Aims

Acridine orange (AO) demonstrates several biological activities. When exposed to low doses of X-ray radiation, AO increases the production of reactive radicals (radiodynamic therapy (AO-RDT)). We elucidated the efficacy of AO-RDT in breast and prostate cancer cell lines, which are likely to develop bone metastases.

Aims. The aim of this study was to investigate the safety and efficacy of 3D-printed modular prostheses in patients who underwent joint-sparing limb salvage surgery (JSLSS) for malignant femoral diaphyseal bone tumours. Methods. We retrospectively reviewed 17 patients (13 males and four females) with femoral diaphyseal tumours who underwent JSLSS in our hospital. Results. In all, 17 patients with locally aggressive bone tumours (Enneking stage IIB) located in the femoral shaft underwent JSLSS and reconstruction with 3D-printed modular prostheses between January 2020 and June 2022. The median surgical time was 153 minutes (interquartile range (IQR) 117 to 248), and the median estimated blood loss was 200ml (IQR 125 to 400). Osteosarcoma was the most common pathological type (n = 12; 70.6%). The mean osteotomy length was 197.53 mm (SD 12.34), and the median follow-up was 25 months (IQR 19 to 38). Two patients experienced local recurrence and three developed distant metastases. Postoperative complications included wound infection in one patient and screw loosening in another, both of which were treated successfully with revision surgery. The median Musculoskeletal Tumor Society score at the final follow-up was 28 (IQR 27 to 28). Conclusion. The 3D-printed modular prosthesis is a reliable and feasible reconstruction option for patients with malignant femoral diaphyseal tumours. It helps to improve the limb salvage rate, restore limb function, and achieve better short-term effectiveness. Cite this article: Bone Jt Open 2024;5(4):317–323

Objectives. We evaluated the accuracy of augmented reality (AR)-based navigation assistance through simulation of bone tumours in a pig femur model. Methods. We developed an AR-based navigation system for bone tumour resection, which could be used on a tablet PC. To simulate a bone tumour in the pig femur, a cortical window was made in the diaphysis and bone cement was inserted. A total of 133 pig femurs were used and tumour resection was simulated with AR-assisted resection (164 resection in 82 femurs, half by an orthropaedic oncology expert and half by an orthopaedic resident) and resection with the conventional method (82 resection in 41 femurs). In the conventional group, resection was performed after measuring the distance from the edge of the condyle to the expected resection margin with a ruler as per routine clinical practice. Results. The mean error of 164 resections in 82 femurs in the AR group was 1.71 mm (0 to 6). The mean error of 82 resections in 41 femurs in the conventional resection group was 2.64 mm (0 to 11) (p < 0.05, one-way analysis of variance). The probabilities of a surgeon obtaining a 10 mm surgical margin with a 3 mm tolerance were 90.2% in AR-assisted resections, and 70.7% in conventional resections. Conclusion. We demonstrated that the accuracy of tumour resection was satisfactory with the help of the AR navigation system, with the tumour shown as a virtual template. In addition, this concept made the navigation system simple and available without additional cost or time. Cite this article: H. S. Cho, Y. K. Park, S. Gupta, C. Yoon, I. Han, H-S. Kim, H. Choi, J. Hong. Augmented reality in bone tumour resection: An experimental study. Bone Joint Res 2017;6:137–143

