Session 7: Knee

Torsdag den 23. oktober
13:00 – 14:30
Lokale: Reykjavik
Chairmen: Jakob Klit / Frank Madsen

61. Feasibility and safety of intensive weight loss before total knee replacement in obese patients: A randomized controlled trial
Anette Liljensøe, Jens Ole Laursen, Henning Bliddal, Kjeld Søballe, Inger Mechlenburg
Department of Orthopedics, Aarhus University Hospital; The Parker Institute, Department of Rheumatology, Copenhagen University Hospital, Bispebjerg-Frederiksberg

Background: Annually 8500 total knee replacements (TKR) are performed in Denmark. About 80% of this population is overweight or obese. The present material is part of a longitudinal randomized study. NCT01469403
Purpose / Aim of Study: To investigate whether it is feasible and safe to implement an intensive weight loss program in order to reduce preoperative body weight of obese patients before total knee replacement (TKR) surgery.
Materials and Methods: We conducted a pragmatic, single- blind, single-center randomized study. Eligible patients were scheduled for TKR due to osteoarthritis (OA) of the knee and obesity (BMI > 30kg/m2). Participants were randomized to either a control group that followed the standard care or a weight loss group that followed a low-energy diet (810 kcal/day) 8 weeks before TKR. Outcomes were assessed before intervention for the weight loss group, and within 1 week preoperatively for both the weight loss group and the control group.
Findings / Results: Included were 77 patients (weight loss group n=38; control group n=39), 71% were females, the mean age was 65 years (range 46-85), and the average BMI was 31. The average weight loss after 8 weeks was 10.7 kg. According to dual energy X-ray absorptiometry (DXA), the weight loss consisted of a 6.7 kg reduction in fat mass, a 3.0 kg reduction in lean body mass, and lean body mass increased by 2.3%. The intensive diets had few and mild adverse effects. Serious cardiac complications were found in two cases in the intervention group and in one case in the control group. All three patients later underwent TKR without complications. No perioperative complications were recorded in any group.
Conclusions: Our results show that it is feasible and safe to implement a weight loss program shortly before TKR.

62. Efficacy of preoperative progressive resistance training on postoperative functional capacity and muscle strength in patients undergoing total knee arthroplasty
Birgit Skoffer, Thomas Maribo, Inger Mechlenburg, Per Møller Hansen, Kjeld Søballe, Ulrik Dalgas
Institute of Clinical Medicine and Department of Physical and Occupational Therapy, Aarhus University and Aarhus University Hospital; MarselisborgCentret, Danish Rehabilitation Research Centre; National Public Health and Quality Impro, Central Denmark Region, Aarhus and Aarhus University; Institute of Clinical Medicine and Orthopaedic Research Centre, Aarhus University and Aarhus University Hospital; Orthopaedic Department, Silkeborg Regional Hospital; Orthopaedic Research Centre, Aarhus University Hospital ; Section of Sport Science, Department of Public Health, Aarhus University

Background: Reduced knee extensor muscle strength and associated impaired functional capacity is a common clinical finding in people with knee osteoarthritis. Furthermore, knee extensor muscle strength is a strong predictor of functional capacity one year after total knee arthroplasty (TKA).
Purpose / Aim of Study: To investigate the efficacy of 4 weeks of preoperative and 4-week post-operative progressive resistance training (PRT) compared to 4 weeks of postoperative PRT alone in patients undergoing total knee arthroplasty. Outcomes were functional capacity, muscle strength and patient reported outcomes.
Materials and Methods: In a single-blinded, clinical, randomized, controlled trial, 59 patients were randomized to 4 weeks of preoperative PRT (PRT group) or to a control group who “lived as usual” (control group). All patients performed 4 weeks of PRT after TKA. At 6 weeks before TKA, and at 6 weeks after TKA functional capacity, knee extensor and flexor muscle strength, patient reported functional capacity, health related quality of life, pain scores and medication was registered.
Findings / Results: A significant group difference was found in favor of the PRT group for the 30sec-sit-to- stand test (3.5± 1.2 rep; p<0.01), the timed- up-and-go test (-1.56± 0.64 sec.; p<0.05), in knee extensor muscle strength (19.3± 6.4 Nm; p<0.01) and in knee flexor muscle strength (16.0± 5.5 Nm, p<0.01) when evaluated 6 weeks after TKA. No differences were found between groups on patient reported outcomes except for the KOOS sport subscale (13.6± 6.6 p<0.05) favoring the PRT group.
Conclusions: Preoperative PRT is an effective intervention improving postoperative functional capacity and muscle strength but not patient reported outcomes, without worsening pain or increasing medication in patients undergoing TKA.

