Biomechanical evaluation contribution of the acetabular labrum to hip stability.
OBJECTIVE
Knowledge of the effect of hip pathologies on hip biomechanics is important to the understanding of the development of osteoarthritis, and the contribution of the labrum to hip joint stability has had limited study. The purpose of this study was to evaluate the effect of labral injury to stability of the femoral head in the acetabular socket.


METHODS
Ten cadaver hip specimens were tested using a robotic system under four different loading conditions: axial loading (80 N) along the femoral axis and axial loading (80 N) combined with either anterior, posterior or lateral loading (60 N). The hip states were examined were intact, with a 1.5 cm capsulotomy and with a 1 cm resection of the anterosuperior labrum.


RESULTS
At 30° of flexion, under axial load, the displacement of the hip with capsulotomy and labral resection (9.6 ± 2.5 mm) was significantly larger then the hip with capsulotomy alone (5.6 ± 4.1 mm, p = 0.005) and the intact hip (5.2 ± 3.8 mm, p = 0.005). Also, at 30° of flexion, the displacement under combined axial and anterior/posterior load was increased with capsulotomy and labral resection.


CONCLUSIONS
The acetabular labrum provides stability to the hip joint in response to a distraction force and combined distraction and translation forces. One centimetre of labral resection caused significant displacement ("wobbling" effect) of the femoral head within the acetabulum with normal range of motion. Successful labral repair could be crucial for restoration of the hip biomechanics and prevention of coxarthrosis.
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Orthopaedic Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Pisit
P
Lertwanich
Bone and Joint Center at Magee-Womens Hospital of UPMC, 300 Halket St., Suite 1601, Pittsburgh, PA, 15213, USA. antonp@pitt.edu.
Anton
A
Plakseychuk
Department of Mechanical Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
Scott
S
Kramer
Benedum Orthopedic Engineering Lab, University of Pittsburgh, Pittsburgh, PA, USA.
Monica
M
Linde-Rosen
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Orthopaedic Surgery, Fukuoka University School of Medicine, Fukuoka, Japan.
Akira
A
Maeyama
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Mechanical Engineering and Material Science, University of Pittsburgh, Pittsburgh, PA, USA.
Freddie H
FH
Fu
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Mechanical Engineering and Material Science, University of Pittsburgh, Pittsburgh, PA, USA.
Patrick
P
Smolinski
D000077:Acetabulum / Q000502:physiology*; D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D002358:Cartilage, Articular / Q000502:physiology; D005260:Female; D005269:Femur; D005270:Femur Head / Q000502:physiology; D051445:Fibrocartilage / Q000502:physiology; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology*
Acetabulum; Coxarthrosis; Hip; Labral injury; Stability