Researchers identify groups at risk for further surgery after ACL reconstruction

They also found 6.5% of people having ACL reconstruction had more knee surgery within 1 year.

Issue: January 2010

A study of patients who underwent ACL reconstruction shows that women, younger patients and those treated by low-volume ACL reconstruction surgeons are more likely to have subsequent knee surgery.

The research conducted by investigators at the Hospital for Special Surgery also indicated that 6.5% of all patients who had an ACL reconstruction underwent an additional knee procedure on either knee within 1 year.

“Younger patients and women should be careful in adhering to rehabilitation protocols and should not rush back to high-risk athletic activities too soon,” Stephen Lyman, PhD, an author of the study, told Orthopedics Today. “This can potentially guide surgeons and physical therapists in their efforts at returning athletes to the playing field. Further study should evaluate the benefit of longer rehabilitation and lower physical demands on the post-ACL reconstructed knee.”

He noted that the volume-outcome relationship for ACL reconstruction had not been previously established.

“The clinical relevance refers to that seemingly old adage that you do not want to be a surgeon’s first case and you do not want to be his last.”

The research appears in the October issue of The Journal of Bone and Joint Surgery.

“This is interesting data, but the root cause of the findings cannot be answered by such a study and needs to await further refinement of population ACL outcome data,” Elizabeth A. Arendt, MD, an Orthopedics Today editorial board member, told Orthopedics Today. “Results of ACL surgery relates to many factors, the majority of which cannot be assessed in such a study. Nonetheless, it clearly outlines troublesome results that merit further study.”

Risk factors

Using the New York State Department of Health’s Statewide Planning and Research Cooperative System database, Lyman and colleagues identified more than 70,000 ACL reconstructions performed in the state between 1997 and 2006.

The investigators discovered that these procedures dramatically increased 21.5% during the study period. They also found a 2.3% readmission rate within 90 days of surgery and a 6.5% rate for subsequent knee surgery within 1 year. Of the subsequent knee surgeries, the investigators discovered that 28.7% were for another ACL reconstruction. Overall, they found that 1.9% of patients had a subsequent ACL procedure within 1 year of their original operation.

In addition, they found that women, patients who were treated at hospitals that performed less than 52 ACL reconstructions per year and those who had a concomitant knee surgery were more likely to have a subsequent knee surgery within a year.

Patients younger than 40 years, those who had a concomitant meniscectomy or knee surgery, and those treated at hospitals that had fewer than 125 ACL reconstructions per year were more likely to undergo a second ACL reconstruction.

Arendt said that the epidemiological data provided by the study is helpful to examine trends and the bigger picture, but noted that it is difficult to draw conclusions.

“The hardest conclusion to draw is the number of ACLs a hospital does influences an individual’s outcome,” she said. “If all 125 ACLs were done by the same surgeon, that is different than 125 ACLs being done by 10 surgeons.”

“In fact, our statistical modeling choice (generalized estimating equation) accounts for both surgeon and hospital volume in the same model, so the effects found are independent of one another,” Lyman told Orthopedics Today.

Limitations

Lyman noted that other studies have shown a higher risk of ACL injury in women, which could be attributed to female anatomy, hormonal differences, muscle density and tissue laxity.

“What had not been previously demonstrated was that after ACL reconstruction, women may also have a higher risk of needing another operation, likely due to these same mechanisms,” Lyman said.

He also noted that the investigators did not have information regarding which limb was treated and the type of graft used.

“The higher need for women to have subsequent surgery could be that women preferentially received hamstring grafts rather than patellar tendon grafts, and that these hamstring grafts were more likely to fail,” Lyman said. “However, we have no information about that, which is a substantial limitation.”

For more information:
Elizabeth A. Arendt, MD, can be reached at the University of Minnesota, Department of Orthopaedics, Box 492, 420 Delaware St. SE, Minneapolis, MN 55455-0374; 1-612-273-8000; e-mail: arend001@umn.edu.

Stephen Lyman, PhD, is the director of epidemiology and biostatistics at the Hospital for Special Surgery. He can be reached at 535 E. 70th St., New York, NY 10021; 212-774-7125; e-mail: lymans@hss.edu. They have no direct financial interest in any products or companies mentioned in this article.

Reference:

Lyman S, Koulouvaris P, Sherman S, et al. Epidemiology of anterior cruciate ligament reconstruction. Trends, readmissions and subsequent knee surgery. J Bone Joint Surg Am. 2009;91:2321-2328.