An Ultrasound Evaluation Of Postpartum Pubic Symphysis Diastasis And Its Relationship To Suprapubic Pain

Michelle T Sugi, Tamar Nobel, Michael Walsh, Yee-Cheen Doung, Kenneth A Egol

NYU Hospital for Joint Diseases
New York, N.Y.
Address for Correspondence:
Michelle T. Sugi
Musculoskeletal Research Center
NYU Hospital for Joint Diseases
310 East 17th Street, Ste 1500
New York, NY 10003

Phone : (212) 598-6460
Fax     : (212) 598-6096
E-mail : michelle.sugi@nyumc.org
 

Abstract:

While pelvic pain in the peripartum period is commonplace, little is known regarding its relation to symphyseal widening. The purpose of this study was to evaluate physiologic change in the widening of the symphysis pubis postpartum, and determine its relationship to suprapubic pain. Sixty-four women who were within 48-hours post vaginal delivery were randomly selected. On postpartum day one or two, participants used a quantitative scale to assess pubic and back pain. Chart reviews were conducted to obtain patient, newborn, and labor characteristics. Ultrasonography was used to measure symphyseal widening. Outcomes were suprapubic pain correlated to symphyseal widening, and these two related to other patient, newborn, and labor characteristics. The results showed that 88% of the women perceived mild to moderate pubic pain, while 98% had mild to moderate back pain. Ultrasonagraphy determined that 41 women had widening greater than 10mm, but mean symphyseal width did not correlate with back pain (p=0.83), or pubic pain (p=0.87). Pubic pain increased with increasing patient age (p=0.02). Back pain increased with precipitous labor, but did not reach significance (p=0.06). No correlation was found between postpartum pain and symphyseal widening, suggesting that there are other mechanisms of peripartum suprapubic pain that must be considered.

J.Orthopaedics 2010;7(1)e8

Keywords:

Pubis symphysis; symphyseal widening; diastasis; postpartum pain

Introduction:

The symphysis pubis is a nonsynovial amphiarthrodial joint that forms the anterior arch of the pelvis.  It is, however, one of the three pelvic joints that are affected during the peripartum period due to hormonal influence and mechanical stressors. 

The normal physiologic width of the symphysis pubis ranges from 4-6 mm.[1]  Relaxation of the symphyseal ligaments during the peripartum period is a well-described phenomenon, beginning in the 10th week of gestation and reaching a maximum at or near term. The average widening during pregnancy ranges from 6 mm to 8 mm, with return to baseline between 4 to 12 weeks postpartum.[2, 3]  It has been hypothesized that relaxin, an insulin-like hormone, influences cartilage swelling and pelvic ligament laxity, and thus symphyseal widening; however, most studies to date have found no association.[4]  Post-mortem studies found that mechanical stressors during labor cause focal and edematous changes in the ligaments in all women with vaginal deliveries of a neonate over 2300 grams.[5]  Sustained symphyseal widening greater than 10 mm is considered to be pathologic, as observations have shown it be associated with significantly increased maternal morbidity and disability postpartum.[6]

The incidence of pubic symphysis diastasis is estimated to be 1 in 521 to 1 in 30,000 vaginal deliveries.[7-9] Factors that are presumed to affect widening include precipitous labor or rapid descent of the presenting part of the fetus. Other factors, such as maternal age, parity, pelvimetry or fetal weight have not been shown to correlate with symphyseal diastasis.[10]

While pelvic pain in the peripartum period is commonplace, little is known regarding the relationship between symphyseal widening and the development of this pain. We conducted a pilot study to evaluate physiologic changes in the widening of the symphysis pubis postpartum utilizing ultrasonagraphy, and correlated these findings with patients’ symptoms defined as suprapubic pain, unrelated to other causes (e.g. uterine cramps).

Materials and Methods:

The design of the study involved prospective analysis of postpartum women in a single urban hospital between October 2006 and May 2007. Patients who were within 48-hours post vaginal delivery were randomly selected and asked to participate in the study. Written and Institutional Review Board (IRB) approved consent was obtained from all subjects who met inclusion criteria and agreed to use of their personal data for research purposes.

Subjects
Sixty-five women were asked to participate in the study. Cesarean sections were excluded for this preliminary study. Sixty-four women (mean age 28.5 years, age range 17-43) completed the study.

