We conducted a case-control study to examine the merit of silver-coated tumour prostheses. We reviewed 85 patients with Agluna-treated (silver-coated) tumour implants treated between 2006 and 2011 and matched them with 85 control patients treated between 2001 and 2011 with identical, but uncoated, tumour prostheses.

In all, 106 men and 64 women with a mean age of 42.2 years (18.4 to 90.4) were included in the study. There were 50 primary reconstructions (29.4%); 79 one-stage revisions (46.5%) and 41 two-stage revisions for infection (24.1%).

The overall post-operative infection rate of the silver-coated group was 11.8% compared with 22.4% for the control group (p = 0.033, chi-square test). A total of seven of the ten infected prostheses in the silver-coated group were treated successfully with debridement, antibiotics, and implant retention compared with only six of the 19 patients (31.6%) in the control group (p = 0.048, chi-square test). Three patients in the silver-coated group (3.5%) and 13 controls (15.3%) had chronic periprosthetic infection (p = 0.009, chi-square test).

The overall success rates in controlling infection by two-stage revision in the silver-coated group was 85% (17/20) compared with 57.1% (12/21) in the control group (p = 0.05, chi-square test). The Agluna-treated endoprostheses were associated with a lower rate of early periprosthetic infection. These silver-treated implants were particularly useful in two-stage revisions for infection and in those patients with incidental positive cultures at the time of implantation of the prosthesis.

Debridement with antibiotic treatment and retention of the implant appeared to be more successful with silver-coated implants.

Cite this article: Bone Joint J 2015;97-B:252–7.

We report our experience of using a computer navigation system to aid resection of malignant musculoskeletal tumours of the pelvis and limbs and, where appropriate, their subsequent reconstruction. We also highlight circumstances in which navigation should be used with caution.

We resected a musculoskeletal tumour from 18 patients (15 male, three female, mean age of 30 years (13 to 75) using commercially available computer navigation software (Orthomap 3D) and assessed its impact on the accuracy of our surgery. Of nine pelvic tumours, three had a biological reconstruction with extracorporeal irradiation, four underwent endoprosthetic replacement (EPR) and two required no bony reconstruction. There were eight tumours of the bones of the limbs. Four diaphyseal tumours underwent biological reconstruction. Two patients with a sarcoma of the proximal femur and two with a sarcoma of the proximal humerus underwent extra-articular resection and, where appropriate, EPR. One soft-tissue sarcoma of the adductor compartment which involved the femur was resected and reconstructed using an EPR. Computer navigation was used to aid reconstruction in eight patients.

Histological examination of the resected specimens revealed tumour-free margins in all patients. Post-operative radiographs and CT showed that the resection and reconstruction had been carried out as planned in all patients where navigation was used. In two patients, computer navigation had to be abandoned and the operation was completed under CT and radiological control.

The use of computer navigation in musculoskeletal oncology allows accurate identification of the local anatomy and can define the extent of the tumour and proposed resection margins. Furthermore, it helps in reconstruction of limb length, rotation and overall alignment after resection of an appendicular tumour.

Cite this article: Bone Joint J 2015;97-B:258–64.

Cancellous allograft bone chips are commonly used in the reconstruction of defects in bone after removal of benign tumours. We investigated the MRI features of grafted bone chips and their change over time, and compared them with those with recurrent tumour. We retrospectively reviewed 66 post-operative MRIs from 34 patients who had undergone curettage and grafting with cancellous bone chips to fill the defect after excision of a tumour. All grafts showed consistent features at least six months after grafting: homogeneous intermediate or low signal intensities with or without scattered hyperintense foci (speckled hyperintensities) on T1 images; high signal intensities with scattered hypointense foci (speckled hypointensities) on T2 images, and peripheral rim enhancement with or without central heterogeneous enhancements on enhanced images. Incorporation of the graft occurred from the periphery to the centre, and was completed within three years. Recurrent lesions consistently showed the same signal intensities as those of pre-operative MRIs of the primary lesions. There were four misdiagnoses, three of which were chondroid tumours.

We identified typical MRI features and clarified the incorporation process of grafted cancellous allograft bone chips. The most important characteristics of recurrent tumours were that they showed the same signal intensities as the primary tumours. It might sometimes be difficult to differentiate grafted cancellous allograft bone chips from a recurrent chondroid tumour.

