Bilateral avascular necrosis leading to hip fracture in pregnancy: A case report

Abstract

Avascular necrosis (AVN) of the hip, a rare cause of pelvic pain in the third trimester of pregnancy, often presents with nonspecific symptoms that resemble common musculoskeletal conditions. This ambiguity, coupled with concerns about the safety of magnetic resonance imaging (MRI) during pregnancy, can hinder timely diagnosis. We report a unique case of a 32-year-old primigravida diagnosed with a hip fracture and bilateral AVN of the femoral head in the immediate postpartum period, a complication seemingly not previously documented in pregnant patients. The initial management involved closed reduction and internal fixation using cannulated screws. However, progressive femoral head collapse necessitated revision to a total hip arthroplasty. This case underscores the importance of early diagnosis and recognition of AVN in pregnancy to prevent severe complications. It highlights the diagnostic challenges and emphasizes the need for heightened awareness and earlier imaging investigations in similar clinical scenarios.

Highlights

• •Avascular necrosis of the hip in pregnancy is very rare.
• •Magnetic resonance imaging (MRI) is the gold standard for diagnosing hip pain in pregnancy.
• •Early diagnosis of avascular necrosis can prevent severe complications.

1. Introduction

Femoral neck fractures rarely occur during pregnancy, a fact reflected in the experience of most obstetricians, who may never encounter such cases throughout their careers. Despite this rarity, it is important to note that hip pain is a relatively common complaint during pregnancy, affecting up to 38 % of pregnant women [1]. Furthermore, pelvic pain syndrome is experienced by approximately 20 % of pregnant women [2]. While most hip pain during pregnancy is due to minor musculoskeletal conditions, obstetricians must have a high index of suspicion for serious underlying pathology and exercise discretion when requesting investigations. In cases of suspicious hip or pelvic pain during pregnancy, magnetic resonance imaging (MRI) is the gold standard investigation [3].

Avascular necrosis (AVN) of the femoral head is a rare yet potentially devastating condition during pregnancy. To date, fewer than 50 cases have been reported in the medical literature since it was first described by Pfeifer in 1957 [4]. Although hip fractures have been documented to occur as a result of AVN, these cases are confined to confined to the non-gravid state. To our knowledge, AVN-related hip fractures have not been reported in pregnant women. Here, we present the case of a 32-year-old pregnant woman who was diagnosed with a displaced hip fracture, ultimately attributed to bilateral avascular necrosis of the femoral heads.

2. Case Presentation

A 32-year-old primigravida presented in her third trimester to the emergency room in the early stages of labour. Labour lasted for 16 h before she gave birth to a healthy male baby by spontaneous vagina delivery. While in the post-natal unit, the patient reportedly fell in the bathroom; the injury was thought to be relatively minor and she was instructed to return to bed and continue breastfeeding her newborn. Two days later, the patient reported severe pain in her right hip and was unable to weight-bear on the limb. Noting these symptoms an urgent orthopaedic consult was requested together with a radiograph of the hip (Fig. 1).

Fig. 1.

Initial anteroposterior (AP) radiograph of the pelvis showing displaced right subcapital hip fracture.

Physical examination revealed a shortened lower limb in mild external rotation with severe groin pain on attempted hip movement. The initial radiograph was unclear, and a MRI scan showed stage III AVN of both femoral heads hip and a Garden IV subcapital fracture of the right hip (Fig. 2 a & b). Further questioning revealed that the patient had complained of pelvic pain on several occasions before delivery and, on one occasion, was admitted overnight for observation; however, a pelvic ultrasound showed no abnormalities, and she was discharged with reassurance. The patient had no risk factors for AVN and did not smoke or drink alcohol, nor had she received corticosteroids during pregnancy. The laboratory tests, including a complete blood count (CBC), erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), renal function tests (RFTs), thyroid function tests (TFTs), and lipid profile, were all within normal limits. It was surmised that the hip fracture was caused by adjacent necrotic femoral head, and although there was a high risk of femoral head collapse because of her young age it was decided to preserve her native femoral head rather than proceed with a hip replacement.

Fig. 2.

a and b Magnetic resonance imaging (MRI) scans of the pelvis coronal (a) and axial (b). The coronal T2-weighted (T2W) image shows diffuse bone marrow oedema and a double-line sign on the right. Note similar changes in the left hip consistent with osteonecrosis.

In theatre, the fracture was reduced and stabilised using two 7.0 mm titanium cannulated screws (Fig. 3). Postoperatively, the patient reported good pain relief and was instructed to maintain touch weight-bearing for six weeks. However, serial radiographs at three and six months demonstrated progressive collapse of the femoral head with intra-articular screw penetration (Fig. 4). At this stage, the patient was in significant pain, and after a shared decision-making process, she elected to undergo a total hip replacement (Fig. 5).

Fig. 3.

Post-operative radiograph showing early fracture collapse following cannulated screw fixation of the femoral neck fracture.

Fig. 4.

Anteroposterior (AP) radiograph of the hip showing advanced osteonecrosis and screw penetration.

Fig. 5.

Anteroposterior (AP) radiograph of right total hip arthroplasty.

3. Discussion

Pelvic pain syndrome affects up to 20 % of pregnant women, and while most cases are trivial, more serious pregnancy-related hip diseases may present in a similar fashion [5].