Pain Evaluation
During the patient's initial enrollment on postpartum day one or two, participants completed a questionnaire using a quantitative scale to assess pubic and back pain postpartum. The pain scale quantified pain on a scale from zero to 10, with mild pain in the 0-3 range, moderate pain in the 4-7 range, and severe pain in the 8-10 range. A concurrent chart review was also conducted on all patients to obtain data on patient and newborn characteristics, as well as on labor. Data obtained from the questionnaire and chart review were used to evaluate pubic and back pain in relation to: symphyseal widening and mobility, parity, length of gestation, age of patient, length of stage two of labor, mode of delivery, neonate birth weight and height, degree of perineal tears, blood loss, and type of the female pelvis (clinically assessed as gynecoid, anthropoid, android, or pletipoid). In this study, precipitous labor was defined as labor less than one hour.

Ultrasound Imaging
Abdominal ultrasonography was used to measure symphyseal widening in supine position with the knees and hips extended, and the knees and hips flexed (Figure 1) on postpartum day one or two. Images were evaluated by a trained ultrasonographer who took two separate measurements of symphyseal widening at the superior aspect of the bony arch in both positions (Figure 2).  The averages of the two measurements in each position were used for statistical analysis. Measurements of symphyseal mobility were calculated by subtracting the difference of the average extended value from the average flexed value.

Figure 1: Ultrasonography was used to measure symphyseal width in supine position with the knees and hips extended, and the knees and hips flexed.

Figure 2: Ultrasound images (right) were evaluated by a trained ultrasonographer who took two separate measurements of symphyseal widening at the superior aspect of the bony arch, as represented in the schematic drawing of pelvic anatomy (left).

Statistical Analysis
Spearman’s correlation coefficient was used to assess the association between symphyseal width and pubic and back pain, as well as all three of these and newborn height and weight.  In addition, Spearman’s correlation coefficients were used to assess the associations between pubic and back pain and maternal characteristics, such as age, and labor characteristics, including parity, estimated blood loss, and degree of perineal tears. Differences in pubic and back pain across ethnicity were assessed using one-way analysis of variance (one-way ANOVA) tests with Bonferroni-adjusted multiple comparisons.  Student’s t-tests were used for two-way comparisons of pain and symphyseal widening across newborn gender, induction, and rupture of membranes.

Results :

There were a total of 64 women, with a mean age of 28.5 years, and age range from 17 to 43 years. The majority of the patients were Hispanic (31/64). The women had a mean height of 63 inches, and a mean weight of 159 pounds. Pregnancy status was para 1 in 26 patients, para 2 in 21 patients, para 3 in 12 patients, and para 4 in 5 patients. The mean parity for the women studied was 1.95. All patients underwent normal spontaneous vaginal deliveries (NSVD), with a mean estimated blood loss during labor of 308 milliliters. Sixteen women had induction with oxytocin. Thirty-two women had artificial rupture of membranes, whereas 30 had spontaneous rupture of membranes. The mean length of stage two of labor was 43 minutes. Fifty of the women gave birth in the Semi-Fowler position, three in the lateral, one in knee-chest, and 10 in lithotomy. Thirty-nine women sustained a tear, consisting of 11 vaginal or labial, 13 first-degree perineal, and 15 second-degree perineal. Thirty-one of the newborn babies were female, and 33 were male. The mean weight for the newborns was 3182 grams, and the mean height was 43 cm. Table 1 summarizes the clinical characteristics of these patients.

The mean symphyseal widening measured was 12 mm, and the mean change in symphyseal mobility was 5 mm. Sixty-four percent (41/64) of patients had widening greater than 10 mm. Only one patient was found to have symphyseal widening greater than 25 mm. This patient, a 29-year old para 5 female who otherwise had average clinical characteristics, underwent NSVD and perceived moderate pubic pain and severe back pain. She was the only subject in our study who perceived severe back pain. Eighty-eight percent of the women (56/64) perceived mild to moderate pubic pain, while 98 percent (63/64) had mild to moderate back pain. Severe pain was a more common complaint among women with pubic pain (8/64) versus those with back pain alone (1/64). The mean symphyseal widening did not correlate to either lower back pain (p=0.83), or pubic pain (p=0.87).  Pubic pain increased with increasing patient age (p=0.02). There was no significant difference in either pubic or lower back pain between race groups.

There was no correlation between parity and pain. There was also no significant relationship between symphyseal widening and parity. Position and rupture of membranes did not significantly affect the change in symphyseal widening or increased severity of pain. Back pain increased with precipitous labor, but did not reach significance (p=0.06), and pubic pain did not (p=0.72) either.  The size and weight of the newborn was not found to correlate to either the change in symphyseal width or increased severity of pain. Two of the deliveries were complicated by shoulder dystocia, but this was too few to assess for statistical significance. The measurements of the symphyseal widening of the two women with this complication were 14 mm and 20 mm.

