Gait analysis in a cat with scapular luxation and contralateral forelimb amputation

Abstract

This report describes the use of a pressure-sensitive walkway to evaluate an uncommon case of a cat with dorsal luxation of the left scapula and an amputated right forelimb. The findings suggest that limb amputation induced load redistribution mostly to the contralateral forelimb despite the scapular luxation.

An approximately 5-year-old spayed crossbred female cat, weighing 3.2 kg was presented to the Veterinary Hospital due to lameness. The animal had been found abandoned on the street about 4 months earlier. Physical examination of the cat revealed previous amputation of the right forelimb below the elbow and prominence of the left scapula (Figures 1a, 1b). The animal showed no signs of pain on palpation. Craniocaudal and lateral radiographs of both forelimbs revealed scapulohumeral luxation and presence of the humerus in the right forelimb, and dorsal luxation of the left scapula with no signs of fracture (Figures 1c, 1d). The complete blood (cell) count (CBC) revealed leukocytosis (26.3 × 10⁹ cells/L), with a mature neutrophilia (14.465 × 10⁹ cells/L); a left shift (2.0 × 10⁹ cells/L); and lymphocytosis (10.257 × 10⁹ cells/L). Serum chemistry yielded no significant abnormal findings. Blood polymerase chain reaction (PCR) tests detected feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV), and an enzyme-linked immunosorbent assay (ELISA) was positive for feline infectious peritonitis (FIP).

Figure 1.

Appearance of the cat with dorsal scapular luxation, and amputation of the right forelimb (a, b). Radiographs showing scapulohumeral luxation and presence of the humerus in the right forelimb and left scapula with no signs of fracture (c, d).

Gait assessment revealed that the cat was able to bear weight on the left forelimb, but the scapula was displaced dorsally during walking. Gait analysis was performed using a 1.951 mm × 447 mm pressure-sensitive walkway (Walkway High Resolution HRV4; Tekscan, South Boston, Massachusetts, USA). Before data collection, the cat was acclimatized to the room and stimulated to walk across the walkway. The sensors of the pressure sensing walkway were equilibrated and calibrated according to the manufacturer’s specifications. The data from the first 5 valid trials were collected. The trial was valid if the cat walked with a velocity of 1.2 to 1.4 m/s and acceleration from −0.15 to 0.15 m/s². For each limb, the gait cycle time (s), stance time (s), swing time (s), and stride length (m) were the determined temporospatial parameters. The stance time percentage was calculated as (stance time/gait cycle time) × 100. The swing time percentage was (swing time/gait cycle time) × 100. The stride corresponded to the distance between 2 consecutive ground contacts of the same limb. The peak vertical force (PVF) and the vertical impulse (VI) were the kinetic parameters determined. The PVF and VI were normalized to the cat’s body weight and represented as a percentage of body weight, %BW and %BW*s, respectively. Body weight distribution among the 3 limbs was calculated as (PVF of the limb/total PVF of the 3 limbs) × 100. A t-test was used to compare the temporospatial parameters and the kinetic data between the right and left hind limbs. The percentage of body distribution was compared with data previously described for healthy cats (1) using a one sample t-test. Differences were considered significant at P < 0.05.

The swing phase was statistically different between hind limbs (P = 0.038). The percentage of body distribution was statistically different between limbs (left forelimb, P < 0.001; right hind limb, P = 0.003; left hind limb, P = 0.006). The values expressed as the means ± standard deviation (SD) of the temporospatial parameters and the kinetic data are listed in Table 1.

Table 1.

Temporospatial and kinetic parameters of the limbs in a cat with luxation of the left scapula and right forelimb amputated

	Left forelimb Mean ± SD	Right hind limb Mean ± SD	Left hind limb Mean ± SD
Stance time (s)	0.22 ± 0.03	0.18 ± 0.02	0.24 ± 0.05
Swing time (s)	0.15 ± 0.02	0.22 ± 0.05	0.16 ± 0.01
Stride time (s)	0.36 ± 0.03	0.39 ± 0.05	0.37 ± 0.05
Stride length (m)	0.44 ± 0.06	0.43 ± 0.04	0.41 ± 0.06
% of stance	62.57 ± 10.42	45.18 ± 7.06	64.67 ± 7.63
% of swing	40.78 ± 5.31	56.35 ± 10.02	43.48 ± 6.16
Peak vertical force (%BW)	75.34 ± 9.66	52.96 ± 7.39	50.56 ± 7.97
Vertical impulse (%BW*s)	11.40 ± 2.15	5.74 ± 0.90	8.04 ± 2.52
% of body distribution	42.12 ± 1.58	29.61 ± 2.96	28.27 ± 2.73

SD — standard deviation.

Scapular luxation is a traumatic injury uncommonly seen in dogs and cats (2–5). The lesion has been associated with motor vehicle accidents, jumping, falling, and bite wounds (5–7). Although the cause was not determined in the present case, the amputation of the contralateral forelimb suggested a severe trauma. In addition, the few reports on cats refer to scapular luxation alone or in combination with scapular fracture (2,5,7), whereas this case featured coexistence of different clinical lesions. There is a gait abnormality because the scapula moves dorsally during weight bearing, as observed in this case, due to multiple tearing of the insertions of the serratus ventralis, trapezius, and rhomboideus muscles on the cranial angle and dorsal border of the scapula (3–6,8).

The compensatory load redistribution is difficult to evaluate, and requires normative studies so that comparisons between normal and abnormal gait can be made (1,9,10). In general, quadrupedal locomotion has been more studied in dogs than in cats (1,9,11,12). In clinically healthy female cats walking at a velocity between 0.54 to 0.74 m/s over a pressure sensing walkway, the PVF was higher in the forelimbs than in the hind limbs with percentage weight distribution of approximately 28.92% for each forelimb and 21.07% for each hind limb (1). In the present case, although the cat had walked at a different velocity, the load of the amputated forelimb when compared to the data described above (1) was redistributed mostly to the contralateral forelimb (approximately 13.2%) and secondarily to the hind limbs (approximately 7.2% for the left limb and 8.54% for the right limb). In a study of large breed dogs walking it was also observed that after a forelimb amputation, 46.9% of the bodyweight was carried on the remaining forelimb and 53.1% on the hind limbs while the control dogs carried 59.8% on the forelimbs and 40.2% on the hind limbs (12). Also, the swing phase was longer in the right hind limb compared to the left hind limb, probably due the absence of the right forelimb.

In acute cases of scapular luxation, closed reduction and a Velpeau sling may be used (3,5,8,13). Another option is to secure the scapular luxation with circumcostal suture and reattach the torn muscles (2–4,7,8). This technique is useful for chronic lesions, as observed in our case, and when conservative methods have failed (6,13). The presence of scapular fracture may require other types of procedure (7). Surgery was not recommended in the present case because the cat had tested positive for FeLV, FIV, and FIP.

In conclusion, the findings suggest that limb amputation induced load redistribution mostly to the contralateral forelimb despite the scapular luxation. The scapular luxation was no impediment to weight-bearing on this limb. CVJ