INTRODUCTION. Bone tumour resection and subsequent reconstruction remains challenging for the surgeon. Obtaining adequate margins is mandatory to decrease the risk of local recurrence. Improving surgical margins quality without excessive resection, reducing surgical time and increasing the quality of the reconstruction are the main goals of today's research in bone tumour surgical management. With the outstanding improvements in imaging and computerised planning, it is now a standard. However, surgical accuracy is essential in orthopaedic oncologic surgery (Grimmer 2005). Patient specific instruments (PSI) may greatly improve the surgeon's ability to achieve the targeted resection. Thanks to its physical support, PSI can physically guide the blade yielding to a better control over the cutting process (Wong, 2014). Surgical time might significantly be reduced as well when compared to conventional method or navigated procedure. Finally, reconstruction may gain in rapidity and quality especially when allograft is the preferred solution as PSI can be designed as well for allograft cutting (Bellanova, 2013). Since 2011, PSI have systematically been used in our institution for bone tumour resection and when applicable allograft reconstruction. This paper reports the mid- to long-term medical outcomes on a large series. MATERIALS AND METHODS. Between 2011 and 2016, we systematically used PSI to remove bone tumours in 30 patients. The pre-operative planning involved the tumour delineation drawn on MRI by the surgeon. The MRI and obtained tumour volume were transferred to the CT-scan by image fusion (co- registration). Cutting planes were positioned around the tumour including a safe margin. The PSI were designed to ensure a sufficient stability but kept thin enough to limit the bone exposure. The PSI was manufactured by 3D-printing in a biocompatible and sterilisable material. PSI has been intraoperatively to cut the bone with predetermined margins. Medical files were reviewed for large data collection: type, size and site of the tumour, pre-and post-operative metastatic status, bone and soft tissues resection margins, local recurrence, use of an allograft and a PSI for graft adjustment or not for the reconstruction, the fusion of the allograft when applicable, the follow-up time and early/late complications. RESULTS. Over a period of 5 years, 30 patients were operated on with PSI (10 osteosarcomas, 4 chondrosarcomas, 10 Ewing sarcomas and 6 other types of bone tumours). Mean follow-up was 27±20 months. 18 cases out of 30 have more than 2 years follow-up and 13 out of 30 have more than 3 years of follow-up. Mean operating time was 6h02±3h44. Mean size of the tumours was 8,4±4,7cm and location was the upper limb in 5 cases, inferior limb in 15 cases and the pelvis in 10 occurrences. Metastatic disease developed postoperatively in 5 patients. Surgical margins in the bone were R0 in all cases but one case where a R1 surgery was planned to preserve a nerve root. We did not observe any local recurrence in the bone. Within soft tissues, margins were classified as R0 in 28 patients and R1 in 2 patients. In 26 cases, an allograft was used to reconstruct the bone defect. In 23 of those patients, the allograft was selected by CT scan and cut using a PSI. In the 3 allografts cut free-handily, only one demonstrated a fusion. Of the 23 cut with a guide, 12 fused completely, 2 demonstrated a partial fusion and 9 were not fused at the last follow-up. At the last follow-up, 2 patients were dead of disease, 5 were alive with metastatic disease and 23 were alive without disease. DISCUSSION. Oncology is probably the field where PSI can bring the largest advantage when compared to the conventional procedure. Several papers have reported the use of PSI for bone tumour resection. All of them have shown very promising results on in-vitro experiments (Cartiaux 2014), cadaver experiment (Wong 2012) or small clinical series (Bellanova 2013, Gouin, 2014). None of these papers report a large patient series associated with a clinically relevant follow-up. This series is the first mid- to long-term follow-up series involving PSI tumour surgery. These results are showing strong evidences of clinical improvements. It comes into contradiction with PSI for total knee arthroplasty where controversial results on the patient's outcome has been reported (Thienpont 2014). R0 margin has been systematically obtained for all bone cuttings, and local recurrence has been strongly decreased (3%) when compared to the usual recurrence rates published in the literature (from 15% to 35% according to the location). Allograft fusion seems improved as well thanks to the shape-matching of the selected allograft and a close contact between host and allograft at bony junctions. With a longer follow-up, these evidences should be stronger to definitely make PSI the best option for bone tumour resection

