SpF® Spinal Fusion Stimulator

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Innovation that stands the test of time 

A Proven Adjunctive Treatment for Posterolateral Lumbar Spine Fusions 

The SpF-XL IIb Implantable Spinal Fusion Stimulator and SpF PLUS-Mini Spinal Fusion Stimulator offer the following features and benefits: 

Proven Clinical History

  • Over 100,000 implanted to date 
  • In one study, high-risk patients undergoing posterior spinal fusions showed an 81% overall fusion success rate in the DC stimulation treated group compared with 54% in the control group1
  • Improves fusion success rates particularly in patients with specific risk factors1-4
  • Provides a constant dose of electrical stimulation for approximately 6 months5

 Proven Technology

  • DC stimulation was shown to enhance the expression of several different osteoinductive growth factors, including BMP-2, BMP-6, and BMP-7 in pre-clinical investigations6,*

Economical

  • Cost-effective, particularly in multi-level fusions7-8

MRI

  • May be performed safely following specific recommendations and precautions using 1.5 Tesla

Product Description

The SpF ® PLUS-Mini is a solid state constant current generator producing a constant current of 60 microamperes and is powered by one lithium manganese dioxide battery. The electronics and power source are hermetically sealed within a titanium generator case; an area of approximately 600 mm2 is platinum coated and functions as the anode.

The SpF PLUS-Mini lead wires consist of two 15 cm leads of drawn brazed strand (DBS) wire covered with silicone and connected to the generator by a titanium connector. The cathodes are available in preformed wave or mesh configurations. In the preformed wave configuration, each lead is terminated in a 12 cm (4 cm preformed wave) uninsulated triple strand titanium wire which acts as a cathode and is connected to the insulated DBS lead by a titanium connector which disconnects at both the generator and cathode. The mesh cathode consists of two strands of titanium wire woven into a flexible grid with nominal dimensions of 1 cm x 4 cm.

SpF-XL IIb is a solid-state constant current generator producing a constant current of 40 microamperes and is powered by one lithium manganese dioxide battery. The electronics and power source are hermetically sealed within a titanium generator case--an area of approximately 400 mm2 is platinum coated and functions as the anode.

The SpF-XL IIb lead wires consist of two 15 cm leads of drawn brazed strand (DBS) wire covered with silicone and connected to the generator by a titanium connector. The cathodes are available in preformed wave or mesh configurations. In the preformed wave configuration, each lead is terminated in a 24 cm (8 cm preformed wave) uninsulated triple strand titanium wire which acts as a cathode and is connected to the insulated DBS lead by a titanium connector which disconnects at both the generator and cathode, or is permanently connected with a titanium crimp (fused lead configuration only). The mesh cathode consists of two strands of titanium wire woven into a flexible grid with nominal dimensions of 1 cm x 8 cm.

 

Indications

The SpF PLUS-Mini Implantable Fusion Stimulators are indicated as a spinal fusion adjunct to increase the probability of fusion success in 1 or 2 levels. The SpF-XL IIb Implantable Spinal Fusion Stimulators are indicated as a spinal fusion adjunct to increase the probability of fusion success in 3 or more levels.

 

Contraindications

Any case where SpF Spinal Fusion Stimulators could come into contact with metallic implant components (i.e., those that contain Titanium, Cobalt Chrome and Stainless Steel).

Any surgical implantation procedure such as minimally invasive surgical –MIS procedures requiring the SpF Spinal Fusion cathodes to be disconnected from their corresponding leads prior to or during implantation since this may seriously compromise the electrical performance of the implantable stimulator’s cathodes to deliver a constant current to the fusion site as intended.

 

Warnings

Do not use with defibrillators.

 

Precautions

Electrosurgery

Electrosurgical instruments are capable of producing radio frequency voltages of such magnitude that direct coupling can occur between the cautery tip and lead system of the generator. To preclude the possibility of burning of tissues adjacent to the electrode or damage to the generator electronics, electrosurgical equipment should not be used on the patient in the vicinity of the generator after the Stimulator has been implanted.

