Danish Knee Ligament Reconstruction Registry Research Articles

Delaying anterior cruciate ligament reconstruction for more than 3 or 6 months results in lower risk of revision surgery

BackgroundThe objective of this study is to investigate the risk of revision surgery when delaying anterior cruciate ligament reconstruction (ACLR) past 3 months or 6 months after injury.Materials and methodsA total of 30,280 patients with isolated ACLR were identified in the Danish Knee Ligament Reconstruction Registry and divided into four groups; ACLR < 3 months, > 3 months, < 6 months, or > 6 months after injury. Primary outcome was revision surgery and secondary outcome were objective and subjective clinical outcome. The 2 year relative risk, crude, and adjusted hazard ratio (HR) were calculated.ResultsComparing ACLR < 3 months to ACLR > 3 months of injury the 2 year relative risk of revision surgery was found to be 1.81 (95% CI 1.46–2.23; P < 0.001) with an adjusted hazard ratio (HR) of 1.27 (95% CI 1.12–1.44; P < 0.001). Comparing ACLR < 6 months to ACLR > 6 months of injury the 2 year relative risk of revision surgery was found to be 1.61 (95% CI 1.34–1.92; P < 0.001) with an adjusted HR of 1.27 (95% CI 1.15–1.40; P < 0.001).ConclusionThe risk of revision ACLR surgery was found to be increased when ACLR was performed within 3 months or 6 months of injury compared with later surgery. The 1 year postoperative objective knee laxity and the subjective patient-related outcome was found to be without a clinically significant difference; however, those with early ACLR (< 3 months or < 6 months) were found to have a higher activity level 1 year postoperatively. The information about increased risk of revision when having early surgery should be informed to patients when deciding timing of ACLR treatment.Level of evidence: II.

Single- or two-stage revision after failed ACL reconstruction: No differences in re-revision rates and clinical outcomes.

The surgeons' choice of a single-stage or a two-stage procedure in revision anterior cruciate ligament reconstruction (ACLr) is based on the possibility of reuse of the tibia and femoral bone tunnels after primary ACLr. The purpose of this study was to compare failure rates and clinical outcomes following single-stage and two-stage ACL revisions in a cohort of patients from The Danish Knee Ligament Reconstruction Registry. Patients identified from 2005 to 2022 with ACL revision and met the following criteria: minimum 2-year follow-up, isolated ACL revision and registered single- or two-stage ACL revision. The primary outcome was ACL re-revision rate. Secondary outcomes were arthrometer sagittal knee laxity (side-to-side difference) and pivot shift (rotational stability difference) evaluated at 1-year follow up. One thousand five hundred seventy-four ACL revisions were included in the study (1331 = single-stage and 243 = two stage). Baseline characteristics showed no difference in relation to age, gender, knee laxity, pivot shift, meniscus injury, cartilage damage or injury mechanism between the two groups. Significant differences were found in relation to the type of graft. No statistical difference in 2-years revision rates between single-stage group 2.79 (95% CI 2.03-3.84) and two-stage group 2.93 (95% CI 1.41-6.05) was found. No significant difference was seen in knee laxity and pivot shift between stage-groups at 1-year follow up. Both groups demonstrated significant improvements in knee stability from baseline to 1-year follow-up. The present study found that ACL revision outcomes were similar in terms of rerevision rates and knee laxity for patients managed with a single- or a two-stage surgical strategy. Level III.

Adjustable-loop implants are non-inferior to fixed-loop implants for femoral fixation in anterior cruciate ligament reconstruction.

Button implants with an adjustable-loop device (ALD) are often used in anterior cruciate ligament reconstruction (ACLR). Clinical research comparing ALDs with fixed-loop devices (FLD) has mainly been conducted in small patient populations with short follow-up times. To determine whether ALDs are safe to use in ACLR, a non-inferiority study with a large sample population and a long follow-up period would be beneficial. This study compared ALDs with FLDs to determine non-inferior revision surgery rates, knee stability, and patient-reported outcomes (PROM) in ACLRs. This non-inferiority register-based cohort study was conducted using data from the Danish Knee Ligament Reconstruction Registry (DKRR). A total of 12,723 patients > 15years of age with primary ACLR using hamstring tendon autografts and either an FLD or ALD for femoral fixation were included: 9719 patients were in the FLD group, and 3014 patients were in the ALD group. The primary outcome was revision ACLR with a non-inferiority margin for ALDs at 4% at the 2-year follow-up. The secondary outcomes were anterior and rotatory knee stability and PROMs based on the Knee Injury and Osteoarthritis Outcome Score (KOOS) at the 1-year follow-up. The crude cumulative revision rates in ALD implants at 2 and 5 years were 2.1% (95% CI 1.62-2.68) and 5.0% (95% CI 4.22-5.96), respectively. In the FLD group, the rates were 2.2% (95% CI 1.89-2.48) at 2 years and 4.7% (95% CI 4.31-5.20) at 5 years. The 1-year side-to-side differences were 0.97mm (95% CI 0.90-1.03) in the ALD group and 1.45mm (95% CI 1.41-1.49) in the FLD group. In the FLD group, 13% had a positive pivot shift, and in the ALD group, 6% had a positive pivot shift. There were no differences in KOOS. ALDs were non-inferior to FLDs regarding revision rates, knee stability, and patient-reported outcomes. Based on this conclusion, ALDs are safe to use for femoral fixation in ACLR. III.

