Fixation Principles in Minimal Incision Hallux Valgus Surgery.

Minimal incision surgical principals rely on the soft tissue envelope to maintain stability that is supplemented by a variety of clinically recommended fixation methods. The extended distal first metatarsal osteotomy has renewed interest because of the ability to laterally translate, angulate, and rotate the metatarsal head in proper alignment with the sesamoids to a neutral alignment. The soft tissue envelope of capsule, ligaments, and tendons will re-align once the bone deformity is corrected. The periosteum is maintained to provide a biologic scaffold for new bone formation and must be minimally disrupted during the intervention."

Outer retinal structure in best vitelliform macular dystrophy.

IMPORTANCE: Demonstrating the utility of adaptive optics scanning light ophthalmoscopy (AOSLO) to assess outer retinal structure in Best vitelliform macular dystrophy (BVMD). OBJECTIVE: To characterize outer retinal structure in BVMD using spectral-domain optical coherence tomography (SD-OCT) and AOSLO. DESIGN, SETTING, AND PARTICIPANTS: Prospective, observational case series. Four symptomatic members of a family with BVMD with known BEST1 mutation were recruited at the Advanced Ocular Imaging Program research lab at the Medical College of Wisconsin Eye Institute, Milwaukee. INTERVENTION: Thickness of 2 outer retinal layers corresponding to photoreceptor inner and outer segments was measured using SD-OCT. Photoreceptor mosaic AOSLO images within and around visible lesions were obtained, and cone density was assessed in 2 subjects. MAIN OUTCOME AND MEASURE: Photoreceptor structure. RESULTS: Each subject was at a different stage of BVMD, with photoreceptor disruption evident by AOSLO at all stages. When comparing SD-OCT and AOSLO images from the same location, AOSLO images allowed for direct assessment of photoreceptor structure. A variable degree of retained photoreceptors was seen within all lesions. The photoreceptor mosaic immediately adjacent to visible lesions appeared contiguous and was of normal density. Fine hyperreflective structures were visualized by AOSLO, and their anatomical orientation and size were consistent with Henle fibers. CONCLUSIONS: AND RELEVANCE: The AOSLO findings indicate that substantial photoreceptor structure persists within active lesions, accounting for good visual acuity in these patients. Despite previous reports of diffuse photoreceptor outer segment abnormalities in BVMD, our data reveal normal photoreceptor structure in areas adjacent to clinical lesions. This study demonstrates the utility of AOSLO for understanding the spectrum of cellular changes that occur in inherited degenerations such as BVMD. Photoreceptors are often significantly affected at various stages of inherited degenerations, and these changes may not be readily apparent with current clinical imaging instrumentation.

Adaptive optics retinal imaging--clinical opportunities and challenges.

The array of therapeutic options available to clinicians for treating retinal disease is expanding. With these advances comes the need for better understanding of the etiology of these diseases on a cellular level as well as improved non-invasive tools for identifying the best candidates for given therapies and monitoring the efficacy of those therapies. While spectral domain optical coherence tomography offers a widely available tool for clinicians to assay the living retina, it suffers from poor lateral resolution due to the eye's monochromatic aberrations. Ophthalmic adaptive optics (AO) is a technique to compensate for the eye's aberrations and provide nearly diffraction-limited resolution. The result is the ability to visualize the living retina with cellular resolution. While AO is unquestionably a powerful research tool, many clinicians remain undecided on the clinical potential of AO imaging - putting many at a crossroads with respect to adoption of this technology. This review will briefly summarize the current state of AO retinal imaging, discuss current as well as future clinical applications of AO retinal imaging, and finally provide some discussion of research needs to facilitate more widespread clinical use.

Lower limb direct skeletal attachment. A Yucatan micropig pilot study.

