Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength.

BACKGROUND: Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength. METHODS: A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen. RESULTS: The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P = .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P = .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089 ± 2,158 N vs 5,960 ± 2,010 N, P < .0025). CONCLUSION: Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Patient-reported outcomes after above-knee amputation for prosthetic joint infection.

BACKGROUND: Prosthetic joint infection (PJI) is a challenging complication after total knee arthroplasty (TKA). Above-knee amputation (AKA) is a salvage procedure that may be performed after revision TKAs fail to eradicate PJI. Few studies have investigated patient-reported outcomes. This study investigates patient-reported functional outcomes and overall satisfaction in a cohort of patients who underwent AKA for PJI. METHODS: We performed a retrospective study of all patients who underwent AKA for PJI from 2002 to 2015 at a tertiary academic institution in the rural northeastern United States, along with prospective phone interviews. Functional outcomes and overall satisfaction were adapted from the Above-The-Knee Amputation Functional Ability Questionnaire. Additional variables included age, sex, American Society of Anesthesiologists (ASA) Score, and mortality. RESULTS: Forty-four patients were included in the study. Eighteen patients died prior to study initiation, with a mean time of 948 days (2.6 years) between AKA and death. The 5-year mortality rate was 50%. Among the 14 patients who completed the survey, 12 (86%) were fit for prosthesis following AKA. Of these, 10 (71%) required the use of an assistive device and one (seven percent) reported being functionally independent with their prosthesis. Five (36%) required further surgery after their AKA. Twelve (86%) stated that they were satisfied with their AKA and 5 (42%) would have done it sooner if offered. CONCLUSIONS: Patients who underwent AKA for PJI reported a low level of independence and ability to ambulate with a high mortality rate. However, most were satisfied with their AKA and would choose it again.

A Survey of Physicians' Attitudes toward Decision-Making Authority for Initiating and Withdrawing VA-ECMO: Results and Ethical Implications for Shared Decision Making.

OBJECTIVE: Although patients exercise greater autonomy than in the past, and shared decision making is promoted as the preferred model for doctor-patient engagement, tensions still exist in clinical practice about the primary locus of decision-making authority for complex, scarce, and resource-intensive medical therapies: patients and their surrogates, or physicians. We assessed physicians' attitudes toward decisional authority for adult venoarterial extracorporeal membrane oxygenation (VA-ECMO), hypothesizing they would favor a medical locus. DESIGN, SETTING, PARTICIPANTS: A survey of resident/fellow physicians and internal medicine attendings at an academic medical center, May to August 2013. MEASUREMENTS: We used a 24-item, internet-based survey assessing physician-respondents' demographic characteristics, knowledge, and attitudes regarding decisional authority for adult VA-ECMO. Qualitative narratives were also collected. MAIN RESULTS: A total of 179 physicians completed the survey (15 percent response rate); 48 percent attendings and 52 percent residents/fellows. Only 32 percent of the respondents indicated that a surrogate's consent should be required to discontinue VA-ECMO; 56 percent felt that physicians should have the right to discontinue VA-ECMO over a surrogate's objection. Those who self-reported as "knowledgeable" about VA-ECMO, compared to those who did not, more frequently replied that there should not be presumed consent for VA-ECMO (47.6 percent versus 33.3 percent, p = 0.007), that physicians should have the right to discontinue VA-ECMO over a surrogate's objection (76.2 percent versus 50 percent, p = 0.02) and that, given its cost, the use of VA-ECMO should be restricted (81.0 percent versus 54.4 percent, p = 0.005). CONCLUSIONS: Surveyed physicians, especially those who self-reported as knowledgeable about VA-ECMO and/or were specialists in pulmonary/critical care, favored a medical locus of decisional authority for VA-ECMO. VA-ECMO is complex, and the data may (1) reflect physicians' hesitance to cede authority to presumably less knowledgeable patients and surrogates, (2) stem from a stewardship of resources perspective, and/or (3) point to practical efforts to avoid futility and utility disputes. Whether these results indicate a more widespread reversion to paternalism or a more circumscribed usurping of decisional authority occasioned by VA-ECMO necessitates further study.