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. 2023 Jul 30;13(15):2462.
doi: 10.3390/ani13152462.

The Effects of Onychectomy (Declawing) on Antebrachial Myology across the Full Body Size Range of Exotic Species of Felidae

Lara L Martens  1 , Sarah Jessica Piersanti  1   2 , Arin Berger  1 , Nicole A Kida  1 , Ashley R Deutsch  1 , Kathryn Bertok  3 , Lauren Humphries  3 , Angela Lassiter  3 , Adam Hartstone-Rose  1
Affiliations

The Effects of Onychectomy (Declawing) on Antebrachial Myology across the Full Body Size Range of Exotic Species of Felidae

Lara L Martens et al. Animals (Basel). .

Abstract

While people are familiar with the practice of declawing domestic cats, "onychectomy", as it is also known, is also performed on non-domesticated species, including pantherines, to prolong their use for entertainment purposes. Although the surgery (the partial or complete removal of the distal phalanx) has clear osteological implications, its myological effects have never been studied. As the mass of an animal increases cubically as a product of its volume, while the areas of its paws only increase as a square, larger felids have higher foot pressures and, therefore, the surgery may have particularly substantial functional effects on larger cats. In this study, we evaluate the forearms of clawed and declawed non-domestic felid specimens that spanned the body size range of the whole family to evaluate the effects of onychectomy on muscle fiber architecture. We found that the deep digital flexors (the muscles most directly affected by onychectomy) of declawed felids are significantly lighter (~73%) and less powerful (46-66%) than those of non-declawed felids, while other muscles do not make up for these reductions. Thus, onychectomy has a substantial effect on the myological capabilities of cats, and because these deficiencies are not compensated for in biomechanically disadvantaged larger felids, it probably has even more functionally devastating consequences for these species.

Keywords: Panthera; captivity; exotic cats; tigers; wild cats.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Forearm muscles of Felis catus. (a,b) show superficial images of the anterior (flexor) and posterior (extensor) compartments, respectively; (c,d) show superficial images of deeper muscles of the same compartments of the forearm. Abbreviations: EI, m. extensor indicis (attaching to ray II only in this specimen); EDV, m. extensor ray V; ECU, m. extensor carpi ulnaris; APL; m. abductor pollicis longus; EDC, m. extensor digitorum communis; FCU, m. flexor carpi ulnaris; ECRB, m. extensor carpi radialis brevis; ECRL; m. extensor carpi radialis longus (ECRB and ECRL are differentiated based on insertion and length) [25,31]; SUP, m. supinator; PT, m. pronator teres; FCR, m. flexor carpi radialis; FDS, m. flexor digitorum superficialis; FDP, m. flexor digitorum profundus–humeral head; PQ, m. pronator quadratus; FCU, m. flexor carpi ulnaris. Colors of the functional groups are designated as follows: Yellow = digital flexors, green = wrist flexors, red = digital extensors, blue = wrist extensors, and pink = pronators/supinators. Although this specimen was dissected for illustrative purposes, only non-domesticated species were included in our analyses.
Figure 2
Figure 2
Schematic illustration of felid retractile claw anatomy and variations in onychectomy. (a) Unaltered anatomy adapted from the study of Bryant et al. (1996) [29]. Onychectomy via (b) removal of the ungual process and claw sheath, (c) removal of the distal phalanx (DP) through severance of the flexor process and lateral dorsal elastic ligament (LDL), or (d) removal of the whole DP through accompanying severance of the LDL and flexor digitorum profundus (FDP) tendon; these methods were adapted from Clark et al.’s schematic drawing (2014) [1]. Notably, in the ungual process and claw sheath removal approach (b), claw propagating tissue may be left behind (e), leading to claw regrowth. Red dotted lines and X’s indicate the approximate surgical plane and structures to be surgically severed, respectively. Abbreviations: FDS, m. flexor digitorum superficialis; FDP, m. flexor digitorum profundus; ED, extensor digitorum communis.
Figure 3
Figure 3
Reduced major axis regression of FDP MM, PCSA, and FL on BM and ANOVAs of residuals. All variables were linearized (i.e., volumetric and area variables taken to the cubic and square root) and logged prior to analysis. The red line represents the clawed (closed symbols) felid RMA regression, and the blue line represents the declawed (open symbols) felid RMA regression. Asterisk = Felis nigripes (excluded from analysis; see text); circle = Leopardus pardalis; upwards pointing triangle = Lynx rufus; right triangle = Prionailurus viverrinus; vertical rectangle = Caracal caracal; diamond = Leptailurus serval; horizontal rectangle = Puma concolor; left triangle = Panthera pardus; square = P. tigris; downwards triangle = P. leo. Declawed felids have significantly lower FDP MM and PCSA than clawed felids; results for FDP FL are not significantly different. Results are similar for FDS.
Figure 4
Figure 4
Residuals of flexor (total and digital) and total forearm PCSA. All variables were linearized and logged prior to analysis. Declawed felids have significantly lower digital and total flexors PCSA than clawed felids, and unlike H4b, the atrophy of these flexor muscles is not compensated for by other muscles, resulting in lower average (though statistically not significantly lower) forearm muscle PCSA (top). Results are similar for MM, though the reduction in the overall forearm MM of declawed felids is statistically significant. Asterisk = Felis nigripes (excluded from analysis; see text); circle = Leopardus pardalis; upwards pointing triangle = Lynx rufus; right triangle = Prionailurus viverrinus; vertical rectangle = Caracal caracal; diamond = Leptailurus serval; horizontal rectangle = Puma concolor; left triangle = Panthera pardus; square = P. tigris; downwards triangle = P. leo.
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References

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This research received no external funding.