What Is Uterine Prolapse?

This JAMA Patient Page describes the condition of uterine prolapse and its risk factors, symptoms, and treatment options.

Uterine prolapse in a non-pregnant bitch

A ten-year-old mixed breed bitch was presented for a tissue prolapse protruding from her vulva. Following detailed examination and stabilization, the ovaries and uterine horns were removed by laparotomy, whereas the prolapsed tissue identified as uterus including cervix was removed vaginally. Histology confirmed uterine prolapse, a rare condition in bitches usually found shortly after birth especially due to dystocia. In contrast, the present case was found in a nulliparous non-pregnant bitch. Diagnostic and therapeutic approaches, including microbiological and histological findings, are described and discussed critically.

Uterine Prolapse in Pregnancy: A Review

Importance

Although not a common occurrence, uterine prolapse during pregnancy can have significant effects for pregnancy outcomes and quality of life of maternal patients. Most data about management exist as case reports; a review of these cases provides some guidance about treatment options.

Objectives

This review examines current literature about uterine prolapse during pregnancy to assess current information about this condition, prevalence, diagnosis, management, and outcomes.

Evidence Acquisition

Electronic databases (PubMed and Embase) were searched using terms "uterine prolapse" AND "pregnancy" AND "etiology" OR "risk factors" OR "diagnosis" OR "therapy" OR "management" limited to the English language and between the years 1980 and October 31, 2022.

Results

Upon review of 475 articles, 48 relevant articles were included as well as 6 relevant articles found on additional literature review for a total of 54 articles. Of those articles, 62 individual cases of uterine prolapse in pregnancy were reviewed including pregnancy complications, mode of delivery, and outcomes. Prevalence was noted to be rare, but much more common in second and subsequent pregnancies. Most diagnoses were made based on symptomatic prolapse on examination. Management strategies included bed rest, pessary use, and surgery (typically during the early second trimester). Complications included preterm delivery, patient discomfort, urinary retention, and urinary tract infection. Delivery methods included both cesarean and vaginal deliveries.

Conclusions

Although a rare condition, uterine prolapse in pregnancy is readily diagnosed on examination. Reasonable conservative management strategies include observation, attempted reduction of prolapse, and pessary use; if these measures fail, surgical treatment is an option.

Relevance

Our review compiles literature and known cases of uterine prolapse during pregnancy and current evidence about prevalence, diagnosis, management, outcomes, and complications of uterine prolapse during pregnancy in order to inform our target audience in their clinical practice.

Incidence, characteristics, and maternal outcomes of pregnancy with uterine prolapse

BACKGROUND

Gravid uterine prolapse refers to abnormal descent of the uterus during pregnancy. It is a rare pregnancy complication and its clinical characteristics and obstetrical outcomes are not well understood.

OBJECTIVE

This study aimed to assess the national-level incidence, characteristics, and maternal outcomes of pregnancies complicated by gravid uterine prolapse.

STUDY DESIGN

This retrospective cohort study queried the Healthcare Cost and Utilization Project's National Inpatient Sample. The study population was 14,647,670 deliveries from January 2016 to December 2019. The exposure assignment was the diagnosis of uterine prolapse. The coprimary outcome measures were incidence rate, clinical and pregnancy characteristics, and delivery outcomes of patients with gravid uterine prolapse. The inverse probability of treatment weighting cohort was created to mitigate the difference in prepregnancy confounding factors, followed by adjusting for pregnancy and delivery factors.

