Abstract. Objectives. Unicompartmental (UKA) and bicompartmental (BCA) knee arthroplasty are associated with improved functional outcomes compared to Total Knee Arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function. Methods. Extensor function was measured for sixteen cadaveric knees and then re-tested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensor efficiency was calculated for ranges of knee flexion associated with common activities of daily living. Data were analyzed with repeated measures analysis of variance (α=0.05). Results. Compared to native, no differences were detected in either extensor moment or efficiency following UKA. Conversion to BCA resulted in a small drop in extensor moment between 70-90° flexion (p<0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extensor moment were measured at low knee flexion angles (p<0.05), resulting in 8–43% reduction in extensor efficiency for daily activity ranges. Conclusion. This cadaveric study found that TKA is associated with inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in function and satisfaction differences between partial and total knee arthroplasty. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Ultra-high molecular weight polyethylene (UHMWPE) is a commonly used as bearing material in joint replacement devices. UHMWPE implants can be hard to see on a standard X-ray because UHMWPE does not readily attenuate X-rays. Radiopaque UHMWPE would enable direct imaging of the bearing both during and after surgery, providing in vivo assessment of bearing position, dislocation or fracture, and potentially a direct measure of wear. The X-ray attenuation of UHMWPE was increased by diffusing an FDA approved contrast agent (Lipiodol) into UHMWPE parts (Zaribaf et al, 2018). The aim of this study was to evaluate the optimal level of radiopacity for a UHMWPE bearing. Samples of un-irradiated medical grade UHMWPE (GUR 1050) were machined into 4mm standard medium Oxford Unicompartmental bearings. Samples were immersed in Lipiodol Ultra Fluid (Guerbert, France) at elevated temperatures (85 °C, 95 °C and 105 °C) for 24 h to achieve three different levels of radiopacity. A phantom set-up was used for X-ray imaging; the phantom contained two perspex rods to represent bone, with the metallic tibial tray and polyethylene bearing fixed to the end of one rod and the metallic femoral component fixed to the other rod. Radiographs of the samples were taken (n=5) with the components positioned in full extension. To ensure consistency, the images of all the samples were taken simultaneously alongside an untreated part. The results of our ongoing study demonstrate that the radiopacity of UHMWPE can be enhanced using Lipiodol and the parts are visible in a clinical radiographs. The identification of the optimal treatment from a clinical perspective is ongoing; we are currently running a survey with clinicians to find the consensus on the optimal radiopacity taking into account the metallic components and alignment. Future work will involve a RSA study to assess the feasibility of measuring wear directly from the bearing

Summary Statement. This is the first report of a new technique for unicompartmental to total knee arthroplasty revision surgery in which patient specific guides are formed based on preoperative CT imaging. This technique can help to make revision surgery less technically demanding. Introduction. Unicompartmental to total knee arthroplasty revision surgery can be a technically demanding procedure. Joint line restoration, rotation and augmentations can cause difficulties. This study describes a new technique in which single way fitting guides serve to position knee system cutting blocks. Methods. Preoperatively an image of the distal femur and proximal tibia are formed using CT-scanning. This image is used to create patient specific guides that fit in one single position on the contours of the bone and prosthesis in situ. These guides are fixed with pins and thereafter removed. The pins determine the position of the cutting blocks. Ten consecutive revisions were performed using this technique. Results. All guides fitted well. All femoral prostheses were properly inserted using this technique. One proximal tibia however did not have not enough bonestock so that conversion to intramedular referencing was performed. This was to be expected after the preoperative planning. Postoperative position of the prosthesis was good in all cases. Discussion. This new technique can help to make unicompartmental to total knee arthroplasty less demanding. Problems such as the need for augmentations can be predicted in the preoperative planning. Radiation issues due to CT scanning are limited. The instrumentation needs to be redesigned in order to make this technique work in cases with minimal bonestock present

Summary Statement. This paper is the first to compare the results of unicompartmental to total knee arthroplasty revision surgery between cases with explained pain and cases with unexplained pain. Revision surgery for unexplained pain usually results in a less favourable outcome. Introduction. Although it is suggested in literature that results of UKA to TKA revision surgery improve when the mechanism of failure is understood, a comparative study regarding this topic is lacking. Methods. All cases of revision surgery in two hospitals in the Netherlands were listed retrospectively. Fifteen cases with unexplained pain were listed in group A and 15 cases with a cause for pain in group B. Oxford knee scores (OKS), visual analogue scores (VAS) and patient satisfaction one year after revision surgery were compared. Results. OKS improved from 19 to 25 within group A and from 23 to 38 within group B. VAS improved from 7, 7 to 5, 4 within group A and from 7, 4 to 1, 7 within group B. The difference in outcome between both groups is statistically significant, p=0,022 for OKS and p=0,002 for VAS. Subgroup analysis in group A, performed in order to define a patient factor that predicts outcome of revision surgery in case of unexplained pain, showed no preoperative differences between both subgroups. Discussion. These results are important to properly inform patients about what to expect of revision surgery, highlighting that UKA to TKA revision surgery for unexplained pain generally results in a less favourable outcome

