Arch Orthop Trauma Surg (1992) 111 : 297-300
A'chi' s°'Orthopaedic a.dTrauma Surgery © Springer-Verlag 1992
Original articles Simple bone cysts A review of 59 cases with special reference to their treatment J. Mylle, A. Burssens, and G. Fabry Department of Orthopaedic Surgery, University Hospital, Catholic University of Leuven, Belgium
Summary. In a retrospective study, 21 simple bone cysts (SBC) treated by curettage (with or without bone grafting) are compared to 20 SBC treated by intralesional injections of methylprednisolone. Curettage led to 43% favourable results and 29% recurrences. Cortisone injections led to 90% favourable results and 5% recurrences. Combined therapy (curettage and injections) led to results comparable to injections only. In our experience, curettage and hydroxyapatite grafting led to 100% complete healing (only 2 cases). We recommend intralesional methylprednisolone injections because the method is easy, effective and safe.
1 22
7 .
Bone cysts were first described by Virchow in 1876 [11]. Since then, various names have been given to there lesions, the most common being "solitary bone cyst". The name implies that the lesion is confined to a single site (a few cases of multiple sites have been described [3, 6]), The purpose of this article is to report and compare the results of different types of treatment which have been used over the last 20 years in our department.
19, 1
1
2"
Patients This is a retrospective review of 59 simple bone cysts (SBC) seen a n d treated at the University Hospital Pellenberg between 1970 a n d 1989, with a mean follow-up of 8,5 years. The total number of SBC treated during that period was 68, but nine patients were not included in this study. In six cases, follow-up was impossible or too short. One patient who had a rib resection and two patients with a total hip replacement were also excluded because comparison was irrelevant in these small groups. There is a clear predominance of male patients in the study population: 37 against 22 females. Mean patient age at first visit was 15 years. The most frequent sites of SBC were the upper metaphysis of the humerus and the femur (Fig. 1). Twenty-one cases were diagnosed at the time of a pathological fracture. In the remaining cases, diagnosis resulted from a radio-
Correspondence to: Prof. Dr. G. Fabry, Afdeling Orthopedie, U Z Pellenberg, Weligerveld 1, 3212 Pellenberg, Belgium
Fig. 1. Sites of the 59 simple bone cysts treated at the University Hospital Pellenberg between 1970 and 1989
graphic examination performed for pain (18 cases) or limping (4 cases). The finding was incidental in 16 cases.
Methods After a cyst was discovered, one of the treatments listed in Table 1 w a s chosen. In order to obtain a pathological diagnosis, curettage (with or without grafting) was performed whenever diagnosis w a s
uncertain after clinical, biochemical and radiological investiga-
298 tions. In 1979, intralesional cortisone injections were introduced for the "typical cases" of SBC because Scaglietti et al. [9] reported 90% good results with this technique. To assess the results, the Neer classification [1] as modified by Campanacci [8] was used. Four responses to treatment are described:
There were no statistical differences in distribution according to sex, age, activity of cyst and location between the surgical (curettage) and the non-surgical (intralesional injection) group.
Results
• Unchanged: No clinical or roentgenographic evidence of amelio-
ration. • Incomplete healing: New bone formation fills the area previously
occupied by the cyst. Small sites of osteolysis remain visible in the boundaries of the cyst. • Complete healing: The space occupied by the SBC is completely filled by new bone or by hydroxyapatite. • Recurrence: Initially the cyst consolidates with new bone. Thereafter, areas of osteolysis with definite cortical thinning appear. Table 1. Different methods of treatment for SBC
• T h e results of the injection group are statistically superior to those of the curettage g r o u p (Fisher's exact test, P = 0.03). • Injection and curettage + injection give almost the s a m e results (Fisher's exact test, P = 1). • C u r e t t a g e + grafting with h y d r o x y a p a t i t e gives the best results: 100% c o m p l e t e healing (only 2 cases).
