Effect of Tissue Expanders Filled With Saline Versus Air on Longitudinal Breast Reconstruction Outcomes

© 2024 HMP Global. All Rights Reserved.

Any views and opinions expressed are those of the author(s) and/or participants and do not necessarily reflect the views, policy, or position of ePlasty or HMP Global, their employees, and affiliates.

Immediate 2-stage breast reconstruction with tissue expanders (TEs) and implants is one of the most common forms of postmastectomy breast reconstruction in the United States.^1,2 The technique provides for reduced strain on the mastectomy skin flap and any inframammary incisions when compared with certain alternatives, such as fixed-volume implants.³

Saline's biocompatibility has popularized it as the standard TE fill material used in stage 1 of 2-stage breast reconstruction. Despite its benefits, however, saline has been criticized for unevenly filling TEs with pooling in the lower pole.⁴ In addition, saline is a noncompressible fluid that maintains a constant volume in normal conditions—unlike air, which readily decreases in volume in response to pressure.⁵ These features of saline increase the risk of dehiscence and can compromise wound healing and tissue necrosis.^4,6

Intraoperative air-filled TEs offer a potential solution to some of the drawbacks associated with saline. Prior studies have demonstrated that, in contrast to saline, air-filled TEs offer the benefit of evenly distributed expansion and, consequently, reduced pressure on the mastectomy skin flap and incisions.^4,6-9 Prior studies have likewise found air tissue expansion to be associated with similar or lower odds of complications than saline tissue expansion following stage 1 reconstruction.^7,10-14 However, there remains an absence of research investigating what effect, if any, air-filled TEs in stage 1 of 2-stage breast reconstruction may have on longitudinal outcomes. We therefore conducted a retrospective chart review of patients who had expander-implant breast reconstruction to examine these effects. We hypothesized that the benefits of air-filled TEs observed in the first stage of breast reconstruction would translate to improved longitudinal outcomes.

Study design

A retrospective chart review that was approved by Stanford's institutional review board (Protocol: 49366) was performed on female adult (>18 years old) patients who underwent 2-stage prepectoral breast reconstruction after mastectomy (for breast cancer or as a prophylaxis) between January 2017 and December 2018 at the senior author's institution. All patients had air- or saline-filled TEs in stage 1 and underwent implant-based reconstruction in stage 2. Patients with missing data, a history of chronic or recent opioid use within 30 days prior to stage 1, or fewer than 30 days clinical follow-up after stage 2 were excluded.

Operative details

For stage 1, mastectomy was performed by 1 of 6 breast surgeons immediately followed by prepectoral TE placement performed by 1 of 5 plastic surgeons. Three brands of TEs and 6 brands of acellular dermal matrix (ADM; for anterior implant coverage) were used among all patients. As noted in our prior study,¹⁰ the choice of air versus saline TEs was not made on a patient-by-patient basis. Retrospective data instead show that there was a general change in institutional practice patterns from saline to air TEs during the study period. Patients who underwent saline fill continued to undergo expansion with saline postoperatively. Patients who initially had air-filled TEs had their TEs replaced with saline at 4 weeks' postoperatively. Patients then continued to undergo saline expansion until stage 2 was undertaken with exchange of TEs for implants. For stage 2, implant-based breast reconstruction was performed by 1 of 5 plastic surgeons using 3 brands of implants. The plastic surgeon who performed the stage 1 breast reconstruction was typically the same plastic surgeon who performed the stage 2 breast reconstruction. The choice of the type of implant was at the discretion of the plastic surgeon performing the surgery.

Independent variables

Independent variables obtained from chart review included body mass index (BMI), history of tobacco use, comorbidities (diabetes, hypertension), American Society of Anesthesiology (ASA) physical status classification, breast cancer treatment (neoadjuvant/adjuvant chemotherapy, radiation), and operative details for first stage of reconstruction (plastic surgeon, ADM type, TE type, TE fill medium/volumes) and second stage of reconstruction (plastic surgeon, ADM type, final volume, and implant type).

