No abstract

The stabilizing capacity of the ligaments and articular surface in the ankle was determined under defined physiologic loading conditions. The concept of primary and secondary constraints was adapted to the ankle. With physiologic loading, the articular surface accounted for 30% and 100% of stability in rotation and version, respectively. That the articular surface was the sole source of inversion and eversion stability under the prescribed physiologic loading conditions has not been previously reported. The demonstration that the articular surface resists inversion displacement in the loaded ankle supports the conclusion of previous studies that rotation, rather than inversion, may account for a type of clinically symptomatic ankle instability. Further, ankle instability may occur during loading and unloading but not once the ankle is fully loaded. The results of our study confirm the importance of the anterior talofibular and calcaneofibular ligaments and suggest an important role for the deltoid ligament.

No abstract

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.

The aim of this study was to analyze short-term metal failures in well-placed Signature-guided Regenerex (Zimmer Biomet, Warsaw, IN) tibial components in a limited patient series. A retrospective, consecutive, nonrandomized, unblinded study from a limited cohort of young active osteoarthritis patients was conducted. All cases received a Regenerex tibial component which we evaluated for metal failure. Patients met the then current indications from the Center for Medicare and Medicaid Services Guidelines for knee replacement. Age, body mass index (BMI),and gender were compared between Regenerex and concurrent non-Regenerex knee arthroplasties. We identified a 4.7% (2 of 43) fracture rate in our Regenerex tibia replacements. Fractures occurred after 17 and 37 months, with a mean follow-up of 65 months (44-77). No statistical difference was seen in age or BMI between the fracture and nonfracture groups. Regenerex compared with standard arthroplasty patients were younger and predominantly male. Our inability to identify our fractures in the Food and Drug Administration (FDA) reporting site is concerning, suggesting additional cases may be unreported. A short-term Regenerex tibial fracture rate of 4.7% is unacceptably high. Inability to identify our fractures on the FDA Web site is a system failure, suggesting additional component fractures may be unreported.