Session 3: Knee

Torsdag den 24. oktober
09:00 – 10:30
lokale: Stockholm/Copenhagen
Chairmen: Poul Torben Nielsen / Henrik Schröder

20. Does “safe-zones” for alignment and component position exist in primary TKA?
Morten Grove Thomsen, Henrik Husted, Thor Bechsgaard, Anders Troelsen
Dept. of Orthopedic Surgery, Copenhagen University Hospital of Hvidovre

Background: To achieve good clinical results and low revision rates after TKA, traditional recommendations have been to aim for anatomical AP alignment (0-7°of valgus) based on a perpendicular cut on the tibia. Accordingly, “safe-zones” for component position have been suggested. Recent studies, however, have challenged the suggested importance of these recommendations.
Purpose / Aim of Study: To investigate 1) the rate of TKAs inside traditional safe-zones of alignment and component position, 2) if outlier TKAs are associated with increased aseptic revision rates.
Materials and Methods: By random selection 678 primary TKAs inserted at our institution between 2007 and 2011 were included. 40 TKAs were excluded because of previous knee surgery or postoperative revision due to infection. Pre- and postoperative radiographs were assessed for anatomical alignment (AP) and position of the individual components (AP and sagittal). 15 of 638 TKAs (2.4%) undergoing revision due to aseptic complications were identified.
Findings / Results: Postoperative safe-zones were achieved for AP alignment in 74%, femoral component AP position in 68%, tibia component AP position in 78%, and femoral component sagittal position in 78%. We found no statistically significant relationships between alignment or component position outside safe-zones and rates of revision due to aseptic complications for AP limb alignment (p=0.86), femur- and tibia AP component positions (p=0.60 and p=0.87) and femur sagittal component position (p=0.52).
Conclusions: Limb alignment and position of TKA components within so-called “safe-zones” is not an easy target. It seems that TKAs outside the safe-zones are not associated with increased risk of aseptic revision. Further investigations looking at both long- term functional outcomes and patient satisfaction are needed.

21. Is fast-track total knee arthroplasty safe regarding manipulation for unacceptable knee flexion?
Christian Wied, Morten Grove Thomsen, Lis Myhrmann, Lotte Skov Jensen, Henrik Husted, Anders Troelsen
Dept. of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Denmark

Background: Fast-track total knee arthroplasty (TKA) has significantly shortened the time available for physiotherapists to optimize knee Range of Motion (ROM) before discharge. Safety aspects concerning knee stiffness and the need for manipulation in a fast- track setting need to be illuminated.
Purpose / Aim of Study: The study aims were to analyze if fast-track TKA can be considered safe considering rates of knee manipulation and if there is an association between knee ROM at time of discharge and the need for later manipulation.
Materials and Methods: Primary TKAs operated in 2011 at our institution were eligible for inclusion (n=398). Of these, we excluded 20 that had revision surgery, and 19 that did not have standardized goniometric measurement of ROM at discharge. The study group consisted of 359 TKAs (338 patients/ 65% females). Knee manipulations within 1 year of surgery were recorded.
Findings / Results: Manipulation of the knee was performed in 21 of 359 knees (5.8%). Median length of stay was 2 days. The prevalence of knee manipulation showed a statistically significant association with the achieved knee flexion at discharge (p=0.02): 13.6 % if discharge flexion was < 70°, 6.6 % if discharge flexion was 70°- <85°, and 2.7 % if discharge flexion was ≥ 85°. Only one of 66 TKAs with a flexion ≥ 85° combined with an extension deficit of ≤ 5° underwent manipulation.
Conclusions: Compared with literature findings fast-track TKA surgery may be considered safe based on the acceptable rate of knee manipulations after TKA. Combined knee ROM of ≤ 5° extension deficit and ≥ 85° flexion at time of discharge can be considered a “safe-zone” with very low risk of manipulation. Extraordinary follow-up may be warranted in TKAs with discharge flexion < 70°.

