Carpal bone replacement using personalized 3D printed tantalum prosthesis.

Objective: Scaphoid and lunate fractures have a relatively high incidence rate. Traditional carpectomy and carpal arthrodesis in the treatment of carpal osteonecrosis will lead to many complications. Three-dimensional (3D) printed tantalum has good biocompatibility and can be designed to match the patient's personalized anatomical carpal structure. This study aims to investigate carpal function and prosthesis-related conditions after carpal bone replacement using 3D printed tantalum prostheses. Methods: From July 2020 to January 2022 at our center, seven patients with osteonecrosis of the carpus received carpal bone replacement using 3D printed tantalum prosthesis. The Disability of the Arm, Shoulder and Hand (DASH) score and patient satisfaction, as well as the Mayo Wrist Scores (Cooney method, modified Green, and O'Brien wrist score), were used to evaluate the preoperative and postoperative wrist function of patients. The Visual Analog Scale (VAS) pain scores were also recorded before and after surgery. The angles of flexion, dorsiflexion, ulnar deviation, and radial deviation were measured using an arthrometer. The grip strength and pinch strength of the operated hand after carpal bone replacement and the contralateral healthy carpus were measured using a dynamometer. Radiographs were taken to confirm the condition and complications of the tantalum prosthesis. Results: All seven patients were followed for 19.6 ± 2.7 months. At the last follow-up, the grip strength of the operated wrist joint after carpal bone replacement was 33.4 ± 2.3 kg, the pinch strength was 8.9 ± 0.7 kg, the flexion was 54.6° ± 0.8°, the dorsiflexion was 54.7° ± 1.7°, the ulnar deviation was 34.6° ± 1.9°, and the radial deviation was 25.9° ± 0.8°, all of which showed no statistically significant difference with the contralateral healthy carpus (p > 0.05). There were significant differences in the VAS, DASH, and MAYO scores between the preoperative and the last follow-up (p < 0.01). Patients had reduced postoperative pain and improved wrist function and range of motion (ROM), and the tantalum prostheses were stable. Conclusion: The 3D printed tantalum brings us new hope, not only for hip or knee replacement, but also for joint replacement of other complex anatomical structures, and patients with other irregular bone defects such as bone tumors and deformity, which could realize personalized treatment and precise medicine.

Effectiveness and safety of arthroscopy combined with radial extracorporeal shockwave therapy for osteochondritis of the talus: a prospective, single-centre, randomized, double-blind study.

Aims: Arthroscopic microfracture is a conventional form of treatment for patients with osteochondritis of the talus, involving an area of < 1.5 cm2. However, some patients have persistent pain and limitation of movement in the early postoperative period. No studies have investigated the combined treatment of microfracture and shortwave treatment in these patients. The aim of this prospective single-centre, randomized, double-blind, placebo-controlled trial was to compare the outcome in patients treated with arthroscopic microfracture combined with radial extracorporeal shockwave therapy (rESWT) and arthroscopic microfracture alone, in patients with ostechondritis of the talus. Methods: Patients were randomly enrolled into two groups. At three weeks postoperatively, the rESWT group was given shockwave treatment, once every other day, for five treatments. In the control group the head of the device which delivered the treatment had no energy output. The two groups were evaluated before surgery and at six weeks and three, six and 12 months postoperatively. The primary outcome measure was the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale. Secondary outcome measures included a visual analogue scale (VAS) score for pain and the area of bone marrow oedema of the talus as identified on sagittal fat suppression sequence MRI scans. Results: A total of 40 patients were enrolled and randomly divided into the two groups, with 20 in each. There was no statistically significant difference in the baseline characteristics of the groups. No complications, such as wound infection or neurovascular injury, were found during follow-up of 12 months. The mean AOFAS scores in the rESWT group were significantly higher than those in the control group at three, six, and 12 months postoperatively (p < 0.05). The mean VAS pain scores in the rESWT group were also significantly lower than those in the control group at these times (p < 0.05). The mean area of bone marrow oedema in the rESWT group was significantly smaller at six and 12 months than in the control group at these times (p < 0.05). Conclusion: Local shockwave therapy was safe and effective in patients with osteochondiritis of the talus who were treated with a combination of arthroscopic surgery and rESWT. Preliminary results showed that, compared with arthroscopic microfracture alone, those treated with arthroscopic microfracture combined with rESWT had better relief of pain at three months postoperatively and improved weightbearing and motor function of the ankle.

