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The Bone & Joint Journal
Vol. 96-B, Issue 7 | Pages 896 - 901
1 Jul 2014
Reiner T Jaeger S Schwarze M Klotz MC Beckmann NA Bitsch RG

Aseptic loosening of the femoral component is an important indication for revision surgery in unicompartmental knee replacement (UKR). A new design of femoral component with an additional peg was introduced for the cemented Oxford UKR to increase its stability. The purpose of this study was to compare the primary stability of the two designs of component. Medial Oxford UKR was performed in 12 pairs of human cadaver knees. In each pair, one knee received the single peg and one received the twin peg design. Three dimensional micromotion and subsidence of the component in relation to the bone was measured under cyclical loading at flexion of 40° and 70° using an optical measuring system. Wilcoxon matched pairs signed-rank test was performed to detect differences between the two groups. . There was no significant difference in the relative micromotion (p = 0.791 and 0.380, respectively) and subsidence (p = 0.301 and 0.176, respectively) of the component between the two groups at both angles of flexion. Both designs of component offered good strength of fixation in this cadaver study. Cite this article: Bone Joint J 2014;96-B:896–901


Bone & Joint Research
Vol. 6, Issue 1 | Pages 22 - 30
1 Jan 2017
Scott CEH Eaton MJ Nutton RW Wade FA Evans SL Pankaj P

Objectives. Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). Materials and Methods. A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µε (pathological loading) and < -7000 µε (yield point) minimum principal (compressive) microstrain and > 3000 µε and > 7000 µε maximum principal (tensile) microstrain was computed. Results. Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µε correlated strongly: R = 0.947, R. 2. = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R. 2. = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µε. Conclusion. AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection. Cite this article: C. E. H. Scott, M. J. Eaton, R. W. Nutton, F. A. Wade, S. L. Evans, P. Pankaj. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model. Bone Joint Res 2017;6:22–30. DOI:10.1302/2046-3758.61.BJR-2016-0142.R1


The Bone & Joint Journal
Vol. 105-B, Issue 12 | Pages 1279 - 1285
1 Dec 2023
Baker JF Nadar AC Jouflas AC Smith LS Sachdeva S Yakkanti MR Malkani AL

Aims

The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design.

Methods

This was a retrospective review of 707 primary TKAs in 590 patients from a single institution, using a cementless, metal-backed patellar component with a mean follow-up of 6.9 years (2 to 12). A total of 409 TKAs were performed in 338 females and 298 TKAs in 252 males. The mean age of the patients was 63 years (34 to 87) and their mean BMI was 34.3 kg/m2 (18.8 to 64.5). The patients were chosen to undergo a cementless procedure based on age and preoperative radiological and intraoperative bone quality. Outcome was assessed using the Knee Society knee and function scores and range of motion (ROM), complications, and revisions.


The Bone & Joint Journal
Vol. 106-B, Issue 9 | Pages 916 - 923
1 Sep 2024
Fricka KB Wilson EJ Strait AV Ho H Hopper, Jr RH Hamilton WG Sershon RA

Aims

The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) remains controversial. The aim of this study was to compare outcomes of fixed-bearing (FB) and mobile-bearing (MB) UKAs from a single high-volume institution.

Methods

Prospectively collected data were reviewed for all primary cemented medial UKAs performed by seven surgeons from January 2006 to December 2022. A total of 2,999 UKAs were identified, including 2,315 FB and 684 MB cases. The primary outcome measure was implant survival. Secondary outcomes included 90-day and cumulative complications, reoperations, component revisions, conversion arthroplasties, range of motion, and patient-reported outcome measures. Overall mean age at surgery was 65.7 years (32.9 to 94.3), 53.1% (1,593/2,999) of UKAs were implanted in female patients, and demographics between groups were similar (p > 0.05). The mean follow-up for all UKAs was 3.7 years (0.0 to 15.6).


The Bone & Joint Journal
Vol. 105-B, Issue 2 | Pages 148 - 157
1 Feb 2023
Koster LA Rassir R Kaptein BL Sierevelt IN Schager M Nelissen RGHH Nolte PA

Aims

The primary aim of this study was to compare the migration of the femoral and tibial components of the cementless rotating platform Attune and Low Contact Stress (LCS) total knee arthroplasty (TKA) designs, two years postoperatively, using radiostereometric analysis (RSA) in order to assess the risk of the development of aseptic loosening. A secondary aim was to compare clinical and patient-reported outcome measures (PROMs) between the designs.

Methods

A total of 61 TKAs were analyzed in this randomized clinical RSA trial. RSA examinations were performed one day and three, six, 12, and 24 months postoperatively. The maximal total point motion (MPTM), translations, and rotations of the components were analyzed. PROMs and clinical data were collected preoperatively and at six weeks and three, six, 12, and 24 months postoperatively. Linear mixed effect modelling was used for statistical analyses.


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 6 | Pages 777 - 781
1 Jun 2011
Kalra S Smith TO Berko B Walton NP

The Oxford unicompartmental knee replacement gives good results in patients with symptomatic osteoarthritis of the medial compartment. Previous studies have suggested that the presence of radiolucent lines (RLLs) does not reflect a poor outcome in such patients. However, the reliability and validity of this assessment have not been determined. Our aim was to assess the intra- and interobserver reliability and the sensitivity and specificity of the assessment of RLLs around both tibial and femoral components using standard radiographs. Two reviewers assessed the radiographs of 45 patients who had loosening of the tibial or femoral component confirmed at revision surgery and compared them with those of a series of 45 asymptomatic patients matched for age and gender. The results suggested that, using standard radiographs, tibial RLLs were 63.6% sensitive and 94.4% specific and femoral RLLs 63.9% sensitive and 72.7% specific for loosening. Overall intra- and interobserver reliability was highly variable, but zonal analysis showed that lucency at the tip of the femoral peg was significantly associated with loosening of the femoral component. Fluoroscopically guided radiographs may improve the zonal reliability of the assessment of RLLs, but further independent and comparative studies are required. In the meantime, the innocence of the physiological RLLs detected by standard radiographs should be viewed with caution


Bone & Joint Open
Vol. 5, Issue 4 | Pages 277 - 285
8 Apr 2024
Khetan V Baxter I Hampton M Spencer A Anderson A

Aims

The mean age of patients undergoing total knee arthroplasty (TKA) has reduced with time. Younger patients have increased expectations following TKA. Aseptic loosening of the tibial component is the most common cause of failure of TKA in the UK. Interest in cementless TKA has re-emerged due to its encouraging results in the younger patient population. We review a large series of tantalum trabecular metal cementless implants in patients who are at the highest risk of revision surgery.

