Citation, DOI and article data
Implant malposition or hardware malposition refer to inappropriately positioned implants or hardware. It can be associated with various complications related to injury of adjacent structures.
For implants with variant positions and no complications or increased risk, the term deviant implant position is more suitable 1.
The frequency of implant and hardware malposition varies significantly with the type of implant, the procedure and the expertise of the health care personnel involved in the implantation. There are also significant discrepancies between deviant implant position or implant malposition and clinical symptoms caused by the condition. For example, pedicle screw breaches in spinal surgery have been reported in up to 5% of cases whereas neurologic symptoms due to implant malpositioning seem to occur in less than 0.2% 1.
Clinical signs and symptoms might be absent or nonspecific. If present they also depend on the associated complications.
Possible complications of malpositioned hardware include the following 2-4:
Plain radiographs are the first-line imaging modality for assessing implanted hardware and detecting deviations from the expected position 2,4.
CT can accurately delineate implant position in respect to adjacent structures. It might be required in the setting of suspected malposition and/or associated complications 2.
MRI is especially useful in evaluating non-metallic implants, assessing the surrounding soft tissues and associated complications.
The radiological report should include a description of the following:
- implant position and deviation from the expected position
- associated complications if present
- hardware failure
- neurovascular injury
In the absence of any complications or visible injury to adjacent structures, implant position should be described with neutral descriptors not least because the clinical importance of the deviant position is unknown.
Treatment and prognosis
Management depends on the type of implant, the presence of symptoms and the risk of complications. It includes watchful waiting, removal, repositioning or revision1,4. Removal is indicated after thorough consideration of the risks versus the benefits 5.
The main differential diagnosis of hardware malposition is a hardware failure and implant migration.
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- 2. Winegar B, Kay M, Chadaz T, Taljanovic M, Hood K, Hunter T. Update on Imaging of Spinal Fixation Hardware. Semin Musculoskelet Radiol. 2019;23(2):e56-e79. doi:10.1055/s-0038-1677468
- 3. Allouni A, Davis W, Mankad K, Rankine J, Davagnanam I. Modern Spinal Instrumentation. Part 2: Multimodality Imaging Approach for Assessment of Complications. Clin Radiol. 2013;68(1):75-81. doi:10.1016/j.crad.2012.05.002
- 4. Machat S, Eisenhuber E, Pfarl G et al. Complications of Central Venous Port Systems: A Pictorial Review. Insights Imaging. 2019;10(1):86. doi:10.1186/s13244-019-0770-2
- 5. Stuby F, Gonser C, Baron H, Stöckle U, Badke A, Ochs B. [Hardware Removal After Pelvic Ring Injury]. Unfallchirurg. 2012;115(4):330-8. doi:10.1007/s00113-012-2157-4