Comparing the Accuracy of Patient-Specific Guide and Universal Guide for Distal Femoral Osteotomy in Dogs

OBJECTIVE

 To introduce a novel universal guide design for distal femoral osteotomy (DFO) to treat femoral deformities and other hindlimb orthopaedic diseases, and to compare its accuracy to the patient-specific guide in vitro and ex vivo on X-ray and computed tomography (CT).

METHODS

 Thirteen anatomic specimens of canine femurs and 13 3D-printed femoral bone models were subjected to DFO using a patient-specific and a universal guide. The anatomical lateral distal femoral angle and anteversion angle were measured on radiographic and CT images before and after surgical procedure and used to compare the accuracy of the surgical guides in treating uniplanar or biplanar deformities. Bone models were used to compare the accuracy with ex vivo models.

RESULTS

 The mean correction errors were -1.18° to 0.72° on X-ray and -1.91° to 0.53° on CT scan. The analysis showed no statistically significant difference in the mean error between the groups based on type of guide used, nor in the mean error between groups based on whether anteversion correction was performed based on both the CT and X-ray imaging data.

CONCLUSION

 Both the patient-specific and universal guides can produce accurate results in DFO surgery, and the universal guide shows potential as a useful surgical tool.

Evaluation of the quadriceps muscle length to femoral length ratio in small breed dogs with medial patellar luxation

OBJECTIVE

To determine the quadriceps muscle length (QML) to femoral length (FL) ratio (QML/FL) and its associated factors in small breed dogs with medial patellar luxation (MPL) and to compare the differences in the QML/FL between MPL grades.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Small breed dogs (<10 kg) with MPL: 78 dogs (134 limbs).

METHODS

Medical records and computed tomography (CT) images from 2008-2020 were reviewed. Furthermore, age, bodyweight, sex, laterality, MPL grade, femoral inclination angle (FIA), femoral torsion angle (FTA), anatomical lateral distal femoral angle (aLDFA), and patellar ligament length to patellar length ratio were included in the regression analysis to determine the factors associated with QML/FL. Each measurement parameter was compared among the four MPL grade groups.

RESULTS

The final model demonstrated that the QML/FL increased with increasing age (p = .004) and decreased with increasing FTA and aLDFA (p = .015 and p < .001, respectively). The MPL grade IV group had a lower QML/FL than the grade I, II, and III groups (p = .002, p < .001, and p < .001, respectively).

CONCLUSION

Among small breed dogs, those with MPL grade IV had a shortened QML associated with femoral deformities.

CLINICAL SIGNIFICANCE

Noninvasive evaluation of the QML/FL improves our understanding of the length mismatch between the quadriceps muscle and the femur.

Biomechanical analysis of canine medial patellar luxation with femoral varus deformity using a computer model

Background

Femoral varus deformities complicating the realignment of the quadriceps muscles are frequently associated with medial patellar luxation (MPL) in dogs. Therefore, distal femoral osteotomy (DFO) is recommended in dogs affected with severe MPL and a distal femoral varus deformity. The presence of an anatomic lateral distal femoral angle (aLDFA) of ≥ 102° has been anecdotally recommended as an indication for performing corrective DFO in large-breed dogs. However, the effect of a femoral varus deformity on MPL has not been scientifically evaluated. We aimed to evaluate the influence of a femoral varus deformity on MPL using a finite element method based computer model.

Three-dimensionally reconstructed computed tomographic images of a normal femur from a Beagle dog were deformed using meshing software to create distal varus deformities. A total of thirteen aLDFAs, including 95°, 98° and 100°–110°, were simulated. The patellar positions and reaction force between the patella and trochlear grooves were calculated for all finite element models under constant rectus femoris muscle activation.

Results

The patella was displaced medially from the trochlear groove at an aLDFA of ≥103°. With an aLDFA of 103° to 110°, the reaction force was equal to zero and then decreased to negative values during the simulation, while other models with aLDFAs of 95°, 98°, and 100°-102° had positive reaction force values. The patella began to luxate at 24.90 seconds (sec) with an aLDFA of 103°, 19.80 sec with an aLDFA of 104°, 21.40 sec with an aLDFA of 105°, 20.10 sec with an aLDFA of 106°, 18.60 sec with an aLDFA of 107°, 15.30 sec with an aLDFA of 108°, 16.60 sec with an aLDFA of 109°, and 11.90 sec with an aLDFA of 110°.

