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The calcaneal cyst – pathogenesis and intraosseous vascularization of the calcaneus
FussSprungg 2:219–225 (2004) DOI 10.1007/s10302-004-0134-0
J. Andermahr A. Jubel A. Prokop H.-U. Kasper A. Elsner K. E. Rehm J. Koebke
Received: 26 August 2004 Accepted: 17 September 2004
MD Jonas Andermahr ()) MD Axel Prokop · MD Andreas Elsner MD Klaus Emil Rehm Clinic of Trauma-, Handand Reconstructive Surgery University of Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany Tel.: +49-221/478 48 02 Fax: +49-2486/20 30 26 E-Mail: [email protected] MD Hans-Udo Kasper Pathology University of Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany
The calcaneal cyst – pathogenesis and intraosseous vascularization of the calcaneus
Die Kalkaneuszyste – Pathogenese und intraossäre Durchblutung des Kalkaneus
Knochennekrose – Biomechanik Fersenbein
n Zusammenfassung Aus der Betrachtung der intraossären Gefäßversorgung und der speziellen Biomechanik des Knochens wird eine neue Theorie zur Entstehung von Kalkaneuszysten generiert (Retrospektive Patientenstudie, n = 4): Es kommt zu einer lokalen Durchblutungsstörung (Embolie, Thrombose, Hämatom) in dem Areal (spannungsfreies Dreieck), wo die Hauptgefäße den Knochen penetrieren und verteilt werden. Gefolgt wird die lokale Durchblutungsstörung von der Resorption geschädigten Gewebes. Die besondere biomechanische Gegebenheit (Spannungsfreiheit) führt dazu, dass es nicht zu einem knöchernen Remodeling kommt, sondern lediglich zu einer Zystenformation, die histologisch einheitlich (Neovaskularisation, Cholesterinablagerungen, Hämosiderin, osteoidartige Zystenwand) imponiert. Die benigne Kalkaneuszyste ist biomechanisch durch einen sklerosierten Randwall für normale Belastungen stabil. Zu Frakturen kommt es nur bei exzentrischen Belastungsspitzen.
n Summary As a response to research investigating the intraosseous vascularization and the special biomechanics of the calcaneus, a new theory of calcaneal cyst development was generated (retrospective patient study, n = 4). A disturbance in local blood circulation occurs, due to, i.e., microembolus, thrombosis, or hematoma, at the neutral triangle where the major vessels penetrate the bone and separate. Following the disturbance in local blood flow, damaged tissues are resorbed. Due to the special biomechanics of the area, resorption is followed not by osseous remodelling, but instead by cyst formation. The two processes are histologically identical, including the presence of neovascularization, cholesterol plaques, hemosiderin and osteoid-lined cyst walls. Because of its sclerosed external wall, the benign calcaneal cyst is stable with normal biomechanics; however, eccentric weight-loading can lead to fractures.
n Schlüsselwörter Fersenbeinzyste – Knochenzyste – Pathogenese – Avaskuläre
n Key words Calcaneal cyst – bone cyst – pathogenesis – avascular bone necrosis – calcaneal biomechanics
Fuß 134
MD, PhD Jürgen Köbke Center of Anatomy University Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany
ORIGINALARBEIT
220
Fuß & Sprunggelenk, Band 2, Heft 4 (2004) © Steinkopff Verlag 2004
Introduction The solitary bone cyst was first described by Virchow in 1877, and later by Elmslie in 1914 [8]. Jaffe and Lichtenstein coined the term unicameral in 1942 [17]. Unicameral bone cysts are completely benign and virtually never metastasize; however, they are prone to recurrence and several factors have been identified as being associated with a high rate of recurrence or persistence of simple cysts [10]. These factors include a patient younger than 10 years, larger versus smaller lesions, the male sex, and existence of multilocular lesions. A simple bone cyst can be asymptomatic, or it may produce localized pain and swelling, tenderness, or stiffness of an adjacent joint. Pathologic fractures of the calcaneus are rare, but have been reported [16]. Three percent of all simple bone cysts arise in the calcaneus and are characteristically located anteriorly within the neutral triangle just inferior to the anterior margin of the posterior facet. The etiology at present is unclear. Several mechanisms have been advocated [9]: a traumatic hematoma which undergoes cystic resorption, cystic degeneration of a pre-existing benign tumor, invagination of the synovial membrane of a large joint through the epiphyseal plate during osseous growth and its later separation [21]. The histologic examination of our own patients’ material with the understanding of the intraosseous blood supply [1–6] and biomechanical factors of the human calcaneus generates a theory of the pathogenesis of the solitary bone cyst of the calcaneus [14, 18–20].
