Preoperative planning for Total Hip Arthroplasty has been acknowledged as a vital step to facilitate a successful outcome. Templating ascertains the dimensions and positioning of the implants, minimizing both intraoperative and postoperative complications. The purpose of this study is to compare the accuracy of digital templating to acetate templating in the preoperative planning of Total Hip Arthroplasty. Preoperative planning was performed on 40 consecutive patients (mean age = 70.5 years), undergoing Total Hip Arthroplasty. Digital templating was performed by the Hip fellow 1, using Orthoview software (Jacksonville, FL, USA) and recorded the sizes of the cup and stem for each of the 40 patients. Subsequently, the same 40 patients were templated by Hip fellow 2, with X-rays done with a lead marker of known size by the side of the femur, using, acetate templating method. Templating results were compared to the actual sizes of the implants used, as noted in operative notes. Templating scores for the acetabular cup were 40% (16/40) with digital templating and 50% (20/40) with acetate templating. The templating scores for stem were 28% (11/40) with digital templating and 90% (36/40) with acetate templating. The differences between templating and actual implant sizes were plotted in Bland–Altman plot. Acetate templating proved to be statistically, significantly more accurate than digital templating (p value= 0.0083). Our results indicate that the traditional acetate method is solid and valid to use for preoperative planning. This method is accurate and offers a more affordable option for preoperative templating. Although the templated size is one, there is a tendency to increase cup size to use bigger heads, which is the recent National Joint Registries trend. We recommend that acetate templating should be used as the default option

Digital radiographs are routinely used for preoperative planning, both in trauma and elective patients; particularly in preoperative templating for total hip replacement. Traditional wisdom holds that radiographs are oversized, though the degree to which this occurs is unclear. Although digital templating systems offer the use of calibration markers, this option is not always availed. We aimed to ascertain the typical magnification in departmental xrays of the hip, both to determine the typical degree of magnification as well as ascertain its consistency. All patients undergoing dynamic hip screw fixation (DHS) in our unit over the past 12 months were identified. Using the PACS system, subsequent xrays of the patient with the implant in situ were identified; both anteroposterior abdominal and pelvic films were used. The width of a standard DHS screw (12.5 mm) was compared with the width measured on the xrays to determine a magnification factor. 164 patients were identified, of these 39 had undergone DHS fixation with subsequent xrays. 3 films were focused on the abdomen but provided good coverage of the hip also. 2 xrays were excluded – both due to limited quality. The average magnification was 26.4% (range 15.5%–42%). There was limited consistency between images. Radiographs are a core investigation in the assessment of the orthopaedic patient. The advent of picture archiving and communications systems (PACS) has allowed the enterprising surgeon to pre-emptively plan their surgical technique and implant use. However, the utility of non-calibrated images in planning implant size is limited by variation in magnification. Surgeons should be cautious in using such images to guide their implant usage

In recent years the majority of X-ray departments have moved to a digital format of recording and archiving radiographs. These digital images (as with previous ‘films’) have a built in magnification factor (variable with each patient), which, may cause errors in templating for joint replacement surgery. Placing a marker of known size at the same level as the joint in question allows calculation of the magnification. This may help to restore hip offset in total hip replacement. To establish the magnification factor for digital radiographs taken in our unit. To assess the usefulness of marker images in accurate preoperative templating. Preoperative marker radiographs were identified retrospectively. The apparent size of the marker was measured on digital image. This value was used to calculate the magnification of the image. The scaled X-ray was up loaded to a digital templating software programme. This software uses a ‘scaling tool’ to calculate the magnification of the image. The hip joint templating tool was the used to calculate the offset of the proximal femur, this was performed with the calculated magnification and also an assumed magnification of 120%. The recommended offset of Exeter V40 stem was noted for both values. Images were identified for 40 patients with markers. The average magnification was 122% for both PACS and Orthoview with a range 113% – 129% and a standard deviation of 4%. The median value for magnification was 120%. The average change in offset between calculated and estimated magnification was 1.275mm with a maximum change of 3mm. In two cases this difference resulted in a change in the recommended offset (5%). The use of marker radiographs is widely described. In this small series the magnification is the same as previously reported in other studies. The difference in offset between calculated and estimated magnification was relatively small and caused a change in the recommended offset in only two patients. Variation in the use of the templating tool in our software can produce a much greater change in offset. Marker radiographs will only be useful as part of a standardised method of pre-operative templating

Summary Statement. Proximal femoral bony deficits present a surgical and biomechanical challenge to implant longevity in revision hip arthroplasty. This work finds comparable primary stability when a distally fixing tapered fluted stem was compared with a conical design in cadaveric tests. Introduction. Proximal bony deficits complicate revision hip surgery and compromise implant survival. Longer distally fixing stems which bypass such defects are therefore required to achieve stability compatible with bony ingrowth and implant longevity. Aims. It is hypothesised that a tapered stem will provide superior rotational stability to a conical design. This work therefore aims to compare the primary stability and biomechanical properties of a new design of tapered fluted modular femoral stem (Redapt®, Smith & Nephew) with that of a conical fluted stem (Restoration®, Stryker). Materials & Methods. 7 Pairs of cadaveric femora were obtained according to strict inclusion/exclusion criteria. Each underwent dual energy x-ray absorptiometry and calibration plain-film radiographs were taken. Digital templating was performed using TraumaCad (Voyant Health, Brainlab) to determine implant sizing. Both stems are fluted, modular and manufactured from titanium. The control stem (Restoration) featured a straight conical design and the investigation stem (Redapt) a straight tapered design. Implantation was performed by a revision arthroplasty surgeon familiar with both systems. Proximal bone deficiency was reproduced using an extended trochanteric osteotomy with removal of metaphyseal bone before reattaching the osteotomy. Primary stability in the axial, sagittal and coronal planes was assessed using micromotion transducers (HBM, Darmstadt, Germany) and also by Radiostereometric Analysis (RSA). RSA employs simultaneous biplanar radiographs to measure relative movement. Two 1mm tantalum beads were mounted on the prosthesis with the centre of the femoral head taken as the third reference point. Beads were placed proximally in the surrounding bone as rigid body markers. Each bone was potted according to the ISO standard for fatigue testing and cyclically loaded at 1Hz for at least 3 increments (750–350N, 1000–350N, 1500–350N) for 1000 cycles. RSA radiographs were taken at baseline and on completion of each cycle. A strain analysis was concurrently performed using a PhotoStress® (Vishay Precision Group, Raleigh, USA) photoelastic coating on the medial femoral cortex. Each bone was loaded intact and then with the prosthesis in-situ at 500N increments until strain fringes were identified. Once testing was completed, the stems were sectioned at the femoral isthmus and data is presented on the cross-sectional fit and fill observed. Results. Both stem designs showed comparable primary stability with all stems achieving clinically acceptable micromotion (<150 μm) when loaded at body weight. A larger proportion of the control stems remained stable as loading increased to x2-3 body weight. Transducer-recorded migration appeared greatest in the axial plane (y axis) with negligible distal movement in the coronal or sagittal planes. Point motion analysis (RSA) indicated most movement to be in the coronal plane (x-axis) whereas segment motion analysis showed rotation about the long axis of the prosthesis to be largest. Photoelastic strain patterns were transferred more distally in both designs, however substantial stress shielding was also observed. Discussion/Conclusion. Both designs achieved adequate distal fixation and primary stability under representative clinical loading conditions. This work supports the continued use of this novel stem design for revision surgery in the presence of extensive proximal bone loss