Revisiting Union: A New Perspective on an Old Outcome

Area of Science:

• Orthopedic Surgery
• Foot and Ankle Surgery
• Biomechanical Engineering

Background:

• Assessing fracture healing in foot and ankle orthopedics presents unique statistical challenges, particularly in measuring time to union.
• Fracture healing is a critical outcome, but its assessment requires robust statistical methodologies.

Purpose of the Study:

• To evaluate the inherent challenges in using fracture healing as an outcome measure in foot and ankle surgery.
• To specifically examine statistical methods for assessing time to union in Jones fractures.
• To determine if early weightbearing affects time to union following intramedullary screw fixation.

Main Methods:

• A comparative analysis of two patient cohorts: early weightbearing (EWB) and delayed weightbearing (DWB) after intramedullary screw fixation of Jones fractures.
• Time to union was assessed using cumulative link model analysis, a form of ordinal regression.
• Delayed union was defined as occurring after 12.5 weeks, based on existing literature.

Main Results:

• Cumulative link model analysis revealed no statistically significant difference in the time to union between the EWB and DWB groups (P = .819).
• The incidence of delayed unions was also comparable between the EWB (20%) and DWB (24%) cohorts (P > .999).
• Specific union rates at 6 and 12 weeks were provided for both groups, showing no significant divergence.

Conclusions:

• Early weightbearing following intramedullary screw fixation for Jones fractures is statistically safe and does not appear to delay fracture healing.
• Cumulative link models (ordinal regression) are a suitable statistical approach for analyzing continuous outcomes with infrequent observations, such as fracture healing.
• This methodology offers a valuable tool for orthopedic research when assessing fracture union.