Causes of Severe Hip Pain in Elderly Patient After Fall with Negative X-ray
In an elderly patient with severe hip pain after a fall and negative plain radiographs, the most likely cause is an occult proximal femoral fracture (present in approximately 33-42% of cases), followed by pelvic fractures (25%) and soft tissue injuries (38%). 1, 2
Understanding the Clinical Problem
Approximately 10% of hip fractures are not visible on initial plain radiographs 1. Negative radiographs alone cannot exclude fracture 1. This represents a critical diagnostic challenge because delays in diagnosis and treatment are directly associated with increased mortality, complication rates, longer hospital stays, and worse short- and long-term outcomes 1.
Specific Differential Diagnoses
Occult Fractures of the Proximal Femur (33-42% of cases)
- Femoral neck fractures (subcapital, transcervical, basicervical)
- Intertrochanteric fractures (15% in one series) 3
- Greater trochanter fractures - often have intertrochanteric extension not visible on radiographs 1
- Subtrochanteric fractures 4
Critical pitfall: Greater trochanter fractures that appear isolated on X-ray frequently have intertrochanteric extension when evaluated with MRI, changing management from conservative to surgical 1.
Pelvic Fractures (25% of cases)
- Pubic rami fractures (often bilateral)
- Sacral fractures (frequently occur with pubic rami fractures)
- Acetabular fractures - particularly posterior wall fractures that can mimic femoral neck fractures on AP radiographs 5
Studies show 38% of patients with negative hip radiographs had proximal femoral fractures, while 33% had pelvic fractures 1.
Soft Tissue Injuries (38% of cases)
- Gluteal muscle group injuries (most common)
- Iliopsoas complex injuries
- Trochanteric bursitis
- Muscle contusions and hematomas
These injuries can cause severe pain and inability to weight-bear but are managed non-operatively 2.
Less Common Causes
Immediate Next Steps: Advanced Imaging
MRI without IV contrast is the gold standard next imaging study with near 100% sensitivity (99%) for detecting occult hip fractures 1. MRI detects:
- Proximal femoral fractures with 99% sensitivity
- Pelvic fractures
- Soft tissue injuries
- Avascular necrosis
- Bone marrow edema indicating incomplete fractures
CT without IV contrast is an acceptable alternative when MRI is contraindicated or unavailable, with 79-94% sensitivity for occult fractures 7, 8. In one study, 26% of elderly patients had at least one contraindication to MRI 8. CT also reduces ED time (430 minutes vs 502 minutes for MRI) 8.
Important caveat: While rare, MRI can occasionally miss fractures initially, particularly subtrochanteric fractures 4. If symptoms persist or worsen despite negative MRI, repeat imaging is mandatory.
Clinical Decision Algorithm
Persistent severe hip pain + inability to weight-bear after fall = occult fracture until proven otherwise, regardless of negative X-rays 1, 9
Order MRI pelvis and affected hip without contrast as the next study 1
Do not discharge based on negative radiographs alone - this leads to delayed diagnosis with increased morbidity and mortality 1
If MRI/CT negative but symptoms persist or worsen: repeat imaging in 2-3 days 9, 4
Fracture detected: Surgical consultation within 24 hours - delays beyond this increase mortality 10, 1
Key Clinical Pitfalls to Avoid
- Never rely on physical examination alone - it cannot reliably diagnose or exclude hip fractures 1
- Never assume negative X-rays mean no fracture - 10% of hip fractures are radiographically occult 1
- Never discharge without advanced imaging when clinical suspicion remains high - this is the most dangerous error 1, 9
- Watch for posterior acetabular wall fractures that project over the femoral neck on AP views and mimic subcapital fractures 5
- Remember that isolated greater trochanter fractures on X-ray often have hidden intertrochanteric extension requiring surgical fixation 1