Table 1 Patients with solitary calcaneal cyst Patient/ Gender
Age
Location
Therapy
BD/m RM/m HD/m SM/m
12 51 16 26
Neutral Neutral Neutral Neutral
operative operative operative conservative
triangle triangle triangle triangle
after eccentric weight loading (distorsion trauma) during sporting activities, and the patients presented with pain. The other 2 cases were incidental findings discovered after routine x-rays of the hind-foot were performed. In the cases treated surgically, a lateral window was opened to the cyst, the cyst content and wall were extracted, and autologous cancellous bone graft was placed in the defect. There were no recurrences post-treatment.
n Radiologic findings Computed tomographic images of all 4 cases revealed a trapezoid shaped cavern lacking bony trabeculae, with a partially thickened and sclerosed wall (Fig. 1). Figs. 1 and 2 display a typical calcaneal cyst located in the neutral triangle, inferior to the dorsal joint facet. All patients’ cysts were located at
Methods Between 1995 and 2002, four cases of bone cysts of the calcaneus were treated at the Departments of Traumatology and Orthopedics at the University of Cologne Hospital. Three were treated operatively, and the removed tissues were prepared for histologic analysis. The extracted material was fixed in 19% formalin, then molded into paraffin and cut into 7 lm slices with a microtome. The samples were treated with hematoxylin-eosin and then van Gieson stains, and examined with a light microscope. Characteristic findings were described, and radiologic and scintigraphic findings were demonstrated.
Results Between 1995 and 2002, 4 patients were diagnosed with an osseous cyst of the calcaneus (Table 1). In 2 cases, the patients sustained a calcaneal fracture
Abb. 1 The CT scan (transverse cut) shows the cyst wall consolidated with the spongy bone. The cyst lies centrally and its borders are within the cortical bone of the calcaneus
J. Andermahr et al. Pathogenisis of calcaneal cysts
221
Abb. 2 The sagittal reconstruction shows the cyst in typical location of the pre-existing neutral triangle Table 2 Scintigraphic data of a patient with a calcaneal cyst ROI Perfusion Vascular phase Osseous phase
[cpm]
Pixel
Quotient
Control side Cyst side
7597 7151
55 55
0.94
Control side Cyst side
10156 10233
880 880
1.01
Control side Cyst side
13024 13099
880 880
1.01
this site. Depending on the age of the cyst, regions of sclerosis of the cyst wall were found close to the neutral triangle, where the cyst structure bordered the normal spongy bone structure.
n Scintigraphic findings On scintigraphic analysis, the cysts demonstrated decreased activity in the osseous and vascular phases when compared with the opposite unaffected side. There was no evidence of increased activity similar to that normally found in cases of malignancy or infection (Table 2, Fig. 3 and 4). Abb. 3 The picture shows the vascular phase (nuclear incoming phase) and the osseous phase of the scintigraphy of a patient with a calcaneal cyst
Abb. 4 The graphic diagram of the uptake in both phases of the examination shows only a slight deficit in relation to the healthy opposite site
n Histologic findings Histologic examination of the extracted tissues revealed centrally mostly fibrous tissue with histiocytic resorption. Hemosiderin and cholesterol plaques were evident either within histiocytes or as crystals in a foreign-body giant cell reaction (Fig. 5 a, d). In three cases fibrous material was infiltrated with fibrous osteoid. The peripheral regions were connected to partially reconstructed bony structures. Hemosiderin plaques were evident in various concentrations (Fig. 5 c, e). Figure 5 f exhibits a cystic structure with an area of central resorption and peripheral osteoid and fibrous bone formation. Figure 5 c demonstrates an area of sparse neo-vascularization in the wall near the neutral triangle. In that area, a common histologic pattern of the remodelling process that normally follows local bleeding or thrombosis is evident. The bone remodelling shows
222
Fuß & Sprunggelenk, Band 2, Heft 4 (2004) © Steinkopff Verlag 2004
Abb. 5 Microscopic slices at 60X enlargement after decalcification, parafin fixation and staining (H/E). Cholesterol plaques are visible (a, d). In the periphery, regions of bone remodelling with fibrous bone, osteoid formations, and mineralized bone (b, d) are visible. Hemosiderin plaques are evident in varying concentrations (c, e). A cyst formation (central resorption zone, peripherel osteoid and fibrous bone formation is shown in f. The neovascularization of the wall-adjacent areas is shown in c
no evidence of lamellar or well-mineralized bone; instead it displays undeveloped fibrous bone without an amorphous extracellular matrix. The cystic fluid consists of serum-like components, but with an approximately ten-fold concentration of alkaline phosphatase.
