Postpartum pelvic stress fractures with subsequent forefoot overload injury: A case report

Abstract

Pelvic stress fractures in the early postpartum period are rare and may occur even in women with normal bone mineral density. This report describes the case of a 39-year-old woman (gravida 2, para 2) who developed bilateral sacral stress fractures and a left pubic ramus fracture three weeks after elective repeat cesarean delivery of a macrosomic infant. Bone mineral density and trabecular bone score were normal. She was managed conservatively with gradual clinical improvement. During recovery, she developed right forefoot pain consistent with metatarsophalangeal capsulitis and probable Morton's neuroma, likely secondary to altered gait mechanics. Postpartum pelvic stress fractures should be considered in women presenting with severe pelvic or low back pain after delivery, even in the absence of osteoporosis. Conservative management leads to favorable outcomes, although altered biomechanics during recovery may predispose to secondary overuse injuries.

Highlights

• •In the reported case, pelvic stress fractures occurred postpartum despite normal bone mineral density.
• •Sacral and pubic ramus fractures presented three weeks after cesarean delivery.
• •MRI is the imaging modality of choice, as early radiographs are often normal.
• •Conservative management achieved full functional recovery within three months.
• •Altered gait during healing caused secondary metatarsophalangeal capsulitis.

1. Introduction

Pelvic insufficiency fractures are uncommon in young women and are typically associated with osteoporosis, metabolic bone disease, or high-impact trauma. However, pregnancy- and partum-related sacral and pubic fractures have been increasingly recognized. Hormonal ligamentous laxity, mechanical pelvic loading, and delivery-related biomechanical stress may contribute to fracture even in women with normal bone density.

Sacral stress fractures are classified into insufficiency fractures, which occur when normal stress is applied to weakened bone, and fatigue fractures, which arise when excessive or repetitive stress is applied to otherwise normal bone [1], [2]. While insufficiency fractures are more frequently reported in older osteoporotic patients, fatigue-type fractures have been described in pregnancy and the postpartum period.

This report presents a case of postpartum bilateral sacral stress fractures with concomitant pubic ramus fracture in a patient with normal bone mineral density (BMD), followed by secondary forefoot pathology during recovery.

2. Case Presentation

A 39-year-old woman (gravida 2, para 2) conceived spontaneously and had regular antenatal follow-up without complications, including no history of gestational diabetes or hypertensive disorders of pregnancy. Her gynecological history was unremarkable. Her medical and surgical history included one previous cesarean delivery for non-reassuring fetal heart tracing and active tobacco use.

She underwent an elective repeat cesarean delivery at 38 weeks and 5 days of gestation. A healthy male infant weighing 4010 g was delivered with Apgar scores of 9 and 10 at 1 and 5 min, respectively. The intraoperative and immediate postpartum courses were uneventful. She received thromboprophylaxis for 10 days postoperatively.

2.1. Initial Presentation

Three weeks postpartum, the patient presented with sudden onset of severe right lower quadrant pain radiating toward the left inguinal region. The pain was described as severe and debilitating, significantly limiting ambulation.

Physical examination revealed normal bilateral hip range of motion without pain on movement. However, marked pelvic discomfort was elicited with weight bearing. Neurological examination was unremarkable.

Given the severity and sudden onset of symptoms, magnetic resonance imaging (MRI) of the lumbar spine and pelvis was obtained.

2.2. Findings

MRI demonstrated bilateral sacral stress fractures and a left closed pubic ramus fracture.

Dual-energy X-ray absorptiometry (DEXA) revealed normal bone mineral density at the spine, hip, and forearm. The trabecular bone score (L1–L4) was 1.54, within the normal range. Mild scoliosis was noted, potentially influencing spinal BMD measurements. There was no radiographic evidence of osteoporosis or osteopenia. Bone mineral density results are shown in Fig. 1. Blood tests, including calcium, phosphate, and 25-hydroxyvitamin D levels, were obtained to exclude underlying metabolic bone disease, and all results were within the normal range.

Fig. 1.

Bone mineral density images and interpretation at initial presentation.

2.3. Management

The patient was managed conservatively with relative bed rest, analgesics as needed, and gradual return to activity as tolerated. Surgical intervention was not required.

