The aim of this study was to determine the diagnostic accuracy of α defensin (AD) lateral flow assay (LFA) and enzyme-linked immunosorbent assay (ELISA) tests for periprosthetic joint infection (PJI) in comparison to conventional synovial white blood cell (WBC) count and polymorphonuclear neutrophil percentage (PMN%) analysis. Patients undergoing joint aspiration for evaluation of pain after total knee arthroplasty (TKA) or total hip arthroplasty (THA) were considered for inclusion. Synovial fluids from 99 patients (25 THA and 74 TKA) were analyzed by WBC count and PMN% analysis, AD LFA, and AD ELISA. WBC and PMN% cutoffs of ≥ 1,700 cells/mm3 and ≥ 65% for TKA and ≥ 3,000 cells/mm3 and ≥ 80% for THA were used, respectively. A panel of three physicians, all with expertise in orthopaedic infections and who were blinded to the results of AD tests, independently reviewed patient data to diagnose subjects as with or without PJI. Consensus PJI classification was used as the reference standard to evaluate test performances. Results were compared using McNemar’s test and area under the receiver operating characteristic curve (AUC) analysis.Aims
Methods
Assess union rate, complications, and outcomes of large series of contemporary extended trochanteric osteotomies (ETOs) performed during revision THAs. From 2003 to 2013, 612 ETOs were performed during revision THAs using 2 techniques. 367 were Paprosky type and 245 were Wagner type. Indications were aseptic loosening (65%), periprosthetic joint infection (18%), periprosthetic fracture (6%), femoral implant fracture (5%), and other (6%). Mean age 69 years, 58% male. Median follow-up 5 years (range, 2.1 to 13 years). Mean Harris Hip Scores increased from 57 preoperatively to 77 at latest follow-up (p=0.0001). Radiographic union of the extended osteotomy occurred in 98%. There were 9 ETO nonunions. Mean time to union of the distal transverse osteotomy was 5.9 months (range, 1 month − 2 years). Mean trochanteric osteotomy fragment migration prior to union was 3 mm (range, 0–29 mm). Over 1 cm of migration occurred in 7.4%. Intraoperative fracture of the ETO diaphyseal fragment occurred in 4%, and postoperative greater trochanter fractures in 8.8%. Other complications: dislocation in 5.7% and infection in 3.4%. Dislocation occurred in 19 of 462 with ETO migration < 1 cm and 4 of 39 with ETO migration ≥1 cm (p=0.08). Ten year survivorship free of revision for aseptic femoral loosening, free of any component removal or revision, and free of reoperation were 97%, 91%, and 82%, respectively. The union rate after ETO was high and notable trochanteric migration was infrequent. The most common complication was fracture intraoperatively or postoperatively of the osteotomy fragment.
Surgeons generally perform total knee replacement using either a gap balancing or measured resection approach. In gap balancing, ligamentous releases are performed first to create an equal joint space before any bony resections are performed. In measured resection, bony resections are performed first to match anatomical landmarks, and soft tissue releases are subsequently performed to balance the joint space. Previous studies have found a greater rate of coronal instability and femoral component lift-off using the measured resection technique, but it is unknown how potential differences in loading translate into component stability and fixation. Patients were randomly assigned at the time of referral to a surgeon performing either the gap balancing or measured resection technique (n = 12 knees per group). Both groups received an identical cemented, posterior-stabilized implant. At the time of surgery, marker beads were inserted in the bone around the implants to enable radiostereometeric analysis (RSA) imaging. Patients underwent supine RSA exams at 0–2 weeks, 6 weeks, 3 months, 6 months, and 12 months. Migration of the tibial and femoral components including maximum total point motion (MTPM) was calculated using model-based RSA software. Knee Society Scores were also recorded for each group.Background
Methods
The purpose of this study was to determine the effect of sectioning the relevant soft tissues and a TKA on the medial and lateral knee joint gap. Twelve intact lower extremity cadaveric specimens (mean (SD) age 76.5 (11.6) years) were tested. A custom designed knee tensioner was developed that allowed the separate application of forces to the medial and lateral components of the knee. The distance between the bottom of the load cell and the top of a compression rod was measured with digital calipers (precision = 0.1mm). Loads of 100N and 200N were then applied to each compartment and the resulting displacement was measured. The two loads were applied to the knee in the following conditions: i) All soft tissues intact; ii) an arthrotomy; iii) ACL sectioned; iv) PCL sectioned; v) release of the mid-coronal tissues; and vi) TKA. Finally, tensions were applied for all conditions from 90° to 0° of knee flexion in 30° increments. There was a significant effect of soft tissue release on the magnitude of the gap at the 100N load application, such that there was an increase in the when the mid-coronal MCL release was performed compared to the intact (2.2mm) and arthrotomy (1.75mm) conditions. With respect to the 200N load application there was a statistically significant tissue release effect, where differences were detected between the mid-coronal MCL release and intact (3.04mm) and arthrotomy conditions (2.31mm). At the 100N load there was a significance increase in the gap compared to the intact knee. There was also a significant condition by knee angle interaction where the gap was approximately 4mm larger following the TKA compared to the intact condition when the knee was flexed at 90°. Furthermore, there was a statistically significant 4.8mm and 3.8mm difference between 90° and 0° and 60° and 0° of knee flexion respectively, for the TKA condition only. At the 200N load application the gap width increased significantly by 2.5mm following the TKA. Finally, there was a significant condition by knee angle interaction where the change in gap width increased significantly from the intact (7.54mm) to the TKA condition (13.88mm) at 90° of knee flexion. There was a statistically significant difference in the TKA condition between 60° and 0° of knee flexion. Releasing the soft tissues increases the gap between the tibia and femur, when compared to the intact condition, with significance occurring only following the mid-coronal release. Furthermore, the TKA did not return the knee to its intact state as was evident by the significant difference between the TKA and intact conditions. This suggests that the resulting kinematics may not accurately match those pre-surgery resulting in un-physiological motion patterns and the possibility of early failure and revision.
