Timing is everything: Impact of combined long bone fracture and major arterial injury on outcomes.

BACKGROUND: Timing of extremity fracture fixation in patients with an associated major vascular injury remains controversial. Some favor temporary fracture fixation before definitive vascular repair to limit potential graft complications. Others advocate immediate revascularization to minimize ischemic time. The purpose of this study was to evaluate the timing of fracture fixation on outcomes in patients with concomitant long bone fracture and major arterial injury. METHODS: Patients with a combined long bone fracture and major arterial injury in the same extremity requiring operative repair over 11 years were identified and stratified by timing of fracture fixation. Vascular-related morbidity (rhabdomyolysis, acute kidney injury, graft failure, extremity amputation) and mortality were compared between patients who underwent fracture fixation prerevascularization (PRE) or postrevascularization (POST). RESULTS: One hundred four patients were identified: 19 PRE and 85 POST. Both groups were similar with respect to age, sex, Injury Severity Score, admission base excess, 24-hour packed red blood cells, and concomitant venous injury. The PRE group had fewer penetrating injuries (32% vs. 60%, p = 0.024) and a longer time to revascularization (9.5 vs. 5.8 hours, p = 0.0002). Although there was no difference in mortality (0% vs. 2%, p > 0.99), there were more vascular-related complications in the PRE group (58% vs. 32%, p = 0.03): specifically, rhabdomyolysis (42% vs. 19%, p = 0.029), graft failure (26% vs. 8%, p = 0.026), and extremity amputation (37% vs. 13%, p = 0.013). Multivariable logistic regression identified fracture fixation PRE as the only independent predictor of graft failure (odds ratio, 3.98; 95% confidence interval, 1.11-14.33; p = 0.03) and extremity amputation (odds ratio, 3.924; 95% confidence interval, 1.272-12.111; p = 0.017). CONCLUSION: Fracture fixation before revascularization contributes to increased vascular-related morbidity and was consistently identified as the only modifiable risk factor for both graft failure and extremity amputation in patients with a combined long bone fracture and major arterial injury. For these patients, delaying temporary or definitive fracture fixation until POST should be the preferred approach. LEVEL OF EVIDENCE: Prognostic study, Level IV.

Retrieval Analysis of Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty and Correlations to Laxity and Wear.

BACKGROUND: Total knee arthroplasty (TKA) with posterior-stabilized (PS) or posterior cruciate-retaining (CR) implants has high success rates and survivorship. However, it is uncertain how laxity and constraint are associated with long-term polyethylene wear under physiological conditions. METHODS: To answer this question, we measured the laxity patterns of 47 harvested cadaver specimens with primary TKAs in a custom knee-testing machine at full extension and at 30°, 60°, and 90° of flexion. The wear patterns of the tibial inserts were assessed using a semiquantitative method which is a modified approach of that proposed by Hood et al in 1983. RESULTS: Statistical analysis found that the PS TKA cohort had a statistically significant increase in varus laxity at 60° and 90° of flexion, as well as total coronal laxity at 60° of flexion when compared to the CR cohort. Furthermore, analysis demonstrated a significant correlation between increased PS coronal laxity and increased tibial wear, a trend that was not seen in the CR specimens. CONCLUSION: Our findings suggest that greater laxity in flexion after primary TKA may increase the wear realized over time and that PS TKAs may be more susceptible due to the loss of support the PCL affords to the flexion space. Whether a CR or PS TKA is used, surgeons need to avoid the pitfalls that may create greater flexion laxity during the procedure to optimize long-term polyethylene wear.

Postmortem Retrieval Analysis of Metallosis and Periprosthetic Tissue Metal Concentrations in Total Knee Arthroplasty.

BACKGROUND: The purpose of this study is to determine the preferred sampling location for tissue analysis in total knee arthroplasty (TKA) and to evaluate metal concentrations, inflammatory cytokines, component damage, and tissue metallosis. METHODS: Twenty TKA systems were collected at necropsy along with tissue samples from 5 distinct locations. Inductively coupled plasma mass spectrometry (ICP-MS) analysis was performed to determine cobalt (Co), chromium (Cr), and titanium (Ti) concentrations. Synovial fluid cytokine analysis was preformed using a Magnetic Luminex Screening Assay. Femoral components were assesed for damage and tissues were visually scored for metallosis. RESULTS: The median metal concentrations were 16 ppb for Co, 46 ppb for Cr, and 9.8 ppb for Ti. There was no association between the tissue collection site and the metal concentration for Co (P = .979), Cr (P = .712), or Ti (P = .854). Twelve of 20 of the necropsy-retrieved TKAs had metallosis, but there was no correlation between Co (P = .48), Cr (P = .89), or Ti (P = .60) concentration and metallosis. Increased Co was associated with decreased tumor necrosis factor alpha (ρ = -0.56, P = .01) and interleukin 1 beta (ρ = -0.48, P = .03). Increased Cr was associated with decreased tumor necrosis factor alpha (ρ= -0.47, P = .03), interleukin 6 (ρ= -0.43, P = .04), and macrophage inflammatory protein 3 alpha (ρ= -0.47, P = .03). CONCLUSION: We observed elevated Co, Cr, and Ti concentrations in tissue from necropsy-retrieved TKA. Our findings did not support the hypothesis that tissue metal concentrations were associated with inflammatory cytokines. The results of this research will be useful for the design of future prospective studies.

Is Soft Tissue Laxity Associated with Tissue Metal Concentrations after Total Knee Arthroplasty?

Increased joint laxity is associated with excessive polyethylene wear, but the correlation between laxity and metal wear has not been established. Fifteen necropsy-retrieved primary total knee replacements were mounted into a custom knee-testing machine that measured anterior-posterior, varus-valgus, and internal-external rotational laxity at 0°, 30°, 60°, and 90° of flexion. Inductively coupled plasma-mass spectrometry analysis was performed to measure the cobalt (Co), chromium (Cr), and titanium (Ti) concentrations in periprosthetic tissue samples. Spearman's rank correlations were performed to determine whether a significant correlation (p < 0.05) existed between soft tissue laxity and tissue metal concentrations. At 0° flexion, decreased posterior displacement was negatively correlated with elevated Co and Cr concentrations. At 30° flexion, decreased external rotation and varus deflection was negatively correlated with elevated Ti concentrations. At 60° flexion, decreased anterior displacement was negatively correlated with elevated Cr concentrations and decreased varus deflection was negatively correlated with increased Ti concentrations. At 90° flexion, decreased anterior displacement was negatively correlated with elevated Co and Cr concentrations. To our knowledge, this is the first study to investigate the correlation between tissue metal concentration and laxity. Decreased laxity was associated with elevated metal concentrations in periprosthetic tissue.