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

UNLABELLED: 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. MATERIAL AND METHODS: 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. RESULTS: 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%. CONCLUSION: 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.

[Computer-assisted positioning of the acetabular cup for total hip arthroplasty based on joint kinematics without prior imaging: preliminary results with computed tomographic assessment]. / Positionnement de la cupule d'une prothèse totale de hanche par navigation sans image basée sur la cinématique articulaire: Premiers résultats avec evaluation tomodensitométrique de l'orientation des implants.

PURPOSE OF THE STUDY: Most navigation systems for computer-assisted total hip arthroplasty (THA) require prior computed tomography (CT) or acquisition of multiple bone landmarks on the pelvis. In order to avoid these problems, we developed a computer-assisted navigation system without CT based on a kinematic approach to the hip joint. The principle is to orient the cup in relation to the cone describing the hip joint range of motion. The purpose of this work was to analyze preliminary results. MATERIAL AND METHODS: Eighteen primary THA were implanted with the system (16 women, two men, mean age 68 +/- 7.8 years, age range 54-83 years, 18 degenerative hip disease). Two optoelectronic captors were fixed percutaneously on the pelvis and the distal femur. The acetabulum was prepared first followed by the femur using reamers and broaches of increasing size. The last broach placed in the femur was equipped with a large head adapted to the newly prepared acetabulum. The range of hip motion was recorded to determine the maximal range of motion cone. The acetabular cup was thus positioned in order the prosthesis range of motion included entirely the maximal range of motion of the hip joint. RESULTS: One patient fell three weeks after implantation causing posterior dislocation; there was no recurrence. The Postel-Merle-d'Aubligné score improved from 8 +/- 2.9 (range 3-12) preoperatively to 17 +/- 0.8 (range 16-18) at last follow-up. None of the patients complained about the captor insertion and there were no cases of hematoma or fracture. Operative time was 35-40 minutes longer for the first four cases and was progressively reduced 15-20 minutes for the last four cases. Mean leg length discrepancy was 5.6 +/- 7.5 mm (range 0-25) before implantation and 0.6 +/- 3 mm (range -5 to 10 mm) at last follow-up. CT-scan measurements revealed a mean anteversion of the femoral implant of 18.2 +/- 8.5 degrees (range 0-31). Anatomic anteversion of the cup (measured from the pelvis landmark and thus independently of the position of the pelvis) was 24.7 +/- 8.8 degrees (range 12-40). The sum of the femoral and anatomic acetabular anteversions was 43 +/- 13.1 degrees (range 22-71). Anteversions were 16 degrees for the cup and 16 degrees for the stem for the one case of dislocation. CONCLUSION: This method can be used in routine without lengthening operative time significantly. It safely controls leg length and helps position the cup. This study demonstrated that there is no ideal position for the cup which can be used for all patients. Because of the wide range of inclination and anteversion figures, half of the cases were outside the safety zone recommended by Lewinnek.

Pulmonary sarcoidosis: role of CT in the evaluation of disease activity and functional impairment and in prognosis assessment.

PURPOSE: To investigate the role of computed tomography (CT) in determining disease activity and functional impairment and in predicting the prognosis of lung involvement in patients with sarcoidosis. MATERIALS AND METHODS: Two groups of patients underwent CT, pulmonary function tests, and bronchoalveolar lavage. Disease activity was based on serum angiotensin converting enzyme activity and/or lymphocytosis at bronchoalveolar lavage. CT findings in group 1 were correlated with indexes of disease activity and functional parameters at diagnosis. In group 2, evaluation initially and at follow-up led to investigation of correlations between initial CT findings and evolution of disease activity and functional impairment. RESULTS: CT abnormalities in group 1 were nodules, air-space consolidation, lung distortion, septal and nonseptal linear areas of high attenuation, ground-glass attenuation, and honeycombing. Profusion of septal lines was the only CT finding that correlated with disease activity. Statistically significant (P < .05) but low correlation (r < .48) was observed between the extent of abnormalities at CT and impairment of lung function, except for nodules. CONCLUSION: Profusion of lung changes reflects functional impairment but not disease activity. CT findings cannot help predict the evolution of lung changes over time.

Computed tomography assessment of ground-glass opacity: semiology and significance.

Among the computed tomography (CT) signs of parenchymal lung disease, the ground-glass pattern is the one most difficult to diagnose and most influenced by CT technique. Ground-glass opacity may result from changes in the airspaces or interstitial tissues in acute or chronic infiltrative lung disease. It may also be seen as a consequence of increased capillary blood volume in redistribution of blood flow due to airway disease, emphysema, or pulmonary thromboembolism. Definition of this sign on high-resolution CT (HRCT) images, its various HRCT patterns, and potential pitfalls in its recognition are described with special attention to optimal HRCT technique.