Radiographic measurement for femoral varus in Pomeranian dogs with and without medial patellar luxation

Combination of closing-wedge distal femoral osteotomy and modified tibial plateau levelling osteotomy for the treatment of medial patellar luxation and concomitant cranial cruciate ligament disease in dogs

Considering the prevalence of cranial cruciate ligament disease (CCLD) and concurrent medial patellar luxation (MPL) among dogs, and the concomitant bone deviations routinely identified, the aim of this study is to evaluate the efficacy of the combination between distal femoral osteotomy (DFO) and modified tibial plateau levelling osteotomy (mTPLO) for the treatment of MPL with distal femoral varus, tibial torsion, and CCLD. Dogs with concurrent MPL and CCLD that underwent DFO and mTPLO procedures were included. Subjective clinical evaluations of gait and pre-operative and immediate post-operative radiographic examinations were performed. Surgical data were documented. The anatomical lateral distal femoral angle (aLDFA), femoral varus angle, mechanical medial proximal tibial angle, and tibial plateau angle (TPA) were compared between the pre- and post-operative periods. A total of 12 dogs were included in this study. Closing-wedge DFO and mTPLO procedures were performed on 14 limbs. The mean pre-operative and post-operative aLDFA values were 104.8 ± 3.9° and 95.4 ± 2.4°, respectively. TPA values were 26.2 ± 3.7° pre-operatively and 6.3 ± 3.2° post-operatively. Bone healing was observed in 7.1 %, 71.3 %, and 85.5 % of patients at the first, second, and third follow-up, respectively. Lameness was resolved in 28.5 %, 78.5 %, and 100 % at 30, 60, and 90 days, respectively. No major peri- or post-operative complications were reported. The combination of mTPLO and DFO aligns the stifle extensor mechanism, promoting dynamic stabilization. It can be considered for the treatment of concurrent MPL and CCLD in dogs, performed as a single procedure, and is associated with favorable short-term outcomes.

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.

Statistical shape modeling of the geometric morphology of the canine femur, tibia, and patella

Bone morphometry varies among dogs of different sizes and breeds. Studying these differences may help understand the predisposition of certain breeds for specific orthopedic pathologies. This study aimed to develop a statistical shape model (SSM) of the femur, patella, and tibia of dogs without any clinical orthopeadic abnormalities to analyze and compare morphological variations based on body weight and breed. A total of 97 CT scans were collected from different facilities and divided based on breed and body weight. The 3D models of the bones were obtained and aligned to a coordinate system. The SSM was created using principal component analysis (PCA) to analyze shape variations. The study found that the first few modes of variation accounted for a significant percentage of the total variation, with size/scale being the most prominent factor. The results provide valuable insights into normal anatomical variations and can be used for future research in understanding pathological bone morphologies and developing 3D imaging algorithms in veterinary medicine.

3D Slicer open-source software plug-in for vector-based angle calculation of canine hind limb alignment in computed tomographic images

BACKGROUND

Severe and complex angular limb deformities in dogs require accurate morphological assessment using diagnostic imaging to achieve successful orthopedic surgery. Computed tomography (CT) is commonly used to overcome projection errors in two-dimensional angular measurements of dog hindlimb alignment. Three-dimensional volume rendering (VR) techniques permit virtual positioning and variable projection, but the final CT-image that defines the projection plane for angular measurements remains two-dimensional.

OBJECTIVE

We wanted to develop a true three-dimensional open-source technique to measure the alignments of the hind limbs of dogs in CT scanners.

METHODS

We developed an open-source 3D Slicer plug-in, to perform angular measurements using vector calculations in three-dimensional space. In 113 CT-scans of canine pelvic limbs, femoral torsion, femoral varus, femorotibial rotation, tibial torsion, tibial varus and tibiotalar rotation angles were calculated and compared to an already validated technique using VoXim®.

RESULTS

Reference points were identified and measurements were possible in the 113 acquisitions. The greatest difference between the two techniques was 1.4° at only one tibial torsion angle. Mean values for all Bland-Altman plots did not show significant differences and were less than 0.07° for all comparisons.

DISCUSSION

Based on these results we considered angular measurements of canine hind limb alignment in CT scans using the 3D Slicer extension program sufficiently accurate for clinical orthopedic and surgical purposes in veterinary medicine.

CONCLUSION

With our open-source 3D Slicer extension software, we provide a free accessible tool for veterinary orthopedic surgeons and thus we hope to improve angular measurements in CT-scans of canine hind limb deformities through true three-dimensionality.

Evaluation of Surgical Technique and Clinical Results of a Procedure-Specific Fixation Method for Tibial Tuberosity Transposition in Dogs: 37 Cases

OBJECTIVE

 The aim of this study was to describe the use of a procedure-specific fixation method for tibial tuberosity transposition and report clinical outcome.

STUDY DESIGN

 This is a multi-institutional case series, evaluating 37 cases that were treated surgically for medial patellar luxation (MPL) and in which the tibial tuberosity transposition (TTT) was performed using the Rapid Luxation Plating System (RLPS). Surgical technique, implants, clinical outcome, and complications are reported.

RESULTS

 Surgery was successfully performed in dogs weighing 2.5 to 36.2 kg. Postoperative minor complications occurred in 13 cases (35%) and major complications occurred in 3 cases (8%). No implant-related complications or tibial tuberosity avulsions or fractures were seen. Outcome related to surgery was good or excellent in all cases.

CONCLUSION

 The RLPS for TTT provides a feasible technique in a large range of patients with MPL and lowers the occurrence of implant-related complications and tibial tuberosity avulsion or fracture.

