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cently published by Taylor et al (2), who reported an overall Recent eLetters to the Editor are available at radiology.rsnajnls success rate of 93% with an average dose of 300 units of .org. eLetters that are no longer posted under ‘‘Recent eLet- thrombin. In addition, use of a lower dose of thrombin may ters’’ can be found as a link in the related article or by brows- potentially reduce the likelihood of complications. At this ing through past Tables of Contents.
time, the minimal necessary thrombin dose to achieve pseu-doaneurysm thrombosis is the subject of ongoing clinicalresearch. Using the same logic that was just hypothesized, we Iatrogenic Femoral Pseudoaneurysms
elected to inject the cavity adjoining the native vessel in allfour cases. Immediate thrombosis of all lobes was observed with the injection of an average of 200 units (1 mL) ofthrombin.
No complications occurred, and no recurrence of pseudo- Department of Radiology, Hadassah University HospitalPO Box 12141, Jerusalem 91120, Israel aneurysm was demonstrated after an average follow-up of 9 months (range, 5–12 months). It is possible that small samplenumbers introduced bias into our results. The difference in the pseudoaneurysm volume in the two reports may explain We would like to comment on the recently published article why a smaller dose of thrombin was effective in our series by Drs Sheiman and Brophy (1). The authors describe a 100% (200 units [1 mL] vs minimum of 1,500 units). It is not clear success rate of percutaneous thrombin injection for the treat- from the report by Drs Sheiman and Brophy what dilution of ment of simple pseudoaneurysms, whereas their success rate thrombin was used, and, consequently, what volume was for complex pseudoaneurysms was only 56% (five of nine pseudoaneurysms). Complex pseudoaneurysm architecture Thus far, we have not encountered any technical difficulty was associated with a procedure failure. Because of realistic in inserting the needle into the cavity nearest the native concern about possible native vessel thrombosis or emboli- vessel by using continuous ultrasonographic guidance. The zation if the lobe directly connected to the native vessel was needle tip and the injection are directed away from the neck to be injected, Drs Sheiman and Brophy elected to inject the of the pseudoaneurysm, and injection is continued until farthest removed lobe first and then perform a second injec- thrombosis occurs. The volume range of the simple pseudo- tion in the directly connected lobe if persistent or recurrent aneurysms in the remaining 10 patients in our series varied flow was observed. It is noted that “. . . we cannot exclude from 5 to 20 cm3 (median, 8.5 cm3). This volume range is also the possibility that direct injection into this lobe (directly smaller than that in the Sheiman and Brophy report (6.4 – joined to the native vessel) could cause thrombosis, eliminate 53.0 cm3; mean, 15.8 cm3 Ϯ 10.4). However, our maximal flow in the more distal lobe, and lead to total spontaneous thrombin dosage was 600 units (mean, 250 units) as opposed thrombosis of the entire pseudoaneurysm.” to 1,000 units (1). We had nine of 10 procedural successes, for Comparison of this report with our recent experience with an overall success rate of 93% (13 of 14 successes). The single 14 patients who had iatrogenic femoral pseudoaneurysms failure occurred in a patient who received warfarin sodium may be useful in helping to determine the most appropriate (Coumadin) therapy and in whom a second thrombin injec- technique for this emerging new therapy. We performed tion after 48 hours also failed. The patient underwent surgical percutaneous topical thrombin (Thrombin-JMI; Jones Medi- repair. A simple pseudoaneurysm with a single neck was cal Industries, St Louis, Mo) injection after obtaining local institutional review board approval. All patients failed a trial It may be that the trade-off between theoretical safety of of nonguided external compression that was continued for a the technique proposed by Drs Sheiman and Brophy is obvi- minimum of 2 and a maximum of 9 days. Heparin therapy ated by the theoretical additional risk of a second thrombin was discontinued prior to thrombin injection but was recom- injection. We propose that injection of the lobe nearest to menced immediately afterward in four cases. Four of the 14 the native vessel is no more risky than injection into any patients had a complex pseudoaneurysm, three of whom had simple pseudoaneurysm. Undoubtedly, as the frequency of two interconnecting lobes, one had four interconnecting this new therapy increases, the incidence of complications lobes, and all had a single neck. None of these patients were will also increase. However, controlled image-guided injec- receiving anticoagulant therapy, but two were receiving an- tion into the nearest lobe of a complex pseudoaneurysm, tiplatelet drugs. The median pseudoaneurysm volume of 7.5 with the lowest possible thrombin dose, appears to be a cm3 (range, 5–12 cm3) in the four complex pseudoaneurysms was lower than that in the cases just described (mean Ϯ SD,23.3 cm3 Ϯ 12.8). The maximal complex pseudoaneurysmdiameter in our series was 5 cm (range, 2.5–5.0 cm).
