS) of 17, 96, and 97 obtained consecutively in 0, 6, and 12 months, respectively. A 24-year-old male with closed comminuted subtrochanteric fracture of the right femur (Seinsheimer V) with HHS of 13, 93, and 97 at 0, 6, and 12 months respectively. A 39-year-old male with non-union, left subtrochanteric femur fracture (Seinsheimer 2C) yielded HHS of 38, 73, and 77 at 0, 6, and 12 months, respectively. A 35-year-old female with close subtrochanteric fracture of the right femur (Seinsheimer IIB) yielded HHS of 23, 40, and 73 at 0, 6, and 12 months, respectively. Mean initial HHS and scores at 6 and 12 months reached 22, 75, and 86, respectively.

Locking design affects the jamming of screws in locking plates

The seizing of locking screws is a frequently encountered clinical problem during implant removal of locking compression plates (LCP) after completion of fracture healing. The aim of this study was to investigate the effect of two different locking mechanisms on the seizing of locking screws. Specifically, the removal torques before and after cyclic dynamic loading were assessed for screws inserted at the manufacturer-recommended torque or at an increased insertion torque. The seizing of 3.5-mm angular stable screws was assessed as a function of insertion torque for two different locking mechanisms (Thread & Conus and Thread Only). Locking screws (n=10 for each configuration) were inserted either according to the manufacturer-recommended torque or at an increased torque of 150% to simulate an over-insertion of the screw. Half of the screws were removed directly after insertion and the remaining half was removed after a dynamic load protocol of 100,000 cycles. The removal torques of locking screws exceeded the insertion torques for all tested conditions confirming the adequacy of the test setup in mimicking screw seizing in locked plating. Screw seizing was more pronounced for Thread Only design (+37%) compared to Thread & Conus design (+14%; P<0.0001). Cyclic loading of the locking construct consistently resulted in an increased seizing of the locking screws (P<0.0001). Clinical observations from patients treated with the Thread & Conus locking design confirm the biomechanical findings of reduction in seizing effect by using a Thread & Conus design. In conclusion, both over-tightening and cyclic loading are potential causes for screw seizing in locking plate implants. Both effects were found to be less pronounced in the Thread & Conus design as compared to the traditional Thread Only design.

Single cycle to failure in bending of three titanium polyaxial locking plates

Objective: Evaluation of the bending properties in one direction of three titanium polyaxial locking plate systems.

Materials and methods: The Polyaxial Advanced Locking System (PAX®) straight plate (PAX SP), the PAX® reconstruction plate (PAX RP), and the VetLOX reconstruction plates (VetLOX) were evaluated individually and as constructs applied to a bone model simulating a fracture gap and compared using a two-way analysis of variance and Tukey posthoc analysis.

Results: The PAX SP had the highest values of bending stiffness, bending structural stiffness and bending strength. When tested as plates alone, the PAX RP and VetLOX showed no differences with regard to bending stiffness and bending structural stiffness, whilst the PAX RP had significantly higher strength. The PAX RP construct had significantly higher bending stiffness, bending structural stiffness and bending strength than the VetLOX construct.

Clinical relevance: The PAX RP and VetLOX reconstruction plates are much more likely to fail when used as bridging implants, thus adjunct support is needed. The lower bending strength of the VetLOX reconstruction plates suggests it should not be used in fractures under high loads.

Masquelet technique with external locking plate for recalcitrant distal tibial nonunion

OBJECTIVE

In the present retrospective study, we aimed to analyze the results of treatment for recalcitrant distal tibial nonunion using Masquelet technique with locking plate as a definitive external fixator.

MATERIALS

We included 15 consecutive cases of distal tibial nonunion treated at our hospital between January 2012 and December 2015. The reconstructive procedure comprised debridement of the nonunion site, deformity correction, stabilization with an external locked plate, defect filling with cement spacer for inducing membrane formation, and bone reconstruction using a cancellous bone autograft (Masquelet technique). All patients were followed-up for at least one year.

RESULTS

Fracture union occurred in all cases after a median of 6.5 months (range, 5-12 months). Mean ankle motion ranged from 12.3 (range, 5-20) degrees of dorsiflexion to 35 (range, 5-55) degrees of plantar flexion. At the final follow-up, the median Iowa ankle score was 83 (range, 68-91). Eight patients had excellent scores, six had good scores, and one had fail score.

CONCLUSION

Although the current study involved only a small number of patients and the intervention comprised two stages, we consider that the used protocol is a simple and valuable alternative for the treatment of recalcitrant distal tibial nonunion.

