What is the appropriate diagnosis and treatment for an adult patient with no significant medical history presenting with osteolytic change in the left calcaneus?

Osteolytic Change in Left Calcaneus: Diagnosis and Treatment

In any adult patient presenting with an osteolytic lesion of the calcaneus, malignancy must be ruled out first, as plain radiographs alone are insufficient for diagnosis and should be followed immediately by MRI. 1

Initial Diagnostic Approach

Imaging Strategy

• Obtain weight-bearing radiographs in two planes as the initial study, but recognize that X-rays alone missed the diagnosis in 41% of calcaneal osteolytic lesions, including 8 of 17 malignant cases 1
• MRI without contrast is mandatory when any osteolytic lesion is identified on plain films, as it is superior to radiographs for detecting the full extent of disease and distinguishing benign from malignant processes 1
• CT without contrast is an equivalent alternative to MRI for further characterization of the lesion 2

Critical History Elements

• Duration and character of pain: Increasing pain for more than 10 days without previous trauma should raise suspicion for malignancy 1
• Trauma history: Post-traumatic osteolytic changes suggest either stress fracture or post-traumatic osteomyelitis 3
• Systemic symptoms: Fever, weight loss, or night pain suggest infection or malignancy 4
• Activity changes: Recent increase in walking or change to harder surfaces suggests stress fracture 2

Physical Examination Findings

• Calcaneal squeeze test: Compress the calcaneus from medial to lateral; pain suggests stress fracture 2
• Point tenderness location: Palpate the lateral calcaneal wall (stress fracture), posterior superior calcaneus (Haglund's deformity), and diffusely (infection or tumor) 2
• Soft tissue changes: Swelling, erythema, or warmth suggest infection 4

Differential Diagnosis by Clinical Context

Malignant Lesions (Must Exclude First)

• Osteosarcoma, Ewing's sarcoma, and metastases accounted for 17 malignant cases in a multicentre study, with 5 osteosarcomas initially misdiagnosed on radiographs alone 1
• Three cases underwent unplanned excision ("whoops procedure") due to failure to recognize malignancy preoperatively 1
• No characteristic distribution pattern exists for different tumor types within the calcaneus using Diard's classification system 1

Infectious Causes

• Calcaneal osteomyelitis presents with less dramatic symptoms than long-bone osteomyelitis, with blood cultures positive in only 41% but tissue cultures positive in 91% 4
• Radiographic changes are often delayed and absent in 12% of osteomyelitis cases 4
• Staphylococcus aureus is the most common pathogen (found in 69% of cases), with Pseudomonas aeruginosa associated with neurological damage 3
• Post-traumatic osteomyelitis accounts for 62% of calcaneal bone infections 3

Benign Lesions

• Stress fractures cause progressively worsening pain following increased activity, with positive calcaneal squeeze test 2
• Osteoid osteoma is rare in the calcaneus but should be considered in young patients with persistent pain; early CT is critical as MRI may not show specific findings until 3 months after symptom onset 5
• Histiocytic neoplasms (Langerhans cell histiocytosis, Erdheim-Chester disease, Rosai-Dorfman disease) can cause osteolytic calcaneal lesions, with LCH showing osteolytic skull and bone lesions in 60% of cases 6

Treatment Algorithm

If Malignancy Cannot Be Excluded

• Obtain tissue diagnosis via biopsy before any definitive surgical intervention to avoid unplanned excisions that compromise oncologic outcomes 1
• Refer immediately to orthopedic oncology for biopsy planning and staging 1

If Infection is Suspected

• Surgical debridement with bone curettage plus appropriate antibiotic therapy is the standard treatment for calcaneal osteomyelitis 3
• Tissue cultures are essential (91% positive rate) and superior to blood cultures (41% positive rate) 4
• Early diagnosis and treatment with antibiotics alone may be effective, but delayed diagnosis leads to complications and chronic disease 4
• Mean healing time is 29 weeks with 40.5% relapse rate and 16.7% amputation rate 3

Prognostic Factors for Osteomyelitis

• Favorable factors: ASA score <2, post-traumatic etiology, age <65 years, absence of neuropathy, absence of diabetes 3
• Poor prognostic factors: Older age, diabetes mellitus, presence of neuropathy 3

Common Pitfalls

• Do not proceed with surgical excision based on radiographs alone, as 41% of diagnoses were incorrect and 8 malignancies were initially missed 1
• Do not rely on routine hematological tests for diagnosing calcaneal osteomyelitis, as they are of little value 4
• Reexamine patients 3-5 days post-injury if initial examination is limited by swelling 2
• Recognize that radiographic changes in osteomyelitis are often delayed and may be completely absent in 12% of cases 4