Abstract

A subgroup of patients that undergo TKR surgery have evidence of neuropathic pain and central sensitization that may predispose to severe postoperative pain. This study assesses the correlation of MRI detected bone marrow lesions (BMLs) and synovitis with markers of neuropathic pain and central sensitization in patients undergoing TKR surgery and healthy volunteers.

31 patients awaiting TKR and 5 healthy volunteers were recruited. Each subject underwent a 3-T knee MRI scan that was graded for BMLs (0–45) and synovitis (0–3) using subsets of the MRI Osteoarthritis Knee Score (MOAKS). All subjects were asked to complete the PainDetect questionnaire to identify nociceptive pain (< 13), unclear pain (13–18) and neuropathic pain (>18). Correlation between BMLs and PainDetect score was the primary outcome measure. Secondary outcomes included the correlation of synovitis to PainDetect and temporal summation (TS) a measure of central sensitization to the PainDetect score. TS was determined using a monofilament to evoke pain. Pilot histological analysis of the prevalence of osteoclasts (TRAP⁺) within BMLs versus normal subchondral bone was performed, implying a role in BML pathology.

Increasing BML MOAKS score correlated with neuropathic pain (painDetect), r_s = 0.38, p=0.013 (one-tailed). There was a positive correlation between synovitis and PainDetect score, τ =0.23, p= 0.031 (one-tailed). TS was greater in the neuropathic pain than in nociceptive pain patients, U = 18.0, p=0.003 (one-tailed). TRAP staining identified more osteoclasts within BMLs than contralateral condyle lesion free subchondral bone, z = −2.232, p = 0.026 (Wilcoxon Signed Rank Test, one-tailed).

BMLs and synovitis are more prevalent in neuropathic pain and central sensitization in knee OA. Higher osteoclast prevalence was seen within BMLs which may help explain the association with BMLs and pain in OA.

Background

High velocity vertical aircraft ejection seat systems are credited with aircrew survival of 80-95% in modern times. Use of these systems is associated with exposure of the aircrew to vertical acceleration forces in the order of 15-25G. The rate of application of these forces may be up to 250G per sceond. Up to 85% of crew ejecting suffer skeletal injury and vertebral fracture is relatively common (20-30%) when diagnosed by plain radiograph. The incidence of subtle spinal injury may not be as apparent.

Aim: In sub-axial cervical vertebrae the lamina appears to project perpendicular to the ipsilateral pedicle axis, and forms a reliable trajectory for avoidance of vertebral artery injury in lateral mass (LM) screw placement: the aim is to confirm these observations.

Material and Methods: 51 digital cervical spine CTs (255 vertebrae; 25 female 26 male; mean age 37.4 range:18–80). Exclusions: Severe degeneration, malformation, tumour, trauma.

Measurement (axial view):

Angle of ipsilateral outer lamina cortex to pedicle axis

Results: Average lamina-pedicle angle (standard deviation):

Females: Right: C3–84.8°(2.6), C4–85.2°(3.1), C5–86.7°(3.3), C6–89.2°(2.5), C7–92.3°(2.4);

Conclusion: The angle formed by the lamina and ipsilateral pedicle ranges from 84° at C3 to 92° at C7. Although the angle is not exactly perpendicular at all levels as hypothesised, the lamina forms a useful reference plane for pedicle screw insertion in the sub-axial cervical spine.

LM screws placed parallel to the lamina find sufficient LM width and are highly unlikely to injure the vertebral artery in bi-cortical placement. This technique appears favourable over conventional 30° LM placement.

Ethics approval: None needed

Interest Statement: None

High velocity vertical aircraft ejection seat systems are credited with aircrew survival of 80–95% in modern times. Use of these systems is associated with exposure of the aircrew to vertical acceleeration forces in the order of 15–25G. The rate of application of these forces maybe upto 250G per sceond. Upto 85% of crew ejecting suffer skeletal injury and vertebral fracture is relatively common (20–30%) when diagnosed by plain radiograph. The incidence of subtle spinal injury may not be as apparent.

A prospective case series, admitted to QMC Nottingham, from 1996 to 2006 was evaluated. During this interval 26 ejectees from 20 aircraft were admitted to the spinal studies unit for comprehensive examination, evaluation and management. The investigations included radiographs of the whole spine and magnetic resonance Imaging (incorporating T1, T2 weighted and STIR saggital sequences). All ejections occurred within the ejection envelope and occurred at an altitude under 2000 feet (mean 460 feet) and at an airspeed less than 500 knots (mean 275 knots).

In this series 6 ejectees (24%) had clinical and radiographic evidence of vetebral compression fractures. These injuries were located in the thoracic and thoracolumbar spine. 4 cases required surgery ( indicated for angular kyphosis greater than 30 degrees, significant spinal canal compromise, greater than 50% or neurological injury. 1 patient had significant neurological compromise, following an AO A3.3 injury involving the L2 vertebra.

11 ejectees (45 %) had MRI evidence of a combined total of 22 occult thoracic and lumbar fractures. The majority of these ejectees with occult injury had multilevel injuries.

This study confirms a high incidence if spinal fracture and particularly occult spinal injury. Evidently vertical emergency aircraft ejection imposes major insults on the spinal column. Once, appropriately prioritised, life preservation measures have been undertaken, an early MRI of the spne is mandatory as part of comprehensive patient evaluation.

Correspondence should be addressed to Major M Butler RAMC, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital, Exeter, Devon.

Study Design: Retrospective review.

Objective: A prospective study to evaluate for the presence of occult spinal injuries using MRI following aircraft ejection.

