Approaches to Septic Arthritis of the Knee Post Anterior Cruciate Ligament Reconstruction

Abstract

Purpose of Review

Septic arthritis of the knee following anterior cruciate ligament reconstruction is a rare but potentially deleterious complication. The main approach to the management of this potentially devastating complication in recent years has involved a more aggressive attempt at preventing graft contamination during surgery with the adoption of the pre-soaking of the graft in broad-spectrum antibiotic solution, and early and adequate treatment of established cases of knee sepsis, with or without retention of the graft. However, what constitutes an early and adequate initial treatment may be a challenging decision for the surgeon to make in certain instances.

Recent Findings

Graft pre-soaking in vancomycin has been noted to significantly reduce the incidence of septic arthritis of the knee following anterior cruciate ligament reconstruction. Other studies have recorded similar satisfactory results with graft pre-soaking in gentamycin. In established cases of infection, irrigation and debridement with either graft retention or graft excision with delayed re-construction of the anterior cruciate ligament have both given satisfactory results in well-selected patients.

Summary

Septic arthritis of the knee following anterior cruciate ligament reconstruction can be prevented by careful patient selection, use of prophylactic antibiotics, strict asepsis during surgery, and graft pre-soaking in antibiotic solution. The choice of antibiotic solution for graft pre-soaking is influenced by the surgeon’s preference, tissue penetrance, effect on graft tensile strength, local bio-gram of the micro-organisms, and the sensitivity pattern. The treatment option in established cases would depend on the stage of infection, state of the graft, and the extent of bony involvement.

Introduction

The anterior cruciate ligament (ACL) is one of the ligaments in the knee that help ensure knee stability. It has a significant role in preventing excessive anterior translation of the tibia on the femur, and avoiding overextension of the knee as well as contributing to rotatory stability. Its proprioceptive role that helps detect changes in the location and direction of the knee joint, and speed of movement of the body has also been described [1, 2]. The ACL is one of the commonly injured ligaments in the knee with a prevalence rate of between 100,000 and 200,000 ruptures per annum reported in the USA while the rate in England has been documented at 24.1/100,000 [3–6]. The injury tends to be commonest in the young and active in the population and this injury can portend a significant functional limitation in this population of people [7]. A rupture of the ACL usually results from pivoting and under cutting movements associated with some activities and sporting events like football, lawn tennis, basketball, and gymnastics. A rupture of the ACL would usually result in knee joint instability with possibly associated meniscal and chondral injuries [8, 9].

One of the treatment options for a ruptured ACL is the use of autografts or allografts to reconstruct the torn ligament. A potential complication of this reconstructive procedure is septic arthritis of the knee postoperatively with the accompanying challenges of prolonged restoration of knee function, multiple surgeries, and possibly unsatisfactory outcome of care in the long term [10, 11••]. Septic arthritis of the knee following ACL reconstruction can result in a lifelong debilitating outcome. It is for this reason that every practical step must be deployed in the active prevention, and prompt treatment of established cases of knee sepsis following anterior cruciate ligament reconstruction.

Epidemiology

Septic arthritis of the knee following ACL reconstruction has been described to be a relatively rare complication and the incidence rate has been reported to be 0.14% to 1.8%, with the higher figures said to be reports from single-center studies [12–16]. Gobbi et al. in their study put the incidence rate at 0.37% while Makhini et al. in their systematic review established an incidence rate of 0.53% [17, 18]. The incidence of infection in allograft has been put at between 0.44 and 1.2% [19, 20].

Pathophysiology

Staphylococci have been described as the commonest organism isolated with a significant number being coagulase-negative; Staphylococcus epidermidis and methicillin-susceptible Staphylococcus aureus (MSSA). Cutibacterium acnes and Enterobacter spp. have also been isolated. [10, 21–23]. Clostridioides difficile knee septic arthritis following ACL reconstruction has also been described in an immunocompromised patient although this is said to be rare. A few cases of fungal infection post ACL reconstruction with organisms such as Candida albicans, and Aspergillus species as isolates, have also been documented. Fungal knee septic arthritis has been noted to run an indolent course with significant destruction of the knee cartilage and underlying bone and a high index of suspicion is advised in arriving at the diagnosis in these instances [24, 25].

