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High 10-year survival rate with an anatomic cementless stem (SPS).

Sariali E, Mouttet A, Mordasini P, Catonné Y - Clin. Orthop. Relat. Res. (2012)

Bottom Line: All stems appeared radiographically stable and one stem was graded nonintegrated but stable.Five patients had revision surgery: one on the femoral side (for posttraumatic fracture) and four on the acetabular side.Considering stem revision for aseptic loosening as the end point, survivorship was 100% (range, 95.4%-99.9%) at 10 years.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Hôpital Pitié Salpétrière, 47-83 Bd de l'Hôpital, 75013, Paris, France. hedisari@yahoo.fr

ABSTRACT

Background: Proximal cementless fixation using anatomic stems reportedly increases femoral fit and avoids stress-shielding. However, thigh pain was reported with the early stem designs. Therefore, a new anatomic cementless stem design was based on an average three-dimensional metaphyseal femoral shape. However, it is unclear whether this stem reduces the incidence of thigh pain.

Questions/purposes: We asked whether this stem design was associated with a low incidence of thigh pain and provided durable fixation and high function.

Methods: One hundred seventy-one patients (176 THAs) who had the anatomic proximal hydroxyapatite-coated stem implanted were reviewed. Eleven (6%) patients were lost to followup and 34 (20%) died without revision surgery. We used the Harris hip score (HHS) to assess pain and function. We evaluated femoral stem fixation and stability with the score of Engh et al. and also calculated a 10-year survival analysis. We assessed 126 patients (131 hips) at a mean followup of 10 years (range, 8-11 years)

Results: At last followup, two patients described slight thigh pain that did not limit their physical activities. All stems appeared radiographically stable and one stem was graded nonintegrated but stable. Five patients had revision surgery: one on the femoral side (for posttraumatic fracture) and four on the acetabular side. Considering stem revision for aseptic loosening as the end point, survivorship was 100% (range, 95.4%-99.9%) at 10 years.

Conclusion: This anatomic cementless design using only metaphyseal fixation with a wide mediolateral flare, a sagittal curvature, and torsion, allowed durable proximal stem stability and fixation.

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(A) With varus morphotypes the SPS stem may not have a good medial fit on the medial cortex. (B) The average SPS shape fits in almost all patients who do not have major dysplasia. (C) In case of a valgus morphotype, the SPS stem may have a punctual contact medially at the upper portion of the neck with a risk of fracture. A-A is the cross section corresponding to the neck osteotomy plane.
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Fig6: (A) With varus morphotypes the SPS stem may not have a good medial fit on the medial cortex. (B) The average SPS shape fits in almost all patients who do not have major dysplasia. (C) In case of a valgus morphotype, the SPS stem may have a punctual contact medially at the upper portion of the neck with a risk of fracture. A-A is the cross section corresponding to the neck osteotomy plane.

Mentions: In contrast to the custom anatomic stems, the average shape of the SPS stem may not have a proper fit in some patients. These outliers may be detected before surgery by performing 3-D computerized planning [34]. In case of a varus morphotype, the stem may not have ideal medial mechanical support. However with a valgus morphotype, as the medial femoral cortex has a lower curvature, the medial contact with the stem may occur on a very small contact area located at the upper portion of the neck, generating higher mechanical constraints medially and therefore a risk of fracture (Fig. 6). In our experience, three types of proximal femur morphotypes exist (Fig. 6). The standard morphotype corresponds to the average intracanalar metaphyseal volume, which we used to design the proximal shape of the SPS stem. The valgus morphotype has a narrower medial flare, so the medial cortex has a lower curvature. However, the varus morphotype has a wider medial flare with a greater curvature of the medial cortex. Theoretically, three types of anatomic stems might be required to achieve intimate contact between the stem and the proximal femur, with a fit and fill equivalent to a custom anatomic stem. However, the high 10-year survival rate of the SPS stem suggests that this average shape seems appropriate for a majority of patients who do not have a major dysplasia. However, custom anatomic stems also allow more accurate reconstruction of the extramedullary anatomy, including the neck length, offset, and femoral anteversion. Some authors [26, 33] reported there is poor correlation between the intracanalar anatomy of the proximal femur and the extramedullary anatomy. Therefore, a modular version of the SPS has been developed to increase accuracy of the hip reconstruction [34] regarding the leg length and offset.Fig. 6A–C


High 10-year survival rate with an anatomic cementless stem (SPS).

