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Young age cited as predictor of contralateral ACL reconstruction
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A 5-year follow-up of patients aged 13 years to 59 years who underwent primary ipsilateral ACL reconstruction revealed patients who were younger than 20 years old at the time of the index reconstruction had an almost three-times greater risk of contralateral ACL reconstruction.
“This is a landmark study as it is, to our knowledge, the first nation-wide registry-based study of contralateral ACL reconstruction,” Daniel Andernord, MD, of Vårdcentralen Gripen, Karlstad, Sweden, told Orthopaedics Today Europe. “It shows that, over a 5-year period, the overall rate of contralateral reconstruction was low, only 3%, with no difference between male and female patients. Age 13 to 19 years and contralateral graft harvest among females predicted a three-times higher risk of requiring future contralateral ACL reconstruction.”
Data from a national register
Andernord and colleagues used data from the Swedish National Knee Ligament Register to identify 9,061 patients who underwent primary ipsilateral ACL reconstruction with either hamstring tendon or bone-patellar tendon-bone autografts. The researchers started study their 5-year follow-up on the date of the index ACL reconstruction. They ended follow-up when patients underwent primary contralateral ACL reconstruction or on Dec. 31, 2013, whichever occurred first. Investigated variables included patient sex, age at index reconstruction, activity at the time of index injury, timing of surgery, graft selection, graft harvest site and meniscal chondral injury. The primary study endpoint was contralateral ACL reconstruction.
The investigators found 270 patients underwent primary contralateral ACL reconstruction during the 5-year follow-up. Female patients younger than 20 years at the time of index reconstruction had 2.9-times higher risk of undergoing contralateral ACL reconstruction in 5 years.
Results showed harvest of a contralateral hamstring tendon autograft at index ACL reconstruction predicted a more than three times higher risk of contralateral ACL reconstruction among female patients undergoing reconstruction using autograft hamstring. Compared with other intervals, female patients with injury-to-surgery intervals of less than 3 months and 6 months had an increased risk of contralateral ACL reconstruction.
Male patients younger than 20 years had a 2.4-times higher risk of undergoing subsequent contralateral ACL reconstruction during the follow-up period. The researchers found no difference in contralateral reconstruction rates between men and women in general.
“We know from previous studies that the hamstring muscles are important ACL agonists and that females have more lax hamstrings and delayed muscle activation, which make them susceptible to ACL injury,” Andernord said. “The findings in our study suggest that the hamstrings protect female athletes from ACL injury.”
Individual treatment
“It is important to investigate the implications of the graft harvest site to see if it is possible to validate the findings in this study, namely that hamstring graft harvest does, in fact, increase the risk of ACL reconstruction among females,” he told Orthopedics Today.
“As always, treatment of individuals with ACL injuries has to be individually tailored,” Andernord added. “The implications are not yet fully investigated and the findings in this study should, of course, be treated with caution, although they are interesting.” – by Casey Tingle
Reference:
Andernord D, et al. Am J Sports Med. 2015;doi:10.1177/0363546514557245.
For more information:
Daniel Andernord, MD, can be reached at Vårdcentralen Gripen, Box 547, SE-651 12 Karlstad, Sweden; email: daniel.andernord@gmail.com.
Disclosure: Andernord reports no relevant financial disclosures.
Perspective
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Shital N. Parikh, MD, FACS
ACL tear is a devastating injury, frequently seen in athletes. More than 90% of patients with an ACL tear undergo ACL reconstruction. After an ACL reconstruction, there is a 15-times greater risk of second ACL injury (ipsilateral or contralateral) when compared with healthy, control subjects. In a systematic review, Wright and colleagues reported an almost 6% risk of ipsilateral ACL tear and an almost 12% risk of contralateral ACL tear at 5 years or more following ACL reconstruction. Other long-term follow-up studies have reported even higher (27%) rates of second ACL injury at 10 years follow-up.
