Session 1: Knee I

Onsdag den 23. oktober
09:00 - 10:30
Lokale: Centersal
Chairmen: Daan Koppens og Lasse Enkebølle Rasmussen

1. 5-Year Results of a Randomized Clinical Trial Comparing Patellofemoral and Total Knee Arthroplasty
Anders Odgaard, Jesper Fabrin, Frank Madsen, Per Wagner Kristensen, Andreas Kappel
Dept. of Orthopaedics, Copenhagen University Hospital Herlev-Gentofte; Dept. of Orthopaedics, Køge University Hospital; Dept. of Orthopaedics, Aarhus University Hospital; Dept. of Orthopaedics, Vejle Hospital; Dept. of Orthopaedics, Aalborg University Hospital

Background: Implant registers show dismissive results of patellofemoral arthroplasty (PFA). Two-year results from this RCT have shown superior outcomes for PFA compared to total knee arthroplasty (TKA) (Clin Orthop 2018; 476:87-100).
Purpose / Aim of Study: This update of the PFA vs. TKA RCT presents 5- year results for patient-reported (PRO), clinical and survival outcomes. A subgroup analysis aiming to identify predictors of outcomes will also be presented.
Materials and Methods: Double-blinded RCT comparing PFA and TKA of 100 patients with isolated PF-OA operated 2007-14 (age 64, range 39-85; females 77%). A number of PROMs were used (incl. SF36, Oxford Knee Score and KOOS) and measured at baseline and at 3, 6, 9 and 12 months and yearly henceforth. Physical findings were recorded at baseline, 2 weeks, 4 months, and 1, 2 and 5 years. Longitudinal data were analysed both at individual time points and using time-weighted measures (area under the curve – AUC). Intention-to-treat analysis was used. Age and baseline diagnosis (posttraumatic, dysplastic or idiopathic PF-OA) were analysed to determine their effects on the primary patient-reported outcome (SF36 pain).
Findings / Results: At 5 years, the AUC for PROMs SF36 physical functioning, SF36 bodily pain, KOOS symptoms and OKS were significatly better for PFA than for TKA (p=0.013, 0.006, 0.002, 0.002, respectively). The remaining PRO dimensions of SF36 and KOOS were all better for PFA but with insignificant p-values. The knee range of movement for PFA patients had returned to the preoperative range at 12 months, while the ROM for TKA had not returned at 5 years (mean=-12deg (SEM=3.9deg), p<0.001). Neither age nor PF-OA pathegenesis had an effect on the patient/reported outcomes. After 5 years, there has been 4 and 2 revisions of PFA and TKA, respectively.
Conclusions: Time-weighted patient-reported outcomes (using intention-to-treat analysis) are better for PFA than TKA patients a five years. PFA patients also have a better range of movement, and the TKA patients have not regained the preoperative ROM at 5 years. Exploratory analyses suggest that neither age nor PF-OA pathogenesis has an effect on patient- reported outcomes, and they should consequently not be considered for indication purposes.

2. Early follow-up of hybrid Total Knee Arthroplasty (TKA) using Persona® prostheses – a prospective study using Model-based Radiostereometric Analysis
Müjgan Yilmaz, Christina Holm, Gunnar Flivik, Thomas Lind, Anders Odgaard, Michael Mørk Petersen
Ortopedic department, Rigshospital; Ortopedic department, Rigshospitalet; Ortopedic department, Skåne University Hospital; Ortopedic department, Gentofte Hospital; Ortopedic department, Gentofte Hospital; Ortopedic department, Rigshospitalet

