UROGYNECOLOGY DIGEST

Urogynecology digestPresented by Rhiannon Bray

Is percutaneous tibial nerve stimulation a safe and effectivelong-term treatment for overactive bladder in patients whooriginally benefited from a 12-week intervention?Kenneth M. Peters, Donna J. Carrico, Leslie S. Wooldridge,Christopher J. Miller, Scott A. MacDiarmid. PercutaneousTibial Nerve Stimulation for the Long-Term Treatment ofOveractive Bladder: 3-Year Results of the STEP Study. J Urol.2013 Jun;189(6):2194–201.

This prospective trial is a continuation of the Sham Effective-ness in Treatment of Overactive Bladder Symptoms (SUmiT)trial. Those patients who met the primary effectiveness endpoint after 12 weekly percutaneous tibial nerve stimulation(PTNS) treatments were recruited to this study. Patients werethen prescribed a 14-week tapering protocol (two PTNS treat-ments at 14-day intervals, followed by two treatments at 21-day intervals, followed by one additional treatment after28 days), followed by a personal treatment plan aimed atsustaining symptom improvement. In total, 29 patients com-pleted the 36-month protocol, receiving a median of 1.1treatments per month after the initial five treatments of thetapering protocol. Analysis using the Bayesian model, whichassumes that patients withdrawing from the study are lesslikely to have met the end point, estimated that 77 % [95 %confidence interval (CI) 64–90] of patients maintained mod-erate or marked improvement in overactive bladder symptomsat 3 years. Compared with baseline, median voids per daydecreased from 12.0 [interquartile range (IQR) 10.3–13.7] to 8.7 (IQR 7.3–11.3); voids per night decreasedfrom 2.7 (IQR 1.7–3.3) to 1.7 (IQR 1.0–2.7); urgencyincontinence episodes per day decreased from 3.3 (IQR 0.7–6.0) to 0.3 (IQR 0.0–1.0) (all p <0.0001). All quality-of-lifeparameters remained markedly improved from baselinethrough 3 years (all p <0.0001). There were no seriousadverse events related to treatment.

This reported efficacy of PTNS was previously demon-strated in randomized controlled trials, but this study suggeststhat patients with a positive response to 12-weekly PTNStreatments may expect to sustain symptom improvementthrough 3 years with an average of about one treatment per

month. The particularly strong point of the Sustained Thera-peutic Effects of Percutaneous Tibial Nerve Stimulation(STEP) study is that it offered individualisation of PTNStreatment following a fixed-schedule, 14-week tapering pro-tocol, which allowed participants to recognise the return ofOAB symptoms and thus schedule their treatments atappropriate intervals. However, the results of this studyshould be interpreted with caution, as only a small number ofpatients (n =50) were originally enrolled and just 29 complet-ed the 36-month follow-up. The group attempted to addressthis limitation with Bayesian analysis, empirically addressingthe sensitivity of the results to different assumptions for themissing responses, but it is very unlikely that any statisticalmethods can make up for such a high rate and help us drawmeaningful clinical conclusions.

What is the prevalence of pubovisceral muscle avulsion?Derpapas A, Digesu AG, Hamady M, Gallo P, Dell’Utri C,Vijaya G, Khullar V. Prevalence of pubovisceral muscle avulsionin a general gynaecology cohort: a computed tomography (CT)study. Neurourol Urodyn. 2013 Apr;32(4):359–62.

Researchers using case–control studies previously demon-strated an increased rate of levator ani muscle (LAM) defectsin women with significant prolapse. These studies do notallow an estimation of prevalence; the aim of this study wasto identify the prevalence of pubovisceral muscle (PM) avul-sion in women presenting at a university hospital fornonurogynaeocological conditions. Women were recruitedfrom the Department of Radiology when they were referredfor a computed tomography (CT) scan of the pelvis due tovarious pathologies. Participants underwent a clinical inter-view, completed the Kings Health and Prolapse Quality ofLife (P-QOL) questionnaires and had a spiral CTof the pelvis.Bilateral attachments of the PM to the pubic rami were iden-tified in the plane of minimal hiatal dimensions; in cases ofcomplete PM detachment, the levator symphysis gap (LSG)was measured. The relationship between PMmaximum thick-ness and obstetric variables was analysed using Spearman’s

# The International Urogynecological Association 2013Int Urogynecol J (2014) 25:289–290DOI 10.1007/s00192-013-2210-z

correlation test. Results from 110 women demonstrated theprevalence of PM avulsion to be 6.4 % (7/110), and LSGranged from 17.30 to 25.40 mm. The left PM was found to besignificantly thinner in parous women and those with a historyof prolonged second stage of labour.

