Curettage remains the current standard of ABC treatment[
6‐
8]. Some authors also report use of en bloc excision but use it only for expendable locations or in the event of multiple recurrences[
5,
9]. Alternative treatment via radiotherapy has been used in the past, but due to the possible induction of malignancy it is no longer employed[
9,
20]. Embolization[
21,
22] or sclerotherapy[
23‐
25] seems a valid alternative to surgery, especially in ABC cases of the axial skeleton (spine, sacrum, pelvis) where surgery is contraindicated, especially in inaccessible lesions. Embolization may be a primary treatment in lesions with substantial soft tissue expansion in the proximity of neurovascular structures such as the spine, or in large lesions to minimize intraoperative hemorrhage, for example, in the pelvis[
21,
22,
26]. Recent advances in ABC treatment also include curettage with an adjuvant such as phenol, hydrogen peroxide, liquid nitrogen, poly(methyl methacrylate) or argon beam, which results in a reduced recurrence rate by broadening the zone of tissue necrosis to include possible residual microscopic tumor cells[
11,
27‐
32].
Recurrences
In a retrospective study evaluating 185 patients, Campanacci
et al. found that the time to recurrence for ABCs was 2 to 72 months[
9]. Similarly, Ramírez and Stanton reported that the mean time to recurrence was 18.7 months (range: 4 to 39 months)[
35]. In our study, the minimum follow-up period of 3 years seems sufficient to reliably assess recurrence.
Vergel de Dios
et al. reported a 21.8% recurrence rate after curettage and did not note any relapses in patients with en bloc excision. A total of 90% of recurrences occurred in subjects below 20 years of age, and the mean age of the patients with treatment failure was lower than the mean age of the whole group (13.1 versus 16.1). The authors associated recurrence with younger age, but the statistical analysis did not confirm this[
10]. In our study group, the mean age of patients (12.9 years) is comparable to that of the patients with recurrences in the study by Vergel de Dios
et al. (13.1 years), but no greater frequency of treatment failures was observed. The authors also suggest that recurrences are associated with the cyst being located in long bones, and that a more favorable prognosis is associated with flat bones. They consider lesion curettage the treatment of choice for ABCs; they state en bloc excision should only be used for lesions in locations enabling affected site resection without functional limitation[
10].
Ramírez and Stanton also noted a 27.5% recurrence rate after ABC treatment, as well as a halving of recurrence rate (from 40% to 21%) after the introduction of a high-speed burr. As 75% of recurrences were seen in children below 5 years of age, the authors hypothesize that ABCs occurring in this age group display a more aggressive evolution. Ramírez and Stanton also suggest that unsatisfactory treatment results may be associated with fear on the part of the surgeon of damaging the growth plate in younger patients[
35]. According to Campanacci
et al., the risk of recurrence after curettage is as high as 21%. Relapses were more common in active (25%) and aggressive (26%) lesions, but absent in cases of curettage of inactive cysts and after en bloc excision. Considering those findings, Campanacci
et al. proposed deeper curettage with addition of phenol or cryotherapy in the treatment of more aggressive cysts. Bone excision was also recommended as the treatment of choice when the cyst is located in the proximal part of the fibula, distal part of the ulna, in ribs, pubic bone rami, and metatarsal and metacarpal bones[
9]. Gibbs
et al. reported a statistically significant correlation between the younger age of the patient, the presence of open growth plates and a higher rate of recurrences. While relapses occurred in four patients (12%) aged 3, 4, 10 and 11 years in the curettage group, no such cases occurred in patients treated with en bloc excision. As noted previously, the authors link higher risks of recurrence to more aggressive lesion types or insufficient excision of the pathological tissue in the growth plate area. On the basis of their own experience and the literature, Gibbs
et al. hypothesized that the use of additional chemical or physical resection does not result in improved treatment outcomes[
5].
Lin
et al. reported an 18.9% recurrence rate is associated with curettage. The cysts recurred significantly more often in patients aged <12 years and in cases when lesions were directly adjacent to the growth plate or articular cartilage[
6].
Similarly, the recurrence rates after curettage and en bloc excision determined by Mankin
et al., 22% and 5%, respectively, were higher than in those found in the present study. The authors saw a higher recurrence rate in children below 10 years of age (24%), but the correlations were not statistically significant. Furthermore, the study indicated a higher recurrence rate for cysts located in the clavicle (50%) or in the distal femur (46%), but this suggestion was based only on a few cases. Out of 150 patients participating in their study, 34 were reoperated, and 11 underwent 3 surgeries. The authors recommend curettage as a treatment of choice and en bloc excision of cysts of the femur, clavicle, foot bones, scapula and fibula[
11].
Schreuder
et al. demonstrated the efficacy of additional chemical resection in ABC surgery and recorded a recurrence rate lower than in our findings (3.7%). The burred surface was covered with sprayed liquid nitrogen several times during the procedure, which allowed the margin of bone excision to be extended without being weakened and forestalling the need for reconstructive surgery. No postoperative wound healing disorders occurred, nor any postoperative fractures[
31].