Fractures of the prosthetic components after total knee arthroplasty (TKA) are rare but dangerous complications, sometimes difficult to diagnose and to manage. Aim of this study is to evaluate the incidence of component breakage and its treatment in our single institution's experience. We retrospectively review our institution registry. From 605 revision knee arthroplasties since 2000 to 2018, we found 8 cases of component breakage, of these 3 belonged to UKA, and 5 belonged to TKA. The UKA fractures were all on the metal tibial component; while 4 TKA fractures were ascribed to the liner (2 Posterior-Stabilized designs and 2 constrained designs) and only one case was on the femoral component. For every patient a revision procedure was performed, in two cases a tibial tubercle osteotomy was performed, while in one case (where the fracture was of the post cam) an arthroscopy was performed prior to the arthrotomy. All of the UKA fractures were treated with a standard revision implant. As regard the TKA, 2 liner fractures were treated with the only liner exchange, while the other 2 liner fractures and the fracture of the metallic component were treated with total knee revision. No intra- and post-operative complications were found. Component breakage after TKA is a serious complication. Its treatment, always surgical, can hide pitfalls, especially if the timing is not correct; indeed apart from the revision of one or more components, the surgeons must address any issues of management of bone defect and ligamentous stability.

Intramedullary (IM) femoral alignment guide for unicondylar knee arthroplasty (UKA) is a classic and generally accepted technique to treat unicompartmental knee osteoarthritis. However, IM system has a risk of excessive blood loss, fat embolism and activation of coagulation.Moreover, the implant placement and limb alignment may be less accurate in IM for UKA than total knee arthroplasty. So we try to use extramedullary (EM) femoral alignment for UKA to avoid above disadvantages. To our knowledge, few current studies have been reported by now. We reported a series of cases treated through a newly developed EM technique and evaluated the accuracy of femoral component alignment and preliminary clinical results. Between January 2009 and January 2010, 11 consecutive patients(15 knees)consisting of 8 males and 3 females were enrolled. There were 7 cases in unilateral knee and 4 cases in bilateral knees. The mean age was 65.2 years (range 60∼72 years). Incision, surgical time, blood loss and complications were measured. The pre- and post operative function of the knees were evaluated by HSS score system. The pre- and postoperative femoral component alignment was measured and compared. All cases were followed up for average 15 months (10-22 months). The mean length of incision was 7.2cm (range 6 to 8cm), the mean surgical time was 115.0min(range 90 to 125min),the mean blood loss was 50.8ml (range 50 to 80ml). The mean preoperative HSS score increased from 75 (range 63 to 83) to 95 (range 88 to 97) postoperatively (p<0.05). All femoral components were within the recommended range for varus/valgus (±10 degree) and lexion/extension (±5 degree) angle. None had complications associated with reamed canal injury. By using our EM technique, we could achieve an accurate femoral component alignment and satisfactory clinical effect. However, strict comparison between EM and cconventional IM technique and large amount of cases are essential. Further mid- and long-term studies are required

Study of failed Oxford medial unicompartmental knee replacements at the Royal Cornwall Hospital.

Background. Medial open wedge high tibial osteotomy (MOWHTO) has been accepted as a highly effective option for the treatment of medial unicompartmental osteoarthritis of the knee. Although pain in the medial joint line is significantly relieved after MOWHTO, some patients complain of pain over pes anserinus after the osteotomy, necessitating implant removal for pain relief. Purpose. The purpose of this study is to define the implant removal rate after MOWHTO due to patient complaints. Methods. 103 knees of 72 patients who underwent MOWHTO for medial unicompartmental osteoarthritis between 2010 and 2018 with a follow-up of at least 24 months were enrolled in the study. Patients were evaluated with the Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS) and Visual Analogue Score (VAS) for pain in the medial knee joint (VAS-MJ). All tests were performed before the surgery, at 12 months after surgery. VAS value for pain over pes anserinus (VAS-PA) was recorded at 12 months after MOWHTO and at 3 months after implant removal. Results. Mean follow-up was 31±5.4 months. TomoFix® medial high tibia plate (DePuy Synthes, Raynham, MA, USA) was used for the fixation of osteotomy in all cases. Significant improvement in KOOS, OKS and VAS-MJ were observed 12 months after MOWHTO. Average values of VAS-MJ and VAS-PA were 21.7±7.1 and 34±8.4, respectively. Implant removal was needed for 65 (63.1%) knees. There were no significant differences in regard of postoperative KOOS (p=0.134), OKS (p=0.287) and VAS-MJ (p=0.416) scores between patients for which implant removal was needed or not. VAS-PA value decreased significantly at 3 months after implant removal (p<0.001). Conclusion. A large portion of patients needed implant removal after MOWHTO to relieve pain over pes anserinus even if knee function was significantly improved. Lower profile plates may be preferred to avoid secondary implant removal surgery after MOWHTO