Discussion Our described findings of calcaneal cysts agree with those listed in the literature [15, 22, 25, 28–30]. Interestingly, it is extremely rare to find bilateral calcaneal cysts. Clinically, the cysts remain silent. Approximately 60 calcaneal cysts have been histologically diagnosed in the literature. All demonstrate an inner fibrous content, and most show hemosiderin and cholesterol plaques. There is in-bleeding and a serous cystic fluid. Until now, there has been no suf-
ficient explanation of the pathogenesis of these cysts. The analysis of the biomechanical properties and the intraosseus vessel configuration of healthy bone and the histomorphologic findings of the calcaneal cysts show four characteristics: n The cysts are found almost exclusively in the projection of the normal calcaneal bone in the spongiosa-free neutral triangle inferior to the dorsal facet. n This area is the major entry point for both medial and lateral blood vessels (Figs. 6, 7) [2–5]. n Normally, this region is vital for blood circulation to both the anterior and posterior aspects of the calcaneus (Fig. 6). n On histologic examination, the cyst wall shows osteogenic metaplasia compared to neighboring trabecular and fibrous bone, with hemosiderin and cholesterol plaques. This type of fibrous tissue is also present in organized hematomas [11, 13].
J. Andermahr et al. Pathogenisis of calcaneal cysts
223
Abb. 6 The region without spongy bone is the conduction area of the lateral and medial intraosseous vessel supplies
Through the combined clinical, histopathologic, and anatomic findings, particularly the new description of calcaneal blood vessel anatomy, the following conclusions about the etiology of solitary calcaneal cysts can be made: The development of a cyst in this area is secondary to a disturbance in local intraosseous blood circulation. This would initially be caused by bleeding (hematoma). The argument against a local thrombosis or microembolic event is the fact that the cyst is always centrally located, in an area supplied by both lateral and medial blood vessels. Because the intraosseous blood vessel anatomy shows equal supply bilaterally, a bilateral local occlusion must occur to engender a centralized cyst. The hematoma theory of bone cyst formation was initially postulated in 1919 by Pommer and later by Jaffe and Lichtenstein (1942) [17, 24]. Due to the special biomechanical properties at the location of the neutral triangle of the calcaneus, remodelling does not result in construction of lamellar bone. According to Kummer (1965) [19, 20] and Frost (1990) [14], the effects of
Abb. 8 Drawn (left) and densiometric (right) pictures of the pressure (continuous line) and tension (broken line) trajectories in a 2-dimensional tension-optical model of the calcaneus, which is moved by pulling the triceps surae muscle, applying hindfoot pressure, and stressing the plantar aponeurosis, cuboidal and talar bones
Abb. 7 The intraosseous arterial supply comes from medial and lateral incoming branches of the tibialis posterior artery, as well as a lateral anastomosis of the fibular artery and the dorsalis pedis artery in the region of the neutral triangle
pressure and tension are the major physical stimuli for osseous remodeling. Sim (1990) [27] demonstrated that the sclerotic cyst wall provides enough stability for normal weight-bearing activities. However, this stability is not enough for eccentric and/or high-performance loading, and fractures may develop as a consequence. Most early authors advocated surgical curettage and bone grafting as the treatment of choice for simple bone cysts [7, 8, 23]. An asymptomatic static residual defect may occur following surgical curettage and packing, but it should not be considered a reflection of success and has been classified as
224
Fuß & Sprunggelenk, Band 2, Heft 4 (2004) © Steinkopff Verlag 2004
healed, with reports that most disappeared within 7 years following surgery [8]. In the late 1970s, the popularity of a surgical approach to the simple bone cyst began to give way to an alternative non-operative approach when Scaglietti et al. reported 90% favorable results with methylprednisone acetate injections [26]. Other authors were able to confirm these results in cases of calcaneal cysts [12]. Our experience highlights the risks of fracture to a normally asymptomatic bone cyst in the context of athletic activities. In cases of young, athletic patients with complaints of progressive pain, we recommend a
surgical procedure for both stabilization and psychological security. We recommend cortisone injection as therapy for patients with an incidental finding of a solitary calcaneal cyst or for patients with contraindications to operative management. Due to the special anatomic position in the neutral triangle of the calcaneus, the use of a bone growth protein (BMP 7) appears to be useful, because normal bone remodelling processes are less effective. n Acknowledgement Translation by Sarah Hamilton, MD.
