Pelvic floor trauma in childbirth

Transcription

1 Australian and New Zealand Journal of Obstetrics and Gynaecology 2013; 53: DOI: /ajo Review Article Pelvic floor trauma in childbirth Hans Peter DIETZ Sydney Medical School Nepean, University of Sydney, Penrith, New South Wales, Australia The investigation of female pelvic floor function and anatomy is moving from the fringes to the mainstream of urogynaecology and female urology, and it is becoming increasingly relevant for obstetrics. We are coming to realise that pelvic floor trauma in labour is common, usually overlooked, and a major factor in the causation of pelvic organ prolapse. Modern imaging methods such as magnetic resonance and 3D/4D ultrasound have enabled us to diagnose such trauma reliably and accurately, most commonly in the form of an avulsion of the puborectalis muscle; that is, a disconnection of the muscle from its insertion on the os pubis. Such damage to the levator muscle is macroscopically evident and can also be palpated, a skill that is available to every clinician, requiring neither investment nor specialised equipment. In this review, I will describe pelvic floor assessment by palpation and ultrasound and illustrate the commonest abnormalities and their clinical consequences. This paper will not focus on magnetic resonance imaging due to technical restrictions, cost and access issues in most jurisdictions, and because several papers have recently shown that ultrasound is at least as effective in diagnosing such trauma. Anal sphincter trauma is generally well covered in the literature and hence not subject of this review. Key words: avulsion, birth trauma, female pelvic organ prolapse, levator ani, vaginal delivery. Introduction After a hiatus of over 50 years, the topic of pelvic floor assessment is increasingly attracting attention. A majority of women who have given birth vaginally are affected by some form of pelvic floor damage. 1 3 We now know that pelvic floor trauma is much more than what we were taught to identify in delivery suite; that is, perineal and anal sphincter trauma. In about half of all women after vaginal childbirth, there is substantial alteration of functional anatomy affecting the puborectalis component of the levator ani muscle. 2 The integrity of this structure, which encloses the largest potential hernial portal in the human body, is currently the best-defined aetiological factor in the pathogenesis of prolapse. Hence, the assessment of a woman with pelvic organ prolapse is incomplete without evaluation of the levator ani. The levator ani muscle is part of the abdominal envelope and constitutes a muscular plate surrounding a central V-shaped levator hiatus, which encloses the urethra, vagina and anorectum. Its shape, size and Correspondence: Prof Hans Peter Dietz, Department of Obstetrics and Gynaecology, Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith NSW 2750 Australia. hpdietz@bigpond.com Received 12 November 2012; accepted 8 January function is a compromise between conflicting priorities. On the one hand, the abdominal organs have to be secured against the pressure differential between inside and outside and against gravity. The latter is a consequence of bipedal gait and has required unusually fast evolutionary adjustment. On the other hand, there has to be a provision for the controlled evacuation of solid and liquid wastes. To make matters worse, there are the requirements of reproduction: sexual intercourse and childbirth. The latter is a particular challenge in view of the size of the baby s head, again a consequence of rapid evolutionary progress. There is considerable confusion in the literature as regards levator ani nomenclature, with the terms pubococcygeus, pubovaginalis, puboperinealis, puboanalis, pubovisceralis, puborectalis and iliococcygeus being used with sometimes overlapping definitions. Agreement is lacking over whether all those structures are part of the levator ani, even though they are likely to all form part of one functional unit. The situation is not helped by the fact that official anatomical nomenclature is contradictory and in some cases clearly obsolete. The above-named subdivisions of the levator ani cannot currently be distinguished easily, neither clinically nor on imaging, or even on cadaver dissection. However, it seems sensible to distinguish between the structures contributing to the levator hiatus, that is, the narrowest part of the opening formed by the levator plate, and those forming the more cranial and lateral components of the levator ani. For reasons The Author The Australian and New Zealand Journal of Obstetrics and Gynaecology

2 Pelvic floor trauma of simplicity and clinical utility, and to remain in the tradition of commonly used clinical terms, the author will discuss primarily the puborectalis muscle (as the V-shaped muscle originating on the os pubis or the inferior pubic ramus and surrounding the anorectal angle posteriorly) and the iliococcygeus muscle (a thin sheet of muscle acting as a continuation of the puborectalis cranially and laterally). However, it is understood that the structure forming the hiatus will also include fibres labelled pubovaginalis, puboperinealis, puboanalis, pubovisceralis and pubococcygeus by other authors. Figure 1 shows the levator ani as seen from caudally, in a fresh cadaver on the left, and in an asymptomatic volunteer on pelvic floor 3D ultrasound on the right. The puborectalis muscle is evident as a V-shaped structure between 5 and 10 mm in thickness, anchored to the inferior pubic rami and the body of the os pubis on both sides. The Pelvic Floor in Childbirth Inevitably, the levator ani muscle plays a major role in childbirth as it is the most substantial soft tissue structure defining the dimensions and biomechanical properties of the birth canal. 4 During a vaginal delivery, it undergoes very substantial distension, varying between individuals by at least a factor of 5. 5,6 Data from muscle physiology research suggest that skeletal muscle will not stretch to more than twice its length without suffering ultrastructural or macroscopic trauma. 