Risk Factors

Factors that may predispose patients to postoperative infection include patient-related factors such as a distant site infection, smoking, immune compromise, diabetes mellitus, male gender, and a high body mass index (BMI). Operative factors such as choice of graft, use of prophylactic antibiotics, prolonged operation and tourniquet times, a breach in aseptic technique, concurrent open surgical procedures around the knee, longer incisions, use of a drain, concurrent cartilage, and/or collateral ligament reconstruction have all been noted to also increase the risk of postoperative infection [26••]. Specifically, age, obesity, and diabetes have been reported to be independent risk factors for septic arthritis following ACL reconstruction [27••]. In a study conducted by Kraus et al., male gender, hamstring tendon autograft, and operating time > 70 min were identified as independent risk factors [11••]. Hence, an optimum operation time of less than 70 min has been advocated as appropriate in the prevention of septic arthritis following anterior cruciate ligament reconstruction. Previous knee surgery is also associated with increased incidence of septic arthritis of the knee with a relative risk of 5.1 if the previous surgery was an ACL reconstruction [22]. In a large single-center cohort study of those who had ACL reconstruction, revision cases and younger patients were found to have higher incidence of intra-articular infection [28••].

Graft choice in ACL reconstruction has an important role in the etiology of septic arthritis of the knee following ACL reconstruction with an increased risk of infection observed with the use of hamstring graft as compared to bone-patellar tendon-bone (BTB) autograft [11••, 19, 22, 28••]. Allografts were initially thought to have a higher predisposition to postoperative septic arthritis of the knee until the use of irradiation and chemicals in the improved processing of allografts was introduced [29, 30]. The incidence of graft bacterial contamination during graft harvest has been reported as 2–23% while the incidence of knee septic arthritis post ACL reconstruction is estimated at 1.8% [16, 31, 32].

Graft contamination has been noted to be a predisposing factor to knee septic arthritis. This contamination may occur during graft preparation or during introduction of the graft into the knee through the arthroscopic portals [12]. Some of the reasons attributed to the higher contamination of hamstring graft include the following: the more complex hamstring preparation procedure and the presence of more sutures that can act as a foreign body and the possible contamination of the instruments used during harvesting by normal skin commensals.

Septic arthritis of the knee after ACL reconstruction has been described to be more likely when there is a high level of virulent organisms in the face of a high level of graft contamination [21].

In addition, the avascular nature of the graft for a period after implantation would imply that the perioperative intravenous antibiotic administered may not attain the necessary minimum inhibitory concentration at the graft site and this could provide a window for a previously contaminated graft to proceed to established infection of the graft and knee sepsis. This point has been one of the reasons for the pre-soaking of the ACL grafts in antibiotic solution prior to implantation of the graft into the knee [33].

Clinical Features

Patients developing septic arthritis of the knee following ACL reconstruction have been observed to present within 6–47 days between the initial surgery and presentation of signs and symptoms of knee sepsis in the hospital [27••, 34]. Barbara et al. [35••] reported a time interval of 6–100 days from reconstruction to onset of symptoms. In our experience, the patients with septic arthritis of knee after ACL reconstruction presented within the first 6 weeks from time of surgery. The common clinical features include knee pain, a swollen warm knee, fever, discharge from the portal sites, and impaired range of motion in the affected knee. Schollin-Borg et al. reported that knee effusion was a common finding on presentation, occurring in 9 of 10 patients in their series. Indolent presentation has also been described in literature with the absence of the above classic symptoms save for some knee pain [34].

