Introduction

Distal femur fractures around a total knee arthroplasty (TKA) are a growing problem for orthopaedic surgeons. The purpose of this study was to identify risks of reoperation for nonunion following open reduction and internal fixation of TKA periprosthetic distal femur fractures (PDFF).

Current treatment options for displaced acetabular fractures in elderly patients include non-surgical management, surgical fixation and surgical fixation with simultaneous hip replacement, the so-called “fix-and-replace”™. There remains a paucity of evidence to guide surgeons in decision making for these difficult injuries. The aim of this study was to assess the feasibility of performing an appropriately powered RCT between treatment options for acetabular fractures in older patients.

This was an NIHR funded feasibility triple-arm RCT with participation from 7 NHS MTCs. Patients older than 60 were recruited if they had an acetabular fracture deemed sufficiently displaced for the treating surgeon to consider surgical fixation. Randomisation was performed on a 1:1:1 basis. The three treatment arms were non-surgical management, surgical fixation and fix-and-replace. Feasibility was assessed by willingness of patients to participate and clinicians to recruit, drop out rate, estimates of standard deviation to inform the sample size calculation for the full trial and completion rates to inform design of a future definitive trial. EQ-5D was the primary outcome measure at 6 months, OHS and Disability Rating Index were secondary outcome measures.

Of 117 eligible patients, 60 were randomised whilst 50 declined study participation. Nine patients did not receive their allocated intervention. Analysis was performed on an intention to treat basis. During the study period 4 patients withdrew before final review, 4 patients died and 1 was lost to follow-up. The estimated sample size for a full scale study was calculated to be 1474 participants for an EQ-5D MCID of 0.06 with a power of 0.8.

This feasibility study suggests a full scale trial would require international collaboration. This study also has provided observed safety data regarding mortality and morbidity for the fix-and-replace procedure to aid surgeons in the decision-making process when considering treatment options.

Introduction

Knee arthroscopy can be used for ligamentous repair, reconstruction and to reduce burden of infection. Understanding and feeling confident with knee arthroscopy is therefore a highly important skillset for the orthopaedic surgeon. However, with limited training or experience, furthered by reduced practical education due to COVID-19, this skill can be under-developed amongst trainee surgeons.

Introduction

A proportion of patients with hip and knee prosthetic joint infection (PJI) undergo multiple revisions with the aim of eradicating infection and improving quality of life. The aim of this study was to describe the microbiology cultured from multiply revised hip and knee replacement procedures to guide antimicrobial therapy at the time of surgery.

Abstract

Periprosthetic joint infections (PJI) are one of the most common reasons for orthopedic revision surgeries. In previous studies, it has been shown that silver modification of titanium (Ti-6Al-4V) surfaces by PMEDM (powder mixed electrical discharge machining) has an antibacterial effect on Staphylococcus aureus adhesion. Whether this method also influences the proliferation of bacteria has not been investigated so far. Furthermore, the effect is only limitedly investigated on the ossification processes. Therefore, the aim of this work is to investigate the antibacterial effect as well as the in vitro ossification process of PMEDM machined surfaces modified by integration of silver.

In this study, we analyzed adhesion and proliferation of S. aureus in comparison to of surface roughness, silver content and layer thickness of the silver-integrated-PMEDM surfaces (N = 5). To test the in vitro ossification, human osteoblasts (SaOs-2) and osteoclasts (differentiated from murine-bone-marrow-macrophages) were cultured on the silver surfaces (N = 3).

We showed that the attachment of S. aureus on the surfaces was significantly lower than on the comparative control surfaces of pure Ti-6Al-4V without incorporated silver, independently of the measured surface properties. Bacterial proliferation, however, was not affected by the silver content. No influence on the in vitro ossification was observed, whereas osteoclast formation was drastically reduced on the silver-modified surfaces.

We showed that 1 to 3% of silver in the surface layer significantly reduced the adhesion of S. aureus, but not the proliferation of already attached bacteria. At the same time, no influence on the in vitro ossification was observed, while no osteoclasts were formed on the surface. Therefore, we state that PMEDM with simultaneous silver modification of the machined surfaces represents a promising technology for endoprostheses manufacturing to reduce infections while at the same time optimizing bone ingrowth.

Aims

The aim of this prospective cohort study was to evaluate the early migration of the TriFit cementless proximally coated tapered femoral stem using radiostereometric analysis (RSA).

Introduction

We are a high-volume arthroplasty unit performing over 800 primary THRs annually at an approximate reimbursement of £6.5 million to the Trust. 70% are hybrid and we have been using the Taperfit - Trinity combination (Corin, Cirencester) since March 2016. We aimed to investigate the potential cost-savings and clinical benefits of instrument rationalisation using this system following GIRFT principles.

