INTRODUCTION:
Periprosthetic distal femur fractures (PPDFFs) are a common complication after total knee arthroplasty (TKA). In the setting of well-fixed TKA components, treatment options include retrograde intramedullary nailing (rIMN) or lateral locked plating. Treatment with rIMN has historically been associated with potential for extension deformity when using conventional nails. We hypothesized that the PPDFFs treated with an intramedullary nail with a specifically designed 10-degree distal bend for periprosthetic fractures would result in improved post-operative sagittal alignment compared to conventional intramedullary nails.

MATERIALS AND METHODS:
The study was conducted at a level-1 trauma center over a 12-year period (2010 - 2022). Patients over the age of 18 who sustained a PPDFF treated with rIMN were identified. The primary outcomes of the study were post-operative coronal and sagittal alignment determined by reviewing post-operative radiographs.

RESULTS:
A total of 50 patients were included. Twenty-three patients were treated with a rIMN with a 10° distal bend. Twenty-seven patients were treated with a rIMN with distal bend of 5° The mean aPDFA for the 10° distal bend group was 81.7° compared to 92.8° in the 5° distal bend group (p< 0.001). There were 3/23 (13%) significant sagittal plane deformities the 10° distal bend group compared to 11/27 (41%) in the 5° distal bend group (p = 0.03). There was one patient with a post-operative extension deformity in the 10° distal bend group compared to 11 patients in the 5° distal bend group (p = 0.02).

CONCLUSION:
Retrograde intramedullary nailing of PPDFF with a 10° distal bend results in significantly better alignment in the sagittal plane when compared to a conventional 5° nail. The use of a 5° nail resulted in an extension deformity significantly more frequently. We therefore recommend the utilization of a rIMN with a 10° distal bend when treating PPDFFs.

SUMMARY:
Periprosthetic distal femur fractures are a common complication following total knee arthroplasty. While several studies report on the use of retrograde intramedullary nails in the treatment of periprosthetic distal femur fractures, there are limited reports of the use of a novel retrograde intramedullary nail with a 10° distal bend in the treatment of these injuries. Herein we present a radiographic study comparing coronal and sagittal postoperative alignment following treatment with retrograde intramedullary nails with a 10° distal bend versus conventional retrograde nails with a 5° distal bend.





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