Introduction: We present a case report of a total hip arthroplasty (THA) in a patient with ipsilateral knee arthrodesis. The direct anterior approach (DAA) was used, and to our knowledge, this has never been described previously in the literature. The purpose of this report is to highlight pre-, per-, and post-operative challenges using the DAA in these rare cases. Case Report: This case report presents the case of a 77 year old female patient with degenerative hip disease in the presence of an ipsilateral arthrodesis of the knee. The patient was operated using the DAA. No complications were found and the patient had an excellent follow-up with a forgotten joint score of 93.75 at 1 year. The difficulty in this case consists in finding the correct stem anteversion with the altered knee anatomy. Using pre-operative templating on X-rays, intraoperative fluoroscopy and the posterior femoral neck the hip biomechanics could be restored. Conclusion: We believe that THA in presence of an ipsilateral knee arthrodesis can be safely performed through a DAA. Keywords: THA, DAA, knee arthrodesis.

We present the case of a 56-year-old male unable to sit because of an ankylosed right hip. This ankylosis originated from combined neurogenic heterotopic ossifications (NHO) and traumatic heterotopic ossifications (THO) as a result of a road traffic accident. Because of multiple ossifications, the proximity of neurovascular structures, and chronic pressure ulcers, a resection was deemed unsafe. We opted for a new articulation distal to the ossifications in unstained tissue. A partial femoral diaphysectomy was performed just distal of the lesser trochanter. and the vastus lateralis was rotated in the new articulation. Postoperatively, the patient was able to sit as his hip could flex again.A partial femoral diaphysectomy with vastus lateralis interposition flap appears to be a valid option in paraplegic patients with extensive heterotopic ossifications (HO) in close proximity to neurovascular structures with a low risk of complications and high gain in hip mobility.