Finite element analysis of the stability of AO/OTA 43-C1 type distal tibial fractures treated with distal tibia medial anatomic plate versus anterolateral anatomic plate.

BACKGROUND: The treatment of a pilon fracture type is possible from a medial, an anterolateral approach or both medial and lateral. The aim of study was compare the stability of two different plate fixation of a tibia pilon AO-43C1 type fractures. MATERIAL AND METHODS: In this study, three-dimensional finite element stress analysis was applied using isotropic materials and static linear analysis. Loading of 400 N force was applied to the model of a patient fixed in a standing position. In the model, first the fibula was treated by plating and then in one group the pilon fracture was treated by medial plating, and in the other by anterolateral plating. The displacement and stress values of the fragments of the fracture line were compared of the same points in each model. RESULTS: The magnitude of the displacement of fragments in the total displacement magnitudes of X, Y, Z axis were measured in the medial plate and anterolateral plate. The anterolateral plate results were similar to those of the medial plate and the displacement values in the Y axis were determined to be lower than in the medial plate. CONCLUSION: In AO 43 C1 distal tibia fractures, medial or anterolateral plates can be used, and the results of this study showed similar biomechanical stiffness in the two plates.

Sagittal patellar tilt and concomitant quadriceps hypotrophy after tibial nailing.

PURPOSE: The aim of the study was to analyse the patellofemoral alignment in the sagittal plane following tibial fracture surgery with intramedullary nailing and its relationship to parapatellar muscle status. METHODS: The patellofemoral MRI results of 27 patients (15 males and 12 females) treated with locked intramedullary nailing following tibia shaft fracture were reviewed. The mean age of the patients was 41.8 (±15) years. The patella-patellar tendon angle (P-PT) and the distance between the inferior patellar pole and the tibial tubercle (DP-TT) were evaluated for both the operated extremity and the contralateral normal side. MRI assessment of the infrapatellar fat pad, quadriceps, sartorius, gracilis, semi-membranosus muscles and biceps muscles was also carried out. The correlation between the changes in skeletal muscle mass, the volume of the infrapatellar fat pad and the alterations in the DP-TT distances and P-PT angles were analysed. RESULTS: The quadriceps muscle cross-sectional diameter had a mean of 157.2 mm(2) (115.6/319.5) in the operated extremity, and it was 193 mm(2) (77.6/282.2) in the non-operated normal side (p = 0.001). For the Gracilis muscle, the mean was 84.4 mm(2) (19.7/171) at the operated extremity and 75.7 mm(2) (26.9/238.2) on the normal side (p = 0.05). The cross-sectional areas of the semi-membranosus, sartorius and biceps muscles in the operated and non-operated extremity were not noticeably different (n.s). The P-PT angle was 153° (129.7/156.4) in the operated extremity and 145.7° (137.6/163.4) in the non-operated normal extremity (p < 0.05). While DP-TT distance was 11.4 mm (9.4/20.4) in the operated extremity, it was 14.1 mm (7.3/17.1) in the non-operated extremity (p = 0.001). The correlation analyses revealed that the quadriceps hypotrophy negatively correlated (r = -0.4, p = 0.02) with the P-PT angle but positively correlated with the increase in gracilis muscle volume (r = 0.4, p = 0.03). CONCLUSION: This study revealed that patellofemoral joint kinematics in the operated extremity was diminished in the sagittal plane correlating with the quadriceps muscle volume loss and gracilis muscle hypertrophy. The modalities focused on both preventing and treating the hypotrophy of the quadriceps muscle following the surgical treatment of tibial fracture, which may help to overcome this quite common pathology.

Performance of modified anatomic plates is comparable to proximal femoral nail, dynamic hip screw and anatomic plates: finite element and biomechanical testing.

AIM: To establish whether the modified anatomic plate (MAP) performs as well as the anatomic plate (AP), dynamic hip screw (DHS) and proximal femoral nail (PFN) from a biomechanical perspective. MATERIALS AND METHODS: The, AP, MAP, DHS and PFN were assessed using finite element (FE) methods and biomechanical tests. A solid model was created based on the fracture lines and results were assessed using analyses of variance. MAIN OUTCOME MEASUREMENTS: Independent variables were the implants (n=4) and axial loads: 0-1000 Newton (N) in 100 N increments. Dependent variables were loads at the intertrochanteric fracture line as measured by load cells. RESULTS: Axial loads ≤400 N generated significantly (p<0.05) greater stress at the fracture line in both the FE model and biomechanical settings: the PFN generated the highest forces at the fracture line followed by the AP, MAP and DHS. For axial loads ≥400 N, the AP and DHS generated nonsignificant (p>0.5) lower forces (almost 50% less) compared with the MAP and PFN. At 1000 N, the DHS generated the highest (p<0.05) load at the fracture line. CONCLUSION: The biomechanical features of the MAP were similar to those of the PFN. The MAP generated optimal loads at both the fracture site and the proximal femur. FE methods and biomechanical tests revealed that the MAP is associated with both intra- and extra-medullary fixation features, even though the load was applied as an extramedullary stimulus.