Background: Total knee arthroplasty (TKA) is generally a very successful treatment for patients with knee osteoarthritis. However, there are a group of patients, so called non-responders that for various reasons (mainly persistent pain) are not satisfied with the implant. The Persona® (ZimmerBiomet) TKA has been designed with the aim of minimizing the group of dissatisfied patients by achieving better biomechanical restoration, with more sizes and an asymmetrical tibial component that allows better coverage of the tibial plateau with less risk of placing the component in in-ward rotation.
Purpose / Aim of Study: 1. Early implant migration 2. Functional outcome
Materials and Methods: Thirty-one patients, (mean age 65 y, F/M= 18/13) scheduled for primary TKA due to osteoarthritis were included. Two patients were excluded, one due to PCL rupture and therefore a ultra-curve insert were used and one due to competing disease, leaving 29 to follow-up, no revision surgeries were registered during follow-up. Surgery were performed at Gentofte Hospital. All received a hybrid Persona® TKA with cemented tibia, uncemented TM femur and a cemented patella Persona® all poly patella components. Implants were evaluated with model-based- RSA after average 7 days, 3, 6, and 12 months. Functional and clinical outcome were evaluated with Knee Society Score (KSS) and Oxford Knee Score (OKS) preoperatively and 1-year after surgery.
Findings / Results: Average Maximal Total Point Motion (MTPM) for the cemented tibial components were at 3 months 0.86 mm (0.28-5.66, n=27), 6 months 0.95 mm (0.18-5.74, n=23) and 1-year 1.56 mm (0.29-5.84, n=24). Average MTPM for the uncemented femur components were at 3 months 0.71 mm (0.28-2.12, n=24), 6 months 0.86 mm (0.22- 2.09, n=21) and 1 year 0.9 mm (0.26-1.97, n=23). KSS-clinical showed an increase from 38 (0-79) preoperatively to 84 (57-93) at 1-year follow-up, KSS-function 54 (10-60) to 92 (60-100) and OKS showed an increase from 25 (13-38) to 43 (32-48).
Conclusions: Early RSA follow-up results are promising, with 1-year average MTPM values on the same levels as seen in previous studies evaluating other well-functioning uncemented and cemented implants. Further follow-up is needed to evaluate if continuous migration is taking place.

3. Tibial Component Overhang of both Total and medial Unicondylar Knee replacement can increase local pain in soft tissues.
Jacob Fyhring Mortensen, Julius Hald, Lasse Enkebølle Rasmussen, Anders Odgaard
Orthopedic hip- and knee replacement, Gentofte Hospital; Orthopedic hip- and knee replacement, Gentofte Hospital; Orthopedic hip- and knee replacement, Vejle Hospital; Orthopedic hip- and knee replacement, Gentofte Hospital

Background: Tibial overhang (TO) of the tibial component (TC) is observed in both total knee replacement (TKR) and medial unicompartmental knee replacement (mUKR). It has generally been claimed that an overhang below 3mm doesn’t have a clinical significance. Use of x-ray to determine TO depends on the x-ray angle used, possibly underestimating TO because of the parallax effect.
Purpose / Aim of Study: Ultrasound (US) can measure the direct distance from TC to bone, and measure local TO at any wished angle. The main objectives are to see if TO of either TKR or mUKR correlate with higher local pain, and if TO correlates to worse Forgotten joint scores (FJS).
Materials and Methods: 64 post-operative (mean 97days) control patients of UKA/TKA were included prospectively. An orthopedic resident performed all measurements. The patients had their pain and TO measured at 10 sites around the prosthesis medially and laterally using a validated self-assembly algometer and ultrasound. The pressure acceleration applied was approximately 0,5kg/cm2 per second, and patients were instructed to verbally indicate when they felt a pain sensation, and the pressure (kg/cm2) was measured. Pain measurements were compared between sites with and without TO, creating an outcome of deltapain between these sites, used for further analysis. FJS was obtained at 6 months.
Findings / Results: TKR had a higher mean deltapain of 6,2 vs mUKR at 3,2, and a lower FJS at 6 months at 44,3 vs 64,9 for UKR. 56% of all had a site of TO >2mm. Of these TO-sites, 72,3% of them were located postero- medially for both TKR and UKR. A Relative Risk of 3,56 (CI 1,2-10-9, p = 0,021) was found for patients with a positive deltapain and with an overhang over 2mm. When comparing AP x-rays to US medially, we found LOA to be -5,8-0,7.
Conclusions: TO over 2mm can increase pain locally, but does not correlate to a worse FJS a 6 months. Ultrasound is a decent but interdependent tool to diagnose a majority of underdiagnosed TO posteromedially, which could be optimized with specialized staff and techniques.