No treatment (= natural course) Curettage • curettage alone • curettage and autografts • curettage and hydroxyapatite grafting Intralesional cortisone injections Curettage and cortisone injections
Table 2. Results in all 59 patients with simple bone cysts Treatment given
n
Corn- Incom- UnRecurplete plete changed rence healing healing
No treatment Curettage Injections Curettage + injections
12 21 20
0 5 5
4 6 13
8 4 1
0 6 1
6
3
3
0
0
Table 3. Results in the various curettage + subgroups
Treatment given
n
Corn- Incom- UnRecurplete plete changed rence healing healing
Curettage Curettage + autografting Curettage + hydroxyapatite grafting
9
1
2
4
2
10
2
4
0
4
2
2
0
0
0
Table 4. Complications of treatment of
simple bone cysts
T h e results are s u m m a r i s e d in T a b l e 2 and 3. Twelve cysts were not treated. Eight r e m a i n e d u n c h a n g e d , four healed incompletely. O f the 21 cysts treated by curettage, six recurred. C u r e t t a g e followed by h y d r o x y a p a t i t e grafting (2 cases) gave 100% c o m p l e t e healing. In the injection group (20 cysts), 18 cysts healed; only one recurred. W h e n b o t h curettage and injection were used, all cysts h e a l e d (three c o m p l e t e l y and three incompletely). T h e following conclusions can be drawn:
T a b l e 4 shows the complications in the different groups. Pathological re-fractures o c c u r r e d only if no t r e a t m e n t is started after the first fracture. G r o w t h disturbance was very rare; only a few cases have b e e n r e p o r t e d in the literature. T h e m o s t serious complication in the t r e a t e d cysts, especially after curettage, was recurrence. T h e r e were no deep infections.
Discussion
A c c o r d i n g to E n n e k i n g [4], t r e a t m e n t of S B C should be designed to p r e v e n t r e p e a t e d pathological fractures and deformity, not - as in a t u m o u r = to obliterate a progressive process. It is true that m a n y S B C are n e v e r disc o v e r e d b e c a u s e they are a s y m p t o m a t i c . O n the o t h e r hand, once a pathological fracture has occurred, in only 15% of cases will the cyst d i s a p p e a r after the fracture has healed. G a l a s k o [5] studied the fate of S B C after fractures and concluded that the natural history of a SBC is n o t altered by a fracture. O n c e the fracture has healed, the cyst should be t r e a t e d if it is large and/or expanding. O u r results confirm this view (see T a b l e 4): re-fractures o c c u r r e d only in the no t r e a t m e n t group. Until 1973, curettage was the t r e a t m e n t of choice for SBC [8]. It is a m i n o r p r o c e d u r e to e n h a n c e local blood
Treatment given
n
Pathological re-fractures
Growth Infection disturbance
Recurfence
No treatment Curettage Injections Injections and curettage
12 21 20 6
10 0 0 0
1 0 0 0
0 6 1 0
0 3 (superficial) 1 (superficial) 1 (superficial)
299
Fig. 2. See text Fig. 3. See text Fig. 4. See text
Decision to inject cyst with cortisone 1. Standard radiography: X~ 2. Densitometry: Y1
® INFILTRATION
Follow-up 3-monthly
®
1. Standard radiography: 1 mm or 2. Densitometry:
Fig. S. Treatment schedule. 7{1, Initial thickness of thinnest cyst wall; X2, thickness of thinnest cyst wall at follow-up; ]71, initial microdensity; I/2, microdensity at follow-up
supply that can be done at the time of biopsy. Our reSults suggest that is should be combined with bone grafting (se e Table 3). Neer [8] studied the influence of different graft materials and concluded that autogenous grafts are superior to allografts. He advises their use in all re-operations and those first procedures where a sufficient quantity of bone can be conveniently obtained to fill the defect. In our experience, curettage and grafting with hydroxyapatite gives 100% complete healing (see Table 3 and Figs. 2, 3). These findings are consistent with the results of Uchida et al. [10] in a recent study of curettage and grafting with hydroxyapatite ceramic: Their success rate in 60 benign tumors was also 100%. In 1973, the treatment of SBC by topical injection of methylprednisolone acetate was introduced by Scaglietti
