The stepped hybrid plate for carpal panarthrodesis

Abstract

In the 1990s, the AO (Arbeitsgemeinschaft für Osteosynthesefragen) Hand Study Group developed several anatomically bent plates (standard and short) for wrist panarthrodesis in humans. However, only straight plates have been used for carpal panarthrodesis (CP) in animals to date. The primary purpose of this study was to determine if precontoured plates are more anatomical for CP in dogs. Measurement of several of the bones that are implicated in CP, as well as the relationship between their surfaces and the surface of a straight plate, were performed in a radiographic and computed tomographic cadaveric study. Axial and transverse measurements taken at different levels of the metacarpal bones 2, 3 and 4 were also included. The second objective of this study was to develop a more anatomical CP plate according to the results obtained. The measurements and images obtained in this study show that, as in human orthopaedics, bent or stepped plates are more anatomically correct than straight plates for CP in dogs.

Mechanical Evaluation of Two Hybrid Locking Plate Designs for Canine Pancarpal Arthrodesis

“…Nevertheless, the radiocarpal hole is one of the most susceptible regions of plate failure because of its location near the apex of the plate bend, which also results in high induced bending moments and some structural weakening of the plate during bending. This has been substantiated by previous clinical studies reporting plate breakage after pancarpal arthrodesis [4,6,7,9,24,25]. An option to mitigate plate strains is to use external coaptation with a cast, although its clinical relevance remains debatable due to adverse side effects, such as soft-tissue injuries and increased treatment costs [26,27].…”

“…To limit the risk of plate yield or fatigue failure due to cyclic bending, carpal fusion at a straight angle of 0° extension has been recommended [ 6 ]. Yet, from a physiological standpoint, radiocarpal joint fusion at approximately 15° to 20° of extension is preferred as it optimizes paw placement during stance and limits flexor tendon pain [ 9 – 11 ]. Regardless of the arthrodesis angle, a dorsally positioned plate is at a mechanical disadvantage that increases plate stress, which can contribute to failure at the level of the radiocarpal joint.…”

Retrospective Comparison of Titanium Hybrid Locking Plate with Stainless Steel Hybrid Dynamic Compression Plate for Pancarpal Arthrodesis: 23 Dogs

“…Postoperative metacarpal fracture rates for HDCP, castless plates and stepped hybrid plates were reported at 7.7, 1.9, and 3.8% respectively. 3 7 9 10 There are no known reported metacarpal fracture rate for ALPS. The lower MCov in our HDCP cohort may have contributed to one case of bilateral PCA (Case 1; Appendix 2 ; MCov 52%) experiencing a metacarpal fracture, with no fracture recorded in the ALPS group.…”

“…10 12 The earliest versions of these PCA procedure-specific plates were made from stainless steel with both round holes and compression holes for application with cortex screws. 9 10 They were referred to as “hybrid PCA plates” because they allowed use of smaller diameter cortex screws in the third metacarpal bone. Also, the “stepped hybrid PCA plate” was anatomically contoured to the dorsal surface of the carpus.…”

“…Also, the “stepped hybrid PCA plate” was anatomically contoured to the dorsal surface of the carpus. 9 The most recent modification to hybrid PCA plates was the addition of Combi holes which allowed the insertion of either locking screws or cortex screws. 2 The latter allowed the generation of interfragmentary compression at the arthrodesis.…”