Individuelle dem Frakturverlauf angepasste Zugangswege

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1 168 Schattauer 2012 Osteoplasty of the spine Treatment of Denis 1, 2 and 3 insufficiency fracture zones of the os sacrum Individual approaches adapted to the course of the fracture in CT- assisted balloon sacroplasty R. Andresen 1 ; S. Radmer 2 ; P. Kamusella 1 ; C. Wissgott 1 ; J. Banzer 3 ; H.-C. Schober 4 1 Institute of Diagnostic and Interventional Radiology/Neuroradiology, Westkuestenklinikum Heide, Academic Teaching Hospital of the Universities of Kiel, Luebeck and Hamburg, Heide/Germany; 2 Center of Orthopedics, Berlin, 3 Radiology, Charité University Berlin, Campus Benjamin Franklin, Berlin/Germany; 4 Department of Internal Medicine, Municipal Hospital Suedstadt Rostock, Academic Teaching Hospital of the University of Rostock/Germany Keywords Balloon sacroplasty, insufficiency fracture, sacral fracture, pain therapy, cement augmentation Summary In elderly patients with reduced bone quality, insufficiency fractures of the sacrum are relatively common and are typically associated with severe and debilitating pain. The objective of our study was to determine the practicability of cement augmentation using a balloon catheter via individual approaches taking into consideration the complex anatomy of the sacrum and the course of the fracture, as well as the post-interventional determination of leakages and representation of the clinical outcome. In 40 patients with severe osteoporosis (24 women with an average age of 74.4 years, 16 men with an average age of 69.7 years), a sacral fracture was detected by CT and MRI. This fracture was unilateral in 17 women and 9 men and bilateral in 7 women and 7 men. The fractures were classified according to Denis. In order to achieve a cement distribution longitudinally in relation to the fracture, the balloon catheter was inserted into the sacrum via a hollow Correspondence to Prof. Dr. Reimer Andresen Institute of Diagnostic and Interventional Radiology/ Neuroradiology, Westkuestenklinikum Heide, Academic Teaching Hospital of the Universities of Kiel, Luebeck and Hamburg, Heide Esmarchstraße 50, Heide, Germany Tel.: / , Fax: / randresen@wkk-hei.de needle either from dorsal to ventral, from caudal to cranial, or from lateral to medial using the transiliac approach. The balloon catheter was then inflated and deflated 1 3 times along the fracture in the respective direction, and the hollow space created was then filled with PMMA cement using a low-pressure procedure. A conventional radiograph in two planes and a control CT were then performed. Pain intensity was determined pre-intervention, on the 2 nd day post-intervention and 6 and 12 months post-intervention, using a visual analogue scale (VAS). In addition, the patients were asked to state how satisfied they were after 12 months. The balloon sacroplasty was performed successfully from a technical point of view in all patients. The radiographic and CT control showed sufficient cement distribution in the sacrum along the course of the fracture, whereby leakage could be ruled out. According to the VAS, the mean pain score was 8.9 before the intervention, while the patients with a Denis 2 fracture tended to have the strongest pain. There was a significant reduction in pain on the 2 nd postoperative day, with an average value of 2.7 (p < 0.001), which was stable at 2.5 after 6 months and 2.3 after 12 months. A high level of patient satisfaction was found after Individuelle dem Frakturverlauf angepasste Zugangswege bei der CT-gesteuerten Ballon-Sakroplastie zur Versorgung von Denis-1-, -2- und -3- Insuffizienzfrakturzonen des Os sacrum Osteologie 2012; 21: received: August 18, 2012 accepted: August 22, months. Approaches that take into account the anatomy of the sacrum and the course of the sacral fracture enable reliable augmentation with an optimum amount of cement. This makes balloon sacroplasty an effective treatment that has few complications, for rapid and significant pain reduction in patients with a sacral fracture. Schlüsselwörter Ballon-Sakroplastie, Insuffizienzfraktur, Ossacrum-Fraktur, Schmerztherapie, Zementaugmentation Zusammenfassung Bei älteren Patienten mit reduzierter Knochenqualität sind Insuffizienzfrakturen des Os sacrum relativ häufig und typischerweise mit starken, invalidisierenden Schmerzen verbunden. Ziel unserer Studie war die Durchführbarkeit der Zementaugmentation mittels Ballonkatheter über individuelle, die komplexe Anatomie des Os sacrum und die Ausrichtung des Frakturgeschehens berücksichtigende Zugangswege sowie die postinterventionelle Erfassung von Leckagen und Darstellung des klinischen Outcomes. Bei 40 Patienten mit schwerer Osteoporose (24 Frauen mit einem Durchschnittsalter von 74,4 Jahren, 16 Männer mit einem Durchschnittsalter von 69,7 Jahren) wurde im CT und MRT eine Ossacrum-Fraktur detektiert. Bei 17 Frauen und neun Männern war diese Fraktur unilateral, bei sieben Frauen und sieben Männern bilateral. Die Frakturen wurden nach Denis eingeteilt. Um eine Zementverteilung in Längsrich- Osteologie 3/2012

