Mark Glyde

Background
Fatigue failure of osteosynthesis plates in load bearing constructs remains a significant clinical challenge, with plate working length (PWL) influencing stress distribution and implant life span. Despite conflicting evidence on PWL's impact, finite element (FE) models offer potential for predicting fatigue life, yet their application to PWL-specific fatigue in bone-plate constructs is limited.

Methods
This study investigated the effect of PWL on fatigue life in load bearing constructs using experimental cyclic testing and FE modeling. Synthetic bone models with a 10 mm osteotomy gap were stabilized with 3.5 mm stainless steel locking compression plates, testing short (1 empty hole), medium (3 empty holes), and long (5 empty holes) PWL configurations (N = 6 per group) under sinusoidal loading (260 N peak, 3 Hz). A second sub-study assessed the medium PWL across nine load levels (220–380 N). FE models, validated against experimental force-displacement curves, predicted cycles to failure using Basquin's stress-based criteria. Statistical analyses compared experimental and FE-predicted cycles.

Results
Shorter PWL significantly increased fatigue life (short: 1.19 × 106 ± 0.28 × 106 cycles; medium: 0.35 × 106 ± 0.07 × 106; long: 0.20 × 106 ± 0.04 × 106; p < 0.003). FE predictions closely matched experimental cycles for medium and long PWL (p > 0.05) but underpredicted for short PWL (p = 0.03), likely due to tied interface assumptions. Most short PWL constructs survived beyond 106 cycles, reaching up to 1.5 million cycles in the very high-cycle fatigue regime without failing, where Basquin's accuracy may decrease. Sub-study 2 showed a strong load-life correlation (R2 = 0.96), with FE predictions achieving high accuracy (CCC = 0.972, REE = 6.3 %).

Conclusion
Shorter PWL enhances fatigue life in load bearing constructs by reducing plate stress, challenging traditional beliefs favoring longer PWL. FE models effectively predict fatigue life for medium and long PWL, supporting preoperative optimization, but require refinement for short PWL, including frictional contact modeling and alternative fatigue models for very high-cycle fatigue. Validation in physiological conditions is needed to enhance clinical applicability.

Objective
To determine the effect of plate–bone distance and screw number on 2.0-mm locking compression plate (LCP) torsional stiffness and plate strain for a fixed working length in a diaphyseal fracture gap model.


Study Design
In vitro biomechanical study.


Methods
The LCP was tested with nine different combinations of plate–bone distance (PBD) (1, 1.5, and 3 mm) and screw number (SN) (two, three, or four screws per fragment) across the same working length. Six replicates per group were tested. Constructs were subjected to quasi-static, non-destructive torsion producing overall construct stiffness data (Nm/degree). Plate surface strain data were recorded from three-dimensional digital image correlation during testing for all constructs.


Results
A greater PBD and a low SN resulted in lower construct stiffness (p = 0.015, and P > 0.0001, respectively) in torsion. Across all PBD, there was significantly less stiffness for constructs with two screws per fragment, compared with three screws or four screws. No significant difference was detected in plate strain for any combination of PBD and SN.


Conclusion
In this model, incrementally increasing the PBD and decreasing the SN resulted in less construct stiffness in torsion, with marked reduction in torsional stiffness in constructs with two screws per fragment compared with three or four screws per fragment.

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.

The abstract sentence “strain was significantly, incrementally, higher as working length was extended” remains true. Strain was higher in the long working length (LWL) constructs than the short (SWL) and medium working length (MWL) constructs. Higher measured strain at a longer working length in our study can be described as a direct relationship. We specifically used the term incremental in our results to highlight that we have measured at three distinct working lengths and have not made inferences about strain assessment between these measured working lengths...

Objective:
To describe the diagnosis, management, and outcome of a dog with a right distal radial osteochondroma that penetrated the ulna, causing expansile lysis and fracture.

Animal:
A 9-month-old entire female German Shorthaired Pointer.

Clinical presentation, progression, and procedures:
The dog had a 2-month history of weight-bearing lameness of the right forelimb and a 2-week history of a progressively enlarging, firm swelling on the distolateral antebrachium. Computed tomography was used to characterize the lesion and for surgical planning.

Treatment and outcome:
A distal ulnar ostectomy removed the affected ulnar segment, and the radial osteochondroma was excised with rongeurs. The dog was sound at 2, 16, and 45 weeks postoperatively. Radiographs at 45 weeks showed a persistent ulnar ostectomy gap with irregular but smoothly marginated edges and focal cortical irregularity at the site of radial osteochondroma excision. There was no evidence of osteochondroma recurrence.

Clinical relevance:
This is a newly recognized presentation of an osteochondroma penetrating the cortex of an adjacent bone in a dog resulting in expansile lysis and cortical fracture. Computed tomography was important in diagnosis and surgical planning, and surgical treatment was successful in removing the osteochondroma and ulnar lesion. This case provides long-term radiographic and clinical follow-up after osteochondroma excision and contributes to the current knowledge on prognosis following osteochondroma excision in dogs.

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.

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.

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.

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).

Conclusions 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.

To examine how to optimise the integration of multiple-choice questions (MCQs) for learning in continuing professional development (CPD) events in surgery, we implemented and evaluated two methods in two subspecialities over multiple years. The same 12 MCQs were administered pre- and post-event in 66 facial trauma courses. Two different sets of 10 MCQs were administered pre- and post-event in 21 small animal fracture courses. We performed standard psychometric tests on responses from participants who completed both the pre- and post-event assessment. The average difficulty index pre-course was 57% with a discrimination index of 0.20 for small animal fractures and 53% with a discrimination index of 0.15 for facial trauma. For the majority of the individual MCQs, the scores were between 30%-70% and the discrimination index was >0.10. The difficulty index post-course increased in both groups (to 75% and 62%). The pre-course MCQs resulted in an average score in the expected range for both formats suggesting they were appropriate for the intended level of difficulty and an appropriate pre-course learning activity. Post-course completion resulted in increased scores with both formats. Both delivery methods worked well in all regions and overall quality depends on applying a solid item development and validation process.