Septic Arthritis (SA) is considered a surgical urgency/ emergency by physicians around the world. As our understanding grows, and improved diagnostic algorithms are developed, it has become apparent that competing interests in terms of accurately diagnosing concurrent osteomyelitis may supercede rapid surgical intervention when the imaging is timely. Nevertheless, even in cases of isolated SA, many patients will require repeat surgery. We aimed to assess factors which could predict this.

A multicenter retrospective redcap database was created involving 20 pediatric centers from the CORTICES study group with the goal of better understanding pediatric musculoskeletal infection (PMSKI). All patients who met inclusion for the database were considered, surgeons for each site determined through imaging and chart review which patients met the diagnosis of isolated SA. Patients with concomitant abscesses or osteomyelitis were expressly excluded. Appropriate non parametric statistics were used to assess univariate significance. Multivariable logistic regression was used to assess clinical factors associated with an increased likelihood of more than one surgery. Receiver characteristics operating curve (ROC) analysis was used to determine optimal cutoffs to discriminate between children who required more than one surgery compared to those who required only one surgery. A probability algorithm was developed for the number of clinical factors present and the likelihood requiring more than one surgery following SA diagnosis.

“Four hundred and fifty-four patients with isolated SA were analyzed from 20 US hospitals. Patients were 5.4 +/− 4.8 years old at admission, and the cohort was 56% male. Of the 454 patients, 47 (10.4%) needed more than one surgery. Bivariate comparisons across surgery groups found significant differences in minimum platelet count (pplatelet, a patient has a 0.3% reduction in the odds of needing more than one surgery (OR=.997; p=0.04). For each additional ten units of CRP, a patient has a 0.1% increase in the odds of needing more than one surgery (OR=1.001; p<0.001). Our predictive algorithm found that children with both risk factors had a 64% chance of requiring multiple surgeries.

Higher CRP values and lower platelet values indicate more severe disease in isolated SA with a greater likelihood of repeat surgery. Higher CRP and lower platelet counts may portend multiple surgeries and caregivers of children with isolated SA should be advised as such.

Introduction

Cross-linked polyethylene in total hip arthroplasty has demonstrated excellent long-term wear resistance, leading to its acceptance as the standard bearing used in hip replacement. Adoption in knee replacement has been tentative, as the cross-linking process can decrease the polyethylene mechanical properties. The current study's purpose was examining survivorship of a fixed bearing knee replacement system featuring a moderately cross-linked polyethylene (MXLK) bearing, a cobalt chrome (CoCr) tibial tray with a highly polished top surface, and a new polyethylene-to-tray locking mechanism. The MXLK is made of ultra-high molecular weight GUR1020 resin irradiated with 5 Mrad gamma radiation, followed by a free radical quenching remelting annealing process, above the 135 degree melting point, that provides wear and fatigue resistance, and oxidative stability.

Proper restoration of posterior condylar offset during TKA has been shown to be important to maximize range of motion and minimize flexion instability. However, there is little information as to the importance of restoration of mid-sagittal femoral geometry. There is controversy as to whether a TKA prosthesis should have a single radius or multiple radii of curvature. The purpose of this study is to evaluate the effectiveness of a multi-radius femoral component at restoring mid sagittal femoral offset.

A consecutive series of 100 TKAs with digital preoperative and postoperative radiographs and standardized radiographic markers were analyzed. There were 71 female and 29 male knees with mean age of 59 years. All TKAs were performed by a single surgeon using a multi-radius femoral component design. The distal femoral resection was set to resect 10 mm from the distal femoral condyle and a posterior referencing system was used to size the femoral component. Using radiographic perfect lateral projections of the knees, a line was drawn along the posterior femoral shaft and another parallel line down the anterior femoral shaft. A 3rd line was then drawn parallel to the posterior shaft at the furthest point posterior on the condyle. A 4th line was drawn parallel to the anterior shaft at the furthest point anterior on the femur. 90 degree angles were constructed to create a grid in the anterior and posterior directions, similar to a previously reported technique. Finally, 45 degree angle lines were created in the grid to assess mid flexion dimensions [Fig-1 and 2]. The percent change in posterior condylar offset (PCO), anterior femoral offset (AFO), mid femoral anterior offset (MAFO) and mid femoral posterior offset (MFPO) were calculated.

The mean reproduction of the mid-anterior femoral offset and mid-posterior femoral offset were 101.1% [range 56.5%–167.5%] and 96.8% [range 54.9%–149.0%] of preoperative measurements respectively. The average restoration of posterior offset and anterior offset were 92.8% [range 49.0%–129.8%] and 115.3% of preoperative measurements [range 35.7%–400.0%] respectively. When the posterior condylar offset was restored to within 10% of the native anatomy, the MPFO restoration more closely resembled normal anatomy (103.0% vs. 93.9%, p = 0.005). When the postoperative posterior condylar offset was decreased greater than 20%, both the MAFO (90.1% vs. 104.5%, p = 0.004) and MPFO (78.5% vs. 102.9%, p < 0.001) decreased compared to the native knee. There was no relationship between restoration of the PCO and the MAFO correction (104.6% vs. 99.4%, p = 0.213). Finally, there was no correlation between restoration of anterior femoral offset within 10% of normal and the restoration of mid sagittal femoral offset; 98.0% vs 102.0% for MAFO (p = 0.320) and 98.7% vs 96.3% for MPFO (p = 0.569).

A modern multi-radius condylar knee design is capable of reproducing the mid-sagittal geometry of the preoperative knee. However, the restoration of mid sagittal offset is largely dependent on the restoration of the posterior condylar offset. Intraoperative adjustments in anterior and posterior femoral resections can have significant impact in the ability of the implant to reproduce mid-sagittal femoral anatomy.