Robotic Testing of Proximal Tibio-Fibular Joint Kinematics for Measuring Instability Following Total Knee Arthroplasty

Pain secondary to instability in total knee arthroplasty (TKA) has been shown to be major cause of early failure. In this study, we focused on the effect of instability in TKA on the proximal tibio-fibular joint (PTFJ). We used a robotics model to compare the biomechanics of the PTFJ in the native knee, an appropriately balanced TKA, and an unbalanced TKA. The tibia (n = 5) was mounted to a six-degree-of-freedom force/torque sensor and the femur was moved by a robotic manipulator. Motion at the PTFJ was recorded with a high-resolution digital camera system. After establishing a neutral position, loading conditions were applied at varying flexion angles (0°, 30°, and 60°). These included: internal/external rotation (0 Nm, ±5 Nm), varus/valgus (0 Nm, ±10 Nm), compression (100 N, 700 N), and posterior drawer (0 N, 100 N). With respect to anterior displacement, external rotation had the largest effect (coefficient = 0.650; p \u3c 0.0001). Polyethylene size as well as the interaction between polyethylene size and flexion consistently showed substantial anterior motion. Flexion and mid-flexion instability in TKA have been difficult to quantify. While tibio-femoral kinematics is the main aspect of TKA performance, the effects on adjacent tissues should not be overlooked. Our data show that PTFJ kinematics are affected by the balancing of the TKA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:47–52, 201

The Use of Proximal Fixed Modular Stems in Revision of Total Hip Arthroplasty

Proximally fixed femoral stems in revision of total hip arthroplasties (THAs) have had inconsistent results. Our aim was to determine the safety and efficacy of a new proximally fixed modular stem in THA revision. Fifty-three patients underwent THA revision with the Exactech AccuMatch M-Series (Gainesville, Fla) modular stem and were followed up prospectively for an average of 2.5 years with preoperative and postoperative Harris Hip Score and SF-12 scores. A small number of complications were reported. One stem was revised within 4 weeks due to subsidence. No later mechanical failure cases were reported. Postoperative Harris Hip Score and SF-12 improved significantly. The use of this modular stem system appears to be safe and efficacious regarding fixation and function in the short term

Hematologic Malignancies Are Associated With Adverse Perioperative Outcomes After Total Hip Arthroplasty.

BACKGROUND: Advancements in treating hematologic malignancies have improved survival, and these patients may be part of the growing population undergoing total hip arthroplasty (THA). Therefore, the purpose of this study was to evaluate the perioperative outcomes of THA in patients with hematologic malignancies. METHODS: The Nationwide Inpatient Sample identified patients who underwent THA from 2000 to 2011 (n = 2,864,412). Patients diagnosed with any hematologic malignancy (n = 18,012) were further stratified into Hodgkin disease (n = 786), non-Hodgkin lymphoma (n = 5062), plasma cell dyscrasias (n = 2067), leukemia (n = 5644), myeloproliferative neoplasms (n = 3552), and myelodysplastic syndromes (n = 1082). Propensity matching for demographics, hospital characteristics, and comorbidities identified 17,810 patients with any hematologic malignancy and 17,888 controls; additional matching was performed to compare hematologic malignancy subtypes with controls. Multivariate regression was used to analyze surgical and medical complications, length of stay (LOS), and costs. RESULTS: Compared to controls, hematologic malignancies increased the risk of any surgery-related complication (odds ratio [OR], 1.4; P \u3c .0001) and any general medical complication (OR, 1.47; P \u3c .0001). Additionally, hematologic malignancies were associated with an increase in LOS (0.16 days; P = .004) and increased costs ($1,101; P \u3c .0001). CONCLUSION: Patients with hematologic malignancies undergoing THA have an increased risk of perioperative complications, longer LOS, and higher costs. The risk quantification for adverse perioperative outcomes in association with increased cost may help to design different risk stratification and reimbursement methods in such populations

Hematologic Malignancies Are Associated with Adverse Perioperative Outcomes following Total Knee Arthroplasty.

