Introduction and aims: The aim of this study was to determine the relationship between pre-operative Single Photon Emission Tomography (SPECT) scan findings and intra-operative assessments of patello-femoral and tibio-femoral OA, in patients undergoing tibio-femoral uni-compartmental knee arthroplasty (UKA).

Method: Over a six-month period 36 knees in 30 patients, undergoing UKA, were investigated pre-operatively with a SPECT scan to confirm single compartment disease. The male to female ratio of patients was 18:12, with an average age of 63 years (range 44–78). A single radiologist reported all cases, and graded uptake in each compartment. At surgery, the degree of OA encountered in each compartment was assessed by size and grade by the two senior authors, and assigned an OA score. The data was analysed statistically for an association between the SPECT scan score and OA score, using Kendall’s Tau-b.

Results: A statistically significant relationship was demonstrated between positive uptake in a compartment and the presence of OA (p < 0.05), and this was consistent for all compartments. When analysed specifically, the associations were strongest in the medial femoral condyle (0.58) and the medial tibial plateau (0.67), and weakest in the patella (0.35) and trochlea (0.46), and lateral tibial plateau (0.34).

Conclusion: We conclude that SPECT scans can provide useful information regarding the degree of OA in knee compartments when planning UKA, particularly with medial compartment disease. The lower degree of association between scan findings and OA encountered in the patello-femoral compartment, and lateral tibial plateau, indicates greater vigilance should be applied when making intra-operative assessments of these areas.