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Breast: Original Articles

A Randomized Prospective Time and Motion Comparison of Techniques to Process Autologous Fat Grafts

Hanson, Summer E. M.D., Ph.D.; Garvey, Patrick B. M.D.; Chang, Edward I. M.D.; Reece, Gregory P. M.D.; Liu, Jun Ph.D.; Baumann, Donald P. M.D.; Butler, Charles E. M.D.

Author Information
Plastic and Reconstructive Surgery: May 2021 - Volume 147 - Issue 5 - p 1035-1044
doi: 10.1097/PRS.0000000000007827

Abstract

Autologous fat grafting is a procedure that transfers fat from one part of the body, processes or purifies the tissue, and delivers it to a different location, most often for volume enhancement. It has been used for a variety of indications, such as soft-tissue defects, contour irregularities, and volume augmentation.1–4 More recently, autologous fat grafting has found some utility in improving fibrosis and scar from burn contracture or radiation injury, peripheral neuropathy, and posttraumatic pain syndrome.5,6 Although the underlying physiology of these many benefits has yet to be fully elucidated, the indications and number of autologous fat grafting procedures are only expected to increase with time.7 It is not surprising, then, that there is increasing interest in improving autologous fat grafting, from preparing a more robust graft to reducing operative time and cost. There are three key steps in an autologous fat grafting procedure—harvest, processing, and delivery—that can affect not only clinical outcomes but also, more directly, operative efficiency and cost.

Before delivery or injection of the adipose graft, the lipoaspirate can be processed or prepared to remove impurities that may have occurred during harvest. For example, cellular debris and oil are proinflammatory,8 and we suspect they may be responsible in part for cyst formation and fibrosis. Although a number of different techniques exist, there is no consensus on whether one technique is superior to another.9–11 A previous survey of American Society of Plastic Surgeons members demonstrated a nearly equal distribution of different techniques, including centrifugation (34 percent), filtration (34 percent), and washing or rinsing (28 percent).12 Since the survey was conducted in 2013, however, device-based processing products have grown in popularity, providing a more efficient, streamlined process and a closed handling system.

The Revolve system (LifeCell Corporation, Branchburg, N.J.)13 is an active filtration system that harvests lipoaspirate using mechanical suction connected to the device and washes with lactated Ringer’s solution. The device consists of an outer canister for debris and an inner filter that collects the lipoaspirate (Fig. 1, left). Adipose tissue is washed with lactated Ringer’s solution for 30 seconds, and the discarded solution is actively drained through the suction port for a total of three washes. There is a minimum volume requirement of 100 ml of lipoaspirate and a maximum capacity of 350 ml. The device can be used multiple times within the same procedure.

Fig. 1.
Fig. 1.:
(Left) The Puregraft 250 system (Cytori Therapeutics, San Diego, Calif.),14 a passive filtration system, similarly uses a lactated Ringer’s solution washing base. Tissue is harvested by handheld syringe or mechanical suction, and lipoaspirate is transferred to a double-layer filtration bag through the afferent port. (Center) The Revolve system (LifeCell Corporation, Branchburg, N.J.),13 an active filtration system, harvests lipoaspirate using mechanical suction connected to the device and washes with lactated Ringer’s solution. The device consists of an outer canister for debris and an inner filter that collects the lipoaspirate. (Right) Centrifugation requires that the lipoaspirate be contained in 10-ml syringes that are centrifuged at 3000 revolutions per minute for 3 minutes. The resulting upper oil layer and more dense blood collection are discarded, and the fat layer is collected for grafting.

The Puregraft 250 system (Cytori Therapeutics, San Diego, Calif.)14 is a passive filtration system that similarly uses a lactated Ringer’s solution washing base (Fig. 1, center). Tissue can be harvested by handheld syringe or mechanical suction. The lipoaspirate is then transferred to a double-layer filtration bag through the afferent port. Lactated Ringer’s solution is added through the same afferent port, and the bag is gently agitated for 30 seconds. The debris-containing solution is passively drained by gravity through the efferent port for approximately 3 minutes. This process is performed twice or for two washes. There is a 50-ml minimum volume requirement and a maximum capacity of 250 ml. The device can be used multiple times within the same procedure.

