Equine field surgery: Distal limb (Proceedings)
Ideally, you need at least one trained assistant to adequately perform most of these selected distal limb, head, and neck surgeries.
Advantages of Field Surgery
• low overhead
• relative mobility
• potentially lower costs for the owner
• usually excellent footing for recovering the horse from anesthesia
• warm, fuzzy feeling when all goes well
Disadvantages
• often less than desirable conditions and assistants
• inevitable complications can be difficult to manage
• a clean field is difficult to maintain
• administration of safe and reliable anesthesia may not always be achieved
• a seemingly unlimited opportunity for failure
What are we talking about?
• Procedures that can be done in < 1 hour
• Procedures that do not enter the abdomen or joint
• Procedures that do not require "Special" equipment.
• Ideally, you need at least one trained assistant to adequately perform most of these selected distal limb, head, and neck surgeries.
• veterinary school training likely did not provide enough experience to perform all of these procedures
• review the anatomy
• study the procedure including potential complications and pitfalls
• practice the procedures on cadaver specimens prior to performing the procedure on a client animal
• learn how to effectively use the anesthetic protocols required for the specific procedures.
Field Anesthesia
• Equine field surgery requires portable anesthesia
• Elective procedures
• Generally healthy
• Requires knowledge of drugs used
• Supportive care
• Epidural procedures
Typical instrument pack
• needle driver
• several mosquito and Kelly forceps
• thumb forceps
• tissue forceps
• suture scissors
• tissue scissors
• several towel clamps
• scalpel handles & blades
• gauze sponges
• disposable drapes
Specific Field Surgeries
Distal limb surgeries
• Periosteal stripping
• Transphyseal bridging
• Annular ligament desmotomy
• Lateral Digital Extensor Tenectomy
• Medial Patellar Ligament Desmotomy
• Distal check ligament desmotomy
• Proximal check ligament desmotomy
• Distal splint bone resection
• Deep digital flexor tenotomy
• Semitendinosus Tenotomy and Myotomy
• Palmar digital neurectomy
Angular Limb Deformity
Carpal Valgus
Etiology
• Growth differential in the distal radial physis
• Collapsed carpal bones
• Collateral ligament laxity
How to differentiate Etiology
Carpal Valgus
• Ligament Laxity – Can manually straighten
– Worsens with exercise
– Radiographically normal
• Carpal collapse – Radiographically incomplete ossification of the carpal bones
– More common in premature or dysmature foals
• Growth differential - Distal Radial Physeal Dysplasia
Treatment
• Ligament laxity - rest +/- intermittent support, Prognosis good
• Carpal/Tarsal bone collapse - Tube cast and stall rest, Prognosis guarded
• Growth Differential - By far most common – Prognosis generally good
• Distal Radial Physeal Dysplasia
Initial Tx - Rest +/- Support
If not improved by 30 days or if condition worsens, surgery may be indicated
Surgery should be performed by 3-4 months of age
Periosteal Stripping vs. Transphyseal Bridging
Annular Ligament Desmotomy
Indications
• annular ligament constriction due to annular ligament desmitis or thickening
• secondary to superficial or deep digital flexor tendonitis
• secondary to septic tenosynovitis
Equipment
• Closed technique options – Mayo scissors
– blunt-tipped bistoury knife
– groove director
Instrument depends on surgeon preference.
Anatomy
• Annular ligament attaches on the abaxial surfaces of the proximal sesamoid bones
• partially surrounds the tendon sheath blending with its palmar/plantar wall and making up the palmar/plantar wall of the fetlock canal
Annular ligament desmotomy - Closed technique
• Preferred method
• Stab incision just proximal to the palmar annular ligament
• Enter sheath and pass instrument to the distal extent of the annular ligament identified by palpation
• Pass bistoury deep to the ligament
• Don't incise the skin or the proximal branch of the proximal digital annular ligament
Post-operative management
• Bandaging – A sterile dressing and a half limb bandage
– Initial bandage changed 24 hours after surgery
– Subsequent bandage changes at least every 4-5 days
– maintained for a minimum of 4 weeks.
