Good validity in the Norwegian Knee Ligament Register: assessment of data quality for key variables in primary and revision cruciate ligament reconstructions from 2004 to 2013

Background: The Norwegian Knee Ligament Register was founded in 2004 to provide representative and reliable data on cruciate ligament surgery. The aim of this study was to evaluate the validity of key variables in the Norwegian Knee Ligament Register to reveal and prevent systematic errors or incompleteness, which can lead to biased reports and study conclusions. Method: We included a stratified cluster sample of 83 patients that had undergone both primary and revision anterior cruciate ligament surgery. A total of 166 medical records were reviewed and compared with their corresponding data in the database of the Norwegian Knee Ligament Register. We assessed the validity of a selection of key variables using medical records as a reference standard to compute the positive predictive values of the register data for the variables. Results: The positive predictive values for the variables of primary and revision surgery ranged from 92 to 100% and from 39 to 100% with a mean positive predictive value of 99% and 88% respectively. Data on intraoperative findings and surgical details had high positive predictive values, ranging from 91 to 100% for both primary and revision surgery. The positive predictive value for the variable “date of injury” was 92% for primary surgeries but only 39% for revision surgeries. The positive predictive value for “activity at the time of injury” was 99% for primary surgeries and 52% for revisions. Conclusion: Overall, the data quality of the key variables examined in the Norwegian Knee Ligament Register was high, making the register a valid source for research.publishedVersio

The Long-Term Risk of Knee Arthroplasty in Patients with Arthroscopically Verified Focal Cartilage Lesions: A Linkage Study with the Norwegian Arthroplasty Register, 1999 to 2020

Background: Focal cartilage lesions are common in the knee. The risk of later ipsilateral knee arthroplasty remains unknown. The purposes of the present study were to evaluate the long-term cumulative risk of knee arthroplasty after arthroscopic identification of focal cartilage lesions in the knee, to investigate the risk factors for subsequent knee arthroplasty, and to estimate the subsequent cumulative risk of knee arthroplasty compared with that in the general population. Methods: Patients who had undergone surgical treatment of focal cartilage lesions at 6 major Norwegian hospitals between 1999 and 2012 were identified. The inclusion criteria were an arthroscopically classified focal cartilage lesion in the knee, an age of ≥18 years at the time of surgery, and available preoperative patient-reported outcomes (PROMs). The exclusion criteria were osteoarthritis or “kissing lesions” at the time of surgery. Demographic data, later knee surgery, and PROMs were collected with use of a questionnaire. A Cox regression model was used to adjust for and investigate the impact of risk factors, and Kaplan-Meier analysis was performed to estimate cumulative risk. The risk of knee arthroplasty in the present cohort was compared with that in the age-matched general Norwegian population. Results: Of the 516 patients who were eligible, 322 patients (328 knees) consented to participate. The mean age at the time of the index procedure was 36.8 years, and the mean duration of follow-up was 19.8 years. The 20-year cumulative risk of knee arthroplasty in the cartilage cohort was 19.1% (95% CI, 14.6% to 23.6%). Variables that had an impact on the risk of knee arthroplasty included an ICRS grade of 3 to 4 (hazard ratio [HR], 3.1; 95% CI, 1.1 to 8.7), an age of ≥40 years at time of cartilage surgery (HR, 3.7; 95% CI, 1.8 to 7.7), a BMI of 25 to 29 kg/m2 (HR, 3.9; 95% CI, 1.7 to 9.0), a BMI of ≥30 kg/m2 (HR, 5.9; 95% CI, 2.4 to 14.3) at the time of follow-up, autologous chondrocyte implantation (ACI) at the time of the index procedure (HR, 3.4; 95% CI, 1.0 to 11.4), >1 focal cartilage lesion (HR, 2.1; 95% CI, 1.1 to 3.7), and a high preoperative visual analog scale (VAS) score for pain at the time of the index procedure (HR, 1.1; 95% CI, 1.0 to 1.1). The risk ratio of later knee arthroplasty in the cartilage cohort as compared with the age-matched general Norwegian population was 415.7 (95% CI, 168.8 to 1,023.5) in the 30 to 39-year age group. Conclusions: In the present study, we found that the 20-year cumulative risk of knee arthroplasty after a focal cartilage lesion in the knee was 19%. Deep lesions, higher age at the time of cartilage surgery, high BMI at the time of follow-up, ACI, and >1 cartilage lesion were associated with a higher risk of knee arthroplasty.publishedVersio

