Gordon L. Bennett

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: Surface excision with machined conical reaming and fixation with a 3.5 mm cortical interfragmentary lag screw. Surface excision with machined conical reaming and fixation with crossed 0.062 Kirschner wires. 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. 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. 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.

First Metatarsalphalangeal Joint Arthrodesis: Evaluation of Plate and Screw Fixation

Background: First metatarsalphalangeal joint (MTPJ) arthrodesis is a commonly performed procedure for the treatment of a variety of conditions affecting the hallux. There are several different methods to accomplish the fusion. We utilized a method incorporating a ball and cup preparation of the joint, followed by stabilization of the arthrodesis site utilizing the Accutrak congruent first MTPJ fusion set. Materials and Methods: We prospectively evaluated two hundred consecutive patients who underwent first MTPJ arthrodeses utilizing the Accutrak congruent first MTPJ fusion set. Patients were evaluated preoperatively, postoperatively, and at a final followup, utilizing the AOFAS forefoot scoring system. Results: Two hundred consecutive patients underwent first MTPJ arthrodeses by the same surgeon. All but three feet (230/233) (98.7%) went on to solidly fuse. Three of the patients did not fuse solidly. One patient broke two of the screws, and the other two patients did not have hardware failure. All patients dramatically improved their AOFAS scores compared with pre-surgical values. There were three minor hardware problems in the group of patients who solidly fused their joint. Conclusion: We concluded that a solid first MTPJ fusion results in excellent function and pain relief. The Accutrak first MTPJ fusion system would appear to be an ideal implant system to accomplish a fusion because of its low profile, strength, and ease of use. Compared to other methods we have used, this procedure results in a very high rate of fusion, with minimal complications and excellent patient satisfaction.

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.

The Use of Magnetic Resonance Imaging in the Diagnosis of Stress Fractures of the Foot and Ankle: Four Case Reports:

Stress fractures result when bone is subjected to repeated loading which causes fatigue, cracking of the bone, and, eventually, a complete fracture. Stress fractures of the foot and ankle are common injuries affecting a broad range of the population, from the young to the elderly, the fitness enthusiast to the chronically debilitated. The diagnosis of stress fracture is not always obvious because radiographs are often negative, especially on initial presentation. In this report, we present four cases in which, after appropriate initial studies proved inconclusive, magnetic resonance imaging (MRI) was used to establish the diagnosis of stress fracture. We propose that MRI is a useful diagnostic modality in a select group of patients with suspected stress fractures of the foot and ankle.

Morton's neuroma

Mortons neuroma is a common problem. Progress has been made in the understanding of this frequent problem since Mortons original description and treatment. Today, we accept a failure rate of 15% to 20%, even in the best of series. We must ask ourselves if this is good enough. What can we do to achieve an acceptable failure of 5% or less? How can we improve? Only through an honest analysis and discussion can we improve the care that we deliver.

Triple Arthrodesis: A Biomechanical Evaluation of Screw Versus Staple Fixation:

The subtalar, talonavicular, and calcaneocuboid joints were internally fixed to simulate triple arthrodesis was performed on eight matched pairs of human cadaver feet. Feet were randomly assigned such that one specimen in each pair was internally fixed with cobalt-chrome staples and one specimen with stainless steel screws. Liquid metal strain gauges were placed in a perpendicular fashion across the three joints of each specimen. Each foot was then secured to the Shore Western Materials Test System where a series of 10 increasing eversion stresses across the foot was created. Displacement was measured at each joint with every increase in eversion stress. Our results show that there is no statistical difference in fixation strength between screws and staples at the talonavicular, calcaneocuboid, or subtalar joints (P = 0.862). Although many studies determining the strength to failure of different implants have been performed, shear stress and micromotion at the joint surfaces have not been evaluated, to our knowledge, and no single implant in this study has shown superior immobilization characteristics to recommend its use as the implant of choice in triple 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 users needs, comfort and activity level.

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. Level of Evidence: IV; Retrospective Case Series

Evaluation of an Innovative Fixation System for Chevron Bunionectomy

Background: Distal chevron metatarsal osteotomy bunionectomy is a commonly performed procedure for the treatment of mild to moderate hallux valgus deformity. There are several different methods to stabilize this osteotomy. We evaluated a new intramedullary plate system. Methods: We prospectively evaluated 57 consecutive patients who underwent distal chevron metatarsal osteotomy bunionectomy utilizing the intramedullary plate system. All operative procedures were performed by the senior author. Patients were evaluated preoperatively, postoperatively, and at a final follow-up utilizing the American Orthopaedic Foot & Ankle Society (AOFAS) forefoot scoring system. Results: Sixty-three surgically corrected feet went on to heal the osteotomy site. There were no hardware failures. We had one patient that expressed mild discomfort over the plate. All patients significantly improved their AOFAS scores compared with preoperative values. Conclusion: We concluded that the distal chevron metatarsal osteotomy bunionectomy resulted in excellent function and pain relief. The new plate system was a reliable and stable implant with a low profile, good strength, and ease of use. Level of Evidence: Level IV, retrospective case series.