References 1. Andermahr J (1999) Anatomie des Rückfußes unter Berücksichtigung der Gefäßsituation bei operativen Maßnahmen. In: Moorahrend U (ed) Funktionelle Behandlung ausgesuchter Verletzungen der unteren Extremität-Grenzen, Möglichkeiten und Konzepte. Sympomed, München Taufkirchen, pp 11–17 2. Andermahr J, Helling H, Mader K, Koebke J, Rehm K (1997) Die Blutversorgung von Talus und Calcaneus. Hefte zu Der Unfallchirurg 268:110– 114 3. Andermahr J, Helling HJ, Landwehr P, Fischbach R, Koebke J, Rehm KE (1998) The lateral calcaneal artery. Surg Radiol Anat 20:419–423 4. Andermahr J, Helling HJ, Rehm KE, Koebke Z (1999) The vascularization of the os calcaneum and the clinical consequences. Clin Orthop 363:212– 218 5. Andermahr J, Notermans H, Helling H, Rehm K, Koebke J (1997) Umsetzung einer klinischen Fragestellung in eine präparatorische Untersuchung am Beispiel; Fersenbeinfraktur. Der Präparator 43:1–5 6. Andermahr J, Zähringer M, Helling H, Krug K, Koebke J, Rehm K (2002) Surgical Aspects of the Hindfoot MR Anatomy. Foot Ankle Surg 8:1–7 7. Baker DM (1970) Benign unicameral bone cyst. A study of forty-five cases with long-term follow up. Clin Orthop 71:140–151 8. Boseker EH, Bickel WH, Dahlin DC (1968) A clinicopathologic study of simple unicameral bone cysts. Surg Gynecol Obstet 127:550–560 9. Chigira M, Watanabe H, Arita S, Udagawa E (1983) Simple bone cyst– pathophysiology and treatment. Nippon Seikeigeka Gakkai Zasshi 57:759– 766
10. Cohen J (1960) Simple bone cysts. Studies of cyst fluid in six cases with a theory of pathogenesis. Am J Orthop 42-A:609–616 11. Dota T, Nakamura K, Saheki M, Sasaki Y (1963) Cholesterol granuloma. Ann Otol 72:346–356 12. Frankel SL, Chioros PG, Sidlow CJ (1988) Steroid injection of a unicameral bone cyst of the calcaneus: literature review and two case reports. J Foot Surg 27:60–65 13. Friedmann I (1959) Epidermoid cholesteatoma and cholesterol granuloma; experimental and human. Ann Otol Rhinol Laryngol 68:57–79 14. Frost HM (1990) Skeletal structural adaptations to mechanical usage (SATMU): 4. Mechanical influences on intact fibrous tissues. Anat Rec 226:433–439 15. Gebhart M, Blaimont P (1996) Contribution to the vascular origin of the unicameral bone cyst. Acta Orthop Belg 62:137–143 16. Grumbine NA, Clark GD (1986) Unicameral bone cyst in the calcaneus with pathologic fracture. A literature review and case report. J Am Podiatr Med Assoc 76:96–99 17. Jaffé H, Lichtenstein L (1942) Solitary unicameral bone cyst. With emphasis on the roentgen picture, the pathologic appearance and the pathogenesis. Arch Surg 44:1004–1025 18. Koebke J (1999) Beanspruchung und funktionelle Morphologie des Rückfußes. In: Moorahrend U (ed) Funktionelle Behandlung ausgesuchter Verletzungen der unteren ExtremitätGrenzen, Möglichkeiten und Konzepte. sympomed, München Taufkirchen, pp 18–25 19. Kummer B (1979) Biomechanics of the calcaneus. Z Orthop Ihre Grenzgeb 117:551–556
20. Kummer B (1965) Development and variations of long bone forms with special reference to mechanical influences. Arkh Anat Gistol Embriol 49:21–29 21. Mirra JM, Bernard GW, Bullough PG, Johnston W, Mink G (1978) Cementum-like bone production in solitary bone cysts. (so-called „cementoma“ of long bones). Report of three cases. Electron microscopic observations supporting a synovial origin to the simple bone cyst. Clin Orthop 135: 295–307 22. Moreau G, Letts M (1994) Unicameral bone cyst of the calcaneus in children. J Pediatr Orthop 14:101–104 23. Neer CS, Francis KC, Johnston AD, Kiernan HA, Jr (1973) Current concepts on the treatment of solitary unicameral bone cyst. Clin Orthop 97:40–51 24. Pommer G (1919) Zur Kenntnis der progressiven Hämatom- und Phlegmasieveränderungen der Röhrenknochen auf Grund der mikroskopischen Befunde im neuen Knochenzystenfall. Arch orthop Unfall-Chir 17:17–69 25. Sandomenico F, Cappabianca S, Iovino M, Conforti R, Cinque T, Del Vecchio W (1996) Aneurysmal bone cyst: diagnostic role of computerized tomography and magnetic resonance. Radiol Med (Torino) 92:525–529 26. 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 61B:200–204 27. Sim E, Haid C (1990) Unicameral cyst of the calcaneus: surgical indications, biomechanical calculations and results of follow-up studies. Z Orthop Ihre Grenzgeb 128:623–631
J. Andermahr et al. Pathogenisis of calcaneal cysts 28. Simon WH, Mayer DP, Schmidt RG, Brooks ML, Mitchell EI, Schwamm HA (1990) Magnetic resonance imaging of calcaneal aneurysmal bone cyst. J Foot Surg 29:448–451
29. Smith SB, Shane HS (1994) Simple bone cyst of the calcaneus. A case report and literature review. J Am Podiatr Med Assoc 84:127–130