A comparison of multi-ligament reconstruction and isolated anterior cruciate ligament reconstruction at one year follow-up: results from the Danish Knee Ligament Reconstruction Registry

IntroductionThe Danish Knee Ligament Reconstruction Registry (DKRR) has monitored the outcomes of surgeries for multi-ligament knee injuries (MLKI) since 2005. This study aimed to compare the subjective clinical outcomes of patients who had undergone surgery after MLKI with those of patients who had received isolated anterior cruciate ligament (ACL) reconstruction.Materials and methodsThis study used patient-reported outcome scores at 1-year follow-up as the primary outcome and contains the outcome data of knee ligament surgeries retrieved from the DKRR. Clinical subjective outcomes and knee function were evaluated with Knee Injury and Osteoarthritis Outcome Scores (KOOS) and Tegner Activity Scale (Tegner) scores. Demographic differences were examined using the Student’s t-test and the chi-square test. Multiple linear regression was used to analyse the data and adjust for potentially confounding factors. P-values < 0.05 were considered to be statistically significant.ResultsA total of 31,686 knee ligament surgeries were registered in the DKRR between 2005 and 2017, resulting in 1,160 multi-ligament patients and 28,843 isolated ACL patients. The mean age of the MLKI group was significantly higher than that of the isolated ACL group (33.2 years [95% CI 32.5–33.9] vs. 28.3 years [95% CI 28.1–28.4]).The adjusted KOOS Sport and Quality of Life (QoL) sub-scores and Tegner scores of the MLKI group significantly improved from the baseline to the 1-year follow-up (16.7 points [95%CI 12.8;20.6], 12.6 points [95%CI 9.6;15.6] and 1.76 points [95%CI 1.43;2.08], respectively). The KOOS Sport and QoL sub-scores of the isolated ACL group were significant and increased more than those of the MLKI group. No differences in the Tegner scores were observed.ConclusionsSurgical reconstruction after multi-ligament knee injury resulted in significant subjective outcome improvements at 1- year follow-up. The KOOS Sport and QoL sub-scores of the isolated ACL group significantly increased compared to those of the MLKI group.

A high level of knee laxity after anterior cruciate ligament reconstruction results in high revision rates.

The literature indicates a lack of consensus on the correlation between knee laxity after anterior cruciate ligament reconstruction (ACLR) and subjective clinical outcomes and the need for revision surgery. Therefore, using high-volume registry data, this study aimed to describe the relationship between objective knee laxity after ACLR and subjective symptom and functional assessments and the need for revision surgery. The hypothesis was that greater postoperative knee laxity would correlate with inferior patient-reported outcomes and a higher risk for revision surgery. In this study, 17,114 patients in the Danish knee ligament reconstruction registry were placed into three groups on the basis of objective side-to-side differences in sagittal laxity one year after surgery: group A (≤ 2mm), Group B (3-5mm) and Group C (> 5mm). The main outcome measure was revision rate within 2years of primary surgery, further outcome measures were the knee injury and osteoarthritis outcome score (KOOS) as well as Tegner activity score. The study found the risk for revision surgery was more than five times higher for Group C [hazard ratio (HR) = 5.51] than for Group A. The KOOS knee-related Quality of Life (QoL) sub-score exhibited lower values when comparing Groups B or C to Group A. In addition, the KOOS Function in Sportand Recreation (Sport/Rec) sub-score yielded lower values for groups B and C in comparison with Group A. These results indicate that increased post-operative sagittal laxity is correlated with an increased risk for revision surgery and might correlate with poorer knee-related QoL, as well as a decreased function in sports. The clinical relevance of the present study is that high knee laxity at 1-year follow-up is a predictor of the risk of revision surgery. III.

