Diagnostic challenge of occult subtrochanteric femoral fracture in an elderly patient with negative initial MRI: a case report

Abstract

Introduction and importance:

Occult fractures of the proximal femur represent a significant diagnostic challenge in elderly patients when initial imaging is negative. Delayed diagnosis can lead to fracture progression and increased morbidity. This case highlights the limitations of initial imaging and the importance of maintaining a high index of suspicion in elderly patients presenting with persistent hip pain and an inability to bear weight.

Case presentation:

A 76-year-old female with a background of hypertension and type 2 diabetes mellitus presented with a 3-day history of progressive left hip pain and inability to bear weight, with no history of trauma. Initial pelvic radiographs and an MRI of the pelvis were negative for fracture. The patient condition was managed conservatively with observation. However, 20 days later, her symptoms worsened, and she developed ecchymosis over the thigh. Repeat radiography revealed a left subtrochanteric femoral fracture. The patient was medically optimized with a blood transfusion and subsequently underwent intramedullary nailing of the femur, 31 days after the initial presentation.

Discussion:

This case demonstrates that occult fractures may not be detected on initial MRI with elderly patients at higher risk. Persistent or worsening symptoms should prompt repeated imaging. Clinical judgment remains paramount in guiding further investigation and treatment. Surgical stabilization using intramedullary fixation remains the gold standard for subtrochanteric fractures.

Conclusion:

In elderly patients presenting with persistent hip pain and an inability to bear weight, an occult femoral fracture must be strongly considered, even when initial imaging results are negative. Repeat imaging and prompt surgical intervention are essential.

Introduction

Insufficiency fractures of the proximal femur and pelvis result from normal physiologic stress applied to a weakened bone, commonly due to osteoporosis, prior radiation therapy, prolonged corticosteroid use, rheumatoid arthritis, chronic renal failure, or mechanical changes following previous hip surgery (Table 1)^[1^]. Bisphosphonates are commonly used to treat osteoporosis; however, long-term use has been associated with atypical femoral fractures, particularly in the subtrochanteric region and femoral shaft^[2^]. These fractures are attributed to excessive suppression of bone turnover, leading to microdamage accumulation and impaired bone remodeling^[3^]. Clinically, they present with symptoms like localized pain and difficulty bearing weight without an identifiable history of trauma^[2^].

HIGHLIGHTS

• Initial radiograph and MRI results can be negative, particularly in cases of early or stress-related fractures.

• Persistent pain and inability to bear weight should prompt repeated imaging, regardless of the initial results.

• Clinical judgment remains essential and should not be overridden by normal initial imaging findings.

Table 1.

Timeline table.

Day	Event
Day 1	Onset of left hip pain with inability to bear weight. No history of trauma.
Day 3	Presented to orthopedic clinic. Initial negative pelvic X-ray and MRI.
Day 3–20	Managed conservatively: observation, oral tramadol 100 mg twice daily.
Day 20	Returned to clinic with worsening pain.
Day 20	Admitted to orthopedic ward with Repeat X-ray positive for left subtrochanteric femoral fracture.
Day 20–31	Inpatient management.
Day 31	Underwent antegrade intramedullary nailing (SIGN femoral nail).
Day 32	Mobilization started (post-operative day 1).
Day 33–34	Discharged home with outpatient follow-up appointment at 1 month and physiotherapy plan.

A particularly challenging subset of these injuries is occult fractures, which are not readily apparent on standard radiographs or, in some cases, even on magnetic resonance imaging (MRI). The reported incidence of occult hip fractures ranges from 2% to 10% among patients with negative initial X-rays^[4^].

Diagnosis requires a high index of clinical suspicion, particularly in elderly patients with risk factors such as prior fractures, osteoporosis, metabolic bone disease, bisphosphonate use, or chronic comorbidities. Although MRI is the gold standard for detecting occult fractures, its sensitivity may be limited.

This case report was prepared following the SCARE Guidelines for reporting surgical case reports, to ensure completeness and transparency in reporting.

