Recently, a canine patient, that had undergone surgery for hip dysplasia approximately 5 months earlier, presented with a limp in the ipsilateral forelimb to the repaired hip. The limp was seen clearly at a walking gait. At a walk, the dog’s stance time was increased and the head was inclined slightly toward the affected forelimb.

Vet diagnosis concluded the change in gait was likely due to a soft tissue issue. On palpation, the dog exhibited significant tone in the lateral and medial shoulder musculature and cervical muscles. At a stand, the dog was not weight bearing fully on the non-repaired hind limb.

The dog was exercising normally and had not had incurred any known injury that would account for the gait change.

This case prompted several questions – How does a dog’s gait change post-surgery for hip dysplasia? What effects does a change in gait post-surgery have on the dog’s entire musculoskeletal system? For how long do these effects last?

Changes in ground forces and hip joint movement after surgery for canine hip dysplasia

A study of five mixed breed dogs sought to quantify the forces and moments in the canine hip joint after total hip replacement surgery. The study performed a unilateral hip replacement on the dogs and then measured hindlimb forces one month and four months after the surgery. Vertical ground forces were measured by lead walking the dogs over a force plate. The joint centres of rotation measured were:

• Hip – Great trochanter of femur

• Stifle – Lateral epicondyle of femur

• Talocrural joint – Lateral malleolus of fibula

• Metatarsophalangeal joint – Disto-lateral end of 5th metatarsal

Pre-operative vs one month post-surgery results

Vertical ground forces

Vertical ground forces occur in two modes during the walking gait. The first mode is the weight acceptance period and the second mode occurs just prior to push off. 20 – 25% of vertical forces are exerted during the weight acceptance period, as the contralateral hindlimb lifts off.

At one month post-surgery, there were significant decreases in the vertical forces the implanted hip exerted. Vertical forces were reduced by 77% at one month post-surgery compared with pre-operative forces.

At one month post-surgery, significant increases in vertical forces exerted by the normal hip were observed. These results suggest that in the initial stages of healing, the dog shifts their weight to the unaffected hip.

Cranio-caudal forces

The greatest magnitude of cranio-caudal (forward and backward) forces occurs when the dog brakes (i.e. paw touches down). Propulsive cranio-caudal forces are applied when the dog pushes off. One month post-surgery, the implanted hip showed significantly lower braking (-30.4%) and propulsive forces (-33.1%) compared with pre-surgery magnitudes.

Hip flexion and extension

Consistent with the reduction in propulsive force in the implanted hip, hip extension was significantly reduced one month post-surgery (-66.2%). The control hip flexion moments increased (+30.1%) but the peak extension in the control hip decreased.

In a side to side comparison at one month post-surgery, hip flexion was decreased by 63.2% and extension by 57.5%. The reduction in hip range of motion one month post-surgery may suggest compensatory weight shifting from the hind quarters to the forelimbs.

Despite the significant changes in forces and extension / flexion moments one month post-surgery, there was little evidence of an antalgic gait (shortened stance phase due to pain). The absence of an antalgic gait may suggest that the loss of function may be due to other factors such as muscle weakness.

One month versus four months post-surgery results

Vertical ground forces

By four months post-surgery, peak vertical forces in the implanted hip are significantly increased (+293.1%) and the control hip are decreased (-38.7%). These results indicate more balanced ground forces between the two hips which suggests a restoration of function.

Cranio-caudal forces

There is a significant decrease in braking and propulsive forces in both the control and implanted hip at four months post-surgery compared with one month post-surgery. Of particular note, is the decrease in braking forces in the control hip. These results may suggest some compensatory change of gait to shift the dog’s weight forward onto the forelimbs.

Hip flexion and extension

Hip flexion and extension results at four months suggests a return to normal gait. Peak flexion is decreased (-25.3%) in the control hip and increased (+77.1%) in the implanted hip. Similarly, hip extension in the implanted hip is increased (+77.1%).

Pre-surgery version four months post-surgery results

Vertical ground forces

By four months post-surgery, there is a decrease in vertical ground forces compared with pre-surgery forces. The decline in vertical ground forces is observed in both the control and implanted hip.

Cranio-caudal forces

Braking and propulsive forces in both hips at four months post-surgery indicated a decrease compared with pre-surgery values. This decrease was particularly evident in the braking forces exerted by the control hip. There was a decrease of 28.7%.

Hip flexion and extension

In the both hips, the peak extension pre-surgery was greater than at 4 months post-surgery. This is particularly the case in the control hip with a decrease of 41.8%. Conversely, peak flexion four months post-surgery were greater in both hips particularly the implanted hip.

Effect of gait changes on dog’s muscles

The bilateral reduction of hip forces at four months post-surgery combined with the absence of an antalgic gait, suggests the dog may compensate for the hip replacement by shifting their weight from the hind limbs to the forelimbs. This suggestion may offer an explanation for my patient developing a limp in the forelimb several months after surgery.

When the animal shifts their centre of mass to compensate for loss of function in the hind quarters, then evidence of muscle damage due to overloading can be observed. Muscle damage induces muscle tenderness and potential inflammation which affects the dog in a number of ways.

• Joint range of motion – Muscle soreness may result in a reduced range of motion in the joints affected by the damaged muscles. Changes in joint flexion and extension may be seen by changes in the animal’s gait such as shortened stride length, weight shifting, or joint stiffness.

• Muscle strength – When muscles are tender, the power they are capable of producing will be reduced. Thus, impacting the animal’s ability to perform.

• Changes in muscle recruitment patterns – Muscle injury may lead to changes in the patterns with which muscles are recruited to facilitate movement. Changes in muscle recruitment patterns and timings can result in loss of co-ordination.

Combined, the impact of muscle damage due to overloading, can increase the animal’s risk of injury. Loss of muscle power, changes in recruitment patterns along with changes in joint kinematics alters the animal’s shock absorbing ability when moving at high speeds or jumping. Additionally, loss of co-ordination increases the risk of slips and falls while a reduction in power may overload tissues unaccustomed to the forces required of them.

The changes in gait that occur post-surgery for hip dysplasia can potentially affect the dog’s entire musculoskeletal system for several months. Remedial massage, range of motion exercises and stretching can be effective in relieving muscle soreness and supporting the healing process.

Full Stride provides remedial canine massage treatments in the Brisbane area.

Until next time, enjoy your dogs.

Sources:

Cheung, K. H., & Patria, A. (2003). Maxwell Linda. Delayed onset muscle soreness: treatment strategies and performance factors. Sports Med, 33(2), 145-64.

Dogan, S., Manley, P. A., Vanderby Jr, R., Kohles, S. S., Hartman, L. M., & McBeath, A. A. (1991). Canine intersegmental hip joint forces and moments before and after cemented total hip replacement. Journal of biomechanics, 24(6), 397-407.

Munehiro, Teppei & Kitaoka, Katsuhiko & Ueda, Yoshimichi & Maruhashi, Yoshinobu & Tsuchiya, Hiroyuki. (2012). Establishment of an animal model for delayed-onset muscle soreness after high-intensity eccentric exercise and its application for investigating the efficacy of low-load eccentric training. Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association.

Image by Manfred Richter from Pixabay