Unequal outside options in the lost wallet game

Experimental evidence suggests the size of the foregone outside option of the first mover does not affect the behavior of the second mover in the lost wallet game. In this paper we experimentally compare the behavior of subjects when they face an outside option with unequal payoffs, i.e., the first mover gets 10 and the second mover gets 0, and when they face an outside option with equal payoffs, i.e., both get 5. Consistent with the most of the literature we do not find a significant difference in behavior of second movers.Experimental economics, fairness, inequality, lost wallet game, outside option

Prehabilitation Before Total Knee Arthroplasty Increases Strength and Function in Older Adults With Severe Osteoarthritis

Preparing for the stress of total knee arthroplasty (TKA) surgery by exercise training (prehabilitation) may improve strength and function before surgery and, if effective, has the potential to contribute to postoperative recovery. Subjects with severe osteoarthritis (OA), pain intractable to medicine and scheduled for TKA were randomized into a usual care (UC) group (n = 36) or usual care and exercise (UC + EX) group (n = 35). The UC group maintained normal daily activities before their TKA. The UC + EX group performed a comprehensive prehabilitation program that included resistance training using bands, flexibility, and step training at least 3 times per week for 4-8 weeks before their TKA in addition to UC. Leg strength (isokinetic peak torque for knee extension and flexion) and ability to perform functional tasks (6-minute walk, 30 second sit-to-stand repetitions, and the time to ascend and descend 2 flights of stairs) were assessed before randomization at baseline (T1) and 1 week before the subject\u27s TKA (T2). Repeated-measures analysis of variance indicated a significant group by time interaction (p \u3c 0.05) for the 30-second sit-to-stand repetitions, time to ascend the first flight of stairs, and peak torque for knee extension in the surgical knee. Prehabilitation increased leg strength and the ability to perform functional tasks for UC + EX when compared to UC before TKA. Short term (4-8 weeks) of prehabilitation was effective for increasing strength and function for individuals with severe OA. The program studied is easily transferred to a home environment, and clinicians working with this population should consider prehabilitation before TKA. [PUBLICATION ABSTRACT

Blood loss in primary total knee arthroplasty-body temperature is not a significant risk factor-a prospective, consecutive, observational cohort study

BACKGROUND: Hypothermia related to anaesthesia and operating theatre environment is associated with increased blood loss in a number of surgical disciplines, including total hip arthroplasty. The influence of patient temperature on blood loss in total knee arthroplasty (TKA) has not been previously studied. METHODS: We recorded patient axillary temperature in the peri-operative period, up to 24 h post-operatively, and analysed the effect on transfusion rate and blood loss from a consecutive cohort of 101 patients undergoing primary TKA. RESULTS: No relationship between peri-operative patient temperature and blood loss was found within the recorded patient temperature range of 34.7–37.8 °C. Multivariable analysis found increasing age, surgical technique, type of anaesthesia and the use of anti-platelet and anticoagulant medications as significant factors affecting blood loss following TKA. CONCLUSION: Patient temperature within a clinically observed range does not have a significant impact on blood loss in primary TKA patients. As long as patient temperature is maintained within a reasonable range during the intra-operative and post-operative periods, strategies other than rigid temperature control above 36.5 °C may be more effective in reducing blood loss following TKA

The effect of total knee arthroplasty on joint movement during functional activities and joint range of motion with particular regard to higher flexion users

Study aimed to evaluate active and functional knee excursion of patients before and after total knee arthroplasty (TKA) and to determine whether TKA restores quality of life related to functional activities of daily living. Found that although TKA offers excellent pain relief and contributes to the overall well-being of the patient, these results suggest that it also leads to a reduced range of active and functional motion in the majority of patients. This is associated with a lower-than-normal physical quality of life. The design of implants and rehabilitation programmes should be reconsidered so that better range of motion and quality of life can be achieved for patients

