Neurogenic heterotopic ossification: epidemiology and morphology on conventional radiographs in an early neurological rehabilitation population.

OBJECTIVE: To retrospectively evaluate neurogenic heterotopic ossification in an early neurological rehabilitation population (phases B and C) with respect to epidemiology and morphology on conventional radiographs. MATERIALS AND METHODS: Over a 4-year period, 1,463 patients treated at a clinic for early neurological rehabilitation were evaluated for clinical symptoms of neurogenic heterotopic ossification. In case of clinical suspicion, plain radiographs of the expected sites were obtained. If heterotopic ossification was detected, the initial and subsequent radiographs were retrospectively analyzed for sites, size, and morphology. Immature lesions were categorized as small (<10 mm) or large (10-100 mm). RESULTS: The prevalence rate of neurogenic heterotopic ossification was 2.05%. The condition was most common in young male adults. The hip was the most common site accounting for more than half of the cases. Two or more ossifications were seen in 56.7% of the affected patients with approximately two-thirds showing bilateral symmetric involvement of corresponding joint regions. The size of ossifications strongly varied interindividually. Small immature lesions demonstrated less progression in size than large lesions during maturation (P < 0.05). CONCLUSION: Standard radiographs, as a fast and inexpensive technique, allow the expected size progression of heterotopic ossifications during maturation to be estimated, which is relevant in terms of therapeutic decisions, patient mobilization, and neurological rehabilitation.

Biomechanics of calcaneal fractures: a model for the motor vehicle.

Changes in legislation, availability of passive or active restraint systems, or both, together with increased public awareness for safety and the need for use of restraint, have shifted the spectrum of trauma in motor vehicle crashes from the head and torso to other regions. Lower extremity trauma in motor vehicle crashes continues to be a significant problem. The objective of this study was to investigate the biomechanics of the human foot and ankle complex under impact loading and replicate calcaneal fractures routinely seen in motor vehicle crashes. Twenty-two unembalmed cadaver lower extremity specimens were subjected to dynamic loads using a minisled pendulum device. Input and output forces and results of pathologic analysis were obtained using load cell data, radiographs obtained before and after testing, and gross dissection. The intraarticular fracture patterns produced were similar to those seen clinically and described in the literature. Maximum forces ranged from 3.6 to 11.4 kN for the fracture, and 0.5 to 7.3 kN for the nonfracture groups. Logistic regression analysis revealed a 50% probability of calcaneal fracture at 5.5 kN and a 25% probability at 4.0 kN. These studies will lead to an understanding of the tolerance of the lower extremity in sustaining calcaneal fractures under impact. Implications of the work are in the design of crash test dummies, data acquisition, and modifications in motor vehicle design and safety.

Migration of a K-wire from the distal radius to the heart.

K-wires and Steinmann pins are used to provide internal fixation for fractures or osteotomies. In some instances, removal of the implant is planned and the implant is left long to facilitate its removal. In other instances, implant removal is not planned and the implant is cut off at the level of the bone. Migration of these implants to solid organs or body cavities has been reported. Extravascular migration may occur along tissue planes assisted by muscle motion. Large vessel penetration can occur and has been reported with subsequent migration of the implant to the heart. This case report documents the loosening of a K-wire used in the distal radius to supplement the fixation of a complex intra-articular fracture, migration of the implant along tissue planes, penetration into a peripheral vein, and continued migration of the implant to the heart. There are multiple reports documenting wandering bullets, venous catheter tips, and invasive monitoring devices in the extremities. This is only the second case report that the authors are aware of that confirms migration of an implant from the distal extremity to the heart.

Experimental production of extra- and intra-articular fractures of the os calcis.

Although studies have been conducted in the past to duplicate traumatic fractures of the os calcis, biomechanical force data as a function of extra- and intra-articular fractures are not available. Consequently, in this study, a dynamic single impact model was used to provide such information. Using intact human cadaver lower extremities, impact loading was applied to the plantar surface of the foot using a mini-sled pendulum equipment. The proximal tibia was fixed in polymethylmethacrylate. Following impact, pathology to the os calcis was classified into intact (no injury; 14 cases), and extra-articular (6 cases) and intra-articular (6 cases) fractures. Peak dynamic forces were used to conduct statistical analysis. Mean forces for the intact and (both) fracture groups were 4144 N (standard error, SE: 689) and 7802 N (SE: 597). Mean forces for the extra- and intra-articular fracture groups were 7445 N (SE: 711) and 8159 N (SE: 1006). The peak force influenced injury outcome (ANOVA, p<0.005). Differences in the forces were found between intact and injured specimens (p<0.01); intact specimens and specimens with extra-articular pathology (p<0.001); intact specimens and specimens with intra-articular pathology (p<0.005). The present experimental protocol, which successfully reproduced clinically relevant os calcis pathology, can be extended to accommodate other variables such as the simulation of Achilles tendon force, the inclusion of other angles of force application, and the application of the impact force to limited regions of the plantar force of the foot in order to study other injury mechanisms.