An in vitro biomechanical investigation of an intramedullary nailing technique for repair of third metacarpal and metatarsal fractures in neonates and foals.

The researchers tested a surgical technique for repairing fractures in the third metacarpal and third metatarsal bones in foals using an 8.25-mm solid-titanium intramedullary (IM) nail. Their findings suggest that although this method can reduce soft tissue disruption at the fracture site, it doesn’t provide enough strength and stability on its own and would require additional support from external means.

Overview of the Study

• The study aimed to assess the effectiveness of a dorsoproximal extra-articular approach, using an 8.25-mm solid-titanium IM nail, for repairing fractures in the MC3 and MT3 bones of foals.
• The authors also sought to compare the mechanical properties of the nailed constructs with those of intact bones and to determine the influence of factors such as age, body weight, and whether the injury was to a forelimb or hindlimb or to a left or right limb.
• Twenty pairs of bones (ten MC3, ten MT3) were taken from ten foals of varying weights and ages. One bone from each pair was randomly chosen to be ostectomized (removal or cutting of bone) and stabilized with the titanium IM nail and four 3.7-mm titanium interlocking screws.
• The constructs and their paired intact bone specimens were then tested in axial compression and palmaro-/plantarodorsal (PD) 4-point bending.

Key Findings

• Nail insertion resulted in bone failure in six of the MC3 bones and two of the MT3 bones.
• On average, intact specimens were significantly stronger and more rigid than the constructs in all age and weight ranges when tested in compression and PD 4-point bending.
• The strength and stiffness of intact specimens tested in compression and bending generally increased linearly with age and weight.
• Despite the potential benefits of IM interlocking nail fixation in terms of reducing soft-tissue disruption at the fracture site, the procedure did not provide sufficient strength or stiffness to repair comminuted MC3 and MT3 fractures in young foals when used alone.

Conclusions and Recommendations

• This study suggests that IM interlocking nail fixation might be useful for mitigating soft-tissue disruption in foal cannon bone fractures. Nevertheless, this approach isn’t without risks, as there is the possibility of bone failure associated with extra-articular insertion.
• Given the lack of sufficient stability offered by this method alone, the researchers advise that it should be paired with other forms of external coaptation (bringing parts together for healing).