Methods

A total of 454 consecutive patients who underwent cementless TKA between August 2004 and December 2021 were reviewed. The mean follow-up was ten years. Plain radiographs were analyzed for radiolucent lines. Patients who underwent revision TKA were recorded, and the cause for revision was determined. Data from the National Joint Registry for England, Wales, Northern Island, the Isle of Man and the States of Guernsey (NJR) were compared with our series.


The Bone & Joint Journal
Vol. 105-B, Issue 1 | Pages 35 - 46
1 Jan 2023
Mills K Wymenga AB Bénard MR Kaptein BL Defoort KC van Hellemondt GG Heesterbeek PJC

Aims

The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA).

Methods

A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years.


Bone & Joint Research
Vol. 11, Issue 7 | Pages 494 - 502
20 Jul 2022
Kwon HM Lee J Koh Y Park KK Kang K

Aims

A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes.

Methods

ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions.


Bone & Joint Open
Vol. 3, Issue 6 | Pages 495 - 501
14 Jun 2022
Keohane D Sheridan GA Masterson E

Aims

Total knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component.

Methods

A retrospective, single-surgeon review was carried out of all of the NexGen Legacy Posterior Stabilized (LPS) TKAs performed in this institute. The specific model used for the index procedures was the NexGen Complete Knee System (Legacy Knee-Posterior Stabilized LPS-Flex Articular Surface, LPS-Flex Femoral Component Option, and Stemmed Nonaugmentable Tibial Component Option).


The Bone & Joint Journal
Vol. 103-B, Issue 6 Supple A | Pages 32 - 37
1 Jun 2021
Restrepo S Smith EB Hozack WJ

Aims

Cementless total knee arthroplasty (TKA) offers the potential for strong biological fixation compared with cemented TKA where fixation is achieved by the mechanical integration of the cement. Few mid-term results are available for newer cementless TKA designs, which have used additive manufacturing (3D printing). The aim of this study was to present mid-term clinical outcomes and implant survivorship of the cementless Stryker Triathlon Tritanium TKA.

Methods

This was a single institution registry review of prospectively gathered data from 341 cementless Triathlon Tritanium TKAs at four to 6.8 years follow-up. Outcomes were determined by comparing pre- and postoperative Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) scores, and pre- and postoperative 12-item Veterans RAND/Short Form Health Survey (VR/SF-12) scores. Aseptic loosening and revision for any reason were the endpoints which were used to determine survivorship at five years.


The Bone & Joint Journal
Vol. 103-B, Issue 9 | Pages 1514 - 1525
1 Sep 2021
Scott CEH Holland G Gillespie M Keenan OJ Gherman A MacDonald DJ Simpson AHRW Clement ND

Aims

The aims of this study were to investigate the ability to kneel after total knee arthroplasty (TKA) without patellar resurfacing, and its effect on patient-reported outcome measures (PROMs). Secondary aims included identifying which kneeling positions were most important to patients, and the influence of radiological parameters on the ability to kneel before and after TKA.

Methods

This prospective longitudinal study involved 209 patients who underwent single radius cruciate-retaining TKA without patellar resurfacing. Preoperative EuroQol five-dimension questionnaire (EQ-5D), Oxford Knee Score (OKS), and the ability to achieve four kneeling positions were assessed including a single leg kneel, a double leg kneel, a high-flexion kneel, and a praying position. The severity of radiological osteoarthritis (OA) was graded and the pattern of OA was recorded intraoperatively. The flexion of the femoral component, posterior condylar offset, and anterior femoral offset were measured radiologically. At two to four years postoperatively, 151 patients with a mean age of 70.0 years (SD 9.44) were included. Their mean BMI was 30.4 kg/m2 (SD 5.36) and 60 were male (40%). They completed EQ-5D, OKS, and Kujala scores, assessments of the ability to kneel, and a visual analogue scale for anterior knee pain and satisfaction.


The Bone & Joint Journal
Vol. 103-B, Issue 10 | Pages 1555 - 1560
4 Oct 2021
Phillips JRA Tucker K

Aims

Knee arthroplasty surgery is a highly effective treatment for arthritis and disorders of the knee. There are a wide variety of implant brands and types of knee arthroplasty available to surgeons. As a result of a number of highly publicized failures, arthroplasty surgery is highly regulated in the UK and many other countries through national registries, introduced to monitor implant performance, surgeons, and hospitals. With time, the options available within many brand portfolios have grown, with alternative tibial or femoral components, tibial insert materials, or shapes and patella resurfacings. In this study we have investigated the effect of the expansion of implant brand portfolios and where there may be a lack of transparency around a brand name. We also aimed to establish the potential numbers of compatible implant construct combinations.

Methods

Hypothetical implant brand portfolios were proposed, and the number of compatible implant construct combinations was calculated.


The Bone & Joint Journal
Vol. 102-B, Issue 8 | Pages 1016 - 1024
1 Aug 2020
Hasan S van Hamersveld KT Marang-van de Mheen PJ Kaptein BL Nelissen RGHH Toksvig-Larsen S

Aims

Although bone cement is the primary mode of fixation in total knee arthroplasty (TKA), cementless fixation is gaining interest as it has the potential of achieving lasting biological fixation. By 3D printing an implant, highly porous structures can be manufactured, promoting osseointegration into the implant to prevent aseptic loosening. This study compares the migration of cementless, 3D-printed TKA to cemented TKA of a similar design up to two years of follow-up using radiostereometric analysis (RSA) known for its ability to predict aseptic loosening.

Methods

A total of 72 patients were randomized to either cementless 3D-printed or a cemented cruciate retaining TKA. RSA and clinical scores were evaluated at baseline and postoperatively at three, 12, and 24 months. A mixed model was used to analyze the repeated measurements.


Bone & Joint Open
Vol. 2, Issue 1 | Pages 48 - 57
19 Jan 2021
Asokan A Plastow R Kayani B Radhakrishnan GT Magan AA Haddad FS

Cementless knee arthroplasty has seen a recent resurgence in popularity due to conceptual advantages, including improved osseointegration providing biological fixation, increased surgical efficiency, and reduced systemic complications associated with cement impaction and wear from cement debris. Increasingly younger and higher demand patients are requiring knee arthroplasty, and as such, there is optimism cementless fixation may improve implant survivorship and functional outcomes.

