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Vascular and Interventional Radiology |
1 From the Central Medical Imaging Service, Centre Hospitalier Universitaire Purpan, Place du Docteur Baylac, F-31059 Toulouse, France. Received July 21, 1998; revision requested August 13; final revision received December 3; accepted March 16, 1999. Address reprint requests to N.S. (e-mail: sans.n@chu-toulouse.fr).
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Abstract |
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 TOP Abstract IntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS: Thirty-eight patients who had undergone treatment by means of this technique were reexamined with a mean follow-up of 3.7 years. The short- and medium-term clinical course and histologic features of the resection specimens were analyzed.
RESULTS: The bone fragment could be analyzed in all cases, and the diagnosis of osteoid osteoma was confirmed in 28 patients (74%). A different diagnosis was made in six patients: mucoid cyst, subchondral arthritic geode, fibrous dysplastic lesion, focal osteochondritis, or focal chronic osteomyelitis. Cure was obtained in 32 patients (84%), whatever the cause. Complications, generally minor and transient, were observed in nine patients (24%). The most severe complications were two femoral fractures and one focal chronic osteomyelitis due to Staphylococcus aureus infection.
CONCLUSION: The results of this study confirm the efficacy of percutaneous resection of osteoid osteomas and the possibility of using this method for successful treatment of other small bone lesions.
Index terms: Computed tomography (CT), guidance, 40.12119 • Interventional procedures, 40.12119, 40.1267 • Osteoma, 40.3122
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Introduction |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Methods
Resection technique.—Percutaneous resection (1–6) required coaxial instruments (Aesculap, Tuttlingen, Germany) comprising a guide wire, a trocar, an 11-mm-diameter external sheath, a toothed drill (7- or 10-mm diameter), and a 9-mm diameter drill (Figs 1, 2). Resection was performed in the CT room with sterile surgical conditions. The procedure was performed with local-regional (four cases) or general (34 cases) anesthesia. The latter made the procedure easier by lessening patient discomfort due to a prolonged period on the table and also ensured perfect immobility.
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RESULTS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Histology
The bone fragment sampled could be analyzed in all cases. If the nidus appeared fragmented, histologic confirmation of the diagnosis was certain or very probable in 28 cases (74%). Complete excision of the lesion was confirmed in 21 cases (55%). However, at histologic examination no nidus was found in the excised specimen in four cases (11%). In addition, at histologic analysis the diagnosis of osteoid osteoma was eliminated formally in six cases (16%), and a different type of bone involvement was revealed. These lesions were two intraosseous mucoid cysts, one subchondral geode of degenerative arthritic type, one benign fibromatous tumor, one focal osteochondritis, and one focal chronic osteomyelitis (Table 2).
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Clinical Course
Pain disappeared durably and completely in 32 of the 38 patients treated. This was the equivalent of a cure rate of 84% for a mean follow-up of 3.7 years. If we excluded the patients whose histologic finding was not osteoid osteoma, the cure rate was about 88% (28 of 32). In most cases (68% [26 of 38]), pain relief was obtained as soon as the patient awakened from anesthesia.
Hospitalization lasted a mean of 4.8 days (range, 2–21 days), and patients were able to use or to bear weight on the extremity at a mean of 30 days. In our series, the patients treated surgically had a much longer hospital stay, but this is not comparable as these cases were therapeutic failures after percutaneous resection. Sporting activities were resumed completely after a mean of 112 days (range, 15 days to 1 year), a period which varied markedly according to the area initially involved.
Treatment failed in four cases, with the return of pain similar in nature and intensity to the pain before the procedure. The interval before the reappearance of pain varied: early in two cases (3 and 7 days) and later in two other cases (6 and 18 months). A curative surgical procedure was performed in three cases; in the fourth case, a second percutaneous excision was performed, which completely and durably eliminated clinical symptoms.
Other Diagnoses
Six bone lesions of a different nature were revealed, and these lesions followed two different courses. Either pain persisted with intensity similar to that of the pain before percutaneous resection (n = 2), or there was clinical cure with complete elimination of pain. Four lesions followed this favorable course: one intraosseous mucoid cyst, one focal osteochondritis, one focal chronic osteomyelitis, and one arthritic geode.
Complications
Nine patients (24%) presented with complications (Table 3). The mean duration before occurrence of complications was 40 days (range, 1–150 days). We differentiated early complications (five cases), which occurred within 2 weeks after the procedure, from later complications (four cases). The early complications were usually local and resolved rapidly, and they were mainly skin burns around the entry site of the resection instruments. In a single case, in a 6-year-old child, superficial thermal damage deepened and became secondarily infected, requiring daily local care for 2 months. Five years after the procedure, the child had no sequelae except an extensive scar on the tibia where the lesion was resected.
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Later complications were often more severe. A case of focal chronic osteomyelitis due to S aureus occurred 25 days postoperatively. A fracture of the femoral shaft occurred 2 months postoperatively, and a stress fracture of the femoral neck occurred 5 months postoperatively. The last complication was a late but more benign case of dysesthesia along the course of the femoral cutaneous nerve.
