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Hip: X. Flecher, S. Parratte, J.-M. Aubaniac, and J.-N. Argenson Three-dimensional custom-designed cementless femoral stem for osteoarthritis secondary to congenital dislocation of the hip J Bone Joint Surg Br 2007; 89-B: 1586-1591 [Abstract] [Full text] [PDF]

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Authors' reply:

Xavier Flecher, Jean-Nöel Argenson   (18 June 2008)

Authors' reply:

Xavier Flecher, Jean-Nöel Argenson   (18 June 2008)

Three-dimensional custom-designed cementless femoral stem for osteoarthritis

Onder M. Delialioglu, Bulent Daglar, Kenan Bayrakci, Erman Ceyhan, Ugur Gunel.   (9 June 2008)

Offset-fact or a dream?

James Geoffrey Horne   (1 February 2008)

Authors' reply: 18 June 2008
Xavier Flecher, MD Center for OA surgery, Marseille, France, Jean-Nöel Argenson Send letter to journal: Re: Authors' reply: xavier.flecher{at}ap-hm.fr Xavier Flecher, et al.	Sir, We agree with the definitions described by Dr Delialioglu et al in their letter regarding anteversion and femoral torsion and thank them for their interest. However, in our experience from previous publications more related to anatomical studies,1,2 these terms are not often used. A common error may be made when using the word “anteversion”, as it can describe femoral anteversion as well as prosthetic anteversion. We then changed “femoral torsion” to “femoral anteversion” and preferred “correction in the prosthetic neck” to “prosthetic anteversion” in order to avoid misunderstanding, being aware that the definitions were different. In the text, the following sentences could be found as they were slightly corrected by the Editor: “Three horizontal slices of the foot in the axis of the second metatarsal, the knee at the level of the epicondylar axis, and 10 mm above the top of the lesser trochanter were necessary for assessment of femoral neck anteversion. (…) From these radiological images femoral anteversion was measured, the correction required to restore the leg length was calculated and the angle required for the neck-shaft angle of the femoral component was identified.” The words are precisely defined in another reference1 on this topic: “The proximal femoral anteversion was defined by the angle between the posterior bicondylar axis and the mediolateral dimension of the medullary canal at 20mm above the lesser trochanter” and should be understood as “femoral torsion”. The proper definition of anteversion is not made in our paper. We tried to avoid mistakes between the “femoral anteversion” and the “prosthetic anteversion”, as the aim of the design of the neck of a custom-made femoral component is to match the desired final prosthetic anteversion which can be different from both (anatomical femoral neck) anteversion and femoral torsion. Moreover, as mentioned by Delialioglu et al, the accurate determination of femoral anteversion is particularly complex. Finally, regarding the use of CT-scans, we routinely use 3D CT-scans for custom-THA with horizontal slices (to determine the different values of upper femoral torsion) and both frontal and lateral reconstructions. Those data are analysed by engineers in order to determine other 2D values as neck shaft angle (NSA) and femoral offset (FO). To have the proper value of pre-operative NSA and FO, the best frontal slice reconstructed from a CT-scan is, in our experience, the one in the axis of the neck anteversion. We do not routinely use CT-scans for post-operative assessment but conventional X-ray, all carried out by the same senior radiology team, with reproducible positioning of the limbs to avoid malrotation. We thank Dr Delialioglu et al for their productive comments. X. Flecher, JN. Argenson, Center for OA Surgery, Marseille, France. 1. Argenson J.-N, Ryembault E, Flecher X, et al. Three-dimensional anatomy of the hip in osteoarthritis after developmental dysplasia. J Bone Joint Surg [Br] 2005;87-B:1192-6. 2. Simonet JY, Argenson JN, Aubaniac JM. The use of uncemented custom made prostheses in high congenital dislocation of the hip. J Bone Joint Surg [Br] 1993;75-B(SuppIII):257.
Authors' reply: 18 June 2008
Xavier Flecher, MD Center for OA surgery, Marseille, France, Jean-Nöel Argenson Send letter to journal: Re: Authors' reply: xavier.flecher{at}ap-hm.fr Xavier Flecher, et al.	Sir, We thank Mr Horne for his comments regarding femoral offset. Increasing attention during the last few years has been given to femoral offset (FO) in total hip arthroplasty. It has been shown that a greater offset may enhance hip stability,1 and improve the range of motion and abductor strength,2 as well as decrease polyethylene wear.3 On the other hand, in vitro and finite element studies have shown that excessive offset may be detrimental for femoral stem loading in the superior and medial part of the femur leading to early failure in varus,4 and confirmed clinically in our experience. Coxa vara may also lead to osteoarthritis, and reproducing the same native anatomy at the time of total hip arthroplasty may not be the correct option. However, we agree that we still do not know if the FO has to be restored (ie. as it was pre-operatively), with the problem of the accuracy of measurement or to be “changed”, meaning that we have to know what the correct value is for each single patient. Since with the use of a custom neck we are able to evaluate the 3D value pre-operatively and propose an individual correction, we are now running a study on the influence of 3D FO on polyethylene wear. The term “correction” in our paper means that the FO assessment is made with the use of CT-scan, avoiding the influence of upper femoral torsion, aiming to have a more accurate value than with X-ray. In this way, it can be addressed as a change or a correction related to the examination used to assess the FO, as CT is used pre-operatively and X-rays post-operatively. No value of FO is mentioned in our paper in order to avoid a false comparison. A true correction may be performed if 1) both ipsilateral and controlateral hips did not allow a proper FO measurement (as the contralateral hip may be used to determine the FO) or 2) in the presence of associated femoral dysplasia with an abnormal neck-shaft angle. In these situations, the FO correction was performed taking care of both Amstutz level arm ratio5 (aiming for a ratio above 0.5) and finite element analysis performed by engineers to validate stem properties on bone loading and neck-stem junction strength, with correction of lower limb length and rotation. X. Flecher, JN. Argenson, Center for OA surgery, Marseille, France. 