34th Annual Scientific Meeting proceedings

Pathologies associated with the distal interphalangeal (DIP) joint are common occurrences in clinical practice. End stage osteoarthritis (OA) and pathologies of the podotrochlear apparatus can cause debilitating lameness. Arthrodesis provides a surgical solution to alleviate pain and restore soundness, however, there are only a few case reports describing DIP joint arthrodesis.^1,2 Problems with current techniques include difficulty removing all the articular cartilage, unstable constructs and an increased risk of sepsis when implants are placed through the hoof wall.³

The objectives were to compare two methods for DIP joint arthrodesis ex vivo under axial load, single cycle to failure using a 3-hole PIP plate (control) and a custom designed 4-hole plate (test). We hypothesized that both constructs would withstand loads applied by a stabled horse.  

Each construct was applied to one of 6 randomly assigned paired cadaver limbs. Limbs were loaded at 2kN increments and computed tomographic imaging performed at each load until failure. Load displacement DIP joint angle and valgus/varus angle was calculated. Maximal load prior to failure was compared between the two methods using a paired t test. The change in DIP joint angle and the valgus/varus angle was analyzed using a mixed effects linear regression model. The significance was set at P < 0.05.

The mean maximal load for the test construct was 9.8kN and 10.3kN for the control (p=0.8). The DIP joint angle increased significantly with increasing load (p=0.002). There was no significant effect of load (p=0.07), technique (p=0.07) or the interaction between load and technique (p=0.2) on the DIP joint varus/valgus angle.

The two constructs failed at similar loads and withstood expected loads for a stabled horse. Limitations include ex vivo study, single cycle to failure, unidirectional loading and small sample size. This new construct withstood similar loads to published reports and doesn’t require placement of the implants through the hoof wall.

Figure 1: Custom designed 4-hole stainless steel DIP joint plate.

Figure 2: Lateromedial (left) and dorsopalmar (right) radiographic images of the custom designed 4-hole stainless steel DIP joint plate with two 5.5mm transarticular cortex screws used for ex vivo DIP joint arthrodesis.

References

1. Busschers E, Richardson DW: Arthroscopically assisted arthrodesis of the distal interphalangeal joint with transarticular screws inserted through a dorsal hoof wall approach in a horse. Journal of the American Veterinary Medical Association 228:909-913, 2006.
2. Schneider RK, Bramlage LR, Hardy J: Arthrodesis of the Distal Interphalangeal Joint in Two Horses Using Three Parallel 5.5-mm Cortical Screws. Veterinary Surgery 22:122-128, 1993.
3. Lischer CJ, Auer JA: Chapter 82 - Arthrodesis Techniques, in Auer JA, Stick JA, Kümmerle JM, et al (eds): Equine Surgery (Fifth Edition), Vol W.B. Saunders, 2019, pp 1374-1398.