Assessment of tissue viability after frostbite injury by technetium-99m-sestamibi scintigraphy in an experimental rabbit model

Research progress in the pathogenic mechanisms and imaging of severe frostbite

PURPOSE

This article reviews the pathological mechanisms and progress of imaging of severe frostbite to assist in the search for targets for clinical diagnosis and treatment of severe frostbite. This review also aims to provide strong evidence for clinical diagnosis and treatment of deep frostbite.

METHODS

The review was based on the summary and analysis of the existing literature, and explored the pathological mechanism of deep frostbite and the advantages and disadvantages of imaging diagnostic methods.

RESULTS

According to the depth of tissue involvement, frostbite is divided into 4 levels. Severe frostbite includes Grade 3 and Grade 4 frostbite. Clinical performance evaluation and imaging diagnostic research have always been the mainstream of severe frostbite diagnosis. Imaging methods focus on vascular patency and tissue vitality. This article introduces angiography, SETCT/CT and MRA, and we summarize the advantages and disadvantages of these imaging methods. We recommend corresponding imaging modalities according to the state of frostbite patients.

CONCLUSIONS

Imaging examination, especially angiography and bone scans, provide useful information for determining the diagnosis and prognosis of severe frostbite. In order to obtain a good clinical prognosis, clinicians should first perform SPECT/CT. MRA does not burden the patient's body, but the balance between cost and benefit must be considered. Angiography provides a good feedback on the changes in blood vessel status before and after treatment, which is helpful for discovering the response of limbs to treatment.

Frostbite: Current status and advancements in therapeutics

Frostbite is a severe ischemic injury which occurs due to the tissue vascular damage after sub-zero temperature tissue exposure. Deep frostbite can result in necrosis and may need amputation of affected tissue. Though a serious injury, it is not very well understood, and further scientific exploration is needed. This work explores the current understanding of the pathophysiology of frostbite. We reviewed the current status of the diagnostics, the drugs, the therapies and the surgical practices for prevention and management of frostbite. Advances in nanotechnology and drug delivery had improved the therapeutic outcomes significantly. This review also explored the latest advancements and researches done for development of newer therapeutics and diagnostics for frostbite care.

Ischemic Muscle Necrosis of Lower Extremities in Peripheral Arterial Disease: The Impact of 99mTc-MDP Scintigraphy on Patient Management

Background and objectives: The objective of this study was to assess the value of a whole-body bone scintigraphy using 99m technetium labelled-methyl diphosphonate (99mTc-MDP) for the diagnosis and the assessment of grades of muscle damage after prolonged acute or chronic obstruction of the main arteries in lower extremities. Material and Methods: Fifty consecutive patients were selected for the study. The patients’ condition had not improved after primary peripheral arterial reconstruction operation or limb amputation and after conservative treatment. The clinical suspicion was of arterial obstruction and muscle necrosis. All the patients underwent whole-body scintigraphy with 99mTc-MDP. Muscle necrosis was identified as an increased soft tissue uptake of 99mTc-MDP. Results: Forty-five patients had gross muscle necrosis detected on whole-body scintigraphy with 99mTc-MDP and were histologically confirmed after repeated surgery (necrectomy or amputation) or by muscle biopsy, if only fasciotomy was performed. The location and extent of muscle injury were assessed preoperatively and the findings were confirmed in all 45 patients. Twelve patients with clinically suspected minor muscle damage, which was confirmed as relatively minor muscle necrosis on 99mTc-MDP scintigraphy, were treated conservatively. The clinical outcome of all 50 patients was favorable. The 99mTc-MDP scintigraphy, in detection of muscular necrosis, demonstrated sensitivity, specificity, and accuracy of 97.3% (95% confidence interval (CI) 85.4 to 99.3%), 30.77% (95% confidence interval (CI) 9.09 to 61.43%), and 80% (95% confidence interval (CI) 66.28 to 89.97%), respectively. Conclusion: The 99mTc-MDP scintigraphy is a valuable tool in the detection of muscular necrosis. It is able to define location, extent, and grade of involvement. Therefore, it has a clinical impact in patient management, allowing clinicians to select adequate treatment policy and specify the scope of necrectomy.

