Comparison of Lateral Internal Sphincterotomy Techniques for Chronic Anal Fissure (SPHINX)

A Prospective Randomized Controlled Trial Comparing Spasm-Controlled, Fissure Apex-Limited, and Dentate Line-Limited Lateral Internal Sphincterotomy Techniques in Chronic Anal Fissure

This prospective randomized controlled trial compares three lateral internal sphincterotomy (LIS) techniques in patients with chronic anal fissure refractory to medical treatment: (1) Spasm-Controlled LIS (serial small sphincterotomies using an anal calibrator until 30 mm anal caliber is achieved, under local anesthesia plus sedation), (2) LIS up to the Fissure Apex (spinal or general anesthesia), and (3) LIS up to the Dentate Line (spinal or general anesthesia). The primary outcomes are fissure healing rate and fecal incontinence incidence at 12 months, assessed using the Wexner Incontinence Score. Secondary outcomes include postoperative pain (VAS), recurrence rate, patient satisfaction, and complications. A total of 150 patients (50 per group) will be enrolled and followed for 12 months.

Study Overview

• Status: Recruiting
• Conditions: Chronic Anal Fissure
• Intervention / Treatment: Procedure: Spasm-Controlled Lateral Internal Sphincterotomy; Procedure: Lateral Internal Sphincterotomy up to Fissure Apex; Procedure: Lateral Internal Sphincterotomy up to Dentate Line

Detailed Description

Chronic anal fissure (CAF) is a longitudinal tear in the anoderm persisting for more than 8 weeks. Lateral internal sphincterotomy (LIS) is the gold-standard surgical treatment for CAF refractory to medical management, achieving healing rates of 90-98%. However, postoperative fecal incontinence remains its most significant complication, with rates ranging from 1-15% for permanent incontinence.

To reduce incontinence risk, various techniques limiting the extent of sphincterotomy have been proposed. Mentes et al. (2005) demonstrated that LIS up to the dentate line provided faster healing but caused significant continence disturbance, while LIS limited to the fissure apex was associated with lower incontinence but a higher treatment failure rate. Mentes et al. (2008) subsequently showed that spasm-controlled LIS using anal calibrators achieved faster pain relief with lower early incontinence rates compared to fissure apex sphincterotomy. However, no randomized trial has compared all three techniques simultaneously.

This single-center, prospective, three-arm RCT will enroll 150 adult patients with CAF refractory to at least 6 weeks of medical treatment. Patients will be randomized (1:1:1) to one of three groups: Group 1 (Spasm-Controlled LIS): serial small sphincterotomies under local anesthesia plus sedation until anal caliber reaches 30 mm using an anal calibrator. Group 2 (LIS up to Fissure Apex): open sphincterotomy extended to the proximal end of the fissure under spinal or general anesthesia. Group 3 (LIS up to Dentate Line): open sphincterotomy extended to the dentate line under spinal or general anesthesia.

All procedures will use the open technique with patients in lithotomy position. Randomization will be performed using computer-generated block randomization (block size 6), stratified by sex and fissure location. Outcome assessors will be blinded to group allocation.

Patients will be evaluated preoperatively and at postoperative day 1, week 1, week 2, month 1, month 2, month 6, and month 12. The Wexner (Cleveland Clinic) Incontinence Score will be used to assess continence at each visit. Fissure healing will be defined as complete epithelialization with no symptoms. Statistical analysis will follow the intention-to-treat principle, with Bonferroni correction applied for multiple comparisons.

• Study Type: Interventional
• Enrollment (Estimated): 150
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Emre Gülçek, MD, Assistant Professor; Phone Number: +905544810964; Email: emre.gulcek@comu.edu.tr

Study Locations

• Turkey (Türkiye)
  • Çanakkale
    • Çanakkale, Çanakkale, Turkey (Türkiye), 00017
      • Recruiting
      • Canakkale Onsekiz Mart University
      • Contact: Emre Gülçek, MD, Assistant Professor; Phone Number: +905544810964; Email: emre.gulcek@comu.edu.tr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 18 years or older
• Diagnosis of chronic anal fissure (duration ≥8 weeks)
• Failure to heal after at least 6 weeks of appropriate medical treatment (topical agents, fiber supplementation, sitz baths)
• Complete preoperative fecal continence (Wexner Incontinence Score = 0)
• Primary anal fissure (posterior or anterior midline location)
• Written informed consent

Exclusion Criteria:

