Aims. Metaphyseal tritanium cones can be used to manage the tibial bone loss commonly encountered at revision total knee arthroplasty (rTKA). Tibial stems provide additional fixation and are generally used in combination with cones. The aim of this study was to examine the role of the stems in the overall stability of tibial implants when metaphyseal cones are used for rTKA. Methods. This computational study investigates whether stems are required to augment metaphyseal cones at rTKA. Three cemented stem scenarios (no stem, 50 mm stem, and 100 mm stem) were investigated with 10 mm-deep uncontained posterior and medial tibial defects using four loading scenarios designed to mimic activities of daily living. Results. Small micromotions (mean < 12 µm) were found to occur at the bone-implant interface for all loading cases with or without a stem. Stem inclusion was associated with lower micromotion, however these reductions were too small to have any clinical significance. Peak interface micromotion, even when the cone is used without a stem, was too small to effect osseointegration. The maximum difference occurred with stair descent loading. Stress concentrations in the bone occurred around the inferior aspect of each implant, with the largest occurring at the end of the long stem; these may lead to end-of-stem pain. Stem use is also found to result in stress shielding in the bone along the stem. Conclusion. When a metaphyseal cone is used at rTKA to manage uncontained posterior or medial defects of up to 10 mm depth, stem use may not be necessary. Cite this article:Bone Joint Res. 2020;9(4):162–172

Abstract. Objectives. 1. To investigate the effect of revision total knee replacement (TKR) on gait kinematics in patients with a primary TKR and instability.2. To compare gait kinematics between patients with a well-functioning TKR and those with a primary TKR and symptoms of instability. Methods. This single-centre observational study is following patients who have had a revision TKR due to knee instability. Data was collected pre- and post-operatively at 8–12 week follow-up. The data was compared to a control group of 18 well-functioning TKR patients. Kinematic gait data was collected during routine clinics using a treadmill-based infrared 3D system (Vicon, Oxford, UK) and a published lower limb marker-set. Patients performed 15 strides at three different speeds: 0.6mph, self-selected, and a ‘slow walk’ normalised to leg length (Froude number 0.09). PROMs questionnaires were collected. NHS ethical approval was obtained. Results. Data was collected for 18 well-functioning TKR patients and 8 revision TKR patients pre- and post-operatively, but only 5 could walk at the normalised speed. When walking at a normalised speed (Froude 0.09), patients with a TKR with instability had reduced range of knee flexion (52° (sd 14)) compared to those with a well-functioning TKR (59° (sd 11)). Short term follow-up after a revision TKR operation demonstrated a stiffer knee (45° (sd 12)). However, those with revision TKR had a more flexed knee during stance phase. Conclusions. At short-term follow-up, this cohort of revision TKR patients appear to have reduced flexion range, while remaining more flexed during stance. This may represent a less efficient gait pattern, which may also adversely affect the implant[1]. Longer term follow-up may demonstrate whether this normalises with post-operative rehabilitation. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Patient function is poorly characterised following revision TKA. Modern semi-constrained implants are suggested to offer high levels of function, however, data is lacking to justify this claim. 52 consecutive aseptic revision TKA procedures performed at a single centre were prospectively evaluated; all were revision of a primary implant to a Triathlon total stabiliser prosthesis. Patients were assessed pre-operatively and at 6, 26, 52 and 104 weeks post-op. Outcome assessments were the Oxford Knee Score (OKS), range of motion, pain rating scale and timed functional assessment battery. Analysis was by repeated measures ANOVA with post-hoc Tukey HSD 95% simultaneous confidence intervals as pairwise comparison. Secondary analysis compared the results of this revision cohort to previously reported primary TKA data, performed by the same surgeons, with identical outcome assessments at equivalent time points. Mean age was 73.23 (SD 10.41) years, 57% were male. Mean time since index surgery was 9.03 (SD 5.6) years. 3 patients were lost to follow-up. All outcome parameters improved significantly over time (p <0.001). Post-hoc analysis demonstrated that all outcomes changed between pre-op, 6 week and 26 weeks post-op assessments. No difference was seen between primary and revision cohorts in OKS (p = 0.2) or pain scores (p=0.19). Range of motion and functional performance was different between groups over the 2 year period (p=0.03), however this was due to differing pre-operative scores, post-hoc analysis showed no difference between groups at any post-operative time point. Patients undergoing aseptic revision TKA with semi-constrained implants made substantial improvements in OKS, pain scores, knee flexion, and timed functional performance, with the outcomes achieved comparable to those of primary TKA. High levels of function can be achieved following revision knee arthroplasty, which may be important considering the changing need for, and demographics of, revision surgery

