Comparison of muscle activity in the empty-can and full-can testing positions using 18 F-FDG PET/CT

Irreparable rotator cuff tears: Current treatment options

Rotator cuff disease is one of the most common causes of shoulder pain, yet controversy still exists regarding treatment of "irreparable" tears. Nonoperative management, including physical therapy and steroid injections, should be reserved for those without significant pain or functional impairment. Debridement may be used for low-demand patients, and should be performed with partial cuff repair, subacromial decompression, and/or acromioplasty to maximize outcomes. Biceps tenotomy and/or tenodesis have been shown to reduce postoperative pain and improve satisfaction when performed in conjunction with rotator cuff repairs, with no difference in functional outcome comparatively. Tendon transfers have been advocated with the potential benefit to improve function and decrease pain. More recently, extracellular matrix and human-derived dermal allografts have been used off-label as patch grafts in irreparable tears. Superior capsular reconstructive techniques and subacromial balloon spacers serve a similar function by acting to depress the humeral head in a cuff-deficient shoulder, however long-term data is needed before widespread adoption of these procedures. Finally, reverse shoulder arthroplasty serves as a salvage option for low demand elderly patients.

Evaluation of muscle activity just after straight leg raising exercise by using 18FDG-PET

BACKGROUND

Exercise therapy is one of the recognized treatment methods for knee osteoarthritis (KOA). One such exercise technique, straight leg raising (SLR), is widely known as a home exercise method for strengthening the quadriceps femoris muscle. However, whether this exercise truly strengthens the quadriceps is not known. The objective of the present study was to investigate which lower limb muscle is stimulated and shows increased activity with SLR.

METHODS

A total of 14 lower limbs in seven healthy adult male volunteers (mean age: 31.3 ± 2.2 years) were investigated. Participants were asked to perform SLR and subsequently underwent FDG-PET/CT examination for evaluation of the muscles of the entire lower limb. The maximum standardized uptake value (SUVmax) of each muscle (iliacus, psoas major, gluteus maximus, gluteus medius, gluteus minimus, vastus medialis, vastus intermedius, vastus lateralis, rectus femoris, biceps femoris, semimembranosus, semitendinosus, adductor, sartorius, gracilis, tibialis anterior, tibialis posterior, soleus, medial head of gastrocnemius, and lateral head of gastrocnemius) was measured in four cross-sections: at the trunk, pelvis, thigh, and lower leg.

RESULTS

SUVmax was significantly greater in: iliacus and adductor compared to vastus medialis, vastus lateralis, biceps, semitendinosus, gracilis, tibialis anterior, and gastrocnemius; psoas major compared to all muscles except for gluteus minimus and adductor; gluteus minimus compared to all muscles except for iliacus, psoas major, gluteus medius, and adductor; and gluteus medius compared to semitendinosus and gracilis.

CONCLUSIONS

After SLR, SUVmax was significantly greater in iliacus, psoas major, gluteus minimus, gluteus medius, and adductor compared to some of the other muscles. Performing SLR increased glucose metabolism of the above muscles in particular, and this may have increased their activity levels.

[18F]-FDG positron emission tomography--an established clinical tool opening a new window into exercise physiology

Positron emission tomography (PET) with [(18)F]-fluorodeoxyglucose (FDG) is an established clinical tool primarily used to diagnose and evaluate disease status in patients with cancer. PET imaging using FDG can be a highly valuable tool to investigate normal human physiology by providing a noninvasive, quantitative measure of glucose uptake into various cell types. Over the past years it has also been increasingly used in exercise physiology studies to identify changes in glucose uptake, metabolism, and muscle activity during different exercise modalities. Metabolically active cells transport FDG, an (18)fluorine-labeled glucose analog tracer, from the blood into the cells where it is then phosphorylated but not further metabolized. This metabolic trapping process forms the basis of this method's use during exercise. The tracer is given to a participant during an exercise task, and the actual PET imaging is performed immediately after the exercise. Provided the uptake period is of sufficient duration, and the imaging is performed shortly after the exercise; the captured image strongly reflects the metabolic activity of the cells used during the task. When combined with repeated blood sampling to determine tracer blood concentration over time, also known as the input function, glucose uptake rate of the tissues can be quantitatively calculated. This synthesis provides an accounting of studies using FDG-PET to measure acute exercise-induced skeletal muscle activity, describes the advantages and limitations of this imaging technique, and discusses its applications to the field of exercise physiology.