Most of the time, anterior cruciate ligament (ACL) repairs or reconstruction go very well. The results are as intended and expected. Patients regain full use of the knee and return to their preferred activities — even at a level equal (or better) than before the injury. But unfortunately, there is a group of patients who end up needing a second knee surgery — and even sometimes surgery on the other leg.
Your question: how can you tell if this scenario might happen to you is a good one. An investigation performed at the Vanderbilt University Medical Center in Nashville, Tennessee may shed some light on both the rate of second surgeries and the risk factors (or “predictors”) for subsequent surgeries.
They followed almost 1,000 patients over a period of six years after ACL reconstructive surgery on one leg. Any further surgeries on the involved leg or the other knee were reported and analyzed. They found a surprising number of patients required additional knee surgery on the same leg that had the first ACL reconstruction (18.9 per cent). That is almost one out of every five patients. And another 10 per cent (one out of every 10 patients) later had surgery on the other knee.
What happened that these patients required further procedures and why? In the first group (rate of 18.9 per cent of revisions), there were four categories of problems. These included: 1) ACL revision (7.7 per cent), 2) cartilage repair or removal (13.3 per cent), 3) scar tissue or fibrosis removal from the joint (5.4 per cent), and 4) problems with the hardware left in the joint (2.4 per cent). In the 10 per cent group who had surgery on the other knee, ACL tears and injuries to the cartilage were the main two reasons for a second surgery.
The majority of patients only had one additional surgery. But there were some individuals who had a second, third, or more surgeries. Further analysis of the data showed that younger patients (younger than 18 years) were more likely to need further surgery. Younger patients with a ruptured ACL may just be more active putting them at increased risk of further problems. Or they may not follow the physician’s and physical therapist’s instructions after surgery. This type of noncompliance could be a factor but was not determined in this study.
One other patient-related factor was mentioned but not studied: the potential for reinjury based on genetic features such as collagen disruption affecting both ligaments and cartilage. A third risk factor (predictor) was the use of an allograft (from a donor rather than from the patient) to reconstruct the damaged ACL. This factor falls under the category of surgical technique (rather than being a patient-related factor).
The authors questioned whether being overweight or female might be other risk factors or predictors of subsequent knee surgeries. But this was not the case in this study. Other studies have reported higher reoperation rates among females.
Additional surgeries cost more money and often lead to decreased patient quality of life and satisfaction. Finding ways to prevent subsequent knee surgery will be the focus of future research efforts. Although age is a nonmodifiable risk factor, the use of allografts will be investigated further. With this information in mind, you can have a frank discussion with your surgeon about your risks and the likelihood of your need for a second (revision) surgery.