Lateral parapatellar and subvastus approaches are superior to the medial parapatellar approach in terms of soft tissue perfusion

PURPOSE

The arthrotomy techniques of knee surgery may cause varying degrees of disruption to the tissue blood supply. The aim of this study was to investigate the effects of the medial parapatellar (MPPa), midvastus (MVa), subvastus (SVa) and lateral parapatellar (LPPa) approaches on regional tissue perfusion of the knee.

METHODS

In this experimental study, a total of 28 female rabbits were applied with four different arthrotomy techniques as Group MPPa, Group MVa, Group SVa and Group LPPa. The blood supply of the tissue around the knee was examined by scintigraphic imaging including the perfusion reserve and T _max, and biochemical alteration of the oxidative stress parameters including malondialdehyde (MDA), fluorescent oxidation products (FlOPs), and histopathological findings were evaluated on tissue samples after 3 weeks.

RESULTS

The perfusion reserve was increased in all four groups compared to the healthy, contralateral knees. In the Group LPPa, the vascularity was significantly increased compared to the Group MPPa (p = 0.006). In the examination of biochemical parameters, the increase in MDA levels was statistically significant in the Group MPPa compared with the Group LPPa (p = 0.004), and in the Group MVa compared with the Group LPPa (p = 0.006). The increase in the value of MDA levels was striking in the Group MPPa and Group MVa compared with the control group (p = 0.004, p = 0.004, respectively). The increase in another oxidative stress parameter, the tissue FlOPs levels, was statistically significant in the Group MPPa compared with the control group (p = 0.035).

CONCLUSION

The LPPa and SVa caused less oxidative stress and less disruption of the muscle blood supply, in biochemical and scintigraphic parameters, compared to the MPPa and MVa. Therefore, in clinical practice, the SVa is preferable to the MPPa and MVa in total knee arthroplasty and the LPPa should be preferred more frequently in selected cases with critical soft tissue viability.

Pathophysiologic Determination of Frostbite Under High Altitude Environment Simulation in Sprague-Dawley Rats

OBJECTIVES

Pathophysiologic changes of frostbite have been postulated but rarely understood, especially the changes caused by chilly high altitude environment. Therefore, we investigated the pathophysiologic changes of high altitude frostbite (HAF) caused by cold and hypoxia.

METHODS

Forty Sprague-Dawley rats were randomly divided into 5 equal groups, namely, control, superficial HAF (S-HAF), partial-thickness HAF (PT-HAF), full-thickness HAF (FT-HAF), and partial-thickness normal frostbite (PT-NF) groups. The S-HAF, PT-HAF, and FT-HAF groups were fed under hypobaric hypoxic conditions simulating an altitude of 5000 m. Then, the PT-NF, S-HAF, PT-HAF, and FT-HAF models were constructed by controlling the duration of the direct freezing by liquid nitrogen. Animal vital signs were measured after the operation, and histopathologic changes were observed after routine hematoxylin and eosin staining. In addition, the microcirculation of frostbite tissues was monitored and compared by contrast ultrasonography during wound healing.

RESULTS

The S-HAF, PT-HAF, and FT-HAF groups showed significant differences in the microcirculatory and histopathologic changes in the various tissue layers (P < .05). In addition, combined cold and hypoxia caused more damage to frostbite tissue than pure cold. The circulation recovery of HAF models was significantly slower relative to NF models (P < .05).

CONCLUSIONS

A safe and reproducible HAF model was proposed. More important, pathophysiologic determination of HAF provided the foundation and potential for developing novel and effective frostbite therapies.

Predictive value of 99mTc-sestamibi scintigraphy for healing of extremity amputation

PURPOSE

Although various non-invasive procedures have been proposed to determine the optimal level of amputation of limbs in patients who have vascular disease, currently there are no consistent criteria that can be applied before surgery. The purpose of this study was to determine whether (99m)Tc-sestamibi imaging can accurately predict the healing of amputation sites.