3D Printing-Assisted Supramalleolar Osteotomy for Ankle Osteoarthritis.

Ankle osteoarthritis (OA) is an important factor that causes pain and dysfunction after ankle joint movement. In early and mid-term ankle OA, supramalleolar osteotomy can delay the progression of disease and maximize the preservation of ankle joint function. Three-dimensional printing (3DP) technology has brought us new hope, which can improve the accuracy of osteotomy, reduce the number of fluoroscopy, reduce the amount of blood loss, and achieve personalized and accurate treatment. The data of 16 patients with ankle OA in our center from January 2003 to July 2020 were retrospectively analyzed and divided into the 3DP group and the traditional group according to different treatment methods. Seven patients in the 3DP group used the 3DP personalized osteotomy guide; nine patients were treated by traditional osteotomy. All patients were followed up for 13.9 ± 3.1 months after the operation. The operation time in the 3DP group was 126.4 ± 11.1 min, its intraoperative blood loss was 85.7 ± 24.1 mL, and its intraoperative fluoroscopy time was 2.4 ± 0.2, which were all significantly less than 167.3 ± 12.2 min, 158.3 ± 22.8 mL, and 5.8 ± 0.2 times in the traditional group (P < 0.05), respectively. In the 3DP group, its postoperative tibial anterior surface (TAS) angle was 90.6 ± 0.3° and the talar tilt (TT) angle was 2.2 ± 0.6°, which were all significantly different compared with its preoperative data of 83.4 ± 1.7 and 8.0 ± 1.5°, respectively (P < 0.05). Compared with traditional osteotomy, 3DP-assisted supramalleolar osteotomy for varus and valgus ankle OA can significantly shorten the operation time and reduce intraoperative bleeding and the frequency of intraoperative fluoroscopy; personalized 3DP osteotomy guides and models can assist in the accurate correction of varus deformity during operation, restore the lower limb alignment, and improve the biomechanical status of the lower limbs. In addition, the 3DP of porous tantalum has good histocompatibility, and its interface structure and porosity are more conducive to bone ingrowth. For complex bone defects and revision prostheses, matching implants can be printed individually, which could realize the personalized precise treatment.

Triple Hemisection Percutaneous Achilles Tendon Lengthening for Severe Ankle Joint Deformity.

OBJECTIVE: To investigate the efficacy of modified percutaneous Achilles tendon lengthening for severe ankle joint deformity. METHODS: This retrospective case series study included 33 patients with an average age of 25.2 years who underwent surgery in our hospital from April 1, 2010 to March 1, 2018. Triple hemisection percutaneous Achilles tendon lengthening was performed. One stage surgery, other soft tissue surgery or bone correction surgery could be performed. After surgery, a plaster cast was used to fix the functional position, and rehabilitation training was carried out as planned. Complications during the perioperative period were recorded. Statistical analysis of the patients' visual analogue scale (VAS) and American Orthopedic Foot and Ankle Society (AOFAS) score before and at the last follow-up was performed. The recurrence rate of Achilles tendon contracture at the last follow-up and the patients' satisfaction rate were investigated. RESULTS: All patients were followed up, with an average follow-up period of 56.31 months (8-104 months). All achieved good ankle joint function and appearance improvement And there were no infection or skin necrosis complications. In two cases, the incision was poorly healed at non-Achilles tendon site and was cured by change of dressing. The average VAS score at the last follow-up was reduced from (2 ± 1.48) points before surgery to (0.26 ± 0.51) points (P = 0.001), and the average AOFAS score was increased from (64.97 ± 13.56) points before surgery to (90.06 ± 10.06) points (P = 0.001). During the follow-up period, there was no chronic rupture of Achilles tendon. There were two cases of recurrence of foot drop (5.7%), and the patients' satisfaction rate was 93.9%. CONCLUSION: In the surgical treatment of severe ankle joint deformity, the application of triple hemisection percutaneous Achilles tendon lengthening for Achilles tendon contracture has the advantages of less trauma, beautiful incision, and reliable efficacy. The satisfaction rate of patients with this treatment is high, and it is worth promoting in the clinic.

