Aims

The purpose of this study was to assess mid-term survivorship following primary total knee arthroplasty (TKA) with Optetrak Logic components and identify the most common revision indications at a single institution.

Aims

Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA.

Introduction. In major orthopaedic departments, typically several total knee systems are used. Each system requires several sets of instruments, each set with many trays of complicated and expensive parts. The logistics and costs of maintainance are considerable. Our overall goal is to investigate the feasibility of autoclavable single-use 3D printed instruments made from a polymeric material, used for any type of total knee design. The procedure will be standardized and adjustments easy to implement. Each set will be packaged individually, and used for a single case. There are many aspects to this study; in this part, the aims are to identify suitable materials for autoclavability and strength, and then to compare the accuracy of a novel design of 3D printed tibial cutting guide with a current metallic guide. Methods. Test samples were designed to simulate shapes in current instruments, such as mating pegs and holes, threaded screws, and slotted blocks. Each set was produced in biocompatible materials, ABS-M30i, VeroClear (MED610), Ultem1010, and Nylon 12. Each part was laser scanned, and then imaged virtually using a reverse engineering software (GeoMagic). Manual measurements of key dimensions were also made using calipers. The parts were autoclaved using a standardized protocol, 30 minutes at 250° F. All parts were re-scanned and measured to determine any changes in dimensions. To test for strength and abrasion resistance, the slotted blocks were pinned to sawbones model tibias, and an oscillating saw used to cut through the slot. A compact 3D printed tibial cutting guide was then designed which fitted to the proximal tibia and allowed varus-valgus, tibial slope and height adjustments. A small laser attached to the guide projected to a target at the ankle. Tests were made on 20 sawbones, and compared with 20 with a standard metal cutting guide. Digitization was used to measure the angles of the cuts. Results. Prior to autoclaving, the mating parts of all parts were congruent, except for Nylon 12 which had processing debris in slots and screw threads. The ABS-M30i shapes became grossly deformed after autoclaving. The other materials experienced only small changes in dimensions without loss of overall shape, but the slot of the Nylon 12 block was stenotic, 1.4 mm compared to 0.9 mm before autoclaving. In saw blade testing, the VeroClear block fractured through the corner of the slot, while the Nylon 12 block deformed due to heating. The Ultem1010 block produced a small amount of debris, but maintained its shape without any structural damage. In the tests of the tibial cutting guide the 3D printed laser-guided tibial cutting guide resulted in a mean absolute error of 1.72°±1.31° and 1.19°±0.93°, for the tibial slope and varus-valgus respectively. For the conventional guides, these values were 3.78°±1.98° and 2.33°±0.98°, respectively. These measurements were found to be statistically significant with p values of 0.004 and 0.001, respectively. Conclusions. Thus far, apart from patient specific cutting guides and trial components, 3D printing has had limited applications in total knee surgery. As cost containment remains prominent, the use of 3D printing to produce standardized instruments may become viable. These instruments would not require pre-op planning such as CT or MRI, yet allow patient-specific angular settings. Our results indicated that Ultem1010 is a promising material, while a novel tibial cutting guide showed higher accuracy than standard, as well as being quicker to use. These initial tests indicated the viability of 3D printed instruments, but further work will include design and evaluation of the other cutting guides, manufacturing logistics such as in-house or company- based, and economics

Aims

Meniscal injuries are common and often induce knee pain requiring surgical intervention. To develop effective strategies for meniscus regeneration, we hypothesized that a minced meniscus embedded in an atelocollagen gel, a firm gel-like material, may enhance meniscus regeneration through cell migration and proliferation in the gel. Hence, the objective of this study was to investigate cell migration and proliferation in atelocollagen gels seeded with autologous meniscus fragments in vitro and examine the therapeutic potential of this combination in an in vivo rabbit model of massive meniscus defect.

Background. The management of chondral lesions in the knee, especially in young fit patients, remains an area of considerable controversy. Articular cartilage repair or reconstruction techniques may offer these patients alternatives to arthroplasty or realignment osteotomy. The TruFit plug (Smith & Nephew, London, UK) is a synthetic biphasic polymer scaffold that is designed for implantation at the site of a focal chondral defect. It is intended to resorb and allow tissue ingrowth 6-9 months following implantation and may be placed either arthroscopically or via an open approach depending on the site of the lesion. Methods. 11 patients with focal chondral defects in the knee underwent TruFit plug implantation. Postoperative management entailed a period of 6 weeks of restricted weight bearing or restricted knee flexion according to implantation site. Radiological evaluation with MRI or CT arthrogram (or both) was conducted at various time points postoperatively according to clinical indication. Functional scoring with the Oxford knee score (OKS), Tegner activity scale and Lysholm score were completed. Results. 35 TruFit plugs were implanted in 12 knees of 11 patients (4 men, 7 women) between June 2007 and December 2009. Mean age at time of surgery 46.9 years (range32-72years). Mean change in OKS 1.33 (range -13 to 29), Lysholm 13.8 (range -19 to 61), Tegner 0.33 (range -2 to 2 levels). Imaging characteristics on MRI and CT arthrogram show delayed incorporation of the grafts in all patients with no osseous integration at up to 24 months follow up. Conclusions. Early results from the TruFit plug show variable functional outcome scores which appear independent of patient age, number of plugs used and site of implantation. All show delayed tissue integration. Our group is currently not implanting any further TruFit plugs pending longer term outcomes from larger case series

Aims

This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty.