1. Fackler CD, Poss R. Dislocation in total hip arthroplasties. Clin Orthop 1980;151:169-78. 2. McGrory BJ, Morrey BF, Cahalan TD, An KN, Cabanela ME. Effect of femoral offset on range of motion and abductor muscle strength after total hip arthroplasty. J Bone Joint Surg [Br] 1995;77-B:865-9. 3. Sakalkale DP, Sharkey PF, Eng K, Hozack WJ, Rothman RH. Effect of femoral component offset on polyethylene wear in total hip arthroplasty. Clin Orthop 2001;388:125-34. 4. Ramaniraka NA, Rakotomanana LR, Rubin PJ, Leyvraz P. Noncemented total hip arthroplasty: influence of extramedullary parameters on initial implant stability and on bone-implant interface stresses. Rev Chir Orthop Reparatrice Appar Mot 2000;86:590-7.[French] 5. Amstutz HC, Sakai DN. Total joint replacement for ankylosed hips. Indications, technique, and preliminary results. J Bone Joint Surg [Am] 1975;57-A:619-25.
Three-dimensional custom-designed cementless femoral stem for osteoarthritis 9 June 2008
Onder M. Delialioglu, Orthopedic surgeon Ankara Numune Training and Research Hospital, Bulent Daglar, Kenan Bayrakci, Erman Ceyhan, Ugur Gunel. Send letter to journal: Re: Three-dimensional custom-designed cementless femoral stem for osteoarthritis drondermurat{at}yahoo.com Onder M. Delialioglu, et al.	Sir, We read with interest the article by Flecher et al1 in the December 2007 issue entitled, "Three-dimensional custom-designed cementless femoral stem for osteoarthritis secondary to congenital dislocation of the hip." We congratulate the authors, however, there are a few corrections needed in an otherwise outstanding article. The authors have made a common error in the accurate measurement of femoral torsion and the definition of the femoral neck axis. Anteversion is an increase in the angle of the head and neck of the femur relative to the frontal plane of the body. The angle between a line drawn along the posterior border of the femoral condyles and a line drawn through the femoral neck axis is femoral torsion.2 Femoral torsion can be determined by computed tomography with good accuracy and precision, provided attention is paid to the selection of the tomogram through the femoral neck. The delineation of the neck axis is, however, a major source of error. The shape of the femoral neck may be a source of poor accuracy if the neck centre is delineated on a tomogram too cranially or too caudally placed, or poor precision if an arbitrary or imprecise selection of tomogram is made.3 It is commonly appreciated that the accuracy of two-dimensional computed tomography is limited by anatomical variables (e.g., femoral antetorsion is harder to determine when the neck shaft angle is increased, as in this study) and positional variables. In such situations, 3D-CT is usually recommended.4 Did the authors use 3D-CT in the current study in order to alter the anatomical variations? If they used two-dimensional computed tomography, which slice did they prefer to use for patients with congenital dislocation of hip pre-operatively and post-operatively? O.M. DELIALIOGLU, Orthopedic Surgeon, B. DAGLAR, K. BAYRAKCI, E. CEYHAN, U. GUNEL, Ankara Numune Training and Research Hospital, Ankara, Turkey. 1. Flecher X, Parratte S, Aubaniac J.-M, Argenson J.-N. Three-dimensional custom-designed cementless femoral stem for osteoarthritis secondary to congenital dislocation of the hip. J Bone Joint Surg [Br] 2007;89-B:1586-91. 2. Beverly Cusick. Let’s Talk about Some Terms. November 9, 2001. http://www.gaitways.com/Docs/Nomenclature.pdf (accessed 09/06/2008). 3. Høiseth A, Reikerås O, Fønstelien E. Evaluation of three methods for measurement of femoral neck anteversion. Femoral neck anteversion, definition, measuring methods and errors. Acta Radiol 1989;30:69-73. 4. Abel MF, Wenger DR, Mubarak SJ, Sutherland DH. Quantitative analysis of hip dysplasia in cerebral palsy: a study of radiographs and 3-D reformatted images. J Pediatr Orthop 1994;14:283-89.
Offset-fact or a dream? 1 February 2008
James Geoffrey Horne, Orthopaedic Surgeon Wellington Hospital Send letter to journal: Re: Offset-fact or a dream? geoff.horne{at}ccdhb.org.nz James Geoffrey Horne	Sir, This paper perpetuates a common myth regarding femoral offset in total hip replacement. In figure 2 the authors note "correction of the femoral offset". However, perusal of the same patient in figure 1 suggests that the surgeon had two potential options: 1) attempt to maintain 'native' femoral offset, or 2) change femoral offset. To suggest that they have 'corrected' offset implies they knew what it should be for that patient. To my knowledge the only aspect of femoral offset that is scientifically validated is that greater offset reduces acetabular wear. There has been too much credence put on 'restoring femoral offset' when we know very little about how to measure it in vivo, or the desirability of changing it from that which mother nature provided. G. Horne, Orthopaedic Surgeon, Wellington Hospital, Wellington, New Zealand.