Aims: The success rates of two-stage revision arthroplasty for infection have evolved since their early description. The implementation of internationally accepted outcome criteria led to the readjustment of such rates. However, patients who do not undergo reimplantation are usually set aside from these calculations. The aim of this study was to investigate the outcomes of two-stage revision arthroplasty when considering those who do not undergo reimplantation, and to investigate the characteristics of this subgroup. Methods: A retrospective cohort study was conducted. Patients with chronic hip or knee periprosthetic joint infection (PJI) treated with two-stage revision between January 2010 and October 2018, with a minimum follow-up of one year, were included. Variables including demography, morbidity, microbiology, and outcome were collected. The primary endpoint was the eradication of infection. Patients who did not undergo reimplantation were analyzed in order to characterize this subgroup better. Results: A total of 162 chronic PJIs were included in the study. After a mean follow-up of 57.3 months (12.1 to 115.7), 18 patients (11.1%) did not undergo reimplantation, due either to medical issues (10), the patient’s choice (4), or death (4). When only considering those who underwent reimplantation, the success rate was 80.6%. However, when those who did not undergo reimplantation were included, the success rate dropped to 71.6%. Advanced age, American Society of Anesthesiologists grade ≥ III, McPherson’s C host, and Gram-negative related PJI were independent risk factors for retention of the spacer. The mortality was higher in the non-reimplanted group. Conclusion: The real success rate of two-stage revision may not be as high as previously reported. The exclusion of patients who do not undergo reimplantation resulted in a 9% overestimation of the success rate in this series. Many comorbidity-related risk factors for retention of the spacer were identified, as well as higher death rates in this group. Efforts should be made to optimize these patients medically in order to increase reimplantation and success rates, while decreasing mortality. Cite this article: Bone Joint J 2020;102-B(12):1682–1688.

Background: Excision of bone tumors and endoprosthetic reconstruction allow patients early weightbearing and a potential functional advantage compared with amputation. These reconstructions do not restore the limb to normal status, however, and patients are subject to complications that may result in revision or loss of the limb. Because better understanding of these complications based on current information might help the patient and surgeon in decision-making, we undertook a systematic review of studies published on this topic. Questions/purposes: (1) What are the primary modes and proportion of failure of tumor endoprostheses in patients undergoing reconstruction after excision of primary extremity bone sarcomas? Methods: We systematically searched MEDLINE, Embase, and the Cochrane Library for all studies published from April 15, 1998, to April 15, 2018. Three reviewers independently reviewed studies reporting endoprosthetic reconstruction survival and events requiring revision for primary extremity bone tumors treated with endoprosthetic reconstruction for inclusion and performed independent data extraction. We excluded all studies with fewer than five patients, any systematic review/meta-analyses, and any study not reporting on primary extremity bone tumors. All discrepancies were resolved by the study’s senior author. Data extracted from included studies were any reoperation event for wound dehiscence, any operative fixation for a pathologic fracture, and any revision of the primary endoprosthesis for implant wear or breakage, deep infection not amenable to prosthesis retention, or for local recurrence. We assessed the overall quality of the evidence with the Methodological Index for Non-Randomized Studies (MINORS) approach with a higher MINORS score representative of a more methodologically rigorous study with a total possible score of 16 points for noncomparative and 24 points for comparative studies. Forty-nine studies met criteria for inclusion from an initial search return of 904 studies, of which no studies were randomized controlled trials. From a total patient population of 2721, there was a mean followup of 93 months (range, 1-516 months) with loss to followup or death occurring in 447 of 2118 (21%) patients with six studies not providing loss to followup data. The mean MINORS score was 14 for prospective studies and 11 for retrospective studies. Results: Overall, there were 1283 reoperations among the 2721 (47%) patients. Reoperation for mechanical endoprosthetic events (soft tissue dehiscence or periarticular soft tissue instability, aseptic loosening, or implant wear/fracture) occurred in 907 of 2721 (33%) patients. Aseptic loosening occurred at a mean of 75 months (range, 1-376 months) in 212 of 315 patients (67%). Deep infection requiring removal of the initial prosthesis occurred in 247 of 2721 (9%) patients with deep infection occurring at a mean of 24 months (range, 1-372 months) in the 190 infections (77%) with time to infection data available. Local recurrence rates requiring revision or amputation occurred in 129 (5%) of all patients. There was an overall primary endoprosthesis survival rate without any surgical reintervention of 63% among reporting studies at a mean of 79 months followup. Conclusions: Failures of endoprosthetic reconstructions after extremity tumor surgery are common, most often resulting from implant wear or fracture, aseptic loosening, and infection. Importantly, the aggregated data are the first to attempt to quantify the time to specific complication types within this patient population. Deep infection not amenable to endoprosthesis retention appears to occur approximately 2 years postoperatively in most patients, with aseptic loosening occurring most commonly at 75 months. Although endoprosthetic reconstruction is one of the most common forms of reconstruction after bone tumor resection, the quality of published evidence regarding this procedure is of low quality with high loss to followup and data quality limiting interstudy analysis. The quality of the evidence is low with high loss to followup and inconsistent reporting of times to reintervention events. Although the most common modes of endoprosthetic failure in this population are well known, creation of quality prospective, collaborative databases would assist in clarifying and informing important elements of the followup process for these patients. Level of Evidence: Level IV, therapeutic study.

