The role of SPECT/CT in painful, noninfected knees after knee arthroplasty: a systematic review and meta-analysis-a diagnostic test accuracy review.

PURPOSE: The aim of this systematic review was to present the current evidence on the clinical use of single-photon emission computed tomography/computed tomography (SPECT/CT) in the evaluation of noninfected painful knees after knee arthroplasty. METHODS: Embase, PubMed, Google Scholar, Ovid, Scopus, Science Direct and the Cochrane Database of Systematic Reviews were searched from database inception to May 2022 following the PRISMA guidelines. As a primary outcome, we defined the role of SPECT/CT in the diagnostic approach to noninfected painful knee arthroplasty; as a secondary objective, we described the noninfection-related factors linked to painful knee arthroplasty. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio values and other indicators were calculated; receiver operating characteristic (ROC) curve analysis results and a summary of the areas under the curve (AUCs) from the included studies were reported. A Fagan plot, likelihood ratio plot and Deeks' funnel plot were generated and analysed. Methodological quality was assessed using the QUADAS-2 tool, and the certainty of evidence was assessed by the GRADE approach. RESULTS: A total of 493 publications were identified, of which eight met the inclusion criteria, with a final pooled sample size of 308 patients. The pooled sensitivity and specificity of SPECT/CT in diagnosing the source of pain in painful knee prostheses were 0.86 (95% CI: 0.75-0.93) and 0.90 (95% CI: 0.79-0.96), respectively, with pooled +LR and -LR values of 8.9 (95% CI: 4.11-19.19) and 0.15 (95% CI: 0.09-0.28). The pooled diagnostic odds ratio was 57.35, and the area under the curve was 0.94. SPECT/CT highly accurately identified different sources of pain, such as loosening of the prosthetic components, patellofemoral overloading, instability, malalignment of the components and degeneration of the patellofemoral compartment. The confidence of the estimates was moderate according to the GRADE approach. CONCLUSION: With demonstrated high sensitivity and specificity, as a diagnostic tool, SPECT/CT can identify the source of pain in painful knees after knee arthroplasty, particularly in cases of loosening, patellofemoral disorders and component malalignment (level of evidence III). These findings have significant clinical repercussions, such as in changing the initial diagnosis, identifying or excluding different causes of painful knee arthroplasties, guiding subsequent treatment and positively impacting the final clinical outcome. We moderately recommend the use of SPECT/CT for identifying the source of pain after knee arthroplasty according to the GRADE assessment. This review was preregistered in Prospero under code CRD42022320457.

Stress Radiographs in the Posterior Drawer Position at 90° Flexion Should Be Used for the Evaluation of the PCL in CR TKA with Flexion Instability.

The purpose of this study was to define a cut-off value for the posterior drawer position in stress radiography that confirms an insufficiency of the posterior cruciate ligament (PCL) in cruciate-retaining (CR) total knee arthroplasty (TKA). In this retrospective study, 20 symptomatic patients with flexion instability and suspected PCL insufficiency in CR TKA were included. Asymptomatic patients served as an age- and sex-matched control group. All of the patients had undergone stress radiography, and the posterior translation was measured in a posterior drawer position at 30° and 90° flexion. The two groups were compared using t-tests and chi-square tests. The stress radiographs showed significantly more posterior translation in the symptomatic group (p < 0.01). Stress radiographs at 90° flexion more effectively discriminated between the patients with and without PCL insufficiency compared with those carried out at 30° flexion. Sensitivity and specificity testing revealed the best sensitivity (90.5%) and the best specificity (94.7%) at 90° posterior drawer radiographs at a cut-off value of 10 mm. Stress radiographs including the posterior drawer position at 90° flexion should be part of the diagnostic algorithm in patients with suspected flexion instability. A posterior translation of more than 10 mm in CR TKA strongly indicates an insufficiency of the PCL.

Correlations of typical pain patterns with SPECT/CT findings in unhappy patients after total knee arthroplasty.

