Rethinking the Coronal Anatomic Axis of the Distal Tibia for Intramedullary Nail Placement: A Cadaveric Study

Background: Recent studies have reported that targeting a center-center position at the distal tibia during intramedullary nailing (IMN) may result in malalignment. Although not fully understood, this observation suggests that the coronal anatomic center of the tibia may not correspond to the center of the distal tibia articular surface. Questions/Purposes: To identify the coronal anatomic axis of the distal tibia that corresponds to an ideal start site for IMN placement utilizing intact cadaveric tibiae. Methods: IMN placement was performed in 9 fresh frozen cadaveric tibiae. A guidewire was used to identify the ideal start site in the proximal tibia and an opening reamer allowed access to the canal. Each nail was then advanced without the use of a reaming rod until exiting the distal tibia plafond. Cadaveric and radiographic measurements were performed to determine the center of the nail exit site in the coronal plane. Results: Cadaveric and radiographic measurements identified the IMN exit site to correspond with the lateral 59.5% and 60.4% of the plafond, respectively. Conclusions: Tibial nails inserted using an ideal start site have an endpoint that corresponds roughly to the junction of the lateral and middle third of the plafond. Further studies are warranted to better understand the impact of IMN endpoint placement on the functional and radiographic outcomes of tibia shaft fractures.

Kirschner Wire as a Reference Marker for the Positioning of a Syndesmotic Screw: a Radiological Study and Clinical Application

Background: Without a reliable and static reference, the rate of eccentrically positioned distal syndesmotic screw is very high. This article describes an additional method to improve surgeons’ ability to ideally place this screw. The purposes of our study were (1) to determine if an ideal space at 2.5 cm proximal to the plafond existed between the tibia and fibula for the placement of a Kirschner (K) wire and (2) to detect if it could act as a reliable and static fibular incisura plane reference. Methods: Computed tomography (CT) scans of 42 uninjured adult ankles with foot fractures were analysed to measure the tibiofibular vertical distance (TFVD) at 2.5 cm proximal to the plafond on transverse images. TFVD was defined as the distance between two lines: Line 1 was tangent to the fibular incisura, and Line 2 was parallel to Line 1 along the medial fibula. Patients were divided into four groups according to our TFVD data: 0–1, 1–2, 2–3, and 3–4 mm, and the number of patients in each group was counted. We assessed 23 patients who underwent syndesmotic screw fixation for ankle fractures. Comparison of the angle between the anatomic axis of the syndesmosis and screw axis (AAS) was performed between patients using conventional method (11 patients) and with K-wire marker (12 patients). Results: TFVD measured 2.23 ± 1.01 mm at 2.5 cm proximal to the plafond. TFVD occurred at 25% of the distance from 2 to 3 mm in 47.6% of patients. This new technique decreased the deformation of AAS by 75%, from 13.06 ± 2.55° to 4.28 ± 1.72°, in the conventional group.Conclusions: Placing a 1.6-mm K-wire in the syndesmosis at 2.5 cm proximal to the tibial plafond is easy because of emerging TFVDs. Compared to the conventional method, this new technique increased the accuracy of syndesmotic screw placement by up to 75 percent. Therefore, K-wire could be used as a reliable and static intraoperative reference of the fibular incisura plane through which surgeons can accurately place a screw trajectory.

Distal Chevron Osteotomy Increases Anatomic Intermetatarsal Angle in Hallux Valgus

Background: Distal chevron metatarsal osteotomy (DCO) is a common technique to address hallux valgus (HV), which involves coronal translation of the capital fragment resulting in a nonanatomic first metatarsal. The purpose of this study was to evaluate the radiographic effect of the DCO on the anatomic vs the mechanical axis of the first metatarsal. Our hypothesis was that patients undergoing DCO would have improvement in the mechanical metatarsal axis but worsening of the anatomic axis. Methods: This was a retrospective case series of consecutive patients who underwent DCO for HV. The primary outcomes were the change in anatomic first–second intermetatarsal angle (a1-2IMA) vs mechanical first–second intermetatarsal angle (m1-2IMA). Secondary outcomes included the change in hallux valgus angle (HVA) and medial sesamoid position. Results: 40 feet were analyzed with a mean follow-up of 21.2 weeks. The a1-2IMA increased significantly (mean, 4.1 degrees) whereas the m1-2IMA decreased significantly (mean, 4.6 degrees) following DCO. There was a significant improvement in HVA (mean, 12.5 degrees). Medial sesamoid position was improved in 21 feet (52.5%). Patients with no improvement in sesamoid position were found to have a larger increase in a1-2IMA (mean, 4.7 vs 3.5 degrees, P = .03) and less improvement in m1-2IMA (mean, 3.8 vs 5.2 degrees, P = .02) compared to patients with improvement in sesamoid position. Conclusion: Distal chevron osteotomy for HV was associated with worsening of the anatomic axis of the first metatarsal despite improvements in the mechanical metatarsal axis, HVA, and medial sesamoid position. Greater worsening of the anatomic axis was associated with less improvement of sesamoid position. Our findings may suggest the presence of intermetatarsal instability, which could limit the power of DCO in HV correction for more severe deformities and provide a mechanism for HV recurrence. Level of Evidence: Level IV, retrospective case series.

Femoral Intramedullary Alignment in Total Knee Arthroplasty: Indications, Results, Pitfalls, Alternatives, and Controversies

While femoral intramedullary alignment has been found to be the most accurate and reproducible method for proper femoral component orientation in total knee arthroplasty, certain situations preclude the use of intramedullary alignment, such as ipsilateral long-stem total hip arthroplasty, femoral shaft deformity (congenital or post-traumatic), capacious femoral canal, and retained hardware. These cases require alternative alignment guides, that is, extramedullary alignment. The purpose of this study was to determine the accuracy of intramedullary alignment in reproducing the femoral anatomic axis. Using 35 adult cadaveric femora without obvious clinical deformity, and 7 with proximal prosthetic devices blocking the passage of an intramedullary guide, the accuracy of the guide rod was assessed both anatomically and radiographically. In the seven femora with proximal femoral devices, the guide rod could not be completely seated, resulting in a greater degree of flexion of the guide rod compared with the mechanical axis of the femur, and a greater degree of varus compared with the anatomical axis, as compared with 35 femora without obvious deformity. In cases where seating of the intramedullary guide rod is either incomplete or impossible, extramedullary femoral guides allow more accurate determination of the distal femoral cut by referencing directly from the mechanical axis, that is, the center of the femoral head. We present case studies as examples of indications for use of an extramedullary femoral guide. In addition, we demonstrate two different techniques for extramedullary femoral alignment using fluoroscopic guidance in cases incompatible with intramedullary alignment.