Proximal suspensory desmopathy in hindlimbs: A correlative clinical, ultrasonographic, gross post mortem and histological study

Abstract

Reasons for performing study: It has been suggested that ultrasonography is unreliable for the detection of hindlimb proximal suspensory desmopathy (PSD) based on comparisons between ultrasonographic and magnetic resonance images.

Objectives: To compare ultrasonography with gross and histopathological post mortem examination in horses with PSD diagnosed based on ultrasonography and control horses.

Study design: Retrospective descriptive study.

Methods: Part 1: 19 horses with hindlimb PSD and 10 control horses were humanely destroyed. Twenty control limbs and 37 lame limbs were examined grossly and 40 suspensory ligaments (SLs) were examined histologically and graded blindly. Part 2: 3 horses with recurrent lameness after surgical management of PSD and 4 with PSD were assessed ultrasonographically and by gross post mortem examination.

Results: Part 1: ultrasonographic lesions were graded moderate in 31/38 (81.6%) and severe in 7/38 (18.4%) lame limbs; in 4/37 (10.8%) limbs adhesion formation between the proximal aspect of the SL and the accessory ligament of the deep digital flexor tendon was predicted. Gross post mortem and histological examinations of control limbs revealed no abnormalities. Gross post mortem examination revealed substantial adhesions between the proximal aspect of the SL and adjacent soft tissues in 10/37 (27.0%) lame limbs; in 10/37 (27.0%) limbs there were adhesions between the body of the SL and the mid plantar aspect of the third metatarsal bone, extending distally in 6 (16.2%) limbs. Histology revealed abnormalities (grades 1-3) of the collagenous tissue in 25/36 (69.4%) limbs; muscle was abnormal (grades 1-3) in 35/36 (97.2%) limbs and adipose tissue (grades 1-3) in 16/36 (44.4%) limbs. Part 2: adhesions between the SL and adjacent soft tissues were predicted ultrasonographically and confirmed post mortem.

Conclusions: Ultrasonography was reliable for the detection of SL pathology based on histology as the gold standard. Adhesions may be a reason for recurrent lameness after surgery.

Keywords: horse; interosseous muscle; lameness; suspensory ligament.