Ferner, F.

Mamisch, T.

Noble, P.

Santore, R.

Siebenrock, K.

Werlen, S.

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REPLY TO LETTER TO THE EDITORReply to Letter to the EditorThe Cam-type Deformity of the Proximal Femur Arises in Childhoodin Response to Vigorous Sporting ActivityK. A. Siebenrock MD, F. Ferner MD,P. C. Noble MD, PhD, R. F. Santore MD, PhD,S. Werlen MD, T. C. Mamisch MDPublished online: 17 September 2011 The Association of Bone and Joint Surgeons1 2011We thank Drs. Ng and Ellis for their well-taken commentsto our article ‘‘The Cam-type Deformity of the ProximalFemur Arises in Childhood in Response to VigorousSporting Activity’’ [3]. We agree with their comment thatalthough there is an exponentially increasing number ofvaried treatment methods in recent years, little is knownregarding the etiology of cam-type morphology. In thepast, cam-type morphologic features were presumed toarise primarily from a mild or silent capital slip [1, 5].However, the typical horizontal orientation of the growthplate with extension of the epiphysis onto the neck [4]contradicts this hypothesis in the majority of patients withcam-type impingement. To the best of our knowledge, ourstudy showed for the first time that high-level sportsactivities (basketball) during childhood and early adoles-cence might be one important factor determining the finalshape of the proximal femur in Caucasians. That meansthat playing basketball at a high level by this age grouprepresents a risk for the development of a cam-typedeformity. Our study however does not provide any con-firmation for the hypothesis of Ng and Ellis [2] that highaxial loading of the hip is the driving factor in the elitebasketball player. Our study simply describes morphologicfindings and differences between highly active athletes anda control group during and shortly after the growth period.In contrast to the suspicion of Ng and Ellis that adolescentactivities, particularly in flexion-internal rotation, mightprotect against cam morphologic features, we rather sus-pect hip activities with vigorous loading during flexion andinternal rotation of the hip might be responsible forabnormal growth and an aspherically shaped femur.However it was beyond the scope of our study to define theactual forces and specific damage mechanism leading tocam-type morphology.References1. Goodman DA, Feighan JE, Smith AD, Latimer B, Buly RL,Cooperman DR. Subclinical slipped capital femoral epiphy-sis: relationship of the hip. J Bone Joint Surg Br. 1997;83:1119–1124.2. Ng VY, Ellis TJ. More than just a bump: cam-type femoroace-tabular impingement and the evolution of the femoral neck. HipInt. 2011;21:1–8.3. Siebenrock KA, Ferner F, Noble PC, Santore RF, Werlen S,Mamisch TC. The Cam-type deformity of the proximal femurarises in childhood in response to vigorous sporting activity. ClinOrthop Relat Res. 2011 Jul 15. [Epub ahead of print].4. Siebenrock KA, Wahab KH, Werlen S, Kahlhor M, Leunig, GanzR. Abnormal extension of the femoral head epiphysis as a cause ofcam impingement. Clin Orthop Relat Res. 2004;418:54–60.5. Stulberg SD, Cordell LD, Harris WH, Ramsey OL, MacEwen GD.Unrecognized childhood disease: a major cause of idiopathicosteoarthritis of the hip. In: Amstutz HC, ed. The Hip: Proceedingsof the Third Open Scientific Meeting of the Hip Society. St Louis,MO: CV Mosby; 1975:212–228.K. A. Siebenrock (&), F. Ferner, T. C. MamischDepartment of Orthopedic Surgery, University of Bern,Inselspital, CH-3010 Bern, Switzerlande-mail: klaus.siebenrock@insel.chP. C. NobleJoseph Barnhart Department of Orthopedic Surgery,Baylor College of Medicine, Houston, TX, USAR. F. SantoreDepartment of Orthopedic Surgery, University of California,Sharp Memorial Hospital, San Diego, CA, USAS. WerlenDepartment of Radiology, Sonnenhof Clinic, Bern, Switzerland123Clin Orthop Relat Res (2011) 469:3508DOI 10.1007/s11999-011-2092-7Clinical Orthopaedicsand Related Research®A Publication of  The Association of Bone and Joint Surgeons®

Reply to Letter to the Editor: The Cam-type Deformity of the Proximal Femur Arises in Childhood in Response to Vigorous Sporting Activity

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Reply to Letter to the Editor: The Cam-type Deformity of the Proximal Femur Arises in Childhood in Response to Vigorous Sporting Activity

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