The patient presented with a 24-hour history of painful left hip and limp. He was pyrexial with a temperature of 39.3°C.
The patient presented with a 24-hour history of painful left hip and limp. He was pyrexial with a temperature of 39.3°C. Physical examination revealed good range of hip movements with minimal restriction. The patient was reluctant to weight bear. Urine dipstick testing showed protein 1+ with no leucocytes or blood. Laboratory results were Hb 12.8 g/dl, WCC 6.19 x 109, plasma viscosity 1.62 and CRP 117 mg/l.
Roentgenograms of the pelvis and femur were normal. An urgent ultrasound scan revealed no hip joint effusion or pelvic collection. On the second day after admission, blood cultures grew Staphylococcus aureus which was sensitive to flucloxacillin. Appropriate parenteral antibiotic therapy was started. A three-phase bone scintigraphy was performed, revealed increased isotope uptake around the left hip on dynamic, blood pool and static images suggestive of an infected hip. An MRI scan of the pelvis showed a localised area of bone marrow oedema involving the left iliac bone around the acetabulum. This abnormality corresponded to that demonstrated on the recent bone scan suggesting osteomyelitis. After 10 days of parenteral antibiotics, he was apyrexial with full range of hip movement.Oral antibiotics were continued for 6 weeks. A further 8 weeks' follow-up did not show any clinical or radiological recurrence.
Pelvic osteomyelitis in children is an uncommon lesion. Pelvic osteomyelitis should be considered in the differential diagnosis in any febrile child presenting with limitation of motion around the thigh or hip and/or with gait disturbance (1). The differential diagnosis of pelvic osteomyelitis in children includes septic arthritis of the hip or sacroiliac joint, Legg-Calve-Perthes disease, toxic synovitis of the hip, and less commonly, collagen-vascular diseases, neoplasm’s involving bone and retroperitonial abscess. The diagnosis of pelvic osteomyelytis is made on the basis of clinical, laboratory and imaging examinations (5). Plain x-ray changes in acute haematogenous osteomyelitis lag between 7 to 10 days behind the evolution of infection, which are well known. The three-phase bone scan is the gold standard and it includes assessment of blood flow (angiographic phase), early uptake by bone (blood pool phase), and late uptake (delayed bone phase, 2 hours later). This permits differentiation of cellulitis from osteomyelitis. The scintigraphic appearance of osteomyelitis is increased uptake in all three phases, especially the third. A photopenic spot (cold) may be encountered in infants and is related to severe medullary thrombosis and compression of the nutrient arteries by high pressure intraosseous pus. Reported sensitivities of bone scans for detection of osteomyelitis vary from 32% to 100% (5). Using the three-phase technique and a high-resolution gamma camera, it has been found by Ferley et al. to have a sensitivity of 89% and specificity of 94% in a large series of children. Gallium–67 citrate was the first scintigraphic agent used to detect inflammatory processes. Despite initially promising results, sequential technetium–gallium scanning has demonstrated an accuracy rate of only 70%. Sequential technetium-gallium scanning is especially unreliable in patients who have another lesion, such as non-union, surgery or a neuropathic joint, at the site of suspected osteomyelitis (5). Indium-111-labelled leukocytes, indium-labelled polyclonal immunoglobulins and technetium-99-m-labelled leukocytes are now being evaluated. In a study of 100 patients with a variety of suspected infections and inflammation, a sensitivity of 100% and a specificity of 95% were reported using Tc-99m-labelled leukocytes (HMPAO-WBC). Marrow abnormality on MRI is a more sensitive indicator of disease than lytic changes seen radiographically and appears much earlier in the course of the disease. Active osteomyelitis shows a low signal on T1-weighted images and appears as a high signal on T2-weighted images (5). This pattern represents a replacement of the marrow fat with water secondary to oedema, exudates, hyperaemia and ischaemia. In a study by Morrison et al, demonstrated an improved sensitivity (88%) and specificity (93%) with fat suppressed contract enhanced MR imaging compared to unenhanced MR imaging (sensitivity of 79% and specificity of 53%). The intravenous contrast agent, gadopentetate di-N-methylglucamine, a paramagnetic material, may also be useful in differentiating vascularized and inflamed tissue from the peripheral rim enhancement characteristic of an abscess. The MRI technique appears promising in the diagnostic work-up of osteomyelitis, but remains of limited use for whole body examination. This is important particularly in the paediatric age group where multifocal disease is seen in 7% of cases. Scintigraphy is preferred to MRI for the initial evaluation, because it is less expensive, rarely requires sedation and children can be scanned more than once, thus improving the detection rate. MRI is reserved for cases that require surgical intervention such as infections in the spine and pelvis, and difficult cases in which there is conflicting clinical data or infection that fails to respond to antibiotic treatment. A comparative study by Unger et al quoted sensitivities of MR and scintigraphy for diagnosis of osteomyelitis were 92% and 82% and the specificities were of 96% and 65% respectively. Because of its ability to separate soft tissue disease from underlying bone marrow, MR may be used to evaluate patients with positive bone scintigraphy to improve the specificity and accuracy of diagnosis for osteomyelitis. CT should be used as a second or confirmatory study when a single nuclear scintigram is normal or equivocal and pelvic osteomyelitis is strongly suspected on clinical grounds. Spiral CT especially is superior to MRI for visualising bony destruction, gas in the bone and bony sequestration and is useful in the spine, pelvis and sternum. Ultrasound scanning is a non-invasive, easily available technique, which does not use ionising radiation; in subperiosteal abscesses, ultrasound-guided aspiration and drainage may prove useful in some cases. In a review of currently used imaging techniques for osteomyelitis Sammak et al. concluded that various techniques are important and complimentary, rather than competitive, in the diagnosis of osteomyelitis. It is vital to understand the limitations of each imaging modality in order to avoid any delay in the diagnosis and management and prevent possible complications.
