Technological improvement of the durability of internal screw surfaces

The methods and some ways of technological improvement of the durability of internal screw surfaces are given. To increase the durability, finishing and strengthening machining with surface plastic deformation and threading with a cutter of a variable average diameter are proposed. The dependences for the specification of machining modes and the results of experimental studies of the screw surface quality parameters and wear resistance of running nuts are given.

A Fixed, Unreducible, Unstable Medial Swivel Dislocation of the Talonavicular Joint with Associated Navicular Fracture

A 32-year-old white male was on a second-story balcony when he fell off and landed on the cement below. With initial X-rays being read as negative on the radiology report due to the subtle nature of the injury, the patient was promptly diagnosed with a medial swivel dislocation by the orthopaedic team, which ended up being fixed, unstable, and irreducible. The patient also had acute skin compromise and needed to be taken to the operating room prior to progression of skin breakdown. This dislocation pattern is a rare variant, especially when paired with the fixed nature of the dislocation and the soft tissue compromise. In the end, open treatment was necessary in order to reduce the talonavicular joint. Because of early recognition and prompt treatment, skin breakdown was avoided. Internal screw fixation of the fractured navicular bone was needed along with K-wire insertion to hold the normal anatomy of the talonavicular joint reduced. All hardware was ultimately removed after healing, and anatomy was restored with excellent patient function. This case report highlights the orthopaedic knowledge needed to not only recognize this rare fracture-dislocation pattern but to also treat it promptly when encountered.

A Comparative 3D Finite Element Computational Study of Three Connections

Masticatory overload on dental implants is one of the causes of marginal bone resorption. The implant–abutment connection (IAC) design plays a critical role in the quality of the stress distribution, and, over the years, different designs were proposed. This study aimed to assess the mechanical behavior of three different types of IAC using a finite element model (FEM) analysis. Three types of two-piece implants were designed: two internal conical connection designs (models A and B) and one internal flat-to-flat connection design (model C). This three-dimensional analysis evaluated the response to static forces on the three models. The strain map, stress analysis, and safety factor were assessed by means of the FEM examination. The FEM analysis indicated that forces are transmitted on the abutment and implant’s neck in model B. In models A and C, forces were distributed along the internal screw, abutment areas, and implant’s neck. The stress distribution in model B showed a more homogeneous pattern, such that the peak forces were reduced. The conical shape of the head of the internal screw in model B seems to have a keystone role in transferring the forces at the surrounding structures. Further experiments should be carried out in order to confirm the present suppositions.