PURPOSE: The diagnostic process in patients after painful total knee arthroplasty (TKA) is challenging. The more clinical and radiological information about a patient with pain after TKA is included in the assessment, the more reliable and sustainable the advice regarding TKA revision can be. The primary aim was to investigate the position of TKA components and evaluate bone tracer uptake (BTU) using pre-revision SPECT/CT and correlate these findings with previously published pain patterns in painful patients after TKA. METHODS: A prospectively collected cohort of 83 painful primary TKA patients was retrospectively evaluated. All patients followed a standardized diagnostic algorithm including 99m-Tc-HDP-SPECT/CT, which led to a diagnosis indicating revision surgery. Pain character, location, dynamics and radiation were systematically assessed as well as TKA component position in 3D-CT. BTU was anatomically localized and quantified using a validated localization scheme. Component positioning and BTU were correlated with pain characteristics using non-parametric Spearman correlations (p < 0.05). RESULTS: Based on Spearman's rho, significant correlations were found between pain and patients characteristics and SPECT/CT findings resulting in nine specific patterns. The most outstanding ones include: Pattern 1: More flexion in the femoral component correlated with tender/splitting pain and patella-related pathologies. Pattern 3: More varus in the femoral component correlated with dull/heavy and tingling/stinging pain during descending stairs, unloading and long sitting in patients with high BMI and unresurfaced patella. Pattern 6: More posterior slope in the tibial component correlated with constant pain. CONCLUSION: The results of this study help to place component positioning in the overall context of the "painful knee arthroplasty" including specific pain patterns. The findings further differentiate the clinical picture of a painful TKA. Knowing these patterns enables a prediction of the cause of the pain to be made as early as possible in the diagnostic process before the state of pain becomes chronic. LEVEL OF EVIDENCE: Level III.

A clinical test examination procedure to identify knee compartment overloading: A reliability and validity study using SPECT-CT as reference.

BACKGROUND: Mechanical forces and joint misalignment are considered risk factors for the development of knee osteoarthritis (KOA). Early detection of KOA and distinction between lateral and medial compartment overloading (CO), might be important to inform appropriate preventative interventions. This study evaluated reliability and validity of a test battery consisting of ten clinical tests to predict knee CO. METHODS: Independent observers examined 30 participants with symptoms of KOA. Inter-rater reliability of the ten tests, as well as the anticipated CO based on the whole test battery, was determined. All participants received a SPECT-CT, which served as reference standard for CO. The agreement for CO between SPECT-CT and clinical examination was assessed to determine criterion validity. RESULTS: The Kappa coefficients (k) for the ten individual clinical tests ranged from 0.19 to 0.80. The k for determining CO was 0.52 (95% CI = 0.28-0.76). The agreement for CO between SPECT-CT and clinical examination (i.e. criterion validity) yielded a k of 0.26 (95% CI = -0.06 - 0.58). Logistic regression indicated that valgus alignment was strongly related with lateral CO. No other relationships were found between individual tests and CO. CONCLUSION: Accurate measurement of frontal plane knee angle is important to determine CO. This particular test yielded good reliability, but low validity. Reliability of the nine remaining clinical tests was fair to moderate. Criterion validity of the clinical examination to predict CO was low. Therefore, this test battery in its current form cannot be used in practice to determine CO.

Change of tibial tuberosity-trochlear groove (TT-TG) distance during total knee arthroplasty had no influence on clinical outcome and anterior knee pain.

PURPOSE: The main purpose of this study was to determine whether there is a correlation between the change of tibial tuberosity-trochlear groove (TT-TG) distance and clinical outcomes after total knee arthroplasty (TKA). METHODS: A total of 52 knees undergoing TKA due to primary osteoarthritis were included in this retrospective study. All patients had pre- and postoperative CT scans. TT-TG distance was measured by two independent observers and the following alignment parameters were measured: hip-knee ankle angle (HKA), femoral mechanical angle (FMA), tibial mechanical angle (TMA), and posterior condylar angle (PCA). Clinical outcome was assessed using Knee Society Score (KSS) pre- and post-operatively and at a minimum of 12-month follow-up. Evidence of AKP was noted from follow-up reports. Pre- and postoperative scores were compared using a paired Student t-test. Pearson correlations were calculated to assess the influence of TT-TG on clinical outcome and of alignment parameters on the change in TT-TG. TT-TG between patients with and without AKP was compared using unpaired Student's t-test (p < 0.05). RESULTS: Neither the absolute postoperative TT-TG nor the amount of change in TT-TG correlated with the post-operative KSS or the change in KSS. Post-operative TT-TG and change in TT-TG did not differ significantly between patients with and patients without AKP. Only the change in FMA showed a correlation with the change in TT-TG (p = 0.01, r = 0.36). CONCLUSION: Despite a missing correlation between outcomes and TT-TG distance in this study, excessive TT-TG distance should be avoided. Furthermore, surgeons need to be aware that changes in femoral joint line orientation might affect TT-TG distance.

Increased focal bone tracer uptake at the popliteus muscle origin in primary TKA compared with revision TKA.

