The successful surgical correction of a leg deformity in a Shetland pony has been described in a case report in the journal Veterinary Surgery.
The Shetland pony was born in Germany with a complex deformity affecting his right front leg. The nine-week-old 47kg male was referred to the equine clinic at the Free University of Berlin.
The foal, they said, was bright, alert, and responsive, with all vital parameters within normal limits. They identified a severe deformity of the mid-radius, with a backward bend and rotation outwards. Carpal valgus (outward turning of the leg) and hyperextension of the metacarpophalangeal joint were also present.
The foal was weight-bearing on all four limbs and was able to walk, trot, and canter, but displayed what appeared to be a moderate mechanical lameness of the right forelimb.
The veterinarians carried out imaging – x-rays and a CT scan – to get a more detailed look at the problems. They calculated the single cutting plane required to correct the long-bone deformity, aided by the use of three-dimensional (3D) software.
Two custom-made stainless-steel plates were subsequently made to stabilize the corrected bone.
Following surgical alignment, the severe valgus deformity of the carpus became more apparent. For correction, a screw was placed at the medial distal radius through a stab incision.
The two wounds were protected with a two-layer bandage, which was kept in place using adhesive tape. Following the four-hour surgery, hand-assisted anesthetic recovery was uneventful.
The foal was fully weight-bearing on the right forelimb throughout his recovery, and wound healing progressed without complications, the authors reported.
Antimicrobial, anti-inflammatory therapy, and gastric protection were continued for five days. A glue-on shoe was attached to the right hoof to aid in the correction of the carpal valgus deformity.
Fifteen weeks after surgery, the foal was admitted for repeated imaging, as well as for the removal of the screw.
“The pony was sound at walk and trot,” they reported. CT imaging identified a remaining deformity of 1 degree in the sagittal plane and 5 degrees in the transverse plane. The frontal plane deformity was corrected completely.
The carpal valgus deformity 15 weeks after surgery was about 5 degrees and the hyperextension of the right metacarpophalangeal joint improved completely.
A telephone follow-up with the owners 18 months after surgery confirmed that the pony had developed normally with a favorable cosmetic and functional outcome, they said.
Discussing the case, the team said the main advantage of the single-cut repair to the long bone was that accurate correction could be achieved without bone loss.
Careful pre-surgical planning was crucial, they said. “Miscalculation can easily result in the inadequate correction of a complex long-bone deformity.”
They continued: “In future cases, we would perform the surgery with a 3D printed cutting guide. After determining the cutting plane, it would be possible to create such a cutting guide using the 3D software.”
They said they would strongly recommend testing the cut in a 3D model before performing the surgery on a patient.
To date, they said, the correction of complex limb deformities in equine patients is considered complicated surgery with a guarded to fair prognosis for athletic activity.
“Additional reports of single-cut osteotomies in large animal cases are needed to determine their limitations and potential contributions for successful outcomes in these species.”
The case report team comprised Schweinsberg, Anna Ehrle, Andrea Noguera Cender and Christoph Lischer, all with the Equine Clinic at the Free University of Berlin; Uwe Schweinsberg, with civil engineers Ingenieurbüro Schweinsberg; and Lucy Meehan, with VetCT, at the St John’s Innovation Centre in Cambridge, England.
Single-cut osteotomy for correction of a complex multiplanar deformity of the radius in a Shetland pony foal
Lorenz P. Schweinsberg, Anna Ehrle, Uwe Schweinsberg, Lucy Meehan, Andrea Noguera Cender, Christoph J. Lischer.
Veterinary Surgery, 14 October 2021 https://doi.org/10.1111/vsu.13725