Detect Trendelenburg sign (excessive contralateral pelvic drop)

A Trendelenburg gait reflects hip-abductor weakness on the stance limb: the contralateral (swing-side) pelvis drops during single-limb stance beyond the normal small obliquity (\(\approx 4-5^{\circ}\)).

Usage

detectTrendelenburg(
  pelvic_obliquity,
  stance = c(10, 50),
  threshold = 5,
  severe = 15,
  drop_sign = 1
)

Arguments

pelvic_obliquity

Pelvic obliquity (degrees) over one gait cycle, with the contralateral drop being positive (see drop_sign).

stance

Percentage window of stance (default c(10, 50), single-limb).

threshold

Drop (deg) above which Trendelenburg is flagged (default 5).

severe

Drop mapped to severity 1 (default 15 deg).

drop_sign

+1 if positive obliquity is a contralateral drop, -1 otherwise.

Value

A gait_pattern_flag object.

References

Perry J, Burnfield JM (2010).

See also

classifyGaitPatterns()

Examples

pct <- seq(0, 100, length.out = 101)
pelvic_obliquity <- rep(0, 101)
pelvic_obliquity[pct >= 10 & pct <= 50] <- 12
detectTrendelenburg(pelvic_obliquity)
#> <gait_pattern_flag> trendelenburg: FLAGGED (severity 0.80)
#>   contralateral_pelvic_drop_deg = 12 (threshold 5, normal 4)