Case Report: Postpartum Sacral Stress Fracture

Background: New mothers often experience lower back pain during the postpartum period, which is a rare but complex complication associated with sacral stress fracture (SSF) that increases specifically during weight lifting.

Case Representation: This case study involved a 36-year-old Irish woman who presented to her general practitioner three weeks postpartum after a normal vaginal delivery. The patient reported pain in the left pelvic region and lower back, which intensified with weight bearing but diminished while at rest. Initial physical examination revealed slight midline point tenderness, and the Gaenslen test result was positive, indicating the presence of sensitivity at the sacrum. Clinicians suspected SSF, and MRI was performed to confirm the diagnosis. MRI resonance imaging revealed bone marrow edema confirming SSF; however, no fracture lines were observed. Therapeutic interventions included a conservative treatment regimen involving non-steroidal anti-inflammatory drugs (NSAIDs) for pain relief and analgesics. Bed rest was advised, and bone supplementation was prescribed, given that lactation-induced osteopenia is generally experienced in postpartum females. The patient was placed for long-term monitoring and consistent follow-up, where weekly follow-ups revealed pain reduction, and three months postpartum follow-up indicated complete resolution of pain and regaining normal physical activity.

Conclusion: Our findings highlight several important findings. Clinicians need to have an increased suspicion index for SSF, particularly in postpartum women, given that its symptoms are often confused with those of normal recovery. MRI has emerged as a gold standard for the accurate identification of bone edema, which is essential for definitive and timely diagnosis.

Introduction

Postpartum women often experience lower back pain (LBP), which varies from 44.6% to 75% and is usually characterized by weight gain, earlier back pain history, and pregnancy at younger ages [1], [2]. Studies have reported its risk factors as biomechanical contributors, ligamentous laxity, sacroiliac joint dysfunction, and musculoskeletal strain [2]–[4]. Sacral Stress Fracture (SSF) has emerged at an incidence of 0.078%, which classifies it as a rare manifestation characterized by LBP, often experienced in postpartum women upon heavy weight lifting and reduced after rest. SSF is explained by increased physiological pressure on the sacrum, while the maternal body already experiences bone mass loss due to lactation-induced osteopenia [5].

Clinically significant biomechanical contributors, such as lumbar lordosis, excessive weight gain during pregnancy, and rapid delivery methods, are major symptoms of SSF, where conditions such as lumbar lordosis exert excessive pressure across the sacral ala (a transitioning area between the sacroiliac joints and flexible lumbar spine). This risk is further increased by the increased calcium demand during pregnancy [6]. Another biomechanical stressor presenting spinal and pelvic laxity is pregnancy-related hormones, such as relaxing, which function as relaxers for the spinal and pelvic ligaments to facilitate childbirth. This increased biomechanical strain is often correlated with pelvic pain or LBP [7]. Studies have reported that pregnant women are likely to lose 4% to 6% of their bone mass as the body’s demand for calcium is increased to support breastfeeding, which ultimately leads to a hypoestrogenic state. This constant vulnerability of bones increases the impact of the mechanical stress [8].

Given the rarity of SSF, its clinical representation is mostly confused with general postpartum and recovery symptoms, which include muscular pain, dull and aching sacral pain in the lower back, pain in the buttock or groin, and weight-bearing. The complexity of SSF lies in its inability to be identified through normal imaging techniques, such as standard X-rays, highlighting the need for advanced imaging techniques, such as MRI, for a definitive diagnosis [9], [10]. Delay caused by definitive or late diagnosis of SSF increases the likelihood of fracture progression to more painful stages or intense radicular symptoms [11]. This highlights an important clinical guideline for clinicians to always have a suspicion margin for SSF when a postpartum patient presents with an increased level of pain, mainly reported during weight bearing; however, it reduces after a sufficient amount of rest. This approach not only minimizes the rate of false diagnosis but also helps reduce long-term pregnancy-related complications and maternal morbidity [11], [12]. The efficacy of MRI, particularly in the context of accurately identifying sacral insufficiency fractures, has been illustrated through various comparative studies. The capability of MRI to accurately visualize soft tissue abnormalities, complex fracture patterns, and bone marrow edema before the appearance of fracture lines increasingly supports its viability and accuracy in increasing the likelihood of on-time or even early diagnosis of SSF [13]–[15].

This case study illustrates the presentation of postpartum sacral stress fractures while highlighting the efficacy of MRI imaging for accurate diagnosis. This study also emphasizes reviewing existing principles for conservative management approaches for SSF, resulting in a more accurate prognosis. This underscores the need for clinicians to make informed choices in the context of this under-represented postpartum complication.

Case Presentation

Patient History

A 36-year-old Irish woman presented with a deep, dull ache in her lower back and left pelvic region. The patient complained of pain for a week, which gradually advanced to the point where it restricted her movement and simultaneously limited her capacity to look after her newborn. The pain intensified during any weight-bearing activity (i.e., lifting or walking); however, the patient also reported that the pain was significantly reduced after rest. no medical history of LBP, heavy exercise, or early metabolic syndrome.

