Arthroscopic images of the knee demonstrating significant synovitis and adhesions in the patellofemoral space before (A) and after (B) arthroscopic débridement. (Reproduced from Cadet ER, Makhni EC, Mehran N, Schulz BM: Management of septic arthritis following anterior cruciate ligament reconstruction: A review of current practices and recommendations. J Am Acad Orthop Surg 2013;21[11]:647-656.)

AAOS Now

Published 6/1/2016
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Peter Pollack

Treating Septic Arthritis, Knee Instability after ACL Reconstruction

Military study looks at factors affecting functional outcomes
Septic arthritis is a rare complication that can occur after anterior cruciate ligament (ACL) reconstruction, with incidence rates estimated to be between 0.14 percent and 1.8 percent of cases. However, the consequences can be devastating, affecting functional outcomes through instability, laxity, chondrolysis, and stiffness.

Arthroscopic débridement with early graft removal and staged revision may be a viable option for treating infection and restoring knee stability in these patients, according to MAJ Brian R. Waterman, MD, who presented his findings at the annual meeting of the Arthroscopy Association of North America.

"Although functional outcomes may vary," Dr. Waterman explained, "graft retention is associated with a higher rate of knee laxity at final follow-up, as well as after revision surgery. Earlier presentation within 2 weeks with graft retention is not associated with a decreased rate of graft laxity versus delayed presentation."

Rare but devastating
The researchers reviewed information from the Military Health System Management Analysis and Reporting Tool (M2) database—a repository of approximately 9.5 million individuals covering all military treatment facilities and purchased care. Using the database, they queried billing and coding data for ACL reconstruction cases and subsequent arthroscopic procedures related to infection. As noted by the investigators, those included in the study were active duty military patients who had undergone primary ACL reconstruction, had presented with secondary septic arthritis, and who had at least 24 months of follow-up.

Patients who had undergone alternate procedures such as revision ACL reconstruction, ACL repair, or synthetic graft were excluded. Other exclusion criteria included non-infectious indications, superficial or localized soft-tissue infections, and insufficient documentation.

"Of all individuals isolated, we found 9,500 primary and revision ACL reconstructions, and of these, we culled a subset of 31 individuals with confirmed septic arthritis after primary ACL reconstruction," said Dr. Waterman, who noted that, at an average follow-up of 27 months, 22 individuals (71 percent) had retained their grafts.

"Overall, 48 patients were able to return to duty," he continued. "There were no recurrent infections, but 10 percent of patients did have some objective loss of range of motion and nearly 25 percent had secondary symptomatic arthritis."

Dr. Waterman pointed out that the median time from surgery to first débridement was 35 days, with 6 patients (19 percent) undergoing débridement within 2 weeks, 19 patients (62 percent) undergoing débridement in the period between 2 weeks and 2 months, and 6 patients undergoing the procedure more than 2 months after ACL reconstruction.

Overall, 15 patients (48 percent) displayed no growth on subsequent aspiration cultures. Of the rest, 10 patients (32 percent) had methicillin-sensitive Staphylococcus aureus, three patients (10 percent) had methicillin-resistant S aureus, two patients (6 percent) had methicillin-resistant S epidermidis, and one patient (3 percent) had Enterobacter.

The average number of débridements was 2.3 per patient, and culture-specific antibiotics were administered for an average of 6.2 weeks.

Of the 22 patients with graft retention, 15 had a stable knee and seven did not. Of those seven, three underwent revision surgeries, and of those three, two finally achieved stability.

Of the nine patients who underwent graft débridement, seven had subsequent revision. Of those seven, all achieved stability.

Predictors
"Interestingly, autograft, bacteria type, number of débridements, and postoperative timing were not predictive [of graft retention]," noted Dr. Waterman.

"Early timing of presentation has been proposed as a protective factor for graft retention," he continued. "And yet, we did not find that in our study, as 50 percent of individuals who presented within 2 weeks had increased graft laxity.

"Similarly," he added, "aside from presence of complications, we found no differences in ability to return to full military duty based on individual variables."

According to Dr. Waterman, study limitations included nonrandomized design, lack of standardized surgical indications, absence of validated patient-reported outcomes, procedures having been performed by multiple surgeons, and various patient-specific factors.

Dr. Waterman's coauthors are CPT William Arroyo, MD, and MAJ Michael Zacchilli, MD. The authors' disclosure information can be accessed at www.aaos.org/disclosure

Peter Pollack is the electronic content specialist for AAOS Now. He can be reached at ppollack@aaos.org

Bottom Line

  • One hundred percent of patients who underwent arthroscopic débridement with early graft removal and staged revision had restored knee stability, although functional outcomes varied.
  • Graft retention was associated with a higher risk of knee laxity at final follow-up, even after revision surgery.
  • Time to presentation with graft retention was not associated with rate of graft laxity.