7 It is remarkable that in about half of all women, there is no appreciable alteration in distensibility or morphological appearance after vaginal childbirth, and we assume that this is somehow due to protective hormonal effects of pregnancy. In addition, it seems likely that the biomechanical properties of the levator ani have an effect on the progress of labour: a more elastic muscle seems to be associated with a shorter second stage of labour and possibly also with delivery mode. 8,9 Childbirth-related trauma to the puborectalis muscle was first reported in 1943, 10 with a second report from the same author 12 years later. 11 While these papers did attract some attention, they remained without any echo in the world literature until about 10 years ago. It is a pity that work on the clinical diagnosis, prevention and treatment of delivery-related trauma to the levator ani muscle was delayed by two full generations. This is despite the fact that this major form of maternal birth trauma is palpable vaginally 12,13 and occasionally visible in delivery suite in women with large vaginal tears 14 (see Fig. 2). The commonest form of macroscopic levator trauma is an avulsion, that is, a traumatic dislodgment of the puborectalis muscle from its bony insertion. There are other forms of localised or generalised morphological abnormalities, affecting both the relative thickness and/or the continuity of the levator ani both at the level of the puborectalis and of the iliococcygeus, but they seem to be less relevant for functional anatomy. 15 This is consistent with the hypothesis that the impact of levator trauma is primarily mediated through its effect on the dimensions of the hernial portal of the levator hiatus. Of course, disconnection of the structure that forms the levator hiatus has a substantial impact on its dimensions. 16 In addition, there is irreversible overdistension of the levator hiatus in more than 1/4 of all women after vaginal childbirth. 2 There is enormous interindividual variation of hiatal dimensions in nulliparae, 17 and the degree of distension required to deliver a term baby vaginally varies widely as a result. 6 It is not surprising that the hiatus is irreversibly overdistended in many women. 2 Limits of normality for hiatal distensibility have been defined both as mean + 2 standard deviations in nonpregnant nulliparae, 17 and with the help of receiver operator characteristics statistics in symptomatic women, 18 with both approaches yielding a cut-off of 25 cm. 2 Excessive distensibility of the hiatus ( ballooning ), whether as a result of childbirth or congenital, is associated with prolapse 18 and prolapse recurrence. 19 Ballooning and avulsion, while often associated, seem to be independent predictors of prolapse and prolapse recurrence. 19,20 Appearances are rarely consistent with pudendal neuropathy, which in the past was considered the main aetiological factor in pelvic floor (a) Figure 1 (a): Intact puborectalis muscle in a fresh cadaver, dissected from caudally. The vulva, mons pubis, clitoris, perineal muscles and perineum to the anus, as well as peri- and postanal skin and the fibrofatty tissue of the ischiorectal fossa have been removed to allow access to the puborectalis muscle. : The appearance of the puborectalis muscle in a rendered volume in the axial plane, using translabial 3D ultrasound The Author 221

3 H. P. Dietz Figure 2 Right-sided puborectalis avulsion after normal vaginal delivery at term. The left image shows appearances immediately after a normal vaginal delivery, with the avulsed muscle exposed by a large vaginal tear. The middle image shows a rendered volume (axial plane, translabial 3D ultrasound) three months postpartum, and the right-hand image shows magnetic resonance findings (single slice in the axial plane) at 3.5 months postpartum. With permission, from ref. 14 dysfunction. 21,22 This seems true even in women after severely obstructed labour. 23 Diagnosis by Palpation In 1943, Howard Gainey published the findings of a palpatory assessment of 1000 women delivered by him personally. 10 From his description, it is quite clear that he did detect avulsion injuries of the puborectalis. In fact, the prevalence reported by Gainey (about 20% in primiparous women) and even the preponderance of right-sided trauma agrees well with modern work using magnetic resonance imaging (MRI) 24 and pelvic floor ultrasound. 1,25 Levator avulsion (as verified by ultrasound or MRI) can certainly be diagnosed by vaginal digital palpation. 12,13,26,27 The skill requires training, but diagnosis by palpation can very likely be as valid as diagnosis by imaging. 28 Hopefully, devices for the training of digital palpation will assist with teaching in future and finally result in widespread adoption of a simple examination technique first proposed about 70 years ago. Until recently, assessment of levator function was limited to grading muscle strength and endurance, using the modified Oxford grading system first suggested by Laycock, 29 see Table 1. Physiotherapists have long been pioneers in this field. Mantle 30 noted that with training and experience, a physiotherapist might be able to discern muscle integrity, scarring and the width between the medial borders of the pelvic floor muscles (PFMs), with palpation. However, the first physiotherapy study on the detection of avulsion was only published in Figures 3 and 4 cover the assessment of the puborectalis muscle by palpation. The index finger is placed parallel to the urethra, with the tip of the finger at the bladder neck, and its palmar surface adjacent to the posterior/dorsal surface of the os pubis. An intact muscle leaves just enough room to fit the palpating finger between urethra medially and insertion of the puborectalis muscle laterally. If there is no muscle palpable on the os pubis and its inferior ramus immediately lateral to a finger Table 1 Modified Oxford grading (Adapted from Ref. 29 with permission) 0: No contraction 1: Flicker 2: Weak 3: Moderate (with lift) 4: Good (with lift) 5: Strong (with lift) placed parallel to the urethra, and if this finger can be moved over the inferior pubic ramus without encountering muscle for 2 3 cm, then a diagnosis of levator avulsion is made. Poor contraction strength can help alert the examiner to an increased likelihood of avulsion, 27 and there are a number of other predictors that can serve the same purpose. 