Ultrasonographic assessment of rectus abdominis muscle adaptation after deep inferior epigastric artery perforator (DIEP) flap surgery: Single institution retrospective study

Abstract

The impact of deep inferior epigastric artery perforator (DIEP) flap on abdominal wall integrity has been the topic of an ongoing debate with previous studies having reported conflicting results using various imaging modalities. Ultrasonography is a noninvasive, cost-effective, and readily available method for evaluating the changes to the rectus muscle after DIEP flap surgery. In the present study, we aimed to compare rectus abdominis muscle thickness between the operated and non-operated sides using ultrasound imaging. The muscle thickness was measured at the cross point of the midclavicular line and the level of the umbilicus and anterior superior iliac spine using real-time B-mode ultrasonography. The muscle anteroposterior diameters of the pedicle-dissected side and the control side were compared using paired t test. In total 31 patients with a mean follow-up of 70.18 weeks were included. The mean diameters at the level of the umbilicus of the operated and non-operated sides were 8.16 ± 1.83 and 8.14 ± 1.43 mm, respectively (P = .94). The mean thicknesses at the anterior superior iliac spine level were 7.74 ± 1.85 on the flap harvested side and 8.04 ± 1.84 mm on the control side (P = .35). There was no statistically significant difference between the 2 groups. Ultrasonography can be a reliable, inexpensive, and easily usable modality for evaluating donor site complication following DIEP flap. DIEP flap seems to have minimal impact on the abdominal donor site, and it may be safe and versatile to reconstruct the breast after mastectomy.

1. Introduction

Breast reconstruction after mastectomy is a complex procedure that aims to restore both the physical appearance and psychological well-being of patients. The deep inferior epigastric artery perforator (DIEP) flap has emerged as a popular technique for breast reconstruction due to the favorable outcomes it achieves and its low donor site morbidity.^[1] However, the impact of DIEP flap surgery on abdominal muscle function has represented a topic of ongoing debate, with previous studies having reported conflicting results.^[2–6]

While some studies have reported a significant decrease in the thickness of the rectus abdominis muscle following DIEP flap surgery, others have shown no significant changes in muscle thickness. These discrepancies may be attributed to differences in study populations, imaging techniques, and follow-up periods. Several previous studies have evaluated the changes in the morphology and function of the rectus abdominis muscle after DIEP flap surgery using various imaging modalities such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI).^[3–6] However, there has been limited research focusing specifically on the use of ultrasound imaging to evaluate changes in the rectus abdominis muscle following DIEP flap surgery.

The use of ultrasound imaging is noninvasive, cost-effective, and readily available, thus making it an attractive option for assessing the changes in the rectus abdominis muscle after DIEP flap surgery. Real-time ultrasound imaging has been proven to objectively measure the thickness, area and volume of skeletal muscles. However, many plastic surgeons are still not familiar with the use of this beneficial imaging tool at their clinical practice.^[7,8]

In the present study, we aimed to use an ultrasound imaging technique to evaluate the changes in the thickness of the rectus abdominis muscle following breast reconstruction using the DIEP flap. We hypothesized that-given the minimally invasive nature of the procedure-the thickness of the rectus abdominis muscle would not decrease significantly following DIEP flap surgery.

2. Materials and methods

2.1. Patients

This study was approved by the Institutional Review Board (protocol number 2023AN0162) and conducted in accordance with the principles of the Declaration of Helsinki. The researchers in the present work conducted a retrospective chart review of patients who underwent immediate and delayed breast reconstruction using free DIEP flap between February of 2020 and February of 2023 to identify those with a follow-up abdominal ultrasonographic scan after the surgery. Patient who underwent bilateral reconstruction were excluded, as were lacking follow-up ultrasonographic scans.

