Objective In osteoarthritis (OA), subchondral bone changes alter the joint’s mechanical environment and potentially influence progression of cartilage degeneration. Joint distraction as a treatment for OA has been shown to provide pain relief and functional improvement through mechanisms that are not well understood. This study evaluated whether subchondral bone remodeling was associated with clinical improvement in OA patients treated with joint distraction. Method Twenty-six patients with advanced post-traumatic ankle OA were treated with joint distraction for three months using an Ilizarov frame in a referral center. Primary outcome measure was bone density change analyzed on CT scans. Longitudinal, manually segmented CT datasets for a given patient were brought into a common spatial alignment. Changes in bone density (Hounsfield Units (HU), relative to baseline) were calculated at the weight-bearing region, extending subchondrally to a depth of 8 mm. Clinical outcome was assessed using the ankle OA scale. Results Baseline scans demonstrated subchondral sclerosis with local cysts. At one and two years of follow-up, an overall decrease in bone density (−23% and −21%, respectively) was observed. Interestingly, density in originally low-density (cystic) areas increased. Joint distraction resulted in a decrease in pain (from 60 to 35, scale of 100) and functional deficit (from 67 to 36). Improvements in clinical outcomes were best correlated with disappearance of low-density (cystic) areas (r=0.69). Conclusions Treatment of advanced post-traumatic ankle OA with three months of joint distraction resulted in bone density normalization that was associated with clinical improvement.

A contact finite element (FE) formulation is introduced, amenable to patient-specific analysis of cumulative cartilage mechano-stimulus attributable to habitual functional activity. CT scans of individual human ankles are segmented to delineate bony margins. Each bone surface is projected outward to create a second surface, and the intervening volume is then meshed with continuum hexahedral elements. The tibia is positioned relative to the talus into a weight-bearing apposition. The articular members are first engaged under light preload, then plantar-/dorsi-flexion kinematics and resultant loadings are input for serial FE solutions at 13 instants of the stance phase of level walking gait. Cartilage stress histories are post-processed to recover distributions of cumulative stress-time mechano-stimulus, a metric of degeneration propensity. Consistency in computed contact stress exposures presented for seven intact ankles stood in contrast to the higher magnitude and more focal exposures in an incongruously reduced tibial plafond fracture. This analytical procedure provides patient-specific estimates of degeneration propensity due to various mechanical abnormalities, and it provides a platform from which the mechanical efficacy of alternative surgical interventions can be estimated.

Objectives Intra-articular fractures predispose patients to post-traumatic osteoarthritis (PTOA), with associated chronic joint pain and decreased function. The success of articular fracture management is dependent on how the fracture is treated and on fracture type and severity. The purpose of the present study was to correlate objective CT-based indices of intra-articular fracture severity with subsequent joint degeneration. It was hypothesized that an injury severity metric that included objective measures of articular disruption, of fracture energy, and of fragment displacement/dispersal would be a useful predictor of PTOA. Methods Novel CT-based image analysis techniques were utilized to quantify acute injury characteristics in a prospective series of twenty tibial plafond fractures managed by articulated external fixation, with later definitive surgical fracture reduction performed after soft-tissue swelling had sufficiently resolved. PTOA severity was assessed two years post-injury using the Kellgren-Lawrence (KL) radiographic grading scale. A predictive model was developed by linearly regressing these two-year KL outcomes on the CT-based severity metrics. Results A combined acute severity score involving articular disruption and fracture energy successfully predicted PTOA severity (R2 = 0.70), whereas fragment displacement / dispersal and surgeon opinion correlated much less well with degeneration (R2 = 0.42 and 0.47). The concordance between the combined metric and PTOA severity was 88%. Conclusions The findings of this study indicate that objective CT-based metrics of acute injury severity can reliably predict intermediate-term PTOA outcomes in this challenging class of articular fractures. Quantitative biomechanical assessment of injury characteristics provides new possibilities to improve fracture management and to guide PTOA research.

