Treatment of Patella Fractures.

Patella fractures comprise 1% of all fractures. Treatment options vary based on fracture displacement, classification, and patient factors. Traditionally, nonoperative treatment has been reserved for nondisplaced fractures. Many operative treatments are available with differing indications and levels of success. Tension band constructs have been the most commonly employed approach to fixation, with cerclage wiring for comminuted fractures. Recently, plate fixation of patella fractures has become more popular. Plating constructs offer a low-profile design with stable fixation, allowing for earlier mobilization and potentially improved functional outcomes. Data regarding the long-term outcomes of plating techniques are limited, and further studies are needed. [Orthopedics. 2018; 41(6):e747-e755.].

Fixation of non-cemented total hip arthroplasty femoral components in a simulated proximal bone defect model.

An accelerated sequential proximal femoral bone loss model was used to measure the initial stability of three noncemented femoral stem designs: fully porous-coated, proximally porous-coated, and dual-tapered, diaphyseal press-fit (N=18). Only dual-tapered, diaphyseal press-fit stems remained stable with as much as 105 mm of bone loss, with average cyclic micromotion remaining below 25 µm in ML and below 10 µm in AP planes. In contrast, with proximally coated and fully coated stem designs with circular or oval cross-sections, 60mm of bone loss, resulting in lower than 10 cm of diaphyseal bone contact length, led to gross instability, increasing average cyclic micromotions to greater than 100 µm prior to failure. Therefore, the results provide support for using a dual-tapered stem in revision cases with proximal bone loss.

Biomechanical testing of pin configurations in supracondylar humeral fractures: the effect of medial column comminution.

OBJECTIVES: We measured biomechanical stability in simulated supracondylar humeral fractures fixed with each of 6 pin configurations, 2 with associated medial comminution, and developed a technique for reproducible pin placement and divergence. METHODS: A transverse supracondylar osteotomy was performed on 36 biomechanical humerus models. Of these, 24 (4 groups of 6 specimens each) were fixed with pins in 1 of 4 lateral entry configurations. The remaining 12 (2 groups of 6 specimens each) had a 30-degree medial wedge removed from the distal humerus and were fixed with 1 of 2 configurations. Half of each group was tested under axial rotation and the other half under varus bending. The distal humerus was divided into 4 equal regions from lateral to medial (1-4). Lateral entry pins were inserted through regions 1-3, whereas the medial pin was inserted through region 4. RESULTS: Without comminution, 3 widely spaced, divergent lateral entry pins resulted in higher torsional stiffness (0.36 Nm/degree) than 2 pins in adjacent regions (P < 0.055), but similar to 2 pins in nonadjacent regions (P = 0.57). Three lateral entry pins had higher bending stiffness (79.6 N/mm) than 2 pins, which ranged from 46.7 N/mm (P < 0.01) to 62.5 N/mm (P = 0.21). With comminution, adding a third medial entry pin increased torsional stiffness (0.13-0.24 Nm/degree, P < 0.01) and increased bending stiffness (38.7-44.7 N/mm, P = 0.10). CONCLUSIONS: For fractures without medial column comminution, fixation using 3 lateral entry pins may provide the greatest combination of torsional and bending stiffness. With medial comminution, adding a third medial pin increased torsional stiffness (P < 0.01) and bending stiffness (P = 0.10).

Failure modes of 433 metal-on-metal hip implants: how, why, and wear.

Metal-on-metal total hip replacements (THRs) and hip resurfacings are coming under increasing scrutiny in light of concerns that they fail because of high wear and elevated metal ions. The aim of this study was to investigate the modes of failure in a collection of 433 metal-on-metal THRs and hip resurfacings and to examine the correlations between the reasons for revision and a range of patient and implant variables considered relevant to implant wear.