Nuclear Medicine for the Orthopedic Foot and Ankle Surgeon

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

Bone Stress Injuries at the Ankle and Foot

Bone stress injuries (BSIs) are a frequent finding in athletes, particularly of the foot and ankle. A BSI is caused by recurring microtrauma to the cortical or trabecular bone exceeding the repair capacity of normal bone. The most frequent fractures at the ankle are low risk, characterized by a low risk for nonunion. These include the posteromedial tibia, the calcaneus, and the metatarsal diaphysis. High-risk stress fractures have a higher risk for nonunion and need more aggressive treatment. Examples are the medial malleolus, navicular bone, and the base of the second and fifth metatarsal bone.Imaging features depend on the primary involvement of cortical versus trabecular bone. Conventional radiographs may remain normal up to 2 to 3 weeks. For cortical bone, early signs of BSIs are a periosteal reaction or the "gray cortex sign," followed by cortical thickening and fracture line depiction. In trabecular bone, a sclerotic dense line may be seen. Magnetic resonance imaging enables early detection of BSIs and can differentiate between a stress reaction and a fracture. We review typical anamnestic/clinical findings, epidemiology and risk factors, imaging characteristics, and findings at typical locations of BSIs at the foot and ankle that may help guide treatment strategy and patient recovery.

Tibial Stress Fracture and "Shin Splint" Syndrome in the Same Patient Diagnosed on 99mTC-Methylene Diphosphonate Bone Scintigraphy and Single-Photon Emission/Computed Tomography

We present a case of an 18-year-old male athlete who presented with complaints of right lower leg pain for 10 days following intense exercise. The most likely diagnosis was a possible tibial stress fracture or a ''shin splint'' syndrome. The radiograph did not reveal any significant abnormality in the form of any fracture or a cortical break. We performed planar bone scintigraphy including single-photon emission computed tomography (CT)/CT that revealed the presence of the two concomitant pathologies in the form of a hot spot which corresponded with a bone lesion in the tibial stress fracture and subtle remodeling activity without evidence of significant cortical lesion in the shin splints in bilateral lower limbs (R>L).

Management of Periprosthetic Bone Cysts After Total Ankle Arthroplasty

Modern improvements in total ankle arthroplasty (TAA) have increased the performance of this procedure for treatment of end-stage ankle arthritis. A common finding after TAA is the formation of periprosthetic bone cysts, which can be clinically silent or result in TAA failure. The exact cause of periprosthetic bones cysts has not been established, but major theories are related to osteolysis secondary to implant wear, micromotion, and stress shielding. Treatment can be nonoperative with clinical observation for small, asymptomatic cysts. Large, progressive, and symptomatic cysts often merit surgical treatment with debridement and grafting, revision TAA, or salvage arthrodesis.

Stage 0 Charcot Neuroarthropathy in the Diabetic Foot: An Emerging Narrow Window of Opportunity?

In a world where popular culture and concepts can become the norm without all the rigors of normal scrutiny, our attention is focused on identifying Charcot neuroarthropathy (CN) at a stage before radiological bone destruction occurs. The rationale is that early recognition can prevent a destructive chain of events and thus potentially reduce the burden to patients and health care providers. In this article, we describe the evolution of stage 0 CN, and the use of modern imaging in characterizing the abnormalities recognized by these modalities and how they aid our understanding and supplement our knowledge. We review the potential of these imaging modalities, assessing how far we have come in characterizing stage 0 and if we have robust criteria for the identification of stage 0 in the natural history of CN.

Evaluating and Managing the Painful Total Ankle Replacement

The number of total ankle replacements (TARs) performed in the United States has dramatically increased in the past 2 decades due to improvements in implant design and surgical technique. Yet as the prevalence of TAR increases, so does the likelihood of encountering complications and the need for further surgery. Patients with new-onset or persistent pain after TAR should be approached systematically to identify the cause: infection, fracture, loosening/subsidence, cysts/osteolysis, impingement, and nerve injury. The alignment of the foot and ankle must also be reassessed, as malalignment or adjacent joint pathology can contribute to pain and failure of the implant. Novel advanced imaging techniques, including single-photon emission computed tomography and metal-subtraction magnetic resonance imaging, are useful and accurate in identifying pathology. After the foot and ankle have been evaluated, surgeons can also consider contributing factors such as pathology outside the foot/ankle (eg, in the knee or the spine). Treatment of the painful TAR is dependent on etiology and may include debridement, bone grafting, open reduction and internal fixation, realignment of the foot, revision of the implants, arthrodesis, nerve repair/reconstruction/transplantation surgery, or, in rare cases, below-knee amputation.Level of Evidence: Level V, expert opinion or review.

Comparison of bone SPECT/CT and MRI in detection of pain generator in ankle and foot pain: a retrospective diagnostic study

OBJECTIVE

To study the sensitivity and specificity of MRI and bone SPECT-CT in detecting the pain generator in ankle and foot pain with diagnostic dilemma.

METHODS

Retrospectively data of patients with ankle or foot pain who underwent both MRI and Bone SPECT-CT were analyzed. The lesions and probable pain generator sites were reported as per MRI and bone SPECT-CT findings. These lesions were correlated clinically, managed accordingly and followed up. The patients who had significant improvement in response to the treatment provided were considered to have been diagnosed accurately. The foot and ankle disability index (FADI) was used to evaluate the patient's pre- and postintervention condition.

