Original article 180

Operative Treatment of Solitary Bone Cysts with Tricalcium Phosphate Ceramic. A 1 to 7 Year Follow-Up S. Altennatt, .11. eh ,öbel,]. P. PocllOn L'ni\'ersity Childrens Hospital Zurich, Switzerland

From 198-l to 1990 ,,'e treated 18 patienls aged .5 to 15 112 years with olitary bone eysls of the humerus, the femur and the ealeaneus. To fill the defeet, tricalcium phosphate (TCP) instead of bone grafling was used. Thc clinieal and radiologieal long-term resulls up to se,'en years postoperatiyely are reported. In 16 patienls TCP "'as weIl ineorporated without any adyerse reaetion to the synthetie material. T,,'o patienls with a reeurrenee of lhe bone eyst "'ere sueeessfully reoperated. \\'e conclude that eeramies are a eheap and easy available substitute for bone grafls in the treatment of solitary bone eysls. Key words Solitary bone eyst- Tricalcium phosphate

Resume ----C'est en 1984 que nous avon utilise pour la premiere fois la ceramique de tricalciumphosphate a la place du ti su osseux spongieux pour le lraitement des kystes osseuxjuveniles.Ju qu'en 1990, 18patienlsenlre5an et15 ans et demi ont ete traite dans nolre clinique avec ce materiel synthetique. Nous avons verifie les resultals 1 a 7 ans apres l'operation. Quatorze d'enlre eux presentaient des resultats lres satisfaisants. Deux cas avec recidive du kyste ont ete reoperes avec succes. Chez deux aulres patients avec grand ky te du col du femur le resultat n'etait pas sati faisant. Ils presentaient deja avant l'operation du kyste une mauvaise position du col du femur dGe au lraitement conservati! de la fracture. Cette mauvaise po ition du col du femur a necessite une correction operatoire apres la guerison du

Introducüon Solitary bone cysts are benign tumor-like lesion and were first described by \'ireho71! in 18i6. They usually oeellr in the proximal metaphysis and diaphysis of the femur Hecei\ed '\o\ember 29, 199 I r~ur I Pediatr Surg 2 (1992) 180-182 © Hippokrate, \ erlag Stuttgart \\asson Edileur Paris

kyste. Dans tous les eas le tricalcium phosphate a ete bien ineOt'pore, aucune infeetion ni fraeture eeondaire n'ont ete oben'ee .

~\ols-cles

Kyste osseux jU"enile - Tricalcium phosphate

Zusammenfassung Die operative Behandlung jU\'eniler Knochenzysten mit autologer Spongiosa und heterologer Spongiosa wurde an unserer Klinik 198-l ,'erlassen und durch die Knoehenersatzpla tik mit Trikalziumpho phat-Keramik (TCP) ersetzt. Seither wurden 18 Patienten im Alter von 5 bi 15 112 Jahren mit TCP behandelt. Wir berichten nun über die Resultate der klinischen und radiologischen NachkontrolIen 1-7 Jahre nach der chirurgi ehen ErsUherapie. Bei 14 Patienten erreichten wir primär, bei zwei Patienten mit Rezidiv erst nach einer zweiten Operation ein gute Resultat. Bei zwei Patienten mit großen Zysten und einer pathologischen Schenkelhalsfraktur bestand schon präoperativ eine Fehlstellung im Bereich des Hüftgelenkes, welche eine spätere orthopädische Korrektur nötig machte. Bei allen Patienten wurde TCP gut eingebaut, Infekte oder Refrakturen traten keine auf.

Schlüsselwörter Ju,'enile Knochenzy te - Tricalciumphosphat-Keramik

and humerus of ehildren and adoleseenls. Other loeations are rare. The eyst does not damage the growth plate but destroys the eortiealis by osteoclastie aeti\'ily in the \\'all of the eyst and may therefore eause pathologie fraetures of the bone.

ja.fJe and Liehtellsteill (2) distinguished between acli,'e and latent forms of solitary bone ey ts and Seer (3) modified this elassification in 1966. He eonsidered eysls reaching doser than 0.5 cm to lhe gro,\th plate as aetiye and eysls of other loeations as inaetiw.