In the current study, Andernord and colleagues report on the predictors of contralateral ACL reconstruction within 5 years of a primary ipsilateral ACL reconstruction, based on the Swedish National Knee Ligament Register. Of 9,061 patients with ACL reconstruction, 270 (3%) underwent contralateral ACL reconstruction within 5 years. The risk factors identified from this study were age younger than 20 years and contralateral hamstring harvest in female patients; each of the two risk factors had three-times higher risk of contralateral ACL reconstruction. None of the other risk factors studied, including patient sex, activity at the time of index injury, graft choice, meniscus or chondral injury, were predictors of contralateral ACL reconstruction.
The 3% rate of contralateral ACL reconstruction reported in the current study appears to be lower compared to the existing literature, for the following potential reasons. First, all previous studies have reported on contralateral ACL tears and not ACL reconstructions. The rate of contralateral ACL tears in the study population may be much higher, but only a few may have required or chose to undergo a second ACL reconstruction. Second, the information related to mechanism of injury or activity level is not collected in the registry. Thus, the denominator of athletic exposure is missing. Third, the average injury to surgery interval was 581 days, which appears to be much longer and may reflect either non-athletic population or wider health care system issues. Lastly, a 5-year follow-up might be insufficient and longer follow-up study may be required in future.
Several previous studies have reported on the association between young patient age and subsequent contralateral ACL injury after ipsilateral ACL reconstruction. The current study found age younger than 20 years at index ACL reconstruction to be associated with three-fold increase risk of contralateral ACL reconstruction in male and female patients. The proportion of adolescents (age 13 years to 19 years) was doubled among female patients (42%) compared with male patients (20%). These findings reflect the existing literature and knowledge that adolescent females constitute a specific “at-risk” group. The increased risk can be secondary to higher activity levels, genetics, hormonal issues, knee kinematics, lower leg alignment including hip adduction and dynamic knee valgus, and narrow intercondylar notch, amongst others. The advantage of such population-based study is that it can help to identify the at-risk group so preventive strategies and research efforts can be focused on these groups.
The three most widely used grafts for ACL reconstruction include hamstring autograft, bone-tendon-bone (BTB) autograft and allograft. Of these, allograft has a four-times higher risk of re-tear compared with autograft and, hence, is not recommended for index procedure in young patients. Several studies on ACL reconstruction have failed to show any significant differences in outcome between hamstring and BTB autograft. The current study, however, reflects a global trend of increased use of hamstring autograft when compared to BTB autograft (88.8% vs. 11.2%) for primary ACL reconstruction.
Contralateral hamstring graft harvest has been recommended for ACL reconstruction to minimize donor site morbidity and allow earlier return to sports. Another potential advantage of contralateral graft harvest is to allow the ipsilateral intact hamstring tendons to provide dynamic stabilization to the ACL injured knee. Besides the obvious drawback of surgery on the contralateral uninvolved knee, contralateral hamstring harvest can lead to the loss of peak hamstring muscle torque in the first year of surgery. In a prospective randomized trial, McRae and colleagues did not find any benefit or deleterious effect of contralateral hamstring harvest for ACL reconstruction. To date, however, the effect of contralateral graft harvest on contralateral ACL injury had not been studied in a systematic fashion. The current study helps to fill this void. There was a three-fold increase in the incidence of contralateral ACL reconstruction after harvest of contralateral hamstring graft in females compared with ipsilateral graft harvest. One possible explanation for this apparent increase may be selection bias, where an athlete contemplating early return to sports opted for or was offered a contralateral hamstring harvest. This selected population being athletic and desiring early return to sports would then be more prone to contralateral knee injury. Other possibility is persistent weakness of hamstring strength after graft harvest with resultant altered knee kinematics, coupled with inadequate rehabilitation or early return to sports. Whatever the reason, the study does caution against harvesting contralateral hamstring graft for ipsilateral ACL reconstruction, especially in female patients.
References:
Kaeding CC, et al. Sports Health. 2011;doi:10.1177/1941738110386185.
McRae S, et al. Am J Sports Med. 2013;doi:10.1177/0363546513499140.
Paterno MV, et al. Clin J Sport Med. 2012;doi:10.1097/JSM.0b013e318246ef9e.
Wright RW, et al. J Bone Joint Surg Am. 2011;doi:10.2106/JBJS.J.00898.
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