Regardless of the type of prosthetic lower limb, successful ambulation requires proper prosthetic attachment. To help alleviate many of the problems associated with prosthetic attachment, direct skeletal attachment (DSA) has been proposed as an alternative to conventional sockets. The purpose of the current study was to evaluate the feasibility of lower limb DSA in a micropig model and to develop a systematic approach to the development and analysis of DSA systems. The DSA device consisted of two stages. The load-carrying stage embedded in the bone canal was designed using bone remodeling theory in conjunction with finite element analysis to approximate implant-induced remodeling and stabilization out to 36 months postimplantation. The skin-interfacing stage was designed to maintain an immutable infection barrier where the prosthesis exited the body. Following successful design, fabrication, and benchtop evaluation, the device was surgically implanted in a Yucatan micropig. The animal trial was successful out to 10 weeks and revealed potential flaws in the surgical protocol related to thermal necrosis. However, no signs of infection were present at the time of implant retrieval. While results of this pilot study support the feasibility of a DSA approach to prosthetic limb attachment, additional animal trials are necessary to prove long-term viability.

Midfoot arthrodesis following multi-joint stabilization with a novel hybrid plating system.

BACKGROUND: Several methods for fixation have been described for midfoot arthrodesis. Multi-joint arthrodesis at this level can be challenging because of bone loss and deformity, making it difficult to obtain a stable construct. We present the results of a novel hybrid plating system that incorporates locked and non-locked compression screws for multi-joint arthrodesis of the midfoot. METHOD: A retrospective multicenter review of patients undergoing multi-joint arthrodesis with hybrid plating of the midfoot was performed to evaluate the time to radiographic arthrodesis. Hybrid plating was defined as a construct that incorporates locked and non-locked compression screws. Neuropathy was the only exclusion criteria. Radiographic arthrodesis was defined as bridging bone on one of the three standard foot radiographs in the absence of a joint gap on the other views, or by 50% or greater bridging bone on computed tomography. Etiology of the arthritis, presurgical comorbidities, body mass index, functional level and postoperative complications were evaluated. RESULTS: Seventy-two patients were evaluated, and arthrodesis was obtained in 67 patients at 6 weeks in 27 patients, 9 weeks in 26, 12 weeks in 11, and at 16 weeks in three. In five patients at least one of the joints were not fused at 16 weeks and were considered a nonunion. Complications were present in 12 patients (17%). CONCLUSIONS: The healing rate and time to arthrodesis compared favorably to similar published studies. Based on these results, hybrid plating was a reliable and consistent alternative for fixation in midfoot arthrodesis, especially in multi-joint disease.

Perfusion pressures and distal oxygenation in individuals with diabetes undergoing chronic hemodialysis.

BACKGROUND: The number of diabetic patients worldwide was estimated to be approximately 285 million in 2010. Approximately 5% of all diabetic patients have foot ulcers, often preceded by neuropathy and delayed healing resulting from peripheral vascular disease which leads to increased risk of infection. Additionally, there is a concern that blood flow to the feet may be reduced in patients with diabetes, which may be further compounded by changes in lower extremity perfusion pressure during hemodialysis. Current laser Doppler technology provides the opportunity to identify changes in vascularityin a non-invasive fashion. MATERIALS AND METHODS: A prospective, parallel-arm, comparison, pilot study was conducted. A total of 15 patients were enrolled, ten of whom had a documented history of diabetes. All patients required hemodialysis. Peripheral perfusion and oxygenation measurements were obtained before, midway and at the conclusion of three separate dialysis sessions within a 3-week interval for each subject. RESULTS: Preliminary results indicate a significant reduction in toe pressure during and after hemodialysis in the diabetic patient group compared to the non-diabetic group. Significant differences were not found in skin perfusion measurements or in the oxygenation measurements at any time in diabetic and nondiabetic patients undergoing hemodialysis. CONCLUSION: Preliminary results suggest hemodialysis may significantly affect pressure of the lower extremities in diabetic patients. Trends from these data indicate the need to further investigate the effect of hemodialysis on techniques used to heal wounds and ulcers in patients with diabetes.

Simultaneous enhancement of photothermal stability and gene delivery efficacy of gold nanorods using polyelectrolytes.

