Ultrasound in Plastic Surgery - How I Use It in My Practice

Ultrasound is not new to medicine. What is less common is its use as a routine point-of-care tool in plastic surgery, not just to confirm a diagnosis, but to guide clinical decisions in real time and spare patients unnecessary risks. The cases below illustrate how.

Case 1 - Ultrasound-Guided Filler Injection

A patient underwent hyaluronic acid filler injection to the chin for augmentation, specifically targeting the labiomental crease, the fold between the lower lip and the chin. Addressing this crease softens the chin profile and improves projection without surgery.

Before injecting, point-of-care ultrasound (POCUS) was performed. This is widely misunderstood. US-guided filler injection does not mean injecting while watching the screen in real time as that is impractical and not the point. The purpose is twofold: first, to map the vasculature in the intended injection zone before the needle goes in; and second, to confirm the depth of placement after injection.

Doppler ultrasound was used to identify vessels in the area. None were found at the midline injection site. The midline chin is anatomically lower risk for vascular injury than more lateral facial zones, but no location carries zero risk. The confirmation that the field was clear before proceeding is the safety step that POCUS provides. Vascular occlusion from filler injection, where filler inadvertently enters a vessel and causes tissue necrosis, is one of the most serious complications of facial filler. It is rare, but the risk of which is much reduced with adequate pre-injection assessment on top of in-depth anatomical knowledge.

Following injection, B-mode ultrasound was used to confirm the depth of placement. The filler was sitting supra-periosteal, directly on the surface of the mandible, the correct plane for this indication. Correct depth in this location matters beyond the immediate aesthetic result as the supraperiosteal placement reduces the risk of filler migration over time compared to more superficial injections into soft tissue planes. Clinically, the labiomental crease was well-effaced, confirming both the correct placement and the desired aesthetic outcome, and obviated the need for further "blind" filler injections

Case 2 - Trigger Finger: Confirming the Diagnosis Before Injecting

An elderly patient presented with a three to four month history of triggering of the ring finger, requiring passive straightening (straightening it out) to unlock. Clinically, the triggering was localised to the A1 pulley, at the base of the finger, the most common site. There had been no prior treatment so a steroid injection was the first line of treatment.

Before injecting, I performed a point-of-care ultrasound (POCUS) assessment. This did not reveal any discrete lump or mass. What it did show was a slightly thickened tendon (most likely due to inflammation) just distal to the A1 pulley, which confirmed why the finger was catching. As the finger bends, this thickened segment slides under A1 but then catches against its edge (see figure below), producing the "triggering" that the patient experiences. Sometimes, this gets stuck which results in the finger being "locked", and stretching it out (so that the thickened part slides back under A1) may or may not work.

While POCUS was used to confirm the diagnosis, it also enabled me to exclude other possible causes such as a ganglion. A steroid injection (triamcinolone mixed with local anaesthetic) was then given near the A1 pulley so that it flows along the tendon sheath to act on the inflamed tendon. The value of POCUS here is therefore primarily diagnostic rather than purely for injection guidance. The patient was told to expect the sensation of fluid flowing up and down the finger as the injection went in. This was a useful heads-up that prevents unnecessary alarm.

The patient improved within two weeks and is happy with the result when I reviewed him at four weeks after his initial visit. This is consistent with the evidence base for steroid injection in trigger finger. The choice of steroid, is associated with up to 83% resolution when triamcinolone was given. For first-time patients, the success rate of one steroid injection alone ranges between 35 to 56%, with an overall recurrence rate of 20.3% that tended to occur around 1 year later. Surgery, at this stage, is then associated with the final and lowest triggering rate of 10%.

The evidence supports a stepwise approach: one injection, reassess, a second if indicated, and surgical A1 pulley release only if conservative management fails. Proceeding directly to surgery without a trial of injection is not justifiable in most cases - it is more invasive, more costly, and unnecessary for the majority of patients who will respond to injection alone. Surgical release under WALANT is an option for those who do not respond after two injections in my practice.

Case 3 - Post-operative Seroma: When Ultrasound Prevents an Unnecessary Procedure

A patient returned after VASER liposuction performed abroad with concerns about post-operative swelling. She mentioned that her pre-operative weight was 56 kg and her current weight was 59 kg. This was a 3 kg gain that was not explained to her. More importantly, this is a clinically significant finding. Post-operative weight gain of this magnitude after liposuction is not normal - it likely reflects a combination of fluid accumulation from a seroma, residual tumescence fluid, and post-operative fluid shifts. This is exactly the kind of change that structured aftercare following cosmetic surgery is designed to detect and intervene, as necessary.

In fact, she had already had the seroma drained once by the overseas clinic before returning home. However, after the drainage, she noticed that her compression garments had become too loose, but she was not provided with a replacement or adjusted garments. In my opinion, after seroma aspiration, the evacuated space must be compressed immediately and adequately to minimise the risk of re-accumulation. A loose garment after drainage provides no meaningful compression.

Not unexpectedly, when the seroma re-accumulated at 2 weeks, she was already back home and did not contact the overseas clinic. Not because she didn't want to, but because she knew they could not do anything from afar. She had also approached several local clinics for help. None responded. That is the reality of the lack of aftercare in cosmetic surgery done abroad.

The clinical question when I saw her in clinic was straightforward: is there residual seroma, and if so, does it need to be drained again? I performed a point-of-care ultrasound (POCUS) and it showed minimal fluid collection, approximately 0.6 cm in thickness in the subcutaneous layer only. In fact, she was quite a thin patient and we could see her bowels moving (normal finding) right under. Based on the POCUS findings, I made the decision not to drain. The collection was small enough to resolve spontaneously, and an unnecessary aspiration carries its own risks: discomfort, introduction of infection, or worse, bowel perforation given how close they were.

This is where POCUS changes management. Without imaging, the clinical options are to aspirate empirically (and accept the risks above) or to watch and wait. With imaging, the decision is well-informed both for the patient and me: the size, location, and character of the collection are visible, and the threshold for intervention becomes objective rather than estimated. She was reassured and I made arrangements for her to be fitted with a new compression garment. No further intervention was required.

Why POCUS Matters in Plastic Surgery

These cases illustrate the same principle: ultrasound in the plastic surgery clinic is not about replacing clinical judgment or imaging - it is about informing in real-time. Absence of blood vessels before injecting filler, a thickened tendon that explains a triggering finger, a seroma too small to drain - these findings change what happens next. They spare patients procedures they don't need, and they give the surgeon a level of certainty that clinical examination alone may not always provide.

For patients considering precision non-surgical facial rejuvenation, and hand and wrist surgery in Singapore, you can read more about fillers, and hand & wrist surgery under WALANT at ZNG. For those interested in liposuction and body contouring, you can read more about my liposuction-assisted approach at ZNG.

Written by Dr Ng Zhi Yang, Singapore Plastic Surgeon, and Founder & Medical Director of Doctor Stitch, a specialist-led cosmetic surgery aftercare, and same-day minor surgery service.

References

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