Background: Treating bone sarcomas in young children, particularly in the proximal femur, is challenging because of the need to preserve growth potential, maintain joint function, and conserve bone for future revisions. In 1997, we introduced a new technique combining a vascularized fibula that preserved the proximal epiphysis to substitute for the femoral head and physis with a massive bone allograft aimed at providing a supportive scaffold for the autograft during growth. This approach initially showed promising results in both anatomic and functional restoration, but because it was a complex operation, we believed that longer term follow-up of this procedure would be helpful to judge its value as a potential reconstructive option. Questions/purposes: (1) What proportion of patients achieved allograft union; what proportion exhibited radiologic signs of vitality in the vascularized fibula, demonstrating bone growth and remodeling; what proportion avoided revision surgery; and what complications were observed with this technique? (2) What were the observed outcome scores using the Musculoskeletal Tumor Society (MSTS) score? (3) What was the status of the hip after treatment? Methods: Between 1997 and 2010, a total of 14 patients who were 6 years old or younger underwent resection of the proximal femur for a bone sarcoma in two sarcoma centers. Six patients were treated with a vascularized fibular autograft plus bulk allograft reconstruction. The median (range) length of the proximal femur resection was 13 (11 to 14) cm. During the period in question, we generally performed the vascularized fibular autograft plus bulk allograft when the acetabular diameter was < 36 mm. None of those who had the fibula autograft plus bulk allograft reconstruction were lost to follow-up before 2 years without meeting a study endpoint (revision, reoperation) or died prior to 2 years with implants intact. All six patients in the original group had either a follow-up of at least 14 years or had met a study endpoint (revision, reoperation) before that minimum surveillance duration; these patients were the focus of the current study. We noted that two patients had follow-up periods of 20 and 27 years but have not been seen in the last 5 years; they were included for survivorship analysis purposes, yet we emphasize that we cannot ascertain their current status. The median (range) follow-up was 17 (14 to 27) years. Results: Six of six patients achieved allograft union, while five of six underwent reoperations, and four of six had the graft removed as part of a revision procedure at a median (range) of 19 (7 to 40) months. Only one patient maintained the original reconstruction after 27 years, despite an epiphysiolysis that occurred 56 months after surgery, which was corrected surgically. The other five patients experienced a complication of the reconstruction at a median (range) onset at 19 (7 to 40) months after surgery. Two of the six patients had a common peroneal nerve palsy at the harvested site. Allograft union was observed a median of 8 months from the index procedure. All patients presented residual limb length discrepancy ranging from 1 to 7 cm. The median (range) MSTS score before any revision was 38% (33% to 93%). Four of the six patients underwent removal of the biological reconstruction and were reconstructed by other methods. They displayed a median (range) MSTS functional score of 88% (73% to 93%) at most recent follow-up. One of the six patients showed progressive diaphyseal hypertrophy, growth, and remodeling of the epiphysis, along with integration with the allograft, and had a final limb length discrepancy of -1 cm. The vascularized fibular epiphysis was enlarged and remodeled to provide a new femoral head and grew similar to the physis of the native femoral head in this one patient. Conclusion: Biological reconstruction using a vascularized fibula and bone allograft in young patients with proximal femur sarcoma was not a durable solution for most patients, and it resulted in frequent unplanned reoperations and revisions. Only one of six patients in this small series had a reconstruction that lasted into adulthood. Even though this was a small group of patients, the poor survival of the construct, the frequent complications, and the unpredictable results associated with it led us to discontinue its use in favor of prosthetic replacement. Level of Evidence: Level IV, therapeutic study.