RESULTS

The incidence of gravid uterine prolapse was 1 in 4209 deliveries (23.8 per 100,000). In a multivariable analysis, older age (≥40 years; adjusted odds ratio, 3.21; 95% confidence interval, 2.70-3.81); age from 35 to 39 years (adjusted odds ratio, 2.66; 95% confidence interval, 2.37-2.99); Black (adjusted odds ratio, 1.48; 95% confidence interval, 1.34-1.63), Asian (adjusted odds ratio, 1.45; 95% confidence interval, 1.28-1.64), and Native American (adjusted odds ratio, 2.17; 95% confidence interval, 1.63-2.88) race/ethnicity; tobacco use (adjusted odds ratio, 1.19; 95% confidence interval, 1.03-1.37); grand multiparity (adjusted odds ratio, 1.78; 95% confidence interval, 1.24-2.55); and history of pregnancy losses (adjusted odds ratio, 2.20; 95% confidence interval, 1.48-3.26) were the patient characteristics associated with increased risk of gravid uterine prolapse. Current pregnancy characteristics associated with gravid uterine prolapse included cervical insufficiency (adjusted odds ratio, 3.25; 95% confidence interval, 1.94-5.45), preterm labor (adjusted odds ratio, 1.53; 95% confidence interval, 1.18-1.97), preterm premature rupture of membranes (adjusted odds ratio, 1.40; 95% confidence interval, 1.01-1.94), and chorioamnionitis (adjusted odds ratio, 1.64; 95% confidence interval, 1.18-2.28). Delivery characteristics associated with gravid uterine prolapse included early-preterm delivery at <34 weeks' gestation (69.1 vs 32.0 per 1000; adjusted odds ratio, 1.86; 95% confidence interval, 1.34-2.59) and precipitate labor (35.2 vs 20.1; adjusted odds ratio, 1.73; 95% confidence interval, 1.22-2.44). Moreover, risks of postpartum hemorrhage (112.1 vs 44.4 per 1000; adjusted odds ratio, 2.70; 95% confidence interval, 2.20-3.32), uterine atony (32.0 vs 15.7; adjusted odds ratio, 2.10; 95% confidence interval, 1.46-3.03), uterine inversion (9.6 vs 0.3; adjusted odds ratio, 31.97; 95% confidence interval, 16.60-61.58), shock (3.2 vs 0.7; adjusted odds ratio, 4.18; 95% confidence interval, 1.41-12.40), blood product transfusion (22.4 vs 11.1; adjusted odds ratio, 2.06; 95% confidence interval, 1.34-3.18), and hysterectomy (7.5 vs 2.3; adjusted odds ratio, 3.02; 95% confidence interval, 1.40-6.51) were increased in the gravid uterine prolapse group compared with the nonprolapse group. Conversely, patients with gravid uterine prolapse were less likely to deliver via cesarean delivery compared with those without gravid uterine prolapse (200.6 vs 322.8 per 1000; adjusted odds ratio, 0.51; 95% confidence interval, 0.44-0.61).

CONCLUSION

This nationwide analysis suggests that pregnancy with gravid uterine prolapse is uncommon but associated with several high-risk pregnancy characteristics and adverse delivery outcomes.

Genome-wide association identifies seven loci for pelvic organ prolapse in Iceland and the UK Biobank

Pelvic organ prolapse (POP) is a downward descent of one or more of the pelvic organs, resulting in a protrusion of the vaginal wall and/or uterus. We performed a genome-wide association study of POP using data from Iceland and the UK Biobank, a total of 15,010 cases with hospital-based diagnosis code and 340,734 female controls, and found eight sequence variants at seven loci associating with POP (P < 5 × 10-8); seven common (minor allele frequency >5%) and one with minor allele frequency of 4.87%. Some of the variants associating with POP also associated with traits of similar pathophysiology. Of these, rs3820282, which may alter the estrogen-based regulation of WNT4, also associates with leiomyoma of uterus, gestational duration and endometriosis. Rs3791675 at EFEMP1, a gene involved in connective tissue homeostasis, also associates with hernias and carpal tunnel syndrome. Our results highlight the role of connective tissue metabolism and estrogen exposure in the etiology of POP.

Sacrospinous hysteropexy versus vaginal hysterectomy with uterosacral ligament suspension in women with uterine prolapse stage 2 or higher: observational follow-up of a multicentre randomised trial

OBJECTIVE

To evaluate the effectiveness and success of uterus preserving sacrospinous hysteropexy as an alternative to vaginal hysterectomy with uterosacral ligament suspension in the surgical treatment of uterine prolapse five years after surgery.

DESIGN

Observational follow-up of SAVE U (sacrospinous fixation versus vaginal hysterectomy in treatment of uterine prolapse ≥2) randomised controlled trial.

SETTING

Four non-university teaching hospitals, the Netherlands.

PARTICIPANTS

204 of 208 healthy women in the initial trial (2009-12) with uterine prolapse stage 2 or higher requiring surgery and no history of pelvic floor surgery who had been randomised to sacrospinous hysteropexy or vaginal hysterectomy with uterosacral ligament suspension. The women were followed annually for five years after surgery. This extended trial reports the results at five years.

