Ludewig and Cook tested whether construction workers with shoulder impingement symptoms move the scapula and recruit the scapular muscles differently from symptom‑free construction workers with similar overhead work exposure.
Laboratory comparison of 52 construction workers who routinely work overhead, 26 per group.
Methods
Patients
52 construction workers with routine overhead work
26 with impingement symptoms
26 without symptoms
Exposure
Impingement symptoms vs none, matched for overhead work exposure
Outcomes
3D motion of trunk, scapula and humerus by electromagnetic sensors
Surface EMG of upper trapezius, lower trapezius and serratus anterior
Recorded during scapular‑plane elevation with no load, 2.3 kg or 4.6 kg in the hand
Analyzed in phases of 31° to 60°, 61° to 90° and 91° to 120°
Key Findings
At 120° of humeral elevation, the scapula was on average 5.8° more anteriorly tipped in the impingement group than in controls (p < 0.003).
Scapular upward rotation was 4.1° lower in the impingement group at 60° of humeral elevation (p < 0.025).
Scapular medial rotation was greater in the impingement group only under load (5.2° with 2.3 kg, 4.4° with 4.6 kg), with no difference unloaded.
Serratus anterior activity was 9% of maximal voluntary contraction lower in the impingement group, averaged over all loads and phases (n = 50, p < 0.05).
Lower trapezius activity was higher in the impingement group, by 13% at 61° to 90° and by 17% at 91° to 120°.
Humeral lateral rotation did not differ between groups, so the authors' hypothesis of reduced lateral rotation in impingement was not supported.
Board pearl
The impingement pattern was less scapular upward rotation early in elevation, more anterior tipping late, and more medial rotation under load, with lower serratus anterior and higher trapezius activity.
Authors' conclusion
Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work.
Ludewig and Cook tested whether construction workers with shoulder impingement symptoms move the scapula and recruit the scapular muscles differently from symptom‑free construction workers with similar overhead work exposure.
Laboratory comparison of 52 construction workers who routinely work overhead, 26 per group.
Methods
Patients
52 construction workers with routine overhead work
26 with impingement symptoms
26 without symptoms
Exposure
Impingement symptoms vs none, matched for overhead work exposure
Outcomes
3D motion of trunk, scapula and humerus by electromagnetic sensors
Surface EMG of upper trapezius, lower trapezius and serratus anterior
Recorded during scapular‑plane elevation with no load, 2.3 kg or 4.6 kg in the hand
Analyzed in phases of 31° to 60°, 61° to 90° and 91° to 120°
Key Findings
At 120° of humeral elevation, the scapula was on average 5.8° more anteriorly tipped in the impingement group than in controls (p < 0.003).
Scapular upward rotation was 4.1° lower in the impingement group at 60° of humeral elevation (p < 0.025).
Scapular medial rotation was greater in the impingement group only under load (5.2° with 2.3 kg, 4.4° with 4.6 kg), with no difference unloaded.
Serratus anterior activity was 9% of maximal voluntary contraction lower in the impingement group, averaged over all loads and phases (n = 50, p < 0.05).
Lower trapezius activity was higher in the impingement group, by 13% at 61° to 90° and by 17% at 91° to 120°.
Humeral lateral rotation did not differ between groups, so the authors' hypothesis of reduced lateral rotation in impingement was not supported.
Board pearl
The impingement pattern was less scapular upward rotation early in elevation, more anterior tipping late, and more medial rotation under load, with lower serratus anterior and higher trapezius activity.
Authors' conclusion
Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work.