Locking attachment plate fixation around a well-fixed stem in periprosthetic femoral shaft fractures

INTRODUCTION

Periprosthetic fractures are difficult to manage. Plating technique has been considered a reliable form of management of periprosthetic fractures with a well-fixed stem, but a dependable and stable method of plate fixation to the bone is lacking. This study reports the clinical results using a locking attachment plate (LAP) instead of cable fixation to fix locking plates to a periprosthetic femoral shaft fracture.

MATERIALS AND METHODS

Nineteen patients with periprosthetic femoral shaft fractures around well-fixed stemmed implants were studied between August 2012 and December 2014. Patients were followed up for at least 1 year postoperatively. Median age was 74 years (range 56-96 years). Fractures were classified according to the Unified Classification System, Vancouver classification, and Su classification.

PROCEDURE

Open reduction was performed under minimal incision and the locking plate was fixed to the lateral cortex of the femoral shaft. The part of the shaft without a stem was fixed to the plate using 5.0-mm locking screws, and the part with an underlying stem was fixed using 3.5-mm locking screws through the LAP instead of cables. Postoperatively, patients were managed using general principles for femoral shaft fractures.

RESULTS

Average follow-up was 16 months (range 12-36 months). All cases achieved fracture healing without loss of reduction. There were no cases of implant breakage or stem loosening at final follow-up. The average number of LAPs per fixation construct was 2.1 (range 1-4), and the average number of 3.5-mm locking screws through each LAP was 3.3 (range 2-4). The average value of plate screw density was 0.55 (range 0.37-0.8), and the average working length was four holes (range 2-8).

CONCLUSIONS

Using the LAP to manage periprosthetic fractures with a well-fixed stem could obviate the need for cable around the stem area and yield acceptable outcomes.

Stabilisation of periarticular fractures and osteotomies with a notched head locking T-plate

OBJECTIVE

To report the clinical outcomes and complications of small animals that had articular or periarticular fractures or osteotomies stabilised with a notched head locking T-plate.

METHODS

Medical records were searched retrospectively to identify animals that had a notched head locking T-plate used to stabilise a small articular or periarticular bone fragment.

RESULTS

Nine dogs and two cats had an articular or periarticular bone fragment stabilised with a 2.0- or 2.4-mm notched head locking T-plate (12 procedures). The median body weight was 4.7 kg. The plate was modified by removing holes in 10/12 procedures and a combination of locking and non-locking screws were used in 7/12 procedures. All fractures or osteotomies progressed to clinical union. There were two intraoperative complications (intra-articular screw placement and overlong screw) and two postoperative complications (skin necrosis and stress protection)

CONCLUSIONS

This study reports the successful use of a 2.0- or 2.4-mm notched head locking T-plate for articular or periarticular fractures or osteotomies in a variety of small-breed dogs and cats. Care must be taken to prevent inadvertent penetration of the articular surface, particularly in regions such as the proximal tibia. The ability to modify the plate dimensions intraoperatively proved beneficial in most cases.

The biomechanical cost of variable angle locking screws

INTRODUCTION

Variable angle (VA) locking plates in fracture fixation surgery allow screws to be fastened to the plate within a conical "locus of vectors" in order to avoid existing prostheses, joint surfaces, or poor quality bone. Clinical failures of VA constructs in which screws have rotated at the plate/screw interface have been reported raising the concern that there may be a biomechanical cost for the increased flexibility that VA provides. The objective of this study was to test the mechanical properties of one commonly used VA locking mechanism with screws placed in both nominal and off-axis trajectories and compare these against the standard locking mechanism.

METHODS

VA locking screws were inserted into plates for distal femur fractures (VA Curved Condylar) at various angles (0° to 15° away from perpendicular). A control group of standard locking screws/plates was also tested. Maximum moment at the screw/plate interface and moment at two reference displacements were determined.

RESULTS

VA screws locked perpendicular to the plate provided the greatest maximum moment and moment at the reference displacements when using the VA system, and demonstrated lower moments compared to standard locking screws/plates (p<0.001). Based on linear regression, there was an average decrease of approximately 0.4 Nm screw-plate interface strength for every 1° increase in screw-plate angle (p<0.001). Decreases (p<0.05) were discovered in both maximum moment and moment at the reference displacements for screws locked at 5° relative to those locked at 0°, 10° relative to 0°, and 15° relative to 10°.

DISCUSSION

Standard locking systems provided greater resistance to rotational failure at the screw/plate interface than variable angle locking systems. Variable angle systems provided the greatest resistance to rotation when the screw was inserted perpendicular to the plate. As the off-axis angle increased, the resistance to rotation at the screw/plate interface decreased almost linearly. It is unknown if these differences are clinically significant in an actual fracture construct, but recent reported failures in the distal femur suggest that they might be.