Comparison of CT-measured angles of pelvic limbs without patellar luxation of six canine breeds

Introduction

Dogs with medial patellar luxation can be affected by pelvic limb deformities whose corrective osteotomies and associated biomechanical rebalancing might provide higher success rates than standard surgical procedures limited to the stifle joint. In bilaterally affected canine patients, comparison with the contralateral normal limb is impossible. Reference values are useful for orthopedic decision-making. Inconsistency of published reference values might depend on methodology or canine breed. We hypothesized that canine pelvic limb alignment is breed-specific.

Methods

CT scans of 42 pelvic limbs of dog breeds predisposed for medial patellar luxation, with an orthotopic patellar position and stability were studied. Several angleswere measured with an open-source 3D Slicer plugin using vector calculations. The breeds were compared with a general linear model with a Bonferonni adjustment using SPSS.

Results

Chihuahuas, Pomeranians, Jack Russel Terriers, Pugs, French Bulldogs, Maltese were examined. In the order of the listed breeds, the angles were as follows: 28.3°±10.7°, 20.1°±2.9°, 35.4°±6.9°, 32.8°±3.0°, 19.0°±7.1°, 26.6°±5.3° for the antetorsion, 5.3°±1.8°, 2.8°±2.8°, 8°±4.4°, 3.8 °±3.1°, 4.7°±3.3°, 2.3°±3.3° for the femoral varus, of -5.5°±6.2°, 1.1°±4.1°, -5.2°±9.5°, 6.1°±8.0°, -0.1°±5.9°, -9.2°±4.7° for the tibial torsion, 2.0°±2.9°, 2.1°±2.7°, 6.4°±6.8°, 0.0°±5.7°, 3.0°±5.8°, 8.8°±8.6° for the tibial valgus, 1.2°±10.4°, 1.8°±3.4°, -1.7°±4.9°, -1.7°±9.4°, 5.1°±8.8°, -0.2°±8.6° for the femorotibial rotation and -3.4°±2.2°, 1.1°±4.1°, -2.8°±3.4°, -5.2°±4.0°, -2.1°±4.4°, -5.4°±3.7° for the tibiotalar rotation. There were significant differences between breeds in femoral torsion, femoral varus, and tibial torsion angles, but no significant differences in tibial valgus, femorotibial, and tibiotalar rotation angles.

Discussion

Our hypothesis is therefore partially correct. Our results are limited to small dogs prone to medial patellar luxation and might not be generalized. To establish robust reference values larger case numbers and more breeds should be evaluated. In conclusion, canine pelvic limb alignment reference values for small dogs with a predisposition for medial patellar luxation should be considered breed-specific.

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.

Accuracy of Caudocranial Canine Femoral Radiographs Compared to Computed Tomography Multiplanar Reconstructions for Measurement of Anatomic Lateral Distal Femoral Angle

OBJECTIVE

 This study aimed to compare the accuracy of sternal recumbency caudocranially obtained radiographs of canine femora to computed tomographic (CT) frontal plane reconstructions of the same femora for assessing anatomic distal lateral femoral angles (aLDFA).

STUDY DESIGN

 Multicentre, retrospective study utilizing 81 matched radiographic and CT studies of clinical patients undergoing assessment for various issues were reviewed. Anatomic lateral distal femoral angles were measured, and accuracy assessed with descriptive statistics and Bland-Altman plot analysis, with CT considered the reference standard. Sensitivity and specificity of a cut-off for measured aLDFA (102 degrees) were determined to assess radiography as a screening tool for significant deformity.

RESULTS

 Radiographs on average overestimated aLDFA by 1.8 degrees compared to CT. Bland-Altman analysis identified a 15.4 degrees 95% limit of agreement range and a tendency for greater overestimation at higher average measured value. Radiographic measurement of aLDFA of 102 degrees or less had a 90% sensitivity, 71.83% specificity, and 98.08% negative predictive value for the CT measurement being less than 102 degrees.

CONCLUSION

 Accuracy of aLDFA measurement by caudocranial radiographs does not demonstrate sufficient accuracy when compared to CT frontal plane reconstructions with unpredictable differences. Radiographic assessment is a useful screening tool to exclude animals with a true aLDFA of greater than 102 degrees with a high degree of certainty.

Comparison of Hindlimb Conformation in Cats with and without Medial Patellar Luxation

OBJECTIVES

 Medial patellar luxation (MPL) is the most common developmental cause of hindlimb lameness in cats. The association between femoral and tibial conformation and MPL measured on computed tomography (CT) has not been reported in cats. The aims were to report femoral and tibial conformation in cats with and without MPL and to report normal femoral and tibial angles.

METHODS

 Angle of inclination of femoral neck (AI), anatomical lateral distal femoral angle (aLDFA), femoral trochanteric angle (FCT), angle of anteversion of femoral neck (AA), distal and proximal anteversion angle (DAA/PAA), overall tibial valgus (TV), tibial torsion (TT), tibial tuberosity displacement (TTD) and trochlear depth:patellar thickness ratio (T:P) were measured by three observers on CT of cats with and without MPL. Comparisons were made between groups. Inter-observer intraclass correlation coefficient (ICC) was calculated.

RESULTS

 Sixteen cats were recruited: eight control and eight with MPL. The aLDFA, PAA, TT, TTD and T:P were significantly less in cats with high-grade MPL. The AI, FCT, AA, DAA and TV were not significantly different. A high correlation was shown with inter-observer ICC in 33.33% and good correlation in 26.67% when comparing measurements between observers.

CLINICAL SIGNIFICANCE

 This study suggests that cats with high-grade MPL have decreased TT, TTD and T:P and may require tibial tuberosity transposition and femoral trochleoplasty. The PAA, TT and aLDFA were decreased, although clinical significance may vary and these cats may not require correctional osteotomies. Results should be interpreted with caution as high/good levels of inter-observer ICC occurred in less than two-thirds of cases between observers.