Recently, several preliminary reports have been issued on the application of computer assistance to bone tumour surgery. Surgical navigation systems can apply three-dimensional images such as CT and MR images to intraoperative visualization. Although CT is better at describing cortical bone status, MRI is considered the best method for defining the extent of marrow involvement for bone tumours and for planning surgical resection in bone tumour surgery. There have been a few reports on the application of MR imaging to navigation-assisted bone tumour surgery through CT–MR image fusion. However, the CT–MRI fusion technique requires additional costs and exposure of the patient to radiation from the preoperative CT, as well as additional time for image fusion. Above all, the image fusion process is a kind of registration (image to image registration) that inevitably leads to registration error. Herein we describe a new method for the direct application of MR images to navigation-assisted bone tumour surgery as an alternative to CT–MRI fusion. Six patients with an orthopaedic malignancy were employed for this method during navigation-assisted tumour resection. Resorbable pin placement and rapid 3-dimensional spoiled gradient echo sequences made the direct application of MR images to computer-assisted bone tumour surgery without CT–MR image fusion possible. A paired-point registration technique was employed for patient-image registration in all patients. It took 20 min on average to set up the navigation (range 15 to 25 minutes). The mean registration error was 0.98 mm (range 0.4 to 1.7 mm). On histologic examination, distances from tumours to resection margins were in accord with preoperative plans. Mean duration of follow-up was 25.8 months (range 18 to 32 months). No patient had a local recurrence or distant metastasis at the last follow-up. Direct patient-to-MRI registration is a very useful method for bone tumour surgery, permitting the application of MR images to intraoperative visualization without any additional costs or exposure of the patient to radiation from the preoperative CT scan

Primary bone tumours of the clavicle are rare. Currently the existing literature is limited to a single case series and case reports or cases. Information regarding the patient's demographics and tumour types is therefore limited. The aim of this study was to investigate the and also suggest a management protocol for suspected primary bone tumours of the clavicle. We retrospectively reviewed the Scottish Bone Tumour Register from January 1971 to January 2012 and included all primary bone tumours of the clavicle. We identified only sixteen primary bone tumours over forty one year's highlighting the rarity of these tumours. There were ten benign and six malignant tumours with a mean age of 32 years (Range 4 to 66). The average presentation to orthopaedics after onset of symptoms was two months with five patients presenting following a pathological fracture. Malignant tumour types identified were consistent with previous literature with two cases of Ewing's sarcoma and osteosarcoma and a single case of osteosarcoma post radiotherapy and a single case of chondrosarcoma. Benign tumours were treated effectively with intralesional procedures. Malignant tumours were treated with wide local excision and subtotal or total clavicle excision. We suggest an investigatory and treatment protocol for patients with a suspected primary bone tumour of the clavicle. This is the largest series of primary bone tumours of the clavicle in the literature

Primary bone tumours of the talus are rare. Currently the existing literature is limited to a single case series and case reports or cases described in series of foot tumours. Information regarding the patient's demographics and tumour types is therefore limited. The aim of this study was to investigate these questions and also suggest a management protocol for suspected primary bone tumours of the talus. We retrospectively reviewed the Scottish Bone Tumour Register from January 1954 to May 2010 and included all primary bone tumours of the talus. We identified only twenty three bone tumours over fifty six years highlighting the rarity of these tumours. There were twenty benign and three malignant tumours with a mean age of twenty eight years. A delay in presentation was common with a mean time from onset of symptoms to diagnosis of ten months. Tumour types identified were consistent with previous literature. We identified cases of desmoplastic fibroma and intraosseous lipodystrophy described for the first time. We suggest an investigatory and treatment protocol for patients with a suspected primary bone tumour of the talus. This is the largest series of primary bone tumours of the talus in the literature

Amputation was once widely practised for primary bone tumours of the limbs. Yet this situation has changed with limb salvage surgery becoming increasingly popular in the last 30 years. Many different techniques are now available. These include allografts, autografts, endoprostheses and allograft-prosthesis composites. This article reviews these methods, concentrating on the functional outcomes and complications that have been reported

