Immune cell populations differ in patients undergoing revision total knee arthroplasty for arthrofibrosis.

Arthrofibrosis following total knee arthroplasty (TKA) is a debilitating condition typically diagnosed based on clinical findings. To gain insight into the histopathologic immune cell microenvironment of arthrofibrosis, we assessed the extent of tissue fibrosis and quantified immune cell populations in specific tissue regions of the posterior capsule. We investigated specimens from three prospectively-collected, matched cohorts, grouped as patients receiving a primary TKA for osteoarthritis, revision TKA for arthrofibrosis, and revision TKA for non-arthrofibrotic, non-infectious reasons. Specimens were evaluated using hematoxylin and eosin staining, picrosirius red staining, immunofluorescence, and immunohistochemistry with Aperio®-based digital image analysis. Increased collagen deposition and increased number of α-SMA/ACTA2 expressing myofibroblasts were present in the arthrofibrosis group compared to the two non-arthrofibrotic groups. CD163 + macrophages were the most abundant immune cell type in any capsular sample with specific enrichment in the synovial tissue. CD163 + macrophages were significantly decreased in the fibrotic tissue region of arthrofibrosis patients compared to the patients with primary TKA, and significantly increased in adipose tissue region of arthrofibrotic specimens compared to non-arthrofibrotic specimens. Synovial CD117 + mast cells were significantly decreased in arthrofibrotic adipose tissue. Together, these findings inform diagnostic and targeted therapeutic strategies by providing insight into the underlying pathogenetic mechanisms of arthrofibrosis.

Lack of Bone-on-Bone Arthritis Is Not a Strict Contraindication for Mobile-Bearing Unicompartmental Knee Arthroplasty.

Unicompartmental knee arthroplasty (UKA) is a viable option for patients with symptomatic knee arthritis isolated to 1 compartment. Previous articles have suggested that mobile-bearing UKA should not be performed in patients without bone-on-bone arthritis. The purpose of this study was to compare the clinical outcomes and survivorship of mobile-bearing UKA in patients with severe osteoarthritis with bone-on-bone contact and patients with severe osteoarthritis but without bone-on-bone contact. METHODS: We retrospectively reviewed a single surgeon's experience with medial compartment mobile-bearing UKA in 219 patients (271 knees) who underwent the procedure between 2007 and 2015. Anteroposterior and posteroanterior radiographs were reviewed, and arthritis was graded using the International Knee Documentation Committee (IKDC) grading system. Only patients with grade D (severe arthritis) were studied. Of the patients who had grade-D arthritis, there were 81 patients (94 knees) with bone-on-bone arthritis and 82 patients (91 knees) without bone-on-bone contact. Functional outcomes were assessed using the Knee Society pain and function scores. Survivorship free of revision in these 2 groups was determined using Kaplan-Meier curves at 8 years. RESULTS: There were no significant differences between the 2 groups in terms of age (p = 0.91), sex (p = 0.21), or body mass index (p = 0.63). At the time of the final follow-up, there was no significant difference in Knee Society pain scores (p = 0.59) or Knee Society function scores (p = 0.9) between the 2 groups. There were 5 revisions in the group with bone-on-bone contact and 2 revisions in the group without bone-on-bone contact. The survivorship free of revision at 8 years was 95% for the group with bone-on-bone contact and 98% for the group without bone-on-bone contact (p = 0.45). CONCLUSIONS: Patients with severe knee arthritis (IKDC grade D) without bone-on-bone contact had similar outcomes of mobile-bearing UKA compared with patients with bone-on-bone contact. UKA is a safe and reliable option in patients with severe osteoarthritis who do not have bone-on-bone contact on preoperative radiographs and it should therefore not be considered a contraindication for mobile-bearing UKA as long as the patient's symptoms are severe enough to warrant surgical intervention. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Total Protein Staining is Superior to Classical or Tissue-Specific Protein Staining for Standardization of Protein Biomarkers in Heterogeneous Tissue Samples.

Protein detection techniques such as western blotting and ELISA rely on housekeeping proteins as standards for sample normalization. However, clinical or animal tissue specimens are heterogeneous due to presence of contaminating cell types and tissues (e.g., blood vessels and muscle) or cellular decay during tissue storage and isolation which may compromise protein integrity. This biological heterogeneity may invalidate the assumption that housekeeping proteins are invariable across various specimens. This study provides data that advocate for protein standardization based on total protein staining in rabbit posterior capsular tissues. We compared the classical normalization markers glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and ß-tubulin (TUBB) with other proteins that have low variation in expression (i.e., FTL, FTH1, EEF1A1, TPT1) based on RNAseq data for human posterior capsular tissues. Histological examination revealed a high degree of qualitative variation in microscopic images of capsular tissue specimens. This variation is reflected by significant differences in specific protein signals for all housekeeping proteins as detected by western blot analysis. However, total protein staining, which combines the intensity of multiple gel electrophoretic bands, normalizes natural biological variation observed for individual housekeeping proteins and permits assessment of protein integrity. Therefore, we propose that normalization based on total protein staining increases accuracy of protein quantification of heterogeneous tissue specimen samples.