Pelvic osteomyelitis (left iliac bone)
1. Pelvic anteroposterior (AP) X-ray: Mildly abnormal bone density is noted in the iliac region on the affected side (left side). However, because radiographic findings of acute osteomyelitis often lag behind clinical presentation, only suspicious structural changes or soft tissue swelling may be observed in the early stages.
2. Bone Scan (Three-phase Bone Scan): Shows significant abnormal radioactive uptake (“hot spot”) in the left pelvic area during the blood flow phase, blood pool phase, and delayed phase, consistent with osteomyelitis.
3. MRI: On T1-weighted images, reduced (low) signal intensity is seen in the left iliac bone and surrounding bone marrow; on T2-weighted images, there is a high signal area, suggesting bone marrow edema or inflammatory exudate. Slight exudate or inflammatory thickening can be seen in the local soft tissue. Overall, these findings are consistent with acute or subacute pelvic osteomyelitis.
Based on the above imaging findings and the child’s clinical symptoms of fever, left hip pain, and limping, the following possibilities are considered:
1. Pelvic (including iliac bone) Osteomyelitis: Three-phase elevation on a bone scan or a clearly high signal on T2-weighted MRI is an important anatomical and functional basis for diagnosing osteomyelitis; acute fever and local pain fit the characteristics of this disease.
2. Pyogenic Arthritis of the Hip or Sacroiliac Joint: Also common in this age group. If only the joint is involved, MRI is more useful for observing joint effusion and cartilage destruction, but a bone scan can also show abnormalities.
3. Legg-Calvé-Perthes Disease: Commonly seen in children, but its characteristic findings usually involve collapse of the femoral head cartilage and structural changes in the femoral head. Prominent involvement of the iliac bone or central pelvic region in this case does not match well.
4. Toxic Synovitis: Usually presents with milder symptoms, and imaging typically does not show distinct bone marrow abnormalities, which does not correspond to the significant bone scan and MRI changes seen here.
5. Other Rare Lesions (e.g., certain tumors, connective tissue diseases, or other abscesses): A local soft tissue mass or tumorous change can produce similar symptoms. However, given the current imaging features and the acute clinical course, malignant tumors are less likely.
Considering the patient’s high fever (up to 39.3°C), pain in the left hip or left iliac region, three-phase increase on the bone scan, and the typical osteomyelitis signal changes on MRI, the most likely diagnosis is:
Acute osteomyelitis of the left pelvis (iliac bone).
If any clinical doubts remain, additional tests such as hematologic indicators (white blood cell count, C-reactive protein, erythrocyte sedimentation rate) and bacteriological cultures (blood culture or biopsy) can be performed for further clarification.
1. Medication:
- Antibiotic Therapy: Empiric broad-spectrum antibiotics targeting common pathogens (e.g., Staphylococcus aureus) are preferred initially. After the causative organism is identified, the regimen can be adjusted based on antibiotic sensitivity test results. The treatment course should be sufficiently long—generally at least 4–6 weeks—to prevent recurrence.
- Antipyretic and Analgesic Treatment: Use acetaminophen or ibuprofen to relieve systemic and local symptoms.
2. Surgical Intervention:
- If there is an abscess, increased intraosseous pressure, or if imaging indicates obvious sequestrum or abscess cavity, consider surgical intervention such as debridement, drainage, or curettage of the lesion.
- The surgical approach should be determined by the extent of the lesion and the overall condition of the child, in consultation with the pediatric orthopedic team.
3. Rehabilitation and Exercise Prescription:
- Before acute inflammation is controlled and pain is alleviated, it is recommended to reduce weight-bearing on the affected side. Use crutches or other assistive devices if necessary, and limit excessive hip movement to prevent further spread of inflammation.
- As symptoms improve, gradually introduce mild joint activities, such as slow flexion, extension, abduction, and adduction exercises of the hip while lying or sitting, closely monitoring for pain and fever.
- Example of the FITT-VP Principle:
① Frequency: Start with 1–2 sessions per day, increasing to 2–3 times per day depending on tolerance.
② Intensity: Begin at a low intensity that does not cause significant pain or fatigue, keeping the pain rating mild (e.g., VAS 2–3).
③ Time: 10–15 minutes per session initially, gradually extending to 20–30 minutes as rehabilitation progresses.
④ Type: Options include active joint movements, hip exercises in water (if available), and light resistance training (initiated after full improvement).
⑤ Progression: Progress the range of movement and training load as the child improves with antibiotic therapy and local symptom relief. Monitor the affected side’s pain level, body temperature, and blood test indicators regularly to decide if further adjustments to the exercise regimen are needed.
- The overall rehabilitation process should be conducted under close supervision by pediatric orthopedic and rehabilitation specialists to ensure safety and prevent relapse due to excessive weight-bearing.
This report is a reference medical analysis based on the currently available information and does not replace in-person diagnosis or the advice of professional physicians. Specific treatment plans should be determined by considering the child’s actual condition and following specialist advice.
Pelvic osteomyelitis (left iliac bone)