Anne Brun Hesselvig, Magnus Arpi, Frank Madsen, Thomas Bjarnsholt, Anders Odgaard
Afdeling for Led- og Knoglekirurgi, Herlev og Gentofte Hospital; Klinisk Mikrobiologisk Afdeling, Herlev og Gentofte Hospital; Ortopædkirurgisk Afdeling, Aarhus Universitetshospital; Costerton Biofilm Center, Institut for immunologi og mikrobiologi; Afdeling for Led- og Knoglekirurgi, Herlev og Gentofte Hospital

Background: Periprosthetic joint infection (PJI) is a devastating incident for the patient. Despite prophylactic measures as pre-operative decontamination, antisepsis and prophylactic antibiotics the infection rate has been constant at 1-2%.
Purpose / Aim of Study: The primary aim of this study was to examine whether the use of iodine impregnated incision drape (IIID) decreased the risk of periprosthetic joint infections (PJIs). The secondary aim was to investigate whether intraoperative contamination could predict postoperative infection.
Materials and Methods: We performed a transregional, prospective, randomized two arm study (IIID vs control group) of 1187 patients undergoing primary knee arthroplasty surgery. A database with patient demographics and surgical observations was established with the purpose of following the patients for ten years. Patients, who developed an infection within the first year of surgery were analyzed for correlation with the intraoperative bacterial findings and the use of IIID.
Findings / Results: 970 patients were available for preliminary analysis. 35/970 (3.6%) patients were re-operated during the follow-up period. 14/35 (40%) patients had positive tissue biopsies taken at revision surgery within one year of initial surgery. 15/35 (42%) were deemed infected and received antibiotic treatment. 9/15 patients deemed infected were male. Of the 15 infected patients 2 were contaminated at the primary surgery. Chi square test showed no correlation between contamination and infection (OR 0.87, 95% CI 0.13-6.0, p=0.89). 6 of the 15 infected patients were operated with IIID at the primary surgery. No correlation was found between the use of IIID at primary surgery and subsequent infection (OR 0.67, 95% CI 0.17-2.58, p=0.56.)
Conclusions: We found no effect of the use of IIID and subsequent development of PJI. Nor did we find a correlation between the intraoperative contamination and development of PJI within the first year of follow-up.

5. Intraoperative Contamination During Primary Knee Arthroplasty Does Not Affect Patient Reported Outcomes for Patients Who Do Not Develop an Infection in the First Year After Surgery: A Prospective Cohort Study of 714 Patients
Jakob Bjørnholdt Olsen, Tobias Justesen, Anne Mørup-Petersen, Anne Brun Hesselvig, Anders Odgaard
Orthopedic surgery, Herlev and Gentofte Hospital; Orthopedic surgery, Herlev and Gentofte Hospital; Orthopedic surgery, Herlev and Gentofte Hospital; Orthopedic surgery, Herlev and Gentofte Hospital; Orthopedic surgery, Herlev and Gentofte Hospital

Background: It is well recognized that some knee arthroplasty (KA) patients present with prolonged post-operative inflammation and some develop persistent pain. It can reasonably be speculated that some of these problems develop because of slow infection with low virulence bacteria caused by intraoperative contamination.
Purpose / Aim of Study: This prospective study was performed to investigate whether intraoperative contamination results in a prolonged inflammatory response, increased discomfort, prolonged rehabilitation and subsequently lower patient-reported outcomes (PRO) in the first post-operative year compared to the outcomes of patients without intraoperative contamination.
Materials and Methods: We combined data from two major prospective studies on patients undergoing primary knee arthroplasty (KA) at two Danish hospitals between September 2016 and January 2018. A total of 714 patients were included in the current study. Pre- and post-operative (1.5, 3, 6, and 12 months) PROs and intraoperative microbiological cultures were obtained on all patients. Based on the microbiological cultures, the patients were divided in two groups, contaminated and non-contaminated. Differences in PROs between contaminated and non-contaminated patients were analyzed at post- operative time points.
Findings / Results: 84 of 714 (11.8%) patients were intraoperatively contaminated without developing clinical infection. The preoperative OKS was 23.2 (SD 6.54) for all patients and 23.7 and 23.1 for contaminated and non-contaminated patients, respectively (p=0.45), improving to 39.5 and 38.9 at one year (p=0.78). The one-year AUC for Oxford Knee Score was 2.80 (SD 1.65) and 2.89 (SD 1.70) for contaminated and non-contaminated patients, respectively, (p=0.69). The absolute improvement at each post-operative time point for Forgotten Joint Score and EQ-5D-5L also did not differ between contaminated and non- contaminated patients (p>0.1).
Conclusions: Based on PROs from 714 patients, intraoperative contamination does not affect the knee-specific or general health related quality of life measured by PROs in primary KA patients within the first year after surgery.