Single-Dose Perioperative Antibiotics Do Not Increase the Risk of Surgical Site Infection in Unicompartmental Knee Arthroplasty.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) is commonly performed as an outpatient procedure. To facilitate this process, a single-dose intravenous (IV) perioperative antibiotic administration is required compared to 24-hour IV antibiotic dosing schedules that are typical of most inpatient arthroplasty procedures. There is a paucity of literature to guide surgeons on the safety of single-dose perioperative antibiotic administration for arthroplasty procedures, particularly those that will be performed in the outpatient setting. The purpose of this study is to evaluate a large series of UKA performed with single-dose vs 24-hour IV antibiotic coverage to determine the impact on risk for surgical site infection (SSI). METHODS: All UKA cases were evaluated from 2007 to 2017 performed by a single surgeon at an academic institution. There were 296 UKAs in the cohort: 40 were outpatient procedures receiving single-dose antibiotics and 256 were inpatient procedures receiving 24-hour antibiotics. No patients were prescribed adjuvant oral antibiotics. Mean age was 64 years, 50% were female, mean body mass index was 32 kg/m2, and mean follow-up was 4.1 years (range 1.0-10.4). Perioperative antibiotic regimen was evaluated and SSI, defined as occurring within 1 year of surgery, was abstracted through a prospective total joint registry and manual chart review. RESULTS: SSI occurred in 2 of 296 cases (0.7%) in the entire cohort, 2 of 256 inpatient UKAs (0.8%), and 0 of 40 outpatient UKAs (0%) (P = 1.00). One SSI was a deep infection occurring 6 weeks postoperatively that required 2-stage exchange and conversion to total knee arthroplasty. The other was a superficial infection treated with 2 weeks of oral antibiotics. CONCLUSION: This study demonstrates a low SSI risk (0.8% or less) following UKA with both single-dose and 24-hour IV antibiotics. Administering single-dose perioperative antibiotics is safe for UKA, which should alleviate that potential concern for outpatient surgery. LEVEL OF EVIDENCE: Level III, Therapeutic.

Are Subchondral Intraosseous Injections Effective and Safe for the Treatment of Knee Osteoarthritis? A Systematic Review.

Knee osteoarthritis (OA) is a highly prevalent disease and treatment options for early stages of OA are needed. Intraosseous injections of bone substitute and biologic materials have been proposed to expand the therapeutic arsenal by potentially halting OA progression and delaying the need for knee arthroplasty in patients with early/moderate-stage disease. Therefore, the goal of this study was assessed the efficacy and safety of subchondral intraosseous injection for the treatment of knee OA. A systematic review was performed on PubMed-Medline, and the Cochrane Database of systematic reviews. English and Spanish retrospective and prospective studies assessing the results of subchondral intraosseous injection of bone substitute materials and/or biologicals in human patients with knee OA, with a minimum of 6 months of follow-up were collected. A total of 1,081 potential articles were identified through our search. Six studies were included with a total of 163 patients. The mean follow-up was 18 months (range: 6-24 months). Patient reported outcomes measures (PROMs), complications, and conversion to total knee arthroplasty (TKA) were collected. All six studies showed PROMs improvement relative to baseline. Overall, the five studies reporting visual-analog scale (VAS) pain outcomes improved from a baseline mean score of 6.68 to 2.74. Also, knee injury and osteoarthritis score (KOOS), Tegner-Lysholm, and/or international knee documentation committee (IKDC) scores rose compared with baseline scores in all studies. Overall, 2.5% (4/163) of patients had a complication attributed to study-related treatment. Most patients (81%, 86/106) remained TKA-free at a 1-year follow-up. Subchondral intraosseous injections of bone substitute materials and platelet-rich plasma (PRP) suggest (1) improved PROMs of pain and functional status, (2) low complication rate, and (3) relatively low rates of conversion to TKA. However, the current studies investigating these treatments exhibited high degree of heterogeneity in both measurement of outcomes and delivery of treatment, with a high risk of bias. This procedure should not be utilized in advanced knee OA. In light of the limitations of the current literature, advising in favor or against this therapy for early to moderate knee OA is challenging.