The influence of hip rotation on femoral offset in plain radiographs

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Abstract

Background and purpose

Adequate restoration of femoral offset (FO) is critical for successful outcome after hip arthroplasty or fixation of hip fracture. Previous studies have identified that hip rotation influences the projected femoral offset (FO _P) on plain anteroposterior (AP) radiographs, but the precise effect of rotation is unknown.

Patients and methods

We developed a novel method of assessing rotation-corrected femoral offset (FO _RC), tested its clinical application in 222 AP hip radiographs following proximal femoral nailing, and validated it in 25 cases with corresponding computed tomography (CT) scans.

Results

The mean FO _RC was 57 (29–93) mm, which differed significantly (p < 0.001) from the mean FO _P 49 (22–65) mm and from the mean femoral offset determined by the standard method: 49 (23–66) mm. FO _RC correlated closely with femoral offset assessed by CT (FO _CT); the Spearman correlation coefficient was 0.94 (95% CI: 0.88–0.97). The intraclass correlation coefficient for the assessment of FO _RC by AP hip radiographs correlating the repeated measurements of 1 observer and of 2 independent blinded observers was 1.0 and 1.0, respectively.

Interpretation

Hip rotation affects the FO _P on plain AP radiographs of the hip in a predictable way and should be adequately accounted for.

Related collections

Most cited references 19

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Effect of femoral offset on range of motion and abductor muscle strength after total hip arthroplasty.

Stephen D Cahalan, Brian J. McGrory, Miguel E Cabanela … (1995)

At a minimum of one year after operation, we studied 64 patients with 86 total hip arthroplasties (THA) by standard anteroposterior hip and pelvic radiographs and measurement of range of motion and of isometric abduction strength. The femoral offset correlated positively with the range of abduction (p = 0.046). Abduction strength correlated positively with both femoral offset (p = 0.0001) and the length of the abductor lever arm (p = 0.005). Using multiple regression, abduction strength correlated with height (p = 0.017), gender (p = 0.0005), range of flexion (p = 0.047) and the abductor lever arm (p = 0.060). Our findings suggest that greater femoral offset after THA allows both an increased range of abduction and greater abductor strength.

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Femoral offset: anatomical concept, definition, assessment, implications for preoperative templating and hip arthroplasty.

G Lecerf, M.H. Fessy, R. Philippot … (2009)

BACKGROUND OBJECTIVE: Femoral offset is supposed to influence the results of hip replacement but little is known about the accurate method of measure and the true effect of offset modifications. This article is a collection of independent anatomic, radiological and clinical works, which purpose is to assess knowledge of the implications of femoral offset for preoperative templating and total hip arthroplasty. There is a strong correlation between femoral offset, abductors lever arm and hip abductor strength. Hip lateralization is independent of the femoral endomedullary characteristics. The abductors lever arm is highly correlated to the gluteus medius activation angle. There were correlations between femoral offset and endomedullary shape. The hip center was high and medial for stovepipe metaphysis while it was lower and lateralized for champagne - flute upper femur. A study was performed to compare the femoral offset measured by X-ray and CT-scan in 50 patients, demonstrated that plain radiography underestimates offset measurement. The 2D templating cannot appreciate the rotation of the lower limb. Taking into account the horizontal plane is essential to obtain proper 3D planning of the femoral offset. A randomized study was designed to compare femoral offset measurements after hip resurfacing and total hip arthroplasty. This study underlined hip resurfacing reduced the femoral offset, while hip replacement increased offset. However, the reduction of femoral offset after hip resurfacing does not affect the function. A pilot study was designed to assess the results of 120 hip arthroplasties with a modular femoral neck. This study showed that the use of a modular collar ensures an easier restoration of the femoral offset. A cohort of high offset stems (Lubinus 117 degrees) was retrospectively assessed. The survival rate was slightly lower that the standard design reported in the Swedish register. Finally, the measurement of offset and leg length was assessed with the help of computer assistance. The software changed the initial schedule (obtained by templating) in 29%. Therefore, femoral offset restoration is essential to improve function and longevity of hip arthroplasty. CT-scan is more accurate than plain radiography to assess femoral offset. Hip resurfacing decreases offset without effect on function. Modular neck and computer assistance may improve intraoperative calculation and reproduction of femoral offset. Increasing offset with a standard cemented design may decrease long-term fixation. Level IV: Retrospective or historical series.

