Abstract
Intraoperative bacterial contamination may contribute to microbial transmission during joint arthroplasty, but its distribution across surgical devices and clinical significance remain uncertain. This study aimed to characterize intraoperative bacterial contamination, compare contamination-positive and contamination-negative patients, evaluate contamination across device types, and assess postoperative infection outcomes. This prospective cohort study included 127 patients undergoing primary joint arthroplasty between February 2016 and April 2017. Samples from an unused control blade, skin-incision blade, deep-tissue blade, povidone–iodine-impregnated drape, and suction tip underwent aerobic and anaerobic culture. Patients were classified according to whether at least 1 specimen yielded bacterial growth. Patient-level characteristics were compared between contamination-positive and contamination-negative groups. Device-specific contamination was compared using generalized estimating equations (GEE) to account for within-patient correlation. Patients were followed for 24 to 38 months. A total of 13 of 127 patients (10.2%) had at least 1 positive culture. After exclusion of suspected sampling or transport contamination, positivity rates were 1.7% for control blades, 5.9% for skin-incision blades, 0.8% for deep-tissue blades, 2.5% for povidone–iodine-impregnated drapes, and 2.6% for suction tips. Patient-level demographic, surgical, and comorbidity characteristics did not differ significantly between groups. Overall contamination rates differed significantly among device types (GEE Wald χ2 = 15.14, df = 4; P = .004), although no individual device differed significantly from the control blade; for skin-incision blades, OR = 3.65 (95% CI, 0.73–18.27; P = .116). No surgical-site infections, periprosthetic joint infection, or deep soft-tissue infection occurred during follow-up. Intraoperative bacterial contamination occurred across multiple surgical devices despite standardized perioperative measures, with overall contamination rates differing by device type. Skin-incision blades had the highest observed positivity rate, but no device showed a statistically significant increase versus the control blade. The absence of postoperative infection underscores the distinction between microbiological contamination and clinical infection.
Keywords: arthroplasty, bacteria, infection, skin knife
1. Introduction
Although periprosthetic joint infection (PJI) is relatively rare – occurring in only about 1% to 2% of all arthroplasty procedures – it remains one of the most serious complications. Beyond the substantial direct medical costs, PJI exacts a significant psychosocial burden on patients. Importantly, PJI has been shown to markedly increase mortality: 1 study demonstrated a significant association between PJI and long-term risk of death following total hip arthroplasty (THA).[1] The underlying mechanisms include septic shock, multi-organ failure, loss of joint function with resulting disability, deterioration in quality of life, prosthesis loosening, and complications arising from prolonged antibiotic therapy.[2] Treatment of PJI is complex, requiring a combination of surgical intervention and prolonged antimicrobial therapy. Patients often face multiple reoperations and extended antibiotic courses. In the United States, the projected annual hospital costs associated with hip and knee PJI are expected to reach $1.85 billion by 2030,[3] In developing countries, the cost of treating PJI is 4.5 times higher than that of an uncomplicated primary total knee arthroplasty.[4] Thus, all efforts must focus on implementing comprehensive preventive strategies throughout the perioperative and postoperative stages to minimize the risk of surgical-site infections (SSI).[5] Surgical site contamination is a principal source of PJI; every operative procedure carries a risk of microbial ingress, and the instruments themselves may harbor bacteria.[6] One study reported that skin-incision blades exhibited a bacterial contamination rate of 15.3% – significantly higher than the 10.8% seen for deep-tissue blades[7] – while suction tips were contaminated in 11.4% of cases[6]For joint replacement, with its exceptionally stringent sterility requirements, these potential microbial reservoirs may act as the “trigger” for PJI.
