Fig. X5A: Smaller fractures of the face of C3 involving only one articular facet may be repaired with one carefully placed screw.
Video DBASICS: Animation about drill basics.
Fig. X5B: For broad fractures of the face of C3, affecting both articular facets, two 3.5 mm cortex screws are employed.
Fig. X5C: The flatter head of the 3.5 mm screw makes it the implant of choice in areas with narrow tolerance as in this sagittal fracture of C3.
Video 31018: Slab fracture of C3.
Passive flexion is an essential component of postoperative physical therapy.
After the screw is inserted, the fracture line is probed and any remaining flaps are debrided. If there is a large fracture trough and a narrow remaining articular rim, the rim is removed with heavy rongeurs or a motorized burr.
For the surgeon not skilled in arthroscopy, repair via arthrotomy is a viable alternative.
Virtually every C3 slab can be repaired arthroscopically, although the advantages are questionable if the surgeon is not an experienced arthroscopist. An arthrotomy consists of a straight 5–6 cm incision located approximately 15 mm medial to the extensor carpi radialis tendon. The extensor carpi radialis tendon sheath should be avoided. A smooth tipped elevator can be placed in the incision and leverage used to retract the joint capsule. The fracture line is debrided with small angled curettes and/or bone picks. It is easiest to debride the fracture with the limb in partial flexion. Hard flexion closes the fracture line and tends to keep the fragment in reduction during placement of the screw. One or both screws must often be placed through a separate stab(s), since the desired position may not be directly under the arthrotomy incision. The standard lag screw technique is used as described above. An Esmarch bandage may be helpful and suction/ irrigation is indispensable.
Only skin sutures are used in the arthroscopic incisions, usually over the screw. If the screw incision is longer than 8–10 mm, a single subcutaneous synthetic absorbable suture is used.
5.3 Postoperative treatment
A lightly padded bandage is used for recovery and to help minimize swelling in the postoperative period. Passive flexion as a major component of physical therapy of the limb is strongly recommended to avoid loss of range of motion.
5.4 Complications
Three specific cautions bear mentioning:
Always keep a 2 or 3 mm diameter K-wire in the hole while changing bits, guides, and the tap. In this way, the hole will not be “lost” during its preparation. This is particularly important when placing a screw in the more central portion of C3 since the instruments and screw will be passing through the thickness of the extensor carpi radialis tendon and its sheath.
Because the thread hole does not usually pass through the palmar cortex, the hole has a “bottom”. Impacting the tap upon this unyielding barrier can result in stripped threads or a broken instrument. A small error in measurement and a screw that is slightly too long will result in failed compression since the screw head will not fully contact the fragment‘s cranial surface.
Note that the hexagonal socket of the 3.5 mm screw head is shallow and can be easily stripped if the screwdriver is not carefully seated.
5.5 Results
Most horses return to racing, albeit at a lower class.
The prognosis is not particularly good for a return to competition at former levels. Although the majority of horses will return to racing, most will drop in class [10]. The prognosis is better if the horse has raced previously, and even better if it has occasionally won. It is also improved by there being only minimal preexisting degenerative joint disease. In general the prognosis is better for Standardbreds than it is for Thoroughbreds.
Sufficient healing time is essential to successful treatment. Although horses with nondisplaced fractures sometimes resume work within 3–4 months, 8–10 months is a more common convalescent time frame. Radiographs are taken at 2–3 month intervals to assess the progress of healing.
5.6 References
1. Thrall DE, Lebel JL, O'Brien TR (1971) A five year study of the incidence and location of equine carpal bone fractures. J Am Vet Med Assoc; 159:1366.
2. Auer J (1980) Diseases of the carpus. Vet Clin North Am [Large Anim Pract]; 2:81–99.
3. Richardson DW (1990) Carpal bone fractures. In: White NA, Moore JN editors. Current Practice of Equine Surgery. Philadelphia: J.B. Lippincott Co., 566.
4. Ross MW, Richardson DW, Beroza GA (1989) Subchondral lucency of the third carpal bone in Standardbred racehorses: 13 cases (1982-1988). J Am Vet Med Assoc; 195:789.
5. McIlwraith CW (1992) Tearing of the medial palmar intercarpal ligament in the equine midcarpal joint. Equine Vet J; 24:367–371.
6. Wozasek GE, Moser KD (1991) Percutaneous screw fixation for fractures of the scaphoid [published erratum appears in (1991) J Bone Joint Surg [Br]; 73:524]. J Bone Joint Surg [Br]; 73:138–142.
7. Richardson DW (1986) Technique for arthroscopic repair of third carpal bone slab fractures in horses. J Am Vet Med Assoc; 188:288–291.
8. Fischer AT, Stover SM (1987) Sagittal fractures of the third carpal bone in horses: 12 cases. J Am Vet Med Assoc; 191:106.
9. Palmer SE (1983) Lag screw fixation of a sagittal fracture of the third carpal bone in a horse. Vet Surg; 12:54.
10. Stephens PR, Richardson DW, Spencer PA (1988) Slab fractures of the third carpal bone in Standardbreds and Thoroughbreds: 155 cases (1977–1984). J Am Vet Med Assoc; 193:353.
5.6.1 Online references
See online references on the PEOS internet home page for this chapter: http://www.aopublishing.org/PEOS/05.htm
Gustave E. Fackelman