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30. Van Linthoudt D, Lagier R (1978) Calcaneal cysts. A radiological and anatomico-pathological study. Acta Orthop Scand 49:310–316
J. Andermahr A. Jubel A. Prokop H.-U. Kasper A. Elsner K. E. Rehm J. Koebke
Received: 26 August 2004 Accepted: 17 September 2004
MD Jonas Andermahr ()) MD Axel Prokop · MD Andreas Elsner MD Klaus Emil Rehm Clinic of Trauma-, Handand Reconstructive Surgery University of Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany Tel.: +49-221/478 48 02 Fax: +49-2486/20 30 26 E-Mail: [email protected] MD Hans-Udo Kasper Pathology University of Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany
The calcaneal cyst – pathogenesis and intraosseous vascularization of the calcaneus
Die Kalkaneuszyste – Pathogenese und intraossäre Durchblutung des Kalkaneus
Knochennekrose – Biomechanik Fersenbein
n Zusammenfassung Aus der Betrachtung der intraossären Gefäßversorgung und der speziellen Biomechanik des Knochens wird eine neue Theorie zur Entstehung von Kalkaneuszysten generiert (Retrospektive Patientenstudie, n = 4): Es kommt zu einer lokalen Durchblutungsstörung (Embolie, Thrombose, Hämatom) in dem Areal (spannungsfreies Dreieck), wo die Hauptgefäße den Knochen penetrieren und verteilt werden. Gefolgt wird die lokale Durchblutungsstörung von der Resorption geschädigten Gewebes. Die besondere biomechanische Gegebenheit (Spannungsfreiheit) führt dazu, dass es nicht zu einem knöchernen Remodeling kommt, sondern lediglich zu einer Zystenformation, die histologisch einheitlich (Neovaskularisation, Cholesterinablagerungen, Hämosiderin, osteoidartige Zystenwand) imponiert. Die benigne Kalkaneuszyste ist biomechanisch durch einen sklerosierten Randwall für normale Belastungen stabil. Zu Frakturen kommt es nur bei exzentrischen Belastungsspitzen.
n Summary As a response to research investigating the intraosseous vascularization and the special biomechanics of the calcaneus, a new theory of calcaneal cyst development was generated (retrospective patient study, n = 4). A disturbance in local blood circulation occurs, due to, i.e., microembolus, thrombosis, or hematoma, at the neutral triangle where the major vessels penetrate the bone and separate. Following the disturbance in local blood flow, damaged tissues are resorbed. Due to the special biomechanics of the area, resorption is followed not by osseous remodelling, but instead by cyst formation. The two processes are histologically identical, including the presence of neovascularization, cholesterol plaques, hemosiderin and osteoid-lined cyst walls. Because of its sclerosed external wall, the benign calcaneal cyst is stable with normal biomechanics; however, eccentric weight-loading can lead to fractures.
n Schlüsselwörter Fersenbeinzyste – Knochenzyste – Pathogenese – Avaskuläre
n Key words Calcaneal cyst – bone cyst – pathogenesis – avascular bone necrosis – calcaneal biomechanics
Fuß 134
MD, PhD Jürgen Köbke Center of Anatomy University Cologne Joseph-Stelzmann-Straße 9 50924 Köln, Germany
ORIGINALARBEIT
220
Fuß & Sprunggelenk, Band 2, Heft 4 (2004) © Steinkopff Verlag 2004
Introduction The solitary bone cyst was first described by Virchow in 1877, and later by Elmslie in 1914 [8]. Jaffe and Lichtenstein coined the term unicameral in 1942 [17]. Unicameral bone cysts are completely benign and virtually never metastasize; however, they are prone to recurrence and several factors have been identified as being associated with a high rate of recurrence or persistence of simple cysts [10]. These factors include a patient younger than 10 years, larger versus smaller lesions, the male sex, and existence of multilocular lesions. A simple bone cyst can be asymptomatic, or it may produce localized pain and swelling, tenderness, or stiffness of an adjacent joint. Pathologic fractures of the calcaneus are rare, but have been reported [16]. Three percent of all simple bone cysts arise in the calcaneus and are characteristically located anteriorly within the neutral triangle just inferior to the anterior margin of the posterior facet. The etiology at present is unclear. Several mechanisms have been advocated [9]: a traumatic hematoma which undergoes cystic resorption, cystic degeneration of a pre-existing benign tumor, invagination of the synovial membrane of a large joint through the epiphyseal plate during osseous growth and its later separation [21]. The histologic examination of our own patients’ material with the understanding of the intraosseous blood supply [1–6] and biomechanical factors of the human calcaneus generates a theory of the pathogenesis of the solitary bone cyst of the calcaneus [14, 18–20].
