Conization of the cervix or cold knife cone (CKC) is a surgical procedure used to treat or diagnose cervical dysplasia. It is the excision of a cone-shaped portion of the cervix to remove a cervical lesion and the entire transformation zone. Practitioners can use this procedure when there are a conflicting pap smear and biopsy specimen. It can be used if histological results are significantly less severe than the cytology result or if there is evidence of severe dysplasia, and even if there is stage 1A1 squamous cell cervical cancer. Conization can be done with a scalpel, a laser, or with an electrosurgical instrument typically referred to as a LEEP (Loop Electrosurgical Excision Procedure). This review will focus mainly on the cold knife cone procedure.
The cervix is the structure that connects the uterus to the vagina. It is composed of two regions which are the ectocervix and the endocervical canal. The ectocervix is the portion that projects into the vagina. A stratified squamous non-keratinized epithelium lines it. The opening in the ectocervix is the external os and marks the transition from ectocervix to the endocervical canal. The endocervical canal runs the length of the cervix and connects the endometrial cavity with the vagina. It is lined with glandular epithelium. The ectocervix has the squamocolumnar junction (SCJ). It is an area of transformation within which the epithelium changes from glandular to squamous, and it is this area that is most susceptible to the human papillomavirus attachment which can lead to dysplasia and malignant transformation. When considering surgical options to perform a conization procedure, keep in mind the main vascular supply of the cervix is at three o'clock and nine o’clock with the descending branches of the uterine artery and vein.
Conization of the cervix is indicated for a variety of reasons. Excisional procedures are warranted for diagnostic purposes and treatment. A surgeon should perform a diagnostic excisional procedure if there is a lesion that is suspicious for invasive cancer or an adenocarcinoma in situ of the cervix. If there is a histological discordance with the cytological screening test and histological results are less severe, then a diagnostic cone is recommended. Unsatisfactory colposcopic evaluation with evidence of dysplasia present or unexplained high grade or an atypical glandular cell cytology needs an excisional cone or if the entire lesion is not completely visualized on colposcopy. These procedures are also adequate to treat severe dysplasia (CIN 2/3, CIS) and stage 1A1 squamous cell cervical cancer if the patient wants to maintain her fertility.
There are few contraindications to the cone procedure. If there is too little cervix to excise due to previous excisions, then a cold knife cone may not be possible. If a patient is a poor surgical candidate, then an office procedure avoiding general anesthesia would be recommended. Pregnancy is a relative contraindication to the cold knife cone and should only be performed when there is a strong suspicion of invasive cancer. Severe cervicitis or a patient on anticoagulant therapy are contraindications to the cone.
The cold knife cone procedure is performed with a knife in the operating room and usually under general anesthetic. Candy cane stirrups or Allen stirrups are used for leg positioning. A colposcope, 5% acetic acid, or Lugol’s solution can be used before the start of the procedure to assist the surgeon in identifying the lesion. A straight catheter to drain the bladder and weighted speculum with right angle retractor are used for visualization. The surgeon will also need a single tooth tenaculum, vasoconstrictive solution, a scalpel mounted on a 45-degree angle handle or a long-handled 11 blade. A pair of long-handled forceps or a long Allis clamp will be used for traction and long-handled Mayo scissors to excise the specimen. Some surgeons utilize stay sutures at the cervicovaginal junction and typically use a 2.0 delayed absorbable suture with the Heaney needle driver. A Bovie cautery tool is needed for hemostasis. A Kevorkian curette is used to perform the endocervical curettage after the cone is removed.
A surgeon and scrub nurse to assist are adequate to perform the procedure. An anesthesiologist would manage the anesthesia.
The anesthesiologist will sedate and intubate the patient. The patient is placed in the dorsal lithotomy position with candy cane stirrups or Allen stirrups to position her legs. Colposcopy with 5% acetic acid or Lugol’s solution can be performed in the operating room depending on the surgeon’s preference and ability to see the cervical lesion. The vagina is prepped and draped in usual sterile fashion with drainage of the bladder. Surgical scrub solutions of Hibiclens antimicrobial scrub or Betadine are adequate for vaginal prep. There are no indicated antibiotics necessary for this procedure. A vasoconstrictor solution is mixed. It is typically vasopressin 20IU diluted with 50cc saline before the start of the procedure. Lidocaine without epinephrine can be added to the solution to provide local anesthesia simultaneously.
A weighted speculum is placed in the vagina; a right angle retractor is used to visualize the cervix; the anterior lip of the cervix is then grasped with a tenaculum. If stay sutures are used, they are placed at the three o'clock and nine o’clock position at the cervicovaginal junction. Current literature does not show a decrease in bleeding or hemorrhage, so it is a surgeon’s preference. Typically, 10 cc to 15 cc of dilute vasopressin is injected into the cervix at 2 o'clock, 4 o'clock, 8 o'clock, and 10 o’clock. Blanching will be seen. An angled blade is used to cut the cervix starting at two o’clock outside the transformation zone. A jigsaw cutting technique is performed circumferentially to include the lesion and the transformation zone. Toothed forceps or an Allis clamp can be used to provide counter traction and elevate the cone bed, take caution not to damage the epithelium. The angled blade creates the cone specimen, and after circumferential excision, the base of the cone is excised with Mayo scissors. The residual endocervical canal is curettage with a Kevorkian curette and specimen captured on a Telfa pad. Then, hemostasis is obtained with Bovie cautery at 40 W ball electrode, or some surgeons will utilize interrupted suture at the cone bed margins. If stay sutures were placed a narrow piece of oxidized cellulose (surgicel) can be placed in the cone bed and tied in with the stay sutures. The patient should be warned that she will pass this packing within the next few weeks. After the cone is removed, a suture is placed at twelve o’clock position to mark for the pathologist.
The most significant complication after cold knife cone is a hemorrhage. This can be intraoperative bleeding or delayed by up to two weeks. Intraoperative bleeding can be managed with multiple techniques utilizing suturing, and even hysterectomy is severe. Post-operative bleeding is between 5% to 15%, but conservative measures in the office using Monsel’s paste, silver nitrate, or packing typically treat the majority of these patients. Occasionally the surgeon must return to the operating room and recauterize or suture the cone bed to obtain hemostasis. Infections following cold knife cone are rare and can be treated with antibiotics. Cervical stenosis and cervical insufficiency are late complications associated with this procedure. Stenosis can be treated with dilation and should be evaluated post-operative if aggressive Bovie cauterization of the endocervical canal was performed or a deep cone bed specimen was obtained. There is mixed data about the risk of preterm delivery and perinatal mortality associated with excisional procedures. There are no randomized controlled trials. Most of the studies show cold knife cone is associated with increased risk of preterm delivery and perinatal mortality, but LEEP is not. Greater depth of excision appears to be an increased risk for PPROM and preterm birth. Increased number of procedures is linked to risk of preterm birth.
Recurrence risk of CIN 2,3 after treatment varies by age, the severity of disease at initial treatment, margin status, and treatment modality. Cold knife cone has the lowest recurrence rate based on treatment modality. Cold knife cone requires the operating room but provides a histological specimen with the best specimen margins.