What is an antalgic (painful) gait? Let the sensors have their say.

Falsehood flies, and the truth comes limping after it, so that when men come to be undeceived, it is too late; the jest is over, and the tale hath had his effect.

Jonathan Swift

One of the things we are taught as medical students and doctors is how to recognise various types of gait. This is an imperfect art, particularly for the less observant among us! I remember telling someone that his painful, slow gait was due to his hip arthritis only to see that after successful hip surgery his gait was still just as slow. It turned out that he also had early Parkinson’s disease, and I had missed the early signs of his neurological condition. And if you think you are immune to such lapses of judgement, perhaps you – like me – were fooled by Virgil’s limp in the film ‘Usual Suspects‘ (one of my favourite cinematic endings).

One of the most basic gaits to recognise is someone walking with a single painful hip joint. This is commonly called the ‘antalgic’ gait, and is characterised by someone spending less time putting their weight on the painful leg compared to the other leg.

When surgeons replace hip joints they hope to relieve pain – but they also need to restore a normal gait pattern. Although pain relief happens quickly in most patients, restoration of normal function is more gradual. The best way to study this scientifically is to apply movement sensors to the limbs – accelerometers or more sophisticated triple component inertial movement sensors (IMUs). A 1999 paper by Aminian et al examined this question in a group of patients who had hip surgery for arthritis in a single hip. It turned out that simply measuring gait speed didn’t show the improvements as clearly as the ‘assymetry of double stance’ time. This is the difference between the time you spend on the bad leg vs. the good leg – i.e a scientific measure of the ‘antalgic gait’.

Using sensors to detect improvements in gait after hip replacement
Sensor detection of changes in assymetric (antalgic) gait after hip replacement surgery

In the top left (pre-op) picture you can see a big spread from the identical line (diagonal) – and then as we move to the bottom right (9 months post-op) you can see that the difference between double-stance time on either leg has narrowed except in one patient (circled in the image below).

Sensor detects Gait in Hip Osteoarthritis after surgery
Sensor detection of changes in assymetric (antalgic) gait after hip replacement surgery: spot the one exception!

Now, as it happens, this poor chap still had pain in his hip. I guess you could have found that out a lot easier just by asking him, but the point is that we’ve found that out through a very objective test. Looking at the trace from the motion sensors, an analyst miles away with no video footage could ‘diagnose’ that he still had an antalgic gait. The same sort of analytics can pick out differences that are just not obvious even to the practised eye.

This is just a simple example taken from what is a rapidly expanding area of the scientific literature – how to accurately measure and define human movement. In this case, the use of movement sensors provided objective evidence of improvements we could have discerned by observing the patient’s gait or by asking them to complete a questionnaire. However, movement analysis can be used to perform much more complex assessments that should help the therapist understand why our patients haven’t quite returned to full function at work or at home. Physiotherapists, sports scientists and experts in biomechanics/computer analytics are leading the way. Watch this space!

Reference: Arminian K et al Med Biol Eng Comput 1999 37 686-691

What is a disease flare in RA? A medical student’s perspective

Introduction: This guest article was written by Anca Smyth, who is currently a fourth year medical student at Queen’s University Belfast. She wrote an essay during her ‘special study component’ three week attachment in Altnagelvin hospital and later submitted it to the Irish Society for Rheumatology. Anca not only won the prestigious Bernard Connor Prize at the 2016 conference, but she was invited to present her paper to the Society. So congratulations to Anca and best wishes for the future! – Philip Gardiner

“When it comes to our health most of us are guilty of thinking that we are invincible. Imagine waking up one morning with excruciating pain, having stiff, swollen joints and weakness which markedly interfere with your ability to carry out the normal activities of daily living. To a rheumatoid arthritis (RA) sufferer such debilitating symptoms may constitute ‘a significant disease flare’, an episodic exacerbation of this chronic, symmetrical, small joint inflammatory condition. Or does it?

Unlike the ACR/EULAR classification criteria for RA [1] which is based on objective measurements of serological parameters, acute phase reactants, numbers and sites of swollen or tender joints and symptom duration, there has been no standard definition of what constitutes a RA flare or how it can be objectively assessed and classified according to severity. Apart from measuring the efficacy and safety of novel pharmacological agents used in the treatment of RA by means of randomised controlled clinical trials, a valid definition and classification of a flare would prove to be an invaluable tool in guiding clinical care and monitoring disease outcome.

