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Surgery of the Knee
Published in Timothy W R Briggs, Jonathan Miles, William Aston, Heledd Havard, Daud TS Chou, Operative Orthopaedics, 2020
Alexander D Liddle, Lee A David, Timothy WR Briggs
Safe and careful implant and cement removal should involve preservation of as much bone stock as possible. It is necessary to use fine, sharp osteotomes (e.g. Lambotte osteotomes), and it may be helpful to have cement-splitting osteotomes, a thin saw blade, Gigli saw and burr available. If a modular polyethylene insert is present it can be removed prior to the cemented components. It is usually preferable to remove the femoral component first as this facilitates easier extraction of the tibial component. With adequate retraction, the bone-cement interface should be carefully disrupted with osteotomes of appropriate width. If the implant is well fixed it may be safer to disrupt the implant-cement interface and remove the cement separately. Only when fully loosened should the implant be removed with the appropriate extraction device using a longitudinal distraction force. The tibial component can be removed in a similar manner. The tibial component should never be ‘levered’ out of bone. It is usually necessary to remove the cement from around the tibial keel and stem with cement-splitting osteotomes or gouges. If a polyethylene patella button has been used it should only be removed if significantly worn, in cases of infection, or if there is a patellofemoral problem. Metal-backed patella components can be very difficult to remove and are often best left if possible.
Augmentation of fracture fixation
Published in Peter V. Giannoudis, Thomas A. Einhorn, Surgical and Medical Treatment of Osteoporosis, 2020
Peter V. Giannoudis, Panagiotis Douras
Elsner et al. studied 18 patients with intra-articular calcaneal fractures treated with open reduction and internal fixation and augmentation with an injectable carbonated apatite cement. Functional follow-up studies using the Zwipp Foot Score and densitometry were performed at 6-month intervals postoperatively. Histological samples of biopsies obtained at the time of hardware removal (6 months postoperatively) were also analyzed. The use of bone cement led to intermediate-term functional outcomes that were no better than those reported with conventional surgical procedures using bone graft. Patients demonstrated postoperative difficulties similar to those seen in other studies of this fracture, including pain, subtalar motion restrictions, peroneal impingement, and difficulties on uneven terrain and with toe- and heel-walking. However, compared to patients treated surgically without injectable carbonated apatite cement, full weight-bearing on the affected extremity was regained at an average of 4 weeks postoperatively. In addition, autogenous bone graft was not required to fill the osseous defect using this technique, minimizing morbidity and discomfort (26).
Biomaterials
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Subhamoy Chatterjee, John Stammers, Gordon Blunn
PMMA has been used in cemented joint arthroplasty for over 50 years. Historically its inert properties were realized during World War II where splinters of PMMA (as Flexiglass/Perspex) were used to make Spitfire aeroplane canopies that did not react in the eye. Primary fixation is provided by anchorage between the gaps of the implant and the trabecular bone. The components of PMMA bone cement are shown in Table 18.2.
Biomechanical comparison of vertebral augmentation and cement discoplasty for the treatment of symptomatic Schmorl’s node: a finite element analysis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Kaiwen Cai, Zhang Zhang, Kefeng Luo, Feng Cao, Bin Lu, Yuanhua Wu, Hongxia Wang, Kai Zhang, Guoqiang Jiang
Theoretically, the etiology of LBP is complex, with possible pathological changes including high disc pressure (Fukui et al. 2018), segment instability (Ohtori et al. 2018), nerve fiber ingrowth (Freemont et al. 1997; Ohtori et al. 2018), and release of cytokines (Cohen and Mao 2014; Molinos et al. 2015; Ohtori et al. 2018). The mechanism of pain relief achieved by PVA is thought to be mediated by a combination of strengthening and stabilization of the edema area of subchondral bone marrow, along with suspension of the processes underlying trabecular injury, and potential thermal effects (Toksvig-Larsen et al. 1995). On the other hand, complete removal of the nucleus during the PCD procedure helps eliminate the release of cytokines, such as IL-1, IL-6, IL-8, PGE-2, NO, and phospholipid A2, etc. (Tian et al. 2017, 2019), and complete intervertebral space filling and support can also eliminate segmental instability (Varga et al. 2015). However, regardless of PVA or PCD, all the above pathological improvements are based on the distribution of bone cement under ideal conditions. Unfortunately, in practice, the distribution of bone cement is not completely controllable, and previous studies have ignored the therapeutic effects and potential risks under suboptimal distribution.
Tibial implant fixation in TKA worth a revision?—how to avoid stress-shielding even for stiff metallic implants
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
B. Eidel, A. Gote, C.-P. Fritzen, A. Ohrndorf, H.-J. Christ
For the material behavior of tibial bone, an isotropic linear elasticity law is assumed to hold. The assumption of linear elasticity is corroborated by recent experimental findings by Juszczyk et al. (2011) and Grassi et al. (2016) (for femoral bone), the validity of isotropic elasticity in simulations is underpinned by Schileo et al. (2014). Cowin presents orthotropic elasticity parameters for the tibia, which are, however, throughout constant and thus do not account for the pronounced non-homogeneity of real bone (Cowin 2009). The figures of the strongly heterogeneous Young’s modulus distribution follow from bone reconstruction as described in Section 2.1. The Poisson’s ratio is assumed to be constant, 1998) as well as for the cobalt-chrome alloy (CoCr) version. The very standard of bone cement is polymethyl methacrylate (PMMA). Polyethylene (PE) is used for the tibial tray; moreover, we consider for its low stiffness a fictitious implant fully made of PE (all-PE). The material parameters of linear elasticity are listed in Table 1.
Computed tomography-guided microwave ablation combined with percutaneous vertebroplasty for treatment of painful high thoracic vertebral metastases
Published in International Journal of Hyperthermia, 2021
Linlin Wu, Jing Fan, Qianqian Yuan, Xusheng Zhang, Miaomiao Hu, Kaixian Zhang
In our study, CT was only used to scan the target plane, reducing the scanning time while simultaneously enabling rapid sagittal reconstruction. The direction and position of the puncture needle can be adjusted in a step-by-step manner, and the puncture needle can be accurately placed parallel to the midline of the vertebral body to reach the anterior one-third of the vertebral body. This positioning prevents the puncture needle from entering the spinal canal and piercing the anterior side of the vertebral body. Moreover, the degree and extent of tumor ablation can be observed during MWA. The diffusion of bone cement can also be clearly observed during injection, and the direction and degree of bone cement leakage can be identified on time. We strictly controlled the speed and total amount of bone cement injected into the high thoracic vertebrae using slow and intermittent injections of a small amount of bone cement. The bone cement was placed in ice-cold saline to prolong the solidification time and CT was performed for each injection of 0.3–0.5 ml. If bone cement has leaked into the spinal canal or intervertebral foramen, the injection of bone cement should be stopped immediately to ensure the safety of the treatment.