MAIN OUTCOME MEASURES

Prespecified primary outcome evaluated at five year follow-up was recurrent prolapse of the uterus or vaginal vault (apical compartment) stage 2 or higher evaluated by pelvic organ prolapse quantification system in combination with bothersome bulge symptoms or repeat surgery for recurrent apical prolapse. Secondary outcomes were overall anatomical failure (recurrent prolapse stage 2 or higher in apical, anterior, or posterior compartment), composite outcome of success (defined as no prolapse beyond the hymen, no bothersome bulge symptoms, and no repeat surgery or pessary use for recurrent prolapse), functional outcome, quality of life, repeat surgery, and sexual functioning.

RESULTS

At five years, surgical failure of the apical compartment with bothersome bulge symptoms or repeat surgery occurred in one woman (1%) after sacrospinous hysteropexy compared with eight women (7.8%) after vaginal hysterectomy with uterosacral ligament suspension (difference-6.7%, 95% confidence interval -12.8% to-0.7%). A statistically significant difference was found in composite outcome of success between sacrospinous hysteropexy and vaginal hysterectomy (89/102 (87%) v 77/102 (76%). The other secondary outcomes did not differ. Time-to-event analysis at five years showed no differences between the interventions.

CONCLUSIONS

At five year follow-up significantly less anatomical recurrences of the apical compartment with bothersome bulge symptoms or repeat surgery were found after sacrospinous hysteropexy compared with vaginal hysterectomy with uterosacral ligament suspension. After hysteropexy a higher proportion of women had a composite outcome of success. Time-to-event analysis showed no differences in outcomes between the procedures.

TRIAL REGISTRATION

trialregister.nl NTR1866.

[Clinical and paraclinical examination in genital prolapses]

The clinical evaluation of a prolapse has several components: a precise interrogation, a careful clinical examination, the evaluation of its maintenance on the quality of life. It must take into account the urinary, genital and anorectal spheres. From this clinical evaluation will depend the choice and interpretation of paraclinical investigations that may be requested. But the complementary examinations must never replace the interrogation and the clinical examination. Only symptomatic genital prolapses should be treated.

Spontaneously resolved uterine prolapse in a neonate with spina bifida

Yapıcıoğlu Yıldızdaş H, Ece Ü, Bilen Yurdakul G, Kolağasıgil E. Spontaneously resolved uterine prolapse in a neonate with spina bifida. Turk J Pediatr 2019; 61: 979-981. Neonatal uterine prolapse is rare and mostly due to spina bifida. It is probably due to abnormal innervation of levator ani and subsequent atrophy of the muscle in patients with spina bifida. Here we report a newborn patient with uterine prolapse after meningomyelocele operation. Foley catheter was used to manage uterine prolapse, however rectal prolapse occurred and catheter was pulled out. She was followed in an outpatient clinic without any management. She is now seven months old and had no uterine prolapse since the age of two months.

Relationship of degree of uterine prolapse between pelvic examination in lithotomy position with cervical traction and pelvic examination in standing position

INTRODUCTION AND HYPOTHESIS

The Pelvic Organ Prolapse Quantification (POP-Q) assessment is a standardized tool for evaluating pelvic organ prolapse (POP). However, intraoperative evaluation reveals greater apical prolapse than do POP-Q scores. There is a need to implement a method for performing POP-Q at the outpatient clinic that reveals maximal prolapse and causes the least pain. This study was performed to compare the degree of uterine prolapse between POP-Q with cervical traction and POP-Q in the standing position. Secondary objectives were to compare pain and acceptability scores between the two examinations.

METHODS

Women with uterine prolapse stage I or II by routine examination were invited to participate. Comparison of degree of uterine prolapse, POP-Q stages, acceptability score, and pain score between the two types of examinations were undertaken.

RESULTS

Seventy-eight participants were recruited. The median point C in routine POP-Q examination was -5 (-9 to +1), -0.5 (-3 to +4) with cervical traction, and -4 (-7 to +2) in the standing position. When examined with cervical traction, 61.5% women were upstaged by one and 9.0% by two compared with examination in the standing position; 39.7% reported visual analog scale (VAS) pain scores of ≥5 under examination with traction, but only 2.6% reported that level of pain in the standing position. There was no significant difference in acceptability scores between groups.

