Biomechanical Comparison of a Notched Head Locking T-Plate and a Straight Locking Compression Plate in a Juxta-Articular Fracture Model

Effect of Plate Screw Configuration on Construct Stiffness and Plate Strain in a Synthetic Short Fragment Small Gap Fracture Model Stabilized with a 12-Hole 3.5-mm Locking Compression Plate

OBJECTIVE

 The aim of the study was to determine the effect of a short and long working length screw configuration on construct stiffness and plate strain in a synthetic, short fragment, small gap fracture model stabilized with a 12-hole 3.5-mm locking compression plate (LCP).

STUDY DESIGN

 Six replicates of short and long working length constructs on a short fragment, small gap fracture model underwent four-point bending. Construct stiffness and plate strain were compared across working length and along the plate.

RESULTS

 With the LCP on the compression surface (compression bending), the short working length had a significantly higher construct stiffness and lower plate strain than the long working length. Conversely, with the LCP on the tension surface (tension bending), transcortical contact between 150 and 155 N induced load sharing at the fracture gap, which significantly increased construct stiffness and decreased plate strain in the long working length. At 100 N (precontact), the short working length had a significantly higher construct stiffness and lower plate strain than the long working length, comparable with our compressing bending results.

CONCLUSION

 In compression bending, and before transcortical contact occurred in tension bending, the short working length had a significantly higher construct stiffness and lower plate strain than the long working length. Load sharing due to transcortical contact observed in our model in tension bending will vary with fracture gap, working length, and loading condition. These results must be interpreted with caution when considering clinical relevance or potential in vivo biomechanical advantages.

Effect of Plate Length on Construct Stiffness and Strain in a Synthetic Short-Fragment Fracture Gap Model Stabilized with a 3.5-mm Locking Compression Plate

OBJECTIVE

 To evaluate the effect of 3.5-mm locking compression plate (LCP) length on construct stiffness and plate and bone model strain in a synthetic, short-fragment, fracture-gap model.

STUDY DESIGN

 Six replicates of 6-hole, 8-hole, 10-hole, and 12-hole LCP constructs on a short-fragment, tubular Delrin fracture gap model underwent four-point compression and tension bending. Construct stiffness and surface strain, calculated using three-dimensional digital image correlation, were compared across plate length and region of interest (ROI) on the construct.

RESULTS

 The 12-hole plates (80% plate-bone ratio) had significantly higher construct stiffness than 6-hole, 8-hole, and 10-hole plates and significantly lower plate strain than 6-hole plates at all ROIs. Strain on the bone model was significantly lower in constructs with 10-hole and 12-hole plates than 6-hole plates under both compression and tension bending.

CONCLUSION

 Incremental increases in construct stiffness and incremental decreases in plate strain were only identified when comparing 6-hole, 8-hole, and 10-hole plates to 12-hole plates, and 6-hole to 12-hole plates, respectively. Strain on the bone model showed an incremental decrease when comparing 6-hole to 10-hole and 12-hole plates. A long plate offered biomechanical advantages of increased construct stiffness and reduced plate and bone model strain, over a short plate in this in vitro model.

Association of fracture gap with implant failure in radius and ulna fractures in toy breed dogs-A multicenter retrospective cohort study

OBJECTIVE

To assess the impact of a postoperative fracture gap on implant failure following radius and ulna fracture repair in toy breed dogs.

STUDY DESIGN

Retrospective multicenter cohort study.

ANIMALS

A total of 80 client-owned toy breed dogs.

METHODS

Medical records and radiographs were reviewed for dogs <3.5 kg that had surgical repair of simple transverse radius and ulna fractures at four institutions from 2005 to 2019. Data collected included signalment, fracture location, implant types and thickness, plate working length, evidence of a postoperative fracture gap in the caudal cortex, postoperative care, occurrence of implant failure, and other complications. The association between potential risk factors and complications was examined using multivariable logistic regression.

