Veterinary Surgery. 20, 1, 15-20, 1991
Mid-metacarpal Deep Digital Flexor Tenotomy in the Management of Refractory Laminitis in Horses
Deep digital flexor tendon transection at the mid-metacarpus was performed in 20 horses with severe acute or chronic laminitis that was not responsive to conventional treatment. Sixteen horses improved within 72 hours, one horse worsened, and two horses were unaffected by the surgery. Eleven horses survived less than 1 month after surgery and six horses survived longer than 6 months. Three horses surviving longer than 6 months have remained lame and no horse has returned to athletic performance. Transection of the deep digital flexor tendon at the mid-metacarpus may decrease the pain associated with the acute refractory stage of laminitis and may be useful as an immediate salvage procedure; however, despite the early clinical improvement observed after tenotomy, the survival rate of affected horses may not be altered.
spective study reported here ua\ undertaken to determine the clinical efficac) of the procedure and to descnbe the surgical technique of deep digital tlexor tenotomy at the middle of the metacdrpus 35 a treatment for acutc and chronic laminitis
R F T M E N T OF HORSES with refractory acute and chronic laminitis has three objectives: ( I ) alleviating the intense pain associated with the disease. ( 2 )prerenting irreversible detrimental alterations of the digit associated with rotation or distal displacement ofthe distal phalanx. and ( 3 ) reestablishing a functional relationship between the third phalanx and the hoof wall if laminar destruction has already occurred. Nonsteroidal anti-i n ilam matory drugs, peripheral vasodilators. antihistamines. heparin, soaking the horse's feet. corrective foot trimming. frog pads. hoof wall resection, corrective shoeing techniqucs, and deep digital flexor tenotomy have been used with varying results.''' Consequently. there is no single treatment or combination oftreatments that will aford a successful outcome for an animal with laminitis. Deep digital flexor tenotomy at the level ofthe proximal interphalangeal joint has been recommended in the treatment of horses with chronic refractory laminitis." The rationale is to remove thc predominant force responsible for the distopalmar/plantar movement of the distal phalanx, remove a source of pain, and prevent further rotation of the distal p h a l a n ~ . ~I n- ~a retrospective study o f t h e efficacy of this procedure, 10 of 13 horses returned to a pasture sound status or to athletic soundness.' Because the tenotomy may be performed more easily at the level of the middle of the metacarpus, the retro-
T
Materials and Methods
The medical records of 20 horses that underwent midmetacarpal deep digital flexor tenotomy for treatment of acute or chronic laminitis at the LJniversity of Georgia. College of Veterinary Medicine. from January 1986 through August I989 were reviewed. Data retrieved included the horse's signalment. clinical disorders associated with the onset of laminitis, severity of laminitis (estimation of Obel grade) at the time oftenotomy. duration of laminitis before tenotoniy. radiographic findings before hoof wall resection. clinical response to tenotomy, hoof care, survival time after tenotomy. and the cause of death for horses not surviving. The horses were grouped according to the degree of rotation of the distal phalanx before tenotomy. Distal phalangeal rotation was determined from lateral radiographs with the use of a protractor. Group I ( n = 3 ) had less than 5.5 degrees ofrotation; Group I1 ( n = 10) had 5.5 to 1 1.5 degrees of rotation: and Group I l l ( n = 7) had more than 1 I .5 degrees of rotation. Ultra-
From the Department of Large Animal Medicine. College of Veterinary Medicine, The University of Georgia. Athens, Georgia. Reprint requests: R . J. Hunt, DVM, MS. Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
15
16
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY
sonographic assessment of healing tenotomies was performed 2 weeks, 4 months, and 6 months after tenotomy in horses 13. 17, and 18. The long-term cosmetic appearance of the tenotomy site in the surviving animals was evaluated subjectively, and complications directly associated with the procedure were reviewed. Horses selected as candidates for tenotomy had severe laminitis (Obel grade I l l or IV). a deteriorating condition. and a clinical course that was not improved by corrective arimming. shoeing. and medical therapy. The decision for surgery also was made for horses with devitalized dorsal
Fig. 2. Mosquito hemostatic forceps have been inserted between the superficial and deep digital flexor tendons.
