Introduction: Spine fractures are common manifestation of osteoporosis. After an acute osteoporotic vertebral compression fracture pain persisting even after 3 months and clinical tenderness should raise the suspicion of pseudarthrosis. Pseudarthrosis is not a rare complication of a benign osteoporotic vertebral collapse occurs in about 10% of cases after an acute collapse. Treatment plan needs to be individualized. Cement augmentation procedures such as kyphoplasty and vertebroplasty can be performed in the absence of neurological deficit, whereas decompression and stabilization is necessary in presence of neurological deficit. Study Design: Prospective cohort study. Methods: 31 patients who were diagnosed to have an acute osteoporotic vertebral compression fracture were managed conservatively. Pain persisting after 3 months and clinical tenderness in 5 patients prompted further investigation, revealing pseudarthrosis. None of them had neurological deficit. Imaging of two patients revealed vacuum sign with intravertebral cleft on plain radiographs and on MRI. All of them were at the Dor-solumbar junction and of crush typeof VCF. Results: The incidence of pseudoarthrosis after an oste-porotic VCF was found to be 16.12%. One patient was treated with kyphoplasty, one with vertebroplasty with good pain relief and restoration of functional ability, and rest three are awaiting kyphoplasty. Conclusion: High suspicion of pseudarthrosis is to be kept in mind as it is not an uncommon complication of benign osteoporotic collapse. Vertebral augmentation procedures such as kyphoplasty and vertebroplasty are promising procedures for treatment in absence of neurological deficit

We investigated the safety and efficacy of treating osteoporotic vertebral compression fractures with an intravertebral cleft by balloon kyphoplasty. Our study included 27 patients who were treated in this way. The mean follow-up was 38.2 months (24 to 54). The anterior and middle heights of the vertebral body and the kyphotic angle were measured on standing lateral radiographs before surgery, one day after surgery, and at final follow-up. Leakage of cement was determined by CT scans. A visual analogue scale and the Oswestry disability index were chosen to evaluate pain and functional activity. Statistically significant improvements were found between the pre- and post-operative assessments (p < 0.05) but not between the post-operative and final follow-up assessments (p > 0.05). Asymptomatic leakage of cement into the paravertebral vein occurred in one patient, as did leakage into the intervertebral disc in another patient. We suggest that balloon kyphoplasty is a safe and effective minimally invasive procedure for the treatment of osteoporotic vertebral compression fractures with an intravertebral cleft

In a prospective study between August 2002 and August 2005, we studied the quantitative clinical and radiological outcome 36 months after percutaneous vertebroplasty for intractable type-II osteoporotic vertebral compression fractures which had been unresponsive to conservative treatment for at least eight weeks. We also examined the quality of life (QoL). The clinical follow-up involved the use of a pain intensity numerical rating scale (PI-NRS, 0 to 10), the Short-Form 36 (SF-36) QoL questionnaire and an anamnestic questionnaire before and at seven days (PI-NRS only), and one, three, 12 and 36 months post-operatively. A total of 30 consecutive patients received percutaneous vertebroplasty for 62 vertebral compression fractures with a mean time between fracture and treatment of 7.7 months (2.2 to 39). An immediate, significant and lasting reduction in the average and worst back pain was found, represented by a decrease of 3.1 and 2.7 points after seven days and 3.1 and 2.8 points after 36 months, respectively (p < 0.00). Comparison of the pre- and post-vertebroplasty scores on the various SF-36 domains showed an ultimate significant increase in six of eight domains and both summary scores. Asymptomatic leakage of cement was found in 47 of 58 (81%) of treated vertebrae. Two minor complications occurred, an asymptomatic pulmonary cement embolism and a cement spur along the needle track. Percutaneous vertebroplasty in the treatment of chronic vertebral compression fractures results in an immediate, significant and lasting reduction in back pain, and overall improvement in physical and mental health

Vertebral compression fractures are the most prevalent complication of osteoporosis and percutaneous vertebroplasty (PVP) has emerged as a promising addition to the methods of treating the debilitating pain they may cause.