2.2. Surgical technique

All surgeries were performed at this institution by 2 plastic surgeons. A dominant perforator was identified according to the preoperative abdominal CT angiography and a handheld doppler. The authors aimed to include at least 1 medial row perforator around the umbilicus. If the flap was large in size, or if an additional perforator could be included with ease, we harvested up to 2 perforators without additional damage to the rectus abdominis muscle. Intramuscular dissection of the pedicle was performed with meticulous muscle splitting without any muscle transection. After the flap elevation and pedicle ligation, the split rectus abdominis muscle was re-approximated using Vicryl 2-0 sutures. The anterior rectus fascia was also closed using Vicryl 2-0 sutures and PDS 1-0 continuous interlocking suture.

2.3. Ultrasonographic evaluation

Ultrasound examinations were performed with a 5 to 13 MHz multifrequency linear transducer (LOGIQ e, GE Healthcare, Chicago, Illinois, Unites States) by the operator at the outpatient clinic. The thickness of the rectus abdominis muscle was evaluated at 2 levels: at the umbilicus level, and at the anterior superior iliac spine (ASIS) level (Fig. 1). To measure the thickness of the muscle and ensure reproducibility, we determined arbitrary reference points: 1 point where the midclavicular line and the horizontal line crossing the umbilicus meet and the other point where the midclavicular line and the horizontal line crossing the asis meet.^[4] We identified the hyperechoic Scarpa fascia and the subcutaneous fat layer above it. Underneath the Scarpa fascia, 2 hyperechoic fasciae could be identified; these correspond to the anterior and posterior rectus abdominis fascia, respectively. The authors measured the longest distance between the 2 fasciae, which was the thickness of the rectus abdominis muscle (Fig. 2). To verify the pedicle harvested side of the rectus abdominis muscle, we also used color doppler mode to evaluate the vascularity of the muscle (Fig. 3).

Figure 1.

Arbitrary reference measure points to ensure reproducibility. Point A denotes the intersecting point of the midclavicular line and the level of umbilicus. Point B denotes the intersecting point of the midclavicular line and the anterior superior iliac spine.

Figure 2.

Ultrasonogram of the reference measurement point. The rectus abdominis muscle is located between the hyperechoic anterior and posterior fascia. The diameter of the rectus abdominis muscle corresponds to the distance between the anterior and posterior fascia.

Figure 3.

Color doppler ultrasonography at the lower reference measure point. Medial row of the right deep inferior epigastric artery was harvested. As a result, blood flow is only observed at the lateral row of the pedicle on the operated side. Both the medial and lateral row are intact on the non-operated side. The thickness of the rectus abdominis muscle is relatively well preserved.

2.4. Statistical analysis

The statistical software package SPSS version 27.0 (IBM Inc., Armonk, NY) was used for data analysis. Postoperative rectus abdominis muscle thickness between the operated site and the non-operated site was compared using the paired t test. P < .05 was considered statistically significant.

3. Results

3.1. Patient demographics

In total 31 patients with available postoperative ultrasonographic data were identified. The patient demographics are listed in Table 1. Their mean age was 57.45 ± 7.52 years old, and their mean preoperative body mass index was 25.58 ± 4.28 kg/m². The follow up period was 70.18 ± 37.58 weeks (range, 23–153 weeks), and the time interval between the surgery and ultrasonographic imaging was 46.76 ± 37.02 weeks (range, 11–153 weeks). Twenty-six patients (83.9%) underwent immediate breast reconstruction using the DIEP flap. Nineteen (61.3%) deep inferior epigastric artery pedicles were harvested from the contralateral side. Thirteen patients (41.9%) underwent either neoadjuvant or adjuvant chemotherapy, with 3 of them having received both. Regarding the underlying comorbidities of the patients, 7 were diagnosed with hypertension, 1 with diabetes mellitus. 4 patients were current smokers to the time of the surgery. Sixteen patients had previous abdominal surgery history, with cesarean section being the most common (37.5%) reason followed by appendectomy (18.8%).

Table 1.

Summary of patient characteristics.