Background:The study aimed to analyse the demographic, clinical, and histological features of patients with a malignant primary bone tumour of the femur presenting with a pathological fracture. Methods: Eighty-six patients with primary malignant bone tumours of the femur presenting with pathological fracture were identified from a unique national database that contains original radiographs, casenotes and histology for all patients diagnosed with a primary bone tumour since september 1936 to the present. Demographic data, presenting features, tumour location, histological diagnosis, treatment, local recurrence, metastasis and survival data were gathered. Results: The median age was 63 years (range 4 to 87 years) and 47% were men. Forty-two percent of patients presented with a history of trauma. Forty percent of lesions were in the proximal femur, 34% in the diaphysis and 26% in the distal femur. The most common histological diagnoses were osteosarcoma (13 patients), Paget’s sarcoma (12 patients), myeloma (11 patients), chondrosarcoma and lymphoma (9 patients each). Other diagnoses were fibrosarcoma, Ewing’s sarcoma, spindle cell sarcoma, reticulum cell sarcoma, malignant fibrous hystiocytoma, and malignant giant cell tumour. The local recurrence rate was 31%. The median survival was 12 months (95% confidence interval 6 to 18 months). Overall 5 and 10-year survival were 22.4% and 17.4% respectively. Specifically for osteosarcoma, chondrosarcoma and Paget’s sarcoma the five year survival rates were 15.4%, 11.1% and 19.0% respectively. Those in whom the age at the time of presentation was over 60 years had a significantly worse prognosis (log rank 13.4, p< 0.001). Conclusion: Pathological fracture as a presenting symptom of primary malignant bone tumours is associated with a poor prognosis in nearly all tumour types studied. The prognosis is worse in those who are over 60 years at the time of presentation

Introduction: Only 4–13 % of all spine tumours are primary bone tumours. We report on 180 cases of primary malignant bone tumours of the spine from the Scottish Bone Tumour Registry. The aim of the study was to analyse the incidence, demography, pathology and survival patterns of primary malignant bone tumours of the vertebral column. Materials and Methods: All of the data in the Scottish Bone Tumour Registry is compiled prospectively. This report is based on a retrospective review of all the data from 180 cases of primary malignant bone tumours (excluding metastatic lesions). Results: Of 4,301 registry cases 4.1% were primary malignant lesions (n=180). Seventy two percent of all spinal tumours were primary malignant neoplasms. There were 22 cervical, 72 thoracic, 45 lumbar and 41 sacrococcygeal lesions. There was a male preponderance (103 males & 77 females). The mean age at presentation was 54 years (range, 4–86 years). The top two ranked tumours were myeloma (42) and chordoma (41). Ewing’ sarcoma (15), Leukaemik-Lymphomatous lesions (13), conventional osteosarcoma (10) and Paget’s sarcoma (9) followed thereafter. The predominant presenting symptom was pain. Pathological fracture occurred in 7 patients. The operative treatment consisted of curettage (21), excision (51) and resection (9) with supplemented bone grafting (13). Adjuvant chemo (=61) and radiotherapy (=131) was also used in selective cases. Thirty patients were alive with no evidence of disease at a mean 5 year follow-up. Six were alive with persistent primary disease and/or local recurrence and/or metastases at the time of review. Eighty four patients died with persistent primary disease, 30 patients died of metastatic disease, 9 due to local recurrence and 17 of unrelated causes. Conclusions: Only 4.1% of the musculoskeletal tumours were spinal: 40% involved the thoracic spine. Mean age at presentation was 54 years. Myeloma, chordoma, chondrosarcoma and Ewing’ sarcoma were the most common pathologies. Myeloma predominated: osteosarcoma was much less common in our series compared to previous reports. Early diagnoses resulted into improved outcome

The surgical treatment of bone tumours can result in large perioperative blood loss due to their large sizes and hypervascularity. Preoperative embolisation has been successfully used to downgrade vascularity, thus reducing perioperative blood loss and its associated complications. Prior to embolization era, blood loss as high as 18,500mL have been reported peri-opratively. Twenty-six patients with a variety of bone tumours (average size 10.5×7.5×5.5cm), who underwent pre-operative embolisation between 2005 and 2009, were retrospectively studied. The group comprised of 17 females and 9 males. Their mean age was 38 years old. All patients underwent surgical resection within 48 hours of embolization. Mean blood loss was 796mL and required on average 1.1units of blood. We experienced no complications. Pre-operative arterial embolisation of large, richly vascular bone tumours in anatomically difficult positions, is a safe and effective method of downstaging vascularity and reducing blood loss

