Effect of rotational prosthetic alignment variation on tibiofemoral contact pressure distribution and joint kinematics in total knee replacement.

In total knee replacement surgery, implant alignment is one of the most important criteria for successful long-term clinical outcome. During total knee replacement implantation, femoral and tibial alignment are determined through appropriate bone resections, which could vary based on patient anatomy, implant design and surgical technique and further influence loading conditions and clinical outcomes. The current research focused on three critical alignment parameters for total knee replacement insertion: femoral component internal/external (I/E) rotation, varus-valgus tibiofemoral angulation and posterior tibial slope. A computational finite element model of total knee replacement implant was developed and validated comparing with kinematic outputs generated from experimentally simulated knee joint motion. The FE model was then used to assess 12 different alignment scenarios based on previous case reports. Postoperative knee kinematics and joint contact pressure during simulated gait motion were assessed. According to the parametric study, FE model cases with femoral rotation revealed extra tibial I/E rotation in the predefined direction but negligible change in tibial anterior-posterior translation; cases with increased tibial slope showed notably increased tibial external rotation and anterior translation; cases with varus tibiofemoral angle presented slightly more tibial external rotation, whereas cases with valgus angle presented an observable increase in tibial internal rotation at the middle phase of the gait cycle. Finally, the response surface obtained from the postprocessing study demonstrated good statistical correlation with existing case study results, providing reliable estimation of peak tibiofemoral contact pressure affected by combinations of alignment parameters. The observations indicate that femoral external alignment should be favored clinically for enhanced patellar tracking and reduced contact pressure concentration for better long-term performance. Posterior tibial slope enables deep knee flexion. Extra femoral internal rotation as well as tibiofemoral varus-valgus alignment could be avoided in surgery due to deficiency in patellar tracking and high pressure concentration.

Perioperative management of diabetes and hyperglycemia in patients undergoing orthopaedic surgery.

Persons with diabetes undergo more surgical procedures, have a higher perioperative risk of complications, and have longer hospital stays than do persons who do not have diabetes. Persons with diabetes are frequently overweight, have a high prevalence of cardiovascular risk factors, and are more likely to suffer from chronic musculoskeletal conditions and traumatic injuries that require orthopaedic attention. Surgery frequently disrupts usual diabetes management, requiring adjustments to the treatment regimen. Suboptimal perioperative glucose control may contribute to increased morbidity, and it aggravates concomitant illnesses. Many patients undergoing elective or urgent orthopaedic surgery may have unrecognized diabetes or may develop stress-related hyperglycemia in the hospital. The challenge is to minimize the effects of metabolic derangements on surgical outcomes, reduce glycemic excursions, and prevent hypoglycemia. Recent guidelines advocate evidence-based glucose targets in the inpatient setting, and regimens for intravenous and subcutaneous insulin are gaining in popularity. Individualized treatment should be based on the ambient level of glycemic control, outpatient treatment regimen, presence of complications, nature of the surgical procedure, and type of anesthesia administered. Management by a multidisciplinary team and attention to discharge planning are key aspects of care during and after orthopaedic surgery.

The relationship between pre- and postoperative range of motion utilizing three cruciate-retaining total knee prostheses.

We prospectively examined the relationship between pre- and postoperative range of motion utilizing three cruciate retaining knees with various mechanical flexion potentials, i.e., two at about 130 degrees -135 degrees (one with posterior lip and the other without) and the third at about 140 degrees -145 degrees . All groups demonstrated mean flexion and range of motion of 116 degrees -122 degrees at one year. Combining data from the three cohorts, patients with the following preoperative flexion values achieved the indicated mean changes (increases) in flexion at one year: < 90 degrees flexion (Delta 23.6 degrees ), 91 degrees -105 degrees flexion (Delta 19.3 degrees ), and > 105 degrees flexion (Delta 1.8 degrees )). Postoperative improvement was inversely related to preoperative flexion. The high flex knee yielded the best improvement in range of motion (9.7 degrees increase) in the highest flex preoperative group compared to that of the other knees (-7.4 degrees to 2.9 degrees ). Hence, a high flex knee design seems to be important in high preoperative range of motion patients obtaining an increase in the postoperative range of motion rather than possible regression.