This cadaveric biomechanical study from Morrey et al. used electromagnetic motion tracking to define the relative contributions of the MCL and radial head to elbow valgus stability during simulated active motion. By serially releasing each structure in varying order across six specimens, the study established a primary-versus-secondary constraint framework that directly guides management of radial head fractures.
The central clinical question this paper answers is straightforward: does a comminuted radial head fracture require prosthetic replacement? The answer depends entirely on the MCL. With an intact MCL, radial head excision does not alter elbow kinematics — a prosthesis adds nothing.
In contrast, when the MCL is disrupted (think Mason Type 4 fracture-dislocation), the radial head becomes the sole remaining valgus stabilizer. In that setting, excising it without replacement or fixation will produce gross instability.
The practical decision rule: evaluate the MCL before deciding what to do with the radial head. If the MCL is intact, excise a comminuted fragment without implant. If the MCL is compromised, fix or replace the radial head.
The finding that the posterior MCL bundle is nearly irrelevant to valgus stability, while the anterior bundle is decisive, also matters for surgical planning. UCL reconstructions target the anterior bundle for exactly this reason.
This cadaveric biomechanical study from Morrey et al. used electromagnetic motion tracking to define the relative contributions of the MCL and radial head to elbow valgus stability during simulated active motion. By serially releasing each structure in varying order across six specimens, the study established a primary-versus-secondary constraint framework that directly guides management of radial head fractures.
The central clinical question this paper answers is straightforward: does a comminuted radial head fracture require prosthetic replacement? The answer depends entirely on the MCL. With an intact MCL, radial head excision does not alter elbow kinematics — a prosthesis adds nothing.
In contrast, when the MCL is disrupted (think Mason Type 4 fracture-dislocation), the radial head becomes the sole remaining valgus stabilizer. In that setting, excising it without replacement or fixation will produce gross instability.
The practical decision rule: evaluate the MCL before deciding what to do with the radial head. If the MCL is intact, excise a comminuted fragment without implant. If the MCL is compromised, fix or replace the radial head.
The finding that the posterior MCL bundle is nearly irrelevant to valgus stability, while the anterior bundle is decisive, also matters for surgical planning. UCL reconstructions target the anterior bundle for exactly this reason.