Clinical Findings

The patient had no symptoms of fever or visible distress while resting during physical examination. Upon manual examination of the lumbosacral region, no midline tenderness was observed; however, the practitioner noticed tenderness across the left sacral ala. Neurological examination revealed normal lower limb function.

Diagnostic Focus and Assessment

For a definitive diagnosis, given the constant symptoms of mechanical pain and a positive Gaenslen test, advanced imaging was considered to confirm or reject the possibility of fracture. Hence, four weeks post-delivery, an MRI of the pelvis was conducted, which revealed a 3.5 cm focus of bone marrow edema along the anterior left sacrum. Moreover, as there was no further indication of any visible fracture lines, imaging revealed an acute sacral stress fracture.

Therapeutic Intervention

Since MRI findings confirmed SSF, a conservative multidisciplinary treatment regimen was formulated and initiated as follows:

1. Pain Management: For the management of inflammatory-mediated bone resorption and analgesia non-steroidal anti-inflammatory drugs (NSAIDs) were prescribed for the management of inflammation-mediated bone resorption and analgesia (e.g., ibuprofen 400 mg).

2. Activity Modification: Given that the patient experienced LBP during weight lifting, the was advised to complete bed rest coupled with caution to avoid any heavy lifting. The patient was also advised that only, if necessary, she could perform shorter distance ambulation until the pain was tolerable.

3. Bone Health Supplementation: Patient was prescribed a continuous bone supplementation regimen (calcium 1000 mg daily and Vitamin D (1000 IU daily), given her postpartum status and vulnerability to lactation-induced osteopenia. A consistent monitoring was also performed.

Follow-Up and Outcome

At the two-week follow-up, the patient reported reduced pain, which was eliminated at the six-week postpartum follow-up. Patients described normal mobility without any pain or need for further administration of analgesics. This monitoring was continued, and at the three-month mark, complete resolution of symptoms was achieved while the patient resumed her normal activities.

Discussion

Pregnancy-related lower back pain, both prenatal and postpartum, is common and affects as many as 68.5% of women. Similarly, this case study also demonstrates that patients with sacral fractures often complain of deep-onset pain in the lower back or pelvic region that may radiate to the groin, buttock, and thigh. A diagnosis of fracture is often missed, as physicians may be distracted by the lack of acute trauma or strenuous activities at the onset of pain [10], [16], [17].

Most of the literature describes cases of postpartum sacral fractures where the pain is aggravated upon exertion or heavy lifting and is relieved by rest. Tenderness of the sacroiliac joint is a common diagnostic feature observed during physical examination. Therefore, it is recommended that the Gaenslen and Patrick tests be used to evaluate sacroiliac joint pathology.

Common risk factors for pregnancy-related SSF [18] include pelvic sensitivity due to increased levels of relaxing, excessive weight gain, hyperlordosis, osteopenia due to higher levels of prolactin, osteoporosis of pregnancy, high birth weight, rapid vaginal delivery, and heparin therapy. Furthermore, acute osteoporosis in young females is often characterized by amenorrhea, eating disorders, chronic inflammatory disease, corticosteroid use, hyperparathyroidism, and renal osteodystrophy. However, in the present case study, no risk factors were observed or reported by the patient.

Radiological investigations using plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy are crucial for definitive diagnosis. Initially, Plain radiographs were employed to screen for lumbar spine or pelvic pathologies. However, they are often non-specific, involving the pelvis and sacrum [19], and fracture lines may only be visible after healing calcification develops. Therefore, Plain radiographs may lack specificity for identifying sacral stress fractures. The sensitivity of CT and bone scintigraphy with technetium to detect sacral fractures has been reported to be as high as 75% and 96%, respectively. However, the use of CT and bone scintigraphy is limited to postpartum use owing to radiation exposure and potential teratogenic effects on the fetus. MRI has emerged as the most effective method for accurately describing postpartum SSF, which is attributed to its relative safety and enhanced sensitivity for the detection of sacral fractures [20].

Common therapeutic approaches for the resolution of SSF encompass [21] adequate pain control using analgesics, intermittent bed rest, and light-weight-bearing exercises. The initial goal for a conservative treatment regimen for sacral stress fractures is pain reduction, and analgesics should be recommended until the pain subsides. Bed rest is essential for healing fractures, and early weight-bearing should be encouraged. Furthermore, patients with a low BMD and insufficiency fractures should be supplemented with calcium and vitamin D.

Conclusion

Sacral Stress Fractures are a rare complication experienced during the postpartum period; hence, this case study underscores the importance of creating a suspicion margin when postpartum women present with characterized LBP to rule out the possibility of SSF and make early informed choices. This case study also highlights the efficacy of MRI techniques in making definitive diagnoses, as they produce more accurate visualization of bone fractures in comparison to standard X-ray approaches. Opting for a conservative treatment regimen has also proved to be a vital strategy for the complete resolution of pain symptoms. Employing NSAIDs, analgesics, and bone supplementation provided a complete solution that not only reduced pain, but also provided bone strength to avoid any future stress fractures.

Conflict of Interest

The authors declare no conflict of interest.