Muscle-sparing pedicled transverse rectus abdominis myocutaneous flaps for breast reconstruction: Combining benefits of both worlds

Introduction

Breast cancer is the most common cancer in women in Singapore, comprising 29% of all cancers diagnosed in women. ¹ Post-mastectomy breast reconstruction is an integral part of breast cancer care, playing a vital role in restoring a natural breast shape as well as restoring normal psyche in these patients. Autologous breast reconstructions using both free as well as pedicled flaps form the bulk of the breast reconstruction in our centre.

Breast reconstruction with autologous techniques has undergone considerable change in recent years. The development of autologous breast reconstruction is shaped by the need to construct a symmetrical and aesthetically pleasing breast mound, and by two opposing factors: donor-site morbidity and blood supply. The pedicled transverse rectus abdominis myocutaneous (TRAM) flap reconstruction is a well-established procedure and remains a workhorse flap in reconstruction to create a soft, ptotic breast mound that restores the patient’s body image. The full rectus abdominis muscle is harvested in the classical pedicled TRAM flap as described by Hartrampf et al., ² giving rise to concerns about donor-site morbidity, such as abdominal bulge, hernia, chronic lower back pain and core muscle instability. This need to minimise donor-site morbidity has given rise to a number of modifications to the original procedure, such as the use of meshes, component separation and various flap-elevation techniques that progressively spare more rectus abdominis muscle.^3,4 These techniques include the free TRAM flap with varying degrees of muscle sparing, the deep inferior epigastric artery perforator (DIEP) flap, and the superficial inferior epigastric artery flap. However, the free TRAM or DIEP flap necessitates dissection through the rectus sheath as well as through a variable amount of rectus abdominis muscle, and requires microanastomosis, thus increasing the technical difficulty of the operation and the surgical time. The aim of this study is to present our experience with the use of a modified pedicled muscle-sparing (MS)-TRAM flap for autologous breast reconstruction and to evaluate it against conventional pedicled TRAM flaps, in terms of relative operative time, difficulty and safety as well as the added benefits of muscle preservation.

Patients and methods

A retrospective analysis of 20 women, 10 of whom had undergone unilateral immediate breast reconstruction with pedicled MS-TRAM flaps after skin-sparing mastectomy (MS group), and 10 who had undergone unilateral immediate breast reconstruction after skin-sparing mastectomy with the conventional pedicled TRAM flap (control group) by the same surgeon (S. Ho) over a two-year period from 2013 to 2015 was performed. The patients in both groups were blinded to the treatment choice. Patients’ records were reviewed, assessing patient demographics including age and smoking status, and evaluating the operative time, time to ambulation, length of hospital stay, pain scores using a 10-point visual analogue pain scale and abdominal bulge rates after 24 months. Patients in the MS and control groups were compared using the unpaired t test for age, operative time, time to ambulation and length of hospital stay. The Mann-Whitney U test was used to compare the pain scores between patients in the MS and control groups.

Surgical technique

Preoperative preparation and positioning for the muscle-sparing pedicled TRAM flap is similar to those outlined for the traditional pedicled TRAM flap. The ipsilateral pedicle is preferred in the unscarred abdomen to reduce initial midline sternal bulging. The modified MS-TRAM technique involves a similar ligation of the deep inferior epigastric vessels and then tracing the course cranially along the inferolateral border of the rectus abdominis muscle. The lowest, and rarely second-lowest, interconnections between the intercostal vessels and the deep inferior epigastric pedicle have to be ligated to allow medialisation of the deep inferior epigastric pedicle. In doing so, the lateral one-third to half of the rectus abdominis muscle can be preserved and the DIE pedicle can be visualised travelling on the undersurface of the medial half of the rectus abdominis muscle to be harvested; in essence an MS1-TRAM. All motor nerves were spared as they entered the muscle laterally and ligated in the muscle substance between the harvested half and the preserved half of the rectus abdominis muscle. The rectus sheath is incised as a long, narrow ellipse to facilitate closure. The sheath is closed primarily and a mesh is placed as an onlay over the sheath. One drain was placed in the breast, another drain was placed in the axillary cavity (if axillary clearance was performed) and two drains were placed in the abdomen. This technique adds on an average of 30 minutes to the entire length of surgery.

