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Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density. A 2-year RSA and 8-year radiographic follow-up study of 34 patients.

Finnilä S, Moritz N, SvedströM E, Alm JJ, Aro HT - Acta Orthop (2015)

Bottom Line: Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03).These differences in cup migration persisted at 24 months.Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48).

View Article: PubMed Central - PubMed

Affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.

ABSTRACT

Background and purpose: Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD.

Patients and methods: We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41-78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ -1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2-10) years.

Results: Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening.

Interpretation: Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.

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Related in: MedlinePlus

A. The custom-modified acetabular cup with 8 RSA beads (arrows) inserted in the opening and additional RSA beads inserted at the tips of the 5 fixation spikes of the cup. B. The anatomical orientation of the coordinate system used to evaluate the translational and rotational migration of the cup.
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Figure 0001: A. The custom-modified acetabular cup with 8 RSA beads (arrows) inserted in the opening and additional RSA beads inserted at the tips of the 5 fixation spikes of the cup. B. The anatomical orientation of the coordinate system used to evaluate the translational and rotational migration of the cup.

Mentions: All patients received a CE-certified custom-modified cementless THA implant with ceramic-on-ceramic bearings (ABG II; Stryker Europe). Both the femoral stem (Aro et al. 2012) and the acetabular cup (Figure 1A) were marked with RSA beads, by the manufacturer. The hemispherical titanium alloy cup had a grit-blasted surface with vacuum plasma-sprayed hydroxyapatite (HA) coating (porosity < 10%, crystallinity > 75%, crystal grain size 20–50 μm, thickness 60 ± 30 μm) and 2 circular grooves aimed at promoting osseointegration. The cups had 8 tantalum beads (1.0 mm) on the outer rim (Figure 1A). The 5-hole version of the cup was designed for use with tapered alumina insert and 28-mm alumina head (Biolox; CeramTec AG, Plochingen, Germany). It accommodated additional RSA beads (1.0 mm) on the tips of 5 custom-modified fixation spikes (Figure 1A).


Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density. A 2-year RSA and 8-year radiographic follow-up study of 34 patients.

Finnilä S, Moritz N, SvedströM E, Alm JJ, Aro HT - Acta Orthop (2015)

A. The custom-modified acetabular cup with 8 RSA beads (arrows) inserted in the opening and additional RSA beads inserted at the tips of the 5 fixation spikes of the cup. B. The anatomical orientation of the coordinate system used to evaluate the translational and rotational migration of the cup.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940591&req=5

Figure 0001: A. The custom-modified acetabular cup with 8 RSA beads (arrows) inserted in the opening and additional RSA beads inserted at the tips of the 5 fixation spikes of the cup. B. The anatomical orientation of the coordinate system used to evaluate the translational and rotational migration of the cup.
Mentions: All patients received a CE-certified custom-modified cementless THA implant with ceramic-on-ceramic bearings (ABG II; Stryker Europe). Both the femoral stem (Aro et al. 2012) and the acetabular cup (Figure 1A) were marked with RSA beads, by the manufacturer. The hemispherical titanium alloy cup had a grit-blasted surface with vacuum plasma-sprayed hydroxyapatite (HA) coating (porosity < 10%, crystallinity > 75%, crystal grain size 20–50 μm, thickness 60 ± 30 μm) and 2 circular grooves aimed at promoting osseointegration. The cups had 8 tantalum beads (1.0 mm) on the outer rim (Figure 1A). The 5-hole version of the cup was designed for use with tapered alumina insert and 28-mm alumina head (Biolox; CeramTec AG, Plochingen, Germany). It accommodated additional RSA beads (1.0 mm) on the tips of 5 custom-modified fixation spikes (Figure 1A).

Bottom Line: Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03).These differences in cup migration persisted at 24 months.Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48).

View Article: PubMed Central - PubMed

Affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.

ABSTRACT

Background and purpose: Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD.

Patients and methods: We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41-78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ -1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2-10) years.

Results: Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening.

Interpretation: Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.

Show MeSH
Related in: MedlinePlus