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Deep Digital Flexor Tenotomy
CHAPTER 16 Deep Digital Flexor Tenotomy Joanne Kramer
INDICATIONS
POSITIONING AND PREPARATION
Severe distal interphalangeal joint contracture or severe laminitis with rotation of the third phalanx (P3) (Figures 16-1 and 16-2).
The procedure is most often performed with the horse standing in adult horses with laminitis and recumbent in foals with severe deep digital flexor tendon (DDFT) contracture. When performed with the horse standing, heel wedges are temporarily placed on the horse to take tension off the DDFT during the procedure. A high palmarpalmar metacarpal nerve block or inverted-U block is performed in the proximal metacarpal region. The limb is clipped circumferentially and prepared for aseptic surgery in the mid metacarpal region. A sterile adhesive drape or short drapes proximal and distal to the site are used.
EQUIPMENT A heel wedge is used during standing procedures. Modified table knives or malleable retractors are useful when isolating the tendon during transection1 (Figure 16-3).
Figure 16-2 Laminitis with rotation of the third phalanx.
Figure 16-1 Severe deep digital flexor tendon contracture.
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Deep Digital Flexor Tenotomy
ANATOMY The heads of the DDFT originate from the medial epicondyle of the humerus, olecranon, and caudal radius and insert as a single tendon on the palmar surface of the third phalanx. Transecting the DDFT eliminates the pull of the deep digital flexor muscle on the coffin bone, reducing shearing forces between the dorsal coffin bone and hoof wall and essentially eliminating coffin joint
Figure 16-3 Bent table knives are useful during isolation and transection of the deep digital flexor tendon. The curvature of the top instrument is greater than that of the bottom instrument.
99
flexion. The incision for mid metacarpal deep digital flexor tenotomy is located above the proximal extent of the digital flexor tendon sheath and is typically below the distal check ligament insertion. At this level, the neurovascular bundles lie directly over and slightly dorsal to the DDFT. Care must be taken to not exteriorize or transect these with the tendon (Figure 16-4).
PROCEDURE A 3-cm incision is made over the DDFT in the middle third of the metacarpus, avoiding the flexor tendon sheath, which extends proximally to the level of the second and fourth metacarpal bones (Figure 16-5). The palmar fascia is incised, and blunt dissection is used to create a space between the superficial digital flexor tendon and the DDFT. A space is then created between the DDFT and the suspensory ligament (interosseous medius tendon). The bent knife with the larger curvature is slid on the palmar surface of the DDFT, and the bent knife with the smaller curvature is slid on the dorsal surface of the DDFT until the instruments overlap (Figure 16-6). Slight
Common digital extensor tendon Lateral digital extensor tendon
MC II
MC IV Dorsal br. of ulnar n.
Interosseous medial m. (suspensory lig.)
Lateral palmar a.v. (palmar common digital a.v. III)
Medial palmar a.v. (palmar common digital a.v. II)
Medial palmar n. Lateral palmar n. DDFT
SDFT
Figure 16-4 Cross sectional anatomy of the deep digital flexor tendon and mid metacarpal region.
100
Limb Surgeries
overlapping of and tension on the instruments bring the DDFT to, but not out of, the incision. The DDFT is then transected with a No. 10 blade (Figure 16-7). If the distal check ligament is present at the level of the incision, it is isolated and transected with the DDFT. After transection, the heel elevation can be removed to check for adequate gap formation between the tendon ends. Closure of the subcutaneous tissue is optional. Closure of the skin is performed with an interrupted apposing or everting pattern using No. 2-0 monofilament suture material.
POSTOPERATIVE CARE Postoperative Care Site of approach
Figure 16-5 tenotomy.
Incision location for deep digital flexor
Figure 16-6 tendon.
Isolation of the deep digital flexor
Bandaging: A sterile dressing is placed over the incision and a half limb bandage is applied. The limb should remain bandaged for 30 days, and the bandage is changed every 5 to 7 days or more frequently if needed. Exercise Restrictions: Horses with laminitis should be rested as their condition indicates and are not allowed significant turnout for a minimum of 6 months. Foals with contracture can be allowed turnout in a small area after 1 week, and the amount of exercise allowed is gradually increased over the next 60 days. Free choice turnout should not be allowed for up to 6 months.2 Medications: Phenylbutazone should be administered for a minimum of 5 days. Suture Removal: Skin sutures are removed 12 days postoperatively. Other: Continued corrective shoeing is an essential component of treatment. Surgery should not be performed without considerations for postoperative corrective trimming and shoeing. Principles of shoeing to reestablish the normal relationship between the solar surface of P3 and the sole following deep digital flexor tenotomy have been described3,4 and are essential when tenotomy is performed as a component of laminitis treatment. Foals with severe flexural deformities should be trimmed in a normal fashion. The need for corrective shoeing in these cases depends on the amount of release achieved after tenotomy.