The number of revision knee arthroplasties performed is projected to rise dramatically in the coming years. Primary knee arthroplasties are also being performed in younger patients increasing the likelihood of multiple revision procedures. Reconstruction can be challenging with bone stock deficiencies and ligament incompetence. The aim of this study was to present our results of revision total knee arthroplasty using metaphyseal sleeve components to aid reconstruction. Sixty seven patients underwent revision total knee arthroplasty between September 2005 and November 2010 using metaphyseal sleeves. There were thirty one male and thirty six female patients. The indication for revision was aseptic loosening in thirty nine, sepsis in fifteen, malalignment in eight and instability in five patients. Thirty four patients had tibial sleeves, thirty patients had both tibial and femoral sleeves and three patients had femoral sleeves during revision. The patients were followed up for a mean of 32 months (Range 12–60) with outcome data collected prospectively. The mean revised oxford knee scores for the patients improved from 15 (Range 2 to 29) preoperatively to 33 (Range 20 to 45) postoperatively. Mean arc of flexion following revision was 87 degrees (Range 55 to 120). Seventy six percent of patients were satisfied or very satisfied with the result of the revision surgery. There have been no radiographic complications specific to the sleeves and no re-operations. There has been one recurrence of infection in a patient revised for sepsis. This has been managed with suppressive antibiotics due to patient co-morbidities. Metaphyseal sleeves are an effective adjunct in revision knee arthroplasty. We have had good results with their use. To our knowledge no larger series has been presented or published

Recent projections expect the number of revision knee replacements performed to grow from 38,000 in 2005 to 270,000 by the year 2030. 1. Although the results of primary total knee arthroplasty are well documented, with overall implant survivorship at 15 years greater than 95%. 2. the results of revision procedures are not as well known. What if the revision TKR fails and what is the prevalence of failure of revision TKRs, the complications and re-operation rates? There are various studies which has either exclusively dealt with the causes or outcomes of revision with a particular prosthesis and survivorship analysis. The effectiveness of revision total knee replacement must be considered in the light of complications rates which could be either medical, orthopaedic surgery related complications or combination of both. The purpose of this study was to evaluate the prevalence of complications, reoperation rates and outcomes in a single surgeon's series between 1984 and 2008. Ninety nine index revision cases were studied. Incidences of surgical complications were 52.5%. The total reoperation rate was 34.3% whilst single re revision accounted for 19.9% whereas multiple re-revision incidences were 4%. The mean outcome in terms of Knee Society Score, Knee Society Function, and Knee society range of motion was statistically and clinically significant between pre operative and posts operative score at one year and remained consistent with time. These results suggest that modern revision total knee replacement are satisfactory operations and the outcomes perhaps can be improved if relatively simple strategies are followed by focusing these operations to specialized that accumulate enough experience from these demanding surgeries. Overall the results asserts that even in the hands of an experienced surgeon the complications do occur which is usually multi factorial, whilst in the light of complications and reoperation incidence the patients can be counselled thoroughly before the procedure

The treatment of bony defects of the tibia at the time of revision total knee replacement is controversial. The place of compacted morsellised bone graft is becoming established, particularly in contained defects. It has previously been shown that the initial stability of impaction-grafted trays in the contained defects is equivalent to that of an uncemented primary knee replacement. However, there is little biomechanical evidence on which to base a decision in the treatment of uncontained defects. We undertook a laboratory-based biomechanical study comparing three methods of graft containment in segmental medial tibial defects and compared them with the use of a modular metal augment to bypass the defect. Using resin models of the proximal tibia with medial defects representing either 46% or 65% of the medial cortical rim, repair of the defect was accomplished using mesh, cement or a novel bag technique, after which impaction bone grafting was used to fill the contained defects and a tibial component was cemented in place. As a control, a cemented tibial component with modular metal augments was used in identical defects. All specimens were submitted to cyclical mechanical loading, during which cyclical and permanent tray displacement were determined. The results showed satisfactory stability with all the techniques except the bone bag method. Using metal augments gave the highest initial stability, but obviously lacked any potential for bone restoration

