Impact of saline irrigation on the early mechanical characteristics and microstructure of bone cement

Abstract

Very high heat is generated during the polymerization of poly (methyl methacrylate) (PMMA) bone cement, which is used for implant fixation in orthopedic surgery. As such, it has been suggested that irrigating the bone cement layer in the surgical site with a saline solution is a way of cooling the layer. In this study, we aimed to determine the influence of irrigation with a saline solution on the flexural strength and the microstructure of the test specimens of two PMMA bone cement brands: Simplex P and FIX 1. Specimens were assigned to three groups: (1) irrigation with normal saline solution at 25 °C (RS group), (2) irrigation with cold saline at 4 °C (CS group), and (3) no irrigation (control group). For each of the groups, the specimens were tested after various times of aging in phosphate-buffered saline solution (PBS) at 37 °C for 1 h, 24 h, and 7 days. Flexural strength was measured following ISO 5833 protocol, and the surface microstructure was determined using scanning electron microscopy (SEM). The flexural strength results showed that for each of the cement brands, the difference between the groups was not significant, except for Simplex P specimens aged for 24 h, for which flexural strength of the RS and CS group specimens was lower than in the control group. The microstructural features of the surface of the specimens were similar across groups. These findings suggest that in a cemented arthroplasty, irrigation of the bone cement for the purpose of cooling it must only be used after very careful consideration.

Keywords: Arthroplasty; Aseptic loosening; Bone cement; Flexural Strength; Scanning Electron Microscopy; Temperature.

Fig. 1

Comparison of flexural strength values of bone cement specimens at different stages (a) Simplex P and (b) FIX 1: 1 h after preparation, after 24 h and 7 days (168 h) storage in PBS and temperature 37 ℃, in three different groups: control, normal saline solution (NS) and cold normal saline solution (Cold NS) at the time of cement preparation. Asterisks indicate significance compared to the control group (**: p < 0.01) (Mean ± SD).

Fig. 2

The microstructures of the fractured surfaces of dry bone cement after 2 h of storage, (A) Simplex P control cement, (B) Simplex P cement exposed to NS (ambient temperature), (C) FIX 1 control cement, (D) FIX-1 cement exposed to NS (ambient temperature), and (E) FIX 1 cement exposed to cold NS.

Fig. 3

The microstructures of the fractured surfaces of bone cement after 24 h of storage, (A) Simplex P control cement, (B) Simplex P cement exposed to NS (ambient temperature), (C) Simplex P cement exposed to cold NS, and (D) FIX 1 cement exposure to cold NS.