Page 487 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 453

neurectomy is often based on the severity of lameness, musculotendinous unit of the DDFT, and minimize the
age and intended use of the horse, known abnormalities compressive forces on the navicular bone. 62,106 The goal
VetBooks.ir ments, and the wishes of the owner. reducing pain and lameness. Further clinical cases will
is to promote tendon healing while simultaneously
based on imaging results, responses to previous treat-
need to be assessed to determine the effectiveness of this
Various methods of PD neurectomy have been
described, and all have been developed to ensure com- procedure.
plete desensitization, prevent painful neuroma forma-
tion, and prevent axonal regrowth, which may result in Endoscopy/Bursoscopy
reinnervation. 26,58,63,74 Choosing which surgical tech-
nique to perform is often a personal preference of the Endoscopy of the navicular bursa has become the
veterinarian as several studies have failed to determine preferred surgical treatment of horses with infections or
the ideal PD neurectomy technique. The pull‐through or wounds that enter the navicular bursa. Endoscopy of the
stripping technique is recommended by the author, and bursa may also be performed as both a diagnostic and
the clinical results appear to be very good. 26,74 The treatment tool in a select group of horses with navicular
advantages of the pull‐through approach are that no disease using a modified surgical approach. 113,114 Horses
special equipment is needed, it can be easily performed with known or suspected abnormalities on the flexor
in the standing or recumbent horse, and the end of the surface of the navicular bone (flexor cortex erosions)
transected nerve is not located within the incision. and those with DDFT lesions (dorsal abrasions) at the
Regardless of the technique used for a PD neurectomy, a level of the navicular bone are the ideal candidates for
clean and atraumatic surgery and diligent postoperative navicular endoscopy (Figure 4.17). In a study of 114
care will minimize complications. 26,63,74 Limited activity horses that had navicular endoscopy, 92 horses had inju-
for 30–60 days and careful bandaging of the limbs for at ries within the bursa, and 98% of the injuries involved
least 3–4 weeks are thought to reduce the inflammatory the DDFT. Sixty‐one percent of horses returned to
113
response created by the surgery and reduce scar tissue work sound with only 42% returning to their previous
formation around the nerve stumps. level of performance. As would be suspected, horses
The prognosis of horses following a PD neurectomy with extensive DDFT lesions and those with combina-
appears to be very good initially but becomes less tion injuries of the DDFT and navicular bone identified
favorable as time progresses. In a study of 57 horses, with MRI had worse outcomes. Although endoscopy of
74% of the horses were sound at 1 year, but this the navicular bursa should be considered as a treatment
decreased to 63% after the second year. In a study of option for selected horses, the overall outcome of horses
63
horses that underwent the pull‐through neurectomy may not be that different than horses managed conserv-
74
technique, 88% were free of lameness at 1 year. atively with rest and rehabilitation. 21,106 Careful case
Survival analysis that was used to assess the time to selection may improve the advantage of surgery over
recurrence of lameness indicated that the mean survival conservative management, but in general the popularity
with no lameness after surgery was estimated at of using bursoscopy to treat horses with DDF tendinop-
74
4.14 ± 0.33 years (median, 5 years). A more recent athy is less than it was a few years ago. Advanced
106
study reported that 92% of horses responded positively imaging with CT or MRI is usually necessary prior to
to surgery and were able to return to previous athletic endoscopy to optimize the potential benefit of surgery.
use for a medial of 20 months. The most significant
58
complications after a neurectomy include rupture of the Prognosis
DDFT, regrowth of the nerves resulting in recurrence of
the lameness, and severe infection within the foot that The prognosis of horses with navicular disease/syn-
goes unnoticed. drome is difficult to predict because of the numerous
bone and soft tissue abnormalities that can occur con-
currently. Radiographs alone are not adequate to com-
Inferior Check Ligament Desmotomy
pletely assess the pathology within the foot and therefore
Inferior check ligament desmotomy has been used in cannot be used alone to determine the prognosis unless
selected cases of horses with navicular syndrome in the abnormalities are advanced. It is also known that the
which dorsal palmar hoof imbalance (either broken‐ absence of radiographic abnormalities of the navicular
forward or broken‐backward axis) appears to be a bone does not indicate the lack of bone pathology.
101
major contributing factor. In one study, four horses with The combination of bone and soft tissue lesions is usu-
navicular syndrome that were treated with an inferior ally present in most horses, which can greatly alter the
check ligament desmotomy all returned to full use, and prognosis. 39,44,101 In addition, most abnormalities are
the surgery made it possible to align the hoof‐pastern degenerative in nature and worsen with time and con-
axis after surgery. This surgery seems to be most use- tinued use of the horse. In general horses with combina-
124
ful in horses with an upright heel conformation and a tion injuries to the DDFT and navicular bone tend to
broken‐forward hoof‐pastern axis, as is sometimes seen have worse outcomes with many remaining persistently
in Quarter horses with mismatched front feet. More lame. 44,106
recently the procedure has been used in horses with In most instances, the numerous treatment protocols
chronic DDF tendinopathy to supposedly reduce the are probably more appropriately termed management
tension on the DDFT, comparable with the superior strategies because the disease/syndrome is unlikely to
check ligament desmotomy procedure that is performed resolve completely. In general, clinical resolution may
in horses with SDF tendinitis. 62,106 The desmotomy is occur in 40%–50% of the horses with navicular disease/
thought to reduce the strain on the DDFT, lengthen the syndrome, but the optimal treatment and prognosis will