Bicruciate retaining total knee arthroplasty: current state and future promise.

Total knee arthroplasty (TKA) is a well-known surgical procedure performed to address end stage osteoarthritis. The main goal is to relieve pain, recover articular function and return to normal function as soon as possible. Over the years it is frequently performed in the elderly, but lately there is an increased demand in a younger and more active population. Up to 25% of patients feel dissatisfied about their TKA. The anterior cruciate ligament (ACL) is considered the main anteroposterior stabilizer of the knee; nevertheless the ACL is usually sacrificed during conventional TKA. Research shows this might be an unnecessary sacrifice in certain cases. The considerable dissatisfaction rate in mainly high-demanding patients, together with the literature reports on the importance of the ACL function, were the two main reasons for the development of bicruciate retaining (BCR) total knee arthroplasty. BCR TKA may offer superior knee kinematics and proprioception, through anterior cruciate ligament preservation, but requires a higher level of attention to obtain an accurate and precise component orientation to reach proper ligamentous balancing and restore the native knee biomechanics. Many surgeons abandoned its use due to its challenging technique and inconsistent results. Recent new BCR implant designs are promising. This systematic literature review aims to summarize the current state of BCR TKA and what to expect in the future.

Fully automated postoperative ventilation in cardiac surgery patients: a randomised clinical trial.

BACKGROUND: Ensuring that lung-protective ventilation is achieved at scale is challenging in perioperative practice. Fully automated ventilation may be more effective in delivering lung-protective ventilation. Here, we compared automated lung-protective ventilation with conventional ventilation after elective cardiac surgery in haemodynamically stable patients. METHODS: In this single-centre investigator-led study, patients were randomly assigned at the end of cardiac surgery to receive either automated (adaptive support ventilation) or conventional ventilation. The primary endpoint was the proportion of postoperative ventilation time characterised by exposure to predefined optimal, acceptable, and critical (injurious) ventilatory parameters in the first three postoperative hours. Secondary outcomes included severe hypoxaemia (Spo2 <85%) and resumption of spontaneous breathing. Data are presented as mean (95% confidence intervals [CIs]). RESULTS: We randomised 220 patients (30.4% females; age: 62-76 yr). Subjects randomised to automated ventilation (n=109) spent a 29.7% (95% CI: 22.1-37.4) higher mean proportion of postoperative ventilation time receiving optimal postoperative ventilation after surgery (P<0.001) compared with subjects receiving conventional postoperative ventilation (n=111). Automated ventilation also reduced the proportion of postoperative ventilation time that subjects were exposed to injurious ventilatory settings by 2.5% (95% CI: 1-4; P=0.003). Severe hypoxaemia was less likely in subjects randomised to automated ventilation (risk ratio: 0.26 [0.22-0.31]; P<0.01). Subjects resumed spontaneous breathing more rapidly when randomised to automated ventilation (hazard ratio: 1.38 [1.05-1.83]; P=0.03). CONCLUSIONS: Fully automated ventilation in haemodynamically stable patients after cardiac surgery optimised lung-protective ventilation during postoperative ventilation, with fewer episodes of severe hypoxaemia and an accelerated resumption of spontaneous breathing. CLINICAL TRIAL REGISTRATION: NCT03180203.

Knee joint laxity is restored in a bi-cruciate retaining TKA-design.

PURPOSE: The goal is to evaluate the passive stability of a bicruciate retaining, cruciate retaining and bicruciate substituting TKA design in relation to the native knee stability in terms of the laxity envelope. A bicruciate retaining knee prosthesis was hypothesized to offer a closer to normal knee stability in vitro. METHODS: Fourteen cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque, distraction/compression force and an anteroposterior shear force. Subsequently, the native knee, bicruciate retaining, cruciate retaining and finally a bicruciate substituting total knee arthroplasty were tested. RESULTS: Through the range of motion, the width of the varus/valgus and internal/external laxity envelope for the native knee and the bicruciate retaining knee were almost equivalent, whereas the cruciate retaining and the bicruciate substituting knee displayed less laxity and more joint distraction. In all prosthetic knees, an equal anteroposterior laxity was seen for the lateral and medial side whereas in the native knee, a difference in laxity was seen between the stable medial side and the more mobile lateral side. CONCLUSION: Bicruciate retaining knee prostheses can restore normal laxity and thus have the potential to offer more normal knee function. Restoration of natural peri-articular soft-tissue tension is clinically important because of its obvious effects on joint stability and range of motion. Furthermore, the results of this study could help to establish the ideal ligament tension and laxity in more conventional implants by approaching the normal values for passive knee evaluation as presented here.