Background. Finite element (FE) models are frequently used in biomechanics to predict the behaviour of new implant designs. To increase the stability after severe bone loss tibial components with long stems are used in revision total knee replacements (TKR). A clinically reported complication after revision surgery is the occurrence of pain in the stem-end region. The aim of this analysis was the development of a validated FE-model of a fully cemented implant and to evaluate the effect of different tibial stem orientations. Methods. A scanned 4th generation synthetic left tibia (Sawbones) was used to develop the FE-model with a virtually implanted fully cemented tibial component. The 500 N load was applied with medial:lateral compartment distributions of 60:40 and 80:20. Different stem positons were simulated by modifying the resection surface angle posterior to the tibias shaft axis. The results were compared with an experimental study which used strain gauges on Sawbones tibias with an implanted tibial TKR component. The locations of the experimental strain gauges were modelled in the FE study. Results. Similar patterns and magnitudes of the predicted and experimentally measured strains were observed which validated the FE-model. An increase of strain at the most distal gauge locations were measured with the stem-end in contact to the posterior cortical bone. More uniform strain distributions were observed with the stem aligned to the intramedullary canal axis. The load distribution of 80:20 shifts the strains to tensile laterally and a large increase of compressive strain in the medial distal tibia. Conclusions. A contributory factor of the clinically reported stem-end pain is possibly the direct effect of contact of the tibial stem-end to the posterior region of the cortical bone. The increased load to the medial tibial compartment is more critical for the development of pain

Summary. The EOS stereography system has been developed for the evaluation of prosthetic alignment. This new low-dose device provides reliable 2D/3D measurements of knee prosthesis alignment. Introduction. Achieving optimal prosthetic alignment during Total Knee Arthroplasty (TKA) is an essential part of the surgical procedure since malpositioning can lead to early loosening of the prosthesis and eventually revision surgery. Conventional weight-bearing radiographs are part of the usual clinical follow-up after both primary TKA and revision TKA (rTKA), to assess alignment in the coronal and sagittal planes. However, proportions and angles may not be correct on radiographs since divergence exists in the vertical and horizontal planes. Furthermore estimating the exact planes by looking at the position of the patella depends on rotation in the hip joint and this may be misinterpreted by the investigator. A computed tomography (CT) scanogram can also be used. However, due to high levels of radiation and costs it is not routinely used. To this end, a new device, the EOS stereography system, has been developed. With this biplanar low-dose X-ray technique, orthogonally made 2D images and 3D reconstructions can be obtained. Advantages of EOS are that images of the leg are obtained on a 1:1 scale with an amount of radiation 800–1000 times lower than CT-scans and 10 times lower than conventional radiographs. Another advantage is that the 3D reconstructions lead to determination of the real coronal and sagittal planes. However, the software for creating 3D reconstructions is developed for the lower limbs without knee prosthesis material. Consequently a reliability study concerning the generation of 2D images and 3D reconstructions of a leg containing a knee prosthesis has not been performed yet. Therefore objective of this study was to investigate interobserver and intraobserver reliability of knee prosthetic alignment measurements after rTKA using EOS. Patients and Methods. Forty anteroposterior and lateral images of 37 rTKA patients were included. Two observers independently performed measurements on these images twice. Measured angles were varus/valgus angle in 2D (VV2D) and 3D (VV3D). Intraclass correlation coefficients (ICCs) were used to determine relative reliability and the Bland and Altman method was used to determine absolute reliability. T-tests were used to test potential differences between the two observers, first and second measurement sessions and 2D and 3D measurements. Results. Relative interobserver reliability was excellent for both VV2D and VV3D with ICCs > 0.95, and no significant differences between the two observers. For the absolute reliability of VV2D, a bias of −0.16° (95%CI: −0.31–0.01) existed between both observers. Absolute reliability of VV3D was good. Relative intraobserver reliability was excellent for both VV2D and VV3D with ICCs > 0.97. No significant difference and no bias between the first and second measurements were found. A significant difference existed between the angles measured in 2D and 3D (p=0.01). Discussion / Conclusion. The EOS low-dose stereography system provides reliable varus/valgus measurements in 2D and 3D for the alignment of the knee joint with a knee prosthesis. However, significant differences exist between the varus/valgus measurements in 2D and in 3D. Therefore, a validation study is suggested to investigate the difference between the 2D measurements and 3D reconstructions and to find a possible explanation for this difference