To prevent bacteria carried on the skin-incision blade from contaminating deeper tissues – and thereby reduce the risk of PJI – most arthroplasty surgeons routinely discard the blade used for the skin incision and switch to a new, sterile scalpel for deeper dissection.[8] However, with modern operating-room protocols enforcing rigorous skin antisepsis, residual skin bioburden is extremely low, leading some early studies to question the necessity of blade exchange.[9,10] Iodophor-impregnated adhesive drapes offer a dual “physical barrier + chemical antisepsis” mechanism to further impede skin flora from entering the surgical field, yet current research on these drapes has focused primarily on cardiac[11] and spinal procedures,[12] with little bacteriological data specific to joint replacement. Theoretically, the longer the arthroplasty – particularly during revision cases – the greater the volume of air drawn through the suction catheter, and thus the higher the risk of contamination.[13] Conversely, adopting these microbial sealants or frequently changing blades and suction tips during arthroplasty increases consumable costs, prolongs procedural steps, and may lengthen the exposure time of the joint and prosthesis – factors that could paradoxically elevate infection risk.[14] As a result, these ostensibly sterile measures lack a clear risk-benefit and cost-effectiveness evaluation. This study therefore aims to assess the necessity of using iodophor-impregnated drapes and exchanging skin blades and suction tips during joint replacement surgery.
2. Patients and methods
2.1. Study population
This study was approved by the Ethics Committee of Peking University First Hospital. Written informed consents were obtained from patients for publication. From February 2016 to April 2017, 127 patients scheduled for primary joint arthroplasty at our institution were enrolled (82 total knee arthroplasties, 30 THAs, 8 unicompartmental knee arthroplasties, and 7 hip hemiarthroplasties), aged 45 to 89 years (mean 66.8 years), with an average operative time of 70 minutes.
The inclusion criteria were as follows: age ≥ 18 years; undergoing primary total hip or knee arthroplasty; receipt of standardized preoperative skin preparation and perioperative antimicrobial prophylaxis; and consent to intraoperative specimen collection from surgical instruments/materials and postoperative follow-up.
The exclusion criteria were: preexisting dermatologic conditions affecting the surgical site; poorly controlled autoimmune or other immunocompromising diseases; active systemic infection at the time of surgery; poorly controlled diabetes mellitus; severe knee valgus/varus deformity or high hip dislocation predicting markedly prolonged operative time compared with routine primary hip or knee arthroplasty; history of malignancy; other contraindications to surgery; prior infection of the target joint; intraoperative duration exceeding 120 minutes for any reason; and intraoperative events suggesting contamination or inability to complete study procedures (Fig. 1).
Figure 1.
Flowchart of patient enrollment, intraoperative specimen collection, and postoperative follow-up.
2.2. Surgical procedure
One day before surgery, patients bathed as usual; bedridden or dependent patients were wiped once with soapy water and twice with clean water to remove visible surface contaminants. On the day of surgery, skin preparation began 1 hour before entering the operating theater: hair was shaved from the surgical and perineal areas, then the operative site was disinfected once with tincture of iodine (homemade by Peking University First Hospital; 3 % iodine, 1.8 % potassium iodide) followed by 2 applications of 75 % alcohol (Yixin Hongda Technology Development Co., Ltd., Beijing), and covered with a single-use sterile drape. The operating room is a Class 100 horizontal laminar-flow suite. Fifteen to thirty minutes before incision, 2 g cefuroxime was infused IV for infection prophylaxis; in patients allergic to cephalosporins, 0.5 g vancomycin was given instead. Hip arthroplasty patients received 1 to 2 g tranexamic acid IV 30 minutes pre-incision to reduce bleeding; knee arthroplasty patients received the same dose 30 minutes before tourniquet release. Anesthesia was either general or spinal.
After skin disinfection with 1 application of tincture of iodine and 3 applications of alcohol to remove residual iodine, a waterproof single-use surgical drape was applied, ensuring at least 4 layers of sterile drape over the operative field, with all edges sealed by adhesive tape. A povidone–iodine adhesive drape was placed over the incision area for additional protection.
All procedures were performed by the same experienced arthroplasty team, following standard protocols. Knee arthroplasties were conducted with a tourniquet in place until wound closure. Total knee arthroplasty used a midline anterior incision with a medial parapatellar approach; unicompartmental knee arthroplasty used a minimally invasive medial parapatellar approach; both THA and hip hemiarthroplasty used a posterolateral approach. The fascia was closed with barbed, absorbable sutures (Johnson & Johnson, SXPP1A405), subcutaneous tissue with antibacterial polyester sutures (Johnson & Johnson, VCP752D and VCP738D), and the skin with barbed, knotless, absorbable intradermal sutures (Shunke, YA-2016Q).
