Cannulated Screws Specification, Uses & Sizes

7.3 mm Locking Cannulated Screw

Cannulated Screws Introduction

Cannulated screws are used in bone and joint surgery to repair breaks and to secure artificial implants which may be used to replace part or all of a joint.

The main advantage of cannulated screws is that they can be inserted over a guide wire or guide pin. The diameter of the guide pin is much smaller than the cannulated screw and can be more accurately placed using fluoroscopy in the operating room. In addition, given its small diameter, the guide pin can be reinserted several times if necessary for accurate placement without excessive damage to bone.

Cannulated Screws

Cannulated screws Specification

Thread on the full Cannulated screws extends into the head profile. Greater gripping ability, especially with osteoporotic bone, allowing for easy removal.
Low-profile head reduces possibility of soft tissue irritation.
Hemispherical head ensures optimal annular contact with washers or plates when screws are angled.
Cancellous thread profile uses deep cutting threads with a large pitch to increase resistance to pullout. Large pitch also accelerates screw insertion and removal.
Self-tapping screw tip facilitates screw insertion. Reduces the need for pre-drilling and tapping.
Reverse cutting flutes for easy removal.

Cannulated Screws

Cannulated screws Sizes

Cannulated screw is generally made of stainless steel or titanium and is self-tapping, which means it can cut its own path through bone as it is screwed into place. Cannulated screws are available in many different sizes such as:

3.5 mm Cannulated
4 mm Locking Cannulated
4 mm Cannulated
4.5 mm Cannulated
5 mm Locking Cannulated
6.5 mm Locking Cannulated
6.5 mm Cannulated
7 mm Cannulated
7.3 mm Locking Cannulated
7.3 mm Cannulated

Cannulated Screws Sizes

Cannulated screws Uses

Cannulated Screws are intended for fixation of fractures, fusions, and osteotomies of Small and large bones appropriate for the size of the device.

Cannulated screw have a hollow central shaft. Both cortical and cancellous screws can be cannulated. Cannulated cancellous screws are used for metaphyseal fractures while cannulated and noncannulated cortical screws are used as lag screws for fixation of diaphyseal fractures.

Partially threaded screws may be used to lag one bone fragment to another, where the bone fragment is captured by the threads of the screw and pulled toward the near cortex fragment on the head side of the screw. Fully threaded screws are intended to be used to stabilize fractures with little to no compression across the fracture.

Cannulated screw system provide emergency closed reduction, percutaneous screw fixation and excellent stability.

Cannulated bone screws in comparation with traditional screws decrease surgical time, allow more precise screw placement and reduce possibility of errors.

One special type of cannulated cancellous screw is the Knowles pin which is a Cannulated screws used for fixation of slipped capital femoral epiphysis in children.

Cannulated screws Uses

Cannulated screws Surgical Technique

Cannulated screw with threads suitable for porous bone are more common, and they are larger in diameter, with bigger spaces between the threads and a relatively narrow inner shaft. Since they are intended to fix softer bone, their design provides a larger surface area for the bone to grip

Cannulated screw enable the performance of what are called percutaneous techniques, where a surgical procedure takes place through puncture holes in the skin rather than making a large open incision. This type of surgery may be used to treat a femoral neck fracture, where the ball-shaped head of the thigh bone breaks off at the narrow point, or neck, where it joins to the shaft. The operation can only be used in cases where the broken bone is still in place, to ensure that the head of the thigh bone has not had its blood supply disrupted and will remain alive after the screws have secured it in place.

Cannulated Screws Surgical Technique

Instruments for Cannulated Screws

Cannulated Screws Instruments Set

A complete instruments set are available for Cannulated Screws. Instruments can be modified according to the customer’s requirement with minimum quantity required. All these instruments can be used several times.

We are keeping wide range of instruments items in this set to ensures that Doctors get almost all required items during Surgery. Below is list of items of this set.

Parallel Wire Guide : 1 Qty
Protection Sleeve : 1 Qty
Cannulated Hexagonal Screw Driver 3.5 mm Tip : 1 Qty
T Handle Cannulated Tap 6.5 mm, Length 230 mm : 1 Qty
T handle Counter Sink : 1 Qty
Direct Measuring Device : 1 Qty
Cannulated Drill Bit 4.5 mm, Length 230 mm : 1 Qty
Stylet 2.0 mm, Length 280 mm : 1 Qty
Guide Wire with Threaded Tip Dia 2.0 mm, Length 230 mm : 5 Qty
Drill and Tap Sleeve (4.5 mm Drill and 6.5 mm Tap) : 1 Qty
Graphics Aluminium Box with Silicone Fittings : 1 Qty

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 “7 mm Cannulated Screws” has an outside diameter of 7 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. Screw 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.

Cannulated Screws Contraindications

Contraindications may be qualified or total, and need to be taken into consideration when evaluating the prognosis in each case. The physician’s education, training and professional judgement must be relied upon to choose the most appropriate device and treatment. Conditions presenting an increased risk of failure include:

Any active or suspected latent infection or marked local inflammation in or about the affected area.
Compromised vascularity that would inhibit adequate blood supply to the fracture or the operative site.
Bone stock compromised by disease, infection or prior implantation that can not provide adequate support and/or fixation of the devices.
Material sensitivity, documented or suspected.
Obesity. An overweight or obese patient can produce loads on the implant that can lead to failure of the fixation of the device or to
failure of the device itself.
Patients having inadequate tissue coverage over the operative site.
Implant utilization that would interfere with anatomical structures or physiological performance.
Any mental or neuromuscular disorder which would create an unacceptable risk of fixation failure or complications in postoperative care.
Other medical or surgical conditions which would preclude the potential benefit of surgery.
All associated diseases which could endanger the function and success of the Cannulated Screws.