Background

Computer-assisted navigation systems for total knee arthroplasty (TKA) were introduced to improve implantation accuracy and to optimize ligament balancing. Several comparative studies in the literature confirmed an effect on the component position and other studies could not confirm these results. For ligament balancing most studies found no significant influence on the clinical outcome using a navigation system for TKA. In the literature there were no reports of mid-term results after navigated TKA. With our study we wanted to show if the use of a navigation system for TKA will have an influence on the component's position and on the clinical results at 5-year follow up.

Background

In the literature are different data about the allogenic blood transfusion rate after total knee replacement. The common intention in orthopedic surgery is to reduce the requirement for allogenic blood transfusions by optimizing the blood management. The aim of this study is to determine the efficacy of the mechanical autotransfusion system OrthoPAT® to reduce the postoperative allogenic blood transfusion (ABT) rate.

The comparison between surgical outcomes of trapeziectomy versus trapeziectomy with ligament reconstruction (LRTI) is well documented in the literature. We could not find any literature comparing these two procedures from a ‘patient-based outcome scoring’ perspective.

The Patient Outcomes Of Surgery (POS) hand/arm questionnaire was used in order to assess the outcomes of 33 patients (23 Trapeziectomy and 10 LRTI). All surgery was carried out by the same hand surgeon. A telephone questionnaire was performed on each patient. The mean time post surgery was 15 months (range 1 to 27) and 20 months (range 7 to 30) for the Trapeziectomy and LRTI group respectively.

There was statistically significant improvement in both groups for symptoms, physical activities and psychological functioning/cosmetic appearance. The Trapeziectomy alone group scored higher in all groups though this did not show statistical significance. There were statistically significant higher rates of complications in the LRTI group. LRTI surgery increased the tourniquet time by 28 minutes on average. Patient overall satisfaction was higher (85/100) in the trapeziectomy alone group than that of the LRTI group (75/100)

Both trapeziectomy and trapeziectomy with LRTI offer a reliably way of treating arthritis of the carpometacarpal joint. In our study, Trapeziectomy alone resulted in better overall patient satisfaction with lower complication rates and reduced operating time.

Irradiation cross-linking of UHMWPE has been shown to reduce wear while generating free radicals that oxidise in the presence of oxygen or oxidising species. Various methods have been used to minimise or eliminate the effect of these free radicals including below-melt annealing, remelting, Vitamin E infusion, or the use of other antioxidants. Each method has benefits and drawbacks with respect to wear properties, mechanical properties, and chemical properties. Accelerated aging techniques are used to evaluate the efficacy of new methods in stabilising free radicals in highly cross-linked UHMWPE.

Various procedures have been described for aging standard gamma-air sterilised UHMWPE to produce oxidation levels that represent shelf-aged bearings. An important factor in evaluating and comparing these aging techniques is validating that they reproduce the profile of oxidation (depth and magnitude) seen both in gamma-air, shelfaged polyethylene and in clinical retrievals. Moreover, the resulting oxidation level in the aged UHMWPE should predict the fatigue and/or wear damage seen in retrieved gamma-air inserts and liners.

The present study compared clinically relevant UHMWPE samples aged with ASTM 2003-00, (Method B: 70°C, 5 atm O2, 14 days) and a published lower temperature, lower oxygen-pressure environment (63° C, 3 atm O2, 28 days). Longer aging times (35 to 42 days) were also tested to examine oxidation rate and time to onset of mechanical degradation.

Both published methods result in oxidation of gamma-air and gamma-barrier sterilised polyethylene, but have little effect on remelted or antioxidant stabilised crosslinked polyethylene. These aging protocols, however, did not bring standard polyethylene to the critical oxidation level necessary for the fatigue damage that is seen in retrieved inserts and liners.

Oxidation of gamma-air and gamma-barrier sterilised UHMWPE increases exponentially with time on the shelf or in the two aging environments. Of note, longer aging times (35 to 42 days) that bring standard UHMWPE to sufficiently high oxidation levels for fatigue to occur also cause increased oxidation levels in remelted UHMWPE.

Oxidation increases were the smallest in antioxidant UHMWPE, though still detectable.

While this oxidation is not high enough in remelted material or antioxidant material to cause the fatigue damage seen in gamma-air sterilised UHMWPE, it does raise concerns about the published aging techniques and the long term stability of the new materials in vivo.

Relying on artificial aging techniques that do not adequately challenge even gamma-air polyethylene may conceal unforeseen weaknesses of new materials. Using longer aging times for existing techniques or novel aging approaches may be necessary to effectively evaluate the long term stability of new bearing materials.