Introduction. Simultaneous correction of knee varus malalignment with medial open wedge high tibial osteotomy (MOWHTO) combined with anterior cruciate ligament (ACL) surgery aims to address symptomatic unicompartmental osteoarthritis in addition to restore knee stability in order to improve outcomes. The aim of this study is to present at least 5 years results of 32 patients who underwent simultaneous knee realignment osteotomy with ACL surgery. Methods. Patients with symptomatic instability due to chronic ACL deficiency or failed previous ACL surgery together with a varus malalignment of ≥6°, previous medial meniscectomy and symptomatic medial compartment pain who were treated with MOWHTO combined with ACL surgery were enrolled. ACL surgery was performed with the anatomical single bundle all-inside technique using TightRope. ®. RT (Arthrex, Naples, FL, USA) and MOWHTO using TomoFix. ®. medial high tibia plate (DePuy Synthes, Raynham, MA, USA) in all cases. Patients were evaluated preoperatively and at 6 months, 12 months and annually postoperatively using the Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS) and Euroqol's Visual Analogue Score (VAS) for pain. Results. 32 patients (22 men and 10 women) with a mean age of 41.2 years and mean BMI of 28.6 kg/m. 2. , underwent the combined procedures. Tibiofemoral neutral re-alignment was achieved in all patients with HTO. Complete subjective and objective scores have been obtained in 84.4% of patients with at least 5 years of follow-up (mean 8.7 years). An improvement in total KOOS of 27.1 points (p<0.003), OKS of 15.1 (p<0.003) and VAS for pain of 24.7 points (p<0.001) were detected. No ACL reconstruction failure was noted. Complications consisted of one superficial wound infection and one delayed union. Plate removal was needed in 20 (62.5%) patients due to pes anserinus pain. Conclusions. Simultaneous restoration of coronal knee axis by applying HTO and stability by ACL reconstruction/revision were reported to offer excellent improvement in early outcomes in patients with ACL rupture and symptomatic unicompartmental osteoarthritis. The combined procedure requires careful pre-operative planning and is therefore technically challenging. However, by restoring the neutral axis and providing stability, it represents a good joint preserving alternative to arthroplasty for active middle-aged patients

