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SINC sign accurately predicts fixation outcomes in periprosthetic femoral fractures around PTSs, study shows

Our research examined whether the radiographic feature subsidence-in-centralizer (SINC) sign can help predict the outcome of internal fixation for periprosthetic femoral fractures (PPFs) around polished-taper stems (PTSs).

Ishvinder Grewal, M.D.

Ishvinder Grewal, M.D.

Periprosthetic hip fractures are among potential postoperative complications following total hip arthroplasty (THA), and they are associated with a high rate of reoperation and mortality. These injuries are projected to become more common as the population ages and the demand for THA increases.

New research published in Cureus has identified a potential radiographic feature to help predict whether a patient may experience bone collapse, or subsidence, after internal fixation surgery for a specific, challenging type of periprosthetic hip fracture.

Distinguishing the exact fracture type is significant when deciding whether to treat PPFs around PTSs with internal fixation. Fractures without loose stems (B1) can be successfully treated with open reduction and internal fixation (ORIF). Fractures around loose stems (B2) can be treated with revisional arthroplasty.

Failure to make this distinction can contribute to poor outcomes for B1 fractures. However, existing worldwide classification systems to guide treatment, such as the Vancouver classification, do not always help differentiate between fracture types.

In pursuit of a clear differentiator, our research investigated the SINC sign, a radiographic feature that can help predict the likelihood of stem subsidence following ORIF for PPFs around PTSs.

Our study involved retrospective identification of PPFs around cemented PTSs with an appreciable centralizer conducted at a single facility in the U.K. A positive SINC sign was defined as greater than 50% reduction in radiographic lucency representing the stem centralizer when compared with pre-injury imaging, or complete obliteration of distal lucency when pre-injury film was unavailable.

The primary outcome was to compare the rate of stem subsidence in fractures with a positive SINC sign on follow-up imaging against those that showed a negative SINC sign. Fifty-four patients were included in the analysis, with a mean age of 76.8 years and mean follow-up of 12.7 months. Of these, 35 fractures were identified as SINC-positive and 19 were SINC-negative.

One hundred percent of SINC-positive fractures managed with fixation experienced further subsidence. Analysis of fractures treated without revision showed a positive SINC sign with demonstrated sensitivity of 90.5% and specificity of 100%. When fixed, SINC-positive fractures showed significantly more subsidence compared to SINC-negative fractures.

Our data suggest that a positive SINC sign may represent a cement mantle that cannot be anatomically reconstituted, leading to risk of subsidence after ORIF. This research indicates that the SINC sign can help predict whether to fix or revise PPFs around PTSs.