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Effect of femoral component offset on polyethylene wear in total hip arthroplasty.

William Hozack, D P Sakalkale, Jimmy K. Eng … (2001)

Seventeen staged, bilateral total hip arthroplasties performed in 17 patients were reviewed to compare side-to-side polyethylene wear. Implants used on both sides were similar except for implant offset: one hip in each patient was replaced using a femoral component having a standard implant offset, whereas the other side had a lateral offset implant. The mean followup was 5.70 years (range, 2-10.2 years) on the side with a standard femoral implant and 5.67 years (range, 2-9.7 years) on the side with a lateralized femoral component. The only statistically different parameter between the sides was the femoral component offset. All other parameters affecting polyethylene wear, such as period of followup, head size, head type, cup size, cup inclination, medialization of cup, and patient-related factors were similar on both sides. On the side with a standard femoral component, the mean actual prosthetic offset (determined by manufacturer's specifications) was 35.2 mm and the radiologic offset was 31.5 mm. On the side with a lateralized femoral component, the actual prosthetic offset was 42.5 mm and the radiologic offset was 40.1 mm. The difference in offsets between the sides was statistically significant. The mean preoperative offset of the femur was 38.8 mm. Regression analysis revealed that only femoral component offset and cup size correlated significantly with linear wear rate. On the side with a standard femoral component, the linear wear rate was 0.21 mm per year, whereas on the side with a lateralized femoral component, the linear wear rate was 0.10 mm per year. The differences in the linear wear rates were significant. Lateralization of the femoral component in this series more closely restored preoperative hip biomechanics and significantly decreased polyethylene wear.

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Author and article information

Journal

Journal ID (nlm-ta): Acta Orthop

Journal ID (iso-abbrev): Acta Orthop

Journal ID (publisher-id): ORT

Title: Acta Orthopaedica

Publisher: Informa Healthcare

ISSN (Print): 1745-3674

ISSN (Electronic): 1745-3682

Publication date (Print): August 2014

Publication date (Electronic): 14 July 2014

Volume: 85

Issue: 4

Pages: 389-395

Affiliations

¹Department of Trauma , Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Germany

²Nuffield Orthopaedic Centre , Oxford, UK

³Department of Orthopaedic Surgery , Regensburg University Medical Center, Regensburg, Germany

⁴Department of Orthopaedic and Trauma Surgery , University Hospital of Cologne, Cologne, Germany.

Author notes

Correspondence: lechler@ 123456med.uni-marburg.de

Article

Publisher ID: ORT_A_931196_O

DOI: 10.3109/17453674.2014.931196

PMC ID: 4105770

PubMed ID: 24954484

SO-VID: 7ef6039b-8ca4-4f80-ba14-9a3cf0932e7c

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This is an open-access article distributed under the terms of the CC-BY-NC-ND 3.0 License which permits users to download and share the article for non-commercial purposes, so long as the article is reproduced in the whole without changes, and provided the original source is credited.

The influence of hip rotation on femoral offset in plain radiographs

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Abstract

Background and purpose

Patients and methods

Results

Interpretation

Related collections

Orthopedics

Most cited references 19

Effect of femoral offset on range of motion and abductor muscle strength after total hip arthroplasty.

Femoral offset: anatomical concept, definition, assessment, implications for preoperative templating and hip arthroplasty.

Effect of femoral component offset on polyethylene wear in total hip arthroplasty.

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