Study compares screw and X-plate repair for equine carpal fractures: full analysis

A newly published Veterinary Surgery study is testing whether a plate-based construct can improve repair of one of equine orthopedics’ trickier fracture patterns: the vertical plane accessory carpal bone fracture. Researchers from Freie Universität Berlin and collaborators compared conventional lag screw fixation with a lateral X-plate technique in an ex vivo cadaver model and found that both methods were feasible, but neither matched the strength of intact bone. (pmc.ncbi.nlm.nih.gov)

That question matters because accessory carpal bone fractures are rare, mechanically demanding injuries that often occur in athletic horses, especially after trauma or hyperextension of the carpus. Published background literature describes the accessory carpal bone as difficult to repair because of its convex shape, limited room for implants, and the distracting pull of attached soft tissues. Historically, many cases have been managed conservatively, and while some horses do return to athletic activity, fibrous union, malunion, or delayed healing are well-recognized concerns. (pmc.ncbi.nlm.nih.gov)

In the new study, investigators first tested eight intact accessory carpal bones to establish baseline strength, then created standardized vertical fractures in 20 cadaver distal forelimbs and randomized them to one of two repairs. Group 1 received two 4.5 mm cortical screws in lag fashion. Group 2 received one 4.5 mm lag screw plus a medium angular-stable X-plate secured with four 2.7 mm locking screws. After fixation, the accessory carpal bones were removed and loaded to failure under axial compression. Native bone had the highest mean maximum strength at 11.26 kN, compared with 6.82 kN in the screw-only group and 7.91 kN in the X-plate group; the difference between the two repaired groups was not statistically significant. All implants showed plastic deformation under testing. (ecvs.org)

Additional reporting tied to the article indicates the X-plate construct produced less implant bending and a smaller fracture gap than screws alone, despite the absence of a significant difference in ultimate strength. That’s a notable detail for surgeons, because construct behavior before catastrophic failure can matter clinically even when load-to-failure endpoints look similar in the lab. The authors concluded that both techniques are viable for fixation of vertical plane fractures, but also pointed to the need for alternative implant designs, including plates that accept larger screws or implants customized to accessory carpal bone anatomy. (pmc.ncbi.nlm.nih.gov)

Industry and clinical commentary around accessory carpal bone fractures has been moving in the same direction: toward more tailored fixation in selected cases. Prior reports have described computer-assisted screw placement and even a 3D-printed locking compression plate for displaced accessory carpal bone fractures, reflecting how difficult implant positioning can be in this region. At the same time, conference case reports have highlighted other management paths, including standing arthroscopic fragment removal for comminuted fractures when reconstruction is not practical. (thieme-connect.com)

Why it matters: For veterinary professionals, this study doesn’t overturn current practice, but it does add evidence that a plate-assisted construct is at least biomechanically comparable to standard lag screws in a controlled model. That could be useful in cases where fragment geometry, bone stock, or implant trajectory make two-screw fixation difficult. The bigger takeaway may be that neither construct restores native strength, reinforcing the need for careful case selection, realistic rehabilitation plans, and caution when extrapolating bench data to return-to-performance decisions. (ecvs.org)

There are also important limitations. This was an ex vivo cadaver study with axial compression testing, not a clinical outcomes study in live horses. It doesn’t answer whether one technique leads to better healing, less osteoarthritis, fewer implant complications, or improved athletic return. Still, for a fracture type with limited published evidence and longstanding debate over conservative versus surgical management, comparative biomechanical data are useful. (ecvs.org)

What to watch: The field now needs clinical follow-up, whether through multicenter case series or prospective surgical reports, to determine which horses actually benefit from plate-assisted fixation, and whether newer customized or larger-fragment implants can close the gap between repair constructs and native bone strength. (pmc.ncbi.nlm.nih.gov)