Morphometric description of the feline tibia using three-dimensional CT

Abstract

Objectives

The aim of the study was to characterise the three-dimensional external and internal morphology of the feline tibia, including bone length, external and internal diameters, cortical thickness, cancellous bone volume and mechanical joint angles using CT.

Methods

Eight paired tibiae from adult domestic feline cadavers were evaluated using CT imaging. Morphometric parameters – including bone length, external and internal diameters, cortical thickness, cancellous bone volume and mechanical joint angles – were measured in triplicate for each bone. The mean of each set of triplicate measurements was recorded for analysis.

Results

Overall tibia length measured 111.61 mm (95% confidence interval [CI] 107.89–115.53). The narrowest internal bone diameter mediolaterally was at 50% tibial length (4.23 mm, 95% CI 4.05–4.42) and craniocaudally at 75% tibial length (3.77 mm, 95% CI 3.57–3.97). The cranial and caudal cortex was thickest at 50% of tibial length. The proximal tibia had a mean cancellous bone volume of 12.45 mm³ (95% CI 11.4–13.49). The distal tibia had a mean cancellous bone volume of 2.09 mm³ (95% CI 1.62–2.55). Mean mechanical joint angles were as follows: tibial plateau angle 31.42° (95% CI 30.09–32.75); mechanical medial proximal tibia angle 95.15° (95% CI 94.63–95.68); mechanical medial distal tibia angle 94.08° (95% CI 93.36–94.79); mechanical cranial distal tibia angle 88.68° (95% CI 87.04–90.32); mechanical caudal proximal tibia angle 58.53° (95% CI 57.20–59.86); and sagittal plane alignment 30.16° (95% CI 28.47–31.84).

Conclusions and relevance

The use of CT allowed for the estimation of internal bone morphometry and joint geometry in feline tibiae. This provided data that may be valuable in planning and developing new techniques for internal fracture fixation in cats.

Keywords

Tibia CT orthopaedics anatomy

Introduction

Feline anatomy is described in anatomic texts, and one CT study focused on surface measurements and area of the feline tibia.^1
–4 However, information regarding detailed bone morphometry is lacking.³ Bone morphometry is the quantitative analysis of the dimensions and microarchitecture of bone.^1,2,5 Previous studies in other regions of the feline body include the skull and pelvis, in addition to several other flat and long bones, which have been valuable in gaining a better understanding of feline sexual dimorphism, development and orthopaedic structure.^2,6,7

The primary objective of this study was to conduct a comprehensive morphometric analysis of the tibia in a population of domestic cats using three-dimensional reconstructed CT images. It quantified parameters, including tibial osteometric and volumetric measurements, particularly cortical and cancellous bone volume. Secondary objectives were to measure joint angles, including tibial plateau angle, mechanical medial proximal tibial angle, mechanical medial distal tibial angle, mechanical cranial distal tibial angle, mechanical caudal proximal tibial angle and sagittal plane alignment. The aim of the study was to provide a detailed description of the tibia’s anatomical features and contribute to our knowledge of feline skeletal morphology.

Materials and methods

Specimens

Eight skeletally mature cats were euthanased for reasons unrelated to this study. The cats weighed between 2.50 kg and 6.10 kg (mean 3.85). All cats included were domestic shorthair cats; there were three female and five male cats. Exclusion criteria included cats that were juvenile with open growth plates, had evidence of previous coxofemoral or pelvic surgery, and trauma or neoplasia of the pelvic limbs, lower spine or pelvis. All the cadavers were thawed overnight at room temperature (24°C) before the CT scans were performed. The cadavers had previously been used for teaching purposes through the Sydney School of Veterinary Science Animal Donation Program; no further permissions were required.