Abstract. Objectives. There is renewed interest in bi-unicondylar arthroplasty (Bi-UKA) for patients with medial and lateral tibiofemoral osteoarthritis, but a spared patellofemoral compartment and functional cruciate ligaments. The bone island between the two tibial components may be at risk of tibial eminence avulsion fracture, compromising function. This finite element analysis compared intraoperative tibial strains for Bi-UKA to isolated medial unicompartmental arthroplasty (UKA-M) to assess the risk of avulsion. Methods. A validated model of a large, high bone-quality tibia was prepared for both UKA-M and Bi-UKA. Load totalling 450N was distributed between the two ACL bundles, implant components and collateral ligaments based on experimental and intraoperative measurements with the knee extended and appropriately sized bearings used. 95th percentile maximum principal elastic strain was predicted in the proximal tibia. The effect of overcuts/positioning for the medial implant were studied; the magnitude of these variations was double the standard deviation associated with conventional technique. Results. For all simulations, strains were an order of magnitude lower than that associated with bone fracture. Highest strain occurred in the spine, under the anteromedial ACL attachment, adjacent to transverse overcut of the medial component. Consequently, Bi-UKA had little effect on strain: <10% increases were predicted when compared to UKA-M with equivalent medial cuts/positioning. However, surgical overcutting/positional variation that resulted in loss of anteromedial bone in the spine increased strain. The biggest increase was for lateral translation of the medial component: 44% and 42% for UKA-M and Bi-UKA, respectively. Conclusions. For a large tibia with high bone quality, Bi-UKA with a well-positioned lateral implant had no tangible effect on the risk of tibial eminence avulsion fracture compared to UKA-M. Malpositioning of the medial component that removes bone from the anterior spine could prove problematic for smaller tibiae. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objectives. Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but monolithic implants disrupt the natural homeostasis of bone which leads to bone loss over time. This can cause problems if the implant needs to be revised. This study aimed to demonstrate that tibial implants made from titanium lattice could replace the tibial condyle surface while minimising disruption of the bone's natural mechanical loading environment. A secondary aim was to determine whether implants perform better if they replicate more closely bone's mechanical modulus, anisotropy and spatial heterogeneity. This study was conducted in a human cadaveric model. Methods. In a cadaveric model, UKA and TKA procedures were performed on 8 fresh-frozen knee specimens by a board-certified consultant orthopaedic surgeon, using tibial implants made from conventional monolithic material and titanium lattice structures. Stress at the bone-implant interfaces was measured with pressure film and compared to the native knee. Results. Titanium lattice implants were able to restore the mechanical environment seen in the native tibia for both UKA and TKA designs. Maximum stress at the bone-implant interface ranged from 1.2–3.3MPa compared to 1.3–2.7MPa for the native tibia. The conventional UKA and TKA implants reduced the maximum stress in the bone by a factor of 10 and 9.7 respectively. The conventional UKA and TKA implants caused 71% and 77% of bone surface area to be underloaded compared to the native tibia. Conclusions. Titanium lattice implants can maintain the natural mechanical loading in the proximal tibia after UKA and TKA. This may help maintain normal bone homeostasis throughout the life of the implant. These encouraging data indicate normal bone homeostasis can be maintained after arthroplasty using manufacturing methods already in widespread use. This would maintain bone quality throughout the life of the implant and alleviate complications at revision surgery

Purpose. To identify genes showing altered expression in osteoarthritic (OA) cartilage and synovium. Dkk3, a member of the Dickoppf family of Wnt signalling inhibitors was overexpressed and this work highlights the potential function of Dkk3 in OA. Methods. Real-time PCR was used to compare the expression of 270 cytokines, chemokines and their receptors in cartilage and synovium from OA and non-OA patients. Expression of Dkk3 was also measured in ATDC5 cells and in bovine nasal cartilage (BNC) explants treated with inflammatory cytokines. The effect of Dkk3 on hydroxyproline and GAG release was measured in BNC explant cultures. To assess the distribution of Dkk3 in OA cartilage immunohistochemistry was carried out on anteromedial gonarthrosis specimens. The level of Dkk3 in synovial fluid tricompartmental and unicompartmental cartilage lesions was measured using ELISA. Results. Dkk3 expression was increased 10- in OA cartilage (p=0.00011) and 3.5-fold increase in OA synovium (p=0.007) when compared to respective control tissues. Dkk3 expression was shown to decrease during chondrogenic differentiation of ATDC5 cells and to be increased by interleukin 1 and oncostatin-M in BNC explants. Dkk3 inhibited the release of hydroxyproline and proteoglycan from BNC explants co-treated with interleukin-1 and oncostatin-M. Immunohistochemistry of anteromedial gonarthrosis specimens demonstrated increased Dkk3 in superficial zone chondrocytes in damaged compared to undamaged cartilage from within the same knee. Increased Dkk3 protein was found in the synovial fluid of individuals with tricompartmental OA (n=4) versus unicompartmental cartilage lesions (n=10) (182ng/ml v 116 ng/ml, p<0.01, a single non-OA control synovial fluid measured 43ng/ml. Conclusions. Dkk3 is a molecule with poorly ascribed function, especially within the musculoskeletal system. In contrast to other members of the Dkk family, Dkk3 does not act consistently as a Wnt inhibitor. Literature on a number of tumour-derived cells have shown that Dkk3 can regulate Wnt, TGFβ, BMP, FGF and Activin signaling and cell proliferation and apoptosis. These cellular processes are highly relevant to OA. In this preliminary study we have shown that Dkk3 is overexpressed in OA cartilage and synovial tissues. The decreased expression of Dkk3 during chondrogenesis, and its increase in inflammatory cytokine stimulated BNC explants is suggestive of a role of Dkk3 not only in articular cartilage maintenance but also in development. The ability of Dkk3 to regulate collagen and proteoglycan breakdown (hallmarks of OA) is further evidence for a role in OA pathogenesis. Dkk3 is a compelling molecule that shows potential to further our understanding of OA and to be used as a biomarker of disease or as a target in OA therapeutics