Since PVP was first reported in the literature in 1987, more than 600 clinical papers have been published on the subject. Most report excellent improvements in pain relief and quality of life. However, these papers have been based mostly on uncontrolled cohort studies with a wide variety of inclusion and exclusion criteria. In 2009, two high-profile randomised controlled trials were published in the New England Journal of Medicine which led care providers throughout the world to question the value of PVP. After more than two decades a number of important questions about the mechanism and the effectiveness of this procedure remain unanswered.

This study prospectively compared the efficacy of kyphoplasty using a Jack vertebral dilator and balloon kyphoplasty to treat osteoporotic compression fractures between T10 and L5. Between 2004 and 2009, two groups of 55 patients each underwent vertebral dilator kyphoplasty and balloon kyphoplasty, respectively. Pain, function, the Cobb angle, and the anterior and middle height of the vertebral body were assessed before and after operation. Leakage of bone cement was recorded. The post-operative change in the Cobb angle was significantly greater in the dilator kyphoplasty group than in the balloon kyphoplasty group (−9.51° (sd 2.56) vs −7.78° (sd 1.19), p < 0.001)). Leakage of cement was less in the dilator kyphoplasty group. No other significant differences were found in the two groups after operation, and both procedures gave equally satisfactory results in terms of all other variables assessed. No serious complications occurred in either group.

These findings suggest that vertebral dilator kyphoplasty can facilitate better correction of kyphotic deformity and may ultimately be a safer procedure in reducing leakage of bone cement.

Objectives. Although vertebroplasty is very effective for relieving acute pain from an osteoporotic vertebral compression fracture, not all patients who undergo vertebroplasty receive the same degree of benefit from the procedure. In order to identify the ideal candidate for vertebroplasty, pre-operative prognostic demographic or clinico-radiological factors need to be identified. The objective of this study was to identify the pre-operative prognostic factors related to the effect of vertebroplasty on acute pain control using a cohort of surgically and non-surgically managed patients. Patients and Methods. Patients with single-level acute osteoporotic vertebral compression fracture at thoracolumbar junction (T10 to L2) were followed. If the patients were not satisfied with acute pain reduction after a three-week conservative treatment, vertebroplasty was recommended. Pain assessment was carried out at the time of diagnosis, as well as three, four, six, and 12 weeks after the diagnosis. The effect of vertebroplasty, compared with conservative treatment, on back pain (visual analogue score, VAS) was analysed with the use of analysis-of-covariance models that adjusted for pre-operative VAS scores. Results. A total of 342 patients finished the 12-week follow-up, and 120 patients underwent vertebroplasty (35.1%). The effect of vertebroplasty over conservative treatment was significant regardless of age, body mass index, medical comorbidity, previous fracture, pain duration, bone mineral density, degree of vertebral body compression, and canal encroachment. However, the effect of vertebroplasty was not significant at all time points in patients with increased sagittal vertical axis. Conclusions. For single-level acute osteoporotic vertebral compression fractures, the effect of vertebroplasty was less favourable in patients with increased sagittal vertical axis (> 5 cm) possible due to aggravation of kyphotic stress from walking imbalance. Cite this article: Y-C. Kim, D. H. Bok, H-G. Chang, S. W. Kim, M. S. Park, J. K. Oh, J. Kim, T-H. Kim. Increased sagittal vertical axis is associated with less effective control of acute pain following vertebroplasty. Bone Joint Res 2016;5:544–551. DOI: 10.1302/2046-3758.511.BJR-2016-0135.R1

The optimal timing of percutaneous vertebroplasty as treatment for painful osteoporotic vertebral compression fractures (OVCFs) is still unclear. With the position of vertebroplasty having been challenged by recent placebo-controlled studies, appropriate timing gains importance.

We investigated the relationship between the onset of symptoms – the time from fracture – and the efficacy of vertebroplasty in 115 patients with 216 painful subacute or chronic OVCFs (mean time from fracture 6.0 months (sd 2.9)). These patients were followed prospectively in the first post-operative year to assess the level of back pain and by means of health-related quality of life (HRQoL). We also investigated whether greater time from fracture resulted in a higher risk of complications or worse pre-operative condition, increased vertebral deformity or the development of nonunion of the fracture as demonstrated by the presence of an intravertebral cleft.