[9]. Although there is no clear-cut evidence of how it affects the natural course of the lesion, Scaglietti felt that the presence of steroids in a cavity ~with a transudate would cause resorption of the fluid (in the same manner as it causes resorption of transudates in synovitis in a joint). In this procedure, three fundamental rules should be followed. First, two needles must be introduced into the cavity before aspiration: forced aspiration with one needle causes profuse venous bleeding which impairs the qualitative diagnosis of the cystic contents. Secondly, a radiopaque medium must be injected in order to visualise complete (fibrous) septa [2]. Campanacci et al. [13] found a higher incidence of incomplete healing as the number of septa increased. One should try to fill all separate cavities with cortisone (Fig. 4). Thirdly, the amount of cortisone injected depends upon the size of the cyst and the age of the patient: according to Scaglietti, 40-80 mg for large cysts in adults. In the literature, favourable results have been obtained in about 90% of patient. In our experience, the technique failed in only 2 patients out of 20, and gave very few complications (see Tables 2, 4). The only difficulty we had was to decide whether to continue or to stop further injections. Microdensitometry might give a better idea of the quantitative change of the density of treated cysts, as suggested by Nakamura et al. [7]. We modified their treatment schedule. In the future, we will use that modified schedule (Fig. 5).
Conclusions Many active simple bone cysts remain active for years, cause repeated fractures and progressively enlarge. The natural history shows that in these cases protracted periods of observation and restricted activity do not seem justifiable. Local injection of methylprednisolone are a good alternative because they are easy, cosmetically advantageous (no scar), effective (90%) and safe (very few complications). If biopsy is indicated for diagnostic pur-
300 poses, c u r e t t a g e a n d ( h y d r o x y a p a t i t e ) grafting can b e c o m b i n e d d u r i n g the s a m e p r o c e d u r e .
Acknowledgement. We are very grateful to Marleen Schoovaerts who prepared the typescript.
References 1. Campanacci M, et al (1986) Unicameral and aneurysmal bone cysts. Clin Orthop Rel Res 204: 25-35 2. Capanna R, et al (1984) Contrast examination as a diagnostic factor in the treatment of solitary bone cyst by cortisone injection. Skeletal Radiol 12 : 97-102 3. Chigira M, et al (1987) A case of multiple single bone cysts with special reference to their etiology and treatment. Arch Orthop Trauma Surg 106: 309-393 4. Enneking WF (1983) Musculoskeletal tumor surgery. Churchill Livingstone, Edinburgh, pp 1494-1513
5. Galasko CSB (1974) The fate of simple bone cysts with fracture. Clin Orthop Rel Res 101 : 302-304 6. Keret D, Kumar SJ (1987) Unicameral bone cysts in the humerus and femur in the same child. J Pediatr Orthop 7 : 712-715 7. Nakamura T, Takagi K, Kitagawa T, Harada M (1988) Microdensity of solitary bone cyst after steroid injection. J Pediatr Orthop 8 : 566-568 8. Neer CS II, et al (1973) Current concepts on the treatment of solitary unicameral bone cyst. Clin Orthop Rel Res 97 : 40-51 9. Scaglietti O, Marchetti PG, Bartolozzi P (1979) The effects of methylprednisolone acetate in the treatment of bone cysts. Results of three years follow-up. J Bone Joint Surg [Br] 61 : 22204 10. Uchida A, et al (1990) The use of calcium hydroxyapatite ceramic in bone tumour surgery. J Bone Joint Surg [Br] 72: 298-302 11. Virchow R (1876) ()ber die Bildung von Knochenzysten. S-B Akad Wiss, Berlin, S 369-381
A'chi' s°'Orthopaedic a.dTrauma Surgery © Springer-Verlag 1992
Original articles Simple bone cysts A review of 59 cases with special reference to their treatment J. Mylle, A. Burssens, and G. Fabry Department of Orthopaedic Surgery, University Hospital, Catholic University of Leuven, Belgium
Summary. In a retrospective study, 21 simple bone cysts (SBC) treated by curettage (with or without bone grafting) are compared to 20 SBC treated by intralesional injections of methylprednisolone. Curettage led to 43% favourable results and 29% recurrences. Cortisone injections led to 90% favourable results and 5% recurrences. Combined therapy (curettage and injections) led to results comparable to injections only. In our experience, curettage and hydroxyapatite grafting led to 100% complete healing (only 2 cases). We recommend intralesional methylprednisolone injections because the method is easy, effective and safe.