Magnetic resonance imaging is the gold standard investigation for hip pain in pregnancy and can detect abnormalities within 48 h of symptoms [6]. Signal changes seen on T1- and T2-weighted images allow differentiation of hip pathologies. For example, transient osteoporosis of the hip typically shows a diffuse increase in signal intensity on T2-weighted images, while features of avascular necrosis include focal changes and the pathognomonic double-line sign [7]. Furthermore, femoral neck stress fractures are readily identified by a fracture line on MRI [8]. Although concerns for the safety of the foetus justify the prudent use of investigations, MRI is considered safe during all stages of pregnancy. Guidelines from the American College of Radiology and the American College of Obstetricians and Gynecologists recommend MR scans without contrast in scanners with magnets ≤3.0 Tesla [3]. In the patient reported here, the MRI scan readily identified the hip fracture and the AVN of both femoral heads. While clinicians should be cautious in requesting investigations during pregnancy, MRI can identify and differentiate hip pathologies and is safe for both the mother and baby, particularly during the third trimester.

Accurate diagnosis of hip pain during pregnancy is critical when treating patients. While transient osteoporosis of the hip and AVN share some similarities on MRI, there are distinct differences in clinical outcomes. Transient osteoporosis of the hip most commonly occurs in the third trimester and is a self-limiting condition which slowly resolves over six to nine months [7]. On the other hand, avascular necrosis of the hip has an insidious onset with progressively worsening pain, and most cases require surgical intervention [7]. Furthermore, AVN is considerably less common than transient osteoporosis of the hip during pregnancy. Bilateral avascular necrosis is even rarer, with only 14 cases reported in the literature since Montella et al. first published their series in 1999 (see also Table 1 [[9], [10], [11], [12], [13], [14], [15], [16], [17], [18]]). The MRI scan of in the present case demonstrated the pathognomonic double-line sign in both femoral heads, which confirmed the diagnosis of bilateral avascular necrosis of the hip (Stage III).

Table 1.

Summary of reports describing bilateral osteonecrosis of the hip associated with pregnancy.

Author year	Age at pregnancy (yrs)	Onset of symptoms	Cause	Stage	Treatment
Hasegawa et al. [10] 1999	31	Third timester	Ovarian stimulation with hMG and hCG	NK	NK
Montella et al. [9] 1999	30	NK	Nil	L-IV R-IV	Free vascularised fibular graft
	35	NK	Baseline hypercoagulability	L-IV R -III	Free vascularized fibular graft, then bilateral THA
Vandenbussche et al. [11] 2004	36	3 weeks post-partum	Idiopathic	L-IV R-IV	Bilateral cemented THA
Ugwonali et al. [12] 2008	32	Third trimester	Beta thalassemia	NK	Bilateral core decompression and grafting/ pulsed electromagnetic fields
	42	Second trimester	Idiopathic	L- II R-?	Core decompression -Left
	32	Post-partum	Thalassemia minor	L-? R-?	Left core decompression Right THR,revision THA 8 years later
	38	3 months post-partum	Idiopathic	L- II R-?	Left Core Decompression, with bone grafting, THA 6 years later
Rao et al. [13] 2009	25	Second trimester	Nil	L- II/III R- II/III	NK
Lin et al. [14] 2011	27	2 weeks post-partum	Ovarian stimulation with clomiphene citrate	NK	Initial bilateral core decompression, bilateral THA 6 months later
	26	6 month post-partum	Ovarian stimulation with clomiphene citrate	L- IV R- IV	Bilateral core decompression and medical treatment
Igrek et al. [15] 2018	24	Third trimester	NK	NK	NK
Wood et al. [16] 2020	34	Third trimester	Idiopathic	L-IV R- II	Left hemiarthroplasty, conversion THA 1 year later
Turgay et al. [17] 2022	30	Third trimester	Idiopathic	L-? R-?	Restricted weight bearing/ Hyperbaric oxygen
El Shintenawy et al. [18] 2022	23	NK	Primary antiphospholipid syndrome	L- III R- III	Bilateral Core Decompression

hMG -human menopausal gonadotropin, hCG - human chorionic gonadotropin, NK-Not known.

Concurrent femoral neck fracture and AVN of the hip is a rare and challenging treatment dilemma. The situation is made more complex when it occurs in a pregnant patient. Treatment options generally involve either head-preserving surgery or arthroplasty. While arthroplasty can be expected to treat older patients successfully, the risk of early revision and restricted function make this option less attractive in a young female. Zuckerman et al. reported the successful treatment of a patient with bilateral hip fractures and AVN using sliding hip screws. The authors postulated that their success may be attributed to the sliding hip screws effectively performing a core decompression in addition to fracture stabilisation [19]. More recently, Nishino et al. documented the progression of AVN of the hip leading to bilateral femoral neck fractures, which were successfully treated by internal fixation [20]. Internal fixation is not always successful, as the case reported here shows. Critical analysis of the outcomes by Zuckerman et al. and Nishino et al. reveal several important features that contribute to success: undisplaced fractures, early diagnosis and treatment, small area of femoral head necrosis and early-stage disease. Unfortunately, many of these features were absent in the patient reported here.

This case emphasizes the significance of diagnosing AVN during pregnancy at an early stage to prevent severe consequences. While serious hip pathology is rarely encountered during pregnancy, obstetricians should feel confident in requesting MRI when it is indicated.