Table 1:   Summary of the demographic and clinical characteristics of subjects.

Table 2:  Location of perceived pain is shown according to quantitative rating by subjects during encounters.

Discussion :

In this study we found the majority of postpartum women to have experienced a “pathologic” symphyseal separation. We found no correlation, however, between perceived postpartum pain and symphyseal widening. In pregnancy, pelvic ligament relaxation and increased joint mobility is observed.[11]  Peripartum pubic and lower back pain is experienced in approximately 50 percent of women during pregnancy, and there is some evidence that pain is associated with symphyseal widening during pregnancy.[12-15]   However, the correlation between antepartum symphyseal widening and pain is debatable, as Bjorklund et al (2000) found that while widening was strongly associated with pain, there was no evidence that the degree of symphyseal widening determined the severity of pubic pain in pregnancy or postpartum.  This finding suggests that there are other mechanisms of peripartum pain that must be considered.[12]

The literature suggests that symphyseal widening during pregnancy is due to both hormonal influence and mechanical stressors. It is possible that postpartum pain is a continuum of antepartum pain and mediated by these same factors; however, the variability of postpartum pain in location and severity suggests that there may be two distinct etiologies. The etiology of mild to moderate postpartum pain that ceases within days after delivery may be explained by the relaxation of the symphysis pubis during delivery. This physiologic widening is consistent with our study finding of 88 percent of women who perceived mild to moderate pubic pain (Table 2).  A retrospective study that examined women with symptomatic symphyseal separation found that 55 percent of women described pubic pain as their only symptom, and only two women did not suffer from pain in this area.[16]  A meta-analysis of case reports found that the predominating symptom of separation of the symphysis pubis is a constant, dull pain located directly over the symphysis.[9]

According to Larsen et al (1999), approximately four percent of women experience severe pain localized to the pubis and low back for several months postpartum.[17]  Though not all of these women sustained a symphyseal diastasis, the etiology of this more intense and prolonged pain is believed to be due to pelvic ring instability at both the pubic symphysis, and if severe enough, also at the sacroiliac joints.[11] Studies have reported that symphyseal diastasis exceeding 40 mm disrupts the sacroiliac ligaments.[18, 19] This suggests that patients who experience mild to moderate postpartum pain suffer from physiologic pelvic dysfunction, while those with severe pain likely suffer symphyseal diastasis due to biomechanical disruption of the muscles and ligaments within the pelvic ring during delivery.[11, 20, 21]  In this study, we define symphyseal diastasis as disruption of the pelvic ring with more than 25 mm of symphysis pubis separation.[22]

Due to similarity in presentation and symptoms, and a lack of objective measures of ligament relaxation or pelvic instability, there is confusion in both the terminology and criteria used to describe and diagnose symphysis pubis dysfunction, symphysis pubis diastasis, and peripartum back and pubic pain.[11, 20, 23] As a result, the diagnosis is often based on the patient’s information about severity and location of pain. In this study, we considered pubic and lower back pain as separate entities with similar etiologies along a spectrum of pelvic ligament laxity.  Though we did not find any significant difference in the frequency or severity of pubic pain versus back pain in the postpartum period, it is hypothesized that pubic pain would not only be a more common complaint, but also less pronounced than back pain due to the more extreme etiology of the latter.

The literature is inconclusive on the relationship between a precipitous second stage of labor and postpartum pain.[24]  While some have found no correlation, a series of case reports suggest that rupture of the symphysis pubis in spontaneous labor is due to marked rapidity of labor.[9]  In our study we found a trend of low back pain increasing with precipitous labor, though it was not statistically significant. A plausible explanation for this observation is that the ligaments may undergo plastic rather than elastic deformation, which may contribute to a higher rate of dysfunction or diastasis, not only at the symphysis pubis, but also at the sacroiliac joint.

