Local anaesthetic failure in joint hypermobility syndrome
When taking biopsies to assess skin strength in Ehlers–Danlos syndrome type III (EDS–III), a Danish group noticed that the patients experienced much pain despite conventional local anaesthesia.1 When asked, all these patients reported previous experience of partial or complete failure of local anaesthesia in dental or obstetric procedures—for which reason some had been dismissed as hysterics. Pursuing this finding, Arendt-Nielsen et al.2 compared the effects of local anaesthesia in 8 patients with EDS–III and 8 controls. Although the patients did gain analgesia from intradermal lidocaine the duration of effect was much shorter than in controls. EDS–III (now known as EDS–hypermobility type) is regarded by many authorities as identical to joint hypermobility syndrome (JHS).3,4 We wish to draw attention to the possibility of resistance to local anaesthesia in individuals with this common and under-diagnosed condition.
Many normal people have hypermobile joints and medical diagnosis of the medical syndrome requires symptoms—which can include chronic pain, impairment of proprioception, and temporomandibular joint dysfunction (a manifestation of which dentists may be unaware).5 JHS is overrepresented in general rheumatology clinic populations and in our experience (RG and AJH)6 many of these patients report failure of local anaesthetics. This matter was addressed briefly in a paper published in 2003.7 A questionnaire was completed by 172 female Caucasian JHS patients, 53 non-hypermobile age-matched controls, and 28 individuals who showed evidence of hypermobility with insufficient features to qualify for JHS (HM-sine-JHS) as defined by the Brighton criteria.8 We asked ‘If you have ever had a local anaesthetic injection (dentist/minor surgery/epidural), did you think that it was as effective as it should have been?’. 58% of JHS patients, 21% of controls and 14% of the HM-sine-JHS group answered in the negative. For JHS versus controls the odds ratio was a highly significant 2.85. Although the question was simplistic, non-exploratory, and reliant on recall and selfperception, the difference between JHS and controls was striking. Neither group had knowledge of any study hypothesis. At the time there was nothing of this nature documented in patient information sheets or published research.
We suspect that in many people JHS goes unrecognized. So, how can a busy clinician, mindful of possible resistance to local anaesthesia, make the diagnosis? There are two easy methods for identifying hypermobility—carry out a Beighton score9 (Box 1); or ask the patient to answer a five-part screening questionnaire7 (Box 2). The phenotype is shown in Box 3.
Box 1
The nine-point Beighton hypermobility score (Ref. 9) One point may be gained for each side for manoeuvres 1–4 so that the hypermobility score will have a maximum of nine points if all are positive. A score of ≥4/9 indicates widespread hypermobility
| Ability to: | ||
| Left | Right | |
| Passively dorsiflex the fifth metacarpophalangeal joint to ≥ 90° | 1 | 1 |
| Oppose the thumb to the volar aspect of the ipsilateral forearm | 1 | 1 |
| Hyperextend the elbow to ≥ 10° | 1 | 1 |
| Hyperextend the knee to ≥ 10° | 1 | 1 |
| Place hands flat on the floor without bending the knees | 1 | |
| Total | 9 | |
Although the pathophysiology of this phenomenon remains unresolved, an important clue that a patient is at risk of local anaesthetic failure might be in front of our eyes.