CONCLUSION

In an outpatient clinic setting, POP-Q examination with cervical traction revealed maximal prolapse at an acceptable level of pain. Accordingly, this method is recommended for POP-Q examination.

Admixture mapping of pelvic organ prolapse in African Americans from the Women's Health Initiative Hormone Therapy trial

Evidence suggests European American (EA) women have two- to five-fold increased odds of having pelvic organ prolapse (POP) when compared with African American (AA) women. However, the role of genetic ancestry in relation to POP risk is not clear. Here we evaluate the association between genetic ancestry and POP in AA women from the Women’s Health Initiative Hormone Therapy trial. Women with grade 1 or higher classification, and grade 2 or higher classification for uterine prolapse, cystocele or rectocele at baseline or during follow-up were considered to have any POP (N = 805) and moderate/severe POP (N = 156), respectively. Women with at least two pelvic exams with no indication for POP served as controls (N = 344). We performed case-only, and case-control admixture-mapping analyses using multiple logistic regression while adjusting for age, BMI, parity and global ancestry. We evaluated the association between global ancestry and POP using multiple logistic regression. European ancestry at the individual level was not associated with POP risk. Case-only and case-control local ancestry analyses identified two ancestry-specific loci that may be associated with POP. One locus (Chromosome 15q26.2) achieved empirically-estimated statistical significance and was associated with decreased POP odds (considering grade ≥2 POP) with each unit increase in European ancestry (OR: 0.35; 95% CI: 0.30, 0.57; p-value = 1.48x10^-5). This region includes RGMA, a potent regulator of the BMP family of genes. The second locus (Chromosome 1q42.1-q42.3) was associated with increased POP odds with each unit increase in European ancestry (Odds ratio [OR]: 1.69; 95% confidence interval [CI]: 1.28, 2.22; p-value = 1.93x10^-4). Although this region did not reach statistical significance after considering multiple comparisons, it includes potentially relevant genes including TBCE, and ACTA1. Unique non-overlapping European and African ancestry-specific susceptibility loci may be associated with increased POP risk.

Two parallel, pragmatic, UK multicentre, randomised controlled trials comparing surgical options for upper compartment (vault or uterine) pelvic organ prolapse (the VUE Study): study protocol for a randomised controlled trial

BACKGROUND

One in three women who have a prolapse operation will go on to have another operation, though not necessarily in the same compartment. Surgery can result in greater impairment of quality of life than the original prolapse itself (such as the development of new-onset urinary incontinence, or prolapse at a different site). Anterior and posterior prolapse surgery is most common (90 % of operations), but around 43 % of women also have a uterine (34 %) or vault (9 %) procedure at the same time. There is not enough evidence from randomised controlled trials (RCTs) to guide management of vault or uterine prolapse. The Vault or Uterine prolapse surgery Evaluation (VUE) study aims to assess the surgical management of upper compartment pelvic organ prolapse (POP) in terms of clinical effectiveness, cost-effectiveness and adverse events.

METHODS/DESIGN

VUE is two parallel, pragmatic, UK multicentre, RCTs (Uterine Trial and Vault Trial). Eligible for inclusion are women with vault or uterine prolapse: requiring a surgical procedure, suitable for randomisation and willing to be randomised. Randomisation will be computer-allocated separately for each trial, minimised on: requiring concomitant anterior and/or posterior POP surgery or not, concomitant incontinence surgery or not, age (under 60 years or 60 years and older) and surgeon. Participants will be randomly assigned, with equal probability to intervention or control arms in either the Uterine Trial or the Vault Trial. Uterine Trial participants will receive either a vaginal hysterectomy or a uterine preservation procedure. Vault Trial participants will receive either a vaginal sacrospinous fixation or an abdominal sacrocolpopexy. Participants will be followed up by postal questionnaires (6 months post surgery and 12 months post randomisation) and also reviewed in clinic 12 months post surgery. The primary outcome is the participant-reported Pelvic Organ Prolapse Symptom Score (POP-SS) at 12 months post randomisation.

DISCUSSION

Demonstrating the efficacy of vault and uterine prolapse surgeries is relevant not only to patients and clinicians but also to health care providers, both in the UK and globally.

TRIAL REGISTRATION

Current controlled trials ISRCTN86784244 (assigned 19 October 2012), and the first subject was randomly assigned on 1 May 2013.