Risk Factors for Jumper’s Knee

Background: The prevalence of jumper’s knee is high in sports characterized by high demands on leg extensor speed and power, such as volleyball, basketball, football and athletics. A prevalence up to 50% has been reported among male, elite volleyball players. The complex process from a healthy tendon to jumper’s knee is not fully understood. Jumper’s knee is usually described as an overuse injury, although previous studies on risk factors are not conclusive. Previous cross-sectional studies among volleyball players have found that athletes with jumper’s knee have higher body mass compared to asymptomatic controls, suggesting a relationship between body composition and jumper’s knee. The “jumper’s knee paradox”, where symptomatic athletes appear to perform better in a counter movement jump (CMJ) compared to asymptomatic controls, is not fully understood. Tendons adapt to mechanical loading, albeit not always adequately. Tendon structural changes from childhood to adulthood are not well investigated, and there is a need for prospective studies examining the response to intensive training during adolescence. In many athletes with symptoms of jumper’s knee, ultrasound or MRI imaging of the painful tendons will reveal morphological abnormalities, typically as localized tendon thickening with hypoechoic areas and increased vascularity. However, it is not clear whether the presence of ultrasound changes in asymptomatic tendons precede (and predict) future tendon problems. Aims: First, we wanted to study whether training load and competition load as well as body composition or change of body composition represented a risk factor for developing jumper’s knee (Paper I). Furthermore, we wanted to investigate jumping ability and change of jumping ability as potential risk factors for developing jumper’s knee (Paper II). We also wanted to investigate the relationship between the development of ultrasound changes in the patellar and quadriceps tendons and symptoms of jumper’s knee, as well as the medium-term effects of intensive training on tendon thickness among adolescent athletes (Paper III). Methods: Papers I-III were based on a prospective cohort study with a total data collection period of 5 years. All participants were recruited from the same cohort, players entering the Toppvolley Norway (TVN) program, but the time and duration of inclusion differed between participants. TVN is located in Sand, Norway and combines an elite volleyball training program with a three-year senior high boarding school program. All students at TVN were eligible for this study. In Paper I & II only athletes without jumper’s knee at baseline were included, while Paper III also included athletes with pre-existing jumper’s knee. The diagnosis of jumper’s knee was based on a clinical examination alone. All athletes were examined twice a year. Training volume and match exposure were recorded prospectively on a weekly basis. Body composition was assessed by measuring height and weight, waist circumference and through skin fold caliper tests. Jumping ability was tested on a portable force plate and included two different jumps (CMJ and standing jump (SJ)). An ultrasound examination was done twice a year as long as students remained at TVN using greyscale and color Doppler. Main results: Altogether, 192 students were registered in the school record at TVN during the 5-year study period. Nearly one in three boys developed jumper’s knee during their time at TVN (32%) compared to only 8% of the girls (Paper I). Paper I: Athletes developing jumper’s knee had higher total training volume and tendon load compared to those who remained asymptomatic. A multivariate regression analysis showed that match exposure was the strongest sports-related predictor for developing jumper’s knee with an OR of 3.88 (95% CI 1.80 to 8.40) for every extra set played per week. Volleyball training had an OR 1.72, (95% CI 1.18 to 2.53) when combined with match exposure and gender. We did not detect any significant differences in body composition at the time of inclusion or change of body composition during the study period between players who developed jumper's knee and those who did not developed jumper’s knee. Males had three to four times higher risk of developing jumper’s knee compared to females, independent on training and match exposure in the multivariate regression analysis. Paper II: At the time of inclusion, male athletes who went on to develop jumper’s knee had significantly better results in CMJ (38.0±5.8 cm) compared to asymptomatic males (34.6±5.5 cm, p=0.03), while no difference was detected in SJ. In a multivariate logistic regression analysis corrected for gender and previous volleyball training, the OR was 2.09 (1.03 to 4.25) per cm difference in CMJ at the time of inclusion. Our results did not reveal any significant differences in the change in jumping ability between the groups, although both groups improved their jumping performance. Paper III: About half of the asymptomatic athletes who went on to develop jumper’s knee (17 of 35 tendons) had hypoechoic areas when they started at TVN, while 10% of the tendons that remained asymptomatic (24 of 238 tendons) had the same changes. Neovascularisation was found in 4% (9 of 238 tendons) of asymptomatic tendons and in 48% (15 of 35 tendons) of those who later developed jumper’s knee. In a multivariate logistic regression analysis, a baseline finding of a hypoechoic tendon area (OR 3.3, 95% CI 1.1 to 9.2) and neovascularisation (OR 2.7, 95% CI 1.1 to 6.5) increased the risk of developing jumper’s knee. Patellar tendon thickness among healthy athletes did not change (Wilk’s lambda, p=0.07) while quadriceps tendon thickness increased (p=0.001). The athletes reported a VISA score of 72 (SD 23) when first diagnosed, and knee function did not change during subsequent examinations and was 73 (SD 21) when they left TVN. Conclusion: A high volume of volleyball training and match exposure were important risk factors for developing jumper’s knee. Body composition or change in body composition were not associated with injury risk. Volleyball players with a natural ability for jumping high have an increased risk of developing jumper’s knee, while change in jumping ability was not identified as a risk factor. Hypoechoic areas and neovascularisation at baseline were risk factors for developing jumper’s knee. Quadriceps tendon thickness increased 7-11% among healthy athletes, while there was no change in patellar tendon thickness

