A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject's legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiation dose was 2.7 mSV. The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation.

The risk of malpositioning of the syndesmotic screws is very high. A lack of standard radiological or physical references for accurate syndesmotic screw placement is a potential contributing factor in syndesmotic screw malpositioning. Malleolar tips are clinically as well as radiologically appreciable bony references. The purpose of this preliminary CT based study was to investigate the axial relations of the central syndesmotic axis with the malleolar tips. Methods: CT based studies of uninjured adult ankle joints with intact syndesmosis, conducted over a six months period were analysed. The axial differences between the coronal plane along the malleolar tips and that along the central syndesmotic axis in the axial plane were measured. Gender-based variations were also analyzed. Results: A total of 70 CT studies were analyzed, and the axial difference between the malleolar tips based coronal plane and that along the central syndesmotic axis was observed to be 3.70 ± 5.61 . The male and female measurements were comparable. Conclusion:Being in a static relation to the syndesmosis independent of the foot position and the limb rotation, the malleolar tips can be reliably used as references for directing syndesmotic screw in the axial plane. A knowledge of this axial difference between malleolar tips and central syndesmotic axis can help surgeons in an accurate syndesmotic screw placement.

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Objectives: The purpose of this study is to design a radiographic map of the femoral neck showing proportion-based locations of the safe zones for screw placement with widest bony extents in anteroposterior and lateral radiographs using normal computed tomography–based data. Methods: We analyzed computed tomography–based studies of 50 intact normal proximal femora equally from male and female subjects. Using software-developed radiographs, the proportionate locations of the maximal anteroposterior and cephalocaudal extents in both constricted zones were measured. The width of the femoral neck in the measurement zone was taken as the reference for calculation of proportions. Results: For anteroposterior radiographs, the anteroposterior safe zones in the femoral neck are located at the gradients of 34.21% and 34.33% from the superior border in midcervical and basicervical regions, respectively. In lateral radiographs, they correlate with the visible anterior extent of femoral neck and lie at a gradient of 7.16% and 11.79% from the visible posterior border in midcervical and basicervical regions, respectively. In lateral radiographs, the calcar-based cephalocaudal safe zone was located at the gradients of 43.49% and 39.53% from the visible posterior border in midcervical and basicervical regions, respectively. In anteroposterior radiographs, cephalic limit of the calcar-based safe zone is located at the gradients of 9.63% and 17.82% from the superior border in midcervical and basicervical regions, respectively. Conclusions: Radiographic margins cannot be reliably trusted for screw fixation of femoral neck fractures. The proportionate locations of the anteroposterior and calcar-based cephalocaudal safe zones with widest bone stock in anteroposterior and lateral fluoroscopic projections can help in the safe placement of screws for fixation of femoral neck fractures.

Segmental neurofibromatosis type 5 (NF5) is a rare form of NF, in which the cutaneous and/or neural changes are confined to one region of the body. It is often underdiagnosed or undetected due to the absence of symptoms. Inheritance of NF is different from other types of NF. Intraosseous neurofibromas are rare tumors which develop from nerves supplying the periosteum or nerves following the intraosseous course. Plexiform neurofibroma with associated intraosseous neurofibroma is extremely rare. We report a case of plexiform neurofibroma in the left axilla of a 17-year-old female with associated intraosseous neurofibroma in adjoining left humerus.