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Summar~y__

Eur J Pediatr Surg 2 (1992)

operative Treatment ofSolitary Bone Cysts with Tricalcium Phosphate Ceramic, A I to 7 Year Follow-L'p

181

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.\\aterials and melhods The ;tudy consists of 21 patients in \\ hom a solitary bone cyst was diagnosed beb\ een June IllR land December 11l90, One patient \\ a' operated later in another hO'ipital and in t\\O patients the cy t healed ,pontaneou'il.\, The 18 surgieall~ treated patient-, \\ere fol lo\\'ed up at regular intel'\'al, in our out patient c1inic and radiographie in\'estigatlon'i ha\'e been undeliaken up 10 'ie\'en year, after the fir;t operation. The TCI' used in all patients \\'as in the form üf gran ule \\ith 1 I tü 2,8 mm grain size and a poro,ity of 60 %. .\fter opening the bone m,IITO\\ channel lea\ing a lid of the eorticalis intact the cyst was curetted and the defeet \\as packed \\ ith TCP. Hadiographs \\ erl' laken to l'CH1firm the complete filling of the eyst and the eOliicalis lid placed o\el the bone defeel. ,\11 pathologie fraetures \\ere operated after the fraeturl' had healed, I'o,tüperati\ely the upper extremit,\' \\as immo bilized for foul' \\eeks anel the 10\\ er extremit~, for six to eight \\ eeks,

Resulls Foul' of our patients \\ere girls and 1 I bo~'s, In 8 paLients the cyst was localised in the proximal humerus. in 9 in the proximal femur and in one girlthe bone cyst was found in the calcaneus, Fi\'e cysts ha\'e been c1assified as acti\e and 12 as inacti\'e, The a\erage age of our patients was 9 1/2 years \\-ith a range from 5 to 15 1/2 years, A pathological fraeture was found in 13 patients while 4 patients present-

ed with pain without \·i ihle bone fracture, In one boy the solitary bone cy t wa detected incidentaJly,

Cysts ofthe humerus Three cysts of the proximal humerus \\ere considered acti\'e and 5 inactive (Table I), All 5 patients with an inacti\-e cyst and 2 of the 3 patients with an aclive cyst sho\\ed an uneventful recoveryand follow-up 1 to 5 years after the operation (Fig. I). In these cases the radiographic examination remained stable without any signs of ad\'erse reaetions to TCP such a increa e of the radiolucent line around the implant or bone sclerosis, One patient ha\'ing an acti\'e eyst of the proxi mal humerus had a local reeurrence that was seen at the radiographie e\'aluation one year after the implantation of TCP, He \\as reoperated and the fU/iher eour;e \\as une\'entful.

Cysts o.rtlze .{emur In the proximal femur 2 aeti\'e and , inaeti\'e bone l'Y'its \\'ere found (fable 2), In 6 of thc II patients the postoperali\'l' course \\'a5 une\'entful and the radiographie eontrol UJl to , ,\-ear, ,ho\\ed an adequately filled bone defeet anrlthe implant ,till in plaee, By radiographie e\aluation one year po'toperati\'eh a reeurrenee \\a, found in a 1Cl ~'ear-old bo,\ \\ith an inaet 1\ e e~''it of the neek of the femur, The patient \\as reoperated sueeessfull,\ In t\\ 0 other patient'> \\ ith pathologie frad ures of the neek of the femur due to a solitary bone e,\sl. an 8-yearold girl \\ ith an aeti\e e~''it and a 15 year,old boy \\ ith an inaeti\'e eyst. \\ e considered the primary resultto be insuffieienl. During immobili;ation für fraeturc healing prior to the operation the neek üf the femur shol'tened in both patients and in the girl a paliial necro;i; of the head of the femur oe eurred postoperati\'ely, In both patients a seeond operation \\'as neee; sar~'to correetthe limb length and the hip angle,

Other localizatiolls In a 15-year-old girl \\e found a solitary bone cyst of the calcaneus. ( years after filling the cyst with TCP the functional and radiological result \\'as excellent (Fig, 2), In the postoperati\'e period we ne\'er sa\\ anyad\'erse reactions to TCP or \\ound heaIing disturbances. Satisfaeto~' filling of the bone defect was achie\'ed in 16 of the 18 palients (89 %), To a\'oid a second pathologie fraeture we reoperated two adoIeseents with reeurrence of the bone cyst diagnosed in the conlrol x-ray taken olle year after the first operalion, The further course in these patients was une\'ent fu!.