METHODS

In a prospective study in 26 patients (21 men, 5 women; age range 23-94 years) presenting with ulcers or gangrene of the foot and hand, (99m)Tc-sestamibi imaging was performed preoperatively. The indications for amputation included gangrene (23 patients), electrical injury (2 patients) and trauma (1 patient) of extremities. Although the amputation levels were chosen according to clinical criteria and scintigraphic results, the final amputation level was defined by scintigraphic results. Two below-knee, one above-knee, 12 toe, 11 transmetatarsal, two phalanx, one finger and one thumb amputations and one shoulder disarticulation were performed. In four cases, the amputation defect was not suitable for coverage using a local dermal flap; rather, it was covered with free tissue transfer. Patients had clinical follow-up for 6-36 months (mean 11.69 months) to assess healing of the stump. Scan results were compared with clinical outcome to assess prediction of healing.

RESULTS

There was healing in all amputations at the end of the follow-up period. When evaluated regarding preoperative (99m)Tc-sestamibi uptake pattern, there was no perfusion to the lesion site in 21 patients and perfusion to an area smaller than the extent of skin necrosis in four patients; thus, in these 25 patients, (99m)Tc-sestamibi scintigraphy suggested non-viable tissue in the extremities with clear-cut edges of perfused muscle tissue. Diffusely decreased uptake was seen below the left knee in one case. How scintigraphy changed management was analysed. The amputation levels proposed before scintigraphy were divided into two groups, "definite" (n=14) and "indefinite" (n=12), based on visual examination and Doppler findings. In nine patients in the definite group, the proposed amputation level before scintigraphy was not altered by the scintigraphic data. However, (99m)Tc-sestamibi scan enabled unnecessarily high amputation levels to be avoided in 12 patients in the indefinite group and in five patients in the definite group. Therefore, there was change in management of 65% of cases based on scintigraphic findings.

CONCLUSION

Since healing of the stump was seen in all cases, outcome was correctly predicted by scintigraphy. This preliminary study supports the use of (99m)Tc-sestamibi scan in selecting the optimal amputation level consistent with subsequent stump healing.

Assessment of digital ischaemia and evaluation of response to therapy by 99mTc sestamibi limb scintigraphy after local cooling of the hands in patients with vasospastic Raynaud's syndrome

AIM

Cold induced arteriolar constriction in patients with vasospastic Raynaud's syndrome (VRS) produces temporary digital ischaemia. The aim of this study was to ascertain whether 99mTc sestamibi scintigraphy is useful in the diagnosis and the monitoring of treatment in VRS.

METHODS

Fifteen patients with VRS and 20 matched normal controls underwent examination. Twelve patients with VRS received therapy. For each patient, one hand was immersed in iced water for 30s while the other hand served as a control. Ten minutes after cooling, 99mTc sestamibi was injected and imaging was performed 60min later. The per cent decrease of the perfusion (%DP) was calculated by semiquantitative analysis to determine the severity of hypoperfusion.

RESULTS

In all patients with VRS, moderate or marked hypoperfusion were seen in 99mTc sestamibi images after exposure to the iced water, while there was minimal or mild hypoperfusion in the control groups. Values for %DP were 46.86 +/- 19.04 and 7.85 +/- 4.53 for the VRS group and normal subjects, respectively. The difference between both groups was statistically significant (P = 0.0000). In 12 treated patients with VRS, pre-treatment and post-treatment %DP values were 51.16 +/- 18.42 and 33.58 +/- 17.83, respectively, and a significant difference was seen between both values (P = 0.001). However, there was still a statistically significant difference between control subjects and post-therapy values (7.85 +/- 4.53 vs. 33.58 +/- 17.83, P = 0.0000). The +/- 95% confidence interval of DP for control subjects was 5.7-10% (chi-squared, P = 0.000). When a DP of 10% was used as a cut-off point, sensitivity, specificity and diagnostic accuracy were 100%, 70% and 83%, respectively, for the 99mTc sestamibi scan. There was also a strong correlation between %DP and the duration of the disease (r = 0.80, P = 0.0003).