• Any degree of preoperative fecal incontinence
• Secondary anal fissure (associated with Crohn's disease, tuberculosis, HIV, syphilis, or other systemic conditions)
• Previous anal sphincter surgery
• History of obstetric sphincter injury
• Active anorectal infection (abscess or fistula)
• Pregnancy or breastfeeding
• Uncorrectable coagulopathy or current anticoagulant use
• Inability to cooperate with study procedures or attend follow-up visits

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Spasm-Controlled LIS; Serial small open sphincterotomies performed under local anesthesia plus IV sedation. Anal caliber is measured with an anal calibrator before and after each increment until a caliber of 30 mm is achieved.	Procedure: Spasm-Controlled Lateral Internal Sphincterotomy; Serial small open sphincterotomies under local anesthesia plus IV sedation using an anal calibrator until anal caliber of 30 mm is achieved.; Other Names: Calibrated LIS
Active Comparator: LIS up to Fissure Apex; Open lateral internal sphincterotomy extended to the proximal end of the fissure (fissure apex) under spinal or general anesthesia. The length of sphincterotomy equals the length of the fissure.	Procedure: Lateral Internal Sphincterotomy up to Fissure Apex; Open LIS extended to the proximal end of the fissure under spinal or general anesthesia.; Other Names: Tailored LIS
Active Comparator: LIS up to Dentate Line; Open lateral internal sphincterotomy extended to the level of the dentate line under spinal or general anesthesia. This is the traditional (classical) LIS technique.	Procedure: Lateral Internal Sphincterotomy up to Dentate Line; Open LIS extended to the level of the dentate line under spinal or general anesthesia.; Other Names: Traditional LIS / Classical LIS

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fissure Healing Rate	Complete epithelialization of the anal fissure with no symptoms at 12 months postoperatively, assessed by clinical examination.	12 months
Fecal Incontinence Incidence	Incidence of de novo fecal incontinence assessed using the Wexner (Cleveland Clinic) Incontinence Score. A score increase of ≥1 point from preoperative baseline is defined as de novo incontinence.	12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postoperative Pain Score	Pain assessed using the Visual Analog Scale (VAS, 0-10) at each follow-up visit.	Day 1, Week 1, Week 2, Month 1, Month 2, Month 6, Month 12
Recurrence Rate	Proportion of patients with recurrence of anal fissure after an initial healing period.	Month 6 and Month 12
Patient Satisfaction	Patient satisfaction assessed on a numeric scale (0-10) at follow-up visits.	Month 2, Month 6, Month 12
Postoperative Complications	Rate of surgical complications including bleeding, hematoma, infection, abscess, and fistula.	12 months

Collaborators and Investigators

• Sponsor: Çanakkale Onsekiz Mart University

Publications and helpful links

General Publications

• Mentes BB, Guner MK, Leventoglu S, Akyurek N. Fine-tuning of the extent of lateral internal sphincterotomy: spasm-controlled vs. up to the fissure apex. Dis Colon Rectum. 2008 Jan;51(1):128-33. doi: 10.1007/s10350-007-9121-3. Epub 2007 Dec 18.
• Elsebae MM. A study of fecal incontinence in patients with chronic anal fissure: prospective, randomized, controlled trial of the extent of internal anal sphincter division during lateral sphincterotomy. World J Surg. 2007 Oct;31(10):2052-7. doi: 10.1007/s00268-007-9177-1.
• Mentes BB, Ege B, Leventoglu S, Oguz M, Karadag A. Extent of lateral internal sphincterotomy: up to the dentate line or up to the fissure apex? Dis Colon Rectum. 2005 Feb;48(2):365-70. doi: 10.1007/s10350-004-0812-8.

Study record dates

Study Major Dates

• Study Start (Actual): May 6, 2026
• Primary Completion (Estimated): May 6, 2027
• Study Completion (Estimated): May 6, 2028

Study Registration Dates

• First Submitted: April 3, 2026
• First Submitted That Met QC Criteria: April 3, 2026
• First Posted (Actual): April 9, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 12, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Fecal incontinence; Chronic anal fissure; Lateral internal sphincterotomy; Spasm-controlled sphincterotomy; Dentate line; Fissure apex
• Additional Relevant MeSH Terms: Intestinal Diseases; Digestive System Diseases; Gastrointestinal Diseases; Rectal Diseases; Fecal Incontinence
• Other Study ID Numbers: CAF-LIS-RCT-2026-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No