Assessment of loading history of compartments in the knee using bone SPECT/CT: A study combining alignment and 99mTc‐HDP tracer uptake/distribution patterns

Abstract

This study investigates if the mechanical/anatomical alignment influences the intensity values as well as the distribution pattern of SPECT/CT tracer uptake. Eighty-five knees (mean age 48 AE 16) undergoing 99mTc-HDP-SPECT/CT due to pain were prospectively included. SPECT/CTs were analyzed using a previously validated localization method. The maximum intensities in each femoral, tibial, and patellar joint compartment (medial, lateral, central, superior, and inferior) were noted using a color-coded grading scale (0-10). The Kellgren-Lawrence osteoarthritis score (KL) was assessed on standardized radiographs. Long leg radiographs were used to assess the mechanical/anatomical leg alignment, which was classified as varus, valgus, or neutral. The alignment and KL was correlated with the intensity of tracer uptake in each area of interest (p < 0.05). The intensity of SPECT/CT tracer uptake in the medial and lateral knee compartment significantly correlated with varus or valgus alignment of the knee. A higher degree of osteoarthritis was significantly related to higher tracer uptake in the corresponding joint compartments. SPECT/CT reflects the specific loading pattern of the knee with regard to its alignment. It is also related to the degree of osteoarthritis. Hence, SPECT/CT should be considered for follow-up of patients after realignment treatments, osteotomies, deloader devices, or insoles. ß

SPECT/CT tracer uptake is influenced by tunnel orientation and position of the femoral and tibial ACL graft insertion site

“…In addition, the time from surgery might have a significant impact on tracer uptake. In a previous study we have shown that a non-ideal mechanical axis such as varus or valgus aligned knee leads to increased SPECT tracer uptake in the stressed compartment [16]. However, the altered tracer uptake in patients with leg deformity is caused by mechanical stress, which is not the case in these patients after ACL reconstruction.…”

“…This standardised algorithm including grading and anatomical localization of SPECT/CT tracer uptake promises the identification of specific pathological tracer uptake patterns and distributions [9]. It now allows the correlation of surgical factors such as tunnel position and orientation with mechanical alignment, clinical outcome and biological factors [9,16]. It also promises the critical assessment of the osseointegration of the bonegraft-fixation complex.…”

“…The intensity and distribution of 99mTc-HDP-SPECT/ CT tracer, which as diphosphonate is targeted towards osteoblastic activity, is influenced by mechanical or anatomical alignment, vascular supply, infection, osteoblastic activity or currently unknown other factors [9,13,14,[16][17][18][19]. In patients after ACL reconstruction it could be hypothesized if the position and orientation of the bone tunnels and the stability and/or laxity of the knee joint are decisive factors.…”

Skeletal SPECT/CT: a review

“…Figure 3 presents a pertinent example. In a series of carefully conducted studies, Hirschmann et al and Rasch et al [63,64] established that intensity of tracer uptake as visualized by SPECT/CT reflects the specific loading patterns of the knee with regard to its alignment and that abnormal increases in tracer uptake are reversible on tibial osteotomy correcting for varus misalignment [65,66]. Furthermore, they proposed a standardized, semiautomatic approach for the evaluation of tracer uptake in the knee in relation to component position following arthroplasty [67].…”

In vivo bone tunnel remodeling in symptomatic patients after ACL reconstruction: a retrospective comparison of articular and extra-articular fixation

“…Hirschmann et al 23 reported that SPECT/CT reflects the loading pattern of the knee joint with regards to the mechanical and anatomical alignment. It is also related to the degree of osteoarthritis of the knee.…”