Tibial Plateau Angle Measurements Research Articles

Postoperative tibial plateau angle changes and their influence on ground reaction forces 6 months after TPLO: a prospective study.

The objectives of the study were to investigate the association between change in postoperative (post-op) tibial plateau angle (TPA) in dogs and cranial cruciate ligament disease (CCLD) after tibial plateau leveling osteotomy (TPLO) during 6 months on the post-op outcome. The inclusion criteria included 60 dogs with CCLD treated with TPLO fulfilled. TPA measurements were taken immediately post-op and 6 months post-op by three observers, and change in TPA was calculated. The outcome was evaluated using lameness score, owner questionnaire, and gait analysis performed preoperatively and 6 months post-op. The mean change in TPA was 0.22 ± 0.75°. The interobserver reliability for TPA measurements was excellent. No differences in TPA measurements between observers were found (p = 0.07-0.105). No association between the change in TPA and outcome was found. The multivariate linear regression model for the symmetry index of peak vertical force (SIPVF) 6 months post-op was significant (R 2 = 0.210; p = 0.031), and the TPA at 6 months post-op was the only significant factor (ß = 0.459; 95% CI: 0.41-1.44; p < 0.001), indicating that a lower TPA 6 months post-op results in lower SIPVF values. The study indicated that lower TPAs 6 months post-op lead to a more symmetrical gait in hindlimbs 6 months post-op. No other significant factor between post-op changes in TPA and outcome after TPLO was found. Our results showed little post-op TPA change up to 6 months. This indicates that change in TPA is not present as reported.

May a Single Presurgical High-Field MRI Sequence Replace Standard Radiographs for TPLO Surgical Planning in Dogs?

Cranial cruciate ligament (CCL) disease causes variable stifle instability assessed by specific clinical tests. Radiographs are performed to measure the tibial plateau angle (TPA) for planning tibial plateau leveling osteotomy (TPLO) surgery. Concomitant damage to other intra-articular structures, for which clinical detection is unreliable, may occur and potentially affect the surgical outcome. Joint assessment during TPLO through instrumented inspection is therefore advised, though it increases the risk of complications. Magnetic resonance imagingoffers a noninvasive alternative, adds information about intra- and periarticular structures, and could potentially be used for TPA measurements. This prospective study aimed to (1) assess the correlation between the TPA measured with the standard presurgical radiographs and with a single sagittal intermediate-weighted fat-saturated MRI sequence and (2) compare the surgical findings with the information obtained by the MRI sequence. Twenty-one stifles were included; TPA correlation using radiographs-MRI was available for 17 stifles, and surgery-MRI comparison was available for 18 stifles. A strong significant correlation was identified between the TPA measurements on radiographs-MRI (Pearson correlation coefficient 0.923; p-value <.0001). The sensitivity and specificity of MRI to detect surgically confirmed complete versus partial CCL rupture were 85.7% and 75%, respectively; MRI identified 7 of 8 surgically confirmed injured menisci and detected abnormal signal intensity in 8 of 10 medial menisci and nine caudal cruciate ligaments reported as normal intra-operatively. The MRI additionally identified abnormal subchondral bone signals in nine stifles and muscular hyperintensity in six cases. This presurgical MRI sequence might replace standard radiographs for TPA measurements and can provide information about concomitant joint injuries with potential prognostic impact.

Long-Term Changes in Tibial Plateau Angle (TPA) Following Tibial Plateau Leveling Osteotomy (TPLO) in Dogs-A Retrospective Study.

Cranial cruciate ligament rupture is a common orthopedic condition in dogs. Tibial plateau leveling osteotomy (TPLO) is a widely accepted method due to its success in stabilizing the stifle joint. This study aims to investigate the changes in the TPA over a 12-month follow-up period in dogs undergoing TPLO. An analysis of medical records from 60 dogs, aged 2 to 8 years and weighing between 7 and 59 kg, who underwent the TPLO procedure was conducted. TPA measurements were recorded before surgery, immediately after surgery, and during follow-up periods at 8 weeks, 6 months, and 12 months post-operation. Results showed a consistent increase in TPA over time, with the mean TPA rising from 4.98 degrees immediately post-surgery to 9.02 degrees at the 12-month follow-up. No patients exhibited a decrease in TPA during the study period. The mean difference between the final and initial TPA was 4.045 degrees, with patients exhibiting smaller initial TPAs showing less variation over time; Conclusions: This is the first report on long-term TPA changes following TPLO, offering essential insights into tibial remodeling and the potential for optimizing surgical outcomes. Based on the results, achieving a lower initial TPA (1-2 degrees) may reduce postoperative TPA changes, supporting more stable stifle function.

