Introduction. Patellofemoral pain and instability can be quantified by using the tibial tuberosity to trochlea groove (TT-TG) distance with more than or equal to 20mm considered pathological requiring surgical correction. Aim of this study is to determine if knee joint rotation angle is predictive of a pathological TT-TG. Methods. One hundred limbs were imaged from the pelvis to the foot using Computer Tomography (CT) scans in 50 patients with patellofemoral pain and instability. The TT-TG distance, femoral version, tibial torsion and knee joint rotation angle ((KJRA) were measured. Limbs were separated into pathological and non-pathological TT-TG. Significant differences in the measured angles between the pathological and non-pathological groups were estimated using the t test. The inter- and intraobserver variability of the measurement was performed. Logistic regression analysis was used to find the best combination of rotational angle predictors for a pathological TT-TG. Results. The intraclass correlation coefficients for inter- and intraobserver variability of the measured parameters was higher than 0.94 for all measurements. A statistically significant difference (P=0.024) was found between the KJRA between the pathological (mean=10.6, SD=7.79 degrees) and the non-pathological group (mean=6.99, SD=5.06 degrees). Logistic regression analysis showed that both femoral version (P=0.03, OR = 0.95) and KJRA (P=0.004, OR=1.15) were, in combination, significant predictors of an abnormal TT-TG. Tibial torsion was not a significant predictor. Conclusion. The KJRA can be used as an alternative measurement when the TT-TG distance cannot be measured as in cases of severe trochlea dysplasia and may act as a surrogate for pathological TT-TG

Biomedical imaging is essential in the diagnosis of musculoskeletal pathologies and postoperative evaluations. In this context, Cone-Beam technology-based Computed Tomography (CBCT) can make important contributions in orthopaedics. CBCT relies on divergent cone X-rays on the whole field of view and a rotating source-detector element to generate three-dimensional (3D) volumes. For the lower limb, they can allow acquisitions under real loading conditions, taking the name Weight-Bearing CBCT (WB-CBCT). Assessments at the foot, ankle, knee, and at the upper limb, can benefit from it in situations where loading is critical to understanding the interactions between anatomical structures. The present study reports 4 recent applications using WB-CBCT in an orthopaedic centre. Patient scans by WB-CBCT were collected for examinations of the lower limb in monopodal standing position. An initial volumetric reconstruction is obtained, and the DICOM file is segmented to obtain 3D bone models. A reference frame is then established on each bone model by virtual landmark palpation or principal component analysis. Based on the variance of the model point cloud, this analysis automatically calculates longitudinal, vertical and mid-lateral axes. Using the defined references, absolute or relative orientations of the bones can be calculated in 3D. In 19 diabetic patients, 3D reconstructed bone models of the foot under load were combined with plantar pressure measurement. Significant correlations were found between bone orientations, heights above the ground, and pressure values, revealing anatomic areas potentially prone to ulceration. In 4 patients enrolled for total ankle arthroplasty, preoperative 3D reconstructions were used for prosthetic design customization, allowing prosthesis-bone mismatch to be minimized. 20 knees with femoral ligament reconstruction were acquired with WB-CBCT and standard CT (in unloading). Bone reconstructions were used to assess congruency angle and patellar tilt and TT-TG. The values obtained show differences between loading and unloading, questioning what has been observed so far. Twenty flat feet were scanned before and after Grice surgery. WB-CBCT allowed characterization of the deformity and bone realignment after surgery, demonstrating the complexity and multi-planarity of the pathology. These applications show how a more complete and realistic 3D geometric characterization of the of lower limb bones is now possible in loading using WB-CBCT. This allows for more accurate diagnoses, surgical planning, and postoperative evaluations, even by automatisms. Other applications are in progress

A risk factor for patellofemoral instability is trochlear dysplasia. Trochleoplasty is a surgical procedure used to reshape the trochlear groove to improve patellar stability. This study seeks to compare pre-op MRI measurements and post operative MRI measurements for patients who have undergone trochleoplasty in correlation with their clinical outcomes scores. Data was collected from a database of patients known to have trochlear dysplasia who underwent trochleoplasty. Radiological Data was collected pre-op and subsequent post op MRI data collected included TT-TG, Patella Tilt, IS, sulcus angle. Data score sheets pre-op and post op trochleoplasty completed by patients were also collected. 10 patients had pre and post op MRI's documented. 80%(8/10) females and 20%(2/10) males, average age of 30 years old (range 23 – 32 years old). Average MRI pre-op scores: IS ratio: 1.2, Patella tilt: 24.14, sulcus angle 160.13, and TT-TG distance of 16.94. 1 year average MRI post-op scores: IS ratio: 1.28, Patella tilt 15.56, sulcus angle 148.66 and TT-TG distance 16.78. 1 year post op Kujala and Norwich instability scores patient reported improved stability, function and confidence post op compared to pre-op. Subjective and objective scores reflected an improvement of stability. MRI demonstrated a deeper trochlear groove post-operatively which should provide resistance against lateral patella movement and patellar dislocations. TT-TG pre and post op remained constant. Pre op and post op Kujala scores reflected improved function. The Norwich instability scores pre and post op reflected satisfaction of treatment. There are not a lot of studies published on trochleoplasty. Based on this study it is clear that patients with patellofemoral instability with severe trochlear dysplasia will benefit from trochleoplasty. The sample size of the data analysis was only 10. However it reflected that function 1 year post procedure remained stable