OBJECTIVE: The purpose of the study was to investigate if the TKA design (cruciate retaining (CR), posterior stabilized (PS), revision prostheses) had an influence on the bone tracer uptake (BTU) pattern at the origin of the popliteus muscle. MATERIALS AND METHODS: A total of 92 knees (male:female = 46:46) which had undergone prior TKA were included in this retrospective study, comprising the following 3 groups: (i) CR primary TKA (n = 45); (ii) PS primary TKA (n = 24); (iii) revision TKA (n = 23). All patients received a SPECT/CT after TKA surgery. SPECT/CT images were reviewed for the presence of BTU in the lateral femoral condyle (origin of the popliteus muscle) by two observers using Syngo.via software (Siemens Healthcare, Erlangen, Germany). The observers recorded the BTU pattern qualitatively in the lateral femoral condyle as either (i) absent; (ii) present and diffuse; and (iii) present and focal in the region of the popliteus muscle origin. RESULTS: In patients with a CR and PS design, focal increased BTU at the origin of the popliteus muscle was found in 80.0% and 83.3% respectively. Diffuse BTU was the predominant finding in patients with revision TKA (60.9%). The patterns of BTU did not show significant differences between the CR and the PS design. However, patterns of BTU differed significantly between primary TKA designs and revision TKA (p < 0.001). CONCLUSION: Differences in patterns of BTU at the popliteus muscle origin between primary TKA and revision prosthesis may be the result of decreased insertional tensile forces of the popliteus muscle after revision surgery due to increased stability provided by the revision design.

Bone SPECT/CT has excellent sensitivity and specificity for diagnosis of loosening and patellofemoral problems after total knee arthroplasty.

PURPOSE: The primary purpose of this retrospective study with prospectively collected data was to evaluate the clinical value of SPECT/CT, in particular its impact on clinical diagnosis and patient management, in patients with pain, stiffness, or swelling after primary total knee arthroplasty (TKA). The secondary purpose was to determine the sensitivity and the specificity of SPECT/CT for different pathologies such as loosening and patellofemoral overloading. METHODS: A retrospective analysis was carried out on 214 knees in 202 consecutive patients (mean age 69 ± 11 years) with persistent or recurrent knee pain after TKA. All patients underwent clinical examination, standardised radiographs, and 99mTc-hydroxymethane diphosphonate (HDP) SPECT/CT as part of a routine diagnostic algorithm. The diagnoses before and after SPECT/CT and final treatment were recorded. TKA component position was routinely measured on 3D-reconstructed images. Intensity and anatomical distribution of bone tracer uptake were determined. RESULTS: SPECT/CT changed the clinical diagnosis and final treatment in 139/214 (65%) knees. In 117 (54.7%) out of 214 patients, revision surgery was proposed following SPECT/CT. Early onset of pain was significantly (p = 0.011) correlated with tibiofemoral stress pattern in SPECT/CT. A total of 86 knees (40.2%) were surgically revised using semi-constrained or fully constrained TKA. In 35 patients, a secondary patellar resurfacing was performed. SPECT/CT showed the clinical diagnosis to be incorrect for suspicion of tibial component loosening in 56 patients (26.2%), femoral component loosening in 53 patients (24.8%), and patellofemoral overloading/progressive patellofemoral osteoarthritis in 26 patients (12.1%) and provided different underlying causes of persistent knee pain after TKA. Likewise, SPECT/CT identified tibial component loosening in 8 patients (3.7%), femoral component loosening in 4 patients (1.9%), and patellofemoral OA in 71 patients (33.2%) without prior clinical suspected diagnosis. The sensitivity and specificity of SPECT/CT for detection of patellofemoral OA was 96.5% and 96.2%, respectively. The sensitivity and specificity for detection of tibial component loosening was 96.0% and 100%, respectively. The sensitivity and specificity for detection of femoral component loosening was 95.0% and 100%, respectively. CONCLUSION: The diagnostic benefits of SPECT/CT in the challenging and complex cohort of patients with pain after primary TKA have been proven. The excellent sensitivity and specificity for detection of tibial or femoral component loosening and diagnosis of patellofemoral OA have been surgically confirmed. Due to the benefits in establishing the correct diagnosis, SPECT/CT should be implemented as part of the routine diagnostic algorithm for patients with pain after primary TKA. LEVEL OF EVIDENCE: II.

Distribution of bone tracer uptake in symptomatic knees after ACL reconstruction compared to asymptomatic non-operated knees: a method for better differentiating patient-specific from disease-specific bone tracer uptake in SPECT/CT.