Tibial Plateau Angle Measurement in Dogs – Comparison of Three Different Methods

Abstract The aim of this study was to establish two new methods for measuring the tibial plateau angle (TPA): proximal tibial circle (PTC) as well as full tibial circle (FTC) method, and to test their reliability in comparison to the classical method (CM). Three radiologists implemented each method, and measurements were repeated three times. The results of consecutive measurements obtained by two observers had excellent reliability with an interclass correlation coefficient (ICC) greater than 0.9 for all methods, while measurements obtained by the third observer had good reliability for the CM (ICC=0.885) and PTC method (ICC=0.851). The results obtained by the three observers for all methods indicate good reliability for the PTC and FTC methods (ICC=0.848 and 0.880, respectively) and excellent reliability for CM (ICC = 0.909); the results of the different observers for each method were not significantly different. The significant difference resulting from the applied measurement method (ICC = 0.447 and P&lt;0.01) was confirmed. Statistically significant differences were not found between the CM and PTC method (P&gt;0.05), while differences between the PTC and FTC, as well as CM and FTC methods, were statistically significant (P&lt;0.01). New methods for TPA measurements based on shorter tibial axes may be an alternative to a method based on the full-length axis. A high correlation between the methods indicates the precision of each of them. Newly established methods can be used when the tarsal joint is not included in radiographs or is affected by degenerative changes, making use of the classical method not possible.

Cranial closing wedge ostectomies for management of canine cranial cruciate ligament insufficiency: Comparison and geometric modelling of errors

Variants of the cranial closing wedge ostectomy (CCWO) may be used to manage cranial cruciate ligament deficient stifles by reduction of the tibial plateau angle (TPA). Concerns have been raised about predictability of achieving target TPA, limb shortening, axis shift, and distalization of the tibial tuberosity. Landmarks derived from tibial radiographs (n=50) by 5 observers, along with outlines of the cranial and caudal proximal tibial cortices, were used to simulate six CCWO variants. Tested variants were Slocum-type (n=2), modified (n=2), isosceles, and anatomical-mechanical axis (AMA)-based CCWO. Observer specific landmarks were used to model pre- and postoperative errors in TPA measurement. Mean landmarks were used to compare key outcome variables between the variants, as well as modelling errors in positioning the wedge apex. Variants differed markedly in TPA, axis shift, mechanical axis length changes, and tibial tuberosity distalization, with more proximally positioned wedges performing better than distally positioned wedges. Errors in TPA identification appeared partially self-correcting due to altered axis shifts. Craniocaudal shifts in wedge apex position had the most severe effects on outcome variables, especially in shorter tibiae with greater initial TPA values. Recent CCWO variants are likely to achieve a satisfactory postoperative TPA with limited axis shift. The AMA-based CCWO technique appears to influence MA length and tibial tuberosity position the least, and apart from the effect on TPA where no advantage could be discerned, it appeared more robust in the face of wedge apex positioning errors than the other techniques.

The Effect of Femur Positioning on Measurement of Tibial Plateau Angle: An In Vitro Study

