ACL Reconstruction: A Rising StarAnytime a common surgical procedure is done, it is important to follow-up and make sure the operation was done safely and had the intended outcomes. In this study, the results of anterior cruciate ligament (ACL) reconstruction were evaluated. The three areas of interest were: 1) number of ACL reconstruction surgeries done between 1997 and 2006, 2) how often these patients need another surgery later, and 3) risk factors to predict readmission and revision rates.
A statewide hospital database from New York was used to gather information. Using hospital identification numbers and physician license numbers, the researchers were able to calculate annual volume for both the 263 facilities and the 1513 surgeons involved. Basic information about over 70,500 patients who had an ACL reconstruction was collected (e.g., age, sex, type of insurance coverage, and the presence of other health problems).
About one-third of the ACL reconstructions were the only procedure performed. But the majority (two-thirds) of the patients had other repairs done to damage in the knee, most often meniscal (cartilage) repair or removal. A small number of patients (45 of the total 70,500) had a total knee replacement at the same time as the ACL surgery. The coding process did not record which knee was being operated on, so the authors were unable to tell if subsequent surgeries were on the same knee or the other knee. For this study, they just gathered information for either knee.
What they found was that most of the procedures were performed on an out-patient basis. Reconstruction procedures done on an inpatient basis were usually for patients who had other health issues that put them at increased risk requiring closer follow-up surveillance. Surgeons who performed at least one ACL reconstruction procedure each week (labeled high volume) had the best results. High volume was defined as at least one ACL reconstruction per week (more than 52 per year). Only doing one procedure every two months for a total of less than six per year placed the surgeon in the low volume category. Likewise, the results were better when the surgeries were done in a high volume hospital (defined as one ACL procedure every other day for a total of at least 125 each year).
Statistically, 2.3 per cent of the patients were readmitted within 90 days of the ACL reconstruction. That is considered a fairly low rate. The reasons for readmission were usually infection, stiffness, or need for further rehab. Less often, the problem was more of a medical (health) issue such as appendicitis or heart attack. More patients (6.5 per cent) ended up having another knee surgery (on either knee) within the first year after the ACL reconstruction. And although this study couldn't report on which knees needed surgery later, other studies have shown that the opposite knee is involved most often. The reasons for subsequent knee surgery ranged from knee pain, to infection, to scar tissue build up.
The patients who had the highest readmission rate (within 90 days) were older men (more than 40 years old) or those who had other health problems. Patients were also more likely to be readmitted for problems if they were operated on by a lower-volume surgeon in a lower-volume hospital. The risk of having a subsequent ACL surgery (within one-year) was highest among patients who were younger than 40 (especially those who were younger than 20 years old). That may be because they are more active and less likely to follow guidelines on restrictions following surgery. One other risk factor for later problems requiring additional surgery was having a meniscectomy (meniscus removal) at the time of the initial ACL reconstruction procedure.
The authors say that ACL reconstruction is still a safe and effective procedure. But it is not without its problems. With the overall number of ACL procedures on the rise each year, it's a good idea to take a look and see how results can be improved. Although the results of this study were reported for patients in just one state (New York), there is no reason to suspect they don't represent the overall picture for outcomes of ACL reconstruction. It may be necessary to take a closer look at the results between patients who have an isolated ACL procedure and those who have other (called concomitant) procedures at the same time.
There are a few other challenges in a study of this type. The finding that younger males are more likely to have subsequent surgeries bears further investigation. Given the fact that younger adults (college age and early 20s) tend to move around, there may be a higher number of revision and second surgeries than was reported here. Age as a factor (older and younger) was the central finding of this study, but other similar studies have not confirmed these results. There seems to be a wide range of results reported when age is analyzed as a predictive factor of outcomes.
Anterior cruciate ligament reconstruction is a technically demanding procedure. The complexity of the procedure is a risk factor of its own. Surgeon and hospital volume are important but there are many other possible risk factors yet to be explored when trying to isolate what it is that causes patients to require readmission or subsequent surgery. Type of injury, time between injury and surgery, presence of concomitant injuries in either knee, and general health history need to be explored further. Future studies are needed to look at technical failures versus additional injuries as risk factors.
For now, we know ACL injuries are common, the number of ACL surgeries is on the rise, and reconstructive surgery is challenging but safe and effective. Finding ways to reduce complications, improve outcomes, and eliminate the need for subsequent surgeries will remain key features of ongoing studies such as this one.
Stephen Lyman, PhD, et al. Epidemiology of Anterior Cruciate Ligament Reconstruction. In The Journal of Bone and Joint Surgery. October 2009. Vol. 91-A. No. 10. Pp. 2321-2329.
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