Cite this article: Bone Joint J 2015;97-B:121–8.

A poor response to chemotherapy (≤ 90% necrosis) for osteosarcomas leads to poorer survival and an increased risk of local recurrence, particularly if there is a close margin of excision. We evaluated whether amputation confers any survival benefit over limb salvage surgery (LSS) with narrow margins in patients who respond poorly to chemotherapy.

We only analysed patients with an osteosarcoma of the limb, a poor response to chemotherapy and close margins on LSS (marginal/intralesional) or primary amputation: 360 patients (36 LSS (intralesional margins), 197 LSS (marginal margins) and 127 amputations) were included. Local recurrence developed in 13 (36%) following LSS with intralesional margins, and 39 (20%) following LSS with marginal margins. There was no local recurrence in patients who underwent amputation. The five-year survival for all patients was 41% (95% confidence interval (CI) 35 to 46), but for those treated by LSS with marginal margins was 46.2% (95% CI 38 to 53), 36.3% (95% CI 27 to 45) for those treated by amputation, and 28% (95 CI 14 to 44) for those treated by LSS with intralesional margins. Patients who had LSS and then developed local recurrence as a first event had the same survival as those who had primary amputation without local recurrence. Prophylactic adjuvant radiotherapy was used in 40 patients but had no discernible effect in preventing local recurrence.

Although amputation offered better local control, it conferred no clear survival benefit over LSS with marginal margins in these patients with a poor overall prognosis.

Cite this article: Bone Joint J 2015;97-B:115–20.

Peri-acetabular tumour resections and their subsequent reconstruction are among the most challenging procedures in orthopaedic oncology. Despite the fact that a number of different pelvic endoprostheses have been introduced, rates of complication remain high and long-term results are mostly lacking.

In this retrospective study, we aimed to evaluate the outcome of reconstructing a peri-acetabular defect with a pedestal cup endoprosthesis after a type 2 or type 2/3 internal hemipelvectomy.

A total of 19 patients (11M:8F) with a mean age of 48 years (14 to 72) were included, most of whom had been treated for a primary bone tumour (n = 16) between 2003 and 2009. After a mean follow-up of 39 months (28 days to 8.7 years) seven patients had died. After a mean follow-up of 7.9 years (4.3 to 10.5), 12 patients were alive, of whom 11 were disease-free. Complications occurred in 15 patients. Three had recurrent dislocations and three experienced aseptic loosening. There were no mechanical failures. Infection occurred in nine patients, six of whom required removal of the prosthesis. Two patients underwent hindquarter amputation for local recurrence.

The implant survival rate at five years was 50% for all reasons, and 61% for non-oncological reasons. The mean Musculoskeletal Tumor Society score at final follow-up was 49% (13 to 87).

Based on these poor results, we advise caution if using the pedestal cup for reconstruction of a peri-acetabular tumour resection.

Cite this article: Bone Joint J 2014;96-B:1706–12.

Previous classification systems of failure of limb salvage focused primarily on endoprosthetic failures and lacked sufficient depth for the effective study of the causes of failure. In order to address these inadequacies, the International Society of Limb Salvage (ISOLS) formed a committee to recommend revisions of the previous systems. The purpose of this study was to report on their recommendations. The modifications were prepared using an earlier, evidence-based model with subclassification based on the existing medical literature. Subclassification for all five primary types of failure of limb salvage following endoprosthetic reconstruction were formulated and a complementary system was derived for the failure of biological reconstruction. An additional classification of failure in paediatric patients was also described.

Limb salvage surgery presents a complex array of potential mechanisms of failure, and a complete and precise classification of types of failure is required. Earlier classification systems lacked specificity, and the evidence-based system outlined here is designed to correct these weaknesses and to provide a means of reporting failures of limb salvage in order to allow the interpretation of outcome following reconstructive surgery.

Cite this article: Bone Joint J 2014;96-B:1436–40.

Atypical cartilaginous tumours are usually treated by curettage. The purpose of this study was to show that radiofrequency ablation was an effective alternative treatment.

We enrolled 20 patients (two male, 18 female, mean age 56 years (36 to 72) in a proof-of-principle study. After inclusion, biopsy and radiofrequency ablation were performed, followed three months later by curettage and adjuvant phenolisation. The primary endpoint was the proportional necrosis in the retrieved material. Secondary endpoints were correlation with the findings on gadolinium enhanced MRI, functional outcome and complications.

