A Report on Three Consecutive Cases using Computer Tomography 3D Preoperative Planning for Conversion of Arthrodesed Hips to Total Hip Replacements

How to perform correct templating in total hip replacement

Templating plays a key role in surgery that is often underestimated. There is a difference between planning and templating: in the first not only the hip is considered but involves the evaluation of the patient in its entirety. Templating instead consists of calculating the position of the implant in order to place it in the best possible position. Fundamental is a correct X-ray of the pelvis, which must follow certain standards. For traditional templating, drawings on appropriately enlarged transparent implants were provided by the prosthesis manufacturer. The implementation of digital software into clinical practice has improved the accuracy and reproducibility of templating, which in most surgical units is performed by standard 2D radiographic images. Thanks to digital preoperative templating in a digital radiology environment, the hip reconstructive surgeon can perform preoperative planning and implant sizing quickly, consistently, and affordably. Currently, 3D templating can also be performed by software used initially to create personalized stems for THA. Aim of the current review is to outline the essentials of correct templating in THA performance, and to report the updates since the introduction of digital and 3D technologies in this setting.

Three-dimensional pre-operative planning of primary hip arthroplasty: a systematic literature review

Three-dimensional (3D) pre-operative planning in total hip arthroplasty (THA) is being recognized as a useful tool in planning elective surgery, and as crucial to define the optimal component size, position and orientation. The aim of this study was to systematically review the existing literature for the use of 3D pre-operative planning in primary THA.A systematic literature search was performed using keywords, through PubMed, Scopus and Google Scholar, to retrieve all publications documenting the use of 3D planning in primary THA. We focussed on (1) the accuracy of implant sizing, restoration of hip biomechanics and component orientation; (2) the benefits and barriers of this tool; and (3) current gaps in literature and clinical practice.Clinical studies have highlighted the accuracy of 3D pre-operative planning in predicting the optimal component size and orientation in primary THAs. Component size planning accuracy ranged between 34-100% and 41-100% for the stem and cup respectively. The absolute, average difference between planned and achieved values of leg length, offset, centre of rotation, stem version, cup version, inclination and abduction were 1 mm, 1 mm, 2 mm, 4°, 7°, 0.5° and 4° respectively.Benefits include 3D representation of the human anatomy for precise sizing and surgical execution. Barriers include increased radiation dose, learning curve and cost. Long-term evidence investigating this technology is limited.Emphasis should be placed on understanding the health economics of an optimized implant inventory as well as long-term clinical outcomes. Cite this article: EFORT Open Rev 2020;5:845-855. DOI: 10.1302/2058-5241.5.200046.

Total Hip Arthroplasty for Femoral Neck Fracture after Postoperative Intertrochanteric Fracture in a Patient with Spontaneous Fused Hip

A 64-year-old woman with a spontaneous fused hip sustained a left femoral neck fracture. It was revealed that her left hip joint had a long-standing spontaneous hip fusion due to end-stage osteoarthritis. Additionally, she sustained an ipsilateral femoral intertrochanteric fracture and underwent osteosynthesis using a dynamic hip screw 8 years ago. The one-stage THA was successfully treated with no major complications and good functional recovery was obtained. The hip range of motion improved remarkably at one year after surgery. The Modified Harris Hip Score improved from an estimated 70 points before fracture to 95 points at final follow-up.

Total hip arthroplasty planning

Preoperative planning is mandatory to achieve the restoration of a correct and personalized biomechanics of the hip.

The radiographic review is the first and fundamental step in the planning. Limb or pelvis malpositioning during the review results in mislead planning.

Correct templating is possible using three different methods: acetate templating on digital X-ray, digital 2D templating on digital X-ray and 3D digital templating on CT scan.

Time efficiency, costs, reproducibility and accuracy must be considered when comparing different templating methods. Based on these parameters, acetate templating should not be abandoned; digital templating allows a permanent record of planning and can be electronically viewed by different members of surgical team; 3D templating is intrinsically more accurate. There is no evidence in the few recently published studies that 3D templating impacts positively on clinical outcomes except in difficult cases.

The transverse acetabular ligament (TAL) is a reliable intraoperative soft tissue reference to set cup position.

Spine–hip relations in osteoarthritic patients undergoing hip joint replacement must be considered.

Cite this article: EFORT Open Rev 2019;4:626-632. DOI: 10.1302/2058-5241.4.180075

Comparison of in vivo vs. ex situ obtained material properties of sheep common carotid artery

Patient-specific biomechanical modelling can improve preoperative surgical planning. This requires patient-specific geometry as well as patient-specific material properties as input. The latter are, however, still quite challenging to estimate in vivo. This study focuses on the estimation of the mechanical properties of the arterial wall. Firstly, in vivo pressure, diameter and thickness of the arterial wall were acquired for sheep common carotid arteries. Next, the animals were sacrificed and the tissue was stored for mechanical testing. Planar biaxial tests were performed to obtain experimental stress-stretch curves. Finally, parameters for the hyperelastic Mooney-Rivlin and Gasser-Ogden-Holzapfel (GOH) material model were estimated based on the in vivo obtained pressure-diameter data as well as on the ex situ experimental stress-stretch curves. Both material models were able to capture the in vivo behaviour of the tissue. However, in the ex situ case only the GOH model provided satisfactory results. When comparing different fitting approaches, in vivo vs. ex situ, each of them showed its own advantages and disadvantages. The in vivo approach estimates the properties of the tissue in its physiological state while the ex situ approach allows to apply different loadings to properly capture the anisotropy of the tissue. Both of them could be further enhanced by improving the estimation of the stress-free state, i.e. by adding residual circumferential stresses in vivo and by accounting for the flattening effect of the tested samples ex vivo. • Competing interests: none declared • Word count: 4716.