Graft Failure, Revision ACLR, and Reoperation Rates After ACLR With Quadriceps Tendon Versus Hamstring Tendon Autografts: A Registry Study With Review of 475 Patients

Background: It has been indicated that anterior cruciate ligament reconstruction (ACLR) with a quadriceps tendon (QT) graft has a higher risk of revision compared with ACLR performed with a hamstring tendon (HT) graft. Purpose/Hypothesis: To investigate whether ACLR with QT graft had a higher risk of graft failure, revision ACLR, or reoperation compared with HT graft in a high-volume center. We hypothesized that there would be no between-group differences. Study Design: Cohort study; Level of evidence, 3. Methods: This was a registry study with review of medical records. Our study cohort consisted of patients who underwent primary ACLR with either QT or HT graft performed at Copenhagen University Hospital Hvidovre between January 2015 and December 2018. The cohort was identified from the Danish Knee Ligament Reconstruction Registry and linked to the Danish National Patient Registry to identify all hospital contacts after ACLR. The outcome variables were graft failure (rerupture or >3-mm side-to-side difference in anteroposterior [AP] laxity), revision ACLR, reoperation due to cyclops lesion, reoperation due to meniscal injury, and reoperation due to any reason. AP laxity and pivot shift were assessed at 1 year. Kaplan-Meier estimates were used to evaluate the rates of events at 2 years, and comparison was performed with Cox regression analysis. Results: A total of 475 patients (252 HT, 223 QT) were included. The rate of graft failure at 2 years was 9.4% for the QT group and 11.1% for the HT group (P = .46). For the QT and HT groups, respectively, the rate of revision ACLR was 2.3% and 1.6% (P = .60), the rate of reoperation due to cyclops lesion was 5.0% and 2.4% (P = .13), and the rate of reoperation due to meniscal injury was 4.3% and 7.1% (P = .16). The rate of reoperation due to any reason was 20.5% and 23.6% (P = .37). At 1-year follow-up, AP laxity was 1.4 mm for QT and 1.5 mm for HT (P = .51), and the proportion of patients with a positive pivot shift was 29-30% for both groups. Conclusion: QT and HT grafts yielded similar rates of graft failure, revision ACLR, and reoperation at 2 years of follow-up after ACLR. Graft failure was found in 9% to 11% of patients. Patients with QT ACLR showed a non–statistically significant trend of higher risk for reoperation due to cyclops lesion, and those with HT showed a non–statistically significant trend of higher risk for reoperation due to meniscal injury.

Low surgical routine increases revision rates after quadriceps tendon autograft for anterior cruciate ligament reconstruction: results from the Danish Knee Ligament Reconstruction Registry.

Recent registry data have demonstrated a higher revision rate of quadriceps tendon (QT) graft compared with hamstring tendon (HT) and patellar tendon (PT) grafts. Clinic routines could be an important factor for revision outcomes. The purpose of this study is to use the Danish Knee Ligament Reconstruction Registry (DKRR) to compare revision rates in patients who have undergone ACLR with QT, HT and PT grafts related to individual clinic surgical routine. Data on primary ACLRs entered in the DKRR from 2012 through 2019 were analysed since QT graft usage started in 2012. Revision rates for QT, HT and PT grafts were compared according to clinic activity (0-100 and > 100 procedures). Revision rates for the three autograft cohorts are presented, as well as adjusted revision hazard rates. Instrumented knee stability and pivot-shift tests were performed at a one-year follow-up. QT revision rate (6.4%) for low-activity clinics was higher than for high-activity clinics (2.9%) (p = 0.003). The adjusted revision hazard ratio for low-activity clinics was 2.3 (p = 0.01). QT autograft was associated with statistically significant, increased side-to-side laxity at follow-up (1.4mm) compared with HT and PT autografts (1.0mm) (p < 0.01), as well as an increased positive pivot-shift rate. QT autografts for ACLR were associated with higher revision rates in clinics with lower than 100 procedures performed from 2012 to 2019. QT graft usage is not associated with a high revision rate when routinely performed. Learning curve is an important factor when introducing QT ACLR. Level III.

Medial collateral ligament (MCL) reconstruction results in improved medial stability: results from the Danish knee ligament reconstruction registry (DKRR).

