• F Iacono, G F Raspugli, D Bruni, G Filardo, S Zaffagnini, W F Luetzow, M Lo Presti, I Akkawi, G M Marcheggiani Muccioli, and M Marcacci.
• 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy, f.iacono@biomec.ior.it.
• Knee Surg Sports Traumatol Arthrosc. 2014 Dec 1;22(12):3034-8.

PurposeThe restoration of the normal joint line (JL) is important both in primary and revision total knee arthroplasty (TKA). However, the assessment of the femoro-tibial JL is still controversial. A strong correlation between femoral width (FW) and distance from adductor tubercle (AT) to JL was found on radiographs, with a ratio of 0.54. The hypothesis was that this ratio was applicable also in the surgical theatre by using measurements obtained intra-operatively with a caliper.MethodsFemoral width, AT to JL distance and the RATIO between AT to JL distance and FW of 40 patients who underwent TKA were measured on radiograph and intra-operatively. Bland-Altman agreement tests with repeated measurements and linear regression analysis were used. The ratio was used to estimate the distance between JL and AT.ResultsThe AT to JL distance/FW ratio calculated with linear regression resulted 0.54 for radiographic measurements and 0.53 for intra-operative measurements. There was no difference (0.009 ± 0.03) between the calculated ratios on radiographic and intra-operative measurements, and the correlation between intra-operative and radiographic measurements was 0.5 (p = 0.0016).ConclusionsThis study shows that the validity of the radiographic method which uses an AT to JL distance/FW ratio to determine the level of the JL is confirmed also when using intra-operatively acquired measurements. Thus, this ratio represents a reliable tool to determine the JL level even in challenging prosthetic revision cases when the anatomical JL is missing.Level Of EvidenceCase series, Level IV.

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