The Timing of Corticosteroid Injections following Knee Arthroscopy Influence Infection Risk

Abstract

Objectives:

Although some surgeons will offer an intra-articular corticosteroid injection to accelerate post-operative recovery and decrease inflammation and swelling following knee arthroscopy, there is a paucity of literature evaluating the safety of this practice. Therefore, the purpose of the present study was to examine any association between between the timing of postoperative corticosteroid injection following knee arthroscopy and infection.

Methods:

Private-payer (PP) and Medicare (MC) national insurance databases were queried for patients who underwent simple arthroscopic knee procedures, including partial meniscectomy and chondroplasty. Patients undergoing concomitant open or more complex procedures with grafts were excluded. Patients who received ipsilateral knee corticosteroid injections within 2, 4, 6, and 8 weeks postoperatively were then identified. Postoperative infection within 90 days after the injection was assessed using ICD-9 and CPT coding for all study groups and compared using a multivariate binomial logistic regression analysis. Adjusted odds ratios (OR) and 95% confidence intervals were calculated with p < 0.05 considered significant.

Results:

5,533 patients were identified and met inclusion criteria, including 725 that received an injection within 2 weeks, 1,236 patients that received within 4 weeks, 1,716 that received an injection within 6 weeks, and 1,856 patients that received an injection within 8 weeks postoperatively. In both the PP and MC datasets the rate of infection was significantly higher in the 2-week cohort compared to the 6 week (PP: OR 3.81, p = 0.012; MC: OR 9.36, p = 0.001) and 8 week (PP: OR 8.59, p = 0.003; MC: OR 7.80, p = 0.001) cohorts [Tables 1, 2]. The rate of infection was also higher in the 4-week cohort compared to the 6 week (PP: OR 2.54, p = 0.024; MC: OR 8.91, p = 0.001) and 8 week (PP: OR 5.64, p = 0.009; MC: OR 7.80, p = 0.001) cohorts [Tables 1,2]. There were no differences in infection rates between the 2 and 4 week cohorts in either dataset (PP: p = 0.278; MC: p = 0.861).

Conclusion:

The findings of the present study add to a growing body of evidence that discourages the use of corticosteroids in the perioperative period for knee arthroscopy due to the risk of infectious complications. There was a significant association between intra-articular knee corticosteroid injections within 4 weeks of surgery and an increased incidence of postoperative infection in both Medicare and private payer patients after knee arthroscopy compared to patients with steroid injections more than 4 weeks postoperatively. In the absence of any prospective studies on this topic, we caution against the use of steroid injections within one month following knee arthroscopy.

Table 1a.

Infection Rate Stratified by Post-Operative Injection Timing (Humana)

Post op Time Point	N Patients	# of Infections	Infection Rate
2 week	462	16	3.5%
1 month	585	12	2.1%
6 week	807	6	0.7%
2 month	870	3	0.3%

Table 1b.

Statistical Analysis (Humana)

	2 Week Injection		1 Month Injection
Comparison Time Point	O.R. [95% C.I.]	P	O.R. [95% C.I.]	P
2 week	n/a	n/a	0.62 [0.26 -1.47]	0.278
1 month	1.61 [0.68-3.82]	0.278	n/a	n/a
6 week	3.81 [1.63-8.91]	0.012	2.54 [1.31-4.93]	0.024
2 month	8.59 [2.59-28.54]	0.003	5.64 [1.77-17.90]	0.009

Table 2a.

Infection Rate Stratified by Post-Operative Injection Timing (Medicare)

Post op Time Point	N Patients	# of Infections	Infection Rate
2 week	263	9	3.4%
1 month	651	21	3.2%
6 week	909	2	0.2%
2 month	986	3	0.3%

Table 2b.

Statistical Analysis (Medicare)

	2 Week Injection		1 Month Injection
Comparison Time Point	O.R. (95% C.I.)	P	O.R. (95% C.I.)	P
2 week	n/a	n/a	0.93 [0.39-2.21]	0.861
1 month	1.08 [0.45-2.59]	0.861	n/a	n/a
6 week	9.36 [2.60-33.8]	0.001	8.91 [2.03-39.1]	0.001
2 month	7.80 [2.29-26.6]	0.001	6.39 [2.30-17.8]	<0.001