The authors found no cases of avulsion amongst nullipa-rous women, which fits with previous studies. The prevalenceof PM avulsion demonstrated by this study is significantlylower than that previously quoted for symptomatic groupsonly. Although CT is not usually the preferred modality bywhich to identify pelvic floor muscle trauma, the authorsreport that they achieved good views of the soft tissue andbony parts by reconstructing axial images using 1-mm-thickslices without gaps. Such a difference in the prevalence ofpubovisceral muscle avulsion may be due to the use ofdifferent imaging modalities to depict the LAM, or itcould perhaps be attributed to the fact that birth-relatedinjuries result in a distortion of the pubovisceral muscle,without necessarily an avulsion. This theory is strength-ened by the demonstration of thinning of the muscle afterprotracted labour.

Do the risk factors for obstetric anal sphincter injurychange after a successful intervention programme in secondstage of labour?StedenfeldtM,Oian P,GisslerM, Blix E, Pirhonen J. Risk factorsfor obstetric anal sphincter injury after a successful multicentreinterventional programme. BJOG 2013; DOI: 10.1111/1471-0528.12274.

Following the initiation of a national strategy in Norway toreduce the number of obstetric anal sphincter injuries(OASIS), the rate dropped significantly from 4.6 % to2.0 %. The main focus of the intervention was: (1) goodcommunication with the woman, (2) adequate perineal sup-port, (3) delivery position that allowed visualisation of the

perineum, and (4) episiotomy only on indication. Followingthis significant drop in OASIS rates, the authors of this studyaimed to identify whether births associated with OASIS andthe risk profiles of the population pre- and postinterventionwere the same. A total of 40,154 deliveries were included, andwomen were analysed in five low- to high-risk groups. Theassociations of OASIS with possible risk factors were thenestimated using odds ratios (OR) obtained by logistic regres-sion analysis. The overall risk of sustaining OASIS decreasedby 59 % (OR 0.41; 95 % CI 0.36–0.46) after the intervention.The associations with obstetric risks remained generally thesame: first vaginal delivery (OR 3.84; 95 % CI 2.90–5.07),birth weight ≥4,500 g (OR 4.42; 95 % CI 2.68–7.27),forceps delivery (OR 3.54; 95 % CI 1.99–6.29) andmediolateral episiotomy (OR 0.89; 95 % CI 0.70–1.12).However, the highest reduction in OASIS (65%)was observedin the low-risk group (OR 0.35; 95% CI 0.24–0.51). A riskreduction of 57 %, 61% and 58%was demonstrated in groupswith one, two and three risk factors, respectively; interestingly,no change was observed in the group with four risk factors.

The significant reduction in OASIS rate following theNorwegian intervention programme was reported on two oc-casions. This subsequent paper aims to identify whether suchreduction would correlate with specific changes in obstetricrisk factors. Although the analysis indicated that the main riskfactors for OASIS remain virtually unchanged, interestingly,the highest rate of reduction in OASIS was noted in the low-risk group, which may highlight the significant role ofmidwifery-led care in preventing a large number of OA-SIS incidences. Overall, this paper confirms that followingan interventional programme aimed at modifying obstetricfactors, OASIS risk factors are essentially unchanged, whichcalls for careful interpretation of the results of such interven-tions before they are widely accepted in obstetric practice.

Conflicts of interest None.

R. Bray (*)Department of Urogynaecology, St Mary’s Hospital,Praed Street, London W2 1NY, UKe-mail: rhiannon.bray@imperial.nhs.uk

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