Computed tomographic angular measurements using a bone-centered three-dimensional coordinate system are accurate in a femoral torsional deformity model and precise in clinical canine patients

Introduction

In small animal orthopedics, angular measurements in the canine femur are often applied in clinical patients with bone deformities and especially in complex and severe cases. Computed tomography (CT) has been shown to be more precise and accurate than two-dimensional radiography, and several methods are described. Measurement techniques evaluated in normal bones must prove accuracy in deformed bones in clinical settings.

Objectives

The goals of our study were to evaluate the accuracy of canine femoral torsion angle measurements in a femoral torsional deformity model and to test repeatability and reproducibility of canine femoral neck inclination, torsion, and varus angle measurements in CT datasets of dogs applying a CT-based technique using a three-dimensional (3D) bone-centered coordinate system.

Materials and methods

For precision testing, femoral torsion, femoral neck inclination, and femoral varus angles were measured in CT data of 68 canine hind limbs by two operators, and their results were compared. For accuracy testing, a femoral torsional deformity model was preset from 0° to +/-90° with a goniometer and scanned. Torsion angles were measured in the CT data and compared to the preset value.

Results

In the femoral torsion model, the Bland-Altman plots demonstrated a mean difference of 2.11°, and the Passing-Bablok analysis demonstrated a correlation between goniometer and CT-based measurements. In the clinical CT scans, intra- and interobserver agreement resulted in coefficients of variation for repeated measurements (%) between 1.99 and 8.26 for the femoral torsion, between 0.59 and 4.47 for the femoral neck inclination, and between 1.06 and 5.15 for the femoral varus angles.

Discussion

Evaluation of femoral malformations with torsional deformities is the target area of this technique. Further studies are required to assess its value in different types, degrees, and combinations of osseous deformities and to establish normal reference values and guidelines for corrective osteotomies.

Conclusion

Based on the results of this study, the accuracy of the torsion angle measurements and the precision of inclination, torsion, and the varus angle measurements were considered acceptable for clinical application.

Introduction of a bone-centered three-dimensional coordinate system enables computed tomographic canine femoral angle measurements independent of positioning

Introduction

Measurement of torsional deformities and varus alignment in the canine femur is clinically and surgically important but difficult. Computed tomography (CT) generates true three-dimensional (3D) information and is used to overcome the limitations of radiography. The 3D CT images can be rotated freely, but the final view for angle measurements remains a subjective variable decision, especially in severe and complex angular and torsional deformities. The aim of this study was the development of a technique to measure femoral angles in a truly three-dimensional way, independent of femoral positioning.

Methods

To be able to set reference points in any image and at arbitrary positions of the CT series, the 3D coordinates of the reference points were used for mathematical calculation of the angle measurements using the 3D medical imaging Software VoXim^®. Anatomical reference points were described in multiplanar reconstructions and volume rendering CT. A 3D bone-centered coordinate system was introduced and aligned with the anatomical planes of the femur. For torsion angle measurements, the transverse projection plane was mathematically defined by orthogonality to the longitudinal diaphyseal axis. For varus angle measurements, the dorsal plane was defined by a femoral retrocondylar axis. Independence positioning was tested by comparison of angle measurement results in repeated scans of 13 femur bones in different parallel and two double oblique (15/45°) positions in the gantry. Femoralvarus (or valgus), neck version (torsion), and inclination angles were measured, each in two variations.

Results

Resulting mean differences ranged between -0.9° and 1.3° for all six determined types of angles and in a difference of <1° for 17 out of 18 comparisons by subtraction of the mean angles between different positions, with one outlier of 1.3°. Intra- and inter-observer agreements determined by repeated measurements resulted in coefficients of variation for repeated measurements between 0.2 and 13.5%.

Discussion

The introduction of a bone-centered 3D coordinate system and mathematical definition of projection planes enabled 3D CT measurements of canine femoral varus and neck version and inclination angles. Agreement between angular measurements results of bones scanned in different positions on the CT table demonstrated that the technique is independent of femoral positioning.

Inter- and Intra-Observer Variations in Radiographic Evaluation of Pelvic Limbs in Yorkshire Terriers with Cranial Cruciate Ligament Rupture and Patellar Luxation

The main aims of the study were to describe bone alignment differences in Yorkshire Terriers (YT) with cranial cruciate ligament rupture (CCLR), patellar luxation (PL), or with a combination of both (CCLR + PL); to verify the theory of increased strain on cranial cruciate ligament (CrCL) due to PL as a predisposing factor; and to evaluate intra- and inter-observer variability of the protocols developed for measurement of femoral and tibial alignment in Yorkshire Terriers. Fifty-five hindlimbs of YT were divided into four groups: Control, CCLR, PL, and CCLR + PL. Thirty parameters were radiographically evaluated including hip joint, femoral, tibial, and intercondylar fossa (ICF) parameters. Three observers evaluated all parameters on two separate occasions with a twelve-week interval between measurements. Significant differences in conjunction with CCLR and PL theories between groups were noticed in: Norberg angle (NA), quadriceps angle (Qa), anatomic lateral distal femoral angle (aLDFA), femoral varus (FVA), mechanical cranial proximal tibial angle (mCrPTA), mechanical caudal proximal tibial angle (mCdPTA), tibial plateau angle (TPA), distal tibial axis/proximal tibial axis angle (DPA). Some interesting findings are the similarity of values between Control and CCLR vs. CCLR + PL and PL groups in Na, Qa, aLDFA; between CCLR + PL and PL in FVA and a significantly lower age of dogs in CCLR + PL compared to CCLR group. Based on our results, we can conclude that YT with different clinical findings have differing bone morphology. Moreover, these findings may support PL as a predisposing factor for CCLR in small breeds. Measurements in which excellent inter- observer agreement was achieved may be used for surgical planning or for further discussions.

