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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 165 - 165
1 Sep 2012
Gebauer M Breer S Hahn M Kendoff D Amling M Gehrke T
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Introduction

Modular tantalum augments have been introduced to manage severe bone defects in hip and knee revision surgery. The porous surfaces of tantalum augments are intended to enhance osseointegration and a number of studies have documented their excellent biocompatibility. However, the characteristics of tantalum augment osseointegration on human ex vivo specimens from re-revision procedures have not been reported so far.

Methods

Out of a total number of 324 hip and knee revisions with a tantalum augment performed in our institution between 2007 and 2010 four patients had to be re-revised at a mean followup time of 15 months. The causes for re-revision were a periprosthetic acetabular fracture in one, a loosening of a tibial component in one and periprosthetic hip infections in two cases. To characterize osseointegration of the tantalum augments, they were removed during revision surgery and subjected to undecalcified processing. All specimens were analysed by contact radiography, histology (toluidine blue, von Kossa) and quantitative histomorphometry.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_IV | Pages 534 - 534
1 Oct 2010
Zustin J Amling M Breer S Hahn M Krause M Morlock M Rüther W Sauter G Von Domarus C
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Introduction: Periprosthetic fractures have long been recognized as one of the major complications after hip resurfacing arthroplasty. Both biomechanical factors and pathological changes of bone tissue might hypothetically influence its occurrence. We analyzed retrieved femoral remnants to identify possibly different fracture modes.

Material and Methods: 83 hips revised for periprosthetic fracture (134.5 days in situ±159.2) were analyzed macroscopically, contact radiographically and histologically. Most cases (80.7%) were treated for advanced stages of osteoarthritis. Hips with preoperative femoral head necrosis were not included. 49 (59.0%) patients were men (57.8 years old±8.5) and 34 (41.0%) women (55.1 years old±10.0; p=.3445). Occurrence of reactive changes and of avascular necrosis in addition to amount of osteonecrosis were used as the major histological criteria for classification of the fracture as acute biomechanical, acute postnecrotic or chronic.

Statistical analyses were performed using statistical software. Probability of Type I error was set to 5% (alpha=0.05).

Results: 37 (44.6%) femoral neck fractures (83.9 days±87.7) occurred earlier than the remaining 46 (55.4%) head fractures (174.1 days±89.7; p=.0129). 50(60.2%) remnants revealed complete osteonecrosis and were thus classified as acute postnecrotic fractures, 29 (34.9%) chronic fractures were characterized by finding of pseudoarthrosis or preformed callus and the remaining 4 (4.8%) were classified as acute mechanic. Acute mechanic fractures (17.5 days±8.0) failed earlier than both acute postnecrotic (146.3 days±181.7; p=.0049) and chronic (130.8 days±120.6; p=.0017) fractures.

Osteonecrosis was found in 81 (97.6%) hips revised after fracture (p< .0001). The vertical size of avascular necrosis in hips after acute postnecrotic fracture (21.1mm±8.5) was bigger (p< .0001) than in both chronic (7.3mm±7.3) and acute mechanic (0.9 mm±1.2) fractures.

Even though 33 (66.0%) of 50 patients with acute postnecrotic fracture were men (p=.0237), no significant differences between males and females were found with respect to age of patients (p=.3445) or duration of prosthesis implantation (p=.1232).

Conclusion: We analyzed hips revised for periprosthetic fracture after the resurfacing arthroplasty. Three distinct fracture modes of this complication could have been identified morphologically. Osteonecrosis secondary to the hip resurfacing arthroplasty appeared to be causative for more than a half of all fractures in present cohort. Mechanical and biomechanical factors related to the procedure might have possibly influenced the occurrence of both postnecrotic fractures and cases with vital reactive changes of tissues neighbouring the fracture line.

The proposed classification may help to understand causes of periprosthetic fractures after hip resurfacing arthroplasty.