Today, SPECT/CT is increasingly used and available in the majority of larger nuclear medicine departments. Several applications of SPECT/CT as a supplement to or replacement for traditional conventional bone scintigraphy have been established in recent years. SPECT/CT of the upper and lower extremities is valuable in many conditions with abnormal bone turnover due to trauma, inflammation, infection, degeneration or tumour. SPECT/CT is often used in patients if conventional radiographs are insufficient, if MR image quality is impaired due to metal implants or in patients with contraindications to MR. In complex joints such as those in the foot and wrist, SPECT/CT provides exact anatomical correlation of pathological uptake. In many cases SPECT increases the sensitivity and CT the specificity of the study, increasing confidence in the final diagnosis compared to planar images alone. The CT protocol should be adapted to the clinical question and may vary from very low-dose (e.g. attenuation correction only), to low-dose for anatomical correlation, to normal-dose protocols enabling precise anatomical resolution. The aim of this review is to give an overview of SPECT/CT imaging of the extremities with a focus on the hand and wrist, knee and foot, and for evaluation of patients after joint arthroplasty.

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Clinical applications of SPECT/CT in imaging the extremities.

The optimal coronal alignment is still under debate. However, in most of the studies, alignment was only assessed using radiographs, which are not accurate enough for assessment of tibial and femoral TKA position. The primary purpose of this study was to assess the relationship between coronal TKA alignment using 3D-reconstructed CTs and clinical outcome in patients with preoperative varus in comparison with patients with natural or valgus deformity. It was the hypothesis that neutral limb alignment shows a better outcome after TKA. Prospectively collected data of 38 patients were included. The clinical and radiological follow-up was 24 months. The patients were grouped into two groups with regard to their preoperative limb alignment. Group A (varus) consisted of 21 patients with preoperative varus of 3° or more, while group B (non-varus) consisted of 17 patients with neutral (− 3   + 3) or valgus alignment (> + 3). For assessment of TKA component position and orientation, 3D-reconstructed CT was used. The measurements of the deviation from the whole limb mechanical axis (HKA angle) and the joint line alignment in the femoral (mLDFA) and the tibial side (MPTA) were assessed in the preoperative leg as well as during follow-up after TKA. For clinical outcome assessment, the Knee Society Score (KSS) was used at 1 and 2 years postoperatively. Correlation between KSS score and each variable was done using a linear and quadratic regression model (p < 0.05). The mean postoperative HKA angle was − 1.3 (varus) in the varus group and + 1.4 (valgus) in the non-varus group. Overall, significant correlations between the preoperative and postoperative alignments were found. In the preoperatively non-varus group, a highly significant correlation was found between neutral limb alignment (HKA = 0° ± 3°) and higher KSS (r
 2 = 0.74, p = 0.00). In the varus group, no correlation was found between the postoperative whole limb alignment and the components’ position in the coronal plane to KSS score. A significant correlation was found between neutral limb alignment and higher KSS only in patients with preoperative non-varus alignment. The concept of constitutional varus alignment is still under debate. Moreover, it appears that one should aim for a more individualized, alignment target based on the individual knee morphotype. Diagnostic study, Level II.

Neutral alignment leads to higher knee society scores after total knee arthroplasty in preoperatively non-varus patients: a prospective clinical study using 3D-CT

Purpose
Bone single photon emission computed tomography (SPECT)/CT is considered as beneficial in unhappy patients with pain, stiffness or swelling after total knee arthroplasty (TKA). The purpose of this study was to identify typical patterns of bone tracer uptake (BTU), distribution and intensity values in patients after TKA. The above findings were correlated with the type and fixation of TKA, the time from TKA and intraoperative findings at revision surgery.

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Clinical value of SPECT/CT in the painful total knee arthroplasty (TKA): a prospective study in a consecutive series of 100 TKA.

The aim of this study was to evaluate femoral and tibial as well as whole leg coronal TKA alignment using 3D-reconstructed CTs and to assess the relationship of coronal TKA alignment and clinical outcome in a large prospective series of patients. It was hypothesized that a coronal deviation of TKA position and leg alignment from the mechanical axis is correlated with poorer patients’ outcome after TKA. A total of 81 consecutive patients who underwent primary TKA were prospectively included. The patient’s demographics such as age, gender and time from primary TKA were noted. All patients underwent clinical and radiological examination including standardized radiographs (anteroposterior and lateral weight-bearing, patellar skyline view) and CT as part of their postoperative follow-up. For assessment of TKA component position and orientation 3D-reconstructed CT was used. For clinical outcome scoring the Knee Society Score (KSS) was used at 1 and 2 years postoperatively. Linear and quadratic regression models were used to test for correlations between alignment variables and KSS (p < .05). The mean Knee Society Score was 181 ± 28 (range 52–200) 2 years postoperatively, while 78% of the patients were completely pain free and 22% had some persisting pain interfering with their daily activities. The mean mechanical whole limb alignment (HKA angle), femoral component alignment and tibial component alignment were 0°, 0.1° and −0.7°, respectively. The component position parameters, as well as the whole limb alignment measurements, did not show any statistically significant correlation with the KSS, after 1 and 2 years postoperatively. In this prospective study, using 3D-CT to measure the component position, the postoperative outcome was not influenced by coronal TKA component position as well as the whole leg alignment. The findings challenge the current target of neutral coronal alignment and point towards a more individualized mechanical alignment target. Prognostic study, Level I.