Deep Digital Flexor Tenotomy
101
ALTERNATIVE PROCEDURES
Figure 16-7 Transection of the deep digital flexor tendon.
EXPECTED OUTCOME Deep digital flexor tenotomy is a salvage procedure, although some horses may become sound for athletic activity. The intended goal should be limited to an improvement in comfort level and pasture soundness. Severe chronic cases of coffin joint contracture may have such severe joint capsule and surrounding tissue contracture that limb position may not improve significantly after tenotomy.5,6 The prognosis for horses with laminitis likely depends on the condition of P3 and blood supply. An improvement in pain, but not survival rate, has been reported in horses with acute refractory laminitis.7 In selected cases of chronic laminitis, an improved prognosis for survival has been reported.8
COMPLICATIONS Incisional dehiscence or drainage is rare. Severance of the palmar artery, vein, or nerve is possible and care must be taken that these structures are not isolated with the DDFT. Pain following tenotomy in foals with contracture may be significant because of stretching of the joint capsule and soft tissue and can be managed with nonsteroidal antiinflammatory medication. Occasionally, temporary heel elevation is used to allow for a more gradual change in foot conformation. Hyperextension of the coffin joint may occur and is managed with heel extension and elevation. Superficial digital flexor tendonitis may result from the increased strain on the superficial digital flexor tendon. Recurrent infection, abscessation, and sequestration of P3 are associated with chronic pain. If chronic pain persists, flexural deformity of the metacarpophalangeal joint may occur.
Tenotomy at the level of the mid pastern has been described.9 The procedure is performed under general anesthesia. A vertical 3-cm midline incision is made on the palmar aspect of the mid pastern. The incision is continued through the subcutaneous tissue and digital flexor tendon sheath. Curved forceps are placed under the tendon, and it is transected with a scalpel. The incision in the tendon sheath is closed with No. 2-0 absorbable suture. The subcutaneous tissues are closed with 2-0 absorbable suture and the skin is closed in an interrupted pattern.
COMMENTS The DDFT can be isolated and elevated outside the incision with curved forceps as has been traditionally described.10 During standing surgery, we prefer to use the modified table knives described by Redden because the neurovascular structures are easily protected from transection without having to exteriorize the tendon. Because of the anatomic location and peritendinous attachments, tenotomy at the level of the pastern may provide greater release than tenotomy at the mid metacarpal level.11 No difference in outcome has been demonstrated between the two techniques, and we prefer mid metacarpal tenotomy because of the lack of tendon sheath in the mid metacarpal region and the more proximal location for standing surgery.
REFERENCES 1. Redden RF: Shoeing the laminitic horse. In Redden RF, editor: Understanding laminitis, Lexington, 1998, The Blood Horse Inc. 2. Sullins KE: Standing musculoskeletal surgery. In Bertone A, editor: Standing surgery in the horse, Vet Clin N Am Equine Pract 7:687, 1991. 3. Nickels FA: Laminitis. In Ross MW, Dyson SJ, editors: Diagnosis and management of lameness in the horse, Philadelphia, 2003, WB Saunders. 4. Redden RF: Shoeing the laminitic horse, Proc Am Assoc Equine Pract 43:356, 1997. 5. Adams SB, Santschi EM: Management of congenital and acquired flexural deformities, Proc Am Assoc Equine Pract 46:117, 2000.
102
Limb Surgeries
6. McIlwraith CW, Fessler JF: Evaluation of inferior check ligament desmotomy for treatment of acquired flexor tendon contracture in the horse, J Am Vet Med Assoc 172:293, 1978. 7. Hunt RJ, Allen DA, Baxter GM, et al: Mid metacarpal deep digital flexor tenotomy in the management of refractory laminitis in horses, Vet Surg 20:15, 1991. 8. Eastman TG, Honnas CM, Hague BA: Deep digital flexor tenotomy as treatment for chronic laminitis in horses: 37 cases, Proc Am Assoc Equine Pract 44:265, 1998.
9. Allen D, White NA, Foerner JF, et al: Surgical management of chronic laminitis in horses: 13 cases (1983-1985), J Am Vet Med Assoc 189:1604, 1986. 10. Adams SB, Fessler JF: Deep digital flexor tenotomy. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders. 11. Hunt RJ: Laminitis. In Ross MW, Dyson SJ, editors: Diagnosis and management of lameness in the horse, Philadelphia, 2003, WB Saunders.