Imaging

Cadavers were placed in a foam trough and positioned in dorsal recumbency. Both pelvic limbs were extended caudally with the stifles oriented perpendicular to the table to maintain rotational alignment. The thoracic limbs were secured in a neutral position. CT scans of the tibiae were performed using a 128 slice helical scanner (128-slice Computed Tomography scanner, Revolution EVO Gen 3; General Electric Company) and images were acquired as a volume with the following parameters: 200 milliampere seconds, 120 kilovoltage peak, slice thickness of 1.25 mm, interval of 0.9 mm, helical pitch of 0.53, matrix of 512 × 512 and rotation time of 1 s.

Data collection

Images were analysed using OsiriX MD v14.0 (Pixmeo). A total of 16 tibiae were used for this study. Any tibiae that were found to have skeletal or joint abnormalities were excluded. Cortical bone volume, external and internal bone diameter, and cancellous bone volume were measured independently by a veterinary surgery registrar and veterinary student (MJAPVP and MC). The mechanical angles were measured independently by a surgical registrar and board-certified surgeon (MJAPVP and RMB). The measurements were collected in triplicate at separate times without randomisation. The average values of the triplicate measurements were used in this study.

Each tibia was viewed using three-dimensional multiplanar reconstruction (MPR) of the CT scans to accurately obtain the sagittal, frontal and transverse planes, and to correct any positional anomalies. Craniocaudal alignment was standardised with the axis reference lines centred through the middle of the tibial diaphysis on the frontal and sagittal reconstructions. The overall length of the tibia was measured in the sagittal plane starting from the most proximal point of the intercondylar eminences to the midpoint between the distal aspect of the distal intermediate ridge of the tibia cranially and the caudodistal aspect of the cochlea tibia caudally. Medial to lateral tuberosity was measured at the first transverse slice though the proximal tibia where the respective prominences were most obvious and a clear corticomedullary junction could be identified. The tibial tuberosity was identified at the point where there was clear insertion of the patella ligament in both the transverse and sagittal reconstructions (Figure 1).

Figure 1

Transverse cross-section of the right tibia proximal to distal: (a) medial to lateral tuberosity; (b) tibia tuberosity; (c) 25% tibia length; (d) juxtaarticular to tibiotarsal joint

The tibial length was divided into four, and each tibia was measured at the level of 25%, 50% and 75% of total tibial length. These levels were calculated for each tibia as a percentage of their overall tibial length: 25% tibial length was measured at one-quarter of the way distal from the intercondylar eminences; 50% tibial length was halfway between the intercondylar eminences and the distal articular surface; and 75% tibial length was one-quarter of the tibial length proximal to the distal tibial articular surface. The distal tibial measurement point was at the first transverse reconstruction proximal to the distal articular surface where it was clear that the corticomedullary junction could be identified. The landmarks are shown in Figure 2.

Figure 2

Landmarks of the tibia in the cranial (left) and medial view (right): 1 = medial to lateral tuberosity; 2 = tibial tuberosity; 3 = 25% tibia length; 4 = 50% tibial length; 5 = 75% tibial length; 6 = just proximal to the distal articular surface

External and internal diameters, and cortical bone thickness were measured using OsiriX bone algorithm (window level 300, window width 1500 Hounsfield Units [HU]). Measurements were taken of each tibia landmark described above in the transverse plane of the three-dimensional MPR (Figure 3).

Figure 3

External and internal measurements taken from the distal tibia. The top of the image is cranial. The left of the image is medial. Blue = external cortical thickness in craniocaudal plane; yellow = internal diameter in craniocaudal plane; red = external cortical thickness in the mediolateral plane; orange = internal diameter in craniocaudal plane. These measurements were taken from the midpoint of the tibia in each section

Because of the triangular shape of the proximal tibia, measurements at the level of the tibial tuberosity were taken at the widest points. All measurements were obtained on the transverse reconstructions, and perpendicular axis lines were used as references for the relative cranial, caudal, medial and lateral orientations of the tibia. The length region of interest tool was used to measure each value. The relationships between bone measurements were expressed as percentages based on the calculated means. Tibial length was measured as the distance from the proximal tibial joint centre to the distal tibial centre on the frontal reconstruction.⁸

Cancellous bone measurements were collected by manually segmenting cancellous bone from other tissues from the transverse CT Digital Imaging and Communications in Medicine (DICOM) images with a window level of 350 HU and window width 850 HU.² The volume of cancellous bone was recorded after segmentation of the DICOM images for each bone. The proximal and distal tibial cancellous bone volumes are shown in Figure 4.