Table 1 Patients with solitary calcaneal cyst Patient/ Gender
Age
Location
Therapy
BD/m RM/m HD/m SM/m
12 51 16 26
Neutral Neutral Neutral Neutral
operative operative operative conservative
triangle triangle triangle triangle
after eccentric weight loading (distorsion trauma) during sporting activities, and the patients presented with pain. The other 2 cases were incidental findings discovered after routine x-rays of the hind-foot were performed. In the cases treated surgically, a lateral window was opened to the cyst, the cyst content and wall were extracted, and autologous cancellous bone graft was placed in the defect. There were no recurrences post-treatment.
n Radiologic findings Computed tomographic images of all 4 cases revealed a trapezoid shaped cavern lacking bony trabeculae, with a partially thickened and sclerosed wall (Fig. 1). Figs. 1 and 2 display a typical calcaneal cyst located in the neutral triangle, inferior to the dorsal joint facet. All patients’ cysts were located at
Methods Between 1995 and 2002, four cases of bone cysts of the calcaneus were treated at the Departments of Traumatology and Orthopedics at the University of Cologne Hospital. Three were treated operatively, and the removed tissues were prepared for histologic analysis. The extracted material was fixed in 19% formalin, then molded into paraffin and cut into 7 lm slices with a microtome. The samples were treated with hematoxylin-eosin and then van Gieson stains, and examined with a light microscope. Characteristic findings were described, and radiologic and scintigraphic findings were demonstrated.
Results Between 1995 and 2002, 4 patients were diagnosed with an osseous cyst of the calcaneus (Table 1). In 2 cases, the patients sustained a calcaneal fracture
Abb. 1 The CT scan (transverse cut) shows the cyst wall consolidated with the spongy bone. The cyst lies centrally and its borders are within the cortical bone of the calcaneus
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221
Abb. 2 The sagittal reconstruction shows the cyst in typical location of the pre-existing neutral triangle Table 2 Scintigraphic data of a patient with a calcaneal cyst ROI Perfusion Vascular phase Osseous phase
[cpm]
Pixel
Quotient
Control side Cyst side
7597 7151
55 55
0.94
Control side Cyst side
10156 10233
880 880
1.01
Control side Cyst side
13024 13099
880 880
1.01
this site. Depending on the age of the cyst, regions of sclerosis of the cyst wall were found close to the neutral triangle, where the cyst structure bordered the normal spongy bone structure.
n Scintigraphic findings On scintigraphic analysis, the cysts demonstrated decreased activity in the osseous and vascular phases when compared with the opposite unaffected side. There was no evidence of increased activity similar to that normally found in cases of malignancy or infection (Table 2, Fig. 3 and 4). Abb. 3 The picture shows the vascular phase (nuclear incoming phase) and the osseous phase of the scintigraphy of a patient with a calcaneal cyst
Abb. 4 The graphic diagram of the uptake in both phases of the examination shows only a slight deficit in relation to the healthy opposite site
n Histologic findings Histologic examination of the extracted tissues revealed centrally mostly fibrous tissue with histiocytic resorption. Hemosiderin and cholesterol plaques were evident either within histiocytes or as crystals in a foreign-body giant cell reaction (Fig. 5 a, d). In three cases fibrous material was infiltrated with fibrous osteoid. The peripheral regions were connected to partially reconstructed bony structures. Hemosiderin plaques were evident in various concentrations (Fig. 5 c, e). Figure 5 f exhibits a cystic structure with an area of central resorption and peripheral osteoid and fibrous bone formation. Figure 5 c demonstrates an area of sparse neo-vascularization in the wall near the neutral triangle. In that area, a common histologic pattern of the remodelling process that normally follows local bleeding or thrombosis is evident. The bone remodelling shows
222
Fuß & Sprunggelenk, Band 2, Heft 4 (2004) © Steinkopff Verlag 2004
Abb. 5 Microscopic slices at 60X enlargement after decalcification, parafin fixation and staining (H/E). Cholesterol plaques are visible (a, d). In the periphery, regions of bone remodelling with fibrous bone, osteoid formations, and mineralized bone (b, d) are visible. Hemosiderin plaques are evident in varying concentrations (c, e). A cyst formation (central resorption zone, peripherel osteoid and fibrous bone formation is shown in f. The neovascularization of the wall-adjacent areas is shown in c
no evidence of lamellar or well-mineralized bone; instead it displays undeveloped fibrous bone without an amorphous extracellular matrix. The cystic fluid consists of serum-like components, but with an approximately ten-fold concentration of alkaline phosphatase.