Evaluation of the Femoral and Tibial Alignments in Dogs: A Systematic Review

Simple Summary

The measurement of limb alignments is an important topic in veterinary orthopedics. These measurements enable veterinarians to assess normal limb functions, diagnose congenital or acquired disorders, and plan proper treatment protocols. Different measurement methods have been reported for fore- and hindlimb measurements in the literature, and reference ranges have been published for different breeds. These standard values can be compared with the measured values in small animal clinics, especially in the case of bilateral deformities, in which a sound extremity does not exist to provide a reference value. In this review, we aimed to compile the relevant values from the literature, sorting them according to the dog breed and the health status of the dog.

Abstract

The assessment of limb conformations in veterinary orthopedics is a significant tool used to determine the quantitative degree of limb malalignments. As in human medicine, various studies have been undertaken in veterinary medicine to determine the values in different dog breeds and to determine the values in healthy and diseased dogs. The objectives of this systematic review were to evaluate the reported values in these articles separately, to compile the standard values, and to compare the values between dogs with and without various orthopedic diseases. All of the articles included in this systematic review were collected by screening the Scopus, PubMed/Medline, and Web of Science databases. The articles were evaluated according to the measured alignments, imaging methods, dog breeds, and the health status of the dogs. Each alignment was investigated separately, and the results are summarized. Twenty-nine studies were included in this systematic review. According to the studies, in the frontal plane, distal femoral alignments, as well as proximal and distal tibial alignments, corresponded to the severity of the medial patellar luxation. The difference between affected and non-affected dogs with cranial cruciate ligament disease was limited to the proximal tibial alignments in the sagittal plane.

Post-operative radiographic measures of pelvic limb alignment in dogs with medial patellar luxation after trochlear wedge recession versus trochlear block recession surgery

Background and Aim:

Anatomical and mechanical femoral angles are quite different among dog breeds. Most published data are about large dog breeds, however, medial luxation of patella is more common in small breeds. Measures of pelvic limb alignment are important for outcome of patellar luxation surgery. Therefore, the aim of the present study was to compare the values of anatomical and mechanical femoral and tibial angles in dogs before, immediately after, and 1 month after surgery for correction of medial patellar luxation (MPL).

Materials and Methods:

The study was conducted with 54 dogs (67 stifle joints) from four small breeds that underwent surgery by either trochlear block recession (36 stifle joints) or trochlear wedge recession (31 stifle joints) techniques.

Results:

In both trochleoplasty techniques, statistically significant differences in the values of the anatomical medial proximal femoral angle (aMPFA), anatomical lateral distal femoral angle (aLDFA), and femoral varus angle (in MPL Grade II) and of aMPFA and Q-angle (in MPL Grade III) were found out.

Conclusion:

After block recession surgery, more angles were positively influenced and this effect was more pronounced in patients with MPL Grade II.

Proximodistal and caudocranial position of the insertion of the patellar ligament on the tibial tuberosity and patellar ligament length of normal stifles and stifles with grade II medial patellar luxation in small-breed dogs

OBJECTIVE

To assess the role of the proximodistal and caudocranial relative position of the patellar ligament insertion on the tibia and patellar ligament length-to-patellar length ratio (PLL:PL) in small-breed dogs with and without grade II medial patellar luxation (MPL).

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Dogs weighing ≤15 kg, including 43 stifles with MPL and 34 control stifles.

METHODS

The proximodistal and caudocranial relative position of the patellar ligament insertion was determined as a ratio using the vertical (VTT) and horizontal distance (HTT) between the tibial tuberosity insertion and the tibial plateau divided by the tibial plateau length (TPL). In addition, PLL:PL and tibial plateau angle (TPA) were determined.

RESULTS

The VTT:TPL ratio was lower in affected stifles (95% CI: 0.86-0.94) than in the control group (0.93-1.01; p = .01). No other difference was identified between affected and normal stifles.

CONCLUSION

The only difference identified in this study consisted of a more proximal position of the patellar ligament insertion in the stifles of small-breed dogs with grade II MPL.

CLINICAL SIGNIFICANCE

The more proximal position of the patellar ligament insertion will result in a more proximal position of the patella in the trochlear groove and may contribute to the development of MPL. Potentially, this will also affect the risk of recurrence of MPL after surgical treatment.

Computed Tomographic Measurement of Trochlear Depth in Three Breeds of Brachycephalic Dog

OBJECTIVE

 The aim of this study was to determine the trochlear sulcus depth of three common brachycephalic breeds at risk of medial patellar luxation.

STUDY DESIGN

 Retrospective blinded clinical study using a previously validated ratio (T/P) of maximal trochlear sulcus depth (T) and maximal patellar craniocaudal thickness (P) measured on computed tomography, to assess trochlear sulcus depth in Pugs, French Bulldogs and English Bulldogs without clinical patellar luxation. The effect of breed on T/P was assessed using one-way linear regression models.

RESULTS

 The mean T/P was affected by breed (p < 0.001). There was significant difference between Pugs (0.45) and French Bulldogs (0.38) and between Pugs and English Bulldogs (0.4). There was no significant difference between Pugs and previously published data for non-brachycephalic and mixed breed dogs (0.46) (p = 0.39). Mean T/P was significantly reduced in the brachycephalic dog breeds combined compared with the previously published data (p < 0.001).