OBJECTIVE: To evaluate the differences of bone tracer uptake (BTU) in symptomatic and asymptomatic contralateral knees in patients after reconstruction of the anterior cruciate ligament (ACL-R) and to identify typical BTU patterns and threshold values to differentiate pathological from physiological BTU. METHODS: 53 patients after unilateral ACL-R were retrospectively included in the study. The population was subdivided into a group of symptomatic operated knees and a group of contralateral asymptomatic non-operated knees. BTU was measured in SPECT/CT using a validated anatomical localization-scheme and normalized mean BTU values were calculated in both knees. Wilcoxon signed rank-test and Pearson's rank-correlation coefficient were used (p < 0.05). RESULTS: Symptomatic knees after ACL-R showed significantly more BTU than asymptomatic ones (p < 0.01).Based on the measured BTU activity in SPECT/CT in symptomatic operated and asymptomatic non-operated knees, intensity thresholds of pathological BTU were established. A BTU threshold of greater than the Median + 1 SD of the asymptomatic non-operated knee was defined as pathological. In both groups the highest mean BTU was found on the femoral, tibial and patellar articular surfaces, the lowest BTU in femoral and tibial regions far from the joint. CONCLUSIONS: The established BTU thresholds for SPECT/CT in knees after ACL-R help to differentiate disease-specific from patient-specific BTU. It could be speculated that BTU in asymptomatic knees equates to the preoperative condition of the knee joint before ACL-R. Therefore, the results of this study help to understand in-vivo loading of the knee and ultimately lead to prediction of development of osteoarthritis in an early stage.

Good correlation between bone tracer uptake in SPECT/CT and intraoperative findings of chondral lesions graded with the ICRS scoring.

The question if bone tracer uptake in SPECT/CT reflects the intraoperative cartilage status of the knee is still unanswered. In this study, thirty-three consecutive patients (male:female = 11:22; mean age ± standard deviation 61 ± 15) with bi- or tri-compartmental knee osteoarthritis who underwent SPECT/CT before total knee arthroplasty (TKA) were collected. The knee was graded in eleven different anatomical regions. In each region, the maximal relative bone tracer uptake (mrBTU) was measured twice by two observers with a six weeks interval. The intraclass correlation coefficients (ICC) showed excellent correlations and mean values were used. Intraoperatively every region was assessed with the macroscopic International Cartilage Repair Society (ICRS) scoring. A factorial analysis and a non-parametrical Spearman's correlation were calculated among the 11 knee regions on both mrBTU and ICRS scores and significant correlations were seen between regions belonging to the same knee compartment (p < 0.05). A non-parametrical Spearman's correlation was also performed to investigate the correlation between rmBTU in SPECT/CT and intraoperative ICRS cartilage grading. Significant correlations were seen on the medial compartment, on the proximal femoral trochlea and on the medial patellar facet (p < 0.05). A significant correlation between SPECT/CT and intraoperative findings was so demonstrated in several regions. The low accuracy of the macroscopic ICRS scoring system on grade I-II lesions could have affected the missing correlations on the lateral compartment since the selected presented mainly a varus gonarthrosis. The use of an objective measure as the rmBTU could overcome the limit of the subjectivity of MRI findings in early osteoarthritis. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:522-528, 2019.

The utility of the ankle SPECT/CT scan to predict functional and clinical outcomes in supramalleolar osteotomy patients.

Combined single-photon emission computed tomography and conventional computed tomography (SPECT/CT) is a hybrid imaging modality that shows a combination of metabolic and structural information about the ankle, including arthritis. We hypothesize that uptake in specific locations within the ankle joint can be associated with both clinical outcomes and may help predict which patients will have a successful SMO. Eighty-five pre-operative SMO patients with varus (37), valgus (41), or neutral (7) alignment of the hindfoot were assessed using SPECT/CT. The level of activation on SPECT/CT scans was measured. Pre and Post-operative functional scores were recorded. Patients with medial gutter activation had significantly worse (p < 0.05) AOFAS alignment (AOFAS-A) scores pre-operatively. Patients with varus or valgus alignment did not have any difference in VAS pain scores, but those in valgus did have worse AOFAS-P (pain) scores. Those with cystic lesions had a worse FAOS score pre-operatively. Ten patients (12.5%) had a treatment failure. Pre or post-operative alignment did not correlate to a treatment failure. The only statistically significant (p = 0.036) poor prognostic indicator was a bipolar lesion. Pre-operative SPECT/CT evaluation of an ankle before a SMO can be used to clinically correlate patient-specific factors such as pain and function in the pre and post-operative period. We caution against performing a SMO in patients with bipolar activation on a pre-operative SPECT-CT scan. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2015-2021, 2018.

Patterns of bone tracer uptake on SPECT-CT in symptomatic and asymptomatic patients with primary total hip arthroplasty.