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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CT has led to a marked advance in the rapidity and reliability of diagnosis after the first clinical signs. It also provides precise localization of the lesion and indication of the size of the nidus. These parameters orient the therapeutic strategy: either surgical excision or excision and percutaneous destruction with CT guidance. When the approach to the osteoma is not without risk, in particular near the course of vessels and nerves, we merely localize it precisely, perhaps by inserting a small-diameter pin, and the tumor is secondarily resected surgically.
While these various imaging techniques allow precise diagnosis, the interval before diagnosis is still astonishingly long (a mean of 1.6 years in our series) and does not seem to have notably decreased in comparison with that in other series in the literature (1,2,5). Every possible means thus must be used to find the osteoma at the slightest clinical suspicion.
Although this tumor may regress spontaneously after some years (7,8), excision is often necessary to relieve the patient and is justified by the necessity of obtaining histologic confirmation. En bloc resection was long the only surgical technique enabling resection of the entire nidus and complete cure. This mode of resection is not always necessary, but it is important to note the difficulties of the surgery or even the damage it can cause in certain locations such as the deep posterior acetabulum.
In spite of the various methods used to localize the nidus during the procedure, this may be difficult and require wide bone excision disproportionate to the small size of the lesion and sometimes is followed by osteosynthesis and bone grafting.
The development of CT-guided percutaneous treatment techniques, associated if necessary with scintigraphic localization (9), has profoundly modified the treatment of osteoid osteoma. Leaving aside the contraindications related to anesthesia and coagulation disorders, the contraindications seem to be nonindications. These are large lesions (>15 mm in diameter) or lesions that cannot be reached without jeopardizing vessels or nerves. In such cases, we merely localize the nidus and perhaps insert a pin.
On the other hand, in the majority of cases (>90% [35 of 38]) the osteoid osteoma was in a superficial or cortical location. A tumor that is endosteal or within the marrow cavity is in no way an obstacle to percutaneous resection. In most cases, percutaneous ablation will remove both the superficial and deep cortical bone (Fig 3d).
Successful Treatments
Treatment by means of CT-guided percutaneous resection appears to be effective. Clinical cure was obtained in 84% of patients and in 88% if patients whose lesion was not an osteoid osteoma are excluded. Four patients were not cured with the first resection and required either a second resection or surgical removal of the lesion.
Among the patients who were cured, four distinct groups were defined at histologic analysis. In group 1, the nidus was present and complete at histologic examination. Cure was complete and the risk of recurrence is nil. This was the case in 21 patients in our series.
In group 2, the nidus was present at histologic examination, but it was not possible to conclude as to the totality of excision because the nidus appeared fragmented or incomplete. Although these patients (three in our series) have been free of symptoms since excision, risk of recurrence in this type of patient cannot be neglected.
In group 3, no lesion was found that appeared to be an osteoid osteoma at histologic examination. This was the case in four patients in our series. These patients presented with clinical and radiologic signs strongly suggestive of osteoid osteoma; in two, pain disappeared immediately after awakening from anesthesia. In the third patient, pain progressively lessened and disappeared about 1 month after treatment. At the present time, these four patients are completely free of symptoms. This leads us to think that in these cases the nidus was probably excised but was not found at histologic examination.
Several hypotheses may explain this phenomenon (10). First, the nidus may have been fragmented during excision, which would make histologic study difficult or impossible.
Second, the nidus was present and not fragmented within the material sent to the laboratory but was not found during examination. When the nidus is very small, only very thin serial sections allow its identification by the pathologist.
Third, the nidus was not resected. In this case, clinical cure may be explained by the theory of Jackson et al (11). According to these authors, surgical treatment may cause traumatic thrombosis of the vessels of the nidus, and this thrombosis may then be responsible for infarction of the lesion and lead to clinical cure. It could be suggested that, like surgery, percutaneous resection may cause lesional trauma. This would explain the fact that the pain decreases progressively and then disappears.
Fourth, it is possible that the nidus was not resected and not infarcted. In this case, the relief from pain could be a result of the decompression that occurs when the lesion is opened; this decrease in intralesional pressure then provides temporary elimination of pain. Progressive regrowth of the lesion accounts for the return of pain in the short or medium term. The risk of recurrence appears to be greatest in such a context.
Last, in the absence of histologic certainty, the possibility cannot be excluded that these three patients had a histologically different lesion, like the patients of group 4.
In group 4, histologic examination revealed a lesion of a different type. Of the six patients who did not have an osteoid osteoma, four obtained durable relief after percutaneous resection (one old focal chronic osteomyelitis, two intraosseous mucoid cysts, and one osteochondritis). Certain authors (12) have raised the hypothesis that if histologic examination cannot lead to a conclusion of osteoid osteoma, the clinical features, imaging findings, and above all the notion of immediate cure after the procedure, will establish the diagnosis. These four examples suggest that a lesion that is cured by means of percutaneous resection and that presents the radiologic and clinical characteristics of an osteoid osteoma may in fact be a bone lesion of a different nature, and a definite diagnosis can be reached only at histologic study.
