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O-Ring / Plastic Sheath Wound Retractor-Protectors

Disposable wound protector-retractors combine circumferential wound-edge retraction with a plastic sheath between the incision and operative field. The Alexis O Wound Protector-Retractor (Applied Medical) is one dual-ring example; Mobius and O Trac have also appeared in clinical studies. These devices can protect and retract an incision but do not replace directed deep-organ retraction when that is required.[7][12][22]

Design​

Single- and dual-ring configurations have been studied; the effect estimates differ by device class and operation.[2][10][13]

Dual-ring (O-ring)​

  • Inner ring is inserted through the incision and seated against the internal surface.
  • Outer ring remains external.
  • Plastic sheath connects the rings and lines the wound circumference.
  • Retraction is generated by flipping or rolling the outer ring until the desired radial exposure is achieved. The current setup guide requires checks for bowel or tissue entrapment before and after tensioning.[22]
  • Ring flexibility, sheath material, conductivity and available sizes are product-specific. Applied Medical currently catalogs Alexis O sizes by incision range rather than a universal XXS-to-XL scheme.[23]

Single-ring​

  • A single ring sits intra-abdominally and connects to a protective drape. Meta-analytic subgroup estimates favored dual-ring devices, but this was not a direct head-to-head comparison and the dual-ring evidence was lower quality.[2][13][25]

Available Products​

DeviceManufacturerTypeNotes
Alexis O Wound RetractorApplied MedicalDual-ringCurrent U.S. O catalog: small–XXXL, selected by incision range[23]
Alexis O C-Section RetractorApplied MedicalDual-ringSized for the transverse lower-abdominal Pfannenstiel
Alexis Laparoscopic SystemApplied MedicalDual-ring + insufflation capWound protector / extraction + pneumoperitoneum-preserving cap[6]
MobiusCooperSurgicalDual-ringSimilar to Alexis
O TracAsung MedicalDual-ringUsed in JAMA Surg 2024 Korean RCT[7]

Mechanism of SSI Reduction​

The plastic sheath is intended to separate the incision from the operative field. Proposed mechanisms include:[2][7][8]

  • Physical barrier. Blocks endogenous (enteric or peritoneal contamination) and exogenous pathogens from embedding in skin, fat, fascia, and peritoneum. A bacteriologic study of 272 patients found no positive cultures from the incision margin when a wound protector was used, even when cultures from the abdominal-cavity side of the device were positive.[8]
  • Distributed radial retraction rather than a few focal blade contacts.
  • Reduced direct contact between the incision and operative field while the sheath is correctly seated.

Avoid claiming that the device is pressure-free, preserves perfusion, or eliminates nerve injury. Deep handheld or frame-mounted retractors may still be used, and positioning-related neuropathy remains possible.

Insertion Technique​

  1. Make the incision and carry it through the abdominal wall layers.
  2. Compress (fold) the inner ring and insert it through the incision into the abdominal cavity.
  3. Allow the inner ring to open and seat against the internal surface; confirm that bowel or other tissue is not trapped.
  4. Flip or roll the outer ring on the external surface until the desired retraction is achieved.
  5. Adjust retraction by adding or removing rolls.
  6. At case end, release the outer ring and remove the inner ring according to the product instructions.[22]

A 4-handed roll-down technique is described for transoral applications.[1]

Reconstructive-Urology and Urogyn Uses​

In reconstructive urology and pelvic surgery, a wound protector-retractor may be considered when a compatible abdominal or extraction incision would benefit from circumferential protection and exposure. Two retrospective open-cystectomy cohorts compared Alexis with metal retraction: Sidhu et al. found no statistically significant 30-day SSI difference versus Bookwalter (3/95 versus 8/73; p = 0.092), whereas Galosi et al. reported lower superficial (8.1% versus 18.9%) and deep incisional SSI (2.7% versus 14.9%) versus a Bracci retractor.[26][27] The following are workflow examples:

