Navigated reconstruction of tibial head depression fractures by inflation osteoplasty.

BACKGROUND: Articular fracture reduction control remains a challenge even with the development of computer-assisted surgery. The Kyphoplasty procedure has shown advantages in treating vertebral fractures. One case report showed successful reduction of acetabular fractures using Kyphoplasty. OBJECTIVE: This study examines the efficacy of this method in reducing depressed tibial plateau fractures. METHODS: An insertion sleeve for the Kyphon balloon that could be calibrated by the navigation system was designed. A total of 30 test series in synthetic bone cubes were performed using fracture instruments of 2.5 mm, 5 mm and 15 mm diameter, respectively, creating three different depression fracture depths (mean 1.87 mm, 4.2 mm and 1.72 mm, respectively). The Kyphon balloon was used to attempt reduction of each fracture. The same setup was used for testing in five cadaveric tibia specimens. RESULTS: After reduction, there was a remaining depression depth mean in the synthetic bone of 0.27 mm for the 2.5 mm instrument; 2.1 mm for the 5 mm instrument; and 1.72 mm for the 15 mm instrument. We could not adequately reduce depression fractures in cadaveric testing. CONCLUSIONS: The Kyphon balloon was accurately placed with the aid of navigation. The depth was the decisive factor in the reduction of the fracture and not the diameter. In cadavers, depression fractures greater than 5~mm depth could not be reduced with our setup.

Influence of femoral malrotation on knee joint alignment and intra-articular contract pressures.

INTRODUCTION: The standard treatment of femoral diaphyseal fractures is intramedullary nailing. Torsion error remains a largely unsolved problem. We hypothesized that femoral malrotation would change the coronal alignment of the lower extremity and the center of force (COF) in the tibiofemoral joint as compared to the native state. METHOD: Ten cadaveric legs were used. Intraarticularly placed sensor foil was used to measure contact pressures for each condyle. The resultant pressure of this two-force measurement was calculated as the COF for the joint. Mechanical axis was defined by the navigation system. Two novel devices were used: (1) to simulate bodyweight with leg attachment and fixation to the anterior pelvis and (2) to fix the femur at various degrees of malrotation. A mid-diaphyseal osteotomy was performed and the distal fragment was rotated both internally and externally in 5° increments to a maximum of 25°. COF and axial alignment were assessed at each step with application of a half-bodyweight specific to each specimen. RESULTS: Internal rotation resulted in valgus deviation of the mechanical axis and a shift in COF towards the lateral condyle (P < 0.05). External rotation caused varus deviation and switched COF towards the medial condyle (P < 0.05). This study shows that femoral malrotation has a significant effect on mechanical axis alignment and force vectors within the knee. Correlation with clinical outcomes is necessary and further research into minimizing such errors of torsion is warranted. CONCLUSION: Torsion errors are not merely cosmetic issues, but may result in further morbidity, such as varus or valgus deformity and shifting of the COF, which may lead to joint arthrosis.