Our results show that 95% to 100% necrosis was obtained in 14 of the 20 patients. MRI had a 91% sensitivity and 67% specificity for detecting residual tumour after curettage. The mean functional outcome (MSTS) score six weeks after radiofrequency ablation was 27.1 (23 to 30) compared with 18.1 (12 to 25) after curettage (p < 0.001). No complications occurred after ablation, while two patients developed a pathological fracture after curettage.

We have shown that radiofrequency ablation is capable of completely eradicating cartilaginous tumour cells in selective cases. MRI has a 91% sensitivity for detecting any residual tumour. Radiofrequency ablation can be performed on an outpatient basis allowing a rapid return to normal activities. If it can be made more effective, it has the potential to provide better local control, while improving functional outcome.

Cite this article: Bone Joint J 2014;96-B:1540–5.

In patients with a tumour affecting the distal ulna it is difficult to preserve the function of the wrist following extensive local resection. We report the outcome of 12 patients (nine female, three male) who underwent excision of the distal ulna without local soft-tissue reconstruction. In six patients, an aggressive benign tumour was present and six had a malignant tumour. At a mean follow-up of 64 months (15 to 132) the mean Musculoskeletal Tumour score was 64% (40% to 93%) and the mean DASH score was 35 (10 to 80). The radiological appearances were satisfactory in most patients. Local recurrence occurred in one patient with benign disease and two with malignant disease. The functional outcome was thus satisfactory at a mean follow-up in excess of five years, with a relatively low rate of complications. The authors conclude that complex reconstructive soft-tissue procedures may not be needed in these patients.

Cite this article: Bone Joint J 2014;96-B:1392–5.

Opinion remains divided as to whether the development of pathological fracture affects the prognosis of patients with an osteosarcoma of the extremities.

We conducted a comprehensive systematic review and meta-analysis of papers which reported the outcomes of osteosarcoma patients with and without a pathological fracture. There were eight eligible papers for final analysis which reported on 1713 patients, of whom 303 (17.7%) had a pathological fracture. The mean age for 1464 patients in six studies was 23.2 years old (2 to 82). The mean follow-up for 1481 patients in seven studies was 90.1 months (6 to 240).

The pooled estimates of local recurrence rates in osteosarcoma patients with and without pathological fractures were 14.4% (8.7 to 20.0) versus 11.4% (8.0 to 14.8). The pooled estimate of relative risk was 1.39 (0.89 to 2.20). The pooled estimates of five-year event-free survival rates in osteosarcoma patients with and without a pathological fracture were 49.3% (95% CI 43.6 to 54.9) versus 66.8% (95% CI 60.7 to 72.8). The pooled estimate of relative risk was 1.33 (1.12 to 1.59). There was no significant difference in the rate of local recurrence between patients who were treated by amputation or limb salvage.

The development of a pathological fracture is a negative prognostic indicator in osteosarcoma and is associated with a reduced five-year event-free survival and a possibly higher rate of local recurrence. Our findings suggest that there is no absolute indication for amputation, as similar rates of local recurrence can be achieved in patients who are carefully selected for limb salvage.

Cite this article: Bone Joint J 2014; 96-B:1396–1403

The aim of this study was to evaluate the functional and oncological outcome of extracorporeally irradiated autografts used to reconstruct the pelvis after a P1/2 internal hemipelvectomy.

The study included 18 patients with a primary malignant bone tumour of the pelvis. There were 13 males and five females with a mean age of 24.8 years (8 to 62). Of these, seven had an osteogenic sarcoma, six a Ewing’s sarcoma, and five a chondrosarcoma. At a mean follow-up of 51.6 months (4 to 185), nine patients had died with metastatic disease while nine were free from disease. Local recurrence occurred in three patients all of whom eventually died of their disease. Deep infection occurred in three patients and required removal of their graft in two while the third underwent a hindquarter amputation for extensive flap necrosis.

The mean Musculoskeletal Tumor Society functional score of the 16 patients who could be followed-up for at least 12 months was 77% (50 to 90). Those 15 patients who completed the Toronto Extremity Salvage Score questionnaire had a mean score of 71% (53 to 85).

