Osteophytes are bony spurs on normal bone that develop as an adaptive reparative process due to excessive stress at/near a joint. As osteophytes develop from normal bone, they are not always well depicted in common imaging techniques (e.g. CT, MRI). This creates a challenge for preoperative planning and image-guided surgical methods that are commonly incorporated in the clinical routine of orthopaedic surgery.

The study examined the accuracy of osteophyte detection in clinical CT and MRI scans of varying types of joints.

The investigation was performed on fresh-frozen ex-vivo human resected joints identified as having a high potential for presentation of osteophytes. The specimens underwent varying imaging protocols for CT scanning and clinical protocols for MRI. After dissection of the joint, the specimens were subjected to structured 3D light scanning to establish a reference model of the anatomy. Scans from the imaging protocols were segmented and their 3D models were co-registered to the light scanner models. The quality of the osteophyte images were evaluated by determining the Root Mean Square (RMS) error between the segmented osteophyte models and the light scan model.

The mean RMS errors for CT and MRI scanning were 1.169mm and 1.419mm, respectively. Comparing the different CT parameters, significance was achieved with scanning at 120kVp and 1.25mm slice thickness to depict osteophytes; significance was also apparent at a lower voltage (100kVp).

Preliminary results demonstrate that osteophyte detection may be dependent on the degree of calcification of the osteophyte. They also illustrate that while some imaging parameters were more favourable than others, a more accurate osteophyte depiction may result from the combination of both MRI and CT scanning.

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has been a popular alternative treatment for young patients with hip osteoarthritis. Despite its advantages over total hip arthroplasty, the use of MoMHRA remains controversial. Achieving the correct positioning of the prosthetic is a concern due to the difficulty and novelty of this procedure. Furthermore, it has been reported that post-operative management using 2D radiographs contains high degrees of variance leading to poor detection of prosthetic malpositioning. In order to compensate for the lack of available technology, current literature has suggested the use of blood metal ion levels as indirect predictors of prosthetic malpositioning due to the abnormal release of metal ions, particularly Chromium and Cobalt, as a result of increase wear and tear. The purpose of this study was to determine whether 2D/3D registration technology can report prosthetic orientation in vivo and, to establish whether 3D technology can accurately deduce prosthetic wear by correlating prosthetic angles with metal ion counts.

To begin this study, post-operative x-rays (n=72) were used as the two-dimensional media to measure acetabular orientation. Only the acetabular component was examined in this study and acetabular orientation was defined as the function of inclination and version angles. Virtual three-dimensional models of the native, pre-operative pelvises and the acetabular implant were generated and were manually superimposed over the post-operative x-ray images according to anatomical landmarks. A manual 2D/3D registration program was specifically designed for this task. Inclination and version angles of the 2D/3D registered product were measured. Post-operative CT models, which offer the most accurate depiction of the prosthetic in vivo, were generated for validation. Contrary to the study's hypotheses and current literature, no significant difference was observed between 2D vs. 2D/3D vs. CT data, suggesting that 2D and 2D/3D measurements were similar to the results of the gold standard CT model (although 2D/3D measurements were more precise compared to 2D media). Furthermore, statistical analyses revealed no significant correlation in either 2D or 2D/3D compared to metal ion levels, although a stronger trend was demonstrated using 2D/3D measurements. These results are suggestive that 2D/3D registered measurements are equivocal to those using the conventional 2D x-ray and, manual 2D/3D registered measurements do not demonstrate greater efficacy in predicting prosthetic wear. Moreover, the data from this study also revealed insignificant correlations between the angles of acetabular orientation and metal ion release. Combined angles within and beyond the acceptable ranges for inclination (30°–50°) and version (5°–20°) angles did not produce significant trends with metal ion release. These results lead to the paradoxical conclusion that acetabular orientation does not influence prosthetic wear. The findings of this study are inconsistent with the reports in current literature and further investigation is required.