Olivier Snoeck

Precision of shoulder anatomical landmark calibration by two approaches: A CAST-like protocol and a new Anatomical Palpator method

The objective of the study was to compare the precision of shoulder anatomical landmark palpation using a CAST-like method and a newly developed anatomical palpator device (called A-Palp) using the forefinger pulp directly. The repeated-measures experimental design included four examiners that twice repeated measurements on eleven scapula and humerus anatomical landmarks during two sessions. Inter-session and inter-examiner precision was determined on volunteers. A-Palp accuracy was obtained from in vitro measurements and using virtual palpation on 3D bone models. Error propagation on the motion representation was also analyzed for a continuous motion of abduction movement performed in the shoulder joint. Palpation results showed that CAST and A-Palp methods lead to similar precision with the Maximal A-Palp calibration error being 1.5mm. In vivo precision of the CAST and A-Palp methods varied between 4mm (inter-session) and 8mm (inter-examiner). Mean propagation of the palpation error on the motion graph representation was 2 degrees and 5 degrees for scapula and humerus, respectively. A-Palp accuracy was 3.6 and 8.1mm for scapula and humerus, respectively. The A-Palp seems promising and could probably become an additional method next to todays marker-based motion analysis systems (i.e., Helen-Hayes configuration, CAST method).

Prediction of joint center location by customizable multiple regressions: Application to clavicle, scapula and humerus

Accurate spatial location of joint center (JC) is a key issue in motion analysis since JC locations are used to define standardized anatomical frames, in which results are represented. Accurate and reproducible JC location is important for data comparison and data exchange. This paper presents a method for JC locations based on the multiple regression algorithms without preliminary assumption on the behavior of the joint-of-interest. Regression equations were obtained from manually palpable ALs on each bone-of-interest. Results are presented for all joint surfaces found on the clavicle, scapula and humeral bone. Mean accuracy errors on the JC locations obtained on dry bones were 5.2+/-2.5 mm for the humeral head, 2.5+/-1.1 mm for the humeral trochlea, 2.3+/-0.9 mm for the humeral capitulum, 8.2+/-3.9 mm for the scapula glenoid cavity, 7.2+/-3.2 mm for the scapular aspect of the acromio-clavicular joint, 3.5+/-1.8mm for the clavicular aspect of the sternoclavicular joint and 3.2+/-1.4 mm for the clavicular aspect of the acromio-clavicular joint. In-vitro and in-vivo validation accuracy was 5.3 and 8.5mm, respectively, for the humeral head center location. Regression coefficients for joint radius dimension and joint surface orientation were also processed and reported in this paper.

The lacertus fibrosus of the biceps brachii muscle: an anatomical study

PurposeThe lacertus fibrosus (LF) is involved in various surgical procedures. However, the anatomy, morphometry, topography and biomechanical involvements of LF are not clear. The purpose of this study was to determine the anatomical and morphometric variations of LF, and to correlate this with anthropometric and morphometric measurements of the upper limb. Furthermore, the presence or absence of a deep layer of LF was verified using forearm cross-sections and dissections.MethodsThis anatomical study was performed by observation of dissections and transverse sections obtained from 50 cadavers. Morphometric analyses [length and width of LF and biceps tendon, stature, length of upper limb, forearm, bi-epicondylar width, forearm perimeter, biceps brachii muscle perimeter (BBm)] were also performed.ResultsThe results demonstrated that there was no significant correlation between LF morphology and morphometric upper limb measurements. The deep layer of LF was observed in all specimens.ConclusionResults of this paper indicate that the LF presents individual characteristics such as length and width. The deeper layer of LF was observed on all specimens. The possible role of LF in force transmission during flexion, BBm moment arm adjustment and supination reduction is discussed in view of these results.

Tendon and fascial structure contributions to knee muscle excursions and knee joint displacement

BACKGROUND Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, and a limited decrease of hamstring muscles force is observed postoperatively despite important changes. The goal was to quantify the influence of the myofascial structures on excursions and moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations. METHODS Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each steps of the surgery. FINDINGS No significant difference was demonstrated for excursions and moment arms after tenotomies and gracilis tendon harvesting (P≥0.05). The first significant semitendinosus excursion (P<1.17×10(-4)) and moment arm (P<6.88×10(-5)) decrease was observed after semitendinosus tendon harvesting (46% of the initial excursion). INTERPRETATION Gracilis and semitendinosus myofascial pathway is crucial for force transmission towards the knee joint.

DEVELOPMENT OF AN ANATOMICAL WAND FOR ANATOMICAL LANDMARK DIGITIZING: PRELIMINARY RESULTS

INTRODUCTION Calibration of anatomical landmarks (ALs) [1] is a key procedure for the determination of anatomical features related to the bones of a particular subject. Such ALs can then be used for the definition of local joint reference frames or registration with other data for advanced visualization or modeling [2]. In all cases the accuracy of the AL location will depend on the system used for such digitizing. The accuracy is directly proportional to the quality of the final registration and the repeatability of the measurements (a key element in a clinical setting, e.g., for patient follow-up) [2]. Standards procedures for AL location include setting of reflective markers on the subject’s skin at relevant spots, leading to relatively high errors because of skin artifacts. A more accurate method is the use of calibrated wands in order to better locate the ALs. Unfortunately, the latter method is time consuming and the protocol requires, 1 first to palpate the relevant AL with the finger pulp; -2 then to remove the finger from the AL; 3 to set the extremity of the wand on the AL; 4 to eventually digitize the AL location. The transition between steps 2 and 3 is prone to introduce errors since the palpating sensitive finger leaves the point of interest to be replaced by a non-sensitive instrument. The aim of this undergoing study is to develop a protocol able to calibrate a customized palpation system made of the palpating finger of the individual performing the palpation (i.e., the “palpator”) and a technical frame attached on this finger. Results will be presented during the conference.

REGISTRATION OF SOFT TISSUES MORPHOLOGY WITH SKELETAL MORPHOLOGY AND KINEMATICS

Realistic and anatomically correct modelling of the spatial behaviour of the human musculoskeletal (MS) system requests combining of data collected from different sources. This study presents a protocol to create 3D MS models based on accurate morphological and kinematics data. Registration procedures for bones morphology and kinematics were available from past work [S. Van Sint Jan, 2005]. The main subject of the study was soft tissue registration and implementation of the results in the ‘LhpBuilder’ software, developed during EC funded project ‘LHDL’ [S. Van Sint Jan 2007 and http://www.biomedtown.org/biomed_town/LHDL].

STEREOPHOTOGRAMMETRY FOR SOFT TISSUE 3D RECONSTRUCTION OF DISSECTION AND MEDICAL IMAGING

3D reconstruction of soft tissue (muscles, ligaments) morphology, including extraction of muscle and tendon fibre topology and attachments, is a time-consuming task. It requests 3D reconstruction of dissected soft tissues as alternative to high resolution MRI that shows some limitations. This paper proposes a method using stereophotogrammetry on the basis of semiprofessional digital cameras allowing soft tissue data collection and maintaining high quality results.