Abstract. Objective. In this systematic review we aim to compare wound complication rates from Negative Pressure Wound Therapy (NPWT) to dry sterile surgical dressings in primary and revision total knee arthroplasty (TKA). Methods. A search was performed using PubMed, Embase, Science Direct, and Cochrane Library. Eligible studies included those investigating the use of NPWT in primary and revision TKA. Exclusion criteria included studies investigating NPWT not related to primary or revision TKA; studies in which data relating to NPWT was not accessible; missing data; without an available full text, or not well reported. We also excluded studies with poor scientific methodology. All publications were limited to the English language. Abstracts, case reports, conference presentations, and reviews were excluded. Welch independent sample t-test was used for the statistical analysis. Results. Our review identified 11 studies evaluating 1,414 patients. Of the 1,181 primary TKA patients analysed (NPWT = 416, surgical dressing = 765), the overall wound complication rates in patients receiving NPWT ranged from 0% – 63% (Median 7.30%, SD ± 21.44) This is in comparison to complication rates of 2.8% – 19% (Median 6.50%, SD ± 6.59) in the dry dressing group. The difference in complication rates between the two groups was not statistically significant (p =0.337). In the revision TKA cohort of 279 patients (NPWT group = 128, dry dressing group = 151), the overall wound complication rates in the NPWT group ranged between 6.7% – 12% (Median 9.80%, SD ± 2.32) vs 23.8% – 30% (Median 26.95%, SD ± 2.53) in the dry dressing group. This difference was statistically significant (p<0.001). Conclusion. NPWT dressing demonstrated statistically significant reduction in wound complication rates when used in revision TKA but not primary TKA when compared to dry sterile dressings. This is probably due to higher wound related risks encountered with revision TKA surgery compared to primary TKA surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction and Objective. Difficult primary total knee arthroplasty (TKA) and revision TKA are high demanding procedures. Joint exposure is the first issue to face off, in order to achieve a good result. Aim of this study is to evaluate the clinical and radiological outcomes of a series of patients, who underwent TKA and revision TKA, where tibial tubercle osteotomy (TTO) was performed. Materials and Methods. We retrospectively reviewed a cohort of 79 consecutives TKAs where TTO was performed, from our Institution registry. Patients were assessed clinically and radiographically at their last follow-up (mean, 7.4 ± 3.7 years). Clinical evaluation included the Knee Society Score (KSS), the pain visual analogue scale (VAS), and range of motion. Radiological assessment included the evaluation of radiolucent lines, osteolysis, cortical bone hypertrophy, time of bone healing of the TTO fragment, and the hardware complication. Results. KSS raised from 40.7 ± 3.1 to 75 ± 4.3 (p < 0.0001). Knee flexion increased from 78.7 ± 9.9° to 95.0 ± 9.5° (p < 0.0001), and VAS improved from 7.9 ± 0.9 to 3.8 ± 1 (p < 0.0001). No signs of loosening or evolutive radiolucency lineswere found. Osteolytic areas around the stem were detected. No significant association was found between the implant design and the outcomes, while aseptic loosening showed significantly better results. Complications were: 4 painful hardware, 3 late periprosthetic infections, 1 extension lag of 5°, and 3 flexion lag. Conclusions. Our experience suggests the use of TTO to improve the surgical approach in difficult primary TKA or revision TKA. A strict surgical technique leads to good results with low risk of complications