It was found that there was an immediate and sustainable improvement in the level of back pain and HRQoL after vertebroplasty, which was independent of the time from fracture. Greater time from fracture was associated with neither worse pre-operative conditions nor increased vertebral deformity, nor with the presence of an intravertebral cleft.

We conclude that vertebroplasty can be safely undertaken at an appropriate moment between two and 12 months following the onset of symptoms of an OVCF.

The August 2024 Spine Roundup. 360. looks at: Laminectomy adjacent to instrumented fusion increases adjacent segment disease; Influence of the timing of surgery for cervical spinal cord injury without bone injury in the elderly: a retrospective multicentre study; Lumbar vertebral body tethering: single-centre outcomes and reoperations in a consecutive series of 106 patients; Machine-learning algorithms for predicting Cobb angle beyond 25° in female adolescent idiopathic scoliosis patients; Pain in adolescent idiopathic scoliosis; Teriparatide prevents surgery for osteoporotic vertebral compression fracture

Abstract. Objectives. The principle of osteoporotic vertebral compression fracture (OVCF) is fixing instability, providing anterior support, and decompression. Contraindication for vertebroplasty is anterior or posterior wall fracture. The study objectives was to evaluate the efficacy and safety of vertebroplasty with short segmented PMMA cement augmented pedicle screws for OVCF with posterior/anterior wall fracture patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ±0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20±5.90 to 5.30±1.40 postoperative with 5% (3.30± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80±11.9% t0 87.6±13.1% postoperative with 4.5±4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because It provides anterior support with cementing that avoids corpectomy. Short segment fixation has less stress risers at the junctional area

Abstract. Objectives. To evaluate the safety and efficacy of vertebroplasty with short segmented cement augmented pedicle screws fixation for severe osteoporotic vertebral compression fractures (OVCF) with posterior/anterior wall fractured patients. Methods. A retrospective study of 24 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. Results. A significant improvement was noted in VAS (preoperative, 7.90 ± 0.60; final follow-up 2.90 ± 0.54) and ODI (77.10 ± 6.96 to 21.30 ± 6.70), (P < 0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20 ± 5.90 to 5.30 ± 1.40 postoperative with 5% (3.30 ± 2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80 ± 11.9% to 87.6 ± 13.1% postoperative with 4.5 ± 4.0% loss at final follow-up. One case had cement leakage was found, but the patient is asymptomatic. No implant-related complication was seen. No iatrogenic dural or nerve injury. Conclusions. Treatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because. Vertebroplasty is viable option for restoring vertebral anterior column in patients who are considered as contraindications for vertebroplasty, like DGOU-4. It provides anterior support avoiding corpectomy, minimise blood loss and also duration of surgery. Addition of short segment fixation gives adequate support with less stress risers at the junctional area

