Introduction

The goal of treating artificial joint infection is to relieve the infection quickly and re-establish joint function, but many patients have underlying diseases, and treatment is often made problematic by the diversity of the causative bacteria. In this study we assessed the factor that enabled revision arthroplasty in patients with infection after artificial hip arthroplasty, including bipolar hip arthroplasty, in our hospital.

The evaluation of the lumbar spine by CT or MR in supine position provides excellent information about the morphology of the spinal structures (inside and outside the spinal canal) but of course cannot give dynamic information. By Newton’s Third Law we know that every axial vector acting on a functional spine unit corresponds a second vector of equal intensity but of opposite direction that counterbalances the first one and brings all the structures in a dynamic equilibrium. The definition of spinal instability by White and Panjabi is well known and X-ray plain film with dynamic testing is not always satisfactory for diagnosis.

From April 2003 through May 2004 we evaluated 45 patients with with a dedicated device able to produce an axial load on the patient with a dynamometer to measure the load applied. The study can be performed in all patients in whom spinal instability is clinically suspected, even if the patients underwent spine surgery. The study was performed by CT or MR but always before in rest and stress conditions. The applied load is 60–70 % of body weight, based on literature data regarding orthostatic load at the L3 S1 level. A spiral multi-slice acquisition technique must be used to obtain thin scans with which excellent 2D multiplanar (MPR) and 3D reconstructions can then be achieved.

Under normal conditions, under an axial loader, we do not see significant changes in spine morphology except for pseudo-protrusion of the disks. In pathologic conditions (38 patients) we must pay attention to the following: disc modifications (appearance or disappearance of vacuum phenomenon, volumetric increasing/appearance of protrusions or herniations); intersomatic findings (increment of the lysthesis, narrowing or widening of disc space, rotational movements, posterior translation of the vertebral body); interarticular joints modifications and neural foramina narrowing; and thickening of the ligamenta flava and narrowing of interspinous spaces and hypermobility of the spinous process.

We believe the CT/MR axial loader currently represents the only way to gain dynamic information in patients in whom spinal instability is clinically suspected.

The utility of vertebroplasty in the treatment of spinal pain has been accepted worldwide. In this co-operative study we show the success and failure rates related to the pathological condition treated (porotic, metastatic or angioma), the incidence of new vertebral fractures adjiacent to the previously treated one, and the incidence of symptomatic and asymptomatic side effects.

In all, 898 patients were treated from April 2001 through January 2004 for a total of 1796 vertebral bodies. Of these, 654 patients (73%) were treated for porotic abnormalities, 213 patients (24%) had neoplastic disease and 27 patients (3%) presented with compressive or painful angioma. Different types of cement were used. All patients were treated after MR and CT examination or, as an alternative to MR, bone nuclear medicine scan, always associated with clinical evaluation. The patients were treated under CT and C-arm fluoroscopy control (2 centres) or under fluoroscopy in an angiography suite (five centres). We never perfomed general anaesthesia, only local sedation or administration of neuroleptic drugs. Blood tests were always performed before the treatment to exclude coagulopathy. Only the presence of local or systemic infection was considered to be a real contraindication.

We had a 93% success rate in patients with porotic abnormalities, one of 73% in patients with neoplastic disease and of 100% in patients with angioma. Asymptomatic venous leak was seen in 135 patients (15%) and CT demonstrated asymptomatic pulmonary embolus in eight patients (0.9%). No symptomatic venous and pulmonary emboli were identified. New fractures adjacent to a previously treated vertebral body developed in 14 patients (1.3%) while six patients showed radiculopathy (0.6%) due to posterior leakage in the lateral lumbar recess that was treated and resolved with medical therapy in 3 weeks. In six patients we also had psoas haematoma treated with medical therapy; no instance of cord compression was found. Mild disc leakage developed in 90 patients (10%) but we did not find any relation with new adjacent vertebral fracture.

Vertebroplasty represents a safe technique in the treatment of spinal pain related to porotic, neoplastic changes or angioma. The technique must be performed with high performance technology. The incidence of symptomatic effects and new fractures related to previously treated vertebrae or disc leakage is very low.