After draping, a new size-20 sterile scalpel blade (Shanghai Pudong Jinhuan Medical Supplies Co., Ltd.) was mounted and immediately removed without use to serve as a blank control. A second new blade was used for the skin incision and then removed for culture as the “skin blade.” A third blade was used for all deeper dissection and collected at the end of the procedure as the “deep-tissue blade.” All 3 blades underwent standard bacterial culture. Intraoperatively, a disposable anti-clog suction device (7.8 mm × 15 cm Paco-flow set, Beijing Niuchuang Technology Co., Ltd.) was connected to wall suction at–200 to–400 mm Hg. At completion, a 1 cm × 7 cm section of the povidone–iodine drape adjacent to the incision (Fig. 2) and the suction tip were also collected for culture. Any specimens suspected of contamination during handling were excluded from analysis.
Figure 2.
Iodophor-impregnated drape (1 cm × 7 cm) removed postoperatively from an area parallel to the incision edge.
2.3. Bacterial culture
All specimens designated for culture were first immersed in sterile saline, and the resulting fluid was inoculated into both aerobic and anaerobic blood culture bottles. Inoculated bottles were incubated in the Clinical Microbiology Department at 35 °C for 5 days, with daily inspections. Any bottle showing positive growth was subcultured immediately. Specimens that remained negative on day 5 were then subcultured onto 5 % horse blood agar and incubated for an additional 7 days in a CO2-enriched environment, with daily checks for bacterial growth. Routine enrichment culture techniques were employed throughout (Fig. 1).
2.4. Outcome assessment and follow-up
All culture results were recorded and compared with their corresponding blank controls. A patient was classified as having intraoperative contamination if bacterial growth was detected from at least 1 intraoperative specimen. All patients were followed for 24 to 38 months to monitor for postoperative wound infection or impaired healing, as well as signs of joint infection such as swelling, pain, or functional impairment. In cases of suspected infection, erythrocyte sedimentation rate and C-reactive protein levels were measured.
2.5. Statistical analysis
Continuous variables are presented as mean ± standard deviation (SD), whereas categorical variables are presented as numbers and percentages. Between-group comparisons between the contaminated and non-contaminated groups were performed using the independent-samples t-test for continuous variables, with Welch’s correction applied when the assumption of equal variances was not met. Categorical variables were compared using Pearson’s chi-square test, or Fisher’s exact test when the expected cell frequency was <5. All statistical analyses were performed using SPSS Statistics, version 26.0 (IBM Corp., Armonk). All tests were 2-sided, and a P-value < .05 was considered statistically significant.
To address the potential differences in contamination rates among individual surgical devices, a device-level analysis was performed using all 127 patients, including 13 patients with intraoperative contamination and 114 patients without detectable intraoperative contamination. For each patient, contamination status was recorded separately for the control knife, skin knife, deep knife, iodophor drape, and suction tip, resulting in 5 repeated binary observations per patient.
Because the 5 device-level observations within each patient were not statistically independent, generalized estimating equations (GEE) were used to account for within-patient correlation. A binomial distribution with a logit link function and an exchangeable working correlation structure was specified, with patient ID used as the clustering variable. The control knife was selected as the reference device. Robust sandwich standard errors were used to estimate odds ratios (ORs), 95% confidence intervals (CIs), and P-values. An overall Wald test was used to assess whether contamination rates differed among the 5 device types. A 2-sided P-value < 0.05 was considered statistically significant.