Laboratory Parameters

Relevant laboratory investigations that may aid in the diagnosis include whole blood cell (WBC) counts and differentials, C-reactive protein (CRP) titer, and erythrocyte sedimentation rate (ESR), knee aspirate for microscopy culture and sensitivity, and knee aspirate white cell count. A rise in the level of inflammatory markers such as ESR, CRP, and a positive culture or elevated white cell count of the knee aspirate may support the diagnosis of septic arthritis of the knee post ACL reconstruction. Analyses of the knee aspirate for white cell count and microscopy have been noted to be the most sensitive diagnostic test for infection [36••]. A diagnostic aid described by Yazdi et al. [37•] in which any one of these laboratory parameters, positive culture or positive gram stain, a purulent knee aspirate, or knee aspirate white cell count of greater than 100,000/µl, was considered diagnostic of knee septic arthritis while at least two of the following criteria: turbid knee aspirate, a synovial white cell count of between 20,000 and 100,000 with a 75 to 90% polymorphonuclear cells, synovial glucose < 50% of serum value, or serum CRP levels > 150 mg/dl at day 3 or > 20 mg/dl at day 3, were described as highly suspicious of knee septic arthritis post ACL reconstruction [37•]. El-kady and Fouad El-Guindy [27••] described a diagnostic criterion in which a cloudy synovial fluid or a negative string sign (an instance in which the viscosity of the synovial fluid is lower compared to normal synovial fluid) along with a synovial WBC count > 50,000 cells/μL and a positive gram staining result of the knee aspirate was suggestive of knee sepsis. Costa et al. [36••] recently proposed a cut-off value of synovial WBC count 28,000 cells/mL and argued that this cut-off provides the highest accuracy in diagnosing septic arthritis after ACL reconstruction. However, Paci et al. [38] suggested a much lower threshold of synovial WBC count of > 16,200/mL be used as an indicator of infection with sensitivity of 86% and specificity of 92%. In a more recent editorial, Paci alluded to the fact that it may be difficult to define a “gold standard” threshold value for synovial fluid white cell count to diagnose post ACL septic arthritis of the knee due to the rarity of this complication. He opined to the use of synovial WBC of ≥ 15,000/mL, elevated polymorphonuclear cells of > 90%, and high clinical suspicion of knee septic arthritis to determine when to return the patient back to the operating room [39••]. These laboratory parameters should be considered along with clinical parameters in arriving at a diagnosis of knee septic arthritis post ACL reconstruction.

We caution against the use of a negative culture from the knee aspirate as the sole criterion to rule out septic arthritis of the knee following ACL reconstruction. We recorded three cases of knee sepsis post ACL reconstruction between January 2016 and January 2023 in our center. The knee aspirate taken for microscopy, culture, and sensitivity in all three cases yielded a negative result. The probable reasons for a negative culture in these instances may include cases of atypical organisms causing knee sepsis, incomplete treatment of the knee sepsis prior to presentation, self-medication with self-prescribed antibiotics prior to presentation in the hospital, or viral arthritis.

Staging of Infection

This is usually done arthroscopically after clinical and laboratory evidences of infection have been confirmed. Gächter [40] graded infection into 4 stages as follows: stage I is defined by joint effusion, redness of the synovial membrane, and possible petechial bleeding; stage II shows a severe inflammation, fibrinous deposition, and pus in the knee; stage III knee infection is associated with thickening of the synovial membrane and multiple pouches due to adhesions; and stage IV is defined by aggressive pannus with infiltration into the cartilage, possibly undermining the cartilage, radiological signs of subchondral osteolysis, and radiological signs with possible osseous erosions and cysts.

Treatment

The goal of treatment is to ensure a satisfactory outcome which is in turn predicated on early intervention to ensure complete eradication of infection with or without graft retention while protecting the articular cartilage and maintaining the range of motion of the knee. Early intervention would imply early institution of empirical antibiotic therapy that would cover the likely organisms involved and a diagnostic knee arthroscopy to visualize the ACL and copious lavage of the knee joint until a clear effluent is observed from the irrigation fluid. Once the microscopy, culture, and sensitivity results are obtained, the antibiotics are adjusted according to the sensitivity pattern. There is no consensus regarding recommendations for open versus arthroscopic treatment, type and duration of antibiotics, graft retention versus excision, and time to ACL revision [13]. What is done to the graft at the time of diagnostic arthroscopy would depend on the state of the graft at the time, whether it looks intact or frayed and compromised. Graft retention is advocated as much as possible, especially if the graft is still intact. However, clear indications for graft removal have been stated which include instances of concomitant osteomyelitis, damaged graft, and severe infection [14, 41–44]. The number of debridement and irrigation procedures may be dependent on the stage of infection and the existence of bony involvement at the time of presentation.