6. Outcome after combined treatment of knee arthrofibrosis
Peter Faunø, Lone Frandsen, Bitten Munk Hansen, Martin Carøe Lind
Dept Sports Traumatology , Aarhus University Hospital; Dept Sports Traumatology, Aarhus University Hospital; Dept Sports Traumatology, Aarhus University Hospital; Dept Sports Traumatology, Aarhus University Hospital

Background: A difficult patient group, With no evidence based treatment options
Purpose / Aim of Study: Clinical outcome following surgical treatment and intensive physiotherapy were evaluated in patients with arthrofibrosis as a complication to varying knee-ligament reconstructions.
Materials and Methods: From 2010 to 2017, 36 patients underwent treatment for arthrofibrosis. Treatment consisted of arthroscopic arthrolysis and Brissement forcé under general anastesia followed by intensive physiotherapy under optimized pain relieve for two weeks. Twenty-one patients were available for one-year follow-up. Objective examination, VAS pain score, SF-36, KOOS and Tegner scores as well as muscle strength measurements scores were used to evaluate the clinical outcome at follow-up.
Findings / Results: : Pain score at rest and during exercise was in average reduced from VAS score 2.8 to 1.9 and 5.1 to 4.3 respectively. The knee extension deficit was in average reduced from 13.9 to 1.9 degrees and the flexion was increased from 99 to 126 degrees. Tegner activity level increased from 1.5 to 2.8. The KOOS score increased from 36,8 to 55.0. The average SF-36 level increased from 37.2 to 51.6. Average muscle strength was elevated from 143 to 153 in index leg. The muscle strength in other leg decreased from 258 to 241.
Conclusions: Surgical arthrolysis combined with intensive physiotherapy improved range of motion,subjective outcome and muscle strength significantly.

7. Knee fracture increases the risk of total knee arthroplasty after initial fracture treatment and throughout life.
Veronique Vestergaard, Alma Becic Pedersen, Kristoffer Borbjerg Hare, Henrik Morville Schrøder, Anders Troelsen
Dept of Orthopaedic Surgery, Slagelse Hospital; Dept of Clinical Epidemiology, Aarhus University Hospital; Dept of Orthopaedic Surgery, Slagelse Hospital; Dept of Orthopaedic Surgery, Naestved Hospital; Dept of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre

Background: Knee fractures can lead to posttraumatic osteoarthritis (OA) and total knee arthroplasty (TKA). Knowing TKA risk and risk factors will establish treatment burden and direct patient counseling after knee fracture.
Purpose / Aim of Study: 1) What is the short-term and long- term risk of TKA after knee fracture? 2) What are the risk factors of TKA in knee fracture patients?
Materials and Methods: A nationwide 20.25-year case- comparison-study included all patients ages ¡Ý15 with knee fracture ICD-10 code/s (knee fracture cases) at knee fracture registration (index-date) from Danish National Patient Registry. Each knee fracture case was matched (sex+age) to 5 persons without knee fracture at index-date (population- controls). Cohorts were followed from index-date to TKA/amputation/knee fusion/emigration/death/end of follow- up date. Hazard Ratios (HRs) with 95% confidence intervals (95%CIs) were estimated for TKA risk and risk factors.
Findings / Results: 48,791 knee fracture cases (median age 58.1; 57.8% females) were matched to 263,593 population- controls. HR for TKA in knee fracture cases vs population-controls was 3.74 (95%CI: 3.44-4.07) 0-3 years after knee fracture and 1.59(95% CI:1.46-1.71) >3 years. 3.7% knee fracture cases had TKA vs 1.4% population-controls. 20.25-year risk factors for TKA in knee fracture cases were: primary knee OA vs no primary knee OA HR 9.57(95%CI:5.39-16.98), external fixation vs open reduction internal fixation and reduction HR 1.92 (95%CI:1.01-3.66), proximal tibia vs patella fracture HR 1.75(95% CI:1.30-2.36), distal femur vs patella fracture HR 1.68(95%CI:1.08-2.64) and increasing age HR 1.02(95% CI:1.02-1.02). HR for TKA in surgically- vs conservatively-treated knee fracture was 2.05(95%CI:1.83-2.30) 0-5 years after knee fracture and 1.19(95% CI:1.01-1.41) >5 years.
Conclusions: Knee fracture patients have higher TKA risk initially after knee fracture and throughout life. Primary knee OA, surgically-treated knee fracture, external fixation, proximal tibia fracture, distal femur fracture and increasing age are TKA risk factors. These findings highlight knee fracture treatment burden especially with increased longevity and activity in elderly patients and inform patients on their patient- and fracture-specific TKA risk.