1 22
7 .
Bone cysts were first described by Virchow in 1876 [11]. Since then, various names have been given to there lesions, the most common being "solitary bone cyst". The name implies that the lesion is confined to a single site (a few cases of multiple sites have been described [3, 6]), The purpose of this article is to report and compare the results of different types of treatment which have been used over the last 20 years in our department.
19, 1
1
2"
Patients This is a retrospective review of 59 simple bone cysts (SBC) seen a n d treated at the University Hospital Pellenberg between 1970 a n d 1989, with a mean follow-up of 8,5 years. The total number of SBC treated during that period was 68, but nine patients were not included in this study. In six cases, follow-up was impossible or too short. One patient who had a rib resection and two patients with a total hip replacement were also excluded because comparison was irrelevant in these small groups. There is a clear predominance of male patients in the study population: 37 against 22 females. Mean patient age at first visit was 15 years. The most frequent sites of SBC were the upper metaphysis of the humerus and the femur (Fig. 1). Twenty-one cases were diagnosed at the time of a pathological fracture. In the remaining cases, diagnosis resulted from a radio-
Correspondence to: Prof. Dr. G. Fabry, Afdeling Orthopedie, U Z Pellenberg, Weligerveld 1, 3212 Pellenberg, Belgium
Fig. 1. Sites of the 59 simple bone cysts treated at the University Hospital Pellenberg between 1970 and 1989
graphic examination performed for pain (18 cases) or limping (4 cases). The finding was incidental in 16 cases.
Methods After a cyst was discovered, one of the treatments listed in Table 1 w a s chosen. In order to obtain a pathological diagnosis, curettage (with or without grafting) was performed whenever diagnosis w a s
uncertain after clinical, biochemical and radiological investiga-
298 tions. In 1979, intralesional cortisone injections were introduced for the "typical cases" of SBC because Scaglietti et al. [9] reported 90% good results with this technique. To assess the results, the Neer classification [1] as modified by Campanacci [8] was used. Four responses to treatment are described:
There were no statistical differences in distribution according to sex, age, activity of cyst and location between the surgical (curettage) and the non-surgical (intralesional injection) group.
Results
• Unchanged: No clinical or roentgenographic evidence of amelio-
ration. • Incomplete healing: New bone formation fills the area previously
occupied by the cyst. Small sites of osteolysis remain visible in the boundaries of the cyst. • Complete healing: The space occupied by the SBC is completely filled by new bone or by hydroxyapatite. • Recurrence: Initially the cyst consolidates with new bone. Thereafter, areas of osteolysis with definite cortical thinning appear. Table 1. Different methods of treatment for SBC
• T h e results of the injection group are statistically superior to those of the curettage g r o u p (Fisher's exact test, P = 0.03). • Injection and curettage + injection give almost the s a m e results (Fisher's exact test, P = 1). • C u r e t t a g e + grafting with h y d r o x y a p a t i t e gives the best results: 100% c o m p l e t e healing (only 2 cases).
