Aims. Surgical treatment of young femoral neck fractures often requires an open approach to achieve an anatomical reduction. The application of a calcar plate has recently been described to aid in femoral neck fracture reduction and to augment fixation. However, application of a plate may potentially compromise the regional vascularity of the femoral head and neck. The purpose of this study was to investigate the effect of calcar femoral neck plating on the vascularity of the femoral head and neck. Methods. A Hueter approach and capsulotomy were performed bilaterally in six cadaveric hips. In the experimental group, a one-third tubular plate was secured to the inferomedial femoral neck at 6:00 on the clockface. The contralateral hip served as a control with surgical approach and capsulotomy without fixation. Pre- and post-contrast MRI was then performed to quantify signal intensity in the femoral head and neck. Qualitative assessment of the terminal arterial branches to the femoral head, specifically the inferior retinacular artery (IRA), was also performed. Results. Quantitative MRI revealed a mean reduction of 1.8% (SD 3.1%) of arterial contribution in the femoral head and a mean reduction of 7.1% (SD 10.6%) in the femoral neck in the plating group compared to non-plated controls. Based on femoral head quadrant analysis, the largest mean decrease in arterial contribution was in the inferomedial quadrant (4.0%, SD 6.6%). No significant differences were found between control and experimental hips for any femoral neck or femoral head regions. The inferior retinaculum of Weitbrecht (containing the IRA) was directly visualized in six of 12 specimens. Qualitative MRI assessment confirmed IRA integrity in all specimens. Conclusion. Calcar femoral neck plating at the 6:00 position on the clockface resulted in minimal decrease in femoral head and neck vascularity, and therefore it may be considered as an adjunct to laterally-based fixation for reduction and fixation of femoral neck fractures, especially in younger patients. Cite this article: Bone Jt Open 2021;2(8):611–617

Introduction:. A surgical hip dislocation provides circumferential access to the femoral head and is essential in the treatment pediatric and adult hip disease. Iatrogenic injury to the femoral head blood supply during a surgical may result in the osteonecrosis of the femoral head. In order to reduce vessel injury and incidence of AVN, the Greater Trochanteric Osteotomy (GTO) was developed and popularized by Ganz. The downside of this approach is the increased morbidity associated with the GTO including non-union in 8% and painful hardware requiring removal in 20% of patients. (reference) Recent studies performed at our institution have mapped the extra-osseous course of the medial femoral circumflex artery and provide surgical guidelines for a vessel preserving posterolateral approach. In this cadaveric model using Gadolinium enhanced MRI, we investigate whether standardized alterations in the postero-lateral surgical approach may reliably preserve femoral head vascularity during a posterior surgical hip dislocation. Methods:. In 8 cadaveric specimens the senior author (ES) performed a surgical hip dislocation through the posterolateral approach with surgical modifications designed to protect the superior and inferior retinacular arteries. In every specimen the same surgical alterations were made using a ruler: the Quadratus Femoris myotomy occurred 2.5 cm off its trochanteric insertion, the piriformis tenotomy occurred at its insertion and extended obliquely leaving a 2 cm cuff of conjoin tendon (inferior gemellus), and the Obturator Externus (OE) was myotomized 2 cm off its trochanteric insertion. (Figure 1) For the capsulotomy, the incision started on the posterior femoral neck directly beneath the cut obturator externus tendon and extending posteriorly to the acetabulum. Superior and inferior extensions of the capsulotomy ran parallel to the acetabular rim creating a T-shaped capsulotomy. After the surgical dislocation was complete, the medial femoral circumflex artery (MFCA) was cannulated and Gadolinium-enhanced MRI performed in order to assess intra-osseous femoral head perfusion and compared to the gadolinium femoral head perfusion of the contra-lateral hip as a non-operative control. Gross-dissection after polyurethane latex injection in the cannulated MFCA was performed to validate MRI findings and to assess for vessel integrity after the surgical dislocation. Results:. In 8 cadaveric specimens MRI quantification of femoral head perfusion was 94.3% and femoral head-neck junction perfusion was 93.5% compared to the non-operative control. (Figure 2) Gross dissection after latex injection into the MFCA demonstrated intact superior and inferior retinacular arteries in all 8 specimens. (Figure 3). Discussion and Conclusions:. In this study, perfusion to the femoral head and head-neck junction is preserved following posterior surgical dislocation through the postero-lateral approach. These preliminary findings suggest that specific surgical modifications can protect and reliably maintain vascularity to the femoral head after surgical hip dislocation. This approach may benefit hip resurfacing and potentially decease risk of femoral neck fracture secondary to osteonecrosis. In addition this may allow a vascular preserving surgical hip dislocation to be performed without the need for a GTO