Details of orthopaedic implants in Scotland are recorded on a national database. The results are used by the Scottish Arthroplasty Project to record survival and complication rates for both knee and hip replacements. The aim of our study was to assess the accuracy of recorded data for unicompartmental knee replacements in the West of Scotland. The national database was searched for all unicompartmental knee replacements carried out in the West of Scotland between March 2000 to October 2004. All patient data was then crosschecked with hospital theatre records and case notes for confirmation of accuracy. A total of 88 cases were coded as unicompartment joint replacements in the study period. 63 cases were confirmed as being accurate (71.6%) and 6 as being inaccurate (6.8%). 19 patient details were not available for review either from notes or theatre records (21.6%). Of those coded inaccurately, five were total knee replacements, one cemented hip hemiarthroplasty and one shoulder replacement. One case of miscoding could be accounted for as an error in documentation while in six cases no cause could be identified. Of the 63 knees confirmed as unicompartmental, seven knees had been revised within 5 years, giving a 5 year survival rate of 87.7%. The current system used by the Scottish Arthroplasty Project in Scotland has at least a 6.8% inaccuracy rate when recording unicompartmental knee replacements

Summary. The mechanical properties of porcine tibial plateau (TP) cartilage are shown to vary topographically. Low Elastic moduli (Em) were found in the positions where unicompartimental knee osteoarthritis (OA) lesions are typically expected to develop. These results suggest that there is a different response to load in these areas. Introduction. OA is one of the ten most disabling diseases in developed countries. OA of the knee, in particular, is a major cause of mobility impairment; up to 40% of the population over the age of 70 suffers from OA of the knee. It has been observed that unicompartmental knee OA occurs with very distinct and repeatable lesion patterns. It is hypothesised that these patterns are the result of differences in the material properties throughout articular cartilage. The aim of this study was to measure the mechanical properties of porcine cartilage in a whole undamaged TP. Materials and methods. A Whole Articular Surface Indentation Machine (WASIM) was used to measure material properties in whole intact articular surface. WASIM has five degrees of freedom (DOF). The vertical axis (Z) holds an indenter tied to a load cell and a high resolution laser. Five porcine TP were scanned using a high resolution laser to obtain the topography. Using a custom program, a grid of equally spaced points (6 mm) was defined. In vivo loading for daily activities occurs normal to the surface, therefore indentation was carried out on the same orientation. The normal vector for each indentation point was calculated by averaging the normal vectors of the points within the contact area at full load. The resulting vector allowed the calculation of angles, rotations and translation to obtain normal indentation of each point. Using a novel whole articular surface indentation machine (WASIM) in combination with a custom program, the TP was rotated to obtain normal indentation. Displacement controlled indentation was performed at 10 percent per second (pps) to 15% of the total cartilage thickness. Em was calculated at each indentation point by using Hertz contact theory and the Field and Swain Method. It was assumed that the initial portion of the unloading was purely elastic. Results and Conclusions. Em of 45 to 50 points throughout the TP were obtained for each knee. Results show low Em values in the anterior medial area. Additionally, it was possible to find an area in the posterior lateral section of the TP delimited with low Em values. These areas correspond to the unicompartimental knee OA lesions. These results suggest a correlation exists between the material properties of the TP and the locations of early lesions in knee OA. This correlation can partly be explained by the relationship between articular cartilage stiffiness and matrix integrity

Using a new, non-invasive method, we measured the patellofemoral force (PFF) in cadaver knees mounted in a rig to simulate weight-bearing. The PFF was measured from 20° to 120° of flexion before and after implanting three designs of knee prosthesis. Medial unicompartmental arthroplasty with a meniscal-bearing prosthesis and with retention of both cruciate ligaments caused no significant change in the PFF. After arthroplasty with a posterior-cruciate-retaining prosthesis and division of the anterior cruciate ligament, the PFF decreased in extension and increased by 20% in flexion. Implantation of a posterior stabilised prosthesis and division of both cruciate ligaments produced a decrease in the PFF in extension but maintained normal load in flexion. There was a direct relationship between the PFF and the angle made with the patellar tendon and the long axis of the tibia. The abnormalities of the patellar tendon angle which resulted from implantation of the two total prostheses explain the observed changes in the PFF and show how the mechanics of the patellofemoral joint depend upon the kinematics of the tibiofemoral articulation

Aims

The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage.

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.

Objectives

During open orthopaedic surgery, joints may be exposed to air, potentially leading to cartilage drying and chondrocyte death, however, the long-term effects of joint drying in vivo are poorly understood. We used an animal model to investigate the subsequent effects of joint drying on cartilage and chondrocytes.

Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty.

All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions.

Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.