PURPOSE: The primary purpose of this study was to compare bone tracer uptake (BTU) on SPECT/CT in symptomatic and asymptomatic total hip arthroplasty (THA) and identify a possible relationship between BTU patterns and patient's symptoms. The secondary purpose was to investigate if the fixation methods (cemented versus uncemented) lead to different BTU patterns. METHODS: A total of 58 THAs, 31 symptomatic (group S) and 27 asymptomatic (group AS), were prospectively collected and retrospectively analyzed. All symptomatic patients underwent standardized detailed history, clinical examination, radiographs and 99mTc-HDP SPECT/CT. BTU in SPECT/CT was quantified in three dimensions and anatomically localized in a scheme of quadrants and levels using a customized previously validated software. T tests were used on both quadrants and levels inside and between groups. A Pearson correlation was performed for BTU within the quadrants. An area under receiver operating characteristic curves was drawn in order to find a BTU value that could differentiate the two groups. Within the groups, patients with cemented and uncemented stems were compared for influences on BTU intensity. RESULTS: The causes of pain were identified in 61% of the patients. The most common problem was aseptic loosening (n = 12). In group AS, levels 1, 2 and 5 had similar BTUs. BTUs in these levels were significantly higher than in level 3, 4 and 6. In group S, no significant differences were seen in terms of BTU in level 1-5. However, BTU here was significantly higher than at level 6 (p < 0.001). In both groups, level 1, the superior, had a significantly higher BTU than level 2 (group AS p < 0.01, group S p < 0.05). Comparing the BTU of the two groups among levels, significant differences were found for level 4, level 5 and the entire stem areas (p < 0.05). The ROC curve calculated on the whole stem allowed identification of a BTU ratio of 3.1 that separated the 92.6% patients of group AS with BTU < 3.1 from the 54.8% of patients of group S with a BTU ≥ 3.1. With regards to the fixation technique, only the BTU at the level 6 in group S presented a significant difference between cemented and uncemented stems (p < 0.05). CONCLUSIONS: Higher BTU levels significantly correlated with symptoms, but a normal BTU could not exclude a specific pathology after THA. A threshold of BTU in SPECT/CT was identified to distinguish between symptomatic and asymptomatic patients after THA.

Increased in vivo patellofemoral loading after total knee arthroplasty in resurfaced patellae.

PURPOSE: The primary purpose of the study was to investigate if and how patellar bone tracer uptake (BTU) distribution in SPECT/CT is influenced by patellar resurfacing and the position of femoral and tibial TKA component position. METHODS: A total of 104 knees of 103 consecutive patients who underwent primary TKA were prospectively investigated. Primary patellar resurfacing was done in 40 knees while 64 had a TKA without patellar resurfacing. All patients underwent clinical assessment using the knee society score (KSS) and standardized radiographs and Tc-99m-HDP-SPECT/CT before and 12 and 24 months after TKA. Measurements of BTU including intensity and anatomical distribution pattern in eight different patellar regions were performed. Tibial and femoral TKA component position was assessed from 3D reconstructed CT data. Patellar height, thickness and tilt were measured and the distance between the tibial tuberosity and the trochlear groove (TT-TG) was measured. Univariate analysis was performed to identify differences between the two groups (p < 0.05). RESULTS: Significantly higher BTU was found in the anterior, non-articular, areas of the patella in patients who underwent patellar resurfacing (p < 0.05). The BTU pattern was similar between the groups, as the maximal uptake in both groups was seen in the superior posterior parts and the minimal uptake was seen in the inferior anterior parts. The mean postoperative KSS was significantly higher in the unresurfaced group after 12 months (p < 0.05), but with no significant difference after 24 months. CONCLUSIONS: Based on the findings of the present study, patellar resurfacing is related to significantly higher BTU in the anterior parts of the patella and lower clinical outcomes. In light of these results, routine patellar resurfacing as part of a primary TKA might be reevaluated. SPECT/CT enables a precise localization of the BTU and might be considered as the ideal imaging modality for evaluation and investigate of patellofemoral disorders after TKA.

Increased bone tracer uptake in symptomatic patients with ACL graft insufficiency: a correlation of MRI and SPECT/CT findings.

PURPOSE: Magnetic resonance imaging (MRI) and single-photon emission computerised tomography/computerised tomography (SPECT/CT) are used as diagnostic tools in symptomatic patients after reconstruction of the anterior cruciate ligament (ACL). The benefit of SPECT/CT in comparison with MRI is under debate. The purpose of this study was to investigate whether and how bone tracer uptake (BTU) intensity and distribution in SPECT/CT correlate with MRI findings in symptomatic patients after ACL reconstruction. METHODS: Twenty-nine patients (male:female = 22:7, mean age ± SD 26 ± 10 years) with symptoms of pain and instability after ACL reconstruction were retrospectively investigated using prospectively acquired SPECT/CT and MRI. On MRI graft tear, graft signal intensity, bone marrow oedema, tunnel cyst formation, roof impingement, roof osteophytes, local arthrofibrosis, joint effusion and synovial thickness were analysed by two readers blinded to the BTU results. BTU was anatomically localised and volumetrically quantified. Spearman's rho test was used for correlation of BTU in SPECT/CT and MRI findings (p < 0.05). RESULTS: SPECT/CT showed increased femoral and tibial BTU in patients with MRI-confirmed graft tear, signal hyperintensity of the intraarticular graft section, joint effusion, synovial thickening, roof osteophytes and bone marrow oedema. Cyst formation in the femoral tunnel results in significantly reduced BTU in femur and tibia. No correlation of increased BTU was found for graft impingement and graft arthrofibrosis. CONCLUSIONS: Bone tracer uptake in SPECT/CT and defined MRI findings in symptomatic patients after ACL reconstruction were correlated. Both imaging modalities have a definite role in post-operative diagnostic and have established their value in those patients. This study provides a better understanding of the clinical value of SPECT/CT versus MRI in the clinical decision-making process. SPECT/CT provides a window into the in vivo loading of the joint as well as bone remodelling and graft incorporation process. In addition, ACL graft insufficiency can be detected by increased BTU. LEVEL OF EVIDENCE: Retrospective cohort study, Level III.