Jumper's knee paradox—jumping ability is a risk factor for developing jumper's knee: A 5-year prospective study

Background The ‘jumper's knee paradox’, where symptomatic athletes appear to perform better in a counter movement jump (CMJ) compared to asymptomatic controls in previous case–control studies is not fully understood. Aim The aim was to examine the relationship between jumping ability and change of jumping ability as potential risk factors for developing jumper's knee. Methods A 5-year prospective cohort study among elite volleyball players, aged 16–18. Jump tests were done on a portable force plate at the time of inclusion and semiannually. Jumper's knee was diagnosed based on a standardised clinical examination. Results All 150 students (68 males and 82 females) were included and 28 developed jumper's knee (22 males and 6 females). At the time of inclusion, male athletes who went on to develop jumper's knee had significantly better results in CMJ (38.0±5.8 cm) compared to asymptomatic males (34.6±5.5 cm, p=0.03), while no difference was detected in standing jump (SJ: jumper's knee: 30.3±7.4 cm, asymptomatic: 28.1±6.1 cm, p=0.23). In a multivariate logistic regression analysis corrected for gender and previous volleyball training, the OR was 2.09 (1.03–4.25) per cm difference in CMJ at the time of inclusion. Our results did not reveal any significant differences in the change in jumping ability between the groups, although both groups improved their jump performance. Conclusions Volleyball players with a natural ability for jumping high are at an increased risk for developing jumper's knee

Genetic variation in candidate genes and patellar tendinopathy: Prospective cohort study of 126 elite volleyball players

Variation in genes coding for structural proteins may represent risk factors for developing tendinopathy among athletes. The purpose of this prospective cohort study of elite volleyball students was to investigate whether specific single nucleotide variants (SNVs) in selected candidate genes, known to be associated with Achilles tendinopathy, were associated with the risk for developing patellar tendinopathy (jumper′s knee). Of 126 Caucasian athletes (64 females and 62 males), 33 cases (athletes developing jumper′s knee) were compared to 93 healthy controls. Six SNVs, distributed in the candidate genes COL1A1, COL5A1, MMP3, and GDF3, were genotyped. Baseline characteristics, genotypes, and minor allele frequencies (MAF) were compared between groups. Neither genotype nor minor allele frequencies differed significantly between the jumper′s knee group and the healthy controls. However, the low‐frequency homozygous T/T genotype of the COL1A1 gene (rs1800012) was absent in the jumper′s knee group (P = .075). Separating the two study groups by gender suggested that there may be a female‐specific genotype pattern, although the sample was too small for statistical calculations. In this study, although limited by sample size, we could not detect any clear relationship between six selected SNVs located in candidate genes and the risk for the development of jumper′s knee in elite volleyball students

