Osteomyelitis: clinical update for practical guidelines

Bone infections represent a diagnostic or therapeutic challenge for the infectivologist, orthopaedic surgeon, radiologist and nuclear medicine physician. Staphylococcus aureus is the major bacterium responsible for bone infections although Mycobacterium tuberculosis is emerging as an infectious agent in Italy because of immigration from Africa and Asia. Osteomyelitis requires long and expensive antibiotic treatment, including rifampicin administered parenterally for several weeks and the use of antimicrobial-impregnated cement in prosthesis substitution. Sometimes it is necessary to carry out surgical debridement of a necrotic bone or the consolidation of compromised bones and joint prosthesis implants. Radiographs and bone cultures are mainstays for the diagnosis of bone infections but are often useless in the lengthy management of these patients. Diagnosis of skeletal infections still includes conventional radiography but magnetic resonance imaging is essential in haematogenous and spinal infections. Bone scans are still useful in acute osteomyelitis whereas scintigraphy using labelled white blood cells is preferred in infections of peripheral bone segments or joint prosthesis. In the axial skeleton a combination of an agent for detecting inflammation ((67)Ga citrate) and a metabolic agent ((99m)Tc-methylene diphosphonate) enables an infection and an area of increased metabolic activity to be distinguished. [(18)F]Fluorodeoxyglucose positron emission tomography, where available, has a significant impact in the study of infections using radionuclides: high-resolution tomographic images represent an effective alternative to gallium in the assessment of inflammation of spine lesions but a comparison with morphological examinations (computed tomography or magnetic resonance imaging) is essential.

Clinical feasibility of two-step streptavidin/111In-biotin scintigraphy in patients with suspected vertebral osteomyelitis

PURPOSE

Streptavidin accumulates at sites of inflammation and infection as a result of increased capillary permeability. In addition to being utilised by bacteria for their own growth, biotin forms a stable, high-affinity non-covalent complex with avidin. The objective of this investigation was to determine the diagnostic performance of two-step streptavidin/111In-biotin imaging for evaluating patients with suspected vertebral osteomyelitis.

METHODS

We evaluated 55 consecutive patients with suspected vertebral osteomyelitis (34 women and 21 men aged 27-86 years), within 2 weeks after the onset of clinical symptoms. Thirty-two of the patients underwent magnetic resonance imaging (MRI) and 24, computed tomography (CT). DTPA-conjugated biotin was radiolabelled by incubating 500 microg of DTPA-biotin with 111 MBq of 111In-chloride. Two-step scintigraphy was performed by first infusing 3 mg streptavidin intravenously, followed 4 h later by 111In-biotin. Imaging was begun 60 min later.

RESULTS

Streptavidin/111In-biotin scintigraphy was positive in 32/34 patients with spinal infection (94.12% sensitivity). The study was negative in 19/21 patients without infection (95.24% specificity). The corresponding results for MRI and CT were 54.17% and 35.29% (sensitivity), and 75% and 57.14% (specificity), respectively. All statistical parameters of diagnostic performance (Youden's J index, kappa measure of agreement with correct classification, accuracy, sensitivity, specificity, positive likelihood and negative likelihood) were clearly better for streptavidin/111In-biotin scintigraphy than for either MRI or CT.

CONCLUSION

Streptavidin/111In-biotin scintigraphy is highly sensitive and specific for detecting vertebral osteomyelitis in the first 2 weeks after the onset of clinical symptoms, and is potentially very useful for guiding clinical decisions on instituting appropriate therapy.

CT-guided radiofrequency ablation of osteoid osteoma: long-term results

The aim of the study was to assess the safety and efficacy of CT-guided percutaneous radiofrequency (RF) ablation of osteoid osteoma (OO). From 1997 to 2001, RF ablation was performed on 38 patients with OO, diagnosed clinically and by radiography, scintigraphy, contrast-enhanced MRI, and CT. Treatment was performed via percutaneous (n=29) or surgical (n=9) access, under CT guidance in all cases, with an 18-gauge straight electrode. Patients were discharged within 24 h and followed up clinically (at 1 week and every 6-12 months) and with MRI (at 6 months) and scintigraphy (after 1 year). The technical success rate was 100%. Complications occurred in two patients, consisting in local skin burns. The follow-up range was 12-66 months (mean +/- SD, 35.5+/-7.5 months). Prompt pain relief and return to normal activities were observed in 30 of 38 patients. Persistent pain occurred in eight patients; two patients refused further RF ablation and were treated surgically; RF ablation was repeated in six cases achieving successful results in five. One patient reported residual pain and is being evaluated for surgical excision. Primary and secondary clinical success rates were 78.9 (30/38 patients) and 97% (35/36 patients), respectively. CT-guided RF ablation of OO is safe and effective. Persistent lesions can be effectively re-treated. Several imaging modalities are needed for the diagnosis of OO and for the follow-up after treatment, particularly in patients with persistent symptoms.