Compared to cemented implants, the National Joint Registry (NJR) currently reports higher revision rates in cementless total knee arthroplasty (TKA), but lower in unicompartmental knee arthroplasty (UKA). However, recent studies are beginning to show excellent outcomes with cementless implants, particularly with UKA which has shown superior performance to cemented varieties. Cementless TKA has yet to show long-term benefit, and currently performs equivalently to cemented in short- to medium-term cohort studies. However, with novel concepts including 3D-printed coatings, robotic-assisted surgery, radiostereometric analysis, and kinematic or functional knee alignment principles, it is hoped they may help improve the outcomes of cementless TKA in the long-term. In addition, though cementless implant costs remain higher due to novel implant coatings, it is speculated cost-effectiveness can be achieved through greater surgical efficiency and potential reduction in revision costs. There is paucity of level one data on long-term outcomes between fixation methods and the cost-effectiveness of modern cementless knee arthroplasty.

This review explores recent literature on cementless knee arthroplasty, with regards to clinical outcomes, implant survivorship, complications, and cost-effectiveness; providing a concise update to assist clinicians on implant choice.

Cite this article: Bone Jt Open 2021;2(1):48–57.


Bone & Joint Research
Vol. 9, Issue 9 | Pages 593 - 600
1 Sep 2020
Lee J Koh Y Kim PS Kang KW Kwak YH Kang K

Aims

Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA.

Methods

Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition.


The Bone & Joint Journal
Vol. 102-B, Issue 8 | Pages 1025 - 1032
1 Aug 2020
Hampton M Mansoor J Getty J Sutton PM

Aims

Total knee arthroplasty is an established treatment for knee osteoarthritis with excellent long-term results, but there remains controversy about the role of uncemented prostheses. We present the long-term results of a randomized trial comparing an uncemented tantalum metal tibial component with a conventional cemented component of the same implant design.

Methods

Patients under the age of 70 years with symptomatic osteoarthritis of the knee were randomized to receive either an uncemented tantalum metal tibial monoblock component or a standard cemented modular component. The mean age at time of recruitment to the study was 63 years (50 to 70), 46 (51.1%) knees were in male patients, and the mean body mass index was 30.4 kg/m2 (21 to 36). The same cruciate retaining total knee system was used in both groups. All patients received an uncemented femoral component and no patients had their patella resurfaced. Patient outcomes were assessed preoperatively and postoperatively using the modified Oxford Knee Score, Knee Society Score, and 12-Item Short-Form Health Survey questionnaire (SF-12) score. Radiographs were analyzed using the American Knee Society Radiograph Evaluation score. Operative complications, reoperations, or revision surgery were recorded. A total of 90 knees were randomized and at last review 77 knees were assessed. In all, 11 patients had died and two were lost to follow-up.


Bone & Joint Research
Vol. 8, Issue 12 | Pages 593 - 600
1 Dec 2019
Koh Y Lee J Lee H Kim H Chung H Kang K

Aims

Commonly performed unicompartmental knee arthroplasty (UKA) is not designed for the lateral compartment. Additionally, the anatomical medial and lateral tibial plateaus have asymmetrical geometries, with a slightly dished medial plateau and a convex lateral plateau. Therefore, this study aims to investigate the native knee kinematics with respect to the tibial insert design corresponding to the lateral femoral component.

Methods

Subject-specific finite element models were developed with tibiofemoral (TF) and patellofemoral joints for one female and four male subjects. Three different TF conformity designs were applied. Flat, convex, and conforming tibial insert designs were applied to the identical femoral component. A deep knee bend was considered as the loading condition, and the kinematic preservation in the native knee was investigated.


Bone & Joint Research
Vol. 8, Issue 10 | Pages 495 - 501
1 Oct 2019
Hampp EL Sodhi N Scholl L Deren ME Yenna Z Westrich G Mont MA

Objectives

The use of the haptically bounded saw blades in robotic-assisted total knee arthroplasty (RTKA) can potentially help to limit surrounding soft-tissue injuries. However, there are limited data characterizing these injuries for cruciate-retaining (CR) TKA with the use of this technique. The objective of this cadaver study was to compare the extent of soft-tissue damage sustained through a robotic-assisted, haptically guided TKA (RATKA) versus a manual TKA (MTKA) approach.

Methods

A total of 12 fresh-frozen pelvis-to-toe cadaver specimens were included. Four surgeons each prepared three RATKA and three MTKA specimens for cruciate-retaining TKAs. A RATKA was performed on one knee and a MTKA on the other. Postoperatively, two additional surgeons assessed and graded damage to 14 key anatomical structures in a blinded manner. Kruskal–Wallis hypothesis tests were performed to assess statistical differences in soft-tissue damage between RATKA and MTKA cases.


The Bone & Joint Journal
Vol. 101-B, Issue 4 | Pages 435 - 442
1 Apr 2019
Zambianchi F Franceschi G Rivi E Banchelli F Marcovigi A Nardacchione R Ensini A Catani F

Aims

The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA).

Patients and Methods

Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded.


Bone & Joint Research
Vol. 7, Issue 3 | Pages 226 - 231
1 Mar 2018
Campi S Mellon SJ Ridley D Foulke B Dodd CAF Pandit HG Murray DW

Objectives

The primary stability of the cementless Oxford Unicompartmental Knee Replacement (OUKR) relies on interference fit (or press fit). Insufficient interference may cause implant loosening, whilst excessive interference could cause bone damage and fracture.

The aim of this study was to identify the optimal interference fit by measuring the force required to seat the tibial component of the cementless OUKR (push-in force) and the force required to remove the component (pull-out force).

Materials and Methods

Six cementless OUKR tibial components were implanted in 12 new slots prepared on blocks of solid polyurethane foam (20 pounds per cubic foot (PCF), Sawbones, Malmo, Sweden) with a range of interference of 0.1 mm to 1.9 mm using a Dartec materials testing machine HC10 (Zwick Ltd, Herefordshire, United Kingdom) . The experiment was repeated with cellular polyurethane foam (15 PCF), which is a more porous analogue for trabecular bone.