32 Avulsion often causes marked asymmetry of the hiatus, 33 and sometimes this asymmetry is evident even on clinical inspection. On Valsalva, the anus and perineum are displaced towards the healthy side, pushed by a prolapse descending on the avulsed side. On PFM contraction, perineum and anus are pulled by the contralateral intact muscle, again resulting in displacement towards the healthy, undamaged side. The extent of avulsion varies greatly: there are several types of incomplete injuries such as generalised thinning of the muscle, partial avulsion of the most inferior aspects or more cranial aspects of the muscle, palpable as a hole, slit or gap in the continuity of the structure. The author proposes a visual recording system for findings obtained on palpation of the puborectalis muscle (see Fig. 4). Such a system should include both some form of strength grading for squeeze and lift bilaterally, as well as grading for resting tone (conveniently graded 0 5 to accord with the Oxford system, see Table 2 for a suggested scale). Morphological findings could be documented either as defects or gaps (black and dark grey areas on the muscle diagram) or thinning (light grey). Such a documentation system could form the basis of teaching efforts to improve The Author

4 Pelvic floor trauma Table 2 A proposed scale for the grading of levator resting tone Figure 3 Digital palpation of the puborectalis muscle insertion. The left image shows a normal muscle, the right an avulsion injury. With permission, from ref. 12 0: Muscle not palpable 1: Muscle palpable but very flaccid, wide hiatus, minimal resistance to distension 2: Hiatus wide but some resistance to distension 3: Hiatus fairly narrow, fair resistance to palpation but easily distended 4: Hiatus narrow, muscle can be distended but high resistance to distension, or pain 5: Hiatus very narrow, no distension possible, woody feel, possibly with pain: vaginismus on our palpatory assessment skills and would allow easier communication amongst clinical practitioners and researchers. Diagnosis by Ultrasound Imaging Figure 4 Suggested schematic for the documentation of puborectalis trauma, modified Oxford grading and grading of resting tone. With permission, from ref. 12 (a) Figure 5 A comparison of ultrasound findings in a normal patient (a) and in a patient with a typical right-sided avulsion in a rendered volume, axial plane, indicated by a *. It is evident that the morphological abnormality documented here is an avulsion of the puborectalis muscle insertion, that is, the muscle has separated from its bony insertion. It seems that the diagnosis of levator trauma is more repeatable when undertaken with the help of imaging. While MRI was historically the first method used to assess the levator ani, 34 it suffers from a number of shortcomings: cost, accessibility, the inability to use the technique in women with ferrous implants, issues with claustrophobia, the lack of dynamic imaging capability and problems with defining correct planes. Most of those shortcomings do not apply to ultrasound, especially not to translabial 3D/4D ultrasound. The latter technology was developed for prenatal diagnosis and is now commonly available. While transvaginal ultrasound has been used to image the levator ani, 9,35,36 this requires side-firing endoprobes that are mostly obsolete and now rarely found in OB/GYN imaging departments. The diagnosis of levator trauma by transperineal (or perineal, or introital) ultrasound was first demonstrated in on rendered volumes, that is, semi-transparent representations of blocks of volume ultrasound data (see Fig. 5), using Voluson- type systems and 3D/4D curved array abdominal volume transducers, a technology developed for fetal imaging. Acceptable quality can be obtained with acquisition angles of up to 85 degrees, encompassing the entire levator hiatus even on maximal Valsalva in a patient with severe prolapse, and at a volume frequency of about 2 Hz. At lower acquisition angles up to 20 Hz can be reached. Hence, temporal resolution in any plane is superior to MR, while spatial resolution of structures within the levator hiatus up to about 4 cm depth is comparable to MR. Modern 3D ultrasound systems commonly allow tomographic imaging, that is, serial cross-sections at arbitrarily variable interslice intervals and angles. Diagnosis by tomographic ultrasound is probably currently the most repeatable technique 38 and has been shown to be comparable to MRI in the diagnosis of levator trauma Figure 6 shows identification of the plane of minimal dimensions of the levator hiatus as reference plane, and Figure 7 demonstrates a tomographic representation of the 2013 The Author 223

5 H. P. Dietz (a) Figure 6 Identification of the plane of minimal hiatal dimensions in an oblique axial plane as identified in the midsagittal plane (a). This plane, while not always sufficient to diagnose avulsion injury, defines the levator hiatus, is used to determine hiatal dimensions and distensibility and serves as a convenient reference plane for tomographic ultrasound imaging. From ref. 90, with permission. entire puborectalis muscle, based on this plane. Tomographic ultrasound is probably best performed by bracketing the area of interest, with the lowermost slice just below the insertion of the puborectalis muscle 42 as shown in Figure 7. This technique is very likely to include the entire puborectalis muscle. 43 Mathematical modelling has been used to define minimal criteria for the diagnosis of avulsion on tomographic imaging, which requires at least the three central slices (plane of minimal dimensions and planes 2.5 and 5 mm cranial) to be abnormal on both sides. The levator urethra gap, that is, the distance between the centre of the urethra and the insertion of the puborectalis, can be used as an adjunct: measurements over 2.5 cm are defined as abnormal. 44 The technique seems valid and sufficiently robust for clinical use, with a low likelihood of false positive results. 45 Avulsion can even be diagnosed with 2D ultrasound, using commonly available abdominal curved array transducers placed in an oblique parasagittal plane (see Fig. 8). However, because there is no obvious point of reference, it is more difficult to be certain of a complete avulsion, and repeatability may be inferior. 