22. Similar Fixation but Increased Stress-Shielding of an I-Beam compared with a Finned Tibial Component Stem Design. A Randomized RSA and DXA Study with 5 years Follow-up.
Maiken Stilling , Claus Fink Jepsen, Lone Rømer, Ole Rahbek, Kjeld Søballe, Frank Madsen
Departmen of Orthopaedics, Aarhus University Hospital; Department of Radiolgy, Aarhus University Hospital

Background: The tibial component often has a stem to aid fixation in the tibial bone.
Purpose / Aim of Study: The purpose of this study was to compare implant fixation, periprosthetic bone change, and clinical outcome of tibial components with different stem design.
Materials and Methods: 54 patients/knees (15 males) with knee osteoarthritis at a mean age of 77 years (70 – 90) were randomly allocated to receive tibial components with either an I-Beam stem (n=27) or a finned stem (n=27) (CoCr modular Tibial Tray Interlok, Biomet Inc). The tibial component was cemented on the cut surface (Palacos R bone cement) but not around the stems. Five patients (I-Beam stems) were lost to follow-up. Implant migration (Model-Based RSA), periprosthetic bone mineral density (BMD), and American Knee Society Score (AKSS) was evaluated through 5 years follow-up.
Findings / Results: At 5 years follow-up, total translation (p=0.10) was 0.84mm (SD 0.76) and 0.45mm (SD 0.49), and total rotation (p=0.08) was 1.51° (SD 1.27) and 0.81° (SD 0.85), for the I-beam stem and the finned stem tibial components, respectively. Between baseline and 1 year the peri-prosthetic BMD on AP scans decreased 10% (0.09 g/cm2) around I-beam and 2% (0.02 g/cm2) around the finned stem components (p=0.02). In the tibia below the stem BMD decreased by 6% and increased by 3% (p=0.01) at 1 year for the I- beam and finned stem components, respectively. At 2 years BMD loss progressed in general in both groups. 5 year DXA data are currently being analyzed. Knee score, function score, pain, and satisfaction were similar.
Conclusions: RSA showed similar stability of the tibial components with I-Beam and finned stems at 5 years follow-up. There was a heterogeneous BMD changes between the groups at 2 years that may jeopardize implant stability of the I-Beam stem and further analyses in the 5 year data are currently being done.

23. Absence of tourniquet does not affect fixation and stability of cemented TKA: a randomised controlled trial using RSA
Ashir Ejaz, Anders C. Laursen, Andreas Kappel, Sten Rasmussen, Mogens B. Laursen, Poul T. Nielsen
Department of Orthopaedics , Aalborg University Hospital; Department of Orthopaedics, Aalborg University Hospital

Background: Use of pneumatic tourniquet to obtain a bloodless surgical field for total knee artroplasty (TKA) has always been highly debated and many parameters such as pain, bloodloss, range of motion, operation time and complications have been investigated. Achieving a stable fixation of the tibial component is still a major challenge and concern when doing TKA. Very little data regarding implant fixation is available.
Purpose / Aim of Study: To investigate whether tibial component fixation is compromised when tourniquet is not used and active bleeding occurs during TKA, assessed with radiostereometric analysis (RSA) and plain radiographs.
Materials and Methods: A RCT with 70 consecutive patients aged 50-85 (mean= 68) underwent primary unilateral TKA performed by a single surgeon. Patients were randomly allocated to one of two groups: Group A surgery with tourniquet and Group B surgery without tourniquet. Tantalum markers were placed in the tibial metaphysis and implant and RSA was performed postoperatively and at 2 months, 6months and 12 months.
Findings / Results: Plain radiograph were assessed for radio lucent lines and RSA performed. All implants appeared stable, except in one case of early loosening otherwise no differences between groups were observed. Micromotions of more than 1 mm and 1º were considered to be clinically relevant. RSA endpoints were maximum total point motion (MTPM), tibial subsidence, lift-off and rotations and translations along the x-, y, z- axis.
Conclusions: At 1 year follow up no cases of clinical loosening of implants had been observed. Performing TKA without use of tourniquet does not seem to affect the fixation of the cemented tibial component.

24. A questionnaire survey regarding the Danish activity on axis corrective osteotomy (ACO) in treatment of uni-compartmental knee osteoarthritis
Toke Kirchberg Nilsson, Andreas Kappel, Anders Christian Laursen, Poul Torben Nielsen
Orthopaedic, Aalborg

Background: Uni-compartmental osteoarthritis of the knee joint has a wide range of different surgical treatment options including uni-compartmental knee arthroplasty (UKA), total knee arthroplasty (TKA) and ACO. ACO is not included in the Danish national registers for systematic analysis, as surgical registry codes cover several different procedures over many indications.
Purpose / Aim of Study: The study aims at estimating the Danish activity of ACO, pre-surgical assessment and surgical techniques.
Materials and Methods: A questionnaire survey among 42 orthopaedic departments and private clinics in Denmark selected on the basis of Danish Regions' and the Departments' own reports. In case of doubt, regarding a clinic's relevance to the survey, a questionnaire was submitted.
Findings / Results: 34/42 (81%) responded to the survey. Fifteen departments/clinics preform ACO with a total national activity estimated between 162 to 221 procedures/year [range 1-70 for single clinics]. Twelve (80%) departments use open wedge technique with internal fixation to treat medial osteoarthritis. Seven (47%) departments offer ACO (varus osteotomy) in lateral osteoarthritis. 8/15 (53%) departments performing ACO preform less than 6 procedures annually. 4/18 (22%) departments, that do not offer ACO, offer UKA instead of ACO.
Conclusions: More then half the departments preforming ACO have low annually activity. The pre-surgical assessment, indication for surgery and surgical options are of wide national variation, and we therefore propose to explore, which pre-surgical assessment and surgical procedure provide best outcome in uni-compartmental knee osteoarthritis.

