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Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

ABSTRACT: In clinical trials of THA, model-based radiostereometric analysis (RSA) techniques may be less precise than conventional marker-based RSA for measurement of femoral stem rotation. We verified the accuracy and clinical precision of RSA based on computer-aided design models of a cementless tapered wedge femoral stem.We asked: (1) Is the accuracy of model-based RSA comparable to that of marker-based RSA? (2) What is the clinical precision of model-based RSA?Model-based RSA was performed using combined three-dimensional computer-aided design models of the stem and head provided by the implant manufacturer. The accuracy of model-based RSA was compared with that of marker-based RSA in a phantom model using micromanipulators for controlled translation in three axes (x, y, z) and rotation around the y axis. The clinical precision of model-based RSA was evaluated by double examinations of patients who had arthroplasties (n = 24) in an ongoing trial. The clinical precision was defined as being at an acceptable level if the number of patients needed for a randomized trial would not differ from a trial done with conventional marker-based RSA (15-25 patients per group).The accuracy of model-based RSA was 0.03 mm for subsidence (translation along the y axis) (95% CI for the difference between RSA measurements and actual displacement measured with micrometers, -0.03-0.00) and 0.39° for rotation around the y axis (95% CI, -0.41 to -0.06). The accuracy of marker-based RSA was 0.06 mm for subsidence (95% CI, -0.04-0.01; p = 0.728 compared with model-based RSA) and 0.18° for the y axis rotation (95% CI, -0.23 to -0.07; p = 0.358). The clinical precision of model-based RSA was 0.14 mm for subsidence (95% CI for the difference between double examinations, -0.02-0.04) and 0.79° for the y axis rotation (95% CI, -0.16-0.18).The accuracy of model-based RSA for measurement of the y axis rotation was not quite as high as that of marker-based RSA, but its clinical precision is at an acceptable level.Model-based RSA may be suitable for clinical trials of cementless tapered wedge femoral stem designs.

SUBMITTER: Nazari-Farsani S

PROVIDER: S-EPMC5014820 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

Nazari-Farsani Sanaz S Finnilä Sami S Moritz Niko N Mattila Kimmo K Alm Jessica J JJ Aro Hannu T HT

Clinical orthopaedics and related research 20160622 10

<h4>Background</h4>In clinical trials of THA, model-based radiostereometric analysis (RSA) techniques may be less precise than conventional marker-based RSA for measurement of femoral stem rotation. We verified the accuracy and clinical precision of RSA based on computer-aided design models of a cementless tapered wedge femoral stem.<h4>Questions</h4>We asked: (1) Is the accuracy of model-based RSA comparable to that of marker-based RSA? (2) What is the clinical precision of model-based RSA?<h4> ...[more]

PMID: 27334320

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Project description:The present study aimed to investigate the prevalence and clinical consequences of occult intra-operative periprosthetic femoral fractures in total hip arthroplasty (THA). Between 2012 and 2017, a total of 113 primary THAs were enrolled. The mean age of the patients was 66.4 ± 7.6 years. We assessed occult intra-operative periprosthetic femoral fractures with the use of computed tomography (CT) and risk factors, including age, sex, body mass index, diagnosis, stem size, and radiographic parameters of proximal femoral geometry were analyzed. We also assessed the differences in thigh pain and stem subsidence and alignment between the patients with and without occult periprosthetic femoral fracture. Occult intra-operative periprosthetic femoral fractures were found in 13 of 113 hips (11.5%). In 9/13 (69.2%) of occult fractures, fracture lines were started from the region below the tip of the lesser trochanter. Six periprosthetic femoral fractures (5.3%) were found during the operation. Out of the five hips that had detected femoral fractures around the lesser trochanter intra-operatively, four hips (80%) showed concurrent occult fractures on different levels. The female sex (P = .01) and canal filling ratio at 7 cm below the tip of the lesser trochanter (P = .01) were significantly different between the patients with and without occult periprosthetic femoral fracture. The sex was significantly associated with an increased risk in predicting an occult intra-operative periprosthetic femoral fracture (odds ratio of male, 0.25 compared with the female; 95% CI, 0.08-0.85; p = .02). There was a significant difference in the incidence of thigh pain between occult fracture group and non-occult fracture group (P < .05). There were no significant differences in stem subsidence and alignment between the patients with and without occult periprosthetic femoral fracture. All 13 cases of occult intra-operative periprosthetic femoral fractures were healed at the final follow-up. Occult periprosthetic femoral fractures are common during a long, trapezoidal, double-tapered cementless femoral stem fixation in primary THA, that CT scans are helpful to identify them, and that these fractures do not adversely affect the implant's survival if a rigid fixation of the implants has been achieved.

Project description:Although tapered-wedge short stem has been widely employed with its availability for minimally invasive surgeries in total hip arthroplasty (THA), post-operative stress shielding matter remains unresolved in cementless procedures. This study aimed to clarify the most optimal femoral canal contact regions of the stem design taking stress shielding incidence into consideration. This investigation included 60 joints from 60 patients (mean age at operation: 65.9 years), of which follow-up duration after primary THA had been more than 2 years. Frequencies of spot welds, subsidence, and stress shielding were examined 2 years after surgery. The most suitable femoral canal contact regions were evaluated by plain radiograph (2D) and 3D-computed tomography analyses according to Nakata's division for fitting manners. Spot welds were observed in 38 cases (63.3%), and no subsidence case was seen. Respective number of stress shielding cases, based on Engh's classification, categorized as degree 0, 1, and 2, were 2 (3.3%), 31 (51.7%), and 27 (45.0%), while no cases for degree 3 or 4 were found. When assessed by 3D fitting analysis, 27 cases of stress shielding degree 2 were constituted by 13/42 cases of mediolateral (ML) fit, 2/4 cases of flare fit, and 12/14 cases of multi point fit. In 42 cases of ML fitting, stem contact rate of the most proximedial region in stress shielding degree 0 and 1 was significantly higher compared to stress shielding degree 2 cases. Meanwhile, the rates of distal regions were significantly lower or absent in stress shielding degree 0 and 1 cases. The initial fixation of this stem design was very good in our cohort regardless of fitting manners. This study successfully revealed that ML fitting with femoral component, especially the most proximedial calcar site restricted fitting, would be optimal for reducing stress shielding occurrence in cementless short, tapered-wedge stem THA. Thus, the ideal stem contact region should be considered during THA procedures in light of the reduction of stress shielding development.

Dataset Information

Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

Publications

Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

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