Influence of a Modified Procedure of Joining Ceramic Head and Adapter Sleeve on the Stem Taper in Revision: An Experimental Study

In revision operations, ceramic heads of modular hip implants can be replaced. As the surface of the stem taper can be damaged, additional adapter sleeves are applied. The components are usually connected manually by the surgeon in a one-step procedure by hammer impacts. In this study, we investigated a two-step joining procedure with reproducible impaction force. First, the adapter sleeve and head were joined quasi-statically with a force of 2 kN using an assembly device. In the second step, these components were applied to the stem taper using a pulse-controlled instrument. For reference, the joints were assembled according to standard conditions using a tensile testing machine. An average pull-off force of 1309 ± 201 N was achieved for the components joined by the instrument, and the average measured values for the components joined by the testing machine were 1290 ± 140 N. All specimens achieved a force >350 N when released and therefore met the acceptance criterion defined for this study. This study showed that a modified procedure in two steps with a defined force has a positive effect on the reproducibility of the measured joining forces compared to previous studies.

Influence of Metallic Deposition on Ceramic Femoral Heads on the Wear Behavior of Artificial Hip Joints: A Simulator Study

Several retrieval studies have reported on metallic depositions on ceramic femoral heads, but the effect on the wear behavior of artificial hip joints has not been investigated in wear simulator studies. In the present study, retrieved ceramic heads with metallic depositions as third particles were tested against cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) liners in a hip wear simulator. The amount of liner wear and expansion of metallic depositions on the heads were determined before and after wear testing with digital microscopy. The surface roughness of the heads was investigated in areas with and without metallic depositions by laser scanning microscopy. After five million load cycles, a non-significant reduction in the metallic formation on the retrieved heads was found. The metallic areas showed a higher surface roughness compared to unconcerned areas. The liners showed a higher wear rate of 1.57 ± 1.36 mg/million cycles for 28 mm heads and 2.42 ± 0.82 mg/million cycles for 36 mm heads with metallic depositions, in comparison with new ceramic heads with a 28 mm size ((-0.06 ± 0.89) mg/million cycles) and 36 mm size ((2.04 ± 0.46) mg/million cycles). Metallic transfer on ceramic heads can lead to an increased surface roughness and higher wear rates at the UHMWPE liners. Therefore, metallic contact of the ceramic femoral head should be avoided.

Proximal humeral osteolysis and glenoid radiolucent lines in an anatomic shoulder arthroplasty: a comparison of a ceramic and a metal humeral head component

BACKGROUND

In vitro wear studies demonstrate decreased polyethylene wear with a ceramic compared with a metal humeral head. In this in vivo study, we analyzed prospectively collected 5-year data, comparing the outcomes of 2 types of humeral implants.

METHODS

Sixty-two anatomic total shoulder arthroplasties (TSAs) (59 patients) were performed using the same glenoid component and 2 types of modular humeral implants (metal-head long-stem prosthesis in group A vs. ceramic-head stemless prosthesis in group B). Radiographic analysis for proximal humeral osteolysis and glenoid component radiolucent lines was performed at an average of 5.5 years. Functional outcomes were prospectively evaluated according to the visual analog scale score for pain; satisfaction level; American Shoulder and Elbow Surgeons score; active elevation; Shoulder Pain and Disability Index score; and Disabilities of the Arm, Shoulder and Hand score.

RESULTS

There were 39 TSAs in group A (mean age, 68.1 years) and 23 TSAs in group B (mean age, 67 years). Clinical improvement was similar for both groups. Some proximal humeral osteolysis occurred in 56% of all TSAs. Group A showed increased osteolysis compared with group B (72% vs. 30%, P = .005). Glenoid radiolucent lines were far more frequent in group A, and group A showed a direct relationship between the extent of humeral osteolysis and the severity of glenoid radiolucent lines (P < .001).

CONCLUSION

The stemless ceramic-head replacements showed fewer glenoid radiolucent lines and less humeral osteolysis than the long-stem metal-head replacements. In the group with metal-head replacements, correlation was shown between glenoid radiolucent lines and humeral osteolysis.