Good validity in the Norwegian Knee Ligament Register: assessment of data quality for key variables in primary and revision cruciate ligament reconstructions from 2004 to 2013

Background: The Norwegian Knee Ligament Register was founded in 2004 to provide representative and reliable data on cruciate ligament surgery. The aim of this study was to evaluate the validity of key variables in the Norwegian Knee Ligament Register to reveal and prevent systematic errors or incompleteness, which can lead to biased reports and study conclusions. Method: We included a stratified cluster sample of 83 patients that had undergone both primary and revision anterior cruciate ligament surgery. A total of 166 medical records were reviewed and compared with their corresponding data in the database of the Norwegian Knee Ligament Register. We assessed the validity of a selection of key variables using medical records as a reference standard to compute the positive predictive values of the register data for the variables. Results: The positive predictive values for the variables of primary and revision surgery ranged from 92 to 100% and from 39 to 100% with a mean positive predictive value of 99% and 88% respectively. Data on intraoperative findings and surgical details had high positive predictive values, ranging from 91 to 100% for both primary and revision surgery. The positive predictive value for the variable “date of injury” was 92% for primary surgeries but only 39% for revision surgeries. The positive predictive value for “activity at the time of injury” was 99% for primary surgeries and 52% for revisions. Conclusion: Overall, the data quality of the key variables examined in the Norwegian Knee Ligament Register was high, making the register a valid source for research

Good validity in the Norwegian Knee Ligament Register: Assessment of data quality for key variables in primary and revision cruciate ligament reconstructions from 2004 to 2013

Background: The Norwegian Knee Ligament Register was founded in 2004 to provide representative and reliable data on cruciate ligament surgery. The aim of this study was to evaluate the validity of key variables in the Norwegian Knee Ligament Register to reveal and prevent systematic errors or incompleteness, which can lead to biased reports and study conclusions. Method: We included a stratified cluster sample of 83 patients that had undergone both primary and revision anterior cruciate ligament surgery. A total of 166 medical records were reviewed and compared with their corresponding data in the database of the Norwegian Knee Ligament Register. We assessed the validity of a selection of key variables using medical records as a reference standard to compute the positive predictive values of the register data for the variables. Results: The positive predictive values for the variables of primary and revision surgery ranged from 92 to 100% and from 39 to 100% with a mean positive predictive value of 99% and 88% respectively. Data on intraoperative findings and surgical details had high positive predictive values, ranging from 91 to 100% for both primary and revision surgery. The positive predictive value for the variable “date of injury” was 92% for primary surgeries but only 39% for revision surgeries. The positive predictive value for “activity at the time of injury” was 99% for primary surgeries and 52% for revisions. Conclusion: Overall, the data quality of the key variables examined in the Norwegian Knee Ligament Register was high, making the register a valid source for research

ACL Reconstruction Patients Have Increased Risk of Knee Arthroplasty at 15 Years of Follow-up : Data from the Norwegian Knee Ligament Register and the Norwegian Arthroplasty Register from 2004 to 2020