All patients received intraoperative analgesia with intravenous morphine and postoperatively received patient-controlled analgesia (PCA) with intravenous morphine and oral analgesia. The dosage of morphine administered by PCA devices was standardised. Pain scores were assessed by the pain team physicians who were blinded to the treatment choice. Patients were encouraged to mobilise with a physiotherapist from the first postoperative day. In all cases, patients received an abdominal binder and were restricted from heavy lifting for 12 weeks.

Results

A total of 20 consecutive patients underwent unilateral immediate breast reconstruction with pedicled MS-TRAM flaps (MS group), and 10 underwent immediate breast reconstruction with the conventional pedicled TRAM flap (control group) after skin-sparing mastectomy. Both groups were followed up for two years after surgery.

The mean age of the MS group was 51.8 years (range, 38 to 63 years) and the mean age of the control group was 49.2 years (range, 40 to 63 years) (p = 0.47). Mean body mass index was 22.9 kg/m² (range, 18.1 to 30.0) in the MS group and 22.8 kg/m² (range, 20.1 to 29.9) in the control group (p = 0.97). All the patients in both groups were nonsmokers. Four patients in each group received adjuvant radiotherapy in both the MS group and the control group.

The patients in the MS group ambulated significantly earlier than the control group. The patients in the control group ambulated at a mean time of 2.7 days after the operation (range, one day to three days) while the MS group patients ambulated 1.5 days after the operation (range, one day to three days) (p = 0.01). The mean pain score related to the abdominal wound was 4 (range, 1 to 8) for the control group and 3.1 (range, 1 to 8) for the MS group while the patients were still on PCA on the first and second postoperative days (p = 0.47).

The mean operative time was four hours (range, 3 hours to 5.1 hours) in the control group and 4.2 hours in the MS group (range, 3.5 hours to 6 hours) (p = 0.59). The patients were discharged to home eight days after the operation for the control group (range, 6 days to 10 days) and 6.6 days after the operation for the MS group (range, 5 days to 10 days) (p = 0.96).

Clinical assessment of abdominal donor-site complications was performed by the operating surgeon who was not blinded to the treatment choice. One case of abdominal bulge occurred in the control group, whereas no bulge occurred in the MS group. There were no cases of complete flap loss in both groups. Superficial skin necrosis occurred in one patient in the MS group and fat necrosis was diagnosed clinically in one patient in the control group.

Discussion

The decision to undergo breast reconstruction is increasingly popular and has been shown to provide substantial psychological benefit. ⁵ Reconstruction options run the entire gamut, from alloplastic implants to autologous flaps in the various forms, be it donor site-differentiated, free or pedicled. Although autologous microvascular reconstruction with the DIEP flap is currently recognised as one of the best choices for breast reconstruction, ⁶ the conventional pedicled TRAM flap remains an extremely popular option in our institution because of its reliable vascularity, lower risk of total flap loss, relative ease of dissection and short operative time. However, full-width muscle harvest results in a number of donor-site concerns, particularly if a wide amount of overlying muscle fascia is concomitantly harvested. Full muscle harvest could result in abdominal wall weakness and a large fascia defect could predispose to abdominal bulges, ⁷ leading to a prolonged time to ambulation and rehabilitation, chronic lower back pain and core muscle instability. In order to address these concerns, MS free flaps, such as the free MS-TRAM flap and the DIEP flap, have been performed, aiming for minimal disruption of the donor muscle, thereby preserving functionality and reducing morbidity. However, these techniques require technically demanding microsurgical intramuscular dissection of the perforating vessels and also greatly increase operating time. Other concerns include the inconsistency in perforator size, quantity, and location, requiring more experience, specialised equipment and skill to perform such flap procedures safely and quickly. Total flap loss rates (0%–5% in DIEP flaps)^8,9 are also higher than the conventional pedicled TRAM flap (0%–3%).^10,11

Theoretically, MS techniques leave the rectus muscle innervated and vascularised by the intercostal vessels and nerves for increased abdominal wall competence postoperatively. The severity of donor-site morbidity varies according to patient factors (age, body habitus), the care with which the repair has been undertaken, the choice of flap procedure, mesh usage and the quality of the fascia to be repaired.

In a study by Nahabedian et al., ³ 108 women with free TRAM flaps, 37 women with pedicled flaps, and 10 women with DIEP flaps were evaluated. Lower-abdominal contour defects were far more common after bilateral free TRAM flaps than with DIEP flaps. Blondeel and colleagues ¹² found that free TRAM flaps that spare minimal or no muscle have a far more negative impact on abdominal strength than do free DIEP flaps but even free DIEP flaps create abdominal weakness to some extent. In a meta-analysis of previously published data, Reece and Kroll ¹³ attempted to collate the evidence concerning abdominal-wall morbidity after TRAM flap reconstruction. High-frequency ultrasound has also been used to demonstrate increased laxity in some TRAM flap patients where the full muscle width had been harvested, when compared to DIEP flap patients. ¹⁴ These studies seem to suggest that the more muscle one harvests, the greater the initial and long-term impact on abdominal strength.

