Clinical use of computer-assisted orthopedic surgery in horses

Accuracy of computer-assisted drilling of equine cervical vertebral bodies using a purpose-built cervical frame-An experimental cadaveric study

OBJECTIVE

To assess the accuracy of computer-assisted surgery (CAS) of equine cervical vertebrae using a purpose-built cervical frame (CF) for neck stabilization.

STUDY DESIGN

Experimental cadaveric study.

SAMPLE POPULATION

Six whole fresh equine cadavers.

METHODS

Cadavers were positioned in dorsal recumbency with the neck extended within the CF. A cone-beam computed tomography (CBCT)-based surgical navigation system with optical tracking was used. A ventral approach exposed cervical vertebrae C3-C5. In each cadaver, 12 drill corridors were prepared with the patient tracker on the CF (position CF), followed by 12 corridors with the patient tracker on C3 (position C3). Surgical accuracy aberration (SAA) was assessed by measuring Euclidean distances between planned and executed entry and target points on merged pre- and postoperative datasets. Descriptive statistics and repeated-measures analyses of variance (rep.-meas. ANOVA) compared SAA measurements between groups.

RESULTS

The mean ± SD SAA (Euclidean distance) was 2.00 ± 0.98 mm in patient tracker position CF, and 2.41 ± 1.31 mm in position C3 (rep.-meas. ANOVA p = .215). At the most dorsal point of the drill corridor, dorsoventral deviations >2 mm occurred in 5/72 measurements in patient tracker position CF, and in 12/72 measurements in position C3.

CONCLUSION

The CF allowed for unrestricted pre- and intraoperative CBCT imaging and computer-assisted drilling with a SAA in the close range of 2 mm. Positioning the patient tracker on the CF, outside the surgical field, did not compromise surgical accuracy.

CLINICAL SIGNIFICANCE

A CF can facilitate CAS for surgeries with a ventral approach to the equine cervical vertebral column.

Feline sacroiliac luxation: comparison of fluoroscopy-controlled freehand vs. computer-navigated drilling in the sacrum-a cadaveric study

Introduction

Sacroiliac luxation is a common traumatic feline injury, with the small size of the sacral body being a challenge for surgical stabilization. This study compared an innovative computer-guided drilling method with the conventional fluoroscopy-controlled freehand technique. Neuronavigation, using CT-based planning and real-time tracking, was evaluated against the freehand method for accuracy and time efficiency.

Materials and methods

Bilateral sacroiliac luxation was induced in 20 feline cadavers. One side of the sacral body was drilled using fluoroscopy, and the other with neuronavigation (Stealth Station S8). A reference frame was affixed to the sacral spinous process for tracking. Ten cats were operated on by an ECVS diplomate and 10 by a resident. Postoperative cone beam CT images were used to assess both techniques, comparing the accuracy of the planned corridor vs. the actual drill hole in the sacrum. A learning curve for both methods was estimated by measuring procedure time.

Results

CT scan assessments showed all 40 drill holes achieved "surgically satisfactory" results. The computer-navigated technique demonstrated an average deviation of 1.9 mm (SD 1.0 mm) at the entry point and 1.6 mm (SD 0.8 mm) at the exit point. The pins of 3/20 reference frames penetrated the vertebral canal, creating a risk for potential clinical complications. The neuronavigation-guided procedures took an average of 23 min and 37 s (SD 8 min 34 s), significantly longer than the freehand technique, which averaged 9 min and 47 s (SD 3 min 26 s). A steep learning curve was observed with neuronavigation.

Discussion

The neuronavigation-guided technique achieved accuracy is comparable to the fluoroscopy-controlled method, is offering real-time feedback and has potential for highly precise surgeries near critical anatomical structures. However, significant attention must be given to the placement of the reference frame, as it is placed blindly and presents a potential risk for errors and complications. Despite its longer duration, the neuronavigation method shows promise for improving precision in complex surgical scenarios.

