Apple Health mobility data may hint at ortho surgery recovery

Mobility metrics in the Apple Health app in iOS 14 [Image courtesy of
Apple]

Apple Health data on people’s iPhones may at least give orthopedic surgeons a hint into whether their patients are properly recovering from leg trauma surgeries.

That seems to be the big takeaway from a study presented last week at the American Academy of Orthopaedic Surgeons (AAOS) annual meeting in San Diego. The lead authors were Dr. Dane J. Brodke, MHA, assistant professor at Oregon Health & Science University in Portland; Dr. Brian Shear, orthopedic surgery resident at the University of Maryland; and Nathan O’Hara, PhD, MHA, associate professor of orthopedics at the University of Maryland Medical System in Baltimore.

Orthopedic device companies have already worked on more sophisticated mechanisms to track outcomes. One that especially shows promise is Zimmer Biomet’s Persona IQ smart knee implant. Launched in 2021, Persona IQ uses an embedded sensor created by Vancouver, British Columbia–based Canary Medical.

Time will tell whether the interest in Apple Health data will translate into orthopedic health professionals seeking more advanced tracking to catch post-operative problems earlier.

The cross-sectional study of Apple Health data involved 42 adult patients with lower extremity fractures who owned iPhones and had at least six months of post-injury follow-up. The study’s patients shared their Apple Health data and completed Patient Reported Outcomes Measurement Information System (PROMIS) surveys. The research team used mixed-effects models to compare mobility parameters at three critical time points: pre-injury (28 days prior), acute post-injury (first 28 days after injury), and six months post-injury (days 152–180).

The researchers examined five gait parameters: step count, walking asymmetry, double support, walking speed, and step length. Out of those five parameters, step count was the only mobility parameter to show a moderate or stronger correlation with patient-reported physical function. Patients with nonunions (fractures that did not heal properly) demonstrated a 55% slower recovery in daily step counts compared to those who healed normally.

“These findings suggest that smartphone-measured step counts not only correlate with adverse clinical outcomes but may also predict them, allowing for earlier intervention and improved patient care,” O’Hara said in a March 10 news release out of AAOS. “Conversely, when a patient’s recovery plateaus, it may indicate they have reached their maximum potential improvement. While the PROMIS survey offers valuable insights from a patient’s perspective, it remains subjective. For the first time, the objective data from Apple Health provides a clearer, more reliable understanding of a patient’s recovery.”

The research team was also able to collect some overall recovery data:

• The average daily step count was 2,430, a 655% increase from early post-injury, but a 52% decrease from before the injury.
• Walking speed and step length continued to decrease during the first six months of recovery, while walking asymmetry and double support time increased.
• Compared to pre-injury, walking asymmetry remained 198% higher and speed 15% lower.

The research team is presently developing an app for patients to download during their initial visit with their orthopedic surgeon to collect Apple Health data, enabling a study with many more participants.

“Since smartphone-based platforms like Apple Health collect data passively in the background, we have a unique opportunity to measure mobility both before and after an injury, providing valuable context for patient recovery,” Brodke said. “This baseline information is vital to contextualizing a patient’s recovery and is generally unavailable with other functional outcome measures.”