Application of a digital head-posture measuring system in children

Quantitative Analysis of the Head Tilt Using Three-Dimensional Temporal Scan in Children with Torticollis

The head tilt of patients with torticollis is usually evaluated subjectively in clinical practice and measuring it in young children is very limited due to poor cooperation. No study has yet evaluated the head tilt using a three-dimensional (3D) scan and compared it with other measurement methods. Therefore, this study aimed to objectively demonstrate head tilt through clinical measurements and a 3D scan in children with torticollis. A total of 52 children (30 males, 22 females; age 4.6 ± 3.2 years) diagnosed with torticollis and 52 adults (26 men, 26 women; age 34.42 ± 10.4 years) without torticollis participated in this study. The clinical measurements were performed using a goniometer and still photography methods. Additionally, the head tilt was analyzed using a 3D scanner (3dMD scan, 3dMD Inc., Atlanta, GA, USA). There was a high correlation between the other methods and 3D angles, and the cut-off value of the 3D angles for the diagnosis of torticollis was also presented. The area under the curve of the 3D angle was 0.872, which was confirmed by a moderately accurate test and showed a strong correlation compared with other conventional tests. Therefore, we suggest that measuring the degree of torticollis three-dimensionally is significant.

Is a Depth Camera in Agreement with an Electromagnetic Tracking Device when Measuring Head Position?

Introduction

Clinicians typically observe and describe abnormal head postures (AHPs) and may also measure them. Depth cameras have been suggested as a reliable measurement device for measuring head position using face-tracking technology. This study compared a depth camera (Microsoft Kinect) to a gold standard electromagnetic tracking system (Polhemus device) to measure head position.

Method

Twenty healthy volunteers (mean age 21 years) had their head position simultaneously recorded using the depth camera (Kinect) and the electromagnetic tracking system (Polhemus). Participants were asked to make 30-degree head movements into chin up, chin down, head turn and head tilt positions. The head movement made and the stability of the head at each position were recorded and analysed.

Results

Compared to the electromagnetic tracking system (Polhemus), the depth camera (Kinect) always measured a smaller head movement. Measurements with the two devices were not statistically significantly different for turn right (P = 0.3955, p > 0.05), turn left (P = 0.4749, p > 0.05), tilt right (P = 0.7086, p > 0.05) and tilt left (P = 0.4091, p > 0.05) head movements. However, the smaller depth camera measurement of chin up and chin down head movements were statistically significant, chin up (P = 0.0001, p < 0.01) and chin down (P = 0.0005, p < 0.001). At each eccentric position, the depth camera (Kinect) recordings were more variable than the electromagnetic tracking system (Polhemus).

Conclusions

Compared to the electromagnetic tracking system (Polhemus), the depth camera (Kinect) was comparable for measuring head turns and tilts but was less accurate at measuring chin up and chin down head positions. Further research is needed before the depth cameras are considered for clinical recordings of head position.

Congenital muscular torticollis: the reliability of visual estimation in the assessment of cervical spine active rotation and head tilt by physiotherapists and the impact of clinical experience

There is a lack of reliable and valid measurement tools to assess neck function in infants with congenital muscular torticollis, and most physiotherapists use visual estimation, which has not been adequately tested for reliability in this population. We examined the reliability of visual estimation of head tilt and active neck rotation in the upright position, on infants with congenital muscular torticollis by physiotherapists. We recruited 31 infants and 26 physiotherapists. Therapists rated videos of infants' head position in the frontal plane (tilt) and transverse plane (active rotation) using visual estimation, on two occasions at least one week apart. Overall, inter-rater reliability was good (mean ICC, 0.68 ± 0.20; mean SEM, 5.1° ± 2.1°). Rotation videos had better reliability (mean ICC, 0.79 ± 0.14) than head tilt videos (mean ICC, 0.58 ± 0.20). Intra-rater reliability was excellent (mean ICC, 0.85 ± 0.08). Both head tilt and rotation had excellent reliability (mean ICC, 0.84 ± 0.08 for head tilt and 0.85 ± 0.09 for rotation). There was no correlation between intra-rater reliability and clinical experience.Conclusion Visual estimation had excellent intra-rater reliability in the assessment of neck active rotation and head tilt on infants with congenital muscular torticollis. Visual estimation had acceptable inter-rater reliability in the assessment of neck active rotation but not of head tilt. There was a wide variation in reliability with no correlation between reliability and clinical experience. Assessment tools for head tilt that are more psychometrically robust should be developed. What is Known: • A thorough assessment of infants presenting with torticollis is essential, using assessment tools with robust psychometric properties • Visual estimation is the most commonly used method of assessment of neck function in infants with torticollis What is New: • Visual estimation had excellent intra-rater reliability in the assessment of neck active rotation and head tilt in the upright position in videos of infants and acceptable inter-rater reliability in the assessment of rotation but not of head tilt • Physiotherapists' clinical experience had minimal relationship with reliability.