Neurological deterioration after head trauma in patients with colloid cysts of the 3rd ventricle. Two case histories

The authors report 2 cases of colloid cyst of the 3(rd) ventricle (both patients previously asymptomatic) diagnosed after head trauma. Neurological deterioration due to biventricular hydrocephalus, rendering necessary an urgent bilateral CSF shunting, was observed. The possible relationship between clinical deterioration and head injury in these cases is discussed.

Improvement of the bone-pin interface strength in osteoporotic bone with use of hydroxyapatite-coated tapered external-fixation pins. A prospective, randomized clinical study of wrist fractures

BACKGROUND

Achieving adequate fixation strength in osteoporotic bone is a challenge. In this study, we examined the use of hydroxyapatite-coated tapered external-fixation pins for the fixation of wrist fractures in patients with osteoporosis.

METHODS

Twenty female patients with osteoporosis and a fracture of the wrist were divided into two paired groups and randomized to receive either standard tapered pins or hydroxyapatite-coated tapered pins. Two pins were inserted in the distal part of the radius, two pins were inserted in the second metacarpal, and an external fixation device was mounted. All fixation devices were removed six weeks after surgery.

RESULTS

The mean pin-insertion torque (and standard deviation) was 461 +/- 254 Nmm in the group managed with standard pins and 332 +/- 176 Nmm in the group managed with hydroxyapatite-coated pins (p = 0.01). The mean pin-extraction torque was 191 +/- 155 Nmm in the group managed with standard pins and 600 +/- 214 Nmm in the group managed with hydroxyapatite-coated pins (p < 0.0001, power 95%). The mean extraction torque was lower than the corresponding insertion torque at each pin position in the group managed with standard pins (p < 0.05), whereas the mean extraction torque was higher than the corresponding insertion torque at each pin position in the group managed with hydroxyapatite-coated pins (p = 0.001). Two patients managed with standard pins and no patient managed with hydroxyapatite-coated pins had a pin-track infection. Pain during pin removal did not differ between the two groups.

CONCLUSIONS

The present study showed that hydroxyapatite-coated tapered external-fixation pins provided improved fixation in the treatment of wrist fractures in patients with osteoporosis.

Combined approach to intrathoracic lesions invading the spinal cord

The treatment of intrathoracic lesions invading the spine has two main issues: the surgical route to be preferred and the incidence of complications following the operation. As a matter of fact surgical treatment, performed in two stages, has a higher risk of cord accidents. Some authors have proposed a combined thoraco-vertebral surgical route which allows the exposition of both the spine and the chest. We experienced the utility of such a surgical approach in the treatment of two endothoracic lesions invading the thoracic spine and requiring the stabilization of the rachis. Satisfactory results were achieved without morbidity.

Clinical validation of the avidin/indium-111 biotin approach for imaging infection/inflammation in orthopaedic patients

