Monoaxial Screw Introduction, Sizes, Uses and Advantages.

Monoaxial Screws

Monoaxial Screw Introduction

Monoaxial Screw are used in a spinal fusion to add extra support and strength to the fusion while it heals. The screws themselves do not fixate the spinal segment, but act as firm anchor points that can then be connected with a rod.

Monoaxial Screw is specifically intended to provide internal fixation to stabilise and immobilise the spine. The screw is put into the vertebrae to encourage fusion, which is the process of connecting two or more vertebrae to form a solid bone mass.

Monoaxial Screw Sizes

Monoaxial Screw made from titanium, come in a variety of shapes and sizes to meet the demands of the patient.

Monoaxial Screws are available in various diameters and lengths.
Diameters: 4.5mm, 5mm, 5.5mm, 6.5mm and 7mm.
Lengths: 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm and 60mm

Monoaxial Screw Uses

Monoaxial Screw System intended to provide immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the treatment of the following acute and chronic instabilities or deformities of the thoracic, lumbar, and sacral spine: degenerative spondylolisthesis with objective evidence of neurologic impairment, fracture, dislocation, scoliosis, kyphosis, spinal tumor, and failed previous fusion.

Monoaxial Screws are placed above and below the vertebrae that were fused. A rod is used to connect the screws which prevents movement and allows the bone graft to heal. After the bone graft grows, the screws and rods are no longer needed for stability and may be safely removed with a subsequent back surgery. Removal isn’t necessary unless they cause the patient discomfort.

Monoaxial Screw Benefits

Monoaxial Screws have transformed orthopaedic and spinal surgery by allowing for greater flexibility and adjustment during screw placement. Their ability to fit specific patient anatomy and optimise screw trajectory helps to increase fusion rates, stability, and spinal deformity repair. However, careful surgical planning, skill, and follow-up are required to maximise the advantages while minimising the hazards associated with these cutting-edge technologies.

There are various benefits of using Monoaxial Screw such as:

Placement Ease: The Monoaxial design makes screw placement easier, especially in difficult anatomical locations. Surgeons can coordinate the screw trajectory with the target anatomy, improving accuracy and lowering the chance of incorrect screw location.

Reduced Screw Strain: Monoaxial Screw evenly disperse forces along their length. This design decreases tension and pressure on the screw-bone interface, reducing the likelihood of screw loosening or breaking over time.

Improved Fusion Rates: Monoaxial Screw can help enhance fusion rates by allowing for appropriate screw positioning. The ability to customise screw trajectory enables surgeons to achieve better contact between the screw and bone, resulting in increased stability and the likelihood for successful fusion.

Correcting Spinal Deformities: Monoaxial Screws are especially useful in spine procedures to repair spinal deformities such as scoliosis or kyphosis. Because these screws are adjustable, surgeons can achieve desired alignment and curvature correction in three-dimensional space.

Monoaxial Screw Advantage

Spinal fusion surgery has advanced significantly over the years, with the development of numerous implants and techniques targeted at improving patient results. The Monoaxial Screw is one such invention.
Below is the benefits and applications of Monoaxial screws in spinal fusion surgeries.

Controlled Screw Placement:
Monoaxial Screw has a single axis of rotation and can only move in one direction. This feature allows for regulated and exact placement during surgery.

Increased Fusion Rates:
The major goal of spinal fusion surgery is to achieve a strong fusion between the vertebrae, which promotes stability and relieves discomfort. Monoaxial screws are essential in this process. The ability to precisely position the screws allows for ideal vertebral body alignment and compression, facilitating the fusion process. Polyaxial screws’ increased rigidity stimulates bone growth and fusion, resulting in better fusion rates and long-term outcomes for patients.

Reduced possibility of screw pullout:
Compared to conventional screws, Monoaxial screws feature a design that allows for a bigger contact area with the bone. The chance of the screw loosening or dislodging after surgery is decreased by the increased contact area, which also improves the screw’s pullout strength. The increased stability contributes to maintaining the spine’s proper alignment and reducing the risk of device failure, which enhances the fusion procedure’s overall success.

Patient-Specific Adaptability:
Because each patient’s spinal structure is different, it can be difficult to insert screws correctly. Monoaxial screws offer a variety of angulation choices to solve this problem. In order to achieve the best fixation and alignment, surgeons can modify the screw angle to correspond to the patient’s unique anatomical requirements. This ability to adjust to each patient encourages personalised surgical care, which leads to better outcomes and increased patient satisfaction.

Promoting Minimally Invasive Methods:
Minimally invasive spinal fusion treatments have grown in popularity because to benefits such as reduced tissue damage, quicker recovery durations, and less postoperative pain. Monoaxial screws are ideal for minimally invasive techniques because they allow for more manoeuvrability through fewer incisions. The ability to modify the screw angle allows surgeons to handle difficult anatomy and perform the fusion process with precision, even in places with limited access.

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Monoaxial Screw 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 Monoaxial Screw.

Warnings and Precautionary for Monoaxial Screw

Before using Monoaxial Screw, 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.

Screw is 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 Monoaxial 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 Monoaxial Screw.
  • Mechanical failure of the implant, including bending, loosening or breakage.
  • Migration of implant resulting in injury.

Preoperative Planning for Monoaxial Screw

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 Monoaxial Screw 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.

Monoaxial Screw 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.

Monoaxial Screw Warnings

  • Monoaxial Screw 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. Screw removal should be followed by adequate post-operative management to avoid refracture.

Monoaxial Screw 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 Monoaxial Screw, reoperation.