Fig. 1. Lateral and cross-sectional views of the anatomic arrangement of the superficial digital flexor tendon (SDF), deep digital flexor tendon (DDF), interosseus ligament (IL), and neurovascular bundle (NVB) at the level of the mid-metacarpus.
hoof wall laminae in which pain was believed to be caused by rotation of the distal phalanx that was attributable to the tension from the deep digital flexor tendon. Surgery was performed with all horses in a standing position. Sedation was provided by xylazine or a com%ination of xylazine and butorphanol. Local anesthesia was done with a high palmar nerve block or local infiltration of mepivacaine just proximal to the mid-metacarpus around the deep digital flexor tendon. The limb was prepared aseptically from the carpometacarpal joint to the metacarpophalangeal joint. A vertically oriented stab incision was made through the skin and subcutaneous tissues between the superficial and deep flexor tendons at the mid-point of the metacarpus on the lateral side of the limb (Fig. 1). A pair of mosquito hemostatic forceps was introduced between the superficial and deep digital flexor tendons in a lateral to medial direction with the curved tip oriented dorsally to separate the two tendons (Fig. 2). The forceps were removed. With the cutting edge oriented proximally, a guarded. single-edged, I cm tendon bistoury* was passed along the dissection plane created with
* Joseph Button End knife (straight). Adler Surgical Associates. Inc.. Atlanta, GA.
HUNT, ALLEN, BAXTER, JACKMAN, AND PARKS
17
the forceps. The bistoury was rotated 90" so thc cutting edge encountered the palmar aspect of the deep digital flexor tendon (Fig. 3 ) . The deep digital flexor tendon was transected by applying dorsal pressure and a fine lateral to medial sawing motion. After transection, the tendon ends immediately retracted approximately 2 cm (Fig. 4). The stab incisions were either left open to heal by second intention or closed with a simple interrupted nonabsorbable skin suture. A sterile. nonadherent dressing and a one half limb support wrap were applied. The bandages were changed every 2 to 3 days and removed altcr I0 days. All horses received tetanus prophylaxis. The use of antimicrobial agents varied. Results The breed distribution was representative of the population of horses treated at this hospital. There was no apparent age or sex predilection. Although no single i n citing factor predominated, gastrointestinal disorders wcre the most frequent accompanying problems (Table I ). N o marked clinical differences were noted regarding the degree of lameness, the response to tenotomy. or the eventual outcome of the horses i n the three groups. The degree of lameness improved one to two Obel gradcs in 16 horses within 7 2 hours after tenotomy: ninc horses improved within 24 hours. The condition of two horses
Fig. 3 A tendon bistoury being used to transect the deep digital flexor tendon.
Fig 4 Aftertransection, the ends of the deep digital flexor tendon retract approximately 2 cm
worsened immediately aftcr surgery. One of these resolved after 48 hours and the degree of lameness subsided; the other horse continued to deteriorate and was euthanatized after 2 weeks. Six horses survived more than 7 months. Five horses are presently alive, four remain lame with chronic laminitis, and one is currently sound in pasture. The most frequent complications leading to euthanasia or chronic lameness were recurring digital infection or septic pedal osteitis (I0 horses) and distal displacement of the distal phalanx ( 1 I horses). Other complications associated with tenotomy included laceration ofthe medial palmar artery ( 2 horses) and distal interphalangeal joint subluxation ( 2 horses). Both arterial lacerations occurred during transection of the tendon; hemostasis was achieved by direct pressure applied to the area. Subluxation of the distal interphalangeal joint resolved with the application of an extended heel reverse shoe and elevation of the heels. Results of ultrasonography of the mid-metacarpal regions of three horses after tenotomy (one each at 2 weeks.
18
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY TABLE 1. Clinical Summary of Twenty Horses With
Group I
II
Horse No.
5
Inciting Cause Septic metritis rhabdomyolosis Pharyngeal cellulitis Medical colic?
24 hrs 5d 3 d
20 d
111
24 hr
Ill
Chronic 2-wk Relapse 11 d
IV
10 d
IV
7 d
111
6 wk 2d
II IV
Middle phalangeal fracture Unknown
5d
111
5d
IV
7d
Ill-IV
3 mos
Ill-IV
Ill-IV
Belgian OH OH
0.25 6
Fe Fe Fe
4
QH
2
S
5
QH
8
Fe
6
QH
6
Fe
Enterolith/diarrhea Unknown
7
QH
12
Fe
Pneumonia
8
QH
13
G
9
American Saddlebred
15
G
Large colon displacement Steroid induced?
