Sören Toksvig-Larsen

Knee injury and Osteoarthritis Outcome Score (KOOS) - validation and comparison to the WOMAC in total knee replacement

BackgroundThe Knee injury and Osteoarthritis Outcome Score (KOOS) is an extension of the Western Ontario and McMaster Universities Osteoarthrtis Index (WOMAC), the most commonly used outcome instrument for assessment of patient-relevant treatment effects in osteoarthritis. KOOS was developed for younger and/or more active patients with knee injury and knee osteoarthritis and has in previous studies on these groups been the more responsive instrument compared to the WOMAC. Some patients eligible for total knee replacement have expectations of more demanding physical functions than required for daily living. This encouraged us to study the use of the Knee injury and Osteoarthritis Outcome Score (KOOS) to assess the outcome of total knee replacement.MethodsWe studied the test-retest reliability, validity and responsiveness of the Swedish version LK 1.0 of the KOOS when used to prospectively evaluate the outcome of 105 patients (mean age 71.3, 66 women) after total knee replacement. The follow-up rates at 6 and 12 months were 92% and 86%, respectively.ResultsThe intraclass correlation coefficients were over 0.75 for all subscales indicating sufficient test-retest reliability. Bland-Altman plots confirmed this finding. Over 90% of the patients regarded improvement in the subscales Pain, Symptoms, Activities of Daily Living, and knee-related Quality of Life to be extremely or very important when deciding to have their knee operated on indicating good content validity. The correlations found in comparison to the SF-36 indicated the KOOS measured expected constructs. The most responsive subscale was knee-related Quality of Life. The effect sizes of the five KOOS subscales at 12 months ranged from 1.08 to 3.54 and for the WOMAC from 1.65 to 2.56.ConclusionThe Knee injury and Osteoarthritis Outcome Score (KOOS) is a valid, reliable, and responsive outcome measure in total joint replacement. In comparison to the WOMAC, the KOOS improved validity and may be at least as responsive as the WOMAC.

Validation of a functional method for the estimation of hip joint centre location

The present study assesses the accuracy with which the subject specific coordinates of the hip joint centre (HJC) in a pelvic anatomical frame can be estimated using different methods. The functional method was applied by calculating the centre of the best sphere described by the trajectory of markers placed on the thigh during several trials of hip rotations. Different prediction methods, proposed in the literature and in the present investigation, which estimate the HJC of adult subjects using regression equations and anthropometric measurements, were also assessed. The accuracy of each of the above-mentioned methods was investigated by comparing their predictions with measurements obtained on a sample of 11 male adult able-bodied volunteers using roentgen stereophotogrammetric analysis (RSA), assumed to provide the true HJC locations. Prediction methods estimated the HJC location at an average rms distance of 25-30 mm. The functional method performed significantly better and estimated HJCs within a rms distance of 13 mm on average. This result may be confidently generalised if the photogrammetric experiment is carefully conducted and an optimal analytical approach used. The method is therefore suggested for use in motion analysis when the subjects hip range of motion is not limited. In addition, the facts that it is not an invasive technique and that it has relatively small and un-biased errors, make it suitable for regression equations identification with no limit to sample size and population typology.

Knee arthroplasty: are patients' expectations fulfilled?: A prospective study of pain and function in 102 patients with 5-year follow-up

Background and purpose With an aging population expecting an active life after retirement, patients’ expectations of improvement after surgery are also increasing. We analyzed the relationship between preoperative expectations and postoperative satisfaction and self-reported outcomes with regard to pain and physical function after knee arthroplasty. Patients and methods 102 patients (39 men) with knee osteoarthritis and who were assigned for TKR (mean age 71 (51–86) years) were investigated with KOOS, SF-36, and additional questions concerning physical activity level, expectations, satisfaction, and relevance of the outcome to the patient. These investigations took place preoperatively and postoperatively after 6 months, 1 year, and 5 years of follow-up. Results Response rate at 5 years was 86%. In general, the patients’ preoperative expectations were higher than their postoperative ability. For example, 41% expected to be able to perform activities such as golfing and dancing while only 14% were capable of these activities at 5 years. Having high or low preoperative expectations with regard to walking ability or leisure-time activities had no influence on the KOOS scores postoperatively. 93% of the patients were generally satisfied 5 years postoperatively, while 87% were satisfied with the relief of pain and 80% with their improvement in physical function at that time. Interpretation With an expanding population of mentally alert elderly, we can expect that great demands will be put on joint replacements. This study shows that patients have high preoperative expectations concerning reduction of pain. To a considerable extent, these expectations are fulfilled after one year. Expectations concerning demanding physical activities are not fulfilled to the same degree; however, most patients reported general satisfaction with the outcome indicating that satisfaction is not equivalent to fulfilled expectations. Preoperative counseling should include realistic information on outcomes concerning physical function and pain relief.

