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- Author or Editor: Scott A. Banks x
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Abstract
Objective—To compare the axial stiffness, maximum axial displacement, and ring deformation during axial loading of single complete and incomplete circular (ring) external skeletal fixator constructs.
Sample—32 groups of single ring constructs (5 constructs/group).
Procedures—Single ring constructs assembled with 2 divergent 1.6-mm-diameter Kirschner wires were used to stabilize a 60-mm-long segment of 16-mm-diameter acetyl resin rod. Construct variables included ring type (complete or incomplete), ring diameter (50, 66, 84, or 118 mm), and fixation wire tension (0, 30, 60, or 90 kg). Axial loading was performed with a materials testing system. Construct secant stiffness and maximum displacement were calculated from the load-displacement curves generated for each construct. Ring deformation was calculated by comparing ring diameter during and after construct loading to ring diameter prior to testing.
Results—Complete ring constructs had greater axial stiffness than did the 66-, 84-, and 118-mm-diameter incomplete ring constructs. As fixation wire tension increased, construct stiffness increased in the 66-, 84-, and 118-mm-diameter incomplete ring constructs. Maximum axial displacement decreased with increasing fixation wire tension, and complete ring constructs allowed less displacement than did incomplete ring constructs. Incomplete rings were deformed by wire tensioning and construct loading.
Conclusions and Clinical Relevance—Mechanical performance of the 66-, 84-, and 118-mm-diameter incomplete ring constructs improved when wire tension was applied, but these constructs were not as stiff as and allowed greater displacement than did complete ring constructs of comparable diameter. For clinical practice, tensioning the wires placed on 84- and 118-mm-diameter incomplete rings to 60 kg is recommended.
Abstract
OBJECTIVE
To compare joint stability and ultimate strength among 4 prosthetic ligament constructs for repair of tarsal medial collateral ligament (MCL) injury in dogs.
SAMPLE
13 canine cadavers (26 hind limbs).
PROCEDURES
Each limb was stripped of all soft tissues except those associated with the tarsal joint and assigned to 1 of 4 prosthetic ligament constructs. The AN construct consisted of 3 bone anchors connected with monofilament nylon suture. The AU construct consisted of low-profile suture anchors connected with multifilament ultrahigh-molecular-weight polyethylene (UHMWPE) suture. The TN and TU constructs involved the creation of 3 bone tunnels and use of nylon or UHMWPE suture, respectively. Each limb underwent biomechanical testing before and after MCL transection and before and after cyclic range-of-motion testing following completion of the assigned construct. Tarsal joint stability (extent of laxity) was assessed with the joint in each of 3 positions (75°, 135°, and 165°). After completion of biomechanical testing, each limb was tested to failure to determine the ultimate strength of the construct.
RESULTS
Relative to intact tarsal joints, joint laxity was significantly increased following completion of all 4 constructs. Construct type was not associated with the magnitude of change in joint laxity. Ultimate strength was greatest for the UHMWPE-suture constructs.
CONCLUSIONS AND CLINICAL RELEVANCE
Results indicated that all 4 constructs effectively stabilized MCL-deficient tarsal joints. Implants used for the TU, TN, and AU constructs had a lower profile than those used for the AN construct, which may be clinically advantageous. In vivo studies are warranted.
Abstract
OBJECTIVE
To quantify the translation and angular rotation of the distal sesamoid bone (DSB) using computed tomography (CT) and medical modeling software.
SAMPLE
30 thoracic limbs from equine cadavers.
PROCEDURES
Partial (n = 12), full (8), and matched full and subsequently transected (10) thoracic limbs were collected. Bone volume CT images were acquired in three positions: extension (200° metacarpophalangeal angle), neutral (180°), and maximal flexion (110°). Mean translation and angular rotation of each DSB were recorded. Differences were determined with two-way ANOVA and post hoc Tukey’s tests for pairwise comparisons; P value was set at < 0.05.
RESULTS
Dorsal translation was significant during extension (1.4 ± 0.4 mm full limbs and 1.3 ± 0.2 mm partial limbs, P < 0.001). Distal translation was significant during extension (1.9 ± 0.4 mm full and 1.1 ± 0.4 mm partial) and flexion (5.4 ± 0.7 mm full and 6.22 ± 0.6 mm partial, P < 0.001). Rotation was significant (P < 0.001) about the mediolateral axis during extension (17.1° ± 1.4°) and flexion (2.6° ± 1.3°). Translation and rotation of the DSB were significantly different (P < 0.001) between full and partial limbs.
CLINICAL RELEVANCE
This study provides the first quantification of translation and angular rotation of the DSB within the equine hoof. Partial limbs had significantly reduced movement compared to full limbs, suggesting that transection of flexor tendons alters distal thoracic limb kinematics. Further studies are required to determine if pathologic changes in the podotrochlear apparatus have an impact in clinical lameness outcomes.
Abstract
OBJECTIVE
This study aims to quantitatively characterize the passive kinematics of the healthy, soft tissue-intact equine stifle to establish an objective foundation for providing insights into the etiology of stifle disorders and developing a possible surgical treatment for stifle degenerative disease.
ANIMALS
5 whole-horse specimens.
PROCEDURES
Reflective markers with intracortical bone pins and a motion capture system were used to investigate the stifle joint kinematics. Kinematics of 5 whole-horse specimens euthanized within 2 hours were calculated for internal/external rotation, adduction/abduction, and cranial/caudal translation of the medial and lateral femoral condyles and estimated joint contact centroids as functions of joint extension angle.