6
S
Small colon irn
15
G
paction Radial fracture
QH
Duration
3 wk
11
Grade
12
QH
3
S
13
QH
13
G
14
Clydesdale
5
Fe
15
TB
2
Fe
Retained placenta Unknown
16
TB
20
Fe
Colitis
5d
17
TB/Con
18
Fe
Unknown
1 mo
18
Arabian
7
G
19
QH
11
Fe
Middle phalangeal fracture Unknown
20
QH
4
S
Group I-< 5.5 degrees of rotation; Group 11-5.5 TB-Thoroughbred; Con-Connamara; Fe-female;
Obel Grade Before Tenotomy
Sex
1 2 3
10
111
Breed
Age (y-1
Small bowel strangulation
111
IV
111
Unknown
IV
Chronic 2 wk 5d
Ill-IV
to 11-5 degrees of rotation; Group HI-> 11.5 degrees of rotation. QH-Quarter G-Gelding; S-Stallion; DWR-dorsal wall resection; NA-not applicable.
at 4 months. and at 6 months) revealed similar findings of a 3 to 4 cm echolucent gap between the proximal and distal ends of the tendon. Horses 13 and 18 had echogenic material distributed throughout the echolucent area. which probably represented fibrous tissue. External palpation of the area in horses 17 and 2 at month 3 revealed a 2 cm gap. N o deficits were palpated in horses 18 (month 4) or 13 (month 6). More than 7 months after surgery, the tenotomy sites on horses 1. 13, 18. and 19 were approximately twice the diameter of the normal tendons.
111 111 Ill-IV
Ill-IV
horse;
Discussion Transection of the deep flexor tendon provided a considerable degree of comfort for most animals during the acute stages of laminitis. These immediate responses were similar to those reported for horses with chronic laminitis that underwent a similar procedure at the level of the proximal interphalangeal joint.5 It has been proposed that deep digital flexor tenotomy at the level of the proximal interphalangeal joint is beneficial in horses with chronic
19
HUNT, ALLEN, BAXTER, JACKMAN, AND PARKS Laminitis Treated With Deep Digital Nexor Tenotomy
Obel Grade After Tenotornv
Clinical Response Time (hr)
Outcome
Foot Care
I I II
24 72 48
Alive Alive Dead
7 rnos 15 rnos 1 mo
Yes No Yes
1-11
72
Dead
1 rno
No
NA NA Chronic infection sloughed digit Unhappy owner
I
72
Dead
6 rnos
Yes
Chronic infection
I
24
Dead
No
Chronic infection
II
48
Dead
Frog pads DWR. Shoes DWR. frog pads Reverse shoes, Pads, DWR Reverse shoes, Pads, DWR Reverse shoes, pads Reverse shoes
3 wk
Yes
I1
24
Dead
15 rnos
Yes
111 (Fore) IV (Hind) IV 1-11
48
Dead
1 wk
Yes
Dead
1 rno
Yes
IV
24 72 72
Dead
Reverse shoes, pads, DWR DWR. frog pads Reverse shoes. Foot cast Frog pad
Chronic infection sloughed digit Chronic laminitis died Sloughed hoof
3d
Yes
1-11
24
Dead
Reverse shoe
1 rno
No
Sloughed hoof died Distal phalangeal sole penetration Chronic laminitis
1-11
24
Alive
7 rnos
No
NA
I
72
Dead
2 rnos
No
111
24
Dead
DWR. reverse shoes, pads Reverse shoes. pads Frog pads
1 rno
No
IV
NA
Dead
2 wk
Yes
1-11
72
Dead
6 wk
Yes
II
72
Alive
Reverse shoes, pads DWR. reverse shoes Reverse shoe
Septic pedal osteitis Septic pedal osteitis Chronic infection Sloughed hoof pain Chronic infection
9 rnos
Yes
NA
1-11
48
Alive
Reverse shoes
7 rnos
No
NA
Ill-IV
12
Dead
Frog pads
laminitis by removing a major force responsible for the distopalmar rotation of the distal phalanx.'.' Because the horses in the current study were in an acute stage o f laminitis. we hypothesized that transection of the tendon would provide relief from pain and yrevcnt further rotation of the distal phalanx. The initial clinical iniprovement in the degree of lameness of these horses slrongl) suggests that the surgery attenuated the pain. The poor long-term survival rate may reflect thc severity of laminitis in these horses.