Tabte 1

Solltary bone eys s of the humerus Actlve forms

n (pa len s) Age (years) Postop follow-up (years) Recurrence

Table 2

Inac Ive forms

3

5

5-12 (mean 8 1 4) 2 1 2-5(mean3 1/2) 1

6-12' 2 (mean 9" 4) 1-5 (mean 2 1 '2)

Soli ary bone ysts

0 1 'he

'eil' cJr

AI t ve torms

r pa' en's Age ,ea's

o

Ina' I\e

rlllS

7 5,

_5" 8 :-7 "lean3 1 1 ~ea

Fig, 1 nactlve solitary bone cyst of the humerus of a lO-year,old giri be ore (a and 5 years after (b) Implantation cf TCP

P')S~op ; I h ,up years, Recurrellre Reop unrelated to TCP

2

o 1

L

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Prior to 1984 symptomatic olitary bane cy ts \rere filled with autogenic or heterogenic bane after resection and curettage of the tumor. After ha\;ng undertaken experimental studies in rats (6) we used tricaJcium pho phate (TCP) a an alternative to bane grafts for the first time in 1984 and inee then this synthetic material was used on all our palients, After having reporled our short-term results in 1986 (7) we now analyze the late results up to 7 years after the first operation,

Eur J Pediatr Surg 2 (1992)

S. Altermatt et al

tory although the TCP was ineorporated in the host bone. Both ehildren had first a eonservative management of their fraeture foIlowed by TCP-grafting 4-6 weeks after the pathologie frac: ture had oceurred. The neek of the femur was shortened and a varisation was evident. After this experienee we operate instable pathologie fraetures of the neek of the femur very early and we stabilise the femur if neeessary with pins 01' angle blade plates.

Fig. 2 7 years after Implantation 01 TCP. The material IS perleetly Ineorporated. There are no slgns 01 biodegradatIon.

We eonelude that TCP is an eeonomie and easiIy available substitute for aIlogenie 01' xenogenie bone grafts with a low reeurrence rate. It can be easily used in combination with internal fixation and its mechanieal strength is eomparable to that of the own bone. If at all, biodegradation oeeu rs very late after more than seven years. Further radiographie studies are neeessary to assess the degree of biodegradation in the long run.

Acknowledgement Longitudinal bone growt.h \\'as disturbed in two patients \\'ith pat.hologie fractures of the neck of the femur. In one of these patients the blood flow to the head of the femur was also compromised. These complications were the result of the primary pathologie fracture and not of the implantat.ion of TCP. The x-ra)' cont.rol one year after the operation showed the cyst fi11ed adequately with no signs of a recurrence of the cyst. Discussion Porous TCP eompares weIl with other bone substitutes sueh as aIlografts 01' xenografts (1, 3,4, 5). In our series of 18 patients, TCP was perfeetly ineorporated in the host bone of 16 ehildren and adoleseents and only two reeurrenees (11 %) oeeurred. After the implantation of the material we never saw a pathologieal fraeture, whieh proves the meehanieal strength of TCP. The synthetie material is available as porous bloek 01' as granules. We ehose the form of granules exelusively beeause we feel that the granules ean be paeked eloser and the osteoblasts may surround the granules more rapidly. Ceramics as TCP and Hydroxyapatite (8) have demonstrated osteoeonduetive qualities. In histologie studies (6, 8) there is evidenee of bone regeneration around and within the implanted eeramies within 12 months. In our first publication we postulated a eertain amount of biodegradation of TCP, but even 7 years after implantation the radiographie evaluation showed no evidenee of biodegradation. The TCP, perfeetly ineorporated in the host bone, is still in its plaee. In two patients, both with a large bone eyst of the neek of the femur, the postoperative results were unsatisfae-

We would thank Dr. U. IVilli, Institute of Radiology, for permitting us to publish Figures 1 and 2.

References

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Dr. S. Altennatt

Chirurgische Klinik Universitäts-Kinderspi tal CH-8032 Zürich

Operative treatment of solitary bone cysts with tricalcium phosphate ceramic. A 1 to 7 year follow-up.

From 1984 to 1990 we treated 18 patients aged 5 to 15 1/2 years with solitary bone cysts of the humerus, the femur and the calcaneus. To fill the defe...
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