Extracorporeal irradiation and re-implantation of bone is a valid method of reconstruction after an internal hemipelvectomy. It has an acceptable morbidity and a functional outcome that compares favourably with other available reconstructive techniques.

Cite this article: Bone Joint J 2014;96-B:1404–10

Resection of a primary sarcoma of the diaphysis of a long bone creates a large defect. The biological options for reconstruction include the use of a vascularised and non-vascularised fibular autograft.

The purpose of the present study was to compare these methods of reconstruction.

Between 1985 and 2007, 53 patients (26 male and 27 female) underwent biological reconstruction of a diaphyseal defect after resection of a primary sarcoma. Their mean age was 20.7 years (3.6 to 62.4). Of these, 26 (49 %) had a vascularised and 27 (51 %) a non-vascularised fibular autograft. Either method could have been used for any patient in the study. The mean follow-up was 52 months (12 to 259). Oncological, surgical and functional outcome were evaluated. Kaplan–Meier analysis was performed for graft survival with major complication as the end point.

At final follow-up, eight patients had died of disease. Primary union was achieved in 40 patients (75%); 22 (42%) with a vascularised fibular autograft and 18 (34%) a non-vascularised (p = 0.167). A total of 32 patients (60%) required revision surgery. Kaplan–Meier analysis revealed a mean survival without complication of 36 months (0.06 to 107.3, sd 9) for the vascularised group and 88 months (0.33 to 163.9, sd 16) for the non-vascularised group (p = 0.035).

Both groups seem to be reliable biological methods of reconstructing a diaphyseal bone defect. Vascularised autografts require more revisions mainly due to problems with wound healing in distal sites of tumour, such as the foot.

Cite this article: Bone Joint J 2014;96-B:1258–63.

We retrospectively reviewed 30 patients with a diffuse-type giant-cell tumour (Dt-GCT) (previously known as pigmented villonodular synovitis) around the knee in order to assess the influence of the type of surgery on the functional outcome and quality of life (QOL). Between 1980 and 2001, 15 of these tumours had been treated primarily at our tertiary referral centre and 15 had been referred from elsewhere with recurrent lesions.

The mean follow-up was 64 months (24 to 393). Functional outcome and QOL were assessed with range of movement and the Knee injury and Osteoarthritis Outcome Score (KOOS), the Musculoskeletal Tumour Society (MSTS) score, the Toronto Extremity Salvage Score (TESS) and the SF-36 questionnaire. There was recurrence in four of 14 patients treated initially by open synovectomy. Local control was achieved after a second operation in 13 of 14 (93%). Recurrence occurred in 15 of 16 patients treated initially by arthroscopic synovectomy. These patients underwent a mean of 1.8 arthroscopies (one to eight) before open synovectomy. This achieved local control in 8 of 15 (53%) after the first synovectomy and in 12 of 15 (80%) after two. The functional outcome and QOL of patients who had undergone primary arthroscopic synovectomy and its attendant subsequent surgical procedures were compared with those who had had a primary open synovectomy using the following measures: range of movement (114º versus 127º; p = 0.03); KOOS (48 versus 71; p = 0.003); MSTS (19 versus 24; p = 0.02); TESS (75 versus 86; p = 0.03); and SF-36 (62 versus 80; p = 0.01).

Those who had undergone open synovectomy needed fewer subsequent operations. Most patients who had been referred with a recurrence had undergone an initial arthroscopic synovectomy followed by multiple further synovectomies. At the final follow-up of eight years (2 to 32), these patients had impaired function and QOL compared with those who had undergone open synovectomy initially.

We conclude that the natural history of Dt-GCT in patients who are treated by arthroscopic synovectomy has an unfavourable outcome, and that primary open synovectomy should be undertaken to prevent recurrence or residual disease.

Cite this article: Bone Joint J 2014; 96-B:1111–18.