Survival Time Or FOIIOW-UP Time
1 rno
12 h
Distal Displacement of Distal Phalanx
No
Reason for Euthanasia
Colic
Performing deep digital tlexor tenotomy at the midmetacarpus offers several advantages. The procedure may be done with the animal standing using sedation and local anesthesia. which avoids general anesthesia i n an animal that may be debilitated and sufenng cardiovascular complications. Performing thc tcnotomy at the level of the proximal interphalangeal joint requires entry into a synovial sheath, allows excessive postoperative retraction of the tendon ends. and in our experience. is also more prone to complications such as wound sepsis. distal interpha-
20
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY
langeal joint subluxation, or synovial sinus foi-mation. Mid-metacarpal deep digital flexor transection avoids entering any synovial structures, and excessive retraction of tendon ends is prevented by surrounding connective tissue fascia. In a previous study on deep digital flexor tenotomy performed at the proximal interphalangeal joint,5 the results were substantially more favorable than in the current report. Reasons for the discrepancy are only speculative. The horses in the former study had chronic laminitis; therefore, their clinical condition may have been stable and their distal phalanges may not have been undergoing any further rotation or distal displacement (sinking). In contrast. the horses in our study were deteriorating and tailing to improve by any other means of therapy. The degree of distal phalangeal rotation in horses with laminitis was found to be inversely correlated with return to athletic performance and has therefore been used as a prognostic indicator.' In that study. horses with less than 5.5 degrees ofdistal phalangeal rotation returned to former athletic function, whereas horses with more than 1 I .5 degrees of rotation were lost to use as performance animals. No horses in the current study have returned to athletic performance although I3 horses had less than 1 1.5 degrees of rotation. The severity and refractory nature of the laminitis in these horses precluded practical application of distal phalangeal rotation as a prognostic indicator. Distal displacement of the distal phalanx or recurrent abscessation and hoof wall separation were the most common causes for euthanasia or chronic debilitation of the horses. Distal displacement of the distal phalanx. which carries a grave prognosis, is caused by necrosis and separation of the sensitive laminae from the entire hoof wall.' Two affected horses in this study survived but are still lame. The effects of deep digital flexor tenotomy on the clinical course of horses that develop distal displacement of the distal phalanx are unknown. Presumably, chronic recurrent infection of the sensitive laminae occurs from compromise of the vascular supply to the foot and
from loss of the normal protective barrier provided by the healthy hoof wall.',' None of the five surviving horses has returned to athletic performance. Even though the long-term appearance of the tenotomy regions was less than optimal, functional problems were not recognized. Four surviving horses remained lame from hoof-related problems associated with the laminitis, and one horse was not lame after 1 year. Because of the relatively small number of horses, the variation in treatments other than tenotomy, and complications associated with laminitis, it was not feasible to correlate the eventual outcome ofeach case with a particular type of therapy or clinical observation. Based on these results, transection of the deep digits1 flexor tendon at the mid-metacarpus may decrease the pain associated with the acute refractory stage of laminiiis and may be a viable option as an immediate salvage procedure. However, despite the early clinical improvement observed after tenotomy, the overall survival rate of affected horses may not be altered.
References I. Goetz TE. The treatment of laminitis in horses. Vet Clin North Am
(Equine Pract) 1989:5:73-108. 7 Stashak TS. Lameness. In: Stashak TS. ed. ildn/nc ' _.
3. 4.
5.
6.
7.
L n i i ~ t w s s/ n
H ( J ~ \ (4th o s ed.). Philadelphia: Lea & Febiger 1987:486-499. Colles CM. Laminitis in the horse. Vet Rec 1977:100:262-264. Yelle M. Clinician's guide to equine laminitis. Equine Vet J 1986:18: 156- 158. Allen D. White NA. Foerner JF. Gordon BJ. Surgical management of chronic laminitis in horses: Thirteen cases. J Am Vet Med Assoc 1986:189:1604-1606. Cotfman JR. Johnson JH. Finocchio EJ. Guffy M M . Biomechanics of pedal rotation in equine laminitis. J .Am Vet Med Assoc 1970: 1562 19-22 I , Stich JA. Jann IHW, Scott EA. Robinson NE. Pedal bone rotation as a prognostic sign in laminitis of horses. J Am Vet Med Assoc
1982:180:25 1-253.
8. Baxter GM. Equine laminitis caused by distal displacement of the distal phalanx: I ? cases. J Am Vet Med Assoc 1986:189:326329.