Diathermy

Therapeutic diathermy should not be used in the treatment of a patient who has an implanted stimulator, since this equipment can produce voltages, which may cause damage to the electronics. Diathermy must never be applied over the site of any bone stimulator implant since high currents induced in the electrode lead will cause burning of the tissues in contact with the electrode tip.

Handling

The energy source and electronics of the generator are well protected within the generator case and will be unaffected by normal handling. However, the possibility of damage by mechanical shock, such as a drop onto a hard floor, cannot be precluded. Any unit subjected to this type of accident should not be implanted. Do not disconnect the leads from the cathodes during the surgical procedure.

Use with Internal Fixation

If the stimulator is used in conjunction with metal internal fixation devices, no metallic part of the stimulator should be allowed to come into contact with the fixation device.

Placement of Generator

To avoid patient discomfort, care should be taken to place the generator in a comfortable tissue pocket so that rising of the skin contour is avoided or minimized.

Placement of Cathodes

The cathodes of the implantable spinal fusion stimulator must be positioned a minimum of 1 cm from nerve roots to reduce the possibility of nerve excitation during a MRI procedure.

  1. Kane, W.J. Direct current electrical bone growth stimulation for spinal fusion. Spine (Phila. Pa 1976), 1988.13(3): p. 363-5.
    Randomized prospective study of “difficult to fuse patients” in an uninstrumented model
    – Independent radiographic assessment 12-18 months postoperatively
    – Success rate (p=0.026): Control (n=28) 54% vs. DC (n=31) 81%
    – Conclusion: DC promotes a higher fusion rate, especially in those instances when the need for supplementation is present
  2. Rogozinski, A. and Rogozinski, C. Efficacy of implanted bone growth stimulation in instrumented lumbosacral spinal fusion. Spine (Phila. Pa 1976), 1996. 21(21): p. 2479-83.
    Randomized prospective study with instrumentation
    – Radiographic assessment average 20.5 months postoperatively   
    – Success rate (p=0.02): Control (n=41) 85%   vs.  DC (n=53) 96%
    – Conclusion: DC stimulation can improve fusion results in instrumented lumbosacral fusion. Patients in high-risk categories also are demonstrated to have higher fusion rates with DC than without.
  3. Kucharzyk, D.W. A controlled prospective outcome study of implantable electrical stimulation with spinal instrumentation in a high-risk spinal fusion population. Spine (Phila. Pa 1976), 1999. 24(5):p. 465-8; discussion 469.
    Prospective study with instrumentation
    – Retrospective control group and DC stimulated group assessed radiographically an average of 45 months postoperatively
    – Success rate (p=0.0005): Control (n=65) 87% vs. DC (n=65) 95.6%
    – Conclusion: DC treatment improves the success rate of instrumented high-risk lumbar fusions
  4. SpF® Implantable Spinal Fusion Stimulator Technical Monograph, BSP196276L 03/19.                          
  5.  SpF® Implantable Spinal Fusion Stimulators Physician’s manual & Full Prescribing Information P/N 1067632L Rev.G – P850035/S020/S022/S031/S033 Approved FDA Trade Names: SpF® PLUS-Mini (60 µA/W), SpF® PLUS-Mini (60 µA/M) and SpF® XL llb Implantable Spinal Fusion Stimulator. Certain models of the SpF® Implantable Spinal Fusion Stimulator have approved trade names preceded with “EBI” designating the former sponsor and/or applicant. 
  6. Fredericks, D.C., Smucker, J., Petersen, E.B., Bobst, J.A., Gan, J.C., Simon, B.J., and Glazer, P. Effects of direct current electrical stimulation on gene expression of osteopromotive factors in a posterolateral spinal fusion model. Spine (Phila. Pa 1976), 2007. 32(2): p. 174-81.
  7. Kahanovitz N, Pashos C. The role of implantable direct current stimulation on the critical pathway for lumbar spinal fusion. J Care Management 1996; 2: 2.
  8. Jean C. Gan & Paul A. Glazer Electrical stimulation therapies for spinal fusions: current concepts. Eur Spine J. 2006 Sep; 15(9): 130 – 1311.

* In vitro cellular and pre-clinical studies may not be indicative of human clinical outcomes.

In support of their research or for preparation of this work, one or more of the authors received remuneration from Zimmer Biomet.

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