Characteristics	No. (%)
No. of patients	31
Age (yr), mean + SD	57.45 ± 7.52
Preoperative BMI (kg/m2), mean ± SD	25.58 ± 4.28
Follow-up period (wk), mean ± SD	70.18 ± 37.58
Time from surgery to imaging (wk), mean ± SD	46.76 ± 37.02
Immediate/Delayed
Immediate	26 (83.9)
Delayed	5 (16.1)
Donor pedicle
Ipsilateral	12 (38.7)
Contralateral	19 (61.3)
Chemotherapy	13 (41.9)
Neoadjuvant	5 (16.1)
Adjuvant	11 (35.5)
Hypertension	7 (22.6)
Diabetes mellitus	1 (3.2)
Smoking history	4 (12.9)
Previous abdominal surgery	16 (51.6)
No. of perforators, mean ± SD	1.19 ± 0.40
One	25 (80.6)
Two	6 (19.4)
Donor site complication*	2 (6.5)

BMI = body mass index, SD = standard deviation.

^*Abdominal bulging, ventral hernia.

3.2. Operative outcomes

The mean number of perforators harvested were 1.19, and in 6 patients we had to harvest 2 perforators due to the large flap size. None of the patients had complete flap loss, but 1 patient returned to the operation room due to hematoma formation. One patient (3%) had partial flap necrosis requiring surgical debridement and 1 other patient had congestion of the neo-umbilicus that improved after intravenous prostaglandin E administration.

Two patients developed abdominal donor site complications diagnosed by subjective symptoms and CT by a colorectal surgeon. One patient was diagnosed with ventral hernia, that eventually needed surgical treatment, and 1 patient developed abdominal bulging which was treated conservatively. However, there were no visible atrophy of the rectus abdominis muscle evaluated using the CT taken at the preoperative and postoperative time period (Figs. 4 and 5).

Figure 4.

Computed tomography of patient 7. The pedicle was harvested from the right side. Seventeen months and 3 wk after the reconstruction, she underwent ventral hernia repair surgery. However, the computed tomography taken 16 mo after the reconstruction, does not show thinning of the right rectus abdominis muscle.

Figure 5.

Computed tomography of patient 8. The pedicle was harvest from the right side. The patient reported bulging of the right lower abdomen and was treated conservatively. The rectus abdominis muscle thickness is well preserved after 21 mo and 1 wk after the reconstruction.

3.3. Sonographic evaluation of muscle thickness

Table 2 presents the postoperative measurements of non-operated and operated rectus abdominis muscle thickness. The thickness values measured at the umbilicus level of the non-operated and operated rectus abdominis muscle were 8.14 ± 1.43 mm and 8.16 ± 1.83, and the difference was not statistically significant (P = .94). At the level of ASIS, the muscle thickness on the non-operated side was 8.04 ± 1.84 mm, whereas the thickness on the operated side was 7.74 ± 1.85 mm with no statistically significant difference (P = .35).

Table 2.

Postoperative ultrasonographic measurement of nonoperative and operative rectus abdominis muscle thickness.

	Nonoperative (mm), mean ± SD	Operative (mm), mean ± SD	Mean difference ± SE (mm)	95% CI (mm)	P value*
Umbilicus level	8.14 ± 1.43	8.16 ± 1.83	−0.02 ± 0.31	−0.65–0.60	.94
ASIS level	8.04 ± 1.84	7.74 ± 1.85	−0.31 ± 0.32	−0.35–0.97	.35

ASIS = anterior superior iliac spine, CI = confidence interval, SD = standard deviation, SE = standard error.

^*Paired t test.

3.4. Subgroup analysis

Subgroup analysis of the rectus abdominis muscle thickness was performed based on previous abdominal surgery history, number of perforators and the timing of the reconstruction. Previous abdominal surgery history and the timing of the reconstruction had no significant impact on the donor site. Patients with 2 perforators harvested (n = 6) showed decreased anteroposterior diameter of the operated rectus abdominis muscle at the ASIS level (Table 3).

Table 3.

Subgroup analysis of preoperative and postoperative muscle thickness.