The Work of the Alien Property Custodian

The aim of the thesis was to investigate deficits and compensatory strategies after total knee arthroplasty (TKA) in different conditions during gait and quiet standing. Although TKA is considered the gold standard treatment for end-stage knee osteoarthritis, it is associated with a number of implications. Reduced physical function after osteoarthritis is partly, but apparently not fully, remedied by surgery. The two most common deficits are reduced knee muscle strength and limited range of knee joint motion (ROM), partly due to prosthesis mechanics. Reduced postural control has also been shown shortly after surgery. In spite of sufficient passive knee joint ROM for normal ambulation, gait patterns are characterized by reduced knee flexion. Several factors such as reduced knee muscle strength, reduced proprioception, habitual strategies or fear of movement may be suggested as explanations for difficulties in gait and posture. As an effect, compensatory strategies may result. In order to focus on the implications of TKA, participants had to be less than 65 years of age and healthy, TKA being the only factor different form controls. The same 23 individuals with unilateral TKA ~ 19 months post-operative and 23 controls participated in all studies.   3D whole body kinematics was used to assess gait and posture and electromyography was used to record muscle activity. Isokinetic measurements were used to determine dynamic knee muscle strength. Gait in the frontal and sagittal planes were assessed. The tasks included in the test protocol were negotiation up and down stairs, gait on hard and soft surface, quiet standing with sensory modulation (with and without vision and on soft surface), and single limb stance.  Primary outcome variables addressed were: knee and hip joint kinematics in frontal and sagittal planes, upper body inclination, postural sway and relative knee muscle activity as an indicator of relative effort. Background factors used to explain group differences in the primary outcomes were derived from demographics, clinical examination, and questionnaires. Demographic factors were age, body mass index (BMI), and time since surgery. Clinical examinations were conducted for passive knee joint ROM, joint position sense, knee muscle strength, anterior knee joint laxity, and leg length. Questionnaires assessed fear of movement, pain, and knee related function and quality of life. The results showed that knee flexion was reduced during stair descent in both the prosthetic and the contralateral knee in the TKA group compared to controls. Although reduced passive knee joint flexion in the TKA group was sufficient for normal stair descent, it was the only factor identified that explained reduced knee flexion in stair descent. As knee muscle strength was significantly reduced in the TKA group, it is reasonable to suggest that as a contributing factor. Furthermore, the TKA group also displayed increased hip adduction during stair descent, which may indicate both a compensatory strategy as well as reduced hip muscle strength. In stair ascent, no significant group differences were found in relative knee muscle activity as expected due to knee muscle weakness. Nor were there any indications of compensatory forward inclination of the trunk to reduce knee joint moments. Instead, probably compensating for muscle weakness, the TKA group ascended stairs at a significantly slower speed. Surface modulation during level gait showed that reduced knee flexion in the prosthetic knee during the stance phase when walking on a hard surface was further decreased during gait on a soft surface. Knee and hip adduction at the stance phase were not affected by surface conditions. Nevertheless, the TKA group displayed increased knee adduction and hip adduction compared to controls, particularly in the prosthetic side. In addition, the TKA group displayed increased step width on the soft compared to hard surface. Single-limb stance for 20 seconds failed in 30 % of the TKA group and in 4 % of the control group. Those in the TKA group who were able to perform single-limb stance performed equally well as controls. During bilateral quiet standing, postural sway was similar in both groups, and inability to stand on one leg did not affect bilateral stance. Older age, higher BMI and reduced quadriceps strength determined the failure to maintain single-limb stance in the TKA group.   In conclusion, this thesis indicates that reduced knee muscle strength is a common denominator as part of the explanatory factors for reduced performance and compensatory strategies in individuals with TKA. Reduced speed during stair ascent as well as reduced knee flexion during stair descent may be compensations for reduced lower extremity strength. Increased hip adduction may compensate for reduced knee flexion in stair descent, but may also represent hip muscle weakness or reduced motor control as increased hip adduction is found also in level gait. The failure to maintain single-limb stance in the TKA group is also partly explained by reduced knee muscle strength. Muscle weakness may be and indicator for reduced physical capacity in general

Popliteus impingement after TKA may occur with well-sized prostheses

To determine the mechanisms and extents of popliteus impingements before and after TKA and to investigate the influence of implant sizing. The hypotheses were that (1) popliteus impingements after TKA may occur at both the tibia and the femur, and (2) even with an apparently well-sized prosthesis, popliteal tracking during knee flexion is modified compared to the preoperative situation. The location of the popliteus in three cadaver knees was measured using computed tomography, before and after implantation of plastic TKA replicas, by injecting the tendon with radiopaque liquid. The pre- and post-operative positions of the popliteus were compared from full extension to deep flexion using normosized, oversized, and undersized implants (one size increments). At the tibia, TKA caused the popliteus to translate posteriorly, mostly in full extension: 4.1 +/- 2 mm for normosized implants, and 15.8 +/- 3 mm with oversized implants, but no translations were observed when using undersized implants. At the femur, TKA caused the popliteus to translate laterally at deeper flexion angles, peaking between 80A degrees and 120A degrees: 2 +/- 0.4 mm for normosized implants and 2.6 +/- 0.5 mm with oversized implants. Three-dimensional analysis revealed prosthetic overhang at the posterosuperior corner of normosized and oversized femoral components (respectively, up to 2.9 mm and 6.6 mm). A well-sized tibial component modifies popliteal tracking, while an undersized tibial component maintains more physiologic patterns. Oversizing shifts the popliteus considerably throughout the full arc of motion. This study suggests that both femoro- and tibio-popliteus impingements could play a role in residual pain and stiffness after TKA