The propensity of nanoparticles to aggregate in aqueous media hinders their effective use in biomedical applications. Gold nanorods (GNRs) have been investigated as therapeutics, imaging agents, and diagnostics. We report that chemically generated gold nanorods rapidly aggregate in biologically relevant media. Depositing polyelectrolyte multilayers on gold nanorods enhanced the stability of these nanoparticles for at least up to 4 weeks. Dispersions of polyelectrolyte (PE)-gold nanorod assemblies (PE-GNRs) demonstrate a stable Arrhenius-like photothermal response, which was exploited for the hyperthermic ablation of prostate cancer cells in vitro. Subtoxic concentrations of PE-GNR assemblies were also employed for delivering exogenous plasmid DNA to prostate cancer cells. PE-GNRs based on a cationic polyelectrolyte recently synthesized in our laboratory demonstrated higher transfection efficacy and lower cytotoxicity compared to those based on polyethyleneimine, a current standard for polymer-mediated gene delivery. Our results indicate that judicious engineering of biocompatible polyelectrolytes leads to multifunctional gold nanorod-based assemblies that combine high stability and low cytotoxicity with photothermal ablation, gene delivery, and optical imaging capabilities on a single platform.

Non-neuropathic midfoot multiplanar deformity: surgical strategies for reconstruction.

The most common multiplanar deformity of the midfoot is pes planovalgus. Clinically, the flatfoot is characterized by a depressed or absent medial longitudinal arch accompanied by forefoot abduction and, in some cases, by supination of the forefoot and valgus angulation of the hindfoot. This article reviews the reconstructive strategies for correction of deformity and fusion of the painful arthritic joints. A stepwise surgical approach is recommended for reproducible correction and midfoot fusion in patients with arthritis combined with a multiplanar deformity. The article focuses on the principles of reconstruction of the planovalgus deformity in the non-neuropathic patient using compression plates for a stable construct fixation.

Tissue-engineered meniscal constructs.

The medial and lateral menisci play important roles in knee biomechanics, kinematics, and stability. Unfortunately, these structures are prone to damage and, because of a tenuous blood supply, have great difficulty healing. Many interventions have been proposed for treatment of damaged meniscal tissue, but most surgical options are fraught with difficulties, from continued osteoarthritic degeneration to potential for disease transmission. The field of tissue engineering has made wide inroads into constructing meniscal tissue. Investigations involving collagenous tissue, meniscal fibrochondrocytes, chondrocytes, synthetic scaffolds, and gene therapy have all been reported in the literature. Despite these advances, however, more work needs to be done, including incorporating concepts and applications from other engineering disciplines, to potentiate the possibility of a tissue-engineered meniscus that approximates native tissue. In particular, the histologic, morphologic, and biomechanical properties of tissue-engineered meniscal constructs must be better understood to facilitate this goal.

First metatarsophalangeal joint arthrodesis: an evaluation of hardware failure.

BACKGROUND: First metatarsophalangeal joint (MTPJ) arthrodesis is commonly used for the treatment of a variety of conditions affecting the hallux. We used a method incorporating a ball-and-cup preparation of the first metatarsal and proximal phalanx, followed by fixation of the arthrodesis with a lag screw and a dorsal plate (Synthes Modular Hand Set). METHODS: Ninety-five consecutive patients had first MTPJ arthrodesis using fixation with the Synthes Modular Hand Set. All patients were evaluated preoperatively, at regular intervals postoperatively, and at final followup. The American Orthopaedic Foot and Ankle Society (AOFAS) forefoot scoring system was used preoperatively and at final followup. RESULTS: Solid fusion occurred in 93 of 107 feet (86.9%). In the 14 that did not fuse, either the screws or plate, or both, broke. Ten of the 14 feet were symptomatic, but only three required further operative treatment. There were no hardware problems or failures in patients who had solid fusions. Preoperative AOFAS scores were improved after surgery in all patients. CONCLUSIONS: A solid first MTPJ fusion results in excellent function and pain relief, but the Synthes Modular Hand Set implants do not appear to be strong enough in all patients for this application; nonunion at the arthrodesis site and failure of hardware occurred in 13% of arthrodeses. We no longer recommend this implant for this application.

Tibiotalocalcaneal arthrodesis: a biomechanical assessment of stability.

