Single-compartment knee arthroplasty and idiopathic necrosis of the medialtibia surface

Purpose of the study Idiopathic necrosis of the medial articular surface of the tibia is exceptional. Diagnosis is quite difficult and often made late . Among the different treatments proposed, we prefered single-compartment a rthroplasty. Material and methods We report 8 cases in women with a mean age of 71.1 yea rs. Diagnosis was suspected due to drug-resistant knee pain, particularly f requent at night initially with radiographically normal knees. The first ra diographic signs, seen 3 months after the onset of pain, were pathognomonic for osteonecrosis evidencing subchondral defects of the surface with a den se peripheral rim and apparently "sequestered" in a notch. Bone scintigraph y evidenced intense uptake in the medial compartment. MRI confirmed the dia gnosis evidencing a band of low intensity signals completely surrounding a sequestered zone reaching the cortical. This band was stable and irreversib le, in 5 cases CT scan and in 3 cases tomography identified the width and h eight of the necrotic area that was limited to the medial compartment in al l cases. All patients were treated with a single compartment implant. The d iagnosis of necrosis was confirmed at pathology. Results At 4,6 years of mean follow up all patients had an excellent outcom e, "forgetting" their knee. No lucent lines developed along the femoral or tibial implants. Discussion Necrosis of the medial articular surface of the tibia is excepti onal and often diagnosed late by bone scintigraphy or MRI. Surgical treatme nt is usually based on tibial osteotomy for valgisation or a single or thre e-compartment prosthesis. In our 8 cases, the necrosis was limited to the m edial compartment, warranting our therapeutic option.