Varus stem positioning does not affect long-term functional outcome in cementless anatomical total hip arthroplasty

Matching the other side at staged bilateral total hip arthroplasty : investigating radiological variations in staged bilateral total hip arthroplasty

Aims

The aim of this study was to assess the variations in the positioning of components between sides in patients who underwent staged bilateral total hip arthroplasty (THA), and whether these variations affected patient-reported outcome measures (PROMs).

Methods

A retrospective review included 207 patients who underwent staged bilateral THA between June 2017 and November 2022. Leg length, the height and anteversion of the acetabular component, and the coronal and sagittal angles of the femoral component were assessed radiologically and compared with the contralateral THA. The effect of the surgical approach and the technology used on this variation was also assessed. Linear regression was used to investigate the variations between the two THAs and the PROMs.

Results

Between the two sides, the mean leg length varied by 4.6 mm (0.0 to 21.2), the mean height of the acetabular component varied by 3.3 mm (0.0 to 13.7), the mean anteversion varied by 8.2° (0.0° to 28.7°), the mean coronal alignment of the femoral component varied by 1.1° (0.0° to 6.9°), and the mean sagittal alignment varied by 2.3° (0.0° to 10.5°). The use of the direct anterior approach resulted in significantly more variation in the alignment of the femoral component in both the coronal (1.3° vs 1.0°; p = 0.036) and sagittal planes (2.8° vs 2.0°; p = 0.012) compared with the use of the posterior approach. The posterior approach generally led to more anteversion of the acetabular component than the anterior approach. The use of robotics or navigation for positioning the acetabular compoment did not increase side-to-side variations in acetabular component-related positioning or leg length. Despite considerable side-to-side variations, the mean Hip disability and Osteoarthritis Outcome, Joint Replacement (HOOS JR) score was not affected by variations in the postioning of the components.

Conclusion

Staged bilateral THA resulted in considerable variation in the positioning of the components between the two sides. The direct anterior approach led to more variations in anteversion of the acetabular component and sagittal alignment of the femoral component than the posterior approach. The use of computer navigation and robotics did not improve the consistency of the positioning of the components in bilateral THA. Variations in the positioning of the components was not associated with differences in PROMs, indicating that patients can tolerate these differences.

Selective laser melting of low-alloyed titanium based alloy with a large solidification range

In this work, thermodynamic calculations for α + β Type Ti-Fe-Cu-Sn alloy were carried out by the Thermo-Calc software. Powders from this alloy were obtained by plasma sputtering and used for subsequent 3D printing of experimental samples. The effect of various selective laser melting (SLM) parameters on porosity and hot cracking susceptibility as well as the electrochemical characteristics of the alloy have been studied. The optimal technological regime for the manufacture of samples by the SLM method was determined. It has been established that to obtain relatively dense samples without cracks, regimes with volumetric energy density Ev = 250-300 J/mm3 are required. It has been established that a change in the electrochemical behavior of the Ti94Fe1Cu1Sn4 alloy is related to the formation of a nonequilibrium Ti2Cu phase. Based on the findings we recomended directions for further research.

Accuracy of Preoperative 3D vs 2D Digital Templating for Cementless Total Hip Arthroplasty Using a Direct Anterior Approach

Background

An important aspect of preoperative planning for total hip arthroplasty is templating. Although two-dimensional (2D) templating remains the gold standard, computerized tomography (CT)-based three-dimensional (3D) templating is a novel preoperative planning technique. This study aims to compare the accuracy of a 2D and 3D plan using an anterior approach for the placement of the same uncemented prosthesis.

Methods

Two consecutive cohorts of 100 patients each were retrospectively analyzed. We analyzed the accuracy of the size of the implant (stem, cup, head), the length of head, and offset. As a secondary criterion, we analyzed the rates of stems with more than 3° of varus, fracture, and/or subsidence at 3 months postoperatively.

Results

Within the exact size, the accuracy of the stem and cup size with the 2D plan was 69% and 56%, respectively. With the 3D plan accuracy being 88% (P = .0046) and 96% (P < .0001), respectively. Regarding size and length of the implant head, accuracy was 86% and 82% with the 2D plan and 100% (P < .0001) and 94% (P = .016), respectively, with the 3D plan. The offset of the implants increased beyond 3 mm in 23% of patients in the 2D group and in 5% of patients in the 3D group (P = .0003). The rate of varus stems was 10% in the 2D group and 2% in the 3D group (P = .03). Two fractures and one case of subsidence occurred in the 2D group. None were identified in the 3D cohort.

Conclusions

A CT-based 3D plan is more accurate for implant size selection, allows better prosthetic offset, and reduces the rate of varus stems.

Femoral Bowing Increases Early Postoperative Stress around the Femoral Stem in Humans: A Finite Element Analysis

Background

This study aimed to clarify the characteristics of stress distribution caused by the placement of tapered wedge stems in bowed femurs compared with that in normal femurs and the effect of varus stem placement.

Methods

Models with normal and enhanced bowing were created from the right-side computed tomography data of a 17-year-old woman with the least bowing among 40 participants who underwent anterior cruciate ligament reconstruction or operative treatment for trauma in our hospital between January 2017 and May 2018. Finite element analysis was performed, assuming the tapered wedge stem was placed in the neutral and varus positions.

Results

Varus stem placement on a femur with normal bowing showed a deviation and increase of von Mises stresses in the medial femur. Stem placement on a bowed femur, even when placed in the neutral position, increased stress across the periprosthetic bone. When the stem was placed in the varus position, von Mises stress across the periprosthetic bone increased. Zone 7, with strong bowing, demonstrated 3.6-fold increased stress compared with normal femurs. The maximum tensile principal stress was greatest in zone 6 and increased in zones 3 and 4.

Conclusions

Surgeons should assess femoral bowing preoperatively and pay particular attention to intraoperative stem alignment for femurs with high bowing.

Direct anterior versus direct lateral hip approach in total hip arthroplasty with the same perioperative protocols one year post fellowship training

BACKGROUND

Variable results have been reported regarding the clinical outcomes in Total hip arthroplasty (THA) based on the surgical approach. The aim of this study is to compare the clinical outcomes between Direct anterior (DA) and direct lateral (DL) approaches in THA when performed immediately after fellowship training.

METHODS

During the 1st year of practice, all consecutive patients who underwent THA via DA and DL hip approaches were retrospectively investigated. Patients'demographics, diagnosis, American society of Anesthesiology (ASA) score, route of anesthesia, length of hospital stay (LOS), leg length discrepancy (LLD), radiographic parameters, operative time, number of opioids refills postoperatively, and complications were collected and compared between the two groups. The short form of Hip Disability and Osteoarthritis Outcome score, Joint Replacement (HOOS, JR) was prospectively collected pre and postoperatively. The minimum follow-up period was 2 years.

RESULTS

Forty patients in DA group and 38 patients in DL group were included. No statistically significant difference was found between the two groups in terms of demographics, diagnosis, ASA scores, route of anesthesia at the time of THA, postoperative radiographic parameters, LOS, LLD, opioid refills and HOOS scores (p > 0.05). Patients in the DA group had shorter operative time (83 ± 17 min) when compared to the DL group (93 ± 24 min) (p = 0.03). No major complications were found except for one early deep infection patient in DL group.

CONCLUSION

Both DA and DL approaches resulted in satisfactory outcomes in THA when performed by a fellowship trained surgeon.