In this study, we evaluated the effects of MIPO with dual plating to treat periprosthetic distal femoral fractures following TKA in 18 patients and found that MIPO with dual LCP is a reliable method for stabilizing periprosthetic distal femoral fractures following TKA, with satisfactory bone union rates and low complication rates.
Recent reports focusing on retrograde IM nailing and LCP plating support the priority of these two procedures over conventional plating [8, 10, 15, 18]. The comparison of LCP plating and retrograde IM nailing showed no statistically significant differences with respect to nonunion rates. LCP plating showed significantly lower malunion rates than retrograde IM nailing in a systematic review , and the authors proposed three reasons for the superiority of the LCP over retrograde IM nailing for malunion rates. First, the starting point for retrograde IM nailing is dictated by the position of the femoral component and can cause malreduction. Second, retrograde IM nailing does not have the capacity to fill the wide metaphyseal intramedullary space, which allows for potential movement of the distal fragment relative to the nail. Third, the LCP plate offers more distal fragment fixation options than retrograde IM nailing.
The recently introduced dual plating technique with medial plate application for extremely distal periprosthetic fractures can provide sufficient stability . In a biomechanical study, dual plating was more effective and had greater stability than simple lateral plating . Medial plating is not widely attempted because of potential injury to the femoral artery. However, in a recent study, a medial plate could be safely applied on the anteromedial aspect of the distal femur to a distance of up to 8 cm distal to the lesser trochanter . A recent cadaveric study has stated that the distal 60% of the femur is a safe zone for medial plating . Hence, medial plating along with MIPO and lateral LCP plating is not only safe but also rigid enough to support a medial-sided fracture.
In a previous study that used double plating in different directions (orthogonal, i.e., lateral and anterior) , various types of periprosthetic fractures (around total hip replacement arthroplasty, TKA, and inter-prosthetic fractures) were assessed, while including only one case of periprosthetic distal femoral fracture following TKA. PHILOS plates has many advantages in medial fixation, including a similar shape to the contour of the medial condyle and a size that does not interfere with the femoral component of TKA. A previously reported limitation of medial plates is that they exert a fixing force mainly in the coronal plane. However, the fixing direction of the screw in the PHILOS plate is from the anteromedial to posterolateral direction, and this fixation force on the sagittal plane is additionally applied to the distal femur, which contributes to additional stabilization in the coronal plane and introduces new stability in the sagittal plane. This diagonal plating has two vectors applied in the coronal and sagittal planes. Additionally, with the use of the PHILOS plate, the application of many screws with various angles is possible and provides a rigid and stable fixation.
No direct evidence exists that malunited periprosthetic fractures post-TKA is associated with early component failure or wear; however, previous literature suggests that component malposition could cause such complications . Malunion of these fractures also causes component malposition, and hence, may be related to component failure or wear. This can be resolved by MIPO with an LCP placed laterally and initial fracture fixation with a PHILOS plate medially for periprosthetic distal femoral fractures. Moreover, double plating with an anteromedial PHILOS plate offers additional stabilization in the coronal plane and introduces stability in the sagittal plane. Hence, this technique could potentially reduce TKA component failure or wear after periprosthetic distal femur fractures.
Despite satisfactory outcomes, our study has some limitations. First, we included a small number of cases, as periprosthetic distal femoral fractures have a low incidence. Second, this was a retrospective study with no control group; therefore, our results should be validated by larger studies in the future.