Aims

We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement.

Aims

The aims of this study were to compare the mean duration of antibiotic release and the mean zone of inhibition between vancomycin-loaded porous tantalum cylinders and antibiotic-loaded bone cement at intervals, and to evaluate potential intrinsic antimicrobial properties of tantalum in an in vitro medium environment against methicillin-sensitive Staphylococcus aureus (MSSA).

Advances in polyethylene (PE) in total hip arthroplasty have led to interest and increased use of highly crosslinked PE (HXLPE) in total knee arthroplasty (TKA). Biomechanical data suggest improved wear characteristics for HXLPE inserts over conventional PE in TKA. Short-term results from registry data and few clinical trials are promising. Our aim is to present a review of the history of HXLPEs, the use of HXLPE inserts in TKA, concerns regarding potential mechanical complications, and a thorough review of the available biomechanical and clinical data.

Cite this article: Bone Joint J 2017;99-B:996–1002.

Aims

The aim of this study was to evaluate the surface damage, the density of crosslinking, and oxidation in retrieved antioxidant-stabilized highly crosslinked polyethylene (A-XLPE) tibial inserts from total knee arthroplasty (TKA), and to compare the results with a matched cohort of standard remelted highly crosslinked polyethylene (XLPE) inserts.

We explored the literature surrounding whether allergy and hypersensitivity has a clinical basis for implant selection in total knee arthroplasty (TKA). In error, the terms hypersensitivity and allergy are often used synonymously. Although a relationship is present, we could not find any evidence of implant failure due to allergy. There is however increasing basic science that suggests a link between loosening and metal ion production. This is not an allergic response but is a potential problem. With a lack of evidence logically there can be no justification to use ‘hypoallergenic’ implants in patients who have pre-existing skin sensitivity to the metals used in TKA.

Cite this article: Bone Joint J 2016;98-B:437–41.

The optimum cementing technique for the tibial component in cemented primary total knee replacement (TKR) remains controversial. The technique of cementing, the volume of cement and the penetration are largely dependent on the operator, and hence large variations can occur. Clinical, experimental and computational studies have been performed, with conflicting results. Early implant migration is an indication of loosening. Aseptic loosening is the most common cause of failure in primary TKR and is the product of several factors. Sufficient penetration of cement has been shown to increase implant stability.

This review discusses the relevant literature regarding all aspects of the cementing of the tibial component at primary TKR.

Cite this article: Bone Joint J 2013;95-B:295–300.

Objectives

Matrix-assisted autologous chondrocyte transplantation (MACT) has been developed and applied in the clinical practice in the last decade to overcome most of the disadvantages of the first generation procedures. The purpose of this systematic review is to document and analyse the available literature on the results of MACT in the treatment of chondral and osteochondral lesions of the knee.

Two-stage revision surgery for infected total knee replacement offers the highest rate of success for the elimination of infection. The use of articulating antibiotic-laden cement spacers during the first stage to eradicate infection also allows protection of the soft tissues against excessive scarring and stiffness. We have investigated the effect of cyclical loading of cement spacers on the elution of antibiotics. Femoral and tibial spacers containing vancomycin at a constant concentration and tobramycin of varying concentrations were studied in vitro. The specimens were immersed and loaded cyclically to 250 N, with a flexion excursion of 45°, for 35 000 cycles. The buffered solution was sampled at set intervals and the antibiotic concentration was established so that the elution could be calculated. Unloaded samples were used as a control group for statistical comparison.

The elution of tobramycin increased proportionately with its concentration in cement and was significantly higher at all sampling times from five minutes to 1680 minutes in loaded components compared with the control group (p = 0.021 and p = 0.003, respectively). A similar trend was observed with elution of vancomycin, but this failed to reach statistical significance at five, 1320 and 1560 minutes (p = 0.0508, p = 0.067 and p = 0.347, respectively). However, cyclically loaded and control components showed an increased elution of vancomycin with increasing tobramycin concentration in the specimens, despite all components having the same vancomycin concentration. The concentration of tobramycin influences both tobramycin and vancomycin elution from bone cement. Cyclical loading of the cement spacers enhanced the elution of vancomycin and tobramycin.

Clinical experience of impaction bone grafting for revision knee arthroplasty is limited, with initial stability of the tibial tray emerging as a major concern. The length of the stem and its diameter have been altered to improve stability. Our aim was to investigate the effect of the type of stem, support of the rim and graft impaction on early stability of the tray.

We developed a system for impaction grafting of trays which we used with morsellised bone in artificial tibiae. Trays with short, long thick or long thin stems were implanted, with or without support of the rim. They were cyclically loaded while measuring relative movement.

Long-stemmed trays migrated 4.5 times less than short-stemmed trays, regardless of diameter. Those with support migrated 2.8 times less than those without. The migration of short-stemmed trays correlated inversely with the density of the impacted groups. That of impaction-grafted tibial trays was in the range reported for uncemented primary trays. Movements of short-stemmed trays without cortical support were largest and sensitive to the degree of compaction of the graft. If support of the rim was sufficient or a long stem was used, impacted morsellised bone graft achieved adequate initial stability.