	Nonoperated (mm), mean ± SD	Operated (mm), mean ± SD	Mean Difference ± SD (mm)	95% CI (mm)	P value*
Previous abdominal surgery
Yes (n = 16)
Umbilicus level	8.05 ± 1.19	8.05 ± 1.19	−0.18 ± 1.85	−1.17–0.80	.695
ASIS level	8.22 ± 2.00	7.55 ± 1.61	0.68 ± 1.47	−0.10–1.46	.085
No (n = 15)
Umbilicus level	8.23 ± 1.70	8.09 ± 1.65	0.15 ± 1.60	−0.74–1.03	.728
ASIS level	7.86 ± 1.69	7.95 ± 2.11	−0.08 ± 2.09	−1.24–1.07	.879
Number of perforators
One (n = 25)
Umbilicus level	8.29 ± 1.51	8.55 ± 1.70	−0.26 ± 1.67	−0.95–0.43	.446
ASIS level	8.09 ± 1.93	8.09 ± 1.72	−0.02 ± 1.80	−0.76–0.72	.953
Two (n = 6)
Umbilicus level	7.52 ± 0.89	6.57 ± 1.53	0.96 ± 1.63	−0.75–2.66	.209
ASIS level	7.97 ± 1.53	6.28 ± 1.78	1.68 ± 1.11	0.52–2.85	.014†
Immediate/delayed
Immediate (n = 26)
Umbilicus level	8.15 ± 1.48	8.14 ± 1.97	0.01 ± 1.84	−0.74–0.75	.983
ASIS level	7.83 ± 1.82	7.52 ± 1.80	0.31 ± 1.91	−0.46–1.09	.413
Delayed (n = 5)
Umbilicus level	8.09 ±± 1.35	8.28 ± 0.85	−0.19 ± 0.82	−1.20–0.82	.631
ASIS level	9.19 ± 1.61	8.91 ± 1.85	0.28 ± 1.27	−1.29–1.86	.638

ASIS = anterior superior iliac spine, CI = confidence interval; n, number, SD = standard deviation.

^*Paired t test.

^†Significant values, P < .05.

4. Discussion

For many years in the past, reconstructive surgeons encountered mastectomy patients in whom the remaining local tissue was inadequate to use implant-based reconstruction, and the treatment of choice was considered to be latissimus dorsi myocutaneous flaps with or without the use of implant. However, the transverse rectus abdominis myocutaneous (TRAM) flap has emerged a technique that could provide adequate soft tissue for breast reconstruction without the use of silicone implants. Holmström and Friedman et al introduced the use of TRAM free flap for breast reconstruction to minimize the donor site morbidities that were present in pedicled TRAM methods.^[9,10]

To further reduce the donor site morbidities such as ventral hernia or muscle weakness, Allen et al introduced the DIEP free flap for breast reconstruction, with which proved that breast reconstruction can be done successfully.^[11] Further studies have proven that using DIEP flap leads to lower rates of abdominal asymmetry, bulging or hernia, and functional disabilities such as those involve flexing or rotating of the upper trunk.^[12,13]

Regarding our focus, several prior studies have attempted to measure rectus abdominis muscle thickness after DIEP surgery. Tønseth et al examined 13 patients and demonstrated that the thickness of the muscle was significantly reduced on the operated side.^[6] In their study, the authors dissected an average of 1.8 perforators, which could have led to more muscle dissection and inevitable muscle damage.

Recently, contrary results have been reported. For example, Lee et al demonstrated that there was no significant decrease in muscle thickness after 1-year follow up.^[4] Han et el. measured the volume of the rectus abdominis muscle after DIEP flap harvest using computed tomographic scan and concluded that there was no statistically significant volume difference between the operated and nonoperated side.^[3] Seal et al analyzed 26 paired rectus abdominis muscles using CT and revealed no significant change in muscle size between preoperative and postoperative values.^[5] This study adds to the evidence that DIEP has little effect on the donor site, finding no statistically significant differences in rectus abdominis muscle thickness at the umbilicus and ASIS levels (mean difference −0.02 ± 0.31 mm; P < .94 and mean difference -0.31 ± 0.32 mm; P < .35, respectively). The timing of the breast reconstruction following mastectomy and the abdominal surgery preceding the DIEP flap had no effect on muscle atrophy. The quantity of harvested perforators may be related to the thickness of the muscle. Six patients had the flap perfused with 2 perforators, and their rectus muscle thickness reduced at the ASIS level as compared to the non-operated side.