CONCLUSION

Surgeons should weigh the risks and benefits of VA systems and attempt to minimize the off-axis angle magnitude when VA systems are selected.

The outcome of Polyax Locked Plating System for fixation distal femoral non-implant related and periprosthetic fractures

The objective of this study was to report on the safety, efficacy and clinical outcomes of the Polyax Locked Plating System (Biomet, Warsaw, IN, USA) in the management of acute (non-implant related and periprosthetic) distal femoral fractures. We retrospectively reviewed 71 patients with 73 distal femoral fractures. Thirty-three of the included fractures occurred around previously placed implants. The average patients' age was 67 years (range 18-98). There were 7 early postoperative complications (9.5%) including one deep surgical site infection, 2 pulmonary embolisms and 4 urinary or respiratory infections. At final follow-up (mean 12, range 9-55 months) all fractures progressed to clinical and radiological union. However, major revision surgery for healing problems was required in 5 cases (6.8%) and minor in 3 cases (4.1%). The average time to healing was 6 (range 3-23) months. Angulation less than 5 degrees in any plane was observed in 66 cases (89.7%), within 5-10 degrees in 5 cases (7.3%) and within 10-15 degrees in 2 cases (2.9%). The mean pre-injury and final follow-up values of Glasgow Outcome Scale were 1.5(1-3) and 1.7(1-3) respectively. Overall 61 patients (83.53%) retained their pre-injury activity status. The Polyax Locked Plating System offers a safe and efficient fixation in distal femoral fractures.

Treatment of type B periprosthetic femur fractures with curved non-locking plate with eccentric holes: Retrospective study of 43 patients with minimum 1-year follow-up

INTRODUCTION

Periprosthetic femur fracture (PFF) is a serious complication after total hip arthroplasty that can be treated using different internal fixation devices. However, the outcomes with curved non-locking plates with eccentric holes in this indication have not been reported previously. The objectives of this study were to determine: (1) the union rate; (2) the complication rate; (3) autonomy in a group of patients with a Vancouver type B PFF who were treated with this plate.

HYPOTHESIS

Use of this plate results in a high union rate with minimal mechanical complications.

MATERIALS AND METHODS

Forty-three patients with a mean age of 79 years ± 13 (41-98) who had undergone fixation of Vancouver type B PFF with this plate between 2002 and 2007 were included in the study. The time to union and Parker Mobility Score were evaluated. The revision-free survival (all causes) was calculated using Kaplan-Meier analysis. The average follow-up was 42 months ± 20 (16-90).

RESULTS

Union was obtained in all patients in a mean of 2.4 months ± 0.6 (2-4). One patient had varus malunion of the femur. The Parker Mobility Score decreased from 5.93 ± 1.94 (2-9) to 4.93 ± 1.8 (1-9) (P = 0.01). Two patients required a surgical revision: one for an infection after 4.5 years and one for stem loosening. The survival of the femoral stem 5 years after fracture fixation was 83.3% ± 12.6%.

CONCLUSION

Use of a curved plate with eccentric holes for treating type B PFF led to a high union rate and a low number of fixation-related complications. However, PFF remains a serious complication of hip arthroplasty that is accompanied by high morbidity and mortality rates.

Complication with removal of a lumbar spinal locking plate

Introduction. The use of locking plate technology for anterior lumbar spinal fusion has increased stability of the vertebral fusion mass over traditional nonconstrained screw and plate systems. This case report outlines a complication due to the use of this construct. Case. A patient with a history of L2 corpectomy and anterior spinal fusion presented with discitis at the L4/5 level and underwent an anterior lumbar interbody fusion (ALIF) supplemented with a locking plate placed anterolaterally for stability. Fifteen months after the ALIF procedure, he returned with a hardware infection. He underwent debridement of the infection site and removal of hardware. Results. Once hardware was exposed, removal of the locking plate screws was only successful in one out of four screws using a reverse thread screw removal device. Three of the reverse thread screw removal devices broke in attempt to remove the subsequent screws. A metal cutting drill was then used to break hoop stresses associated with the locking device and the plate was removed. Conclusion. Anterior locking plates add significant stability to an anterior spinal fusion mass. However, removal of this hardware can be complicated by the inherent properties of the design with significant risk of major vascular injury.

