In vivo sliding distance on the metal-on-polyethylene total hip arthroplasty articulation using patient-specific gait analysis

Prospective randomized controlled trial on the accuracy of prosthesis positioning in total hip arthroplasty assisted by a newly designed whole-process robotic arm

INTRODUCTION

The purpose of this article is to study whether the newly designed whole-process total hip arthroplasty (THA) robotic arm can improve the accuracy of prosthesis placement in THA.

METHOD

In this study, 72 patients undergoing THA were prospectively included and randomly divided into two groups. The experimental group was treated with THA assisted by a newly designed robotic arm. The control group received THA with conventional surgical methods. The imaging data were compared after operation.

RESULT

Compared with the conventional operation, the whole-process robotic arm can more accurately place the acetabular prosthesis in the anteversion safe zone of 5 ~ 25°, but in terms of the inclination angle, whether the reference is the safe zone of 30 ~ 50° or 30 ~ 45°, there is no statistical difference between the two groups. The average lower limb length discrepancy (LLLD) in the experimental group was 3.77 ± 8.31 mm longer than contralateral side, while the counterpart in the control group was 8.39 ± 9.11 mm, with significant difference (P = 0.029). The femoral prosthesis was fixed in neutral position in 35 (100%) cases in the experimental group and only 30 (83.3%) in the control group (P = 0.036). There was no significant difference in the recovery of hip offset, femoral anteversion, and canal fill ratio (CFR) between the two groups.

CONCLUSION

Robotic arm can improve the accuracy of anteversion of acetabular cup, restore the consistency of the length of lower limbs, and more accurately implant the femoral prosthesis to the neutral position in the coronal position.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2100044124 (date of registration: 2021-3-11).

Biomechanical performance of the cemented acetabular cup with combined effects of bone quality, implant material combinations and bodyweight

The objective of this study is to understand the combined effects of bone quality, implant materials and bodyweight on the biomechanical performance of cemented acetabular cup. Additionally, the performance of the cemented acetabular cup was evaluated for obesity cases or obese people. A total of 84 FE models (based on CT data) were developed based on combinations of three different cancellous bone material distributions to represent bone quality, four different implant material combinations and seven different bodyweights. The biomechanical performance of the acetabular cup was evaluated based on bone stress (both cortical and cancellous bone), cement mantle stress, micromotion and contact pressure between the acetabular cup and femoral head. Cortical bone stress, cancellous bone stress, cement stress, the contact pressure between implants and micromotion between implants are affected by different bone quality, implant material combinations and bodyweights. An increase in bodyweight would increase the cortical bone stress, cancellous bone stress, cement stress, contact pressure between implants and micromotion between implants. However, bodyweight affects the cortical and cancellous bone stress more (stiff rise of the bone stresses; nonlinear relation) as compared to other output parameters (mostly linear relation). Comparing cortical and cancellous bone stress, the stress versus bodyweight curve is much stiffer (stiff rise in the curve) for cortical bone than cancellous bone and that even further increases as bone quality decreases. Especially considering obesity cases or obese people (very high bodyweight), the performance of the cemented acetabular component is poor.

Graphical abstract

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Three-dimensional kinematic analysis of dislocation mechanism in dual mobility total hip arthroplasty constructs

Dual mobility (DM) total hip arthroplasty (THA) is associated with reduced dislocation rates; however, the kinematic mechanism of dislocation in DM THA constructs is still not well understood. This study hypothesizes that the difference in kinematics between DM THA and conventional THA designs contributes to reduced dislocation rates of DM THA. In addition, this study aims to quantify and compare those kinematic parameters between DM THA and conventional THA using a validated dual fluoroscopy imaging system (DFIS) and finite element (FE) modelling. Fresh frozen cadavers were measured to compare the impingement-free range of motion and provocative subluxation kinematics among three THA constructs: (1) DM, (2) constrained liner (CS), and (3) 36 mm head diameter neutral liner (NL). The DFIS was used to measure the in vitro kinematics of the hip. Subject-specific FE models were developed to assess the horizontal dislocation distance and resistive torque at dislocation. The DM construct head exhibited increased provocative anterior and posterior subluxation range of motion before dislocation when compared to CS constructs (p = .05; p = .03), as well as NL constructs (p = .05). The DM THA showed a significantly larger posterior horizontal dislocation distance, as well as smaller resistive torque at dislocation, when compared to NL (p = .05; p = .03) and CS constructs (p = .04; p = .01). Our findings demonstrate there was increased provocative subluxation range of motion as well as normalized jump distance for the DM constructs compared to the NL and CS constructs, suggesting the DM THA may provide increased stability hip during at-risk functional hip positions.

The impact of polyethylene abrasion on the occurrence of periprosthetic proximal femoral fractures in patients with total hip arthroplasty

INTRODUCTION

In addition to abrasion-induced osteolysis and ensuing instabilities, the polyethylene (PE) abrasion of total hip arthroplasty (THA) inlays can also cause gait instability due to the decentralization of the hip joint. The current literature yields, as yet, insufficient findings whether these two factors are linked directly or indirectly to a higher risk for periprosthetic proximal femoral fractures (PPFF). The aim of our retrospective evaluation is to analyse the impact of PE abrasion on the pathology of PPFF in patients with THA.