The aim of this study was to compare outcome data after isolated and combined (MCL) plus anterior cruciate ligament (ACL) reconstruction based on objective and subjective measures using data from the (DKRR). There are only a few small-sized case studies on outcomes after MCL reconstruction. MCL reconstruction was hypothesised to improve both objective and subjective outcomes. All patients who were registered in the DKRR between 2005 and 2016 (N = 25,281) and who underwent isolated ACL (n = 24,683), isolated MCL (n = 103) or combined MCL plus ACL (n = 495) reconstructions were retrospectively identified. Objective (valgus knee stability and sagittal knee laxity) and subjective (Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity scale score) outcomes in these three cohorts were evaluated at the 1-year follow-up by comparing pre- and post-operative values. Medial stability improved significantly pre- to post-operatively after both isolated MCL and combined MCL plus ACL reconstruction, with 26 (53%) and 195 (69%) of the patients, respectively, having normal valgus stability (0-2mm laxity). Sagittal stability was similar after MCL plus ACL reconstruction and isolated ACL reconstruction (1.7 and 1.5mm, respectively). At the 1-year follow-up, although the KOOS of the patients in the isolated MCL and combined MCL plus ACL reconstruction cohorts improved significantly, they were lower than those of the patients in the isolated ACL reconstruction cohort. Both isolated MCL reconstruction and combined MCL plus ACL reconstruction resulted in significant and clinically relevant improvements in the subjective outcomes from pre-operative conditions to the 1-year follow-up. Valgus stability also improved significantly, with two-thirds of patients obtaining normal valgus stability after MCL reconstruction. Subjective outcomes were similar between isolated MCL reconstruction and combined MCL plus ACL reconstructions, but were poorer than isolated ACL reconstructions. Level III.

Anteromedial Portal Drilling Yielded Better Survivorship of Anterior Cruciate Ligament Reconstructions When Comparing Recent Versus Early Surgeries With This Technique

To compare anteromedial (AM) and transtibial (TT) femoral drilling hole techniques in primary anterior cruciate ligament reconstruction, using the Danish Knee Ligament Reconstruction Register, comparing revision rates and clinical outcomes from 2 time periods, 2007 to 2010 and 2012 to2015. A total of 8,386 primary anterior cruciate ligament reconstructions were registered between January 2007 to December 2010 and 8,818 in the period January 2012 to December 2015. Revision ACL was the primary endpoint. Secondary endpoints were the objective and subjective clinical outcomes. Crude and adjusted relative risks (RRs) with 95% confidence interval (CIs) were calculated. The adjusted RR for revision surgery in the AM (2007-10) group compared with the TT (2007-10) group was 1.45 (95% CI, 1.17-1.78; P < .05), but when comparing the AM (2012-15) group with TT (2012-15) group, the RR was 0.99 (95% CI, 0.68-1.45; P= .96). One-year postoperative objective stability testing showed an RR= 1.38 (95% CI, 1.19-1.60; P < .01) for rotational stability and an RR= 1.37 (95% CI, 0.99-1.89; P < .01) for sagittal stability when comparing AM (2007-10) to TT (2007-10). No significant difference in objective stability was found in the more recent period. Lastly, comparing the subjective scores, the AM (2012-15) had a significantly higher Tegner score 1year postoperatively compared with the TT-group (2012-15). This study found an increased RR of revision anterior cruciate ligament and rotational and sagittal instability 1year postoperatively for the AM technique in the period from 2007 to 2010. However, there was no significant difference in revision surgery and objective measures between the techniques from 2012 to 2015. Nevertheless, a higher activity level was found in the AM group. The results could indicate that the results found in the period 2007 to 2010 may have been caused by a learning curve when introducing a new and more complex procedure (AM). Level III, retrospective comparative trial.

Complications and technical failures are rare in knee ligament reconstruction: analyses based on 31,326 reconstructions during 10years in Denmark.

Knowledge about treatment injuries (technical failures and complications) in relation to knee ligament reconstructions is sparse. Our purpose was to describe treatment injuries to knee ligament reconstruction in Denmark during a 10-year period and to suggest initiatives to reduce the risk for treatment injuries. Treatment injuries after knee ligament reconstructions reported to the Danish Patient Compensation Association (DPCA) 2005-2014 were analyzed and compared to information from the Danish Kneeligament Reconstruction Register and Danish National Patient Register. The number of knee ligament reconstructions in Denmark 2005-2014, including revisions, was 31,326. Of the 704 cases claimed to DPCA, 371 were approved as treatment injuries (1.42% of all operations). Tunnel malpositioning (135 = 0.43% of all operations), deep infection (0.27%), nerve injury (0.17%), pain (0.12%) and unrecognized combined instability (0.11%) were the most common. Patients operated with anteromedial technique for femoral tunnel placement had a lower incidence (p < 0.0001) of tunnel malpositioning compared to other techniques. Public and private hospitals had the same risk of treatment injures. Hospitals that performed the largest number of reconstructions/year had the smallest risk of a treatment injury (p < 0.001). The total compensation was 7.6m EURO, which equals 243 EURO/performed knee ligament reconstruction. Treatment injuries as defined in this study were rare, with tunnel malpositioning being the most common. Analyses of the results indicate that it may be clinically relevant to reduce the number of treatment injures that knee ligament reconstructions are concentrated in clinics with high volume. Also, malpositioning might be reduced by routine documentation of K-wire position before tunnels are drilled. III.

