TY - JOUR
T1 - A Novel Model of Hip Femoroacetabular Impingement in Immature Rabbits Reproduces the Distinctive Head-Neck Cam Deformity
AU - Kamenaga, Tomoyuki
AU - Haneda, Masahiko
AU - Brophy, Robert H.
AU - O’Keefe, Regis J.
AU - Clohisy, John C.
AU - Pascual-Garrido, Cecilia
N1 - Funding Information:
One or more of the authors has declared the following potential conflict of interest or source of funding: This study was supported in part by a National Institutes of Health K08 Clinical Investigator Award (1K08AR077740-01) and an Orthopaedic Research and Education Foundation Mentored Clinician-Scientist Grant. The Curing Hip Disease Fund and the Jackie and Randy Baker Research Fellowship provided partial support for the research personnel. R.H.B. has received consulting fees from Sanofi, support for education from Elite Orthopaedics and Arthrex, and speaking fees from Arthrex. J.C.C. has received research support from Zimmer Biomet; consulting fees from MicroPort Orthopedics, Smith & Nephew, and Zimmer Biomet; royalties from Wolters Kluwer Health and Zimmer Biomet; and speaking fees from Synthes. C.P.-G. has received grants from Sanofi and Zimmer Biomet, support for education from Elite Orthopaedics, and hospitality payments from Zimmer Biomet and Stryker. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Publisher Copyright:
© 2022 The Author(s).
PY - 2022/6
Y1 - 2022/6
N2 - Background: Femoroacetabular impingement (FAI) is a leading cause of hip pain in young adults and often leads to degenerative osteoarthritis (OA). A small animal model of hip deformities is crucial for unraveling the pathophysiology of hip OA secondary to FAI. Purposes: To (1) characterize a new minimally invasive surgical technique to create a proximal femoral head–neck deformity in a skeletally immature rabbit model and (2) document the effect of an injury to the medial proximal femoral epiphysis on head–neck morphology at 28 days after the injury. Study Design: Controlled laboratory study. Methods: Six-week-old New Zealand White rabbits (n = 10) were subjected to right hip surgery, with the left hip used as a control. An epiphyseal injury in the medial femoral head was created using a 1.6-mm drill. Hips were harvested bilaterally at 28 days after surgery. Alpha and epiphyseal shaft angles were measured on radiographs. Alpha angles at the 1- and 3-o’clock positions were measured on the oblique axial plane of micro–computed tomography images. Bone bar formation secondary to growth plate injuries was confirmed using alcian blue hematoxylin staining. Results: All hips in the study group showed a varus–type head-neck deformity, with lower epiphyseal shaft angles on anteroposterior radiographs versus those in the control group (133°± 8° vs 142°± 5°, respectively; P =.022) and higher epiphyseal shaft angles on lateral radiographs (27°± 12° vs 10°± 7°, respectively; P <.001). The mean alpha angles in the study group were higher at both the 1- (103°± 14° vs 46°± 7°, respectively; P <.002) and 3-o’clock (99°± 18° vs 35°± 11°, respectively; P <.002) positions than those in the control group. Alcian blue hematoxylin staining of all hips in the study group indicated that the injured physis developed a bony bar, leading to growth plate arrest on the medial femoral head. Conclusion: The proposed model led to growth arrest at the proximal femoral physis, resulting in a femoral head–neck deformity similar to human FAI. Clinical Relevance: Our novel small animal model of a femoral head–neck deformity is a potential platform for research into the basic mechanisms of FAI disease progression and the development of disease–modifying therapies.
AB - Background: Femoroacetabular impingement (FAI) is a leading cause of hip pain in young adults and often leads to degenerative osteoarthritis (OA). A small animal model of hip deformities is crucial for unraveling the pathophysiology of hip OA secondary to FAI. Purposes: To (1) characterize a new minimally invasive surgical technique to create a proximal femoral head–neck deformity in a skeletally immature rabbit model and (2) document the effect of an injury to the medial proximal femoral epiphysis on head–neck morphology at 28 days after the injury. Study Design: Controlled laboratory study. Methods: Six-week-old New Zealand White rabbits (n = 10) were subjected to right hip surgery, with the left hip used as a control. An epiphyseal injury in the medial femoral head was created using a 1.6-mm drill. Hips were harvested bilaterally at 28 days after surgery. Alpha and epiphyseal shaft angles were measured on radiographs. Alpha angles at the 1- and 3-o’clock positions were measured on the oblique axial plane of micro–computed tomography images. Bone bar formation secondary to growth plate injuries was confirmed using alcian blue hematoxylin staining. Results: All hips in the study group showed a varus–type head-neck deformity, with lower epiphyseal shaft angles on anteroposterior radiographs versus those in the control group (133°± 8° vs 142°± 5°, respectively; P =.022) and higher epiphyseal shaft angles on lateral radiographs (27°± 12° vs 10°± 7°, respectively; P <.001). The mean alpha angles in the study group were higher at both the 1- (103°± 14° vs 46°± 7°, respectively; P <.002) and 3-o’clock (99°± 18° vs 35°± 11°, respectively; P <.002) positions than those in the control group. Alcian blue hematoxylin staining of all hips in the study group indicated that the injured physis developed a bony bar, leading to growth plate arrest on the medial femoral head. Conclusion: The proposed model led to growth arrest at the proximal femoral physis, resulting in a femoral head–neck deformity similar to human FAI. Clinical Relevance: Our novel small animal model of a femoral head–neck deformity is a potential platform for research into the basic mechanisms of FAI disease progression and the development of disease–modifying therapies.
KW - animal model
KW - femoroacetabular impingement
KW - head-neck deformity
KW - immature rabbit
UR - http://www.scopus.com/inward/record.url?scp=85129335953&partnerID=8YFLogxK
U2 - 10.1177/03635465221090645
DO - 10.1177/03635465221090645
M3 - Article
C2 - 35416068
AN - SCOPUS:85129335953
VL - 50
SP - 1919
EP - 1927
JO - American Journal of Sports Medicine
JF - American Journal of Sports Medicine
SN - 0363-5465
IS - 7
ER -