The Knee
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Refined prosthetic designs and surgical techniques for unicompartmental knee arthroplasty have recently been associated with improved outcomes. The purpose of the present study was to evaluate the clinical and radiographic outcomes of the EIUS unicompartmental design, which has an all-polyethylene tibial component, and to compare these outcomes with published reports of other unicompartmental prostheses. Between February 2002 and March 2005, 113 patients (144 knees) underwent a medial unicompartmental knee arthroplasty, all performed by a single surgeon who used the EIUS prosthesis. ⋯ Multiple regression analysis revealed that age, gender, and body mass index were not significantly correlated with success or failure of this design, although nine of the 16 patients who required revision were obese. This prosthesis was associated with higher revision rates than components which utilize metal-backed implants. Further modifications in the design, indications, or technique may be necessary to improve outcomes of this unicompartmental knee arthroplasty system.
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Periprosthetic tibial plateau fractures (TPF) are rare but represent a serious complication of unicompartmental knee arthroplasty (UKA). As TPFs usually occur perioperatively, these can be associated with extended sagittal saw cuts during surgery. The aim of the study was to evaluate TPF as a function of extended sagittal saw cuts. ⋯ Extended sagittal saw cuts in UKA weaken the tibial bone structure. Our results show that descendent extended sagittal saw cuts of 10 degrees reduce fracture loads by about 30%. Surgeons should be aware of the potential pitfalls of an extended sagittal saw cut, as this can lead to reduced loading capacity of the tibial plateau and increase the risk of periprosthetic TPF.
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The viability of unicondylar knee arthroplasty (UKA) as a stand-alone or temporising option for the management of gonarthrosis is a topic of considerable contention. Despite recent advances in prosthesis design and surgical technique, as well as mounting evidence of long-term survivorship, UKA remains infrequently used, accounting for just 8-15% of all knee arthroplasties. Instead this group is more typically managed using total knee arthroplasty (TKA). ⋯ We show in a series of 200 knees that candidacy for UKA is widespread; representing 47.6% of knees. Furthermore, we also show for the first time, that not only is UKA functionally superior to TKA (based on Total Knee Questionnaire (TKQ) scores), but scores in medial and lateral UKA knees do not differ significantly from normal, non-operative age- and sex-matched knees (t=1.14 [38], p=0.163; and t=1.16 [38], p=0.255 respectively). Finally, we report that UKA offers a substantial cost saving over TKA ( pound 1761 per knee) indicating that UKA should be considered the primary treatment option for unicompartmental knee arthritis.
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The purpose of this study was to describe the intra- and inter-observer variability of the registration of bony landmarks and alignment axes on a Computed Axial Tomography (CT) scan. Six cadaver specimens were scanned. Three-dimensional surface models of the knee were created. ⋯ This study demonstrates low intra- and inter-observer variability in the CT registration of landmarks that define the coordinate system of the femur and the tibia. In the femur, the horizontal plane projections of the posterior condylar line and the surgical and anatomical transepicondylar axis can be determined precisely on a CT scan, using the described methodology. In the tibia, the best result is obtained for the tibial transverse axis.
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As implants are made in incremental sizes and usually do not fit perfectly, surgeons have to decide if it is preferable to over or undersize the components. This is particularly important for unicompartmental knee replacement (UKR) tibial components, as overhang may cause irritation of soft tissues and pain, whereas underhang may cause loosening. One hundred and sixty Oxford UKRs were categorised according to whether they had minor (<3 mm, 70%) or major (>or=3 mm, 9%) tibial overhang, or tibial underhang (21%). ⋯ There was no difference between the 'minor overhang' and the 'underhang' group. We conclude that surgeons must avoid tibial component overhang of 3 mm or more, as this severely compromises the outcome. Although this study showed no difference between minor overhang or underhang, we would advise against significant underhang because of the theoretical risk of component subsidence and loosening.