CONCLUSION

 The trochlear sulcus varies by breed and was more shallow in French and English Bulldogs than Pugs, hence a shallow sulcus may be a breed-driven characteristic. The three breeds assessed are at risk of patellar luxation but sulcus depth did not directly correlate with previously published risk factors-the contribution of sulcus depth to the aetiopathogenesis of patellar luxation remains unclear. Trochlear recession to achieve patellar coverage of 50% may be excessive considering maximal breed normal depth.

Segmental Femoral Ostectomy for the Reconstruction of Femoropatellar Joint in Dogs with Grade IV Medial Patellar Luxation

OBJECTIVE

 The aim of this study was to describe a new surgical method of segmental femoral ostectomy for the reconstruction of the femoropatellar joint (FPJ) in dogs with medial patellar luxation (MPL) grade IV.

STUDY DESIGN

 The medical records of six dogs that underwent segmental femoral ostectomy to reconstruct the FPJ for MPL grade IV were retrospectively reviewed. The data included breed, age, body weight, comorbidities, history of orthopaedic abnormalities, pre- and postoperative radiographic findings, morphological indicators measured on three-dimensional computed tomographic multiplanar reconstruction images, surgical methods and postoperative complications.

OUTCOMES

 Eleven hindlimbs with MPL grade IV in six dogs underwent segmental femoral ostectomy to reconstruct the FPJ with the four basic surgical procedures. Six stifle joints with femoral varus deformity were treated by closing wedge ostectomy and segmental ostectomy, while five stifle joints were treated by segmental ostectomy alone. The mean resected femoral length was 11.7 mm. The mean resected femoral length relative to the preoperative femoral length was 14.3%. The stability and congruity of the FPJ was markedly improved, with an increased range of motion in all dogs compared with their preoperative status.

CONCLUSION

 Segmental femoral ostectomy was a useful treatment method for MPL grade IV with shortened quadriceps muscle length relative to the femoral length. Reconstruction of the FPJ is important for recovery of limb function.

Femoral and tibial alignments in chihuahuas with patellar luxation by radiograph: Angular values and intra- and inter-observer agreement of measurements

Measurement of fore and pelvic limb alignment in veterinary orthopedics is significant, as it is in human medicine. The establishment of reference ranges for alignments and comparing measured ranges in diseased animals to these reference values would allow veterinarians to specify the quantitative degree of an angular deformity, plan suitable treatments and evaluate treatment outcomes. Patellar luxation is a common orthopedic disease in small animal clinics. Severe grades of MPL may present with bone deformities or abnormal alignments; therefore, evaluation of the measurement methods of femoral and tibial alignment in dogs with different grades of patellar luxation to assess the accuracy and reliability of the measurements could be useful. In this retrospective study radiographs of 21 client-owned Chihuahuas that had been presented to the Small Animal Surgery of Vetmeduni Vienna from 2012-2016 with a diagnose of patellar luxation were selected. The measurements were performed on frontal, lateral and axial view radiographs to determine the femoral and tibial angles and to evaluate the intra- and inter-observer variabilities of the protocol. Radiographs of each dog were investigated by three observers. Intra-observer variability was based on measurements by each observer who repeated the protocol two times to evaluate repeatability. Inter-observer variability was based on the measurements between the three observers to evaluate the reproducibility of the protocol. The results of the study showed that 92.85% of inter-observer ICC (intra-class correlation coefficient) had high correlation, and the remaining 7.15% had good correlation. Intra-observer ICCs for measurements of the first observer were 28.57% high correlation and 50% good correlation. For the second observer, 100% high correlation was recorded, and for the third observer 71.42% high correlation and 14.28% good correlation was recorded. These results show that the selected methods have high correlation and could be used as a reliable method in veterinary orthopedics.

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.

Radiographic determination of pelvic limb orthopaedic measurements in maned wolf (Chrysocyon brachyurus)

The aim of this study was to determine some radiographic reference values for hip joint, femur and patella in maned wolves. Ten maned wolves (Chrysocyon brachyurus), five live (G1) and five cadavers (G2), were used. There were no statistically significant differences in the radiological measurements between right and left pelvic limbs of the G1 and G2, except for mechanical lateral proximal femoral angle (mLPFA) in both Groups. The comparison of the measurements between Groups showed difference only for mechanical lateral distal femoral angle (mLDFA). Norberg angle values were 113.1° and 112.9° for G1 and G2. The values of femoral angle of inclination by Hauptman A and Hauptman B methods were 139.7° and 128.6° for G1, and 139.3° and 128.7° for G2. Femoral varus angle values were 5.5° for G1 and 3.9° for G2. The values of anatomic lateral distal femoral angle and anatomic lateral proximal femoral angle were 96.8° and 95.2° for G1, and 95.0° and 95.6° for G2. The values of mLDFA for G1 and G2 were 96.5° and 95.7°. The values of mLPFA were 95.8 (right) and 93.5 (left) for G1, and 95.7 (right) and 93.8 (left) for G2. The values of patellar ligament length, patellar length and L:P ratio were 4.6, 2.4 cm and 1.9 for G1, and 4.4, 2.3 cm and 1.8 for G2. In conclusion, the radiographic reference values described for the hip joint, the femur and the patella, may be useful in the diagnosis of diseases and deformities in maned wolves.