Introduction: Based on the benefits of less postoperative pain and accelerated rehabilitation associated with minimally invasive implanted unicompartmental knee joint replacement new surgical approaches have been developed for total knee replacement. New side-cutting implantation instruments were proposed for the minimally invasive surgical technique. Different randomized studies have shown improved component position in association with the use of navigation systems for TKA as compared with standard implantation instruments. There is a lack of randomized studies showing whether the same level of accuracy provided by computer-assistance is possible when using a minimally invasive approach and the side-cutting jigs. We hypothesized an imageless navigation system leads to improved component positioning in the coronal and sagittal plane when compared with a non-navigated study group. Both cohorts were operated on with a mini-subvastus surgical approach using side-cutting instruments. We questioned whether clinical outcomes were affected by the application of the navigation system at 3 months followup.

Methods: 100 patients were randomized to undergo computer-assisted TKA or non-navigated TKA using a mini-subvastus surgical approach and side-cutting implant instrumentation. The radiographic parameters, clinical outcomes and knee scores were evaluated 3 months postoperative.

Results: The mechanical axis of the limb was within 3° varus/valgus in 76 % of the patients who had navigated procedures versus 66 % of patients who had conventional surgery. The tibial slope showed a rate of inaccuracy of 3° or less for 78 % of the patients in the navigated total knee arthroplasty group versus 66 % of the patients in the conventional group. Clinical outcomes and knee scores were similar in both groups.

Conclusion: The navigated study group showed a trend to a higher implantation accuracy but the differences were not significant. We think the reasons were the cutting direction from medial to lateral – longer cutting distance – and the insufficient cutting-jig fixation. We cannot recommend the use of the MIS Quad-Sparing™ instrumentation without a navigation system. With computer-assistance the implantation accuracy could duplicate the findings in the literature for non-navigated cohorts using a standard surgical approach. Using a navigation system for minimal invasive subvastus TKA did not influence the 3-month clinical outcome.

Background: In the literature are different data about the allogenic blood transfusion rate after total knee replacement. The common intention in orthopedic surgery is to reduce the requirement for allogenic blood transfusions by optimizing the blood management. The aim of this study is to determine the efficacy of the mechanical autotransfusion system OrthoPAT (Haemonetics Corp., MA, USA) to reduce the postoperative allogenic blood transfusion rate.

Method: According to the preliminary performed power analysis we did a prospective controlled study including 104 patients which were randomized in a group A (OrthoPAT for intra- and postoperative blood salvage and retransfusion, n = 52 patients) and a control group B (no retransfusion system was used, n = 52 patients) All patients had a primary osteoarthritis of the knee and were operated on without use of a tourniquet. We implanted in all patients a cemented posterior stabilized total knee prosthesis design (LPS-Flex Mobile, Zimmer, IN, USA). In group A the autotransfusion system was used for 6 hours (intra- and postoperatively) and the collected blood was retransfused. The retransfused blood is anticoagulanted, filtered and centrifuged to separate waste products. Red cells are washed with saline and reconcentrated to a high haematocrit. The preoperative data for cardiopathy, angiopathy, preoperative anemia or anticoagulant treatment showed no significant differences for group A and B. Because of missing data we finally were able to use the results of 98 patients: 48 group A and 50 in group B. The indications for a blood transfusion were influenced by the clinical symptoms of anemia, the hemoglobin value (hemoglobin < 8.0 g/dl) and the anamnesis of cardiovascular diseases. Evaluation was done with the medical history and the pre-/postoperative hemoglobin values, postoperative blood loss and postoperative need of allogenic blood transfusion.

Results: The two groups showed no significant differences relating to the demographic data or the medical history. 16 patients (33 %) of the retransfusion group who in mean received 281 ml of salvaged blood needed allogenic blood transfusion compared with 22 patients (44 %) of the control group B (p = 0,306). The hemoglobin values of group A versus the control group showed after the donation of the salvaged blood a significant difference (p = 0,027) but no longer at the 3rd and 5th day postoperative.

Conclusions: The use of the autotransfusion system seems to reduce the postoperative allogenic blood transfusion rate but not statistical significant. At the 3rd and 5th day postoperatively no significant differences of the hemoglobin values could be stated comparing group A with group B. For us this was a clue showing that the quality of the erythrocytes after the reclamation was reduced.

Introduction: With non-fusion stabilization surgery technique, the demands on the pedicle screw system have increased. The screw implants require a high press fit for optimum bone integration and a high pullout strength to guarantee primary stability. We compared the cylindrical screw design from a pedicle screw system with the conical design in regard to the insertional torque and pullout strength.