Passive Knee Stability After Anterior Cruciate Ligament Reconstruction Using the Endobutton or ToggleLoc With ZipLoop as a Femoral Fixation Device: A Comparison of 1654 Patients From the Danish Knee Ligament Reconstruction Registry.

Background:Biomechanical studies show varying results regarding the elongation of adjustable fixation devices. This has led to growing concern over the stability of the ToggleLoc with ZipLoop used in anterior cruciate ligament (ACL) reconstruction (ACLR) in vivo.Purpose/Hypothesis:The purpose of this study was to compare passive knee stability 1 year after ACLR in patients in whom the Endobutton or ToggleLoc with ZipLoop was used for femoral graft fixation. The hypothesis was that the ToggleLoc with ZipLoop would be inferior in knee stability to the Endobutton 1 year after primary ACLR.Study Design:Cohort study; Level of evidence, 2.Methods:Data from 3175 patients (Endobutton: n = 2807; ToggleLoc with ZipLoop: n = 368) were included from the Danish Knee Ligament Reconstruction Registry (DKRR) between June 2010 and September 2013. Data were retrieved from standardized ACL forms filled out by the operating surgeon preoperatively, during surgery, and at a clinical examination 1 year after surgery. Passive knee stability was evaluated using 1 of 2 arthrometers (Rolimeter or KT-1000 arthrometer) and the pivot-shift test. Using the same database, the number of reoperations performed up to 4 years after primary surgery was examined.Results:Full data were available for 1654 patients (Endobutton: n = 1538; ToggleLoc with ZipLoop: n = 116). ACLR with both devices resulted in increased passive knee stability (P < .001). Patients who received the ToggleLoc with ZipLoop were found to have a better preoperative (P = .005 ) and postoperative (P < .001) pivot-shift test result. No statistically significant difference regarding the number of reoperations (P = .086) or the time to reoperation (P = .295) was found.Conclusion:Patients who underwent fixation with the ToggleLoc with ZipLoop had improved passive knee stability 1 year after surgery, measured by anterior tibial translation and pivot-shift test results, similar to patients who underwent fixation with the Endobutton. No difference was seen in knee stability or reoperation rates between the 2 devices.

Allograft Use Results in Higher Re-revision Rate for Revision Anterior Cruciate Ligament Reconstruction.

Background:The literature on revision anterior cruciate ligament (ACL) reconstruction (ACLR) outcomes is generally sparse, but previous studies have demonstrated that autograft use results in improved sports function and patient-reported outcome measures compared with allograft. However, knowledge is still lacking regarding the impact of graft type on rates of re-revision.Purpose:To investigate the clinical outcomes and failure rates of revision ACLRs performed with either allograft or autograft.Study Design:Cohort study; Level of evidence, 3.Methods:A search of the Danish Knee Ligament Reconstruction Registry identified 1619 revision ACLRs: 1315 were autograft procedures and 221 were allograft procedures (type of graft was not identified for 83 procedures). Clinical outcomes after 1 year were reported via the Knee injury and Osteoarthritis Outcome Score (KOOS), the Tegner activity score, and an objective knee stability measurement that determined side-to-side differences in instrumented sagittal knee laxity. Failure was determined as re-revision. Outcomes for revision were provided for the full life of the registry, up to 10 years.Results:The re-revision rate was significantly higher for allograft compared with autograft (12.7% vs 5.4%; P < .001), leading to a hazard ratio for re-revision of 2.2 (95% CI, 1.4-3.4) for allografts compared with autografts when corrected for age. At 1-year follow-up, objective knee stability was significantly different (2.1 ± 2.1 mm for allograft vs 1.7 ± 1.8 mm for autograft; P = .01), and the KOOS subscale scores for symptoms, pain, activities of daily living, sports, and quality of life were 67, 76, 84, 49, and 46 for allograft and 67, 78, 84, 51, and 48 for autograft, respectively, with no difference between groups.Conclusion:In this observational population-based study, the ALCR re-revision rate was 2.2 times greater for allograft compared with autograft procedures. Allograft was associated with greater knee laxity at 1-year follow-up. However, subjective clinical outcomes and knee function were not inferior for allograft patients. These results indicate that autograft is a better graft choice for revision ALCR.

Both isolated and multi-ligament posterior cruciate ligament reconstruction results in improved subjective outcome: results from the Danish Knee Ligament Reconstruction Registry.