2 R. Andresen et al.: Treatment of Denis 1, 2 and 3 insufficiency fracture zones of the os sacrum 169 tung zur Fraktur zu erreichen, wurde der Ballonkatheter über eine Hohlnadel in das Os sacrum entweder von dorsal nach ventral, von caudal nach cranial oder von lateral nach medial transiliacal eingebracht. Der Ballonkatheter wurde daraufhin entlang der Fraktur in der entsprechenden Richtung einbis dreimal in- und deflatiert. Der dadurch geschaffene Hohlraum wurde dann mit PMMA-Zement im Niederdruckverfahren aufgefüllt. Anschließend erfolgte eine konventionelle Röntgenaufnahme in zwei Ebenen sowie ein Kontroll-CT. Die Schmerzintensität wurde prä interventionem, am zweiten Tag sowie sechs und zwölf Monate post interventionem mittels visueller Analogskala (VAS) bestimmt. Zusätzlich wurde die Patientenzufriedenheit nach zwölf Monaten abgefragt. Bei allen Patienten ließ sich die Ballon- Sakroplastie technisch gut anwenden. In der Röntgen- und CT-Kontrolle fand sich im Os sacrum entlang der Frakturausdehnung eine ausreichende Zementverteilung, wobei eine Leckage ausgeschlossen werden konnte. Der Mittelwert für Schmerzen lag nach VAS vor Intervention bei 8,9, die Patienten mit einer Denis-2-Fraktur hatten tendenziell die stärksten Schmerzen. Am zweiten postoperativen Tag zeigte sich eine signifikante Schmerzreduktion (p < 0,001) mit einem Durchschnittswert von 2,7; dieser war mit 2,5 nach sechs Monaten und mit 2,3 nach zwölf Monaten stabil. Nach zwölf Monaten fand sich eine hohe Patientenzufriedenheit. Zugangswege, welche die Anatomie des Os sacrum und die Frakturausrichtung im Os sacrum berücksichtigen, erlauben eine mengenoptimierte und sichere Zementaugmentation. Die Ballon-Sakroplastie wird hierdurch zu einer effektiven, komplikationsarmen Behandlungsmethode zur schnellen und signifikanten Schmerzreduktion bei Patienten mit einer Os-sacrum-Fraktur. Introduction Insufficiency fractures, both of the central and the peripheral skeleton, are a common entity in (demineralised bone diseases) osteoporosis. Vertebral body, femoral neck and radius fractures are most commonly observed. In recent years, however, insufficiency fractures of the sacrum have also increasingly been found, elderly patients with known osteoporosis primarily being affected here, while further risk factors are rheumatoid arthritis, long-term cortisone medication or the administration of radiotherapy with subsequent radio-osteonecrosis and pathological fracture (1 5). An incidence of 1 % to 5 % is suspected among patients in such risk groups (5), and it can be assumed that there will be a marked increase given the current demographic development (2). The main clinical feature is deep-seated, sometimes immobilising low back pain, which especially occurs when standing and sitting (6, 7). Sacral fractures often remain undetected in conventional radiographs, up to 70 % being overlooked prospectively and up to 50 % retrospectively (4, 8). Bone scintigraphy shows a strong activity enrichment in the area of the fracture process, with a sensitivity of > 90 % (9). In computed tomography (CT), the fractures display radiolucent lines with and without sclerosis, but often remain undetected in axial tomograms as they generally take a sagittal course in the sacrum. Coronal slicing improves the sensitivity to > 70 % and visualises the course of the fracture to its full extent (10). Magnetic resonance imaging (MRI) with the fat-suppressed strongly T2-weighted sequences provides early evidence of oedema, with a sensitivity of almost 100 %, and is thus superior to CT in detecting insufficiency fractures (11). Sacral fractures are classified according to Denis et al. (12) into transalar (type 1), transforaminal (type 2) and central (type 3) fracture zones, type 1 fractures being the most common, followed by type 2 and type 3 ( Fig. 1). In addition, horizontal fracture lines can also occur (10), and the fractures can be uni- or bilateral. The neurological symptoms increase markedly from fracture type 1 to type 2 and again up to type 3 (12). The standard therapy of sacral insufficiency fractures up to now has been a conservative treatment with bed rest and adjuvant analgesic therapy, followed by mobilisation in a walking frame or on forearm crutches with painadapted weight-bearing (6, 8, 13). The problem with conservative therapy is the increased risk of complications, which include deep vein thromboses, consecutive pulmonary artery emboli, pneumonia, decubital ulcers and depression, while immobilisation leads to a further loss of muscle and bone mass (13, 14). The formation of a pseudarthrosis with persistent symptoms is a further problem of the conservative approach (14). As a surgical treatment option, various osteosynthesis techniques are available, but stable conditions