Figure 4

Feline tibia shown in three-dimensional maximum intensity projection. Left: cranial view; right: lateral view. Green = proximal cancellous bone; light blue = distal cancellous bone

Joint angles were measured from screen captures taken of the correctly aligned images based on the three-dimensional MPR and transferred into a veterinary surgical planning program (vPOP Pro; Veterinary Preoperative Orthopaedic Planning). To ensure that there was consistency in creating MPR images, the sagittal plane was reconstructed so that the origin of the orthogonal planes was moved to the most caudal and central part of the proximal tibia (Figure 5a). The sagittal plane orientation line in the frontal plane image was moved to intersect a line drawn from the centre of the tibial condyles proximally to the centre of the talus distally. The sagittal plane orientation line in the transverse image was moved to intersect the most caudal point of the medial tibial condyle. The frontal plane was reconstructed using methodology described by other authors in calculating the mechanical medial proximal tibial angle in dogs, and three-dimensional rendering was added to improve identification of anatomical landmarks (Figure 5b).⁹ The tibial plateau angle was measured as previously described by Slocum and Devine.¹⁰ The mechanical axis of the tibia was drawn from the centre of the proximal tibial articular surface, between the intercondylar eminences to the distal articular surface in between the medial and lateral malleoli.¹¹ The mechanical medial proximal tibial angle (mMPTA), mechanical medial distal tibial angle (mMDTA), mechanical cranial distal tibia angle (mCrDTA) and mechanical caudal proximal tibia angle (mCaPTA) were measured as described previously.¹² The sagittal plane alignment (SPA) was calculated by subtracting the mCaPTA from mCrDTA.¹³ A positive number was indicative of a procurvatum and a negative number indicative of a recurvatum.¹³

Figure 5

Three-dimensional multiplanar reconstructions in (a) the sagittal plane and (b) the dorsal plane. (a) The sagittal plane was used to calculate the total plateau angle, sagittal plane alignment, mechanical cranial distal tibia angle and mechanical caudal proximal tibia angle; (b) the dorsal plane was used to calculate the mechanical medial proximal tibial angle and mechanical medial distal tibial angle. mCaPTA = mechanical caudal proximal tibia angle; mCrDTA = mechanical cranial distal tibia angle; mMDTA = mechanical medial distal tibia angle; mMPTA = mechanical medial proximal tibia angle; TPA = tibial plateau angle

Statistical analysis

Summary statistics were calculated using Excel (Microsoft). The intraclass correlation coefficient (ICC) was calculated for the measurements collected by all observers for each angle using the ‘irr’ package within RStudio (PBC). The inter-observer ICC was calculated between the surgical resident and veterinary student for external and internal bone diameter and cancellous bone volume, and between the surgical resident and board-certified surgeon for the mechanical joint angles. An ICC in the range of 0.75–1 indicated excellent correlation, 0.60–0.74 indicated good correlation, 0.40–0.59 indicated fair correlation and below 0.40 indicated poor correlation.¹⁴

Results

Overall tibia length

The mean tibia length was 111.61 mm (95% confidence interval [CI] 107.89–115.53).

External bone diameter

External bone diameter at each landmark is presented in Table 1. On transverse reconstruction, the proximal tibial metaphysis had a triangular shape (Figure 1b).