[Method of Surgical Management of Genital Prolapse with Cervical Elongation]

Objectives

According to different authors, the percentage of genital prolapse among gynaecological diseases that require surgical correction reaches 28−38,9%. Pelvic muscle wasting is a special kind of pelvic prolapse, often leading to cervical elongation and hypertrophy. Contemporary methods of treatment for this condition have the high rate of relapse― 8,9−22%, thus urging to improve the existing techniques.

Purpose

This research was to estimate the effectiveness of novel modification of Manchester operation in comparison with classic Manchester operation in the management of pelvic prolapse with cervical elongation.

Methods

We enrolled 83 patients with pelvic prolapse and cervical elongation and divided them into two groups. In GroupI (n=47) we used the novel surgical method, supplementing original Manchester procedure with cervical stump fixation and other improvements. In GroupII we used original Manchester procedure. We compared laboratory measures as well as surgery duration, blood loss, incidence of complications, and duration of post-operational hospital stay. Patients were followed-up for 2years to estimate long-term effectiveness of surgical intervention. Statistical analysis was performed in SPSS 17.0.

Results

Surgery duration in GroupII was significantly longer (47,8±26,2 vs 57,5±35,1 minutes, p<0.05). There were no significant differences in lab tests, post-operational hospital stay (5,2±0,9 vs 7,3±1,2) and incidence of post-operational complications (3 vs 4 cases). Over the 2 years of follow-up we registered 1 case of relapse in Group I and 3 cases of relapse in Group II, thus estimating the effectiveness of surgery as 97,9 vs 91,7%, a non-significant difference. We noticed that all relapsed women had signs of systemic dysplasia of connective tissue.

Conclusion

Suggested modification of Manchester operation improves duration of surgical intervention itself, while providing a comparable level of effectiveness.

Etiopathogenic, therapeutic and histopathological aspects upon the anterior vaginal wall prolapse

The pelvine organ prolapse (POP) is a condition affecting million of women, with a major impact upon the social and professional life of the patients. According to various studies, it affects approximately 40% of the women aged over 50 years. About 10% of women with POP require a surgical procedure for POP or urinary incontinence. Our study comprised a number of 14 patients, aged between 55 and 70 years, hospitalized and treated in the Clinic of Urology within the Emergency County Hospital of Craiova, Romania, between 2011 and 2013, for second-degree cystocele. Of these, 11 (78.57%) patients had more than two natural deliveries, 10 suffered more than three abortions, and eight (57.14%) women suffered from obesity. The increase of abdominal pressure, induced by chronic coughing, constipation or hard physical work, was identified in more patients. Thus, six (42.8%) patients presented chronic bronchitis, four (28.57%) patients were smokers, eight (57.14%) patients presented chronic constipation, and 10 (71.42%) patients stated that they had performed hard physical work. The presence of effort urinary incontinence, associated to the cystocele, was found in eight (57.14%) cases. The surgical intervention consisted in the performance of a direct cystopexia with a synthetic tent, placed in a transobturatory way, in a "tension free" manner (Perigee System). The post-operatory evolution was a good one; the results after six months showed that 12 (85.71%) women were cured, two (14.29%) cases of cystocele relapsed, while in two patients there maintained the effort urinary incontinence. The histopathological examination of the anterior vaginal wall fragments, harvested during the surgical intervention, showed the presence of a chronic inflammatory infiltrate in the lamina propria of the uterine mucosa, which may cause the post-operatory relapses. We consider that the reduction of the inflammatory process through the administration of anti-inflammatory drugs could reduce the POP onset and progress.

Modified cervicopexy: a novel, less-invasive technique for Stages III and IV uterine prolapse

OBJECTIVE

To evaluate modified anterior abdominal wall cervicopexy (AWC) as a less invasive (via 3-cm minilaparotomy) and more augmented (via securing posterior vaginal wall to uterosacral ligaments) technique.

METHODS

Case series of 30 women with Stages III and IV apical uterine prolapse assessed by the pelvic organ prolapse quantification system.

RESULTS

The modified AWC procedure was performed successfully for 17 cases with Stage III uterovaginal prolapse and 13 cases with Stage IV uterovaginal prolapse. The procedure was conducted safely with no operative or postoperative complications, apart from two cases with postoperative urinary retention. Operative time ranged from 45 to 70min. Follow-up was available for 1-3 years. Overall, 27 cases were satisfied with the procedure, and three cases developed recurrence after caesarean section due to cutting the supporting sutures.