Case presentation

A 76-year-old female with known hypertension and type 2 diabetes mellitus on medical treatment (losartan and metformin) presented to the orthopedic clinic with a 3-day history of left hip pain. The pain was aggravated by weight bearing and was associated with a complete inability to bear weight on the left lower limb. There was no history of trauma, recent falls, or constitutional symptoms such as fever or weight loss.

She had a history of a right fifth metatarsal stress fracture 6 months ago, which had been successfully managed non-operatively using a short leg cast. She did not report any history of bisphosphonate therapy.

On local examination, the left lower limb revealed severe pain on passive and active movement around the hip joint, no obvious deformity, and an intact distal neurovascular status, with a reduced range of motion, no signs of deformity, and no shortening of the limb.

An initial pelvic X-ray showed mild osteoarthritic changes in the hip joint but no visible fracture. The patient was referred for an MRI of the pelvis to rule out an occult fracture (Fig. 1). The MRI of the pelvis with bilateral hip joints demonstrated normal joint spaces without effusion or synovial thickening. The femoral heads showed normal marrow signal intensity with no evidence of avascular necrosis. No abnormalities were identified in the femoral necks, trochanters, shafts, or acetabula.

Figure 1.

Initial MRI with no fracture evidence.

Initially, the patient condition was managed conservatively with an ongoing observation, analgesics made of tramadol 100 mg twice a day, and plans to begin physiotherapy after 2 weeks.

After 20 days, she returned to the clinic complaining of worsening pain and a persistent inability to bear weight. On examination, in addition to severe hip pain, there was ecchymosis noted on her thigh and forearm.

A repeat pelvic X-ray scan was performed, which revealed a left subtrochanteric femoral fracture (Fig. 2).

Figure 2.

First X-ray with no fracture evidence.

The patient was admitted to the orthopedic ward, and management included skeletal traction, anticoagulation therapy, and analgesia consisting of intravenous paracetamol 1 g three times a day.

Pre-operative laboratory investigations revealed the following: hemoglobin: 8.7 g/dL, INR: 1.5, and PT: 20.6 seconds. She received one unit of blood transfusion, which raised her hemoglobin level to 9 g/dL and was medically optimized for surgery.

After 11 days, the patient underwent intramedullary nailing of the femur. An antegrade SIGN femoral nail was inserted, maintaining satisfactory alignment. Proximal locking was achieved with cephalomedullary screws, followed by distal interlocking using a freehand technique (Fig. 3). The procedure was successful and without complications. In the post-operative image, a mild varus was observed. The patient was discharged and given a follow-up appointment within 1 month. She continues to undergo outpatient follow-up and physiotherapy^[5^].

Figure 3.

Second X-ray showing the fracture and post-operative X-rays.

Discussion

Occult hip fractures are defined as fractures not visible on initial standard radiographs. They occur in 2–10% of patients with suspected hip fractures^[4^]. MRI is considered the gold standard for detection, with nearly 100% sensitivity and specificity for femoral-neck and intertrochanteric fractures^[1^]. However, early stress or insufficiency fractures may still be radiologically occult, as in this case.

Clinical vigilance is paramount. Persistent, severe hip pain, inability to bear weight, and evolving signs such as ecchymosis should prompt repeat imaging (Fig. 3).

Comorbidities such as diabetes mellitus, hypertension, chronic corticosteroid use, rheumatoid arthritis, bisphosphonates, and prior fractures further compromise bone quality and healing capacity^[1,6^]. In this case, the patient had hypertension and diabetes mellitus, which were under treatment with losartan and metformin, and were controlled well. Additionally, the patient did not report any history of bisphosphonate therapy.

In this patient, a prior metatarsal stress fracture suggested underlying bone fragility, predisposing her to a subtrochanteric insufficiency fracture. Pathological fractures are very common in osteoporotic bones.

Why was the initial MRI negative?