RESULTS

The study included 37 patients retrospectively (18 women and 19 men). The lesions were classified into soft tissue lesions (ligaments/tendons), joint lesions (arthritis) and bony lesions (fractures/osteomyelitis/osteochondral lesions). Overall, MRI had sensitivity, specificity, positive predictive value and negative predictive value of 82, 31, 74 and 42%, respectively, and SPECT-CT had sensitivity, specificity, positive predictive value and negative predictive value of 84, 60, 84 and 60%, respectively. The mean FADI score pretreatment for all patients was 61.5 (SD = 13.8) and posttreatment 88.4 (SD = 13.01) showing significant improvement in the score (P < 0.05), suggesting that the final diagnosis of these patients was accurate. Overall, management change due to bone SPECT-CT over MRI was seen in 26% of patients.

CONCLUSION

Bone SPECT-CT has incremental value over MRI in the diagnosis of pain generator in foot and ankle pain. The overall specificity of bone SPECT-CT is higher than MRI in detection of pain generators. Bone SPECT-CT performed better than MRI in detection of culprit pathology in the bone, whereas MRI is better in soft tissue lesions.

ADVANCES IN KNOWLEDGE

There are only a few published literature with direct comparison of bone SPECT-CT scintigraphy and MRI in detection of foot and ankle pain generator. This study directly compares diagnostic utility of bone SPECT-CT scintigraphy and MRI in foot and ankle pain. In the present study, the bone SPECT-CT performed better than MRI in detection of culprit pathology in the bone, whereas MRI is better in soft tissue lesions.

Men who stare at bone: multimodal monitoring of bone healing

Knowledge of the physiological and pathological processes, taking place in bone during fracture healing or defect regeneration, is essential in order to develop strategies to enhance bone healing under normal and critical conditions. Preclinical testing allows a wide range of imaging modalities that may be applied both simultaneously and longitudinally, which will in turn lower the number of animals needed to allow a comprehensive assessment of the healing process. This work provides an up-to-date review on morphological, functional, optical, biochemical, and biophysical imaging techniques including their advantages, disadvantages and potential for combining them in a multimodal and multiscale manner. The focus lies on preclinical testing of biomaterials modified with artificial extracellular matrices in various animal models to enhance bone remodeling and regeneration.

Diagnosis and conservative management of great toe pathologies: a review

Acute great toe (Hallux) pain is a common complaint encountered by the primary care physician. Pathological conditions can vary from acute trauma to acute exacerbation of underlying chronic conditions. Delay in treatment or misdiagnosis can lead to debilitating loss of function and long-lasting pain. This review endeavors to discuss the pertinent history, physical exam findings, radiographic evidence, conservative treatment options, and surgical management for the musculoskeletal causes of acute and acute on chronic great toe pain in the adult population. The acute pathologies discussed in this review are hallux fractures and dislocations, turf toe, sand toe, and sesamoid disorders. The chronic pathologies discussed include hallux rigidus, hallux valgus, and chronic sesamoiditis.

Pathogenesis, Evaluation, and Management of Osteolysis Following Total Ankle Arthroplasty

Periprosthetic osteolysis is a common occurrence after total ankle arthroplasty (TAA) and poses many challenges for the foot and ankle surgeon. Osteolysis may be asymptomatic and remain benign, or it may lead to component instability and require revision or arthrodesis. In this article, we present a current and comprehensive review of osteolysis in TAA with illustrative cases. We examine the basic science principles behind the etiology of osteolysis, discuss the workup of a patient with suspected osteolysis, and present a review of the evidence of various management strategies, including grafting of cysts, revision TAA, and arthrodesis.Level of Evidence: Level V, expert opinion.

The Role of Bone Scintigraphy with SPECT/CT in the Characterization and Early Diagnosis of Stage 0 Charcot Neuroarthropathy

We describe the use of Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) in the investigation and diagnosis of Charcot neuroarthropathy (CN) in patients with a hot swollen foot but normal radiographs and clinical suspicion of CN, usually termed Stage 0. This was a retrospective cohort review of 46 diabetes patients who underwent 3 phase bone scintigraphy with “High Resolution” SPECT/CT. The imaging demonstrated that Stage 0 Charcot foot has a distinct bone pathology, which can be classified into three groups: (1) fractures on Computed Tomography (CT) with accompanying focal uptake of tracer on SPECT, (2) bony abnormalities apart from fracture on CT with focal uptake of tracer on SPECT, and (3) normal CT but focal bony uptake of tracer on SPECT. The CT component of SPECT/CT detected bony fractures in 59% of patients. Early treatment with below knee cast and follow-up for 24 months showed only 4 patients who developed Stage 1 Eichenholtz Charcot foot. Our findings support the use of 3 phase bone scintigraphy with SPECT/CT in the characterization and early diagnosis of CN. Stage 0 Charcot foot has a distinct bone pathology which requires urgent treatment to prevent progression to Stage 1 Eichenholtz Charcot foot. If SPECT/CT is unavailable, CT alone will detect bone fracture in 59% patients.