The incidence of periprosthetic fractures of the femur around a total knee arthroplasty (TKA) is rising and this is owed to the increased longevity that today's TKA implants allow for, as well as an aging population. These injuries are significant as they are related to increased morbidity and mortality. We retrospectively reviewed all periprosthetic fractures around a TKA that presented to our NHS Trust between 2011 to 2020. Medical records were reviewed. Treatment, complications and mortality were noted.Abstract
Background
Methods
Differing descriptions of patellar motion relative to the femur have resulted from many in-vitro and in-vivo studies. The aim of this study was to examine the tracking behaviour of the patella. We hypothesized that patellar kinematics would correlate to the trochlear geometry. Seven normal fresh-frozen knees were CT scanned and their kinematics with quadriceps loading was measured by an optical tracker system and calculated in relation to the previously-established femoral axes. CT scans were used to reliably define frames of reference for the femur, tibia and the patella. A novel trochlear axis was defined, between the centres of best-fit medial and lateral trochlear articular surfaces spheres.Introduction
Method
Tibial patho-morphology has been described as a factor that predisposes to medial compartment osteoarthritis of the knee in 2D analysis. The aim of this study was to investigate whether the morphology of normal and pre-OA medial compartments are really different in 3 dimensions. A total of 20 normal (group A) and 20 pre-OA knees (group B) were included. Group A consisted of contra-lateral knees of young patients awaiting hip surgery and group B of asymptomatic contra-lateral knees of patients awaiting unicompartmental knee arthroplasty (UKA). Using 3D reconstructions from CT scans, femurs were aligned to the transcondylar and anatomical axes. The medial femoral extension facet was modelled as a sphere. Its radius and the offsets between its centre and the medial flexion facet centre were measured. The tibias were aligned to a flat portion of the flexion facet (flexion facet plane. A model of analysis was developed by rotating several increments towards and away from the midline to obtain several sagittal section images. For each sagittal section the extension facet angle (EFA), its length, and the submeniscal plane angle and length were analysed.Introduction
Method
SPECT/CT might be a promising diagnostic modality in patients with painful total knee arthroplasty. It was the purpose of our study to introduce a novel standardised SPECT/CT algorithm for assessing patients with painful primary total knee arthroplasty and to evaluate its clinical applicability and inter- and intra-observer variation and reliability. A novel SPECT/CT localisation scheme, which consists of 9 tibial, 9 femoral and 4 patellar regions on standardised transverse, coronal, and sagittal slices was introduced. It was assessed in 18 consecutive patients with painful knees after total knee arthroplasty. The localisation and level of the tracer uptake on SPECT/CT were noted using a color coded 10 steps graded scale (0-100). The inter and intra-observer reliability were assessed. The femoral and tibial prosthetic component position was assessed in the CT images after 3D reconstruction and aligning them to standardised frames of reference. The average root mean square difference±standard deviations and ranges of these measured angles are presented along with the intraclass correlation coefficients for inter- and intraobserver reliability.Introduction
Methods
The trochlear groove plays a major role in the mechanics and patho-mechanics of the patellofemoral joint. Our primary goal was to compare normal, osteoarthritic and dysplastic PFJs in terms of angles and distances. Computed tomography scans of 40 normal knees (>55 years old), 9 knees with patellofemoral osteoarthritis (group A) and 12 knees with trochlear dysplasia (group B) were analysed using 3D software. The femurs were orientated using a robust frame of reference. A circle was fitted to the trochlear groove. The novel trochlear axis was defined as a line joining the centres of two spheres fitted to the trochlear surfaces, lateral and medial to the trochlear groove. The relationship between the femoral trochlea and the tibiofemoral joint was measured in term of angles and distances (offsets).T-test for paired samples was used (p<0.05).Introduction
Method
We studied the intra- and interobserver reliability of measurements of the position of the components after total knee replacement (TKR) using a combination of radiographs and axial two-dimensional (2D) and three-dimensional (3D) reconstructed CT images to identify which method is best for this purpose. A total of 30 knees after primary TKR were assessed by two independent observers (an orthopaedic surgeon and a radiologist) using radiographs and CT scans. Plain radiographs were highly reliable at measuring the tibial slope, but showed wide variability for all other measurements; 2D-CT also showed wide variability. 3D-CT was highly reliable, even when measuring rotation of the femoral components, and significantly better than 2D-CT. Interobserver variability in the measurements on radiographs were good (intraclass correlation coefficient (ICC) 0.65 to 0.82), but rotational measurements on 2D-CT were poor (ICC 0.29). On 3D-CT they were near perfect (ICC 0.89 to 0.99), and significantly more reliable than 2D-CT (p <
0.001). 3D-reconstructed images are sufficiently reliable to enable reporting of the position and orientation of the components. Rotational measurements in particular should be performed on 3D-reconstructed CT images. When faced with a poorly functioning TKR with concerns over component positioning, we recommend 3D-CT as the investigation of choice.
The rotational alignment of the tibia is an unresolved issue in knee replacement. A poor functional outcome may be due to malrotation of the tibial component. Our aim was to find a reliable method for positioning the tibial component in knee replacement. CT scans of 19 knees were reconstructed in three dimensions and orientated vertically. An axial plane was identified 20 mm below the tibial spines. The centre of each tibial condyle was calculated from ten points taken round the condylar cortex. The tibial tubercle centre was also generated as the centre of the circle which best fitted eight points on the outside of the tubercle in an axial plane at the level of its most prominent point. The derived points were identified by three observers with errors of 0.6 mm to 1 mm. The medial and lateral tibial centres were constant features (radius 24 mm ( Alignment of the knee when based on this anatomical axis was more reliable than either the posterior surfaces or any axis involving the tubercle which was the least reliable landmark in the region.