Methods: Three human cadaver specimens L1 – L5 (15 vertebrae, 30 pedicles) were fitted with pedicle screws on both sides. The pedicles were randomized to one of two screw types: 1) cylindrical pedicle screw, 2) conical. A computer tomographic bone density measurement was performed beforehand. The insertional torque was measured while inserting the pedicle screws. The correct position of the screw was verified using computer tomography. In order to test the pullout strength, the preparations were divided up into individual vertebrae and fixed.

Results: The mean peak insertional torque for the conical screws was significantly higher than that for the cylindrical screws. The pullout strength showed no significant difference between the two types of pedicle screws. With both the conical and the cylindrical pedicle screws, the pullout strength and insertional torque significantly decreased with decreasing bone density in the preparations.

Conclusions: Statements in the literature about the effect on insertional torque and pullout strength of using a conical or cylindrical pedicle screw design vary. The two screw designs in our study only differed in regard to their internal diameter. The significantly higher insertional torque values found for the conical screws could describe the improved screw press-fit behavior. The pullout strength was not significantly affected by the conical design. No correlation was found between the insertional torque and pullout strength. In order to optimize the adjustment of insertional torque and pullout strength, we recommend the conical pedicle screw design for non-fusion surgical techniques for the surgical treatment of degenerative diseases of the lumbar spine.

Approximately 5 – 10% of all bone fractures are associated with impaired healing. It is thought that regenerative medicine has the potential to improve on existing treatments for non-union fractures, and the European market for such treatments is projected to reach £2.2 billion in 2010. The use of scaffolds for the delivery of both growth factors and human Marrow Stromal Cells (hMSCs) is thought to be a promising approach. It may be desirable to promote proliferation and chemotaxis of hMSCs at the defect site shortly after implantation, and differentiation in the longer term. This is likely to require a dual delivery system, capable of releasing multiple drugs with different release profiles. Our aim has been to develop a polymer scaffold capable of releasing bioactive molecules that are able to direct the differentiation of primary hMSCs down the osteoblastic lineage. We have examined two mutually compatible drug delivery systems: collagen coating for short term release, and polymer encapsulation for longer term release.

Polymer scaffolds were manufactured and coated with Type I Collagen containing BMP-7. hMSCs from three different patient sources were exposed to the scaffolds for 14 days. The cells were then histochemically stained for Alkaline Phosphatase (ALP) and photographed. The areas of ALP staining were then normalised against the total cell count.

Normalised ALP expression was increased compared to the controls for three different patients (‘110 ± 39% SE, n=6, p=0.005’, ‘540 ± 270% SE, n=6, p=0.001’, and ‘32 ± 17% SE, n=6’). Scaffolds were also manufactured either with 1,25 Vitamin D3 (another active compound) in a coating of Collagen, or encapsulated using proprietary methodologies. It was found that both treatments significantly increased normalised Alkaline Phosphatase expression within the 14d experimental period demonstrating release of the active 1,25 Vitamin D3 (’88 ± 37% SE, n=6, p=0.012’ and ‘100 ± 32% SE, n=6, p=0.012’ respectively).

Our findings suggest that, subject to future testing and development, such bioactive scaffolds could form the basis for a dual drug delivery system, suitable for applications in bone regenerative medicine.

Aim: Cycling is a common activity after TKA and it has been shown that up to 50 % of the TKA patients are riding a bike and 25 % think that cycling has an important place in their life. The specific contact mechanics of tibiofemoral joint is well known during walking, however, there is little data during cycling for TKA patients. The purpose of this study was to determine the tibiofemoral contact mechanics during cycling for TKA patients.

Methods: We recruited 10 patients implanted with a mobile bearing and 10 patients with a fixed bearing posterior stabilized prosthesis. An age-matched, asymptomatic control group consisted of 10 subjects. The patients were physically examined, and WOMAC index and knee society score were taken. Motion analysis was performed using a retroreflective marker based technique called “PCT”. Forces and moments during cycling were recorded with load cells at the crank shafts of the bike. Motion and load data were synchronized.

Results: Resultant pedal forces showed no significant differences between study groups but the generated impulse was higher in the mobile bearing group. Patients with contra-lateral osteoarthritis showed higher forces and impulse at the operated leg. The motion analysis showed the following mean values ±SD for TKA patients/Normals: maximum flexion angle 132.5° ±16.0°/131.5° ±18.3°, minimum flexion angle 41.4° ±12.0°/40.3° ±15.7°, range of rotation in transversal plane 12.6° ±4.7°/9.9° ±3.6° and range of anterior-posterior translation 5.3 mm ±5.1 mm/2.7 mm ±0.4 mm. There were no significant differences between study groups.