In the six cases in which the diagnosis of osteoid osteoma had been presumed erroneously, retrospective analysis of the records always revealed an atypical element, whether in clinical, scintigraphic, radiologic, or CT findings. Moreover, the diagnosis of osteoid osteoma is rare after the age of 45 years and exceptional after 65 years. More advanced age is an atypical factor, which we found in patients 2, 25, and 26 in our study; a differential diagnosis of osteoid osteoma was made at histologic examination. The relative simplicity of the resection procedure and its low morbidity rate have contributed to the increase in the number of indications for this method of treatment. Moreover, the fact that the biopsy procedure and the therapeutic procedure are indissociably linked also indirectly increases the number of indications; if the lesion is small, percutaneous resection allows not only good quality histologic analysis but also total excision.
These diagnostic errors emphasize the necessity for histologic confirmation, even when clinical examination and medical imaging results appear typical (8). This incites us to remain prudent and to weigh carefully the indications for treatments that do not permit histologic confirmation: laser photocoagulation (13), alcoholization (14), and simple trituration or ablation with radio-frequency electrodes (15).
Unsuccessful Treatments
Treatment has failed if pain persists or recurs after excision (16), and this reflects incomplete ablation of the nidus. The number of recurrences decreases with time, but recurrences may occur very late—up to 10 years later in one case in the literature (17). In our series, the failure rate seems acceptable (16% [six of 38]), taking into account the simplicity of application and performance of the technique. The main source of failure seems to be the large size of the lesion, and this is one of the limitations of the technique. Thus, in two cases, resection was incomplete because the size of the lesion (21 and 25 mm) was disproportionate to the size of the material excised with a Kohler toothed drill with a 9-mm outer diameter (Fig 1). The follow-up CT scan performed at the end of the procedure showed that in these two cases the nidus had not been removed completely. However, resection had to be interrupted because of the risk of fracture.
To our knowledge, there are no objective criteria for assessing fracture risk at the time of or during percutaneous resection. According to Caillieret et al (12), the risk is high when resection includes the deep cortex of a long bone shaft, and osteosynthesis is desirable in such cases. From our experience, a lesion larger than 15 mm appears difficult to extract, extraction is often incomplete, and repeated resections are required. The occurrence of fracture, in particular in long bones, also seems correlated with the amount of cortical bone resected. In such cases, removal of the osteoid osteoma should be performed by means of directed surgery after placing a pin in the nidus with CT guidance.
Preventive osteosynthesis is performed according to the location and volume of resection. In such cases, primary surgical treatment seems preferable so that osteosynthesis can be performed if necessary in the course of the same procedure. However, as it is difficult to localize the nidus during surgery, some teams continue to use percutaneous resection in large lesions and associate it at the end of the procedure with destruction of the nidus by means of trituration or alcoholization.
According to the theory of McLeod et al (18), lesions more than 15 mm in diameter may be potentially malignant osteoblastomas. In such cases, treatment must always be surgical and oncologically satisfactory (19).
Complications
The complications we observed were in general early and minor. Skin burns occurred immediately after the procedure at the entry site of the resection instruments; they were due to the heat caused by the high rotation speed of the toothed drill. These minor complications most frequently observed in our series usually required only treatment of symptoms and resolved without sequelae. When we were aware of this complication, we were able to decrease its frequency by means of constant surveillance of the state of the skin during resection.
Irritation of the femoral cutaneous nerve occurred twice during resection of osteoid osteomas of the femoral neck. The femoral cutaneous nerve gives rise to a femoral branch that runs in the superficial planes of the lateral inguinofemoral region, which it innervates. Planning the course of resection on the initial CT scan makes it possible to avoid only the major nerve and vascular trunks. Patients who had this complication still had hypoesthesia in the territory of the affected nerve up to 3 years after the procedure.
Hematomas were unpredictable and seemed to be unavoidable. They were generally of moderate size and regressed spontaneously, only exceptionally requiring secondary surgical evacuation.
Major complications mainly were femoral fractures. Bone resection in these two cases was not extensive—the bone defect was less than 10 mm in diameter—but these fractures appeared to be related to resumption of professional or sporting activities too early and against medical advice.
We had one patient with focal chronic osteomyelitis due to S aureus, which occurred 25 days after the procedure. This emphasizes the necessity for strict surgical asepsis in the CT room throughout any resection procedure.
The results of this study confirm the medium-term efficacy of CT-guided percutaneous resection of osteoid osteomas. This technique allows minimal and generally complete bone resection owing to precise and reliable localization. Hospital stay is reduced to 2 or 3 days, and weight-bearing and physical activity can be resumed at an early date. In comparison with other treatment methods that are being developed, with this method histologic confirmation of the lesion is obtained in the majority of cases, and we believe this is indispensable. These varied reasons tend to widen the indications for percutaneous resection, which we believe should be considered as first-line therapy if it seems technically possible. However, it would seem permissible to resect only lesions with a diameter of less than 10 mm. This study also shows that percutaneous resection may be useful in treating other small localized bone lesions.
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Footnotes |
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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This article has been cited by other articles:
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