Five canine cadaveric pelvic limbs with intact cranial cruciate ligaments were used to quantify the effect of variation in limb positioning on the radiographic measurement of the tibial plateau angle (TPA) with reference to the degree of femoral condyle superimposition. Intra-osseous pin placement and a custom jig design allowed the controlled three-dimensional manipulation of limbs. Medio-lateral digital radiographic projections were taken with perfect femoral hemicondylar superimposition to establish a "reference" TPA (difference in position = 0 mm), and subsequently in varying degrees of supination/pronation and abduction/adduction. The lack of femoral hemicondylar superimposition for each radiograph was quantified using a tangential line technique with reference to the long tibial axis. A total of 176 radiographs were each assessed by three observers. "True" TPA was measured and it ranged within 17-25° across all limbs assessed. Variation in femoral condylar positioning ranged from -13 mm to +13 mm proximo-distally, and -11 mm to +11 mm cranio-caudally. Moreover, 3 mm non-superimposition of the femoral condyles produced 90.6% of measurements with 1° difference between measured and "true" TPA, and a sensitivity of 97.9% for a 2° difference. Further reduction in femoral condylar superimposition to 4 mm reduced the frequency of 1° difference between measured and "true" TPA to 84.9%, and to 94.8% for a 2° difference. In conclusion, measurement of TPA in large breed dogs from radiographs with greater than 3 mm variation in femoral condylar superimposition should be interpreted with caution.

Rock back phenomenon in 32 dogs that underwent tibial plateau levelling osteotomy

The aim of this study was to evaluate the postoperative temporal changes in the tibial plateau angle (TPA) after a tibial plateau levelling osteotomy (TPLO) in dogs. The TPA of thirty-two dogs were measured before surgery (TPA&lt;sub&gt;1&lt;/sub&gt;), immediately after the TPLO (TPA&lt;sub&gt;2&lt;/sub&gt;), and later at the healing of the osteotomy site (TPA&lt;sub&gt;3&lt;/sub&gt;). Three observers carried out three TPA measurements for each patient at the time of the evaluation. TPA changes were observed over the bone healing (2.05 ± 3.05°); however, no statistical significance was noted when comparing TPA&lt;sub&gt;3&lt;/sub&gt; and TPA&lt;sub&gt;1&lt;/sub&gt;. There were no statistical differences in the inter-observer measurements among TPA&lt;sub&gt;1&lt;/sub&gt;, TPA&lt;sub&gt;2&lt;/sub&gt;, and TPA&lt;sub&gt;3&lt;/sub&gt; (P &amp;gt; 0.05). The comparison between the preoperative TPA&lt;sub&gt;1&lt;/sub&gt; and the rock back showed a low positive correlation (S = 4 735.9, P = 0.471 5, r = 0.131 976 9). There was also a low positive correlation between the body weight (kg) and the change in the TPA during the bone healing (S = 4 581.8, P = 0.381, r = 0.160 234 7). Although changes in the TPA have been observed over the time of the bone healing, they were not influenced by the preoperative and postoperative TPA, or by the body weight. The magnitude of the variation in the TPA is not determined by the previous inclination or by the degree of rotation in the plateau.

Effect of tibial rotation on the tibial plateau angle measurement in dogs: An ex vivo study.

To determine the effect of tibial rotation on radiographic tibial plateau angle (TPA) measurement in normal and cranial cruciate ligament (CrCL)-deficient stifles. Cadaveric study. Five pairs of canine cadaver hind limbs with no stifle osteoarthritis. Mediolateral radiographs of each specimen were obtained at 0°, 10°, 20°, and 30° of internal and external rotation of the tibia with both intact and transected CrCL. Two Kirschner wires were placed at the cranial and caudal landmarks of the tibial plateau, and the 0° views were imaged again, representing the anatomic TPA. Five observers measured the TPA twice on all images. Measurements were compared by using a mixed-model ANOVA. Intraobserver and interobserver variability were evaluated by using the coefficient of variation. Tibial plateau angle did not differ among the anatomic, CrCL-intact, and CrCL-deficient 0° views or between the CrCL-intact and CrCL-deficient views at the various tibial rotations. The only difference detected was between CrCL-intact stifles radiographed at 0° and external rotation (range, 1.16°-1.6°; P = .016, P = .001, and P < .001). Tibial rotation, CrCL transection, and their interaction all failed to influence intraobserver and interobserver variability (P > .05). In CrCL-deficient stifles, tibial rotation of up to 30° internally and externally did not result in clinically relevant changes in TPA measurements. The TPA can be successfully measured with up to 30° of internal and external tibial rotation in CrCL-deficient stifles with no osteoarthritic changes.

