Undifferentiated Back Pain — Viva

Long Case Viva Defence

Candidate's opening statement (model answer)

"Mr David Tran is a 34-year-old software engineer presenting with a three-year history of progressive inflammatory low back pain — pain that is worse in the morning, that improves with exercise, that wakes him at night and improves on rising, with morning stiffness over an hour — on a background of psoriasis and a prior episode of anterior uveitis. [1]

His main problems are:

1. Axial spondyloarthritis, most likely ankylosing spondylitis, supported by the inflammatory back pain criteria (he meets at least four of five), the psoriasis, the uveitis, the raised inflammatory markers (CRP 24, ESR 38), the HLA-B27 positivity, and the bilateral grade 2 sacroiliitis on the pelvic X-ray.
2. Psoriasis of the scalp and the extensor surfaces.
3. A prior episode of anterior uveitis, at risk of recurrence.
4. A functional limitation — the reduced lumbar flexion (modified Schober increase of 3 cm) and the reduced chest expansion (4 cm), with the risk of the progressive spinal rigidity. [1]

My priorities are the confirmation of the diagnosis with an MRI of the sacroiliac joints to assess the active inflammation, the rheumatology referral for the treat-to-target management, the assessment of his cardiovascular and pulmonary risk (the aortic regurgitation, the conduction disease and the apical pulmonary fibrosis), the ophthalmology link for the recurrent uveitis, and the lifestyle discussion — the smoking cessation (he is a non-smoker, which I will reinforce), the physiotherapy and the ergonomic advice." [1]

Examiner probing questions and model answers

Q1: "How do you distinguish his inflammatory back pain from mechanical back pain?" [1]

"The ASAS inflammatory back pain criteria are my framework. Mr Tran meets at least four of the five: the age of onset under 40 (he is 34), the insidious onset, the improvement with exercise, the lack of improvement with rest, and the night pain improving on rising. He also has the morning stiffness over an hour. The discriminating features from mechanical pain are the opposite response to activity — the inflammatory pain improves with exercise and worsens with rest, while the mechanical pain worsens with activity and is relieved by rest. The night pain that improves on rising is the inflammatory signature; the mechanical pain is typically relieved by lying down. The morning stiffness over 30 minutes is the inflammation, not the brief stiffness of the osteoarthritis. The extra-articular features — the psoriasis and the uveitis — are the clinching evidence that this is a spondyloarthritis [6]. The registrar who attributes this presentation to a lumbar strain has missed the diagnosis by years."

Q2: "His pelvic X-ray shows bilateral grade 2 sacroiliitis. Does he need an MRI?" [1]

"The X-ray confirms the structural sacroiliitis, which is sufficient for the modified New York criteria for ankylosing spondylitis, so the MRI is not needed to make the diagnosis. But I would arrange the MRI of the sacroiliac joints to assess the active inflammation — the bone marrow oedema — because the presence and the degree of the active inflammation guide the escalation to a biologic. The MRI is also the investigation that detects the early sacroiliitis before the radiographic change, which is the value of the ASAS imaging arm in the patient with the clinical picture but the normal X-ray. The teaching point is that the X-ray confirms the structural damage and the MRI assesses the active inflammation — they answer different questions [6]."

Q3: "He is HLA-B27 positive. Does that confirm the diagnosis?" [1]

"No. The HLA-B27 is neither necessary nor sufficient for the diagnosis. It is a supporting feature in the ASAS clinical arm (the HLA-B27 positive plus at least two SpA features), but Mr Tran already meets the imaging arm (the sacroiliitis on imaging plus one SpA feature), so the HLA-B27 is confirmatory rather than diagnostic. The HLA-B27 is present in about 90 per cent of patients with ankylosing spondylitis but also in about 8 per cent of the general population, most of whom never develop the disease — so a positive test in isolation does not diagnose the axial SpA, and a negative test does not exclude it. The test is a supportive feature, not a screening test, and it is most useful in the patient with the clinical picture and the normal imaging, where it raises the pre-test probability enough to justify the MRI [6]."