Histopathological and electron microscopic study in dogs with patellar luxation and skin hyperextensibility

Patellar luxation is abnormal displacement of the patella from the femoral trochlear groove. It is seen primarily in small breed dogs and causes pain and limited mobility of the stifle joint. This study aimed to investigate the relationship among patellar luxation, skin extension, and skin collagen fibril diameter. Nine dogs with patellar luxation and five clinically normal dogs were enrolled in the study. We measured the skin extension and investigated the ultrastructure of the skin and patellofemoral ligament by histopathology and transmission electron microscopy. The mean skin extension in dogs with patellar luxation was 18.5 ± 5.5% which is greater than the reference value (14.5%). Mean skin extension in controls was 8.8 ± 1.7% and was within the normal range. In dogs with patellar luxation, histopathology of the skin and patellofemoral ligament showed sparse and unevenly distributed collagen fibers. Transmission electron microscopy identified poorly organized, irregularly shaped, thin collagen fibrils. Collagen fibril thickness in dogs with patellar luxation was significantly less than fibril thickness in controls (P<0.001). There was a significant negative correlation (ρ= −0.863; P<0.001) between skin collagen fibril diameter and skin extension. Skin extension was correlated with patellar luxation and disease severity. Dogs with patellar luxation, joint dysplasia, and hyperextensible skin appear to be pathologically related. This might represent a phenotype of the Ehlers–Danlos syndrome, a hereditary connective tissue disorder in humans.

Patellar luxation in dogs

Patellar luxation is a common orthopedic problem in dogs. Medial luxation is more common than lateral luxation and is usually diagnosed in dogs of small breed. Diagnosis is based on clinical evidence of patellar instability; however, diagnostic imaging is required to assess the amount of skeletal deformity and then the most appropriate method of treatment. Surgical options include both soft tissue and osseous techniques, however, in most of the cases, a combination of more procedures is used to achieve the correction of the luxation. Complication rate is generally low and the most common complications include reluxation and implant-associated complications. Prognosis is generally favorable, with most of the dogs returning to normal limb function. This article describes patellar luxation features in dogs, including clinical presentation, diagnosis, and treatment options available.

Radiographic measurements of the hindlimbs in crab-eating foxes (Cerdocyon thous, Linnaeus, 1766)

Life expectancy of crab-eating foxes in captivity is approximately 11 years, which favours the development of diseases including orthopaedic disorders. However, to understand disorders that may affect these animals, it is worth determining a normal range of measurements. Therefore, this study aimed to evaluate radiographic measurements of joint angles of the hindlimbs and the ratio of patellar ligament length to patellar length in healthy crab-eating foxes. Fifteen captive crab-eating foxes (Cerdocyon thous), eight males and seven females, aged more than 1 year old, weighing 5.5-7.9 kg were used. Anatomic and mechanical femoral joint angles were assessed in ventrodorsal radiographic views, and mediolateral views were taken to measure patellar ligament length and patellar length, and the tibial plateau angle. The right and left hindlimbs were evaluated. All measurements were conducted in triplicate by the same investigator. No statistically significant differences were observed between sides in the radiographic measurements. The anatomic lateral proximal femoral angle and the anatomic lateral distal femoral angle recorded mean values of 95.43° and 92.75°, respectively. The mechanical lateral proximal femoral angle and the mechanical lateral distal femoral angle recorded mean values of 93.39° and 96.75°, respectively. Inclination angles measured according to the Tomlinson, Hauptman A and Hauptman B methods were 133.80°, 147.32° and 128.63°, respectively. The tibial plateau recorded 18.77°, and the ratio of the patellar ligament length to the patellar length was 1.99. In conclusion, the collected data are important to characterize the normal values of crab-eating fox limbs.

Comparison of osteotomy technique and jig type in completion of distal femoral osteotomies for correction of medial patellar luxation

Objectives: Femoral osteotomies are frequently completed to correct malalignment associated with patellar luxation. The objectives of this study were to compare the use of: 1) two different types of jig; and 2) different types of osteotomy in the realignment of canine femoral bone models which possessed various iterations of angular deformity.

Methods: Models of canine femora possessing distal varus, external torsion and a combination of varus and torsion underwent correction utilizing two alignment jigs (Slocum jig and Deformity Reduction Device) and either a closing wedge ostectomy (CWO) or an opening wedge osteotomy (OWO). Post-correctional alignment was evaluated by radiographic assessment and compared between groups.

Results: The use of the Slocum jig resulted in frontal plane overcorrection when used with CWO in models of femoral varus, and when used with OWO in models of femoral varus and external torsion when compared to other techniques. The Deformity Reduction Device tended to realign the frontal plane closer to the post-correction target value in all angulation types. The use of both jigs resulted in undercorrection in the transverse plane in models with varus and torsion.

Clinical significance: Jig selection and osteotomy type may lead to different post-correctional alignment results when performing distal femoral osteotomies. Whereas OWO allows accurate correction when used with either jig to address frontal plane deformities, the Deformity Reduction Device can be utilized with both CWO and OWO to correct torsion-angulation femoral deformities to optimize frontal plane alignment.

Major complications and risk factors associated with surgical correction of congenital medial patellar luxation in 124 dogs

Dogs treated for congenital medial patellar luxation were reviewed for the purpose of determining the incidence of postoperative major complications requiring surgical revision and the risk factors for their occurrence. Major complications occurred in 18.5% of the patellar luxation stabilization procedures with implant associated complications being the most frequent, patellar reluxation the second, and tibial tuberosity avulsion the third most common major complication. Other complications included patellar ligament rupture and trochlear wedge displacement. When recession trochleoplasty was performed in addition to tibial tuberosity transposition, a 5.1-fold reduction in the rate of patellar reluxation was observed. Release of the cranial belly of the sartorius muscle further reduced the incidence of patellar reluxation, while patella alta (pre- or postoperative) and patellar luxation grade were not found to influence the rate of reluxation. Tibial tuberosity avulsion was 11.1-times more likely when using a single Kirschner wire to stabilize a transposition, compared with two Kirschner wires. Independent to the number of Kirschner wires used, the more caudodistally the Kirschner wires were directed, the higher the risk for tibial tuberosity avulsion. Tension bands were used in 24.4% of the transpositions with no tuberosity avulsion occurring in stifles stabilized with a tension band. Overall, grade 1 luxations had a significantly lower incidence of major complications than other grades, while body weight, age, sex, and bilateral patellar stabilization were not associated with risk of major complication development.