Objectives: This pre-clinical feasibility study evaluates the accuracy of a novel augmented reality-based (AR-based) guidance technology using head-mounted displays (HMDs) for the placement of patient-specific instruments (PSIs)—also referred to as surgical guides—and osteotomy performance in pelvic tumour resections. The goal is to improve PSI placement accuracy and osteotomy execution while assessing user perception and workflow efficiency. Methods: The study was conducted on ten 3D-printed pelvic phantoms derived from CT scans of cadaveric specimens. Custom PSIs were designed and printed to guide osteotomies at the supraacetabular, symphysial, and ischial regions. An AR application was developed for the HoloLens 2 HMD to display PSI location and cutting planes. The workflow included manual supraacetabular PSI placement, AR-guided placement of the other PSIs and osteotomy execution. Postoperative CT scans were analysed to measure angular and distance errors in PSI placement and osteotomies. Task times and user feedback were also recorded. Results: The mean angular deviation for PSI placement was 2.20°, with a mean distance error of 1.19 mm (95% CI: 0.86 to 1.52 mm). Osteotomies showed an overall mean angular deviation of 3.73° compared to planned cuts, all within the predefined threshold of less than 5°. AR-assisted guidance added less than two minutes per procedure. User feedback highlighted the intuitive interface and high usability, especially for visualising cutting planes. Conclusions: Integrating AR through HMDs is a feasible and accurate method for enhancing PSI placement and osteotomy performance in pelvic tumour resections. The system provides reliable guidance even in cases of PSI failure and adds minimal time to the surgical workflow while significantly improving accuracy. Further validation in cadaveric models is needed to ensure its clinical applicability.

Objectives: Pelvic tumor resections demand high surgical precision to ensure clear margins while preserving function. Although patient-specific instruments (PSIs) improve osteotomy accuracy, positioning errors remain a limitation. This study evaluates the feasibility, accuracy, and usability of a novel dual-function augmented reality (AR) system for intraoperative guidance in PSI positioning and osteotomy execution using a head-mounted display (HMD). The system provides dual-function support by assisting both PSI placement and osteotomy execution. Methods: Ten fresh-frozen cadaveric hemipelves underwent AR-assisted internal hemipelvectomy, using customized 3D-printed PSIs and a new in-house AR software integrated into an HMD. Angular and translational deviations between planned and executed osteotomies were measured using postoperative CT analysis. Absolute angular errors were computed from plane normals; translational deviation was assessed as maximum error at the osteotomy corner point in both sagittal (pitch) and coronal (roll) planes. A Wilcoxon signed-rank test and Bland–Altman plots were used to assess intra-workflow cumulative error. Results: The mean absolute angular deviation was 5.11 ± 1.43°, with 86.66% of osteotomies within acceptable thresholds. Maximum pitch and roll deviations were 4.53 ± 1.32 mm and 2.79 ± 0.72 mm, respectively, with 93.33% and 100% of osteotomies meeting translational accuracy criteria. Wilcoxon analysis showed significantly lower angular error when comparing final executed planes to intermediate AR-displayed planes (p < 0.05), supporting improved PSI positioning accuracy with AR guidance. Surgeons rated the system highly (mean satisfaction ≥ 4.0) for usability and clinical utility. Conclusions: This cadaveric study confirms the feasibility and precision of an HMD-based AR system for PSI-guided pelvic osteotomies. The system demonstrated strong accuracy and high surgeon acceptance, highlighting its potential for clinical adoption in complex oncologic procedures.

3D-printed patient-specific instruments (PSIs), also known as 3D guides, have been shown to improve accuracy in resection of pelvic tumors in cadaver studies and achieve better surgical margins in vivo. This study evaluates the clinical impact of 3D-printed guides on medium-term local and distant disease control, as well as disease-free and overall survival in patients. A cohort study included 25 patients with primary pelvic or sacral sarcomas: 10 in the 3D group and 15 in the control group, with a median follow-up of 47 months. Demographic and clinical data, including tumor histology, stage, resection technique, associated reconstruction, adjuvant therapies, and complications, were evaluated. Surgical margins (free, marginal, and contaminated) and relapse-free and overall survival curves were analyzed. The 3D group achieved a higher rate of free margins (80% vs 66.7%, p=0.345). Local recurrence (50% vs 60%, p=0.244) and distant disease relapse (20% vs 47%, p=0.132) rates were lower in the 3D group. At the end of the follow-up, the 3D group had a higher overall survival rate (60% vs 40%, p=0.327). The complication rate was similar in both groups, with a deep infection rate of 40%. The use of 3D guides in resecting primary pelvic tumors not only achieves a higher rate of free margins compared to conventional techniques but also shows a trend towards higher local, distant, and overall disease-free survival. Further studies with larger sample sizes and higher levels of evidence are necessary to validate these clinical trends.