63. EOS imaging for assessing lower limb alignment and implant positioning after Total Knee Arthroplasty (TKA)
Kirill Gromov, Viktor Hansen, Dov Goldvasser, Orhun Muratoglu, Henrik Malchau, Anders Troelsen
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Harris Orthopaedic Laboratory, Massachusetts General Hospital

Background: The lower limb axis and implant alignment are traditionally assessed to evaluate the success of primary TKA surgery. EOS imaging is a novel technology that can provide the surgeon with full body images, while exposing the patient to significantly lower radiation dosage
Purpose / Aim of Study: In this study we seek to evaluate the precision of EOS imaging for measuring lower limb axes as well as implant alignment following primary TKA
Materials and Methods: 32 patients that underwent TKA and had EOS radiography performed pre- and postoperatively were included in the study. Hip-Knee-Ankle (HKA) axis and tibiofemoral angle (TFA) was measured pre- and postoperatively. Tibial and femoral implant alignment was assessed in anterior- posterior (AP) and lateral plane in respect to anatomical as well as mechanical axis. Two readers each assessed all images with reassessment by one reader.. Intra- and inter-reader variability was assessed by the mean difference and 95% limits of agreement (LoA)
Findings / Results: 95% LoA for postoperative HKA and TFA were +/- 0.41° and +/-0.80°, respectively. 95% LoA for AP implant alignment in respect to the mechanical axes were all within +/-0.80° and within +/-1.47° in respect to anatomical axes. 95% LoA for tibial lateral implant alignment were within +/-1.50° and within +/-3.65° for femoral lateral implant alignment. There were no systematic differences between observers. Mean difference and LoA for tibial component alignment in the AP plane in respect to the mechanical compared to anatomical axis was -0.18° +/-2.86°
Conclusions: EOS imaging can be used for precise measurements of lower limb axis and implant alignment following primary TKA. This allows EOS imaging to be potentially implemented as a clinical tool for evaluation of results following TKA

64. Early progressive strength training to enhance recovery after fast-track total knee arthroplasty. A randomized controlled trial
Thomas Linding Jakobsen, Henrik Kehlet, Henrik Husted, Janne Petersen, Thomas Bandholm
Lundbeck Foundation Centre for Fast-track Hip and Knee Arthroplasty, Clinical Research Centre, Physi, Hvidovre Hospital, University of Copenhagen; Section for Surgical Pathophysiology 4074, Lundbeck Foundation Centre for Fast-track Hip and Knee Ar, Rigshospitalet, University of Copenhagen; Department of Orthopaedic Surgery, Hvidovre Hospital, University of Copenhagen; Clinical Research Centre, Hvidovre Hospital, University of Copenhagen; Physical Medicine and Rehabilitation Research - Copenhagen (PMR-C), Department of Physical Therapy, , Hvidovre Hospital, University of Copenhagen

Background: A pronounced loss of muscle strength and functional performance has been found after total knee arthroplasty (TKA). A rehabilitation modality known to increase muscle strength and functional performance over time - such as progressive strength training (PST) - seems rational to enhance recovery after TKA. However, the effect of rehabilitation with PST has not been investigated in a large assessor-blinded randomized controlled trial.
Purpose / Aim of Study: To compare 7 weeks of supervised rehabilitation with or without PST commenced early after fast-track TKA on functional performance.
Materials and Methods: Eighty-two patients with a unilateral primary TKA were randomized to 7 weeks of supervised rehabilitation with (PST-group) and without (CON-group) PST commenced early after fast-track TKA. The primary outcome was the maximal distance walked in 6 minutes (6- minute walk test). Secondary outcomes were lower limb strength and power, knee joint effusion and range of motion, knee pain and self-reported disability and quality of life. All outcome measures were assessed before (baseline) and 4, 8 and 26 weeks after TKA.
Findings / Results: There was no statistically significant difference between the PST- and CON- group 8-week postoperatively (primary endpoint) for the 6-minute walk test (mean difference between groups: -11.3 meters, 95% confidence interval -45.4 to 22.7 meters; analysis of variance , p=0.51). There were no statistically significant or clinically meaningful differences between groups in change scores from baseline to any other time point for all secondary outcomes.
Conclusions: Seven weeks of supervised rehabilitation with PST was not superior to 7 weeks of supervised rehabilitation without PST in improving functional performance, measured as the maximal walking distance in 6 minutes, at the primary endpoint 8 weeks after fast-track TKA.