Open-wedge osteotomy by hemicallotasis or the closed-wedge technique for osteoarthritis of the knee: A RANDOMISED STUDY OF 50 OPERATIONS

We describe the results of 50 operations carried out on 46 patients with medial osteoarthritis of the knee of Ahlbäck grade 1 to 3. Patients were randomised either to a closed-wedge high tibial osteotomy (HTO) or an open-wedge procedure based on the hemicallotasis technique (HCO). Their median age was 55 years (38 to 68). The preoperative median hip-knee-ankle (HKA) angle was 171 degrees (164 to 176) in the HTO group and 173 degrees (165 to 179) in the HCO group. After six weeks, the median HKA angle was 185 degrees (176 to 194) in the HTO group and 184 degrees (181 to 188) in the HCO group. In the HTO group, seven patients were within the range of 182 degrees to 186 degrees compared with 21 in the HCO group (p < 0.001). One year later, ten HTO patients were within this range while the HKA angulation in the HCO group was unchanged. At two years the numbers were 11 and 18, respectively. We evaluated the clinical results on the Hospital for Special Surgery, Lysholm and Wallgren-Tegner activity scores, and patients completed part of the Nottingham Health Profile questionnaire. An impartial observer at the two-year follow-up concluded that all scores had improved, but found no clinical differences between the groups.

Clodronate prevents prosthetic migration: A randomized radiostereometric study of 50 total knee patients

In a double-blind study, we randomized 50 patients to receive peroral clodronate medication or placebo from 3 weeks before until 6 months after a total knee replacement with a cemented NexGen implant. Migration of the tibial components was measured by radiostereometry at 1 year. Clodronate reduced prosthetic migration, as measured by maximum total point motion, from 0.40 mm to 0.29 mm (p = 0.01). This confirms that the early postoperative migration is related to bone resorption and thus the biology of the bone bed. Since early migration is related to late loosening, 6 months of clodronate medication might reduce the risk of loosening.

Cement interface temperature in hip arthroplasty

The temperature was measured using thermocouples in the bone-cement interface during cement curing in 30 total hip replacement operations. A modern technique was used, including lavage and precooled vacuum-mixed cement. The mean maximum temperature in the acetabulum was 43 (38-52) degrees C and in the femur 40 (29-56) degrees C. The use of a precooled femoral prosthesis did not affect the peak temperature.

A 5 year prospective study of patient-relevant outcomes after total knee replacement

OBJECTIVE To prospectively describe self-reported outcomes up to 5 years after total knee replacement (TKR) in Osteoarthritis (OA) and to study which patient-relevant factors may predict outcomes for pain and physical function (PF). METHODS 102 consecutive patients with knee OA, 63 women and 39 men, mean age 71 (51-86) assigned for TKR at the Department of Orthopaedics at Lund University Hospital were included in the study. The self-administered questionnaires Knee injury and Osteoarthritis Outcome Score (KOOS) and SF-36 were mailed preoperatively and 6 months, 12 months and at 5 years postoperatively. RESULTS Response rate at 5 years was 86%. At 6 months significant improvement was seen in all KOOS and SF-36 scores (P<0.001). The percentage of patients performing more demanding functions related to sports and recreation increased postoperatively. The best postoperative result was reported at the 1 year follow-up. Compared to the 1 year follow-up, a significant (P<or=0.01) decline was seen at 5 years in the KOOS subscale activity of daily living (ADL) function (82-73) and the SF-36 subscale bodily pain (72-63), PF (61-51) and vitality (69-59). Patients who scored in the lowest quartile preoperatively in the KOOS subscales pain and ADL made the greatest improvements to 1 year (18-82, 22-80) but also declined the most from 12 months to 5 years (82-72, 80-66). Being 10 years older pre-operatively predicted 5-7 points worse scores in KOOS pain and KOOS symptoms at 1 and 5 years. When adjusted for age, sex and comorbid conditions, pre-operative SF-36 scores did not predict postoperative KOOS pain or PF scores. CONCLUSION Compared to preoperatively, a significant improvement was still seen 5 years postoperatively. However, the best result was reported at 1 year, indicating a decline from 1 to 5 years after TKR. To fully evaluate the results of TKR with regard to pain and PF, follow-ups longer than 2 years are needed, and items of more demanding PFs should be included. Older age to some extent predicted more postoperative pain and other symptoms, however, no predictors of postoperative PF were found, indicating the difficulty of determining preoperatively who will benefit more or less from the procedure.