Graft preparation by centrifugation is the most often reported technique in the literature and varies in both time and speed. The method reported here is similar to that described by Coleman.1 Small-diameter cannulas are recommended for handheld harvesting via 10-ml syringes. The syringes are then centrifuged at 3000 revolutions per minute for 3 minutes (Fig. 1, right). The resulting upper oil layer and the more dense blood collection are discarded. As originally described, the graft is then transferred to a 1-ml syringe for injection.

When a procedure has multiple steps or several ways to accomplish the task, time and motion methodology is a way to evaluate performance and efficiency.15,16 This is particularly useful in health care when more traditional outcomes are harder to define or quantify, such as engraftment. The data obtained from well-designed time and motion studies offer a comprehensive, objective assessment of workflow. Furthermore, one can assess performance and identify areas of improvement. The purpose of this time and motion study was to compare the rate of fat graft processing of three commonly used systems and determine how time is allocated in the process in an active filtration system (Revolve), a passive filtration system (Puregraft 250), and centrifugation.

PATIENTS AND METHODS

Study Design

The authors performed a randomized prospective study using time and motion principles to compare outcomes of processing techniques for autologous fat grafting. The protocol was approved by the Institutional Review Board (P2015-0006) and the Clinical Oncology Research Department of the University of Texas M. D. Anderson Cancer Center, and registered with the U.S. National Library of Medicine at ClinicalTrials.gov (study identification no. NCT02677012). We previously reported our pilot study comparing active and passive filtration systems,16 demonstrating a significant difference in rate of processing between these two systems. From these data, we performed a power analysis which demonstrated that 15 patients would be needed in each cohort for the current randomized study. In addition, since the most often performed technique reported in use is centrifugation, a third study arm was included, requiring 45 study participants total. Patients were excluded if they were younger than 18 years of age, unable to give consent, actively undergoing cancer treatment not including hormonal therapy, or pregnant; had a body mass index less than 18; or could not achieve the minimum volume of lipoaspirate (100 ml). All consecutive patients undergoing autologous fat grafting were enrolled and randomized into each arm (Fig. 2).

Fig. 2.
Fig. 2.:
Study design. Consecutive patients were stratified by a core group of participating surgeons (five blocks to include nine patients per arm) and subsequently randomized by technique at 1:1:1 for each arm. There were 46 eligible participants enrolled, with one intention-to-treat patient after a failed secondary screen. ITT, intention to treat; AF, active filtration; PF, passive filtration; C, centrifugation.

Four core surgeons who were familiar with all three modalities and had completed each technique at least five times before the study performed all of the operations included in the study analysis. Participants were thus randomized by technique and stratified by surgeon, so that each surgeon would contribute the same number of cases per technique. Only the research coordinator had access to the computer-generated randomization list. Randomization was concealed from the surgeon and scrub technician until the day of surgery. A behavioral checklist, identifying the key steps involved in each technique, was developed and approved before inception of the study based on experience with each technique and the manufacturer’s instructions. (See Document, Supplemental Digital Content 1, which shows the Standardization and Behavioral Checklist developed for standardization of the fat grafting protocol used for each of the processing techniques in this study, http://links.lww.com/PRS/E405.) This document illustrates how time and motion principles can be applied to a multistep process such as fat grafting, in which each step required to complete the task is identified, as well as the outcome and duration of each step. Ultimately, this information was collected for each of the many steps within the fat grafting procedure, with the primary objective being rate of processing (volume/time). The protocol and checklist were reviewed with all participants, including the operating surgeon, physician assistant, surgical technician, and independent observer, to ensure the protocols and key steps were performed and completed consistently and uniformly.