65. Bone remodelling of the of the tibia after total knee arthroplastry with uncemented tibia implants
Mikikel Rathsach Andersen, Nikolaj Winther, Thomas Lind, Henrik Schrøder, Michael Mörk Petersen
Knæklinikken, Ortopædkirurgisk afdeling, Gentofte Hospital, Region Hovedstaden; Ortopædkirurgisk klinik U, Hovedortocenteret, Rigshospitalet, Region Hovedstaden

Background: Loss of bone stock as a response to the bone trauma and postoperative immobilisation is a well known complication to joint replacement surgery.
Purpose / Aim of Study: This study investigates the adaptive bone remodelling of the tibia, after total knee arthroplasty (TKA) with two uncemented total knee arthroplastries.
Materials and Methods: We performed 1 year follow up of 54 patients (mean age 61,7 (38-70) years, 28/26=x/y, BMI 29,5) that received an uncemented TKA in a prospective randomised controlled trial, where the patients were randomised into two groups that recieved different tibial components. The TKAs were performed using the uncemented Zimmer Nexgen® trabecular metal tibia implants with either a monoblock (A) or modular (B) polyethylene design. Measurements of bone mineral density (BMD) were done postoperatively and after 3, 6, and, 12 months. BMD was measured in 3 regions of interest (ROI) medially, laterally, and distally around the tibial component. Statistics: Paired and unpaired t-test (P< 0.05 were considered significant).
Findings / Results: Significant changes in BMD after 12 months of follow-up was only seen in group A, where BMD decreased medially by 9.4% (p=0.002) and laterally by 6.7% (p=0.009). When comparing BMD changes between the groups after 12 months differences was found in the medial (p=0.01) and lateral (p=0.053) ROIs.
Conclusions: A significantly different bone remodelling pattern of the proximal tibia was seen in the two groups with a higher degree of bone loss seen in knees that received the monoblock design.

66. Similar polyethylene wear of cementless and cemented Oxford Partial Knee’s at 2 years follow-up. A Randomized RSA Study
Maiken Stilling, Anders Odgaard , Claus Fink Jepsen, Kjeld Søballe, Per Wagner Kristensen, Frank Madsen
Department of Orthopaedic Research, Aarhus University Hospital; Department of Orthopaedics, Copenhagen University Hospital Gentofte

Background: Wear of polyethylene is a significant cause of revision surgery in partial knee replacement. The Oxford Partial Knee has a fully-congruent, mobile, polyethylene (PE) bearing designed to minimize wear. Well-functioning knees have low PE wear, but impingement or incongruous articulation may affect the wear rate. Cementless components are hydroxyapatite coated, which may risk higher polyethylene wear.
Purpose / Aim of Study: To compare PE wear of cementless (CL) and cemented (C) Oxford Partial Knee’s at 2 years by radiostereometric analysis (RSA).
Materials and Methods: 80 patients (48 men) were randomly allocated to surgery with CL hydroxyapatite-coated (n=25) or C (n=55) Oxford Partial Knee’s (Biomet Inc.) and UHMWPE at 2 hospital sites. Refobacin bone cement (Biomet Inc.) was used. Evaluations of PE wear (model-based RSA y-translation, weight bearing set-up) and clinical outcomes (OKS, AKSS) was performed between baseline and 2 years.
Findings / Results: At 2 years followup mean PE wear of 0.43 (sd 0.98) mm in cementless knees was similar (p=0.10) to 0.11 (sd 1.08) mm in cemented knees. The wear rate including creep was 0.21 (sd 0.48) mm in cementless knees and 0.06 (sd 0.54) mm in cemented knees (p=0.10). PE wear did not correlate to age (p=0.45), OKS (p=0.54), pain in general (p=0.61), pain during work (p=0.50), side instability (p=0.67), knee axis (p=0.96), walking aids (p=0.50) or patient reported walking distance (p=0.27). At 2 years mean OKS was 40 (range 21-47) (p=0.53) with similar improvement from baseline (p=0.11). Satisfaction was high in both groups. No revisions.
Conclusions: Cementless Oxford Partial Knee’s had a tendency towards higher PE wear at 2 years followup, and all knees had higher wear rate than reported for well- functioning partial knees in the literature. Functional results were good and similar in both groups.