Mid-metacarpal Deep Digital Flexor Tenotomy in the Management of Refractory Laminitis in Horses
Deep digital flexor tendon transection at the mid-metacarpus was performed in 20 horses with severe acute or chronic laminitis that was not responsive to conventional treatment. Sixteen horses improved within 72 hours, one horse worsened, and two horses were unaffected by the surgery. Eleven horses survived less than 1 month after surgery and six horses survived longer than 6 months. Three horses surviving longer than 6 months have remained lame and no horse has returned to athletic performance. Transection of the deep digital flexor tendon at the mid-metacarpus may decrease the pain associated with the acute refractory stage of laminitis and may be useful as an immediate salvage procedure; however, despite the early clinical improvement observed after tenotomy, the survival rate of affected horses may not be altered.
spective study reported here ua\ undertaken to determine the clinical efficac) of the procedure and to descnbe the surgical technique of deep digital tlexor tenotomy at the middle of the metacdrpus 35 a treatment for acutc and chronic laminitis
R F T M E N T OF HORSES with refractory acute and chronic laminitis has three objectives: ( I ) alleviating the intense pain associated with the disease. ( 2 )prerenting irreversible detrimental alterations of the digit associated with rotation or distal displacement ofthe distal phalanx. and ( 3 ) reestablishing a functional relationship between the third phalanx and the hoof wall if laminar destruction has already occurred. Nonsteroidal anti-i n ilam matory drugs, peripheral vasodilators. antihistamines. heparin, soaking the horse's feet. corrective foot trimming. frog pads. hoof wall resection, corrective shoeing techniqucs, and deep digital flexor tenotomy have been used with varying results.''' Consequently. there is no single treatment or combination oftreatments that will aford a successful outcome for an animal with laminitis. Deep digital flexor tenotomy at the level ofthe proximal interphalangeal joint has been recommended in the treatment of horses with chronic refractory laminitis." The rationale is to remove thc predominant force responsible for the distopalmar/plantar movement of the distal phalanx, remove a source of pain, and prevent further rotation of the distal p h a l a n ~ . ~I n- ~a retrospective study o f t h e efficacy of this procedure, 10 of 13 horses returned to a pasture sound status or to athletic soundness.' Because the tenotomy may be performed more easily at the level of the middle of the metacarpus, the retro-
T
Materials and Methods
The medical records of 20 horses that underwent midmetacarpal deep digital flexor tenotomy for treatment of acute or chronic laminitis at the LJniversity of Georgia. College of Veterinary Medicine. from January 1986 through August I989 were reviewed. Data retrieved included the horse's signalment. clinical disorders associated with the onset of laminitis, severity of laminitis (estimation of Obel grade) at the time oftenotomy. duration of laminitis before tenotoniy. radiographic findings before hoof wall resection. clinical response to tenotomy, hoof care, survival time after tenotomy. and the cause of death for horses not surviving. The horses were grouped according to the degree of rotation of the distal phalanx before tenotomy. Distal phalangeal rotation was determined from lateral radiographs with the use of a protractor. Group I ( n = 3 ) had less than 5.5 degrees ofrotation; Group I1 ( n = 10) had 5.5 to 1 1.5 degrees of rotation: and Group I l l ( n = 7) had more than 1 I .5 degrees of rotation. Ultra-
From the Department of Large Animal Medicine. College of Veterinary Medicine, The University of Georgia. Athens, Georgia. Reprint requests: R . J. Hunt, DVM, MS. Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
15
16
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY
sonographic assessment of healing tenotomies was performed 2 weeks, 4 months, and 6 months after tenotomy in horses 13. 17, and 18. The long-term cosmetic appearance of the tenotomy site in the surviving animals was evaluated subjectively, and complications directly associated with the procedure were reviewed. Horses selected as candidates for tenotomy had severe laminitis (Obel grade I l l or IV). a deteriorating condition. and a clinical course that was not improved by corrective arimming. shoeing. and medical therapy. The decision for surgery also was made for horses with devitalized dorsal
Fig. 2. Mosquito hemostatic forceps have been inserted between the superficial and deep digital flexor tendons.