• Medications – Phenylbutazone for 1-5 days
– Antibiotic therapy is dictated by the underlying problem
• Exercise – Stall rest ~10 days
– gradual increase in daily hand walking to minimize adhesion formation
– In cases without underlying tendon pathology, light daily lunging at a trot or limited small paddock turnout may be performed 3 weeks post operatively
– Gradual return to work may begin in 6 weeks or as indicated by the healing of any underlying tendon injury
Complications - wound dehiscence, septic tenosynovitis, synovial fistula formation, adhesions
Lateral Digital Extensor Tenectomy
Indications - Treatment of conventional stringhalt
Equipment - Large Carmalt forceps
Anatomy • Origin - lateral collateral ligament of the stifle
• enters its tendon sheath in the groove of the lateral malleolus of the tibia
• joins the long digital extensor tendon just distal to the tarsus
Surgical Procedure
• A 3 cm incision is made over the lateral digital extensor tendon
• The tendon is elevated to the level of the incision
• A second 5-7 cm vertical skin incision is made over the lateral digital extensor tendon and the tendon elevated
• The tendon excised distally
• The entire tendon is then pulled proximally and laterally through the proximal incision
• Muscle severed in the proximal incision so that at least 2 cm of muscle is removed
Postoperative Management
• Bandaging – A sterile dressing and hock bandage applied
– Bandage changed at least every 3 days
– Maintained until the incisions healed
• Exercise – Stall rest for two weeks, followed by small area turnout for two weeks, followed by return to normal exercise
• Medications – Phenylbutazone is administered for 24 hours.
Complications • Dehiscence especially if a stringhalt gait persists
• Seroma or hematoma formation
• No improvement or recurrence
Medial Patellar Ligament Desmotomy
Indications • persistent upward patellar fixation
• continued intermittent upward patellar fixation after appropriate conditioning and maturation have been achieved.
Equipment • A blunt-tipped bistoury
Anatomy • Origin – medial aspect of the patella through the parapatellar fibrocartilage
• Insertion – proximomedial aspect of the tibial tuberosity
Surgical Procedure
• weight-bearing and the stifle extended
• a 2 cm vertical skin incision is made just cranial to the distal part of the medial patellar ligament
• Curved Kelly forceps are advanced under the medial patellar ligament to create a plane of dissection behind the ligament
Post operative management
• Stall rest with hand walking for two weeks followed by small paddock turnout for a minimum of 90 days after surgery
• Phenylbutazone is administered for 1-2 days
Complications
• Surgical errors include
– entrance into the femoropatellar joint capsule
– severance of the middle patellar or medial femorotibial ligament
– incomplete transection of the medial patellar ligament
• Distal fragmentation of the patella
• Persistent lameness
Distal Check Ligament Desmotomy
Indications • DDFT contracture with flexion of the coffin joint
• fetlock flexural deformities
• caudal foot lameness with upright hoof wall or pastern conformation
Anatomy
• located dorsal to the DDFT and often forms a slight C-shape around the DDFT
• palmar vein, artery and nerve lie close to the DDFT and distal check ligament
Surgical Procedure
• A 6 cm skin incision is made near the distal end of the proximal third of the cannon bone over the DDFT
• The subcutaneous tissues and palmar fascia are incised and the intersection between the distal check ligament and DDFT is palpated or visualized
• Blunt dissection separates the two structures
• The check ligament is exteriorized with curved forceps or scissors, and the ligament is transected with a scalpel blade
• Complete transection is assessed
• If fibers of the check ligament remain these should be transected
Post operative management
• Bandaging
– A sterile dressing and half limb bandage is applied
– Bandage changed at least every 3-4 days
– maintained for 3 weeks
• Medications
– Phenylbutazone is administered for 1-3 days
– Continued phenylbutazone administration at lower doses or less frequent dosing intervals may be necessary for pain management
• Post operative exercise
– Hand walking should be introduced 5 days post-operatively and the duration of hand walking gradually increased over the following 3 weeks up to 30-45 minutes twice daily. When controlled exercise is not possible, turnout in a small area is provided.
Complications - Incisional dehiscence, scar tissue formation, recurrent contracture
Proximal check ligament desmotomy
Indications • metacarpophalangeal flexural deformities
• superficial digital flexor tendonitis
Anatomy
• PCL originates on the caudomedial aspect of the radius and inserts on the craniomedial aspect of the SDFT at the musculotendinous junction.
• The palmar carpal branch of the proximal radial artery is the nutrient artery for the SDFT. It is exposed at the proximal aspect of the PCL and runs in a distolateral direction between the superficial and deep layers of the PCL.
