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TANDEM

Bipolar and Unipolar Hip System

TANDEM Bipolar and Unipolar Hip System

Product Information

TANDEM Product Information

TandemBipolarandUnipolarHipSystem _Overview

The TANDEM Bipolar and Unipolar Hip System is a comprehensive partial hip replacement system. The TANDEM bipolar and unipolar systems restore joint stability by designs that are intended to simplify implantation and minimize concerns for wear. With both unipolar and bipolar options, the TANDEM system offers double the simplicity of traditional partial hip systems - with just one easy-to-use set of instruments.

TANDEM Bipolar Features and Benefits

  • Assembly
  • Disassembly
  • Sizing

Assembly

Easy implant assembly. The assembly requires less than 5 lbs of finger pressure. This eliminates the need for bulky assembly tools and creates less frustration with the OR staff.

Wear Performance Features

The preassembled poly component is designed to minimize micromotion and backside wear. The anti-rotation boss located on the top polyethylene locking ring is intended to minimize rotation and wear at the periphery of the shell.  TANDEM has a minimum thickness of 5 mm in the majority of sizes.

ROM

Range of motion is important in reducing rim impingement in bipolar prostheses. Because ROM is not only dependent upon neck design, TANDEM is designed with a wide liner chamfer.

Disassembly

The disassembly feature allows the surgeon to change femoral head neck lengths if soft tissue tensioning is not adequate. It also allows easy implant removal when revising the prosthesis.

Sizing

Implants are available in outer diameter sizes 38 mm - 55 mm, 57 mm, 59 mm, 61 mm, 64 mm, 67 mm, 70 mm, 73 mm

TANDEM Unipolar Features and Benefits

  • Versatile
  • The unipolar continues to use two components, a taper sleeve and a CoCr metal head.
  • Unipolar components come in a full range of sizes, 40-55 mm in 1mm increments and a 57, 59, and 61 mm.
  • Five neck length options, -3 to +12 are available to adjust the neck length of the unipolar.

For additional information, please contact your local sales representative.

References

1. Bartel, DL; Burstein, AH; Toda, MD; Edwards, DL: The effect of conformity and plastic thickness on contact stresses in metal-backed plastic implants. J Biomech Eng. 1985 Aug; 107(3):193-9.
2. Smith & Nephew internal testing.

 

 

Design and Technology

Design and Technology

TANDEM◊ Bipolar Design Features

  • Easy implant assembly
  • More options
  • Mechanical strength
  • Positive eccentricity
  • Biocompatible material

TANDEM Unipolar Design Features

  • Versatile

 

 References

1. Bartel, DL; Burstein, AH; Toda, MD; Edwards, DL: The effect of conformity and plastic thickness on contact stresses in metal-backed plastic implants. J Biomech Eng. 1985 Aug; 107(3):193-9.
2. Smith & Nephew internal testing.

 

 

 

 

Indications

TANDEM Indications

  • Hemi-arthroplasty or Partial hip replacement. Replacement of the femoral head and neck only.
  • Non-inflammatory degenerative joint disease including osteoarthritis, osteonecrosis, avascular necrosis and post traumatic arthritis;
  • Rheumatoid arthritis;
  • Arthritis secondary to a variety of diseases and anomalies and correction of functional deformity such as congenital hip dysplasia or ankylosing spondylitis;
  • Revision procedures where other treatments have failed; and
  • Treatment of proximal femoral non-union, femoral neck fracture, and trochanteric fractures of the proximal femur with head involvement.

 

FAQs

TANDEM Frequently Asked Questions

Is there a concern about micromotion from the top poly ring?
It is well-known that minimizing motion reduces the incidence for polyethylene debris. Unlike 2nd generation bipolars, TANDEM was designed to minimize polyethylene debris. The bottom portion of the liner is thermally fixed into the shell preventing rotation. In addition, the top poly ring is free from rotation due to the anti-rotation boss built into the liner. If the two components are free from rotation, then micromotion is minimized.

Why aren't the 38 mm and 39 mm trials included the instrument set?
They are not included in the set because the 38 mm and 39 mm are not offered in the unipolar implant. The coordination of sizing among the implants and the trials was important to the simplicity of the instrument design. In addition, these sizes are used in less than 1% of the cases. However, you can order the 38 and 39 mm TANDEM bipolars separately.

Does the TANDEM bipolar have eccentricity?
Yes, the TANDEM bipolar does have positive eccentricity. Eccentricity is the concept of alignment of the femoral head with the joint reaction force of the body. Eccentricity prevents the bipolar from going into a valgus position. The positive eccentricity is varied based on inner and outer diameter dimensions.