Fig. 1. Lateral and cross-sectional views of the anatomic arrangement of the superficial digital flexor tendon (SDF), deep digital flexor tendon (DDF), interosseus ligament (IL), and neurovascular bundle (NVB) at the level of the mid-metacarpus.
hoof wall laminae in which pain was believed to be caused by rotation of the distal phalanx that was attributable to the tension from the deep digital flexor tendon. Surgery was performed with all horses in a standing position. Sedation was provided by xylazine or a com%ination of xylazine and butorphanol. Local anesthesia was done with a high palmar nerve block or local infiltration of mepivacaine just proximal to the mid-metacarpus around the deep digital flexor tendon. The limb was prepared aseptically from the carpometacarpal joint to the metacarpophalangeal joint. A vertically oriented stab incision was made through the skin and subcutaneous tissues between the superficial and deep flexor tendons at the mid-point of the metacarpus on the lateral side of the limb (Fig. 1). A pair of mosquito hemostatic forceps was introduced between the superficial and deep digital flexor tendons in a lateral to medial direction with the curved tip oriented dorsally to separate the two tendons (Fig. 2). The forceps were removed. With the cutting edge oriented proximally, a guarded. single-edged, I cm tendon bistoury* was passed along the dissection plane created with
* Joseph Button End knife (straight). Adler Surgical Associates. Inc.. Atlanta, GA.
HUNT, ALLEN, BAXTER, JACKMAN, AND PARKS
17
the forceps. The bistoury was rotated 90" so thc cutting edge encountered the palmar aspect of the deep digital flexor tendon (Fig. 3 ) . The deep digital flexor tendon was transected by applying dorsal pressure and a fine lateral to medial sawing motion. After transection, the tendon ends immediately retracted approximately 2 cm (Fig. 4). The stab incisions were either left open to heal by second intention or closed with a simple interrupted nonabsorbable skin suture. A sterile. nonadherent dressing and a one half limb support wrap were applied. The bandages were changed every 2 to 3 days and removed altcr I0 days. All horses received tetanus prophylaxis. The use of antimicrobial agents varied. Results The breed distribution was representative of the population of horses treated at this hospital. There was no apparent age or sex predilection. Although no single i n citing factor predominated, gastrointestinal disorders wcre the most frequent accompanying problems (Table I ). N o marked clinical differences were noted regarding the degree of lameness, the response to tenotomy. or the eventual outcome of the horses i n the three groups. The degree of lameness improved one to two Obel gradcs in 16 horses within 7 2 hours after tenotomy: ninc horses improved within 24 hours. The condition of two horses
Fig. 3 A tendon bistoury being used to transect the deep digital flexor tendon.
Fig 4 Aftertransection, the ends of the deep digital flexor tendon retract approximately 2 cm
worsened immediately aftcr surgery. One of these resolved after 48 hours and the degree of lameness subsided; the other horse continued to deteriorate and was euthanatized after 2 weeks. Six horses survived more than 7 months. Five horses are presently alive, four remain lame with chronic laminitis, and one is currently sound in pasture. The most frequent complications leading to euthanasia or chronic lameness were recurring digital infection or septic pedal osteitis (I0 horses) and distal displacement of the distal phalanx ( 1 I horses). Other complications associated with tenotomy included laceration ofthe medial palmar artery ( 2 horses) and distal interphalangeal joint subluxation ( 2 horses). Both arterial lacerations occurred during transection of the tendon; hemostasis was achieved by direct pressure applied to the area. Subluxation of the distal interphalangeal joint resolved with the application of an extended heel reverse shoe and elevation of the heels. Results of ultrasonography of the mid-metacarpal regions of three horses after tenotomy (one each at 2 weeks.
18
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY TABLE 1. Clinical Summary of Twenty Horses With
Group I
II
Horse No.
5
Inciting Cause Septic metritis rhabdomyolosis Pharyngeal cellulitis Medical colic?
24 hrs 5d 3 d
20 d
111
24 hr
Ill
Chronic 2-wk Relapse 11 d
IV
10 d
IV
7 d
111
6 wk 2d
II IV
Middle phalangeal fracture Unknown
5d
111
5d
IV
7d
Ill-IV
3 mos
Ill-IV
Ill-IV
Belgian OH OH
0.25 6
Fe Fe Fe
4
QH
2
S
5
QH
8
Fe
6
QH
6
Fe
Enterolith/diarrhea Unknown
7
QH
12
Fe
Pneumonia
8
QH
13
G
9
American Saddlebred
15
G
Large colon displacement Steroid induced?