The tricipital aponeurosis--a reliable soft tissue landmark for humeral plating

This study aims to identify the relationship of the radial nerve as it descends across the humerus with reference to a reliable soft tissue landmark, the tricipital aponeurosis. Following cadaveric dissection of 10 adult humerii, the radial nerve was located as it crossed the lateral midsagittal point of the humeral diaphysis. A horizontal line was then subtended medially from this point to another line subtended vertically from the lateral border of the tricipital aponeurosis. The vertical distance from this intersection to the lateral apex of the aponeurosis was recorded in three positions (full flexion, 90° of flexion and full extension). The location of the radial nerve on the posterior aspect of the humeral diaphysis to the medial apex of the tricipital aponeurosis was also noted. In 90° of flexion the radial nerve at the lateral midsagittal point of the humerus was 0.9 mm proximal to the lateral apex of the tricipital aponeurosis. Flexion and extension of the elbow changed the interval to 16.3 mm (nerve proximal) in full flexion and 7.1 mm in full extension (nerve distal). On the posterior aspect of the humerus the radial nerve was 21.8 mm proximal to the medial aspect of the tricipital aponeurosis. The aponeurosis provides a reference point from which the nerve can be easily located on the lateral aspect of the humerus intraoperatively in a range of positions, whilst the medial apex provides a guide to the location of the nerve on the posterior aspect of the arm.

Does the lateral plate need to overlap the stem to mitigate stress concentration when treating Vancouver C periprosthetic supracondylar femur fracture?

The effect of construct length on cortical strain and load to failure between locked compression plating and cemented femoral stem in a fall model was analyzed. Eight Sawbone femurs with cemented stems were instrumented with increasing fixation lengths starting 8cm distal to stem tip and progressing proximally to overlapping constructs. Uniaxial strain gauges measured cortical strain. Load to failure was performed with 8cm gap between implants, 2cm gap, and proximally overlapping configurations. Strain was significantly reduced as the 8cm gap transitioned to an overlapped construct with most comparisons. Load to failure in the overlapped construct was 273% greater compared to 2cm gap construct. Overlapping the stem with a locking compression plate resulted in reduced strain and increased load to failure.

Effect of off-axis screw insertion, insertion torque, and plate contouring on locked screw strength

OBJECTIVES

This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs.

METHODS

Groups of locking screws (n = 6-11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same ("+") or opposite direction ("-") of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure.

RESULTS

Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413-2778 N), whereas any off-axis insertion significantly weakened constructs (165-1285 N, at 100% torque) (P < 0.05). For "+" loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the "-" direction consistently resulted in higher strengths than "+" loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05).

CONCLUSIONS

To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism.

Topical review: locking plate technology in foot and ankle surgery

The use of locking plate technology in foot and ankle surgery has increased over the last decade. Reported applications include fracture repair, deformity correction, and arthrodesis. There is limited evidence, however, to guide clinicians with regard to the appropriate and optimal use of this technology. This work aims to examine the current biomechanical and clinical evidence comparing locking construct technology to other forms of fixation in the field of foot and ankle surgery.

Mechanical effects of off-axis insertion of locking screws: should we do it?

OBJECTIVES

The purposes of this study were to evaluate the cantilevered bending strength and failure modes of locking screws inserted at various angles in a plate with fully circumferential threaded holes. As an additional measure, the amount of screw head prominence at these angles was also assessed.

METHODS

Standard 3.5-mm locking screws were inserted into round fully circumferential threaded holes through a standard straight 3.5-mm locking plate at various angles. The achieved angle of insertion and its prominence protruding from the far-bone side of the plate was measured using an optical luminescence technique. Each screw was then loaded at a constant rate until failure in a cantilevered bending scenario. The maximum cantilevered bending strength was measured, and the moment at failure was calculated.

RESULTS

There was a positive correlation between increasing insertion angle and increasing prominence; a higher screw insertion angle yielded greater prominence. Prominence values ranged from negligible to 2 mm. As screw insertion angle increased, the bending moment at failure decreased. Screws inserted to 3 degrees or below primarily failed through screw deformation at the minor diameter below the head, whereas screws inserted to greater than 3 degrees primarily failed through locking mechanism disengagement.

CONCLUSIONS

These findings indicate that cross threading may not be biomechanically advantageous and may change screw mode of failure. Based on these findings, screws inserted to 3 degrees or higher would reduce the bending moment at failure to approximately 50% of an orthogonally inserted screw.

A biomechanical study comparing polyaxial locking screw mechanisms

OBJECTIVE

Locking plates have become ubiquitous in modern fracture surgery. Recently, manufacturers have developed locking plates with polyaxial screw capabilities in order to optimise screw placement. It has already been demonstrated that inserting uniaxial locking screws off axis results in weaker loads to failure. Our hypothesis was that even implants specifically designed for polyaxial insertion would experience a drop-off in resistance when using non-perpendicular screws.

