Knee Effusion after Arthroscopic Partial Meniscectomy: Prospective Study Comparing Preventing Methods

Background: Knee joint effusion is a common adverse event after arthroscopic procedures and its prevention is crucial to achieve better clinical outcomes, such as pain relief, improved range of movement and global satisfaction. Objective: The aim of this study is to compare joint effusion after partial arthroscopic meniscectomy between a common postoperative management and a short period in deep flexion. Methods: A prospective study ran-domizes 62 patients who underwent arthroscopic partial meniscectomy into 2 groups of postoperative care: compression elastic bandage with elevation for 24 hours (compression group) versus immediate postoperative deep flexion for 2 hours (flexion group). Clinical evaluation of effusion was made at 24 hours, 7 days and 1-month post-surgery. Results: Overall at 24 hours patients showed 53% absent effusion, 35% minimum, 11% had mild or more severe effusion. Effusion rates in the compression group were 13%, 10% and 0%; in the flexion group 10%, 6.4% and 0%, at 24 hours, 7 days and 1 month, respec-tively. There was no statistically significant difference between them (p > 0.05). Conclusion: In the studied population, position of the knee in deep flexion had similar influence in effusion outcomes than a standard widely used treatment, offering an alternative in the postoperative care of the patients.

process secondary to intraoperative trauma or intra articular injuries is effusion.
It is known that articular effusion causes postoperative inconvenience such as pain; also influences recovery process, tissue repair, range of movement (ROM), muscle activation, clinical evolution and global satisfaction of the procedure [1] [2] [3] [4]. Knee arthroscopy is a minimally invasive procedure in which the whole joint sustains a traumatic process of variable intensity due to penetration of surgical instruments and fluid. It is associated to reduce hospital stay, less morbidity, earlier recovery and less radiologic changes in comparison to open surgery [5]. Depending on the type of procedure performed, there will be different degrees of inflammation and trauma, being bleeding the most common cause of effusion [6] [7]. Partial meniscectomy consists in removing injured meniscal tissue aiming to preserve as much healthy tissue as possible in an attempt to reduce pain and long-term chondral damage [8]. This procedure is indicated in different types of meniscal lesions resulting in the most common of all orthopedic surgeries [9].
Reducing knee effusion after arthroscopic procedures is an important operative goal in order to achieve earlier and a comfortable postoperative period. A frequent, postoperative care to avoid effusion after partial meniscectomy, is installing compressive elastic bandage, leaving the knee in elevation and semi flexion during the postoperative period until hospital discharge. This management takes time in the operating room, leaves the patient with the bandage and in a reduced mobility position that is often uncomfortable especially in the overnight patients.
Ewing and associates [10] described that the mean intra articular pressure during arthroscopy while the knee is in forced flexion is 159 mmHg and in flexion just 78 mmHg [1]. Based on these findings we postulate that an immediate postoperative period in deep flexion could prevent bleeding by raising the intraarticular pressure and thus diminishing the appearance of joint effusion. Accordingly, we compared the postoperative care previously mentioned with a postoperative period in flexion in order to determine the efficacy of this innovative position.
After thorough research of 2 medical databases (Medline & Embase) by 2 independent reviewers we did not find any study regarding the effects of knee position on articular effusion post arthroscopic procedures.

Methods
We designed a randomized prospective study which included only patients who underwent partial meniscectomy by the same surgical team (one surgeon) in a private practice clinic between April 1 st , 2013 and May 30 th , 2013. Partial meniscectomy was performed in a standard fashion using mechanical debridement with shaver and tissue stabilization with low grade radiofrequency. Patients who required additional procedures due to associated intraarticular pathology, requiring removal of bone, cartilage procedures or wide synovectomy, were ex-

Results
After  (Table 1). We did not find statistically significant differences in the level of effusion in neither the 24 hours, 7 days nor 1-month clinical evaluations.
None of the patients had clinically significant effusion (≥Mild) 1 month after surgery.
Effusion levels dropped importantly within a week and after a month clinically significant effusion was absent in both groups. Minimal effusion had the highest prevalence within all groups of effusion at 24 hours, reaching 35%, more details regarding the level of effusion at 24 hours can be seen in Table 2. The prevalence of preoperative effusion was 3% in both groups. Effusion prevalence at 24 hours, 7 days and 1 month, in the flexion group was 10%, 6.4% and 0%; and in compression group was 11%, 8% and 0%, respectively. More details about prevalence of effusion can be seen in Table 3.
Patients of the flexion group had good tolerance of the deep knee flexion positioning ( Figure 1) and none of the patients complained of discomfort. The above was addressed by the nurse in charge of the recovery and hospitalization, who was specifically instructed to release the position after 120 minutes after surgery. Also, neither of the patients in this group presented vascular abnormalities nor cutaneous lesions.

Discussion
Knee arthroscopy is a low morbidity procedure, in accordance with findings made by Lubowitz [11] who describes 82% unease walking rate at 7 days post-surgery in his 72 patient's cohort and Stetson and Tamplin [12] who found that prior to 20 days all their patients return to normal activity levels. Siemieniuk et al. [13] described a recovery period between 2 and 6 weeks post arthroscopy in which pain, effusion and limited function was present.
Alkan found rates around 70% for mild or superior effusion the first week after arthroscopy with a confidence interval between 56% and 85% in the control group of his effusion prevention study [14]. Unlike our study, that shows just 8% effusion prevalence one week after partial meniscectomy (confidence interval: 0.3% -18%). This difference could be explained due to inclusion of patients with wide synovectomy, different surgical technique and postoperative care.
Tatari [15] in his study of 57 patients who underwent partial meniscectomy, found that none of them presented significant effusion at 4, 7 nor 15 days after the procedure. Concordantly, our group found similar results with 92% of patients not presenting significant effusion at 7 days post intervention. In addition, Chana's study has similar results, showing minimal or absent effusion at 2 weeks post arthroscopy [16].
Regarding therapeutic alternatives to prevent effusion, other authors compare the usual management versus postoperative drainage and other alternatives.
They found no statistically significant difference between the usual care [14] [15] [17] [18]. Yakin and Rogers [19] in their study of comparison between conventional therapy and laser therapy, they obtained an effusion absent rate of 74.4% after one month in the conventional therapy group (n = 43, confidence interval 59% -86%). Laser therapy had statistically significant lower rates of effusion but was not a cost-effective therapy. If we compare our results with Yakin and Rogers's trial, our rate of absent effusion at one month is 100%. One of the pitfalls in our study is the lack of a control group that would need to be without any postoperative care procedures, elevation, compression nor special positioning. The latter was analyzed but not included due to ethical reasons.
Our study also has a limitation of presenting wide confidence intervals, similar to what was found in the literature regarding this issue. Methods found in the literature are varied, thus making difficult the comparison between them. Definitely this study is an innovative postoperative care as we didn't find studies that compared knee positioning in the immediate postoperative care to prevent effusion.

Conclusion
In