There are few descriptions of outcomes after posterior cruciate ligament (PCL) reconstruction in the literature due to the rarity of this type of knee injury. Since 2005, the Danish Knee Ligament Reconstruction Registry (DKRR) has monitored outcomes of PCL reconstructions. This study describes the epidemiology of PCL reconstruction and subsequent outcomes in a Danish population. Of 23,253 knee ligament reconstructions performed in 2005-2015, 581 were registered as PCL reconstructions in the DKRR. The types of reconstruction were classified as isolated (n=237) or multi-ligament (n=344), and the cause of injury and concomitant meniscus and cartilage injury data were extracted. The outcome at 1-year follow-up was based on the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity level. The outcome data were compared with data on 21.820 primary anterior cruciate ligament (ACL) reconstructions. Isolated PCL reconstruction was performed in 43% of cases. Meniscus lesions and cartilage lesions were seen in 19 and 15% of cases, respectively. The main causes of PCL injuries were sports (43%) and traffic accidents (33%). The KOOS improved from pre-operative to 1-year follow-up for both isolated PCL reconstructions and multi-ligament PCL reconstructions but did not reach the levels of those recorded in ACL reconstructions. Multi-ligament reconstructions showed the highest improvement in KOOS. The Tegner activity levels for isolated and multi-ligament PCL reconstructions were 4 (0-7) and 4 (0-8), respectively. PCL reconstructions represented only 2.6% of all knee ligament reconstructions in Denmark. Sports and traffic accidents were the main causes of injury. Meniscus and cartilage injuries were less frequent in PCL injuries as compared to ACL injuries. Isolated PCL and multi-ligament PCL reconstructions showed significant improvements in subjective outcomes but did not reach those observed in ACL reconstructions. Patients should be counselled about expected outcomes after PCL reconstruction. III.

Potential serious bias in National Clinical Databases with low degree of reported follow‐up

We identified reasons for the low follow-up rate in the Danish Knee ligament Reconstruction Register (DKRR) and evaluated its influence on the data quality. All 946 primary ACL-reconstructed patients in the Capital Region of Denmark during 2012 were identified in the databases of 8 participating hospitals. We studied the patient files and compared them to figures reported to the DKRR. 92.5% of the operated patients was registered in DKRR. The 1-year follow-up rate reported to DKRR was 33.4%, and 14.5% filled in patient reported outcomes (KOOS and Tegner) at 1year. Only 65% had actually been invited for follow-up, but among the patients who had been invited 91% were seen. 41% of existing follow-up data was not reported. Contemporary technology and structured motivation should be introduced to increase validity of data in national clinical databases. Follow-up >90% in the DKRR is realistic if patents are invited and reported. The unreported data is potentially a serious bias. It is suggested that data from clinics with low follow-up should not be used in studies involving outcomes based on national databases because of risk of bias.

Comorbidities in Patients With Anterior Cruciate Ligament Reconstruction Compared With Matched Controls Without Anterior Cruciate Ligament Injury From Danish Registries

To describe and compare comorbidity among anterior cruciate ligament (ACL)-reconstructed patients and a gender- and age-matched group without ACL injury. Furthermore, we sought to evaluate the impact of comorbid diseases on the risk of ACL revision surgery. This case-control study included 13,443 unilateral primary ACL-reconstructed patients from the Danish Knee Ligament Reconstruction Register matched on gender and age with a comparison group without ACL injury. Information on medical comorbid conditions was obtained from the Danish National Registry of Patients. The prevalence of all comorbid conditions was described for ACL-reconstructed patients and the comparison group in terms of (1) the Charlson Comorbidity Index (CCI); (2) International Classification of Diseases, Tenth Revision disease chapters; and (3) more common chronic diseases in a younger population. Finally, we assessed the risk of ACL revision surgery according to the more common chronic diseases in a younger population, using Cox regression analysis. Although we found a large variety of diseases present among ACL-reconstructed patients, the percentage of patients with a CCI equal to 0 was high in both groups. ACL-reconstructed patients generally had a slightly lower prevalence of almost all International Classification of Diseases, Tenth Revision-classified comorbid disease groups compared with the comparison group without ACL injury. As expected, the prevalence of most diseases increased slightly with rising age. Furthermore, we found that having back pain or diseases of the back did alter the risk of revision surgery. ACL-reconstructed patients are found to be generally healthy individuals with a low prevalence of serious and chronic diseases compared with an age- and gender-matched control group from the general population. A large variety of diseases are present in the ACL-reconstructed group but with very low prevalence rates and low CCIs, indicating that the severity of their illness is limited. Level III, case-control study.

Is the Use of Oral Contraceptives Associated With Operatively Treated Anterior Cruciate Ligament Injury?