67. Does knee awareness differ between knees in bilateral simultaneous TKA? Predictors of high knee awareness.
Katrine Abildgaard Nielsen, Morten Grove Thomsen, Roshan Latifi, Thomas Kallemose, Henrik Husted, Anders Troelsen
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Denmark

Background: Low knee awareness during activities of daily living has become the primary goal when evaluating outcome after Total Knee Arthroplasty (TKA). However, it is still unclear how patient derived factors (e.g. knee alignment) influence postoperative knee awareness and functional outcome. The Forgotten Joint Score (FJS) evaluates to what extent the patient is aware of the artificial knee and thereby, whether the knee feels natural or not.
Purpose / Aim of Study: To evaluate knee awareness of patients undergoing bilateral simultaneous TKA and to clarify the factors that predict a high or low score.
Materials and Methods: This cross sectional study was conducted on 120 simultaneous bilateral TKAs (cemented CR AGC, Biomet) performed at our institution between 2008 and 2012 (2-6 years follow-up). All patients received 1 set of questionnaires (FJS and Oxford Knee Score (OKS)) for each knee. 99 patients (45 men, 54 women, mean age at operation 66,6 years) completed the survey and were eligible for analysis. Based on FJS scores patients’ knees were divided into two groups - “best” and “worst” knees. The FJS and OKS scores were compared between groups.
Findings / Results: The absolute difference in FJS and OKS score between the knees within each patient was calculated, a non-parametric bootstrap was used to create a 95 % confidence interval (CI) for the median of these differences. The results was a median of 1 (CI: 0-4) for the FJS score and 1 (CI: 0- 1) for the OKS score. A predictive model found that KL-score (p=0.006) and preoperative knee-alignment (p=0.017) had a significant effect on FJS score.
Conclusions: Knee awareness and functional outcome did not differ significantly between the best and worst knee in patients undergoing bilateral simultaneous TKA. More severe preoperative varus alignment and more severe KL-grades predict lower knee awareness after TKA.

68. Evaluation of peri-implant bone mineral density changes after femoral osseointegrated prosthesis surgery
Rehne Lessmann Hansen, Peter Holmberg Jørgensen, Kjeld Søballe, Klaus Kjær Petersen, Maiken Stilling
Department of orthopaedic research, University Hospital of Aarhus; Department of orthopaedic surgery, University Hospital of Aarhus

Background: Trans-femoral amputees have reduced bone mineral density (BMD) in the residual femur, hip and ipsilateral pelvis. Insertion of an osseointegrated (OI) prosthesis may affect the BMD additionally.
Purpose / Aim of Study: To study the effects of unloading/loading and stress shielding after OI-prosthesis surgery.
Materials and Methods: 20 patients (13 males) mean age 48 (range 30-66) years, were operated with an OI femoral implant in two stages. DXA scans were performed at baseline and at intervals of 3, 6, 9, 12, 18 months postoperatively. The first 9 months partial weight bearing (PW) was allowed, and after 9 months full weight bearing (FW) was encouraged. The femoral peri- implant bone was evaluated in 3 regions of interest (ROIs), proximally (Rp), medially (Rm) and laterally (Rl) to OI implant.
Findings / Results: From baseline to 18 months follow-up total peri-prosthetic BMD was unchanged (p=0.44). However, during PW periprosthetic BMD decreased (p=0.005) 25% and during FW BMD increased (p=0.04) 17%. All 3 periprosthetic ROIs had a decrease in BMD (p<0.0007) during the PW rehabilitation period of 30%, 20% and 24% for Rp, Rm and Rl, respectively. During FW rehabilitation BMD increased (p<0.04) in Rp 19% and in Rm 14%, whereas the BMD in Rl was similar (p=0.06). However, baseline values were not reached at 18 months.
Conclusions: Unloading, or less than full weight bearing, in the first 9 months after IO implantation causes pronounced stress-shielding and peri-implant BMD loss. Increased or full loading between 9 and 18 months increases BMD, but not to baseline values. Patients will be followed to investigate if direct femoral bone loading from the OI implant will result in continued BMD increase of the peri-implant bone.

