Background: Despite significant advancements in surgical protocols and biomaterials for orthopedics, peri-prosthetic joint infection (PJI) remains a leading cause of implant failure. Staphylococcus aureus nasal colonization is an established risk factor for PJI, with methicillin-sensitive S. aureus a leading cause of orthopedic implant-related infections. The purpose of these in vitro studies was to investigate the antibacterial activity of a tailored bacteriophage cocktail against planktonic and biofilm-associated S. aureus. Methods: The S. aureus strains (n = 30) were screened for their susceptibility to a library of S. aureus-specific bacteriophage (n = 31). Five bacteriophage preparations that demonstrated bactericidal activity against >90% of S. aureus strains tested were combined as a StaPhage cocktail and assessed for their antibacterial activity toward planktonic and biofilm-associated S. aureus, with biofilms established on three-dimensional-printed porous titanium scaffolds. Results: StaPhage treatment immediately after bacterial inoculation inhibited growth of S. aureus by >98% in eight hour cultures when multiplicity of infection of phages to bacteria was greater than 1:1 (p < 0.01). Viable bacterial numbers within biofilms on titanium surfaces were significantly reduced (6.8 log₁₀ to 6.2 log₁₀ colony forming units [CFU]; p < 0.01) after exposure to the StaPhage cocktail, in vitro. No significant reduction was observed in biofilms exposed to 100 times the minimal inhibitory concentration of cefazolin (log₁₀ 6.81 CFU). Conclusions: Combined, these data demonstrate the in vitro efficacy of S. aureus-specific bacteriophage cocktails against S. aureus growing on porous titanium and warrant further in vivo studies in a clinically relevant animal model to evaluate the potential application of bacteriophage in the management of PJI caused by S. aureus.

Purpose: In up to a fifth of total knee replacements (TKR), surgeons are not capable of achieving good clinical and functional results. Despite comprehensive diagnostic workup, an underlying cause is not always identified in these patients. The purpose of this study is to compare native and prosthetic trochlear anatomies, to evaluate a potential source of morphologic mismatch and theoretically, of poor clinical outcomes.Methods: Native trochlear angles of 4116 knee CTs from 360 Knee Systems database of arthritic pre‐operative TKR patients were evaluated. A semi‐automated tridimensional analysis was performed to define the native trochlear angle in the coronal plane (NTA) among other 142 parameters. An active search was conducted to identify currently available TKR models; prosthetic trochlear orientation in the coronal plane (PTA) was extracted from the technical data provided by manufacturers.Results: The mean native trochlear angle (NTA) was 1.6° ± 6.6° (valgus) with a range from − 23.8° (varus) to 30.3°(valgus). A valgus NTA was present in 60.6% of the knees and 39.4% of them had a varus NTA. 89 TKR models were identified; trochlear details were available for 45 of them, of which 93% were designed with a valgus orientation of the prosthetic trochlear angle (PTA) and 6.9% showed a neutral (0°) PTA. Varus alignment of PTA was not present in any system. Angular numeric values for PTA were available for 34 models; these ranged from 0° to 15° of valgus, with a median value of 6.18° (SD ± 2.88°).Conclusion: This study shows a significant mismatch between native and prosthetic trochlear angles. A relevant proportion of the studied knees (41.45%) fall out of the trochlear angle range of currently available implants; representing a potential source for biomechanical imbalance. While further research is warranted to fully understand the clinical implications of the present study, manufacturers may need to take these findings into account for future implant designs.Level of evidence: Level III, retrospective cohort study.

Tranexamic acid (TXA) is commonly used in orthopedic surgery to reduce excessive bleeding and transfusion requirements. Our aim was to examine if TXA was required in all osteoarthritis patients undergoing TKA surgery, and its possible effects on systemic inflammation and coagulation properties. Twenty-three patients (Oxford Score 22–29) were recruited consecutively; 12 patients received TXA before (IV, 1.2 g/90 kg) and immediately after surgery (intra-articular, 1.4 g/90 kg). Inflammatory mediators and ROTEM parameters were measured in blood at baseline, after the first bone-cut, immediately after surgery, and postoperative days 1 and 2. After the bone cut and surgery, TXA significantly increased MCP-1, TNF-α, IL-1β and IL-6 levels compared to non-TXA patients, which was further amplified postoperatively. During surgery, TXA significantly prolonged EXTEM clot times, indicating a thrombin-slowing effect, despite little or no change in clot amplitude or fibrinogen. TXA was associated with three- to fivefold increases in FIBTEM maximum lysis (ML), a finding counter to TXA’s antifibrinolytic effect. Maximum lysis for extrinsic and intrinsic pathways was < 8%, indicating little or no hyperfibrinolysis. No significant differences were found in postoperative hemoglobin between the two groups. TXA was associated with increased systemic inflammation during surgery compared to non-TXA patients, with further amplification on postoperative days 1 and 2. On the basis of little or no change in viscoelastic clot strength, fibrinogen or clot lysis, there appeared to be no clinical justification for TXA in our group of patients. Larger prospective, randomized trials are required to investigate a possible proinflammatory effect in TKA patients.