Measurement properties of instruments for assessment of cervical spine function in infants with torticollis: a systematic review

The aim of this study was to systematically review the measurement properties of instruments which assess cervical spine function in infants with torticollis. Electronic searches were performed in MEDLINE, CINAHL, Embase, Web of Science and the Cochrane Library, combining three constructs ('torticollis', 'cervical spine assessment' and 'measurement properties'). Two reviewers independently rated the methodological quality and the quality of measurement properties of identified articles, using both the COSMIN (COnsensus-based Standards for the selection of health status Measurement INstruments) checklist and quality criteria for measurement properties. Five studies, using six instruments, met the inclusion criteria and were analysed. Included instruments were the goniometer, electronic pendular goniometer, protractor, still photography, Muscle Function Scale and a range of motion limitation scale. All studies assessed reliability, and one study also assessed content validity and hypothesis testing. The methodological quality of the studies varied from poor to excellent according to the COSMIN checklist. Two instruments were found to have good measurement properties from high-quality studies: still photography for the assessment of habitual head tilt in supine and the Muscle Function Scale for the assessment of side-flexor muscle function in lateral head righting.Conclusion: This systematic review identified two reliable tools for the assessment of cervical spine function in infants with torticollis. Further research is required to assess the measurement properties of tools already described in the literature and to develop further tools for use in this population. What is known? • A thorough assessment of the infant presenting with torticollis is essential, in order to correctly diagnose, rule out 'red flags' and manage appropriately • Assessment tools need to have robust measurement properties in order to be of value for clinical practice and research What is new? • This systematic review identified two valid and reliable tools for the assessment of cervical spine function in infants with torticollis • Further research is required to assess the measurement properties of tools already described in the literature and to develop further tools for use in infants with torticollis.

The Cambridge Face Tracker: Accurate, Low Cost Measurement of Head Posture Using Computer Vision and Face Recognition Software

Purpose

We validate a video-based method of head posture measurement.

Methods

The Cambridge Face Tracker uses neural networks (constrained local neural fields) to recognize facial features in video. The relative position of these facial features is used to calculate head posture. First, we assess the accuracy of this approach against videos in three research databases where each frame is tagged with a precisely measured head posture. Second, we compare our method to a commercially available mechanical device, the Cervical Range of Motion device: four subjects each adopted 43 distinct head postures that were measured using both methods.

Results

The Cambridge Face Tracker achieved confident facial recognition in 92% of the approximately 38,000 frames of video from the three databases. The respective mean error in absolute head posture was 3.34°, 3.86°, and 2.81°, with a median error of 1.97°, 2.16°, and 1.96°. The accuracy decreased with more extreme head posture. Comparing The Cambridge Face Tracker to the Cervical Range of Motion Device gave correlation coefficients of 0.99 (P < 0.0001), 0.96 (P < 0.0001), and 0.99 (P < 0.0001) for yaw, pitch, and roll, respectively.

Conclusions

The Cambridge Face Tracker performs well under real-world conditions and within the range of normally-encountered head posture. It allows useful quantification of head posture in real time or from precaptured video. Its performance is similar to that of a clinically validated mechanical device. It has significant advantages over other approaches in that subjects do not need to wear any apparatus, and it requires only low cost, easy-to-setup consumer electronics.

Translational Relevance

Noncontact assessment of head posture allows more complete clinical assessment of patients, and could benefit surgical planning in future.