Q4: "What is your approach to his pharmacological management?" [1]

"The first-line is a full-dose NSAID at the maximum tolerated dose for at least two to four weeks — naproxen 500 mg twice daily, or celecoxib 200 mg twice daily, with a proton pump inhibitor for the gastroprotection. The response to NSAIDs is itself a SpA feature in the criteria, and about half to two-thirds of the patients respond adequately. If the NSAID is insufficient, or if there are contraindications (the renal impairment, the peptic ulcer, the cardiovascular disease), or if the disease is high-activity (the raised CRP, the active sacroiliitis on the MRI, the reduced function), I escalate to a biologic under the rheumatology guidance — a tumour necrosis factor inhibitor (adalimumab 40 mg subcutaneously every two weeks, etanercept 50 mg weekly, infliximab) or an interleukin-17 inhibitor (secukinumab), guided by the NICE NG65 and the international treat-to-target recommendations. I avoid the systemic corticosteroid for the axial disease (it is largely ineffective) and I reserve the intra-articular corticosteroid for the peripheral joint or the sacroiliac joint injection in the selected cases. The non-pharmacological management — the structured physiotherapy, the daily spinal mobility and the postural exercise, and the smoking cessation — is the other cornerstone [6]."

Q5: "What are the extra-articular complications you would screen for?" [1]

"The anterior uveitis — the commonest, in about a third of the patients — I ask about the eye pain, the redness and the photophobia, and I link him to the ophthalmology for the early treatment of the recurrence (the uveitis of the axial SpA is typically acute, unilateral, and responsive to the topical corticosteroids, but the severe case may need the systemic immunosuppression). The cardiovascular associations — the aortic regurgitation from the aortic root dilatation, and the conduction disease — I arrange a baseline echocardiogram and an ECG. The pulmonary associations — the apical pulmonary fibrosis and the restrictive chest wall disease from the costovertebral rigidity — I monitor the chest expansion and the spirometry; his chest expansion is already reduced at 4 cm, which I track over time. The osteoporosis — the inflammation and the immobility increase the fracture risk — I monitor the bone density with the DEXA scan. The inflammatory bowel disease — I ask about the chronic diarrhoea, the abdominal pain and the rectal bleeding, and I screen with the faecal calprotectin and the gastroenterology referral if any of these are present. The teaching point is that the axial SpA is a systemic disease, not just a back pain, and the surveillance spans the eyes, the heart, the lungs, the bones and the gut [6]."

Q6: "He is a software engineer. What lifestyle advice would you give?" [1]

"The smoking cessation is the single most important lifestyle message — the smoking accelerates the radiographic progression, the spinal rigidity and the functional limitation, and it worsens the pulmonary complications. He is a non-smoker, which I reinforce. The exercise is the second cornerstone — a daily programme of the spinal mobility, the postural exercise, the swimming and the core strengthening, ideally with a physiotherapist. The ergonomic advice — the upright posture at the desk, the standing desk, the regular breaks — protects the spine. And the occupational therapy and the workplace accommodation — the flexible hours, the adjustable workstation — support the function. The psychological support — the reassurance that the condition is manageable in the modern era, the link to a patient support group — addresses the anxiety that comes with the chronic inflammatory diagnosis [6]."

Short Case Discussion

The systematic spine examination

Examiner instruction: "Examine this patient's spine. Present your findings and offer a differential diagnosis." [1]

Candidate's model answer: [1]

*"My routine is the end of the bed, the hands, the abdomen, the spine (inspection, palpation, movement), the nerve root tests, the lower limb neurological examination, the per rectal in the suspected cauda equina, and the extra-spinal signs. Before I touch the patient, I take five seconds at the end of the bed — the look test: is he in pain, is the posture abnormal (a list, a scoliosis, a kyphosis, a forward stoop), is the gait abnormal (an antalgic gait, a foot drop)? [1]

Hands. I look for psoriasis (the nails and the extensor surfaces), the stigmata of spondyloarthritis (dactylitis — a sausage digit, and the enthesitis at the Achilles tendon), and the general inspection. [1]