Approach to Treatment

Use of Antibiotics

The choice of antibiotics should be such as offers good cover against staphylococcal infections which is the commonest organism associated with this condition but should be a broad-spectrum intravenous antibiotic started empirically as soon as a diagnosis is made or there is a strong clinical suspicion of postoperative knee sepsis [45]. Antibiotic combinations are generally advised for clinical efficacy, and should be based on the cultured organism and chosen often in consultation with an infectious disease specialist. Various combinations that have been described in the literature include a third-generation cephalosporin and gentamycin or vancomycin [16, 17, 22, 46]. However, the use of aminoglycosides for a prolonged course should raise concerns over the possible complications of ototoxicity and nephrotoxicity. Data has also shown that the combination of rifampicin with either a third-generation cephalosporin or quinolones could be very effective in the eradication of staphylococcal implant-associated infections [47]. The choice of antibiotics should also be guided by ease of bone penetration, effective action against the biofilm that may form over the graft, and the existence of resistant strains. After the debridement and irrigation, an initial average of 3 weeks of intravenous antibiotics is advised, and then a change to oral antibiotics based on the results of the microscopy, culture, and sensitivity of knee aspirate or synovial biopsy for another 3 weeks, or until resolution of clinical symptoms and inflammatory markers. Lourtet-Hascoët et al. [48••] proposed empirical treatment with daptomycin and ceftriaxone, followed by an early switch to an oral combination of levofloxacin and rifampicin, for a total treatment duration of 6 weeks. An extended period of antibiotic therapy of up to 12 weeks has been described to allow for better graft incorporation in instances where infection control is achieved early with graft retention [28••].

Diagnostic Arthroscopy, Irrigation, and Debridement

This step is critical to early control of infection, rehabilitation, and eventual outcome. Arthroscopy helps to visualize the joint with the aim of staging the infection, examining the ACL graft, and offering appropriate treatment. The joint should be copiously irrigated with normal saline and synovectomy should be done in all cases with or without hardware removal. Schulz et al. [49] in using this approach to treatment reported a successful treatment of infection with or without the need for a repeat debridement. They advised early infections (stages I and II) be managed with arthroscopic irrigation and debridement while chronic or advanced infections (stages III and IV) be managed with a more radical open medial or lateral arthrotomy approach to achieve a favorable outcome. Peterson et al. [50] also treated these patients based on the stage of infection and recommended removal of hardware and debridement of the tunnel in cases of chronic infection. They concluded that an arthrotomy with open debridement may be required in stage IV with osteolysis.

Diagnostic Arthroscopy and Decision on Graft Retention or Removal

After debridement and joint lavage, the decision to retain or excise the graft at initial diagnostic arthroscopy is usually at the discretion of the surgeon and remains a topic of debate. This decision largely depends on the stage of infection, state of the graft at diagnostic arthroscopy, and sensitivity of the organism. Instances of diagnostic arthroscopy, arthroscopic debridement, and lavage with graft retention have recorded varied success rates in the literature [16, 22, 49, 51••]. The proponents of graft retention would argue that excision of the graft could lead to knee instability and subsequent articular cartilage damage. On the other hand, some surgeons believe that retaining the graft after debridement could make infection control very difficult.

Early graft removal is recommended if at initial diagnostic arthroscopy the graft appears already macerated and compromised or if there is persistence of clinical and laboratory evidence of septic arthritis of the knee after initial debridement and intravenous antibiotic therapy, guided by microscopy, culture, and sensitivity of the knee aspirate [52]. More specifically, some authors advise graft excision if infection persists after the second arthroscopic debridement and irrigation, as persistence of infection would imply the formation of a biofilm around the graft that makes antibiotic penetration difficult [28••, 53]. Immediate graft removal is also advisable if at diagnostic arthroscopy, a thick purulent exudate is tightly adherent to the graft, or the graft is noted to be elongated and non-functional [52]. However, if at diagnostic arthroscopy the ACL is observed to be intact and functional, most authors would prefer to retain the graft [34, 41, 42].