Plogmeier and colleagues ¹⁵ investigated the impact of a free MS-TRAM flap with the use of electromyographic (EMG) examination and ultrasonography. EMG examination revealed that harvesting of an MS-TRAM flap did not impair the rectus muscle compared to the intact contralateral muscle. However, motor units of the preserved rectus abdominis muscle were enlarged. Myosonography detected damage of isolated muscle fibres indicating nerve-related muscle changes without impairment of the muscle function. These findings contradict the postulation that the MS technique does not preserve significant functional muscle as the intercostal supply penetrates the rectus muscle in its middle third, thereby leaving no innervation and probably little, if any, blood supply to the lateral muscle strip.

The benefits of the pedicled MS-TRAM flap for breast reconstruction are numerous as compared to the conventional pedicled TRAM flap. Our comparative study with the conventional pedicled TRAM flap shows that the patients in the MS group had lesser postoperative pain and were able to ambulate earlier. There is no increase in operative time with the MS-TRAM technique. Grotting et al. described the successful transfer of an abdominal island flap as a free flap in 1989. ¹⁶ This technique spared the majority of rectus muscle and was associated with a slight decrease in length of hospitalisation and earlier ability to ambulate. MS techniques have been demonstrated to possess lower risk for postoperative abdominal donor-site morbidity, with rates of approximately 5%.^4,17 In particular, Nahabedian et al. reported on 89 women who received MS-2 free TRAM flaps and found only three with abdominal wall laxity following unilateral reconstruction. ⁴ The remainder demonstrated no abdominal complications, and the majority of these women were able to perform sit-ups postoperatively.

It is clear that donor-site morbidity can be lowered by reducing the amount of muscle taken with the flap and the disruption to the remaining muscle. In particular, we suggest the pedicled MS-TRAM flap as a valuable option for non-microsurgeons to preserve rectus volume and function. Our technique preserves innervated rectus muscle similar to a free MS-TRAM flap with minimal muscle harvest. The pedicled MS-TRAM flap also has decreased risk of total flap loss without the need for microvascular anastomosis. Tan et al. reported a mean length of hospital stay of 7.13 days after immediate breast reconstruction with pedicled TRAM flaps. ¹⁸ This is comparable to our patients in the MS group who had a mean hospital stay of 6.6 days.

Limitations

A significant disadvantage of pedicled TRAM flaps in any form is the rate of fat necrosis as compared to a free flap. The incidence of fat necrosis in the conventional pedicled TRAM flap has been found to be up to 26.9%, compared to an 8.2% incidence in free TRAM flaps, due to a more robust blood supply in the latter. ⁷ This is likely to be similar in pedicled MS-TRAM flaps, but would be partially surmountable using supercharging. ¹⁹ Furthermore, the MS-TRAM modification results in a much longer DIE vessel length, allowing for easier positioning and anastomosis to the thoracodorsal vessels if supercharging is required.

As the study was performed by a single surgeon, there was no variation in surgical techniques. However, the small sample size in the study reduced the power of the study and could be addressed by including more patients in a subsequent study. Because a prospective, longitudinal design was not used, a definite cause-effect relationship could not be determined. The surgeon was not blinded to the treatment choice in the assessment of abdominal donor site complications and could potentially result in observer bias in the study. Length of hospital stay was also affected by the presence of drains and the duration of fluid drainage, which may artificially prolong hospital stay. Another limitation was that long-term pain scores and abdominal strength testing, which would help to assess abdominal wall function, were not studied.

Conclusion

In conclusion, the pedicled MS-TRAM flap is an excellent breast reconstruction option that is comparable to conventional TRAM. The pedicled MS-TRAM preserves innervated muscle in the donor site that reduces time to ambulation and postoperative pain. It does not add significantly to surgical time and does not require microvascular anastomosis, whilst minimising donor-site morbidity and retaining adequate vascularity. Early mobilisation afforded by the MS-TRAM procedure allows for speedier rehabilitation, earlier return to ambulation, less postoperative pain and a reduced length of hospital stay.