Good clinical results but moderate osseointegration and defect filling of a cell-free multi-layered nano-composite scaffold for treatment of osteochondral lesions of the knee.

PURPOSE: The aim of this retrospective study was to evaluate the clinical and radiological results of a nano-composite multi-layered three-dimensional biomaterial scaffold for treatment of osteochondral lesions (OCL) of the knee. It was a particular radiological interest to analyse the osseointegration, filling of the defects and the bone tracer uptake (BTU), and it was hypothesised that this scaffold, which was created to mimic the entire osteo-cartilaginous unit, is integrated within the bone 12 months postoperatively and comes along with improved patients symptoms and function. METHODS: Fourteen patients (male:female = 11:3, mean age ± SD 33.1 ± 10.7 years) treated for OCL (size 1.0-3.5 cm2) were clinically and radiologically evaluated at 1 year postoperatively. The data were prospectively collected including SPECT/CT, Tegner and Lysholm scores. BTU was anatomically localised and volumetrically quantified in SPECT/CT. Defect filling was analysed in CT. Spearman's rho and Wilcoxon test were used for correlation of BTU in SPECT/CT and clinical scores (p < 0.05). RESULTS: A significant improvement in Lysholm knee score (p < 0.001) and slight deterioration in Tegner score were found (p < 0.01). A complete filling of the defect was shown in 14%, a partial filling in 14% and only minor filling was seen in 72%. A significant correlation (p < 0.001) was found between location of osteochondral lesions and increased BTU. At the lesion sites pre- and postoperative BTU was markedly increased and did not show any decrease at 12-month follow-up. Median Tegner and mean Lysholm scores did not correlate with BTU at any time. CONCLUSIONS: Treatment of OCL in the knee joint with a nano-composite multi-layered three-dimensional biomaterial scaffold resulted in a significant clinical improvement at 1-year follow-up. However, osseointegration was still ongoing at 12-month follow-up. LEVEL OF EVIDENCE: Case series, Level IV.

Coronal femoral TKA position significantly influences in vivo patellar loading in unresurfaced patellae after primary total knee arthroplasty.

PURPOSE: As patellar tracking and loading is influenced by tibial tuberosity and trochlear groove (TT-TG) distance, patellar height, thickness and tilt as well as TKA component position, it was our hypothesis that these parameters significantly correlate with patellar BTU intensity and localization in SPECT/CT. The purpose of the study was to investigate whether TKA component position as well as the height, thickness and tilt of the unresurfaced patella influences the intensity and the distribution pattern of BTU in SPECT/CT. METHODS: A total of 62 consecutive patients who underwent primary TKA without patellar resurfacing were prospectively included. Demographic data such as age, gender, side and type of primary TKA were noted. All patients underwent clinical and radiological examination in a specialized knee clinic, including standardized radiographs (anterior-posterior and lateral weight bearing, patellar skyline view) and Tc-99m-HDP-SPECT/CT before, 12 and 24 months after TKA. SPECT/CT images were analysed on 3D reconstructed images. Rotational, sagittal and coronal position of the tibial and femoral TKA components was assessed using a previously validated analysis software. Measurements of BTU including intensity and anatomical distribution pattern were also performed from 3D data. The patellar height, thickness and tilt were measured, and the distance between TT and TG was measured using axial CT images. Univariate analysis was performed to identify any correlations between BTU and TKA component position and patellar measurements (p < 0.05). RESULTS: The highest median BTU was measured in the superior posterior parts of the patella. A statistically significant correlation was found between valgus alignment of the femoral TKA and increased BTU at the lateral patellar regions (p < 0.05). External rotation of the tibial TKA correlated with increased BTU at the lateral superior joint adjacent part (p < 0.05). No correlation was found between the tibial TKA position (varus-valgus, anterior and posterior slope), TT-TG distance, patellar height and patellar BTU values. CONCLUSIONS: A significant correlation of increased patellar BTU was found with femoral valgus TKA alignment. These findings highlight the importance of femoral TKA position in coronal plane with regard to post-operative patellar tracking. Moreover, these facts might explain anterior knee pain in unhappy TKA with femoral valgus alignment. LEVEL OF EVIDENCE: Diagnostic study, Level II.