Impact of femoral varus on complications and outcome associated with corrective surgery for medial patellar luxation

OBJECTIVES

To evaluate the association of femoral varus with postoperative complications and outcome following standard corrective surgery for medial patellar luxation (MPL) without distal femoral osteotomy (DFO) in dogs.

METHODS

In a retrospective study spanning a 12 year period, 87 stifles with MPL that were treated by standard surgical techniques were included. Inclination angle (ICA), femoral varus angle (FVA), anatomical lateral distal femoral angle (aLDFA), and mechanical lateral distal femoral angle (mLDFA) were measured. Postoperative complications were noted and outcome evaluated. Associations between potential risk factors and both complication rate and outcome were assessed.

RESULTS

Postoperative complications occurred in 19 stifles, five of which were major. There was no evidence of an association between FVA (p = 0.41) or aLDFA (p = 0.38) and any complication. There was also no evidence of an association between FVA (p = 0.31) or aLDFA (p = 0.38) and any major complication. Dogs with a larger aLDFA had increased odds of a poorer outcome (p = 0.01) as did dogs that suffered a major complication (p = 0.0001).

CLINICAL SIGNIFICANCE

Based on radiographic measurements, there is no evidence of an association between FVA and the incidence of postoperative complications following standard MPL correction. Traditional surgical techniques appear to be appropriate for most cases of MPL and further work is required to better define selection criteria for including DFO in the treatment of these cases.

Pelvic limb alignment measured by computed tomography in purebred English Bulldogs with medial patellar luxation

OBJECTIVES

The aim of the study was to describe the differences in pelvic limb alignment between healthy purebred English Bulldogs and those with medial patellar luxation through the measurement of femoral and tibial angles on computed tomography images in multiplanar reconstruction modality (MPR-CT).

METHODS

Twenty-one purebred English Bulldogs were included and divided into two groups: one including healthy dogs (15 limbs) and the other including those with medial patellar luxation (24 limbs). Three different observers used MPR-CT to measure the following angles: anatomical lateral proximal femoral angle (aLPFA), anatomical lateral distal femoral angle (aLDFA), mechanical lateral proximal femoral angle (mLPFA), mechanical lateral distal femoral angle (mLDFA), angle of inclination of the femoral neck (AI), angle of anteversion (AA), mechanical medial proximal tibial angle (mMPTA), mechanical medial distal tibial angle (mMDTA), mechanical caudal distal tibial angle (mCdDTA), mechanical caudal proximal tibial angle (mCdPTA), and the tibial torsion angle (TTA). A Mann-Whitney U test was used to compare each variable in both groups.

RESULTS

The values for aLDFA and mLDFA in the medial patellar luxation population were significantly increased compared to healthy subjects (p <0.05). No significant differences were observed for the other variables.

CLINICAL SIGNIFICANCE

In our population, an increased distal femoral varus was associated with medial patellar luxation. Our results could be useful to determine whether or not angular deformity of the femur is present and help determine the degree of correction necessary to restore alignment.

Computed tomographic evaluation of femoral and tibial conformation in English Staffordshire Bull Terriers with and without congenital medial patellar luxation

OBJECTIVE

To compare hindlimb conformation of English Staffordshire Bull Terriers with and without medial patellar luxation using computed tomography.

METHODS

Hindlimb computed tomography (CT) was performed on six English Staffordshire Bull Terriers with grade II or III medial patellar luxation, and six without medial patellar luxation. Inclination angle, femoral condyle trochanteric angle, anteversion angle (AA), distal anteversion angle (DAA), proximal anteversion angle (PAA), femoral varus angle (FVA), tibial valgus angle (TVA), and tibial torsion angle (TTA) were measured. Student's T-test was conducted to compare normal limbs to limbs with medial patellar luxation, all limbs of dogs with medial patellar luxation to limbs of the control group, and medial patellar luxation affected limbs (normal limbs of unilaterally affected dogs excluded) to the control group. P-values less than 0.05 were considered significant.

RESULTS

Two dogs with medial patellar luxation were only affected unilaterally. Limbs of English Staffordshire Bull Terriers with medial patellar luxation had significantly diminished AA and DAA, in addition to decreased TVA. These differences were similar regardless of how the unaffected limbs from affected dogs were treated in our analysis.

DISCUSSION AND CONCLUSION

Medial patellar luxation in this population of English Staffordshire Bull Terriers was characterized by a decrease in femoral anteversion, external rotation of the femoral diaphysis, and decreased tibial valgus. These findings may help inform clinical decision making when performing osteotomy for treatment of medial patellar luxation in this breed.

The epidemiology of patellar luxation in dogs attending primary-care veterinary practices in England

BACKGROUND

Canine patellar luxation is one of the most common orthopaedic disorders of dogs and is a potential welfare concern because it can lead to lameness, osteoarthritis and pain. However, there are limited epidemiological data on the disorder relating to the general population of dogs in England. This study aimed to investigate the VetCompass Programme database of dogs attending primary-care veterinary practices in England to report on the prevalence, risk factors and clinical management of diagnosed patellar luxation cases.