Background: The incidence of anterior cruciate ligament (ACL) injuries is 2 to 9 times higher in women than in men. In addition, in vitro studies have demonstrated that ACL is an estrogen target tissue, and some studies have therefore suggested a protective association between oral contraceptives (OC) and the likelihood of sustaining ACL injury. Hypothesis: There is a protective association between OC use and the likelihood of operatively treated ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: The study population included 4497 women with an operatively treated ACL injury registered in the Danish Knee Ligament Reconstruction Registry for the 2005 to 2011 period and 8858 age-matched controls with no ACL injury. The study evaluated exposure to OC use at the time of ACL injury (index date) and in the 5 previous years (“ever user”) or no OC use (“never user”). Ever users were further classified as either new users (patients who redeemed their first prescription within the first year before the index date), long-term users (redeemed additional prescriptions 1 to 5 years before the index date), or recent users (redeemed their most recent prescription >1 year before the index date). Finally, a dose-response analysis of OC use was performed. Conditional logistic regression was used to calculate the relative risk (RR) with a 95% CI of sustaining an operatively treated ACL injury according to OC use. Results: The adjusted RR associating OC with ACL injury was 0.82 (95% CI, 0.75-0.90) between ever users and never users. Furthermore, there was a decreased RR of sustaining ACL injury of 0.80 (95% CI, 0.74-0.91) in long-term users and 0.81 (95% CI, 0.72-0.89) in recent users. Using OC for more than 4 years did not seem to alter the likelihood of sustaining an operatively treated ACL injury. Conclusion: This population-based pharmacoepidemiological study including 13,355 women indicates that a protective association exists between OC use and the likelihood of sustaining an operatively treated ACL injury. Although this study does indicate a protective association of OC use, OC should not be used as a prophylactic measure before additional clinical studies have further clarified the biological and causal association between OC use and the likelihood of sustaining operatively treated ACL injury.

Risk for Revision After Anterior Cruciate Ligament Reconstruction Is Higher Among Adolescents: Results From the Danish Registry of Knee Ligament Reconstruction.

Background:The number of children and adolescents with anterior cruciate ligament (ACL) reconstructions is increasing, and disturbing reports on high rerupture rates in this group have been noted.Purpose:To describe the outcome of ACL reconstruction in children and adolescents based on data from the Danish Knee Ligament Reconstruction Registry (DKRR).Study Design:Cohort study; Level of evidence, 3.Methods:Data were retrieved from the DKRR, a national population-based registry. The analysis was based on a population of 14,806 ACL-reconstructed patients. The outcome was evaluated using risk of ACL revision, subjective outcome score (Knee injury and Osteoarthritis Outcome Score [KOOS]), Tegner function score, and objective knee laxity. Three age groups were defined (A, <13 years; B, 13-15 years; and C, 15-20 years) and compared with D, patients ≥20 years (adults). There were 95 patients in group A, 327 in B, 2888 in C, and 11,496 in D.Results:There was a significantly increased risk of revision surgery in the age groups B (6.7%) and C (4.9%) compared with the adults in group D (2.0%). Objective knee laxity did not differ between the 4 groups. Groups A, B, and C had a higher score on the combined KOOS symptoms, pain, sport, and quality of life subscales (KOOS4; 79.6, 76.6, and 73.1, respectively) compared with the adults (69.7). Group B had higher KOOS quality of life (76.6) and sports (71.1) scores than did group C (73.1 and 66.4, respectively). The Tegner activity score did not differ between the 4 groups. No impact of the use of extracortical graft fixation was detected in the youngest age group.Conclusion:Study results indicated an increased risk of graft failure in patients between 13 and 20 years of age. This is in contrast to the better subjective and equal objective knee score found in the same age groups.Clinical Relevance:The new knowledge about the high revision rate among ACL-reconstructed teenagers is important for evidence-based preoperative information of ACL patients and their parents.

Comparison of Hamstring Tendon and Patellar Tendon Grafts in Anterior Cruciate Ligament Reconstruction in a Nationwide Population-Based Cohort Study