METHODS

Four different types (one monoaxial and three polyaxial locking plates) of readily available small fragment plates were tested. A biomechanical model was developed to test the screws until failure (defined as breakage and rapid loss of >50% force). Screws were inserted at 0, 10 and 15°.

RESULTS

The standard monoaxial locking mechanism sustained saw a 60% reduction in force (332N vs. 134N) when screws were inserted cross-threaded at 10°. Two polyaxial systems saw similar significant reductions in force of 45% and 34%, respectively at 15°. A third system utilizing an end cap locking mechanism showed highly variable results with large standard deviations. Polyaxial screws showed on average only limited reduction at 10 degrees of insertion angle.

CONCLUSION

Newer designs of locking plates have attractive properties to allow more surgical options during fixation. However this freedom comes at the price of reduced force. Our results show that the safe zone for inserting these screws is closer to 20°, rather than the 30° indicated by the manufacturers. Also, the various polyaxial locking mechanisms seem to influence the overall resistance of the screws.

A biomechanical comparison of one-third tubular plates versus periarticular plates for fixation of osteoporotic distal fibula fractures

OBJECTIVES

The purpose of this study was to test the biomechanical properties of locking and nonlocking plates using one-third tubular and periarticular plate designs in an osteoporotic distal fibula fracture model.

METHODS

Twenty-four cadaveric specimens, whose bone mineral densities were obtained using dual x-ray absorptiometry scans, were tested. The fracture model simulated an OTA 44-B2.1 fracture. The constructs included (1) nonlocking one-third tubular plate, (2) locking one-third tubular plate, (3) nonlocking periarticular plate, and (4) locking periarticular plate. The specimens underwent axial loading followed by torsional loading to failure. Statistical analysis was performed using Kruskal-Wallis testing and further analysis with Mann-Whitney testing.

RESULTS

The periarticular plates had greater rotational stiffness compared with the one-third tubular plates (P = 0.04). The nonlocking plates had greater torque to failure than the locking plates (P = 0.01). The nonlocking one-third tubular plate had greater torque to failure than the locking one-third tubular plate (P = 0.03). No significant differences were found in any of the comparisons regarding axial stiffness.

CONCLUSIONS

In biomechanical testing using an osteoporotic model of OTA 44-B2.1 fractures, periarticular plates were superior to one-third tubular plates in rotational stiffness only. Locking plates did not outperform their nonlocking counterparts. Periarticular plates should be considered when treating osteoporotic distal fibula fractures, but one-third tubular plates and nonlocking plates provide adequate fixation for these injuries.

New techniques and alternative fixation for the lapidus arthrodesis

Arthrodesis of the first metatarsocuneiform joint is a powerful and durable procedure to help correct moderate to severe hallux valgus and/or first ray hypermobility. However, painful nonunion remains a notoriously high potential outcome. Research regarding locking plates seems promising, and data show lower rates of nonunion. Innovative fixation techniques are new and should be considered in the future as further literature is available on their long-term use. Regardless of the fixation, proper joint preparation and good compression is fundamentally the most important. A case of Lapidus fusion with locking plates after a failed arthrodesis with screws alone is presented.

Biomechanical assessment of a novel bone lengthening plate system - a cadaveric study

BACKGROUND

Although many types of external fixators have been developed for distraction osteogenesis, all have some drawbacks. We recently developed a novel bone lengthening plate to overcome these problems. The purpose of this study is to conduct biomechanical analyses using cadavers to assess the stability of the bone lengthening plate in relation to distraction length and femoral bone mineral density.

METHODS

We used human cadaveric femurs (n=18) to assess the effects of distraction length and bone mineral density on the biomechanical stability of the bone lengthening plate. After establishing control (n=6, 0mm lengthening) and experimental groups (n=12, 30 mm lengthening), we measured biomechanical stability (structural stiffness, ultimate load, and displacement) under a compressive load. The experimental group was subdivided into a group with normal bone mineral density (n=6) and a group with osteoporosis (n=6), and the biomechanical stability of these groups was compared.

FINDING

Structural stiffness differed significantly between the control (417.6 N/mm) and combined experimental groups (185.6 N/mm, p=0.002). Ultimate load also differed significantly between the control (1327.8 N) and combined experimental (331.4 N, p=0.002) groups. Bone mineral density was unrelated to structural stiffness (p=0.204), ultimate load (0.876), or displacement (0.344). In all cases, failure of the bone lengthening plate occurred at the longitudinal connectors, such as the connecting columns between the upper and lower plates, and the lengthening shaft of the bone lengthening plate.