RESULTS

The study included all dogs with at least one electronic patient record in the VetCompass database from September 1(st), 2009 to August 31(st), 2014. Candidate patellar luxation cases were identified using free-text word searching of the clinical notes and VeNom diagnosis term fields. Univariable and multivariable binary logistic regression modelling was used for risk factor analysis. The overall dataset comprised 210,824 dogs attending 119 clinics in England. The prevalence of patellar luxation diagnosis in dogs was 1.30 % (95 % confidence interval (CI) 1.21-1.39). Of the 751 incident cases, 293 (39.0 %) received medical management, 99 (13.2 %) received surgical intervention and 28 (3.7 %) were referred for further management. Multivariable modelling documented 11 breeds with increased odds of patellar luxation compared with crossbred dogs, including the Pomeranian (odds ratio [OR]: 6.5, 95 % CI 4.0-10.7, P < 0.001), Chihuahua (OR: 5.9, 95 % CI 4.4-7.9, P < 0.001), Yorkshire Terrier (OR: 5.5, 95 % CI 4.3-7.1, P < 0.001) and French Bulldog (OR: 5.4, 95 % CI 3.1-9.3, P < 0.001). Dogs with bodyweight below their mean for breed and sex had a 1.4 times odds of diagnosis (95 % CI 1.2-1.6, P < 0.001). Dogs aged ≥ 12.0 years showed 0.4 times the odds (95 % CI 0.3-0.5, P < 0.001) compared with dogs aged < 3.0 years. Females had 1.3 times the odds (95 % CI 1.1-1.5, P < 0.001), neutered dogs had 2.4 times the odds (95 % CI 1.8-3.2, P < 0.001) and insured dogs had 1.9 times the odds (95 % CI 1.6-2.3, P < 0.001).

CONCLUSIONS

Patellar luxation warrants inclusion as a welfare priority in dogs and control strategies that include this disorder should be considered as worthwhile breeding goals, especially in predisposed breeds.

Evaluation of bone deformities of the femur, tibia, and patella in Toy Poodles with medial patellar luxation using computed tomography

OBJECTIVES

To evaluate morphological parameters of the femur, tibia, and patella in Toy Poodles with medial patellar luxation (MPL) using three-dimensional (3D) computed tomography (CT) and to compare these parameters between radiography and CT.

METHODS

Thirty-five hindlimbs of Toy Poodles were divided into normal and grade 2 and 4 MPL groups. The anatomical and mechanical lateral proximal femoral angle, anatomical and mechanical lateral distal femoral angle (aLDFA, mLDFA), femoral varus angle (FVA), inclination of the femoral head angle, procurvation angle, anteversion angle (AA), frontal angle of the femoral neck, mechanical medial proximal or distal tibial angle, mechanical cranial proximal or distal tibial angle, tibial plateau angle, tibial torsion angle (TTA), Z angle, relative tibial tuberosity width, ratio of the medial distance of tibial tuberosity to the proximal tibial width (MDTT/PTW), patella size, and the patellar ligament length: patellar length (L:P) ratio were evaluated on radiography and 3D CT.

RESULTS

The aLDFA, mLDFA, FVA, and TTA were significantly larger and the AA, MDTT/PTW, and patella were significantly smaller in the grade 4 MPL group. There were significant differences in many parameters between imaging tools, and CT was considered less susceptible to potential artefacts and rotational deformities.

CLINICAL SIGNIFICANCE

Toy Poodles with grade 4 MPL had significant femoral varus deformity, medial displacement of the tibial tuberosity, internal torsion of the proximal tibia, and hypoplasia of the patella.

Proximo-distal patellar position in three small dog breeds with medial patellar luxation

INTRODUCTION

Medial patellar luxation is thought to be associated with a high proximal position of the patella in the trochlear groove.

OBJECTIVE

To determine whether the ratio of patellar ligament length and patellar length (L:P) is influenced by the stifle angle (75°, 96°, 113°, 130°, and 148°) in small dog breeds and to compare the L:P ratio in dogs of three small dog breeds with and without medial patellar luxation.

METHODS

A mediolateral radiograph of the stifle joint was used to measure the L:P ratio in the stifle joints of dogs of three small breeds with and without medial patellar luxation. The L:P ratio was evaluated at five stifle angles (75°, 96°, 113°, 130°, and 148°) in 14 cadavers (26 stifle joints) of small dog breeds in order to identify the best stifle angle to measure the L:P ratio. Then the mean ± SD L:P ratio was calculated for normal stifles and stifles with medial patellar luxation grades 1, 2, and 3 in 194 Pomeranians, 74 Chihuahuas, and 41 Toy or Standard Poodles.

RESULTS

The L:P ratio was the same for all five stifle angles in the cadavers (p = 0.195). It was also not significantly different in the three breeds (p = 0.135), in normal and medial patellar luxation-affected stifles overall (p = 0.354), and in normal and medial patellar luxation-affected joints within each breed (p = 0.19).

CLINICAL SIGNIFICANCE

We conclude that a proximo-distal patellar position is not associated with medial patellar luxation in Pomeranians, Chihuahuas, and Toy or Standard Poodles. Thus a longer patellar ligament length does not play a role in the pathophysiology of medial patellar luxation in these small dog breeds.

Evaluation of surgical treatment of medial patellar luxation in Pomeranian dogs

In a prospective study, the outcome of surgical correction of medial patellar luxation of 70 stifle joints in 55 Pomeranian dogs was evaluated. Trochlear block recession alone was performed in 46 stifle joints, or in combination with tibial tuberosity transposition in 24 stifle joints in cases with grade II, III or IV medial patellar luxation. Additional procedures were performed to restore lateral and medial retinacular function. The recurrence of patellar luxation and the degree of lameness were evaluated up to at least 16 weeks after surgery. The overall recurrence rate was 10%. The outcome of surgery was considered good for grade II luxation with a 100% success rate. Recurrent medial patellar luxation was diagnosed in approximately 11% of dogs with grade III and in 36% of dogs with grade IV luxation. The postoperative lameness score decreased significantly in comparison with the preoperative score at four weeks and thereafter until the end of the study.