INTRODUCTION. We conducted a review of the Leeds Regional Bone Tumour Registry for primary bone tumours of the spine since establishment in 1958 until year 2000. AIM. To analyze the incidence of primary tumours of the spine and to record the site of occurrence, sex distribution, survival and pathology of these tumours. Summary of the Background Data. Primary tumours of the spine are particularly rare, accounting for between 4% and 13% of published series of primary bone tumours. METHOD. The Leeds Bone Tumour Registry was reviewed and a total of 2750 cases of bone tumours and tumour-like cases were analyzed. Consultants in orthopaedic surgery, neurosurgery, oncology and pathology in North and West Yorkshire and Humberside contribute to the Registry. RESULTS. Primary bone tumours of the osseous spine constitute only 126 of the 2,750 cases (4.6%). Chordoma was the most frequent tumour in the cervical and sacral regions, while the most common diagnosis overall was multiple myeloma and plasmacytoma. Osteosarcoma ranked third. The mean age of presentation was 42 years and pain was the most common presenting symptom, occurring in 95% of malignant and 76% of benign tumours. Neurological involvement occurred in 52% of malignant tumours and usually meant a poor prognosis,. CONCLUSIONS. The establishment of Bone Tumour Registries is the only way that sufficient data on large numbers of these rare tumours can be accumulated to provide a valuable and otherwise unavailable source of information for research, education and clinical follow-up

Purpose: We conducted a review of the Leeds Regional Bone Tumour Registry for primary bone tumours of the axial skeleton since establishment in 1958 until year 2000 to analyze the incidence of primary tumours of the axial skeleton and to record their site of occurrence, sex distribution, survival and pathology. Method: Primary tumours of the axial skeleton are particularly rare, accounting for between 4% and 13% of published series of primary bone tumours. The Leeds Bone Tumour Registry was reviewed and a total of 2750 cases of bone tumours and tumour-like cases were analyzed. Consultants in orthopaedic surgery, neurosurgery, oncology and pathology in North and West Yorkshire and Humberside contribute to the Registry. Results: Primary bone tumours of the axial skeleton constitute only 126 of the 2,750 cases (4.6%). Chordoma was the most frequent tumour in the cervical and sacral regions, while the most common diagnosis overall was myeloma. Osteosarcoma ranked third. Mean age of presentation was 42 years. Pain was the most common presenting symptom, occurring in 95% of malignant and 76% of benign tumours. Neurological involvement occurred in 52% of malignant tumours and usually meant a poor prognosis,. Conclusions: The establishment of Bone Tumour Registries is the only way that sufficient data on large numbers of these rare tumours can be accumulated to provide a valuable and otherwise unavailable source of information for research, education and clinical follow-up

In proximal humerus reconstructions, osteoarticular massive allograft (OA) allows a biologic reattachment of tendineous structures of the host providing stability and functional recovery. Allograft-prosthesis composites (APC) are more technically demanding, but functional advantages with new prosthetic design are expected with lower fracture and failure rate with time. We compared the outcome of patients treated with OA reconstruction (group A) and patients treated with an APC (group B) after humerus resection for bone tumours. Thirty six patients treated between 1996 and 2009 were included in the study (18 group A; 18 group B). The diagnosis was a malignant bone tumour in 28 cases, an aggressive benign bone tumour in 6 and a bone metastasis in 2. Three total humerus resections were performed (two in group A and one in group B). Three different type of prosthesis were used (conventional, reverse and resurfacing). In group A, at an average follow-up of 66 months (2-116), 16 patients were continuously disease free. Ten patients (56%) had no complication; in 6 cases (33%) we observed a fracture of the graft and in 3 cases (17%) a pseudoarthrosis. In group B, at an average follow up of 44 months (3-164), 16 patients were continuously disease free. Thirteen patients (72%) had no complication, in 2 cases (11%) stem loosening, in 2 cases (11%) dislocation, in 1 case pseudoarthrosis and in 1 case resorption and detachment of allograft's great tuberosity was observed. Functional outcome was evaluated using MSTS scoring system: a mean score of 24 (13-30) in group A and 23 (15-27) in group B was observed. In our experience, proximal humerus APC showed functional results comparable to OA allograft with lower complication rate. In conclusion, in biologic reconstruction of the proximal humerus, APC seems to provide a more reliable solution than OA allograft at long term

