Evaluation of Pseudo-Haptic Interactions with Soft Objects in Virtual Environments

This paper proposes a pseudo-haptic feedback method conveying simulated soft surface stiffness information through a visual interface. The method exploits a combination of two feedback techniques, namely visual feedback of soft surface deformation and control of the indenter avatar speed, to convey stiffness information of a simulated surface of a soft object in virtual environments. The proposed method was effective in distinguishing different sizes of virtual hard nodules integrated into the simulated soft bodies. To further improve the interactive experience, the approach was extended creating a multi-point pseudo-haptic feedback system. A comparison with regards to (a) nodule detection sensitivity and (b) elapsed time as performance indicators in hard nodule detection experiments to a tablet computer incorporating vibration feedback was conducted. The multi-point pseudo-haptic interaction is shown to be more time-efficient than the single-point pseudo-haptic interaction. It is noted that multi-point pseudo-haptic feedback performs similarly well when compared to a vibration-based feedback method based on both performance measures elapsed time and nodule detection sensitivity. This proves that the proposed method can be used to convey detailed haptic information for virtual environmental tasks, even subtle ones, using either a computer mouse or a pressure sensitive device as an input device. This pseudo-haptic feedback method provides an opportunity for low-cost simulation of objects with soft surfaces and hard inclusions, as, for example, occurring in ever more realistic video games with increasing emphasis on interaction with the physical environment and minimally invasive surgery in the form of soft tissue organs with embedded cancer nodules. Hence, the method can be used in many low-budget applications where haptic sensation is required, such as surgeon training or video games, either using desktop computers or portable devices, showing reasonably high fidelity in conveying stiffness perception to the user

Regional variations in the density and arrangement of elastic fibres in the anulus fibrosus of the human lumbar disc

Elastic fibres are critical components of the extracellular matrix in dynamic biological structures that undergo extension and recoil. Their presence has been demonstrated in the anulus fibrosus of the human lumbar intervertebral disc; however, a detailed regional analysis of their density and arrangement has not been undertaken, limiting our understanding of their structural and functional roles. In this investigation we have quantitatively described regional variations in elastic fibre density in the anulus fibrosus of the human L3-L4 intervertebral disc using histochemistry and light microscopy. Additionally, a multiplanar comparison of patterns of elastic fibre distribution in the intralamellar and interlamellar zones was undertaken. Novel imaging techniques were developed to facilitate the visualization of elastic fibres otherwise masked by dense surrounding matrix. Elastic fibre density was found to be significantly higher in the lamellae of the posterolateral region of the anulus than the anterolateral, and significantly higher in the outer regions than the inner, suggesting that elastic fibre density in each region of the anulus is commensurate with the magnitude of the tensile deformations experienced in bending and torsion. Elastic fibre arrangments in intralamellar and interlamellar zones were shown to be architecturally distinct, suggesting that they perform multiple functional roles within the anulus matrix structural hierarchy

Fluoroscopically-guided indirect posterior reduction and fixation of thoracolumbar burst fractures without fusion

This article presents an evaluation of fluoroscopy for indirect, posterior reduction and fixation of thoracolumbar burst fractures. A prospective study of 25 patients with thoracolumbar burst fractures who underwent C-arm machine-guided posterior indirect reduction and short segment fixation without fusion is described. No laminotomies were performed. All patients had a mean follow-up of 30.4 months. At postoperative review, the average anterior and posterior vertebral heights were corrected from 57.9% to 99.0% and 89.0% to 99.5%, respectively. The Cobb angle was corrected from 18.4° to 0.17°. The canal compromise ratio was improved from 35.2% to 8.6%. In all 25 cases, neurological status was intact at last follow-up. Fluoroscopy guidance is an effective method to accomplish indirect reduction and fixation. Reduction was confirmed on lateral fluoroscopic views by looking for a “one-line sign,” which is the reconstitution of the posterior border of the vertebral body

Comparative study of knee anterior cruciate ligament reconstruction with or without Xuoroscopic assistance : a prospective study of 73 cases

Introduction Correct placement of both tibial and femoral tunnels is one of the main factors for a favorable clinical outcome after anterior cruciate ligament (ACL) reconstruction. We used an original system of computer assisted surgery (CAS). The system, based on Xuoroscopic guidance combined with special graphical software of image analyzing, showed to the surgeon, before drilling, the recommended placement of tibial and femoral tunnel centers. We compared the Wrst anatomical and clinical results of this procedure to the usual one single incision technique. Materials and methods We conducted a prospective study on 73 patients; 37 patients were operated on with CAS and 36 without CAS, by the same senior surgeon. The mean age was 27 years for both groups. Every patient was reviewed at an average of 2.2 years (range 1–4.5) by an independent observer, using IKDC scoring system, KT-1000, and passive stress radiographs. Results Time between ACL rupture and reconstruction averaged 30 months for both groups. CAS needed 9.3 min extra surgery time. Clinical evaluation was graded from A to C as per the IKDC scoring system: 67.6% A, 29.7% B, 2.7% C with CAS; and 60% A, 37.1% B, 2.9% C without CAS. IKDC subjective knee evaluation score averaged 89.7 with CAS and 89.5 without CAS. Pre operative KT-1000 maxi manual diVerential laxity averaged 7. At revision time, all the patients after CAS had a diVerential laxity less than 2 and 97.7% without CAS. Stress X-rays diVerential laxity averaged 2.4 mm with CAS and 3 mm without CAS. The area of dispersion of the tunnels’ center was smaller on the femoral side using the CAS method. There was no statistically signiWcant diVerence between both groups using IKDC score, KT-1000 and passive stress radiographs. Conclusions The CAS method provided a more accurate and reproducible tunnels placement without clinical signiWcant eVect. Introduction Correct placement of both tibial and femoral tunnels is one of the main factors for a favorable clinical outcome after anterior cruciate ligament (ACL) reconstruction. We used an original system of computer assisted surgery (CAS). The system, based on Xuoroscopic guidance combined with special graphical software of image analyzing, showed to the surgeon, before drilling, the recommended placement of tibial and femoral tunnel centers. We compared the Wrst anatomical and clinical results of this procedure to the usual one single incision technique. Materials and methods We conducted a prospective study on 73 patients; 37 patients were operated on with CAS and 36 without CAS, by the same senior surgeon. The mean age was 27 years for both groups. Every patient was reviewed at an average of 2.2 years (range 1–4.5) by an independent observer, using IKDC scoring system, KT-1000, and passive stress radiographs. Results Time between ACL rupture and reconstruction averaged 30 months for both groups. CAS needed 9.3 min extra surgery time. Clinical evaluation was graded from A to C as per the IKDC scoring system: 67.6% A, 29.7% B, 2.7% C with CAS; and 60% A, 37.1% B, 2.9% C without CAS. IKDC subjective knee evaluation score averaged 89.7 with CAS and 89.5 without CAS. Pre operative KT-1000 maxi manual diVerential laxity averaged 7. At revision time, all the patients after CAS had a diVerential laxity less than 2 and 97.7% without CAS. Stress X-rays diVerential laxity averaged 2.4 mm with CAS and 3 mm without CAS. The area of dispersion of the tunnels’ center was smaller on the femoral side using the CAS method. There was no statistically signiWcant diVerence between both groups using IKDC score, KT-1000 and passive stress radiographs. Conclusions The CAS method provided a more accurate and reproducible tunnels placement without clinical signiWcant eVect