Bone versus soft tissue hydatid disease: a retrospective comparative cohort study

Abstract

Background

Musculoskeletal hydatid disease is uncommon and often mimics neoplastic lesions. Comparative evidence between bone and soft tissue involvement remains limited. We aimed to compare demographic characteristics, laboratory parameters and surgical outcomes between bone and soft tissue hydatid disease in an endemic region.

Methods

We retrospectively reviewed 64 consecutive patients who underwent surgery for histopathologically confirmed musculoskeletal hydatid disease between January 2010 and January 2024 (bone, n = 26; soft tissue, n = 38). Groups were compared regarding demographics, presenting symptoms, inflammatory indices White Blood Cell Count (WBC), Erythrocyte Sedimentation Rate (ESR), and C-Reactive Protein (CRP), Eosinophil count, Eosinophil-to-Lymphocyte Ratio (ELR), hemagglutination test, cyst morphology (uni- vs. multilocular), complications, concomitant liver/lung involvement, and recurrence. Appropriate parametric/non-parametric and categorical tests were used.

Results

Demographic characteristics and baseline WBC/ESR/CRP and hemagglutination positivity did not differ between groups. Bone involvement presented predominantly with pain (22/26, 84.6%), whereas soft tissue disease frequently presented with isolated swelling (20/38, 52.6%) (p = 0.001). Eosinophil count (2.00 ± 1.26 vs. 0.89 ± 0.68; p = 0.013) and ELR (0.23 ± 0.13 vs. 0.12 ± 0.08; p = 0.014) were significantly higher in bone disease. Bone involvement had higher rates of intraoperative rupture (20/26, 76.9% vs. 10/38, 26.3%; p = 0.005), concomitant organ involvement (14/26, 53.8% vs. 8/38, 21.1%; p = 0.045), and recurrence (20/26, 76.9% vs. 8/38, 21.1%; p = 0.002). Multiloculated morphology was more frequent in soft tissue lesions (30/38, 78.9% vs. 10/26, 38.5%; p = 0.005). Among the cases treated for bone hydatid cysts, recurrence was observed in 20 out of 26 patients, while anaphylaxis occurred in 15 out of 26 patients during surgery. In contrast, among 38 patients who underwent surgery for soft tissue hydatid cysts, recurrence was observed in 8 (p = 0.002) and anaphylaxis developed in 7 during surgery (p = 0.041).

Conclusions

Bone hydatid disease demonstrates a more aggressive clinical course than soft tissue disease, with substantially higher rupture, recurrence, and concomitant organ involvement rates. Elevated eosinophil count and ELR at presentation may support the suspicion of bone involvement. Future prospective studies incorporating multivariable modeling are warranted to identify independent predictors of recurrence.

Introduction

Hydatid disease is a zoonotic parasitic infection caused by Echinococcus species and remains a significant public health problem in endemic areas worldwide [1]. Humans most often become accidental intermediate hosts through contact with infected dogs or by ingesting parasite eggs via contaminated food and water [2]. The disease predominantly affects the liver and lungs; however, musculoskeletal involvement is rare and accounts for only a small fraction of all reported cases [3–5].

Musculoskeletal hydatid disease represent uncommon and diagnostically challenging manifestations [6]. Osseous involvement is characterized by infiltrative growth, delayed diagnosis, and high recurrence rates, whereas soft tissue lesions are generally more localized and amenable to surgical treatment [7]. The more aggressive behaviour of osseous hydatid disease is attributable to several biological and anatomical factors: bone lacks a well-defined fibrous pericyst, allowing the parasite to expand along the path of least resistance through the Haversian canals and medullary cavity; cortical rigidity prevents the containment that surrounding soft tissues can provide; and intramedullary pressure fluctuations may facilitate haematogenous spread to distant organs [8]. These features make complete surgical eradication difficult and predispose to intraoperative cyst rupture, dissemination, and high recurrence rates. Due to non-specific clinical and radiological findings, it can be confused with neoplasia, which often leads to misdiagnosis of the lesions and consequently delayed or inappropriate treatment [9].