  • Open urinary diversion, radical cystectomy or continent cutaneous pouch. Bowel anastomosis through a transversely-protected sheath, with the device replacing a Balfour for wound retraction at the time the bowel is open.
  • Augmentation cystoplasty and bowel-segment harvest. Protects the incision during enterotomy and reservoir construction.
  • Open neobladder or Indiana pouch creation. Particularly through Pfannenstiel; an Alexis-versus-Collins-style decision in non-obese patients.
  • Selected prosthetic or reconstructive access incisions when the device fits; the reviewed GI/colorectal studies do not report AUS or IPP infection outcomes.
  • Open sacrocolpopexy, urethral diverticulectomy, complex VVF, RVF or vaginoplasty. When a transverse lower-abdominal access is used.
  • Specimen extraction in laparoscopic or robotic RU. Vaginal or Pfannenstiel mini-laparotomy specimen extraction during robotic cystectomy, partial nephrectomy, or sacrocolpopexy revision.
  • Pediatric abdominal urology when an appropriately sized device is labeled and available; the WHO guideline did not identify pediatric SSI studies in its wound-protector evidence set.[24]

Evidence — SSI Reduction​

General abdominal / GI surgery​

A Korean multicenter, patient-blinded RCT at 13 hospitals randomized 458 patients undergoing open GI surgery; 457 entered the intention-to-treat analysis after one control exclusion (74.6% had clean-contaminated wounds). The trial reported 30-day SSI in 25/229 (10.9%) with a dual-ring protector versus 47/229 (20.5%) with surgical gauze (relative risk reduction 46.8%, 95% CI 16.6–66.1%).[7]

Colorectal surgery​

A 2026 meta-analysis of 6 RCTs (666 patients) reported lower SSI after open colorectal surgery (RR 0.44, 95% CI 0.22–0.88); its four-Alexis-study subgroup reported RR 0.21 (95% CI 0.09–0.48).[9] The ASCRS 2024 guideline states that wound protectors can decrease SSI after colorectal surgery, a strong recommendation based on high-quality evidence.[10]

A double-blinded RCT of elective open colorectal resection through a midline laparotomy (64 analyzed) reported no SSI with the Alexis O-ring (0/34) versus superficial incisional SSI in 6/30 (20%) with conventional wound protection (p = 0.006).[18]

Cesarean section — mixed, BMI-dependent​

  • A single-center randomized trial of low-risk women undergoing their first planned cesarean (98 Alexis O C-Section Retractor versus 100 Collins metal retractor) reported SSI in 1% versus 8% (p = 0.035).[5]
  • Obese (median BMI 40): the trial did not show a reduction in the 30-day composite of SSI or wound disruption (20.6% versus 17.6%; p = 0.62).[11]
  • Meta-analysis (Waring 2018, 6 RCTs, 1,669 women): no overall SSI reduction at cesarean (RR 0.76, 95% CI 0.34–1.70). A planned BMI <35 subgroup favored O-ring use (RR 0.34, 95% CI 0.12–0.98), but the authors concluded that evidence did not justify routine cesarean use.[12]

Dual-ring vs single-ring​

A 2015 meta-analysis of 16 RCTs (3,695 patients) reported a larger subgroup effect estimate for dual-ring devices (RR 0.29, 95% CI 0.15–0.55) than for single-ring devices (RR 0.71, 95% CI 0.54–0.92), and cautioned that the lower-quality dual-ring data could explain part of the difference.[25] A 2018 meta-analysis of 14 RCTs (2,684 patients) found the same direction (dual-ring RR 0.31, 95% CI 0.15–0.58; single-ring RR 0.84, 95% CI 0.71–1.00).[13] Both are indirect subgroup comparisons, not randomized dual-versus-single trials. The WSES 2020 position paper states that dual-ring protectors appear superior (Grade 1B).[2]

Guideline Positioning​

SocietyRecommendationStrength
WHO 2018 second editionConsider wound protectors in clean-contaminated, contaminated and dirty abdominal surgeryConditional; very-low-quality evidence[24]
WSES 2020Dual-ring devices appear superior to single-ring for SSI preventionGrade 1B[2]
ASCRS 2024Wound protectors decrease SSI after colorectal surgeryStrong (high quality)[10]

The 2016 WHO recommendations publication remains useful historical context, but the official 2018 second-edition guideline is the current source cited above.[3][24]

Reported Adaptations​

Published case series and feasibility reports describe uses beyond routine abdominal incision protection:[1][4][6][14][15]

