Effect of high hip center on stress for dysplastic hip

Primary Stability in Hip Revision Arthroplasty: Comparison of the Stability of Cementless Fixed Augments on a Modular Acetabular Cage System with and without Cranial Straps

The goal of this study is to evaluate the primary stability of a cementless augment-and-modular-cage system with and without the addition of cranial straps in a standardized in vitro setting. As the surrogate parameter for the evaluation of primary stability, the measurement of relative motion between the implant components themselves and the bone will be used. Acetabular revision components with a trabecular titanium augment in combination with a large fourth-generation composite left hemipelvis were assembled. These constructs were divided into two groups with (S) and without cranial straps (nS). A total of 1000 cycles was applied at each of three load levels. Relative movements (RM) between the components were measured. Load levels display a significant effect on the amount of RM at all interfaces except between shell/augment. The group assignment appears to have an effect on RM due to significantly differing means at all interfaces. Between bone/shell RM increased as load increased. NS displayed significantly more RM than S. Between shell/augment RM remained constant as load increased. Between shell/cup S showed more RM than nS while both groups' RM increased with load. We conclude a significant increase of primary stability between the shell and the bone through the addition of cranial straps. Relative motion between components (shell/cup) increases through the addition of cranial straps. A clinical impact of this finding is uncertain and requires further investigation. Finally, the cementless fixation of the augment against the rim-portion of the shell appears stable and compares favorably to prior investigation of different fixation techniques.

Best bone of acetabulum for cup component placement in Crowe types I to III dysplastic hips: a computer simulation study

BACKGROUND

During cup implantation, vertical height of the cup center (V-HCC) should be precisely controlled to achieve sufficient bone-cup coverage (BCC). Our study aimed to investigate the acetabular bone stock and the quantitative relationship between V-HCC and BCC in Crowe types I to III hips.

METHODS

From November 2013 to March 2016, pelvic models of 51 patients (61 hips) with hip dysplasia were retrospectively reconstructed using a computer software. Acetabular height and doom thickness were measured on the mid-acetabular coronal cross section. V-HCC was defined as the vertical distance of cup rotational center to the interteardrop line (ITL). In the cup implantation simulation, the cup was placed at the initial preset position, with a V-HCC of 15 mm, and moved proximally by 3-mm increments. At each level, the BCC was automatically calculated by computer. Analysis of variance and Kruskal-Wallis test were used to compare the differences between groups.

RESULTS

There were no significant between-group differences in maximum thickness of the acetabular doom; however, peak bone stock values were obtained at heights of 41.63 ± 5.14 mm (Crowe type I), 47.58 ± 4.10 mm (Crowe type II), and 55.78 ± 3.64 mm (Crowe type III) above the ITL. At 15 mm of V-HCC, median BCC was 78% (75-83%) (Crowe type I), 74% (66-71%) (Crowe type II), and 61% (57-68%) (Crowe type III). To achieve 80% of the BCC, the median V-HCC was 16.27 (15.00-16.93) mm, 18.19 (15.01-21.53) mm, and 24.13 (21.02-28.70) mm for Crowe types I, II, and III hips, respectively.

CONCLUSION

During acetabular reconstruction, slightly superior placement with V-HCC <25 mm retained sufficient bone coverage in Crowe I to III hips.

Comparison of the stability of three fixation techniques between porous metal acetabular components and augments

Objectives

In order to address acetabular defects, porous metal revision acetabular components and augments have been developed, which require fixation to each other. The fixation technique that results in the smallest relative movement between the components, as well as its influence on the primary stability with the host bone, have not previously been determined.

Methods

A total of 18 composite hemipelvises with a Paprosky IIB defect were implanted using a porous titanium 56 mm multihole acetabular component and 1 cm augment. Each acetabular component and augment was affixed to the bone using two screws, while the method of fixation between the acetabular component and augment varied for the three groups of six hemipelvises: group S, screw fixation only; group SC, screw plus cement fixation; group C, cement fixation only. The implanted hemipelvises were cyclically loaded to three different loading maxima (0.5 kN, 0.9 kN, and 1.8 kN).

Results

Screw fixation alone resulted in up to three times more movement (p = 0.006), especially when load was increased to 100% (p < 0.001), than with the other two fixation methods (C and SC). No significant difference was noted when a screw was added to the cement fixation. Increased load resulted in increased relative movement between the interfaces in all fixation methods (p < 0.001).