Next, the behavioral checklist was introduced as standard practice by participating faculty and staff, and two study coordinators were trained in time and motion principles as independent observers for the study. Both observers participated in several trial procedures and their independent scores were compared. The interrater reliability was 0.6, and a linear mixed model was applied to calculate the intraclass correlation coefficient of 0.999. Each observer was then allowed to observe independently.

The patient information collected included age, body mass index, prior surgical history, prior chemotherapy, and prior radiation therapy. The following definitions were adapted from our pilot study16 for this protocol: “Adipose tissue harvested” was defined as the volume (in milliliters) of lipoaspirate before processing. “Adipose tissue prepared” was defined as the volume (in milliliters) of adipose tissue that remained after processing per defined technique. “Adipose grafted” was defined as the volume (in milliliters) of adipose graft delivered to the recipient site. “Percentage of available fat” was defined as the ratio of “adipose prepared” to “adipose harvested.” “Time to harvest” was defined as the time (in minutes) from when the liposuction cannula is introduced to the donor site to when liposuction is complete (for either machine-assisted or hand-assisted liposuction); for the passive filtration system, this includes the transfer of lipoaspirate from the handheld syringes to the processing apparatus; for the active filtration system, the lipoaspirate is collected in the processing apparatus; and in centrifugation, this includes adding caps and placing the syringes in the centrifuge. “Time to process” was defined as the time (in minutes) from when processing the graft is initiated, such as when the lactated Ringer’s solution is introduced to the apparatus for rinsing, until the adipose tissue is transferred to syringes for grafting; for passive filtration, two rinses were performed, with the fluid and impurities allowed to drain after each cycle; for active filtration, three rinses were performed, with the resulting fluid and impurities allowed to drain after each rinse; and for centrifugation, the 10-ml syringes were centrifuged at 3000 revolutions per minute (1200 relative centrifugal force) for 3 minutes, and the oil and blood layers were discarded.

The procedure then continued as per surgeon technique with regard to recipient-site preparation, graft placement, or additional procedures performed in the same operative setting. In addition, the observers made note of the time to break down the set-up and equipment, any of the disposable items needed for the procedures, and the personnel time during the operation for both circulating staff and scrub technologists.

Statistical Methods

Descriptive summary statistics for continuous variables included number of patients, mean, standard deviation, median, interquartile range, range, and 95 percent confidence interval. Descriptive summary statistics for categorical variables included frequency counts and percentages. The primary and secondary outcomes were evaluated using a linear model with covariates for surgical technique and surgeon. The Welch-Satterthwaite equation was used to adjust for unequal variances. The primary objective was to compare the processing rates among the three techniques. As such, three pairwise statistical comparisons were conducted. Tukey’s method was applied to adjust for multiplicity to ensure an overall significance level of 5 percent. Similar analysis was performed for the secondary outcomes. In addition, bootstrap confidence intervals were calculated for the mean difference in outcomes among surgical techniques for the primary and secondary endpoints to validate the findings. A total of 1000 bootstrap samples (with replacement) at a sample rate of 1, stratified by surgical technique and surgeon, were selected, and mean pairwise difference in outcomes was assessed using the linear model. The percentile confidence interval was evaluated from the 1000 estimates and presented. The measurements of primary and secondary endpoints were slightly different than normal distribution, which was assumed for linear regression models. Considering violation not severe and effectiveness on data interpretation, we used linear regression models to calculate the difference and confidence intervals adjusted by Tukey’s method. All significance tests were two-sided and used a 5 percent significance level for main effects. All data processing, summarization, and analyses were performed using SAS 9.4 software (SAS Institute, Inc., Cary, N.C.).