The pre-operative differentiation between enchondroma, low-grade chondrosarcoma and high-grade chondrosarcoma remains a diagnostic challenge. We reviewed the accuracy and safety of the radiological grading of cartilaginous tumours through the assessment of, first, pre-operative radiological and post-operative histological agreement, and second the rate of recurrence in lesions confirmed as high-grade on histology. We performed a retrospective review of major long bone cartilaginous tumours managed by curettage as low grade between 2001 and 2012. A total of 53 patients with a mean age of 47.6 years (8 to 71) were included. There were 23 men and 30 women. The tumours involved the femur (n = 20), humerus (n = 18), tibia (n = 9), fibula (n = 3), radius (n = 2) and ulna (n = 1). Pre-operative diagnoses resulted from multidisciplinary consensus following radiological review alone for 35 tumours, or with the addition of pre-operative image guided needle biopsy for 18. The histologically confirmed diagnosis was enchondroma for two (3.7%), low-grade chondrosarcoma for 49 (92.6%) and high-grade chondrosarcoma for two (3.7%). Three patients with a low-grade tumour developed a local recurrence at a mean of 15 months (12 to 17) post-operatively. A single high-grade recurrence (grade II) was treated with tibial diaphyseal replacement. The overall recurrence rate was 7.5% at a mean follow-up of 4.7 years (1.2 to 12.3). Cartilaginous tumours identified as low-grade on pre-operative imaging with or without additional image-guided needle biopsy can safely be managed as low-grade without pre-operative histological diagnosis. A few tumours may demonstrate high-grade features histologically, but the rates of recurrence are not affected.

Cite this article: Bone Joint J 2014; 96-B:1098–105.

Giant cell tumour is the most common aggressive benign tumour of the musculoskeletal system and has a high rate of local recurrence. When it occurs in proximity to the hip, reconstruction of the joint is a challenge. Options for reconstruction after wide resection include the use of a megaprosthesis or an allograft-prosthesis composite. We performed a clinical and radiological study to evaluate the functional results of a proximal femoral allograft-prosthesis composite in the treatment of proximal femoral giant cell tumour after wide resection. This was an observational study, between 2006 and 2012, of 18 patients with a mean age of 32 years (28 to 42) and a mean follow-up of 54 months (18 to 79). We achieved excellent outcomes using Harris Hip Score in 13 patients and a good outcome in five. All allografts united. There were no complications such as infection, failure, fracture or resorption of the graft, or recurrent tumour. Resection and reconstruction of giant cell tumours with proximal femoral allograft–prosthesis composite is a better option than using a prosthesis considering preservation of bone stock and excellent restoration of function.

A good result requires demanding bone banking techniques, effective measures to prevent infection and stability at the allograft-host junction.

Cite this article: Bone Joint J 2014; 96-B:1106–10.

In this case study, we describe the clinical presentation and treatment of 36 patients with periosteal chondrosarcoma collected over a 59-year period by the archive of the Netherlands Committee on Bone Tumours. The demographics, clinical presentation, radiological features, treatment and follow-up are presented with the size, location, the histological grading of the tumour and the survival.

We found a slight predominance of men (61%), and a predilection for the distal femur (33%) and proximal humerus (33%). The metaphysis was the most common site (47%) and the most common presentation was with pain (44%). Half the tumours were classified histologically as grade 1. Pulmonary metastases were reported in one patient after an intra-lesional resection. A second patient died from local recurrence and possible pulmonary and skin metastases after an incomplete resection.

It is clearly important to make the diagnosis appropriately because an incomplete resection may result in local recurrence and metastatic spread. Staging for metastatic disease is recommended in grade II or III lesions.

These patients should be managed with a contrast-enhanced MRI of the tumour and histological confirmation by biopsy, followed by en-bloc excision.

Cite this article: Bone Joint J 2014;96-B:823–8.

Bone sarcomas are rare cancers and orthopaedic surgeons come across them infrequently, sometimes unexpectedly during surgical procedures. We investigated the outcomes of patients who underwent a surgical procedure where sarcomas were found unexpectedly and were subsequently referred to our unit for treatment. We identified 95 patients (44 intra-lesional excisions, 35 fracture fixations, 16 joint replacements) with mean age of 48 years (11 to 83); 60% were males (n = 57). Local recurrence arose in 40% who underwent limb salvage surgery versus 12% who had an amputation. Despite achieving local control, overall survival was worse for patients treated with amputation rather than limb salvage (54% vs 75% five-year survival). Factors that negatively influenced survival were invasive primary surgery (fracture fixation, joint replacement), a delay of greater than two months until referral to our oncology service, and high-grade tumours. Survival in these circumstances depends mostly on factors that are determined prior to definitive treatment by a tertiary orthopaedic oncology unit. Limb salvage in this group of patients is associated with a higher rate of inadequate marginal surgery and, consequently, higher local recurrence rates than amputation, but should still be attempted whenever possible, as local control is not the primary determinant of survival.