Early and accurate diagnosis of musculoskeletal hydatid disease remains difficult. Imaging modalities such as magnetic resonance imaging and computed tomography are useful for lesion characterization but lack sufficient specificity [10]. Therefore, closed core needle biopsy can be diagnostically beneficial, especially in patients with bone hydatid cysts [11]. Serological tests and routine laboratory parameters, including inflammatory and eosinophilic markers, may provide supportive diagnostic information; however, their clinical utility in differentiating bone and soft tissue involvement has not been clearly established [12, 13].

In regions where echinococcosis is endemic, musculoskeletal involvement appears more frequently than reported in the literature, underscoring the need for region-specific clinical data. Despite this, most available studies consist of isolated case reports or small case series [14, 15]. To the best of our knowledge, comparative analyses of demographic characteristics, laboratory findings, surgical outcomes, and recurrence patterns between these two forms of musculoskeletal hydatid disease are limited in the literature. Therefore, the present retrospective cohort study aimed to compare the clinical characteristics, laboratory parameters, and surgical outcomes of patients with bone and soft tissue hydatid disease. By evaluating potential differences in disease behavior, recurrence rates, and diagnostic markers, this study seeks to improve diagnostic accuracy and optimize treatment strategies for these rare but challenging manifestations of echinococcosis.

Materials and methods

Study design and patient selection

This study was designed as a retrospective cohort study and was conducted after obtaining approval from the local institutional ethics committee. All patients were informed in detail about the study procedures prior to enrollment. Written informed consent was obtained from all participants and, when applicable, from their parents or legal guardians. Patients with extremity involvement whose radiological, clinical and demographic findings were available in the hospital automation system were included in the study. Patients with a follow-up period shorter than 18 months were excluded from the study to monitor the possibility of recurrence and potential additional complications, and to ensure data consistency. In our study, we aimed to compare hydatid cyst cases in soft tissue and appendicular skeletal bones; therefore, we excluded hydatid cyst cases involving the axial skeleton, including the spine, ribs, and skull bones. Patients were divided into two groups according to the involvement type (bone or soft tissue). The groups were compared in terms of age, sex, body mass index (BMI), smoking status, comorbidities, living environment (rural vs. urban), and livestock exposure. Radiological and clinical variables, including cyst morphology on magnetic resonance imaging (MRI), lesion location (upper vs. lower extremity), postoperative wound complications, recurrence, intraoperative cyst rupture, intraoperative anaphylactic reaction and concomitant organ involvement, were also compared between the two groups. By “concomitant organ involvement,” we mean when the hydatid cyst is detected in another part of the body, such as the liver or lungs, in addition to its original location.

Laboratory parameters — WBC (×10⁹/L), ESR (mm/h), CRP (mg/L), eosinophil count (×10⁹/L), ELR, and hemagglutination test results — were obtained from the first available blood sample recorded at the time of initial clinical presentation to our institution, prior to any surgical intervention or antiparasitic treatment. The ELR was calculated as the ratio of the absolute eosinophil count to the absolute lymphocyte count, both derived from the same complete blood count sample. These parameters were analyzed for their potential value in distinguishing between the two groups. Only histopathologically confirmed cases that underwent surgery were included; therefore, clinically diagnosed patients managed conservatively are not represented in this cohort, which is acknowledged as a source of selection bias. Recurrence management was performed using ultrasound for soft tissues and direct radiography for bone. MRI and CT (Computed Tomography) scans were used when necessary.

Surgical procedure

Preoperative diagnosis was established based on clinical presentation, radiological findings, serological tests, and multidisciplinary evaluation. Preoperative biopsy was not routinely performed because of the risk of cyst rupture, dissemination, and anaphylactic reaction. However, biopsy was considered selectively in cases with atypical imaging findings or when differentiation from neoplastic lesions remained uncertain.

