according to the first randomized controlled trial comparing both types of lithotomy stirrups.
“Participants positioned in candy cane stirrups had greater hip abduction than those positioned in boot stirrups, which could provide a rationale for our findings,” suggested Ankita Gupta, MD, MPH, of the University of Louisville (Ky.), and colleagues. Their report is in Obstetrics & Gynecology.
But one expert questions this interpretation, calling it a major limitation of the study.
“The only difference between the two arms of the study is associated with the angles between the femurs,” said Rosanne M. Kho, MD, a gynecologic surgeon at Cleveland Clinic, who was not involved in the study. “The difference of the angles at the femur is not inherent to the type of stirrup but in the method in which the patients were positioned using the two different types of stirrups,” she said. “The same wide angle between the femurs can be attained with the boot stirrups if the patient is not positioned properly. To determine if the same benefit in physical function is achieved with a lesser angle between the femur, the investigators should use only one type of stirrup (whether the candy cane or the boot stirrups) and change only the angles of the femur.”
Dr. Rosanne M. Kho
The study was a single-masked, randomized controlled trial of women undergoing vaginal surgery at the University of Louisville’s division of urogynecology between March 2018 and Oct. 2019. Surgeries included any combination of vaginal hysterectomy, vaginal vault suspension (uterosacral or sacrospinous ligament fixation), vaginectomy (partial or total), mid-urethral slings, or other surgeries such as urethral diverticulectomy, fistula repair, or mesh excision.
Among the 138 women included in the intention-to-treat analysis, 72 were randomized to candy cane, and 66 to boot (Yellofin) stirrups. They were positioned in the assigned stirrup by the attending surgeon, with assistance from the surgical team, after administration of anesthesia and were not informed of their allocation until the end of the study at 6 weeks post surgery.
On day 1 post surgery, a 100-point visual analog scale (VAS) questionnaire was administered for pain in the lower back, hips, buttocks, thighs, knees, calves, and feet, followed by a series of questionnaires at 6 weeks post surgery, including the PROMIS (Patient-Reported Outcomes Measurement Information System) forms on physical function, pain intensity, and pain interference, as well as the Pelvic Floor Disability Index (PFDI-20) and the Patient Global Impression of Improvement forms.
While the authors acknowledged that neurologic injuries following vaginal surgery are rare, and therefore difficult to measure, physical function is a “prudent” alternative measurement.
Although the study was designed to compare lithotomy stirrups, patient positioning also was measured. Once the patient was anesthetized, the surgeon used a goniometer to measure flexion at the hip and knee joints, the angle of abduction and external rotation at the hip. The “angle between the femurs” was measured by placing the fulcrum of the goniometer at the anal opening.
While the angles of flexion at the hips and knees were similar between groups, the study found a significant difference between groups in the angle between the femurs (mean ± standard deviation, 88.7 ± 13.4 candy cane vs. 77.2 ± 13.3 boot, P < .01).
In addition, the primary outcome, change in physical function based on the PROMIS physical function shortform-20a, was significantly different between the two groups: While subjects in the candy cane group demonstrated a decline of 1.9 in mean physical function score at 6 weeks compared to baseline, those in the boot stirrup group showed an increase of 1.9 from baseline. The mean 6-week postoperative scores were 45.8 versus 49.8 for the candy cane and boot stirrup groups respectively (P < .01).
Although it was “well executed by a well-respected group of vaginal surgeons at a major academic institution,” the study has other limitations, noted Dr. Kho.
“Though the measurements were obtained with the goniometer at the beginning of the surgery, it does not appear that a repeat measurement was performed at the end of the case. Is it possible that positioning could have shifted and resulted in further change in the angle of the femur/hip/knees compared to the beginning of the surgery?” she asked.
In addition, “compared to the candy canes, the boot stirrup has bulky boots that could limit opportunities for bedside assistants who were standing next to the primary surgeon to lean against the patient’s thighs during the surgery. Were there measures done to ensure that assistants were not leaning against the [candy cane] patients?”
In terms of the 6-week outcome measure, Dr. Kho suggested PROMIS outcomes measured at 2 weeks and at 4 or 6 weeks “would have provided greater insight to the study question.
“The authors acknowledge that neuropathies due to patient positioning manifest soon after surgery and tend to be transient. Incidence of neuropathy is extremely low in both groups and is equivalent. Factors that could impair quick return to normal activity as a result of the neuromuscular effects due to patient positioning should have been measured earlier,” she suggested.
Finally, Dr. Kho noted that the authors “fail to provide any likely rationale for the impaired physical function measured at 6 weeks that can be attributed to the difference in the angles at the femur. The findings of decreased physical function at 6 weeks in the candy cane group may be incidental, and may be different if measured at an earlier time (which would be more pertinent for this study) or at a later time such as 3 months.”
Individual authors acknowledged personal funds from Society of Gynecologic Surgeons, Elsevier publishing, RBI Medical, and AMAG Pharmaceuticals. Dr. Kho had no relevant financial disclosures.
SOURCE: Gupta A et al. Obstet Gynecol. 2020 July 8. doi: 10.1097/AOG.0000000000003954.