Perico, Diego Alarcon

AbstractTo minimize periprosthetic joint infection (PJI) risk, some clinicians prescribe extended antibiotic prophylaxis (EAP) following total joint arthroplasty (TJA). Given the limited evidence supporting EAP, we sought to evaluate impact of prophylactic antibiotic duration on PJI risk in a murine TJA model. A titanium prosthesis was implanted into the proximal tibia of 89 mice and inoculated with 102 colony forming units (cfu) of Staphylococcus aureus Xen36. Control mice (n = 20) did not receive antibiotics. Treated mice received either 24 h (n = 35) or 4 days (n = 34) of cefazolin prophylaxis. Cultures were obtained from the prostheses, tibia, femur, and knee tissues 3 weeks after surgery. All mice in the control group developed PJI. Both prophylaxis regimens reduced the rate of PJI relative to the control, with only 2/35 mice in the 24‐h cohort (p < 0.0001) and 1/34 in 4‐day cohort developing PJI (p < 0.0001). CFU counts from the prostheses, bone and knee tissues were reduced for the 24‐h and 4‐day prophylaxis cohorts relative to the control (p < 0.0001 for both). There was no difference in rates of PJI or CFU counts between the two prophylaxis cohorts (p = 0.58). Prophylactic cefazolin profoundly reduced rates of PJI in a murine model of TJA in which all control animals developed PJI. Extending cefazolin prophylaxis duration from 24 h to 4 days did not result in improved PJI rates or decreased bacterial loads in infected cases. While these results strongly support use of antibiotic prophylaxis for TJA, EAP did not appear to add benefit in the described mouse model.

Background: Unicompartmental knee arthroplasty (UKA) is a reliable procedure to treat medial compartment knee osteoarthritis (OA). The reported survivorship of UKA has varied in the literature 3–7 . In part, the higher failure rates of UKA seen in registries could be related to the caseload and experience of the reporting surgeon 8 . The introduction of techniques that make procedures more reliable, especially in the hands of inexperienced surgeons, can decrease the rate of failure. With the Oxford UKA implant (Zimmer Biomet), the recommended surgical technique involves cutting the tibia first, followed by the femoral preparation. However, a technique that allows for preparation of the femur first, as well as the use of the femoral component as a reference for the tibial cut, may reduce the common technical errors seen with the procedure. We have utilized the femur-first technique in cases of medial Oxford UKA. Description: The femur-first method outlined in the present article does not require any unique instruments beyond what is supplied by the manufacturer. Before beginning, the femoral positional guide needs to be decoupled from its base. To start, the intramedullary guide is introduced approximately 1 cm anterior and medial to the intercondylar notch. Once the femoral osteophytes are removed, the surgeon identifies the center of the femoral condyle and marks it. The posterior tibial cartilage is then removed with a saw to facilitate the placement of the appropriately sized femoral spherical guide. The size of the femoral component is determined by selecting the implant that aligns best with the width of the femoral condyle. The femoral drill guide is detached from its base because there is not enough space for the base, as the tibia has not yet been resected. The decoupled femoral guide is connected to the intramedullary rod, allowing the precise positioning of the femoral component in approximately 10° of flexion relative to the femoral sagittal plane and drilling of the 2 peg holes. The posterior condylar resection guide is impacted into position, and the osteotomy of the posterior condyle is made. The distal femur is then milled with use of a number-0 spigot, and the femoral component trial is positioned into place. The femoral condyle is “resurfaced” with the femoral component, which restores joint obliquity and the natural height, a critical element of the femur-first technique. Following this, the 1-mm (size-dependent) spherical gauge is placed around the femoral component trial. The tibial guide is secured with the G-clamp and a number-0 resection block, and is pinned into place. We recommend swapping the number-0 cutting guide for a +2 when making the cut in order to avoid over-resection. Recutting is advised if a minimum 3-mm feeler gauge does not adequately occupy the flexion space. The final step is to balance the flexion and extension gaps in the usual fashion. Alternatives: The alternative technique is a traditional tibia-first approach, in which tibial resection is performed prior to femoral resection. As described in the original manufacturer’s manual, the tibial cut is accomplished with use of a number-0 cutting guide, and the tibial rotation is based on the axis formed by the anterior superior iliac spine and knee center, irrespective of the femoral condyle. Rationale: The femur-first technique is advantageous in several ways. When performing the femoral cut first, the surgeon can better align the drill guide at the center of medial femoral condyle. This will result in the femoral component being positioned more in line with the coronal plane of the femoral condyle. Additionally, the tibial resection is made with the femoral trial in place; therefore, the depth of resection can be more accurate, potentially avoiding excessive bone resection. Finally, with the femoral trial in place, the surgeon can judge the rotation and medial-lateral position of the tibial component more precisely, hence lowering the possibility of bearing spin-out, impingement, and dislocation or unexplained pain. Expected Outcomes: The femur-first technique is a bone-preserving procedure that results in thinner bearings when compared with a tibia-first approach 1 . The femur-first approach also improves radiographic outcomes, including femoral coronal, femoral sagittal, and tibial sagittal alignments, while tibial coronal alignment does not differ. There is an early trend toward improved 5-year survivorship with the femur-first (98%) versus tibia-first (94%, p = 0.35) techniques. There has been no significant difference reported in Knee Society Scores between techniques. Important Tips: Perform a preliminary cut of the posterior tibial cartilage in order to allow insertion of the femoral drill guide under the femoral condyle. Make sure the femoral drill guide lies in the center of the marked medial femoral condyle. Align the tibial sagittal cut with the femoral component trial in order to avoid bearing impingement. Be conservative in the tibial cutting by utilizing a +2 cutting guide (since the coupling is performed with the intramedullary guide in place, which drives the tibial guide distally). Acronyms and Abbreviations: UKA = unicompartmental knee arthroplasty FF = femur-first M-L = medial-lateral AP = anteroposterior PA = posteroanterior ASA = acetylsalicylic acid (aspirin) BID = bis in die, twice a day PT = physical therapy TF = tibia-first FCA = femoral coronal angle FSA = femoral sagittal angle TSA = tibial sagittal angle IM = intramedullary OA = osteoarthritis