cannot always be achieved due to the strongly rarefied bone structure. The most established method is percutaneous, transiliac screw fixation (15). An alternative minimally invasive treatment form is the insertion of cement via hollow needles, analogous to vertebroplasty (16 19). Whitlow et al. (20) confirmed this, achieving equivalent improvement in a comparison of vertebral and sacral cementation. The first percutaneous sacroplasty for the treatment of an insufficiency fracture was described by Garant in 2002 (21). A rapid and almost complete reduction in pain was demonstrated with the new method (16, 17, 22, 23), although a possible complication is leakage and its potential symptoms (24, 25). Sacroplasty with balloon augmentation, analogous to kyphoplasty, was first described by Deen and Nottmeier in three patients (26). A most recent study confirmed the initial promising good clinical results (27). In our own experience a significant post-interventional reduction in pain was found (28). The objective of the present study was to determine the practicability of cement augmentation using a balloon catheter via individual approaches taking into consideration the complex anatomy of the sacrum and the course of the fracture. The occurrence of possible post-interventional leakages, the clinical outcome, and patient satisfaction were to be determined. Material and methods A sacral fracture was diagnosed in 40 patients (24 women with an average age of 74.4 years, 16 men with an average age of 69.7 years) by CT (axial spiral with a layer thickness of 5 mm and a coronal and sagittal reformation with a reconstruction interval of 2 mm). In spinal quantitative computed tomography (sqct), all patients showed severe osteoporosis of the axial skeleton, with average values of 41 mg/dl in Schattauer 2012 Osteologie 3/2012

3 170 R. Andresen et al.: Treatment of Denis 1, 2 and 3 insufficiency fracture zones of the os sacrum the women and 53 mg/dl in the men. In all patients a pharmacotherapy according to the german guidelines for osteoporosis has been started before the intervention (29). As an expression of the continued presence of a bone remodelling process, MRI revealed marked oedema in the strongly T2-weighted images in all patients. This fracture was unilateral in 17 women and 9 men, and bilateral in 7 women and 7 men. The fractures were classified according to Denis et al. (12). A conservative treatment initiated over a period of 3 18 weeks failed to achieve satisfactory Fig. 1 Illustration of the os sacrum: on the left side demonstration of the fracture zones Denis 1, 2 and 3. On the right side visualization of the long axis and transiliac axis approach. reduction in pain. The intervention was performed after an interdisciplinary case conference with specialists in geriatric and internal medicine, orthopaedic and trauma surgeons, neurosurgeons and interventional radiologists. The intervention was performed under general anaesthesia and monitoring. Single-shot antibiosis (cefazolin 2 g i. v.) was routinely administered immediately before the intervention. In all patients, the balloon sacroplasty was CTassisted, for which purpose the patients were placed in the prone position on the CT table. In order to achieve a cement distribution in a longitudinal axis relative to the course of the fracture, the balloon catheter (15 mm balloon, Kyphon Medtronic) was inserted into the sacrum through a hollow needle via the so-called short axis from craniodorsal to caudoventral (16, 21, 22, 26, 28) ( Fig. 2 and Fig. 3a c), the modified slightly angulated short axis (18) ( Fig. 2), the so-called long axis from caudal to cranial (28, 30 32)] ( Fig. 1 and Fig. 2), or via the transiliac approach from lateral to medial (33) ( Fig. 1), taking into account anatomical landmarks such as the neuroforamina and the cortical margins of the sacrum. The balloon catheter was then inflated and deflated 1 3 times along the fracture in the respective direction, and the hollow space created was then filled with polymethyl methacrylate (PMMA) cement using a low-pressure procedure. A conventional radiograph in two planes and a control CT in axial slicing with multiplanar reformations were then performed. Pain intensity was determined pre-intervention, on the 2 nd day post-intervention and six and twelve months post-intervention, using a visual analogue scale (VAS). Patients with a pre-interventional pain intensity < 5 on the VAS continued to be treated conservatively with adequate analgesic medication, thrombosis prophylaxis, and mobilisation supervised by a physiotherapist under pain-adapted partial weight-bearing on forearm crutches or on a walking frame, and were excluded from the intervention. Patients with additional fractures in the pelvic girdle were also excluded from the study and assigned for surgery. The statistical results were evaluated by rank variance analysis for several samples according to Friedman. Finally, the patients were asked to state how satisfied they were after twelve months. Fig. 2 Illustration of the os sacrum in the sagittal view with demonstration of the short axis, modified slightly angulated short axis and long axis approach. Results The balloon sacroplasty was performed successfully from a technical point of view in all patients. Complications such as wound-healing disorders, infections, bleeding or neurological disturbances were not observed. The radiographic and CT controls showed good cement distribution over the area of the sacral fracture. Cement Osteologie 3/2012 Schattauer 2012