Surgical treatment for insertional Achilles tendinopathy and retrocalcaneal bursitis: more than 1 year of follow-up.

OBJECTIVE: To analyse the imaging changes in bone marrow oedema of the calcaneal prominence, retrocalcaneal bursa and degenerative Achilles tendon after the surgical treatment of insertional Achilles tendinopathy (IAT). METHODS: This retrospective study analysed patients with IAT and retrocalcaneal bursitis that were diagnosed based on their symptoms and radiographic and magnetic resonance imaging (MRI) examinations. For patients that had received 3 months of conservative treatment but still presented with symptoms, arthroscopic debridement of the retrocalcaneal bursa and resection of calcaneal prominence were undertaken. Patients with degeneration of the Achilles tendon underwent debridement of Achilles tendon calcification with an open incision. The last follow-up included radiographic and MRI imaging, Visual Analogue Scale (VAS) pain scores and American Orthopedic Foot and Ankle Society (AOFAS)-Ankle and Hindfoot scores. RESULTS: Thirty patients were included (mean ± SD follow-up, 3.1 ± 0.5 years). The VAS pain and AOFAS-Ankle and Hindfoot scores were significantly improved after surgery. MRI showed that bone marrow oedema of the calcaneal prominence and the retrocalcaneal bursa was significantly reduced compared with preoperative values. There was no significant change in the high signal area of the IAT. CONCLUSION: Surgical treatment of IAT and retrocalcaneal bursitis effectively alleviated local pain and restored function.

Bone Marrow Edema Syndrome of the Foot Treated with Extracorporeal Shock Wave Therapy: A Retrospective Case Series.

To determine the validity and safety of extracorporeal shock wave therapy (ESWT) in the treatment of bone marrow edema syndrome (BMES) of the foot. Twenty patients diagnosed as foot BMES in our Center were followed and treated by ESWT for 1 to 2 courses. The target of the ESWT treatment was the most obvious foot tenderness, or the most obvious part of bone edema on magnetic resonance imaging (MRI). One course of ESWT was 1 time/week, 5 times in total, with the shock wave energy flow density 0.18 mJ/mm2. The visual analog scale (VAS) and the American Orthopedic Foot and Ankle Society (AOFAS) scores of the foot were recorded before treatment, at 3 months after treatment and the last follow-up; the areas of BME before treatment and at the last follow-up were measured by the fat suppression MRI. Complications during treatment were also recorded. Twenty follow-up patients were obtained. Compared with the pretreatment, the patients had significant improvement in various indicators at 3 months after treatment (p < 0.01). The sagittal MRI at the last follow-up showed that the BME area decreased significantly (p < 0.01). Two patients developed transient erythema on their skin after treatment and alleviated after 2 days of rest. No serious complications were found during treatment. Our findings show that for patients with foot BMES, the use of ESWT treatment can effectively relieve local pain, improve the motor function of the foot and ankle. Two courses of treatment may be required for some patients.

Proliferation ability of particulated juvenile allograft cartilage.

BACKGROUND: Particulated juvenile allograft cartilage (PJAC) has a good short-term clinical efficacy in repairing articular cartilage defects, but the proliferation ability of PJAC and the biological characteristics of transplanted cells after transplantation are still unclear. PURPOSE: To study the cartilage proliferation ability of PJAC in repairing full-thickness cartilage defects and the reasons for proliferation to provide experimental evidence for its clinical application. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty Guizhou minipigs were randomly divided into the experimental group and control group. In all minipigs, an 8-mm cylindrical full-thickness cartilage defect was created in the femoral trochlea of one knee. The experimental group received PJAC transplantation from five juvenile donors of Guizhou minipigs (PJAC group; n = 10) and the control group received transplantation of autologous cartilage chips (ACC group; n = 10). Both groups were followed at 1 and 3 months after surgery, immunohistochemical evaluation of the tissue sections Ki-67 and Lin28 was conducted, the positive rate was calculated according to the staining, and the proliferation ability of PJAC was analyzed. RESULTS: All 20 Guizhou minipigs were followed, and there was no infection or incision healing disorder after surgery. By Ki-67 and Lin28 immunohistochemical tests, the positive rate of Ki-67 was 88.9 ± 0.2% in the PJAC group and 28.3 ± 3.6% in the ACC group at 1 month, and the difference was statistically significant (P < 0.05); the positive rate of Lin28 was 34.6 ± 3.3% in the PJAC group and 7.6 ± 1.4% in the ACC group at 1 month, and the difference was statistically significant (P < 0.05). At 3 months, the positive rates of Ki-67 in the PJAC group and ACC group were 53.6 ± 6.9% and 1.97 ± 0.3%, respectively (P < 0.05); the positive rates of Lin28 were 86.6 ± 3.3% and 1.4 ± 0.3%, respectively (P < 0.01). CONCLUSION: A large animal model was established with Guizhou minipigs, and the expressions of Ki-67 protein and Lin28 protein detected by immunohistochemistry in the repaired transplanted tissue of the PJAC group were stronger than those of adult cartilage. The proliferation of PJAC within 3 months of transplantation was stronger than that of adult cartilage. The enhanced expression of Lin28 may be one of the mechanisms by which PJAC achieved stronger proliferation ability than adult cartilage. PJAC technology has shown good application prospects for repairing cartilage defects.