Equipment • Gelpi or Weitlaner retractors
• electrocautery
• suction
Surgical Procedure
• An 8-10 cm incision is made on the medial aspect of the limb
– 1 cm caudal to the radius
– dorsal to the cephalic vein
– starting 1 cm proximal to the distal physis and extending proximal
• The proximal radial branch of the cephalic vein is ligated and transected
• The cephalic vein is then retracted caudally
• The superficial sheet of flexor retinaculum and antebrachial fascia is incised to expose the tendon of the flexor carpi radialis
• Gelpi or Weitlaner retractors are used to retract the flexor carpi radialis caudally
• The PCL is fused with the deep sheet of flexor retinaculum
• The palmar carpal branch of the proximal radial artery courses through the proximal margin of the PCL
Postoperative Management
• Bandaging – A sterile dressing and pressure bandage applied
– The limb is then bandaged from the incision site distally
– Bandage changed at least every 3-4 days
– Bandage maintained for 3 weeks
• Exercise – The horse is stall rested for two weeks without hand walking and then stall rested with hand walking for the following two weeks. Exercise is then gradually increased as indicated by the primary problem
Postoperative Management
• Medications – Phenylbutazone for 1-3 days
– Continued phenylbutazone administration at lower doses or less frequent dosing intervals may be necessary
– Perioperative antibiotics
Complications
• Seroma formation
– should be left to reabsorb spontaneously
– If persistent or increasing can be aseptically aspirated or surgically drained (rarely) after the 12-14th post-operative day
• Incisional or carpal sheath infections
• Suspensory ligament desmitis due to increased strain on the suspensory ligament after proximal check ligament desmotomy
Distal Splint Bone Resection
• Indications – Fractures of the middle or distal third of the splint bones with non-union
– excessive callus
– Bone sequestra
– septic osteitis
• Equipment – chisel or osteotome
– bone rasp
– tourniquet
Anatomy
• The distal aspect of the splint bone has rudimentary attachments to the palmar fascia and proximal ligament of the ergot.
• The interosseous ligament attaches the splint bones to the third metacarpal/metatarsal bones
• In the hind limb the dorsal metatarsal artery lies between the 3rd and 4th metatarsal bones
• The dorsal branch of the ulnar nerve (lateral) and the palmar metacarpal nerve (lateral and medial) run in the area of the distal end of the splint bone.
Surgical Procedure
• vertical incision starting 2-4 cm proximal to the fracture site and ending 2 cm distal to the distal aspect of the splint bone.
• Identify the distal end and dissect it from its distal attachments.
• a curved osteotome or chisel is used to sever the attachments to the third metacarpal or metatarsal bone.
• avoid damaging the greater metatarsal artery
• Osteotome used 2 cm proximal to the affected area to create the proximal amputation site.
• All sequestra, surrounding mineralized tissue and discolored tissue should be removed.
• The proximal aspect of the remaining splint bone may be tapered or smoothed with a bone rasp to avoid residual sharp edges.
• Tourniquet application facilitates the procedure
• Most cases can be managed without a drain
Postoperative Management
• Bandaging – A sterile bandage applied
– Bandage changed at least every 3-4 days
– Bandage maintained for 3 weeks
– If a drain has been placed it should be removed within 3 days
• Exercise – Strict stall rest for the first 10 days
– followed by stall rest with hand walking for 2 weeks
– Exercise limited to small area turnout for at least one month
– Return to activity dependent on the degree of concurrent suspensory ligament damage
Complications - seroma formation, incisional dehiscence, excessive bone reaction, Suspensory desmitis
Deep Digital Flexor Tenotomy
Indications • severe distal interphalangeal joint contracture
• severe laminitis with rotation of the third phalanx
Equipment • A heel wedge can be used during standing procedures
• Modified butter knives or malleable retractors are useful when isolating the tendon during transection
Anatomy • The neurovascular bundle is directly over the DDFT on the medial side and dorsal to the DDFT on the lateral side
Surgical Procedure
• incision over DDFT in the middle 1/3 of the metacarpus
• avoid the flexor tendon sheath
• incise palmar fascia
• Create a space between the SDFT and DDFT
• Create a space between the DDFT and the SL
• Elevate & transect the DDFT
• Remove heel elevation to check for gap formation
Post operative management
• Bandaging – A half limb bandage is placed
– change at least every 5-7 days
– Maintain bandage for 30 days
• Medications – Phenylbutazone - minimum of 5 days.
Post operative exercise
• Horses with laminitis should be rested as their condition indicates and 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 gradually increased over the next 60 days
• Free choice turnout should not be allowed for up to 6 months.