8. The incidence of primary knee replacement and radiographic severity of osteoarthritis prior to surgery varies between Danish regions – reports from the SPARK study
Anne Mørup-Petersen, Kristian B.G. Mongelard, Mogens Laursen, Frank Madsen, Michael R. Krogsgaard, Lone Rømer, Matilde Winther-Jensen, Anders Odgaard
Department of Orthopaedic Surgery, Herlev and Gentofte Hospital; Department of Radiology, Herlev and Gentofte Hospital; Department of Orthopaedic Surgery, Aalborg University Hospital, Farsoe; Department of Orthopaedic Surgery, Aarhus University Hospital; Department of Orthopaedic Surgery, Section for Sports Traumatology, Bispebjerg and Frederiksberg Hospital; Department of Radiology, Aarhus University Hospital; Department of Clinical Epidemiology, Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital; Department of Orthopaedic Surgery, Herlev and Gentofte Hospital

Background: Persistent regional differences in revision rates after primary knee arthroplasty (KA) have given rise to speculations of whether surgical quality or patient selection differs between Danish regions. Previously, the SPARK-study has shown how preoperative patient-reported outcome measures (PROMs) were the same across three regions. Now, objective measures are presented as well.
Purpose / Aim of Study: The present study presents regional incidence of KA and compares radiological severity of knee osteoarthritis (OA) in KA patients across hospitals in three Danish regions.
Materials and Methods: As part of a prospective cohort study, two radiologists made blinded Ahlbäck (0-5) and Kellgren-Lawrence (K-L: 0-4) classifications on standing AP- radiographs of 1,051 patients scheduled for KA. Disagreements were settled in separate consensus rounds. Moreover, thirteen experienced knee arthroplasty surgeons made 17,214 head-to-head comparisons of radiographs resulting in a complete ranking of pictures by OA severity based on clinical experience free of classifications. From the National Patient Register, 2017-incidence of KA was extracted by the ICD10-code KNGB.
Findings / Results: Surgeons’ ranking and K-L score differed significantly between centers (overall P <0.001/=0.013). In one hospital known to have low revision rates (Aarhus), KA patients with K-L grade 0-2 were less common (12.7%) than in Aalborg/Farsoe (20.7%) and Gentofte (20.1%), overall P=0.028. Particularly K-L/Ahlbäck scores of 0-1 were more rare in Aarhus (2.1/24.9%) than elsewhere (7.6/38.0% and 5.9/34%, respectively), overall P=0.030/0.015. The incidence of KA in the whole Capital Region exceeded that of the Central Region of Denmark by 28 % (534 vs. 416 per 100.000 persons aged 60-79 years, P<0.001).
Conclusions: Variation in incidence of knee replacement and in radiological severity of OA prior to surgery suggests some regional differences in thresholds for primary knee replacement. This contradicts the uniformity of baseline PROMs recorded in the same population, and it may have an influence on regional revision rates.

