Objective evaluation of fat tissue induration after breast reconstruction using a deep inferior epigastric perforator (DIEP) flap

The "Halo Appearance" of Shear Wave Elastography in the Setting of Fat Necrosis: A Potentially Useful Sonographic Discriminator

OBJECTIVE

To describe the morphologic sonographic appearances and frequency of the "halo sign" in the setting of fat necrosis on shear wave elastography (SWE).

METHODS

Patients with clinically suspected fat necrosis were prospectively scanned using SWE in addition to standard gray-scale and Doppler images. Cases were qualitatively grouped into one of three sonographic appearances: focal hypoechoic lesion with increased internal tissue stiffness ("focal stiffness"), focal hypoechoic lesion with isoechoic or hyperechoic periphery demonstrating increased tissue stiffness relative to the central hypoechoic lesion ("halo stiffness"), heterogeneously echogenic lesion with diffusely increased stiffness ("heterogeneous stiffness").

RESULTS

Exactly 19 patients met inclusion criteria (female n = 14; male n = 5). Shear wave velocities were recorded and retrospectively evaluated. The mean clinical follow-up was 11.4 months (range 3.0-25.5). Lesions demonstrated higher average tissue stiffness than background tissue (overall mass shear wave velocity 3.26 m/s, background 1.42 m/s, P < .001; lesion Young's modulus 40.85 kPa vs background 7.22 kPa, P < .001). The halo sign was identified in 10/19 (55%) patients.

CONCLUSION

The halo sign is a potentially useful sign in the setting of fat necrosis seen in the majority of clinically suspected cases.

Applications of ultrasound elastography to hand and upper limb disorders

Ultrasound elastography is a recently developed method for accurate measurement of soft tissue stiffness in addition to the clinician's subjective evaluation. The present review briefly describes the ultrasound elastography techniques and outlines clinical applications for tendon, muscle, nerve, skin and other soft tissues of the hand and upper limb. Strain elastography provides a qualitative evaluation of the stiffness, and shear-wave elastography generates quantitative elastograms superimposed on a B-mode image. The stiffness in degenerative tendinopathy and/or tendon injury was significantly lower than in a normal tendon in several studies. Elastography is also a reliable method to evaluate functional muscle activity, compared to conventional surface electromyography. The median nerve is consistently stiffer in patients with carpal tunnel syndrome than in healthy subjects, on whatever ultrasound elastography technique. Elastography distinguishes normal skin from scars and can be used to evaluate scar severity and treatment. Elastography has huge clinical applications in musculoskeletal tissues. Continued development of systems and increased training of clinicians will expand our knowledge of elastography and its clinical applications in the future.

The influence of venous system patterns on DIEP flap viability for breast reconstruction

A deep inferior epigastric artery perforator (DIEP) flap has unique variations in the anatomy of the vascular supply, and this idea has been adapted to the venous system. Venous system patterns, including connections between the superficial and deep inferior epigastric vein (SDC) or connections of the superficial inferior epigastric vein across the midline-crossing linking veins (MCLV), have gradually become recognized as a cause of fat necrosis and induration due to venous congestion. Therefore, it is important to select patients who are appropriate for transplantation by evaluating blood flow in the flap based on these patterns. The subjects were 52 consecutive patients who underwent DIEP flap breast reconstruction. Relationships of fat necrosis and induration of a transplanted flap and venous system patterns (presence of SDC on the contralateral side: cSDC or MCLV, direction and diameter of perforator vein) in the flap were investigated. Logistic regression and univariate and multivariate analyses were used to identify predictors of fat necrosis and induration of the flap. Fat necrosis and induration were detected in 17.4 and 34.8% of cases, respectively. These incidences were significantly linked to the absence of cSDC and MCLV patterns in the flap. Patients without a cSDC or MCLV pattern had harder fat tissue in Zone II, especially in the distal portion. These results suggest that the absence of a cSDC or MCLV pattern causes complications such as fat necrosis and induration in a transplanted flap. If neither pattern is detected before surgery, improvement of venous drainage is recommended.