No treatment (= natural course) Curettage • curettage alone • curettage and autografts • curettage and hydroxyapatite grafting Intralesional cortisone injections Curettage and cortisone injections
Table 2. Results in all 59 patients with simple bone cysts Treatment given
n
Corn- Incom- UnRecurplete plete changed rence healing healing
No treatment Curettage Injections Curettage + injections
12 21 20
0 5 5
4 6 13
8 4 1
0 6 1
6
3
3
0
0
Table 3. Results in the various curettage + subgroups
Treatment given
n
Corn- Incom- UnRecurplete plete changed rence healing healing
Curettage Curettage + autografting Curettage + hydroxyapatite grafting
9
1
2
4
2
10
2
4
0
4
2
2
0
0
0
Table 4. Complications of treatment of
simple bone cysts
T h e results are s u m m a r i s e d in T a b l e 2 and 3. Twelve cysts were not treated. Eight r e m a i n e d u n c h a n g e d , four healed incompletely. O f the 21 cysts treated by curettage, six recurred. C u r e t t a g e followed by h y d r o x y a p a t i t e grafting (2 cases) gave 100% c o m p l e t e healing. In the injection group (20 cysts), 18 cysts healed; only one recurred. W h e n b o t h curettage and injection were used, all cysts h e a l e d (three c o m p l e t e l y and three incompletely). T h e following conclusions can be drawn:
T a b l e 4 shows the complications in the different groups. Pathological re-fractures o c c u r r e d only if no t r e a t m e n t is started after the first fracture. G r o w t h disturbance was very rare; only a few cases have b e e n r e p o r t e d in the literature. T h e m o s t serious complication in the t r e a t e d cysts, especially after curettage, was recurrence. T h e r e were no deep infections.
Discussion
A c c o r d i n g to E n n e k i n g [4], t r e a t m e n t of S B C should be designed to p r e v e n t r e p e a t e d pathological fractures and deformity, not - as in a t u m o u r = to obliterate a progressive process. It is true that m a n y S B C are n e v e r disc o v e r e d b e c a u s e they are a s y m p t o m a t i c . O n the o t h e r hand, once a pathological fracture has occurred, in only 15% of cases will the cyst d i s a p p e a r after the fracture has healed. G a l a s k o [5] studied the fate of S B C after fractures and concluded that the natural history of a SBC is n o t altered by a fracture. O n c e the fracture has healed, the cyst should be t r e a t e d if it is large and/or expanding. O u r results confirm this view (see T a b l e 4): re-fractures o c c u r r e d only in the no t r e a t m e n t group. Until 1973, curettage was the t r e a t m e n t of choice for SBC [8]. It is a m i n o r p r o c e d u r e to e n h a n c e local blood
Treatment given
n
Pathological re-fractures
Growth Infection disturbance
Recurfence
No treatment Curettage Injections Injections and curettage
12 21 20 6
10 0 0 0
1 0 0 0
0 6 1 0
0 3 (superficial) 1 (superficial) 1 (superficial)
299
Fig. 2. See text Fig. 3. See text Fig. 4. See text
Decision to inject cyst with cortisone 1. Standard radiography: X~ 2. Densitometry: Y1
® INFILTRATION
Follow-up 3-monthly
®
1. Standard radiography: 1 mm or 2. Densitometry:
Fig. S. Treatment schedule. 7{1, Initial thickness of thinnest cyst wall; X2, thickness of thinnest cyst wall at follow-up; ]71, initial microdensity; I/2, microdensity at follow-up
supply that can be done at the time of biopsy. Our reSults suggest that is should be combined with bone grafting (se e Table 3). Neer [8] studied the influence of different graft materials and concluded that autogenous grafts are superior to allografts. He advises their use in all re-operations and those first procedures where a sufficient quantity of bone can be conveniently obtained to fill the defect. In our experience, curettage and grafting with hydroxyapatite gives 100% complete healing (see Table 3 and Figs. 2, 3). These findings are consistent with the results of Uchida et al. [10] in a recent study of curettage and grafting with hydroxyapatite ceramic: Their success rate in 60 benign tumors was also 100%. In 1973, the treatment of SBC by topical injection of methylprednisolone acetate was introduced by Scaglietti