Summary of Background Data: The use of an ejection seat in order to escape from a stricken aircraft is associated with the exposure of significant forces. These vertical accelerative forces on the body are in the order of 15 – 25G with rates of onset of up to 250G per second. Therefore, it is common to see vertical compression fractures, mainly in the thoraco-lumbar region. Although most vertebral fractures are evident on plain radiographs, other subtle spinal injuries elsewhere may not be immediately apparent.

Methods: Between 1996 and 2003, 22 ejectees from 18 aircrafts, mean age 32 years (range 24 to 48), were admitted to a regional spinal unit for comprehensive evaluation of their injuries that included whole spine radiographs and Magnetic Resonance Imaging (T1, T2 weighted and STIR sagittal sequences). All ejections occurred within the ejection envelope and were flying below 2000 ft (mean 460 feet) and below 500 knots airspeed (mean 275 knots).

Results: All 5 ejectees (23%) with vertebral compression fractures (one at T6 and 4 in thoraco-lumbar region) had pain and tenderness in the appropriate area of the spine that was evidently detected on plain radiographs. 3 of these patients with a thoraco-lumbar fracture (AO A3.3) had more than 50% canal compromise and more than 30 degrees angular kyphosis underwent surgery. Neurological compromise consisting of acute cauda equine syndrome occurred in one patient with a L2 AO A3.3 fracture. More importantly 10 ejectees (45%) had MRI evidence totalling 21 occult thoracic and lumbar vertebral fractures. 4 ejectees had a single occult fracture, 4 had double, 1 had 3 and 1 had 6 occult fractures.

Conclusion: This study confirms the high incidence of occult vertebral injuries following vertical acceleration insult to the spine consequent to emergency aircraft ejection. Once life-saving priority measures have taken place, MRI of the entire spine remains mandatory as part the comprehensive evaluation of the patient. Early use of MRI scanning in the management will significantly increase an ejectee’s safe return to flying duties.

To determine how long after injury a single photon emission computed tomography (SPECT) scan may remain positive in cases of symptomatic posterior element lumbar stress injuries.

SPECT scans can identify posterior element lumbar stress injuries earlier than other imaging modalities. As these lesions evolve and the spondylolysis becomes chronic, the SPECT scan tends to revert to normal even though healing of the defect has not occurred. The aim of this study was to determine how long after initial injury a SPECT scan might remain positive.

One hundred and sixty-five patients (85 male, 80 female) between the ages of 8 and 38 years with suspicion of lumbar spondylolysis or posterior element lumbar stress injuries were investigated. All patients underwent plain radiographs, planar bone scintigraphy and SPECT imaging. The duration of symptoms at clinical assessment was recorded. The age, sex, symptom reproduction on flexion or extension, level of sporting activity, and the Oswestry Disability Index both pre- and post-treatment were also recorded. SPECT positive images (hot scans) were depicted as cases and SPECT negative images as controls. Univariate and multivariate analysis was performed.

Eighty-five patients (63 male, 22 female) had positive SPECT scans (cases); eighty had negative scans (controls). The mean age at onset of symptoms was 20.2 years for cases and 17.4 years for controls. Bilateral increased uptake on SPECT scan was more common than unilateral. The commonest site for increased uptake was the posterior elements of the fifth lumbar vertebra. Low back pain in extension was more common in SPECT positive cases. The mean time from injury / onset of symptoms to a positive SPECT scan was 7.1 months (range 5.2–9.2 months) and to a negative SPECT scan was 22.5 months (range 16.8–28.4 months).

Intense scintigraphic activity in the posterior elements of the lumbar spine was associated with a more recent injury and was concordant with the patient’s history and physical examination. Chronic, un-united spondylolysis was often scintigraphically occult. There was a window of approximately six months from the onset of symptoms to investigation after which the sensitivity of SPECT imaging diminished.

The incidence of symptomatic pars defect varies between 15% and 47% in the young athletic population. We have analysed the outcome of direct repair spondylolysis on young professional athletes.

We have prospectively studied 22 young athletes with lumbar spondylolysis in whom conservative treatment has failed. Fifteen male and 7 female patients with a mean age of 20.2 years (range 15–34 years) were surgically treated for radiographically confirmed spondylolysis between 1994 and 1999. Eleven patients were professional footballers and four were professional cricketers. Pre-operative assessment included plain X rays, SPECT imaging with planar bone scan and reverse gantry CT scans. All patients had the Oswestry disability index (ODI) and 19 patients had Short Form 36 (SF-36) scores recorded pre-operatively and two years post operatively. Nineteen patients underwent Buck’s fusion and 3 underwent Scott’s fusion. At two-year follow-up nineteen patients had ODI and SF36 scores recorded. Return to the sporting activity at the previous level was regarded as a successful outcome.

The average duration of back pain prior to surgery was 8.9 months (range 1-36 months). The mean lysis defect determined by CT was 3.5 mm (range 1–8 mm). The mean pre-operative ODI was 39.5 (SD=8.7) and the mean post-operative ODI was 10.7 (SD=12.9). The mean scores of the physical health component of SF-36 improved from 27.1 (SD=5.1) to 47.8 (SD=7.7). The mean scores of the mental health component of SF-36 improved from 39.0 (SD=3.9) to 55.4 (SD=6.3) [P < 0.001].

The surgical repair of bilateral spondylolysis with modified Buck’s fusion in professional sportsmen and women results in a significant improvement in Oswestry Disability scores (p< 0.001) and in all domains of SF36 health questionnaire (p< 0.001). Ninety five percent of patients in this group return to active sport within seven months of surgery.

Injury to the spinal cord without radiological abnormality often occurs in the skeletally immature cervical and thoracic spine. We describe four adult patients with this diagnosis involving the cervical spine with resultant quadriparesis. The relevant literature is reviewed. The implications for initial management of the injury, the role of MRI and the need for a high index of suspicion are highlighted.