Dependent variables

Dependent variables of interest included opioid use and breast pain in each 30-day postoperative period following both stage 1 and stage 2 of breast reconstruction, respectively, as well as length of time (in days) and number of office visits between both stages. Postoperative breast pain was captured through review of clinical notes, and patient-reported pain symptoms on postoperative follow-up visits were recorded and correlated with need for opiate prescription refills.  

Statistical analysis

Analyses were conducted in accordance with Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines and were completed using SAS version 9.4 (SAS Institute) with a 2-sided level of significance of sim.¹⁵ The Schapiro-Wilk test was used to determine whether continuous variables were normally distributed. Chi-square and Fisher exact testing (for categorical variables) and analysis of variance (ANOVA) and Kruskal Wallis testing (for continuous variables) were used to determine significant differences between study cohorts (air vs saline fill). Logistic regression was used to compare odds of opioid refills and breast pain, with and without risk adjustment for patient characteristics. Post-hoc analyses were completed using G*Power Software (HHU).

Patient characteristics

A total of 69 patients (119 breasts) met inclusion criteria, 22 (31.9%) of whom received intraoperative saline fill and 47 (68.1%) of whom received air fill (Table 1). Of the 119 breasts, 36 (30.3%) breasts were expanded intraoperatively with saline, while 83 (69.7%) were expanded intraoperatively with air. Across all patients, mean age was 48 years, 33.3% (23 patients) were obese, 24.6% (17 patients) had a smoking history, 39.1% (27 patients) had comorbidities (diabetes and hypertension), and 29% (20 patients) were categorized as having an ASA > 3 (Table 1). Patient demographics were similar between study cohorts (Table 1), with no significant difference (P > .05) in mean age, BMI, history of tobacco use, or comorbidities (diabetes and hypertension). The proportion of patients categorized as having an ASA > 3 was higher in the air-fill cohort (38.3% vs. 9.0%; P = .03) (Table 1).

Breast cancer/reconstructive characteristics

Most patients in each cohort underwent bilateral (vs unilateral) breast procedures (77.8% in saline-fill cohort and 86.7% in air-fill cohort), and the laterality (unilateral vs bilateral) of breast procedures in each cohort was similar (Table 2). There was no significant difference in neoadjuvant or adjuvant chemoradiation therapy between cohorts, but none of the patients in the saline-fill cohort received postmastectomy radiation therapy (PMRT; Table 2). Nipple-sparing mastectomy was predominantly used across both study cohorts (98 breasts, 82.4%). Intraoperative TE fill volumes, along with the proportion of patients receiving textured TEs, were similar between study cohorts (P > .05).

Opioid refills and postoperative breast pain

Air fill (vs saline fill) was associated with a significantly lower percentage and odds of requiring an opioid refill (25.3% vs 63.9%, P < .001; odds ratio [OR] 0.19, P < .001) and reporting breast pain at postoperative follow-up (15.7% vs 63.9%, P < .001; OR 0.15, P = .002) when evaluated by breast (Table 3) during the reconstructive process. Even after adjusting for potential confounders (ASA > 3, BMI, diabetes, hypertension, and smoking history) in multivariable regression analysis, air fill (vs saline fill) was associated with significantly lower odds of requiring an opioid refill (adjusted odds ratio [aOR] = 0.27, P = .009) and reporting breast pain (aOR = 0.10, P < .001; Table 3). These associations were also observed independently in the 30-day period following stage 1 (requiring an opioid refill: aOR = 0.21, P = .003 and reported breast pain: aOR = 0.11, P < .001) and in the 30-day period following stage 2 (required an opioid refill: aOR = 0.21, P = .008 and reported breast pain: aOR = 0.15, P = .003; Table 3).

Office visits and days between stages

No significant difference was observed between the air and saline cohorts in the number of office visits or the number of days that elapsed between stages 1 and 2 breast reconstruction, regardless of whether evaluated by breast or by patient (Table 5).

Post-hoc power analyses

In post-hoc power analyses, the observed effect size between the saline and air cohorts with respect to opioid refills, breast pain, office visits, and time between stages had significant statistical power (> .8).