3. Results
A total of 127 patients were included in the study, including 13 patients in the contaminated group and 114 patients in the non-contaminated group. The baseline demographic, surgical, and comorbidity characteristics of the 2 groups are presented in Table 1. No statistically significant differences were observed between the contaminated and non-contaminated groups with respect to age (P = .773), sex (P = .581), body mass index (P = .704), type of arthroplasty (P = .956), operative time (P = .916), intraoperative blood loss (P = .879), diabetes mellitus (P = .782), smoking status (P = .697), potential immunosuppression (P = 1.000), or ASA physical status classification (P = .938). Overall, the baseline characteristics were well balanced between the 2 groups.
Table 1.
Baseline characteristics of participants according to intraoperative contamination status.
| Variable | Contaminated group | Non-contaminated group | P-value |
|---|---|---|---|
| No. of patients, n | 13 | 114 | – |
| Demographics | |||
| Age, yr, mean ± SD | 67.3 ± 16.8 | 68.7 ± 10.3 | .773 |
| Male sex, n (%) | 3 (23.1%) | 15 (13.2%) | .581 |
| BMI, kg/m2, mean ± SD | 26.8 ± 3.5 | 27.2 ± 3.8 | .704 |
| Surgical characteristics | |||
| Type of arthroplasty, n (%) | .956 | ||
| THA | 2 (15.4%) | 24 (20.9%) | |
| TKA | 9 (69.2%) | 76 (67.0%) | |
| UKA | 1 (7.7%) | 8 (7.0%) | |
| HHA | 1 (7.7%) | 6 (5.3%) | |
| Operative time, min, mean ± SD |
81.8 ± 21.4 | 82.5 ± 29.1 | .916 |
| Intraoperative blood loss, mL, mean ± SD | 220.0 ± 110.0 | 225.0 ± 115.0 | .879 |
| Infection-related comorbidities, n (%) | |||
| Diabetes mellitus | 3 (23.1%) | 18 (15.8%) | .782 |
| Smoking | 2 (15.4%) | 9 (7.9%) | .697 |
| Possibly immunosuppression | 0 (0%) | 6 (5.3%) | .000 |
| ASA physical status, n (%) | .938 | ||
| I | 1 (7.7%) | 12 (10.5%) | |
| II | 7 (53.8%) | 62 (54.4%) | |
| III | 5 (38.5%) | 40 (35.1%) | |
HHA = hip hemiarthroplasty, THA = total hip arthroplasty, TKA = total knee arthroplasty, SD = standard deviation, UKA = unicompartmental knee arthroplasty.
After excluding specimens contaminated or possibly contaminated during collection and transport, this study included 118 sets each of blank control blades, skin-incision blades, and deep-tissue blades; 119 povidone–iodine drapes; and 116 suction tips. The culture-positive rates and isolated organisms were as follows:
Blank control blades: 2 of 118 (1.7 %) positive – Pseudomonas aeruginosa (×1) and Staphylococcus hominis (×1).
Skin-incision blades: 7 of 118 (5.9 %) positive – Acinetobacter baumannii (×2), Staphylococcus haemolyticus (×1), S hominis (×1), P aeruginosa (×1), Staphylococcus cohnii (×1), and Escherichia coli (×1).
Deep-tissue blades: 1 of 118 (0.8 %) positive – P aeruginosa (×1).
Povidone–iodine drapes: 3 of 119 (2.5 %) positive – Staphylococcus epidermidis (×1), Klebsiella pneumonia (×1), and Candida albicans (×1).
Suction tips: 3 of 116 (2.6 %) positive – A baumannii (×1), S haemolyticus (×1), and S hominis (×1).
Two patients had identical organisms recovered from both their skin-incision blades and suction tips, including A baumannii in 1 patient and S haemolyticus in the other. In another patient, the same organism, P aeruginosa, was recovered from both the skin-incision and deep surgical blades. All patients in both the contaminated and non-contaminated groups completed 24 to 38 months of follow-up. During the follow-up period, no cases of PJI or SSI, including deep soft-tissue infection, were observed in either group. Nevertheless, bacterial contamination was detected in some skin-incision blades, povidone–iodine-impregnated drapes, and suction tips despite standardized antiseptic preparation and sterile draping protocols. Detailed microbiological findings are presented in Tables 1 and 2.
Table 2.