Conclusion

Severe distal femoral varus with an aLDFA of ≥103° caused MPL when other anatomical factors were controlled. Thissimplified computer model provides complementary information to anecdotal cutoffs for DFO, hence it should be applied to clinical patients with caution.

Evaluation of a Fixed-Angle Wedge Osteotomy Guide

OBJECTIVE

 The aim of this study was to evaluate a fixed-angle cutting guide designed to aid in the performance of coplanar wedge osteotomies using a proximal tibial cranial closing wedge ostectomy model.

STUDY DESIGN

 A 30-degree cranial closing wedge ostectomy was created using canine tibia models with either a standard template (method T) or a wedge osteotomy guide (method G) by two surgeons. One surgeon was experienced with both procedures, and one surgeon had no previous experience with the wedge guide. The ostectomy wedges were evaluated for wedge angle, using a digital protractor, and coplanarity by using digital photographs and screen-measuring software.

RESULTS

 The mean (standard deviation) wedge angles of the T and G groups were 28.16 (1.33) and 28.4 degrees (1.46) respectively. The mean (standard deviation) divergence angles of the T and G groups were 3.21 (1.86) and 2.22 degrees (1.69) respectively. The measured reference angles of the template and cut guides were 31.27 and 29.60 degrees respectively. Individual and cross-surgeon analysis of outcomes found no significant differences when comparing wedge angle or coplanarity with either method regardless of surgeon experience. However, mean wedge angle of group G was significantly closer to the measured reference angles than group T (p < 0.01).

CONCLUSION

 Use of a fixed-angle surgical wedge guide was successful in consistently producing accurate closing wedge ostectomies regardless of surgeon experience. These results show that use of the guide is a valid method for performing wedge ostectomies.

Radiographic determination of normal canine femoral alignment in the sagittal plane: A cadaveric pilot study

OBJECTIVE

To establish a reliable methodology for radiographic determination of alignment of the normal canine femur in the sagittal plane.

STUDY DESIGN

Cadaveric pilot study.

SAMPLE POPULATION

Twenty-nine cadaveric canine femurs.

METHODS

Femoral specimens were collected from the University of Missouri veterinary anatomy laboratory, and standardized sagittal plane radiographs were obtained. The anatomic and mechanical axes, joint orientation, lines and joint orientation angles were determined in the sagittal plane by using the center of rotation of angulation methodology. Landmarks were clearly described to allow repeatability and reliability of measurements. Three observers with various degrees of experience measured two centers of rotation of normal angulation, the anatomic caudoproximal femoral angle, and the mechanical caudodistal femoral angle for all femurs on three separate days. Interobserver and intraobserver reliability were measured by using two-way mixed intraclass correlation coefficients (ICC) with associated 95% CI.

RESULTS

Twenty-nine medium to large breed canine femora were measured. A high degree of correlation was present both among and between observers for all measurements performed, as defined by an ICC >0.8 for each.

CONCLUSION

The described methodology was reliable and repeatable for measurement of angulation of grossly normal canine femora in the sagittal plane when performed by observers with varying degrees of clinical experience, as evidenced by a high degree of correlation for all values measured.

CLINICAL SIGNIFICANCE

This methodology may be used for standardized evaluation of alignment of canine femora in the sagittal plane.

A computed tomographic graphical approach to guide correction of femoral torsion

OBJECTIVE

To report geometric methods to assess femoral transverse bone morphology and develop a virtual method to guide the surgical correction of femoral torsional deformities.

STUDY DESIGN

Observational study.

SAMPLE POPULATION

Sixteen client-owned dogs comprising 14 normal femurs and 14 femurs with angulation-rotation bone deformities.

METHODS

Femoral torsion angle was measured with computed tomographic (CT) three-dimensional (3D) multiplanar reconstruction. Distal femoral transverse morphology was estimated with geometric methods and compared to direct measurements to span a target 20° angle on 3D reconstructions. A virtual correction of 20° was performed, and 3D-printed bone models were created. Femoral torsion of corrected bone models was compared to precorrection.

RESULTS

Geometric estimates with an arc and chord of the metaphyseal area and chord of a best fit circle did not differ from direct measurement of femoral cortical length along the cranial cortex. Femoral torsion differed between normal femurs (25.8° ± 6°) and those with deformity (36.9° ± 8.4°, P < .001). Torsion that was measured on corrected 3D bone models did not differ from the expected torsion (preoperative +20°).

