The Reliability of Kager's Triangle in Detecting Acute Achilles Tendon Ruptures

Abstract

The Achilles tendon is a common site of anatomical injury among athletes and those participating in recreational sporting activities. Acute Achilles tendon ruptures are often misdiagnosed as a sprained ankle and are more common in the male population. Mechanism of injury is often a noncontact injury, resulting from sudden forced plantar flexion or violent dorsiflexion in a plantar flexed foot. Delays in diagnosis and treatment may complicate the clinical outcome. Because findings may be subtle on history and physical examination, the use of readily available adjunctive studies is important for practitioners. One method is the analysis of Kager's triangle on lateral ankle radiographs. Obscuration of Kager's triangle has been described as a radiographic indicator of Achilles tendon rupture, but the sensitivity and specificity of this finding have been poorly reported. [ Orthopedics . 2020; 43(2): e91–e94.]

Diagnostic Value of Lateral Ankle Radiography in Achilles Tendon Rupture

“…26 Several studies and case reports have previously suggested that Kager’s fat pad sign may be helpful in diagnosing ATR. 15,21,24 Cetti and Andersen 15 reported the sensitivity of Kager’s fat pad sign as 100% and its specificity as 98.3%, for the diagnosis of ATR. These diagnostic values are much higher than those we observed in our study.…”

“…A positive Kager’s fat pad sign is defined as the sharp edges of Kager’s triangle disappearing or becoming indistinct and obscured, or the triangle becoming more radio dense and covered by a network-like shadow (Figure 1). 15,24…”

“…A positive Kager's fat pad sign is defined as the sharp edges of Kager's triangle disappearing or becoming indistinct and obscured, or the triangle becoming more radio dense and covered by a network-like shadow (Figure 1). 15,24 The tibio-first metatarsal angle: This is the angle between a line drawn along the tibial mechanical axis and a line drawn parallel to the first metatarsal and divided into 2 (Figure 2). 20 The tibiocalcaneal angle: This is the angle between a line drawn along the tibial mechanical axis and a line drawn at the plantar border of the calcaneus (Figure 3).…”

“…The higher specificity values we found in our study may be due to our use of the radiographs of patients diagnosed with ankle sprain as the control group. In contrast, in the study of Belyea et al, 24 the control group consisted of the radiographic images of 50 patients without Achilles tendon pathologies and who had a history of soft tissue surgery on the ankle. As this may increase the false-positive rate, it could explain the lower specificity of Kager's fat pad sign in that study.…”

Kager’s sign; an underestimated radiographic feature in detecting acute Achilles tendon rupture: A report on two cases

“…Because the findings of the history and physical examination may be ambiguous (3), radiographic imaging plays a key role in diagnosis in emergency situations. Although Kager's sign has been defined as a radiographic sign of Achilles tendon rupture, its diagnostic efficacy has not been well studied and has not been frequently used in clinical practice (4). Magnetic resonance imaging (MRI) is the gold standard imaging method in the diagnosis of tendinopathies ( 5), however, it has disadvantages such as being impractical in emergency situations, not being accessible in all facilities, and being expensive.…”