A statistically significant correlation was seen between recurrence and use of adjuvant (
P = 0.044) in a study by Cummings
et al. that evaluated the effectiveness of curettage with or without the use of an argon beam[
30]. The authors did not observe any relapses in the group treated with an adjuvant argon beam and no perioperative or postoperative complications were seen. Another evaluation of curettage surgery with an argon beam, by Steffner
et al., also reported a statistically significant correlation between the risk of the recurrence and use of the argon beam[
29].
Where surgery is contradicted due to a difficult surgical approach, embolization[
21,
22] or percutaneous sclerotherapy[
23‐
25] can be an optional treatment: another indication for embolization being a reduction in operative blood loss that facilitates curettage, especially in the pelvis or spine[
26]. Both techniques can be used in cases of postsurgical recurrence. Embolization is usually performed with use of polyvinyl alcohol,
N-2-butyl cyanoacrylate or Ethibloc®[
36]. De Cristofaro
et al. described the treatment of 14 patients with ABC where polyvinyl alcohol was used. Although embolization was not possible in 5 of these patients due to lack of a recognizable artery or common vascular supply to the lesion and spinal column, the authors obtained almost complete ossification in 11 cases, recurrences with pathological fracture in 2 cases and an unchanged cyst in 1 case, after a mean number of 2.3 procedures per patient. No complications were reported[
21].
The most encouraging results can be seen in a paper by Rossi
et al., who indicated that arterial embolization with cyanoacrylate may be the treatment of choice for ABC because it is less invasive, cheaper and simpler than surgery and is easily repeatable. The treatment was found to be effective in 32 patients (94%) and complications were noticed only in 3 procedures, which were cases of skin necrosis and transient paresis[
22]. Although recent studies show this treatment to have good results, pulmonary embolism or ischemia of vital structures not related to the tumor can occur[
37].
Another new procedure that is both simple and minimally invasive is the aforementioned percutaneous sclerotherapy using a thrombogenic substance, which induces an inflammatory reaction to a foreign body but lacks osteogenic properties. The use of one such substance in ABC management, Ethibloc®, was first reported by Adamsbaum
et al., who achieved satisfactory healing in two cases[
38]. Other studies show that percutaneous embolization may be considered a reliable alternative to surgery but, due to possible complications, this therapy is recommended only in deep located ABCs without marked venous drainage. Guiband
et al. treated 14 patients with ABCs with total lesion healing in 13 cases (87%) and partial healing in 2 cases (13%), without recurrences, the complications being 1 case of aseptic osteitis and a small pulmonary infarct[
23]. Garg
et al., who assessed the outcomes of CT-guided percutaneous injection of Ethibloc® into ABCs in ten patients, obtained total resolution of the lesion in seven patients and partial response in three, with the only complication being an aseptic abscess[
24]. However, Topouchian
et al. reported a high rate of local and general complications after Ethibloc® injection including one pulmonary embolism and four aseptic fistulizations; the authors abandoned fibrosing agent injections in the treatment of ABC[
39]. In a comparison of sclerotherapy with curettage in ABC treatment by Varshney
et al., it was reported that repetitive sclerotherapy using polidocanol is a minimally invasive method that is safer than curettage, although similar recurrence rates are noted for the two treatment methods[
25].
In the study group used in the present work, more radical treatment methods than those presented in the previous studies were used. En bloc excisions of bone fragments were performed in as much as 40% of patients, especially in the case of an Enneking’s III central lesion or expendable bones, which could be associated with more frequent postoperative complications. In the group of en bloc excision, only one complication occurred, versus two complications in the curettage group. In fact, it could not be demonstrated that bone fragment excision was associated with more frequent postoperative complications. Unfortunately, due to the small size of the sample, this remains only a hypothesis. It should also be noted that excision of a bone fragment and its replacement with bone graft is technically more difficult, more time consuming and often requires autograft bone harvesting, therefore it is not a standard treatment.
Pain and ROM limitation on follow-up were more common in the group where en bloc excision of bone fragments was performed, but no statistically significant differences between the procedures were found. All issues reported by our patients were mild in nature and occurred in rather non-specific situations, and although they did not interfere with any of our patient’s daily activities, they might impair athletic performance. Moreover, reduced ROM in this group applied usually to only one plane. Furthermore, no significant intergroup difference was found in muscle strength assessment. However, weakening of isometric muscle force in at least one range was observed in as much as half of the patients in the en bloc excision group: four patients in one plane, and one in two planes. This may result from soft tissue damage during an extensive procedure, from a pathological fracture or from prolonged postoperative immobilization in comparison with the curettage group. Muscle force reduction in eight patients applied only to one ROM plane, four from the curettage group and four from the en bloc excision group. In the remaining two patients, one in each treatment arm, the limitation applied to two ROM planes, and exceeded 50% when compared to the healthy side. Such disproportion seriously affects the physical activity of the patient.
The weakness of our study is an insufficient number of patients to draw statistically significant conclusions. For this reason, we limited this paper to cohort description and to forming hypotheses that should be investigated on larger patient samples. However, taking into account the low annual incidence of primary ABC (0.14 per 100,000 individuals), building up a more numerous study cohort would be a challenge[
34].