Is augmentation a possible salvage procedure after lateral migration of the proximal femur nail antirotation?

S Erhart, C Kammerlander, R El-Attal, W Schmoelz
Archives of Orthopaedic and Trauma Surgery 2012, 132 (11): 1577-81

INTRODUCTION: Failed fracture fixation of proximal femur fractures in the elderly usually results in prosthetic replacement. In case of the proximal femur nail antirotation (PFNA), during lateral blade migration or periimplant fracture at the femoral shaft, the femoral head remains intact and therefore a joint preserving procedure might be performed. However, implant anchorage in the femoral head after the second blade implantation generally results in reduced anchorage in the remaining cancellous bone. Therefore, we hypothesize that in the above mentioned cases augmentation of the PFNA blade could be a treatment option before prosthetic surgery has to be performed.

MATERIALS: Biomechanical investigations were performed in eight fresh frozen femoral heads. Implant anchorage in case of blade extraction and reinsertion was investigated by rotation and pull out of a PFNA blade with a servohydraulic testing machine. After reinsertion of the blade and augmentation with bone-cement, the anchorage of the blade was investigated again to observe changes in torque and pull-out force.

RESULTS: Rotational stability of the implant significantly increased after augmentation of the prior extracted PFNA blade. Pull-out strength was higher in the revised case than in the initial tests but without statistical significance. After augmentation, correlation between bone mineral density and pull-out strength which was found during initial pull-out disappeared.

DISCUSSION: Augmentation of simulated blade exchange after lateral blade migration demonstrated a good anchorage. There was superior rotational stability in the revised case and no inferiority during pull out for the investigated specimens. Furthermore, augmentation could compensate for destroyed trabeculae and poor bone stock. It could furthermore be an option when a failed implant has to be replaced by a long PFNA in case of shaft fracture at the tip of the implant to increase anchorage in the femoral head. From a biomechanical point of view, reosteosynthesis and augmentation in selected cases of PFNA revision could be an alternative to initial prosthetic replacement. In the case of cut-out or medial implant protrusion, the suggested salvage technique is not feasible.

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