The Bone & Joint Journal
Vol. 100-B, Issue 8 | Pages 1033 - 1042
1 Aug 2018
Kayani B Konan S Pietrzak JRT Huq SS Tahmassebi J Haddad FS

Aims

The primary aim of this study was to determine the surgical team’s learning curve for introducing robotic-arm assisted unicompartmental knee arthroplasty (UKA) into routine surgical practice. The secondary objective was to compare accuracy of implant positioning in conventional jig-based UKA versus robotic-arm assisted UKA.

Patients and Methods

This prospective single-surgeon cohort study included 60 consecutive conventional jig-based UKAs compared with 60 consecutive robotic-arm assisted UKAs for medial compartment knee osteoarthritis. Patients undergoing conventional UKA and robotic-arm assisted UKA were well-matched for baseline characteristics including a mean age of 65.5 years (sd 6.8) vs 64.1 years (sd 8.7), (p = 0.31); a mean body mass index of 27.2 kg.m2 (sd 2.7) vs 28.1 kg.m2 (sd 4.5), (p = 0.25); and gender (27 males: 33 females vs 26 males: 34 females, p = 0.85). Surrogate measures of the learning curve were prospectively collected. These included operative times, the Spielberger State-Trait Anxiety Inventory (STAI) questionnaire to assess preoperative stress levels amongst the surgical team, accuracy of implant positioning, limb alignment, and postoperative complications.


Bone & Joint Research
Vol. 7, Issue 1 | Pages 20 - 27
1 Jan 2018
Kang K Son J Suh D Kwon SK Kwon O Koh Y

Objectives

Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA.

Methods

The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs.


The Bone & Joint Journal
Vol. 97-B, Issue 2 | Pages 185 - 191
1 Feb 2015
Kendrick BJL Kaptein BL Valstar ER Gill HS Jackson WFM Dodd CAF Price AJ Murray DW

The most common reasons for revision of unicompartmental knee arthroplasty (UKA) are loosening and pain. Cementless components may reduce the revision rate. The aim of this study was to compare the fixation and clinical outcome of cementless and cemented Oxford UKAs.

A total of 43 patients were randomised to receive either a cemented or a cementless Oxford UKA and were followed for two years with radiostereometric analysis (RSA), radiographs aligned with the bone–implant interfaces and clinical scores.

The femoral components migrated significantly during the first year (mean 0.2 mm) but not during the second. There was no significant difference in the extent of migration between cemented and cementless femoral components in either the first or the second year. In the first year the cementless tibial components subsided significantly more than the cemented components (mean 0.28 mm (sd 0.17) vs. 0.09 mm (sd 0.19 mm)). In the second year, although there was a small amount of subsidence (mean 0.05 mm) there was no significant difference (p = 0.92) between cemented and cementless tibial components. There were no femoral radiolucencies. Tibial radiolucencies were narrow (< 1 mm) and were significantly (p = 0.02) less common with cementless (6 of 21) than cemented (13 of 21) components at two years. There were no complete radiolucencies with cementless components, whereas five of 21 (24%) cemented components had complete radiolucencies. The clinical scores at two years were not significantly different (p = 0.20).

As second-year migration is predictive of subsequent loosening, and as radiolucency is suggestive of reduced implant–bone contact, these data suggest that fixation of the cementless components is at least as good as, if not better than, that of cemented devices.

Cite this article: Bone Joint J 2015; 97-B:185–91.


The Bone & Joint Journal
Vol. 99-B, Issue 11 | Pages 1467 - 1476
1 Nov 2017
van Hamersveld KT Marang-van de Mheen PJ Tsonaka R Valstar† ER Toksvig-Larsen S

Aims

The optimal method of tibial component fixation remains uncertain in total knee arthroplasty (TKA). Hydroxyapatite coatings have been applied to improve bone ingrowth in uncemented designs, but may only coat the directly accessible surface. As peri-apatite (PA) is solution deposited, this may increase the coverage of the implant surface and thereby fixation. We assessed the tibial component fixation of uncemented PA-coated TKAs versus cemented TKAs.

Patients and Methods

Patients were randomised to PA-coated or cemented TKAs. In 60 patients (30 in each group), radiostereometric analysis of tibial component migration was evaluated as the primary outcome at baseline, three months post-operatively and at one, two and five years. A linear mixed-effects model was used to analyse the repeated measurements.


The Bone & Joint Journal
Vol. 98-B, Issue 7 | Pages 867 - 873
1 Jul 2016
Dalury DF

As the number of younger and more active patients treated with total knee arthroplasty (TKA) continues to increase, consideration of better fixation as a means of improving implant longevity is required. Cemented TKA remains the reference standard with the largest body of evidence and the longest follow-up to support its use. However, cementless TKA, may offer the opportunity of a more bone-sparing procedure with long lasting biological fixation to the bone. We undertook a review of the literature examining advances of cementless TKA and the reported results.

Cite this article: Bone Joint J 2016;98-B:867–73.


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 8 | Pages 1009 - 1015
1 Aug 2012
Scott CEH Biant LC

Stems improve the mechanical stability of tibial components in total knee replacement (TKR), but come at a cost of stress shielding along their length. Their advantages include resistance to shear, reduced tibial lift-off and increased stability by reducing micromotion. Longer stems may have disadvantages including stress shielding along the length of the stem with associated reduction in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic fracture and end-of-stem pain. These features make long stems unattractive in the primary TKR setting, but often desirable in revision surgery with bone loss and instability. In the revision scenario, stems are beneficial in order to convey structural stability to the construct and protect the reconstruction of bony defects. Cemented and uncemented long stemmed implants have different roles depending on the nature of the bone loss involved.

This review discusses the biomechanics of the design of tibial components and stems to inform the selection of the component and the technique of implantation.


The Bone & Joint Journal
Vol. 95-B, Issue 7 | Pages 917 - 922
1 Jul 2013
Sabouret P Lavoie F Cloutier J

We report on the long-term results of 163 bicruciate-retaining Hermes 2C total knee replacements in 130 patients at a mean follow-up of 22.4 years (20.3 to 23.5). Even when the anterior cruciate ligament had a partially degenerative appearance it was preserved as long as the knee had a normal anterior drawer and Lachman’s test pre-operatively. The description and surgical technique of this minimally constrained prosthesis were published in 1983 and the ten-year clinical results in 1999.

A total of 12% of the knees (20 of 163) in this study were revised because of wear of the polyethylene tibial insert. Excellent stability was achieved and the incidence of aseptic component loosening was 4.3% (seven of 163). The survival rate using revision for any reason as the endpoint was 82% (95% confidence interval 76.2 to 88.0).

