Dynamic trial fitting by an expanding trial cup does not jeopardize primary acetabular component stability

BACKGROUND

Trial fitting of the acetabular component in uncemented total hip replacement is traditionally done by trial cups. Since trial cups do not resemble the real press-fit obtained by the definitive cup, a dynamic trial inserter, called the X-pander ®, was developed to mimic the real amount of press-fit. However, the concern is raised of losing the initial press-fit by using the X-pander® due to pre-expansion of the acetabulum. The purpose of this study was to assess if there is a difference in primary stability between both methods.

METHODS

A biomechanical randomized study was performed with bovine calf acetabula, with randomization between either using the X-pander® or the traditional trial cups to assess primary stability. The primary outcome was the force needed to achieve lever out of the implanted cup (Anexys, Mathys or Trident, Stryker), measured in Newton meter (Nm) with a biomechanical testing set up.

FINDINGS

In total, 54 cups (19 Anexys, 35 Trident) were inserted and tested after randomized trial fitting. Overall mean lever out was 45.1 Nm (SD 14.6) for the X-pander® group and 45.0 Nm (SD 14.5) for the trial cups group. After adjustment for potential confounders (cup size and type) mixed model analysis did not reveal a significant difference in lever out force between both testing devices (mean 1.0 Nm, 95%CI (-5.9; 8.0), p = .77).

INTERPRATION

Initial press-fit of the implanted cup is not lost by pre-expansion as done with dynamic trial fitting with the X-pander®.

Indications and Predictors for Reconstructive Surgery After Hand Burns

PURPOSE

The objective of this study was to analyze the prevalence, indications, and type of reconstructive surgery and predictors of the outcomes of reconstructive surgery after hand burns.

METHODS

A retrospective cohort study was conducted that included all patients admitted with acute hand burns in the Dutch burn centers from January 1998 through December 2002. The details of reconstruction including frequency, timing, indication, and techniques were collected over a 10-year follow-up period.

RESULTS

Hand burns were seen in 42% (n = 562 of 1,334) of all patients admitted with acute burns. Reconstructive surgery during the 10-year follow-up period was required in 15%. Contractures, especially of the first web space and little finger, were the most frequent indications for reconstructive surgery. Web spaces 1 to 3 and the little finger were the location most frequently operated on. The most frequently performed surgical technique was release of the contractures and the use of a random flap. Eighty percent of the reconstructive surgery patients required more than 1 reconstructive procedure, most often within 2 years of the initial injury. Secondary operations at the same location were required in 12%. In 40% of the patients, the first reconstructive surgery was performed within the first postburn year. Significant independent factors related to the need for reconstructive hand surgery were a larger area of full-thickness burns and surgical treatment of the hand during the acute phase.

CONCLUSIONS

Reconstructive surgery was required in 15% of patients who sustained hand burns. The majority of the patients requiring reconstructive surgery of the hand needed 2 or more operations to correct the contractures of the hand. Contractures of the little finger and first web space were the locations most frequently operated on. Patients with more extensive burns and who required hand surgery during the acute phase were more likely to need reconstructive surgery.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Resistance of the melibiose carrier to inhibition by the phosphotransferase system due to substitutions of amino acid residues in the carrier of Salmonella typhimurium

The melibiose carrier of Salmonella typhimurium is under the control of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). We isolated mutants of the melibiose carrier that showed resistance to inhibition via the PTS. Growth of the mutants on melibiose was not inhibited by 2-deoxyglucose, a non-metabolizable substrate of the PTS, although growth of the parent strain was inhibited. Transport activity of the melibiose carrier in the mutants was fairly resistant to inhibition by 2-deoxyglucose, although the activity in the parent was sensitive to inhibition. We cloned the mutated melB gene that encodes the melibiose carrier, determined the nucleotide sequences, and identified replaced nucleotides. The mutations resulted in substitutions of Asp-438 with Tyr, Arg-441 with Ser, or Ile-445 with Asn. All of these residues are in the COOH-terminal region of the carrier. The secondary structure of this region is predicted to be an alpha-helix, and the mutated residues were on the same side of the helix. This region showed sequence similarity to a region of the MalK protein, in which substitution of amino acid residues also resulted in PTS-resistant mutants. Thus the COOH-terminal portion of the melibiose carrier is important for the interaction of dephosphorylated IIIGlc, which is an entity causing reversible inactivation of the carrier.