46 Regardless of which imaging method is used, palpation and imaging are best seen as complementary. The palpating finger provides biomechanical information on tone and contractility that is not available on imaging. On the other hand, imaging information is more objective and reproducible, and it provides information on deeper structures that are not accessible on palpation. In general, it is safe to assume that vision, as our primary and most developed sense, is easier and faster to train than other senses such as palpation. Risk Factors While about 10 30% of women will suffer macroscopic levator trauma, 1,2,47 52 there is an even greater number that sustain what has been termed microtrauma, that is, irreversible overdistension of the levator hiatus. The predictors of microtrauma may vary from those that predict levator avulsion. 2 It is not yet clear what the long- Figure 7 Assessment of the puborectalis muscle by tomographic or multislice ultrasound. The top left hand image (0) represents a reference image in the coronal plane. Images 1 8 show slices parallel to the plane of minimal hiatal dimensions. Slices 1 and 2 are 5 and 2.5 mm below this plane, slice 3 represents the plane of minimal dimensions, and slices 4 8 are mm above this plane, likely encompassing the entire insertion of the puborectalis. Slice 1 is clearly below the muscle insertion, guaranteeing that the area of interest is imaged in its entirety. From ref. 15, with permission The Author

6 Pelvic floor trauma (a) (c) Figure 8 2D parasagittal oblique views of the puborectalis muscle obtained by translabial ultrasound (a) showing an avulsion on the patient s right, marked by a *, an intact muscle on the patient s left). Image (c) shows a tomographic representation of the puborectalis muscle in the same patient, with the avulsion evident in most slices (marked by *). From ref. 91, with permission. (a) Figure 9 The effect of levator avulsion on hiatal dimensions: Antepartum and postpartum ultrasound images (single slice axial planes in the plane of minimal hiatal dimensions) of a patient with left sided avulsion after Forceps delivery. The hiatal area on maximum Valsalva at 38 weeks (on the left, image a) was 15.6 cm 2. It was measured at 29.3 cm 2 at 4 months postpartum (image b). Figure 10 The relationship between age at first delivery and levator avulsion. From ref. 57, with permission. term impact of such morphological and functional changes is, but neither ongoing deterioration nor healing is likely to be common. 53 It is likely that factors such as birthweight, length of second stage, size of the fetal head and forceps delivery increase the probability of avulsion injury. 1,2,47 52,54 Figure 9 demonstrates a case of hiatal enlargement and asymmetry due to avulsion after forceps. The clear association between forceps delivery and avulsion suggests that primary forceps should probably be regarded as obsolete. However, such predictors are of limited use in clinical practice because they are not available prior to the onset of labour. To reliably prevent levator avulsion converting forceps to vacuum deliveries would not be enough. We would need predictors that can be determined during pregnancy. It is plausible that the risk of trauma to the insertion of the puborectalis muscle will depend not just on the required distension, but also on the biomechanical properties of muscle and muscle bone interface, which are hitherto undefined. It is not surprising that, in some studies, avulsion seems associated with maternal age at first delivery. 1,55,56 The likelihood of major levator trauma at vaginal delivery more than triples during the reproductive years from under 15% at age 20 to over 50% at 40 (Fig. 10). Finally, there is some evidence suggesting that it is usually the first vaginal delivery that causes by far the most morphological and functional alteration, both in terms of actual tears as well as in terms of levator distensibility or pelvic organ support Consequences of Levator Trauma It is not surprising that traumatic disconnection of the levator ani from its insertion has substantial consequences for function. Contraction strength as estimated by Oxford grading 27 and instrumented speculum 61 is reduced by about 1/3, an observation that may help diagnose levator trauma. Avulsion results in a hiatus that is larger (by The Author 225

7 H. P. Dietz 30%), especially in the coronal plane 62 more distensible and less contractile. 61,63 Most importantly, avulsion is associated with symptoms and signs of prolapse. 13,27 Women seem to notice the effect of avulsion as a reduction in contraction strength on PFM contraction 64 and as increased vaginal laxity and reduced tone on intercourse. 65 Figure 9 shows the effect of avulsion on hiatal dimensions in a patient after forceps delivery at term, a fairly typical situation in modern obstetrics that remains unnoticed in most units. Prolapse Levator avulsion is associated with anterior and central compartment prolapse and likely represents at least part of the missing link between childbirth and prolapse. 66 The larger a defect is, both in width and depth, the more likely are symptoms and/or signs of prolapse. 38 Figure 11 shows typical findings in a patient with bilateral avulsion, marked hiatal ballooning and a third degree cystocele. There seems to be less of an effect on posterior compartment descent, although a link between rectal intussusception and avulsion has recently been demonstrated. 67 The effect of avulsion on prolapse seems largely independent of ballooning 20 or abnormal distensibility of the levator hiatus, which also is associated with prolapse. 18 It is not clear as to why it frequently takes decades for symptoms to develop, although DeLancey s ship in dock hypothesis provides a plausible explanation. 68 It should also be mentioned that there are many women who present with prolapse without having suffered an avulsion injury. There are other deleterious effects of childbirth on the levator, resulting in traumatic, irreversible overdistension, 69 and then, there are young nulliparous women who show evidence of abnormal hiatal distensibility and pelvic organ descent that is very likely congenital. 