Postpartum Pubic Symphysis Diastasis

Etiology

Identified risk factors for postpartum pubic symphysis diastasis include primigravid women, multiple gestations, and prolonged active labor.[2] Forceps deliveries, deliveries of newborns weighing over 4000 gm, and infant macrosomia are also possible etiologies in cases of pubic separation.[2] Epidural analgesia and shoulder dystocia or McRoberts maneuver are also reported as possible risk factors.[1] A review of case reports also notes a higher incidence in Scandinavian women. While increased serum relaxin hormone levels have been identified in women with pubic symphysis diastasis, no direct correlation has been proven between these elevated levels and an increased incidence of post-partum separation. Other theoretical causes or predisposing factors for pubic symphysis diastasis include:[3]

• Biomechanical strain of the pelvic ligaments and associated hyper-lordosis; anatomical pelvic variations and "contracted pelvis"
• Metabolic (calcium) and hormonal (relaxin and progesterone) changes leading to ligamentous laxity
• Extreme weakening of the joint
• Tearing of the fibrocartilaginous disc during delivery
• Narrowing, sclerosis, and degeneration of the pubic joint
• Muscle weakness
• Increased pregnancy-related weight gain
• A very long or a very short second stage of labor

Epidemiology

The incidence of pathologic, complete separation of the pubic symphysis following pregnancy is reported to be within 1 in 300 to 1:30,000, with many instances likely undiagnosed.[4] In a published case series out of the University of Pennsylvania School of Medicine, they reported the incidence at a single institution to be 1 in 569 deliveries over two years. Under-reporting is likely, due to inconsistencies in diagnosis and patients often presenting with mild symptoms and limited debility. Magnetic resonance studies show a high incidence of pubic lesions following vaginal childbirth even in low-risk pregnancies (bone marrow edema, bone fracture, capsule fracture), but they normally tend to recover and are not associated with prolapse or incontinence.[5][6][7]

Pathophysiology

Relaxin, a hormone secreted by the placenta during pregnancy, peaks during the first trimester and again in the peripartum period in females.[8] A modulator of arterial compliance and cardiac output during pregnancy, relaxin also serves to relax the pelvic ligaments and contribute to softening of the cartilage of the pubic symphysis for preparation of the birth canal for delivery.[8] As seen in most pelvic ring injuries that separate anteriorly at the pubic symphysis, there is often an associated posterior pelvic ring injury as well, with stretch, partial tears, or complete tears of the sacroiliac ligaments. Complicated deliveries (contracted pelvis, macrosomia, shoulder dystocia, a long second stage of labor) are prone to soft tissue (levator anis muscle) and bone lesions due to the stretching forces.

History and Physical

Patients can present with pubic symphysis diastasis before delivery, during delivery, or most commonly postpartum. The postpartum presentation is most common, and presentation can encounter delay as spinal epidural anesthesia administered during the birthing process can mask the symptoms. The typical presentation involving pubic symphysis diastasis following pregnancy is unrelenting pain in the anterior pelvis and suprapubic region, with or without pain localized over the sacroiliac joints from associated posterior pelvic ring ligamentous injury. Pain from the anterior pelvis can radiate and manifest in the hip joints and radiate down the legs. Patients will often have extreme difficulty with weight-bearing and can retain urine often requiring the use of an indwelling Foley catheter.

Patients will have difficulty with both active and passive straight leg raise and changes in bed positioning. On physical examination, patients will often present in distress secondary to pain, pain with palpation or attempted manipulation of the pelvic girdle, and pain with attempted weight-bearing or ambulation. The literature describes soft tissue edema or hematoma on the pubis and perineum,[9] as well as a palpable gap in the pubic symphysis in several case studies.[4] The literature does not describe associated nerve and vascular injury.

Evaluation

When postpartum pubic diastasis is suspected clinically, an ultrasound scan can be diagnostic and used for screening,[10] but then a standard AP pelvis radiograph should be obtained. On the evaluation of plain film imaging, pubic symphysis diastasis greater than 1 cm indicates a pathologic process of the pelvic girdle.[11] The bilateral sacral iliac joints should also undergo evaluation on plain radiography for gapping or gross separation. A computed tomography (CT) scan with a three-dimensional reconstruction is also helpful in the further evaluation of the pubic symphysis and sacral iliac joints. If plain radiographs show a significant pubic separation greater than 4 cm, treatment algorithms support obtaining non-contrast-enhanced magnetic resonance imaging to assess for surrounding soft tissue injury.[12]

Treatment / Management

Treatments described for pelvis diastasis include non-operative treatment with application of pelvic binder coupled with physical therapy and immediate weight-bearing, non-weight bearing with bedrest, closed reduction with application of binder, application of anterior external fixator with or without sacroiliac screw fixation, and anterior internal fixation with plate and screws. In most cases, conservative, non-operative management is recommended and yields good functional outcomes. While early operative management has been advocated in cases where pubic diastasis measures more than 4 cm, the patient is at increased risk for perioperative complications in the postpartum state. Distorted pelvic anatomy, increased pelvic vascularity, and peripartum hypercoagulability complicates surgical intervention and must be considerations.

Differential Diagnosis

Diagnosis of pubic symphysis diastasis is often straightforward, however other causes of hip, back, and leg pain all warrant consideration by the evaluating clinician. Considerations include an examination for labial and perianal tears and lacerations, venous thrombus embolisms, musculoskeletal low back pain, and lumbosacral radiculopathy. Additionally, pubic osteolysis, osteitis pubis, bone infection (osteomyelitis, tuberculosis, syphilis), tumors, postpartum fracture, abscess, and osteomyelitis have to be considered.[3] A careful history, clinical examination, and ultrasound or plain film radiography can aid in the diagnosis process.

Prognosis

The prognosis is very good for the majority of patients who experience postpartum pubic symphysis diastasis, and in most cases, full recovery without persistent pain is the expectation.[1] Follow-up radiographs in most case studies show near-complete closure of the pubic symphysis and complete resolution of symptoms within 3 months. Some patients do require further physical therapy for up to 6 months. No significant long-term sequelae have been identified. No definitive recommendations exist regarding alteration of care for future pregnancies, and this would be a good area for future study.

Complications

Reported complications from pubic symphysis separation during pregnancy are rare. Urinary outflow obstruction, hematoma formation, and sustained painful ambulation are the most common complaints in case studies. Venous thrombus embolism is also reported and likely attributable to prolonged immobilization.