Purpose

To evaluate the use of cutaneous marking of the sacrum for percutaneous iliosacral screw fixation. Iliosacral screw placement is dependent upon spatial perception, multiplanar fluoroscopic imaging, and an appreciation of pelvic anatomy which often makes learning the technique difficult for residents. Cutaneous marking of the sacrum may facilitate iliosacral screw insertion by providing additional cues to the orientation of the sacrum.

The twelve matte and twelve polished surfaces of hemi-arthroplasties were contaminated with Staph. epidermidis and then irrigated with bulb or pulse irrigation. The surfaces were then quantitatively cultured using a standardized swabbing technique. Results are expressed as the percentage of contaminant bacteria recovered. The matte finish groups showed median values of 1.46 and 2.88x10⁻² while the polished finish groups showed 1.49x10⁻³ and 2.83x10⁻⁶ with bulb and pulse irrigation, respectively. The difference between irrigation types was significant (p=0.002) for both matte and polished surfaces. Pulse irrigation was more effective than bulb irrigation in removing contaminant bacteria from the prosthetic surfaces studied.

Tremendous suffering is associated with infection following total joint arthroplasty. To reduce infection risk, some surgeons use pulse irrigation prior to wound closure. This practice is based on the assumption that pulse irrigation will more effectively remove adherent bacteria. However, there has been no study of the effectiveness of pulse irrigation in clearing bacteria from prosthetic surfaces. The hypothesis of this study is that pulse irrigation is more effective than bulb irrigation in removing intra-operative bacterial contaminants from prosthetic surfaces.

The matte and polished surfaces of hemiarthroplasties were studied separately. Each surface was contaminated with Staph. epidermidis and then irrigated with pulse or bulb irrigation. A third group without irrigation was also studied. The surface was then swabbed three times using a standardized technique. The swab tips were quantitatively cultured.

Twelve matte and twelve polished surfaces were examined using both irrigation types with corresponding non-irrigation reference values. Results are expressed as the percentage of contaminant bacteria recovered. The matte finish groups showed median values of 1.46 and 2.88x10⁻² while the polished finish groups showed 1.49x10⁻³ and 2.83x10⁻⁶ with bulb and pulse irrigation, respectively. The difference between irrigation types is significant (p=0.002) for both matte and polished surfaces.

Pulse irrigation was more effective than bulb irrigation in removing contaminant bacteria from the prosthetic surfaces studied.

Funding: Hip Hip Hooray, Zimmer-Sadler

This study assesses a method of optimizing the polyethylene-cement interface when cementing a constrained liner into a pre-existing acetabular shell. We tested several configurations of liner modification including random roughening, 2mm and 4mm wide grooves Statistical analysis showed that the grooved liners had significantly higher moment to failure than both the unmodified and roughened liners. There was no difference between the 2 and 4mm grooved liners.

The purpose of this study was to answer the question: what liner preparation will provide the most stable polyethylene – cement interface?

Two and 4mm circumferential grooves and meticulous cementing technique can significantly increase the strength of the polyethylene-cement interface.

All samples failed at the polyethylene – cement interface. Statistically significant differences were found between the following groups: unmodified vs. 2mm (p=0.005) and 4mm groove (p=0.012) and roughened vs. 4mm groove (p=0.011).

Modification of a constrained liner with circumferential grooves may improve the stability of the cement interface enough to make this a more reliable technique in revision hip surgery.

Polyethylene was machined into 50mm diameter liners. These were cemented using PMMA into aluminum acetabular shells ensuring a 3mm cement mantle. Lever-out testing was performed on four groups; no modification, random roughening, 2mm and 4mm grooves.

When an acetabular component is well fixed/positioned, the option of cementing a constrained liner into the fixed shell is an option. Experience has shown that the most common mode of failure in this technique is the polyethylene-cement interface.

Funding: This study was funded by the Division of Orthopedics, Department of Surgery, and the Department of Mechanical Engineering, University of Saskatchewan.