INDICATIONS
POSITIONING AND PREPARATION
Severe distal interphalangeal joint contracture or severe laminitis with rotation of the third phalanx (P3) (Figures 16-1 and 16-2).
The procedure is most often performed with the horse standing in adult horses with laminitis and recumbent in foals with severe deep digital flexor tendon (DDFT) contracture. When performed with the horse standing, heel wedges are temporarily placed on the horse to take tension off the DDFT during the procedure. A high palmarpalmar metacarpal nerve block or inverted-U block is performed in the proximal metacarpal region. The limb is clipped circumferentially and prepared for aseptic surgery in the mid metacarpal region. A sterile adhesive drape or short drapes proximal and distal to the site are used.
EQUIPMENT A heel wedge is used during standing procedures. Modified table knives or malleable retractors are useful when isolating the tendon during transection1 (Figure 16-3).
Figure 16-2 Laminitis with rotation of the third phalanx.
Figure 16-1 Severe deep digital flexor tendon contracture.
98
Deep Digital Flexor Tenotomy
ANATOMY The heads of the DDFT originate from the medial epicondyle of the humerus, olecranon, and caudal radius and insert as a single tendon on the palmar surface of the third phalanx. Transecting the DDFT eliminates the pull of the deep digital flexor muscle on the coffin bone, reducing shearing forces between the dorsal coffin bone and hoof wall and essentially eliminating coffin joint
Figure 16-3 Bent table knives are useful during isolation and transection of the deep digital flexor tendon. The curvature of the top instrument is greater than that of the bottom instrument.
99
flexion. The incision for mid metacarpal deep digital flexor tenotomy is located above the proximal extent of the digital flexor tendon sheath and is typically below the distal check ligament insertion. At this level, the neurovascular bundles lie directly over and slightly dorsal to the DDFT. Care must be taken to not exteriorize or transect these with the tendon (Figure 16-4).
PROCEDURE A 3-cm incision is made over the DDFT in the middle third of the metacarpus, avoiding the flexor tendon sheath, which extends proximally to the level of the second and fourth metacarpal bones (Figure 16-5). The palmar fascia is incised, and blunt dissection is used to create a space between the superficial digital flexor tendon and the DDFT. A space is then created between the DDFT and the suspensory ligament (interosseous medius tendon). The bent knife with the larger curvature is slid on the palmar surface of the DDFT, and the bent knife with the smaller curvature is slid on the dorsal surface of the DDFT until the instruments overlap (Figure 16-6). Slight
Common digital extensor tendon Lateral digital extensor tendon
MC II
MC IV Dorsal br. of ulnar n.
Interosseous medial m. (suspensory lig.)
Lateral palmar a.v. (palmar common digital a.v. III)
Medial palmar a.v. (palmar common digital a.v. II)
Medial palmar n. Lateral palmar n. DDFT
SDFT
Figure 16-4 Cross sectional anatomy of the deep digital flexor tendon and mid metacarpal region.
100
Limb Surgeries
overlapping of and tension on the instruments bring the DDFT to, but not out of, the incision. The DDFT is then transected with a No. 10 blade (Figure 16-7). If the distal check ligament is present at the level of the incision, it is isolated and transected with the DDFT. After transection, the heel elevation can be removed to check for adequate gap formation between the tendon ends. Closure of the subcutaneous tissue is optional. Closure of the skin is performed with an interrupted apposing or everting pattern using No. 2-0 monofilament suture material.
POSTOPERATIVE CARE Postoperative Care Site of approach
Figure 16-5 tenotomy.
Incision location for deep digital flexor
Figure 16-6 tendon.
Isolation of the deep digital flexor
Bandaging: A sterile dressing is placed over the incision and a half limb bandage is applied. The limb should remain bandaged for 30 days, and the bandage is changed every 5 to 7 days or more frequently if needed. Exercise Restrictions: Horses with laminitis should be rested as their condition indicates and are not allowed significant turnout for a minimum of 6 months. Foals with contracture can be allowed turnout in a small area after 1 week, and the amount of exercise allowed is gradually increased over the next 60 days. Free choice turnout should not be allowed for up to 6 months.2 Medications: Phenylbutazone should be administered for a minimum of 5 days. Suture Removal: Skin sutures are removed 12 days postoperatively. Other: Continued corrective shoeing is an essential component of treatment. Surgery should not be performed without considerations for postoperative corrective trimming and shoeing. Principles of shoeing to reestablish the normal relationship between the solar surface of P3 and the sole following deep digital flexor tenotomy have been described3,4 and are essential when tenotomy is performed as a component of laminitis treatment. Foals with severe flexural deformities should be trimmed in a normal fashion. The need for corrective shoeing in these cases depends on the amount of release achieved after tenotomy.
