Three internal fixation methods for Danis-Weber-B distal fibular fractures: A biomechanical comparison in an osteoporotic fibula model

Finite element analysis and a pilot study of different fixation constructs for Danis-Weber A and B lateral malleolus fractures

BACKGROUND

Displaced lateral malleolus fractures are typically stabilised through open reduction and internal fixation. The biomechanically and clinically efficacy of locking plates and lag screws, particularly in Weber A and B distal fibular fractures remains a subject of contention. This study examines two locking plate designs for lateral malleolus fractures, evaluating their performance with and without interfragmentary screws using finite element models.

METHODS

Utilising CT images of a healthy adult male volunteer, a three-dimensional finite element model was constructed. The Fibula-specific Flank Multiaxial Locking Anatomic Plate (FMLP) and the Conventional Locking Plate (CLP) were subjected to stabilisation, both with and without an interfragmentary screw, mimicking the Danis-Weber A and B lateral malleolus oblique fracture fixation. Loads of 140 N and 70 N, equivalent to 20% of the body weight, were applied to simulate the single-leg and two-leg standing conditions in the axial direction. The von Mises stress (VMS) distributions and element displacements were subsequently analyzed.

RESULTS

In the Danis-Weber A fracture model group, the FMLP with an interfragmentary screw fixation exhibited the lowest peak VMS values: 51.9 MPa in the fibula, 89.0 MPa in the plate, and 61.3 MPa in the screws for simulating single-leg conditions. Under two-leg standing conditions, these peak VMS values decreased to 25.9 MPa in the fibula, 44.5 MPa in the plate, and 30.6 MPa in the screws, respectively. Furthermore, the overall structural peak displacements during single-leg standing for both Weber-A and B fractures with different implants ranged from 1.61 to 2.54 mm. While standing on two feet, the ranged was from 0.80 to 1.27 mm. An interfragmentary screw at the oblique fracture site resulted in reduced the peak value of VMS in the fibula, plate, screws, consequently decreased the overall structural displacement for FMLP and CLP fixation in lateral malleolus fractures.

CONCLUSIONS

The current finite element analysis (FEA) demonstrates that FMLP exhibits superior mechanical characteristics in Danis-Weber A and B lateral malleolus fractures compared to CLP. The inclusion of an interfragmentary screw, combined with locking plate design, enhances stability for simple oblique distal fibular fractures. The FMLP presents itself as potential as an alternative for lateral malleolus fractures from a biomechanical perspective. Nevertheless, further verification of these results is imperative through subsequent clinical studies.

Similar Clinical Outcome in Locking and Conventional Plate Osteosynthesis for the Treatment of AO 44-B2 Ankle Fractures

INTRODUCTION

Biomechanical studies have proved that locking plates have better primary stability besides versatility regarding fracture pattern while reducing bone contact and bridging the gap, whereas conventional nonlocking plates (plus lag screw) depend on bone-plate compression. The clinical benefit of locking plates over nonlocking plates remains unanswered, however. Therefore, this retrospective cohort study was set up to test the hypothesis that the use of locking plates for unstable ankle fractures will result in fewer re-displacements, superior bony healing, and functional and clinical outcomes better than observed in the nonlocking cohort.

METHODS

Bimalleolar ankle fractures (AO 44-B2) without syndesmotic injury treated with either a locking or a nonlocking plate were included. Groups were compared for complications, bone healing, secondary dislocation, progressions of osteoarthritis, and clinical outcome using patient-reported outcome measures.

RESULTS

Data revealed no clinical outcome differences (Olerud-Molander Ankle Score: nonlocking 88.2 ± 14.4, locking 88.8 ± 12.3, P = .69, robust two 1-sided test for equality (RTOST): P = .03; American Orthopaedic Foot and Ankle Score: nonlocking 91.2 ± 12.9, locking 91.8 ± 11.3, P = .96, RTOST: P = .04). Nevertheless, a significant postoperative progression of osteoarthritis was detected in both groups (P = .04). This was independent of implant (P = .16). Although difference was not significant, locking plates were preferred in older (P = .78) and sicker patients (P = .63) and in cases with severer osteoarthritis (P = .16), and were associated with a higher complication rate (P = .42) and secondary dislocation (nonlocking 9.4%, locking 18.2%; P = .42). Re-displacement, however, was not a compelling reason for revision.

CONCLUSIONS

The present study shows statistically significant equality of both types of implants. Contrary to our expectation, locking plates seemed to be associated with a higher risk for re-displacement. Overall, the use of either locking or nonlocking plates for unstable AO 44-B2 fractures is safe and successful despite significant progression of osteoarthritis.

LEVEL OF EVIDENCE

III, Retrospective observational cohort study.

Determining the Tightrope Tightening Force for Effective Fixation of the Tibiofibular Syndesmosis during Osteomeatal Synthesis of Fibula Injuries

The issue of choosing the method for optimal surgical treatment of a broken fibula has been debatable for many years. At the same time, concomitant repair of tibiofibular syndesmosis injuries does not have a unified approach. It has been determined that osteosynthesis of broken shin bones with syndesmosis injury should combine stable fixation of the broken bone and should not limit the elastic properties of the syndesmosis. In case of a broken fibula, it is recommended to use a stable extracortical fixator and an elastic connection of the syndesmosis injury using a tightrope. An analytical model of the broken fibula, which is blocked with an extracortical fixator metal plate and elastically fixed with a tightrope, has been developed. The research object is the stress–strain state of the “broken fibula–extracortical titanium plate” composition under the action of tightrope tightening fixation. The main research result is an analytical dependence, which makes it possible to determine the permissible value of the tightrope tightening force for elastic fixation of the tibiofibular syndesmosis. The research results have been tested numerically, and the influence of the parameters of plate, bone and damage localization on the permissible value of the tightrope tightening force has been analyzed. By using the rational tightrope tightening force with stable–elastic fixation of the broken shin, it is possible to reduce the time before the start of loading on the injured extremity and accelerate the functional recovery of the patient.