Use of a new aiming compression device and technique for the repair of navicular bone fractures in horses: A cadaveric study

OBJECTIVE

To assess the use of a newly developed aiming compression device (ACD) for screw insertion in non-fractured navicular bones (NB) in cadavers.

STUDY DESIGN

Cadaveric study.

SAMPLE POPULATION

A total of 10 cadaveric front limbs of adult horses.

METHODS

Placement of a 3.5 mm cortical screw in non-fractured NB under radiographic guidance was performed in 10 cadaver limbs in a standing position. An ACD was used to stabilize the NB and to guide the drilling process. Preparation and surgical time as well as the number of radiographic images were noted. A postoperative scoring system was used to assess screw placement by cone beam computed tomography (CBCT) and gross examination by two evaluators.

RESULTS

The total procedure time was 25-62 min (median 33.5). During the procedure, 11-21 radiographs (median 18.5) were taken. The postoperative gross examination revealed an excellent screw placement in nine NB and poor in one. This could not be reliably assessed with post-procedure CBCT.

CONCLUSION

The described technique achieves an excellent screw placement in 9/10 bones without disrupting the articular or flexural surface of the NB and with no protrusion of the screw head or tip, in a median procedure time of under 35 min.

CLINICAL SIGNIFICANCE

Adequate screw placement is paramount for NB fracture repair. The described approach under radiographic guidance allows adequate screw placement using the ACD to stabilize the NB by lateral to medial compression. This technique facilitates adequate screw placement within the NB without the use of advanced imaging techniques.

A transmandibular lateral transsphenoidal navigated surgical approach to access a pituitary macroadenoma in a warmblood mare

A 16-year-old warmblood mare was referred with a progressive history of behavioral changes and left-sided blindness. Following neuroanatomical localization to the forebrain, magnetic resonance imaging of the head revealed a well-delineated, 4.5 cm in diameter, round pituitary mass causing marked compression of the midbrain and optic chiasm. Euthanasia was recommended but declined by the owners. Veterinary specialists and a human neurosurgeon collaboratively prepared for surgical case management. A novel navigated transmandibular lateral transsphenoidal approach was developed to access the region of the sella turcica and practiced on cadaver specimens. The horse was anesthetized and placed in sternal recumbency with the head above the heart line. Using a cone beam computed tomography (CBCT)-coupled navigation system, a navigated pin traversing the vertical ramus of the mandible and the lateral pterygoid muscle was placed in a direct trajectory to the predetermined osteotomy site of the basisphenoid bone. A safe corridor to the osteotomy site was established using sequential tubular dilators bypassing the guttural pouch, internal and external carotid arteries. Despite the use of microsurgical techniques, visualization of critical structures was limited by the long and narrow working channel. Whilst partial resection of the mass was achieved, iatrogenic trauma to the normal brain parenchyma was identified by intraoperative imaging. With consent of the owner the mare was euthanized under the same general anesthesia. Post-mortem magnetic resonance imaging and gross anatomical examination confirmed partial removal of a pituitary adenoma, but also iatrogenic damage to the surrounding brain parenchyma, including the thalamus.

A novel transcoronal surgical technique for the treatment of cystic lesions of the distal phalanx: A cadaveric study

OBJECTIVE

To assess the feasibility of a novel transcoronal approach for the treatment of axial type 3 cysts of the palmar/plantar aspect of the distal phalanx (P3).

STUDY DESIGN

Ex vivo, experimental study.

SAMPLE POPULATION

Ten cadaveric specimens, four forelimbs and six hindlimbs.

METHODS

All cadaveric specimens underwent radiographically guided drilling, followed by cortical screw placement. The cartilage was macroscopically assessed after disarticulation of the distal interphalangeal joint. The entry point and trajectory were evaluated with computed tomography. Results were categorized as: axial, near-axial and abaxial. The minimal distance from the outer margin of the drill hole and the proximal border of the subchondral bone plate was measured using frontal computed tomographic slices.