4 R. Andresen et al.: Treatment of Denis 1, 2 and 3 insufficiency fracture zones of the os sacrum 171 leakage in the direction of the neuro - foramina, the sacroiliac joints, trans - cortically to the visceral surface or into the dorsal soft-tissues, or into the discal space between the lumbar vertebral body L4 and the sacral vertebral body S1 has not been found. The amount of PMMA cement inserted per fracture according to the approach used was 2 6 ml via the short axis, 4 8 ml via the angulated short and long axis and 2 4 ml via the transiliac approach. As regards fracture type, Denis 1 was most common, followed by combined forms in the sense of a Denis as well as Denis fracture, pure Denis 2 fracture zones were rare, while isolated vertebral body fractures corresponding to a Denis 3 fracture were not found ( Tab. 1). The mean pain score on the VAS was 8.9 (SD 0.737) at baseline, while the patients with a Denis 2 fracture tend to have the most severe pain. There was a significant reduction in pain at the 2 nd postoperative day (p < 0.001), with an average value of 2.7 (SD 0,547), which continued at 2.5 (SD 0.509) after 6 months and 2.3 (SD 0.489) after twelve months ( Fig. 4). All patients were successfully remobilised. In the follow-up period, two patients became bedridden due to a stroke and two further patients died of cancer not related to the intervention. Clinically, no evidence of renewed fractures in the sacrum or pelvic region was found in 38 of the 40 patients examined in the 12-month follow up. With regard to patient satisfaction, 36 out of 40 patients were very satisfied, and all of them said that they would undergo the intervention again without reservation. Discussion Fig. 3 Illustrative case of a bilateral fatigue fracture of the os sacrum, right type Denis 1, left type Denis 1 and 2, treated via the short axis approach: in (a) the inflated balloon is exactly placed in the fracture zone. In (b) the PMMA-cement filling is visualized on both sides in the axial CT scan with good distribution in the fracture zone. In (c) demonstration of the PMMA cement distribution in the fracture zone in the coronal reformation. In both views there is no sign of cement leakage. a b c In the case of sudden severe back pain, beside degenerative changes and vertebral body fractures, sacral insufficiency fractures should be considered as a possible cause in elderly patients (1, 2, 7). After detection of a fracture, especially if corresponding trauma is lacking, more sensitive diagnostic must be performed to determine the underlying cause. Most commonly the cause is generalised osteoporosis (2), whereby other causes such as vitamin-d deficiency syndrome or hypophosphataemia must be considered as a differential diagnosis. Along with basic osteological laboratory tests, bone density should be determined in all cases (29). Variant from the DXA measurement recommended by the DVO guideline, we determined bone density by sqct in the group presented. Strongly reduced values were found for bone mineral content, with average values of 41 mg/ml in the women and 53 mg/ml in the men, values that indicate severe osteoporosis in which insufficiency fractures can be expected (34). Conservative treatment measures that are initially implemented, with bed rest and pharmacotherapy for pain and osteoporosis, can lead to side effects, further comorbidities as a result of immobilisation and often achieve only clinical improvement in the long term (4, 6, 8, 13). Since a rapid analgesic effect with a positive effect on mobility and activities of daily living has repeatedly been shown after sacroplasty (18 20, 23, 27, 28, 32, 35), this therapeutic option should be taken in account if conservative therapy has been unsuccessful and incapacitating pain persists. Alternative options available are open reduction and internal fixation methods such as open or percutaneous screw osteosynthesis, direct plate fixation, ilioiliac plate osteosynthesis, ilioiliac sacral bars, the insertion of an internal fixation device, or also methods combining osteosynthesis and cement augmentation (15, Schattauer 2012 Osteologie 3/2012

