We report on a cadaveric study and early experience using patient specific drill guides to prevent cortex perforations and reduce the need for a trochanteric osteotomy in revision THA. Mimic software (Materialise) was used for 3D analysis of the cement mantle and cement plug. Based on the CT findings a Cannulated drill guide with the shape of the femoral stem was printed in medical graded nylon intraoperative findings and complications were recorded on videotape using a standard 5mm laparoscope for medullary inspection. Surgical Technique was to attain a pre-operative CT scan with MARS protocol of the proximal femur to evaluate the femoral stem positioning, the 3D anatomy of the cement mantle, the length of the cement plug and the quality of the surrounding bone. Subsequent a 3D printing of patient specific cannulated drill guide with the shape of the removed femoral component but an eccentric cannulation was made. Endoscopic inspection was performed of the inside of the cement mantle, then insertion of the autoclaved cannulated drill guide in the existing cement mantle. After perforation of the distal plug through the PSI drill guide using either a long drill or an ultrasound plug perforation tool (Zimmer Biomet, Warsaw) the excessive cement was removed with standard available flexible femoral shaft reamers (Zimmer Biomet). Further laproscopic examination of the femoral canal performed to verify completeness of the cement removal. Results. CT scans with 3D reconstruction of the existing cement mantle is possible using Modern CT with MARS protocols. After the training on sawbones and cadaveric bones a predictable plug perforation was obtained in all clinical cases. There were no intraoperative cortex perforations and no intraoperative femoral fractures. Conclusion. CT scan analysis of femoral cement mantles together with patient specific drill guides are promising tools to reduce the risk of femoral perforation in revision total hip arthroplasty

Introduction. The achieved anteversion of uncemented stems is to a large extent limited by the internal anatomy of the bone. A better understanding of this has recently become an unmet need because of the increased use of uncemented stems. We aimed to assess plan compliance in six degrees of freedom to evaluate the accuracy of PSI and guides for stem positioning in primary THAs. Materials and Methods. We prospectively collected 3D plans generated from preoperative CTs of 30 consecutive THAs (17 left and 13 right hips), in 29 patients with OA, consisting of 16 males and 13 females (median age 68 years, range 46–83 years). A single CT-based planning system and cementless type of implant were used. Post operatively, all patients had a CT scan which was reconstructed using state-of-the-art software solution: the plan and CT reconstruction models were. Outcome measures: 1) discrepancy between planned and achieved stem orientation angles Fig.2&3; 2) clinical outcome. Results. 1) The mean (±SD) discrepancy was low for: Varus-valgus −1.1 ± 1.4 deg (IQR −2.2 – 0.3 deg); Anterior-posterior 0.1 ± 1.6 deg (IQR −0.7 – 1.3 deg). The discrepancy was higher for femoral version −1.4 ± 8.2 deg (IQR −8.3 – 7.2 deg). 3D-CT planning correctly predicted sizes in 93% of the femoral components. 2) There was no intra-operative fracture, no case showed evidence of early periprosthetic osseous injury. Discussion. Surgeons and engineers should be cautious with their expectation of achieving the planned femoral stem version of an uncemented femoral stem from the pre-operative 3D-CT plan. Conclusion. This is the first study to 3D-mensionally evaluate 3D-printed patient-specific instrumentation and guides for achieved femoral stem component orientation vis-à-vis to the plan. The tools allow accurate implant orientation, however there is still potential for improvement. For any figures or tables, please contact the authors directly

Objectives. Metal-on-metal (MoM) hip resurfacing was introduced into clinical practice because it was perceived to be a better alternative to conventional total hip replacement for young and active patients. However, an increasing number of reports of complications have arisen focusing on design and orientation of the components, the generation of metallic wear particles and serum levels of metallic ions. The procedure introduced a combination of two elements: large-dimension components and hard abrasive particles of metal wear. The objective of our study was to investigate the theory that microseparation of the articular surfaces draws in a high volume of bursal fluid and its contents into the articulation, and at relocation under load would generate high pressures of fluid ejection, resulting in an abrasive water jet. Methods. This theoretical concept using MoM resurfacing components (head diameter 55 mm) was modelled mathematically and confirmed experimentally using a material-testing machine that pushed the head into the cup at a rate of 1000 mm/min until fully engaged. Results. The mathematical model showed the pattern but not the force of fluid ejection, the highest pressures were expected when the separation of the components was only a fraction of one millimetre. The experimental work confirmed the results; with the mean peak ejection pressure of 43 763 N/m. 2. equivalent to 306 mmHg or 5 psi. Conclusions. The mechanical effect of the high-pressure abrasive water jet is the likely cause of the spectrum of complications reported with metal-on-metal resurfacing. Investigating serum levels of metallic elements may not be the best method for assessing the local mechanical effects of the abrasive water jet

Introduction. Total hip arthroplasty (THA) is an effective surgery for the treatment of advanced osteoarthritis but increasing numbers of these procedures are having a significant impact on healthcare budgets. One route to mitigate the increasing costs is outpatient THA, discharging patients on the same day as their surgery. The purpose of this study was to determine the cost of outpatient THA compared to standard overnight stay in hospital. Methods. This was a prospective-randomized controlled trial for patients undergoing primary THA through a direct anterior approach. Participants were randomized to be discharged on the same day as surgery, as outpatients, or on day one post-surgery, as inpatients, using a Zelen consent model. Adverse events were assessed, and participants completed self-reported cost questionnaires at two-, six- and 12-weeks post-surgery, and the WOMAC preoperatively and at 12-weeks post-surgery. We performed a cost analysis from health care payer (HCP) and societal perspectives. Results. 106 patients were enrolled in this study, with 50 randomized to outpatient and 56 randomized to inpatient THA. Seven patients from the outpatient group and five patients from the inpatient group crossed-over. Adverse event rate was similar between the groups with seven events in four participants in the inpatient group and three events in two participants in the outpatient group. WOMAC scores were not significantly different between the groups (p=0.12). From both a HCP and societal perspective, inpatient THA was more costly than outpatient THA. The cost difference was $3,353.15 for HCP (p<0.0001) and $3,703.30 for societal (p=0.003) in favour of outpatient THA. Conclusion. Our results suggest that outpatient THA is a cost-saving procedure when compared to inpatient THA from both HCP and societal perspectives. We will continue recruitment to investigate whether these results hold true in a larger sample as well as assess for cost-effectiveness, patient safety and satisfaction. Acknowledgements. This study was supported by the Opportunities Fund of the Academic Health Sciences Centre Alternative Funding Plan of the Academic Medical Organization of Southwestern Ontario (AMOSO). We also received funding from the PSI Foundation. For any tables or figures, please contact the authors directly

Aims

Acetabular retroversion is a recognized cause of hip impingement and can be influenced by pelvic tilt (PT), which changes in different functional positions. Positional changes in PT have not previously been studied in patients with acetabular retroversion.

Aims

Accurate placement of the acetabular component during total hip arthroplasty (THA) is an important factor in the success of the procedure. However, the reported accuracy varies greatly and is dependent upon whether free hand or navigated techniques are used. The aim of this study was to assess the accuracy of an instrument system that incorporates 3D printed, patient-specific guides designed to optimise the placement of the acetabular component.

This conversation represents an attempt by several arthroplasty surgeons to critique several abstracts presented over the last year as well as to use them as a jumping off point for trying to figure out where they fit in into our current understanding of multiple issues in modern hip and knee arthroplasty.