ACLR Study Wins 2018 OREF Clinical Research Award

By: Mark Crawford


Gregory B. Maletis, MD

During Thursday’s Your Academy 2018 event, Gregory B. Maletis, MD, and coauthors Tadashi Funahashi, MD; Maria Inacio, PhD; and Liz Paxton MA, will be presented with the 2018 OREF Clinical Research Award for their study “Optimizing Anterior Cruciate Ligament Reconstruction.”

The research team from Kaiser Permanente analyzed 39,379 cases from the Kaiser Permanente Anterior Cruciate Ligament Reconstruction Registry (KPACLRR) to identify patterns that could lead to improved surgeon decision-making and patient outcomes.

Anterior cruciate ligament (ACL) injuries, many of which are sports-related, often require reconstructive surgery. Although studies show that approximately 70 percent to 80 percent of athletes who undergo ACL reconstruction (ACLR) return to sports, only about half of them return to the same level of play. These inconsistent outcomes demonstrate the need for developing more effective ACLR methods.

“Many factors contribute to the outcome of ACLR surgery,” said Dr. Maletis. “Graft choice is one factor that has been extensively evaluated, but many questions remain regarding the best graft for ACLR.”

For example, the bone-patellar tendon-bone (BPTB) autograft is a standard approach, but patients may suffer knee pain at the graft harvest site. Hamstring autografts are also effective, but require tendon-to-bone healing and may cause hamstring weakness. Allografts have advantages over autografts including no harvest site morbidity, shorter operative time, improved cosmesis, and less postoperative pain. However, studies show that revision rates are two- to four-times higher with allografts, compared to autografts.

“Despite years of study, controversy regarding the optimal graft for ACLR remains, suggesting that a single graft type is not ideal for all patients,” Dr. Maletis stated. To better understand the factors that impact graft performance, he and his colleagues studied a large community-based ACLR registry with the hope of identifying patterns that could help surgeons determine which surgical procedure works best for individual patients.

Nearly 39,400 cases analyzed

The Kaiser Permanente team utilized the KPACLRR, which was established in 2005 to gather data on clinical practices and patient outcomes. At the time of this research, more than 340 sports medicine surgeons had contributed ACLR case files to the Kaiser Permanente registry.

“Registries can help identify good and poor outcomes,” said Dr. Maletis. “If that data is provided to surgeons, it can be used to change practice patterns and improve patient care within a system of care. In general, it is very difficult to measure the effect that particular studies have on how physicians practice, but a registry provides the ability to track practice patterns and outcomes over time, and changes can be measured.”

As of 2016, the KPACLRR contained 39,379 cases. Of these, 36,186 were primary ACLRs and 3,193 were revision ACLRs. Numerous statistical methods were used to analyze the registry data, including descriptive statistics for reporting and multivariable regression, survival, and propensity scores to control for potential confounding variables. Machine-learning methods were also used for outlier identification and risk calculator development. 

To promote personalized preoperative counseling, the team developed a risk calculator using the KPACLRR data. The risk calculator can predict the probability of graft survival within a period of time based on specific patient characteristics that were identified as risk factors for revision. Twenty-two variables were screened; the top four predictive variables of revision were age, activity, body mass index, and graft type.

“When entered into the risk calculator, these variables can predict the probability of graft survival through the first 6 years after surgery, and provide comparative risks depending upon selectable risk factors,” said Dr. Maletis.

Dr. Maletis said he was surprised by what the data revealed, including the high number of allografts being performed within Kaiser Permanente, especially in younger patients. He also found it surprising that BPTB allografts were associated with a higher risk of revision than soft-tissue allografts, and that allograft processing techniques had a time-dependent impact on revision rates.

“Over time we have seen a decrease in the overall usage of allografts within our organization—especially in younger patients—and in the usage of higher-risk allografts, specifically those with higher dose irradiation or that are chemically processed,” he noted. “This will lead to better outcomes for our patients.”

Future possibilities

“The key clinical findings from our studies indicate that allografts, despite their popularity, have a higher rate of revision compared to autografts,” said Dr. Maletis. “In addition, processing techniques of soft-tissue allografts have a time-dependent impact on the rate of revision: Irradiated allografts and chemically processed allografts tend to fail at earlier time points than nonirradiated, nonchemically processed allografts. Regardless of irradiation or chemical processing, BPTB allografts have higher failure rates than soft-tissue allografts, and probably should be avoided. We are continuing to follow the nonirradiated and nonprocessed soft-tissue allografts to see if longer-term follow-up reveals differential failure rates compared to autografts.”

The references for this article can be found in its online version, available at

Mark Crawford is a contributing writer for OREF.

© Orthopaedic Research and Education Foundation (OREF)


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