The literature is inconsistent with regards to peripartum pain and age of the mother. Some authors found that younger women were more likely to have pain postpartum, while others reported no effect.[14]  Our findings suggest that pain increased with maternal age. One author with similar findings suggested that this result may be related to the women in their population having a higher age at their first pregnancy.[25] Another similar observation was reported for back pain experienced during pregnancy, but the author was unable to separate the effects of age on pain from those of parity.[26]  We found that parity was not correlated to back pain or pelvic pain, but did not examine whether there were any confounding effects caused by maternal age. Wu et al suggest that the real pattern of association between pain is a “U” shape – there is high risk for very young women whose bodies are not yet ready for pregnancy, then risk decreases until women get much older, or undergo more pregnancies.[23]  The literature is not conclusive as to whether postpartum pain increases with the number of pregnancies; however, it has been shown that pain in the back and pubis after previous pregnancies increases the risk for peripartum pain in subsequent pregnancies.[27]  It is likely that pain may be due to the aging process and ligamentous laxity associated with increasing age, rather than parity.[28]

It has been suggested that postpartum pain may occur as a result of traumatic delivery, such as in shoulder dystocia.[11] There is some evidence that shoulder dystocia is associated with symphyseal separation.  In the only case of its type to be reported, shoulder dystocia was resolved through spontaneous separation of the pubis symphysis.[29] Other reports have found separation of the pubis symphysis following the McRobert’s maneuver.[30, 31]  In our study, we had two patients with complications of shoulder dystocia during delivery, both of which had widening greater than 1 cm. A larger sample size would enable us to consider the relationship between the McRobert’s maneuver, symphyseal widening, and related pain.

Ultrasound is a consistent, cost-effective and harmless means of measurement. Although discrepancies exist regarding ultrasound technology for measurement of symphyseal widening, we considered the upper margin of the symphysis pubis joint with the patient supine as the true symphyseal width. The measurements in this study are consistent with other authors who have found ultrasonography to be a reliable and reproducible method to measure symphyseal width.[27].

The limitation of this study is its small sample size. A post hoc power analysis was performed. This showed that if we increased the number of patients 50-fold (3,064) we would increase our power to 80 percent. In addition, the relationship between parity and pain in relation to maternal age may be further elucidated by gaining a greater sample of women. Pain is subjective and patient-to-patient variations may have a psychological component as well as a physical component which was not measured.

Future directions of this study include consideration of antepartum pain to determine whether postpartum pain is residual antepartum pain or due to dysfunction and rupture of ligaments.  Postpartum pubic pain and back pain are similar in etiology, yet unique in frequency, location, and severity. The diagnosis is most commonly made based on clinical presentation, although the literature on ultrasonography to aid in the diagnosis continues to grow.

In conclusion, we believe that although a diagnosis of symphyseal dysfunction or diastasis does not change the management during labor, a better understanding of the etiology of postpartum pain will help in the management of patients with this condition as well as potentially aid patients who sustain this condition with subsequent pregnancies.

Reference :

1. Wurdinger, S., et al., MRI of the pelvic ring joints postpartum: normal and pathological findings. J Magn Reson Imaging, 2002. 15(3): p. 324-9.

2. Heyman, J., Lundquist A., The symphysis pubis in pregnancy and parturition. Acta Obstet Gynecol Scand, 1932. 12: p. 35.

3. Alicioglu, B., et al., Symphysis pubis distance in adults: a retrospective computed tomography study. Surg Radiol Anat, 2008. 30(2): p. 153-7.

4. Dietrichs, E. and O. Kogstad, "Pelvic girdle relaxation"--suggested new nomenclature. Scand J Rheumatol Suppl, 1991. 88: p. 3.

5. Scriven, M.W., D.A. Jones, and L. McKnight, The importance of pubic pain following childbirth: a clinical and ultrasonographic study of diastasis of the pubic symphysis. J R Soc Med, 1995. 88(1): p. 28-30.

6. Lindsey, R.W., et al., Separation of the symphysis pubis in association with childbearing. A case report. J Bone Joint Surg Am, 1988. 70(2): p. 289-92.

7. Heckman, J.D. and R. Sassard, Musculoskeletal considerations in pregnancy. J Bone Joint Surg Am, 1994. 76(11): p. 1720-30.

8. Luger, E.J., R. Arbel, and S. Dekel, Traumatic separation of the symphysis pubis during pregnancy: a case report. J Trauma, 1995. 38(2): p. 255-6.

9. Reis RA, B.J., Arens RA et al., Traumatic separation of the symphysis pubis during spontaneous labor: With a clinical and X-ray study of the normal symphysis pubis during pregnancy and the puerperium. . Surg Gynecol Obstet, 1932. 55: p. 18.

10. Snow, R.E. and A.G. Neubert, Peripartum pubic symphysis separation: a case series and review of the literature. Obstet Gynecol Surv, 1997. 52(7): p. 438-43.