These results may be attributable to advances in surgical technique and preoperative imaging evaluations. Using preoperative CT provides important information about the inferior abdominal wall vascular anatomy to aid the identification of the dominant perforator, thus facilitating DIEP flap elevation, saving operative time and reducing donor site morbidities such as abdominal bulging.^[14–16] In our study, most of the cases (n = 25) included 1 perforator, but a reliable perforator was sufficient to perfuse the whole flap based on the preoperative CT angiogram and could minimize the muscle damage.

Reproducible and standardized setting of the reference measuring point is an important point of interest. In our study, we set 2 different reference points, based on previous studies and reproducible anatomic landmarks. The dominant perforator of the deep inferior epigastric artery usually arises at the upper third point between the level of the umbilicus and ASIS (Fig. 6). First, point B, which was first introduced be Lee at al as a standardized measuring point, was also used by Seal et al.^[4,5] It is an important measuring point because it is located around the mid-point of the dissected portion of the rectus abdominis muscle. Meanwhile, point A is located above the level of the perforator. We set this additional measuring point to evaluate the possible impact of muscle dissection itself or the nerve damage accompanied by the dissection.

Figure 6.

Three-dimensional reconstruction of the computed tomography angiography. Dissection of the rectus abdominis muscle to harvest the deep inferior epigastric vessels is performed along the yellow dotted line.

CT, MRI, and dual energy X-ray absorptiometry are widely known to be the most accurate and reproducible methods for assessing skeletal muscle mass.^[17,18] However, these methods can be very costly and time consuming, and CT scans or dual energy X-ray absorptiometry expose the patient to ionizing radiation whereas MRI scans are not available to patients with metal implants or pacemaker. Ultrasonography can be an alternative for these modalities, and many studies have proven that ultrasonography can similarly estimate muscle volume as MRI.^[7,18–20] Aside from its reliability, using B-mode ultrasound can also be more cost-effective than CT or MRI.^[21]

Our study enrolled 31 patients, thus making it the largest study population to date, to our knowledge. We used ultrasound imaging to evaluate the thickness of the rectus abdominis muscle. However, our study has several limitations: First, due to its retrospective nature, we had to rely on electronic medical records regarding patient characteristics or evaluating complication. Second, preoperative ultrasonographic scan with which to compare the initial thickness of the muscle was not available. Third, even though our results showed no statistically significant difference of the muscle thickness between the operated and non-operated side, a small minority of patients reported abdominal complications such as hernia or bulging. Lastly, although our study has the largest study population to date, it still has a relatively small population size. Further large-scale studies, patient reported outcomes and function evaluating studies might be needed to further elucidate the impact of DIEP flap harvest, especially the impact of the number of perforators harvested on the abdominal donor site.

Our study has important implications for postoperative rehabilitation programs, as well as for surgical planning and monitoring. The preservation of abdominal muscle function is crucial for patient recovery and quality of life, and our findings may inform future surgical techniques to help improve patient outcomes. Our study also contributes to a better understanding of the impact of DIEP flap surgery on abdominal muscle function, which may help guide future research and surgical practices.

5. Conclusion

Our results demonstrate that using the DIEP free flap had minimal effect on the rectus abdominis muscle and did not lead to muscle atrophy. There were no statistically significant differences seen in muscle thickness between the pedicle-dissected side and the non-operated side of the rectus abdominis muscle. Using real-time ultrasound imaging may be a useful and cost-effective modality for evaluating the possible complications of DIEP flap on the donor site.

Author contributions

Conceptualization: Eul-Sik Yoon.

Data curation: Haneul Kim, Hyung Chul Lee.

Formal analysis: Haneul Kim, Hyung Chul Lee.

Supervision: Jae-Ho Chung, Seung Pil Jung, Eul-Sik Yoon.

Validation: Seung Pil Jung.

Writing – original draft: Haneul Kim, Hyung Chul Lee.

Writing – review & editing: Jae-Ho Chung, Eul-Sik Yoon.