Results including microbiology.
| Surgery | Sex/age | Control knife | Skin knife | Deep knife | Iodophor drape | Suction tip | SSI/PJI during the 24–38-mo follow-up period |
|---|---|---|---|---|---|---|---|
| Knee | M/82 | Pseudomonas aeruginosa | – | – | – | – | – |
| Knee | F/77 | Staphylococcus hominis | – | – | – | – | – |
| Hip | M/55 | – | Acinetobacter baumannii | – | – | Acinetobacter baumannii | - |
| Knee | M/63 | – | Acinetobacter baumannii | – | – | - | – |
| Knee | F/53 | – | Staphylococcus haemolyticus | – | – | Staphylococcus haemolyticus | – |
| Knee | F/75 | – | Staphylococcus hominis | – | – | – | – |
| Knee | F/84 | – | Pseudomonas aeruginosa | Pseudomonas aeruginosa | – | – | – |
| Knee | F/65 | – | Staphylococcus cohnii | – | – | – | – |
| Knee | F/77 | – | Escherichia coli | – | – | – | – |
| Knee | M/89 | – | – | – | Staphylococcus epidermidis | – | – |
| Knee | F/72 | – | – | – | Klebsiella pneumoniae | – | – |
| Knee | F/65 | – | – | – | Candida albicans | – | – |
| Hip | F/50 | – | – | – | – | Staphylococcus hominis | – |
PJI = periprosthetic joint infection, SSI = surgical-site infections.
Device-specific contamination rates were additionally evaluated to determine whether the frequency of positive cultures differed among individual surgical devices. Among the 127 patients, positive cultures were detected in 2 (1.57%) control knives, 7 (5.51%) skin knives, 1 (0.79%) deep knife, 3 (2.36%) iodophor drapes, and 3 (2.36%) suction tips. Within the subgroup of 13 patients with intraoperative contamination, the corresponding positivity rates were 15.4%, 53.8%, 7.7%, 23.1%, and 23.1%, respectively (Table 3).
Table 3.
Device-specific contamination rates and comparison using generalized estimating equations.
| Device | Contamination-positive | Contamination-negative | Overall positivity (%) | OR vs control knife | 95% CI | P-value |
|---|---|---|---|---|---|---|
| Control knife | 2 | 125 | 1.57 | Reference | – | – |
| Skin knife | 7 | 120 | 5.51 | 3.65 | 0.73–18.27 | .116 |
| Deep knife | 1 | 126 | 0.79 | 0.50 | 0.04–5.61 | .571 |
| Iodophor drape | 3 | 124 | 2.36 | 1.51 | 0.24–9.37 | .657 |
| Suction tip | 3 | 124 | 2.36 | 1.51 | 0.24–9.37 | .657 |
CI = confidence interval, OR = odds ratio.
A generalized estimating equation model was subsequently applied to account for the within-patient correlation arising from the repeated sampling of 5 device types from each patient (Table 3). Using the control knife as the reference category, the odds of contamination were higher for skin knives (OR, 3.65; 95% CI, 0.73–18.27; P = .116) and iodophor drapes (OR, 1.51; 95% CI, 0.24–9.37; P = .657), whereas the odds were lower for deep knives (OR, 0.50; 95% CI, 0.04–5.61; P = .571) and identical for suction tips (OR, 1.51; 95% CI, 0.24–9.37; P = .000). Although none of the individual comparisons with the control knife reached statistical significance, the overall Wald test demonstrated a statistically significant difference in contamination rates across the 5 device types (χ2 = 15.14, df = 4; P = .004). These findings indicate that contamination was not uniformly distributed across the different device types, with skin knives showing the highest observed contamination rate.