25. Early full weight-bearing in open-wedge high tibia valgus osteotomy: A randomized, controlled RSA trial with 2 years follow-up
Anders Christian Laursen, Thomas Lind-Hansen, Mogens Berg Laursen, Poul Torben Nielsen
Orthopaedic Research Unit, Aalborg University Hospital; Dept. of Orthopaedics, Vejle Hospital; Dept. of Arthroplasty, Aalborg University Hospital

Background: In open-wedge, valgus osteotomy of the upper tibia, there are concerns regarding initial stability. Rehabilitation protocols vary depending on the surgical technique, type of implant, fixation method and tradition. Angle stable implants theoretically offer initial stability, and it has been indicated that early full weight-bearing is feasible.
Purpose / Aim of Study: To validate early full weight-bearing in patients with the Dynafix implant, by means of radiostereometric analysis (RSA), plain radiograph, and clinical outcome.
Materials and Methods: 26 consecutive primary open-wedge valgus osteotomies were performed. Patients were randomized at surgery between two rehabilitation protocols, one including full early weight-bearing, and one with 6 weeks restricted weight- bearing of 20 kgs. Migration and stability of the osteotomy was measured by RSA, post-operatively, at 6 weeks, and 1 & 2 years, with both reclining and standing analysis. Plain radiographs and clinical outcome (KOOS score) were recorded at the same intervals.
Findings / Results: No difference in stability or retainment of correction between the groups was detected. All patients in both groups were healed and stable in plain radiograph and clinically fully healed at end of trial. No significant differences in clinical outcome scores or pains were recorded: In both groups, pain and function improved substantially. Patients in the early weight- bearing group achieved the same clinical and radiological outcome of surgery, with faster and more convenient rehabilitation
Conclusions: Open-wedge high tibia valgus osteotomy using the Dynafix implant allows early full weight-bearing, without risk of instability or clinicallly relevant loss of corrrection, and with similar clinical outcome compared with restricted weightbearing.

26. Similar and good fixation of cementless and cemented Oxford® Partial Knee Tibial Trays at 2 years follow-up. A Randomized RSA Study.
Maiken Stilling, Frank Madsen, Claus Fink Jepsen, Kjeld Søballe, Per Wagner Kristensen, Anders Odgaard
Department of Orthopaedics, Aarhus University Hospital

Background: The Cementless Oxford® Partial Knee Tibial Tray (TT) was introduced to the commercial market 5 years ago.
Purpose / Aim of Study: To compare fixation of cementless and cemented (gold standard) Oxford® Partial Knee TT up to 2 years follow-up by radiostereometric analysis (RSA).
Materials and Methods: 79 patients (48 men) were randomly allocated to surgery with cementless hydroxyapatite-coated or cemented Oxford® Partial Knee TT (Biomet Inc.) at 2 hospital sites. Femoral components were either single-pegged or double-pegged in the cemented group and double-pegged in the cementless group. Refobacin bone cement (Biomet Inc.) was used. Evaluation of implant migration, radiolucent lines (RLL), and clinical outcomes (OKS) was performed at 6 weeks, 3 and 6 months, and 1 and 2 years.
Findings / Results: Between 1 and 2 years follow-up cementless TT (n=25) migrated 0.06mm (sd 0.06) and cemented TT (n=45) migrated 0.12mm (sd 0.20) mean total translation (p=0.22). 13% (6/39) of cemented and 8% (2/25) of cementless TT migrated more than 0.2mm between 1 and 2 years follow- up (p=0.40). The cementless TT (n=25) migrated more than the cemented TT (n=55) at all follow-ups (p<0.01), however migration had stabilized at 6 months follow-up. At 2 years mean OKS was 40 (range 21- 47) (p=0.53) with similar improvement from baseline (p=0.11) and satisfaction was high in both groups. Analysis of RLL at 2 years follow-up is ongoing.
Conclusions: Cementless Oxford® Partial Knee TT migrate initially but stabilize at 6 months probably because of achieved bony anchorage. Between 1 and 2 years follow-up cementless fixation is as good as cemented fixation (gold standard). Functional results were good and similar in both groups.