5 172 R. Andresen et al.: Treatment of Denis 1, 2 and 3 insufficiency fracture zones of the os sacrum Tab. 1 Distribution of the fatigue fractures of the os sacrum according to the Denis classification (12). Overall 54 fractures were treated in 40 patients, whereby 26 had a unilateral and 14 a bilateral fracture. Type of fracture zone Denis 1 26 (48.1) Denis 2 2 (3.7) Denis 3 0 (0) Denis 1 and 2 19 (35.2) Denis 1, 2 and 3 7 (13) Number (percentage of fractures) 33, 36, 37). These methods should primarily be used in the case of unstable fractures or neurological disturbances. In our patient population, exclusively isolated, stable sacral fractures were treated, so that the minimally invasive method of balloon sacroplasty was preferred. Our patients experienced a significant reduction in pain on the VAS, with average scores declining from 8.9 before to 2.7 short after the intervention. Those remarkable benefits for the patients have been described by other groups in the literature before (16, 22, 27), with almost identical mean score values from pre-operative to post-operative being reported. A sustained pain reduction was found in our patients as well, with a mean score of 2.3 after one year. In a prospective multicentre study on 52 patients who underwent sacroplasty, Frey et al. (18) report a comparable improvement in symptoms one year after treatment. As in the spine (38), pain reduction in the sacrum after the insertion of cement via hollow needles analogous to vertebroplasty (22, 24, 39) or after the insertion of cement with a balloon augmentation analogous to kyphoplasty (26 28) seems not to be different. Apart from the treatment of insufficiency fractures (16, 18, 22, 23, 40), sacroplasty also appears to be a good therapeutic option for reducing pain in the case of pathological fractures and osseous destruction (27, 39, 41 43). In an in-vitro study, after the injection of PMMA cement, finite element analysis suggested that fracture-related mechanical stress and micro-movements can be minimised in the area of the sacral fracture (44). Another experimental investigation used finite element analysis to demonstrate an approximately % improvement in biomechanical competence after the injection of cement into the non-fractured osteoporotic sacrum (45). If one considers that a sacral fracture, as a result of its instability, often means additional mechanical stress for the remaining pelvic girdle, which can cause further insufficiency fractures in the demineralised bone (3), biomechanical considerations would also suggest that sacroplasty should be performed for stabilisation and the prevention of further fractures. This might be a reason for the lack of subsequent clinical fractures in our patients in the twelve months follow-up. The complex anatomy of the sacrum must be taken into account in the technical performance of a sacroplasty (46, 47), and a fracture analysis by means of imaging procedures is essential before the intervention (48). The CT-guided insertion of the Conclusion Balloon sacroplasty is an effective and reliable treatment method for rapid and significant pain reduction in patients with insufficiency fractures of the sacrum. Different approaches that take into account the anatomy and the fracture alignment in the sacrum together with the use of a balloon catheter enable a targeted augmentation with an optimum amount of cement. Fig. 4 Development of pain according to VAS: there is a significant reduction in pain within two days post intervention. This effect is lasting over twelve months. needle systems and balloon catheters as required is sufficiently accurate with appropriate practice, and all fracture zones can be reached via the short, long and transiliac axis (42, 46, 47). Concurrent conventional fluoroscopy with an additional C-arm has been found to be helpful for cement application (16, 24), which is consistent with our experience (28). The use of a balloon catheter enables to create a central hollow space for insertion of the cement, whereby a compaction of the adjacent fracture zone closes possible fracture gaps and thus prevents cement leakage in the direction of the neuroforamina, the sacroiliac joints, the visceral surface and dorsal soft-tissues of the sacrum (27, 28, 49). Reduction of the rate of cement leakages represents an advantage of sacro-kyphoplasty (27, 28) over sacro-vertebroplasty (18, 25). In all of our patients cement leakage after balloon sacroplasty was ruled out by means of conventional radiography and CT. The amount of cement required depends on the extent of the fracture and the approach used. In an approach via the short axis 2 8 ml per fracture are reported (16, 19, 22, 24), compared with 2 10 ml via the angulated short axis (18) and long axis (32, 47, 48, 50). These are cement volumes that we also found to be sufficient for cement augmentation (28). Details of the amount of cement required for cement augmentation via a transiliac approach are not to be found in the literature, however we injected 2 4 ml PMMA cement in our patients. Osteologie 3/2012 Schattauer 2012

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