Repeat Irrigation and Debridement

A patient with persistent clinical infection despite debridement and lavage would be a candidate for a repeat procedure which could be an arthroscopic joint lavage or open debridement with or without graft excision. The timing of repeat irrigation and debridement varied in the literature. Timely intervention based on clinical evaluation with or without laboratory results remains key to take an early and appropriate decision. Buck et al. [52] had a repeat irrigation and debridement with graft excision two days after the first procedure in all patients with stage II infection. Hantes et al. [53] adopted a protocol of another arthroscopic debridement and irrigation with graft and hardware removal when symptoms persisted or did not resolve three to five days after the initial debridement. Localization of the infection to the femoral insertion point has been observed as a cause for serial debridement for eradication of the infection [54].

Decision on Open Arthrotomy With or Without Soft Tissue Procedures

Open arthrotomy, graft excision, and hardware removal with curettage of tunnels have also been described particularly in cases of persistent infection. This may be followed by placement of antibiotic-coated polymethylmethacrylate (PMMA) beads to allow for better infection control before graft reimplantation 6 to 8 months later [49]. Open debridement with a soft tissue procedure to cover surrounding soft tissue defect has been advocated in instances of persistent infection with attendant risk of osteomyelitis and soft tissue compromise as a means of achieving early infection control [55•].

Timing of Graft Re-implantation in a Staged Reconstruction

Graft re-implantation can be safely performed after adequate infection control has been achieved as evident by resolution of clinical symptoms and return of inflammatory markers to normal limits. Buck et al. [52] re-implanted a new ACL graft within 6 weeks of completion of intravenous antibiotic therapy. However, some authors reported a more favorable outcome with a delayed graft re-implantation at least 6–9 months after graft resection and infection control was achieved [12, 42, 44, 49].

Outcome of Treatment

The outcome of treatment varies from excellent to poor; depending on factors such as extent of disease at presentation and response to antibiotic and joint debridement with lavage. Generally, results have been described as less satisfactory when compared to cases in which no postoperative knee infection [22, 42]. Saper et al. [43] reported an average overall success rate of 85% in eradicating infection with graft retention and arthroscopic debridement and irrigation. Knee stability, range of knee motion, return to activity of daily living, and degenerative changes on imaging are some of the outcome measures studied in the available literature. Waterman et al. [56•] observed that the rate of return to active duty was low in the graft resection group when compared with the graft retention group. However, there was no difference in the ligament laxity between the two groups. They demonstrated that early debridement and graft resection with revision reconstruction yielded a reliable rate of knee stability when compared to graft retention. In contrast, Pogorzelski et al. [57•] reported superior postoperative clinical outcome in patients who had graft retention when compared to those who had initial graft resection. They concluded that graft retaining protocols should be given higher priority and immediate graft re-implantation should be performed in cases where graft resection becomes necessary, to avoid cartilage and meniscal lesions. Some authors have reported good functional outcomes of treatment with arthroscopic debridement, graft retention, and intravenous antibiotics but there was no comparison with the resection group [10, 43, 58]. A recent publication by Themessl et al. [59••] compared the rate of return to work and sport between patients who had initial graft retention and those with graft removal and consecutive revision ACL reconstruction. They observed that there was no statistically significant difference in the rate of return to work and sports between the two groups.

