Successful appendectomy was first described by McBurney [1] in 1894, and the open surgical approach remained the gold standard for nearly a century. Surgical advancement in the form of laparoscopy emerged in the 1980s as a promising alternative to traditional laparotomy. Semm [2] first reported a successful laparoscopic appendectomy in 1983.

Once laparoscopic appendectomy was shown to be a safe and equivalent substitute for laparotomy, evidence quickly accumulated showing the benefits of laparoscopic surgery versus the traditional open approach in several prospective studies [3–8]. Faster recovery, earlier resumption of diet, improved wound healing, and decreased infection rates all have been documented in the transition from laparotomy to multiport laparoscopy, begging the question whether an even more minimally invasive approach may offer additional benefit.

Single-incision laparoscopic (SILS) surgery has emerged as an alternative to traditional multiport laparoscopy, with potential advantages in terms of cosmesis and patient satisfaction. Investigators continue to evaluate its safety profile, but a consensus regarding the objective benefits of single-incision laparoscopy has not been reached. The available evidence is limited and at times conflicting. Larger reviews and prospective studies are required to determine objectively whether SILS surgery is safe and feasible and has substantial benefits other than cosmesis. Additionally, the potential drawbacks to minimizing ports of entry must be quantified and studied.

For the aforementioned reasons, a retrospective review of single-incision and traditional three-port laparoscopic appendectomy was performed at our institution to allow for statistical comparison of demographics, operative times, conversion rates, and outcomes. We hypothesized that SILS appendectomy is both safe and effective and does not have a substantial impact on operative times or hospital length of stay (LOS).

Materials and methods

Patient selection

All SILS and multiport laparoscopic (MP) appendectomies performed by three surgeons between August 2008 and June 2012 were reviewed. This period included our initial experience with SILS appendectomy, although 15 SILS cholecystectomies had been performed previously. The decision to perform the procedure as SILS or MP was made according to patient and surgeon discretion. The primary outcomes recorded included operative time, conversion rates, LOS, and postoperative complications. Additional data points collected included patient age, gender, and body mass index (BMI).

Surgical technique

For the SILS approach, a 2-cm incision is made within the umbilical folds and carried down to the fascia (Fig. 1). A three-trocar SILS port (Covidien, Mansfield, MA, USA) is inserted using a Kelly clamp. A 5-mm bariatric 30° angled scope and standard 5-mm nonarticulating instruments are used through the SILS port. Diagnostic laparoscopy is performed, the appendix identified, and dissection and mobilization completed.

Fig. 1
figure 1

Single incision within the umbilical folds

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The appendix and mesoappendix are divided at the base using a linear stapler. The specimen is placed in a specimen bag, and the purulent fluid is suctioned free. The SILS port and specimen bag are removed through the fascial incision. The abdomen is closed using two figure eights with 0 polyglycolic acid suture. The soft tissues are irrigated and loosely approximated using 3-0 polyglycolic acid suture in a deep dermal interrupted fashion, after which a suction dressing is applied. The dressing is created by applying a small amount of triple antibiotic ointment and gauze covered with a clear adhesive bandage, after which air is aspirated using a 60-ml syringe and a 27-gauge needle (Fig. 2) [9].

Fig. 2
figure 2

Application of suction dressing over the umbilical incision

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For the traditional approach, the Hasson technique is used to gain access to the umbilicus. Two additional 5-mm trocars are placed in the lower abdomen, and removal of the appendix occurs as described earlier. The trocars are removed under direct vision, and the specimen is delivered through the Hasson trocar site. The wound is irrigated and closed using 0 polyglycolic acid suture in a figure eight fashion. All trocar sites are closed using 4-0 absorbable monofilament suture and dermal adhesive.

Statistical analysis

This was an intent-to-treat study. All variables are described using means ± standard deviations or percentages as appropriate. Bivariate analysis compared LOS, operative time, conversion rate, and complication rate between the two surgical techniques. This consisted of either t-tests or chi-square/Fisher’s exact tests, as appropriate. Performing a multivariate analysis allowed for statistical analysis of each outcome variable with an accounting for more than one covariate at a time. In this portion of the analysis, linear regression models were built for LOS and operative time, including as covariates surgical approach and any demographic factor reaching a significance level of 0.2 in the aforementioned bivariate analyses. A logistic regression model for conversion and complication was built as described earlier as well.

Results

The study compared 168 consecutive patients who underwent SILS appendectomy and 108 who underwent MP appendectomy (Table 1). The data set included 149 men (53.99 %), and the patients had a mean age of 36.07 ± 18.77 years (range 8–87 years). For 127 patients, BMI was missing due to incomplete records, but for the remainder, the mean BMI was 27.62 ± 6.64 kg/m2 (range 17.0–45.3 kg/m2). The indications for surgery included acute appendicitis, appendiceal mass, interval appendectomy, chronic appendicitis, and incidental to intraoperative surgical consult. Complicated cases were defined as those involving perforated appendicitis or the presence of an intraabdominal abscess at the time of surgery.