Effect of patellar luxation on radiographic measurements of tibial plateau angle in small-breed dogs.

OBJECTIVE To determine whether medial patellar luxation would affect radiographic tibial plateau angle (TPA) measurements in small-breed dogs. DESIGN Prospective cross-sectional study. ANIMALS 15 small-breed dogs (25 stifle joints) with grade 2 or 3 medial patellar luxation (5 dogs with unilateral luxation and 10 dogs with bilateral luxation). PROCEDURES Digital mediolateral radiographic images of each affected stifle joint were acquired with the patella in manually reduced (n = 25) and luxated (25) positions. In 2 measurement sessions separated by > 48 hours, 3 observers unaware of patella status (luxated or reduced) measured the TPA in each image twice in random order. Mixed linear modeling was performed to determine the effect of patella status on TPA measurements, and intraobserver and interobserver variation in measurements were calculated. RESULTS TPA measurements by all observers differed significantly between the first and second measurement sessions, but by a mean value of only 0.7°. A few significant differences were identified between 1 pair of observers by patella status and between patella statuses for 1 observer, but all mean differences were ≤ 1.7°. No significant difference in intraobserver variation was identified between patella statuses for any observer. Interobserver variation was not affected by patella status and measurement session. CONCLUSIONS AND CLINICAL RELEVANCE Although some significant differences were identified in radiographic TPA measurements in dogs with medial patellar luxation, depending on whether the patella was luxated or manually reduced, these differences were so small they could be considered clinically unimportant. Consequently, we believe that in small-breed dogs with patellar luxation, patella status would be unlikely to have a clinically meaningful effect on the measured TPA.

Cranial cruciate ligament structure in relation to the tibial plateau slope and intercondylar notch width in dogs.

Cranial cruciate ligament (CCL) rupture is one of the most common orthopedic conditions in dogs. The pathogenesis of CCL rupture is not fully described and remains to be elucidated fully. Several hypotheses have been proposed to explain the etiology of these changes. The objective of this study was to investigate structural changes in the CCL in relation to the tibial plateau angle (TPA) and the intercondylar notch (ICN) width in dogs. Fifty-five skeletally mature dogs were included in this study. ICN width and TPA measurements were obtained from intact CCL stifles. Samples of the CCL, caudal cruciate ligament (CaCL), and femoral head ligament (FHL) were harvested and stained for routine histological and immunohistochemical analysis. Microscopic changes in the ligaments were observed and were found to correlate with the TPA and ICN width values. The degree of structural changes within the CCL was observed to correlate with an increasing TPA and a narrowing ICN width. Changes in the CCL are likely to be caused by excessive forces acting through the ligament in stifles with a high TPA. Chondroid metaplasia of the CCL is an adaptation to abnormal mechanics within the stifle joint caused by altered bone morphology.

A modified technique for radiographic measurement of the tibial plateau angle in dogs

This prospective study was aimed at testing a modified method for the measurement of the tibial plateau angle on radiographs of the stifle joint and the proximal part of the tibia. Forty-four stifle joints of 32 client-owned dogs were included in this study. Dogs were presented for hindlimb lameness and suspected cranial cruciate ligament rupture. The diagnostic procedures included radiographic examination. The mediolateral projection of the stifle joint including the tibia and the tarsal joint was used in this study. We tested the most widely used gold standard method as well as three additional methods for tibial plateau angle measurement on each joint. The tibial plateau angle, the positioning of the stifle joint and the presence of osteoarthrosis were recorded. Only 29 (66%) joints had correct position on the radiograph and were used for further study. Repeated-measures ANOVA identified significant differences in mean tibial plateau angle between the different measuring methods. Dunnett’s post-hoc test identified a significant difference between the TA-2 and TA-2i methods and TA-0. No significant differences in tibial plateau angle were identified between joints with and without osteoarthrosis. The positioning of the limb significantly influenced the tibial plateau angle. One of the modified methods was found to not differ significantly from the gold standard method; thus, it can be recommended for further testing.

A novel jig arm to measure tibial plateau angle during tibial plateau leveling osteotomy.