Conclusion

Cement fixation between a porous titanium acetabular component and augment is associated with less relative movement than screw fixation alone for all implant interfaces, particularly with increasing loads. Adding a screw to the cement fixation did not offer any significant advantage. These results also show that the stability of the tested acetabular component/augment interface affects the stability of the construct that is affixed to the bone.Cite this article: N. A. Beckmann, R. G. Bitsch, M. Gondan, M. Schonhoff, S. Jaeger. Comparison of the stability of three fixation techniques between porous metal acetabular components and augments. Bone Joint Res 2018;7:282-288. DOI: 10.1302/2046-3758.74.BJR-2017-0198.R1.

Determination of the hip rotation centre from landmarks in pelvic radiograph

OBJECTIVE

The hip rotation centre (HRC) is an important reference point in cases of total hip arthroplasty (THA). The aim of this study is to investigate the reference points in the Turkish population that enable the identification of the HRC in standard pelvic radiographs.

METHODS

The pelvic radiographs of 50 women and 50 men were examined. The mean age was 46.2 (range; 18-91). Patients with deformity of the hip joint and non-standard pelvic radiograph due to hip flexion contracture were excluded from the study. The pelvic height (PH), the distance between the HRC and teardrop (HRC-Td), and the HRC and the line tangent tuber ischiadicums (HRC-TI) were measured. The ratio of HRC-Td and HRC-TI to PH were calculated. The first is called "the horizontal-HRC ratio" and the second, "the vertical-HRC ratio".

RESULTS

Mean PH was 239 (±13.58) mm in males and 225 (±12.52) in females (p < 0.0001). The distances of HRC-TI were 71 (±6.35) and 65 (±6.72) mm (p < 0.0001) and the distance of HRC-Td were 34 (±3.73) and 30 (±4.05) mm (p = 0.0007), respectively. The vertical-HRC ratios were 30.01% (±2.05) for males, 29.10% (±2.35) for females, the horizontal-HRC ratio, 14.25% (±1.42) and 13.69% (±1.38), respectively (p > 0.05).

CONCLUSION

Although the quantitative values obtained in the present study differ between the genders, the ratios ("vertical-HRC" and "horizontal-HRC") are comparable in both sexes. The results show that these proposed ratios can be used in THA planning, regardless of gender in the Turkish population LEVEL OF EVIDENCE: Level IV, diagnostic study.

The direct anterior approach for acetabular augmentation in primary total hip arthroplasty

Addressing acetabular bone defects can be difficult and depends on the amount of bone loss. Augments, either with bone or highly porous metals, are options that still allow the use of a hemispherical cup. Almost all previous research and publication on acetabular augments have focused on revision hip arthroplasty utilizing either a modified lateral or a posterolateral surgical approach. We describe 3 cases of augmenting acetabular bone defects through a direct anterior approach for primary total hip arthroplasty. We achieved proper cup placement, alignment, and augment incorporation while reconstructing complex acetabular deficiencies. All patients had complete pain relief and a satisfactory clinical outcome with stable radiographs at follow-up. With appropriate training, acetabular augmentation can be performed safely and efficiently with excellent clinical results through this approach.

Cross-sectional Anatomy of Ilium for Guiding Acetabular Component Placement Using High Hip Center Technique in Asian Population

BACKGROUND

Many clinical studies have been published involving the use of a high hip center (HHC), achieved good follow-up. However, there is a little anatomic guidance in the literature regarding the amount of bone stock available for initial implant coverage in this area of the ilium. The purpose of this study was to evaluate the thickness and width of the human ilium and related acetabular cup coverage for guiding acetabular component placement in HHC.

METHODS

A total of 120 normal hips in 60 cases of adult patients from lower extremities computer tomographic angiography Digital Imaging and Communications in Medicine data were chosen for the study. After importing the data to the mimics software, we chose the cross sections every 5-mm increments from the rotational center of the hip to the cephalic of the ilium according the body sagittal axis, then we measured the thickness and width of the ilium for each cross section in axial plane, calculated the cup coverage at each chosen section.

RESULTS

At the acetabular dome, the mean thickness and width of the ilium were 49.71 ± 4.88 mm and 38.92 ± 3.67 mm, respectively, whereas at 1 cm above the dome, decreased to 41.35 ± 5.13 and 31.13 ± 3.37 respectively, and 2 cm above the dome, decreased to 31.25 ± 4.04 and 26.65 ± 3.43, respectively. Acetabular cup averaged coverage for 40-, 50-, and 60-mm hemispheric shells, was 100%, 89%, and 44% at the acetabular dome, 100%, 43.7%, and 27.5% for 1 cm above the dome, and 37.5%, 21.9%, and 14.2% for 2 cm above the dome.

CONCLUSIONS

HHC reconstructions within 1 cm above the acetabular dome will be an acceptable and smaller diameter prosthesis would be better.