Because osseous hydatid disease may closely mimic primary bone tumors or metastatic lesions, preoperative core needle biopsy was performed in 7 of the 26 (26.9%) patients with bone involvement when the diagnosis remained uncertain after clinical, radiological, and multidisciplinary evaluation. All patients who underwent biopsy were diagnosed with hydatid cyst. Biopsy-related anaphylaxis occurred in two patients, and soft tissue dissemination was observed in one patient. Although soft tissue hydatid cysts can be confused with soft tissue sarcomas, biopsy was not required in either case because the mass was extensively resected during treatment. The diagnosis was considered sufficiently supported by clinical, radiological, and multidisciplinary assessment, and the lesions were therefore managed with wide surgical excision. Definitive diagnosis was confirmed histopathologically in all cases.

In patients with soft tissue hydatid cysts, surgical intervention was performed with meticulous care because of the fragile nature of the cyst wall and the associated risk of rupture-induced anaphylaxis. Careful dissection was undertaken to separate the cyst from the surrounding tissues while preserving cyst integrity whenever possible. Wide excision was attempted according to the lesion margins identified on preoperative magnetic resonance imaging (MRI) (Figs. 1 and 2). All procedures were conducted using a standardized surgical protocol. In cases of intraoperative cyst rupture, immediate irrigation with 20% hypertonic saline (NaCl) and povidone–iodine solution was performed, followed by extensive lavage.

Fig. 1.

Coronal T2-weighted MRI demonstrates a predominantly hyperintense intramuscular lesion with a multiloculated, multi-compartmental configuration, findings highly suggestive of hydatid disease involving the deltoid muscle

Fig. 2.

A representative case of a multiloculated intramuscular hydatid cyst involving the deltoid muscle following surgical excision

The extent of bone involvement was preoperatively evaluated using MRI and computed tomography (CT). Following soft tissue dissection, sterile gauze pads soaked in 20% hypertonic saline were placed between the affected bone and adjacent soft tissues to minimize contamination. An oval cortical window corresponding to the lesion size was then created to access the cyst cavity (Figs. 3 and 4). Thorough curettage was subsequently performed, and the cystic and intramedullary contents were carefully removed using curettes while avoiding dissemination into the surrounding bone or soft tissues. The intramedullary cavity was then treated with 20% hypertonic saline, followed by sequential irrigation with povidone–iodine and normal saline. The excised cortical window was similarly decontaminated by immersion in 20% hypertonic saline and povidone–iodine solution, followed by copious saline irrigation before replacement. In cases with extensive bone defects or marked cortical thinning, additional stabilization with plate-and-screw fixation was performed. Cement augmentation was not routinely used as a first-line treatment; however, it was considered in recurrent cases to reduce the risk of further recurrence. Prosthetic reconstruction represented another treatment option for periarticular lesions associated with substantial bone loss. In selected patients with localized disease, en bloc resection was also considered.

Fig. 3.

Coronal T1-weighted MRI reveals a predominantly hypointense intramedullary lesion with a multiloculated configuration, findings suggestive of osseous hydatid disease

Fig. 4.

Intraoperative view of a multiloculated osseous hydatid cyst following cortical windowing, prior to curettage

All patients received albendazole at a dose of 400 mg twice daily for 3 weeks before surgery or biopsy and for 3 months postoperatively according to the institutional treatment protocol. Due to the retrospective design, long-term treatment adherence and minor side effect data were not always available in detail; however, patients had serum blood counts monitored every 3 weeks. Nevertheless, no serious side effects leading to discontinuation of treatment were identified. There was no clinical or observational difference between the two groups regarding medication use and medication adherence.

Statistical analysis

The normality of continuous variables was assessed using the Shapiro–Wilk test. Normally distributed variables were compared between groups using the Student’s t test, whereas non-normally distributed variables were analyzed using the Mann–Whitney U test. Categorical variables were compared using the chi-square test and Bonferroni correction, when appropriate. All statistical analyses were performed using SPSS software (version 22.0; IBM Corp., Armonk, NY, USA). A p value of < 0.05 was considered statistically significant.