4. Discussion
PJI remains one of the most serious complications following joint arthroplasty, with a reported incidence of approximately 2.0% to 2.5% even in high-volume and advanced centers.[5] Accordingly, identifying and minimizing potentially avoidable sources of intraoperative contamination remains an important component of infection prevention. In this prospective cohort study, we evaluated bacterial contamination of multiple materials and devices routinely encountered during primary joint arthroplasty and followed patients for 24 to 38 months. The principal findings were threefold. First, bacterial growth was detected in a subset of intraoperative specimens despite standardized perioperative antiseptic and sterile procedures. Second, at the patient level, 13 of 127 patients had at least 1 positive intraoperative culture, but the contaminated and non-contaminated groups did not differ significantly in the baseline characteristics examined. Third, device-level analysis demonstrated that contamination was not uniformly distributed across the 5 sampled device types, with skin knives showing the highest observed positivity rate; however, no individual device demonstrated a statistically significant difference compared with the control knife. Importantly, no patient developed SSI, PJI, or deep soft-tissue infection during the 24 to 38-month follow-up period, indicating that microbiological contamination detected in the present study did not translate into clinically evident postoperative infection within the observed cohort.
4.1. Intraoperative contamination despite standardized aseptic procedures
Our findings support the concept that bacterial contamination can occur even under rigorous perioperative antisepsis and sterile operating conditions. Skin antisepsis substantially reduces the microbial burden at the operative site, but microorganisms residing within skin folds, hair follicles, or deeper skin structures may not be completely eradicated and may subsequently migrate to the wound or surgical instruments. Shroff et al reported an 11.8% positive culture rate from the initial skin-cutting scalpel used during shoulder arthroplasty, providing clinical evidence that the skin incision itself may represent a potential source of bacterial contamination.[15] These observations provide a biological rationale for the long-standing use of the double-blade technique, in which the blade used for skin incision is discarded before deeper tissue dissection.[16]
However, the clinical necessity of routine blade exchange remains controversial. Several studies have reported no significant difference in contamination rates between skin-cutting blades and unused control blades during total hip or knee arthroplasty, raising questions regarding whether routine blade exchange provides sufficient clinical benefit to justify the additional cost and instrument handling.[17,18] Conversely, Schindler et al argued that the potential reduction in deep infection risk may outweigh the cost associated with routine blade replacement.[7] These apparently conflicting findings highlight an important distinction between detecting bacterial contamination and demonstrating a clinically meaningful reduction in PJI. The present study contributes additional microbiological evidence to this discussion but does not by itself establish that replacing a contaminated or potentially contaminated device reduces postoperative infection.
A similar issue applies to iodophor-impregnated adhesive drapes. Although these drapes are intended to provide an additional antimicrobial barrier around the incision and continuously suppress bacterial migration at the wound margin,[19] evidence regarding their ability to prevent SSI remains limited.[20] Furthermore, studies evaluating non-iodophor adhesive drapes have reported no reduction, and in some circumstances an increase, in SSI compared with procedures performed without drapes.[21,22] Therefore, the microbiological role of iodophor drapes should be distinguished from their ultimate clinical effectiveness in preventing SSI or PJI. Rigorous randomized controlled trials remain necessary to determine whether specific draping strategies provide clinically meaningful protection in joint arthroplasty.[12,23]
4.2. Patient-level contamination and subsequent clinical infection
To provide a clinically interpretable exposure classification and avoid treating multiple specimens obtained from the same patient as statistically independent observations, we first conducted a patient-level analysis. Patients were classified as having intraoperative contamination if at least 1 collected specimen yielded bacterial growth, whereas patients with negative cultures from all collected specimens were classified as non-contaminated. Using this definition, 13 patients were classified as contaminated and 114 as non-contaminated. The baseline characteristics examined, including age, sex, BMI, type of arthroplasty, operative time, blood loss, diabetes mellitus, smoking status, possible immunosuppression, and ASA physical status, were broadly comparable between the 2 groups. These findings do not suggest that the detected contamination was obviously concentrated in patients with particular demographic, comorbidity, or surgical characteristics. Nevertheless, the relatively small number of patients in the contaminated group limits the statistical power to detect modest associations, and the absence of statistically significant differences should therefore not be interpreted as evidence that these factors are unrelated to intraoperative contamination.