Technical factors related to the MRI protocol

The MRI was described as “of the pelvis with bilateral hip joints,” but specific sequences were not reported. Occult fractures are best visualized on fat-suppressed T2-weighted or STIR (short tau inversion recovery) sequences, which demonstrate bone marrow edema. If these sequences were omitted or suboptimal, a subtle insufficiency fracture could be missed^[7^].

Early stage of insufficiency fracture

Studies have shown that MRI sensitivity for occult hip fractures approaches 100% for femoral neck and intertrochanteric fractures, but subtle subtrochanteric insufficiency fractures may be less conspicuous due to thicker cortical bone and less pronounced early edema^[1^].

Patient-specific factors

The patient had well-controlled diabetes and hypertension, but no history of bisphosphonate use. However, her prior metatarsal stress fracture confirms systemic bone fragility. Osteopenic bone may exhibit atypical patterns of stress response that do not produce classical edema^[8^].

Subtrochanteric fractures in the elderly are best treated surgically, with intramedullary nailing as the preferred method (Fig. 3). This technique provides biomechanical stability by allowing load-sharing through the nail and resisting the varus and rotational deforming forces^[2^]. A mild varus was noted on the postoperative images in this patient.

Alhough medical optimization is necessary, early surgical management is crucial, as prolonged delays increase the risk of morbidity and mortality. In this case, preoperative correction of anemia and stabilization of comorbidities ensured safer anesthesia and reduced perioperative risk^[5^].

Early mobilization after surgical fixation is essential, and guidelines from the National Institute for Health and Care Excellence (NICE) and the Australian and New Zealand Hip Fracture Registry (ANZHFR) emphasize a multidisciplinary approach, including physiotherapy, occupational therapy, and coordinated medical management. Mobilization should ideally begin the day after surgery^[2,9^]. In this case, mobilization started the following day after surgery to improve recovery and reduce morbidity and mortality.

This case underscores the importance of integrating clinical assessment with imaging. Reliance solely on radiographs or even MRI may result in missed diagnoses (Figs 1 and 2). A high index of suspicion and prompt repeat imaging are essential.

The patient had a clear concern of the delay in the diagnosis and was very glad we repeated the imaging with a high index of suspicion of occult fracture. She was disappointed that an expensive imaging study had missed the diagnosis and considered it a waste of resources, but she was happy we repeated it with a cheaper imaging method and were able to help her.

Conclusion

Occult subtrochanteric femoral fractures can present with a negative initial MRI in elderly patients, and this case yields specific actionable lessons. In an elderly patient with an inability to bear weight and a prior stress fracture, a negative MRI should prompt repeat plain radiography within 7–14 days, not the 20-day delay that occurred here. Discharge to outpatient physiotherapy without a definitive diagnosis is unsafe; admission or very close follow-up is required. A prior fragility fracture is a red flag that should lower the threshold for repeat imaging. In resource-limited settings, repeated plain X-ray is a practical diagnostic alternative to repeat MRI with its own strengths and limitations.

Strengths

This case documents a complete clinical course from a false-negative MRI to surgical fixation. It highlights a real-world diagnostic pitfall often omitted from guideline discussions and adds to the small body of literature on MRI-occult subtrochanteric fractures, particularly from an African setting. The 20-day delay in diagnosis, while unfortunate, allowed for the observation of the natural history of fracture progression.

Limitations

This is a single retrospective case; we cannot definitively determine the cause of MRI negativity.

Ethical approval

Ethical clearance was obtained from the ethics committee board.

Consent

Written informed consent was obtained from the patient for publication and any accompanying images. A copy of the written consent is available for review from the Editor-in-Chief of this journal upon request.

Sources of funding

No financial support was provided for this work.

Author contributions

E.K.R.: conceptualization, first draft writing, revision, and editing; D.J.Y.: conceptualization, revision; William James Harrison: conceptualization, revision.

Conflicts of interest disclosure

The authors declare to have no known competing interests.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

All authors in the article accept full responsibility for the work, have access to the patient’s information, and have decided to publish.

Data availability statement

The data sets of the present study are available from the corresponding author upon request.

SCARE guideline

The work has been reported in line with the SCARE criteria.