Occult Hip Fracture Until Proven Otherwise
This 67-year-old man with anterior hip tenderness and inability to bear weight comfortably two weeks after a fall most likely has an occult hip fracture, and requires immediate MRI of the hip if plain radiographs are negative or equivocal. 1, 2, 3
Most Likely Diagnosis
The clinical presentation strongly suggests an occult hip fracture (likely femoral neck or basicervical fracture) based on:
- Age >65 years with fall mechanism - the single strongest risk factor for hip fracture 3, 4
- Anterior hip/groin tenderness ("in front of his hip bone") - classic for femoral neck fractures 5, 6
- Persistent pain two weeks post-fall - occult fractures commonly present with ongoing symptoms despite initially negative imaging 1, 3
- Difficulty bearing weight - even patients who can walk may have occult fractures 3, 7
Critical Pitfall to Avoid
Never dismiss hip pain in elderly patients with normal initial radiographs. Up to 33% of patients investigated for occult hip fractures actually have proximal femoral fractures that require surgical intervention 7. Patients may present with only vague pain in the buttocks, knees, thighs, groin, or back without classic shortening and external rotation 3.
Immediate Workup Algorithm
Step 1: Plain Radiographs (If Not Already Done)
- Obtain AP pelvis and frog-leg lateral hip views immediately 8, 5
- These identify most displaced fractures, but miss occult/nondisplaced fractures 1, 2
Step 2: MRI Hip Without Contrast (Urgent - Within 24-48 Hours)
- MRI is the gold standard for occult hip fractures and should be obtained when radiographs are negative but clinical suspicion remains high 1, 8, 2, 3
- MRI detects femoral neck fractures, basicervical fractures, intertrochanteric fractures, and greater trochanteric fractures 1, 7
- Do NOT use bone scan - it has been superseded by MRI 1
Step 3: Laboratory Evaluation
- Complete blood count (assess for anemia, infection) 2
- Basic metabolic panel (electrolytes, renal function) 2
- ECG (required in all elderly patients with hip fracture) 2
Differential Diagnoses to Consider
While occult fracture is most likely, the MRI will also identify:
Other Fracture Patterns (25% of cases)
- Pelvic fractures (pubic rami, sacral fractures) - managed non-operatively 7
- Isolated greater trochanteric fractures without femoral neck extension - non-operative management 1, 7
Soft Tissue Injuries (38% of cases with normal radiographs)
- Iliopsoas tendinopathy or bursitis - anterior hip pain, managed conservatively 1, 7
- Gluteal muscle injuries - lateral/posterior pain 7
- Trochanteric bursitis - lateral hip pain 1, 7
Less Common but Important
- Osteonecrosis of femoral head - insidious onset, requires MRI for early detection 8
- Lumbar radiculopathy - referred pain to hip region 1, 5
Management Based on MRI Findings
If Hip Fracture Confirmed
- Surgical intervention within 24-48 hours reduces mortality 2
- Femoral neck/basicervical fractures typically require arthroplasty or internal fixation 1
- Intertrochanteric fractures require cephalomedullary nail fixation 1
- Immediate weight-bearing as tolerated postoperatively 1, 2
- VTE prophylaxis with sequential compression devices plus pharmacological prophylaxis for 4 weeks 1, 2
- Orthogeriatric comanagement to reduce mortality and improve outcomes 2
- Bone health referral for osteoporosis evaluation and secondary fracture prevention 1, 2
If Soft Tissue Injury or Pelvic Fracture
- Non-operative management with protected weight-bearing 7
- Physical therapy for rehabilitation 6
- Consider ultrasound-guided injection for persistent bursitis 1, 9
If MRI Negative
- Reconsider diagnosis - evaluate for referred pain from lumbar spine, intra-abdominal pathology, or vascular claudication 5, 6
- Consider diagnostic hip injection under ultrasound or fluoroscopic guidance to confirm intra-articular vs extra-articular source 1, 8
Key Clinical Pearl
The combination of age >65, fall mechanism, anterior hip tenderness, and difficulty weight-bearing mandates aggressive investigation even with normal radiographs. 3 Delayed diagnosis of occult hip fractures leads to displacement, increased surgical complexity, and worse outcomes including higher mortality 1, 2, 4.