Mechanical Axis Method to Determine First Intermetatarsal Angle and Tibial Sesamoid Position.

Utilizing the mechanical axis can decrease load on the joint and be beneficial when analyzing bony deformities and planning surgical correction with osteotomies. The aim of this study was to identify the normal mechanical axes of the first and second metatarsals and use them to obtain the first/second mechanical intermetatarsal angle (mIMA). The mechanical axis of the first metatarsal was used to obtain the mechanical tibial sesamoid position (mTSP), which provides a mechanical relationship with the sesamoid apparatus. The angular difference between the anatomic and mechanical axis lines (anatomic-mechanical angle [AMA]) was determined for the first metatarsal and for the second metatarsal. The commonly used first/second anatomic intermetatarsal angle (aIMA) and anatomic tibial sesamoid position (aTSP) were also obtained and compared with the first/second mIMA and mTSP. In this retrospective analysis, radiographs of 50 normal feet (40 patients) were assessed. Pearson's correlation coefficients were used to measure reliability between obtained measurements. Mean first/second aIMA was 8.6 ± 3.0 degrees, and first/second mIMA was 8.6 ± 2.6 degrees. First metatarsal AMA was 1.1 ± 1.0 degrees; second metatarsal AMA was 2.0 ± 1.6 degrees. The mTSP was 2.8 ± 1.1, and aTSP was 2.9 ± 1.0. The TSP median was 3 (range, 1-5). Using the mechanical axis method to obtain the first/second mIMA and the mTSP is reproducible and not affected by anatomic changes to the shape of the metatarsal. Unlike the anatomical axis, the mechanical axis does not change, therefore we recommend using the mechanical axis during surgical planning and when obtaining preoperative and postoperative measurements for the long bones of the foot, particularly for forefoot conditions such as hallux valgus.

The Use of Hexapod External Fixation in the Management of Charcot Foot and Ankle Deformities.

Charcot neuroarthropathy (CN) and its sequela is a disabling pathology in the foot and ankle. The 2-stage computer hexapod-assisted technique is an effective tool to address midfoot Charcot and ankle-hindfoot deformities to restore function and decrease the risk of amputation secondary to ulceration and infection. Although this is not the only technique available, it is an excellent option in cases with significant angular deformity or subluxation, need to reduce shortening of the foot, and in the presence of soft tissue defects, with or without concurrent soft tissue or bone infection.

Lengthen, Alignment, and Beam Technique for Midfoot Charcot Neuroarthropathy.

Charcot neuroarthropathy is a disabling pathology in the foot and ankle. Midfoot Charcot is most common and results in progressive deformity. We describe a 2-step approach to surgical reconstruction, referred to as the lengthen, alignment, and beam technique. There is an initial surgery involving acute equinus correction through Achilles tendon lengthening and gradual correction with hexapod external fixation to align the deformity, followed by minimally invasive medial and lateral column beaming. This surgical protocol allows for adequate reduction of deformity. The second stage allows for rigid intramedullary fixation extending beyond the pathologic joints via a minimally invasive technique.