References
Despite many similarities between our technique and that Sheiman RG, Brophy DP. Treatment of iatrogenic femoral of Drs Sheiman and Brophy (1), there are some important pseudoaneurysms with percutaneous thrombin injection: expe-rience in 54 patients. Radiology 2001; 219:123–127.
differences. First, from the outset of our experience, we chose Taylor BS, Rhee RY, Muluk S, et al. Thrombin injection versus to use a low concentration of bovine thrombin (ie, 200 compression of femoral artery pseudoaneurysms. J Vasc Surg units/mL saline). This decision was based on the results re- 292 ⅐ Radiology ⅐ January 2002
Drs Sheiman and Brophy respond:
References
1.
Kent KC, McArdle CR, Kennedy B, Baim DS, Anninos E, Skillman We are in agreement with Dr Bloom that the technique for JJ. A prospective study of the clinical outcome of femoral the treatment of iatrogenic femoral pseudoaneurysms with pseudoaneurysms and arteriovenous fistulas induced by arterial thrombin has not yet been optimized and thank him for puncture. J Vasc Surg 1993; 17:125–133.
contributing his experience. However, on the basis of the Kang SS, Labropoulos N, Mansour A, Baker WH. Percutaneousultrasound guided thrombin injection: a new method for treating data presented, we cannot agree with the recommendation postcatheterization femoral pseudoaneurysms. J Vasc Surg 1998; that performing image-guided injection into the cavity of a complex pseudoaneurysm directly joined to the native vesselis reasonable. First, the median volume of Dr Bloom’s four Robert G. Sheiman, MD, and David P. Brophy, MD complex pseudoaneurysms (7.5 cm3) was approximately one- Department of Radiology, Beth Israel Deaconess third that of ours (20.0 cm3). Hence, the volumetric flow encountered in our complex pseudoaneurysms was nearly three times as great. The lack of complications from the e-mail: rsheiman@caregroup.harvard.edu injection of thrombin into the lobe directly in contact withthe native vessel in his four cases does not necessarily extrap-olate into a low acceptable complication rate for our cases orfor this technique in general.
Schmorl Nodes: Lack of Relationship between
Additionally, Dr Bloom does not formally present his def- Degenerative Changes and Osteopenia
inition of a complex pseudoaneurysm. A clear distinctionbetween a pseudoaneurysm that we formally define as com- plex (multiple compartments separated by a patent tract, Emilio Gonza´lez-Reimers,* Marı´a Mas-Pascual,* Matilde which has a diameter smaller than the minimal dimension of Arnay-de-la-Rosa,† J. Velasco-Va´zquez,† and F. Santolaria- the smallest lobe) and one, for example, that has a single lobe but is potentially considered complex due to multiple septa- Department of Internal Medicine, Hospital Universitario tions must be made. Although Dr Bloom’s proposal may turn out to be correct, he cannot advocate this approach on the basis of experience with four small complex pseudoaneu- Department of Prehistory, Anthropology, and rysms (at least two of which, per data published at our insti- tution [1], could potentially thrombose spontaneously). Pres- Universidad de La Laguna, Tenerife, Canary Islands, Spain† ently, the theoretical safety offered by our technique hasbeen successfully applied to 11 additional complex pseudoan- eurysms (all with total volumes exceeding 6 cm3) without We have read with interest the article by Drs Pfirrmann and complication. Therefore, the theoretical additional risk of a Resnick (1) in which the relationship between Schmorl nodes second injection does not appear to be an issue.
and degenerative spinal changes was analyzed. Herniation of Dr Bloom also required lower thrombin doses for the suc- the nucleus pulposus of the intervertebral disk into the adja- cessful treatment of his four complex and 10 simple pseudo- cent vertebral body leads to the formation of Schmorl nodes.
aneurysms, when compared with those in our cases. He right- Several mechanisms may underlie the formation of Schmorl fully identifies that this difference may be the result of his nodes (2,3), including degeneration of the cartilage and al- smaller pseudoaneurysm volumes. Indeed, Kang et al (2) terations of the subchondral bone of the vertebral body, found a direct relationship between pseudoaneurysm size which in turn may be due to developmental defects or sys- and the dose required for obliteration. This has also been our experience, though other factors such as patient coagulation In the Pfirrmann and Resnick study, Schmorl nodes were status and blood pressure likely play a role. However, there is associated with moderate but not advanced degenerative implication in his letter that the larger doses of thrombin changes. We have conducted a similar study to test whether used in our study may not be warranted. We point out that Schmorl nodes are related to degenerative changes of the spine the proposal by Dr Bloom to use the lowest possible throm- or to vertebral osteopenia in vertebrae belonging to pre-His- bin dose for successful pseudoaneurysm treatment is a given panic inhabitants buried in a collective cave on the island of El and one that we have adhered and continue to adhere to.