Of the three cases of knee septic arthritis in our case series, only one presented within the first week postoperatively and had a successful outcome of care with a single arthroscopic knee debridement, graft retention, and therapeutic antibiotic use over a 6-week period. The second case presented 5 weeks postoperatively and had arthroscopic knee debridement and lavage with graft retention but had significant reduction in the range of motion of the knee following infection control. The third case presented 6 weeks postoperatively and showed no improvement in symptoms after the second knee debridement and graft retention. She had persistent knee pain, persistent but scanty purulent discharge from the knee, and features in keeping chronic osteomyelitis in the distal femur on repeat plain radiograph of the knee. She subsequently had a distal femoral resection, placement of an antibiotic spacer, and then a distal femoral replacement following satisfactory control of infection in the knee with satisfactory functional outcome.

Prevention

Prevention remains key to the management of postoperative knee sepsis following ACL reconstruction and having an institution-based standardized prevention and treatment protocol has been observed to yield good results. Such protocols would incorporate pre-, peri-, and postoperative guidelines that help lower the incidence and complication of knee sepsis when it does occur [60]. It is important that such protocols should be designed based on the best available evidence and should include a guide to the choice of antiseptic agents used for skin preparation, option of antiseptic baths, and type and duration of prophylactic intravenous antibiotics use. Also, the choice of grafts, optimum duration of surgery, and the choice and duration of postoperative antibiotics should be included in the protocol [33, 61, 62]. Also, decision on the need to adopt the practice of pre-soaking of the graft in antibiotic solution prior to implantation should be included.

Previous studies have established the eradication of bacterial contaminants in grafts soaked in vancomycin prior to implantation in the joint [33, 62, 63•]. Vancomycin has assumed the front line lately as the antibiotic of choice in the pre-soaking of grafts during ACL reconstruction surgery. However, it is debatable whether it should be recommended for universal use or should be reserved for high-risk patients such as use of hamstring graft, revision cases, and medical conditions like diabetes [64••]. The bactericidal action is by the intra-articular elution of the antibiotic beyond the minimum inhibitory concentration (MIC) of the organism present [65••]. Pre-soaking of autografts in vancomycin solution has been noted to be highly effective in preventing postoperative septic arthritis of the knee [63•, 64••, 65••, 66••, 67••]. This prophylaxis against knee septic arthritis has not come without its own reservations. Questions have been raised on the fragility of initial research findings validating its use because knee sepsis following ACL reconstruction is an uncommon complication, hence the need for a very large sample size to adequately assess the impact of its use in the prophylaxis against knee sepsis. Also, the fact that most studies detailing the efficiency of the use of vancomycin has focused on its use on hamstring grafts only [67••]. In addition, the cost-effectiveness, possible development of antibiotic resistance, and alteration of the mechanical properties of the ACL graft are other concerns that have been expressed with the use of vancomycin in the pre-soaking of ACL grafts [64••, 68••].

The use of gentamycin for graft pre-soaking represents an alternative option in a resource-constrained environment like ours where patients largely pay out of pocket for their healthcare needs. Gentamycin has the advantages of affordability, availability, and broad-spectrum coverage against both gram positive and negative organisms as compared to vancomycin which is more expensive and is predominantly active over gram positive organisms. However, concerns have been expressed over the narrow therapeutic index of gentamycin which may predispose to ototoxicity and nephrotoxicity, and this may be a problem particularly in the elderly and with prolonged use. The neurotoxic effect may affect the auditory and vestibular system. Also, an added risk exists if used in patients with impaired renal function [37•, 69, 70]. The use of gentamycin for a short duration in a predominantly young population of patients with no renal impairment may help make the risk of nephrotoxicity lower. The possibility of nephrotoxicity and neurotoxicity has also been described in relation to vancomycin [71•, 72•].

Concerns have also been expressed on further development of multi-resistance in bacteria with the use of a broad-spectrum antibiotic like gentamycin for antibiotic prophylaxis during ACL reconstruction. However, vancomycin, which is the other alternative antibiotic used in the prophylaxis against infection of ACL grafts, tends to be one of the first-line antibiotic in the treatment of MRSA [73].

In a study by Yazdi et al. [37•] in which gentamycin solution was used for joint irrigation following ACL reconstruction, they observed a lower incidence of knee sepsis with the group that had gentamycin irrigation of the joint in addition to the use of systemic antibiotic as compared to the group that had systemic antibiotics only. Previous studies have found no significant difference in the intra-articular infection rate when gentamycin is used to pre-soak the graft compared to vancomycin solution [74••].