Although this series included a relatively small number of replacements, it demonstrated that the anterior cruciate ligament, even when partially degenerated at the time of TKR, remained functional and provided adequate stability at a long-term follow-up.

Cite this article: Bone Joint J 2013;95-B:917–22.


The Bone & Joint Journal
Vol. 98-B, Issue 10_Supple_B | Pages 28 - 33
1 Oct 2016
Lum ZC Lombardi AV Hurst JM Morris MJ Adams JB Berend KR

Aims

Since redesign of the Oxford phase III mobile-bearing unicompartmental knee arthroplasty (UKA) femoral component to a twin-peg design, there has not been a direct comparison to total knee arthroplasty (TKA). Thus, we explored differences between the two cohorts.

Patients and Methods

A total of 168 patients (201 knees) underwent medial UKA with the Oxford Partial Knee Twin-Peg. These patients were compared with a randomly selected group of 177 patients (189 knees) with primary Vanguard TKA. Patient demographics, Knee Society (KS) scores and range of movement (ROM) were compared between the two cohorts. Additionally, revision, re-operation and manipulation under anaesthesia rates were analysed.


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 3 | Pages 334 - 338
1 Mar 2012
Hooper GJ Maxwell AR Wilkinson B Mathew J Woodfield TBF Penny ID Burn PJ Frampton C

We carried out a prospective investigation into the radiological outcomes of uncemented Oxford medial compartment unicondylar replacement in 220 consecutive patients (231 knees) performed in a single centre with a minimum two-year follow-up. The functional outcomes using the mean Oxford knee score and the mean high-activity arthroplasty score were significantly improved over the pre-operative scores (p < 0.001). There were 196 patients with a two-year radiological examination performed under fluoroscopic guidance, aiming to provide images acceptable for analysis of the bone–implant interface. Of the six tibial zones examined on each knee on the anteroposterior radiograph, only three had a partial radiolucent line. All were in the medial aspect of the tibial base plate (zone 1) and all measured < 1 mm. All of these patients were asymptomatic. There were no radiolucent lines seen around the femoral component or on the lateral view. There was one revision for loosening at one year due to initial inadequate seating of the tibial component. These results confirm that the early uncemented Oxford medial unicompartmental compartmental knee replacements were reliable and the incidence of radiolucent lines was significantly decreased compared with the reported results of cemented versions of this implant. These independent results confirm those of the designing centre.


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 10 | Pages 1321 - 1329
1 Oct 2012
Sarmah SS Patel S Hossain FS Haddad FS

Radiological assessment of total and unicompartmental knee replacement remains an essential part of routine care and follow-up. Appreciation of the various measurements that can be identified radiologically is important. It is likely that routine plain radiographs will continue to be used, although there has been a trend towards using newer technologies such as CT, especially in a failing knee, where it provides more detailed information, albeit with a higher radiation exposure.

The purpose of this paper is to outline the radiological parameters used to evaluate knee replacements, describe how these are measured or classified, and review the current literature to determine their efficacy where possible.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 12 | Pages 1585 - 1593
1 Dec 2008
Henricson A Linder L Nilsson KG

We compared the performance of uncemented trabecular metal tibial components in total knee replacement with that of cemented tibial components in patients younger than 60 years over two years using radiostereophotogrammetric analysis (RSA). A total of 22 consecutive patients (mean age 53 years, 33 to 59, 26 knees) received an uncemented NexGen trabecular metal cruciate-retaining monobloc tibial component and 19 (mean 53 years, 44 to 59, 21 knees) a cemented NexGen Option cruciate-retaining modular tibial component.

All the trabecular metal components migrated during the initial three months and then stabilised. The exception was external rotation, which did not stabilise until 12 months. Unlike conventional metal-backed implants which displayed a tilting migration comprising subsidence and lift-off from the tibial tray, most of the trabecular metal components showed subsidence only, probably due to the elasticity of the implant.

This pattern of subsidence is regarded as being beneficial for uncemented fixation.


Bone & Joint Research
Vol. 1, Issue 10 | Pages 263 - 271
1 Oct 2012
Sharma GB Saevarsson SK Amiri S Montgomery S Ramm H Lichti DD Lieck R Zachow S Anglin C

Objectives

Numerous complications following total knee replacement (TKR) relate to the patellofemoral (PF) joint, including pain and patellar maltracking, yet the options for in vivo imaging of the PF joint are limited, especially after TKR. We propose a novel sequential biplane radiological method that permits accurate tracking of the PF and tibiofemoral (TF) joints throughout the range of movement under weightbearing, and test it in knees pre- and post-arthroplasty.

Methods

A total of three knees with end-stage osteoarthritis and three knees that had undergone TKR at more than one year’s follow-up were investigated. In each knee, sequential biplane radiological images were acquired from the sagittal direction (i.e. horizontal X-ray source and 10° below horizontal) for a sequence of eight flexion angles. Three-dimensional implant or bone models were matched to the biplane images to compute the six degrees of freedom of PF tracking and TF kinematics, and other clinical measures.


The Bone & Joint Journal
Vol. 97-B, Issue 5 | Pages 649 - 653
1 May 2015
Hawi N Kendoff D Citak M Gehrke T Haasper C

Knee arthrodesis is a potential salvage procedure for limb preservation after failure of total knee arthroplasty (TKA) due to infection. In this study, we evaluated the outcome of single-stage knee arthrodesis using an intramedullary cemented coupled nail without bone-on-bone fusion after failed and infected TKA with extensor mechanism deficiency. Between 2002 and 2012, 27 patients (ten female, 17 male; mean age 68.8 years; 52 to 87) were treated with septic single-stage exchange. Mean follow-up duration was 67.1months (24 to 143, n = 27) (minimum follow-up 24 months) and for patients with a minimum follow-up of five years 104.9 (65 to 143,; n = 13). A subjective patient evaluation (Short Form (SF)-36) was obtained, in addition to the Visual Analogue Scale (VAS). The mean VAS score was 1.44 (SD 1.48). At final follow-up, four patients had recurrent infections after arthrodesis (14.8%). Of these, three patients were treated with a one-stage arthrodesis nail exchange; one of the three patients had an aseptic loosening with a third single-stage exchange, and one patient underwent knee amputation for uncontrolled sepsis at 108 months. All patients, including the amputee, indicated that they would choose arthrodesis again. Data indicate that a single-stage knee arthrodesis offers an acceptable salvage procedure after failed and infected TKA.