RESULTS

Eight of the 10 screws were in an axial to near-axial position and nine followed the desired axial to near-axial trajectory. One screw was inserted axially but continued in an abaxial trajectory. Iatrogenic damage to the joint cartilage, flexor cortex and solar canal of P3 was not observed. All cortical screws were placed close to the proximal subchondral bone-plate of P3.

CONCLUSION

The desired axial/near-axial drilling and screw placement, under radiographic guidance, was achieved in nine out of 10 specimens.

CLINICAL SIGNIFICANCE

This novel technique seems promising for the treatment of inaccessible P3 cysts. Additional studies are required to investigate its feasibility in clinical cases, and the long-term outcome following transcystic screw placement of type 3 P3 cysts.

Equine subchondral lucencies: Knowledge from the medial femoral condyle

Equine subchondral lucencies (SCL) have been described since the first availability of suitable radiographic equipment. The initial clinical sign can be lameness, but SCLs are often first found on surveys of juvenile horses and are primarily a radiographic concern for public auctions. When lameness is present, it varies from subtle to obvious and can be intermittent. Some SCLs heal spontaneously, and some remain blemishes, but when the SCL and lameness are persistent, further damage to the joint and limitations to an athletic career are likely. SCLs were initially described in the distal limb followed by the stifle, and the medial femoral condyle (MFC) is now considered the most common location. The aim of this review is to highlight the initial pathology and discuss the clinical and experimental information available on equine SCLs. SCL treatment has evolved from rest alone and has progressed to debridement, grafting, intralesional injection, and most recently, transcondylar screw and absorbable implant placement. Comparison of success rates between techniques is difficult due to variations in follow-up and outcome measures, and no single technique is best for all SCLs. Treatment appears to increase success by 15%-20% over rest alone, but the method chosen depends on many factors. This review emphasizes the need for further work to fully understand SCL formation and all aspects of trabecular bone healing to optimize surgical therapy and improve treatment success.

Computed tomography and fluoroscopy versus radiographic guidance for internal fixation of simulated dorsomedial-plantarolateral central tarsal bone fractures in nonracehorses

OBJECTIVE

The aim of this study was to assess screw placement in simulated dorsomedial-plantarolateral central tarsal bone (CTB) fractures using two imaging guidance techniques - computed tomography (CT) with fluoroscopy compared to digital radiography alone (DR).

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Equine cadaver hindlimbs (n = 10 pairs).

METHODS

One tarsus per pair was randomly assigned to have a 4.5 mm cortical screw placed across the CTB using CT and fluoroscopy (CT/F group) or digital radiography alone (DR group). Postoperative CT was performed on all limbs. Variables related to marker placement, procedure time, and screw positioning were recorded and compared using a paired t-test for dependent means (p < .05).

RESULTS

Time for marker placement was longer for the CT/F group (p = .001), with no difference in total procedure time (p = .12). CT/F was not superior to radiography alone (p > .05) for parameters related to screw positioning. Based on the 95% CI, there was greater range in relative screw length using radiography (76.5%-91.2%) versus CT/F (78.4%-84.0%).

CONCLUSION

Internal fixation of CTB fractures can be successfully performed using either technique for imaging guidance. CT and fluoroscopy did not result in faster or more accurate screw placement compared to radiographs alone, except in determining screw length.

CLINICAL SIGNIFICANCE

Mild adjustments in fluoroscopic or radiographic angle appeared to be a point of variability in the perception of screw placement. While CT is recommended for improved understanding of fracture configuration and surgical planning, radiographic guidance may be a suitable alternative for internal fixation of dorsomedial-plantarolateral fractures.

Computer-assisted surgery for placing toggle constructs across the coxofemoral joints of small equids using a minimally invasive approach-A proof-of-concept cadaveric study

OBJECTIVE

To develop a minimally invasive technique for placing a toggle construct across the coxofemoral joint of small equids using computer-assisted surgery.

STUDY DESIGN

Experimental cadaveric study.