MATERIAL AND METHODS

The retrospective evaluation comprises all PPFF in patients with THA in the period from 01/2010 up to 12/2016. The study group (SG) included 66 cases (n = 66). The control group (CG) was comprised of patients with asymptomatic THA (n = 66), who were treated by our outpatient department including routine check-ups and X-ray examinations. We used the matched-pair methodology to scale the period of postsurgical care of the CG to the lifetime of the implant up to PPFF in the SG. We included epidemiologic data, radiological femoral head decentralization, osteolysis (Gruen classification), instabilities, acetabular cup position, and implant properties in our analysis. For the SG, we also included intra-operative signs of abrasion.

FINDINGS

The SG showed significantly higher numbers of decentralized THA as signs of inlay erosion with 73% compared to only 41% in the CG (p > 0.001). The SG showed 1 ± 0.68 mm hip joint decentralization as to 0.5 ± 0.59 mm in the CG (p = 0.004). We found significantly more cases of osteolysis in the SG (n = 25) than in the CG (n = 13) (p = 0.003). We found no notable differences in acetabular cup inclination or anteversion as well as cup size. However, differences were significant in femoral head size (SG 32 ± 2.3 mm, CG 36 ± 2.4 mm; p = 0.042) and head material. We found more widespread use of metal femoral heads in the SG than in the CG (SG 1:1, CG 1:21; p = 0.001).

CONCLUSION

PPFF patients showed significantly higher rates of inlay erosion, resulting in femoral head decentralization and osteolysis. The higher rate of fracture is likely caused by the increasing instability of the implant fixation due to abrasion-induced osteolysis and the associated degradation of bone quality. It is conceivable that the abrasion and decentralization of the THA can also lead to gait instability, and thus, a higher proneness to falls. Gait instability can also be aggravated by increased granulation tissue and effusion due to the inlay abrasion. Although this cannot be substantiated by the investigation. In patients with decentralization of the THA and osteolysis, a radiological follow-up should be performed, and in case of gait instability (femoral head and) inlay replacements should be considered.

Efficacy of vitamin E for mechanical damage and oxidation of polyethylene rim by stem neck impingement

BACKGROUND

The aim of this study is to determine the influence of crosslinking and addition of 0.3 wt% vitamin E in a polyethylene rim on its mechanical damage and oxidation caused by impingement.

METHODS

Six ultrahigh-molecular weight polyethylene samples were studied (control; crosslinked; vitamin-E containing; crosslinked and vitamin-E containing; aged control; and aged crosslinked and vitamin-E containing). Crosslinking was attained by irradiation with a 300 kGy electron beam; vitamin E incorporation was at 0.3 wt%; and aging was performed through forced oxidation for 14 days. Resistance to impingement was evaluated by stereoscopic observations, three-dimensional measurements, and oxidation measurements by Fourier transform infrared spectroscopy.

FINDINGS

Rim breakage (delamination and fracture) due to impingement was observed only for the aged control specimen. In contrast, crosslinked specimens containing vitamin E showed no failure of the rim after aging. The addition of vitamin E to polyethylene suppressed its oxidation and reduced the oxidation caused by crosslinking or impingement. The impingement resistance of the control sample deteriorated upon oxidation, whereas that of vitamin E-containing crosslinked polyethylene remained high due to the antioxidant property of vitamin E.

INTERPRETATION

Vitamin E-containing polyethylene showed a reduced risk of wear/breakage of polyethylene rims by impingement.

In Vivo analysis of spinopelvic kinematics and peak head-cup contact in total hip arthroplasty patients with lumbar degenerative disc disease

Anterior instability after total hip arthroplasty (THA) has been described in patients with thoracolumbar kyphotic deformity. Although compensatory posterior pelvic tilt with subsequent increased functional anteversion has been described as the mechanism, there is a paucity of in vivo data. The purpose of our study was to compare pelvic tilt, anteversion, inclination, and position of head-cup contact points in patients with lumbar degenerative disc disease (DDD) and a matched patient cohort without DDD. A total of 50 THA, 18 hips with lumbar DDD and 32 hips without DDD, underwent CT imaging for 3D hip reconstruction. Component orientations and in vivo hip gait kinematics was quantified using a validated dual fluoroscopic imaging system. Hip kinematics and head-cup contact points were compared. Patients with lumbar DDD demonstrated decreased maximum (5.9° ± 4.2° vs. 9.3° ± 5.4°, p = 0.02) and minimum (2.4° ± 4.1° vs. 6.2° ± 5.6°, p = 0.01) anterior pelvic tilt, and increased maximum cup anteversion (29.3° ± 8.7° vs. 25.1° ± 8.1°, p = 0.05). The peak head-cup contact points were shifted closer to the anterior edge of the polyethylene (7.8 ± 1.7 mm vs. 9.6 ± 2.2 mm, p = 0.02). Patients with lumbar degenerative disc disease demonstrated increased posterior pelvic tilt, functional acetabular anteversion, inclination as well as shifting of the peak head-cup contact pattern significantly closer to an anterior edge, suggesting sagittal spinopelvic deformity may predispose to anterior instability in THA patients during upright activities. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.