The Flint Lock: A Novel Technique in Total Knee Arthroplasty Closure.

Conventional interrupted sutures are traditionally used in extensor mechanism closure during total knee arthroplasty (TKA). In recent years, barbed suture has been introduced with the proposed benefits of decreased closure time and a watertight seal that is superior to interrupted sutures. Complication rates using barbed sutures and conventional interrupted sutures are similar. We propose a novel closure technique known as the Flint Lock, which is a double continuous interlocking stitch. The Flint Lock provides a quick and efficient closure to the extensor mechanism in TKA. In addition, similar to barbed suture, the Flint Lock should provide a superior watertight seal. It utilizes relatively inexpensive and readily available materials.

Optimizing Hybrid Plate Fixation with a Locked, Oblique End Screw in Osteoporotic Fractures.

BACKGROUND: The end screw in a fracture plate creates the greatest resistance to bending. For osteoporotic fractures treated with plates, there is some question as to the optimal screw insertion technique for the screw farthest from the fracture. A locked, oblique end screw was previously shown to increase resistance to periprosthetic fracture. It is unknown, however, how this end screw configuration would resist pullout when subjected to bending. METHODS: Narrow, low contact 3.5 mm locking compression plates with 6 and 12 holes were anchored to simulated bone material with material properties representing osteoporotic bone. Four configurations were evaluated for the end screw: perpendicular and angulated 30 degrees away from the fracture for both non-locked and locked screws (n=6 per group). The constructs were subjected to 3 point bending until the peak load and finally total construct failure was achieved. RESULTS: Peak force, stiffness, energy to peak load, and the failure mode of each construct were determined. All four 12-hole construct groups failed by gross plastic bending deformation of the plate at the fulcrum past a previously established clinically relevant limit for failure (15°). All 12-hole plate constructs failed at statistically higher loads and energy than any of the 6-hole plate constructs, with the exception of the 6-hole locked, oblique construct. CONCLUSION: The locked, oblique end screw provides equivalent pull out strength for 3.5 mm low contact plates regardless of plate length. Combined with its resistance to periprosthetic fracture, this end screw configuration appears to be the best option for the construct integrity of hybrid plating for osteoporotic fractures. CLINICAL RELEVANCE: Osteoporotic fractures are challenging to treat. The current study and the existing literature show that resistance to both bending loads and refracture at the end of a plate are minimized with a locked screw angled away from the fracture.

Reducing Fracture Risk Adjacent to a Plate With an Angulated Locked End Screw.

OBJECTIVES: Locking screws often are used in the treatment of osteoporotic fractures. Studies show that locking screws can increase bone stresses at the plate end, which increases the possibility of peri-implant fracture. This study evaluates whether the technique used to insert the end screw is related to the fracture tolerance adjacent to the plate. METHODS: Twelve groups of plate constructs were evaluated using a fibular diaphyseal surrogate with mechanical properties similar to osteoporotic bone. All inboard screws were nonlocked with only the end screw fixation differing among groups. The end screws were inserted either perpendicularly to the plate or at an angle of 30 degrees for 6- and 12-hole plates. For both orientations, the end screws were inserted nonlocked, locked, or by a locked overdrilling technique, resulting in 6 groups per plate length. The perpendicular nonlocked screws represented a control group. The constructs were tested to failure in 4-point bending to determine peak load, failure energy, and stiffness. RESULTS: All constructs failed by peri-implant fracture along a plane through the 2 cortical holes of the end screw. Compared with the control group, an angulated locked screw at the plate end significantly increased the peak bending moment and energy required to produce a fracture for both plate lengths (6-hole, P = 0.008, P < 0.001; 12-hole, P = 0.006, P < 0.001). CONCLUSIONS: The use of an angulated locked end screw may enhance the resistance of osteoporotic bone to peri-implant fractures caused by bending forces.

Reverse oblique end screws in nonlocking plates decrease construct strength in synthetic osteoporotic bone medium.

Fracture stability can be challenging for osteoporotic individuals. The end screw of nonlocked plates is subjected to the greatest loading and is typically the site of construct failure. To enhance fixation, the end screw can be angled away from the fracture. The current study biomechanically evaluated screws angled the other direction: toward the fracture using 3.5-mm dynamic compression plates in an osteoporotic bone model. Three different plate lengths (6-, 8-, 12-hole) were tested in three-point bending with an oblique, perpendicular, or reverse oblique end screw. The peak load for loss of screw fixation for the reverse oblique end screw constructs was significantly less than the other screw orientations for all plate lengths. The 12-hole peak load, energy, and displacement magnitudes for all three screw orientations were significantly greater than all 6- and 8-hole constructs. The use of a reverse oblique end screw is inferior to both perpendicular and oblique end screws.