The energy of producing a fracture is considered one of the most important factors relating to injury severity, prognosis, and risk of complications, yet there has been no objective way to measure this important variable. The purpose of this study was to compare assessments of fracture severity made using new objective computed tomography (CT)-based methods versus the expert opinion of experienced orthopedic traumatologists. Fracture energy, fragment displacement, and soft tissue swelling were quantified in twenty tibial plafond fractures by analyzing injury CT scans. Three experienced orthopedic traumatologists then independently performed a rank order analysis of fracture severity, using plain radiographs. The concordance among the three clinicians ranged from 87% to 91%. Objective fracture severity measurements made with the CT algorithm agreed well with the clinical assessments (fracture energy concordance from 73% to 76%, fragment displacement from 82% to 89%, and soft tissue swelling from 61% to 65%). These are the first objective, CT-based measures of fracture severity. With further refinement, this conceptually novel method has the potential to serve as a valuable tool to provide objective measurement of fracture severity, allowing one to control for this previously confounding variable in large multicenter studies. ß 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res Keywords: fracture severity; intra-articular; post-traumatic arthritis Intra-articular fractures often portend secondary osteoarthritis (OA), chronic pain, and decreased joint function. The success of periarticular fracture management is dependent not only on how the fracture is treated but also on the fracture type and severity. 1-5 Decision making in treating complex articular injuries with comminution ( Fig. 1) requires that a surgeon assess the relative injury severity of a given case, and with this information, factor in the complexity of available treatment techniques, estimate prognosis, and weigh the risk for complications. Currently, no practical way exists to measure injury severity objectively. Existing methods have generally taken the form of fracture classification systems, based upon visual assessment of specified characteristics. Poor interobserver reliability is a persistent problem for these observer-based techniques, 20,22 with inaccurate identification and inconsistent interpretation of classification guidelines explaining much of the variability. With such poor reliability, comparisons among different studies is reduced to ''apples to oranges,'' hindering the compilation of a collective experience to guide patient care.The concept that ''the extent of bone, cartilage, and soft tissue damage is directly related to the energy imparted to these structures'' 6 is widely accepted among orthopedic traumatologists, and it provides a basis for objectively quantifying injury severity. To assess the mechanical energy involved in a fracture, a new computed tomography (CT)-based methodolog...

Background: The purposes of this study were (1) to develop a physical model to improve articular fracture reduction

A system for the semi-automatic reconstruction of highly fragmented bone fractures, developed to aid in treatment planning, is presented. The system aligns bone fragment surfaces derived from segmentation of volumetric CT scan data. Each fragment surface is partitioned into intact-and fracture-surfaces, corresponding more or less to cortical and cancellous bone, respectively. A user then interactively selects fracture-surface patches in pairs that coarsely correspond. A final optimization step is performed automatically to solve the N-body rigid alignment problem. The work represents the first example of a 3D bone fracture reconstruction system and addresses two new problems unique to the reconstruction of fractured bones : (1) non-stationary noise inherent in surfaces generated from a difficult segmentation problem and (2) the possibility that a single fracture surface on a fragment may correspond to many other fragments.Keywords: 3D reconstruction, bone segmentation, surface registration, CT Figure 1. Radiographs of a range of comminuted tibial pilon factures, varying in the number of bone fragments, the amount of fragment dispersal and the degree of intra-articular extension into the ankle.

The combination of high-resolution three-dimensional medical imaging, increased computing power, and modern computational methods provide unprecedented capabilities for assessing the repair and healing of fractured bone. Fracture healing is a natural process that restores the mechanical integrity of bone and is greatly influenced by the prevailing mechanical environment. Mechanobiological theories have been proposed to provide greater insight into the relationships between mechanics (stress and strain) and biology. Computational approaches for modeling these relationships have evolved from simple tools to analyse fracture healing at a single point in time to current models that capture complex biological events such as angiogenesis, stochasticity in cellular activities, and cell-phenotype specific activities. The predictive capacity of these models has been established using corroborating physical experiments. For clinical application, mechanobiological models accounting for patient-to-patient variability hold the potential to predict fracture healing and thereby help clinicians to customize treatment. Advanced imaging tools permit patient-specific geometries to be used in such models. Refining the models to study the strain fields within a fracture gap and adapting the models for case-specific simulation may provide more accurate examination of the relationship between strain and fracture healing in actual patients. Medical imaging systems have significantly advanced the capability for less invasive visualization of injured musculoskeletal tissues, but all too often the consideration of these rich datasets has stopped at the level of subjective observation. Computational image analysis methods have not yet been applied to study fracture healing, but two comparable challenges which have been addressed in this general area are the evaluation of fracture severity and of fracture-associated soft tissue injury. CT-based methodologies developed to assess and quantify these factors are described and results presented to show the potential of these analysis methods.

Reconstructing highly comminuted articular fractures poses a difficult surgical challenge, akin to solving a complicated three-dimensional (3D) puzzle. Pre-operative planning using CT is critically important, given the desirability of less invasive surgical approaches. The goal of this work is to advance 3D puzzle solving methods toward use as a pre-operative tool for reconstructing these complex fractures. Methodology for generating typical fragmentation/dispersal patterns was developed. Five identical replicas of human distal tibia anatomy, were machined from blocks of high-density polyetherurethane foam (bone fragmentation surrogate), and were fractured using an instrumented drop tower. Pre-and post-fracture geometries were obtained using laser scans and CT. A semi-automatic virtual reconstruction computer program aligned fragment native (nonfracture) surfaces to a pre-fracture template. The tibias were precisely reconstructed with alignment accuracies ranging from 0.03-0.4mm. This novel technology has potential to significantly enhance surgical techniques for reconstructing comminuted intra-articular fractures, as illustrated for a representative clinical case.