Discussion: In this study, force and impulse of TKA patients with contemporary prostheses were comparable to healthy subjects indicating functional restoration of the joint. Contralateral osteoarthritis may cause higher forces at the operated leg and thus, relatively higher stresses at the artificial articulation.

As expected, the generated forces at the bike pedal were low (20–25% body-weight) calling for little muscle activity and low compressive joint forces. However, with a mean maximum flexion angle of 131.5°, the observed motion ranges were higher than expected. Prostheses not designed for high flexion activities could lose tibio-femoral contact during cycling with detrimental effects on wear. Still, the measured range of rotation in the transverse plane indicates that despite its posterior-stabilized design rotation is taking place with approximately the same amount as it occurs in normal subjects. This may have detrimental effects on the post at the tibial plateau and could explain the previously observed rotational damage patterns on retrieved posterior stabilized TKA specimens.

Data are suggesting that leisure activities should be considered to determine the appropriate TKA design. This study will provide useful data for future design and wear testing scenarios.

Aims: Because of the limitation of exposure inherent in minimally invasive surgical techniques for total knee replacement surgery, there is a significant risk of malalignment, malrotation, femoral notching and failure of soft tissue balance.

Methods: In this randomized study 50 patients with osteoarthritis of the knee, underwent TKR through a minimally invasive exposure using a navigation system; while a control group of 50 patients underwent the same surgery without navigation.

A subvastus approach was used with a less than 10 cm incision. Femoral component alignment is established with an intramedullary, and the tibial component, with an extramedullary alignment guide. The navigation system was used for fine adjustment and verification of cutting block position. The navigation system used for the study was the VectorVision® CT-Free Knee 1.5.1.

Results: The accuracy of prosthetic components positioning was significantly higher in the navigation group. The navigation system offered an objective analysis of medial and lateral ligament tension in full extension and 90 ° of flexion. In 8 cases navigation avoided femoral notching. No navigation related complications were registered. The additional surgery time for computer-assisted TKR was a mean 21 minutes. The nonnavigated implantation technique reached perfect component positioning in 62 % of the TKR.

Conclusion: Computer-assisted TKR results in predictable and accurate alignment, avoidance of femoral notching, avoidance of malrotation and appropriate balance of the soft tissue. Performing minimally invasive TKR without navigation has a higher risk of increased rate of unsatisfactory outcomes with shorter prosthetic survivorship when compared to the use of navigation.

Introduction: Optimal component position in all planes and well balanced soft tissues lead to a good clinical outcome and long-term survival after total knee arthroplasty. We investigated the implantation accuracy of navigated total knee arthroplasty at 3 months followup and the influence on the clinical outcome at 2 years followup.

Patients and Methods: Forty-four patients (44 procedures) were enrolled in our prospective study. One half of the surgeries were performed using a computed tomography based navigation system, and one half of the surgeries were performed without computed tomography navigation. Outcomes were based on the Insall knee score parameters, anterior knee pain, patient satisfaction, feeling of instability, and step test. The radiographic parameters were the mechanical axis, tibial slope, lateral distal femoral angle, and medial proximal tibial angle.

Results: The radiographic measurements showed no differences between both groups (patients within ± 3° inaccuracy range in computed tomography based/computed tomography free groups; mechanical axis 86%/81%, tibial slope 95%/91%, lateral distal femoral angle 95%/91%, medial proximal tibial angle 91%/95%). The cumulative error of alignment showed no difference between the study groups. Seventeen of 21 (81%) patients fulfilled four criteria in the CT based group, and 15 of 21 (71.4%) patients fulfilled four criteria in the comparison group. Nineteen of 21 (90.5%) patients in both groups achieved three criteria in an optimal manner. An increased (p < 0.001) Insall knee score was found for changes over time in both study groups; however, there were no differences between the CT based or CT free patient groups. The postoperative ROM in both groups showed no difference at the 3-month and 2-year followup examinations. Both groups had an increase (p ≤ 0.002) in ROM between the 3-month and 2-year followup examinations. The examination of ligament balancing in full extension showed a higher rate of a stable soft tissue situation in the CT free navigation group but the difference was not significant. In 30° of flexion we detected a better (p = 0.004) ligament situation medially and laterally in the CT free group. The anterior drawer test showed a better (p = 0.035) stability in the CT free navigation group.

Discussion: The computed tomography free system provided equal radiographic results, but we found improved ligament balancing in the computed tomography free group. The computed tomography based module has an optimal preoperative planning procedure, but is more expensive and time consuming.