Donor Cell Fate in Particulated Juvenile Allograft Cartilage for the Repair of Articular Cartilage Defects.

BACKGROUND: Particulated juvenile allograft cartilage (PJAC) has demonstrated good clinical efficacy in repairing articular cartilage defects, but the related repair mechanism after transplant and the biological characteristics of the transplanted cells are still unclear. PURPOSE: To study the efficacy of PJAC in repairing full-thickness cartilage defects and the specific fate of donor cells to provide experimental evidence for its clinical application. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty female Guizhou minipigs were randomly divided into an experimental group and a control group. An 8-mm cylindrical full-thickness cartilage defect was created in the femoral trochlea of 1 knee in all minipigs. The experimental group received transplant of PJAC from 5 male juvenile Guizhou minipigs (PJAC group; n = 10) and the control group received autologous cartilage chips (ACC group; n = 10). Follow-up assessments were conducted at 1 month and 3 months to track the transplanted cells by the male-specific sex-determining region Y-linked (SRY) gene; tissue sections were hybridized in situ, and O'Driscoll histological scoring was performed according to hematoxylin and eosin staining, safranin O and fast green staining, and toluidine blue O staining, as well as immunohistochemical evaluation of aggrecan and Sry-type HMG-box 9 (SOX9). RESULTS: All 20 Guizhou minipigs were followed; no infection or incision healing disorder occurred after the operation. By SRY in situ hybridization, the SRY signal of the transplanted cells was positive in the repaired tissue of the defect, and the SRY positive signal could still be detected in repaired tissue at 3 months postoperatively. The average number of positive cells was 68.6 ± 11.91 at 1 month and 32.6 ± 3.03 at 3 months (confocal microscope: ×400), and the difference was statistically significant. The O'Driscoll histological scores were 14 ± 0.71 in the ACC group and 9.8 ± 0.84 in the PJAC group at 1 month, and 18 ± 1.20 in the ACC group and 17.4 ± 1.14 in the PJAC group at 3 months. The scores were statistically significant between the ACC group and PJAC group at 1 month. The positive rates of SOX9 in the PJAC and ACC groups at 1 month were 67.6% ± 3.78% and 63.4% ± 5.30%, respectively, and the difference was not statistically significant (P > .05). The positive rates of SOX9 in the PJAC and ACC groups at 3 months were 68.8% ± 2.69% and 17.1% ± 1.26%, respectively, and the difference was statistically significant (P < .05). The positive rates of aggrecan in the PJAC and ACC groups at 1 month were 40.5% ± 2.78% and 42.4% ± 0.54% respectively, and the difference was not statistically significant (P > .05). The positive rates of aggrecan in the PJAC and ACC groups at 3 months were 40.8% ± 1.50% and 30.1% ± 2.44%, respectively, and the difference was not statistically significant (P > .05). CONCLUSION: An animal model was established with Guizhou minipigs, and the cartilage defect was repaired with PJAC from male minipigs. The SRY gene positive signal could be detected from the repaired tissue by in situ hybridization, indicating that the transplanted cells survived at least 3 months. The key genes of cartilage formation, SOX9 and aggrecan, were expressed at 1 month and 3 months, and SOX9 expression was stronger in the PJAC group than the ACC group at 3 months. CLINICAL RELEVANCE: This study suggests that it is feasible to study the biological characteristics of transplanted cells in the cartilage region by the sex-determining gene.

