The anatomical shape of the proximal femur correlates with the distal femur anatomy.

PURPOSE: In the case of stemmed implants for lower limb joint arthroplasty procedures, implant stability and survivorship generally rely on the strength of fixation in the medullary canal regardless of whether the procedure is primary or revision surgery. This study aimed to investigate the relationship between the proximal (Dorr classification) and distal (Citak classification) femoral canal geometry classification systems.

METHODS: A total of 200 patients who received standing long leg radiographs (hip to ankle) at our institution were identified using our institutional electronic radiology database. Patients were recruited into 4 groups. There were 100 male and 100 female patients with each of those being split into 50 right-sided and 50 left-sided long-leg standing anteroposterior (AP) radiographs. Two independent, blinded observers reviewed each radiograph on two separate occasions, with a minimum of a one-week interval between sittings to review each respective radiograph.

RESULTS: No statistically significant correlation was found between demographic data and clinical measurements. A statistically significant correlation was found between the patient's age and BMI results and Citak and Dorr measurements. There was excellent inter-observer and intra-observer agreement for the Citak and Dorr Classifications. The mean Cronbach's α coefficient was 0.96 (range 0.93-0.98) for the Citak Classification and 0.95 (range 0.83-0.97) for the Dorr Classification. There was also an excellent intra-observer agreement with 95% average pairwise per cent agreement for the Citak Classification and 95% average pairwise per cent agreement for the Dorr classification. A statistically significant positive correlation was found between Dorr Calcar Isthmus and Citak Ratio (p < 0.05).

CONCLUSION: In this study, the Dorr and Citak classifications are put into relation to each other for the first time. The morphology of the femur was investigated in its entirety and it was shown that there was a positive correlation between the anatomical shape of the proximal and distal medullary canals.