INTERPRETATION

The biomechanical stability of the bone lengthening plate was affected by the lengthening length but not by bone mineral density. In addition, biomechanical stability during lengthening was most strongly influenced by the longitudinal connectors.

The effect of polyelectrolyte multilayer coated titanium alloy surfaces on implant anchorage in rats

Advances have been achieved in the design and biomechanical performance of orthopedic implants in the last decades. These include anatomically shaped and angle-stable implants for fracture fixation or improved biomaterials (e.g. ultra-high-molecular-weight polyethylene) in total joint arthroplasty. Future modifications need to address the biological function of implant surfaces. Functionalized surfaces can promote or reduce osseointegration, avoid implant-related infections or reduce osteoporotic bone loss. To this end, polyelectrolyte multilayer structures have been developed as functional coatings and intensively tested in vitro previously. Nevertheless, only a few studies address the effect of polyelectrolyte multilayer coatings of biomaterials in vivo. The aim of the present work is to evaluate the effect of polyelectrolyte coatings of titanium alloy implants on implant anchorage in an animal model. We test the hypotheses that (1) polyelectrolyte multilayers have an effect on osseointegration in vivo; (2) multilayers of chitosan/hyaluronic acid decrease osteoblast proliferation compared to native titanium alloy, and hence reduce osseointegration; (3) multilayers of chitosan/gelatine increase osteoblast proliferation compared to native titanium alloy, hence enhance osseointegration. Polyelectrolyte multilayers on titanium alloy implants were fabricated by a layer-by-layer self-assembly process. Titanium alloy (Ti) implants were alternately dipped into gelatine (Gel), hyaluronic acid (HA) and chitosan (Chi) solutions, thus assembling a Chi/Gel and a Chi/HA coating with a terminating layer of Gel or HA, respectively. A rat tibial model with bilateral placement of titanium alloy implants was employed to analyze the bones' response to polyelectrolyte surfaces in vivo. 48 rats were randomly assigned to three groups of implants: (1) native titanium alloy (control), (2) Chi/Gel and (3) Chi/HA coating. Mechanical fixation, peri-implant bone area and bone contact were evaluated by pull-out tests and histology at 3 and 8 weeks. Shear strength at 8 weeks was statistically significantly increased (p<0.05) in both Chi/Gel and Chi/HA groups compared to the titanium alloy control. No statistically significant difference (p>0.05) in bone contact or bone area was found between all groups. No decrease of osseointegration of Chi/HA-coated implants compared to non-coated implants was found. The results of polyelectrolyte coatings in a rat model showed that the Chi/Gel and Chi/HA coatings have a positive effect on mechanical implant anchorage in normal bone.

Fractures of the acetabulum in elderly patients: an update

The incidence of acetabular fractures in elderly patients is increasing. Poor bone quality and concomitant diseases are the main features of these patients. Fracture patterns are marked by a high degree of variability in terms of patient and fracture characteristics. Preoperative planning with plain radiographs and computed tomography, including 3-dimensional reconstructions, is recommended. Treatment remains challenging because of precarious general health, severe osteopenia, comminution, and associated femoral head damage. Treatment options available include closed management, open reduction with internal fixation, percutaneous fixation in situ, and acute or staged total hip arthroplasty (THA) whether alone or combined with osteosynthesis. In the case of significant destruction of the articular cartilage, primary THA may provide the best solution. Whichever surgical method is chosen, the objective is rapid mobilisation of the patient on a walker or crutches. Late local complications that may occur after nonoperative or operative treatment include posttraumatic arthritis, nonunion, malunion, wound infection, dislocation, intrusive hardware, nerve palsy, and heterotopic bone formation. In this article an overview of the current trends in the management of acetabulum fractures in the elderly is presented.

Distal tibial hypertrophic nonunion with deformity: treatment by fixator-assisted acute deformity correction and LCP fixation

Distal tibial hypertrophic nonunion with angular deformity has been successfully treated by circular external fixator. The inconvenience of the bulky external fixator and frequent pin tract infection would not be accepted in certain cases. This study included thirteen patients (mean age 39 years) with angular deformity of the distal dia-/metaphyseal tibial shaft. Five patients were originally treated by interlocking nail, three were treated by plate and screws fixation, four treated conservatively and one had deformity secondary to fracture of a lengthening regenerate. All patients were treated by osteotomy and acute correction of the deformity using temporary unilateral fixator and internal fixation by a locking compression plate (LCP). The external fixator was removed at the end of surgery. The results were evaluated both clinically and radiologically. All osteotomies healed within 3 (2–4) months. All patients were able to work within an average of 2.3 months. The function of the upper ankle joint was unrestricted in twelve cases, and in 1 case there was a mild functional deficit. The mean follow-up was 60 months (24–120). The frontal plane alignment parameters (the mechanical axis deviation, the lateral distal tibial angle and the medial proximal tibial angle) and the sagittal alignment parameters (the posterior proximal tibial angle and the anterior distal tibial angle) were within normal values postoperatively. No cases of deep infection or failure of fixation were encountered. Acute correction of distal tibial shaft hypertrophic nonunion with deformity and LCP fixation is a reliable option in well-selected cases.

