SPECT/CT and triple-phase bone scan: A valuable diagnostic approach for identifying indications for secondary patellar resurfacing in patients with unexplained anterior knee pain post-TKA

Objective The efficacy of secondary patellar resurfacing (SPR) in alleviating anterior knee pain (AKP) following total knee arthroplasty (TKA) remains uncertain. The purpose of this study was to assess the suitability of SPR using single photon emission computed tomography/computed tomography (SPECT/CT) in conjunction with triple-phase bone scan (TPBS). Methods We performed a retrospective analysis on a prospectively-enrolled cohort of patients suffering from AKP in the context of TKA. In this cohort, we identified a subset of 17 patients (involving 18 knees), who had unexplained AKP and were potential candidates for secondary patellar resurfacing (SPR). The candidates for SPR were designated the experimental group, and subjects receiving other forms of treatment were referred to as the Control group. The selection for these treatment options was based on the findings from SPECT/CT and triple-phase bone scan (TPBS). Data collection spanned from preoperative to postoperative follow-up periods and encompassed basic demographics, preoperative findings of SPECT/CT plus TPBS, and Knee Society Score (KSS). Results SPECT/CT and TPBS revealed focal radionuclide concentration in the patella in 12 patients (13 knees) and in other locations in 5 patients (5 knees) with unexplained AKP, complementing the findings from medical history and physical examinations. The Experimental group showed signs of patellar maltracking or early-stage patellofemoral osteoarthritis (OA) following TKA and received SPR treatment. Postoperatively, the objective knee indicators score was significantly higher than preoperative scores (88.46 +/- 5.77 vs. 76.38 +/- 7.64, P < 0.05). Similarly, the functional activities score was significantly improved postoperatively (74.31 +/- 6.68 vs. 50.46 +/- 9.01, P < 0.05). Patient satisfaction score was substantially elevated after SPR (33.38 +/- 2.87 vs. 17.08 +/- 5.69, P < 0.05). The control group mainly included patients who experienced loosening, periprosthetic joint infection (PJI), or instability. These patients received revision surgeries tailored to their individual pathologies and postoperative follow-ups showed favorable outcomes. Conclusions SPECT/CT in combination with TPBS may serve as a valuable tool for assessing the suitability of SPR for the post-TKA management of unexplained AKP.