Results

The study included 64 patients who were treated at our institution between January 2010 and January 2024 and had histopathologically confirmed hydatid cyst disease. Of these patients, 26 (40.6%) had bone involvement and 38 (59.4%) had soft tissue involvement. Of the 26 patients with bone hydatid cysts, 8 were located in the femur, 5 in the pelvis, 4 in the humerus, 4 in the tibia, 2 in the radius and ulna, 2 in the metacarpal and metatarsal, and 1 in the fibula. Vertebral involvement was intentionally excluded because spinal hydatid disease represents a distinct clinical entity associated with unique neurological and surgical considerations. Of the 38 patients with soft tissue hydatid cysts, 11 had the cyst in the thigh, 9 in the gluteal region and groin, 8 in the shoulder, 5 in the calf and foot, and 5 in the forearm and hand. The median follow-up duration was 61 months (range: 18– 118 months) in the bone group and 53 months (range: 18–92 months) in the soft tissue group. The difference in median follow-up between groups was not statistically significant (p = 0.21), and both groups met the minimum 18-month follow-up criterion required for recurrence assessment. Recurrence was assessed systematically at each outpatient visit using a standardized surveillance protocol: ultrasound for soft tissue cases and plain radiography for bone cases, supplemented by MRI or CT when clinically indicated.

No statistically significant differences were observed between the two groups in terms of age, sex, body mass index (BMI), smoking status, comorbidities, living environment (rural vs. urban), or livestock exposure (Table 1). Among patients with soft tissue involvement, 20 (52.6%) presented solely with swelling, whereas 22 patients with bone involvement (84.6%) presented exclusively with pain (p = 0.001) (Table 1). Regarding residential status, 16 of 38 patients with soft tissue hydatid disease (42.1%) lived in rural areas, compared with 10 of 26 patients with bone hydatid disease (38.5%); (p = 0.837). Similarly, livestock exposure was reported in 12 of 38 patients with soft tissue hydatid disease (31.6%) and in 8 of 26 patients with bone hydatid disease (30.8%), (p = 0.961).

Table 1.

Demographic and clinical characteristics between soft tissue and bone hydatid disease groups

		Hydatid disease
		Soft tissue (n = 38)	Bone (n = 26)	p value
Age (year)		42,79 ± 11,87	41,46 ± 11,35	0,754
BMI (kg/m2)		25,12 ± 2,16	25,36 ± 2,42	0,765
gender	Female	20 (52,6 )	12 (46,2 )	0,719
	Male	18(47,4 )	14 (53,8 )
cigarette	No	22 (57,9 )	18 (69,2 )	0,513
	Yes	16 (42,1 )	8 (30,8 )
comorbidity	No	28 (73,7 )	20 (76,9 )	0,835
	Yes	10 (26,3 )	6 (23,1 )
Presenting complaint	Pain	8 (21,1 )	22 (84,6 )	0,001*
	Swelling	20 (52,6 )	2 (7,7 )
	Pain and swelling	10 (26,3 )	2 (7,7 )
living environment	Urban	22 (57,9 )	16 (61,5 )	0,837
	Rural	16 (42,1 )	10 (38,5 )
animal husbandry	No	26 (68,4 )	18 (69,2 )	0,961
	Yes	12 (31,6 )	8 (30,8 )

Chi-square and Bonferroni tests were used for the comparison of numerical data. Data are presented as mean ± standard deviation or number (%)

*Statistically significant p-values (p < 0.05) are shown in bold

Laboratory parameters obtained at initial presentation, including WBC, ESR, CRP, eosinophil count, ELR and hemagglutination test results, were compared between the two groups. No significant differences were observed in WBC, ESR, or CRP levels (p > 0.05). However, eosinophil count and ELR were higher in patients with bone involvement( p = 0.013 and p = 0.014 respectively) (Table 2).

Table 2.