Arthroscopic Ankle Arthrodesis for End-Stage Tuberculosis of the Ankle: A 2-Year Follow-Up.

Surgical treatment for end-stage ankle joint tuberculosis (TB) has rarely been reported. This study followed cases treated by arthroscopic arthrodesis for ankle joint TB to evaluate its efficacy and safety in the clinic. Patients who underwent arthroscopic ankle arthrodesis for ankle joint TB between April 11, 2010, and December 31, 2016, were followed. Their diagnoses were confirmed by bacterial culture or pathological examination. During arthroscopy, tissue samples were first obtained to further confirm the diagnosis. Then the necrotic tissue, hyperplasia of synovial tissue, and exfoliated cartilage were removed. Ankle joint arthrodesis was performed if the area of articular cartilage damage was >2 cm2. Continued nutritional support and standardized anti-TB drug treatment were given after surgery. Follow-up measurements included visual analogue scale score, American Orthopaedic Foot and Ankle Society score, erythrocyte sedimentation rate, and radiographic imaging. All 9 patients in this study, with an average age of 54 (range 37 to 68) years, were followed. The mean follow-up duration was 55.44 ± 31.15 (range 24 to 96) months. There were significant differences in the visual analogue scale scores, American Orthopaedic Foot and Ankle Society scores, and erythrocyte sedimentation rate between before treatment and 18 months postoperatively (p < .05). All patients (100%) showed union at 18 ± 4 weeks. Arthroscopic treatment for ankle joint TB has the advantages of minor trauma and low complications. It can be used to accurately obtain samples from specific areas of TB for further diagnosis. According to the degree of articular cartilage damage, the surgeon can determine whether to perform arthrodesis. Thorough debridement of necrotic tissue and residual articular cartilage on the fusion surface can improve the rate of ankle fusion.

Endoscopic Treatment of Symptomatic Foot and Ankle Bone Cyst with 3D Printing Application.

OBJECTIVE: To study the efficacy of arthroscopy for treating symptomatic bone cysts of the foot and ankle through the follow-up of patients and to further explore the application value of 3D printing technology in this treatment. METHODS: Twenty-one patients with symptomatic bone cysts in the foot and ankle who underwent arthroscopic surgery in our Center from March 2010 to December 2018 were enrolled, including 11 in the experimental group and 10 in the control group. For the control group, C-arm fluoroscopy was used intraoperatively to confirm the positioning of the cysts; for the experimental group, a 3D model of the lesion tissue and the 3D-printed individualized guides were prepared to assist the positioning of the cysts. Debridement of the lesion tissues was conducted under an arthroscope. Regular follow-ups were conducted. The time of establishing arthroscopic approaches and the times of intraoperative fluoroscopy between the two groups were compared. Significance was determined as P < 0.05. RESULTS: The postoperative pathology of the patients confirmed the diagnosis. No significant perioperative complications were observed in either group, and no recurrence of bone cysts was seen at the last follow-up. The VAS scores and AOFAS scores of the two groups at the last follow-up were significantly improved compared with the preoperative data, but there was no statistical difference between the two groups. All surgeries were performed by the same senior surgeon. The time taken to establish the arthroscopic approaches between the two groups was statistically significant (P < 0.001), and the times of intraoperative fluoroscopy required to establish the approach were also statistically significant (P < 0.001). The intraoperative bleeding between the two groups was statistically significant (P < 0.01). There was 1 case in each group whose postoperative CT showed insufficient bone grafting, but no increase in cavity volume was observed during the follow-up. CONCLUSION: With the assistance of the 3D printing technology for treating symptomatic bone cysts of the ankle and foot, the surgeon can design the operation preoperatively and perform the rehearsal, which would make it easier to establish the arthroscopic approach, better understand the anatomy, and make the operation smoother. This trial is registered with http://www.clinicaltrials.govNCT03152916.

Modified Percutaneous Achilles Tendon Lengthening by Triple Hemisection for Achilles Tendon Contracture.

