Article

Managing bone loss in acetabular revision

University of Iowa, Iowa City, Iowa, United States
Instructional course lectures 02/2006; 55(7):287-97.
Source: PubMed

ABSTRACT The management of bone loss encountered during acetabular revision remains challenging. In order to obtain a successful surgical result, preoperative planning is required to estimate the severity and location of bone defects. Most acetabular revisions can be treated with the use of a cementless hemispherical component. However, a successful surgical reconstruction requires component stability. Depending on the degree of bone loss, the surgical reconstruction may require the use of cancellous or structural bone graft, acetabular augmentation, an acetabular cage, a custom implant, or an acetabular transplant.

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    ABSTRACT: Hintergrund: Beim Hüftpfannenwechsel werden heute überwiegend zementfreie Implantate verwendet. In der vorliegenden Arbeit wird erstmals über die Ergebnisse der Anwendung der Hüftpfanne Plasmacup der Fa. Aesculap bei dieser Indikation berichtet. Methode: Retrospektiv wurden 72 zementfreie Hüftpfannenwechsel aus dem Zeitraum vom 1. Januar 1996 bis 31. Dezember 2003 erfaßt, welche im Kreiskrankenhaus Frankenberg unter Verwendung der drei sich in den wesentlichen Parametern gleichenden Plasmacup vom Typ P (33 Fälle, 46%), Typ S (17 Fälle, 24%) und Typ SC (22 Fälle, 30%) vorgenommen wurden. Die mittlere Nachbeobachtungszeit betrug 7 Jahre (0,5 bis 12,5 Jahre). Das Durchschnittsalter der Patienten bei der Implantation war 65,4 Jahre. Die Acetabulumdefekte wurden anhand der präoperativen Bilder nach Paprosky eingeteilt. Es fanden sich 9 Paprosky Typ 1, 40 Typ 2, 10 Typ 3a und 1 Typ 3b. In 20% wurde zusätzlich autogener, in 10% allogener und in 1% xenogener Knochenersatz verwendet. 90% der Typen S und SC erhielten eine zusätzliche Schraubenfixierung. Bei 68 Patienten (94%) konnte das Schicksal der Pfanne verfolgt werden. 14 Patienten (19%) waren verstorben, hier wurden die Angehörigen oder der Hausarzt befragt. 44 Patienten (61%) konnten persönlich untersucht werden und bei 10 (14%) erfolgte ein standardisiertes Telefoninterview. Die verfügbaren Röntgenaufnahmen (336 Aufnahmen, davon 74 Hüft- und 262 Beckenaufnahmen) wurden hinsichtlich Osteointegration der Pfannen sowie Osteolysen in den DeLee Zonen beurteilt. Die Entwicklung einer Pfannenmigration wurde mit Hilfe des computergestützten Programmes Wristing überprüft, welches die gleichseitige Tränenfigur als wesentlichen Referenzpunkt benutzt. Zur Bewertung des klinischen Befundes wurde der Harris Hip Score und der WOMAC Score erhoben. Ergebnisse: Der Harris Hip Score betrug bei der Nachuntersuchung im Median 88,5 Punkte und der WOMAC Score 18,5 Punkte. 93% der nachuntersuchten Patienten zeigten sich mit dem Ergebnis der Wechseloperation zufrieden. Eine der Hüftpfannen musste wegen einer Infektion entfernt werden. Weitere Pfannenlockerungen traten im Nachuntersuchungszeitraum nicht auf. Röntgenologische Hinweise auf eine Pfannenlockerung in Form von zunehmenden strahlentransparenten Säumen fanden sich nicht. Postoperativ in 24% der Fälle vorhandene Säume bildeten sich zurück. Die zusätzliche Verschraubung der Pfanne oder die Verwendung von Knochentransplantaten beeinflusste das Ergebnis nicht. Am Gesamtkollektiv der Pfannen war keine signifikante Migration in longitudinaler oder transversaler Richtung festzustellen. Allerdings vergrößerte sich der Inklinationswinkel um 3,5° signifikant (p < 0,001). Schlussfolgerung: Die Plasmacup erscheint für zementfreie Wechseloperationen geeignet, die Ergebnisse der Studie sind, wie der Literaturvergleich zeigt, mit denen gut untersuchter ähnlicher Pfannen anderer Hersteller vergleichbar. Die Pfanne zeigt langfristig eine stabile Osteointegration nach Implantation auch bei größeren Knochendefekten im Acetabulum. Background: A cementless component is currently used in most acetabular revisions. The present study gives the first report about the application of the Plasmacup from Aesculap, which is a hemispherical porous socket as a revision component. Methods: 72 cementless cup revisions were performed in the Frankenberg district hospital between 1st January 1996 and 31st