Postmastectomy breast reconstruction patients may face debilitating postoperative pain, with cancer patients particularly susceptible to prolonged opioid use.^16-18 Therefore, efforts to reduce breast pain and opioid use are critical to prevent postmastectomy breast reconstruction patients from facing the deleterious sequelae associated with chronic opioid use. In the current study, we found that intraoperative air-filled TEs during stage 1 were associated with significantly lower odds of opioid refills and breast pain overall and during each stage of the reconstructive process. While the TE medium's effect on breast pain and opioid use in stage 2 reconstruction does not appear to have been previously investigated, studies that have evaluated breast pain between stages 1 and 2 have found air-filled TEs to result in similar or lower pain than saline-filled TEs. For example, 2 studies found no significant difference in pain between TE mediums;^7,14 another found pain with air-filled TEs to be on the lower end of the pain scale in a single-arm study;¹⁹ and another found pain to be a more common reason for expander removal among saline- (vs air-) filled patients.²⁰

Intraoperative air- (vs saline-) filled TE during stage 1 may result in longitudinally reduced levels of breast pain and opioid use for several reasons. First, air-filled TEs during stage 1 may facilitate postoperative mastectomy flap healing, thereby providing a more robust soft tissue pocket into which an implant can be placed in stage 2 with reduced pain. Unlike saline, which is denser and applies dependent pressure to the inferior mastectomy flap, air filling provides a more uniform pressure distribution within the implant shell.^4,10 This reduces the outward pressure to the skin flap and inframammary incisions and leads to less discomfort to the patient. The increased density of saline, together with the disproportionate pressure at the lower pole of the breast pocket and any inframammary incisions, may also result in compressed microvascular circulation, reduced perfusion of breast skin, and ultimately more compromised mastectomy flaps with potential delayed wound healing.²¹ Second, air insufflation can be more effective in achieving ADM engraftment than saline. ADM better defines the mastectomy space, provides support to soft tissue, and helps maintain the implant in the optimal position.^22,23 However, several studies have demonstrated a higher incidence of postoperative complications, including infection, skin flap necrosis, and reconstructive failure, with the use of ADM in prosthetic reconstructions.^24-26 These outcomes may be the result of improper ADM engraftment. Analogous to skin grafts in this context, inosculation and vascularization of the ADM is critical for proper incorporation and prevention of encapsulation.²⁷ ADM and the mastectomy skin must therefore achieve close apposition which prevents fluid from collecting between the ADM and the mastectomy skin and allows for better ADM engraftment.²⁸ However, simply increasing TE fill volumes with saline to achieve such apposition may compromise perfusion of the mastectomy skin and cause skin necrosis.^28-31 Air insufflation may decrease dead space and provide the pressure necessary for proper ADM engraftment without excess pressure associated with saline fill.^10,24 The enhanced ADM engraftment after stage 1 reconstruction may translate to reduced pain and opioid use after stage 2 reconstruction.

Prior studies have also shown that severity of postoperative pain is associated with the development of chronic pain.^32,33 Perioperative opioid consumption has similarly been associated with the development of persistent pain following breast reconstruction.³⁴ Similar to the findings in prior studies,^19,20 we observed that the use of intraoperative air-filled TEs were associated with significantly lower odds of opioid refills and breast pain in stage 1. The reduced breast pain and opioid use we observed in post–stage 2 reconstruction may be the result of reduced overall pain between stage 1 and stage 2 of breast reconstruction with air (vs saline) tissue expansion.