2.4. Follow-up

At three months postpartum, the patient reported significant improvement in low back and inguinal pain. She resumed ambulation comfortably and gradually returned to normal activities.

Repeat MRI demonstrated healing of the left pubic fracture. Bilateral sacral stress changes persisted, more pronounced on the right, with suspicion of a small incomplete nondisplaced sacral stress fracture. Mild multilevel degenerative lumbar changes were noted without nerve compression. MRI images are shown in Fig. 2, Fig. 3.

Fig. 2.

Magnetic resonance imaging performed three months after the initial presentation demonstrates bilateral stress-related changes in the sacrum, more pronounced on the right, with suspicion for a small incomplete nondisplaced sacral fracture.

Fig. 3.

Magnetic resonance imaging performed three months after the initial presentation demonstrates a nondisplaced stress fracture involving the left pubic bone adjacent to the pubic symphysis.

2.5. Development of Secondary Foot Symptoms

During recovery, the patient reported right forefoot pain characterized by intermittent discomfort between the third and fourth toes, occasionally associated with numbness, particularly when wearing certain footwear. She also described pain over the plantar aspect of the forefoot (“ball of the foot”), most pronounced at the level of the second and third metatarsophalangeal (MTP) joints.

On examination, there was tenderness in the third web space as well as over the plantar plate of the second and third MTP joints. Ankle and hip examinations were otherwise unremarkable.

The clinical findings were consistent with right MTP joint capsulitis, with findings suggestive of a concomitant Morton's neuroma.

Management included orthotics with a metatarsal pad, footwear modification, and gradual return to full activity. The patient subsequently resumed normal activities with good functional recovery.

3. Discussion

Spontaneous sacral fractures were first described by Lourie in 1982 as an underrecognized cause of low back pain in older osteoporotic patients [3]. Since then, sacral stress fractures have been increasingly recognized in younger women during pregnancy and the postpartum period, even in the absence of underlying osteoporosis [4], [5]. Although considered rare, these injuries may be underdiagnosed due to their nonspecific presentation and low clinical suspicion.

Postpartum sacral fractures may arise through two principal mechanisms: pregnancy-associated osteoporosis (PAO) and injury related to mechanical stress. PAO is characterized by reduced BMD and often presents with vertebral compression fractures. In contrast, mechanical stress fractures occur despite normal densitometry and are attributed to physiologic and biomechanical changes of pregnancy [1], [2], [5]. In a review of reported cases of pregnancy-related sacral stress fractures, Wu et al. found that approximately 65% of patients had onset of symptoms postpartum and that the majority of patients had no identifiable traditional risk factors for bone fragility [5].

The patient demonstrated normal BMD and a normal trabecular bone score, strongly arguing against pregnancy-associated osteoporosis. The fracture pattern is therefore most consistent with a mechanical stress mechanism. Importantly, previous studies have reported that a substantial proportion of postpartum sacral stress fractures occur in women with normal bone mineral density. Bone mineral density was available in approximately 70% of reported cases, and only a small minority demonstrated reduced bone density, indicating that most patients had values within the expected range for age [5]. This supports the concept that transient pregnancy-related metabolic or biomechanical changes may contribute to localized bone vulnerability even when standard densitometry is normal. Similarly, Speziali et al. described a postpartum sacral stress fracture in a woman without osteoporosis following cesarean delivery of a macrosomic infant, emphasizing that pregnancy and lactation themselves may represent sufficient risk factors for sacral stress injury [4].

Several contributing factors may have increased pelvic stress in this case. Pregnancy induces increased lumbar lordosis, anterior pelvic tilt, weight gain, and relaxin-mediated ligamentous laxity, all of which alter pelvic biomechanics and load distribution [6]. Delivery of a macrosomic infant (4010 g) likely further increased axial and pelvic ring loading. Additionally, active tobacco use likely adversely affected bone health and increased fracture susceptibility through impaired bone remodeling and microvascular perfusion potentially affecting bone resilience and healing [7]. Because excess body weight is a major modifiable mechanical risk factor, postpartum weight management should also be incorporated into recovery counseling to limit excessive loading across the pelvis and lower extremities and reduce the risk of mechanical and overuse injuries.