Discussion Our described findings of calcaneal cysts agree with those listed in the literature [15, 22, 25, 28–30]. Interestingly, it is extremely rare to find bilateral calcaneal cysts. Clinically, the cysts remain silent. Approximately 60 calcaneal cysts have been histologically diagnosed in the literature. All demonstrate an inner fibrous content, and most show hemosiderin and cholesterol plaques. There is in-bleeding and a serous cystic fluid. Until now, there has been no suf-
ficient explanation of the pathogenesis of these cysts. The analysis of the biomechanical properties and the intraosseus vessel configuration of healthy bone and the histomorphologic findings of the calcaneal cysts show four characteristics: n The cysts are found almost exclusively in the projection of the normal calcaneal bone in the spongiosa-free neutral triangle inferior to the dorsal facet. n This area is the major entry point for both medial and lateral blood vessels (Figs. 6, 7) [2–5]. n Normally, this region is vital for blood circulation to both the anterior and posterior aspects of the calcaneus (Fig. 6). n On histologic examination, the cyst wall shows osteogenic metaplasia compared to neighboring trabecular and fibrous bone, with hemosiderin and cholesterol plaques. This type of fibrous tissue is also present in organized hematomas [11, 13].
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223
Abb. 6 The region without spongy bone is the conduction area of the lateral and medial intraosseous vessel supplies
Through the combined clinical, histopathologic, and anatomic findings, particularly the new description of calcaneal blood vessel anatomy, the following conclusions about the etiology of solitary calcaneal cysts can be made: The development of a cyst in this area is secondary to a disturbance in local intraosseous blood circulation. This would initially be caused by bleeding (hematoma). The argument against a local thrombosis or microembolic event is the fact that the cyst is always centrally located, in an area supplied by both lateral and medial blood vessels. Because the intraosseous blood vessel anatomy shows equal supply bilaterally, a bilateral local occlusion must occur to engender a centralized cyst. The hematoma theory of bone cyst formation was initially postulated in 1919 by Pommer and later by Jaffe and Lichtenstein (1942) [17, 24]. Due to the special biomechanical properties at the location of the neutral triangle of the calcaneus, remodelling does not result in construction of lamellar bone. According to Kummer (1965) [19, 20] and Frost (1990) [14], the effects of
Abb. 8 Drawn (left) and densiometric (right) pictures of the pressure (continuous line) and tension (broken line) trajectories in a 2-dimensional tension-optical model of the calcaneus, which is moved by pulling the triceps surae muscle, applying hindfoot pressure, and stressing the plantar aponeurosis, cuboidal and talar bones
Abb. 7 The intraosseous arterial supply comes from medial and lateral incoming branches of the tibialis posterior artery, as well as a lateral anastomosis of the fibular artery and the dorsalis pedis artery in the region of the neutral triangle
pressure and tension are the major physical stimuli for osseous remodeling. Sim (1990) [27] demonstrated that the sclerotic cyst wall provides enough stability for normal weight-bearing activities. However, this stability is not enough for eccentric and/or high-performance loading, and fractures may develop as a consequence. Most early authors advocated surgical curettage and bone grafting as the treatment of choice for simple bone cysts [7, 8, 23]. An asymptomatic static residual defect may occur following surgical curettage and packing, but it should not be considered a reflection of success and has been classified as
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healed, with reports that most disappeared within 7 years following surgery [8]. In the late 1970s, the popularity of a surgical approach to the simple bone cyst began to give way to an alternative non-operative approach when Scaglietti et al. reported 90% favorable results with methylprednisone acetate injections [26]. Other authors were able to confirm these results in cases of calcaneal cysts [12]. Our experience highlights the risks of fracture to a normally asymptomatic bone cyst in the context of athletic activities. In cases of young, athletic patients with complaints of progressive pain, we recommend a
surgical procedure for both stabilization and psychological security. We recommend cortisone injection as therapy for patients with an incidental finding of a solitary calcaneal cyst or for patients with contraindications to operative management. Due to the special anatomic position in the neutral triangle of the calcaneus, the use of a bone growth protein (BMP 7) appears to be useful, because normal bone remodelling processes are less effective. n Acknowledgement Translation by Sarah Hamilton, MD.