December using one of three types of Plasmacup, each having identical main features Type P was used in 33 cases (46%), type S in 17 cases (24%) and type SC in 22 cases (30%). The mean follow up period was 7 years (range 0.5 – 12.5 years). The mean age of the patients at the index operation was 65.4 years. The pre-operative X-rays were used for grading the bone defects according to the Paprosky score. There were 9 Paprosky type 1, 40 type 2, 10 type 3a and 1 type 3b defects. Autografts were used in 20%, allografts in 10% and xenografts in 1% of the revisions. The fate of 68 cups (94%) could be followed up. 44 (41%) patients could be examined in person, 10 (14%) were interviewed by telephone by the means of a standardised questionnaire, 14 patients (19%) died, and therefore the relatives or the GP were interviewed. 336 X-rays were evaluable (74 of the hip and 262 of the pelvis) and analysed in respect of osseointegration of the cups and osteolysis according to the DeLee zones. Cup migration was checked with the help of the computer-program Wristing, with the teardrop as main reference point. For the clinical evaluation the Harris Hip Score and the WOMAC score were used. Results: At the final examination the mean Harris Hip Score was 88.5 points and the mean WOMAC score 18.5 points. 93% of the personally examined patients expressed their satisfaction with the result of the operation. During the follow up period no aseptic loosening could be observed and only one cup had to be removed due to infection. Regarding the acetabular implants as an entirety, no significant migration could be observed in the longitudinal and the transversal direction. The inclination showed a significant alteration of 3.5° (p < 0,001). There was no progressive radiolucency in the aseptic cases and the postoperative radiolucency which occured in 24% of the cups decreased. Neither the application of screws (done in 90% of type S and SC) nor grafting influenced the outcome. Conclusion: The Plasmacup is suitable for cementless cup revision. It achieves results comparable to cups from other manufacturers which have been well examined and described in the literature. A solid osseointegration can even be expected in the event of major bone loss.
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    ABSTRACT: Acetabular defects are frequently grafted during revision THA. Previous studies using plain radiographs report high rates of graft incorporation. However, given plain radiographs underestimate osteolysis, it is unclear whether plain radiographs adequately reflect graft fill or incorporation. We determined if (1) graft fill; or (2) incorporation (measured as graft-bone contact) differed with complete revision and grafting compared to liner exchange and grafting; (3) defect fill and incorporation could be assessed on plain radiographs; and (4) the cost of bone grafting differed with these two procedures. We identified 40 patients who underwent revision THA for aseptic loosening or polyethylene wear and osteolysis, either with retention of a well-fixed cup or complete acetabular revision in which bone graft was used. Lesion size, percent fill, and graft healing was quantified from CT scans. A limited cost analysis was performed using the current hospital costs for implants, bone grafts, and bone graft substitutes. The minimum followup was 1 year (mean, 4.8 years; range, 1-11 years). The average defect fill was 30% (range, 0%-81%). The average percent of healing to host bone was 24% (range, 0-66%). Complete revisions had a higher percent defect fill compared to head/liner changes (47% versus 17%) as well as a higher degree of graft healing to host bone compared to head/liner changes (36% versus 14%). High resolution CT demonstrated lower percentages of defect fill and graft healing than previous reports based on plain radiographs. Bone grafting costs exceeded implant costs in the head/liner exchange group; however, the overall cost was higher in the complete revision group. Higher degrees of defect fill and healing were seen with complete revisions compared to head/liner exchanges. Compared to CT scans, plain radiograph assessment tended to overestimate defect fill and healing.
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