SAMPLE POPULATION

Three pilot specimens: One donkey, one Shetland pony and one Warmblood foal. Six main study specimens: Three Shetland ponies, one American Miniature Horse, one Warmblood foal and one donkey.

METHODS

Experimental surgeries were performed on both coxofemoral joints of each cadaver. Using a minimally invasive surgical approach, 5.5 mm bone canals were drilled through the femur and acetabulum, traversing the coxofemoral joint. Intraoperative guidance was provided by a cone-beam computed tomography (CBCT)-coupled surgical navigation system. A toggle construct was introduced through the bone canals. Surgical accuracy aberrations (SAA) were measured at the femoral entry and exit points and at the acetabular entry point on merged pre- and postoperative CBCT scans. The coxofemoral joint was assessed for articular cartilage damage by gross dissection.

RESULTS

A toggle construct was placed across all 18 coxofemoral joints. The overall median SAA in the main study was 2.8 mm (range: 0.4-8.0 mm). No cartilage damage was found in the cadaveric specimens of the main study.

CONCLUSION

The described technique allowed for the placement of a toggle construct across the coxofemoral joint of small equid cadaveric specimens without prior coxofemoral luxation.

CLINICAL RELEVANCE

This technique may serve as an option for surgical stabilization of coxofemoral joints in small equids. Further biomechanical investigations are required to assess optimal implant positioning and toggle constructs.

Dynamic three-dimensional computed tomographic imaging facilitates evaluation of the equine cervical articular process joint in motion

BACKGROUND

Dynamic computed tomography (CT) imaging has been introduced in human orthopaedics and is continuing to gain popularity. With dynamic CT, video sequences of anatomical structures can be evaluated in motion.

OBJECTIVES

To investigate the feasibility of dynamic CT for diagnostic imaging of the equine cervical articular process joints (APJs) and to give a detailed description of the APJ movement pattern.

STUDY DESIGN

Descriptive cadaver imaging.

METHODS

Cervical specimens of twelve Warmblood horses were included. A custom-made motorised testing device was used to position and manipulate the neck specimens and perform dynamic 2D and 3D CT imaging. Images were obtained with a 320-detector-row CT scanner with a 160 mm wide-area (2D) solid-state detector design that allows image acquisition of a volumetric axial length of 160 mm without moving the CT couch. Dynamic videos were acquired and divided into four phases of movement. Three blinded observers used a subjective scale of 1 (excellent) to 4 (poor) to grade the overall image quality in each phases of motion cycle.

RESULTS

With an overall median score of 1 the image quality, a significantly lower score was observed in the dynamic 3D videos over the four phases by the three observers compared with the 2D videos for both flexion (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .007) and extension movement (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .008). Median Translational displacement of the APJ surface was significantly greater in flexion than in extension movement (P = .002).

MAIN LIMITATIONS

The small number of specimens included. Excision of spines and removal of musculature.

CONCLUSIONS

The study is a first step in the investigation of the potential of dynamic 3D CT in veterinary medicine, a technique that has only begun to be explored and leaves much room for refinement prior to its introduction in routine practice. CT with a detector coverage of 16 cm and a rotation speed of 0.32 seconds provides high-quality images of moving objects and gives new insight into the movement pattern of equine cervical APJs.

Feasability of a Frameless Brain Biopsy System for Companion Animals Using Cone-Beam CT-Based Automated Registration