No correlation between coronal alignment of total knee arthroplasty and clinical outcomes: a prospective clinical study using 3D-CT

Purpose
One of the most important factors leading to revision of total knee arthroplasties (TKA) is malrotation of femoral and/or tibial component. Rotation measurements performed on radiographs are limited and less reliable compared to 2D computed tomography (CT). Nowadays, 2D-CT and 3D-CT can be distinguished in measuring rotation of the TKA components. The aim of this systematic review is to determine the most reliable CT techniques in measuring rotation of the TKA components and to investigate possible cut-off points that can be used in the clinician’s decision for a possible revision of the TKA.

How to assess femoral and tibial component rotation after total knee arthroplasty with computed tomography: a systematic review

Objective
The purpose was to evaluate the intra- and inter-observer reliability of combined quantitative 3D-volumetric single-photon emission computed tomography (SPECT)/CT analysis including size, intensity and localisation of tracer uptake regions and total knee arthroplasty (TKA) position.

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4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty

size patients’ but also as one that is ‘expected not to be exceeded for standard procedures’. The ARSAC Notes for Guidance go on to say that ‘in many cases, it will be possible to administer activities less than those recommended. This is encouraged’ [5]. In the case of F-FDG we feel that stronger guidance on adapting the injected activity dependent on patient size and acquisition parameters is overdue.

SPECT/CT for the assessment of painful knee prosthesis.

Twenty to forty percent of patients after primary total knee arthroplasty (TKA) are not satisfied. A considerable number report persistent or recurrent pain. As most common causes infection, aseptic loosening, instability, malposition of the TKA, arthrofibrosis and patellofemoral problems have been reported. However, in many cases after TKA the cause for the patient9s problems cannot be identified unambiguously. The current clinical and radiological diagnostics including radiographs, CT, MRI, scintigraphy, SPECT or PET/CT fail to accurately establish the correct diagnosis. Recently we have highlighted the clinical value of SPECT/CT as diagnostic tool in patients with problems after TKA. We reported near perfect inter- and intra-observer reliability for their proposed standardized, easily applicable and reliable SPECT/CT algorithm including a localization scheme, intensity value and 3D prosthetic component analysis. With this specific algorithm the authors aim to identify typical distribution patterns and intensity thresholds of SPECT/CT tracer uptake, which reflect pathologies such as mechanical loosening, instability, component malposition or patellofemoral problems. The primary purpose of the present study is to evaluate the clinical value of the proposed 4D SPECT/CT algorithm including a localization scheme, intensity value evaluation and 3D analysis of TKA component position. The 4th dimension is the assessment of component position in 3D CT in relation to the mechanical axis. The secondary aim is to identify typical pattern of tracer uptake distribution and intensity values in unhappy patients after TKA and relate those to specific pathologies. One hundred unhappy patients after TKA are prospectively included. 99mTc-HDP-SPECT/CT is performed as part of the diagnostic algorithm using our previously validated protocol, which includes for the CT 3 mm slices of the hip joint, 0.75 mm slices of the knee and 3 mm slices of the ankle joint. SPECT/CT tracer uptake is localised using a specific localisation scheme, which divides the knee joint in anatomical and biomechanical regions of interest. Quantitative volumetric 3D analysis of tracer uptake intensity is performed using a customised validated software. In addition, the fermoral and tibial TKA component position (flexion-extension, varus-valgus, internal rotation-external rotation) as tibiofemoral angle is measured using another customised and validated software. The above findings is correlated with the type and design of TKA, the time from primary TKA, cemented or non cemented approach and intraoperative findings at revision surgery (loose vs well fixed TKA). With the intended results of the study we aim for a better understanding of unhappy knee joints after TKA and an improved diagnostics in a challenging group of patients. Our approach is entirely novel as it combines biomechanical data such as leg alignment and TKA component position as well as information on the bony remodelling, which is inherent in the SPECT information.

https://bjsm.bmj.com/content/bjsports/47/10/e3.26.full.pdf

Clinical value of 4d-spect/ct in patients with painful total knee arthroplasty

This chapter deals with the clinical value of nuclear medicine, in particular SPECT/CT, in patients with knee injuries. A thorough overview of nuclear medicine imaging protocols, diagnostic algorithms and the clinical value for different knee pathologies is given. These knee pathologies or variants include patients with anterior knee pain; jumper’s knee; runner’s knee; patellar dislocation; patellar maltracking; patellar fractures; meniscal lesions; ligament tears such as anterior cruciate ligament, posterior cruciate ligament or collaterals; Stieda-Pellegrini lesion; cartilage lesions; osteochondral lesions; overloading of a knee compartment; osteoarthritis and fractures. The clinical value is further illustrated by images and typical instructional case descriptions.

Nuclear Medicine Imaging of Knee Injuries

Radiosynoviorthesis (RSO) or radiation synovectomy is a local radionuclide therapy for patients with chronic synovitis. RSO is safe and has a low complication rate. For the knee, radiolabelled yttrium-90-labelled colloids are injected into the joint. The indication for RSO is persistent joint pain, effusion and swelling. However, RSO should only be used as a salvage procedure in patients with unidentified cause of the persistent pain. In these patients RSO leads to attenuation of the symptoms in 50 % of patients.

Flavio Forrer

Papers

4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty

SPECT/CT for the assessment of painful knee prosthesis.

Clinical value of 4d-spect/ct in patients with painful total knee arthroplasty

Nuclear Medicine Imaging of Knee Injuries

38 Radiosynoviorthesis in Painful Total Knee Replacement