Background: The choice of graft for anterior cruciate ligament reconstruction (ACLR) remains controversial, and despite numerous studies, there is still an ongoing debate on this topic. The 2 most widely used grafts are the hamstring tendon and patellar tendon. Hypothesis: In this study, we hypothesized that the revision rate after primary ACLR is greater when using hamstring tendon grafts compared with patellar tendon grafts. Study Design: Cohort study; Level of evidence, 2. Methods: From the nationwide population-based Danish Knee Ligament Reconstruction Registry, we identified all primary ACLR procedures (n = 13,647) performed in Denmark between July 2005 and December 2011. The end point was revision ACLR. As other end points, we used objective measurements and patient-reported outcome scores. Revision rates and relative risk estimates for revision ACLR were calculated using Cox multiple regression. Results: The use of hamstring tendon grafts increased from 68% in 2005 to 85% in 2011. The cumulative revision rates for hamstring tendon grafts at 1 and 5 years were 0.65% (95% confidence interval [CI], 0.51%-0.82%) and 4.45% (95% CI, 3.94%-5.01%), respectively. For patellar tendon grafts, the revision rate was 0.16% (95% CI, 0.05%-0.50%) at 1 year and 3.03% (95% CI, 2.27%-4.05%) at 5 years. The adjusted overall relative risk of revision surgery in the hamstring tendon group compared with the patellar tendon group was 1.41 (95% CI, 1.03-1.92), and the adjusted relative risk of undergoing revision surgery performed after 1 and 5 years was 3.82 (95% CI, 1.20-12.2) and 1.90 (95% CI, 0.43-8.40), respectively. Conclusion: In this population-based study, the use of hamstring tendon grafts in ACLR was associated with an increased risk of revision compared with patellar tendon grafts, in particular during the first year after surgery. These results demonstrate that both hamstring and patellar tendon grafts reveal good results after ACLR and suggest that graft selection should be based on an individual evaluation of patient demands and graft morbidity.

Validation of 14,500 operated knees registered in the Danish Knee Ligament Reconstruction Register: registration completeness and validity of key variables

IntroductionThe aim of this study was to validate the registration in the Danish Knee Ligament Reconstruction Register (DKRR) by assessing the registration completeness of the anterior cruciate ligament (ACL) reconstruction code and detecting the validity of important key variables. Furthermore, we assessed data quality of patient-related outcome scores.Material and methodsAll operation codes for ACL reconstruction from 2005–2011 were identified in the Danish National Registry of Patients and were compared with the cases registered in the DKRR to compute the completeness of registration. We also assessed the validity of key variables in the DKRR using medical records as a reference standard to compute the positive predictive value. Finally, we assessed potential differences between responders and nonresponders to subjective patient-related outcome scores (Knee Injury and Osteoarthritis Outcome Score [KOOS] and Tegner scores) 1 year after surgery.ResultsThe completeness of the registration of patients in the DKRR increased from 60% (2005) to 86% (2011). Large-volume hospitals had a higher completeness than small-volume hospitals. With a positive predictive value between 85%–100%, the validity of key variables was good. KOOS scores versus Tegner scores for responders and nonresponders were comparable.ConclusionThe results show a good registration of ACL reconstruction procedures in the DKRR, but there is room for improvement mainly at small-volume hospitals. Overall, the validity of the key variables in the DKRR was good and no difference was found in KOOS and Tegner scores for responders versus nonresponders. Therefore, we conclude that the DKRR is a valid source for future research.

Increased Risk of Revision After Anteromedial Compared With Transtibial Drilling of the Femoral Tunnel During Primary Anterior Cruciate Ligament Reconstruction: Results from the Danish Knee Ligament Reconstruction Register

The goal was to study revision rates and clinical outcome after anterior cruciate ligament (ACL) reconstruction using the anteromedial (AM) technique versus the transtibial (TT) technique for femoral drill hole placement. A total of 9,239 primary ACL reconstruction procedures were registered in the Danish Knee Ligament Reconstruction Register between January 2007 and December 2010. The failure of the 2 different femoral drilling techniques was determined using revision ACL reconstruction as the primary endpoint. As secondary endpoints, we used the pivot-shift test and instrumented objective test as well as patient-reported outcome, registered in the Danish Knee Ligament Reconstruction Register. Relative risks (RRs) with 95% confidence intervals (CI) were calculated. We identified 1,945 AM and 6,430 TT primary ACL procedures. The cumulative revision rates for ACL reconstruction after 4 years with the AM and TT techniques were 5.16% (95% CI: 3.61%, 7.34%) and 3.20% (95% CI: 2.51%, 4.08%), respectively. The adjusted overall RR for revision ACL surgery in the AM group was 2.04 (95% CI: 1.39, 2.99), compared with the TT group. Use of the AM technique increased from 13% of all operations in 2007 to 40% in 2010. AM technique was further associated with increased RRs of positive pivot shift of 2.86 (95% CI: 2.40, 3.41) and sagittal instability of 3.70 (95% CI: 3.09, 4.43), compared with the TT technique. This study found an increased risk of revision ACL surgery when using the AM technique for femoral drill hole placement, compared with the TT technique, in the crude data as well as the stratified and adjusted data. Our finding could be explained by technical failures resulting from introduction of a new and more complex procedure or by the hypothesis put forward in prior studies that compared with a nonanatomic graft placement, a greater force is carried by the anatomic ACL reconstruction and, hence, there is a concomitant higher risk of ACL rupture. Level II, prospective comparative study.