CONCLUSION

The results of this study indicate that a 99mTc sestamibi scan is a valuable imaging method for the determination of digital ischaemia in vasospastic Raynaud's syndrome, and may play a role in evaluating the response to therapy.

Combined 99mTc MDP bone SPECT and 99mTc sestamibi muscle SPECT for assessment of bone regrowth and free muscle flap viability in an electrical burn of scalp

A case of deep high energy electrical burn of the skull is presented. For assessment of bone regrowth and muscle flap viability after application of latissimus dorsi free flap, combined 99mTc MDP bone SPECT and 99mTc sestamibi muscle SPECT scintigraphy were used. Whereas 99mTc MDP bone SPECT showed absent uptake at the beginning, there was good uptake 3 months after flap application. 99mTc sestamibi SPECT revealed good uptake indicating normal perfusion of flap muscle tissue.

Imaging of frostbite injury by technetium-99m-sestamibi scintigraphy: a case report

The appearance of superficial tissue is often an unreliable indicator of deep-tissue viability in cases of frostbite. We present a 34-year-old black man who was brought to the emergency department at fourth post-injury day with frostbite injury involving both lower extremities after prolonged exposure to subzero temperatures. In our previous experimental study, 99mTc sestamibi scintigraphy has been employed for evaluating frostbite injuries in rabbit hindlegs. In the case presented, 99mTc sestamibi scintigraphy, as a new diagnostic tool, was performed for detection of skeletal muscle perfusion on the fourth post-injury day. The scintigraphic images show diffusely reduced uptake in soft tissues of both calves and feet. It was thought that this hypoperfusion was due to viable but ischemic tissue. Five days after medical therapy, 99mTc sestamibi scan showed prominently increased uptake in both calves and feet and skin necrosis was observed. Debridement of necrotic skin and subcutaneous tissue was performed, and split-thickness skin graft was applied for coverage of the skin defect. Healing was good 15 days after grafting. We think 99mTc sestamibi scan can be used for assessment of soft-tissue perfusion and evaluation of treatment in frostbite injury.

99mTc-sestamibi muscle scintigraphy to assess the response to neuromuscular electrical stimulation of normal quadriceps femoris muscle

OBJECTIVES

Neuromuscular electrical stimulation (NMES) is widely used for improving muscle strength by simultaneous contraction in the prevention of muscle atrophy. Although there exist many clinical methods for evaluating the therapeutic response of muscles, 99mTc-sestamibi which is a skeletal muscle perfusion and metabolism agent has not previously been used for this purpose. The aim of our work was to ascertain whether 99Tc-sestamibi muscle scintigraphy is useful in the monitoring of therapeutic response to NMES in healthy women.

METHODS

The study included 16 women aged between 21 and 45, with a mean age of 32.7 +/- 6.4. Both quadriceps femoris muscles (QFM) of each patient were studied. After randomization to remove the effect of the dominant side, one QFM of each patient was subjected to the NMES procedure for a period of 20 days. NMES was performed with an alternating biphasic rectangular current, from a computed electrical stimulator daily for 23 minutes. After measurement of skinfold thickness over the thigh, pre- and post-NMES girth measurements were assessed in centimeters. Sixty minutes after injections of 555 MBq 99mTc-sestamibi, static images of the thigh were obtained for 5 minutes. The thigh-to-knee uptake ratio was calculated by semiquantitative analysis and normalized to body surface area (NUR = normalized uptake ratio).

RESULTS

The difference between the pre and post NMES NUR values was significant (1.76 +/- 0.31 versus 2.25 +/- 0.38, p = 0.0000). The percentage (%) increase in NUR values also well correlated with the % increase in thigh girth measurements (r = 0.89, p = 0.0000).

CONCLUSION

These results indicated that 99mTc-sestamibi muscle scintigraphy as a new tool may be useful in evaluating therapeutic response to NMES.