Objectives To assess the accuracy of patient-specific instruments (PSIs) versus standard manual technique and the precision of computer-assisted planning and PSI-guided osteotomies in pelvic tumour resection. Methods CT scans were obtained from five female cadaveric pelvises. Five osteotomies were designed using Mimics software: sacroiliac, biplanar supra-acetabular, two parallel iliopubic and ischial. For cases of the left hemipelvis, PSIs were designed to guide standard oscillating saw osteotomies and later manufactured using 3D printing. Osteotomies were performed using the standard manual technique in cases of the right hemipelvis. Post-resection CT scans were quantitatively analysed. Student’s t-test and Mann–Whitney U test were used. Results Compared with the manual technique, PSI-guided osteotomies improved accuracy by a mean 9.6 mm (p < 0.008) in the sacroiliac osteotomies, 6.2 mm (p < 0.008) and 5.8 mm (p < 0.032) in the biplanar supra-acetabular, 3 mm (p < 0.016) in the ischial and 2.2 mm (p < 0.032) and 2.6 mm (p < 0.008) in the parallel iliopubic osteotomies, with a mean linear deviation of 4.9 mm (p < 0.001) for all osteotomies. Of the manual osteotomies, 53% (n = 16) had a linear deviation > 5 mm and 27% (n = 8) were > 10 mm. In the PSI cases, deviations were 10% (n = 3) and 0 % (n = 0), respectively. For angular deviation from pre-operative plans, we observed a mean improvement of 7.06° (p < 0.001) in pitch and 2.94° (p < 0.001) in roll, comparing PSI and the standard manual technique. Conclusion In an experimental study, computer-assisted planning and PSIs improved accuracy in pelvic tumour resections, bringing osteotomy results closer to the parameters set in pre-operative planning, as compared with standard manual techniques. Cite this article: A. Sallent, M. Vicente, M. M. Reverté, A. Lopez, A. Rodríguez-Baeza, M. Pérez-Domínguez, R. Velez. How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study. Bone Joint Res 2017;6:577–583. DOI: 10.1302/2046-3758.610.BJR-2017-0094.R1.

Background: Surgical reconstruction of large bone defects with structural bone allografts can restore bone stock but is associated with complications such as nonunion, fracture, and infection. Vascularized reconstructive techniques may provide an alternative in the repair of critical bone defects; however, no studies specifically addressing the role of vascularized periosteal flaps in stimulating bone allograft revascularization and osseointegration have been reported. Questions/purposes: (1) Does a vascularized periosteal flap increase the likelihood of union at the allograft-host junction in a critical-size defect femoral model in rats? (2) Does a vascularized periosteal flap promote revascularization of a critical-size defect structural bone allograft in a rat model? (3) What type of ossification occurs in connection with a vascularized periosteal flap? Methods: Sixty-four rats were assigned to two equal groups. In both the control and experimental groups, a 5-cm critical size femoral defect was created in the left femur and then reconstructed with a cryopreserved structural bone allograft and intramedullary nail. In the experimental group, a vascularized periosteal flap from the medial femoral condyle, with a pedicle based on the descending genicular vessels, was associated with the allograft. The 32 rats of each group were divided into subgroups of 4-week (eight rats), 6-week (eight rats), and 10-week (16 rats) followup. At the end of their assigned followup periods, the animals were euthanized and their femurs were harvested for semiquantitative and quantitative analysis using micro-CT (all followup groups), quantitative biomechanical evaluation (eight rats from each 10-week followup group), qualitative confocal microscopic, backscattered electron microscopic, and histology analysis (4-week and 6-week groups and eight rats from each 10-week followup group). When making their analyses, all the examiners were blinded to the treatment groups from which the samples came. Results: There was an improvement in allograft-host bone union in the 10-week experimental group (odds ratio [OR], 19.29 [3.63–184.50], p < 0.05). In contrast to control specimens, greater bone neoformation in the allograft segment was observed in the experimental group (OR [4-week] 63.3 [39.6–87.0], p < 0.05; OR [6-week] 43.4 [20.5–66.3], p < 0.05; OR [10-week] 62.9 [40.1–85.7], p < 0.05). In our biomechanical testing, control samples were not evaluable as a result of premature breakage during the embedding and assembly processes. Therefore, experimental samples were compared with untreated contralateral femurs. No difference in torsion resistance pattern was observed between both groups. Both backscattered electron microscopy and histology showed newly formed bone tissue and osteoclast lacunae, indicating a regulated process of bone regeneration of the initial allograft in evaluated samples from the experimental group. They also showed intramembranous ossification produced by the vascularized periosteal flap in evaluated samples from the experimental group, whereas samples from the control group showed an attempted endochondral ossification in the allograft-host bone junctions. Conclusions: A vascularized periosteal flap promotes and accelerates allograft-host bone union and revascularization of cryopreserved structural bone allografts through intramembranous ossification in a preclinical rat model. Clinical Relevance: If large-animal models substantiate the findings made here, this approach might be used in allograft reconstructions for critical defects using fibular or tibial periosteal flaps as previously described.