The most clinically important observation was that no patient in either group developed PJI, SSI, or deep soft-tissue infection during the 24 to 38-month follow-up period. This finding emphasizes the distinction between microbiological contamination and clinically significant infection. Recovery of bacteria from an intraoperative material does not necessarily indicate contamination of the operative field at a level sufficient to cause infection. Low-level environmental or procedural contamination may be subsequently eliminated by host immune defenses, perioperative antimicrobial prophylaxis, wound closure, or other components of standard perioperative care. Therefore, the detection of bacterial growth should not automatically be interpreted as evidence of an increased risk of PJI.
At the same time, the absence of postoperative infection should be interpreted cautiously. Only 13 patients were classified as contaminated, and PJI is a relatively uncommon outcome following primary arthroplasty. Because no SSI or PJI events occurred in either group, conventional regression models estimating relative risk or odds ratios for postoperative infection would not provide meaningful or stable estimates. The absence of observed infection events is therefore best regarded as a descriptive clinical finding rather than evidence that intraoperative contamination has no clinical relevance. Larger prospective cohorts with a sufficient number of postoperative infection events will be necessary to determine whether specific microorganisms, contamination burdens, or contamination patterns are associated with subsequent PJI.
4.3. Device-specific contamination and the importance of within-patient correlation
In addition to the patient-level analysis, we performed a device-level analysis to determine whether contamination was distributed differently among individual surgical devices. This analysis was particularly important because each patient contributed multiple device-level specimens, and these observations cannot reasonably be assumed to be statistically independent. We, therefore, used a generalized estimating equation (GEE) model with patient-level clustering to account for within-patient correlation.
The device-level analysis demonstrated a significant overall difference in contamination rates among the 5 sampled device types. Skin knives had the highest observed positivity rate, with positive cultures detected in 7 of 127 patients (5.51%), corresponding to 7 of the 13 patients with intraoperative contamination (53.8%). The positivity rates were lower for iodophor drapes (3/127, 2.36%), control knives (2/127, 1.57%), suction tips (3/127, 2.36%), and deep knives (1/127, 0.79%). These findings suggest that bacterial contamination may not be evenly distributed across different components of the operative environment.
The relatively higher positivity observed for skin knives is biologically plausible because these instruments directly contact the skin and superficial operative field during the initial incision. Even after preoperative skin preparation, microorganisms that persist within skin structures may be transferred to the blade during incision. This interpretation is consistent with previous reports of bacterial recovery from skin-incision blades[15] and provides a plausible explanation for why skin knives showed the highest numerical contamination rate in our cohort. However, this proposed mechanism remains hypothesis-generating because the present study was designed to detect contamination rather than to establish the biological mechanism responsible for device-specific differences.
Importantly, although the overall GEE analysis demonstrated heterogeneity among device types, none of the individual comparisons with the control knife reached statistical significance. For example, skin knives showed an estimated 3.65-fold higher odds of contamination than control knives, but the confidence interval was wide and included unity (OR, 3.65; 95% CI, 0.73–18.27; P = .116). Thus, the significant overall test should not be interpreted as definitive evidence that skin knives or any other individual device has a statistically higher contamination risk than the control knife. The wide confidence intervals reflect the limited number of positive culture events and indicate substantial uncertainty in the individual device-specific estimates. Nevertheless, the consistent numerical predominance of positive cultures from skin knives provides a potentially relevant signal that warrants confirmation in larger cohorts.
4.4. Clinical implications
Taken to gether, our findings suggest that intraoperative bacterial contamination should be considered a microbiological phenomenon that is distinct from postoperative clinical infection. The identification of bacteria on surgical devices demonstrates that contamination can occur despite standardized aseptic procedures, but the absence of SSI or PJI during follow-up indicates that such contamination did not result in clinically evident infection in this cohort.