Hierro, in the Canary Archipelago. The sample was composed of Use of lower thrombin doses for pseudoaneurysm treat- 90 T12, 151 L1, and 91 L2 vertebrae. The number and location ment in general and treatment of a complex pseudoaneu- of Schmorl nodes were assessed at inspection. The area of these rysm by means of injection into the lobe that is in direct nodules was measured. The severity of degenerative changes communication with the native vessel may be shown to be was recorded at both the vertebral body and the interapophy- optimal with future research. However, we do not believe seal articular surfaces and was graded as minimal or absent, that either technique can currently be conclusive on the basis slight, moderate, or severe on the basis of size and extent of of Dr Bloom’s experience with the small number and size of the pseudoaneurysms he presents. A technique that advo- In 74 cases, osteopenia was assessed with histomorphometry cates needle placement far away from the pseudoaneurysm in undecalcified vertebral bone specimens by measuring trabec- neck while maintaining success should still be favored at this ular bone mass (TBM); and in 115 cases, by measuring bone mineral density (BMD) with dual-energy x-ray absorptiometry Volume 222 ⅐ Number 1
Radiology ⅐ 293
(QDR 2000 software w 5.54; Hologic, Boston, Mass). Conven- Dr Gonza´lez-Reimers and colleagues analyzed the presence tional radiographs were also obtained in all the vertebrae.
of Schmorl nodes and the degenerative changes of the spine.
We found Schmorl nodes in 16.67% of T12 vertebrae, in Because they used whole paleontologic vertebrae, they were 47.68% of L1, and in 40.66% of L2; the total incidence was also able to analyze the posterior elements of the spine, 37.35% (124 cases). In 61 cases, the nodes were multiple. In 107 which was not done in our work. The presented results are in cases, the nodes were in the superior vertebral plate, whereas in line with the results of our investigation. In the statistical 58 cases, they were in the inferior plate. In 41 cases, the nodes analysis, Dr Gonza´lez-Reimers and co-workers found a trend appeared in both the superior and inferior plates. There was no for the association of Schmorl nodes with degenerative association between degenerative changes in the vertebral body changes of the spine. In a larger sample and with the analysis and the Schmorl nodes (although there was a trend, ␹2 ϭ 2.68; of the intervertebral disk height, this trend would probably P ϭ .105), between Schmorl nodes and degenerative changes at the interapophyseal articular surfaces, or between the area of Osteoporosis has been emphasized as a cause of Schmorl the Schmorl nodes and degenerative changes at both the ver- nodes, but this correlation is not yet certain (2,3). Analysis of tebral body and the articular surfaces. Vertebrae with Schmorl this association is inherently difficult. Most investigations nodes showed a significantly higher mean BMD (0.53 g/cm2 Ϯ0.11) than vertebrae without Schmorl nodes (0.44 Ϯ 0.11, t ϭ have been performed after the formation of Schmorl nodes, 4.0, P Ͻ .001). There was also a trend for higher TBM in the that is, after the healing of the osseous structures. With the vertebrae with Schmorl nodes (18.25% Ϯ 5.19) than in those healing of bone, sclerosis and callus formation increase the without Schmorl nodes (16.11% Ϯ 5.01, t ϭ 1.72, P ϭ .089). A BMD, and preexisting osteoporosis may be masked. Weak- significant correlation was observed between BMD and TBM ness of the end plate and of the underlying trabecular bone (r ϭ 0.56, P Ͻ .001).
that is caused by reduced bone mineral density at the time of Thus, we failed to find any relationship between vertebral the formation of the Schmorl node seems intuitive but re- degenerative changes and Schmorl nodes or between osteope- nia and Schmorl nodes. The higher BMD and the nonsignifi-cantly higher TBM values of the vertebrae with Schmorl nodesare probably explained by the distorting effect of the sclerotic References
rim that surrounds long-standing chronic Schmorl nodes.
Pfirrmann CW, Resnick D. Schmorl nodes of the thoracic andlumbar spine: radiographic-pathologic study of prevalence, char- References
acterization, and correlation with degenerative changes of 1,650spinal levels in 100 cadavers. Radiology 2001; 219:368 –374.
Pfirrmann CWA, Resnick D. Schmorl nodes of the thoracic and Boukhris R, Becker KL. Schmorl’s nodes and osteoporosis. Clin lumbar spine: radiographic-pathologic study of prevalence, char-acterization, and correlation with degenerative changes of 1650 spinal levels in 100 cadavers. Radiology 2001; 219:368 –374.
Hansson T, Roos B. The amount of bone mineral and Schmorl’s Fahey V, Opeskin K, Silberstein M, Anderson R, Briggs C. The nodes in lumbar vertebrae. Spine 1983; 8:266 –271.
pathogenesis of Schmorl’s nodes in relation to acute trauma: anautopsy study. Spine 1998; 23:2272–2275.
Resnick D, Niwayama G. Intravertebral disk herniations: cartilag- Christian W. A. Pfirrmann, MD,* and Donald Resnick, MD† inous (Schmorl’s) nodes. Radiology 1978; 126:57– 65.
Department of Radiology, Orthopedic University Drs Pfirrmann and Resnick respond:
Forchstrasse 340, Zurich CH-8008, Switzerland* We appreciate the comments by Dr Gonza´lez-Reimers and colleagues and the interest in our study (1). In their letter, Department of Radiology, Veterans Affairs San Diego they mention two interesting points that deserve comment.
294 ⅐ Radiology ⅐ January 2002

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