The aim of the present study was to evaluate the use of a novel intraoperative cone-beam computed tomography (CBCT)-based automated registration system for frameless stereotactic brain biopsy in companion animals. An experimental cadaveric study evaluated thalamic and piriform lobe target site needle placement error in three dogs and three cats without a history of intracranial disease. Diagnostic accuracy and diagnostic yield were prospectively evaluated in twenty-four client-owned dogs and four cats with intracranial disease. Twenty-one procedures were performed post mortem (eighteen dogs and three cats), and seven biopsy procedures were performed in alive patients (six dogs and one cat). Procedural duration was evaluated in ten post mortem and four living patients. Outcome was evaluated in six dogs and one cat. In dogs, the calculated median needle placement error was 1.8 mm (range 0.71–2.84 mm) and 1.53 mm (range 1.45–1.99 mm) for piriform lobe and thalamus target sites, respectively. In cats, the calculated median needle placement error was 0.79 mm (range 0.6–1.91 mm) for the piriform lobe target site and 1.29 mm (range 0.47–2.69 mm) for the thalamic target site. The diagnostic yield was 96.4% (95% CI 0.81–0.99), the diagnostic accuracy was 94.4% (95% CI 0.72–0.99). Median total procedural duration for post mortem biopsies was 57.5 min (range 41–69 min). Median total procedural duration for intra vitam biopsies was 122.5 min (range 103–136 min). Three dogs were discharged 1 day after biopsy and one dog after 6 days. Two dogs and one cat were euthanized 24 and 48 h after biopsy. Intraoperative CBCT-based automated image registration for frameless stereotactic biopsies in companion animals is capable of providing diagnostic brain biopsy specimens independent of skull size and morphology with diagnostic yield and accuracy comparable to published values for diverse frameless and frame-based stereotaxy systems used in veterinary medicine. Duration of the procedure is not negatively affected and within the published range with other systems. Mobile intraoperative CBCT-based registration combined with neuronavigation delivers diagnostic brain biopsies in companion animals.

Fluoroscopic Navigation for a Surgical Robotic System Including a Continuum Manipulator

We present an image-based navigation solution for a surgical robotic system with a Continuum Manipulator (CM). Our navigation system uses only fluoroscopic images from a mobile C-arm to estimate the CM shape and pose with respect to the bone anatomy. The CM pose and shape estimation is achieved using image intensity-based 2D/3D registration. A learning-based framework is used to automatically detect the CM in X-ray images, identifying landmark features that are used to initialize and regularize image registration. We also propose a modified hand-eye calibration method that numerically optimizes the hand-eye matrix during image registration. The proposed navigation system for CM positioning was tested in simulation and cadaveric studies. In simulation, the proposed registration achieved a mean error of 1.10±0.72 mm between the CM tip and a target entry point on the femur. In cadaveric experiments, the mean CM tip position error was 2.86±0.80 mm after registration and repositioning of the CM. The results suggest that our proposed fluoroscopic navigation is feasible to guide the CM in orthopedic applications.

Imaging the Equine Foot

Over the past 5 years, advancements in diagnostic imaging technology have led to improvement of radiographic technique and development of standing computed tomography (CT) and PET-CT scanners. Although these modalities are in their initial stages of development and clinical applications, they are meant to revolutionize the diagnosis and management of diseases of the foot in the standing patient, in particular detecting subclinical lesions, and the establishment of computer-assisted surgical suits. This article also reviews the improved radiographic projections of the equine foot and benefits of high-field and contrast magnetic resonance imaging (MRI) in diagnosis of cartilage and ligamentous pathologies.

Evaluation of depth gauge accuracy in a canine tibial plateau leveling osteotomy model

OBJECTIVE

To evaluate the accuracy of six depth gauges used in three tibial plateau leveling osteotomy (TPLO) plate holes.

STUDY DESIGN

Ex vivo experimental study.

ANIMALS AND SAMPLE POPULATION

Cadaveric canine limbs (n = 10), one 25-mm-thick wood board, and one 33.8-mm-diameter polyvinyl chloride (PVC) pipe.

METHODS

A TPLO was performed on 10 canine cadaveric pelvic limbs. Three 3.5-mm plate holes were filled with screws. The remaining three plate holes: a compression hole, a combination compression-locking hole, and a stacked combination compression-locking hole were measured by three observers using six commercial depth gauges and using a micrometer as gold standard. The process was repeated on one wood board and one PVC pipe.