27. How does strength training influence knee joint pain shortly following total knee arthroplasty?
Thomas Bandholm, Kristian Thorborg, Troels Haxholdt Lunn, Henrik Kehlet , Thomas Linding Jakobsen
(1) Physical Medicine & Rehabilitation Research – Copenhagen (PMR-C), Department of Physical Therapy, Copenhagen University Hospital, Hvidovre; (1) Arthroscopic Centre Amager, Department of Orthopedic Surgery, (2) Physical Medicine & Rehabilita, Copenhagen University Hospital, Hvidovre; (1) Department of Anesthesiology, (2) The Lundbeck Foundation Centre for Fast-Track Hip and Knee Art, Copenhagen University Hospital, Hvidovre; (1) Section for Surgical Pathophysiology, (2) The Lundbeck Foundation Centre for Fast-Track Hip and , Rigshospitalet; (1) Lundbeck Foundation Centre for Fast-Track Hip and Knee Arthroplasty, Copenhagen, (2) Physical Me, Copenhagen University Hospital, Hvidovre

Background: Loading and contraction failure (muscular exhaustion) are strength training variables known to influence muscle strength and muscle mass gains in healthy subjects, and may have potential benefits for rehabilitation after total knee arthroplasty (TKA).
Purpose / Aim of Study: To investigate the effect of loading and contraction failure on knee pain during strength training, shortly following TKA.
Materials and Methods: Seventeen patients (72.0 ± 10.7 yrs, 11 women) were included 1 to 2 weeks after their TKA. In a randomized order, they performed 1 set of 4 standardized knee extensions, using relative loads of 8, 14, and 20 repetition maximum (RM) (load experiment), and ended with 1 single set to contraction failure (14 RM load) (failure experiment). The kilograms, corresponding to the 8, 14, and 20 RM loadings, were determined no less than 72 hours prior, during a familiarization session. The patients rated their knee pain during each repetition, using a numerical rating scale. Patients as well as the pain assessor were blinded to the loads. 1.5 points was pre-specified as the minimal clinically important change in pain, and used to power the study.
Findings / Results: Two patients were lost to follow up. Knee pain increased with increasing load (20 RM: 3.1 ± 2.0, 14 RM: 3.5 ± 1.8, 8 RM: 4.3 ± 2.5, P=0.006), and repetitions to contraction failure (10% failure: 3.2 ± 1.9, 100% failure: 5.4 ± 1.6, P<0.001). Resting knee pain 60 seconds after the final repetition (2.7 ± 2.4) was no different from that recorded before strength training (2.7 ± 1.8, P=0.88).
Conclusions: Repetitions performed to contraction failure during knee extension strength training seems to induce a clinically relevant – but transient – increase in post-operative knee pain during strength training, shortly following TKA. NCT01713140.

28. Early outcome after aseptic revision total knee arthroplasty in Denmark. A 2 year nationwide study.
Martin Lindberg-Larsen, Christoffer Calov Jørgensen, Torben Bæk Hansen, Søren Solgaard, Anders Odgaard, Henrik Kehlet
Section of Surgical Pathophysiology and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty, Rigshospitalet; Department of Orthopedic Surgery and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty., Holstebro Hospital

Background: Limited data exist on early outcomes after revision total knee arthroplasty (TKA) (1,2) , and especially with a fast- track set-up (2).
Purpose / Aim of Study: To investigate length of stay (LOS), readmissions and mortality ¡Ü 90 days after aseptic revision TKA in Denmark (DK).
Materials and Methods: All patients undergoing TKA revision procedures in DK from 01.10.2009 to 30.09.2011 were analyzed using the Danish National Patient Registry with additional information from the Danish Knee Arthroplasty Registry. Only elective, aseptic revisions were included. The revisions were subdivided into 3 groups: 1. Replacement of both tibia- and femur components, 2. Replacement of one of the components (tibia or femur), 3. Replacement of the liner, patellar button or secondary insertion of the patella button.
Findings / Results: 1042 aseptic TKA revision procedures were performed in 42 centres in DK in the study period. Mean age was 65.7 (range: 27-92), median LOS 6 days (IQR: 4-10), mean LOS 8.5 (1-120) days, 90 days readmission rate 12.5 % and 90 days mortality 0.6 %. In group 1 (n = 713) median LOS was 7 days (4-10), readmission rate 12.5 % and mortality 0.8 %. In group 2 (n = 150) median LOS was 5 days (3-10) and readmission rate 16.0 %. In group 3 (n = 179) median LOS was 5 days (4-9) and readmission rate 9.5 %. No deaths in group 2 and 3.
Conclusions: Revision TKA procedures are performed in multiple centres in DK and the fast- track methodology is not implemented in relation to these procedures, calling for improvement. A multicenter study on revision TKA in a fast-track setting is in the planning phase. (1): Cram P et al. Total knee arthroplasty volume, utilization, and outcomes among medicare beneficiaries, 1991-2010. JAMA. 2012;308:1227-36. (2): Husted H et al. Fast-track revision knee arthroplasty. A feasibility study. Acta Orthop. 2011;82:438-40.

