Background

Previously, we demonstrated the effectiveness of phase symmetry (PS) features for segmentation and localisation of bone fractures in 3D ultrasound for the purpose of orthopedic fracture reduction surgery. We recently proposed a novel real-time image-processing method of bone surface extraction from local phase features of clinical 3D B-mode ultrasound data. We are presenting a computational study and outline planned future developments for integration into a computer aided orthopedic surgery framework.

Previously, we demonstrated the effectiveness of phase symmetry (PS) features for segmentation and localisation of bone fractures in 3D ultrasound for the purpose of orthopaedic fracture reduction surgery. We recently proposed a novel real-time image-processing method of bone surface extraction from local phase features of clinical 3D B-mode ultrasound data. We are presenting a computational study and outline of planned future developments for integration into a computer aided orthopaedic surgery framework.

Our image-processing pipeline was implemented on three platforms: (1) using an existing PS extraction C++ algorithm on a dual processor machine with two Xeon x5472 CPUs @ 3GHz with 8GB of RAM, (2) using our proposed method implemented in MATLAB running on the same machine as in (1), and (3) CUDA implementation of our method implemented on a professional GPU (Nvidia Tesla c2050).

We ran these three implementations 20 times each on 128×128×128 scans of the iliac crest in live subjects and repeated the processing for 15 combinations of filter parameters. On average, the C++ implementation took 1.93s per volume, the MATLAB implementation 1.28s, and the GPU implementation 0.08s. Overall, our GPU implementation is between 15 and 25 times faster than the state-of-the-art method.

Implementing our algorithm on a professional grade GPU produced dramatic computational improvements, enabling full 3D datasets to be processed in an average time of under 100ms, which, if proven in a clinical system, would allow for near real time computation. We are currently implementing our algorithm on an open research sonography platform (Ultrasonix Medical Corporation). High-powered graphic cards can easily be integrated into the open architecture of this system, thus enabling GPU computation on diagnostic medical and research ultrasound devices.

We intend to use this platform within a surgical environment for accurate and automatic detection of fractures and as an integral part of our developing computer aided surgery pipeline, in which we use PS features to register intra-operative ultrasound to pre-operative computed tomography images.

Background: The treatment of extensive soft tissue injury with bony involvement due to orthopaedic trauma or other pathologic conditions has undergone great improvement in the last decade.

The main fields that assisted with that progress are: the ability to transfer autogenous vascularized soft and/or bony tissues to the injured areas and the possibility to apply external fixation either statistically for acute stabilization of a limb or using dynamic frames to correct late occurring contractures or deformities.

Objectives: To present our experience in treating young patients with severe, post traumatic or tumor resection soft tissue and bony injuries including bone loss and late joint contractures. That was treated by a combination of free vascularized flaps and static or dynamic circular external fixation with special emphasis on preplanning and technical issues critical for the success of such complex procedures.

Methods: Seven patients were included in the study; six post traumatic patients who received free vascularized myocutaneous latissimum dorsi or fasciocutaneous anterolateral thigh flaps to the calf and foot. All six patients had an Ilizarov frame for initial stabilization; two of them needed late dynamic correction of equines with the frame. The seventh patient had surgery for removal of osteosarcoma and received a vascularized osteocutaneous fibula flap with fixation by Ilizarov frame, this patient also needed late dynamic frame application for equines correction.

Results: The mean age at surgery was 11.6 years (range 7–14 years); mean follow up was 1.8 years (range 2 months – 3.4 years).

All microvascular flaps but one survived where the patient with the failed latissimus dorsi flap had the second muscle transferred at the next day. One patient needed 2 vascular revisions. All bone flap showed solid union at 3 months post operatively. Four patients achieved plantigrade foot initially. The three patients with dynamic correction achieved plantigrade foot at frame removal.

Complications: Equinus contracture of the ankle in three patients, injury to the vascular anastomosis in one patient. Pin tract infection in all patients that responded well to antibiotics.

Conclusions: The circular external fixator is a reliable method for initial fixation of injured limb. It is advised to apply the fixator before the transfer of the free flap. Position of the fixation pins should be discussed before hand with the plastic surgeons to allow free access to the microvascular anastomosis site. Free flaps allow the coverage of large soft tissue defects while the external fixators maintain anatomical position of the limb. Late occurring contractures after the incorporation of the flap can be safely corrected gradually with the circular frame. It is of paramount importance to include the foot in the frame and maintain neutral position of the ankle joint to prevent equines contractures.