BACKGROUND. Osteoporosis with subsequent osteoporotic vertebral compression fractures is an increasingly important disease due not only to its significant economic impact but also to the increasing age of our population. Pain reduction and stabilization are of primary importance with osteoporotic vertebral compression fractures. OBJECTIVE. To compare the efficacy and safety of balloon kyphoplasty and vertebroplasty for the treatment of vertebral compression fractures. MATERIALS & METHODS. From January 2004 to December 2009, 142 patients (32 males and 110 females), from 54 to 84 years old (mean age 67.4) were treated for 185 osteoporotic vertebral fractures of the thoracic or lumbar spine (level of fracture at Th5 or lower), with back pain for more than 8 weeks, and a visual analogue scale (VAS) score of 5 or more. Twenty-two patients (29 fractures) were lost at follow-up period and excluded. Patients were randomly allocated to percutaneous kyphoplasty (64%) or vertebroplasty (36%). All fractures were analyzed for improvement in sagittal alignment (Cobb angle, kyphotic angle, sagittal index, vertebral height). The patients were evaluated using the visual analog scale (VAS) and the Oswestry Disability Score. Radiographs were performed postoperatively, and at 1, 3, 6, and 12 months. RESULTS. The score according to pain, the patient's ability to ambulate independently and without difficulty, and the need for medications improved significantly (P < 0.001) after kyphoplasty or vertebroplasty. No significant difference could be found between both groups for the mean VAS and ODI preoperative and postoperative. Vertebral body height and kyphotic wedge angle of the T-L spine were also improved (p < 0.001); although kyphosis correction seems to be improved better in kyphoplasty than vertebroplasty. The rate of leakage was 12% for kyphoplasty and 32% for vertebroplasty; nevertheless most of the leakage was clinically asymptomatic and the rate of serious problems remained low (pulmonary embolism 0.01% kyphoplasty vs 0.6% vertebroplasty). New fractures in the next 6 months at the adjacent vertebrae were observed ∼ 15% in both groups. More PMMA was used in the kyphoplasty group than in the vertebroplasty group (5.5 +/− 0.8 vs. 4.1 +/− 0.5 mL, p < 0.001). Operation time was longer in balloon kyphoplasty compared to vertebroplasty (mean time 20±5min/vertebral fracture in group B vs 30±5min in group A). CONCLUSION. Both balloon kyphoplasty and vertebroplasty provided a safe and effective treatment for pain and disability in patients with vertebral compression fractures due to trauma or osteoporosis. Balloon kyphoplasty led to an ongoing reduction of fractured vertebrae and was followed by a lower rate of cement leakage

Introduction. The risk factors for new adjacent vertebral compression fracture (NAVCF) after Vertebroplasty (VP) or Kyphoplasty (KP) for osteoporotic vertebral compression fractures (VCFs) were investigated. Materials and methods. The authors retrospectively analyzed the incidence of NAVCFs in 135 patients treated with VP or KP for osteoporotic VCFs. Study period was from 2004 to 2008 with minimum follow-up of 2 years. Possible risk factors were documented: age, gender, body mass index, bone mineral density (BMD), co-morbidities, location of treated vertebra, treatment modality and amount of bone cement injected. Anterior-posterior vertebral body height ratio, intra-discal cement leakage into the disc space and pattern of cement distribution of the initial VCF and adjacent vertebral bodies were assessed on lateral thoracolumbar radiographs by 2 independent assessors. Results. 21 patients (15.6%) had subsequent symptomatic NAVCFs with a median time to new fracture was of 125 days. There was no difference in incidence of NAVCF between VP and KP groups (P>0.05). Significant differences were found between patients with and without NAVCF in terms of age, BMD, and the proportion of cement leakage into the disc space (P < 0.05). Greater age, intra-discal cement leakage and low BMD were found in patients with NAVCF. Conclusion. The most important risk factors affecting NAVCFs were age, osteoporosis and intra-discal cement leakage

Introduction. This study compares outcomes of vertebroplasty(VP) and kyphoplasty(KP) in 125 consecutive female Asian patients above 65 years with L1 osteoporotic vertebral compression fractures. Methods. 57 and 68 patients underwent VP and KP respectively from 2004 to 2008. Outcomes were measured prospectively at pre-operation, 1 month, 6 months and 2 years post-operation by blinded assessors. Radiographic outcome: Anterior, middle and posterior vertebral heights of the L1 vertebral body Functional outcome: Short-Form 36(SF-36) score, Visual Analogue Scale(VAS) score for back pain. Results. There was greater improvement of anterior and middle vertebral heights immediately post-surgery for the KP group as compared to the VP group(P<0.001). At 2 years post-surgery, the KP group had better maintenance of L1 vertebral body height with percentage loss of 16.4%, 17.3% and 8.84% of anterior, middle and posterior vertebral height respectively as compared to the VP group who had a greater loss of 29.2%, 42.3% and 17% respectively(p<0.001). Back pain improved post-operatively in both groups with no significant difference in VAS back pain score between the two groups at each follow-up time point(P>0.05). SF-36 score improved post-operatively in both groups (P=0.001). At 2 years post-surgery, the physical functioning domain of SF-36 was better in the KP group (P=0.01). Conclusion. KP provides better restoration and maintenance of anterior and middle vertebral heights with better physical function outcome”