Abstract. Approximately 20% of primary and revision Total Knee Arthroplasty (TKA) patients require multiple revisions, which are associated with poor survivorship, with worsening outcomes for subsequent revisions. For revision surgery, either endoprosthetic replacements or metaphyseal sleeves can be used for the repair, however, in cases of severe defects that are deemed “too severe” for reconstruction, endoprosthetic replacement of the affected area is recommended. However, endoprosthetic replacements have been associated with high complication rates (high incidence rates of prosthetic joint infection), while metaphyseal sleeves have a more acceptable complication profile and are therefore preferred. Despite this, no guidance exists as to the maximal limit of bone loss, which is acceptable for the use of metaphyseal sleeves to ensure sufficient axial and rotational stability. Therefore, this study assessed the effect of increasing bone loss on the primary stability of the metaphyseal sleeve in the proximal tibia to determine the maximal bone loss that retains axial and rotational stability comparable to a no defect control. Methods. to determine the pattern of bone loss and the average defect size that corresponds to the clinically defined defect sizes of small, medium and large defects, a series of pre-operative x-rays of patients with who underwent revision TKA were retrospectively analysed. Ten tibiae sawbones were used for the experiment. To prepare the bones, the joint surface was resected the typical resection depth required during a primary TKA (10mm). Each tibia was secured distally in a metal pot with perpendicular screws to ensure rotational and axial fixation to the testing machine. Based on X-ray findings, a fine guide wire was placed 5mm below the cut joint surface in the most medial region of the plateau. Core drills (15mm, 25mm and 35mm) corresponding to small, medium and large defects were passed over the guide wire allowing to act at the centre point, before the bone defect was created. The test was carried out on a control specimen with no defect, and subsequently on a Sawbone with a small, medium or large defect. Sleeves were inserted using the published operative technique, by trained individual using standard instruments supplied by the manufacturers. Standard axial pull-out (0 – 10mm) force and torque (0 – 30°) tests were carried out, recording the force (N) vs. displacement (mm) curves. Results. A circular defect pattern was identified across all defects, with the centre of the defect located 5mm below the medial tibial base plate, and as medial as possible. Unlike with large defects, small and medium sized defects reduced the pull-out force and torque at the bone-implant interface, however, these reductions were not statistically significant when compared to no bony defect. Conclusions. This experimental study demonstrated that up to 35mm radial defects may be an acceptable “critical limit” for bone loss below which metaphyseal sleeve use may still be appropriate. Further clinical assessment may help to confirm the findings of this experimental study. This study is the first in the literature to aim to quantify “critical bone loss” limit in the tibia for revision knee arthroplasty. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

To determine risk factors of infection in total knee arthroplasty. This descriptive study was conducted in the Department of Orthopedics for a duration of three years from January 2016 to January 2019. All patients undergoing primary total knee replacement were included in the study. Exclusion criteria were all patients operated in another hospital and revision total knee replacement. All patients were followed up at 2, 4, 8, 12 and 24 weeks post-operatively. Signs of inflammation and inflammatory markers such as total leukocyte count (TLC), C-reactive protein (CRP) and ESR were measured. Risk factors like age, body mass index (BMI), ASA, co-morbid conditions were also noted. A total of 78 patients underwent primary unilateral Total Knee Replacement (TKR) during the study period. Of these, 30 (34.09%) were male and 48 (61.54%) female patients. Mean age of patients was 68.32 ± 8.54 years. Average BMI 25.89 Kg/m2 .Osteoarthritis was the pre-dominant cause of total knee replacement (94.87%). Among co-morbid factors 33.33% were diabetic, 28.20% having ischemic heart disease and 12.82% with chronic lung disease. Upon anaesthesia fitness pre-operatively, 91.02% patients had an American society of anaesthesiologist score (ASA) between 0–2 while 07 (8.97%) between 3- 5. Average duration of surgery was 85.62± 4.11 minutes. 6.41% cases got infected. In majority of the infected cases (60%), Staphylococcus aureus was the infective organism. Diabetes Mellitus (p=0.01) and Obesity (p=0.02) had a significant relation to post-operative infection. Pre-operative risk evaluation and prevention strategies along with early recognition of infection and control can greatly reduce the risk of joint infection post-TKR which will not only improve the mobility of patient but also its morbidity and mortality as well. Key Words:. C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR), Staphylococcus aureus, Total Knee Arthroplasty (TKA)