17 The most important issue for clinical practice is that both avulsion and ballooning seem to be risk factors for prolapse recurrence both on ultrasound and on MRI. 74 This implies that such findings should be obtained preoperatively and are likely to be useful for surgical (a) Figure 11 Typical findings in a patient with a third degree cystocele (indicated with a C in image (a)), bilateral avulsion and marked hiatal ballooning, the latter visible in the axial plane in, with a dotted line illustrating the hiatus. A, anal canal; C, cystocele; R, rectal ampulla, S, symphysis pubis; U, uterus. planning. Diagnosing levator avulsion and/or hiatal ballooning may not require imaging. Both avulsion[20] and ballooning (via genital hiatus (gh) and perineal body (pb) measurements included in the ICS POP-Q system) can be diagnosed clinically, and we have determined a cut-off of 7 cm for the sum of gh and pb to define ballooning clinically. 75,76 It is likely that levator avulsion and ballooning can be used to select patients for mesh surgery, especially in the anterior compartment. Any randomised controlled trial of mesh use that does not allow for a proper diagnostic work-up prior to implantation, or at least an assessment for avulsion at some time point during the trial follow-up, risks wasting large amounts of resources. Once it is possible to identify patients who are at increased risk of recurrence, trials ought to first be performed in that patient group, and the power of a study of given size would be markedly enhanced as a result. It appears that the effect of anterior compartment mesh on recurrence is much more marked in those with avulsion, that is, those at high risk of recurrence. 19,77 Urinary Incontinence It is generally assumed that urinary incontinence is a sign of a weak pelvic floor. This may be a misconception. There is some evidence that major levator avulsion defects may be negatively associated with stress urinary incontinence and urodynamic stress incontinence, 78,79 a highly counterintuitive finding. How then can we account for the fact that PFM training is a recognised and proven therapeutic intervention in women with stress urinary incontinence? 80 If the puborectalis muscle is part of the urinary continence mechanism, should not it matter if this muscle is disconnected from the inferior pubic ramus? One should point out that the therapeutic success of PFM training does not prove a role of the puborectalis muscle in stress urinary continence. The intervention affects not just the puborectalis muscle but likely trains all muscle innervated by the second to fourth sacral segments. In addition, there are other potential mechanisms by which childbirth might affect urinary continence. Denervation is one candidate, 22 damage to the urethral rhabdosphincter or the longitudinal smooth muscle of the urethra may be another. And finally, there is the issue of pressure transmission, likely mediated through the pubourethral ligaments and/or suburethral tissues. Faecal Incontinence Another major clinical symptom that has been attributed to an abnormal puborectalis muscle is faecal incontinence. Some investigators have found no significant association between this symptom and levator trauma; 81,82 others have identified levator avulsion as an independent risk factor for faecal incontinence after primary obstetric anal sphincter tear repair. 83 On balance, it appears unlikely that any intervention The Author

8 Pelvic floor trauma targeting levator dimensions or function would have a major impact on faecal continence. Any improvement in symptoms is more likely to be due to other associated therapeutic effects. Sexual Function The puborectalis muscle is the main determinant of intravaginal pressures 4 and has been termed the love muscle in the popular press. It is not surprising that women notice the effect of avulsion on PFM strength 64 and sexual function. The latter seems to primarily manifest as reduced tone and vaginal laxity. 65 Considering the popularity of cosmetic genitoplasty procedures aimed at tightening the vagina, this may become an important consideration in the future. Clinical Repercussions Abnormal function or morphology of the levator ani muscle clearly has an effect on recurrence risk after pelvic reconstructive surgery. A number of authors have found that avulsion at least doubles the risk of recurrence after anterior colporrhaphy, and this effect is evident as early as 6 weeks after surgery. 74 It appears that the increased recurrence risk conveyed by avulsion can largely be compensated for by anterior compartment anchored mesh, 19 which in some women implies a halving of recurrence rates, see Figure 12. To date, patient selection has played a very small role in the increasingly acrimonious discussion regarding the use of mesh implants in reconstructive surgery. This is likely to change once clinicians learn to diagnose levator trauma and hiatal ballooning, that is, to identify patients at high risk of recurrence. In the opinion of the author, it makes little sense to perform a traditional anterior repair in women with bilateral avulsion because such a procedure is very likely to fail. Prediction One approach to reducing the incidence of levator trauma in childbirth would be to consider preventative intervention in women identified to be at high risk of avulsion or irreversible overdistension of the levator. At this point in time, such risk assessment does not appear to be feasible, but the potential benefits of such an approach should make this a high priority for research. The only currently documented prelabour risk factor is maternal age at first delivery. 1,55,56 Other factors such as body mass index, ethnicity and pelvic floor biomechanical properties, are currently being investigated. Computer modelling has been used by a number of units to investigate pelvic organ support and pelvic floor dysfunction. While such modelling has enabled important insights into mechanisms of trauma, 5 significant progress is unlikely until input variables are sufficiently well defined, rather than estimated. To date, there is very little information on boundary conditions and the material properties of bone, muscle and their interface at present. Data on a few individuals, whether obtained in vivo or in cadavers, are unlikely to illustrate the degree to which static and dynamic dimensions of the levator hiatus can vary between individuals. 