6
S
Small colon irn
15
G
paction Radial fracture
QH
Duration
3 wk
11
Grade
12
QH
3
S
13
QH
13
G
14
Clydesdale
5
Fe
15
TB
2
Fe
Retained placenta Unknown
16
TB
20
Fe
Colitis
5d
17
TB/Con
18
Fe
Unknown
1 mo
18
Arabian
7
G
19
QH
11
Fe
Middle phalangeal fracture Unknown
20
QH
4
S
Group I-< 5.5 degrees of rotation; Group 11-5.5 TB-Thoroughbred; Con-Connamara; Fe-female;
Obel Grade Before Tenotomy
Sex
1 2 3
10
111
Breed
Age (y-1
Small bowel strangulation
111
IV
111
Unknown
IV
Chronic 2 wk 5d
Ill-IV
to 11-5 degrees of rotation; Group HI-> 11.5 degrees of rotation. QH-Quarter G-Gelding; S-Stallion; DWR-dorsal wall resection; NA-not applicable.
at 4 months. and at 6 months) revealed similar findings of a 3 to 4 cm echolucent gap between the proximal and distal ends of the tendon. Horses 13 and 18 had echogenic material distributed throughout the echolucent area. which probably represented fibrous tissue. External palpation of the area in horses 17 and 2 at month 3 revealed a 2 cm gap. N o deficits were palpated in horses 18 (month 4) or 13 (month 6). More than 7 months after surgery, the tenotomy sites on horses 1. 13, 18. and 19 were approximately twice the diameter of the normal tendons.
111 111 Ill-IV
Ill-IV
horse;
Discussion Transection of the deep flexor tendon provided a considerable degree of comfort for most animals during the acute stages of laminitis. These immediate responses were similar to those reported for horses with chronic laminitis that underwent a similar procedure at the level of the proximal interphalangeal joint.5 It has been proposed that deep digital flexor tenotomy at the level of the proximal interphalangeal joint is beneficial in horses with chronic
19
HUNT, ALLEN, BAXTER, JACKMAN, AND PARKS Laminitis Treated With Deep Digital Nexor Tenotomy
Obel Grade After Tenotornv
Clinical Response Time (hr)
Outcome
Foot Care
I I II
24 72 48
Alive Alive Dead
7 rnos 15 rnos 1 mo
Yes No Yes
1-11
72
Dead
1 rno
No
NA NA Chronic infection sloughed digit Unhappy owner
I
72
Dead
6 rnos
Yes
Chronic infection
I
24
Dead
No
Chronic infection
II
48
Dead
Frog pads DWR. Shoes DWR. frog pads Reverse shoes, Pads, DWR Reverse shoes, Pads, DWR Reverse shoes, pads Reverse shoes
3 wk
Yes
I1
24
Dead
15 rnos
Yes
111 (Fore) IV (Hind) IV 1-11
48
Dead
1 wk
Yes
Dead
1 rno
Yes
IV
24 72 72
Dead
Reverse shoes, pads, DWR DWR. frog pads Reverse shoes. Foot cast Frog pad
Chronic infection sloughed digit Chronic laminitis died Sloughed hoof
3d
Yes
1-11
24
Dead
Reverse shoe
1 rno
No
Sloughed hoof died Distal phalangeal sole penetration Chronic laminitis
1-11
24
Alive
7 rnos
No
NA
I
72
Dead
2 rnos
No
111
24
Dead
DWR. reverse shoes, pads Reverse shoes. pads Frog pads
1 rno
No
IV
NA
Dead
2 wk
Yes
1-11
72
Dead
6 wk
Yes
II
72
Alive
Reverse shoes, pads DWR. reverse shoes Reverse shoe
Septic pedal osteitis Septic pedal osteitis Chronic infection Sloughed hoof pain Chronic infection
9 rnos
Yes
NA
1-11
48
Alive
Reverse shoes
7 rnos
No
NA
Ill-IV
12
Dead
Frog pads
laminitis by removing a major force responsible for the distopalmar rotation of the distal phalanx.'.' Because the horses in the current study were in an acute stage o f laminitis. we hypothesized that transection of the tendon would provide relief from pain and yrevcnt further rotation of the distal phalanx. The initial clinical iniprovement in the degree of lameness of these horses slrongl) suggests that the surgery attenuated the pain. The poor long-term survival rate may reflect thc severity of laminitis in these horses.