Table 1

CT external diameter and internal diameter measurements of the bone radius

Location	Direction	External bone diameter (mm)	Internal bone diameter (mm)
Medial to lateral tuberosity	CC	14.24 (13.69–14.79)	11.68 (11.2–12.15)
Medial to lateral tuberosity	ML	17.40 (16.71–18.08)	15.03 (14.13–15.92)
Tibial tuberosity	CC	15.24 (14.65–15.84)	11.96 (11.36–12.57)
Tibial tuberosity	ML	16.40 (15.45–17.35)	14.3 (13.32–15.29)
25% tibial length	CC	10.95 (10.63–11.26)	7.53 (7.28–7.78)
25% tibial length	ML	7.87 (7.57–8.18)	5.10 (4.92–5.28)
50% tibial length	CC	8.66 (8.28–9.04)	4.10 (3.78–4.43)
50% tibial length	ML	7.59 (7.32–7.87)	4.23 (4.05–4.42)
75% tibial length	CC	7.22 (6.94–7.50)	3.77 (3.57–3.97)
75% tibial length	ML	7.77 (7.56–7.97)	4.58 (4.36–4.80)
Juxta-articular to tibiotarsal joint	CC	8.06 (7.85–8.26)	6.09 (5.89–6.30)
Juxta-articular to tibiotarsal joint	ML	11.34 (10.92–11.76)	8.95 (8.37–9.54)

Data are mean (95% confidence interval)

CC = craniocaudal; ML = mediolateral

The bone was widest in the mediolateral direction at the level of the medial-to-lateral tuberosity (17.40 mm, 95% CI 16.71–18.08). The tibia was widest in the craniocaudal direction distal to this, at the level of the tibial tuberosity (15.24 mm, 95% CI 14.65–15.84). The tibia then narrowed in a triangular shape before widening again distally in the mediolateral direction juxta-articular to the tibiotarsal joint (Figure 1d). Overall, the tibia was wider mediolaterally than craniocaudally, except at 25% and 50% of tibial length (Figures 2 and 3). The tibia was 231% wider in the mediolateral direction at the level of the medial-to-lateral tuberosity compared with the narrowest point at 50% tibial length (Figures 2 and 3). In the craniocaudal direction, the tibia was 212% wider at the level of the tibial tuberosity than at the narrowest point at 50% tibial length. The length of the tibial crest, measured proximally from the tibial tuberosity to the most distal extent of the tibial crest, was in the range of 23–31% (mean 22) of the length of the tibial diaphysis. The distal landmark for the extent of the tibial crest was indistinct and was identified as the point where there was an abrupt reduction in the diameter of the diaphysis.

Internal bone diameter

Internal bone diameter at each landmark is presented in Table 1. Similar to the external diameter measurements, the internal diameter of the tibia was widest mediolaterally at the medial to lateral tuberosity and craniocaudally at the tibial tuberosity. The narrowest internal diameter mediolaterally was at 50% tibial length (4.23 mm, 95% CI 4.05–4.42). The narrowest internal diameter craniocaudally was at 75% tibial length (3.77 mm, 95% CI 3.57–3.97).

Cortical bone thickness

Cortical bone thickness at each landmark is presented in Table 2. The cranial and caudal cortex was thickest at 50% tibial length, measuring 2.72 mm (95% CI 2.46–2.99 mm) and 1.86 mm (95% CI 1.64–2.08), respectively. The cortex then thinned proximally and distally. The cortex was thinnest at the lateral tuberosity (0.94 mm, 95% CI 0.86–1.02) followed by the medial aspect of the tibial tuberosity (0.98 mm, 95% CI 0.88–1.07).