Deep Digital Flexor Tenotomy
101
ALTERNATIVE PROCEDURES
Figure 16-7 Transection of the deep digital flexor tendon.
EXPECTED OUTCOME Deep digital flexor tenotomy is a salvage procedure, although some horses may become sound for athletic activity. The intended goal should be limited to an improvement in comfort level and pasture soundness. Severe chronic cases of coffin joint contracture may have such severe joint capsule and surrounding tissue contracture that limb position may not improve significantly after tenotomy.5,6 The prognosis for horses with laminitis likely depends on the condition of P3 and blood supply. An improvement in pain, but not survival rate, has been reported in horses with acute refractory laminitis.7 In selected cases of chronic laminitis, an improved prognosis for survival has been reported.8
COMPLICATIONS Incisional dehiscence or drainage is rare. Severance of the palmar artery, vein, or nerve is possible and care must be taken that these structures are not isolated with the DDFT. Pain following tenotomy in foals with contracture may be significant because of stretching of the joint capsule and soft tissue and can be managed with nonsteroidal antiinflammatory medication. Occasionally, temporary heel elevation is used to allow for a more gradual change in foot conformation. Hyperextension of the coffin joint may occur and is managed with heel extension and elevation. Superficial digital flexor tendonitis may result from the increased strain on the superficial digital flexor tendon. Recurrent infection, abscessation, and sequestration of P3 are associated with chronic pain. If chronic pain persists, flexural deformity of the metacarpophalangeal joint may occur.
Tenotomy at the level of the mid pastern has been described.9 The procedure is performed under general anesthesia. A vertical 3-cm midline incision is made on the palmar aspect of the mid pastern. The incision is continued through the subcutaneous tissue and digital flexor tendon sheath. Curved forceps are placed under the tendon, and it is transected with a scalpel. The incision in the tendon sheath is closed with No. 2-0 absorbable suture. The subcutaneous tissues are closed with 2-0 absorbable suture and the skin is closed in an interrupted pattern.
COMMENTS The DDFT can be isolated and elevated outside the incision with curved forceps as has been traditionally described.10 During standing surgery, we prefer to use the modified table knives described by Redden because the neurovascular structures are easily protected from transection without having to exteriorize the tendon. Because of the anatomic location and peritendinous attachments, tenotomy at the level of the pastern may provide greater release than tenotomy at the mid metacarpal level.11 No difference in outcome has been demonstrated between the two techniques, and we prefer mid metacarpal tenotomy because of the lack of tendon sheath in the mid metacarpal region and the more proximal location for standing surgery.
REFERENCES 1. Redden RF: Shoeing the laminitic horse. In Redden RF, editor: Understanding laminitis, Lexington, 1998, The Blood Horse Inc. 2. Sullins KE: Standing musculoskeletal surgery. In Bertone A, editor: Standing surgery in the horse, Vet Clin N Am Equine Pract 7:687, 1991. 3. Nickels FA: Laminitis. In Ross MW, Dyson SJ, editors: Diagnosis and management of lameness in the horse, Philadelphia, 2003, WB Saunders. 4. Redden RF: Shoeing the laminitic horse, Proc Am Assoc Equine Pract 43:356, 1997. 5. Adams SB, Santschi EM: Management of congenital and acquired flexural deformities, Proc Am Assoc Equine Pract 46:117, 2000.
102
Limb Surgeries
6. McIlwraith CW, Fessler JF: Evaluation of inferior check ligament desmotomy for treatment of acquired flexor tendon contracture in the horse, J Am Vet Med Assoc 172:293, 1978. 7. Hunt RJ, Allen DA, Baxter GM, et al: Mid metacarpal deep digital flexor tenotomy in the management of refractory laminitis in horses, Vet Surg 20:15, 1991. 8. Eastman TG, Honnas CM, Hague BA: Deep digital flexor tenotomy as treatment for chronic laminitis in horses: 37 cases, Proc Am Assoc Equine Pract 44:265, 1998.
9. Allen D, White NA, Foerner JF, et al: Surgical management of chronic laminitis in horses: 13 cases (1983-1985), J Am Vet Med Assoc 189:1604, 1986. 10. Adams SB, Fessler JF: Deep digital flexor tenotomy. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders. 11. Hunt RJ: Laminitis. In Ross MW, Dyson SJ, editors: Diagnosis and management of lameness in the horse, Philadelphia, 2003, WB Saunders.