29. Current trends of TKA fixation and cruciate ligament retention: Are surgeons on track?
Erik Malchau, Kirill Gromov, Henrik Husted, Henriks Malchau, Anders Troelsen
Orthopaedic Surgery, Copenhagen University Hvidovre Hospital

Background: Registry data from multiple countries have documented an ongoing shift in THA fixation towards uncemented fixation despite reports of inferior survivorship. Similar paradoxical trends in TKA surgery could be a concern.
Purpose / Aim of Study: To investigate: 1) current trends in TKA fixation and cruciate ligament retention, and 2) if these trends are in accordance with registry reported TKA survival.
Materials and Methods: Data regarding tibia component fixation, cruciate ligament retention (CR vs. PS) and implant survivorship in primary TKA were extracted from publicly available national joint registries’ annual reports from 2008 through 2012. Reports from Australia (AUS), Denmark (DK), England-Wales (E-W), Norway (NOR), Sweden (SWE) and New Zealand (NZ) were assessed.
Findings / Results: During the 5-year period an increase in cemented fixation was reported by AUS (76% to 77%), DK (93% to 94%) and E-W (90% to 95%). A decrease in cemented fixation was observed in NOR (82% to 78%) and SWE (100% to 96%). NZ reported no change. AUS, DK, E-W, NOR, NZ and SWE reported significantly higher risks of revision comparing uncemented with cemented fixation. AUS reported an increase in the use of PS TKA and E-W reported no change. Both countries and DK reported a higher risk of revision for PS vs. CR TKA.
Conclusions: Cemented TKA still appears to be the gold standard in TKA surgery in most countries. However, there were considerable regional differences in current use of uncemented TKA (4-23 %). Countries with increases, though small in absolute numbers, in utilization of uncemented fixation and PS TKA should monitor this as it could result in deteriorating survivorship over time.

30. Tourniquet induced ischemia and changes in metabolism during TKA: a randomised controlled trial using microdialysis
Ashir Ejaz, Anders C. Laursen, Andreas Kappel, Poul T. Nielsen, Sten Rasmussen
Department of Orthopaedics , Aalborg University Hospital; Department of Orthopaedics, Aalborg University Hospital

Background: Use of tourniquet to obtain a bloodless surgical field during TKA is known to induce ischemia, especially beneath the cuff. Little is known regarding the extent of ischemia and metabolic changes in the skeletal muscle distal to the cuff. Microdialysis (MD) is a unique In vivo technique to monitor metabolites in the interstitial space of the tissue of interest.
Purpose / Aim of Study: Investigate the metabolic changes during ischemia and reperfusion in skeletal muscle distal to the tourniquet
Materials and Methods: A RCT with 70 consecutive patients aged 50-85 (mean= 68) underwent primary unilateral TKA. Patients were randomly allocated to one of two groups: Group A surgery with tourniquet and Group B surgery without tourniquet. Prior to surgery, MD catheters were inserted in the gastrocnemius muscle of both legs, non-operated leg served as reference. Dialysate samples were collected before and until 5hours after surgery at intervals of 20 min. Concentrations of ischemia markers pyruvate, glucose, lactate, glycerol were analysed.
Findings / Results: In group A, for a period of 60-75 min of tourniquet induced ischemia interstitial levels of pyruvate and glucose decreased significantly to 26 µmol/l CI95%[24;31] and 2,3 mmol/l CI95%[2;3] respectively, compared to the reference leg. Simultaneously, accumulation of lactate to 2,6 mmol/l CI95%[2,3;3,1] and glycerol 244 µmol/l CI95%[200; 249] were observed. A return to normal baseline values occurred during a period of 120-180 min. After 5 hours no changes were detected compared with baseline. In Group B no significant ischemia was detected.
Conclusions: We determined that performing TKA with tourniquet is associated with significant ischemia in the muscle distal to the cuff and ischemia markers are affected until 2-3 hours after surgery. Tourniquet induced ischemia may impair early recovery.