We report here the results of a validation study of the avidin/indium-111 biotin approach in patients with skeletal lesions. This study involved 54 patients with orthopaedic conditions: 20 patients with intermediate suspected osteomyelitis of the trunk, 19 patients with infection/inflammation of prosthetic joint replacements, and 15 patients with suspected osteomyelitis of appendicular bones. Avidin (3 mg) was injected as an i.v. bolus, followed 4 h later by 111In-biotin; imaging was acquired 30 min and 16-18 h after administration of 111In-biotin. Technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO)-labelled leucocyte scintigraphy was performed in 39/54 patients. The overall sensitivity of the avidin/111In-biotin scan was 97.7% (versus 88.9% for 99mTc-HMPAO leucocyte scintigraphy). While the diagnostic performance of avidin/111In-biotin scintigraphy was similar to that of 99mTc-HMPAO leucocyte scintigraphy in patients with prosthetic joint replacements or osteomyelitis of appendicular bones, the avidin/111In-biotin approach clearly performed better than 99mTc-HMPAO leucocyte scintigraphy in patients with suspected osteomyelitis of the trunk (100% sensitivity, specificity and accuracy versus 50% sensitivity, 100% specificity and 66.7% accuracy for 99mTc-HMPAO-leucocyte scintigraphy). These results demonstrate the feasibility of the avidin/111In-biotin approach for imaging sites of infection/inflammation in the clinical setting. Although no systematic advantages of avidin/111In-biotin scintigraphy were found versus 99mTc-HMPAO leucocyte scintigraphy, the newer scintigraphic method is more practicable and involves lower biological risk for the operators.

Distal posterior inferior cerebellar artery saccular and giant aneurysms: report of two new cases and a comprehensive review of the surgically-treated cases

Aneurysms of the distal posterior inferior cerebellar artery are rare comprising less than 0.5 to 3% of all aneurysms. The authors report two cases of distal PICA aneurysms: a case of a ruptured saccular aneurysm arising on the tonsillomedullary segment of the PICA and a case of a giant aneurysm arising on junctional site of lateral-medullary and tonsillo-medullary segments. In the first case subarachnoid and intraventricular hemorrhage was diagnosed by CT and four vessel-angiography visualized the aneurysm which was clipped successfully. In the second case MRI was suggestive for posterior fossa giant aneurysm; four vessel angiography confirmed the suspicion, detected distal PICA origin of the giant aneurysm and disclosed the association with a middle cerebral artery saccular aneurysm. Because of lacking of a clippable neck and important perforating vessels to brainstem, the aneurysm was trapped and excised successfully. The literature is exhaustively reviewed. Discussion regarding to distal PICA aneurysm distribution (location, age, sex, multiplicity and associated vascular anomalies), pathophysiology, clinical presentation, neuroradiological findings, surgery and outcome is presented.

Craniofacial pain and incomplete oculomotor palsy associated with ipsilateral primitive trigeminal artery. Case report

A case is reported of persistent primitive trigeminal artery associated with recurrent facial pain and noncomitant strabismus by partial ipsilateral oculomotor palsy. Transcranial Doppler disclosed indirectly persistent carotid-basilar anastomosis. CT and angiography allowed complete diagnosis excluding a posterior communicating artery aneurysm, a Tolosa-Hunt syndrome and an ophthalmoplegic migraine. Steroid therapy is recommended treatment. Surgery should be considered when symptoms are intractable to medical therapy.

Orbital "blow-in" fracture: MRI

A case of traumatic orbital encephalocele following a "blow-in" fracture is presented. Computed tomography (CT) and magnetic resonance imaging (MRI) findings are shown. Although CT was useful for identifying the orbital roof fracture, bone fragments and soft tissue abnormalities, MRI was more sensitive to brain herniation and an intraorbital haematoma.

CT morphology of a median nerve neurilemmoma at the arm. Case report and review

Computed tomography was performed in a patient with a median nerve tumor at the arm, histologically confirmed as neurilemmoma. Neurilemmoma was a slightly hypodense, solid tumor with no vascular contrast enhancement. To our knowledge this is the first CT description of a median nerve neurilemmoma at the arm. According to our experience and to previous literature, CT gives useful information regarding extent, anatomic location, size and relationship of peripheral nerve neoplasm to surrounding structures and may be an useful tool for evaluation arm nerve mass and for appropriate planning of surgical therapy.

67Ga-citrate imaging in rhabdomyosarcoma

A 22-year-old female patient with a swelling in the right forearm near the elbow underwent a 67Ga-citrate scan because of paraesthesia on the ulnar side of the right hand. The 67Ga total body scan showed intense focal uptake on the forearm in the same position as the swelling. At surgery a histological diagnosis of alveolar rhabdomyosarcoma was made. Five months later, a repeat 67Ga scan was normal. Eight months after the diagnosis, the patient complained of pain in the left lumbar region extending to the hypogastric area. A third 67Ga scan showed intense uptake near the spinal column which at surgery was found to be a metastasis of the primary tumor.