RESULTS

Patient Characteristics

A total of 46 patients were enrolled in the study between June of 2016 and December of 2017. Fifteen patients were randomized to active filtration, 15 were randomized to passive filtration, and sixteen were randomized to centrifugation when one patient failed the initial screening. Patient characteristics are outlined in Table 1. Mean patient age was 54 ± 10 years. The mean body mass index was 28.6 ± 4.1 kg/m2. Most patients were nonsmokers (76 percent) and had no active medical comorbidities. Although gender and type of reconstruction were not exclusion criteria, given the time period of the study and the required volume of 100 ml of lipoaspirate, all patients were female with a history of breast cancer treated at our institution. In total, there were eight cases of autologous fat grafting only, meaning 83 percent of operative cases had additional procedures, such as implant exchange (18 percent), mastopexy (29 percent) scar revision (79 percent), or other (30 percent). The majority of procedures included an abdominal or flank donor site (80 percent) and supine positioning (100 percent). There were no position changes in any of the procedures. There were no statistical differences in patient demographics or reconstruction characteristics among the three cohorts.

Table 1. - Patient Characteristics by Technique and Overall Intention-to-Treat Population
Demographics AF System (n = 15) PF System (n = 15) Centrifugation (n = 16) Total (n = 46) p*
Age, years 0.665
 No. 15 15 16 46
 Mean (SD) 55.45 (10.21) 52.64 (10.95) 53.86 (9.59) 53.98 (10.09)
 Median 56.97 54.51 53.80 54.09
 IQR 51.20–62.38 43.45–60.38 48.53– 57.28 48.35–60.38
 Range 32.52–68.26 28.59–74.78 34.86–71.50 28.59–74.78
 95% CI 49.80, 61.11 46.58, 58.71 48.75, 58.96 50.98, 56.98
Sex, no. (%)
 Male 0 (0) 0 (0) 0 (0) 0 (0)
 Female 15 (100) 15 (100) 16 (100) 46 (0)
Race, no. (%) 0.445
 Caucasian 10 (66.67) 11 (73.33) 12 (75.00) 33 (71.74)
 Black 4 (26.67) 1 (6.67) 1 (6.25) 6 (13.04)
 Other 1 (6.67) 3 (20.00) 3 (18.75) 7 (15.22)
BMI, kg/m2 0.086
 No. 15 15 16 46
 Mean (SD) 30.21(4.34) 28.39 (3.31) 27.23 (4.33) 28.58 (4.13)
 Median 30.73 27.42 26.39 27.64
 IQR 27.69–33.28 26.83–31.50 23.20–30.62 25.90–31.50
 Range 23.06–37.86 22.10–34.78 22.00–34.18 22.00–37.86
 95% CI 27.81, 32.61 26.56, 30.22 24.92, 29.54 27.35, 29.81
AF, active filtration (Revolve); PF, passive filtration (Puregraft); BMI, body mass index; IQR, interquartile range.
*The p values were calculated by using Fisher’s exact test.

Adipose Tissue Processing

The time to accomplish each step defined in the behavioral checklist was recorded, as was the volume of lipoaspirate or adipose tissue following each step (Tables 2 through 5), with our primary interest being the rate of fat processing for each technique (Fig. 3). Overall, there was a significantly faster rate of processing found with active filtration compared with passive filtration or centrifugation (9.98 versus 5.66 versus 2.47 ml/min, respectively; p = 0.0008; p < 0.0001). When comparing passive filtration to centrifugation, the rate was significantly faster with passive filtration (p = 0.0014).