Cite this article: Bone Joint J 2015;97-B:649–53.


The Bone & Joint Journal
Vol. 97-B, Issue 10 | Pages 1358 - 1363
1 Oct 2015
Hooper N Snell D Hooper G Maxwell R Frampton C

This study reports on the first 150 consecutive Oxford cementless unicompartmental knee arthroplasties (UKA) performed in an independent centre (126 patients). All eligible patients had functional scores (Oxford knee score and high activity arthroplasty score) recorded pre-operatively and at two- and five-years of follow-up. Fluoroscopically aligned radiographs were taken at five years and analysed for any evidence of radiolucent lines (RLLs), subsidence or loosening. The mean age of the cohort was 63.6 years (39 to 86) with 81 (53.1%) males. Excellent functional scores were maintained at five years and there were no progressive RLLs demonstrated on radiographs. Two patients underwent revision to a total knee arthroplasty giving a revision rate of 0.23/100 (95% confidence interval 0.03 to 0.84) component years with overall component survivorship of 98.7% at five years. There were a further four patients who underwent further surgery on the same knee, two underwent bearing exchanges for dislocation and two underwent lateral UKAs for disease progression. This was a marked improvement from other UKAs reported in New Zealand Joint Registry data and supports the designing centre’s early results.

Cite this article: Bone Joint J 2015;97-B:1358–63.


The Journal of Bone & Joint Surgery British Volume
Vol. 87-B, Issue 11 | Pages 1502 - 1506
1 Nov 2005
Arora J Ogden AC

We analysed at a mean follow-up of 7.25 years the clinical and radiological outcome of 117 patients (125 knees) who had undergone a primary, cemented, modular Freeman-Samuelson total knee replacement. While the tibial and femoral components were cemented, the patellar component was uncemented. A surface-cementing technique was used to secure the tibial components. A total of 82 knees was available for radiological assessment. Radiolucent lines were seen in 41 knees (50%) and osteolytic lesions were seen in 13 knees (16%). Asymptomatic, rotational loosening of the patellar implant was seen in four patients and osteolysis was more common in patients with a patellar resurfacing. Functional outcome scores were available for 41 patients (41 knees, 35%) and the mean Western Ontario McMasters Universities score was 77.5 (sd 19.5) and the cumulative survival was 93.4% at ten years with revision for aseptic loosening as an endpoint. Increased polyethylene wear from modular components, a rotationally-loose patella, and the surface-cementing technique may have contributed to the high rate of osteolysis seen in our study.


The Bone & Joint Journal
Vol. 95-B, Issue 2 | Pages 181 - 187
1 Feb 2013
Liddle AD Pandit H O’Brien S Doran E Penny ID Hooper GJ Burn PJ Dodd CAF Beverland DE Maxwell AR Murray DW

The Cementless Oxford Unicompartmental Knee Replacement (OUKR) was developed to address problems related to cementation, and has been demonstrated in a randomised study to have similar clinical outcomes with fewer radiolucencies than observed with the cemented device. However, before its widespread use it is necessary to clarify contraindications and assess the complications. This requires a larger study than any previously published.

We present a prospective multicentre series of 1000 cementless OUKRs in 881 patients at a minimum follow-up of one year. All patients had radiological assessment aligned to the bone–implant interfaces and clinical scores. Analysis was performed at a mean of 38.2 months (19 to 88) following surgery. A total of 17 patients died (comprising 19 knees (1.9%)), none as a result of surgery; there were no tibial or femoral loosenings. A total of 19 knees (1.9%) had significant implant-related complications or required revision. Implant survival at six years was 97.2%, and there was a partial radiolucency at the bone–implant interface in 72 knees (8.9%), with no complete radiolucencies. There was no significant increase in complication rate compared with cemented fixation (p = 0.87), and no specific contraindications to cementless fixation were identified.

Cementless OUKR appears to be safe and reproducible in patients with end-stage anteromedial osteoarthritis of the knee, with radiological evidence of improved fixation compared with previous reports using cemented fixation.

Cite this article: Bone Joint J 2013;95-B:181–7.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 8 | Pages 1039 - 1044
1 Aug 2008
Lützner J Krummenauer F Wolf C Günther K Kirschner S

After obtaining informed consent, 80 patients were randomised to undergo a navigated or conventional total knee replacement. All received a cemented, unconstrained, cruciate-retaining implant with a rotating platform. Full-length standing and lateral radiographs and CT scans of the hip, knee and ankle joint were carried out five to seven days after operation.

No notable differences were found between computer-assisted navigation and conventional implantation techniques as regards the rotational alignment of the femoral or tibial components. Although the deviation from the transepicondylar axis was relatively low, there was a considerable range of deviation for the tibial rotational alignment. There was no statistically significant difference regarding the occurrence pattern of outliers in mechanical malalignment but the number of outliers was reduced in the navigated group.


The Bone & Joint Journal
Vol. 97-B, Issue 2 | Pages 197 - 201
1 Feb 2015
Kallala RF Vanhegan IS Ibrahim MS Sarmah S Haddad FS

Revision total knee arthroplasty (TKA) is a complex procedure which carries both a greater risk for patients and greater cost for the treating hospital than does a primary TKA. As well as the increased cost of peri-operative investigations, blood transfusions, surgical instrumentation, implants and operating time, there is a well-documented increased length of stay which accounts for most of the actual costs associated with surgery.

We compared revision surgery for infection with revision for other causes (pain, instability, aseptic loosening and fracture). Complete clinical, demographic and economic data were obtained for 168 consecutive revision TKAs performed at a tertiary referral centre between 2005 and 2012.

Revision surgery for infection was associated with a mean length of stay more than double that of aseptic cases (21.5 vs 9.5 days, p < 0.0001). The mean cost of a revision for infection was more than three times that of an aseptic revision (£30 011 (sd 4514) vs £9655 (sd 599.7), p < 0.0001).

Current NHS tariffs do not fully reimburse the increased costs of providing a revision knee surgery service. Moreover, especially as greater costs are incurred for infected cases. These losses may adversely affect the provision of revision surgery in the NHS.

Cite this article: Bone Joint J 2015;97-B:197–201.