Abdomen. I feel for a pulsatile mass (the abdominal aortic aneurysm) and the organomegaly (the malignancy). [1]

Spine — inspection. I look for the scoliosis, the kyphosis, a step in the spine (suggesting spondylolisthesis), the muscle spasm, the scars, and the skin lesions — a hairy patch, a lipoma or a sinus over the lumbar spine suggests a spinal dysraphism. [1]

Spine — palpation. I palpate the spinous processes for a step and for tenderness, the paraspinal muscles for spasm and trigger points, and the sacroiliac joints. [1]

Spine — movement. I assess the flexion (the modified Schober test — mark the lumbosacral junction and 10 cm above, ask the patient to bend forward; an increase of less than 5 cm indicates the reduced lumbar flexion, the screening test for the axial SpA), the extension (limited and painful in the spinal stenosis and the facet joint disease), the lateral flexion, and the rotation. I measure the chest expansion at the fourth intercostal space — a reduction to less than 2.5 cm is one of the modified New York criteria for the ankylosing spondylitis. [1]

Nerve root tests. The straight leg raise (the Lasegue test) — the reproduction of the radicular pain (not the back pain) between 30 and 70 degrees indicates the L4, L5 or S1 root irritation. The crossed straight leg raise — lifting the asymptomatic leg reproduces the pain in the symptomatic leg — is highly specific for a large central disc. The femoral stretch test — the hip extension with the knee flexed in the prone patient, reproducing the anterior thigh pain — indicates the L2, L3 or L4 root irritation. [1]

Lower limb neurological examination. The power (hip flexion L2, knee extension L3 to L4, ankle dorsiflexion L4 to L5, great toe extension L5, ankle plantar flexion S1 to S2), the sensation (the dermatomes), the reflexes (knee L3 to L4, ankle S1 to S2, and the plantar response), and the gait (the heel and the toe walk). [1]

Per rectal examination. In the suspected cauda equina, the per rectal is mandatory — the anal tone at rest and on squeeze, the perianal sensation to pinprick (the S2 to S4 dermatomes), and the bulbocavernosus reflex. [1]

Extra-spinal signs. The eyes (the uveitis), the pulses (the vascular claudication), the chest (the breast lump, the lung mass — the primaries of the bony metastasis), and the skin (the psoriasis, the erythema nodosum, the injection sites of the intravenous drug use). [1]

The examination does not stop at the spine if the findings suggest a systemic cause — I extend it to the abdomen, the pulses, the eyes and the skin, because the back pain is often the presenting symptom of a disease elsewhere [1]."*

Examiner: "Why is the per rectal examination so important in suspected cauda equina?" [1]

"The per rectal examination assesses the anal tone and the perianal sensation — the S2 to S4 dermatomes — which are the objective findings of the cauda equina compression. The patient may not volunteer the saddle anaesthesia or the sphincter dysfunction, and the reduced anal tone and the perianal numbness are the signs that confirm the clinical suspicion. The teaching from the Lavy review is that the classic complete triad of the cauda equina is often absent at presentation — the diagnosis is made by a high index of suspicion and the objective findings, and the per rectal examination and the post-void residual on the bladder scan are the two investigations that must be performed whenever the cauda equina is on the differential [4]. The registrar who omits the per rectal in the suspected cauda equina has not completed the assessment."

Examiner: "What is the single most important lesson from this examination for a registrar managing undifferentiated back pain?" [1]

"The single most important lesson is that the spine examination is integrated — it does not stop at the musculoskeletal system. The registrar who walks to the back first and palpates the paraspinal muscles has failed the question. The correct routine is the end of bed, the hands, the abdomen, the spine, the nerve root tests, the neurological examination, the per rectal, and the extra-spinal signs. The integrated examination that discriminates the mechanical from the inflammatory, the radicular, the infective, the malignant and the referred causes — and that screens for the cauda equina in every patient — is what keeps the back pain patient safe. The corollary is the triage: the examination sorts the patient into the bin, and the bin drives the investigation and the management [1][2][3]."