Table 2. - Rates of Fat Processing by Technique, Intention-to-Treat Population
Descriptive Statistics AF System (n = 15) PF System (n = 15) Centrifugation (n = 16)
Rate of fat processing, ml/min*
 Mean (SD) 10.15 (4.28) 5.83 (1.32) 2.68 (1.83)
 Median (IQR) 11.04 (6.42–12.14) 5.58 (4.77–6.79) 2.16 (2.01–2.69)
Comparison among Three Arms AF vs. Centrifugation AF vs. PF Centrifugation vs. PF
 Difference (SE) 7.51 (1.13) 4.32 (1.08) −3.19 (0.56)
  95% CI 4.70, 10.32 1.62, 7.03 −4.59, −1.78
   p <0.001 <0.001 0.001
  95% CI§ 5.73, 9.37 2.68, 6.08 −4.10, −2.14
AF, active filtration (Revolve); PF, passive filtration (Puregraft); IQR, interquartile range.
*Calculated as follows: processing input fat volume/total time for fat processing.
Estimated from linear model for processing rate with covariates for surgical technique and surgeon, adjusting for unequal variances. The p values were adjusted by using Tukey’s method.
Statistically significant.
§Percentile confidence interval from 1000 bootstrap replicates.

Table 3. - Comparison of Fat Harvesting by Technique, Intention-to-Treat Population
Descriptive Statistics AF System (n = 15) PF System (n = 15) Centrifugation (n = 16)
Volume of fat harvested, ml
 Mean (SD) 264.67 (118.89) 397.67 (169.67) 312.31 (188.98)
 Median (IQR) 250 (175–350) 360 (295–455) 240 (177.5–350)
Total harvest time, min
 Mean (SD) 30.19 (16.07) 60.14 (25.07) 45.01 (21.32)
 Median (IQR) 24.37 (18.4–36.5) 58.62 (38.25–73.43) 40.47 (30.11–60.15)
Comparison among Three Arms AF vs. Centrifugation AF vs. PF Centrifugation vs. PF
Volume of fat harvested, ml
 Difference (SE)* −41.83 (47.50) −133.00 (47.71) −91.17 (53.87)
  95% CI* −159.77, 76.10 −251.74, −14.52 −224.91, 42.57
   p* 0.657 0.026 0.229
  95% CI −131.12, 35.41 −217.80, −49.30 −189.37, 7.59
Total harvest time, min
 Difference (SE)* −14.2 (6.16) −29.94 (7.15) −15.73 (7.44)
  95% CI* −29.45, 1.03 −47.65, −12.24 −32.16, 2.69
   p* 0.071 0.0007 0.105
  95% CI −24.33, −5.15 −43.43, −18.43 −29.26, −3.23
AF, active filtration (Revolve); PF, passive filtration (Puregraft); IQR, interquartile range.
*Estimated from linear model for processing rate with covariates for surgical technique and surgeon, adjusting for unequal variances. The p values were adjusted by using Tukey’s method.
Percentile confidence interval from 1000 bootstrap replicates.
Statistically significant.

Table 4. - Comparison of Fat Processing by Technique, Intention-to-Treat Population
Descriptive Statistics AF System (n = 15) PF System (n = 15) Centrifugation (n = 16)
Volume of fat processed, ml
 Mean (SD) 248.67 (118.09) 397.67 (169.67) 309 (189.73)
 Median (IQR) 215 (175–325) 360 (295–455) 240 (177.5–342.5)
Total processing time, min
 Mean (SD) 27.48 (14.17) 70.69 (31.71) 136.13 (83.25)
 Median (IQR) 27.75 (15.3–38.82) 60.77 (46.93–91.03) 121.11 (80.8–150.43)
Comparison among Three Arms AF vs. Centrifugation AF vs. PF Centrifugation vs. PF
Volume of fat processed, ml
 Difference (SE)* −54.74 (48.35) −149.00 (48.50) −94.26 (54.30)
  95% CI* −174.85, 65.38 −269.50, −28.50 −229.16, 40.60
   p* 0.503 0.013 0.211
  95% CI −142.70, 21.79 −238.33, −61.87 −191.38, 4.66
Total processing time, min
 Difference (SE)* −108.52 (20.99) −43.21 (9.05) 65.31 (22.11)
  95% CI* −162.02, −55.02 −66.28, −20.14 8.94, 121.67
   p* 0.0002 0.0004 0.0218
  95% CI −144.32, −77.44 −59.13, −27.66 32.50, 104.88
AF, active filtration (Revolve); PF, passive filtration (Puregraft); IQR, interquartile range.
*Estimated from linear model for processing rate with covariates for surgical technique and surgeon, adjusting for unequal variances. The p values were adjusted by using Tukey’s method.
Percentile confidence interval from 1000 bootstrap replicates.
Statistically significant.