CONCLUSIONS

The modified AWC procedure is less invasive, simple and effective for Stages III and IV uterine prolapse.

Complete uterine prolapse without uterine mucosal eversion in a queen

A five-year-old female cat weighing 3 kg was presented by the owner after noticing a large pink, bilobed mass protruding through the vulva during labour. The cat was in good condition, with appropriate lactation, and the newborn kittens were nursing normally. The uterus was not reverted or invaginated at examination, and there was rupture of the mesovarium, mesometrium and uterine-vaginal connection around the cervix. Manual reduction of the prolapsed uterus was not possible because of torn ligaments. A coeliotomy was performed to remove the ovaries, and the apex of the uterine horns was passed by the vaginal route. The remaining part of the mesometrium was disconnected, and the prolapsed uterus was removed. The queen and kittens were discharged from the hospital on the second day after surgery. An unusual feature of this case is that the prolapse was complete, without eversion of any part of the uterus through a vaginal tear.

Neonatal uterine prolapse - a case report

Uterine prolapse is commonly seen in the geriatric age group. Congenital vaginouterine prolapse is a rare condition occurring in neonates and is usually associated with spinal cord malformations in about 85% of cases. Several modalities of treatment have been described for neonatal uterine prolapse. Conservative treatment in the form of simple digital reposition, use of pessary or other self-retaining device is usually sufficient to treat this condition, which is self-limiting and regressive. Here we report our first case of neonatal uterine prolapse, managed successfully with simple digital reposition.

A novel technique to measure in vivo uterine suspensory ligament stiffness

OBJECTIVE

The purpose of this study was to describe a new computer-controlled research apparatus for measuring in vivo uterine ligament force-displacement behavior and stiffness and to present pilot data for women with and without prolapse.

STUDY DESIGN

Seventeen women with varying uterine support underwent testing in the operating room (OR) after anesthetic induction. A tripod-mounted computer-controlled linear servoactuator was used to quantify force-displacement behavior of the cervix and supporting ligaments. The servoactuator applied a caudally directed force to a tenaculum at 4 mm/sec velocity until the traction force reached 17.8 N (4 lbs). Cervix location on Pelvic Organ Prolapse Quantification system (POP-Q) in the clinic, in the OR, at rest, and with minimal force (<1.1 N); maximum force (17.8 N) was recorded. Ligament "stiffness" between minimum and maximum force was calculated.

RESULTS

The mean ± SD subject age was 54.5 ± 12.7 years; parity was 2.9 ± 1.1; body mass index was 29.0 ± 4.3 kg/m(2), and POP-Q point C was -3.1 ± 3.9 cm. POP-Q point C was correlated most strongly with cervix location at maximum force (r = +0.68; P = .003) and at rest (r = +0.62; P = .009). Associations between cervix location at minimum force (r = +0.46; P = .059) and ligament stiffness (r = -0.44; P = .079) were not statistically significant. Cervix location in the OR with minimal traction lay below the lowest point found on POP-Q for 13 women.

CONCLUSION

POP-Q point C was correlated strongly with cervix location at rest and at maximum traction force; however, only 19% of the variation in POP-Q point C location was explained by ligament stiffness. The cervix location in the OR at minimal traction lay below POP-Q point C value in three-fourths of the women.

[Pelvic floor disorders from the surgeon's viewpoint]

Pelvic floor disorders present very differently with regard to symptoms and manifestation. Both diagnostic and treatment options require specific experience and an interdisciplinary approach. Diagnostic work-up is primarily based on medical history, physical examination and procto-rectoscopy. Furthermore, endosonography and perineal sonography have also gained importance. In almost all cases following these basic examinations conservative therapy options should be considered. As the interdisciplinary concept is very important, for careful diagnosis of pelvic floor disorders it became crucial to find an adequate form of treatment. Every decision for surgical therapy should not only focus on the results of previous examinations but should also consider the individual situation of each patient. In pelvic floor disorders a large variety of symptoms are confronted with a vast number of different and often highly specific procedures. The decisions on who to treat and how to treat are not only based on individual patient requests and desires but also on the experience and preference of the surgeon.