Aims

The standard of surgical treatment for lower limb neoplasms had been characterized by highly interventional techniques, leading to severe kinetic impairment of the patients and incidences of phantom pain. Rotationplasty had arisen as a potent limb salvage treatment option for young cancer patients with lower limb bone tumours, but its impact on the gait through comparative studies still remains unclear several years after the introduction of the procedure. The aim of this study is to assess the effect of rotationplasty on gait parameters measured by gait analysis compared to healthy individuals.

Introduction. Bony tumours of foot account for approximately 3% of osseous tumours. However, literature regarding calcaneal tumours comprises individual case reports, short case series or literature reviews, with last large case series in 1973. Literature on bony tumours of the talus is limited to case reports only. Methods. We retrospectively reviewed medical notes and imaging for all patients with calcaneal or talar tumours recorded in the Scottish Bone Tumour Registry since the 1940's. Demographics, presentation, investigation, histology, management and outcome were reviewed. Results. 38 calcaneal tumours and 24 talar tumours were identified. Calcaneal tumours. Mean age at presentation 30 with heel pain and swelling, average length of symptoms 9 months. 4 cases present with pathological fracture. 24 tumours benign including 6 unicameral bone cysts, 3 chondroblastoma, 3 PVNS with calcaneal erosion, and wide variety of individual lesions. 13 malignant tumours comprising 6 osteosarcoma, 5 chondrosarcoma and 2 Ewing's sarcoma. 1 metastatic carcinoma. Talar Tumours. Mean age at presentation 28 with ankle pain and occasionally swelling, average length of symptoms 5 months. 20 benign cases including 7 osteoid osteoma, 4 chondroblastoma, and variety of individual lesions. 3 malignant lesions comprising 2 chondrosarcoma, one osteosarcoma. Discussion. Tumours of hindfoot frequently are delayed in diagnosis due to rarity and lack of clinician familiarity. They are more common in men especially talar tumours which are most commonly benign osteoid osteoma or chondroblastoma. Calcaneal tumours have 1 in 3 risk of malignancy. Diagnosis is often made on plain radiograph but MRI is the gold standard. Conclusion. We present largest case series of calcaneal tumours and first case series of talar tumours from the Scottish Bone Tumour Registry. Despite their rarity clinicians should maintain a high index of suspicion as accurate and timely diagnosis is important to management and outcome

Aim: To calculate the incidence and timing of metal failure in endoprostheses used for bone tumour reconstructions and to analyse the mode of failure. Methods: A retrospective analysis was performed on 468 endoprostheses with an average follow-up of 50 months. The explanted prostheses were studied to determine the mode of failure and the design and material features that might have contributed to the failure. Results: There were 18 mechanical failures of metal. A total of 19 cases were revised for loosening one of which was noted to have a metal fracture pending at the time of the revision. There were three cases of failure of the coupling between components of modular systems. All of the remaining cases (16) were in the lower limb and these failed by fracture of the metal. The fractures occurred at an average of 92 months. The majority of the fractures that were seen were simple fatigue fractures but in three cases other types of failure were also involved. There were no fatigue fractures in forged cobalt chrome components. Fatigue fracture of the cast cobalt chrome implants could always be attributed to a local stress riser or a local area of high stress due to features of the design. Fatigue fractures of titanium implants were often related to notching. Discussion: The large skeletal defects left by resection of bone tumours can often be reconstructed with endo-prostheses. The mechanical demands on these implants are great resulting in a relatively high incidence of metal failure. Improvements in design and materials can minimise these failures