To determine the ability of a novel device attached to the proximal tibial plateau leveling osteotomy (TPLO) jig pin to accurately predict intraoperative change in tibial plateau angle (TPA). In vitro cadaveric study. Left hindlimbs of adult dogs (n = 9). A modified Slocum tibial plateau leveling (TPL) jig with the Rotational Osteotomy Measuring Arm (ROMA) was placed on the tibia and a radial TPLO osteotomy was performed. Based on preoperative radiographic TPA measurements, the proximal segment was rotated using the traditional method of marking points on the osteotomy a specified distance apart. After rotation, the predicted TPA was recorded based on the ROMA. Postoperative TPA was measured on radiographs. The ability of the ROMA to predict postoperative TPA was compared to that of the traditional method. The average final TPA achieved with the traditional method was 6.4° (range, 3.0-10.0°). The ROMA predicted a final TPA of 5.8° (range, 3.8-10.1°). No significant difference was found between the TPA predicted based on the traditional method and ROMA method. The ROMA may be an alternative to the traditional method of measuring proximal segment rotation during TPLO procedure. Performing a TPLO with the ROMA may accurately predict the postoperative TPA while eliminating the need for measuring chord length, making reference marks, or referencing TPA charts for various osteotomy blade sizes.

Factors contributing to the variability of a predictive score for cranial cruciate ligament deficiency in Labrador Retrievers

BackgroundWe recently reported that a conformation score derived from the tibial plateau angle (TPA) and the femoral anteversion angle (FAA), best discriminates limbs predisposed to, or affected by cranial cruciate ligament disease (CCLD), from those that are at low risk for CCLD. The specificity and sensitivity of this score were high enough to support further investigations toward its use for large-scale screening of dogs by veterinarians. The next step, which is the objective of the current study, is to determine inter-observer variability of that CCLD score in a large population of Labrador Retrievers. A total of 167 Labradors were enrolled in this cross-sectional study. Limbs of normal dogs over 6 years of age with no history of CCLD were considered at low risk for CCLD. Limbs of dogs with CCLD were considered at high risk for CCLD. Tibial plateau and femoral anteversion angles were measured independently by two investigators to calculate a CCLD score for each limb. Kappa statistics were used to determine the extent of agreement between investigators. Pearson’s correlation and intraclass coefficients were calculated to evaluate the correlation between investigators and the relative contribution of each measurement to the variability of the CCLD score.ResultsThe correlation between CCLD scores calculated by investigators was good (correlation coefficient = 0.68 p < 0.0001). However, interobserver agreement with regards to the predicted status of limbs was fair (kappa value = 0.28), with 37% of limbs being assigned divergent classifications. Variations in CCLD scores correlated best with those of TPA, which was the least consistent parameter between investigators. Absolute interobserver differences were two times greater for FAAs (4.19° ± 3.15) than TPAs (2.23° ± 1.91).ConclusionsThe reproducibility of the CCLD score between investigators is fair, justifying caution when interpreting individual scores. Future studies should focus on improving the reproducibility of TPA and FAA measurements, as strategies to improve the agreement between CCLD scores.

Tibial plateau angle: methods of measurement, value, applicability

The tibial plateau angle measurement and its applicability have been reviewed based on the literature. The measurement was made on radiographs of the stifle joint with superimposition of the femoral condyles (with maximum tolerance of 2.0-4.0mm). Due to great variation among dog populations (size, breed), mean tibial plateau angles were found to be between 16.9° and 34°, but an excessive angle was described as &gt;35°. An appropriate measurement of the tibial plateau angle can be made at about 108 days of age. The influence on the magnitude of the measured tibial plateau angle were the limb position during radiographic examination, the measurement technique (with modifications) and the experience level of the observer. Differences in magnitudes of the tibial plateau angles in dogs with and without cranial cruciate ligament rupture were not observed. The tibial plateau angle is commonly used in osteotomy of the tibia and its magnitude in order to select the proper surgical technique. The significance of the tibial plateau angle on the aetiopathogenesis of cranial cruciate ligament disease is questionable. Other measurements of the proximal tibia were attained to determine the risk factor of cranial cruciate ligament insufficiency. Knowledge of the tibial plateau angle and factors influencing measurement errors have great clinical importance.