Background. Frequency of primary total hip (THA) and total knee (TKA) arthroplasty procedures is increasing, with a subsequent rise in revision procedures. This study aims to describe timing and excess surgical mortality associated with revision THA and TKA compared to those on the waiting list. Methods. All patients from 2003–2013 in a single institution who underwent revision THA and TKA, or added to the waiting list for the same procedure were recorded. Mortality rates were calculated at cutoffs of 30- and 90-days post-operation or addition to the waiting list. Results. 561 and 547 patients were available for the survivorship analysis in the revision THA and TKA groups respectively. Following exclusion, 901 and 832 patients were available for the 30-day analysis and 484 and 568 patients for the 90-day analysis in the revision THA and revision TKA waiting list groups respectively. The 30- and 90-day mortality rate was significantly greater for the revision THA group compared to the waiting list group (excess surgical mortality of 0.357%, 95% confidence interval 0.098% to 0.866%; p=0.037) (odds ratio of 5.22, 95% confidence interval 0.626 to 43.524; excess surgical mortality of 0.863%, 95% confidence interval 0.455% to 1.153%; p=0.045). The 30- and 90-day mortality rate was not significantly greater for the revision TKA group compared to the waiting list group (excess surgical mortality of zero) (excess surgical mortality of 0.366%, 95% confidence interval 0.100% to 0.651%; p=0.075). Conclusions. Revision THA is associated with a significant excess surgical mortality rate at 30- and 90-days post operation when compared to the waiting list for the same procedure. However, we have been unable to quantify any increased risk after revision TKA. We would encourage other authors with access to larger samples to use our method to quantify excess mortality after revision TKA. Level of Evidence. III-Retrospective Cohort Study

Total knee arthroplasty (TKA) is a common orthopaedic procedure with over 1,500 done in 2016 in Ireland alone. 96% of all TKAs are due to pain in the knee associated with osteoarthritis. According to the UK National Joint Registry (NJR), there is a 0.47%, 1.81%, 2.63% and 4.34% probability risk of undergoing a revision TKA within one, three, five and ten years respectively post-index surgery. A variety of reasons for failure of TKA have been described in the literature including infection, aseptic loosening, pain, instability, implant wear, mal-alignment, osteolysis, dislocation, peri-prosthetic fracture and implant fracture. The NexGen Posterior Stabilised Fixed has NJR revision rates of 0.44%, 1.61% and 2.54% at years one, three and five respectively. A retrospective review was carried out of 350 NexGen TKAs that were performed directly by, or under the supervision of, a fellowship trained arthroplasty surgeon in a dedicated orthopaedic hospital between April 2013 and December 2015. 26 (7.4%) of these were revised as of 31 December 2017. Three were for septic arthritis with the remaining 23 (6.6%) for aseptic loosening. Patients typically started to experience symptoms of medial tibial pain with supra-patellar swelling from a combination of effusion and synovial thickening at 12–24 months. Inflammatory markers were normal in all cases. Radiographs of symptomatic knee replacements showed bone loss on the medial tibia with a tilt of the tibial component into a varus alignment. The high number of revisions of this particular prosthetic has led to its use being discontinued at this centre

Instability accounts for approximately 20% of revision total knee arthroplasty (TKA) operations, however, diagnostic tests remain relatively subjective. The aim of this examination was to evaluate the feasibility of using pressure mat analyses during functional tasks to identify abnormal biomechanics associated with TKA instability. Five patients (M = 4; age = 69.80±7.05 years; weight = 79.73±20.12 kg) with suspected TKA instability were examined compared to 10 healthy controls (M = 4; age = 44.6±7.52 years; weight = 70.80±14.65). Peak pressure and time parameters were measured during normal gait and two-minute bilateral stance. Side-to-side pressure distribution was calculated over 10-second intervals during the second minute. Mann-Whitney tests compared loading parameters between groups and side-to-side differences in TKA patients (significance level = p<0.05). Pressure distribution was expressed relative to bodyweight. Notable differences were seen during bilateral stance. Uneven side loading was greater – favouring the non-operated limb – in TKA patients during bilateral stance compared to controls. This was significantly different at 30s (p=0.0336) and 60s (p=0.0336). Gait analyses showed subtle pressure distribution differences in unstable TKA patients. Stance time was indifferent. TKA patients tended to exhibit longer heel contact time (0.76s vs. 0.64s and reduced weight acceptance (50.75% vs. 56.75%) on the operated limb compared to the non-operated limb. Side-to-side differences in peak toe-off forces were significantly more pronounced in TKA patients versus controls (9.25% +/− 1.5% vs. 1.67% +/−5.79%; p=0.0039). Conclusion: This feasibility work demonstrates subtle differences in limb loading mechanics during simple clinical tests in unstable TKA patients that might be invisible to the naked eye. In the long-term, pressure analyses may be a useful diagnostic tool in identifying patients that would benefit from revision surgery for TKA instability

