Herbert Screw 4.5mm/5.5mm

Herbert Screw 4.5mm/5.5mm uses

Herbert Screws are designed for the management of fractures where minimal tissue coverage makes standard screw use inappropriate or where extreme precision in fragment alignment is imperative. Such locations might include fractures of the: Olecranon and malleolar region, Distal femur, Proximal tibia, Distal tibia.

Herbert Screw 4.5mm/5.5mm are indicated for fracture fixation, reconstruction, osteotomy, and arthrodesis of various bones and bone fragments including joint fusions (arthrodeses) in the foot and fixation of intra-articular fractures of the humerus, femur and tibia.

Herbert Screw 4.5mm/5.5mm Surgical Technique

STEP 1: Guide Pin
After initial reduction of the fracture fragments is obtained, the specifically designed Herbert Cannulated Guide Pin is placed through the fragments to act as a Guide Wire for the rest of the placement operation. The Guide Pin should not perforate the opposite cortex.

STEP 2: Depth Gauge
Use the Depth Gauge to measure the length of the Guide Pin in the bone. If the Guide perforates the opposite cortex, corresponding compensation must be made when selecting the implant length.

STEP 3: Proximal Drill Bit
Insert the Proximal Drill Bit over the Guide Pin to drill the cortex. The Drill Bit should be advanced until the built-in stop contacts the cortex of the bone.

STEP 4: Distal Drill Bit
Insert the Distal Drill Bit over the Guide Pin and drill to the desired depth. At this time the surgeon may choose to drill 5mm less than the pilot length.

STEP 5: Cannulated Tap
Insert the Cannulated Tap over the Guide Pin and tap the channel to prepare for the leading screw threads of the implant. Tap depth should be equal to the depth created by the Distal Drill Bit.

STEP 6: Insert Screw
In determining screw length, the surgeon may wish to choose an implant 5mm to 10mm shorter than the measured pilot length. Using the Cannulated Screwdriver, insert the Herbert Cannulated Screw. As the trailing threads engage the bone, reduction is achieved. These trailing threads should be seated approximately 1mm below the cortex of the bone to ensure that there is no intra-articular protrusion or interference with the joint function.

Bone screws are the most commonly used orthopedic implants. There are many different types and sizes of screws for different types of bones. Most bone screws are made out of stainless steel or titanium alloys. The outer diameter, root diameter, and thread pitch and angle are important in determining screw mechanics.

In orthopedics, screws are typically described by their outer diameter, for example, a “Herbert Screw 4.5mm/5.5mm” has an outside diameter of 5.5 mm. The pitch of a screw is the linear distance travelled by a screw for one full turn of the screw. The screw advances by a distance equal to the distance between the threads with each full turn. Cortical screws have a lower pitch and therefore more number of threads. Cancellous bone screws have a greater depth of the screw to increase the surface area and therefore improve the purchase, as the bone is weaker.

Screws function by converting the tightening torque into internal tension in the screw and elastic reactions in the surrounding bone. This creates compression between the fracture fragments that the screw is holding together. Herbert Screw 4.5mm/5.5mm is typically inserted into holes drilled equal to the root diameter and are either self-tapping or are inserted tapped (threaded) holes. The torque to insert cortical bone screws can be high, so the screws must be properly inserted into the correct size drilled hole and designed to withstand insertion torque levels expected in cortical bone. Cancellous bone screws have large, deep threads that grip the spongy bone well. Because of the relatively low strength of the cancellous bone, failure of the screw itself during insertion is rare, but pull out can be an issue.