A novel technique to assess rotational deformities in lower extremities using CT-based motion analysis

Abstract

Rotational deformities following intramedullary (IM) nailing of tibia has a reported incidence of as high as 20%. Common techniques to measure deformities following IM nailing of tibia are either based on clinical assessment, plain X-rays or Computed Tomography (CT) comparing the treated leg with the uninjured contralateral side. All these techniques are based on examiners manual calculation inherently subject to bias. Following our previous rigorous motion analysis and symmetry studies on hemi pelvises, femurs and orthopaedic implants, we aimed to introduce a novel fully digital technique to measure rotational deformities in the lower legs. Following formal institutional approval from the Imperial College, CT images of 10 pairs of human lower legs were retrieved. Images were anonymized and uploaded to a research server. Three dimensional CT images of the lower legs were bilaterally reconstructed. CT-based motion analysis (CTMA) was used and the mirrored images of the left side were merged with the right side proximally as stationary and distally as moving objects. Discrepancies in translation and rotation were automatically calculated. Our study population had a mean age of 54 ± 20 years. There were six males and four females. We observed a greater variation in translation (mm) of Centre of Mass (COM) in sagittal plane (95% CI − 2.959–.292) which was also presented as rotational difference alongside the antero-posterior direction or Y axis (95% CI .370–1.035). In other word the right lower legs in our study were more likely to be in varus compared to the left side. However, there were no statistically significant differences in coronal or axial planes. Using our proposed fully digital technique we found that lower legs of the human adults were symmetrical in axial and coronal plane. We found sagittal plane differences which need further addressing in future using bigger sample size. Our novel recommended technique is fully digital and commercially available. This new technique can be useful in clinical practice addressing rotational deformities following orthopaedic surgical intervention. This new technique can substitute the previously introduced techniques.

Computed tomography micromotion analysis in the follow-up of patients with surgically treated pelvic fractures: a prospective clinical study

“…Using this knowledge, we were now able in this current study to use CTMA in the clinical follow-up of pelvic fracture patients. Bakhshayesh et al also verified the use of CTMA in comparing contralateral tibias and hemi pelvises in patients, were the results indicated symmetry between both sides [7][8][9]. Additionally, the CTMA method has previously been evaluated in a clinical setting for detecting early migration of hip implants by Brodén et al [9,10].…”

“…Bakhshayesh et al also verified the use of CTMA in comparing contralateral tibias and hemi pelvises in patients, were the results indicated symmetry between both sides [7][8][9]. Additionally, the CTMA method has previously been evaluated in a clinical setting for detecting early migration of hip implants by Brodén et al [9,10]. In their clinical study from 2021, 10 patients underwent both CTMA and RSA after total hip arthroplasty (THA) and the findings suggested a comparable precision between the two methods [9].…”

“…Using this knowledge, we were now able in this current study to use CTMA in the clinical follow-up of pelvic fracture patients. Bakhshayesh et al also verified the use of CTMA in comparing contralateral tibias and hemi pelvises in patients, were the results indicated symmetry between both sides [ 7 – 9 ].…”

“…The method has so far, like the Radiostereometric Analysis (RSA), mainly been used to detect implant motion in hip arthroplasty. In contrast to RSA, CTMA does not need marker bead implantation and the method uses a true three-dimensional (3D) input data instead of plain radiographs as in classic RSA [6][7][8][9]. Previous studies using CTMA have shown a precision in the same order of magnitude as in RSA [7,[9][10][11].…”

“…In contrast to RSA, CTMA does not need marker bead implantation and the method uses a true three-dimensional (3D) input data instead of plain radiographs as in classic RSA [6][7][8][9]. Previous studies using CTMA have shown a precision in the same order of magnitude as in RSA [7,[9][10][11]. Current literature on the use of CTMA in the follow-up of fracture patients is as of today non-existing.…”