Principal component analysis as a tool for determining optimal tibial baseplate geometry in modern TKA design.

Optimal tibial component fixation in total knee arthroplasty (TKA) requires maximal tibial bone coverage, optimized mediolateral cortical fit as well as component rotation. Failure to achieve an optimal fit may result in component subsidence and loosening in case of undersizing, or overhang with subsequent soft tissue impingement in case of overhang. To date there is no consensus on optimal tibial component shape, and significant variability exists among different design manufacturers. In this study "principal component analysis" was used as a statistical tool in order to determine the ideal tibia baseplate shape, based upon anthropometric CT- scan data defining an average proximal tibial shape and variations. Gender specificity was evaluated and differences in geometry depending on anatomic constitution (varus, neutral, valgus) were analyzed. The results from our study indicate that in the arthritic knee differences in proximal tibial morphology at the resection level were mainly attributed to size and not shape. This is true for both Caucasian men and women, and is independent from the anatomical constitution.

Beneficial Effects of Early Enteral Nutrition After Major Rectal Surgery: A Possible Role for Conditionally Essential Amino Acids? Results of a Randomized Clinical Trial.

OBJECTIVES: To investigate direct postoperative outcome and plasma amino acid concentrations in a study comparing early enteral nutrition versus early parenteral nutrition after major rectal surgery. Previously, it was shown that a low plasma glutamine concentration represents poor prognosis in ICU patients. DESIGN: A preplanned substudy of a previous prospective, randomized, open-label, single-centre study, comparing early enteral nutrition versus early parenteral nutrition in patients at high risk of postoperative ileus after surgery for locally advanced or locally recurrent rectal cancer. Early enteral nutrition reduced postoperative ileus, anastomotic leakage, and hospital stay. SETTING: Tertiary referral centre for locally advanced and recurrent rectal cancer. PATIENTS: A total of 123 patients with locally advanced or recurrent rectal carcinoma requiring major rectal surgery. INTERVENTIONS: Patients were randomized (ALEA web-based external randomization) preoperatively into two groups: early enteral nutrition (early enteral nutrition, intervention) by nasojejunal tube (n = 61) or early parenteral nutrition (early parenteral nutrition, control) by jugular vein catheter (n = 62). Eight hours after the surgical procedure artificial nutrition was started in hemodynamically stable patients, stimulating oral intake in both groups. Blood samples were collected to measure plasma glutamine, citrulline, and arginine concentrations using a validated ultra performance liquid chromatography-tandem mass spectrometric method. MEASUREMENTS AND MAIN RESULTS: Baseline concentrations were comparable for both groups. Directly after rectal surgery, a decrease in plasma amino acids was observed. Plasma glutamine concentrations were higher in the parenteral group than in the enteral group on postoperative day 1 (p = 0.027) and day 5 (p = 0.008). Arginine concentrations were also significantly increased in the parenteral group at day 1 (p < 0.001) and day 5 (p = 0.001). CONCLUSIONS: Lower plasma glutamine and arginine concentrations were measured in the enteral group, whereas a better clinical outcome was observed. We conclude that plasma amino acids do not provide a causal explanation for the observed beneficial effects of early enteral feeding after major rectal surgery.

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs.

PURPOSE: Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs. METHODS: All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras. RESULTS: The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle. CONCLUSION: Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.

Reduction of postoperative ileus by early enteral nutrition in patients undergoing major rectal surgery: prospective, randomized, controlled trial.

BACKGROUND: The current trend in postoperative nutrition is to promote a normal oral diet as early as possible. However, postoperative ileus is a frequent and common problem after major abdominal surgery. This study was designed to investigate whether early enteral nutrition (EEN), as a bridge to a normal diet, can reduce postoperative ileus. METHODS: Patients undergoing major rectal surgery for locally advanced primary or recurrent rectal carcinoma (after neoadjuvant (chemo)-radiation, with or without intraoperative radiotherapy) were randomly assigned to EEN (n = 61) or early parenteral nutrition (EPN, n = 62) in addition to an oral diet. Early nutrition was started 8 hours after surgery. Early parenteral nutrition was given as control nutrition to obtain caloric equivalence and minimize confounding. The primary endpoint was time to first defecation; secondary outcomes were morbidity, other ileus symptoms, and length of hospital stay. RESULTS: Baseline characteristics were similar for both groups. In intention-to-treat analysis, the time to first defecation was significantly shorter in the enteral nutrition arm than in the control arm (P = 0.04). Moreover, anastomotic leakage occurred significantly less frequently in the enteral group (1 patient) compared with parenteral supplementation (9 patients, P = 0.009). Mean length of stay in the enteral group was 13.4 ± 2.2 days versus 16.7 ± 2.3 days in the parenteral group (P = 0.007). CONCLUSIONS: Early enteral nutrition is safe and associated with significantly less ileus. Early enteral nutrition is associated with less anastomotic leakage in patients undergoing extensive rectal surgery.