11. Leadbetter, R.E., D. Mawer, and S.W. Lindow, Symphysis pubis dysfunction: a review of the literature. J Matern Fetal Neonatal Med, 2004. 16(6): p. 349-54.

12. Bjorklund, K., et al., Symphyseal distention in relation to serum relaxin levels and pelvic pain in pregnancy. Acta Obstet Gynecol Scand, 2000. 79(4): p. 269-75.

13. Fast, A., et al., Low-back pain in pregnancy. Spine (Phila Pa 1976), 1987. 12(4): p. 368-71.

14. Ostgaard, H.C. and G.B. Andersson, Postpartum low-back pain. Spine (Phila Pa 1976), 1992. 17(1): p. 53-5.

15. Ostgaard, H.C., G.B. Andersson, and K. Karlsson, Prevalence of back pain in pregnancy. Spine (Phila Pa 1976), 1991. 16(5): p. 549-52.

16. Owens, K., A. Pearson, and G. Mason, Symphysis pubis dysfunction--a cause of significant obstetric morbidity. Eur J Obstet Gynecol Reprod Biol, 2002. 105(2): p. 143-6.

17. Larsen, E.C., et al., Symptom-giving pelvic girdle relaxation in pregnancy. I: Prevalence and risk factors. Acta Obstet Gynecol Scand, 1999. 78(2): p. 105-10.

18. Callahan, J.T., Separation of the symphysis pubis. Am J Obstet Gynecol, 1953. 66(2): p. 281-93.

19. Hagen, R., Pelvic girdle relaxation from an orthopaedic point of view. Acta Orthop Scand, 1974. 45(4): p. 550-63.

20. Hansen, A., et al., Postpartum pelvic pain--the "pelvic joint syndrome": a follow-up study with special reference to diagnostic methods. Acta Obstet Gynecol Scand, 2005. 84(2): p. 170-6.

21. Owens K., P.A., Mason G., Pubic Symphysis Separation. Fetal and Maternal Medicine Review, 2002. 13: p. 13.

22. Kellman, J.F., Browner B.D., ed. In Skeletal Trauma. Fractures, Dislocations, and Ligamentous Injuries. Fractures of the Pelvic Ring, ed. J.J.B. Browner B.D., Levine A, Trafton PG. Vol. 1. 1992, W.B. Saunders: Philidelphia. pp. 859-863.

23. Wu, W.H., et al., Pregnancy-related pelvic girdle pain (PPP), I: Terminology, clinical presentation, and prevalence. Eur Spine J, 2004. 13(7): p. 575-89.

24. Breen, T.W., et al., Factors associated with back pain after childbirth. Anesthesiology, 1994. 81(1): p. 29-34.

25. Mens, J.M., et al., Understanding peripartum pelvic pain. Implications of a patient survey. Spine (Phila Pa 1976), 1996. 21(11): p. 1363-9; discussion 1369-70.

26. Mantle, M.J., R.M. Greenwood, and H.L. Currey, Backache in pregnancy. Rheumatol Rehabil, 1977. 16(2): p. 95-101.

27. Bjorklund, K., M.L. Nordstrom, and S. Bergstrom, Sonographic assessment of symphyseal joint distention during pregnancy and post partum with special reference to pelvic pain. Acta Obstet Gynecol Scand, 1999. 78(2): p. 125-30.

28. Conn, M., ed. Handbook of Models for Human Aging. A Model for Understanding the Pathomechanics of Osteoarthritis in Aging, ed. M.A. Andriacchi TP. 2006, Elsevier: Amsterdam. pp. 351-366.

29. Niederhauser, A., et al., Resolution of infant shoulder dystocia with maternal spontaneous symphyseal separation: a case report. J Reprod Med, 2008. 53(1): p. 62-4.

30. Culligan, P., S. Hill, and M. Heit, Rupture of the symphysis pubis during vaginal delivery followed by two subsequent uneventful pregnancies. Obstet Gynecol, 2002. 100(5 Pt 2): p. 1114-7.

31. Heath, T. and R.B. Gherman, Symphyseal separation, sacroiliac joint dislocation and transient lateral femoral cutaneous neuropathy associated with McRoberts' maneuver. A case report. J Reprod Med, 1999. 44(10): p. 902-4.
     

This is a peer reviewed paper 

Please cite as: Michelle T. Sugi: An Ultrasound Evaluation Of Postpartum Pubic Symphysis Diastasis And Its Relationship To Suprapubic Pain

J.Orthopaedics 2010;7(1)e8

URL: http://www.jortho.org/2010/7/1/e8

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