69. Functional capacity is associated with both extensor and flexor strength in patients scheduled for total knee arthroplasty: a cross-sectional study
Birgit Skoffer, Ulrik Dalgas, Inger Mechlenburg, Kjeld Søballe, Thomas Maribo
Institute of Clinical Medicine and Department of Physical and Occupational Therapy, Aarhus University and Aarhus University Hospital; Section of Sport Science, Department of Public Health, Aarhus University; Institute of Clinical Medicine and Orthopaedic Research Centre, Aarhus University and Aarhus University Hospital; Orthopaedic Research Centre, Aarhus University Hospital; MarselisborgCentret, Danish Rehabilitation Research Centre; National Public Health and Quality Impro, Central Denmark Region and Aarhus University

Background: Impairment of the knee extensor muscle strength in patients with knee osteoarthritis (OA) is well documented. Furthermore, pain and reduced functional capacity in combination with radiographically confirmed severe OA are the main indications for total knee arthroplasty (TKA).
Purpose / Aim of Study: To test in people scheduled for TKA if muscle strength would be 1) strongly associated with both objectively measured functional capacity and patient-reported measures; 2) more closely associated with lower extremity function when measured during concentric than during isometric contractions and; and 3) more strongly related to the 30-sec-sit-to-stand (30sSTS) test than to the timed-up-and- go (TUG) and walking tests.
Materials and Methods: In fifty nine patients (70.4±6.8 years). Associations between muscle strength and objectively measured functional capacity and patient reported outcomes were calculated.
Findings / Results: Both knee extensor and knee flexor strength were associated with functional capacity outcomes. Generally, the isokinetic knee flexor muscle strength was more strongly associated with functional capacity than the isometric knee flexor strength. Isokinetic and isometric knee extensor strength were of equal importance. The 30sSTS test was better than the TUG and the walking tests at determining muscle strength.
Conclusions: Knee extensor and knee flexor muscle strength and functional capacity are generally associated. Focus on knee extensor and knee flexor muscle strength is of equal importance to improve or maintain functional capacity. Furthermore, the 30sSTS test was found to be the best proxy measure of muscle strength when more advanced equipment for measurement of muscle strength is not available.

70. Does knee awareness differ between different TKA designs? A matched, case-control, cross-sectional study.
Morten Grove Thomsen, Roshan Latifi, Thomas Kallemose, Henrik Husted, Anders Troelsen
Dept. of Orthopedic surgery, Copenhagen University Hospital of Hvidovre, Denmark

Background: Low knee awareness after TKA has become the ultimate goal in trying to achieve a natural feeling knee that meet patient expectations. To accommodate this manufacturers of TKAs have developed new prosthetic designs that potentially could give patients a more natural feeling knee during activities.
Purpose / Aim of Study: To compare the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) of patients treated with a previous generation standard CR TKA to the scores obtained by patients treated with a newer generation CR TKA or a mobile bearing CR TKA.
Materials and Methods: We identified all patients receiving a new generation CR TKA or mobile bearing TKA at our institution between 2010 and 2012. These were matched to a population of patients receiving a standard CR TKA regarding age, gender, year of surgery, KL- grade and pre- and postoperative knee alignment. Patients were asked to complete the FJS and OKS questionnaires. Of the 316 patients completing the survey 64 standard CR TKAs to 45 new generation CR TKAs and 121 standard CR TKAs to 68 mobile bearing TKAs were matched. The FJS and OKS scores of the three TKA designs were compared.
Findings / Results: When comparing the new generation CR TKAs to the standard CR TKAs we found statistically significant higher OKS and FJS scores (6 (p=0.04) and 16 (p=0.03) points respectively) for the new generation CR TKAs. When comparing the mobile bearing TKAs to the standard CR TKAs we found a statistically significant higher OKS score (3 points, p=0.04), and a higher FJS score (4 points, p=0.48) for the mobile bearing TKAs.
Conclusions: Patients receiving the new generation CR and mobile bearing CR TKAs obtained higher FJS and OKS scores when compared to patients receiving a standard CR TKA, indicating that the use of these newer prosthetic designs facilitate less knee awareness and better function after TKA.