Table 5. - Comparison of Event Times by Technique, Intention-to-Treat Population
Descriptive Statistics AF System (n = 15) PF System (n = 15) Centrifugation (n = 16)
Total fat graft time, min
 Mean (SD) 89.07 (32.62) 158.3 (56.49) 217.79 (123.25)
 Median (IQR) 89.15 (64.65, 105.68) 163.43 (119.67, 198.45) 184.67 (136.54, 246.99)
Total procedure time, min
 Mean (SD) 93.8 (50.16) 94.24 (40.03) 124.86 (49.98)
 Median (IQR) 77.4 (55.72, 113.9) 74.95 (63.58, 130.32) 118.28 (92.73, 169.38)
Total OR time, min
 Mean (SD) 179.82 (78.5) 168.87 (62.68) 202.19 (72.220)
 Median (IQR) 136.57 (130.77, 253.07) 158 (113.28, 227.17) 179.32 (158.19, 250.33)
Comparison among Three Arms AF vs. Centrifugation AF vs. PF Centrifugation vs. PF
Total fat graft time, min
 Difference (SE)* −127.14 (29.61) −69.23 (15.36) 57.91 (31.25)
  95% CI* −202.19, −52.08 −108.19, −30.27 −21.31, 137.12,
   p* 0.0010 0.0006 0.179
  95% CI −178.87, −84.47 −97.07, −42.14 12.24, 113.25
Total procedure time, min
 Difference (SE)* −29.07 (14.03) −0.44 (14.65) 28.63 (13.46)
  95% CI* −63.86, 5.75 −36.81, 35.94 −4.78, 62.05
   p* 0.115 0.999 0.104
  95% CI −52.92, −6.61 −25.09, 24.27 7.54, 50.98
Total OR time, min
 Difference (SE)* −19.34 (23.06) 10.95 (21.78) 30.29 (19.58)
  95% CI* −79.40, 37.71 −42.94, 64.84 −18.15, 78.74
   p* 0.682 0.871 0.285
  95% CI −56.74, 17.91 −23.40, 47.65 −2.21, 64.27
AF, active filtration (Revolve); PF, passive filtration (Puregraft); IQR, interquartile range; OR, operating room.
*Estimated from linear model for processing rate with covariates for surgical technique and surgeon, adjusting for unequal variances. The p values were adjusted by using Tukey’s method.
Percentile confidence interval from 1000 bootstrap replicates.
Statistically significant.

Fig. 3.
Fig. 3.:
There were significantly different rates of processing autologous fat for grafting among the three methods of preparing adipose tissue: the rate for the active filtration system (system AF; Revolve) was 10.15 ml/min; the rate for passive filtration (system PF; PureGraft) was 5.83 ml/min; and that for centrifugation (system C) was 2.68 ml/min. More specifically, the rate of adipose tissue preparation with active filtration was significantly higher than the rate with passive filtration (difference = 4.32 ml/min, p = 0.0008) or centrifugation (difference = 7.51 ml/min, p < 0.0001). Furthermore, the rate of adipose tissue preparation with passive filtration was significantly higher than that with centrifugation (difference = 3.19 ml/min, p < 0.001).

The time to complete the harvesting or processing steps of the procedure was significantly less using active filtration compared with passive filtration or centrifugation. Time to harvest lipoaspirate ranged from 30 to 60 minutes (Table 3), while processing ranged from 27 to 136 minutes (Table 4). Likewise, the cumulative amount of time dedicated to the fat grafting portion of the operation was significantly less for active compared with passive filtration or centrifugation (Table 5; 89 minutes versus 158 minutes, p = 0.0005; versus 217 min, p = 0.0005, respectively). However, the total operative time (time that the patient was in the operating room) was not statistically different among the three techniques (active filtration: 168 minutes versus passive filtration: 157 minutes versus centrifugation: 187 min, p > 0.05).