Warnings and Precautionary for Cannulated Screws

Before using Cannulated Screws, the surgeon and ancillary staff should study the safety information in these instructions, as well as any product-specific information in the product description, surgical procedures and/or brochures.

Screws are made from medical grade materials and are designed, constructed and produced with utmost care. These quality screw assure best working results provided they are used in the proper manner. Therefore, the following instructions for use and safety recommendations must be observed.

Improper use of screw can lead to damage to the tissue, premature wear, destruction of the instruments and injury to the operator, patients or other persons.

It is vital for the operating surgeon to take an active role in the medical management of their patients. The surgeon should thoroughly understand all aspects of the surgical procedure and instruments including their limitations. Care in appropriate selection and proper use of surgical instruments is the responsibility of the surgeon and the surgical team. Adequate surgical training should be completed before use of implants.

Factors which could impair the success of the operation:

Allergies to implanted materials.
Localized bone tumours.
Osteoporosis or osteomalacia.
System disease and metabolic disturbances.
Alcohol and drug abuse.
Physical activities involving excessive shocks, whereby the implant is exposed to blows and/or excessive loading.
Patients who are mentally unable to understand and comply with the doctor’s instructions.
Poor general health.

Possible Adverse Effects

The following adverse effects are the most common resulting from implantation:

Loosening of the screw, which may result from cyclic loading of the fixation site and/or tissue reaction of the implant.
Early and late infection.
Further bone fracture resulting from unusual stress or weakened bone substance.
Temporary or chronic neural damage resulting from pressure or hematomata.
Wound hematomas and delayed wound healing.
Vascular disease including venal thrombosis, pulmonary embolism and cardiac arrest.
Heterotopic ossification.
Pain and discomfort due to presence of the implants.
Mechanical failure of the implant, including bending, loosening or breakage.
Migration of implant resulting in injury.

Preoperative Planning for Cannulated Screws

The operating planning is carried out following a thorough clinical evaluation of the patient, Also, x-rays must be taken to allow a clear indication of the bony anatomy and associated deformities. At the time of the operation, the corresponding implantation instruments in addition to a complete size of Cannulated Screws must be available.

The clinician should discuss with the patient the possible risks and complications associated with the use of implants. It is important to determine pre-operatively whether the patient is allergic to any of the implant materials. Also, the patient needs to be informed that the performance of the device cannot be guaranteed as complications can affect the life expectancy of the device.

Cannulated Screws Precautions

Confirm functionality of instruments and check for wear during reprocessing. Replace worn or damaged instruments prior to use.
It is recommended to use the instruments identified for this screw.
Handle devices with care and dispose worn bone cutting instruments in a sharps container.
Always irrigate and apply suction for removal of debris potentially generated during implantation or removal.

Cannulated Screws Warnings

Cannulated Screws can break during use (when subjected to excessive forces). While the surgeon must make the final decision on removal of the broken part based on associated risk in doing so, we recommend that whenever possible and practical for the individual patient, the broken part should be removed. Be aware that implants are not as strong as native bone. Implants subjected to substantial loads may fail.
Instruments, screws and cut plates may have sharp edges or moving joints that may pinch or tear user’s glove or skin.
Take care to remove all fragments that are not fixated during the surgery.
While the surgeon must make the final decision on implant removal, we recommend that whenever possible and practical for the individual patient, fixation devices should be removed once their service as an aid to healing is accomplished. Implant removal should be followed by adequate post-operative management to avoid refracture.

Cannulated Screws General Adverse Events

As with all major surgical procedures, risks, side effects and adverse events can occur. While many possible reactions may occur, some of the most common include: Problems resulting from anesthesia and patient positioning (e.g. nausea, vomiting, dental injuries, neurological impairments, etc.), thrombosis, embolism, infection, nerve and/or tooth root damage or injury of other critical structures including blood vessels, excessive bleeding, damage to soft tissues incl. swelling, abnormal scar formation, functional impairment of the musculoskeletal system, pain, discomfort or abnormal sensation due to the presence of the device, allergy or hypersensitivity reactions, side effects associated with hardware prominence, loosening, bending, or breakage of the device, mal-union, non-union or delayed union which may lead to breakage of the implant, reoperation.

Cannulated Screws Specification, Uses & Sizes

3.5 mm Cannulated Screw

4 mm Locking Cannulated Screw

4 mm Cannulated Screw

4.5 mm Cannulated Screw

5 mm Locking Cannulated Screw

6.5 mm Cannulated Screw

7 mm Cannulated Screw

7.3 mm Locking Cannulated Screw

7.3 mm Cannulated Screw

Cannulated Screws Introduction

Cannulated screws Specification

Cannulated screws Sizes

Cannulated screws Uses

Cannulated screws Surgical Technique

Instruments for Cannulated Screws

Cannulated Screws Contraindications

Warnings and Precautionary for Cannulated Screws

Factors which could impair the success of the operation:

Possible Adverse Effects

Preoperative Planning for Cannulated Screws

Cannulated Screws Precautions

Cannulated Screws Warnings

Cannulated Screws General Adverse Events

Instruments

Bone Plates

Other Implants

Bone Screws