Spina Ventosa (Tuberculous Dactylitis) - Complete Guide

Definition and Etymology

"Spina Ventosa is a destructive cortical lesion surrounding the medullary canal along with progressive subperiosteal hyperplasia, resembling roentgenographically like a tumour." - American Journal of Translational Research, 2024

Etiology

Causative Organism

• Mycobacterium tuberculosis is the primary pathogen
• Rarely, atypical (nontuberculous) mycobacteria may cause a similar picture - as emphasized in Campbell's Operative Orthopaedics 15th Ed 2026

Route of Infection

• Haematogenous spread (lympho-hematogenous) is the dominant route - the lung acts as the primary focus in approximately 75% of cases
• Less commonly: direct inoculation or contiguous spread from adjacent structures

Risk Factors and Epidemiology

• Primarily a disease of children under 6 years (most common under 5 years); rare after age 6 due to changes in blood supply pattern
• Males and females equally affected
• Poverty, malnutrition, overcrowding, and immunocompromise (HIV) are major risk factors
• Endemic in South Asia, Sub-Saharan Africa, and Southeast Asia
• Exposure to an adult with pulmonary tuberculosis is often traceable
• Skeletal TB accounts for only 1-5% of all TB cases; of those, spina ventosa is uncommon but characteristic

Why Short Tubular Bones?

Pathology

Gross Pathology - Stage by Stage

• Mycobacteria carried in blood lodge in the centre of the marrow cavity through the large nutrient artery
• The nutrient artery of the short tubular bone enters centrally, depositing the first inoculum in the medullary canal

• The interior of the short tubular bone is gradually converted into a tuberculous granuloma
• Typical caseating granulomas form: epithelioid macrophages, Langhans giant cells, lymphocytes, plasma cells, and central caseation necrosis
• The nutrient artery becomes occluded by granulomatous inflammation

• Granulomatous destruction expands outward, causing:
  • Destruction of internal bone lamellae
  • Thinning and expansion of the cortex
  • Subperiosteal new bone formation (periosteal reaction lifts the cortex outward)
• The bone takes on a fusiform/spindle-shaped expanded appearance
• Sequestra may form (though less common than in pyogenic osteomyelitis)

• Natural course: healing with shortening of the bone and deformity of the neighbouring joint
• Complications: sinus formation (discharging sinuses through skin), secondary pyogenic infection, pathological fracture

Histopathology

• Caseating epithelioid granulomas with Langhans giant cells
• Acid-fast bacilli (AFB) demonstrable by Ziehl-Neelsen (ZN) stain (though often paucibacillary and difficult to detect)
• Caseation necrosis in the centre of granulomas
• Surrounding fibrous reaction in chronic cases

Clinical Features: Signs and Symptoms

Characteristic Presentation

Local Signs

• Fusiform/spindle-shaped swelling of the affected digit - this is the hallmark
• Swelling is initially small, gradually progressive
• Bony hard consistency on palpation, fixed to underlying bone
• Mildly tender; local temperature may be slightly raised
• No joint involvement initially (joints typically spared in early stages)
• Skin over the swelling is normal in appearance early on
• Sinus formation may occur in advanced cases with discharge of caseous material

Systemic Signs

• Anorexia and weight loss are common
• Low-grade fever (may be absent - unlike pyogenic osteomyelitis where fever is high)
• No acute inflammatory signs (no intense redness, warmth, or severe pain) - this "quiet" presentation is a key differentiating feature from pyogenic infection
• Signs of primary pulmonary tuberculosis (cough, lymphadenopathy) may coexist
• Multiple digits may be affected simultaneously in children

Distribution

• Hand > foot (hands more commonly involved than feet)
• Phalanges > metacarpals > metatarsals
• Index and middle fingers most commonly affected
• Multiple bones may be involved simultaneously in some children

Investigations

1. Blood Investigations

• ESR - elevated (e.g. 72 mm/1st hour in reported cases)
• CRP - elevated
• CBC - mild anaemia, lymphocytosis possible
• Mantoux test (TST) - positive in the majority of cases; note that a positive test only indicates TB infection, not necessarily disease
• IGRA (Interferon-Gamma Release Assay) - more specific than TST; useful in BCG-vaccinated children