Table 2

CT cortical bone thickness measurements of the tibial radius

Location	Direction	Measurement (mm)
Medial to lateral tuberosity	Cr	1.27 (1.16–1.38)
	Ca	1.29 (1.15–1.44)
	M	1.43 (0.83–2.04)
	L	0.94 (0.86–1.02)
Tibial tuberosity	Cr	1.93 (1.72–2.15)
	Ca	1.45 (1.16–1.73)
	M	0.98 (0.88–1.07)
	L	1.07 (0.95–1.19)
25% tibial length	Cr	2.30 (2.07–2.53)
	Ca	1.25 (1.00–1.50)
	M	1.44 (1.35–1.53)
	L	1.33 (1.25–1.42)
50% tibial length	Cr	2.72 (2.46–2.99)
	Ca	1.86 (1.64–2.08)
	M	1.62 (1.51–1.74)
	L	1.77 (1.54–2.00)
75% tibial length	Cr	1.77 (1.62–1.92)
	Ca	1.66 (1.54–1.78)
	M	1.54 (1.43–1.64)
	L	1.66 (1.56–1.75)
Juxta-articular to tibiotarsal joint	Cr	1.07 (0.72–1.43)
	Ca	1.18 (1.02–1.35)
	M	1.05 (0.91–1.19)
	L	1.34 (1.12–1.55)

Data are mean (95% confidence interval)

Ca = caudal; Cr = cranial; M = medial; L = lateral

Cancellous bone

The proximal tibia had a mean cancellous bone volume of 12.45 mm³ (95% CI 11.4–13.49). The distal tibia had a mean cancellous bone volume of 2.09 mm³ (95% CI 1.62–2.55).

Tibial plateau angle

The mean tibial plateau angle (TPA) was 31.24° (95% CI 30.09–32.75).

Mechanical angles

Mechanical joint angles are presented in Table 3.

Table 3

CT tibial plateau angle and mechanical angle measurements of the radius

Angles	Degrees (°)
TPA	31.42 (30.09–32.75)
mMPTA	95.15 (94.63–95.68)
mMDTA	94.08 (93.36–94.79)
mCrDTA	88.68 (87.04–90.32)
mCaPTA	58.53 (57.20–59.86)
SPA	30.16 (28.47–31.84)

Data are mean (95% confidence interval)

mCaPTA = mechanical caudal proximal tibia angle; mCrDTA = mechanical cranial distal tibia angle; mMDTA = mechanical medial distal tibia angle; mMPTA = mechanical medial proximal tibia angle; SPA = sagittal plane alignment; TPA = tibial plateau angle

The inter-observer ICC showed excellent correlation in 72.13% of the measurements, good in 8.20%, fair in 11.48% and poor in 4.92% (refer to Table S1 in the supplementary material). Moderate ICC was seen with TPA and SPA, and poor ICC was seen with medial to lateral tibial tuberosity cortical thickness caudal (MTLTCd), medial to lateral tibial tuberosity cortical thickness cranial (MTLTCr), medial to lateral tibial tuberosity cortical thickness latera (MTLTlat) and juxta-articular to tibiotarsal joint cortical thickness cranial (JACr).

Discussion

This study utilised CT to describe the morphometry of the feline tibia that includes the external and internal bone diameter, cortical bone thickness, cancellous bone volume and mechanical joint angles in domestic cats. The use of CT can potentially provide clinicians with better spatial and contrast resolution, and in turn analysis of the internal architecture of the bone that would not otherwise be seen on radiographic imaging.^15,16 The accuracy of using a medical imaging software such as OsiriX to perform three-dimensional reconstructions and measurements has been validated for use in human medicine.^17,18

References for tibial length in domestic shorthair cats using radiography have been previously established.¹⁹ The aforementioned study measured a mean length of 80.59 ± 4.84 mm in females and 86.77 ± 5.29 mm in males. The present study measured the tibial length of all cats in the cohort regardless of sex as 111.61 mm (95% CI 107.89–115.53), which is similar to another study where mean measurements were 108.14 ± 3.06 mm for females and 113.27 ±4.84 mm for males.³ The authors speculate that the difference in the measurements of CT vs radiography may be due to the variation in cat size, breed, age and sex among studies.^3,19