84 For the time being, it seems that computer modelling is unlikely to be relevant for clinical practice or for research until biomechanical properties of the levator hiatus are better defined. Equally, modelling is unlikely to play a role in the prediction of trauma for the foreseeable future. Prevention Because levator avulsion is exclusively caused by vaginal childbirth, elective caesarean section (C/S) can be expected to completely prevent both avulsion and irreversible overdistension of the puborectalis muscle. In view of the ever-increasing caesarean section rate, it is possible that pelvic floor trauma will cease to be much of an issue within a generation or two. However, at present a policy of universal caesarean section is clearly neither affordable nor politically feasible even in the most affluent countries on earth. Quite apart from resource issues, C/S has substantial disadvantages, both for mother and infant, which are beyond the scope of this review. Other forms of prevention may be more practicable, such as attempts to change the biomechanical properties of the levator hiatus. There is a commercially available device, the Epi-No TM, that is used to dilate the perineum and vagina in the last few weeks of pregnancy, and this device has been shown to reduce perineal trauma. 85 The Epi-No is currently under investigation regarding a potential role in pelvic floor protection in the unit of the author, and results of a (a) Probability Avulsion, no mesh Avulsion, mesh Hiatal area on Valsalva 70 Probability No avulsion, no mesh No avulsion, mesh Hiatal area on Valsalva 70 Figure 12 Risk of prolapse recurrence at 2.5 years after anterior colporrhaphy +/ mesh (n = 334) in women with (a) and without avulsion relative to hiatal area and use of anchored anterior compartment mesh. From ref. 19, with permission 2013 The Author 227

9 H. P. Dietz pilot study are promising. 86 There are several other interventions that could be tested for a potential protective role. Because the degree of trauma sustained by skeletal muscle on stretching is directly proportional to the amount of work needed to elongate the muscle, 7 it seems reasonable to expect that muscle paralysis (via a pudendal nerve block or a dense epidural) could affect a reduction in trauma. We are about to commence a pilot randomised controlled trial to test such a hypothesis. Treatment There have been several reports of intrapartum 14 and interval reconstruction 87,88 of levator defects, none of them very promising. Immediately after childbirth, the levator ani is massively overdistended, and splinting of a reconstructed muscle appears to be impossible. Hence, the creation of a mechanically durable repair seems a major challenge. In symptomatic women seen later in life, frank avulsion is frequently not the only problem encountered by the pelvic reconstructive surgeon. Incomplete contralateral trauma and irreversible overdistension frequently coexists with complete avulsion, reducing the effect of avulsion repair on the levator hiatus. In a series of 17 patients, we have been able to reduce the levator hiatus by about 20%, which seems to have a rather limited effect on prolapse recurrence. 88 It may be necessary to develop more global means of reducing the hernial portal, that is, the levator hiatus, and first attempts have proven more promising. 89 Conclusions Urogynaecology is undergoing a period of rapid change and development. This is not without pain, as evidenced by the discussions surrounding mesh use in reconstructive pelvic surgery. However, there also is enormous opportunity, mainly centred around functional imaging and the issue of childbirth-related pelvic floor trauma. The latter is a very interesting case of arrested development. As early as the 1940s, our predecessors had the opportunity to identify the major aetiological factor behind female pelvic organ prolapse, to diagnose it clinically, and to develop therapeutic and preventative approaches. This opportunity was missed, which is why these tasks are now for our generation to accomplish. Pelvic floor trauma in the form of puborectalis avulsion can be diagnosed by digital palpation, and overdistension of the levator hiatus ( ballooning ) is assessed clinically by determining the distance between external urethral meatus and anus on Valsalva. Imaging will play a major role in the confirmation and quantification of trauma and functional impairment, and 4D ultrasound is clearly superior to MRI in this task. Tomographic or multislice imaging is in the process of becoming the standard for assessment of the levator ani. Once diagnosis is established, we have the opportunity to investigate means of treatment or compensatory interventions, which is already well underway at several centres. Finally, we will learn how to prevent such trauma, most likely by modifying the biomechanical properties of the tissues at risk, either during the antepartum period or during the first stage of labour. At the moment, only about one-third of all first-time mothers in the developed world are able to deliver their baby via the vaginal route without suffering substantial maternal birth trauma in the process. Hopefully, this percentage will grow rather than shrink over the coming decades. Conflict of interest HP Dietz has in the past acted as a consultant for American Medical Systems (AMS), Materna Inc. and Continence Control Systems (CCS), has accepted Speaker s fees from General Electric (GE), AMS and Astellas, has benefited from equipment loans provided by GE, Bruel and Kjaer and Toshiba and has accepted an educational grant from GE Medical. References 1 Dietz H, Lanzarone V. Levator trauma after vaginal delivery. Obstet Gynecol 2005; 106: Shek K, Dietz H. Intrapartum risk factors of levator trauma. BJOG 2010; 117: Andrews A, Sultan A, Thakar R, Jones P. Occult anal sphincter injuries myth or reality? BJOG 2006; 113: Jung S, Pretorius D, Padda B et al. Vaginal high-pressure zone assessed by dynamic 3-dimensional ultrasound images of the pelvic floor. Am J Obstet Gynecol 2007; 197: Lien KC, Mooney B, DeLancey JO, Ashton-Miller JA. Levator ani muscle stretch induced by simulated vaginal birth. Obstet Gynecol 2004; 103: Svabik K, Shek K, Dietz H. How much does the levator hiatus have to stretch during childbirth? BJOG 2009; 116: Brooks S, Zerba E, Faulkner