In vivo failure analysis of intramedullary cement restrictors in 100 hip arthroplasties

Design and In Vitro Validation of an Orthopaedic Drill Guide for Femoral Stem Revision in Total Hip Arthroplasty

OBJECTIVE

Cemented total hip arthroplasty (THA) demonstrates superior survival rates compared to uncemented procedures. Nevertheless, most younger patients opt for uncemented THA, as removing well-fixed bone cement in the femur during revisions is complex, particularly the distal cement plug. This removal procedure often increases the risk of femoral fracture or perforation, haemorrhage and weakening bone due to poor drill control and positioning. Aim of this study was to design a novel drill guide to improve drill positioning.

METHODS AND PROCEDURES

A novel orthopaedic drill guide was developed, featuring a compliant centralizer activated by a drill guide actuator. Bone models were prepared to assess centralizing performance. Three conditions were tested: drilling without guidance, guided drilling with centralizer activation held, and guided drilling with centralizer activation released. Deviations from the bone centre were measured at the entry and exit point of the drill.

RESULTS

In the centralizing performance test, the drill guide significantly reduced drill hole deviations in both entry and exit points compared to the control ([Formula: see text]). The absolute deviation on the exit side of the cement plug was 10.59mm (SD 1.56) for the 'No drill guide' condition, 3.02mm (SD 2.09) for 'Drill guide - hold' and 2.12mm (SD 1.71) for 'Drill guide - release'. The compliant drill guide centralizer significantly lowered the risk of cortical bone perforation during intramedullary canal drilling in the bone models due to better control of the cement drill position. Clinical and Translational Impact Statement: The drill guide potentially reduces perioperative risks in cemented femoral stem revision. Future research should identify optimal scenarios for its application.

Canal occlusion in cemented primary total hip replacement: autologous compacted bone block compared to a commercially available gelatine plug

AIMS

To evaluate the stability of 2 canal occlusion systems; an autologous, compacted bone block and the biodegradable C-plug. We also sought to investigate any relationship between stability of the systems and the quality of cementation. A retrospective radiographic comparative review was conducted.

METHODS

A total of 203 consecutive patients were analysed, 89 received an autologous bone block and 114 had C-plugs. There was no significant differences between the groups in terms of age, sex and primary diagnosis. The mean cement tail length in the bone block group (6.42 mm; range 0-31) was significantly shorter than in the C-plug group (17.11 mm; range 0-65.7).

RESULTS

The proportion of patients with good quality of cementation (Barrack grade A) was significantly higher in the bone block group (80.6%) as compared to the C-plug group (56%) (p < 0.001). There was a negative correlation between the length of the cement tail and the Barrack grade, indicating that a short cement tail is associated with better quality cementation.

CONCLUSIONS

We have shown that improved cement penetration and shorter cement tails can be achieved with the cheapest of all options for canal occlusion, an autologous compacted bone block and hence recommend this technique.

Effect of stem preheating on the fatigue behaviour of bone cement around hip prostheses

Tensile fatigue behaviour of bone cement specimens obtained from cement mantles moulded in vitro, simulating the surgical scenario, was investigated. The effect of stem preheating, before its insertion into the cement dough, on specimen fatigue life was studied. A commercial bone cement was selected for this study. Bone cement mixing was conducted in air, following the manufacturer's instructions, and injected simulating the clinical practice. Two conditions were considered: stem maintained at the surgical room temperature (23 degrees C), and stem preheated to 45 degrees C. Four repetitions of the whole procedure were performed for each condition obtaining a total of 32 specimens. All specimens underwent fatigue testing (stress ratio, 0; maximum tensile stress, 15 MPa) until failure. Both two-parameter and three-parameter Weibull distributions were initially used to analyse the fatigue life data set. However, the two-parameter distribution was chosen for both groups on the basis of the coefficient of determination used to test the goodness of fit. Stem preheating seems to have a negligible effect on fatigue behaviour of the studied bone cement in the low range of fatigue lives (up to 10(4)). However, above this number of cycles, stem preheating seems to reduce the probability of failure. These findings are discussed in the text.