RESULTS

Bone measurements collected using two depth gauges with base diameter < 5 mm were smaller than measurements collected using the four depth gauges with base diameter > 5.5 mm (p ranging from < .001 to .038). Mean depth gauge measurements were smaller than micrometer measurements by 2.20 mm for the compression hole, 0.82 mm for the combination hole, and 3.57 mm for the stacked combination hole. Measurement differences among depth gauges were also present for wood board and PVC pipe measurements. Bone measurement variability between depth gauges was less for the combination and compression holes than for the stacked combination hole.

CONCLUSION

Depth gauges lacked accuracy. Measurements differed among gauges and measurement variability varied based on plate hole geometry.

CLINICAL RELEVANCE

Depth gauge measurement accuracy varies based on measuring devices and on 3.5-mm plate hole geometry.

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

OBJECTIVE

 The aim of this study was to evaluate the surgical execution of a virtual surgical plan (VSP) with three-dimensional (3D) guides against a freehand approach in the equine navicular bone using an automated in silico computer analysis technique.

STUDY DESIGN

 Eight pairs of cadaveric forelimb specimens of adult horses were used in an ex vivo experimental study design with in silico modelling. Limbs received either a 3.5 mm cortical screw according to a VSP or using an aiming device. Using computed tomography and computer segmentation, a comparison was made between the executed screw and the planned screw using the Hausdorff distance (HD).

RESULTS

 Navicular bone mean HD registration error was -0.06 ± 0.29 mm. The VSP with 3D printing demonstrated significantly superior accuracy with a mean deviation of 1.19 ± 0.42 mm compared with aiming device group (3.53 ± 1.24 mm, p = 0.0018). The VSP group was 5.0 times more likely to result in a mean aberration of less than 1.0 mm (95% confidence interval, 0.62-33.4). A 3.5 mm screw with an optimal entry point can have a maximum deviation angle of 3.23 ± 0.07, 2.70 ± 0.06 and 2.37 ± 0.10 degrees in a proximal, dorsal and palmar direction respectively, prior to violating one of the cortical surfaces.

CONCLUSION

 Procedures performed using the 3D guides have a high degree of accuracy, with minimal mean deviations (<1 mm and <1 degree) of a VSP compared with those using the conventional aiming device. The use of VSP and the HD for evaluation of orthopaedic surgeries and outcome measures shows promise for simplifying and improving surgical accuracy.

Feasibility, indications, and radiographically confirmed diagnoses of standing extremity cone beam computed tomography in the horse

OBJECTIVE

To report on the feasibility, indications, and diagnostic yield of cone beam computed tomography (CBCT) of horses' extremities performed under standing sedation.

STUDY DESIGN

Retrospective clinical case series.

SAMPLE POPULATION

Fifty-nine CBCT examinations in 58 horses.

METHODS

Examinations were categorized for indications for CBCT dependent on a suspicion, presence, or absence of a diagnosis prior to CBCT. The number of acquisitions per examination, total time for the examination, diagnostic score of each acquisition (diagnostic, diagnostic-compromised, nondiagnostic), and additional diagnostic information regarding preexisting diagnostic information were recorded.

RESULTS

Three (median) acquisitions were performed per examination in a median study time of 14 minutes. In 24 of 33 cases with a suspected diagnosis, this diagnosis was confirmed or definitively refuted; in seven of 33 cases, the suspected diagnosis was refuted without a new diagnosis; and, in two of 33 cases, the suspected diagnosis could not be confirmed nor could a new diagnosis be made. In five of nine cases without a preexisting diagnosis, a diagnosis was established. In 16 cases with a diagnosis prior to CBCT, additional information was recorded, or a surgical plan was prepared. In 14 of 18 cases in which additional contrast techniques were used, additional information was gained.

CONCLUSION

Standing CBCT of the horses' extremities is feasible and can produce diagnostic information in a timely fashion.

CLINICAL SIGNIFICANCE

The results provide evidence of the practicality and diagnostic potential of standing CBCT of horses' extremities.