There was more lipoaspirate harvested and processed in procedures using passive filtration compared with active filtration and centrifugation (374 ml versus 241 ml versus 283 ml, respectively). Overall volume was determined by surgeon discretion, patient body habitus, volume of graft needed to address the contour, and volume replacement. Due to the nature of the closed systems, a minimum volume of 100 ml was required; however, we did not set a maximum limit. When we compared the ratio of prepared fat that is yielded from each system (Table 6), there was a significantly higher percentage of available fat resulting from active filtration compared with passive filtration or centrifugation (71 percent versus 39 percent versus 43 percent, p < 0.0001), though there is some lipoaspirate that is discarded through the filtration canister in active filtration.

Table 6. - Comparison of Fat Ratios by Technique, Intention-to-Treat Population
AF System (n = 15) PF System (n = 15) Centrifugation (n = 16)
Ratio of available fat
 Mean (SD) 0.71 (0.18) 0.39 (0.12) 0.43 (0.17)
 Median (IQR) 0.72 (0.53–0.83) 0.38 (0.3–0.46) 0.39 (0.34–0.47)
Comparison among Three Arms AF vs. Centrifugation AF vs. PF Centrifugation vs. PF
Ratio of available fat
 Difference (SE)* 0.28 (0.06) 0.32 (0.05) 0.05 (0.04)
  95% CI* 0.13, 0.42 0.19, 0.45 −0.06, 0.15
   p* 0.0001 <0.0001 0.555
  95% CI 0.18, 0.37 0.23, 0.41 −0.02, 0.12
AF, active filtration (Revolve); PF, passive filtration (Puregraft); IQR, interquartile range.
*Estimated from linear model for processing rate with covariates for surgical technique and surgeon, adjusting for unequal variances. The p values were adjusted by using Tukey’s method.
Percentile confidence interval from 1000 bootstrap replicates.
Statistically significant.

Staff Demographics

Four core surgeons participated in the study. The mean age of the attending surgeon was 47 years, with an average of 10 years in practice. In addition, 24 core surgical technicians participated in the study, and all were familiar with each of the three harvesting techniques. The mean age of the scrub technicians participating in the study was 36 years, with a mean experience with fat grafting procedures of 4 years. The total resource use of labor time collected in the study was similar among the three systems (active filtration: 186 minutes versus passive filtration: 209 minutes versus centrifugation: 218.5 minutes; p > 0.05).

DISCUSSION

Time and motion studies allow observers to continuously monitor workflow and record time spent or time allocated to each step.15,17–21 In particular, surgical procedures can be objectively assessed in an effort to streamline the procedure, define roles and expectations of team members, improve resource utilization, and identify areas of improvement.16,22,23 This is the first prospective, randomized clinical study in autologous fat grafting using time and motion methodology to compare the rate of tissue processing of three commonly used systems in autologous fat grafting. There was a significantly faster rate of processing found with the active filtration system compared with the passive filtration system or centrifugation.

Our data demonstrated no statistical difference in overall operative time or the time from when the patient entered the operating room to when the patient was transferred to the recovery room, and autologous fat grafting was often performed with other procedures in the operative setting. As the number of autologous fat grafting procedures performed continues to increase, the ability to maximize fat graft take and engraftment is critical. Future studies are actively investigating the quality of the fat graft harvested using each technique, and coupled with the differences in efficiency and processing, selecting the appropriate technique can have a dramatic impact on costs and patient outcomes. Given that overall operative time was comparable among the three groups, the study supports the use of a standardized, behavioral checklist, in-service training, and repetition for surgeons and staff to streamline the process. Tasks were assigned in a defined and consistent manner that allowed for performance of multiple steps within the procedure in an overlapping fashion. This did not interfere with execution of each step or the procedure overall.

