Postoperative: Medical Complications (Deep Venous Thromboembolism, Infection)

Introduction

Medical complications are uncommon following anterior cruciate ligament reconstruction (ACLR), yet their impact is not insignificant because of the frequency with which this procedure is performed. Further, these adverse events involve significant patient morbidity and represent a financial burden of over $1 billion annually, underscoring the importance of adequate management and prevention. This chapter will focus on the two medical complications most frequently encountered following ACLR: septic arthritis and venous thromboembolism. Although the relatively low incidence of these events precludes the establishment of robust clinical guidelines, the current literature allows for conclusions to be drawn regarding appropriate practices for diagnosis, treatment, and prevention.

Septic Arthritis

Background

The incidence of septic arthritis following ACLR is low, with accounts in the literature placing the incidence rate at 0.15% to 0.98%. Yet, septic arthritis has been reported as the third most common reason for reoperation after ACLR, accounting for approximately 15% of returns to the operating room. ACLR procedures involve several factors that may increase the risk of septic arthritis compared with simple arthroscopy. Drilling of bone tunnels and passage of a graft requires extensive soft tissue dissection, creating surgical sites that are easily contaminated. The incision for the tibial tunnel allows hematoma formation in the pretibial subcutaneous tissue, making it a particularly common site for infection. Although superficial infections are typically benign, newly formed bone tunnels may provide a conduit to the intraarticular space. ^, ^, ^, Furthermore, ACLR involves a high foreign body load. Graft tissue, suture material, and interference screws can all serve as a nidus for glycocalyx formation. ^, ^,

Recent studies demonstrate lower rates than those reported historically, indicating that our ability to prevent postoperative infection has improved. Despite this, the implications of knee septic arthritis cannot be underemphasized. Bacterial toxins are destructive, and can destroy greater than half the glycosaminoglycan content of articular cartilage within one week. ^, ^, Consequences range from chondral thinning to full-thickness lesions, accelerating the development of osteoarthritis. ^, ^, ^, ^, Toxins may also contribute to arthrofibrosis, meniscal tears, and graft failure. If not addressed appropriately, the resulting joint dysfunction and instability can prolong recovery and lead to poor outcomes. ^, ^, ^,

Risk Factors

Patient-Specific Factors

Diabetes mellitus appears to be the patient-specific factor that confers the highest relative risk for infection. Although the prevalence of diabetes is low among the population undergoing ACLR, these patients have almost twenty times the odds of infection relative to nondiabetics, and patients should be counseled appropriately. Tobacco use, known for its broad detrimental effects on tissue healing, was recently identified as an independent risk factor for infection after ACLR. Patients with a prior intraarticular surgery of the ipsilateral knee, as well as those requiring concomitant procedures at the time of ACLR, are also at increased risk of infection. This is likely influenced by a combination of factors, including prolonged operative and tourniquet time, additional or larger incisions, and increased foreign-body loads. ^, ^, ^, ^, ^, Interestingly, status as a professional athlete is associated with an increased risk of infection compared with amateurs. This may be explained by a greater exposure to infective organisms and a higher likelihood of undergoing more extensive procedures in this population.

Surgeon-Dependent Risk Factors

The primary surgeon-dependent factor associated with infection following ACLR is the choice of graft material for reconstruction. Bone-patellar tendon-bone (BPTB) autograft carries a low incidence of postoperative infection. ^, Hamstring tendon, the other primary source of autograft, has been shown by multiple authors to be associated with an increased risk of infection after ACLR compared with other graft types. ^, ^, ^, ^, ^, Although the reason for this disparity is unclear, several possible explanations exist. Soft tissue dissection during hamstring tendon harvest may increase the likelihood of hematoma formation, facilitating bacterial growth near the tibial tunnel. Further, additional time required for hamstring graft harvest and preparation may increase exposure to bacterial contamination. ^, Others have postulated that the lack of bone and presence of suture material makes hamstring grafts more susceptible to infection. ^, Although initial studies comparing autograft and allograft tissue showed conflicting results, a recent metaanalysis reported no difference in the incidence of infection between these two groups. Among allograft choices, there is also no difference between processed and nonprocessed grafts.

A higher incidence of infection has been reported in cases using flash sterilization compared with standard methods. Although the difference was not statistically significant, this topic warrants mention. Flash sterilization meets only minimum sterilization standards, and flash-sterilized instruments can easily be contaminated during transport because they are not enclosed in sterile packaging.

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