Prior studies have found air-filled TEs to have shorter expansion and overall reconstruction times compared to saline-filled TEs.^7,11,14,35 While we did not observe shorter expansion and overall reconstruction times, we found that the use of air-based (vs saline-based) expansion does not adversely affect the number of office visits or days elapsed between stage 1 and stage 2 of breast reconstruction. The discrepancy in outcomes in timing that was observed in the current study and prior studies may be attributable to the difference in the duration of time air-fill TEs were used in the studies. The senior author's institution uses air insufflation in the intraoperative and immediate postoperative time periods, after which continued postoperative expansion is completed with saline. This institutional protocol allows patients to undergo radiation treatment with traditional saline, which avoids potential toxicity or underdosing associated with radiotherapy that has not been adjusted to account for an air medium.¹² In addition, given the inherent properties of air, the air-fill medium in TEs tends to dissipate in soft tissue and leak out of the TE at a higher rate over time than saline-fill TEs. The institutional protocol of switching to saline-fill TEs to complete the postoperative expansion therefore allows for more accurate volume determination for stage 2 reconstruction. This institutional protocol may also allow for a smoother transition to implants in the second stage of reconstruction, as saline TEs better approximate the weight and sensation of breast implants.¹⁰ Most prior studies, however, that observed shorter expansion times used air expansion for the entire period between stages. This may have allowed patients to garner increased expansion with air insufflation. Further studies are needed to determine whether the benefits of air expansion for the entire period between stages outweighs its drawbacks.

Prolonged opioid use for postoperative pain has been shown to result in long-term, chronic opioid use.¹⁷ Studies have demonstrated that over 60% of patients on >90 days of prescription opioids remain on opioids almost 5 years later.³⁶ States that have taken initiatives to curb excessive opioid prescribing practices have observed a marked decline in morbidity and mortality related to opioid use—highlighting the effectiveness of methods that reduce opioid use.^37,38 Given that breast reconstruction represents one of the most common cancer reconstructions performed,³⁹ studies investigating breast reconstruction techniques and practices that reduce opioid use without compromising patient care are critical. This study demonstrates that an alternative surgical technique significantly reduces opioid use and breast pain during the reconstructive process without adversely affecting the length of time to definitive reconstruction. Future studies are needed to compare, among other factors, actual narcotic use and patient perspectives, but air-fill TEs appear to offer a promising means to effectively reduce opioid usage in 2-stage expander-implant breast reconstruction.

There are several limitations to this study. Since our data was collected through a chart review, the accuracy of our results relies on the accuracy of what was documented in the patients' charts by numerous health care providers. Patients were also treated by different breast and plastic surgeons and had different brands of TEs and implants; these differences may play a role in the differing outcomes observed in this study. In addition, breast pain was evaluated based on subjective patient experience and variations may be partially due to patients and not necessarily the TE medium. Breast pain was also assessed in this study based on patient-reported pain symptoms in our review of clinical notes. Given the retrospective nature of our analysis, a standardized pain scale was not employed in this study, precluding a nuanced quantification of pain severity. This approach inherently limited our ability to capture the multidimensional aspects of pain experience and its potential variability across individuals. Future prospective studies could benefit from the incorporation of validated pain scales to allow for a more detailed and comparative evaluation of pain intensity and character. Lastly, none of the patients in the saline-fill cohort received PMRT, and this may have impacted the results of our study. For example, PMRT has been associated with postoperative complications and may be masking a difference in the number of office visits or days elapsed between stages.^40,41 Due to postoperative complications associated with PMRT, patients undergoing air-fill TE may have needed additional office visits or longer healing time between stages than those undergoing saline fill TE. Similarly, the difference in opioid use and breast pain observed in our study may have also been underestimated due to the lack of PMRT in the saline-fill cohort.

Air-fill tissue expansion is a relatively new method that prior studies have shown offers distinct advantages over traditional saline after stage 1 reconstruction. This study is the first to our knowledge that investigates whether use of air-fill TEs in stage 1 also affects post-stage 2 outcomes. In our retrospective chart review of 69 patients who underwent intraoperative tissue expansion with air or saline in 2-stage breast reconstruction, we found air-filled TEs to be associated with significantly lower odds of opioid refills and breast pain overall and during each stage of the reconstructive process. We also observed that air-filled (vs saline-filled) TEs did not adversely impact the length of time or number of office visits between stages. Larger, multicenter, and randomized controlled trials are needed to confirm these findings and further explore safety considerations and patient perspectives. The results of this study supplement existing studies evaluating air-filled tissue expansion as an alternative to traditional saline and should help counsel postmastectomy patients about their reconstructive options.