Comparison of laboratory parameters between soft tissue and bone hydatid disease groups

	Hydatid disease
	Soft Tissue Hydatid Disease Median (IQR)	Bone Hydatid Disease Median (IQR)	P value
ELR	0,09 (0,06 − 0,14 )	0,23 (0,19 − 0,32 )	0,014*
ESR (mm/h)	14 (9–36 )	35 (11–42 )	0,136
CRP (mg/L)	4,9 (3,5–26,2 )	18,5 (5,6–25,6 )	0,426
WBC (×10⁹/L)	7,8 (6,9–9,9 )	8,5 (7,2–10,5 )	0,505
Eosinophil Count (×10⁹/L)	0,6 (0,4 − 1,6 )	2,1 (0,9 − 3,2 )	0,013*

Quantitative variables are presented as median (interquartile range, IQR). Mann–Whitney U test was used for group comparisons

Abbreviations CRP C-reactive protein, ESR erythrocyte sedimentation rate, WBC white blood cell coun, ELR Eosinophil-to-Lymphocyte Ratio

*Statistically significant p-values (p < 0.05) are shown in bold

In addition, the positivity rates of the hemagglutination test was similar in both groups (p = 0,131) (Table 3). However, recurrence was significantly more frequent in patients with bone involvement (76.9%) than in those with soft tissue involvement (21.1%) (p = 0.002). In the bone group recurrence was observed in 18 out of 20 patients treated with curettage. Moreover recurrence occurred in two of 6 patients eventhough bone resection was made. Also concomitant organ involvement (53.8%) vs. (21.1%) (p = 0.045) and intraoperative cyst rupture (76.9%) vs. (26.3%) (p = 0.005) were significantly more common in the bone hydatid cyst group (Table 3). With respect to cyst morphology, multilocular lesions were more frequently observed in soft tissue hydatid cysts (78.9%) vs. (38.5%), whereas unilocular cysts were more commonly detected in bone lesions. (p = 0.005). The results between the two groups were similar based on postoperative wound complications. (p:0,208) (Table 3). Intraoperative cyst rupture occurred in 7 of 38 soft tissue patients, and one of these patients developed an anaphylactic reaction. In our series, cyst opening was performed in 20 of 26 patients with bone involvement, and anaphylactic reactions occurred in 15 patients (p = 0.041) (Table 3).

Table 3.

Comparison of clinical, laboratory, and radiological characteristics between soft tissue and bone hydatid disease groups

		Hydatid Disease
		Soft Tissue	Bone
		n(%)	n(%)	p value
Cyst morphology	Unilocular	8 (21,1 )	16 (61,5 )	0,019*
	Multilocular	30 (78,9 )	10 (38,5 )
Hemagglutination	Negative	22 (57,9 )	8 (30,8 )	0,131
	Pozitive	16 (42,1 )	18 (69,2 )
Localization	Upper extremity	12 (31,6 )	6 (23,1 )	0,597
	Lower extremity	26 (68,4 )	20 (76,9 )
Recurrence	No	30 (78,9 )	6 (23,1 )	0,002*
	Yes	8 (21,1 )	20 (76,9 )
Concomitant organ involvement	No	30 (78,9 )	12 (46,2 )	0,045*
	Yes	8 (21,1 )	14 (53,8 )
Intraoperative rupture	No	28 (73,7 )	6 (23,1 )	0,005*
	Yes	10 (26,3 )	20 (76,9 )
Postoperative wound complications	No	26 (68,4 )	12 (46,2 )	0,208
	Yes	12 (31,6 )	14 (53,8 )
intraoperative anaphylactic reaction	No	31(81,6)	11(42,3)	0,041*
	Yes	7(18,4)	15 (57,7)

Ki-kare ve Bonferroni were used for the comparison of numerical data

*Statistically significant p-values (p < 0.05) are shown in bold. Data are presented as number (%)

Discussion

Musculoskeletal cyst disease is rarely reported in the literature and is often misdiagnosed as neoplastic lesions [16]. Our study has a relatively large cohort of 64 patients, consisting of 26 bone and 38 soft tissue cyst cases, addressing the limited data available on this parasitic disease, and Our findings contribute meaningful comparative evidence to the limited literature on musculoskeletal hydatid disease and may help inform future diagnostic and therapeutic strategies. To the best of our knowledge, this is the first study to categorize musculoskeletal hydatid cysts into bone and soft-tissue involvement and to compare these two groups with respect to demographic characteristics, clinical features, and laboratory parameters. This approach highlights the novelty and significance of our study and contributes valuable evidence to the existing literature.

