Abstract
Introduction: Activities that require extreme hip movement can dislocate hip implants in the early post operative phase. The aim of this study was to assess the movement of the hip using four different techniques to retrieve an object from the floor.
Methods: An electromagnetic tracker was used to measure hip movement during these retrieval techniques:-
Flexing forward to pick up an object between the feet
Standing to the side of the object and bending
Squatting to pick up an object between the feet
Kneeling on one knee to pick up.
Measurements were taken from 50 hips in 25 normal subjects aged 21 to 61. Sensors were attached over the iliac crest and the mid-shaft of the lateral thigh. Data was collected as each technique was repeated 3 times. The tracker recorded hip flexion and rotation data at 10 hertz, with an accuracy of 0.15 degree.
Results: For each of the four techniques the respective mean (SD) movements were:-
Flexion: 75.8(28.6), 79.2(27.2), 87.5(29.7) and 30.4(17.3).
Extension: −0.2(2.5), 0.5(1.9), 0.1(2.3) and −0.4(3.3).
Internal rotation: 2.9(5.2), 1.4(3.4), 10.1(9.9) and 8.5(6.9).
External rotation: 12.6(10.3), 20.1(12.1), 11.9(6.5) and 7.3(7.1)
Kneeling had significantly less flexion and external rotation than all the other techniques (paired t-test, P< < 0.001).
Discussion: Flexion and external rotation were the most significant movements for each technique. The movements with the least and most flexion were kneeling (30.40) and squatting (87.50). The movement with the least and most external rotation were kneeling (7.30) and side pick up (20.10).
Kneeling has the least amount of movement, therefore, it minimises the risk of dislocation when retrieving an object from the floor.
Correspondence should be addressed to BHS c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