  • Transoral robotic surgery (TORS). Intraoral self-retaining retraction for tonsillectomy, pharyngoplasty, and head-and-neck tumor resection; protects lips and mucosa; electrically non-conducting.[1][14]
  • Transoral robotic thyroidectomy. Vestibular-incision sealed tunnel that accommodates CO₂ insufflation around the SP cannula.[15]
  • Ventriculoperitoneal shunt surgery. Abdominal-zone visualization for single-surgeon free-hand placement, particularly in obese patients.[4]
  • Presumed-benign giant ovarian-cyst aspiration and resection. A technical report describes selected use of the Alexis Laparoscopic System to limit cyst spillage and permit subsequent laparoscopy through an insufflation cap; oncologic outcomes were not assessed.[6]

Advantages vs Traditional Metal Retractors​

  • Circumferential retraction without fixed lateral metal blades; pressure and neuropathy can still occur during the operation.
  • Physical barrier against endogenous and exogenous wound contamination.[2][8]
  • Distributed wound-edge contact is a manufacturer-described design feature; perfusion superiority was not verified.
  • Material and electrosurgery compatibility is product-specific and should be checked in the current IFU; a transoral case report is not a universal electrical-safety label.[1]
  • Self-retaining once rolled. Can reduce the need for continuous handheld wound-edge retraction.
  • Transparent. Wound-edge visualization.

Disadvantages​

  • Disposable, single-use. Higher per-case cost than reusable Balfour or Collins.
  • No central or cephalad blade. Does not provide directed retraction of the bladder flap or any specific structure the way the Balfour family does; usually combined with handheld Deaver or malleable retractors for deep pelvic exposure.
  • Size-sensitive. Under-sized devices retract inadequately; over-sized devices fail to anchor.
  • Cesarean evidence varies by population: one obese-patient RCT was negative, while the 2018 meta-analysis found no overall benefit and a favorable BMI <35 subgroup. These results are specific to the cesarean populations studied.[11][12]
  • Contamination at insertion or removal. Some bacterial transfer occurs at the moments the device is not yet (or no longer) sealed.[2]

Cost-Effectiveness​

Cost-effectiveness is context-dependent and should not be inferred from device price alone. Two analyses reached different conclusions because they evaluated different populations, devices, assumptions, health systems and time horizons.[16][17]

Favorable evidence — colorectal / GI surgery​

A decision-analytic model (Chomsky-Higgins & Kahn 2019) found double-ring devices clinically superior and cost-saving under its colorectal-surgery inputs:[16]

  • 230 QALYs gained per 1,000 patients and $2.2 million saved per 1,000, driven largely by modeled SSI cost.
  • Dual-ring devices held a distinct advantage over single-ring alternatives.

Unfavorable evidence — ROSSINI trial (mixed laparotomy, single-ring)​

The ROSSINI trial economic evaluation (Gheorghe 2014; 760 randomized, 735 in the primary analysis) in UK general laparotomy found wound protectors not cost-effective:[17]

  • Mean cost £5,420 (protector) versus £5,130 (standard).
  • QALYs essentially identical (0.02131 versus 0.02133).
  • More costly and equally effective; robust to sensitivity analysis.

ROSSINI used a single-ring device in mixed laparotomy. ROSSINI’s result may not apply to modern dual-ring colorectal programs; modeled cost savings depend on local conditions.[2][10][19]

Reconciling the two​

FactorFavors cost-effectivenessAgainst
Device evidenceDual-ring subgroup estimate RR 0.29Single-ring subgroup estimate RR 0.71; these were indirect, not head-to-head estimates[13][25]
SettingColorectal or contaminated GI surgery with a high baseline SSI riskClean or mixed lower-risk laparotomy
Patient/procedure evidenceHigh baseline SSI and populations represented in positive trialsPopulations with negative or uncertain trial evidence, including routine cesarean overall[11][12]
Economic modelInputs with high SSI-treatment cost and a large modeled treatment effectDifferent treatment-effect assumptions, local costs or time horizon

Exposure-per-incision-length advantage​

An animal-tissue exposure study measured more surgical surface area per incision length with an Alexis than with traditional metal self-retainers; for a 5-cm incision, the values were 12.25 cm² (Alexis small) versus 6.17 cm² (Mollison), p = 0.038. This bench model supports an exposure claim only; it did not test patient complications, recovery or cost.[20]