No significant differences were identified in baseline demographic and clinical characteristics, including age, sex, body mass index, smoking status, comorbidities, living environment, and livestock exposure, underscoring the comparability of the study cohorts. Nevertheless, consistent with the epidemiological profile of hydatid disease, a higher proportion of patients in both groups resided in rural areas (57.9% in soft tissue involvement and 61.5% in bone involvement). Clinically, a distinct pattern of presentation was observed: bone hydatid disease predominantly manifested with pain, likely reflecting cortical compromise and associated inflammatory processes, whereas soft tissue involvement was chiefly characterized by localized swelling [17–19].

Morphological differences between the two entities were also evident. In agreement with prior reports, soft tissue hydatid cysts were predominantly multiloculated, whereas bone lesions more frequently exhibited a unilocular architecture [20, 21]. This consistent divergence in cyst morphology may reflect fundamental differences in tissue resistance and growth dynamics, and could serve as a valuable adjunct in the differential diagnosis of musculoskeletal hydatid disease.

Inflammatory markers have been extensively investigated in hepatic and pulmonary hydatid disease, and elevated eosinophil count and eosinophil-to-lymphocyte ratio (ELR) have been reported as potential prognostic indicators [12, 13]. Other diagnostic laboratory parameters, particularly hemagglutination tests, have been reported as supportive diagnostic tools in hydatid disease [22]. However, comparative data between bone and soft tissue involvement are limited. In our cohort, no difference was observed in hemagglutination test positivity between the two groups at the time of diagnosis. Also WBC, CRP, ESR leves were similar in both groups. Therefore, although these tests demonstrate diagnostic relevance, they appear insufficient for reliably discriminating between the two groups. This limitation highlights the need for additional complementary parameters to improve the evaluation of musculoskeletal hydatid disease. While no significant differences were observed in hemagglutination and WBC, CRP, and ESR levels, eosinophil count and ELR were significantly higher in patients with bone hydatid disease than in those with soft tissue involvement. Although these parameters are not diagnostic on their own, they may serve as supportive tools in patients presenting with bone pain and radiologically detected osseous lesions.

The role of preoperative biopsy in suspected musculoskeletal hydatid disease remains controversial and warrants specific discussion. In soft tissue lesions with classic imaging morphology (multiloculated cystic mass, absence of solid components, characteristic daughter cysts), supportive serology, and an epidemiologically appropriate background, the clinical diagnosis is sufficiently confident to proceed directly to surgery without biopsy — and this was indeed our approach for all 38 soft tissue patients, none of whom underwent preoperative biopsy [16]. However, osseous hydatid disease presents a more complex diagnostic challenge, as its radiological features — including lytic expansile lesions, cortical thinning, and bone destruction — can closely resemble primary bone tumours such as giant cell tumour or aneurysmal bone cyst, as well as metastatic disease [10, 16]. In such ambiguous cases, tissue sampling may be required to exclude malignancy before committing to a surgical plan. Nevertheless, biopsy of a hydatid cyst carries well-recognised risks, including cyst rupture with secondary dissemination of viable protoscolices, anaphylactic reaction to spillage of antigenic cyst fluid, and seeding along the biopsy tract [11]. For these reasons, biopsy should not be performed routinely and, when considered necessary, should be carried out using image-guided closed core needle technique with appropriate surgical draping and availability of anaphylaxis management. In the present series, preoperative closed core needle biopsy was performed in 7 of the 26 patients with bone hydatid disease (26.9%), exclusively in those where imaging alone could not reliably exclude a neoplastic process; in our study Biopsy-related anaphylactic reactions occurred in two patients, and soft tissue dissemination was observed in one patient.