[9]. Although there is no clear-cut evidence of how it affects the natural course of the lesion, Scaglietti felt that the presence of steroids in a cavity ~with a transudate would cause resorption of the fluid (in the same manner as it causes resorption of transudates in synovitis in a joint). In this procedure, three fundamental rules should be followed. First, two needles must be introduced into the cavity before aspiration: forced aspiration with one needle causes profuse venous bleeding which impairs the qualitative diagnosis of the cystic contents. Secondly, a radiopaque medium must be injected in order to visualise complete (fibrous) septa [2]. Campanacci et al. [13] found a higher incidence of incomplete healing as the number of septa increased. One should try to fill all separate cavities with cortisone (Fig. 4). Thirdly, the amount of cortisone injected depends upon the size of the cyst and the age of the patient: according to Scaglietti, 40-80 mg for large cysts in adults. In the literature, favourable results have been obtained in about 90% of patient. In our experience, the technique failed in only 2 patients out of 20, and gave very few complications (see Tables 2, 4). The only difficulty we had was to decide whether to continue or to stop further injections. Microdensitometry might give a better idea of the quantitative change of the density of treated cysts, as suggested by Nakamura et al. [7]. We modified their treatment schedule. In the future, we will use that modified schedule (Fig. 5).
Conclusions Many active simple bone cysts remain active for years, cause repeated fractures and progressively enlarge. The natural history shows that in these cases protracted periods of observation and restricted activity do not seem justifiable. Local injection of methylprednisolone are a good alternative because they are easy, cosmetically advantageous (no scar), effective (90%) and safe (very few complications). If biopsy is indicated for diagnostic pur-
300 poses, c u r e t t a g e a n d ( h y d r o x y a p a t i t e ) grafting can b e c o m b i n e d d u r i n g the s a m e p r o c e d u r e .
Acknowledgement. We are very grateful to Marleen Schoovaerts who prepared the typescript.
References 1. Campanacci M, et al (1986) Unicameral and aneurysmal bone cysts. Clin Orthop Rel Res 204: 25-35 2. Capanna R, et al (1984) Contrast examination as a diagnostic factor in the treatment of solitary bone cyst by cortisone injection. Skeletal Radiol 12 : 97-102 3. Chigira M, et al (1987) A case of multiple single bone cysts with special reference to their etiology and treatment. Arch Orthop Trauma Surg 106: 309-393 4. Enneking WF (1983) Musculoskeletal tumor surgery. Churchill Livingstone, Edinburgh, pp 1494-1513
5. Galasko CSB (1974) The fate of simple bone cysts with fracture. Clin Orthop Rel Res 101 : 302-304 6. Keret D, Kumar SJ (1987) Unicameral bone cysts in the humerus and femur in the same child. J Pediatr Orthop 7 : 712-715 7. Nakamura T, Takagi K, Kitagawa T, Harada M (1988) Microdensity of solitary bone cyst after steroid injection. J Pediatr Orthop 8 : 566-568 8. Neer CS II, et al (1973) Current concepts on the treatment of solitary unicameral bone cyst. Clin Orthop Rel Res 97 : 40-51 9. Scaglietti O, Marchetti PG, Bartolozzi P (1979) The effects of methylprednisolone acetate in the treatment of bone cysts. Results of three years follow-up. J Bone Joint Surg [Br] 61 : 22204 10. Uchida A, et al (1990) The use of calcium hydroxyapatite ceramic in bone tumour surgery. J Bone Joint Surg [Br] 72: 298-302 11. Virchow R (1876) ()ber die Bildung von Knochenzysten. S-B Akad Wiss, Berlin, S 369-381