Treatment of hypophosphatemia in the intensive care unit: a review.

INTRODUCTION: Currently no evidence-based guideline exists for the approach to hypophosphatemia in critically ill patients. METHODS: We performed a narrative review of the medical literature to identify the incidence, symptoms, and treatment of hypophosphatemia in critically ill patients. Specifically, we searched for answers to the questions whether correction of hypophosphatemia is associated with improved outcome, and whether a certain treatment strategy is superior. RESULTS: Incidence: hypophosphatemia is frequently encountered in the intensive care unit; and critically ill patients are at increased risk for developing hypophosphatemia due to the presence of multiple causal factors. SYMPTOMS: hypophosphatemia may lead to a multitude of symptoms, including cardiac and respiratory failure. TREATMENT: hypophosphatemia is generally corrected when it is symptomatic or severe. However, although multiple studies confirm the efficacy and safety of intravenous phosphate administration, it remains uncertain when and how to correct hypophosphatemia. OUTCOME: in some studies, hypophosphatemia was associated with higher mortality; a paucity of randomized controlled evidence exists for whether correction of hypophosphatemia improves the outcome in critically ill patients. CONCLUSIONS: Additional studies addressing the current approach to hypophosphatemia in critically ill patients are required. Studies should focus on the association between hypophosphatemia and morbidity and/or mortality, as well as the effect of correction of this electrolyte disorder.

Clinical outcome of immunonutrition in a heterogeneous intensive care population.

OBJECTIVE: To study the effect of a high-protein enteral formula enriched with arginine, glutamine, and antioxidants and containing omega3 fatty acids and a mixture of fibers, on the clinical outcome of a heterogeneous intensive care (ICU) population. DESIGN AND SETTING: A randomized, prospective, double blind, controlled, two-center clinical trial in two intensive care units in The Netherlands. PATIENTS AND PARTICIPANTS: A total of 597 adult ICU patients expected to require enteral tube feeding for more than 2 days were randomized to receive immunonutrition or an isocaloric control formula. INTERVENTIONS: Patients received either the immunonutrition or the control feed. MEASUREMENTS AND RESULTS: Intention-to-treat and per-protocol analyses showed no statistically significant difference in clinical outcome parameters between the two groups. Results of the intention-to-treat analysis in control vs. immunonutrition were: median ICU length of stay in days, 8.0 (IQR 5.0-16.0) vs. 7.0 (4.0-14.0); median hospital length of stay in days, 20.0 (IQR 10.0-34.0) vs. 20.0 (10.0-35.0); median days of ventilation, 6.0 (IQR 3.0-12.0) vs. 6.0 (IQR 3.0-12.0); ICU mortality, 26.8% vs. 28.2%; in-hospital mortality, 36.4% vs. 38.5%; infectious complications, 41.7% vs. 43.0%. CONCLUSIONS: The results of this largest randomized, controlled trial found that in the general ICU population immunonutrition has no beneficial effect on clinical outcome parameters. These results are consistent with the literature that is currently available.

Myositis ossificans circumscripta of the triceps due to overuse in a female swimmer.

Myositis ossificans is a rare condition characterized by non-neoplastic heterotopic bone formation in soft tissue and skeletal muscle. It is a benign and often self-limiting disease with no need for surgery. Here, we describe a young female swimmer with myositis ossificans circumscripta of the triceps due to overuse. Because of the benign character of the lesion, conservative treatment was initiated with rest and anti-inflammatory drugs. She obtained complete resolution after 6 months and was able to return to normal sporting activities. Myositis ossificans circumscripta is a rare benign lesion with an excellent prognosis. Most lesions in athletes occur due to contusions or strains; however, overuse is now described as well. Spontaneous resolution is seen in almost all cases. Cases in which, despite conservative treatment, a painful mass persists, surgical excision can be considered.