Indications and contraindications for implant removal

There is still no controlled trial that would justify a valid trade-off between the benefits and detriments of implant removal and scientifically grounded counseling of patients. Indications for implant removal will differ with respect to the age and general condition of the patient, as well as to the location of the implant. For example, an implant left in the lower, weight-bearing extremities leads to different bone metabolism caused by the implant, and depending on changes of the biomechanical properties risks peri-implant failures [ 7], whereas the effects of an implant left in situ to the bone metabolism of the upper extremities may be insignificant. Current literature fails to offer systematic guidelines. The decision to remove an implant must be made after careful consideration of the risks and benefits of the procedure.

The following are considered straightforward absolute indications for implant removal:

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  Infection at implant site

  
  
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  Implant migration

  
  
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  Implant protrusion or intrusion into a joint

  
  
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  Broken implants

  
  
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  Nonstable fixations or loosening with build-up of fretting particles

  
  
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  Soft-tissue irritation, or prevention of free movement of gliding tissues, such as tendons

  
  
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  Allergic reaction to the implant

  
  
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  Nonunion with implant loosening or breakage

  
  
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  Malunion that requires removal for reconstruction

  
  
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  Obvious mechanical problems

  
  
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  Skin and soft-tissue irritation caused by a prominent implant

  
  
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  Exposure of the implant in the oral cavity

  
  
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  Perioperative implant failure

The uses of external fixator or K-wires are also absolute indications for removal because of the risk of pin-track infection or implant migration.

Relative indications for implant removal must be measured against the risks of leaving implants in place. These include:

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  Changes in the bone metabolism

  
  
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  Late infections by bacterial colonization

  
  
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  Allergies

  
  
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  Skeletally immature patients

  
  
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  Prevention of postunion stress shielding

  
  
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  Prevention of bacterial colonization

  
  
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  Avoidance of difficult surgery owing to the potential for refracture or implant failure

  
  
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  Potential functional improvement with implant removal

  
  
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  Artifacts with later MRI and CT imaging

  
  
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  At the patient‘s request: for cosmetic reasons, pain, discomfort, protrusion under skin, (even visually), cold intolerance, patient‘s fear of carcinogenesis

An indication for implant removal is in most cases not obligatory and must be made on an individual basis with respect to and in consultation with the patient. The listed risks of leaving implants in place are relative indications and should not lead directly to a surgical procedure. One contraindication for implant removal is if the extent of the surgical procedure is extensive and the risk of complications are disproportionate to the benefits of the operation (eg, pelvis surgery). The decision to remove implants in elderly patients with comorbidities and the high risk of anesthetic complications, must be balanced with the severity of symptoms caused by the implant and the risk of removal.

Influencing factors on implant removal

Removal of an internal fracture fixation (IFF) device can be problematic, despite being generally considered as a “routine” procedure. A major cause of complication is the amount of excessive bone ongrowth and ingrowth in and around a device. In children, about 13% of complications are encountered during scheduled IFF device removal, which is related to the occurrence of excessive bone overgrowth on the device [ 8, 9]. When bone grows into the “dead” empty spaces of a device, such as through empty holes in a plate, between a screw thread and a plate, into a screw head, or into the interlocking holes in a nail, the surgeon may subsequently face a variety of problems during removal, such as implant breakage, implant-debris tissue contamination, bone refracture, nerve damage, or excessive blood loss ( Fig 26-1 ). Surface microtopography of an implant is a major determinant of both osteoblast (bone forming) cells [ 10] and actual bone tissue [ 11– 13] interactions with the implant. The influence of surface microtopography persists from the moment of implantation until a final tissue response has been completed, be that integration or encapsulation. With metal plates and nails surface microtopography does not appear to have an influence on infection susceptibility (within the ranges and current metals used in clinics) [ 14, 15]. For details as to what happens to the device surface upon implantation within the body from protein to cell adhesion, from local factor production and control of terminal osteoblast cell differentiation and subsequent bone formation, the reader is referred elsewhere [5, 10].

For a surface-provoked cell response to arise it is essential that the actual cells perceive the surface‘s microroughness. Hence, the dimensions of the surface need to be within the dimensions of an actual cell. There is an optimal range for a substrate-mediated cell response, the “effective roughness spectrum” within which cells and tissues will optimally react to a surface [5]. Within this range osseointegration (direct bone-implant integration) will occur, which can impede device removal; whereas outside this range bone may approach the device yet will not osseointegrate and will ease device removal. With long-term or permanent metal implant devices, such as prosthetics, osseointegration is vital to their success. Consequently, many studies have focused on increasing osseointegration. However, this is not generally desired for trauma, including pediatric IFF, since many of these implants may have to be removed (due to the reasons outlined in 1 Introduction).

Microrough surfaces have been extensively identified as the most important determinant for bone osseointegration to clinically produced and used metals. Reducing the microroughness of these devices has been shown in vitro [10] to delay osteoblast differentiation and in vivo to reduce extraosseous formation and osseointegration, and accordingly ease of implant removal of cortex screws [11], locking compression plates (LCP) and screws [ 12], and intramedullary nails [13]. Histological observations from certain studies [11–13] challenge the overall assumption that osseointegration is essential for implant stability. The challenge of this general assumption is supported by the lack of published data describing direct osseointegration for stainless-steel implants (checked by the team of RG Richards at the AO Research Institute, Davos) at the macro level, but not at the micro level (where it needs to be evaluated). Osseointegration is not required for IFF stability when using locked implant systems, since the stability is inherent from the device itself (when correctly implanted) [5]. Reducing the microroughness of fracture fixation devices does not negatively affect bone apposition whereas microrough surfaces, as used currently in clinics, accelerate bone apposition. Reducing the surface microroughness with, eg, polishing, prevents long-term strong bone adherence. Thus, the combination of the reduced strength of matrix adhesion to smooth/polished samples with the slower rate of remodeling/apposition relative to standard microrough devices would directly reduce the occurrence of bone overgrowth/integration.

Current fracture fixation implants (locked plates or nails) achieve immediate stability through their design and consequently direct osseointegration is not required for their stability. The implants only require stability for the period of the biological fracture healing. Surfaces that do not encourage direct osseointegration, or surfaces that discourage protein and cell attachment and direct osseointegration, are preferred for such devices. This would also aid implant removal and help allow gliding tissues to freely move (nerves, tendons, muscles) over the implant surface. Future developments for IFF trauma implants should produce surfaces which discourage protein and cell attachment and biofilm formation in osteosynthesis implants.