Clinical failure of anterior cruciate ligament (ACL) reconstructions continues to be a too-common scenario. The increasing incidence of ACL revision is due to a variety of factors, including greater intensity of postsurgical physical activity, technical issues, and anatomical influences of the proximal tibia and distal femur. Registries are important sources of data for ACL-related investigations, but I think they are most useful in clarifying experimental designs for more sophisticated clinical research.
In a cohort study in the October 16, 2019 issue of The Journal, Snaebjornsson et al. examined the influence of ACL graft diameter on the risk of revision surgery over 2 years in >18,000 subjects whose data resided in the national knee ligament registries of Sweden and Norway. The vast majority of those patients (92.8%) received a hamstring autograft, with 7.2% receiving a patellar tendon autograft. Overall, the 2-year rate of ACL revision was 2.63% for patellar tendon autografts and 2.08% for hamstring autografts, a statistically nonsignificant difference in relative risk.
However, the authors found an important correlation between graft diameter in the hamstring tendon cohort, with autografts <8 mm in diameter being associated with a higher risk of revision, compared with larger-diameter hamstring autografts. Additionally, patients treated with hamstring graft diameters of ≥9 mm or ≥10 mm had a lower risk of ACL revision surgery than those treated with patellar tendon grafts of any size.
One key limitation that should influence our interpretation of this study is a lack of detail regarding how compliant surgeons were intraoperatively with the use of the measurement device that is depicted in the manuscript and shown above. In addition, the limitations of registry data did not permit the authors to adjust for postsurgical exposures, such as return to sport, the increasing intensity of which makes rerupture more likely. Additional relevant information that would have aided interpretation of the findings includes the relative size of the tibia and femur, lateral condyle size and shape, and proximal tibial slope.
Despite these limitations, this study should prompt further research that uses robust clinical designs to more fully investigate the impact of graft diameter on ACL rerupture rates.
Marc Swiontkowski, MD
Every month, JBJS publishes a Specialty Update—a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in 13 subspecialties. Click here for a collection of all OrthoBuzz Specialty Update summaries.
This month, OrthoBuzz asked Warren Dunn, MD, a co-author of the April 20, 2016 Specialty Update on sports medicine, to select the five most clinically compelling findings from among the more than 30 studies cited in the article.
–What happens to asymptomatic rotator cuff tears over time? According to a long-term prospective study of patients who had an asymptomatic tear in one shoulder and a symptomatic contralateral rotator cuff tear, the asymptomatic tears enlarged in almost one-half of the patients over a median of three years. Those patients who experienced tear enlargement tended to have an onset of new pain and progressive degenerative changes within the supraspinatus and infraspinatus muscles. The authors concluded that many formerly asymptomatic tears will progress to become symptomatic.
–Does tendon repair yield better outcomes than physical therapy (PT) when treating rotator cuff tears? A randomized trial of 103 patients with tears not exceeding 3 cm found that 12 of 51 patients (24%) in the PT group subsequently underwent secondary cuff repair over a 5-year follow-up period. Statistically, patients in the primary repair group had significantly better group-mean improvements on the Constant score, ASES score, and VAS for pain and patient satisfaction than those who underwent secondary repair, but the authors noted that these differences “may be below clinical importance.” Thirty-seven percent of those treated with PT only experienced a >5 mm increase in tear size, which was associated with inferior outcomes.
–Are estimates of Propionibacterium acnes colonization rates in surgical shoulder wounds accurate? A controlled diagnostic study examined P. acnes colonization in 117 open shoulder surgeries that utilized the deltopectoral approach. In 20.5% of the procedures, at least one surgical specimen was positive for P. acnes growth, but 13% of cultures from sterile-sponge control samples also had positive growth. This led the authors to surmise that prior estimates of P. acnes incidence may be higher than actual because of frequent culture contamination. Male sex and preoperative corticosteroid injections were associated with a higher likelihood of bacterial growth.
–Most people who undergo ACL reconstruction experience significant improvement in physical quality of life and quality-adjusted life years, but who is more or less likely to benefit? A 2- and 6-year longitudinal analysis of a multicenter cohort found that those who underwent revision, smoked cigarettes, had lateral tibial plateau chondromalacia, or had less education were more likely to score lower on the Physical Component Summary of the Short Form-36. Those who tended to have higher postoperative functional scores were those with higher baseline function, younger age, lower BMI, and either no lateral meniscal treatment or >50% lateral meniscectomy.
–Hamstring injuries are common among soccer players. A Level I randomized controlled trial among 579 high-level amateur soccer players found that 13 weeks of participation in Nordic hamstring exercises significantly reduced injury incidence and risk for injury compared with a control group over a 1-year period. No differences in injury severity were found.1
- van der Horst N, Smits DW, Petersen J, Goedhart EA, Backx FJG. The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial. Am J Sports Med. 2015 Jun;43(6):1316-23. Epub 2015 Mar 20.