Reoperation for metalwork complications following the use of volar locking plates for distal radius fractures: a United Kingdom experience

Volar locking plates are increasingly used in the management of distal radius fractures. As with any new implant, understanding the rate and type of potential metalwork related complications is important. In this study, we reviewed 114 distal radius fractures treated with volar locking plating. Our aim was to determine the type and rate of metalwork complications requiring reoperation. In our series, 12 cases (10%) underwent further surgery for metalwork related complications mainly for screw protrusion into the radiocarpal joint following fracture collapse. Our results suggest that volar locking plates are associated with a high rate of metal work related complications requiring further surgery. Technical aspects to reduce such complications are discussed.

A New System to Improve Screw Fixation to Bones

Plates and non-locked screws used in the treatment of osteoporotic bone fractures frequently become loose due to everyday mechanical demands. Currently, locking plates and screws are the gold standard treatment for these fractures. However, their use has several limitations and complications as they are technically demanding, and their cost is very expensive. To improve the fixation strength of traditional unlocked plate and screw constructs, we have developed a new fixation system based on a very old concept. The system consists of a screw locking element (SLE) manufactured from PEEK, which is attached to the end of the screw shaft once it has traversed both bone cortices. A specially designed tool is used to facilitate its attachment to the screw. This tool makes it possible for the screw to traverse an osteosynthesis plate or lockwasher as well as both bone cortices and to easily find the SLE, fixing it against the far cortex. We tested the pull-out strength of SLEs and compared the results with previously published data for human femoral cortex pull-out strength. Our laboratory tests demonstrate that the mean SLE pull-out strength was 3864 ± 47.61 N, while that observed for a human femoral diaphysis cortex was 4071.54 ± 1461.69 N. This difference was not significant (p > 0.05). This new system can easily be used with any type of osteosynthesis in osteoporotic or osteopenic bones, with the screws being placed on weakened areas of the bone (e.g., fissure lines, previous orifices, or thinned metaphyseal bone cortex), or to replace over-torqued screws. It is particularly suitable for veterinary trauma, where immediate weight-bearing protection after fracture treatment is nearly impossible.

Pitfalls in the application of distal femur plates for fractures

Despite design features intended to aid the surgeon in restoring proper alignment, malunion and implant-related problems are relatively common after a distal femur fracture treated with plate fixation. This article presents case examples of these problems followed by a discussion of the relevant distal femoral anatomy, design features of modern locked distal femur plating systems, and technical points necessary to avoid malunion and implant-related problems when using these devices.

Screw locking elements: a means to modify the flexibility of osteoporotic fracture fixation with DCPs without compromising system strength or stability

This paper analyses whether it is possible to use dynamic compression plates (DCPs) and screw locking elements (SLEs) to vary the flexibility of osteoporotic fracture fixation without compromising the strength and stability of the construct. Compression, torsion and four-point bending static strength tests were conducted. Cyclic load tests of up to 10,000 load cycles were also carried out to determine stiffness performance. Four fixation systems were mounted onto polyurethane bone models. Group 1 consists of the DCP and six cortical screws. Group 2, idem, but with the addition of two SLEs. Group 3, idem, but with the addition of six SLEs. Group 4 used the locking compression plate (LCP) and locking screws. The results indicated no significant difference (p>0.05) in the strength of groups 2-4. It was also observed that the torsional stiffness of group 3 (0.30 Nm/°) was higher than that of group 2 (0.23 Nm/°) and similar to that of group 4 (0.28 Nm/°). Compression stiffness of group 4 (124 N/mm) was higher than that of group 2 (102 N/mm), but lower than that of group 3 (150 N/mm). No notable differences were observed for structural bending stiffness. It is concluded that by using the DCP with SLEs it is possible to modify the stiffness of the fixation construct for the repair of osteoporotic fractures and, in this way, facilitate the conditions suitable on secondary bone healing.

Locking and Non-locking Constructs Achieve Similar Radiographic and Clinical Outcomes for Internal Fixation of Intra-articular Distal Humerus Fractures

BACKGROUND

Locking plates have been used increasingly for the management of distal humerus fractures. Studies that compare patient-centered outcomes between locking and non-locking fixation for distal humerus fractures are lacking.

