[Distal femoral fractures]

Impact of fracture morphology on the biomechanical stability of osteosynthetic fixation

Biomechanical testing is essential for evaluating osteosyntheses, particularly in assessing stability, stiffness, and fragment motion. However, traditional flat-fracture models created via osteotomy fail to replicate the complex morphology of real-world fractures, potentially reducing the applicability of results. This study introduces patient-specific distal femur fracture models to investigate the impact of fracture morphology on the biomechanical performance of osteosyntheses. Realistic fracture models were generated using 3D printing and molding, based on CT-derived geometry, alongside traditional osteotomy models. Four groups were tested: osteotomized and realistic fracture models, with and without gaps. All constructs were treated with distal femur locking plates and subjected to axial and torsional loading. Dynamic testing simulated physiological conditions and tracked interfragmentary motions with a 3D optical motion system. Realistic fracture models exhibited higher torsional stiffness and reduced interfragmentary motion compared to osteotomized models, particularly in closed fracture gaps. Axial stiffness increased significantly upon fracture gap closure in all gap groups, transitioning from exclusively plate-bearing to construct-bearing configurations. The irregular geometry of realistic fractures provided enhanced interlocking, improving stability under both axial and torsional loads. Patient-specific fracture models better replicate the mechanical behaviour of clinical distal femur fractures, demonstrating advantages over osteotomized fracture models. The inclusion of realistic fracture geometries in biomechanical testing improves the transfer of biomechanical results into a clinical setting and offers valuable insights for optimizing designs and improving clinical outcomes.

Determination of the ideal plate for medial femoral condyle fracture fixation: an anatomical fit and biomechanical study

BACKGROUND

The aim of this study is to determine the best plate to use as a substitute to fix a medial femoral condyle fracture.

MATERIALS AND METHODS

The first part is to measure the best fit between several anatomical plates including the Proximal Tibia Anterolateral Plate (PT AL LCP), the Proximal Tibia Medial Plate (PT M LCP), the Distal Tibia Medial Locking Plate (DT M LCP) and the Proximal Humerus (PHILOS) plate against 28 freshly embalmed cadaveric distal femurs. Measurements such as plate offset and number of screws in the condyle and shaft shall be obtained. The subsequent part is to determine the compressive force at which the plate fails. After creating an iatrogenic medial condyle fracture, the cadavers will be fixed with the two plates with the best anatomical fit and subjected to a compression force using a hydraulic press.

RESULTS

The PT AL LCP offered the best anatomical fit whereas the PHILOS plate offered the maximal number of screws inserted. The force required to create 2 mm of fracture displacement between the two is not statistically significant (LCP 889 N, PHILOS 947 N, p = 0.39). The PT AL LCP can withstand a larger fracture displacement than the PHILOS (LCP 24.4 mm, PHILOS 17.4 mm, p = 0.004).

DISCUSSION AND CONCLUSION

Both the PT AL LCP and the PHILOS remain good options in fixing a medial femoral condyle fracture. Between the two, we would recommend the PT AL LCP as the slightly superior option.

Biomechanical analysis of bridge combined fixation system as a novel treatment for the fixation of type A3 distal femoral fractures

Background

To compare the biomechanical parameters of AO/OTA type A3 distal femoral fractures fixed bilaterally with a bridge combined fixation system (BCFS) and lateral locking compression plate + locking reconstruction plate (LCP + LRP).

Methods

Twelve A3 distal femoral fracture models with medial cortical defects of the distal femur were created using synthetic femoral Sawbones. BCFS and LCP + LRP were used for bilateral fixation, with six in each group. Axial compression and torsion tests were performed on the two groups of fracture models to determine their stiffness during axial compression and the Torsional stiffness during torsion tests. Axial compression failure tests were performed to collect the vertical loads of the ultimate failure tests.

Results

In the test conducted on the fixed type A3 distal femoral fracture models, the axial stiffness in the BCFS group (group A) (1,072.61 ± 113.5 N/mm) was not significantly different from that in the LCP + LRP group (group B) (1,184.13 ± 110.24 N/mm) (t = 1.726, P = 0.115), the Torsional stiffness in group A (3.73 ± 0.12 N.m/deg) was higher than that in group B (3.37 ± 0.04 N.m/deg) (t = 6.825, P < 0.001),and the ultimate failure test of type A3 fracture model showed that the vertical load to destroy group A fixation (5,290.45 ± 109.63 N) was higher than that for group B (3,978.43 ± 17.1 N) (t = 23.28, P < 0.05). Notably, intertrochanteric fractures occurred in groups A and B.

Conclusions

In the fixation of type A3 distal femoral fractures, the anti-axial compression of the BCFS group was similar to that of the LCP + LRP group, but the anti-torsion was better.

Treatment of distal femur fractures with retrograde intramedullary nailing utilizing a tibial nail

Abstract Aim Retrograde intramedullary nailing for the treatment of femur fractures is a sound option due to its advantages including ease of implant placement and better control of the distal segment, especially in distal femur fractures. Unfortunately, retrograde femoral nails are not available in most developing countries or rural areas. The primary aim of the study is to investigate the outcomes of an alternative treatment of distal femur fracture with retrograde intramedullary nailing using a tibial nail. Material and Method Patients who had distal femur fractures and underwent retrograde intramedullary nailing with a tibial nail between January 2020 – March 2022 are retrospectively evaluated. Patients who were treated other than a tibial nail, aged below 18, had follow-up less than 6 months, multiple fractures, and open fractures were excluded. Patients’ demographics, time to union, and complications were recorded. Functional outcomes included visual analogue pain score (VAS), Lysholm score, Tegner activity scale, Knee Society Score (KSS), and Short Form-36 (SF36) on the latest follow-up. Results A total of 15 patients (11 male, 4 female) met the inclusion criteria and included in the study. The mean age of the patients was 42.9 ± 17.3 (range, 18 to 72) months. The mean follow-up period was 10.1 ± 5.2 (range, 6 to 18). There was no reduction loss and implant failure during follow-ups. One patient had nonunion. No intraoperative fracture occurred. Persistent knee pain was seen in a patient due to an intraarticular screw and removed arthroscopically. In the latest follow-up, the mean VAS was 0.73 ± 0.70 (range, 0 to2), the mean Tegner score was 5.0 ± 1.5 (range, 3 to 7), the mean Lysholm score was 90.9 ± 9.9(range, 64 to 100), the mean KSS was 86.6 ± 8.6 (range, 70 to 97), and the mean SF-36 score was 96.5 ± 4.7 (range, 87 to 100). Conclusion The results of this study suggest that a tibial nail with retrograde intramedullary nailing has good functional outcomes in the treatment of distal femur fractures. The tibial nail should be considered as an alternative treatment option where distal femoral nails are not available.