When a patient is experiencing a flare, a significant increase in the disease activity so that it requires a change of treatment [2], there is often discrepancy in the interpretation of the severity of signs and symptoms between the doctor and the patient [3]. This may lead to inappropriate treatment, patient dissatisfaction and non-adherence to therapeutic interventions [4, 5]. Such discordance is due to the heterogeneous nature of the patient experience during this acute episode, which not only affects objectively measured clinical parameters but also generates self-reported symptoms such as pain, weakness, sleeplessness or fatigue [6, 7]. From the patient’s perspective the experience of a flare is also about functional impairment, disability and social participation [8, 9] which interfere with the patient’s quality of life and psychological well-being.

There is also variation between RA sufferers regarding what constitutes a significant disease flare. Reasons for this include the fact that patients report the severity of a flare according to their baseline disease activity and previous experiences with the disease [10], thus what seems a severe flare to an early RA patient may be classified as a normal fluctuation of disease activity by someone who has been living with this disease for an extended period of time. Additional factors in defining a significant flare include the level of a patient’s tolerance to worsening of signs and symptoms, health beliefs and coping skills [11, 12].

Current methods of assessing RA patients include measuring the disease activity in 28 joints using the DAS28 score and evaluating physical disability by means of a Health Assessment Questionnaire (HAQ28) and patient’s global health status by employing a 10cm Visual Analogue Scale (VAS).  However, none of these approaches are without flaws. Two of the main determinants of the patient’s global health are pain and fatigue [13], subjective symptoms which cannot be measured accurately and which are influenced by many factors including mental health status and co-morbidities [14]. Considering the ACR/EULAR disease remission criteria of a score of 1 or less on the patient’s global assessment scale of 0-10 such targets may be difficult to achieve accounting for the fact that many RA patients suffer from depression [15] or chronic pain syndrome [16].

The HAQ tool, limited by its ‘ceiling effect’ due to lack of adequate sensitivity in detecting a worsening of disability towards its upper limits or assessing lower limb function [17] does not accurately evaluate the severity of a RA flare. The DAS 28 score, a weighted composite of the number of swollen joints, level of the inflammatory marker ESR (erythrocyte sedimentation rate) and patient global assessment score is currently employed in clinical practice to classify disease activity, guide therapeutic treatment and function as an outcome measure in the treat-to-target approach [18]. Limitations of this approach include a misleadingly low DAS28 score if the flare predominantly affects the patient’s feet, which are not included in the DAS28 joint count, or if it is concentrated on a single joint, causing debilitating pain and rendering the patient unable to work. Conversely, a high DAS28 score based on a large number of swollen joints in the absence of pain or elevated ESR may initiate an unnecessary escalation in therapeutic treatment [19]. Some studies have used the inverse of the improvement criteria based on the DAS28 score to assess the severity of a flare but such a correlation seems inappropriate [20].

Given the complexity of patient experiences and heterogeneity of assessment tools that affect the interpretation of a significant disease flare, there is no ‘one size fits all’ approach to monitoring a flare. In an era of demedicalisation, there is an emphasis on treating the individual in the community, with medical care providers offering evidence based patient education and counselling regarding management of flares or side-effects of medication in the form of leaflets, telephone consultation with various members of the multi-disciplinary team or telecare services for people to report and be advised on their flares [21]. Such a model of care not only promotes self-efficacy and helps achieve an internal locus of control but it also increases accessibility and reduces travelling time for patients in the rural communities.

Since RA is a chronic condition, the patient may be the expert in monitoring their condition and self-management of a flare by means of non-pharmacological (such as exercise, bed rests, applying ice or heat packs or via complementary and alternative therapies) or pharmacological interventions (by increasing the dose of glucocorticoids, analgesics or non steroidal anti-inflammatory medication alongside a fixed-dose of disease modifying anti-rheumatic drugs) seems to be the approach employed by most RA sufferers [22]. There are times, however, when self-management of a flare is ineffective and the patient decides to seek medical help. Although the threshold at which such a decision is made is unknown, the doctor must adopt a holistic approach in assessing the patient and based on shared-decision making determine an appropriate change in treatment.

In conclusion, the concept of a significant disease flare in RA is complex, non-standardised and its interpretation depends on interplay between a patient’s physical and psychological parameters, previous disease experience and health beliefs. Monitoring of this acute episode should occur in the community, with health professionals providing ongoing patient education and counselling and facilitating timely review by the clinician when the patient seeks medical help.”


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