The coexistence of sacral and pubic ramus fractures reflects the biomechanics of the pelvic ring. Disruption in one component redistributes mechanical stress across the ring, predisposing to additional fractures. Although rare, similar patterns of combined pelvic stress fractures have been described in pregnancy-related pelvic injuries and highlight the interconnected load-bearing structure of the pelvic ring [6], [8].

Diagnosis is often delayed due to nonspecific symptoms and preserved hip motion, as seen in this case. Patients typically present with severe low back, buttock, or pelvic pain that may mimic musculoskeletal strain, sacroiliitis, or lumbar radiculopathy. Lumbar radicular symptoms have been reported in approximately 17% of patients with sacral stress fractures [5]. Plain radiographs are frequently normal in early stages. Speziali et al. demonstrated that conventional radiography may fail to detect early sacral fractures, while MRI and CT can confirm the diagnosis [4]. MRI is therefore considered the imaging modality of choice, as it allows early detection of bone marrow edema and nondisplaced fractures while avoiding radiation exposure [4], [5]. Similar diagnostic challenges have been described in postpartum cases reported by Roller et al. and Hilal and Nassar [1], [9]. When symptoms are unilateral, consideration should also be given to imaging the contralateral side, because bilateral stress injury may be present or become clinically apparent sequentially, with symptoms initially predominating on one side.

Conservative management is the standard of care and typically results in excellent outcomes. Most patients experience substantial improvement within 8 to 16 weeks [6]. Surgical intervention is rarely required unless fractures are displaced or unstable. Most postpartum sacral stress fractures are successfully treated with analgesia, relative rest, and modified weight bearing, with most patients achieving complete symptom resolution [5].

An additional notable aspect of this case is the development of secondary forefoot pathology during the recovery phase. Altered gait mechanics, including guarded ambulation and asymmetric weight bearing during fracture healing, likely increased plantar loading across the forefoot [10]. This redistribution of forces places increased stress on the second and third MTP joints, predisposing to plantar plate strain and capsular inflammation. Concurrently, increased compression within the intermetatarsal space may contribute to interdigital nerve irritation, particularly in the third web space, explaining the development of capsulitis with associated features of Morton's neuroma. The favorable response to orthotic support further supports a biomechanical etiology, as these interventions function to redistribute plantar pressures and offload the affected structures.

This case underscores the importance of considering sacral stress fractures in postpartum women presenting with severe pelvic or low back pain, even in the presence of normal bone mineral density. Early recognition and MRI evaluation are essential to avoid delayed diagnosis and prolonged morbidity. Furthermore, clinicians should remain vigilant for secondary musculoskeletal complications related to altered gait during recovery. To the best of the authors' knowledge, this is the first reported case describing the development of metatarsophalangeal capsulitis following a postpartum sacral stress fracture.

4. Conclusion

Postpartum sacral and pubic stress fractures may occur in women without osteoporosis and should be included in the differential diagnosis of severe pelvic or low back pain in the early postpartum period. Early MRI evaluation facilitates prompt diagnosis and prevents prolonged morbidity. Conservative management is typically effective and associated with excellent functional outcomes. Postpartum recovery should include attention to modifiable mechanical factors, including excess weight, and clinicians should remain vigilant for secondary biomechanical complications arising from altered gait during recovery.

Contributors

Pamela Moukarzel contributed to patient care, conception of the case report, acquiring the data, drafting the manuscript and undertaking the literature review.

Lara Nahouli contributed to interpreting the data, drafting the manuscript and revising the article critically for important intellectual content.

Mustafa Abazied contributed to acquiring and interpreting the data and revising the article critically for important intellectual content.

Ghina Ghazeeri contributed to patient care, conception of the case report, interpreting the data and revising the article critically for important intellectual content.

All authors approved the final submitted manuscript.

Patient consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Provenance and peer review

This article was not commissioned and was peer reviewed.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the authors used ChatGPT (OpenAI) for language editing and improvement of clarity. The authors reviewed and edited the output as needed and take full responsibility for the content of the published article.

Funding

No funding from an external source supported the publication of this case report.

Declaration of competing interest

The authors declare that they have no competing interest regarding the publication of this case report.