BACKGROUND: Both percutaneous Achilles tendon lengthening by triple hemisection and the traditional open Z-lengthening are effective methods for Achilles tendon contracture. This study aims to evaluate the efficacy and safety of this new therapeutic method, which is based on the percutaneous sliding technique with three hemi-cuts in the tendon, as compared with the traditional open Z-lengthening. METHODS: Retrospective analysis of the Achilles tendon contracture cases in our hospital between January 2010 and September 2016 was conducted. Twenty-five cases received percutaneous Achilles tendon lengthening (group A), and 30 patients who underwent open Z-lengthening during the same period were in the control group (group B). Operative time and hospital stay were statistically analyzed. Incision complication, equinus recurrence rate and Achilles tendon rupture morbidity were recorded. The function was assessed by American Orthopaedic Foot & Ankle Society (AOFAS) score. All cases in group A received Magnetic Resonance Imaging (MRI) of ankle preoperatively and in the follow-ups. RESULTS: The mean follow-up period was 42.04 months in group A and 61.7 months in group B. The entire operative time and the mean hospitalization days were lower in group A than in group B. No incision and infection complication occurred in group A. The infection rate in group B was 3.3%. Equinus recurrence rate was 4% in group A and the equinus recurrence rate in group B was 21.4%. In group A, the mean AOFAS score increased from 64 ± 10.16 points preoperatively to 96.08 ± 3.17 at final follow-up, while the score in group B increased from 63.48 ± 6.2 points to 85.4 ± 10.3. MRI showed continuity of the Achilles tendon and homogeneous signal in group A. CONCLUSION: Modified surgery can significantly reduce the risk of Achilles tendon rupture, provide better balance in soft tissue strength between ankle dorsiflexion and ankle plantarflexion, helping to avoid recurrence of the deformity.

[Surveillance and risk assessment system of schistosomiasis in Jiangsu Province. II. Surveillance pattern and effect of Oncomelania hupensis snail status in Dongtai City, Jiangsu Province].

OBJECTIVE: To explore the method of Oncomelania hupensis snail surveillance in transmission-interrupted regions of schistosomiasis, so as to provide a new pattern for the surveillance of snail status in the transmission-interrupted areas. METHODS: In Dongtai County, north of Jiangsu Province where the transmission of schistosomiasis was interrupted, the surveillance of snail status was performed by means of the village-level general survey, village-level sampling survey, snail survey in key settings of township and county, and snail reporting by residents. In addition, quality-control snail sites were set up for quality control. The effectiveness and cost of the four methods of snail surveillance was compared. RESULTS: A total of 163 079 settings and 22 785.62 hm2 were surveyed in Dongtai County from 2008 to 2013, and 89 residual snail breeding sites were found, with a snail area of 1.48 hm2. The patterns of village-level general survey, village-level sampling survey, and snail survey in key settings of township and county were employed for investigation of 94 550, 45 033 and 23 496 settings, consisting of 57.98%, 27.61% and 14.41% of total settings, and 2, 0 and 6 settings were found with snails, with 0.021/thousand, 0, and 0.255/thousand detection rates of settings with snail breading sites, respectively. The pattern of snail survey in key settings of township and county was more effective than that of village-level survey to detect-snail breeding sites (χ2 = 19.158, P = 0). The recovery rate of quality-control snail breeding sites was 52.56%, 38.27% and 73.62% for the three patterns of snail survey, respectively, and the pattern of snail survey in key settings of township and county showed a higher quality for snail survey than that of village-level survey (χ2 = 111.597 and 85.991, both P = 0). During the period from 2008 to 2013, 289 person-times reported 279 suspected snail habitats and 1 501 living snails, and no Oncomelania snails were found. During the 6-year period, there were 1617.5, 964.7 and 527.7 thousand RMB invested for village-level general survey, village-level sampling survey, and snail survey in key settings of township and county, and the cost of snail survey per hm2 was 129.88, 133.6 and 162.57 RMB/hm2, respectively. The cost of village-level general survey and snail survey in key settings of township and county to detect a snail-breeding site was 808 800 and 88 000 RMB, respectively (t = 12.850, P = 0.000), and the cost of snail survey in key settings of township and county was 10.88% of that of village-level general survey. CONCLUSION: The snail survey in key settings of township and county is a highly effective and high-quality method for snail surveillance, which miay serve as a prior way for the surveillance of snail status in the transmission-interrupted areas of schistosomiasis.