Evaluation of patients with painful total hip arthroplasty using combined single photon emission tomography and conventional computerized tomography (SPECT/CT) - a comparison of semi-quantitative versus 3D volumetric quantitative measurements.

BACKGROUND: It was the primary purpose of our study to evaluate the inter- and intra-observer reliability of a standardized SPECT/CT algorithm for evaluating patients with painful primary total hip arthroplasty (THA). The secondary purpose was a comparison of semi-quantitative and 3D volumetric quantification method for assessment of bone tracer uptake (BTU) in those patients. METHODS: A novel SPECT/CT localization scheme consisting of 14 femoral and 4 acetabular regions on standardized axial and coronal slices was introduced and evaluated in terms of inter- and intra-observer reliability in 37 consecutive patients with hip pain after THA. BTU for each anatomical region was assessed semi-quantitatively using a color-coded Likert type scale (0-10) and volumetrically quantified using a validated software. Two observers interpreted the SPECT/CT findings in all patients two times with six weeks interval between interpretations in random order. Semi-quantitative and quantitative measurements were compared in terms of reliability. In addition, the values were correlated using Pearson`s correlation. A factorial cluster analysis of BTU was performed to identify clinically relevant regions, which should be grouped and analysed together. RESULTS: The localization scheme showed high inter- and intra-observer reliabilities for all femoral and acetabular regions independent of the measurement method used (semiquantitative versus 3D volumetric quantitative measurements). A high to moderate correlation between both measurement methods was shown for the distal femur, the proximal femur and the acetabular cup. The factorial cluster analysis showed that the anatomical regions might be summarized into three distinct anatomical regions. These were the proximal femur, the distal femur and the acetabular cup region. CONCLUSIONS: The SPECT/CT algorithm for assessment of patients with pain after THA is highly reliable independent from the measurement method used. Three clinically relevant anatomical regions (proximal femoral, distal femoral, acetabular) were identified.

Intra- and inter-observer reliability of a new standardized diagnostic method using SPECT/CT in patients with osteochondral lesions of the ankle joint.

BACKGROUND: Single Photon Emission Computed Tomography-Computed Tomography (SPECT/CT) gains an important part of diagnostics in patients with osteochondral lesions (OCL). SPECT/CT is a hybrid imaging modality, which combines a 3D scintigraphy (SPECT) and computerized tomography (CT) into one single procedure and combines metabolic data, structural and mechanical information. The purpose of the study was to develop and evaluate a standardized method to anatomically localize and quantitatively analyze the bone SPECT tracer activity of the ankle joint using SPECT/CT. METHODS: OCL on the talus were diagnosed in 16 patients by 99mTc-HDP-SPECT/CT and MRI by specialized orthopedic surgeons and radiologists and retrospectively included. The articular superior surface of the talus was subdivided in six anatomical regions (T1-T6). Using customized software, absolute bone SPECT values for each anatomical area were analyzed. Relative bone tracer uptake was calculated in relation to specific reference regions representing bone SPECT tracer background activity. All measurements were performed twice by two independent observers, blinded to clinical information. Intraclass correlation coefficients (ICC) were calculated for inter- and intra-observer reliability. The intraclass correlation coefficients (ICC) showed an excellent inter- and intra-observer reliability. RESULTS: The intraclass correlation coefficients (ICC) of all six regions are between 1.00 and 0.84 which is defined as very good. Results from region T1 to T6 impair slightly due to measurement regime. All ICCs of observer 1 were nearly the same as the results of observer 2 in all regions. CONCLUSION: The presented standardized SPECT/CT algorithm is clinically feasible and showed high inter- and intra-observer reliability. It might help to better understand the complex pathology of OCL on the talar dome. The major potential benefit of SPECT/CT is the assessment of the subchondral bone plate and the subchondral bone.

