Femoral Neck Fracture Nonunion

The femoral neck is prone to nonunion for biological and mechanical reasons. Biologically it is intracapsular, with a precarious retrograde retinacular blood supply from the medial femoral circumflex artery that the fracture can disrupt, it is bathed in synovial fluid, and there is essentially no periosteal callus, so healing depends on direct union which is unforgiving of instability. Mechanically, a vertical fracture - a high Pauwels angle, Pauwels III - is loaded in shear, which displaces rather than compresses the fragments, and his fracture was both displaced and vertical, the highest-risk combination, especially if the reduction was imperfect. To decide treatment, the two key questions are the patient's age and the viability of the femoral head. He is young, so the goal is to preserve his native head if it is viable - I would assess head viability with radiographs and an MRI to look for avascular necrosis. If the head is viable, I would perform a head-preserving valgus intertrochanteric osteotomy, which reorients the fracture so the vertical shear line becomes more horizontal and is loaded in compression - the Pauwels principle - fixed with a blade plate and often supplemented with bone graft; this unites the large majority. If, however, the head is non-viable from avascular necrosis or has collapsed, then despite his age arthroplasty - a total hip replacement - is the appropriate choice.

I would choose arthroplasty, usually a total hip replacement, when head preservation is not appropriate: in elderly or lower-demand patients, for whom a single reliable operation with immediate weight-bearing is preferable; when the femoral head is non-viable from avascular necrosis or has collapsed, because a dead or collapsing head cannot be salvaged by an osteotomy; when there is established post-traumatic arthritis; and after a failed osteotomy. The limitations of the valgus intertrochanteric osteotomy are, first, that it depends on a viable head, so it is the wrong operation if there is significant AVN; second, that avascular necrosis remains a recognised complication that can develop or progress afterwards and necessitate later arthroplasty; third, that it can have mechanical failure, particularly in osteopenic bone; and fourth, that it alters proximal femoral anatomy and leg length, although modern variants such as the SALVA osteotomy actually restore the abductor lever arm and correct leg-length discrepancy and are designed so that a later conversion to arthroplasty remains technically straightforward. So the osteotomy is the head-preserving operation of choice in the young viable hip, while arthroplasty is the definitive solution for the elderly or the non-viable head.