Histological, histomorphometric and microtomographic analyses of retrieval hip resurfacing arthroplasty failed at different times.
BACKGROUND
Metal-on-metal hip resurfacing arthroplasty (HR) has been gaining popularity especially for young and active patients. Although different series report good mid-term results, the long-term outcome and failure mechanisms are still concerning. In this consecutive revision case series, 9 retrieved specimens of a failed Birmingham Hip Resurfacing (BHR) were divided according to the time to fracture: 3 specimens failed at less than 6 months (Group 1), 3 failed between 6 months and 3 years (Group 2) and 3 failed later than 3 years (Group 3). The objective of the study was to examine by a specific quantitative histomorphometry and microtomography (micro-CT) method the characteristics of bone quality and its microarchitecture in retrieved metal-on-metal HR.


METHODS
A series of 948 BHR were performed between 2001 and 2009. Among these implants 10 failures occurred and nine of these underwent revision surgery and were examined by histomorphometry and micro-CT.


RESULTS
Histomorphometry showed a significant increase in trabecular separation (Tb.Sp) in Group 3 in comparison with Group 1 (113%, p < 0.05). In the top region, micro-CT showed that Groups 2 and 3 presented significant lower bone volume (Group 2: 61%, p < 0.005; Group 3: 1%, p < 0.05), trabecular number (Group 2: 53%, p < 0.005; Group 3: 40%, p < 0.05), and higher Tb.Sp (Group: 71%,p < 0.05) when compared to Group 1. Additionally, histomorphometry showed that the top regions in Group 1 had a significantly lower mean percentage of empty osteocyte lacunae than the top regions in both Group 2 and 3 (p < 0.05).


CONCLUSIONS
This study showed that the morphometric parameters considered are crucial for a good understanding of mechanical properties of HR and may be of significant importance in the pathogenesis of HR failure particularly in the development of late fractures.
Rizzoli Research Innovation Technology, Rizzoli Orthopaedic Institute, Bologna, Italy. francesca.salamanna@ior.it
Francesca
F
Salamanna
Milena
M
Fini
Annapaola
A
Parrilli
Matteo
M
Cadossi
Nicolò Nicoli
NN
Aldini
Gianluca
G
Giavaresi
Deianira
D
Luciani
Sandro
S
Giannini
D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D009010:Monte Carlo Method; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D017211:Treatment Failure; D055114:X-Ray Microtomography
D008670:Metals