9. Heuristic ranking delivers more detail than ordinal grading of knee osteoarthritis radiographs
Kristian Mongelard, Anne Mørup-Petersen, Lone Rømer, Karl Bang Christensen, Anders Odgaard
Dept. of Radiology, Copenhagen University Hospital Herlev-Gentofte; Dept. of Orthopaedics, Copenhagen University Hospital Herlev-Gentofte; Dept. of Radiology, Horsens Hospital; Dept. of Biostatistics, Copenhagen University; Dept. of Orthopaedics, Copenhagen University Hospital Herlev-Gentofte

Background: Ordinal scales (Kellgren-Lawrence (KL), Ahlbäck etc.) are used to express the severity of radiographic knee osteoarthritis (OA). With clinical experience, formal gradings are used selectively and more weight is placed on intuition and rules of thumb (heuristics). Advanced analytical methods allow ranking of observations based on two-by-two comparisons rather than assessing individual cases.
Purpose / Aim of Study: To quantify the details observed by clinicians when assessing knee OA radiographs, and to investigate morphological features that are part of the clinicians’ tacit knowledge and hence forms their heuristics.
Materials and Methods: 1087 knee OA radiographs were assessed in three ways. First, 13 knee arthroplasty surgeons performed 17,214 two-by-two comparisons: for each comparison, the surgeon selected the radiograph expected to cause more symptoms. Second, two radiologists individually graded the radiographs by the KL and Ahlbäck systems, and consensus was reached in cases of disagreement. Third, 20 morphological features, e.g. medial joint space narrowing or presence of metal, was judged in comparisons similar to the first step. A statistical model was formed, that calculated an OA strength and morphological feature strengths for each radiograph.
Findings / Results: The frequencies of KL grades were 0:0.6%, I:5.7%, II:13.3%, III:74.2%, IV:6.1%. The analytical OA strength ranged from 3.6E-7 to 3.8E2. The OA strength allowed a much more detailed distinction between radiographs than the classic grading systems. Seven classes could be defined, that with 95% certainty distinguished neighbouring classes. In contrast, there was a very large overlap between the classic gradings. Only 52% and 51% of KL and Ahlbäck gradings corresponded to the surgeons’ assessments. The analysis of morphological features revealed that both classic systems lacked important information.
Conclusions: It was demonstrated, that clinicians observe morphological features other than those, that are part of the classic grading systems, and that the features are considered when judging radiological OA strength. Surgeons make a clearer distinction between radiographs than the classic systems. Neither the KL nor the Ahlbäck system agrees well with surgeons’ assessments.

10. Knee Osteoarthritis: A comparison of Preoperative Radiographic Grading based on OARSI score and Its Correlation with Histopathological findings
Ahmed Salam N. Kurmasha, Daan Koppens, Jess Pilgaard, Torben Bæk Hansen
Orthopaedic Department, Holstebro Hospital; Orthopaedic Department, Holstebro Hospital; Pathology Department, Holstebro Hospital; Orthopaedic Department, Holstebro Hospital

Background: Medial unicompartmental knee arthroplasty (UKA) has been used to treat patients with medial osteoarthritis (OA) of the knee in many years with excellent clinical outcome. Histopathological grading is accurate, though impractical in a clinical situation. The OARSI score for OA is applied both to assess the grade of radiological OA from grade 0 to 3 in addition to assess the stage of OA based on the extent of joint involvement from 0 to 4.
Purpose / Aim of Study: To evaluate the correlation between the radiographical assessment and histopathological degree of OA of the tibial condyle based on OARSI score in patients undergoing medial UKA.
Materials and Methods: 57 patients with medial OA undergoing a UKA were selected, all patients provided written informed consent. Weight-bearing radiographs were obtained before surgery. At surgery, the tibial plateau was resected and placed in 4% neutral buffered formalin. Femoral and tibial osteophytes and joint space narrowing (JSN) in the medial compartment will be scored using the radiographic OARSI criteria. A summary score will be determined. Regression analyses is applied to evaluate the correlation. Histopathological grading is done according to OARSI grading. The histopathological OARSI score is obtained as grade X stage. In the abstract, the grade is presented, at the time of conference grade X stage will be presented.
Findings / Results: The mean radiographic summary score was 5.3 (range 2 – 9) and the mean grade for histopathology was 3.8 (range 2 – 4). Regression analysis showed no association between radiographic and histopathologic grading of OA, R2 = 0.1
Conclusions: We found no correlation between radiographical OA and histopathological grade of OA of the medial compartment of the knee. This might be due to selection bias as only patients with severe OA who were eligible for UKA were included. Histopathological grade X stage will be presented at the time of conference as it could provide further details and higher correlation value.