Guideline cost framing​

  • WHO 2018 second edition. Notes that wound-protector use may not take priority over other interventions in resource-limited settings because of cost and availability.[24]
  • ASCRS 2024. Makes a clinical recommendation for colorectal surgery.[10]
  • SHEA/IDSA/APIC 2022 update. Includes impervious plastic wound protectors for gastrointestinal and biliary surgery among essential practices. Its evidence synthesis reports an approximately 30% reduction across 14 randomized trials; the dual-ring subgroup estimate was larger than the single-ring estimate, but this was not a direct device comparison.[21]

RU / urogyn implications​

No reviewed economic study modeled urinary diversion, augmentation, AUS, IPP, sacrocolpopexy or urethral diverticulectomy. Local use should therefore be based on labeling, incision fit, anticipated contamination, institutional SSI data and actual purchasing or reprocessing costs rather than an extrapolated claim of dominance.

  • Collins and Balfour: metal wound-edge self-retainers; reusable; the comparators in the cesarean and abdominal-surgery RCTs.
  • Bookwalter, Omni-Tract, Thompson: modular table-mounted systems for deeper or longer cases; only Bookwalter uses a continuous ring.
  • Lone Star and Denis Browne: other circumferential or ring exposure systems for perineal, vaginal or pediatric work; their mechanics and labeling differ from abdominal sheath protectors.

References​

1. Perenyei M, Dobbs TD, Fraser LR, Winter SC. Use of the self-retaining Alexis ring retractor in transoral robotic surgery. Head Neck. 2017;39(10):2132-2134. doi:10.1002/hed.24882

2. De Simone B, Sartelli M, Coccolini F, et al. Intraoperative surgical site infection control and prevention: a position paper and future addendum to WSES intra-abdominal infections guidelines. World J Emerg Surg. 2020;15(1):10. doi:10.1186/s13017-020-0288-4

3. Allegranzi B, Zayed B, Bischoff P, et al. New WHO recommendations on intraoperative and postoperative measures for surgical site infection prevention: an evidence-based global perspective. Lancet Infect Dis. 2016;16(12):e288-e303. doi:10.1016/S1473-3099(16)30402-9

4. Krauss P, Oertel MF, Stieglitz LH. Introduction of a self-holding retractor for optimized abdominal visualization in ventriculoperitoneal shunt surgery: first experiences at a single center. Acta Neurochir. 2019;161(7):1361-1365. doi:10.1007/s00701-018-03794-0

5. Hinkson L, Siedentopf JP, Weichert A, Henrich W. Surgical site infection in cesarean sections with the use of a plastic sheath wound retractor compared to the traditional self-retaining metal retractor. Eur J Obstet Gynecol Reprod Biol. 2016;203:232-8. doi:10.1016/j.ejogrb.2016.06.003

6. Dubuisson J, Fehlmann A, Petignat P. Management of presumed benign giant ovarian cysts: a minimally invasive technique using the Alexis Laparoscopic System. J Minim Invasive Gynecol. 2015;22(4):540. doi:10.1016/j.jmig.2015.01.027

7. Yoo N, Mun JY, Kye BH, et al. Plastic wound protector vs surgical gauze for surgical site infection reduction in open GI surgery: a randomized clinical trial. JAMA Surg. 2024;159(7):737-746. doi:10.1001/jamasurg.2024.0765

8. Horiuchi T, Tanishima H, Tamagawa K, et al. A wound protector shields incision sites from bacterial invasion. Surg Infect (Larchmt). 2010;11(6):501-3. doi:10.1089/sur.2009.072

9. Desai A, Bisht R, Misra S, et al. Efficacy of wound protectors in reducing surgical site infections in patients undergoing open colorectal surgery: a systematic review and meta-analysis. Colorectal Dis. 2026;28(2):e70401. doi:10.1111/codi.70401

10. Shogan BD, Vogel JD, Davis BR, et al. The American Society of Colon and Rectal Surgeons clinical practice guidelines for preventing surgical site infection. Dis Colon Rectum. 2024;67(11):1368-1382. doi:10.1097/DCR.0000000000003450

