Assessment of passive musculoarticular ankle stiffness in children, adolescents and young adults with haemophilic ankle arthropathy.

OBJECTIVES: To measure passive musculoarticular ankle stiffness (PMAAS) and its intra- and interday reliability in adult control subjects without ankle disorders. We also sought to quantify PMAAS in children, adolescents and young adults with haemophilia (CAAwH) taking into account the accurate tibiotalar and subtalar joints structural status obtained by magnetic resonance imaging (MRI). METHODS: We included 23 CAAwH and 23 typically developing boys (TDB) matched by age, weight and height, along with 25 healthy volunteers for reliability assessment. All CAAwH underwent bilateral ankle MRI, with anatomical status assessed using the International Prophylaxis Study Group MRI scale. All CAAwH underwent PMAAS testing for both sides randomly vs the dominant side (DS) in TDBs. For assessing viscous stiffness (VS) and elastic stiffness (ES), eight different oscillation frequencies were randomly repeated three times for each subject. RESULTS: Good-to-excellent intra- and interday reliability was observed for ES and VS variables. No relevant differences were observed between the ankle viscoelastic properties in CAAwH without joint damage and matched TDBs, whereas the study revealed significantly increased ES in the affected ankles of CAAwH with severe unilateral joint involvement compared to the non-affected joint. CONCLUSION: This study confirmed increased ES in the severely affected ankles of CAAwH compared to non-affected sides. No differences in the ankle viscoelastic properties of CAAwH with or without joint damage were observed, however, compared to matched TDB.

Radiation exposure to the patients in thoracic and lumbar spine fusion using a new intraoperative cone-beam computed tomography imaging technique: a preliminary study.

PURPOSE: The goals of this paper are to assess the ionizing radiation exposure to the patients during thoracic and lumbar spinal fusion using a new intraoperative 3D imaging system and to evaluate the factors that could explain the variability in the observed doses. METHOD: We retrospectively reviewed 97 patients who underwent posterior instrumented thoracic and/or lumbar spinal fusion from December 2013 to November 2014. Primary data were the total dose area product (total DAP, Gy cm2) and total skin dose (total SD, mGy). Influence of different variables (patient characteristics, surgical technique, and intraoperative imaging system parameters) that could influence patients' exposure was analyzed. RESULTS: Radiation dose imparted to patients depended on four parameters including acquisition protocol, surgical technique, patient's BMI and operative time. Minimally invasive surgery (MIS) resulted in twofold higher dose for patients, compared to open surgery. The use of low dose acquisition protocols reduced patient exposure by a factor three. CONCLUSION: Patient exposure was highly variable. Four parameters were found to explain about 68% of its variance when using a multi-axis robotic C-arm system. MIS technique (with navigation or not) as well as the acquisition protocol dramatically increases the radiation dose for patients. These results show the necessity to develop specific strategies adapted to patients and surgical procedures.

Registration accuracy in computer-assisted pelvic surgery.

INTRODUCTION: An in vitro study was performed to assess the global registration accuracy of a computer-assisted system in pelvic orthopaedic surgery. The system was applied to a putative tumor resection in a pelvic sawbone. METHODS: Twenty landmarks were created on the surface of the pelvis, and a virtual model of the sawbone was constructed based on surface extraction from computed tomography. The coordinates of the landmarks were defined in the CT-scan coordinate system, and registration of the sawbone with the virtual model was achieved using a surface-based matching algorithm. The landmarks were considered as control points, and deviations between their physical locations and their locations in the virtual model were calculated, thereby quantifying the global accuracy error. RESULTS: The location of the initialization points was unimportant. The dynamic reference base gave the best results when placed far from the working area. Accuracy was improved when the sampling area was increased, but was decreased by its excessive expansion. CONCLUSIONS: It is recommended that the DRB be located on the contralateral side of the pelvis. Extending the approach posteriorly and including the entire working area in the sampling surface area, if possible, will also help increase accuracy in computer-assisted pelvic surgery.