Biomechanical Effect of Coronal Alignment and Ligament Laxity in Total Knee Arthroplasty: A Simulation Study.

The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater contact force at the medial compartment and medial/posterior cruciate ligament tension. The medial laxity with neutral alignment model showed a similar contact force with decreased medial ligament tension compared to the balanced neutral alignment model, whereas the lateral laxity with the neutral alignment model showed a greater contact force and decreased lateral ligament tension. The cruciate-retaining total knee arthroplasty model was validated using in vivo contact forces (r = 0.939) Two degrees of valgus alignment adjustment with balanced ligament or neutral alignment with 2° of medial laxity can be safe without increasing contact force or ligament tension compared to neutral alignment with a balanced extension gap. However, 2° of varus alignment adjustment with balanced ligament or neutral alignment with 2° of lateral laxity may be unfavorable due to the overloading of the joints and knee ligaments.

Relevance of radiological and clinical measurements in predicting difficult intubation using light wand (Surch-lite™) in adult patients.

OBJECTIVE: To determine the correlation between anatomical features of the upper airway (evaluated via computed tomography imaging) and the ease of light wand-assisted endotracheal intubation in patients undergoing ear, nose and throat surgery under general anaesthesia. METHODS: Mallampati class, laryngoscopic grade, thyromental distance, neck circumference, body mass index, mouth opening and upper lip bite class were assessed. Epiglottis length and angle, tongue size and narrowest pharyngeal distance were determined using computed tomography imaging. Intubation success rate, time to successful intubation (intubating time) and postoperative throat symptoms were documented. RESULTS: Of 152 patients, 148 (97.4%) were successfully intubated on the first attempt (mean intubating time 11.5 ± 6.7 s). Intubating time was positively correlated with laryngoscopic grade and body mass index in both male and female patients, and Mallampati class and neck circumference in male patients. Epiglottis length was positively correlated with intubating time. CONCLUSIONS: Ease of intubation was influenced by epiglottis length. Radiological evaluation may be useful for preoperative assessment of patients undergoing endotracheal intubation with light wand.