11. Scolari Childress KM, Gavard JA, Ward DG, Berger K, Gross GA. A barrier retractor to reduce surgical site infections and wound disruptions in obese patients undergoing cesarean delivery: a randomized controlled trial. Am J Obstet Gynecol. 2016;214(2):285.e1-285.e10. doi:10.1016/j.ajog.2015.09.096

12. Waring GJ, Shawer S, Hinshaw K. The use of O-ring retractors at caesarean section: a systematic review and meta analysis. Eur J Obstet Gynecol Reprod Biol. 2018;228:209-214. doi:10.1016/j.ejogrb.2018.06.037

13. Kang SI, Oh HK, Kim MH, et al. Systematic review and meta-analysis of randomized controlled trials of the clinical effectiveness of impervious plastic wound protectors in reducing surgical site infections in patients undergoing abdominal surgery. Surgery. 2018;164(5):939-945. doi:10.1016/j.surg.2018.05.024

14. Lee J, Yu JW, Lee ZH, Levine JP, Jacobson AS. Alexis retractor: institutional experience of its applications in head and neck surgery and review of the literature. Cleft Palate Craniofac J. 2020;57(5):656-659. doi:10.1177/1055665619900833

15. Park D, Shaear M, Chen YH, et al. Transoral robotic thyroidectomy on two human cadavers using the Intuitive da Vinci single port robotic surgical system and CO₂ insufflation: preclinical feasibility study. Head Neck. 2019;41(12):4229-4233. doi:10.1002/hed.25939

16. Chomsky-Higgins K, Kahn JG. Interventions and innovation to prevent surgical site infection in colorectal surgery: a cost-effectiveness analysis. J Surg Res. 2019;235:373-382. doi:10.1016/j.jss.2018.09.048

17. Gheorghe A, Roberts TE, Pinkney TD, et al. The cost-effectiveness of wound-edge protection devices compared to standard care in reducing surgical site infection after laparotomy: an economic evaluation alongside the ROSSINI trial. PLoS One. 2014;9(4):e95595. doi:10.1371/journal.pone.0095595

18. Cheng KP, Roslani AC, Sehha N, et al. Alexis O-ring wound retractor vs conventional wound protection for the prevention of surgical site infections in colorectal resections. Colorectal Dis. 2012;14(6):e346-51. doi:10.1111/j.1463-1318.2012.02943.x

19. Zhang L, Elsolh B, Patel SV. Wound protectors in reducing surgical site infections in lower gastrointestinal surgery: an updated meta-analysis. Surg Endosc. 2018;32(3):1111-1122. doi:10.1007/s00464-017-6012-0

20. Lawson J, McGill A, Meares H, et al. Wound protectors for improved exposure in open hernia repair. Hernia. 2019;23(6):1215-1219. doi:10.1007/s10029-019-01952-6

21. Calderwood MS, Anderson DJ, Bratzler DW, et al. Strategies to prevent surgical site infections in acute-care hospitals: 2022 update. Infect Control Hosp Epidemiol. 2023;44(5):695-720. doi:10.1017/ice.2023.67

22. Applied Medical. Alexis O Wound Protector-Retractor Setup Guide. January 2025. PDF

23. Applied Medical. Alexis O Wound Protector-Retractor reorder information. Product catalog

24. World Health Organization. Global Guidelines for the Prevention of Surgical Site Infection. 2nd ed. 2018. Official guideline

25. Mihaljevic AL, Müller TC, Kehl V, Friess H, Kleeff J. Wound edge protectors in open abdominal surgery to reduce surgical site infections: a systematic review and meta-analysis. PLoS One. 2015;10(3):e0121187. doi:10.1371/journal.pone.0121187

26. Sidhu AS, Marten E, Bodoukhin N, et al. "Alexis wound retractor for radical cystectomy: A safe and effective method for retraction." Adv Urol. 2018;2018:8727301. doi:10.1155/2018/8727301

27. Galosi AB, Delle Fave RF, Perpepaj L, et al. "Does Alexis wound protector/retractor reduce the risk of surgical site infections after open radical cystectomy for bladder cancer? Results from a single center, comparative study." Urology. 2024;184:162–168. doi:10.1016/j.urology.2023.09.054