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

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. METHODS: A total of 100 knees of 84 consecutive patients (mean age ± SD 70 ± 11 years) after TKA with persistent knee pain were prospectively included. All patients underwent clinical examination, standardized radiographs and (99m)Tc-hydroxymethane diphosphonate (HDP) SPECT/CT as part of a routine diagnostic algorithm. The diagnosis before and after SPECT/CT and final treatment were recorded. TKA component position was determined on 3-D reconstructed images. Intensity and anatomical distribution of BTU was determined. Maximum intensity values were recorded as well as ratios in relation to the proximal midshaft of the femur. Univariate analyses (chi-square test, Pearson's correlation and t test for independent samples) were performed (p < 0.05). RESULTS: SPECT/CT changed the clinical diagnosis and final treatment in 85/100 (85 %) knees. Intraoperative findings confirmed the preoperative SPECT/CT diagnosis in 32/33 knees (97 %). TKA loosening as well as progression of patellofemoral osteoarthritis (OA) was correctly diagnosed in 100 % of knees. Typical patterns of BTU for specific pathologies were identified. Loose femoral TKA components significantly correlated with increased BTU at the lateral femoral regions (p < 0.05). Loose tibial TKA components significantly correlated with increased BTU at all tibial regions (p < 0.05) and around the tibial peg (p > 0.01). CONCLUSION: The diagnostic benefits of SPECT/CT in patients after TKA have been proven. Typical pathology-related BTU patterns were identified, which will improve reporting quality. Due to the benefits in establishing the correct diagnosis, SPECT/CT should be part of the routine diagnostic algorithm for patients with pain after TKA.

A novel standardized algorithm using SPECT/CT evaluating unhappy patients after unicondylar knee arthroplasty--a combined analysis of tracer uptake distribution and component position.

BACKGROUND: The introduction of a standardized SPECT/CT algorithm including a localization scheme, which allows accurate identification of specific patterns and thresholds of SPECT/CT tracer uptake, could lead to a better understanding of the bone remodeling and specific failure modes of unicondylar knee arthroplasty (UKA). The purpose of the present study was to introduce a novel standardized SPECT/CT algorithm for patients after UKA and evaluate its clinical applicability, usefulness and inter- and intra-observer reliability. METHODS: Tc-HDP-SPECT/CT images of consecutive patients (median age 65, range 48-84 years) with 21 knees after UKA were prospectively evaluated. The tracer activity on SPECT/CT was localized using a specific standardized UKA localization scheme. For tracer uptake analysis (intensity and anatomical distribution pattern) a 3D volumetric quantification method was used. The maximum intensity values were recorded for each anatomical area. In addition, ratios between the respective value in the measured area and the background tracer activity were calculated. The femoral and tibial component position (varus-valgus, flexion-extension, internal and external rotation) was determined in 3D-CT. The inter- and intraobserver reliability of the localization scheme, grading of the tracer activity and component measurements were determined by calculating the intraclass correlation coefficients (ICC). RESULTS: The localization scheme, grading of the tracer activity and component measurements showed high inter- and intra-observer reliabilities for all regions (tibia, femur and patella). For measurement of component position there was strong agreement between the readings of the two observers; the ICC for the orientation of the femoral component was 0.73-1.00 (intra-observer reliability) and 0.91-1.00 (inter-observer reliability). The ICC for the orientation of the tibial component was 0.75-1.00 (intra-observer reliability) and 0.77-1.00 (inter-observer reliability). CONCLUSIONS: The SPECT/CT algorithm presented combining the mechanical information on UKA component position, alignment and metabolic data is highly reliable and proved to be a valuable, consistent and useful tool for analysing postoperative knees after UKA. Using this standardized approach in clinical studies might be helpful in establishing the diagnosis in patients with pain after UKA.

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

BACKGROUND: there is only a paucity of studies dealing with bone remodeling within the tunnels after anterior cruciate ligament (ACL) reconstruction. The objective of this study was to evaluate the influence of tendon graft type and surgical fixation technique on bone tunnel remodeling in patients with symptomatic knees after ACL reconstruction. METHODS: in a retrospective study 99mTc-HDP bone tracer uptake (BTU) in SPECT/CT of 57 knees with symptoms of pain and/or instability after ACL reconstruction was investigated. All 57 knees were subdivided according their anatomy (femur and tibia), fixation (articular versus extra-articular fixation) and graft types into eight groups: femoral-articular versus extra-articular fixation using bone-patellar tendon-bone (BPTB) and hamstring autografts; tibial-articular versus extra-articular fixation using patellar tendon and hamstring autografts; BTU grading for each area of the localisation scheme were recorded. Tunnel diameter and length was measured in the CT scans. RESULTS: BTU was higher for the articular fixation in the femur and for the extra-articular fixation in the tibial tunnel. Patellar tendon graft fixation showed a significantly higher BTU in the superior-lateral and posterior-central area of the tibia, meaning the areas of the tibial tunnel near the entrance into the joint. Tunnel enlargement correlated significantly with increased BTU (p<0.05). CONCLUSION: assessment of in vivo bone tunnel remodelling in symptomatic patients after ACL reconstruction revealed different patterns of BTU with regards to graft and fixation method.