Introduction. Polymethylmethacrylate(PMMA) bone cement has been used in joint reconstruction surgery and recently introduced for treatment of osteoporotic vertebral compression fracture. However, the use of PMMA bone cement in vertebroplasty leads to extensive bone stiffening and high rate of adjacent vertebrae fracture. Aim. The purpose of this study was to investigate the properties of PMMA bone cement augmented with collagen and assess its characteristics and relevance for the reduction of complication rate associated with vertebroplasty. Methods. Bone cement was produced using 2 types of PMMA based bone cement. Augmented groups were prepared using 40g of bone cement with 1% of rat tail liquid collagen. Mixing was conducted in controlled laboratory environment and at room temperature. The working and setting time and the mechanical properties were determined in accordance to ASTM standards for acrylic cements. The effect of ageing in simulated body fluid(SBF) on mechanical properties of these cements and the microstructure were studied. Results. Addition of collagen to bone cement has shown no marked effect on the working and setting time and produces bone cement with good injectability. The compressive strength is not affected but the modulus shows the material is less brittle than PMMA. Conclusion. Addition of liquid collagen to PMMA based bone cement does not necessarily compromise the properties of the cements and produce cement with good injectability and less brittle than PMMA based bone cement alone. However, bone cement augmented with different concentration of collagen need to be studied further in order to assess its clinical relevance especially in vertebroplasty

Percutaneous vertebroplasty is an effective procedure for the treatment of osteoporotic vertebral compression fractures, spinal metastasis and other pathologic spinal diseases. However, there has been no mention in the relevant literature of the use of percutaneous vertebroplasty for the treatment of spinal pseudarthrosis in ankylosing sponyloarthritis. A 58-year-old male with a long standing ankylosing spondylitis presented with increasing, intolerable and non-intractable back pain. There was a 16- month-old history of a non-significant minor fall. Various radiological imaging technicques showed spinal pseudarthrosis with extensive discovertebral destruction and fracture of the posterior elements at the level T11–T12. Under local anaesthesia, and through a transpedicular approach with the guidance of CT, the cannula of a large bore needle was introduced into the level of spinal pseudarthrosis. Bone cement was then instilled into the affected spinal level. Results were documented by spiral CT and with sagittal reconstructions. Extraosseous cement leakage was seen at the puncture site of the vertebra and in the epidural veins and the paravertebral vessels. However, the patient did not present any immediate or late neurological and systemic complications. Percutaneous vertebroplasty of spinal pseudarthrosis in patients with ankylosing spondylitis is an effective procedure for stabilization of the affected spine segments and pain management

Aim: To show the place of percutaneous vertebroplasty (PV) in the treatment of painful osteoporotic vertebral compression fractures (VCF). VCF is a common and often debilitating complication of osteoporosis. Although most fractures heal within a few weeks or months, a minority of patients continues to suffer with pain that does not respond to conservative therapy. Methods: PV is accomplished by percutaneous injection of cement into the fractured vertebral body. Reinforcing and stabilizing the fracture provides pain relief. Injection of cement is accomplished under real time using a bilateral transpedicular approach or a unilateral transpedicular or parapedicular route. Results: PV is indicated in patients with severe, persistent and often incapacitating focal back pain not responding to a standard medical therapy of 4 to 12 weeks duration and related to one or more collapsed vertebral bodies. PV should be used earlier in patients at risk of immobilization complications and requiring narcotics. The success rate exceeds 90% and the complication rate is lower than 1%. Most of the complications are transient and should be avoided using good technique. Conclusion: PV should be always considered as a good alternative treatment compared to medical therapy in painful patients with osteoporotic compression fractures