Complications • Incisional dehiscence or drainage rare
• Severed palmar artery, vein or nerve
• Superficial digital flexor tendonitis or suspensory desmitis
• Flexural deformity of the fetlcok joint may occur if chronic pain persists
• Pain following tenotomy in foals
– stretching of joint capsules & soft tissue
– managed with NSAIDs
Semitendinosus Tenotomy and Myotomy
• Indications – Fibrotic myopathy
• Equipment – Blunt-tipped bistoury
Anatomy
• The semitendinosus muscle originates from the caudal vertebrae and the ventral surface of the ischiatic tuberosity. It inserts on the tibial crest, crural fascia proper and calcaneal tuber
• The semimembranosus and biceps femoris muscles may also be affected.
Surgical Procedure
• The horizontally oriented tendon is ~8 cm distal to the proximal tibia
• Vertical incision over the tendon and caudal to the medial saphenous vein
• The incision is extended through the subcutaneous tissues and dense crural fascia to expose the tendon
• Curved forceps are passed underneath the tendon and the tendon is transected
• A 6-10 cm vertical incision is made over the caudal aspect of the semitendinosus muscle beginning at the distal extent of the fibrosis and extending distally
• deepen the incision to the level of palpable fibrosis
• transect the muscle with a blunt-tipped bistoury at the distal extent of the fibrotic area
• Taut vertical fibrotic bands that appear to limit cranial movement when the limb is pulled forward by an assistant are transected
Postoperative management
• Bandaging
– If myotomy is performed the gauze packing is changed the following day and removed in 2 days
• Exercise
– Stall rest with hand walking for the first two weeks followed by gradually increasing exercise until full turnout is allowed at 6 weeks following surgery
• Medications
– Phenylbutazone is administered for 3-5 days
– Antibiotic therapy is continued until 24 hours after drain or packing removal.
Complications • dehiscence
• seroma formation
• infection
• All can occur with either procedure, however if myotomy is performed, the likelihood of these complications increases
• Extensive fibrosis may result in recurrence of the gait abnormality
Palmar Digital Neurectomy
Indications
• Chronic lameness that improves significantly after palmar digital anesthesia and has not improved with alternative treatment options
• Includes selected cases of:
– navicular syndrome
– navicular bone fractures
– wing fractures of the third phalanx
– idiopathic heel pain
– palmar/plantar foot injuries
Anatomy
• The palmar digital neurovascular bundle
• Between the palmar border of the pastern and the abaxial border of the DDFT
• The nerve is just palmar to the artery and just deep to the ligament of the ergot in the mid-region of the pastern
• A 3 cm skin incision is made over the abaxial border of the DDFT in the mid to distal pastern region
• Blunt dissection is used to isolate the palmar digital nerve.
Surgical Procedure
Guillotine method
• Identification of the nerve
– smooth, white, and glistening
– crimped appearance of the nerve after it has been stretched and released
– palpating longitudinal fibers when the nerve is stretched over the smooth portion of an instrument
• A 2-3 cm section of the nerve is freed from the surrounding tissues
• The nerve is stretched and the proximal end is transected sharply. The distal portion is then transected sharply
Black's method
Epineural Capping
Post operative management
• Bandaging – applied for a minimum of 3 weeks.
• Exercise – Stall rest is provided for 4 weeks. After 10 days hand walking is allowed. After 4 weeks the horse may resume normal activity
• Medications – Phenylbutazone is administered for 3-5 days
Complications • progression of the underlying problem
• deep digital flexor tendon rupture
• navicular bone fracture
• foot abscesses
• reinnervation
• neuroma formation
• ischemia with loss of the hoof wall
References
Adams SB, Fessler JF, editors: Atlas of Equine Surgery, Philadelphia, 2000, WB Saunders Co.
Auer JA, Stick JA, editors: Equine Surgery, 3rd ed. Philadelphia, 2006, WB Saunders Co.
McIlwraith CW, Robertson JT, Turner AS, editors: Equine Surgery: Advanced Techniques, 2nd ed. Ames, IA, 1998, Blackwell Publishing.
McIlwraith CW, Robertson JT, Turner AS, editors: Equine Surgery, 2nd ed. Philadelphia, 1998, Lippincott Williams & Wilkins.
Wilson DA, Kramer J, Constantinescu GM, Branson KR, editors. Manual of Equine Field Surgery, St Louis, 2006, Elsevier.