The treatment of hematologic malignancies has advanced over the years, resulting in an improved survival of patients. As a result, these patients may be a part of the increasing population requiring total knee arthroplasty (TKA); however, they might be at a higher risk of adverse perioperative outcomes. The purpose of this study was to determine the perioperative outcomes (complications, length of stay [LOS], and costs) of patients with hematologic malignancies following TKA. This study used the Nationwide Inpatient Sample (NIS) to identify patients who underwent TKA in the United States from 2000 to 2011. Patients diagnosed with any hematologic malignancy (N = 24,714) were then stratified by Hodgkin\u27s disease (N = 791), Non-Hodgkin\u27s lymphoma (N = 7,096), plasma cell dyscrasias (N = 1,621), leukemia (N = 8,005), myeloproliferative disease (N = 5,746), and/or myelodysplastic syndromes (N = 1,608) for determining the complications that occurred during admission. Propensity matching was performed for demographics, hospital characteristics, and comorbidities, which yielded 24,491 patients with any hematologic malignancy and 24,458 control patients. Additionally, propensity matching was performed for the hematologic malignancy subtypes. Multivariable regression models were used to analyze the surgical and medical complications, LOS, and costs. The annual frequency of THA in patients with any hematologic malignancy increased from 2000 to 2011 (p \u3c 0.0001). Hematologic malignancies were associated with an increased risk of any surgery-related complication (odds ratio [OR] = 1.31, p \u3c 0.0001) and any general medical complication (OR = 1.38, p \u3c 0.0001). Patients with any hematologic malignancy had increased odds of complications, including acute postoperative anemia (OR = 1.29, p \u3c 0.0001), hematoma/seroma (OR = 1.65, p \u3c 0.02), peripheral vascular disease (OR = 2.23, p = 0.046), deep venous thrombosis (DVT) (OR = 1.95, p = 0.02), and blood transfusion (OR = 1.61, p \u3c 0.0001). Hematologic malignancies were associated with an increased incremental LOS (0.13 d, p \u3c 0.0001) and an increased incremental cost ($788, p \u3c 0.0001). Thus, we conclude that following TKA, patients with hematologic malignancies are at an increased risk of perioperative complications, longer LOS, and higher costs. The risk quantification for adverse perioperative outcomes in association with an increased cost may help design different risk stratification and reimbursement methods in such patients when undergoing TKA

The Contribution of the Acetabular Labrum to Hip Joint Stability: A Quantitative Analysis Using a Dynamic Three-Dimensional Robot Model

The acetabular labrum provides mechanical stability to the hip joint in extreme positions where the femoral head is disposed to subluxation. We aimed to quantify the isolated labrum\u27s stabilizing value. Five human cadaveric hips were mounted to a robotic manipulator, and subluxation potential tests were run with and without labrum. Three-dimensional (3D) kinematic data were quantified using the stability index (Colbrunn et al., 2013, Impingement and Stability of Total Hip Arthroplasty Versus Femoral Head Resurfacing Using a Cadaveric Robotics Model, J. Orthop. Res., 31(7), pp. 1108-1115). Global and regional stability indices were significantly greater with labrum intact than after total labrectomy for both anterior and posterior provocative positions. In extreme positions, the labrum imparts significant overall mechanical resistance to hip subluxation. Regional stability contributions vary with joint orientation

The Contribution of the Acetabular Labrum to Hip Joint Stability: A Quantitative Analysis Using a Dynamic Three-Dimensional Robot Model

The acetabular labrum provides mechanical stability to the hip joint in extreme positions where the femoral head is disposed to subluxation. We aimed to quantify the isolated labrum\u27s stabilizing value. Five human cadaveric hips were mounted to a robotic manipulator, and subluxation potential tests were run with and without labrum. Three-dimensional (3D) kinematic data were quantified using the stability index (Colbrunn et al., 2013, Impingement and Stability of Total Hip Arthroplasty Versus Femoral Head Resurfacing Using a Cadaveric Robotics Model, J. Orthop. Res., 31(7), pp. 1108-1115). Global and regional stability indices were significantly greater with labrum intact than after total labrectomy for both anterior and posterior provocative positions. In extreme positions, the labrum imparts significant overall mechanical resistance to hip subluxation. Regional stability contributions vary with joint orientation