2. Imaging Studies

Plain X-Ray (First-Line, Most Important)

• Cyst-like lytic cavities within the expanded bone
• Diaphyseal expansion - fusiform/balloon-like widening of the bone shaft
• Cortical thinning with periosteal new bone
• Soft tissue swelling around the affected digit
• Absence of sequestra (or small sequestra) - distinguishes from pyogenic osteomyelitis
• Diffuse osteopenia of the involved bone - distinguishes from pyogenic infection
• Internal septations may be visible
• Sclerotic margins in long-standing cases

"Tuberculous dactylitis is rare but classically appears as cyst-like cavities associated with diaphyseal expansion more commonly affecting the bones of the hands than the feet - known as spina ventosa." - Grainger & Allison's Diagnostic Radiology

Ultrasound (US)

• Simple, non-invasive, no radiation
• Identifies soft tissue swelling, periosteal reaction, fluid collections
• Guides fine needle aspiration (FNAC)

CT Scan

• Defines extent of cortical destruction more precisely
• Identifies sequestra if present
• Shows bony sclerosis and destruction
• Not always required but useful in atypical cases

MRI (Gold Standard for Soft Tissue and Early Marrow Involvement)

• Highest sensitivity and specificity
• T1: low signal in medullary cavity (granuloma/pus)
• T2: high signal (oedema, caseous material)
• Gadolinium-enhanced: avid enhancement of granulation tissue
• Shows early marrow involvement before X-ray changes appear
• Identifies soft tissue abscess and sinus tracks
• Best for evaluating extent of disease and surgical planning

3. Microbiological Investigations

• Fine Needle Aspiration Cytology (FNAC) - first-line diagnostic procedure; shows caseating granulomas with epithelioid cells and Langhans giant cells
• AFB smear (ZN staining) of aspirated material - often negative due to paucibacillary nature
• Culture (Lowenstein-Jensen medium / MGIT BACTEC) - gold standard but slow (4-8 weeks)
• GeneXpert MTB/RIF - rapid molecular diagnosis; detects MTB DNA and rifampicin resistance within 2 hours; increasingly used as first-line
• Histopathology (biopsy) - confirmatory; shows typical caseating granulomas

4. Chest X-Ray

• Mandatory in all cases to identify primary pulmonary focus or miliary TB
• Pulmonary TB found in approximately 75% of cases

5. Sputum / Nasopharyngeal Swabs

• In children: induced sputum or gastric lavage for AFB smear and culture

Differential Diagnosis

Treatment

1. Anti-Tubercular Therapy (ATT) - Mainstay of Treatment

Intensive Phase (2 months) - 4 drugs (2HRZE)

Continuation Phase (7-10 months) - 2 drugs (HR)

2. Supportive Measures

• Splinting/immobilisation of the affected digit in the early phase to reduce pain
• Analgesics (NSAIDs)
• Nutritional support, iron supplementation
• Pyridoxine (Vitamin B6) supplementation with isoniazid to prevent peripheral neuropathy

3. Surgical Treatment (Secondary - Limited Role)

4. Monitoring Response

• Clinical: reduction in swelling, pain resolution, weight gain, improved appetite
• ESR and CRP normalisation
• Serial plain X-rays: progressive healing, sclerosis, reconstitution of bone

Prognosis

• Excellent with early diagnosis and complete ATT
• Natural (untreated) course leads to shortening of the affected bone and joint deformity
• Early treatment prevents bone shortening and deformity
• Recurrence is rare with complete treatment
• Drug resistance (MDR-TB) should be suspected and tested for in non-responders

Key Points Summary

• Campbell's Operative Orthopaedics 15th Ed 2026, p.1068 - Figure 25.17 and spina ventosa description
• Grainger & Allison's Diagnostic Radiology - Osteomyelitis section
• Gupta S et al., Am J Transl Res 2024 - Paediatric Spina Ventosa case report (PMID 39262713)
• Abebe W, PMC 2016 - Tuberculous Dactylitis: An Uncommon Presentation