Bony tumours of the foot account for approximately 3% of all osseous tumours. However, literature regarding os calcis tumours comprises individual case reports, short case series or literature reviews, with the last large case series in 1973. We retrospectively reviewed the medical notes and imaging for all patients with calcaneal tumours recorded in the Scottish Bone Tumour Registry since the 1940's. Demographics, presentation, investigation, histology, management and outcome were reviewed. 38 calcaneal tumours were identified. Male to female ratio 2:1, mean age at presentation 30 with heel pain and swelling, average length of symptoms 9 months. 4 cases present with pathological fracture. 24 tumours benign including 6 unicameral bone cysts, 3 chondroblastoma, 3 PVNS with calcaneal erosion, and a wide variety of individual lesions. 13 malignant tumours comprising 6 osteosarcoma, 5 chondrosarcoma and 2 Ewings sarcoma. 1 metastatic carcinoma. Tumours of the calcaneus frequently are delayed in diagnosis due to their rarity and lack of clinician familiarity. They are more common in men and have a 1 in 3 risk of malignancy, covering a wide variety of lesions. Outcome is dependent on early diagnosis, timely surgery and most importantly neo-adjuvant chemotherapy. Diagnosis is often made on plain radiograph but MRI is the gold standard. We present the largest case series of calcaneal tumours, from our experience with the Scottish Bone Tumour Registry. Despite their rarity clinicians should maintain a high index of suspicion as accurate and timely diagnosis is important to management and outcome

Aims

While internet search engines have been the primary information source for patients’ questions, artificial intelligence large language models like ChatGPT are trending towards becoming the new primary source. The purpose of this study was to determine if ChatGPT can answer patient questions about total hip (THA) and knee arthroplasty (TKA) with consistent accuracy, comprehensiveness, and easy readability.

Resecting bone tumours within the pelvis is highly challenging and requires good cutting accuracy to achieve sufficient margins. Computer-assisted technologies such as intraoperative navigation have been developed for pelvic bone tumour resection. Patient-specific instruments have been transposed to tumour surgery. The present study reports a series of 11 clinical cases of PSI-assisted bone tumour surgery within the pelvis, and assesses how accurately a preoperative resection strategy can be replicated intraoperatively with the PSI. The patient series consisted in 11 patients eligible for curative surgical resection of primary bone tumor of the pelvis. Eight patients had a bone sarcoma of iliac bone involving the acetabulum, two patients had a sacral tumor, and one patient had a chondrosarcoma of proximal femur with intra-articular hip extension. Resection planning was preoperatively defined including a safe margin defined by the surgeon from 3 up to 15 mm. PSI were designed using a computer-aided design software according to the desired resection strategy and produced by additive manufacturing technology. Intraoperatively, PSI were positioned freehand by the surgeon and fixed on the bone surface using K-wires. The standard surgical approach has been used for each patient. Dissection was in accordance with the routine technique. There was no additional bone exposure to position the PSI. Histopathological analysis of the resected tumor specimens was performed to evaluate the achieved resection margins. Postoperative CT were acquired and matched to the preoperative CT to assess the local control of the tumor. Two parameters were measured: achieved resection margin (minimum distance to the tumor) and location accuracy (maximum distance between achieved and planned cuttings; ISO1101 standard). PSI were quick and easy to use with a positioning onto the bone surface in less than 5 minutes for all cases. The positioning of the PSI was considered unambiguous for all patients. Histopathological analysis classified all achieved resection margins as R0 (tumor-free), except for two patients : R2 because of a morcelised tumour and R1 in soft tissues. The errors in safe margin averaged −0.8 mm (95% CI: −1.8 mm to 0.1 mm). The location accuracy of the achieved cut planes with respect to the desired cut planes averaged 2.5 mm (95% CI: 1.8 to 3.2 mm). Results in terms of safe margin or the location accuracy demonstrated how PSI enabled the surgeon to intraoperatively replicate the resection strategies with a very good cutting accuracy. These findings are consistent with the levels of bone-cutting accuracy published in the literature. PSI technology described in this study achieved clear bone margins for all patients. Longer follow-up period is required but it appears that PSI has the potential to provide clinically acceptable margins