Although formal time and motion studies such as this are not routinely utilized in plastic surgery, there are a few examples of such observational work leading to optimal practices in surgical technique. Perhaps the best examples of this are in breast augmentation, which has demonstrated improved patient experience and reproducible results with a multistep patient pathway.24–26 Time and motion studies have improved patient outcomes in plastic surgery through checklists that address preoperative assessment, intraoperative technique, and postoperative recovery.27–29 Furthermore, time and motion principles are widely applied in a less regimented manner for technique papers describing reproducible operative steps in breast augmentation, recipient vessel preparation, or modifying current techniques to improve autologous fat graft harvest volumes.24,30,31 The current study is unique in that it compares the time and motion outcomes of different interventions used in fat grafting.

A recent systematic review looked at autologous fat grafting technique and found no evidence to suggest one method is better than others.32 This may be due in part to inconsistency in outcome measures and reporting. For instance, graft retention is reported as ranging from 20 percent to 90 percent9; however, there are no reliable methods to quantify graft volume over time, and most studies lack adequate follow-up to demonstrate long-term volume changes. Unfortunately, clinical outcomes are very subjective, and while validated patient-reported outcome measures exist, some inevitable bias occurs when assessing patient and surgeon satisfaction. While most would agree that overcorrection of contour and volume deficits is necessary to account for some percentage of fat graft resorption, most reconstructive surgeons perform multiple, sequential fat grafting procedures to achieve the most optimal results. This may be more common in previously radiated fields, which may compromise adipose tissue engraftment, or in the setting of larger contour defects. Although clinical outcomes are beyond the scope of the current study, the data obtained are useful in developing best practices in autologous fat grafting. In the absence of evidence showing one graft preparation technique to be clinically superior, time and motion data can translate to improved operative efficiency and reduced cost.33,34

One of the primary limitations of the current time and motion study is a result of research not keeping up with technology, particularly in the development of new devices. For example, there is a new version of the passive filtration system that accommodates machine-assisted suction and larger volumes of lipoaspirate if indicated. It is expected that this would further streamline the technique utilizing the dual-filtration bag of the passive filtration system; perhaps a next iteration of this time and motion study could include the updated system. The current study set a minimum volume of lipoaspirate at 100 ml to accommodate each of the devices. For smaller volume grafting, as commonly seen in head and neck reconstruction, a centrifugation technique may be more appropriate35 rather than discarding excess lipoaspirate to meet the minimum volume of a device. Another limitation is practice setting. This study was conducted in a large-volume academic cancer center, where additional members of the operative team (such as a resident or assistant) may facilitate the procedure. The multiple fat grafting steps from the behavioral checklist were performed entirely by the participating attending surgeon and scrub technician. Although the participating surgeons had varying levels of experience, all were proficient with the three techniques. A different practice setting may have variably experienced staff or an assistant who is not as independent; therefore, the efficiency of these systems may be less than that demonstrated here. Alternatively, if one has the same four team members for every case, the addition of fat grafting to a revision case can very much be like a well-executed offense and there may be even more efficiency. It is unclear how the findings of this study would directly translate to a single-surgeon or private practice model, but our results are consistent with those of others comparing the active system with centrifugation.33,34

CONCLUSIONS

This is the first randomized prospective study to use time and motion principles as a means to measure objective data on human and time burden associated with the process of autologous fat grafting. As the use of grafting rapidly expands, numerous methods of harvesting, processing, and reinjecting fat have evolved, most notably among devices and systems to streamline the process. While there is considerable debate regarding the benefits of one system over another, the present prospective study demonstrates that a closed-circuit filtration system is more efficient for larger volumes than centrifugation, and that the addition of active mechanical suction versus passive suction improves the graft processing rate even more.

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