[Retrograde intramedullary nailing for periprosthetic fractures of the distal femur].

OBJECTIVE: Intramedullary stabilization of periprosthetic distal femoral fractures by interlocking nailing. Closed reduction by retrograde nail can be combined with the use of transmedullary support screws (TMS principle of Stedtfeld).

INDICATIONS: Supracondylar fractures above stable knee arthroplasty (Rorabeck types I and II), femoral shaft fractures ipsilateral of stable hip and/or knee arthroplasty, contraindications for antegrade nailing

CONTRAINDICATIONS: Closed box design of femoral implant, intercondylar distance of the femoral component smaller than nail diameter, more than 40° flexion deficit of the knee, inability to place two bicortical distal interlocking screws. Relative contraindication: insufficient overlap with proximal implants

SURGICAL TECHNIQUE: Supine position and knee flexion of approximately 45°. Fluoroscopy should be possible between the knee and hip. Longitudinal skin incision into the pre-existing scar over the patellar tendon which is then split. The nail entry point is located in the intercondylar groove at the deepest point of Blumensaat's line, often predetermined by the femoral arthroplasty component. Reaming is rarely necessary. Transmedullary support screws may correct axial malalignment during nail insertion. Static interlocking in a direction from lateral to medial by the aiming device. Insertion of locking cap.

POSTOPERATIVE MANAGEMENT: Retrograde nailing normally allows full weight bearing. Range of motion does not need to be restricted.

RESULTS: Out of 101 fractures treated between 2000 and 2013 with a Targon RF nail (Aesculap, Tuttlingen, Germany) 10 were periprosthetic, all were classified as Rorabeck type II and of these 6 fractures were metaphyseal and 4 were diaphyseal. In four cases proximal implants were present. The mean operative time for periprosthetic fracture fixation did not significantly differ from that for normal retrograde femoral nailing. There were no postoperative infections, fixation failures or delayed unions. There was one revision for secondary correction of maltorsion.