Instability accounts for approximately 20% of all revision total knee arthroplasty (TKA), however diagnostic tests remain crude and subjective. The aim of this examination was to evaluate the feasibility of pressure mat (SB Mat, TekScan) analyses of functional tasks to differentiate instability in a clinical setting. Five patients (M = 4; age = 69.80±7.05 years; weight = 79.73±20.12 kg) with suspected TKA instability were examined compared to five healthy controls (M = 1; age = 46.80±7.85 years; weight = 71.54±16.17 kg). Peak pressure and time parameters were measured during normal gait and two-minute bilateral stance. Side-to-side pressure distribution was calculated over 10-second intervals during the second minute. Pressure distributions were expressed relative to bodyweight (%BW). T-tests compared loading parameters between groups (significance level = p<0.05). Analyses showed subtle differences in pressure distribution in unstable TKA patients versus healthy controls. Stance time during gait was indifferent. TKA patients tended to exhibit longer heel contact time (0.76 vs. 0.64 sec) and reduced weight acceptance (50.75% vs. 56.75%) on the operated versus non-operated limb. Side-to-side differences in toe-off forces were significantly more pronounced in TKA patients versus controls (9.25% vs. 3.75%; p=0.0088). Uneven loading was significantly greater – favouring the non-operated limb – in TKA patients during bilateral stance compared to controls (p<0.05). This feasibility work demonstrates subtle differences in limb loading and biomechanics during simple clinical tests in unstable TKA patients that might be undetectable to the naked eye. Pressure analyses may therefore be a useful diagnostic tool. These findings warrant further investigation

Introduction. As the demand for primary total knee arthroplasty (TKA) has been on the rise, so will be the demand for revision knee surgery. Nevertheless, our knowledge on the modes of failure and factors associated with failure of knee revision surgery is considerably lower to that known for primary TKA. To date, this has been mostly based on case series within the literature. Therefore, the aim of this study was to evaluate the survivorship of revision TKA and determine the reasons of failure. Methods. A retrospective study was conducted with prior approval of the institutional audit department. This involved evaluation of existing clinical records and radiographs of patients who underwent revision knee surgery at our institution between 2003 and 2015. Re-revision was identified as the third or further procedure on the knee in which at least one prosthetic component was inserted or changed. Results. 95 patients were identified who had re-revision knee replacement. Of these, there were 46 men (48%) and 49 women (52%) with an average age of 65 yrs. Infection was the main cause of failure (35.8%) followed by aseptic loosening (27.4%) and extensor mechanism problems leading to reduced range of motion (7.4%). Other causes included MCL Laxity (3.2%), oversized implants (3.2%) and fracture of the cement mantle (1.1%). The mean survivorship of revision knee replacements in our cohort was 31 months (Range between 1 – 119 months). Conclusion. The survival of knee re-revision implants is considerably different from primary TKA implants. The results of our study provide an improved understanding of the modes of failure of re-revision knee replacements, enabling orthopaedic surgeons the opportunity to better understand the current problems associated with revision knee surgery and the potential to improve our outcomes by tackling these issues

The properties of impacted morsellised bone graft (MBG) in revision total knee arthroplasty (TKA) were studied in 12 horses. The left hind metatarsophalangeal joint was replaced by a human TKA. The horses were then randomly divided into graft and control groups. In the graft group, a unicondylar, lateral uncontained defect was created in the third metatarsal bone and reconstructed using autologous MBG before cementing the TKA. In the control group, a cemented TKA was implanted without the bone resection and grafting procedure. After four to eight months, the animals were killed and a biomechanical loading test was performed with a cyclic load equivalent to the horse’s body-weight to study mechanical stability. After removal of the prosthesis, the distal third metatarsal bone was studied radiologically, histologically and by quantitative and micro CT. Biomechanical testing showed that the differences in deformation between the graft and the control condyles were not significant for either elastic or time-dependent deformations. The differences in bone mineral density (BMD) between the graft and the control condyles were not significant. The BMD of the MBG was significantly lower than that in the other regions in the same limb. Micro CT showed a significant difference in the degree of anisotropy between the graft and host bone, even although the structure of the area of the MBG had trabecular orientation in the direction of the axial load. Histological analysis revealed that all the grafts were revascularised and completely incorporated into a new trabecular structure with few or no remnants of graft. Our study provides a basis for the clinical application of this technique with MBG in revision TKA