Background: Anterior cruciate ligament (ACL) injury is considered a risk factor for osteoarthritis. The primary aim of the present study was to investigate the cumulative risk of, and risk factors associated with, a subsequent knee arthroplasty after an ACL reconstruction at up to 15 years of follow-up. The secondary aim was to compare the relative risk of knee arthroplasty after ACL reconstruction compared with that in the general population. Methods: Data were analyzed by combining data from 2 national registries, the Norwegian Knee Ligament Register and the Norwegian Arthroplasty Register. The cumulative risk of knee arthroplasty after undergoing ACL reconstruction was calculated as 1 minus the corresponding Kaplan-Meier estimate, and possible risk factors for knee arthroplasty after ACL reconstruction were assessed in a Cox regression model with hazard ratios (HRs) as estimated effect measurements. The relative risk of knee arthroplasty for patients managed with ACL reconstruction as compared with that in the general population was calculated in stratified age groups. Results: From the study population of 27,122 knees, 115 knees underwent knee arthroplasty. We found a 1.1% (95% confidence interval [CI], 0.9 to 1.4) cumulative risk of knee arthroplasty 15 years after ACL reconstruction. Deep cartilage injury, ICRS (International Cartilage Repair Society) grade 3 to 4 (HR, 4.8; 95% CI, 3.1 to 7.6), revision of the ACL (HR, 3.9; 95% CI, 2.2 to 7.1), and a 2-year postoperative KOOS Sport/Recreation subscore of <44 (HR, 3.1; 95% CI, 1.5 to 6.2) were important risk factors for knee arthroplasty. We found a higher risk of knee arthroplasty at the age of 30 to 39 years after a previous ACL reconstruction as compared with the general population (relative risk, 3.3; 95% CI, 1.6 to 6.7). Conclusions: Fifteen years after an ACL reconstruction, the overall cumulative risk of knee arthroplasty was 1.1%. Cartilage injury at the time of ACL reconstruction, revision ACL reconstruction, and a KOOS Sport/Recreation subscore of <44 (at 2 years postoperatively) were major risk factors for subsequent knee arthroplasty. We found a 3.3-times higher risk of knee arthroplasty at the age of 30 to 39 years after a previous ACL reconstruction as compared with that in the general population.publishedVersio

Predicting subjective failure of ACL reconstruction: A machine learning analysis of the Norwegian Knee Ligament Register and patient reported outcomes

Objectives: Accurate prediction of outcome following anterior cruciate ligament (ACL) reconstruction is challenging, and machine learning has the potential to improve our predictive capability. The purpose of this study was to determine if machine learning analysis of the Norwegian Knee Ligament Register (NKLR) can (1) identify the most important risk factors associated with subjective failure of ACL reconstruction and (2) develop a clinically meaningful calculator for predicting the probability of subjective failure following ACL reconstruction. Methods: Machine learning analysis was performed on the NKLR. All patients with 2-year follow-up data were included. The primary outcome was the probability of subjective failure 2 years following primary surgery, defined as a Knee Injury and Osteoarthritis Outcome Score (KOOS) Quality of Life (QoL) subscale score of <44. Data were split randomly into training (75%) and test (25%) sets. Four models intended for this type of data were tested: Lasso logistic regression, random forest, generalized additive model (GAM), and gradient boosted regression (GBM). These four models represent a range of approaches to statistical details like variable selection and model complexity. Model performance was assessed by calculating calibration and area under the curve (AUC). Results: Of the 20,818 patients who met the inclusion criteria, 11,630 (56%) completed the 2-year follow-up KOOS QoL questionnaire. Of those with complete KOOS data, 22% reported subjective failure. The lasso logistic regression, GBM, and GAM all demonstrated AUC in the moderate range (0.67–0.68), with the GAM performing best (0.68; 95% CI 0.64–0.71). Lasso logistic regression, GBM, and the GAM were well-calibrated, while the random forest showed evidence of mis-calibration. The GAM was selected to create an in-clinic calculator to predict subjective failure risk at a patient-specific level (https://swastvedt.shinyapps.io/calculator_koosqol/). Conclusion: Machine learning analysis of the NKLR can predict subjective failure risk following ACL reconstruction with fair accuracy. This algorithm supports the creation of an easy-to-use in-clinic calculator for point-of-care risk stratification. Clinicians can use this calculator to estimate subjective failure risk at a patient-specific level when discussing outcome expectations preoperatively. Level of evidence: Level-III Retrospective review of a prospective national register