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Case Report: Elective, multiple deep digital flexor tenotomy in a Labrador Retriever to treat Contracture secondary to Ischaemic Myelopathy.

History

A six-year-old, female, entire Labrador Retriever presented with collapse and right-sided Horner’s syndrome. 

Fig. 1a - T2W sagittal MR-scan of cervical spine showing increased signal within the cord over the Ce6-7 disc.

fig. 1b - transverse T2W MR-scan of spine showing increased signal within the cord, lateralised to the right.

Onset was instantaneous and occured during mild exercise the previous day.  Neurological examination localised the lesion to the Ce5-T3 segements of the spinal cord, lateralised to the right.  MR-scans of this region of the spine revealed a diffuse area of malacia within the right side of the spinal cord, level with the Ce6-7 intervertebral disc (figs.1a&b).  The underlying disc appeared degenerate, but there was no evidence of a compressive lesion. CSF (collected via a cisternal tap), haematology, serum biochemistry, clotting times, serology for toxoplasma/ neospora and thyroid function testing were all found to be normal; consistent with a diagnosis of ischaemic myelopathy secondary to fibrocartilagenous embolism.

Over the following six months, the patient made a good recovery with intensive physical therapy; she was ambulatory after three months, but remained persistently paretic on the right thoracic limb and habitually knuckled over at the carpus.  Attempts were made to support the carpal joint with a brace, but she was still unable to use the limb effectively without traumatising the dorsal aspect of the digits.

Examination

Gait examination revealed a good range of motion of the right shoulder and elbow joints.  Carpal extension was noted on weight-bearing.  However, contracture of the digital flexor tendons resulted in knuckling over of the digits of the right manus during walking (see fig. 2 or video clip below)

fig. 2 - preoperative stance showing knuckling over of the right manus


http://www.youtube.com/watch?v=8PGHpOOqbxQ).

Treatment

Elective tenotomy of the deep digital flexors II-V were performed via a lateral approach (fig.3), using a tourniquet to limit peri-operative haemorrhage.

fig. 3 - intraoperative photograph of the approach to the flexor tendons


Follow-up

The dog made an uneventful recovery from surgery.  Repeat gait analysis two weeks after surgery revealed improved function of the right manus with the digital pads contacting the ground (fig. 4 or see video clip 2 http://www.youtube.com/watch?v=Iz_wmLFmst0).  Since then, the patient has continued to make steady progress and continues to use the limb well.

Discussion

fig. 4 - post op still of correct placement of the manus

Approximately 20% of patients suffering ischaemic myelopathy will be left with significant deficits.  In this case, damage to the cord within the cervicothoracic intumescence resulted in malacia of the lower motor neurones of the right brachial outflow, resulting in chronic paresis of the right thoracic limb.  This in turn, resulted in disuse atrophy and contracture of the flexor tendons and an inability to extend the manus to allow weight-bearing by the digital pads.  Differing management options were considered included amputation, continued use of the brace and carpal/ metacarpal arthrodesis.  However, it was thought that long-term use of the brace may become problematic from a soft-tissue/ compliance perspective.  Tenotomy of the digital tendons was a relatively simple and rapid procedure which greatly improved limb function.