Explorative study of the sensitivity and specificity of the pronator quadratus fat pad sign as a predictor of subtle wrist fractures

Abstract

ObjectiveTo investigate the value of post-traumatic pronator quadratus (PQ) fat pad sign as a reliable predictor of subtle wrist fractures.Materials and methodsThis was a prospective study of 68 patients undergoing X-ray for traumatic wrist injuries and subsequent MRI. The reliability of a positive PQ fat pad sign on X-ray, defined as either raised, interrupted or obliterated, was evaluated in detection of subtle wrist fractures.ResultsOut of 68 patients, 28 had a positive PQ sign without any obvious bony injuries on plain radiographs; of these, the PQ fat pad was obliterated in 11, disrupted in 12, and raised in five cases. Fractures defined as cortical interruption or trabecular fractures were revealed in 13/28 (46 %) patients with a positive PQ sign but only in 7/40 (18 %) patients with a negative sign. With regards to different types of abnormal PQ fat planes, fractures were present in 7/12 patients with a disrupted plane (58 %), 6/11 patients with an obliterated plane (54 %), and none of the patients with a raised plane. The overall sensitivity and specificity of a positive PQ sign in the prediction of occult wrist fractures were 65 and 69 %, respectively.ConclusionsOur findings indicate that a positive pronator quadratus (PQ) fat pad sign is not a reliable predictor of subtle fractures of the wrist, although we believe that it is a useful radiographic sign in justifying MRI for further clarification of possible joint abnormalities including occult fracture and cortex interruption.

Reliability of the pronator quadratus fat pad sign to predict the severity of distal radius fractures

“…Mac Ewan was first to characterize the pronator quadratus fat pad sign consisting of a radiolucent (fat containing) stripe which runs parallel to the pronator quadratus muscle covering the distal radius and ulnar (Figure 1 )[ 1 , 2 ]. Studies on healthy subjects have shown that thickness of the pronator quadratus complex (PQC) is significantly greater in men (values up to 9 mm) than in women (values up to 8 mm) and increases with age[ 3 , 4 ].…”

“…In the past several studies have analyzed the usefulness of the PQS to detect subtle fractures or inflammation of adjacent e in their detecting[ 7 ]. Sensitivity of the PQS measured on lateral X-rays to detect occustructures[ 3 , 4 , 5 , 7 ]. While earlier studies described the PQS as a useful adjunctive to detect subtle fractures[ 1 ], more recent studies, which used MRI as a reference, have found this sign to be unreliabllt distal forearm fractures has been reported to range between 26% and 65%.…”

Examination of the Pronator Quadratus Muscle during Hardware Removal Procedures after Volar Plating for Distal Radius Fractures

“…During the fracture repair through a volar approach, the pronator quadratus (PQ) muscle is stripped off the radius in order to apply the volar plate 3). However, it is generally difficult to repair the PQ muscle at the end of the operation, because the muscle fascia is not strong enough to hold sutures,4,5,6) and the muscle can also be injured due to the fracture 7,8). However, a recent study evaluated the integrity of the PQ muscle repair radiographically by using radiopaque hemoclips, and it reported that PQ repairs are generally durable 9)…”

A woman with wrist pain

“…In patients with distal forearm fractures, blood may displace the fat plane anteriorly and create the pronator quadratus fat pad sign (figure 1). 1 False-negatives occur if radiographs are poor quality or obtained before blood can accumulate, or if fractures are not under the pronator quadratus muscle. False-positives occur in some arthritides, infections and soft tissue injuries.…”

“…Sensitivity and specificity of the sign are 26–65% and 70%, respectively 1 2. Patients with a positive fat pad sign but otherwise normal radiographs may require additional imaging to assess for fracture.…”