Jozef Vander Sloten

Longitudinal prospective long-term radiographic follow-up after treatment of single-level cervical disk disease with the Bryan Cervical Disc.

BACKGROUNDMany short- and intermediate-term radiological and clinical studies on cervical arthroplasty with the Bryan Cervical Disc have been published, providing, most of the time, satisfactory results. OBJECTIVETo prospectively assess the intermediate and long-term radiographic characteristics of disk replacement surgery with the Bryan Cervical Disc and to correlate these results with clinical outcome. METHODSRange of motion was measured with a validated tool. Intervertebral disk degeneration was assessed with a quantitative scoring system. Heterotopic ossification was evaluated with a previously published scoring system. Device stability was investigated by measuring subsidence and anteroposterior migration. General clinical patient outcome was assessed with the Odom classification system. RESULTSEighty-nine patients were initially included in this prospective long-term study. One patient was reoperated on at the index level and 4 were reoperated on at an adjacent level; those patients were not further analyzed. The mobility at the treated level was preserved in ≥ 85% of our cases. The insertion of the prosthesis did not lead to an increase in mobility at the adjacent levels. The degeneration score increased at both adjacent levels. Heterotopic ossification was present in 34% to 39% of the patients, depending on the follow-up point. No cases of anteroposterior migration or subsidence were found. More than 82% of all patients had a good to excellent clinical outcome in the long run. CONCLUSIONThe device maintains preoperative motion at the index and adjacent levels, seems to protect against acceleration of adjacent-level degeneration as seen after anterior cervical discectomy and fusion, and remains securely anchored in the adjacent bone mass in the long run. Heterotopic ossification was frequently seen. The vast majority of all patients had a good to excellent clinical outcome.

An EMG-based finite state approach for a microcomputer-controlled above-knee prosthesis

A novel self-contained microcomputer-controlled above-knee prosthesis (AKP) has been developed. The knee mechanism is equipped with a magnetic particle brake providing a continuously variable resistive moment. Several sensors measure the contact pressure under the prosthetic foot, the knee angle and EMG-signals from the stump muscles. This information enables the microcomputer to adjust the braking moment automatically depending on gait mode, gait velocity and other locomotion requirements. The control action is based on a finite state representation of the gait cyclus.

Unobtrusive Assessment of Motor Patterns During Sleep Based on Mattress Indentation Measurements

This study investigates how integrated bed measurements can be used to assess motor patterns (movements and postures) during sleep. An algorithm has been developed that detects movements based on the time derivate of mattress surface indentation. After each movement, the algorithm recognizes the adopted sleep posture based on an image feature vector and an optimal separating hyperplane constructed with the theory of support vector machines. The developed algorithm has been tested on a dataset of 30 fully recorded nights in a sleep laboratory. Movement detection has been compared to actigraphy, whereas posture recognition has been validated with a manual posture scoring based on video frames and chest orientation. Results show a high sensitivity for movement detection (91.2%) and posture recognition (between 83.6% and 95.9%), indicating that mattress indentation provides an accurate and unobtrusive measure to assess motor patterns during sleep.

Postoperative segmental malalignment after surgery with the Bryan cervical disc prosthesis: is it related to the mechanics and design of the prosthesis?

Study Design In a radiographic study, postoperative segmental alignment was compared between 2 cohorts of 20 consecutive patients operated with a Bryan Cervical Disc Prosthesis. In group 2, patients with severe preoperative kyphosis were excluded for disc replacement surgery and the surgical technique was slightly altered to avoid asymmetric overdrilling of the posterior part of the cranial endplate of the caudal vertebral body. Objective The aim was to investigate whether this change in patient inclusion criteria and modification of the surgical technique had an influence on postoperative segmental alignment and whether postoperative kyphosis is related to the mechanical properties and/or the design of the prosthesis. Summary of Background Data Several research groups reported segmental kyphosis after treatment of degenerative disc disease with the Bryan Cervical Disc Prosthesis. Methods On the basis of lateral radiographs, the disc insertion angle (as a postoperative estimate for the intraoperative angle of approach) and the angle of the functional spinal unit (FSU) and disc angle (both as measures for segmental alignment) were calculated. Results In group 1, 80% of the patients had a kyphotic FSU angle and 40% had a kyphotic disc angle preoperatively. At follow-up, 65% of the patients had a kyphotic FSU angle, whereas 55% had a kyphotic disc angle. In group 2, 40% of the patients had a kyphotic FSU angle and 5% had a kyphotic disc angle preoperatively. At follow-up, 40% of the patients had a kyphotic FSU angle, whereas 5% had a kyphotic disc angle. Due to the change in patient inclusion criteria, there was a significant difference in preoperative FSU angle between groups 1 and 2; however, no significant difference in preoperative disc angle was found. Owing to the change in surgical technique, the disc insertion angle was significantly different between both the groups. A difference in postoperative FSU angle, however, nonsignificant, between both the groups was observed. There was a significant difference in postoperative disc angle between both the groups; group 1 showed significantly more kyphosis of the shells, than group 2. Conclusions This study shows that segmental malalignment with the Bryan Disc can be reduced and is therefore not device related. Proper patient selection and a modified surgical technique can prevent this adverse outcome.