A group of researchers from the Department of Orthopaedics and Rehabilitation at Walter Reed Army Medical Center, Washington DC have undertaken a study looking at the effect of drain use in the early post-operative period following ACL reconstruction. It is an interesting topic and a valuable piece of work, as there is very little published research in this area.
Previous research found that 51% of sports medicine fellowship directors routinely used post-operative drains after ACL reconstruction. This was a North American study and it must be said that the practice of using a drain following ACL reconstruction is very much more common in the United States than in the UK. The theory behind using a drain is based on removing serous fluids and blood from the operated joint with the aim of allowing greater range of movement and reducing scar formation and adhesions. However, previous orthopaedic research has shown no benefit of drain placement, with many studies reporting increased complication rates associated with post-operative drain usage, most notably post-operative infection.
The authors undertook a prospective randomized blinded evaluation on the effect of drain use in the early post-operative period after arthroscopically assisted ACL reconstruction with bone-patellar tendon-bone graft in 21 patients. The treatment group consisted of 12 patients, and 9 were in the control group. The drain was removed from the treatment group 24 hours after the operation, as is standard practice. Four outcome measures (pain, knee flexion, knee extension and suprapatellar girth) were examined over the first seven post-operative days.
Pain scores on a visual analogue scale demonstrated the same improving trend over time for both the treatment and control groups; however, the treatment group had significantly higher average pain scores, except on day 7. The authors acknowledged that pain management may have been a confounding variable affecting the outcome of pain scores, since they did not track the volume or frequency of drug use to control pain.
What's more, comparing average pain scores between two groups is a contentious method as pain is highly subjective. In measuring pain, researchers are as much assessing the pain tolerance of the subjects as they are assessing the pain involved in the two methods. Averaging out the group scores will have the effect of attenuating any true differences, especially given the small sample size. From a methodological point of view, to truly assess the differences in pain between the two methods the same person would have to have two surgical procedures on the same knee, one with and one without a drain - then the pain scores could be compared. Obviously this is impractical in most cases. Perhaps it could be assessed in athletes who have repeat surgical procedures throughout their career.
Differences in the objective data - suprapatellar girth, flexion and extension - were not found to be statistically significant between groups. There is some ambiguity in the knee extension data - it was not clear if the degrees of extension represented hyperextension, or more likely degrees of extension lacking, in which case the data should have been presented as negative numbers.
The authors concluded that the use of a drain after arthroscopically assisted anterior cruciate ligament reconstruction provided no benefit in terms of range of motion, effusion, or pain in the early post-operative period. This fits with general clinical findings where, whether or not drains are used, knee swelling resolves and the patient makes a good recovery in most cases. Given the negligible value of the use of a drain in the first seven post-operative days, and the potential disaster of knee infection associated with its use, it is clear why so many surgeons prefer not to use this technique. Advocates of drain use may argue that other variables, such as knee joint adhesions, observed at long term follow up, may be more relevant variables to examine.