QUESTIONS/PURPOSES

The purposes of this study were to (1) determine whether locking plates offered superior fixation compared with non-locking plates for distal humerus fractures, (2) determine whether the use of locking plates was associated with fewer complications, and (3) determine whether locking plate use resulted in superior radiographic outcome compared with non-locking plates. Lastly, another aim was to determine the average cost difference associated with locking plate use versus non-locking plate use for distal humerus fracture fixation.

PATIENTS AND METHOD

Demographic, clinical, and radiographic data including loss of fixation, range of motion, rate of infection, nonunion and reoperation, as well as measures of fixation were collected retrospectively and compared on 96 patients with surgically treated AO type 13C distal humerus fractures (65 locking, 31 non-locking) at 6-week and 6-month follow-up. Average costs of locking and non-locking constructs were calculated and compared.

RESULTS

Three in 96 (3.1%) of all cases experienced loss of fixation, with no difference between the two groups. There was no difference between locking and non-locking groups with regard to the rate of nonunion, infection, and reoperation at 6 weeks and 6 months. On average, locking plate constructs were 348% more expensive than non-locking constructs.

CONCLUSION

While there are some significant differences in radiographic parameters and cost between locking and non-locking constructs for internal fixation of intra-articular distal humerus fractures, there were no statistically significant differences in clinical outcome.

Improving fixation of the osteoporotic fracture: the role of locked plating

The use of locking technology has expanded significantly over the last decade. This technology has led to improvements in implant design for fixation in osteoporotic bone and allowed more secure and stable constructs. Locking plates and screws have been helpful in surgical repair of metaphyseal fractures and those with significant comminution and in the elderly. Biomechanically, creating a fixed-angle design leads to stronger constructs and potentially decreases failure rates. The use of this technology must be tempered by awareness of the complications associated with both the technique and implants.

Surgical correction of midfoot arthritis with and without deformity

The goals of midfoot reconstruction are to create a painless, functional, and plantigrade foot, which are generally accomplished with arthrodesis and realignment as indicated. The latter requires not only the correction of midfoot deformity when present, but also coexisting hindfoot and forefoot deformities. Once the initial decisions have been made regarding the need for realignment and which joints to include in the arthrodesis, the surgical plan needs to account for the approach, arthrodesis preparation, order of fixation, and choice of fixation.

Mechanical evaluation of a 4-mm cancellous "rescue" screw in osteoporotic cortical bone: a cadaveric study

OBJECTIVES

Obtaining sufficient fracture fixation in osteoporotic bone is challenging. The purposes of the current study were (1) to compare the pullout strength of a 4-mm cancellous screw (cancellous screw group) with that of a 3.5-mm cortical screw (cortical screw group), and (2) to measure the pullout strength of a 4-mm cancellous screw placed as a rescue screw (rescue screw group) in a stripped 3.5-mm cortical screw (stripped screw group) hole while controlling for bone density and cortical thickness.

METHODS

We inserted 4 screws, one from each experimental group, into 11 osteoporotic cadaveric radii, while recording the insertion torque. Radii were mounted on a servohydraulic testing machine, and each screw was pulled out at a rate of 5 mm/min. Pullout strength was recorded. The effects of cortical thickness (near, far, and total), bone density, insertion torque, and the experimental screw group (cortical, cancellous, stripped, and rescue screw groups) on pullout strength were analyzed using multiple linear regression with random effects. Statistical significance was set at P < 0.05.

RESULTS

There was no significant difference in pullout strength between the cortical and cancellous screw groups. The rescue screw group had significantly less pullout strength than did the cortical and cancellous screws, and only partly increased pullout strength compared with stripped screws. Bone density significantly affected pullout strength, but insertion torque and cortical thickness were not significant covariates.

CONCLUSIONS

There seems to be no advantage in using a cancellous screw over a cortical screw in bicortical fixation in osteoporotic bone. Although the rescue screw provided greater pullout strength than the stripped screw, it is unknown if the purchase it provides is clinically sufficient.

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.

The role of locking technology in the upper extremity

The technique of locked plating has been a major advance in Orthopaedic fracture surgery and has had an equal impact on the management of upper extremity fractures. The recognition of the role of vascularity and soft tissues in fracture healing was central to the research and development of newer plate designs that left minimal footprints on the surface of the bone. Subsequently, innovative locking technology has improved our ability to manage cases with extensive communition, inadequate bone stock, and peri-articular fractures. This paper will review the role of locking technology in the management of fractures of the upper extremity.