Biomedical subjects

David B Kay

Publications and source records attributed to David B Kay.

4 recordsLinked to original sources

PubMed2005

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.

Ankle Joint↗

PubMed2005

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.

Arthrodesis↗

PubMed2003

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.

Amputation, Surgical↗

PubMed2003

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.

Analysis of Variance↗