Cite this article: Bone Joint J 2014;96-B:665–72.

We retrospectively reviewed the outcomes of 33 consecutive patients who had undergone an extra-articular, total or partial scapulectomy for a malignant tumour of the shoulder girdle between 1 July 2001 and 30 September 2013. Of these, 26 had tumours which originated in the scapula or the adjacent soft tissue and underwent a classic Tikhoff–Linberg procedure, while seven with tumours arising from the proximal humerus were treated with a modified Tikhoff-Linberg operation. We used a Ligament Advanced Reinforcement System for soft-tissue reconstruction in nine patients, but not in the other 24.

The mean Musculoskeletal Tumor Society score (MSTS) was 17.6 (95% confidence interval (CI) 15.9 to 19.4); 17.6 (95% CI 15.5 to 19.6) after the classic Tikhoff–Linberg procedure and 18.1 (95% CI 13.8 to 22.3) after the modified Tikhoff–Linberg procedure. Patients who had undergone a LARS soft-tissue reconstruction had a mean score of 18.6 (95% (CI) 13.9 to 22.4) compared with 17.2 (95% CI 15.5 to 19.0) for those who did not.

The Tikhoff–Linberg procedure is a useful method for wide resection of a malignant tumour of the shoulder girdle which helps to preserve hand and elbow function. The method of soft-tissue reconstruction has no effect on functional outcome.

Cite this article: Bone Joint J 2014;96-B:684–90.

Osteoid osteoma is treated primarily by radiofrequency (RF) ablation. However, there is little information about the distribution of heat in bone during the procedure and its safety. We constructed a model of osteoid osteoma to assess the distribution of heat in bone and to define the margins of safety for ablation. Cavities were drilled in cadaver bovine bones and filled with a liver homogenate to simulate the tumour matrix. Temperature-sensing probes were placed in the bone in a radial fashion away from the cavities. RF ablation was performed 107 times in tumours < 10 mm in diameter (72 of which were in cortical bone, 35 in cancellous bone), and 41 times in cortical bone with models > 10 mm in diameter. Significantly higher temperatures were found in cancellous bone than in cortical bone (p <  0.05). For lesions up to 10 mm in diameter, in both bone types, the temperature varied directly with the size of the tumour (p < 0.05), and inversely with the distance from it. Tumours of > 10 mm in diameter showed a trend similar to those of smaller lesions. No temperature rise was seen beyond 12 mm from the edge of a cortical tumour of any size. Formulae were developed to predict the expected temperature in the bone during ablation.

Cite this article: Bone Joint J 2014; 96-B:677–83

Monostotic fibrous dysplasia of the proximal femur has a variable clinical course, despite its reported limited tendency to progress.

We investigated the natural history and predisposing factors for progression of dysplasia in a group of 76 patients with a mean follow-up of 8.5 years (2.0 to 15.2). Of these, 31 (41%) presented with an asymptomatic incidental lesion while 45 (59%) presented with pain or a pathological fracture. A group of 23 patients (30%) underwent early operative treatment for pain (19: 25%) or pathological fracture (4: 5%).

Of the 53 patients who were initially treated non-operatively, 45 (85%) remained asymptomatic but eight (15%) needed surgery because of pain or fracture. The progression-free survival of the observation group was 81% (sd 6.4%) at five-years follow-up. An initial presentation of pain (p < 0.001), a limp (p < 0.001), radiological evidence of microfracture (p = 0.001) and younger age (< 17 years) (p = 0.016) were significant predisposing factors for disease progression.

The risk of experiencing pain or pathological fracture is considerable in monostotic fibrous dysplasia of the proximal femur. Patients presenting with pain, a limp or radiological evidence of microfracture have a high chance of needing surgical treatment.

Cite this article: Bone Joint J 2014;96-B:673–6.

Objectives

The most concerning infection of allografts and operative procedures is methicillin resistant Staphylococcus aureus (MRSA) and no current iontophoresed antibiotics effectively combat this microbe. It was initially hypothesised that iontophoresis of vancomycin through bone would not be effective due to its large molecular size and lack of charge. The aim of this study was to determine whether this was a viable procedure and to find the optimum conditions for its use.