## 1 Introduction  
Solitary enchondromas are benign bone tumors arising from the persisting cartilaginous cells from the growth plate. They are located in the hand bones in more than 50% of cases [1]. The incidence of this pathology is frequently underestimated because, in many cases, the enchondroma evolves in the absence of any symptoms. The diagnosis of the enchondroma is established frequently by an accidental X-ray or due to local pain, swelling or a pathological fracture. The radiographs show a well-defined lytic lesion, which usually does not affect the bone cortex or soft tissues, with or without calcification [2]. [PERSON] developed probably, the most reliable radiological classification with type A--central; type B--eccentric; type C--associated; type D--polycentric and type E--giant form [3]. Treatment of benign tumors of the hand bones, including enchondroma, consists of tumor curettage or curettage and filling of the remaining cavity with autologous bone or bone substitute [4]. Although the use of autologous bone is the gold standard for the treatment of bone defects, to avoid complications and morbidity at the donor sites, bone substitutes are increasingly used. In cases of bone defects of the hand, the most common sites used for cancellous bone harvesting are the distal radius or olecranon of the ulna. These sites usually offer enough cancellous bone for the defects in carpal bones, metacarpals and phalanges and are preferred because they are present in the same operation field and under the same regional anesthesia [5; 6]. Initially, bone substitutes were rarely used in the treatment of hand bone defects, but currently, an increasing number of studies report their results for this pathology [7]. An effective bone substitute is a synthetic or natural material that promotes bone healing by at least one of the following properties: osteogenesis, osteoinduction or osteoconduction [8; 9]. The biological mechanisms of the various types of bone substitutes vary due to their different composition and mechanical strength. Hydroxyapatite and tricalcium phosphate are bone substitutes whose use and efficacy have been reported in the literature. Other relatively new techniques of bone bioengineering are those that involve biological components such as mesenchymal stem cells, platelet-rich plasma, platelet-rich fibrin, bone morphogenetic proteins, deantigenated heterologous bone matrix or their association with ceramics [10; 11]. These substitutes are available in different forms, such as pellets, granules or fluids [12; 13]. Regarding the use of bone graft or solid bone substitutes, the surgeon must adjust the shape of the implant to that of the bone defect. This process results in bone loss, additional trauma and prolonged operating time. In contrast, chitosan-based injectable bone substitutes are easy to handle and ensure complete filling of the defect [14]. k-IBS\({}^{\circledR}\) is a fully resolvable injectable substituent that comes in prefilled, ease-to-use syringes. It contains rapidly oseointegrable ceramic granules due to its components: Hydroxyapatite (HA) (Ca\({}_{10}\) (PO\({}_{4}\))\({}_{6}\) (OH)\({}_{2}\)) and \(\beta\)-TCTolcium Phosphate (\(\beta\)-TCP) (Ca\({}_{3}\) (PO\({}_{4}\))\({}_{2}\)). The granules are disseminated in a liquid polymeric matrix consisting of chitosan (((C\({}_{6}\)H\({}_{11}\)O\({}_{4}\)N)\({}_{n}\)) and polyethylene glycol ((C\({}_{2}\)H\({}_{4}\)O)\({}_{n}\) H\({}_{2}\)O). The HA/\(\beta\)-TCP ratio is 3/1 in the k-IBS\({}^{\circledR}\) bone substitute, and the ceramic granule dimensions are between 125 and 355 \(\mu\)m [15]. The HA/\(\beta\)-TCP ratio in the composition of ceramics seems to be a good indicator of new bone formation, according to recent studies. The ceramics that have 100% HA or those with 75% HA and 25% \(\beta\)-TCP showed the best results in terms of new bone formation and resorbability in vivo [16].