Due to the frequent infiltrative growth pattern of bone hydatid disease, cyst opening is often unavoidable in non-resected cases, resulting in parasite dissemination, difficulty in achieving clear surgical margins, and an increased risk of recurrence and anaphylaxis [23]. In bone hydatid cysts, the first-line surgical treatment for limb-sparing involves carefully opening the flap in the bone, performing curettage, and then applying antiseptic irrigation. Despite our careful approach during flap opening and curettage, we can still cause micro-spread of cyst contents and parasites. This can lead to anaphylaxis during surgery and subsequently increase the recurrence rate. However, in our patients, we chose to perform only curettage and chemical irrigation as limb-sparing treatment in the first-line treatment. Consistent with these observations, recurrence was more frequent in patients with bone involvement in our study. Soltany et al. reported recurrence in 11 of 15 patients with bone involvement [7]. Similarly, in our cohort, recurrence was detected in 20 of 26 patients with bone hydatid disease. In contrast, Kayaalp et al. reported no recurrence in their series of 22 patients with soft tissue hydatid disease [24], whereas recurrence occurred in 8 of 38 patients (21.1%) of soft tissue hydatid disease in our study. Overall, recurrence was significantly more common in bone involvement than in soft tissue involvement. We remove soft tissue hydatid cysts without opening the cyst, but bone hydatid cysts are opened and curetted. However, in bone tissue, the parasite may not be completely removed during curettage, and if the cyst is opened, the parasites may spread further into the bone cortex and surrounding tissues, which we believe may be the reason for the more frequent recurrence compared to soft tissue cysts. One method of preventing the recurrence of bone hydatid cysts is to remove the cystic bone as a block in selected cases [25]. Several caveats regarding the high recurrence rate in bone disease merit consideration. Follow-up was longer in the bone group (median 61 vs. 53 months), which could increase the probability of detecting late recurrences; however, the difference in median follow-up was not statistically significant. Recurrence was assessed using a standardized protocol at every outpatient visit in both groups, making differential surveillance intensity an unlikely sole explanation for the observed difference. The disparity in surgical approach — curettage in bone versus en bloc excision in soft tissue — is itself a reflection of the biological constraints imposed by the osseous disease and should be considered an integral part of the explanation rather than a confound. Nevertheless, multivariable analysis adjusting for follow-up duration, surgical technique, and lesion extent was not feasible in this cohort and should be a priority in future studies.

The transmission route of bone hydatid disease remains unclear [26]. Previous studies have also reported a high frequency of concomitant organ involvement in patients with osseous disease [27]. In line with these findings, we observed a higher rate of concomitant organ involvement in patients with bone hydatid disease compared with those with soft tissue involvement. However, it remains unclear whether bone lesions represent a primary focus followed by systemic dissemination or secondary involvement after visceral disease.

In patients with osseous involvement, individualized treatment strategies tailored to the extent of disease, in addition to standard surgical techniques, constitute the cornerstone of management.Various surgical techniques have been described for the management of bone hydatid disease, ranging from wide resection to curettage, irrigation with 20% hypertonic saline, and cementation [16, 28, 29]. In our study, some patients underwent resection of the affected bone, whereas others were treated with curettage followed by irrigation with 20% hypertonic saline and povidone–iodine solution and subsequent polymethylmethacrylate cementation. In cases with severe cortical thinning, internal fixation with plates and screws was performed to prevent pathological fractures. For soft tissue hydatid disease, complete excision without rupture of the cyst wall is recommended [30, 31]. Accordingly, we aimed to remove the cysts en bloc without damaging the cyst wall. Nevertheless, intraoperative rupture occurred in 10 patients (26.3%), reflecting the technical challenges associated with surgical management of this disease.