The Bone & Joint Journal
Vol. 95-B, Issue 11 | Pages 1480 - 1483
1 Nov 2013
Hooper GJ Gilchrist N Maxwell R March R Heard A Frampton C

We studied the bone mineral density (BMD) and the bone mineral content (BMC) of the proximal tibia in patients with a well-functioning uncemented Oxford medial compartment arthroplasty using the Lunar iDXA bone densitometer. Our hypothesis was that there would be decreased BMD and BMC adjacent to the tibial base plate and increased BMD and BMC at the tip of the keel.

There were 79 consecutive patients (33 men, 46 women) with a mean age of 65 years (44 to 84) with a minimum two-year follow-up (mean 2.6 years (2.0 to 5.0)) after unilateral arthroplasty, who were scanned using a validated standard protocol where seven regions of interest (ROI) were examined and compared with the contralateral normal knee. All had well-functioning knees with a mean Oxford knee score of 43 (14 to 48) and mean Knee Society function score of 90 (20 to 100), showing a correlation with the increasing scores and higher BMC and BMD values in ROI 2 in the non-implanted knee relative to the implanted knee (p = 0.013 and p = 0.015, respectively).

The absolute and percentage changes in BMD and BMC were decreased in all ROIs in the implanted knee compared with the non-implanted knee, but this did not reach statistical significance. Bone loss was markedly less than reported losses with total knee replacement.

There was no significant association with side, although there was a tendency for the BMC to decrease with age in men. The BMC was less in the implanted side relative to the non-implanted side in men compared with women in ROI 2 (p = 0.027), ROI 3 (p = 0.049) and ROI 4 (p = 0.029).

The uncemented Oxford medial compartment arthroplasty appears to allow relative preservation of the BMC and BMD of the proximal tibia, suggesting that the implant acts more physiologically than total knee replacement. Peri-prosthetic bone loss is an important factor in assessing long-term implant stability and survival, and the results of this study are encouraging for the long-term outcome of this arthroplasty.

Cite this article: Bone Joint J 2013;95-B:1480–3.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 2 | Pages 185 - 189
1 Feb 2009
Pandit H Jenkins C Beard DJ Gallagher J Price AJ Dodd CAF Goodfellow JW Murray DW

We randomised 62 knees to receive either cemented or cementless versions of the Oxford unicompartmental knee replacement. The implants used in both arms of the study were similar, except that the cementless components were coated with porous titanium and hydroxyapatite. The tibial interfaces were studied with fluoroscopically-aligned radiographs.

At one year there was no difference in clinical outcome between the two groups. Narrow radiolucent lines were seen at the bone-implant interfaces in 75% of cemented tibial components. These were partial in 43%, and complete in 32%. In the cementless implants, partial radiolucencies were seen in 7% and complete radiolucencies in none. These differences are statistically significant (p < 0.0001) and imply satisfactory bone ingrowth into the cementless implants.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 3 | Pages 351 - 356
1 Mar 2009
Parratte S Argenson JA Pearce O Pauly V Auquier P Aubaniac J

We retrospectively reviewed 35 cemented unicompartmental knee replacements performed for medial unicompartmental osteoarthritis of the knee in 31 patients ≤50 years old (mean 46, 31 to 49). Patients were assessed clinically and radiologically using the Knee Society scores at a mean follow-up of 9.7 years (5 to 16) and survival at 12 years was calculated. The mean Knee Society Function Score improved from 54 points (25 to 64) pre-operatively to 89 (80 to 100) post-operatively (p < 0.0001). Six knees required revision, four for polyethylene wear treated with an isolated exchange of the tibial insert, one for aseptic loosening and one for progression of osteoarthritis.

The 12-year survival according to Kaplan-Meier was 80.6% with revision for any reason as the endpoint. Despite encouraging clinical results, polyethylene wear remains a major concern affecting the survival of unicompartmental knee replacement in patients younger than 50.


The Bone & Joint Journal
Vol. 95-B, Issue 7 | Pages 911 - 916
1 Jul 2013
Small SR Ritter MA Merchun JG Davis KE Rogge RD

Stress shielding resulting in diminished bone density following total knee replacement (TKR) may increase the risk of migration and loosening of the prosthesis. This retrospective study was designed to quantify the effects of the method of fixation on peri-prosthetic tibial bone density beneath cemented and uncemented tibial components of similar design and with similar long-term survival rates. Standard radiographs taken between two months and 15 years post-operatively were digitised from a matched group of TKRs using cemented (n = 67) and uncemented (n = 67) AGC tibial prostheses. Digital radiograph densitometry was used to quantify changes in bone density over time. Age, length of follow-up, gender, body mass index and alignment each significantly influenced the long-term pattern of peri-prosthetic bone density. Similar long-term changes in density irrespective of the method of fixation correlated well with the high rate of survival of this TKR at 20 years, and suggest that cemented and uncemented fixation are both equally viable.

Cite this article: Bone Joint J 2013;95-B:911–16.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 6 | Pages 750 - 756
1 Jun 2009
Mannan K Scott G

We describe the survivorship of the Medial Rotation total knee replacement (TKR) at ten years in 228 cemented primary replacements implanted between October 1994 and October 2006, with their clinical and radiological outcome. This implant has a highly congruent medial compartment, with the femoral component represented by a portion of a sphere which articulates with a matched concave surface on the medial side of the tibial insert.

There were 78 men (17 bilateral TKRs) and 111 women (22 bilateral TKRs) with a mean age of 67.9 years (28 to 90). All the patients were assessed clinically and radiologically using the American Knee Society scoring systems. The mean follow-up was for six years (1 to 13) with only two patients lost to follow-up and 34 dying during the period of study, one of whom had required revision for infection.

There were 11 revisions performed in total, three for aseptic loosening, six for infection, one for a periprosthetic fracture and one for a painful but well-fixed replacement performed at another centre.

With revision for any cause as the endpoint, the survival at ten years was 94.5% (95% CI 85.1 to 100), and with aseptic loosening as the endpoint 98.4% (95% CI 93 to 100). The mean American Knee Society score improved from 47.6 (0 to 88) to 72.2 (26 to 100) and for function from 45.1 (0 to 100) to 93.1 (45 to 100). Radiological review failed to detect migration in any of the surviving knees.

The clinical and radiological results of the Medial Rotation TKR are satisfactory at ten years. The increased congruence of the medial compartment has not led to an increased rate of loosening and continued use can be supported.