71. Composition of The Knee Index, a novel three-dimensional biomechanical index for knee joint load, in subjects with mild to moderate knee osteoarthritis
Brian Clausen, Thomas Andriacchi, Dennis Brandborg Nielsen, Ewa Roos, Anders Holsgaard-Larsen
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark; Department of Mechanical Engineering, Department of Orthopedic Surgery, Stanford University, Stanford, USA; Veterans Administration, Palo Alto; Department of Orthopaedics and Traumatology, Department of Clinical Research, Odense University Hospital, University of Southern Denmark

Background: Knee joint load is an important factor associated with progression of knee osteoarthritis. To provide an overall understanding of knee joint loading, the Knee Index (KI) has been developed to include moments from all three planes (frontal, sagittal and transversal). However, before KI is used in clinical trials a biomechanical analysis identifying the respective contributions of the knee moments derived from the three planes is needed.
Purpose / Aim of Study: The purpose of this study was therefor to investigate how the frontal, sagittal and transversal moments contribute to KI, a novel biomechanical index of joint load for the knee, in patients with mild to moderate knee osteoarthritis.
Materials and Methods: The contribution of frontal, sagittal and transversal plane knee moments to KI was investigated in 24 subjects (13 women, age: 58 ± 7.6 years, BMI: 27.1 ± 3.0) with clinically diagnosed mild to moderate knee osteoarthritis according to the ACR criteria. Three dimensional gait analysis was performed. Subjects walked barefoot at self-selected walking speed. The first peak magnitude KI from all three planes were calculated using inverse dynamics.
Findings / Results: Frontal plane kinematics contributed with 59.3% (SD 25.6) of KI while sagittal plane kinematics contributed with 40.5% (SD 26.1). A substantial inter-subject variation in the relative contribution of the flexion and extension moment components to KI was observed.
Conclusions: Our findings support the notion that the primary contributor to KI is the frontal plane kinematics (i.e. the knee adduction moment), and secondarily the sagittal plane kinematics (i.e. the knee flexion moment). This holds promise for using KI in clinical trials since both frontal and sagittal knee joint moments have been suggested to be associated with the knee osteoarthritis disease progression.

72. Pelvic movement strategies and leg extension power in patients with end-stage medial knee osteoarthritis: A cross-sectional study
Signe Kierkegaard, Peter Bo Jørgensen, Ulrik Dalgas, Kjeld Søballe, Inger Mechlenburg
Orthopaedic Research, Aarhus University Hospital; Department of Sport Science, Aarhus University

Background: While it is well-known that knee osteoarthritis (OA) and knee extensor muscle strength are associated, less is known about leg extension power although leg power is closely related to functional performance in elderly persons. Patients with medial knee OA use a variety of compensatory movement strategies to minimize the joint load in the affected leg. Little is known about these movement strategies of the pelvis during functional performance tests.
Purpose / Aim of Study: The aim of the study was to investigate leg extension power and pelvic movements during walking, stair climbing and stepping in patients with end-stage medial knee OA and in healthy controls.
Materials and Methods: 57 patients (mean age 65.6 years) scheduled for medial uni-compartmental knee arthroplasty (UKA) were included in the cross-sectional study together with 29 age and gender matched controls. Leg extension power was tested in the Nottingham Leg Extension Power-Rig and pelvic movements were derived from an inertial sensor with gyroscope placed between the posterior superior iliac spines during walking, stair and step ascending and descending.
Findings / Results: Both the affected and the contralateral leg of the patients were weaker than the matched control legs. Patients used a greater pelvic movement than controls during stair and step ascending and descending, which was especially evident during descending. Furthermore a significant inverse association between leg extension power and pelvic movements during stair and step descending was found in the patient group.
Conclusions: Compared to controls, patients with medial knee OA use greater pelvic movements during advanced functional performance tests, especially during descending tasks. Further longitudinal studies are required to investigate pelvic movements after UKA.