RESULTS
From 41.7° to 121.6° (mean ± SD, range of motion: 107.5° ± 7.2°) of joint extension, 13° ± 3.7° of tibial external rotation and 6° ± 2.7° of adduction were observed. The lateral femoral condyle demonstrated significantly greater cranial translation than the medial during extension (23.7 mm ± 9.3 mm vs. 14.3 mm ± 7.0 mm, P = .01). No significant difference was found between the cranial/caudal translation of estimated joint contact centroids in the medial and lateral compartment (13.3 mm ± 7.7 mm vs. 16.4 mm ± 5.8 mm, P = .16).
CLINICAL RELEVANCE
The findings share similarities with kinematics for human knees and sheep and dog stifles, suggesting it may be possible to translate what has been learned in human arthroplasty to treatment for equine stifles.
Abstract
Objective—To compare accuracy of a noninvasive single-plane fluoroscopic technique with radiostereometric analysis (RSA) for determining 3-D femorotibial poses in a canine cadaver with normal stifle joints.
Sample—Right pelvic limb from a 25-kg adult mixed-breed dog.
Procedures—A CT scan of the limb was obtained before and after metal beads were implanted into the right femur and tibia. Orthogonal fluoroscopic images of the right stifle joint were acquired to simulate a biplanar fluoroscopic acquisition setup. Images were obtained at 5 flexion angles from 110° to 150° to simulate a gait cycle; 5 cycles were completed. Joint poses were calculated from the biplanar images by use of RSA with CT-derived beaded bone models and compared with measurements obtained by use of CT-derived nonbeaded bone models matched to single-plane, lateral-view fluoroscopic images. Single-plane measurements were performed by 2 observers and repeated 3 times by the primary observer.
Results—Mean absolute differences between the single-plane fluoroscopic analysis and RSA measurements were 0.60, 1.28, and 0.64 mm for craniocaudal, proximodistal, and mediolateral translations, respectively, and 0.63°, 1.49°, and 1.58° for flexion-extension, abduction-adduction, and internal-external rotations, respectively. Intra- and interobserver repeatability was strong with maximum mean translational and rotational SDs of 0.52 mm and 1.36°, respectively.
Conclusions and Clinical Relevance—Results suggested that single-plane fluoroscopic analysis performed by use of CT-derived bone models is a valid, noninvasive technique for accurately measuring 3-D femorotibial poses in dogs.
Abstract
Objective—To compare accuracy of a noninvasive single-plane fluoroscopic analysis technique with radiostereometric analysis (RSA) for determining 3-D femorotibial poses in a canine cadaver stifle joint treated by tibial-plateau-leveling osteotomy (TPLO).
Sample—Left pelvic limb from a 25-kg adult mixed-breed dog.
Procedures—A CT scan of the left pelvic limb was performed. The left cranial cruciate ligament was transected, and a TPLO was performed. Radiopaque beads were implanted into the left femur and tibia, and the CT scan was repeated. Orthogonal fluoroscopic images of the left stifle joint were acquired at 5 stifle joint flexion angles ranging from 110° to 150° to simulate a gait cycle; 5 gait cycles were completed. Joint poses were calculated from the biplanar images by use of a digitally modified RSA and were compared with measurements obtained by use of hybrid implant-bone models matched to lateral-view fluoroscopic images. Single-plane measurements were performed by 2 observers and repeated 3 times by the primary observer.
Results—Mean absolute differences between results of the single-plane fluoroscopic analysis and modified RSA were 0.34, 1.05, and 0.48 mm for craniocaudal, proximodistal, and mediolateral translations, respectively, and 0.56°, 0.85°, and 1.08° for flexion-extension, abduction-adduction, and internal-external rotations, respectively. Intraobserver and interobserver mean SDs did not exceed 0.59 mm for all translations and 0.93° for all rotations.
Conclusions and Clinical Relevance—Results suggested that single-plane fluoroscopic analysis by use of hybrid implant-bone models may be a valid, noninvasive technique for accurately measuring 3-D femorotibial poses in dogs treated with TPLO.
OBJECTIVE
To quantify 3-D femorotibial joint kinematics during ambulation in dogs with cranial cruciate ligament (CCL) rupture treated with lateral fabellotibial suture stabilization (LFTS).
ANIMALS
9 adult dogs (body weight, 15 to 35 kg [33 to 77 lb]) with unilateral complete CCL rupture.
PROCEDURES
Digital 3-D bone models of the femur and fabellae and tibia and fibula were created from CT scans. Lateral fluoroscopic images of stifle joints were collected during treadmill walking before surgery and 6 months after LFTS. The LFTS was performed with nylon leader material secured with knots. Gait cycles were analyzed with a 3-D to 2-D image registration process. Femorotibial joint kinematics (craniocaudal translation, internal-external rotation, and flexion and extension angles) were compared among CCL-deficient stifle joints before LFTS, CCL-deficient stifle joints 6 months after LFTS, and unaffected contralateral (control) stifle joints. Owners and veterinarians subjectively assessed lameness by use of a visual analog scale and gait examination, respectively, at each time point.
RESULTS
At midstance phase, medial cranial tibial translation decreased from 9.3 mm before LFTS to 7.6 mm after LFTS but remained increased when compared with control stifle joint values. Following LFTS, axial rotation and stifle joint flexion and extension angles were not significantly different from control stifle joints. On the owner survey, the median walking lameness score improved from 9.3 of 10 before surgery to 0.3 after surgery. On gait examination, median walking lameness score improved from 2 of 4 before surgery to 0 after surgery.
CONCLUSIONS AND CLINICAL RELEVANCE
Stifle joint instability was only slightly mitigated at 6 months following LFTS performed with knotted nylon leader material in medium to large dogs with CCL rupture, despite improvement in lameness.
