2015 ISAKOS Biennial Congress ePoster #1290
Incidence of ACL Rupture in Iceland: A Nationwide Study
Micah Nicholls, DO, MEng, Foothill Ranch, CA UNITED STATES
Orn Thorstensen, MD, Reykjavik ICELAND
Thorvaldur Ingvarsson, MD, PhD, Reykjavik ICELAND
Kristin Briem, PT, PhD, Reykjavík ICELAND
University of Iceland, Reykjavik, ICELAND
FDA Status Not Applicable
Summary: A nationwide study of all ACL ruptures in Iceland showed that 60% of all ruptures were repaired and, in contrast to previous data, women were older than men as a result of a second peak of ruptures in women occurring later in life.
Anterior cruciate ligament (ACL) rupture continues to be a focus of research on knee injuries. Despite this, data on the total number of ruptures on a national basis including both reconstructed and non-reconstructed injuries are limited. To date studies on national ACL injury incidence have focused on surgical reconstruction. ACL registries from Scandinavia have shown incidence rates for primary ACL reconstruction (ACLR) of between 32 and 38 per 100000. The incidence of all ACLR, including revisions, was seen to be 52/100000 in Australia. One Swedish study estimated a population incidence of ACL rupture of 81/100000 between the ages of 10 and 64, based on admissions to one emergency department. In Iceland all suspected ACL injuries have undergone routine assessment via MRI since 2001. The purpose of this study was to determine the national incidence of MRI diagnosed ACL ruptures in Iceland.
All MRI knee reports from 2002 to 2010 were gathered and read to identify complete ACL ruptures. Duplicate records were removed to prevent multiple counting of the same tear and to ensure the inclusion of primary tears only. Yearly incidence for gender and age groups was determined using data from Statistics Iceland. Data from the Icelandic national insurance data was used to determine the yearly incidence of ACLR.
30160 records from the 9 year period were collected and reviewed. A total of 1873 (6%) included a diagnosis of ACL rupture while 27345 (91%) records classified the ligament as normal or reconstructed and 942 (3%) reports were inconclusive. The national insurance data confirmed 1252 primary ACLR during that same period. There was a yearly incidence of 69/100000 for total ACL ruptures and 42/100000 for ACLR. The average age of individuals with ACL rupture was 34±15 and 64% were male. Women were significantly older than men on average (35±16 vs. 33±14; p<0.01). Women demonstrated two peaks: in their late teens and in their early forties in contrast to men who had one peak in their early twenties. For ACLR men were significantly older (27±8 vs 25±11 p<0.01). Those who underwent surgical vs. non-surgical management were significantly younger (27±9 vs 41±15 p<0.01) and males were more likely to be operated on than females (OR 1.23; 95% CI 1.01 – 1.50). Between the ages of 10 and 64 the incidence rate was 88/100000.
To our knowledge this is the first report on the true incidence of all ACL ruptures based on a complete national dataset. We demonstrated a total ACL rupture incidence 65% higher than the reconstruction rate, meaning that 60% of all ruptures were repaired. In contrast to previous research based on ACLR, women with an MRI diagnosis of ruptured ACL were on average older than men . The second peak occurring at an age when ACLR is less likely could explain this discrepancy. The potentially largest source of error in our data results from ambiguous reports which accounted for 3% of the overall cohort. However numerous studies have shown a high accuracy for MRI diagnosis of complete ACL tears.