J. Injury to muscle fibres after single stretches of passive and maximally stimulated muscle in mice. J Physiol 1995; 488: Lanzarone V, Dietz H. 3 Dimensional ultrasound imaging of the levator hiatus in late pregnancy associations with delivery outcomes. Aust N Z J Obstet Gynaecol 2007; 47: Balmforth J, Toosz-Hobson P, Cardozo L. Ask not what childbirth can do to your pelvic floor but what your pelvic floor can do in childbirth. Neurourol Urodyn 2003; 22: Gainey HL. Post-partum observation of pelvic tissue damage. Am J Obstet Gynecol 1943; 46: Gainey HL. Postpartum observation of pelvic tissue damage: further studies. Am J Obstet Gynecol 1955; 70: Dietz HP, Shek KL. Validity and reproducibility of the digital detection of levator trauma. Int Urogynecol J 2008; 19: Kearney R, Miller JM, Delancey JO. Interrater reliability and physical examination of the pubovisceral portion of the levator ani muscle, validity comparisons using MR imaging. Neurourol Urodyn 2006; 25: Dietz H, Gillespie A, Phadke P. Avulsion of the pubovisceral muscle associated with large vaginal tear after normal vaginal delivery at term. Aust N Z J Obstet Gynaecol 2007; 47: The Author

10 Pelvic floor trauma 15 Dietz H, Bernardo M, Kirby A, Shek K. Minimal criteria for the diagnosis of avulsion of the puborectalis muscle by tomographic ultrasound. Int Urogynecol J 2011; 22: Abdool Z, Shek K, Dietz H. The effect of levator avulsion on hiatal dimensions and function. Am J Obstet Gynecol 2009; 201 (1): 89.e Dietz H, Shek K, Clarke B. Biometry of the pubovisceral muscle and levator hiatus by three-dimensional pelvic floor ultrasound. Ultrasound Obstet Gynecol 2005; 25: Dietz H, De LeonJ, Shek K. Ballooning of the levator hiatus. Ultrasound Obstet Gynecol 2008; 31: Rodrigo N, Shek K, Wong V et al. Hiatal ballooning is an independent risk factor of prolapse recurrence. Int Urogynecol J 2012; 23: S 129 S Dietz H, Franco A, Shek K, Kirby A. Avulsion injury and levator hiatal ballooning: two independent risk factors for prolapse? An observational study. Acta Obstet Gynecol Scand 2012; 91: Swash M, Snooks SJ, Henry MM. Unifying concept of pelvic floor disorders and incontinence. J R Soc Med 1985; 78: Allen RE, Hosker GL, Smith AR, Warrell DW. Pelvic floor damage and childbirth: a neurophysiological study. Br J Obstet Gynaecol 1990; 97: Dietz H, Habtemariam T, Williams G. Does obstructed labour in women with urogenital fistula lead to atrophy of the levator ani muscle? J Urol 2012; 188: DeLancey JO, Kearney R, Chou Q et al. The appearance of levator ani muscle abnormalities in magnetic resonance images after vaginal delivery. Obstet Gynecol 2003; 101: Dietz HP, Steensma AB. The prevalence of major abnormalities of the levator ani in urogynaecological patients. BJOG 2006; 113: Dietz HP, Hyland G, Hay-Smith J. The assessment of levator trauma: a comparison between palpation and 4D pelvic floor ultrasound. Neurourol Urodyn 2006; 25: Dietz HP, Shek C. Levator avulsion and grading of pelvic floor muscle strength. Int Urogynecol J 2008; 19: Dietz H, Moegni F, Shek K. Diagnosis of levator avulsion injury: a comparison of three methods. Ultrasound Obstet Gynecol 2012; 40: Laycock J. Assessment and treatment of pelvic floor dysfunction. Thesis, Postgraduate School of Biomedical Sciences. Bradford: University of Bradford, Mantle J. Urinary function and dysfunction. In: Mantle J, Haslam J, Barton S, eds. Physiotherapy in Obstetrics and Gynaecology. Edinburgh: Butterworth Heinemann, Kruger J, Dietz H, Botelho C, Dumoulin C. Can we feel with our fingers as well as we see with ultrasound? Int Urogynecol J 2010; 21: S372 S Dietz H, Kirby A. Modelling the likelihood of levator avulsion in a urogynaecological population. Aust N Z J Obstet Gynaecol 2010; 50: Dietz H, Bhalla R, Chantarasorn V, Shek K. Avulsion of the puborectalis muscle causes asymmetry of the levator hiatus. Ultrasound Obstet Gynecol 2011; 37: Debus-Thiede G. Magnetic resonance imaging (MRI) of the pelvic floor. In: Schuessler B, Laycock J, Norton P, Stanton SL, eds. Pelvic Floor Reeducation Principles and Practice. London: Springer, Toosz-Hobson P, Athanasiou S, Khullar V et al. Does vaginal delivery damage the pelvic floor? Neurourol Urodyn 1997; 16: Athanasiou S, Chaliha C, Toozs-Hobson P et al. Direct imaging of the pelvic floor muscles using two-dimensional ultrasound: a comparison of women with urogenital prolapse versus controls. BJOG 2007; 114: Dietz H. Ultrasound imaging of the pelvic floor: 3D aspects. Ultrasound Obstet Gynecol 2004; 23: Dietz H. Quantification of major morphological abnormalities of the levator ani. Ultrasound Obstet Gynecol 2007; 29: Zhuang R, Song Y, Chen Q et al. Levator avulsion using a tomographic ultrasound and magnetic resonance-based model. Am J Obstet Gynecol 2011; 205 (3): 232.e Notten K, Weemhoff M, Schweitzer K et al. Diagnosing levator defects on 3D transperineal ultrasound compared to MR imaging. Ultrasound Obstet Gynecol 2012; 40 (S1): Vergeldt T, Weemhoff M. Comparison of two scoring systems for diagnosing levator ani muscle damage. Ultrasound Obstet Gynecol 2012; 40 (S1): Dietz HP, Shek K. Tomographic ultrasound of the pelvic floor: which levels matter most? Ultrasound Obstet Gynecol 2009; 33: Kashihara H, Shek K, Dietz H. Can we identify the limits of the puborectalis/pubovisceralis muscle on tomographic translabial ultrasound? Ultrasound Obstet Gynecol 2012; 40: Dietz H, Abbu A, Shek K. The levator urethral gap measurement: a more objective means of determining levator avulsion? Ultrasound Obstet Gynecol 2008; 32: Adisuroso T, Shek K, Dietz H. Tomographic imaging of the pelvic floor in nulliparous women: limits of normality. Ultrasound Obstet Gynecol 2012; 39: Dietz H, Shek K. Can 2D translabial ultrasound be used to diagnose levator avulsion? Int Urogynecol J 2008; 19: S163 S Krofta L, Otcenasek M, Kasikova E, Feyereisl J. Pubococcygeus-puborec talis trauma after forceps delivery: evaluation of the levator ani muscle with 3D/4D ultrasound. Int Urogynecol J 2009; 20: Albrich S, Laterza R, Skala C et al. Impact of mode of delivery on levator morphology: a prospective observational study with 3D ultrasound early in the postpartum period. BJOG 2012; 119: Valsky DV, Lipschuetz M, Bord A et al. Fetal head circumference and length of second stage of labor are risk factors for levator ani muscle injury, diagnosed by 3-dimensional transperineal ultrasound in primiparous women. Am J Obstet Gynecol 2009; 201 (1): 91.e Blasi I, Fuchs I, D Amico R et al. Intrapartum translabial three-dimensional ultrasound visualization of levator trauma. Ultrasound Obstet Gynecol 2011; 37: Cassado Garriga J, Pessarodona Isern A, Espuna Pons M et al. Tridimensional sonographic anatomical changes on pelvic floor muscle according to the type of delivery. Int Urogynecol J 2011; 22: Chan S, Cheung R, Yiu A et al. Prevalence of levator ani muscle injury in Chinese primiparous women after first delivery. Ultrasound Obstet Gynecol 2012; 39: Dickie K, Shek K, Dietz H. The relationship between urethral mobility and parity. BJOG 2010; 117: The Author 229

11 H. P. Dietz 54 Shek K, Dietz H. Does levator trauma heal? Int Urogynecol J 2011; 22: S12 S Kearney R, Fitzpatrick M, Brennan S et al. Levator ani injury in primiparous women with forceps delivery for fetal distress, forceps for second stage arrest, and spontaneous delivery. Int J Gynaecol Obstet 2010; 111: Kearney R, Miller J, Ashton-Miller J, Delancey J. Obstetric factors associated with levator ani muscle injury after vaginal birth. Obstet Gynecol 2006; 107: Dietz H, Simpson J. Does delayed childbearing increase the risk of levator injury in labour? Aust N Z J Obstet Gynaecol 2007; 47: Dietz HP, Clarke B, Vancaillie TG. Vaginal childbirth and bladder neck mobility. Aust N Z J Obstet Gynaecol 2002; 42: Horak A, Guzman Rojas R, Shek K, Dietz H. Pelvic floor trauma: does the second baby matter? Int Urogynecol J 2012; 23: S175 S Kamisan Atan I, Shek KL, Gerges B, Dietz HP. The association between vaginal childbirth and hiatal dimensions. Int Urogynecol J 2012; Brisbane. 61 DeLancey J, Morgan D, Fenner D et al. Comparison of levator ani muscle defects and function in women with and without pelvic organ prolapse. Obstet Gynecol 2007; 109: Otcenasek M, Krofta L, Baca V et al. Bilateral avulsion of the puborectal muscle: magnetic resonance imaging-based threedimensional reconstruction and comparison with a model of a healthy nulliparous woman. Ultrasound Obstet Gynecol 2007; 29: Abdool Z, Shek K, Dietz H. The effect of levator avulsion on hiatal dimensions and function. Am J Obstet Gynecol 2009: 201 (1): 89.e Dietz H, Shek K, Chantarasorn V, Langer S. Do women notice the effect of childbirth-related pelvic floor trauma? Aust N Z J Obstet Gynaecol 2012; 52 (3): Thibault-Gagnon S, Yusuf S, Langer S et al. Do women notice the impact of childbirth-related tevator trauma on pelvic floor and sexual function? Int Urogynecol J 2012; 23: S183 S Dietz H, Simpson J. Levator trauma is associated with pelvic organ prolapse. BJOG 2008; 115: Rodrigo N, Shek K, Dietz H. Rectal intussusception is associated with abnormal levator structure and morphometry. Tech Coloproctol 2011; 15: DeLancey JO. Anatomy. In: Cardozo L, Staskin D, eds. Textbook of Female Urology and Urogynaecology. London, UK: Isis Medical Media, Shek K, Dietz H. The effect of vaginal childbirth on levator hiatal dimensions. Int Urogynecol J 2008; 19: S Dietz HP, Chantarasorn V, Shek KL. Levator avulsion is a risk factor for cystocele recurrence. Ultrasound Obstet Gynecol 2010; 36: Model A, Shek KL, Dietz HP. Levator defects are associated with prolapse after pelvic floor surgery. Eur J Obstet Gynecol Reprod Biol 2010; 153: Weemhoff M, Vergeldt T, Notten K et al. Avulsion of puborectalis muscle and other risk factors for cystocele recurrence: a 2-year follow-up study. Int Urogynecol J 2012; 23: Wong V, Shek K, Goh J et al. Is levator avulsion a predictor for cystocele recurrence following anterior compartment mesh? Neurourol Urodyn 2011; 30: Morgan D, Larson K, Lewicky-Gaupp C et al. Vaginal support as determined by levator ani defect status 6 weeks after primary surgery for pelvic organ prolapse. Int J Gynaecol Obstst 2011; 114: Khunda A, Shek K, Dietz H. Can ballooning of the levator hiatus be determined clinically? Am J Obstet Gynecol 2012; 206 (3): 246.e Gerges B, Kamisan Atan I, Shek K, Dietz H. How to determine ballooning of the levator hiatus on clinical examination. Int Urogynecol J 2012; 23: S52 S Wong V, Shek K, Goh J et al. Should mesh be used for cystocele repair? Long- term outcomes of a case- control series. Int Urogynecol J 2011; 22: S Dietz H, Kirby A, Shek K, Bedwell P. Does avulsion of the puborectalis muscle affect bladder function? Int Urogynecol J 2009; 20: Morgan D, Cardoza P, Guire K et al. Levator ani defect status and lower urinary tract symptoms in women with pelvic organ prolapse. Int Urogynecol J 2010; 21: Wilson PD, Hay Smith EJ, Nygaard IE et al. Adult conservative management. Vol 2. In: Abrams P, Cardozo L, Khoury S, Wein A, eds. Incontinence: Third International Consultation on Incontinence. Paris: Health Publications Ltd, Chantarasorn V, Shek K, Dietz H. Sonographic detection of puborectalis muscle avulsion is not associated with anal incontinence. Aust N Z J Obstet Gynaecol 2011; 51: van de Geest L, Steensma AB. Three-dimensional transperineal ultrasound imaging of anal sphincter injuries after surgical primary repair. Ultrasound Obstet Gynecol 2010; 36: Shek K, Guzman Rojas R, Dietz HP. Residual defects of the external anal sphincter are common after OASIS repair. Neurourol Urodyn 2012; 31: Svabik K, Shek KL, Dietz HP. How much does the puborectalis muscle have to stretch in childbirth? Ultrasound Obstet Gynecol 2009; 116: Kovacs G, Heath P, Heather C. First Australian trial of the birth-training device Epi-No: a highly significantly increased chance of an intact perineum. Aust N Z J Obstet Gynaecol 2004; 44: Shek K, Langer S, Chantarasorn V, Dietz H. Does the Epi- No device prevent levator trauma? A randomised controlled trial. Int Urogynecol J 2011; 22: Rostaminia S, Shobeiri S, Quiroz L. Surgical repair of bilateral levator ani muscles with ultrasound guidance. Int Urogynecol J 2013; 24 (2): Dietz H, Shek K, Daly O, Korda A. Can levator avulsion be repaired surgically? Int Urogynecol J 2012; doi: / s Dietz H, Korda A, Benness C et al. Surgical reduction of the levator hiatus. Neurourol Urodyn 2012; 31: Dietz HP. Pelvic floor assessment: a review. Fetal Matern Med Rev 2009; 20: Dietz HP, Shek KL. Levator trauma can be diagnosed by 2D translabial ultrasound. Int Urogynecol J 2009; 20: The Author