Accuracy of a radiographic stitching technique to measure tibial plateau angle in large and giant breed dogs.

To determine if a novel radiographic stitching technique yields accurate tibial plateau angle (TPA) measurements in large and giant breed dogs. Three medio-lateral digital radiographic projections (traditional TPLO, stifle-centred, tarsus-centred) were obtained from each of 17 pairs of pelvic limbs from skeletally mature large and giant breed dogs. Eight observers performed image stitching followed by TPA measurements on the stitched (sTPA) and traditional radiographs (tTPA). The TPA was also measured on photographs made of isolated anatomical tibial specimens (aTPA). Measurements were compared between observers and between image type using ANOVA and correlation coefficients. There was no statistically significant difference in TPA between observers for tTPA or sTPA radiographs (p >0.05); both sTPA and tTPA were highly correlated with aTPA and with each other (r = 0.88, 0.89, and 0.97 respectively). This novel digital stitching method provides an alternative technique for accurately measuring TPA utilizing a stifle-centred radiograph that may be useful when traditional TPLO radiographs are difficult to obtain. This may be particularly useful in large and giant breed dogs because collimation to include the entire tibial length can preclude proper centring of the radiographic beam over the stifle.

Effect of anatomic variation in caudal tibial plateau on the tibial plateau angle in dogs: a cadaveric study

To determine the effect of using two different landmarks to identify the caudal point on the joint orientation line in the sagittal plane in tibial plateau angle measurement in dogs: the caudal margin of the medial condyle as the anatomic tibial plateau angle and the tibial insertion of the caudal cruciate ligament as the conventional tibial plateau angle. A total of 170 tibiae from 85 mid- and large-breed dogs were used. The two joint orientation lines were drawn on photographic images of the bones. The angles between the line perpendicular to the tibial axis and the two lines were then measured as the anatomic and conventional tibial plateau angle. The mean conventional tibial plateau angle (25·2 ±2·60°) and anatomic tibial plateau angle (23·5 ±2·59°) differed significantly (P<0·001), and the degree of this difference varied significantly among seven breeds (P<0·01). The results of this study suggest that the locations of the caudal margin of the medial condyle and the tibial insertion of the caudal cruciate ligament differed, leading to inconsistent identification of the joint orientation line depending on the landmark used.

Radiographic Quantitative Assessment of Caudal Proximal Tibial Angulation in 100 Dogs with Cranial Cruciate Ligament Rupture

To evaluate inter- and intraobserver variability in the measurement of distal tibial axis/proximal tibial axis angle (DPA) from lateral radiographs of canine tibia in dogs with cranial cruciate ligament rupture (CCLR). Retrospective clinical study. Dogs (n=100) with cranial cruciate ligament rupture. Medical records of dogs diagnosed with CCLR were reviewed. In addition to signalment and TPA measurements, measured DPA (mDPA) was calculated for each lateral view of the tibia in each animal, twice, by 3 blinded observers. Subjective scoring of DPA (sDPA) was also recorded, twice, by 3 additional blinded observers from lateral views of the proximal half of the tibia in each dog. Inter- and intraobserver variability was measured by intraclass correlation coefficient (ICC) for each measurement. Correlation between mDPA and sDPA was also determined. Median tibial plateau angle (TPA) of the subject population was 27.9° (range 18.8-41.3°; IQR: 25.5-30.75°). Mean ± SD mDPA was 6.50 ± 2.81° (confidence intervals [CI]: 5.94-7.06°; range 0-13.33°). There was no correlation between age and weight of dogs and the mDPA (P=.58 and .12). There was a moderate correlation between mDPA and TPA (r(2)=0.49, P<.0001). There was a moderate correlation between sDPA and mDPA (r(2)=0.27, P<.0001). Good inter- and intraobserver agreement was found in the measurement of mDPA. mDPA is a reproducible measurement of caudal angulation of proximal tibia. Furthermore, mDPA of dogs with cranial cruciate ligament disease in this report are in concordance with previous reports.

