Newborn joint mechanics.

Introduction: We aimed to evaluate joint mechanics in newborn by goniometric assessment of major joints in healthy babies born at different gestational ages (GAs).

Materials and methods: An institution based observational study was carried out on healthy newborn babies within two days of birth. Study subjects were born at 28-41 completed weeks of gestation. The major joints of upper and lower limbs were assessed with manual goniometer for joint angles in relation to specific passive movements and range of motion (ROM) calculated where applicable. All measurements were made by a single observer with careful consideration of plane of movement and axes involved. Strength of association between joint angles and GA was quantified by Pearson's r coefficient.

Results: Six major joints (shoulder, elbow, wrist, hip, knee, and ankle) were evaluated on either side in 433 babies. No significant differences were found between male and female babies and left or right side of the body. For most joints, a secular declining trend of joint angle or ROM was noted with good to strong inverse correlation with GA. The strongest associations were for flexion-extension ROM and adduction-abduction ROM at shoulder, palmar flexion at wrist and dorsiflexion at ankle joint with r values of -0.76, -0.75, -0.75, and -0.75, respectively.

Conclusions: The reading of a specific joint angle in the newborn infants was found to be dependent on GA. Precise calibration of gestation appropriate joint angles had laid down the foundation for functional assessment of multimodal joint mechanics.HighlightsEvaluation of newborn joint angles require stringent attention toward the plane and axis of the particular joint movement being assessed.Major joint angles and range of motion in newborn infants were observed to follow a secular declining trend according to the gestational age.Precise estimation of gestation appropriate joint angle will be helpful to understand the mechanics of musculoskeletal medicine in newborn.