Intra-operative blood salvage in total hip and knee arthroplasty

Purpose To review records of 371 patients who underwent total hip or knee arthroplasty (THA or TKA) with intra-operative blood salvage to determine the allogeneic blood transfusion rate and the predictors for allogeneic blood transfusion. Methods Records of 155 male and 216 female consecutive patients aged 17 to 95 (mean, 70) years who underwent primary THA or TKA by a single surgeon with the use of intra-operative blood salvage were reviewed. Results The preoperative haemoglobin level was &lt;120 g/dl in 15% of THA patients and 5% of TKA patients; the allogeneic transfusion rate was 24% in THA patients and 12% in TKA patients. Despite routine use of intra-operative blood salvage, only 59% of THA patients and 63% of TKA patients actually received salvaged blood, as a minimum of 200 ml blood loss was required to activate blood salvage. In multivariable analysis, predictors for allogeneic blood transfusion were female gender (adjusted odds ratio [OR]=2.8, p=0.02), age &gt;75 years (adjusted OR=5.9, p&lt;0.001), and preoperative haemoglobin level &lt;120 g/l (adjusted OR=30.1, p&lt;0.001), despite the use of intra-operative blood salvage. Patients who received allogeneic blood transfusion had a longer hospital stay and greater complication rate. Conclusion Intra-operative blood salvage is not effective in preventing allogeneic blood transfusion in patients with a preoperative haemoglobin level &lt;120 g/l. It should be combined with preoperative optimisation of the haemoglobin level or use of tranexamic acid. </jats:sec

Implementing a perioperative efficiency initiative for orthopedic surgery instrumentation at an academic center: A comparative before-and-after study.

Optimizing surgical instrumentation may contribute to value-based care, particularly in commonly performed procedures. We report our experience in implementing a perioperative efficiency program in 2 types of orthopedic surgery (primary total-knee arthroplasty, TKA, and total-hip arthroplasty, THA).A comparative before-and-after study with 2 participating surgeons, each performing both THA and TKA, was conducted. Our objective was to evaluate the effect of surgical tray optimization on operating and processing time, cost, and waste associated with preparation, delivery, and staging of sterile surgical instruments. The study was designed as a prospective quality improvement initiative with pre- and postimplementation operational measures and a provider satisfaction survey.A total of 96 procedures (38 preimplementation and 58 postimplementation) were assessed using time-stamped performance endpoints. The number and weight of trays and instruments processed were reduced substantially after the optimization intervention, particularly for TKA. Setup time was reduced by 23% (6 minutes, P = .01) for TKA procedures but did not differ for THA. The number of survey respondents was small, but satisfaction was high overall among personnel involved in implementation.Optimizing instrumentation trays for orthopedic procedures yielded reduction in processing time and cost. Future research should evaluate patient outcomes and incremental/additive impact on institutional quality measures

Surgical site infection and transfusion rates are higher in underweight total knee arthroplasty patients.

BACKGROUND: Underweight (UW) patients undergoing total hip arthroplasty have exhibited higher complication rates, including infection and transfusion. No study to our knowledge has evaluated UW total knee arthroplasty (TKA) patients. We, therefore, conducted a study to investigate if these patients are at increased risk for complications, including infection and transfusion. METHODS: A case-control study was conducted using a prospectively collected institutional database. Twenty-seven TKA patients were identified as UW (body mass index [BMI] \u3c 18.5 kg/m RESULTS: The average BMI was 17.1 kg/m CONCLUSIONS: Our study demonstrates that UW TKA patients have a higher likelihood of developing SSI and requiring blood transfusions. The specific reasons are unclear, but we conjecture that it may be related to decreased wound healing capabilities and low preoperative hemoglobin. Investigation of local tissue coverage and hematologic status may be beneficial in this patient population to prevent SSI. Based on the results of this study, a prospective evaluation of these factors should be undertaken

Fracture of the tibial baseplate in bicompartmental knee arthroplasty

Introduction. Bicompartmental knee arthroplasty (BKA) addresses combined medial and patellofemoral compartment osteoarthritis, which is relatively common, and has been proposed as a bridge between unicompartmental and total knee arthroplasty (TKA). Case Presentation. We present the case report of a young active man treated with BKA after unsuccessful conservative therapy. Four years later, loosening with fracture of the tibial baseplate was identified and the patient was revised to TKA. Discussion. Although our case is only the second fractured tibial baseplate to be reported, we believe that the modular titanium design, with two fixation pegs, is too thin to withstand daily cyclic loading powers. Light daily routine use, rather than high-impact sports, is therefore advised. Failures may also be related to the implant being an early generation and known to be technically complex, with too few implant sizes. We currently use TKA for the treatment of medial and patellofemoral compartment osteoarthritis