BACKGROUND: Combined ankle and subtalar (tibiotalocalcaneal) arthrodesis is a procedure that can be used to successfully treat disabling foot and ankle arthropathy and is a reasonable salvage alternative to amputation for the treatment of nonbraceable neuropathic, diabetic, degenerative, or rheumatoid joints. Although many methods of tibiotalocalcaneal (TTC) arthrodesis have been described in the literature, the most popular current methods involve the use of crossed cancellous bone screws, plates, or a locked retrograde intramedullary rod. Fusion in these patients can be difficult, with significant complications including infection, malunion, and nonunion. A persistent nonunion can lead to failure of the hardware and recurrent deformity. METHODS: We biomechanically tested the stability and micromotion in four methods of TTC arthrodesis using liquid metal strain gauges and Instron (Norwood, MA) material testing systems. Anatomically identical synthetic bones with properties very similar to human bone were instrumented and tested. Four instrumentation techniques were tested: 1) three crossed 6.5-mm cancellous screws, 2) two crossed 6.5-mm cancellous screws, 3) locked retrograde intramedullary rod, and 4) locked retrograde intramedullary rod augmented with a single anteromedial bone staple. Six separate specimens for each technique were tested. RESULTS: The three crossed cancellous screw technique provided the greatest stability with respect to micromotion (p < 0.05). The addition of a tibiotalar staple to the locked intramedullary rod conferred stability nearly equal to that of the three crossed cancellous screw fixation (p < 0.05). The locked intramedullary rod group and the two crossed cancellous screw group allowed significant micromotion at the arthrodesis sites, which was a full order of magnitude higher (p < 0.05) than in the three crossed cancellous screw group and the staple augmented intramedullary rod group. CONCLUSIONS: Biomechanically, a staple augmented locked intramedullary rod for TTC arthrodesis confers excellent stability nearly equal to the three crossed cancellous screw technique for TTC arthrodesis.

First metatarsal-phalangeal joint arthrodesis: a biomechanical assessment of stability.

BACKGROUND: First metatarsal phalangeal joint (MTP) arthrodesis is a commonly performed procedure for the treatment of hallux rigidus, severe and recurrent bunion deformities, rheumatoid arthritis and other less common disorders of the joint. There are different techniques of fixation of the joint to promote arthrodesis including oblique lag screw fixation, lag screw and dorsal plate fixation, crossed Kirschner wires, dorsal plate fixation alone and various types of external fixation. Ideally the fixation method should be reproducible, lead to a high rate of fusion, and have a low incidence of complications. METHODS: In the present study, we compared the strength of fixation of five commonly utilized techniques of first MTP joint arthrodesis. These were: 1. Surface excision with machined conical reaming and fixation with a 3.5 mm cortical interfragmentary lag screw. 2. Surface excision with machined conical reaming and fixation with crossed 0.062 Kirschner wires. 3. Surface excision with machined conical reaming and fixation with a 3.5 mm cortical lag screw and a four hole dorsal miniplate secured with 3.5 mm cortical screws. 4. Surface excision with machined conical reaming and fixation with a four hole dorsal miniplate secured with 3.5 mm cortical screws and no lag screw. 5. Planar surface excision and fixation with a single oblique 3.5 mm interfragmentary cortical lag screw. Testing was done on an Instron materials testing device loading the first MTP joint in dorsiflexion. Liquid metal strain gauges were placed over the joint and micromotion was detected with varying loads and cycles. RESULTS: The most stable technique was the combination of machined conical reaming and an oblique interfragmentary lag screw and dorsal plate. This was greater than two times stronger than an oblique lag screw alone. Dorsal plate alone and Kirschner wire fixation were the weakest techniques. CONCLUSIONS: First MTP fusion is a commonly performed procedure for the treatment of a variety of disorders of the first MTP joint. The most stable technique for obtaining fusion in this study was the combination of an oblique lag screw and a dorsal plate. This should lead to higher rates of arthrodesis.

Finite element analysis as a tool for parametric prosthetic foot design and evaluation. Technique development in the solid ankle cushioned heel (SACH) foot.

In this study, we developed an approach for prosthetic foot design incorporating motion analysis, mechanical testing and computer analysis. Using computer modeling and finite element analysis, a three-dimensional (3D), numerical foot model of the solid ankle cushioned heel (SACH) foot was constructed and analyzed based upon loading conditions obtained from the gait analysis of an amputee and validated experimentally using mechanical testing. The model was then used to address effects of viscoelastic heel performance numerically. This is just one example of the type of parametric analysis and design enabled by this approach. More importantly, by incorporating the unique gait characteristics of the amputee, these parametric analyses may lead to prosthetic feet more appropriately representing a particular user's needs, comfort and activity level.