Comparing Two Methods of Hoof Immobilization for Stabilization of Type III Distal Phalanx Fractures in the Horse: A Cadaveric Study

Abstract

Type III distal phalanx (third phalanx; coffin bone; P3) fractures in horses are sagittal fractures with an articular component involving the distal interphalangeal (coffin) joint. Type III fractures of P3 results in a guarded to good prognosis for return to athletic function that appears to be dependent on age demographic. Internal fixation of type III fractures of P3 have been debated when compared to conservative management. Younger horses (<3 years of age) with articular fractures of the P3 have been reported to have a better prognosis when managed conservatively compared to mature horses, which had a more favorable prognosis with surgical management. In general, the major objective of articular fracture repair and healing to obtain joint congruity. A smooth and stable joint surface is needed for more rapid and complete healing, which decreases convalescence time and minimizes future development of degenerative joint disease of the coffin joint. Whether the P3 fracture is repaired surgically or not, hoof immobilization with a foot cast or bar shoe is traditionally utilized during fracture healing. The objective of this study was to determine the effect of different methods of hoof immobilization on minimizing fracture gap increase in type III fractures of P3 in cadaveric limbs under compressive load with and without internal fixation. We hypothesized that the treatment group with internal fixation and a foot cast (IFFC) would provide the most stability of the fracture as determined by the smallest change in fracture gap under compressive load. The study utilized 48 cadaveric equine distal limbs (n=48) from a total of 19 horses. A type III fracture was created in P3 of each limb. Limbs were randomly allocated to six equally numbered treatment groups (n = 48): barefoot (BF, no internal fixation or hoof wall support), hoof wall support with foot cast (FC) or bar shoe with clips (BS), internal fixation and no external support (IFBF), internal fixation with external support with foot cast (IFFC) or bar shoe with five clips (one toe clip, two quarter clips and two side clips) (IFBS). Serial radiographs were taken of the hoof to assess changes in fracture gap were performed at successive 50kg increases in monotonic compressive load applied. Interactions between independent and dependent variables were assessed via statistical testing. IFFC resulted in the smallest change in fracture gap displacement under increasing compressive loads compared to the other treatment groups. In conclusion, greatest stability of the fracture was acquired using internal fixation and a foot cast as external coaptation. These data suggest that surgical management provides more stability to Type III fractures of P3 and should be considered for treatment in vivo, however, prospective studies are needed to confirm.