Effect of stifle angle on the magnitude of the tibial plateau angle measurement in dogs with intact and transected cranial cruciate ligament

To determine the effect of stifle angle on the magnitude of the radiographic tibial plateau angle (TPA) in normal and cranial cruciate ligament (CCL) -deficient stifles. Three pairs of canine cadaver hindlimbs from three skeletally mature dogs were positioned in a custom-made positioning device. A lateral radiograph of each specimen was obtained before and after transection of the CCL at four stifle angles (90°, 110°, 135° and 140-150° [i.e. maximum extension]), based on goniometric measurements. Four observers determined the radiographic TPA twice for each radiograph with a minimum of two days between each measurement. The radiographic TPA measurements in all specimens at different stifle angles with intact CCL and transected CCL were compared with mixed-model ANOVA. The effect of stifle angle, CCL transection, and interaction between the two on observer TPA measurement variability was also determined using the coefficient of variation. Tibial plateau angle was not statistically different in the stifle angles for either the intact or transected CCL. There was also no statistical difference for TPA between intact and transected CCL groups at each of the stifle angles. Stifle angle, CCL transection and interaction between the two did not have any significant effect for intra-observer and inter-observer variation. The angle of the stifle during radiography does not influence the magnitude of the TPA measurement as determined on true lateral radiographs of the stifle and tibia in cadaveric canine limbs.

Evaluation of Intra- and Interobserver Variability and Repeatability of Tibial Plateau Angle Measurements with Digital Radiography Using a Novel Digital Radiographic Program

To compare the intra- and interobserver variability occurring when observers with differing experience levels measure tibial plateau angles (TPAs) with a novel digital radiographic projection program (tibial plateau leveling osteotomy [TPLO] planning program), the Kodak Picture Archiving and Communications System (PACS), and standard sized printed films (SF). Cross-sectional study. Dogs (n=36) with cranial cruciate ligament (CCL) rupture that had a TPLO. Six observers, divided into 3 equal groups based on experience level, measured TPA on 36 digitally captured radiographic images of tibiae of dogs clinically affected with CCL rupture. Each observer used 3 methods of measuring TPA and repeated the measurements 3 times with each method. The intra- and interobserver variability was compared using the coefficient of variation. Averaged over all replications and images, there was no significant difference (P>.05) in the average variability occurring with each method for all but 1 observer. There was no effect of experience level on measurement variability; however, interobserver variability was significantly less with measurements made with the PACS and TPLO planning program compared with measurements made from SF (P<.05). Repeated measurements of TPA made using digital images and computer-based measurement programs were significantly less variable between observers than those made from images printed on standard radiographic films. Digital radiography and computer-based measurement programs are effective for determining the TPA, allowing less variability in measurements compared with SF. The ability to manipulate the image may allow better identification of anatomic landmarks.

Direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact

Anterior tibial loading is a major factor involved in the anterior cruciate ligament (ACL) injury mechanism during ski impact landing. We sought to investigate the direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact of intact knee joints without quadriceps activation. Twelve porcine knee specimens were procured. Four specimens were used as non-impact control while the remaining eight were mounted onto a material-testing system at 70 degrees flexion and subjected to simulated landing impact, which was successively repeated with incremental actuator displacement. Four specimens from the impacted group underwent pre-impact MRI for tibial plateau angle measurements while the other four were subjected to histology and microCT for cartilage morphology and volume assessment. The tibial plateau angles ranged from 29.4 to 38.8 degrees . There was a moderate linear relationship (Y=0.16X; R(2)=0.64; p<0.001) between peak axial impact compressive load (Y) and peak anterior tibial load (X). The anterior and posterior regions in the impacted group sustained surface cartilage fraying, superficial clefts and tidemark disruption, compared to the control group. MicroCT scans displayed visible cartilage deformation for both anterior and posterior regions in the impacted group. Due to the tibial plateau angle, increased axial impact compressive load can directly elevate anterior tibial load and hence contribute to ACL failure during simulated landing impact. Axial impact compressive load resulted in shear cartilage damage along anterior-posterior tibial plateau regions, due to its contribution to anterior tibial loading. This mechanism plays an important role in elevating ACL stress and cartilage deformation during impact landing.