RESULTS

A postoperative fracture gap in the caudal cortex was noted in 37 cases, and 10 cases experienced implant failure. Of the 43 cases without a gap, one case experienced implant failure. After adjusting for other variables, the fracture gap was significantly associated with implant failure (odds ratio = 23.0 [95% confidence interval: 2.7; 197.9], p = .004). Prolonged external coaptation was associated with minor and major complications other than implant failure (p = .04), while the absence of coaptation confounded the effects of the fracture gap on implant failure.

CONCLUSION AND CLINICAL SIGNIFICANCE

Reduction of the caudal cortex of the radius is imperative to promote bone healing and prevent implant failure in transverse radius and ulna fractures of toy breed dogs.

Clinical and Radiographic Outcomes of 1.5-mm Locking Plate Fixation for 30 Radial and Ulnar Fractures in Dogs

OBJECTIVE

 This study aimed to report clinical and radiographic outcomes of dogs that underwent radial and ulnar fracture repair using 1.5-mm locking plate systems.

STUDY DESIGN

 Dogs that had radial and ulnar fractures repaired using 1.5-mm locking compression plate systems at four referral hospitals were retrospectively included. Signalment, body weight, fracture aetiology, fracture location and configuration, radius diameter, plate-bone ratio, repair method, clinical and radiographic outcomes, complications, and time to last follow-up were recorded.

RESULTS

 Thirty fractures in 28 dogs were included. Median body weight was 2.4 kg (range 1.3-5.5 kg). The mean length of the proximal segment relative to the total length of the radius was 67% (range 33-93%). The mean diameter of the radius at its isthmus was 4.9 mm (range 3.1-6.1 mm). The mean plate-bone ratio was 64% (range 48-89%). Radiographic union was documented in 29/30 fractures at a median of 8 weeks postoperatively. Of the cases with long-term follow-up available, 21/24 had a full function and 3/24 had an acceptable function. Five complications occurred, including infection (n = 2), screw migration (n = 1), bandage sores (n = 1), and peri-plate fracture (n = 1).

CONCLUSION

 In this population of miniature and toy-breed dogs, 1.5-mm locking plates provided effective fixation for radial and ulnar fractures. Despite complications in 5/30 fractures, radial union occurred in 29/30, and no dog had an unacceptable function at the last follow-up.

Effect of an Orthogonal Locking Plate and Primary Plate Working Length on Construct Stiffness and Plate Strain in an In vitro Fracture-Gap Model

OBJECTIVE

 The aim of this study was to compare stiffness and strain of an in vitro fracture-gap model secured with a primary 3.5-mm locking compression plate (LCP) at three primary plate working lengths without and with an orthogonal 2.7-mm LCP.

STUDY DESIGN

 Primary plate screw configurations modeled short working length (SWL), medium working length (MWL), and long working length (LWL) constructs. Construct stiffness with and without an orthogonal plate during nondestructive four-point bending and torsion, and plate surface strain measured during bending, was analyzed.

RESULTS

 Single plate construct stiffness was significantly, incrementally, lower in four-point bending and torsion as working length was extended. Addition of an orthogonal plate resulted in significantly higher bending stiffness for SWL, MWL, and LWL (p < 0.05) and torsional stiffness for MWL and LWL (p < 0.05). Single plate construct strain was significantly, incrementally, higher as working length was extended. Addition of an orthogonal plate significantly lowered strain for SWL, MWL, and LWL constructs (p < 0.01).

CONCLUSION

 Orthogonal plate application resulted in higher bending and torsional construct stiffness and lower strain over the primary plate in bending in this in vitro model. Working length had an inverse relationship with construct stiffness in bending and torsion and a direct relationship with strain. The inverse effect of working length on construct stiffness was completely mitigated by the application of an orthogonal plate in bending and modified in torsion.

