Callus patterns in femoral lengthening over an intramedullary nail

Abstract

Our objectives were to evaluate callus patterns seen in femoral lengthening over an intramedullary nail by Li classification regarding shape and type and to predict the result while using the nail to reduce the external fixation period and its complications. Eight hundred digital radiographs of 15 patients with 15 segments of femur shortening who underwent femoral lengthening with a monolateral external fixator over an intramedullary nail were analyzed retrospectively by four observers. Each radiograph was studied for callus shape, feature type, and callus density using pixel values. The classification was tested for concurrence and reproducibility by interobserver studies and callus patterns were compared with treatment indices to evaluate how they correlated with the outcome. Mean length gained was 4.5 cm (range: 2-8 cm). External fixator index (EFI) was 21.68 days/cm. Average distraction consolidation index (DCI) was 48.49 days/cm. Fusiform callus was seen in three cases, cylindrical in seven, and lateral in five. The homogenous pathway had higher DCI (43.7) than the heterogeneous pathway (32.9), and mixed pathways making up the rest had a DCI of 50.1. Pixel value of callus showed gradual increase in density until 20-24 weeks, then density gradually fell for 8 weeks, again increased after 32 weeks, again gradually fell, and was comparable to adjacent normal bone by 44-48 weeks. Our results suggest that the Li classification can be satisfactorily applied to lengthening procedures over intramedullary nails. The radiologic pattern and pixel value of regenerate can be correlated with the clinical outcome and can be an aid of prognostic value for the surgeon. Keywords: callus pattern; femoral lengthening; intramedullary nail; callus density; healing pathwayThe most common dilemma of any orthopedic surgeon doing distraction osteogenesis is the reproducible method of ascertaining the progression of osteogenesis and the eventual timing of removal of the external fixator.1,2 Since the constant presence of the fixator has been a source of irritation, pain, and stiffness for most patients, the lengthening done over an intramedullary nail is an aesthetic and biomechanically stable option for early removal. Better patient compliance, rapid improvement in range of joint movement, additional construct stability, and reduced incidence of deformities are advantages of such a procedure.3 Routinely, the consolidation phase is two to four times the duration of the distraction phase. Hence, accurate assessment of the mineralization of the regenerate assumes significance considering that inaccurate timing of removal may lead to stiffness and pin tract infection or deformity, shortening, and non union. Li et al. 4 developed a classification based on the shape and pattern of regenerate that, according to them, can help the surgeon to diagnose a particular abnormal callus pattern to determine its etiology, and with early intervention improve the end result. In the Li et al. 4 study, callus patterns were described in the adu...

Experimental study of progressive tibial lengthening in dogs using the Ilizarov technique. Comparison with and without associated intramedullary K-wires

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Distraction Osteogenesis in the Combined and Sequential Use of Transosseous and Intramedullary Osteosynthesis: Experimental Study

“…Регенераты имели преимущественно веретенообразную форму, когда в контрольной группе отмечена как веретенообразная, так и цилиндрическая форма регенератов. Эти данные соответствуют клиническим исследованиям плотности и формы регенератов при УПг [37,38]…”

Reamed Intramedullary Nailing has an Adverse Effect on Bone Regeneration During the Distraction Phase in Tibial Lengthening

“…First, the accuracy and reliability of the pixel value ratio is not fully established as an objective tool for measuring bone regeneration. Several objective diagnostic tools for assessment of regenerate bone have been introduced such as dual x-ray absorptiometry [10,23], CT [32,35], and pixel value ratio [12,24,38,45]. Serial evaluation of callus during the distraction phase in leg lengthening using dual x-ray absorptiometry or CT is limited because of repeated radiation exposure and metal interference.…”