These findings do not provide sufficient evidence to recommend routine replacement of any particular device solely on the basis of microbiological contamination. Instead, they provide a basis for considering whether contamination-prevention strategies should be tailored according to the role, tissue exposure, and timing of individual devices. The higher observed positivity rate of skin knives may be particularly relevant to the ongoing debate surrounding the double-blade technique, whereas the detection of bacteria on iodophor drapes and suction tips suggests that contamination may occur through multiple potential pathways rather than through a single instrument. Existing studies have often focused on individual instruments, such as scalpel blades or suction tips,[24,25] whereas simultaneous assessment of multiple device types may provide a more comprehensive understanding of the intraoperative contamination pathway.
From an infection-control perspective, the present findings support continued attention to maintaining a sterile operative field, minimizing unnecessary contact between devices and nonsterile surfaces, and carefully handling implants and instruments throughout the procedure. Hsu et al have similarly emphasized heightened caution when handling implants and the importance of maintaining sterility in the operative field.[26] However, whether specific interventions, including routine blade exchange or alternative draping strategies, ultimately reduce SSI or PJI cannot be determined from the present observational microbiological study.
4.5. Limitations and methodological considerations
Several limitations should be acknowledged. First, the contaminated group included only 13 patients, resulting in limited statistical power and wide confidence intervals for the device-specific estimates. Second, although specimens were collected prospectively, bacterial culture results may be influenced by sampling location, timing, transport, and laboratory procedures; further standardization and appropriate quality-control measures may reduce potential measurement bias. Third, the study was conducted in a single standardized surgical environment, which may limit the generalizability of the findings to other institutions and perioperative protocols. Finally, the observational design and absence of SSI/PJI events precluded causal inference regarding the relationship between device contamination and postoperative infection or the effectiveness of device-replacement strategies.
4.6. Future perspectives
Future studies should include larger, preferably multicenter prospective cohorts with standardized sampling and microbiological protocols to validate the device-specific contamination patterns observed in this study. Serial intraoperative sampling could further clarify the temporal dynamics of contamination, particularly in relation to operative duration.[27] Ultimately, adequately powered randomized controlled trials comparing blade exchange and other contamination-control strategies are needed to determine whether reducing microbiological contamination can translate into lower SSI/PJI rates and improved cost-effectiveness.
5. Conclusion
Intraoperative bacterial contamination occurred on multiple surgical devices despite standardized skin antisepsis, antimicrobial prophylaxis, and sterile operating procedures. Contamination was not uniformly distributed across device types, with skin-incision blades showing the highest observed positivity rate; however, no individual device demonstrated a statistically significant difference in contamination compared with the control blade. Importantly, no SSI, PJI, or deep soft-tissue infection occurred during 24 to 38 months of follow-up, emphasizing that microbiological contamination should not be equated with clinically significant postoperative infection. These findings provide microbiological evidence of potential contamination pathways but do not establish that routine device replacement or other contamination-control interventions reduce postoperative infection. Larger multicenter prospective studies and adequately powered randomized trials are warranted to determine the clinical significance of intraoperative contamination and the effectiveness and cost-effectiveness of specific contamination-prevention strategies.
Acknowledgments
We confirm that all individuals named in the Acknowledgments section have given their permission to be named in the manuscript.
Author contributions
Conceptualization: Heng Liu.
Data curation: Heng Liu.
Formal analysis: Heng Liu.
Supervision: Talante Juma.
Validation: Talante Juma.
Writing – original draft: Guang-Hua Liang.
Writing – review & editing: Guang-Hua Liang.
Abbreviations:
- PJI
- periprosthetic joint infection
- SSI
- surgical-site infections
- THA
- total hip arthroplasty
- TKA
- total knee arthroplasty
- UKA
- unicompartmental knee arthroplasty.
This study was approved by the Ethics Committee of Peking University First Hospital. Written informed consents were obtained from patients for publication.
The authors have no funding and conflicts of interest to declare.
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
How to cite this article: Liang G-H, Juma T, Liu H. Bacterial contamination of surgical blades, suction tips, and iodophor drapes in primary joint arthroplasty: A prospective cohort study. Medicine 2026;105:39(e50858).
G-HL and TJ contributed to this article equally.
Contributor Information
Guang-Hua Liang, Email: 2111210218@stu.pku.edu.cn.
Talante Juma, Email: tazxzx@126.com.
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