The Bone & Joint Journal
Vol. 95-B, Issue 10 | Pages 1339 - 1347
1 Oct 2013
Scott CEH Eaton MJ Nutton RW Wade FA Pankaj P Evans SL

As many as 25% to 40% of unicompartmental knee replacement (UKR) revisions are performed for pain, a possible cause of which is proximal tibial strain. The aim of this study was to examine the effect of UKR implant design and material on cortical and cancellous proximal tibial strain in a synthetic bone model. Composite Sawbone tibiae were implanted with cemented UKR components of different designs, either all-polyethylene or metal-backed. The tibiae were subsequently loaded in 500 N increments to 2500 N, unloading between increments. Cortical surface strain was measured using a digital image correlation technique. Cancellous damage was measured using acoustic emission, an engineering technique that detects sonic waves (‘hits’) produced when damage occurs in material.

Anteromedial cortical surface strain showed significant differences between implants at 1500 N and 2500 N in the proximal 10 mm only (p < 0.001), with relative strain shielding in metal-backed implants. Acoustic emission showed significant differences in cancellous bone damage between implants at all loads (p = 0.001). All-polyethylene implants displayed 16.6 times the total number of cumulative acoustic emission hits as controls. All-polyethylene implants also displayed more hits than controls at all loads (p < 0.001), more than metal-backed implants at loads ≥ 1500 N (p < 0.001), and greater acoustic emission activity on unloading than controls (p = 0.01), reflecting a lack of implant stiffness. All-polyethylene implants were associated with a significant increase in damage at the microscopic level compared with metal-backed implants, even at low loads. All-polyethylene implants should be used with caution in patients who are likely to impose large loads across their knee joint.

Cite this article: Bone Joint J 2013;95-B:1339–47.


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 11_Supple_A | Pages 85 - 89
1 Nov 2012
Drexler M Dwyer T Marmor M Abolghasemian M Sternheim A Cameron HU

In this study we present our experience with four generations of uncemented total knee arthroplasty (TKA) from Smith & Nephew: Tricon M, Tricon LS, Tricon II and Profix, focusing on the failure rates correlating with each design change. Beginning in 1984, 380 Tricon M, 435 Tricon LS, 305 Tricon 2 and 588 Profix were implanted by the senior author. The rate of revision for loosening was 1.1% for the Tricon M, 1.1% for the Tricon LS, 0.5% for the Tricon 2 with a HA coated tibial component, and 1.3% for the Profix TKA. No loosening of the femoral component was seen with the Tricon M, Tricon LS or Tricon 2, with no loosening seen of the tibial component with the Profix TKA. Regarding revision for wear, the incidence was 13.1% for the Tricon M, 6.6% for the Tricon LS, 2.3% for the Tricon 2, and 0% for the Profix. These results demonstrate that improvements in the design of uncemented components, including increased polyethylene thickness, improved polyethylene quality, and the introduction of hydroxyapatite coating, has improved the outcomes of uncemented TKA over time.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 1 | Pages 34 - 38
1 Jan 2007
Epinette J Manley MT

This study describes 146 primary total knee replacements, either fully or partially coated with hydroxyapatite of which 74 knees in 68 patients were available for clinical and radiological assessment at a mean of 11.2 years (10 to 15). The global failure rate was 1.37% and survival rate with mechanical failure as the end-point was 98.14%. Radiological assessment indicated intimate contact between bone and the hydroxyapatite coating. Over time the hydroxyapatite coating appears to encourage filling of interface gaps remaining after surgery. Our results compare favourably with those of series describing cemented or porous-coated knee replacements, and suggest that fixation with hydroxyapatite is a reliable option in primary total knee replacement.


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 4 | Pages 484 - 489
1 Apr 2011
Charalambous CP Abiddin Z Mills SP Rogers S Sutton P Parkinson R

The low contact stress patellofemoral replacement consists of a trochlear component and a modular patellar component which has a metal-backed mobile polyethylene bearing. We present the early results of the use of this prosthesis for established isolated patellofemoral arthritis in 51 consecutive patellofemoral replacements in 35 patients. The mean follow-up was 25 months (5 to 60). The estimated survival rate at three years was 63% (95% confidence interval 47 to 80) with revision as the endpoint and 46% (95% confidence interval 30 to 63) with revision and ongoing moderate or severe pain as the endpoint.

The early results of the use of the low contact stress patellofemoral replacement are disappointing with a high rate of revision. We cannot therefore recommend its use.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 1 | Pages 39 - 44
1 Jan 2007
Uvehammer J Kärrholm J Carlsson L

We have carried out a radiostereometric study of 50 patients (54 knees) with osteoarthritis of the knee who were randomly allocated to receive a cemented or a hydroxyapatite-coated femoral component for total knee replacement. The patients were also stratified to receive one of three types of articulating surface (standard, rotating platform, Freeman-Samuelson (FS)1000) all based on the Freeman-Samuelson design. The tibial components were cemented in all cases. Radiostereometry was performed post-operatively and at 3, 12 and 24 months. The analysis was restricted to rotation of the femoral component over time.

After two years, rotation of the femoral components in the transverse, longitudinal and sagittal planes did not differ between the cemented and the hydroxyapatite-coated implants (p = 0.2 to 0.9).

In total knee replacements with a rotating platform, the femoral component tended to tilt more posteriorly than in the other two designs, regardless of the choice of fixation (cemented or hydroxyapatite-coated, p = 0.04). The standard version of the femoral component, whether cemented or hydroxyapatite-coated, rotated more into valgus than was observed with the rotating-platform and FS1000 designs (p = 0.005). The increased constraint provided by the FS1000 component did not appear to have any adverse effect on fixation of the femoral component.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 4 | Pages 471 - 476
1 Apr 2007
Kim Y Kim J Yoon S

Bilateral sequential total knee replacement was carried out under one anaesthetic in 100 patients. One knee was replaced using a CT-free computer-assisted navigation system and the other conventionally without navigation. The two methods were compared for accuracy of orientation and alignment of the components. There were 85 women and 15 men with a mean age of 67.6 years (54 to 83). Radiological and CT imaging was carried out to determine the alignment of the components. The mean follow-up was 2.3 years (2 to 3).

The operating and tourniquet times were significantly longer in the navigation group (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). The results of imaging and the number of outliers for all radiological parameters were not statistically different (p = 0.109 to p = 0.920).

In this series computer-assisted navigated total knee replacement did not result in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement.