Abstract
Prevalence
Periprosthetic fractures around a total knee are uncommon but not rare; various large database studies suggest 0.3–2.5%. Patients at highest risk are typically older patients and those with poor quality bone from various etiologies. Supracondylar femur fractures are often associated with a high stress zone at the metaphysis/diaphysis junction near the superior edge of femoral component.
Etiology
Low energy trauma is the most common preceding event as most of these occur in patients with poor bone quality. Elderly patients are at particular risk because standing-height falls generate enough energy to create fractures. Given the durable nature of most modern TKA designs the prosthesis is usually fixed well.
Goals
The goals of treatment are typically fracture union, avoidance of infection, avoidance of stiffness, and maintenance of overall limb alignment. Recent gains in knowledge indicate the need to attain maximal distal fragment fixation in order to achieve the surgical goals. Correct alignment, length and rotation are often best assessed with a combination of radiographic images and intra-operative clinical inspection. Modern internal fixation principles emphasise the need to minimise stripping/devascularization of comminuted zones.
Options
Three major treatment options exist for supracondylar fractures. Retrograde nails have advantages in that they are tissue-friendly and are mechanically advantageous in the face of medial comminution. Difficult to use with most posterior stabilised TKA (box). There are limited distal fixation options and malalignment is often hard to avoid. With plating the distal fixation can be maximised and there is less risk for malalignment. Typically requires more soft tissue dissection. Locked plates provide good coronal plane stability and 2nd generation locked plates allow variable screw angles such that far distal fixation is possible. Revision TKA is required when implants are loose. Revision may be more reliable than fixation options in very elderly with badly comminuted bone. Be aware that a hinged tumor type implant may be needed in many cases.