Fracture is the only clinically relevant aspect of osteoporosis—a major public health problem in many countries. The strongest predictor for a new fragility fracture is a previous one. For instance, a patient with one osteoporotic vertebral compression fracture has about a seven-fold increased hip fracture risk; a patient with two compression fractures a 14-fold hip fracture risk. Today, we have evidence based and efficient osteoporosis drugs as well as non-pharmacologic methods for fracture prophylaxis. In risk group patients it often is possible to halve the fracture risk. The orthopaedic surgeon is the first and sometimes the only doctor a fracture patien sees. Therefore, as orthopaedic surgeons, we have a great opportunity—and indeed an onus—to identify patients with increased fracture risk, and to do something about it. Imagine patients with myocardial infarction or stroke discharged from hospital without blood pressure control or having a biochemical profile taken? Such negligence is, alas, not uncommon for patients with fragility fractures. We must think in terms of absolute fracture risk, and implement today’s evidence based knowledge. Secondary prophylaxis should be an integrated part in fracture treatment. And this calls for a multidisciplinary and multiprofessional teamwork including surgeons, geriatricians, endocrinologists and general practitioners, as well as nurses, physiotherapists and a wide range of other paramedical specialists. Such “fracture chains” will reduce the number of unnecessary and preventable injuries and will have a great impact in terms of cost and suffering. This symposium will give an overveiw of fracture-preventing strategies

Background: Guidelines for the management of Low Back Pain (LBP) consistently recommend that the initial assessment focuses on the detection of serious spinal pathologies. In 1994 the UK Clinical Standards Advisory Group introduced the concept of “red flags”. One of these red flags is the first presentation of LBP in people over the age of 55 years. The aim of this study was to investigate the incidence of serious spinal pathologies in patients presenting with new onset of LBP over the age of 55 years. Method/Results: This was a prospective analysis of all patients presenting to a secondary care spinal triage service over a 3 year period (2005–2008). During the study period, in excess of 3000 patients were seen. Of these, a total of 70 patients presented with a first onset of LBP aged over 55 years and had no other red flags. Analysis of this group of patients revealed 2 serious spinal pathologies. Both of which were osteoporotic vertebral compression fractures. Both patients were over age 75. In addition 1 patient had severe central lumbar canal stenosis. Therefore, 2.3% of patients presented with the first onset of LBP > 55 years, of which 2.9% has serious pathology. Patients > 55 years with cancer or infection had other red flags in addition. Conclusion: In isolation the first onset of LBP over the age > 55 accounts for a small percentage of this secondary care population, of which 2.9% had vertebral compression fractures. Further research into the clinical value of this independent red flag or its added value in combination with other red flags is recommended

Acute osteoporotic vertebral compression fractures (VCFs) are frequently misdiagnosed as there is often no history of preceding trauma. VCFs not only cause back pain, but can also result in a loss of function, spinal deformity and increased mortality. Cement augmentation has been shown to effectively treat these fractures. It is impossible to diagnose an acute fracture on plain x-ray and therefore identify those likely to benefit from this treatment. The definitive investigation to determine the presence of an acute fracture is a MR scan, but this is a limited resource. The aim of this paper is to evaluate 2 new clinical signs which we believe aid in the diagnosis of an acute VCF: firstly closed fist percussion at the level of an acute VCF resulting in a severe, sharp fracture pain, and secondly the inability of a patient to lie supine. This was a prospective study of 78 patients with suspected acute VCFs. 48/78 had an acute fracture on MR. 42/45 patients who were positive for closed fist percussion, had an acute fracture on their MR scan. There were 6 patients who were negative for closed fist percussion who had an acute fracture (sensitivity 87.5%, specificity 90%). 39/41 patients who were positive for the supine sign had an acute fracture on their MR scan. There were 9 patients who were comfortably able to lay supine who had an acute fracture (sensitivity 81.25%, specificity 93.33%). Either a positive closed fist percussion sign or a positive supine sign is a reliable indicator of the presence of an acute VCF. By incorporating these signs into our routine clinical assessment we are better able to predict which patients have an acute fracture, and therefore decide which patients need a MR scan