Current recommendations for intramedullary pin diameter relative to internal diameter of the isthmus of the tibia are 30–40% for plate–rod constructs and 70–90% for the interlocking nail to achieve appropriate stiffness.^15,20 The narrowest internal bone diameter of cats in this study was mediolaterally at 50% tibial length (4.23 mm, 95% CI 4.05–4.42) and craniocaudally at 75% tibial length (3.77 mm, 95% CI 3.57–3.97). These measurements can serve as guidelines for the maximum diameter that can be used for placement of intramedullary implants in cats. Similarly, external bone diameter is narrowest at these levels. This is useful information for implant selection where iatrogenic bone fracture is a risk, such as with external skeletal fixation using pins or internal fixation using a bone plate and screws.^15,21

Feline bones have been previously described as brittle, with fractures occurring most commonly in the distal tibia.^21
–25 In this study, cortical bone was thickest at the mid to distal diaphysis, while the external diameter of the bone reduced distally. This anatomic configuration may contribute to a structurally weaker construct despite cortical thickening and potentially explain the increased incidence of fractures at the distal tibia.⁸ It is important to note that this correlation is observational and warrants further biomechanical testing and investigation. The authors speculate that the reduced bone radius, resulting in a smaller area moment of inertia of the distal tibial diaphysis, may contribute to this finding.

The tibia is one of the few bones in which an intramedullary implant should be inserted normograde because of the risk of damaging the stifle joint components.²⁶ In this study, the proximal and distal tibia had a mean cancellous bone volume of 12.45 mm³ (95% CI 11.4–13.49) and 2.09 mm³ (95% CI 1.62–2.55), respectively. The implication of this finding is that if a surgeon were to preferentially engage the distal cancellous bone to seat intramedullary implants, they would need to be placed within millimetres of the distal joint surface to be able to achieve this.

Canine and feline tibia reference joint angles have previously been measured using radiography.^{11,12,27
–30} These angles are usually used as a reference for congenital angular limb deformities or fractures that have healed as a malunion.^11,28 The authors wanted to determine whether CT measurements would be like previous reports. One study noted the mean TPA of cats with and without cruciate disease were 24.7 ± 4.5° and 21.6 ± 3.7°, respectively, and found this to be significantly different.²⁷ The mean TPA in this study was 31.42° (95% CI 30.09–32.75), which is higher than that of previous studies.^11,27 Although CT provides superior spatial resolution and anatomical accuracy compared with radiographs, certain details, such as the cranial and caudal extent of the subchondral line of the medial tibial plateau or the intercondylar eminences, can be more difficult to identify across specimens, especially without thin-slice acquisitions or contrast-enhanced protocols. In contrast, these landmarks, which have been established for plain radiography, may be more easily identifiable on standardised lateral radiographs where two-dimensional projections simplify complex anatomy.¹⁰

The mean mechanical medial proximal tibial angles (95.15°, 95% CI 94.63–95.68) were similar and the mechanical medial distal tibial angles (94.08°, 95% CI 93.36–94.79) in this study were smaller than those reported by previous authors.^11,28 Only one other study has measured the mechanical cranial distal tibial angle, and it is greater than the measurements in this study (88.68°, 95% CI 87.04–90.32).¹¹ The authors acknowledge that future studies directly comparing the difference in joint angles between radiography and CT are required to validate this observation. CT could be advantageous over radiography as it removes the need for meticulous subject positioning, thereby decreasing sedation or anaesthetic time and accelerating surgical planning. CT data can also be reformatted in specific planes or as three-dimensional projections to create representations of anatomic structural relationships.¹⁶

In this study, the authors adapted the calculation of SPA to determine the curvature of the feline tibia in the craniocaudal direction.¹³ It is known that the feline tibia has a craniocaudal procurvatum; however, to the authors’ knowledge, no acceptable reference interval has been established.^4,31 The SPA in this study had a mean of 30.16° (95% CI 28.47–31.84), which may serve as a reference for procurvatum in cats. This could be a consideration in intraoperative contouring of implants, such as interlocking nails and bone plates, or for correction of angular limb deformities in cats.^32,33 There is evidence to suggest that pre-contouring interlocking nails in dogs increases their ability to resist bending from compressive loads; however, this research has yet to be conducted in cats.³⁴