Sariali E, Mouttet A, Mordasini P, Catonné Y - Clin. Orthop. Relat. Res. (2012)

(A) With varus morphotypes the SPS stem may not have a good medial fit on the medial cortex. (B) The average SPS shape fits in almost all patients who do not have major dysplasia. (C) In case of a valgus morphotype, the SPS stem may have a punctual contact medially at the upper portion of the neck with a risk of fracture. A-A is the cross section corresponding to the neck osteotomy plane.
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Related In: Results  -  Collection

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Fig6: (A) With varus morphotypes the SPS stem may not have a good medial fit on the medial cortex. (B) The average SPS shape fits in almost all patients who do not have major dysplasia. (C) In case of a valgus morphotype, the SPS stem may have a punctual contact medially at the upper portion of the neck with a risk of fracture. A-A is the cross section corresponding to the neck osteotomy plane.
Mentions: In contrast to the custom anatomic stems, the average shape of the SPS stem may not have a proper fit in some patients. These outliers may be detected before surgery by performing 3-D computerized planning [34]. In case of a varus morphotype, the stem may not have ideal medial mechanical support. However with a valgus morphotype, as the medial femoral cortex has a lower curvature, the medial contact with the stem may occur on a very small contact area located at the upper portion of the neck, generating higher mechanical constraints medially and therefore a risk of fracture (Fig. 6). In our experience, three types of proximal femur morphotypes exist (Fig. 6). The standard morphotype corresponds to the average intracanalar metaphyseal volume, which we used to design the proximal shape of the SPS stem. The valgus morphotype has a narrower medial flare, so the medial cortex has a lower curvature. However, the varus morphotype has a wider medial flare with a greater curvature of the medial cortex. Theoretically, three types of anatomic stems might be required to achieve intimate contact between the stem and the proximal femur, with a fit and fill equivalent to a custom anatomic stem. However, the high 10-year survival rate of the SPS stem suggests that this average shape seems appropriate for a majority of patients who do not have a major dysplasia. However, custom anatomic stems also allow more accurate reconstruction of the extramedullary anatomy, including the neck length, offset, and femoral anteversion. Some authors [26, 33] reported there is poor correlation between the intracanalar anatomy of the proximal femur and the extramedullary anatomy. Therefore, a modular version of the SPS has been developed to increase accuracy of the hip reconstruction [34] regarding the leg length and offset.Fig. 6A–C

Bottom Line: All stems appeared radiographically stable and one stem was graded nonintegrated but stable.Five patients had revision surgery: one on the femoral side (for posttraumatic fracture) and four on the acetabular side.Considering stem revision for aseptic loosening as the end point, survivorship was 100% (range, 95.4%-99.9%) at 10 years.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Hôpital Pitié Salpétrière, 47-83 Bd de l'Hôpital, 75013, Paris, France. hedisari@yahoo.fr

ABSTRACT

Background: Proximal cementless fixation using anatomic stems reportedly increases femoral fit and avoids stress-shielding. However, thigh pain was reported with the early stem designs. Therefore, a new anatomic cementless stem design was based on an average three-dimensional metaphyseal femoral shape. However, it is unclear whether this stem reduces the incidence of thigh pain.

Questions/purposes: We asked whether this stem design was associated with a low incidence of thigh pain and provided durable fixation and high function.

Methods: One hundred seventy-one patients (176 THAs) who had the anatomic proximal hydroxyapatite-coated stem implanted were reviewed. Eleven (6%) patients were lost to followup and 34 (20%) died without revision surgery. We used the Harris hip score (HHS) to assess pain and function. We evaluated femoral stem fixation and stability with the score of Engh et al. and also calculated a 10-year survival analysis. We assessed 126 patients (131 hips) at a mean followup of 10 years (range, 8-11 years)

Results: At last followup, two patients described slight thigh pain that did not limit their physical activities. All stems appeared radiographically stable and one stem was graded nonintegrated but stable. Five patients had revision surgery: one on the femoral side (for posttraumatic fracture) and four on the acetabular side. Considering stem revision for aseptic loosening as the end point, survivorship was 100% (range, 95.4%-99.9%) at 10 years.

Conclusion: This anatomic cementless design using only metaphyseal fixation with a wide mediolateral flare, a sagittal curvature, and torsion, allowed durable proximal stem stability and fixation.

Show MeSH
Related in: MedlinePlus