Fixation Strength and Pin Tract Infection of Hydroxyapatite-coated Tapered Pins

In a multicenter, prospective, randomized study, the biomechanical and clinical properties of the bone-pin interface were compared with standard tapered pins and hydroxyapatite-coated tapered pins implanted in patients who underwent femoral and tibial external fixation treatments. The results showed that the hydroxyapatite-coated tapered pins are clinically effective in improving the strength of fixation of the bone-pin interface. This improvement corresponded to a lower rate of pin tract infection. In the hydroxyapatite-coated pin group, there were no differences in strength of fixation between the pins removed from the infected and uninfected pin tracts. In this pin group, the mean pin extraction torque was 531 ± 225 Ncm in the infected pin tracts and 508 ± 233 Ncm in the uninfected pin tracts. In the standard pin group, the mean pin extraction torque was 73 ± 142 Ncm in the infected pin tracts and 211 ± 216 Ncm in the uninfected pin tracts. The advantages provided by the hydroxyapatite-coated pins were higher in cancellous bone than in cortical bone.

A Comparison of Hydroxyapatite-Coated, Titanium-Coated, and Uncoated Tapered External-Fixation Pins. An in Vivo Study in Sheep*

Three types of surfaces for external fixation pins were compared. One hundred and eight stainless-steel tapered 5/6-millimeter pins were divided into three groups: thirty-six pins remained uncoated (Group A), thirty-six were plasma-sprayed with hydroxyapatite (Group B), and thirty-six were plasma-sprayed with titanium (Group C). The pins were implanted in the left tibia of eighteen sheep, with each sheep receiving six pins from the same group. A unilateral fixator then was assembled on the pins. The medial aspect of the mid-part of the tibial diaphysis was exposed, and a five-millimeter-long cylinder of bone was removed so that load would be borne by the bone-pin interfaces. Six weeks after the procedure, radiographs demonstrated rarefaction of twenty-nine pin tracks in Group A, fifteen in Group B, and thirty in Group C (p = 0.021 for Group A compared with Group B and p = 0.016 for Group B compared with Group C). The mean final insertion torque (and standard deviation) was 4360 ± 1050 newton-millimeters in Group A, 3420 ± 676 newton-millimeters in Group B, and 3740 ± 643 newton-millimeters in Group C. With the numbers available, no significant differences could be detected among these values. The mean extraction torque was 253 ± 175 newton-millimeters in Group A, 3360 ± 1260 newton-millimeters in Group B, and 1720 ± 1030 newton-millimeters in Group C (p = 0.002 for Group A compared with Group B, p = 0.017 for Group A compared with Group C, and p = 0.03 for Group B compared with Group C). The extraction torque was significantly lower than the corresponding insertion torque in both Group A (p < 0.001) and Group C (p = 0.003); no significant difference could be found, with the numbers available, in Group B (hydroxyapatite-coated pins). At sixty times magnification, direct contact was seen along a mean of 16 ± 9 per cent of the bone-pin interface in Group A, 30 ± 12 per cent of the interface in Group B, and 28 ± 15 per cent of the interface in Group C (p = 0.042 for Group A compared with Group C). However, at 10,000 times magnification, direct bone-pin contact was found only in Group B. CLINICAL RELEVANCE: The better fixation and greater interface strength of the hydroxyapatite-coated tapered pins should lead to a substantial decrease in the frequency of loosening and infection and consequently to a remarkable improvement in the clinical results of external fixation.

Digital automated RSA compared to manually operated RSA

The accuracy of digital Roentgen stereophotogrammetric analysis (RSA) was compared to the accuracy of a manually operated RSA system. For this purpose, we used radiographs of a phantom and radiographs of patients. The radiographs of the patients consisted of double examinations of 12 patients that had a tibial osteotomy and of double examinations of 12 patients that received a total hip prosthesis. First, the radiographs were measured manually with an accurate measurement table. Subsequently, the images were digitized by a film scanner at 150 DPI and 300 DPI resolutions and analyzed with the RSA-CMS software. In the phantom experiment, the manually operated system produced significantly better results than the digital system, although the maximum difference between the median values of the manually operated system and the digital system was as low as 0.013mm for translations and 0.033 degrees for rotations. In the radiographs of the patients, the manually operated system and the digital system produced equally accurate results: no significant differences in translations and rotations were found. We conclude that digital RSA is an accurate, fast, and user friendly alternative for manually operated RSA. Currently, digital RSA systems are being used in a growing number of clinical RSA-studies.