CONCLUSION

Geometric methods provided an accurate estimate of distal femoral transverse bone morphology. Rotation of the distal femur based on geometric methods resulted in an accurate correction of torsion.

CLINICAL SIGNIFICANCE

Femoral bone diameter can be measured on a CT cross-section, and rotation distance can be calculated to achieve a desired correction of torsion. This approach provides a simple and accurate method to guide the correction of femoral torsion.

Ex vivo evaluation of a novel surgical guide on the accuracy of closing wedge osteotomies

OBJECTIVE

To determine the influence of a novel surgical guide on the accuracy and technical difficulty of closing wedge osteotomies (CWO).

STUDY DESIGN

Ex vivo experimental study.

SAMPLE POPULATION

Canine tibia models (n = 40).

METHODS

A 20° cranial CWO (CCWO) was created without (standard procedure; STCCWO) or with the aid of a novel wedge osteotomy guide (WOCCWO). Procedures were performed by diplomate (n = 4) and resident (n = 6) surgeons, with each performing 2 STCCWO followed by 2 WOCCWO. To prevent bias, surgeons were unaware of the study purpose until after completing the STCCWO. The wedges were evaluated by comparing the deviation from the 20° target angle, divergence of the 2 osteotomies (osteotomy divergence angle [ODA]), and measurements of the wedge height at the caudomedial cortex (CMC) and caudolateral cortex (CLC). Technique difficulty was explored through a surgeon questionnaire.

RESULTS

The WOCCWO resulted in smaller mean ODA (WOCCWO = 0.86°, SD ± 0.38°, P < .001), and smaller mean difference between CMC and CLC (WOCCWO = 0.29 mm, SD ± 0.19, P < .001) than for the STCCWO (4.22°, SD ± 2.16° and 1.39 mm, SD ± 0.65 respectively). Deviation from the target 20° wedge angle was greater after STCCWO (1.46°, SD ± 1.27°) than after WOCCWO (0.53°, SD ± 0.33°, P = .004). No difference was reported regarding the difficulty of the procedures, but resident surgeons stated that they were more likely to use the guide in a clinical setting compared with diplomates.

CONCLUSION

The wedge osteotomy guide improved the accuracy of CCWO compared with standard technique.

CLINICAL SIGNIFICANCE

The clinical significance of the differences detected in this study is unclear and warrants in vivo investigation.

Accuracy of patient-specific three-dimensional-printed osteotomy and reduction guides for distal femoral osteotomy in dogs with medial patella luxation

OBJECTIVE

To compare precorrectional and postcorrectional femoral alignment following distal femoral osteotomy using patient-specific 3-dimensional (3D)-printed osteotomy and reduction guides in vivo and ex vivo.

STUDY DESIGN

Prospective study.

SAMPLE POPULATION

Ten client-owned dogs and matching 3D-printed plastic bone models.

METHODS

Distal femoral osteotomy was performed via a standard approach using osteotomy and reduction guides developed with computer-aided design software prior to 3D-printing. Femoral osteotomy and reduction was also performed on 3D-printed models of each femur with identical reprinted guides. Femoral varus angle (FVA) and femoral torsion angle (FTA) were measured on postoperative computed tomographic images by 3 observers.

RESULTS

In vivo, the mean difference between target and achieved postoperative was 2.29° (±2.29°, P = .0076) for the FVA, and 1.67° (±2.08°, P = .300) for the FTA. Ex vivo, the mean difference between target and achieved postoperative was 0.29° (±1.50°, P = .813) for the FVA, and -2.33° (±3.21°, P = .336) for the FTA. Intraobserver intraclass correlation coefficients (ICC; 0.736-0.998) and interobserver ICC (0.829 to 0.996) were consistent with an excellent agreement.

CONCLUSION

Use of 3D-printed osteotomy and reduction guides allowed accurate correction of FTA in vivo and both FVA and FTA ex vivo.

CLINICAL SIGNIFICANCE

Use of 3D-printed osteotomy and reduction guides may improve the accuracy of correction of femoral alignment but warrant further evaluation of surgical time, perioperative complications, and patient outcomes compared with conventional techniques.