Survival Time Or FOIIOW-UP Time
1 rno
12 h
Distal Displacement of Distal Phalanx
No
Reason for Euthanasia
Colic
Performing deep digital tlexor tenotomy at the midmetacarpus offers several advantages. The procedure may be done with the animal standing using sedation and local anesthesia. which avoids general anesthesia i n an animal that may be debilitated and sufenng cardiovascular complications. Performing thc tcnotomy at the level of the proximal interphalangeal joint requires entry into a synovial sheath, allows excessive postoperative retraction of the tendon ends. and in our experience. is also more prone to complications such as wound sepsis. distal interpha-
20
MID-METACARPAL DEEP DIGITAL FLEXOR TENOTOMY
langeal joint subluxation, or synovial sinus foi-mation. Mid-metacarpal deep digital flexor transection avoids entering any synovial structures, and excessive retraction of tendon ends is prevented by surrounding connective tissue fascia. In a previous study on deep digital flexor tenotomy performed at the proximal interphalangeal joint,5 the results were substantially more favorable than in the current report. Reasons for the discrepancy are only speculative. The horses in the former study had chronic laminitis; therefore, their clinical condition may have been stable and their distal phalanges may not have been undergoing any further rotation or distal displacement (sinking). In contrast. the horses in our study were deteriorating and tailing to improve by any other means of therapy. The degree of distal phalangeal rotation in horses with laminitis was found to be inversely correlated with return to athletic performance and has therefore been used as a prognostic indicator.' In that study. horses with less than 5.5 degrees ofdistal phalangeal rotation returned to former athletic function, whereas horses with more than 1 I .5 degrees of rotation were lost to use as performance animals. No horses in the current study have returned to athletic performance although I3 horses had less than 1 1.5 degrees of rotation. The severity and refractory nature of the laminitis in these horses precluded practical application of distal phalangeal rotation as a prognostic indicator. Distal displacement of the distal phalanx or recurrent abscessation and hoof wall separation were the most common causes for euthanasia or chronic debilitation of the horses. Distal displacement of the distal phalanx. which carries a grave prognosis, is caused by necrosis and separation of the sensitive laminae from the entire hoof wall.' Two affected horses in this study survived but are still lame. The effects of deep digital flexor tenotomy on the clinical course of horses that develop distal displacement of the distal phalanx are unknown. Presumably, chronic recurrent infection of the sensitive laminae occurs from compromise of the vascular supply to the foot and
from loss of the normal protective barrier provided by the healthy hoof wall.',' None of the five surviving horses has returned to athletic performance. Even though the long-term appearance of the tenotomy regions was less than optimal, functional problems were not recognized. Four surviving horses remained lame from hoof-related problems associated with the laminitis, and one horse was not lame after 1 year. Because of the relatively small number of horses, the variation in treatments other than tenotomy, and complications associated with laminitis, it was not feasible to correlate the eventual outcome ofeach case with a particular type of therapy or clinical observation. Based on these results, transection of the deep digits1 flexor tendon at the mid-metacarpus may decrease the pain associated with the acute refractory stage of laminiiis and may be a viable option as an immediate salvage procedure. However, despite the early clinical improvement observed after tenotomy, the overall survival rate of affected horses may not be altered.
References I. Goetz TE. The treatment of laminitis in horses. Vet Clin North Am
(Equine Pract) 1989:5:73-108. 7 Stashak TS. Lameness. In: Stashak TS. ed. ildn/nc ' _.
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L n i i ~ t w s s/ n
H ( J ~ \ (4th o s ed.). Philadelphia: Lea & Febiger 1987:486-499. Colles CM. Laminitis in the horse. Vet Rec 1977:100:262-264. Yelle M. Clinician's guide to equine laminitis. Equine Vet J 1986:18: 156- 158. Allen D. White NA. Foerner JF. Gordon BJ. Surgical management of chronic laminitis in horses: Thirteen cases. J Am Vet Med Assoc 1986:189:1604-1606. Cotfman JR. Johnson JH. Finocchio EJ. Guffy M M . Biomechanics of pedal rotation in equine laminitis. J .Am Vet Med Assoc 1970: 1562 19-22 I , Stich JA. Jann IHW, Scott EA. Robinson NE. Pedal bone rotation as a prognostic sign in laminitis of horses. J Am Vet Med Assoc
1982:180:25 1-253.
8. Baxter GM. Equine laminitis caused by distal displacement of the distal phalanx: I ? cases. J Am Vet Med Assoc 1986:189:326329.