Table 1 Comparison of data between SILS and MP appendectomies
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Combination cases were defined as those requiring a secondary procedure at the time of appendectomy. The distribution of combination cases did not differ between SILS and MP (p = 0.54, Fisher’s exact test), so the operative times for combination cases were removed from all further calculations involving operative time. The mean operative time for SILS appendectomy was 43.63 min versus 40.95 min for MP appendectomy. The difference was not significant (p = 0.29). A multivariate regression for operative time did not indicate that surgical technique was a significant covariate. It did show, however, that perforated appendicitis, appendiceal mass, and interval appendectomy all were indicators for longer operative times.

Four of the SILS cases (2.38 %) and one of the MP cases (0.93 %) were converted to open procedure. The difference was not statistically significant (p = 0.65, Fisher’s exact test). For 11 SILS cases (3.66 %), conversion to multiport laparoscopy was required. The reasons listed for conversion included extensive adhesions, extensive inflammation, intraabdominal abscess, retraction difficulty, and retrocecal appendix.

The complication rates were slightly higher for MP appendectomy (10 cases) than for SILS appendectomy (5 cases) (Table 1). One incisional hernia was documented in the SILS cohort during the initial follow-up period, which ranged from 6 to 46 months. A multivariate analysis using surgical approach, gender, and case complexity as covariates indicated that a complicated case was a significant risk factor for having a complication.

The mean LOS was 0.32 days for SILS and 0.55 days for MP appendectomy. The difference was not statistically significant (p = 0.22). Complicated cases had a mean LOS of 2.68 ± 3.17 days, whereas noncomplicated cases had mean LOS of 0.18 ± 0.46 days. This difference was significant (p < 0.001, t-test). In a linear model for LOS that included surgical approach, gender, age, and complicated case as covariates, only complicated case was a significant factor.

Discussion

The goal of this chart review was to compare outcomes between SILS appendectomy and traditional laparoscopic surgery to ascertain the safety and feasibility of the less invasive technique. Our results indicate that the outcomes expected for traditional MP appendectomy are reproducible when the SILS technique is used by experienced laparoscopic surgeons.

The objective evidence for SILS in the literature is limited and mostly concerns laparoscopic cholecystectomy. Findings have shown SILS cholecystectomy to be a safe alternative to multiport laparoscopy, equivalent in terms of complications and at times superior in terms of patient-centered outcomes [10–13]. Even more advanced laparoscopic procedures such as partial colectomy show promise in the literature. In a case-matched comparison of single-incision, conventional, and hand-assisted laparoscopic right colectomies, Papaconstantinou et al. [14] demonstrated a reduction in postoperative LOS of about 1.5 days.

Criticism of SILS has historically concerned longer operative times, poor instrumentation, and difficulty overcoming the inherent learning curve. Advanced instruments such as roticulating and articulating graspers or electrocautery can help compensate for loss of triangulation and potentially reduce operative times by improving instrument crowding [10, 15, 16]. Such devices, however, can be costly and, as shown in our study, are not essential to the performance of SILS in an efficient and safe manner. Even with the routine use of standard nonarticulating laparoscopic instruments in our facility, the average operative times for SILS appendectomy were competitive, and only 3.66 % of cases required conversion to a multiport procedure due to surgical difficulty.

Our analysis indicated no statistically significant difference in operative time between SILS and MP appendectomies, with an observed average difference of about 3 min. This is supported in the literature by a large randomized controlled trial comparing the two approaches, which showed an increase of only 5 min for SILS appendectomy [17].

Although our review included the presumed learning curve for SILS appendectomy, all three surgeons had prior experience with SILS cholecystectomy. During these 15 initial cases, we developed a standardized technique for instrumentation, hand positioning, and incision closure. This may account for the relatively insignificant difference in operative times for the two techniques at our facility, implying that the learning curve for the single-incision technique may be overcome with such standardization in other procedures as well.

With regard to safety, our review indicated comparable LOS, competitive complication rates, and no significant increase in conversions to an open procedure. This is consistent with prior small studies that have shown SILS appendectomy to be safe and feasible [17–19]. The higher complication rate in the multiport group is likely be explained by the retrospective nature of the study as well as the possibility of selection bias.

Although cost analysis was not an end point in our study, we can extrapolate easily definable additional hard costs by subtracting the price of multiport access trocars from that of a SILS port. At our institution the net increase in hard costs is $225. Harder to quantify is the additional cost of 3 min in the operating room.

The limitations of this study were those inherent to a retrospective analysis, including lack of prospective validation and inability to establish causal relationships. A prospective randomized trial could more conclusively demonstrate any equivalences or superiority that may exist for the less invasive technique. Validated prospective collection of patient satisfaction, quality of life, and pain scores also is needed to highlight any improvements in patient-centered outcomes.

As mentioned earlier, the standardization of technique used by the participating surgeons offered a unique strength to the study’s results. All three surgeons involved in the management of our patients were experienced with SILS cholecystectomy before undertaking SILS appendectomy. Additionally, this is one of the largest comparative reviews of SILS and traditional MP appendectomy, adding to the growing body of evidence investigating this innovative technique.

The benefits of SILS surgery are continuing to emerge. Our study indicates that SILS appendectomy is safe and feasible with regard to operative time, LOS, conversion, and complications. A prospective randomized controlled trial investigating these outcomes as well as postoperative pain, cosmesis, and patient satisfaction currently is underway at our institution for more conclusive determination of any advantages or disadvantages to performing SILS appendectomy.