Biomechanical analysis of combi-hole locking compression plate during fracture healing: A numerical study of screw configuration

Locking compression plates (LCPs) have become a widely used option for treating femur bone fractures. However, the optimal screw configuration with combi-holes remains a subject of debate. The study aims to create a time-dependent finite element (FE) model to assess the impacts of different screw configurations on LCP fixation stiffness and healing efficiency across four healing stages during a complete fracture healing process. To simulate the healing process, we integrated a time-dependent callus formation mechanism into a FE model of the LCP with combi-holes. Three screw configuration parameters, namely working length, screw number, and screw position, were investigated. Increasing the working length negatively affected axial stiffness and healing efficiency (p < 0.001), while screw number or position had no significant impact (p > 0.01). The time-dependent model displayed a moderate correlation with the conventional time-independent model for axial stiffness and healing efficiency (ρ ≥ 0.733, p ≤ 0.025). The highest healing efficiency (95.2%) was observed in screw configuration C125 during the 4-8-week period. The results provide insights into managing fractures using LCPs with combi-holes over an extended duration. Under axial compressive loading conditions, the use of the C125 screw configuration can enhance callus formation during the 4-12-week period for transverse fractures. When employing the C12345 configuration, it becomes crucial to avoid overconstraint during the 4-8-week period.

Effect of Plate-Bone Distance and Working Length on 2.0-mm Locking Construct Stiffness and Plate Strain in a Diaphyseal Fracture Gap Model: A Biomechanical Study

OBJECTIVE

 The aim of this study was to determine the effect of plate-bone distance (PBD) and working length on 2.0-mm locking compression plate (LCP) stiffness and strain in four-point bending and torsion in a diaphyseal fracture gap model.

STUDY DESIGN

 A total of 54 LCP with three screws per fragment were assigned to one of nine combinations of working length (WL; short, medium, and long), and PBD (1, 1.5, and 3 mm) for a sample size of six per construct configuration. Stiffness was measured under quasistatic, nondestructive four-point compression bending and torsion. Plate surface strain was recorded using three-dimensional (3D) digital image correlation during four-point compression bending.

RESULTS

 WL had a significant effect on overall construct stiffness in both compression bending and in torsion, with shorter WL constructs having higher stiffness (p < 0.0001). PBD had no effect on construct stiffness in compression bending; however, a significant reduction in stiffness was noted in torsion (p = 0.047) as PBD incrementally increased. WL had a significant effect on plate strain in compression bending, with shorter WL constructs having lower plate strain (p < 0.0001). PBD had no effect on plate strain in compression bending except for lower plate strain recorded in long WL constructs with 1-mm PBD, compared with 1.5- and 3-mm PBD constructs (p < 0.0001).

CONCLUSION

 Longer WL constructs, regardless of PBD, had lower stiffness in compression bending, while in torsion, some modulation of this effect was noted with incremental decreases in PBD. Longer WL resulted in high plate strain, regardless of PBD.

Biomechanical Comparison of Use of Two Screws versus Three Screws Per Fragment with Locking Plate Constructs under Cyclic Loading in Compression in a Fracture Gap Model

OBJECTIVES

 The aim of this study was to measure and compare the stiffness and cyclic fatigue of two plate-bone model constructs, with either two or three locking screws per fragment, under cyclic compression.

METHODS

 A 10-hole 3.5 mm stainless steel locking compression plate (LCP) was fixed 1 mm from a synthetic bone model in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled compression test until failure.

RESULTS

 The three-screw constructs were stiffer than the two-screw constructs (196.75 ± 50.48 N/mm and 102.43 ± 22.93 N/mm, respectively) and the actuator displacements of the two-screw constructs were higher (18.02 ± 1.07 mm) than those of the three-screw constructs (14.48 ± 2.25 mm). The number of cycles to failure of the two-screw constructs was significantly lower (38,337.50 ± 2,196.98) than the that of the three-screw constructs (44,224.00 ± 1,515.24). Load at irreversible deformation was significantly lower in the two-screw constructs (140.93 ± 13.39 N) than in the three-screw constructs (184.27 ± 13.17 N). All constructs failed by plate bending at the gap between the two cylinders.

CLINICAL SIGNIFICANCE

 Omission of the third innermost locking screw during bridging osteosynthesis subjected to compression forces led to a 13.3% reduction in the number of cycles to failure and a 23.5% reduction of the load withstood by the plate before plastic deformation occurred.