The risk of anaphylaxis in hydatid cyst disease increases markedly in cases of cyst rupture [32, 33]. In our cohort, intraoperative anaphylaxis occurred in 15 of 26 patients (57.7%) undergoing surgery for bone hydatid cysts, compared with 7 of 38 patients (18.4%) treated surgically for soft-tissue hydatid cysts. The incidence of anaphylaxis was significantly higher in the bone hydatid cyst group. We speculate that this difference may be In bone hydatid disease, the lesions do not have a true pericyst and show infiltrative growth patterns; this increases the likelihood of cortical disruption, cyst rupture, and spread of highly antigenic cyst fluid during surgery, which can trigger an anaphylactic reaction.

Limitations

This study has several limitations that must be considered when interpreting the findings. First, the retrospective single-center design introduces inherent risks of information bias and limits generalizability to other healthcare settings. Second, selection bias is present because only surgically treated and histopathologically confirmed cases were included; patients managed conservatively with albendazole alone or by percutaneous techniques are not represented, and their clinical characteristics and outcomes may differ substantially from the surgical cohort. Third, although median follow-up was comparable between groups and no significant difference was detected, the wide range of follow-up (18–118 months) means that differential surveillance intensity between groups cannot be fully excluded as a contributor to the observed differences in recurrence detection rates. Fourth, the preoperative diagnostic approach, including decisions regarding biopsy, was not standardized across the entire 14-year study period and reflected individual multidisciplinary team decisions, which may introduce variability in the diagnostic workup. Fifth, eosinophil count and ELR were analysed as exploratory biomarkers without pre-specified thresholds, which increases the risk of type I error and limits the validity of conclusions about their discriminative value. Sixth, differences in surgical technique between the two groups — wide excision for soft tissue versus curettage-based procedures for bone — and variability in the extent of bone disease may have confounded the comparison of recurrence and complication rates, as these are influenced not only by biological factors but also by achievable surgical margins.

Future prospective multicenter studies incorporating standardized diagnostic algorithms, surgical strategies, predefined biomarker thresholds, and uniform follow-up protocols are warranted to validate these findings, clarify the diagnostic and prognostic utility of inflammatory biomarkers, and identify independent predictors of recurrence in musculoskeletal hydatid disease.

Conclusions

Bone hydatid disease is more challenging to treat than soft tissue hydatid disease and is associated with higher recurrence rates and more frequent concomitant organ involvement. Patients with bone involvement most commonly present with pain, whereas localized swelling is the predominant symptom in soft tissue disease. In this retrospective cohort, eosinophil count and ELR were statistically higher in the bone involvement group; however, given the retrospective design, the modest sample size, and the absence of standardized biomarker thresholds, these findings should be interpreted with caution and are not sufficient to draw conclusions about their independent diagnostic value. They may represent hypothesis-generating observations to be evaluated in future prospective studies with multivariable modelling.

Abbreviations

WBC

White Blood Cell Count

ESR

Erythrocyte Sedimentation Rate

CRP

C-Reactive Protein

ELR

Eosinophil-to-Lymphocyte Ratio

BMI

Body Mass Index

MRI

Magnetic Resonance Imaging

CT

Computed Tomography

Authors’ contributions

I.H.D.: Conceptualization, study design, data collection, statistical analysis, interpretation of data, and drafting of the manuscript.T.S.C.: Data analysis, interpretation of results, and critical revision of the manuscript.M.O.K.: Data collection and contribution to manuscript drafting.M.D.: Data acquisition and literature review.İ.P., and OK : Data collection and assistance in data interpretation.H.Y.Y.: Study supervision, critical revision of the manuscript, and final approval of the version to be published.All authors read and approved the final manuscript.

Funding

No funding was received for this work.

Data availability

The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The Ethical Approval Study Protocol was approved by the local Ethics Committee of Gaziantep City Hospital on October 15, 2025, with decision number 342/2025. All methods were carried out in accordance with relevant guidelines and regulations (Helsinki Declaration). Informed consent to participate was obtained from all of the participants in the study.

Consent for publication

All written informed consent for publication of identifying images or other personal or clinical details was obtained from all of the participants.

Competing interests

The authors declare no competing interests.