Use of Hausdorff Distance and Computer Modelling to Evaluate Virtual Surgical Plans with Three-Dimensional Printed Guides against Freehand Techniques for Navicular Bone Repair in Equine Orthopaedics

Influence of the Vertek aiming device on the surgical accuracy of computer-assisted drilling of the equine distal sesamoid bone-An experimental cadaveric study

OBJECTIVE

To determine the effect of the Vertek aiming device (VAD) on the surgical accuracy of navigated drilling of the distal sesamoid bone (DSB).

STUDY DESIGN

Experimental cadaveric study.

SAMPLE POPULATION

A total of 30 paired equine cadaveric limbs from 15 horses.

METHODS

Each specimen was placed in a purpose-built frame (PBF). Preoperative cone beam computed tomography (CBCT) images were acquired with an imaging unit coupled with a surgical navigation system. In the DSB of each specimen, a 4.5 mm glide hole and a 3.2 mm thread hole were drilled under navigation guidance, to simulate drilling for the repair of a mid-sagittal DSB fracture. In the VAD group navigated drilling was assisted by using the VAD. In the free-hand drilling group navigated drilling was performed without the VAD. Pre-and postoperative CBCT scans were merged and surgical accuracy aberrations (SAA) between the planned drill corridor and the created bone tunnel were measured. Descriptive statistics and repeated-measures analyses of variance (rep.-meas. ANOVA) were performed to compare SAA measurements between the study groups.

RESULTS

The SAA measurements ranged from 0 to 2.9 mm in the free-hand group and from 0 to 2.8 mm in the VAD group. The median overall SAA was lower in the VAD group than in the free-hand navigated group (0.6 mm ± [0.5-0.7] vs. 0.8 mm ± [0.7-1], rep.-meas. ANOVA p = .007).

CONCLUSION

The additional use of the VAD in the described set-up for navigated drilling significantly improved surgical accuracy.

CLINICAL SIGNIFICANCE

The combined use of the VAD and PBF may help improve surgical accuracy in navigated lag screw repair of DSB fractures.

Efficacy of virtual surgical planning and a three-dimensional-printed, patient-specific reduction system to facilitate alignment of diaphyseal tibial fractures stabilized by minimally invasive plate osteosynthesis in dogs: A prospective clinical study

OBJECTIVE

To evaluate the efficacy of a three-dimensional (3D)-printed, patient-specific reduction system for aligning diaphyseal tibial fractures stabilized using minimally invasive plate osteosynthesis (MIPO).

STUDY DESIGN

Prospective clinical trial.

SAMPLE POPULATION

Fifteen client owned dogs.

METHODS

Virtual 3D models of both pelvic limbs were created. Pin guides were designed to conform to the proximal and distal tibia. A reduction bridge was designed to align the pin guides based on the guides' spatial location. Guides were 3D printed, sterilized, and applied, in conjunction with transient application of a circular fixator, to facilitate indirect fracture realignment before plate application. Alignment of the stabilized tibiae was assessed using postoperative computed tomography scans.

RESULTS

Mean duration required for virtual planning was 2.5 h and a mean of 50.7 h elapsed between presentation and surgery. Guide placement was accurate with minor median discrepancies in translation and frontal, sagittal, and axial plane positioning of 2.9 mm, 3.6°, 2.7°, and 6.8°, respectively. Application of the reduction system restored mean tibial length and frontal, sagittal, and axial alignment within 1.7 mm, 1.9°, 1.7°, and 4.5°, respectively, of the contralateral tibia.

CONCLUSION

Design and fabrication of a 3D-printed, patient-specific fracture reduction system is feasible in a relevant clinical timeline. Intraoperative pin-guide placement was reasonably accurate with minor discrepancies compared to the virtual plan. Custom 3D-printed reduction system application facilitated near-anatomic or acceptable fracture reduction in all dogs.

CLINICAL SIGNIFICANCE

Virtual planning and fabrication of a 3D-printing patient-specific fracture reduction system is practical and facilitated acceptable, if not near-anatomic, fracture alignment during MIPO.

Three-Dimensional Modeling and In Silico Kinematic Evaluation of Interspinous Ligament Desmotomy in Horses

Background: Interspinous ligament desmotomy (ISLD) has been shown to improve the comfort of horses diagnosed with overriding dorsal spinous processes (DSP), but its effects on spine mobility are unknown.

Objective: To objectively quantify the change in mobility of thoracic vertebrae following ISLD using CT and medical modeling software.

Study design: Prospective cadaveric manipulation of seven equine thoracolumbar spines collected from T11-L1.

Methods: Spines were collected from T11-L1 with the musculature intact. Flexion and extension phases were achieved with a ratchet device calibrated to 2000N. Bone volume CT scans were performed in resting, flexion, and extension phase preoperatively. Interspinous ligament desmotomy was performed at each intervertebral space (n = 8), and bone volume CT imaging was repeated for each phase. The spinal sections were individually segmented and imported into medical software for kinematic evaluation. T11 of each phase were superimposed, the distance between each dorsal spinous process, the total length of the spine, and the maximal excursion of the first lumbar vertebra along with angular rotational information were recorded.

Results: The mean distance between each dorsal spinous process increased by 5.6 ± 4.9 mm, representing a 24 ± 21% increase in mobility following ISLD. L1 dorsoventral excursion increased by 15.3 ± 11.9 mm, craniocaudal motion increased by 6.9 ± 6.5 mm representing a 47 ± 36.5% and 14.5 ± 13.7% increase, respectively. The rotation of L1 about the mediolateral axis increased by 6.5^° post-ISLD.

Conclusion and Clinical Relevance: ISLD increases dorsoventral, craniocaudal, and rotational motion of the equine spine. The computer modeling methodology used here could be used to evaluate multiplanar spinal kinematics between treatments.

Three-Dimensional Segmentation and in silico Comparison of Equine Deep Digital Flexor Tendon Pathology in Horses Undergoing Repeated MRI Examination

The use of magnetic resonance imaging (MRI) has led to increased clinical and research applications using 3D segmentation and reconstructed volumetric data in musculoskeletal imaging. Lesions of the deep digital flexor tendon (DDFT) are a common pathology in horses undergoing MRI. Three-dimensional MRI reconstruction performed for volumetric tendon analysis in horses has not previously been documented. The aim of this proof-of-concept study was to evaluate the 3D segmentation of horses undergoing repeated MRI at several time points and to perform an analysis of the segmented DDFTs across time. MRI DICOM files were acquired from six horses undergoing repeated MRI examination of the foot for DDFT injury. Once segmented, volumetric tendon surface tessellation language (STL) files were created. Thickness and volumetric data were acquired for each tendon in addition to a tendon comparison across timepoints within each horse. Pearson correlation coefficients were calculated for comparison of MRI reports to computer analysis. There was a significant and positive correlation between MRI and medial record reports of clinical improvement or deterioration and computer analysis (r = 0.56, p = 0.01). The lower end range limit for tendon thickness varied between 0.16 and 1.74 mm. The upper end range limit for DDFT thickness varied between 4.6 and 23.6 mm. During tendon part comparison, changes in DDFT were reported between −3.0 and + 14.3 mm. Changes in DDFT size were non-uniform and demonstrated fluctuations throughout the tendon. The study was successful in establishing the volumetric appearance and thickness of the DDFT as it courses in the foot and tracking this over time. We encountered difficulties in accurate segmentation of the distal insertion of the DDFT as it blends with the distal phalanx. The data demonstrated that the DDFT can be segmented and volumetric studies based on size and shape can be performed using an in silico approach.