Page 753 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 719

six equally distributed sites along the MPL. The descrip- observed in experimental horses subjected to MPD and
tion includes a similar amount in the MidPL. Most stall rested for 120 days, but no patellar fragmentation
VetBooks.ir days after the injections. Daily mild exercise is recom- athy were discovered in a horse presented for purchase
was detected. Long‐term MidPL desmitis and enthesop-
horses exhibit a slight stiffness and swelling for a few
61
with obvious previous MPD and patellar fragmenta-
mended, so there is minimal loss of muscle tone. While
most horses respond well to this treatment, a few require tion, and 2 of 9 horses with patellar ligament desmopa-
56
re‐treatment. thy had MidPL desmitis associated with previous MPD. 30
The commonly held opinion about the effectiveness of Although not in its original form, the MPL heals after
counterirritant injections into the MPL is that the liga- MPD. Most suggest that the risk of lameness and com-
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ment tightens, thereby mimicking increased tone from plications subsides after a suitable convalescence; there-
conditioning. In one histologic study the majority of the fore a minimum 90‐day rest period has been
(severe) inflammatory reaction and all of the drug were recommended. One experimental study that kept the
102
found in the endotenon and peritenon. The solutions horses stall confined for 120 days revealed positional
12
appeared to follow the planes of least resistance. Within change in the patella and MidPL enthesopathies, but
the dense collagen bundles, collagen fibers were disrupted neither lameness nor patellar fragmentation or femoro-
without the same severe reaction, although there was patellar synovitis was reported. 6
fibrous tissue production and overall thickening. The
mechanism of action, although still unproven, could be a Prognosis
reduction in the expansile ability of the fibrous MPL.
Ethanolamine oleate, a sclerosing agent, was com- The prognosis is good for horses that respond to a
pared with 2% iodine in almond oil for injection of conditioning program and maintain that fitness level.
MPL and MidPL in experimental horses. Although After conditioning and ensuring correct shoeing, the logi-
98
both induced inflammation, 2% iodine in almond oil cal progression is counterirritant injection, MPL splitting,
caused more thickening and a more significant inflam- and then medial patellar ligament desmotomy. The diag-
matory reaction, which would be expected to lead to nosis should be confirmed before surgery is performed
more functional shortening of the ligaments. None of because more complications have appeared when MPD is
the horses were lame after the injections. A report of 70 performed on unaffected horses. A 90‐day convalescence
horses treated with weekly homeopathic anti‐inflamma- period following surgery is also recommended.
tory injections two to four times revealed an 82% In one retrospective study, 46 of 49 diversely occu-
success, with the remainder requiring surgery. Possibly pied horses undergoing uni‐ or bilateral MPD over a 10‐
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the number and frequency of injections may have con- year period by multiple surgeons became sound. The
8
tributed to local fibrosis. authors theorized that the good results were because the
When nothing else helps or the UFP cannot be surgery was only performed on horses that were actu-
reduced, an MPD can be performed using local anesthe- ally suffering from UFP and that these horses had differ-
sia in the standing horse. Complications from that proce- ent stifle angles than normal horses that may prevent the
dure should deem it the treatment of last resort. 38,50,62,84,91,102 development of complications. In another study of 15
The procedure is usually performed in the standing horses and 6 ponies, no recurrence of UFP was observed
horse, although an alternative procedure performed in 19 of 21 horses following MPD. However, postop-
70
with the horse under general anesthesia in dorsal recum- erative radiographs revealed no abnormalities in the
107
bency has been described. The ligament is usually iso- ponies but FDP was present in 4 horses and ossification
lated with hemostats and transected with a suitable at the tibial insertion of the MPL was seen in 8 horses. 70
blunt bistoury. The horse should be confined to a stall,
with hand walking gradually increasing over a period of
90 days. A conservative conditioning program can then DESMITIS OF THE PATELLAR LIGAMENTS
begin until regular work resumes. Failure of MPD to
102
correct the problem has been reported supposedly due Desmitis of patellar ligaments is an infrequently
to persistent tissue continuing to displace over the medial reported condition most often diagnosed in the MidPL
trochlear ridge. 26,45 Accidental transection of the middle (Figure 5.124). 30,79,80 Affected horses are usually athletes,
patellar ligament produces a catastrophic result. 107 mostly eventers, jumpers, or steeplechasers for which
40
As early as 1979, FDP following MPD was reported. direct trauma from striking a jump is a risk factor. 27,30,79
Gibson et al. observed articular cartilage fibrillation or Among event horses, the frequency of patellar ligament
38
fragmentation in all horses 3 months after MPD. The injuries followed only cruciate ligament and meniscal
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patellar lesions were located distolaterally or centrally. injuries in one report. Many cases are diagnosed after
There are also several other reports of distal patellar a prolonged lameness with no recognized inciting inci-
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fibrillation, fragmentation, or subchondral lysis associ- dent. Injuries to the MidPL combined with lateral
ated with varying degrees of lameness, femoropatellar patellar ligament (LPL) injury is thought to be most
synovitis, periarticular fibrosis, or enthesopathy at the common followed by LPL desmitis alone and MidPL
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origin or insertion of the MPL in horses having under- injury alone. Desmitis of the LPL may accompany
gone MPD. 62,84,91,108 fracture of the tibial tuberosity. 79
A lateral shift in the patellar position and increase in
6
the patellofemoral angle 6,84 along with traction from Clinical Signs and Diagnosis
the MidPL may explain the distal and lateral lesions
that typically appear on the patella following MPD. Lameness is variable and usually exacerbated by stifle
Ultrasonographic evidence of MidPL desmitis was flexion. The desmitis may not be evident upon physical
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