Gentamycin represents a ready alternative in our study environment where most patients pay out of pocket for their healthcare needs. Gentamycin has the advantage of being inexpensive; an ampoule of gentamycin in our study environment costs N60 (14 cents) as compared to a vial of vancomycin which costs N3750 ($9). Gentamycin also has a broad-spectrum activity against gram positive and negative organisms and is very much available in our study setting. If used at the appropriate dose in well-selected patients, its potential nephrotoxic and neurotoxic side effects can be well minimized.

In a study on antibiotic prophylaxis in shoulder arthroplasty, 160 mg of gentamycin was administered intra-articularly into the shoulder and the authors concluded that intra-articular intraoperative gentamycin administration may reduce postoperative infection [75]. Similarly, Lawing et al. [69] in their study using a locally administered aminoglycoside for open fractures at a concentration of 2 mg/ml as an adjunct to systemic antibiotics observed a significantly reduced infection rate in the group with local use of aminoglycoside.

Author’s Practice

Our practice evolved from the use of peri-operative intravenous antibiotics only to the addition of graft pre-soaking in gentamycin solution, in addition to other standard infection prophylactic measures against septic arthritis of the knee following ACL reconstruction. This current practice of graft pre-soaking involves soaking the hamstring autograft in 2.4 mg/ml of gentamycin solution for 10 min to help decontaminate the graft prior to implantation. The continued irrigation of the joint after graft insertion also helps to reduce the eventual concentration of gentamycin in the implanted graft. The implanted graft is avascular for a period until incorporation to bone occurs and the addition of a local gentamycin helps to ensure a good concentration of a broad-spectrum antibiotic at the graft site in the immediate postoperative period. Additional steps that may be taken to substantiate this technique would include measuring the serum levels of gentamycin over a 24-h period immediately postoperative to determine the serum profile.

Over a 7-year period (January 2016–January 2023), we had 46 cases of ACL reconstruction for isolated ACL tears using autogenous hamstring grafts that were not pre-soaked and recorded three cases of knee septic arthritis in the first two and a half years. We reconstructed 82 ACL tears using autogenous hamstring graft with pre-soaking of the graft in gentamycin solution over the next four and a half years with no case of knee septic arthritis following ACL reconstruction.

Conclusion

The incidence of knee sepsis following ACL reconstruction can be reduced by careful patient selection, use of prophylactic antibiotics, and strict asepsis during surgery. It is also evident from existing literature that pre-soaking of grafts in vancomycin or gentamycin solution during ACL reconstruction significantly reduces the incidence of postoperative septic arthritis of the knee. The choice of antibiotic solution is predicated on the surgeon’s preference, tissue penetrance, effect on tensile strength, local bio-gram of the micro-organisms, and the sensitivity pattern. Although there is no significant difference in the infection rate between vancomycin and gentamycin solution in pre-soaking of graft, the authors have preference for gentamycin solution. Most patients with knee sepsis following ACL reconstruction present within the first 4–6 weeks with knee pain, warmth, swelling, discharge from the portals, and reduced range of motion of the knee. Diagnosis is confirmed by elevated inflammatory markers; turbid or purulent joint aspirate; and positive gram staining, elevated WBC counts, and positive culture of joint aspirate. The treatment option for established infection is dependent on the stage of infection, state of the graft, and the extent of bony involvement. Intravenous antibiotic administration, early arthroscopic debridement, and extensive joint lavage with or without graft retention are initial steps to achieving a successful outcome. Good-to-excellent functional outcomes have been recorded with graft retention at the initial irrigation and debridement, and we advise ACL graft resection should only be undertaken if merited based on virulence of infection and graft integrity.

Compliance with Ethical Standards

Ethics Approval

All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study was approved by the Institution’s Health Research and Ethics Committee.

Conflict of Interest

Babalola Oladimeji, Babalola Adebukola, and Alatishe Kehinde declare they have no conflict of interest.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.