References 1. Andermahr J (1999) Anatomie des Rückfußes unter Berücksichtigung der Gefäßsituation bei operativen Maßnahmen. In: Moorahrend U (ed) Funktionelle Behandlung ausgesuchter Verletzungen der unteren Extremität-Grenzen, Möglichkeiten und Konzepte. Sympomed, München Taufkirchen, pp 11–17 2. Andermahr J, Helling H, Mader K, Koebke J, Rehm K (1997) Die Blutversorgung von Talus und Calcaneus. Hefte zu Der Unfallchirurg 268:110– 114 3. Andermahr J, Helling HJ, Landwehr P, Fischbach R, Koebke J, Rehm KE (1998) The lateral calcaneal artery. Surg Radiol Anat 20:419–423 4. Andermahr J, Helling HJ, Rehm KE, Koebke Z (1999) The vascularization of the os calcaneum and the clinical consequences. Clin Orthop 363:212– 218 5. Andermahr J, Notermans H, Helling H, Rehm K, Koebke J (1997) Umsetzung einer klinischen Fragestellung in eine präparatorische Untersuchung am Beispiel; Fersenbeinfraktur. Der Präparator 43:1–5 6. Andermahr J, Zähringer M, Helling H, Krug K, Koebke J, Rehm K (2002) Surgical Aspects of the Hindfoot MR Anatomy. Foot Ankle Surg 8:1–7 7. Baker DM (1970) Benign unicameral bone cyst. A study of forty-five cases with long-term follow up. Clin Orthop 71:140–151 8. Boseker EH, Bickel WH, Dahlin DC (1968) A clinicopathologic study of simple unicameral bone cysts. Surg Gynecol Obstet 127:550–560 9. Chigira M, Watanabe H, Arita S, Udagawa E (1983) Simple bone cyst– pathophysiology and treatment. Nippon Seikeigeka Gakkai Zasshi 57:759– 766
10. Cohen J (1960) Simple bone cysts. Studies of cyst fluid in six cases with a theory of pathogenesis. Am J Orthop 42-A:609–616 11. Dota T, Nakamura K, Saheki M, Sasaki Y (1963) Cholesterol granuloma. Ann Otol 72:346–356 12. Frankel SL, Chioros PG, Sidlow CJ (1988) Steroid injection of a unicameral bone cyst of the calcaneus: literature review and two case reports. J Foot Surg 27:60–65 13. Friedmann I (1959) Epidermoid cholesteatoma and cholesterol granuloma; experimental and human. Ann Otol Rhinol Laryngol 68:57–79 14. Frost HM (1990) Skeletal structural adaptations to mechanical usage (SATMU): 4. Mechanical influences on intact fibrous tissues. Anat Rec 226:433–439 15. Gebhart M, Blaimont P (1996) Contribution to the vascular origin of the unicameral bone cyst. Acta Orthop Belg 62:137–143 16. Grumbine NA, Clark GD (1986) Unicameral bone cyst in the calcaneus with pathologic fracture. A literature review and case report. J Am Podiatr Med Assoc 76:96–99 17. Jaffé H, Lichtenstein L (1942) Solitary unicameral bone cyst. With emphasis on the roentgen picture, the pathologic appearance and the pathogenesis. Arch Surg 44:1004–1025 18. Koebke J (1999) Beanspruchung und funktionelle Morphologie des Rückfußes. In: Moorahrend U (ed) Funktionelle Behandlung ausgesuchter Verletzungen der unteren ExtremitätGrenzen, Möglichkeiten und Konzepte. sympomed, München Taufkirchen, pp 18–25 19. Kummer B (1979) Biomechanics of the calcaneus. Z Orthop Ihre Grenzgeb 117:551–556
20. Kummer B (1965) Development and variations of long bone forms with special reference to mechanical influences. Arkh Anat Gistol Embriol 49:21–29 21. Mirra JM, Bernard GW, Bullough PG, Johnston W, Mink G (1978) Cementum-like bone production in solitary bone cysts. (so-called „cementoma“ of long bones). Report of three cases. Electron microscopic observations supporting a synovial origin to the simple bone cyst. Clin Orthop 135: 295–307 22. Moreau G, Letts M (1994) Unicameral bone cyst of the calcaneus in children. J Pediatr Orthop 14:101–104 23. Neer CS, Francis KC, Johnston AD, Kiernan HA, Jr (1973) Current concepts on the treatment of solitary unicameral bone cyst. Clin Orthop 97:40–51 24. Pommer G (1919) Zur Kenntnis der progressiven Hämatom- und Phlegmasieveränderungen der Röhrenknochen auf Grund der mikroskopischen Befunde im neuen Knochenzystenfall. Arch orthop Unfall-Chir 17:17–69 25. Sandomenico F, Cappabianca S, Iovino M, Conforti R, Cinque T, Del Vecchio W (1996) Aneurysmal bone cyst: diagnostic role of computerized tomography and magnetic resonance. Radiol Med (Torino) 92:525–529 26. 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 61B:200–204 27. Sim E, Haid C (1990) Unicameral cyst of the calcaneus: surgical indications, biomechanical calculations and results of follow-up studies. Z Orthop Ihre Grenzgeb 128:623–631
J. Andermahr et al. Pathogenisis of calcaneal cysts 28. Simon WH, Mayer DP, Schmidt RG, Brooks ML, Mitchell EI, Schwamm HA (1990) Magnetic resonance imaging of calcaneal aneurysmal bone cyst. J Foot Surg 29:448–451
29. Smith SB, Shane HS (1994) Simple bone cyst of the calcaneus. A case report and literature review. J Am Podiatr Med Assoc 84:127–130
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30. Van Linthoudt D, Lagier R (1978) Calcaneal cysts. A radiological and anatomico-pathological study. Acta Orthop Scand 49:310–316