Background: Current classification systems for intra-articular pathology intraoperatively have been described for patients with femoroacetabular impingement rather than dysplasia. Purpose: To (1) describe intra-articular findings in dysplastic hips undergoing combined hip arthroscopy and periacetabular osteotomy (PAO); (2) propose a new chondrolabral classification system for dysplastic hips based on these findings; and (3) correlate patient-reported outcome measures (PROM) with the newly proposed classification. Study Design: Case series; Level of evidence, 4. Methods: A total of 46 hips underwent combined hip arthroscopy and PAO at our institution between September 2013 and December 2014, irrespective of symptoms or radiographic findings. PROMs were evaluated preoperatively and at 2 years postoperatively. At the time of hip arthroscopy, the chondrolabral junction was classified as normal without tear (1 hip, type 1); hypertrophic labrum without chondrolabral disruption (19 hips, type 2); chondrolabral disruption on the articular side, not extending into the capsular side (16 hips, type 3A); chondrolabral disruption extending through the capsular side (3 hips, type 3B); and exposed acetabular subchondral bone (7 hips, type 4). Results: There was a significant difference in postoperative modified Harris Hip Score (mHHS) ( P = .020), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores ( P = .037), and WOMAC total scores ( P = .049) between chondrolabral junction types. Post hoc analyses demonstrated significant differences between type 2 (84.9 ± 12.9) and type 3A (67.8 ± 20.7; P = .198), and between type 2 and type 4 (59.3 ± 24.3; P = .011) in postoperative mHHS scores; and between type 2 (83.9 ± 12.9) and type 3A (68.9 ± 23.7; P = .045) in postoperative WOMAC total scores. In multivariate analysis, chondrolabral type 3 or type 4, age >35 years, and previous surgery were significantly correlated with worse mHHS scores at 2 years. Conclusion: This new chondrolabral classification is proposed to describe intra-articular pathology seen during combined hip arthroscopy and PAO, specifically in dysplastic hips. More advanced chondrolabral disease was associated with worse PROMs at 2 years.

Abstract Background Periprosthetic joint infection (PJI) is a devastating complication following joint replacement, associated with morbidity and mortality. Here, we established a clinically representative murine model of knee arthroplasty and determined the ideal bacterial inoculum that would result in PJI without causing significant limb compromise.Figure 1.An example of an uninfected titanium prosthesis osseointegrated into the tibia of a mouse. Methods A titanium tibial prosthesis designed for the murine knee was 3D printed and surgically implanted into the proximal tibia (Figure 1) of 38 C57BL/6 mice. The prosthesis is designed to osseointegrate into the tibia and has a smooth articular surface to allow for immediate weight bearing and range of motion. At the time of surgery, the arthroplasty was inoculated with five inocula of Staphylococcus aureus Xen36, ranging from 29 to 14,000 colony forming units (CFU) (Table 1). Mice were sacrificed at 3 weeks, or earlier if necessary due to infectious sequelae, and the joint tissue, tibia, femur, and prosthesis quantitatively cultured. Results All mice inoculated with 181 to 14,000 CFU developed PJI as did 90% inoculated with 29 CFU. Bacterial loads from joint tissues and tibial prostheses are shown in Table 1. All mice inoculated with 14,000 and 760 CFU had overt findings of infection (abscesses, sinus tracts, significant limb dysfunction) requiring early euthanasia (Table 2). Mice inoculated with 640 CFU had swelling, redness, and small sores in first 3 days, and 1 death, but otherwise appeared well; only 2/9 had a visible abscess at 3-week sacrifice. 2/10 mice receiving 181 CFU had small sores that resolved in the first week; all limbs functioned well prior to sacrifice. Mice receiving 29 CFU had no external evidence of infection, however 9/10 had purulence within the joint at sacrifice. Conclusion This study demonstrates that inoculum size directly impacts clinical manifestations of infection in a murine model of S. aureus PJI. An inoculum of 181 CFU resulted in universal infection without significantly compromising the limb. The ability of this model to create PJI without overt infectious sequela will allow for evaluation of therapeutics, including those locally delivered. Disclosures Robin Patel, MD, Abbott Laboratories: Advisor/Consultant|Adaptive Phage Therapeutics: Grant/Research Support|Adaptive Phage Therapeutics: Mayo Clinic has a royalty-bearing know-how agreement and equity in Adaptive Phage Therapeutics.|BIOFIRE: Grant/Research Support|CARB-X: Advisor/Consultant|ContraFect: Grant/Research Support|Day Zero Diagnostics: Advisor/Consultant|HealthTrackRx: Advisor/Consultant|Mammoth Biosciences: Advisor/Consultant|Netflix: Advisor/Consultant|Oxford Nanopore Technologies: Advisor/Consultant|PhAST: Advisor/Consultant|See details: Patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic|See details: continued, patent on an anti-biofilm substance issued|TenNor Therapeutics Limited: Grant/Research Support|Torus Biosystems: Advisor/Consultant|Trellis Bioscience, Inc.: Advisor/Consultant Nicholas Bedard, MD, Stryker: Advisor/Consultant