Inter-observer ICCs were interpreted according to the guidelines proposed by Cicchetti.¹⁴ Based on these criteria, 72.13% of the measurements demonstrated excellent correlation, 8.20% good, 11.48% fair and 4.92% poor reliability. The differences in ICC values among measurements likely reflect variation in the ease of identifying anatomical landmarks and the influence of minor discrepancies in measurement plane alignment. Measurements involving subtle or irregular anatomical contours are more susceptible to variability. In addition, small differences in image orientation or reconstruction angle may have contributed to reduced consistency between observers. Future studies incorporating standardised measurement protocols and observer training may reduce inter-observer variation and improve reproducibility.

The limitations of the present study include cat cadavers being skeletally mature, although the exact ages were not recorded. Our results therefore could not take into consideration juvenile or geriatric anatomical differences. It has been reported in canine and rodent models that cortical and cancellous bone volume decreases with age.^35,36 A study that concurrently assesses bone volume and bone mineral content across different age groups would be required to assess whether bone density decreases with age in cats. This has implications regarding implant purchase in metaphyseal bone in cats as they age. Another limitation is that the cadavers were not specifically positioned for measurement of the tibia; this required manipulation of the images in three-dimensional MPR to perform angle measurements. Although this allows correction of limb malalignment, it does introduce an element of subjectivity based on the plane that the measurements are taken. Slice thickness in this study was 1.25 mm, which is larger than what previous studies have achieved for bone morphometry in animals, specifically 0.4 mm, 0.5 mm or micro-CT.^2,3,37 Future studies using standardised limb positioning, thinner CT slices or automated segmentation and rendering protocols may help improve comparability with radiographic measurements, particularly in determining tibial plateau angle.

Conclusions

This study describes the external and internal bone diameter, cortical thickness, cancellous bone volume, TPA, mechanical joint angles and SPA of normal feline tibiae using CT. Routine fracture and angular limb deformity planning consists of plain orthogonal radiographic views; however, a three-dimensional understanding of the feline tibia may lead to improved outcomes with osteosynthesis. This may also have potential implications for future orthopaedic surgery planning, implant creation and comparative anatomy research.

Supplemental Material

Table S1

Inter-observer intraclass correlation coefficient (ICC) for each site and joint angle.

Supplemental Material

Table S1 key.

Footnotes

Acknowledgements

The authors would like to thank Evelyn Hall for providing guidance and performing statistical analyses on the mechanical angle data sets and inter-observer intraclass correlation coefficient.

Accepted: 25 February 2026

Author note

This manuscript was previously posted to a pre-print server with the DOI . The data sets generated and analysed during the current study are included in this published article.

Supplementary material

The following files are available as supplementary material:

Table S1. Inter-observer intraclass correlation coefficient (ICC) for each site and joint angle.

Table S1 key.

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The work described in this manuscript involved the use of non-experimental (owned or unowned) animals. Established internationally recognised high standards (‘best practice’) of veterinary clinical care for the individual patient were always followed and/or this work involved the use of cadavers. Ethical approval from a committee was therefore not specifically required for publication in JFMS. Although not required, where ethical approval was still obtained, it is stated in the manuscript.

Informed consent

Informed consent (verbal or written) was obtained from the owner or legal custodian of all animal(s) described in this work (experimental or non-experimental animals, including cadavers, tissues and samples) for all procedure(s) undertaken (prospective or retrospective studies). No animals or people are identifiable within this publication, and therefore additional informed consent for publication was not required.

ORCID iD

Marie JAPV Pantangco

Rachel M Basa

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