Diagnostic medical ultrasound in the management of hand injuries

Sensitivity and Accuracy of High-Resolution Ultrasound for Diagnosis of Flexor Tendon Repair Integrity

BACKGROUND

The authors examined whether ultrasound sensitivity, specificity, and accuracy in identifying intact repairs or flexor tendon gapping after zone 2 repair are affected by the number of suture strands crossing the repair or gap or imaging modality (static versus dynamic).

METHODS

A total of 144 fresh-frozen cadaveric digits (thumbs excluded) were randomized to either an intact repair (0-mm gap) or simulated failed repair (4-mm gap), as well as to either a two- or eight-strand locked-cruciate repair of a zone 2 flexor digitorum profundus tendon laceration using 4-0 Fiberwire. Examinations were performed by a blinded musculoskeletal ultrasonographer in static and dynamic modes using an 18-MHz transducer. Gaps were remeasured after scanning, and the final gap width recorded. McNemar exact test was used to determine whether there were differences in sensitivity, specificity, and accuracy affected by modality (static versus dynamic), and chi-square test was used to compare sensitivity, specificity, and accuracy between number of strands (two versus eight) crossing the intact repair or repair gap (≥4 mm).

RESULTS

Sensitivity, specificity, and accuracy improved with increased number of suture strands crossing the repair or gap (eight versus two), irrespective of modality (static versus dynamic), and dynamic compared with static scanning modes, irrespective of number of suture strands crossing the repair or gap site.

CONCLUSIONS

The most sensitive and accurate means of assessing flexor tendon repair integrity and gapping were seen using the dynamic scanning mode. Increased number of suture strands did not negatively affect sensitivity, specificity, or accuracy, regardless of scanning mode (dynamic or static).

Comparative sensitivity and accuracy of 24 vs. 18 MHz ultrasound probes for the diagnosis of flexor tendon repair integrity

Purpose

To determine whether a 24 MHz transducer significantly improves sensitivity, specificity and accuracy in evaluating flexor tendon repair integrity compared with an 18 MHz transducer.

Methods

One hundred and twelve cadaveric digits were randomised to an intact repair or simulated 'failed' repair, and to a two- or eight-strand repair of a flexor digitorum profundus laceration. A blinded sonologist evaluated specimens in static mode using 18 and 24 MHz transducers. Gaps were remeasured after scanning, and final gap width recorded. McNemar's exact test calculated differences between sensitivity, specificity and accuracy, and chi-squared test to compare sensitivity, specificity and accuracy between number of strands (2 vs. 8) and repair gap (≥4 mm).

Results

The 24 MHz transducer had higher sensitivity (81 vs. 59%), lower specificity (67 vs. 70%) and higher overall accuracy (74 vs. 64%), than the 18 MHz transducer. The difference for sensitivity was significant (P = 0.011), but not differences for specificity and overall accuracy (P > 0.05). Pearson's correlation (r = 0.61) demonstrated a moderate-to-strong positive correlation between measured and true gap sizes. Increased number of suture strands (2 vs. 8) did not impair sensitivity, specificity nor accuracy.

Discussion

Ultrasound may tend to overestimate gap width, and a slight risk that some intact repairs, or those with small, clinically insignificant gaps may undergo surgical exploration that may not be indicated.

Conclusions

A 24 MHz transducer is a more sensitive and accurate transducer for assessing flexor tendon repair integrity and measuring small gaps.

Evaluation of a Diagnostic-Therapeutic Algorithm for Finger Epiphyseal Growth Plate Stress Injuries in Adolescent Climbers

BACKGROUND

Finger epiphyseal growth plate stress injuries are the most frequent sport-specific injuries in adolescent climbers. Definitive diagnostic and therapeutic guidelines are pending.

PURPOSE

To evaluate a diagnostic-therapeutic algorithm for finger epiphyseal growth plate stress injuries in adolescent climbers.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

On the basis of previous work on diagnostics and treatment of finger epiphyseal growth plate stress injuries (EGPIs) in adolescent climbers, we developed a new algorithm for management of these injuries, which was implemented into our clinical work. During a 4-year period, we performed a prospective multicentered analysis of our patients treated according to the algorithm. Climbing-specific background was evaluated (training years, climbing level, training methods, etc); injuries were analyzed (Salter-Harris classification and UIAA MedCom score [Union Internationale des Associations d'Alpinisme]); and treatments and outcomes were recorded: union, time to return to climbing, VAS (visual analog scale), QuickDASH (shortened version of the Disabilities of the Arm, Shoulder, and Hand), and a climbing-specific outcome score.

RESULTS

Within the observation period, 27 patients with 37 independent EGPIs of the fingers were recorded (mean ± SD age, 14.7 ± 1.5 years; 19 male, 8 female; 66.7% competitive athletes). Regarding maturity at time of injury, the mean age at injury did not differ by sex. Average UIAA climbing level was 9.5 ± 0.8, with 6 ± 4.6 years of climbing or bouldering and 14 ± 9.1 hours of weekly climbing-specific training volume. Among the 37 injuries there were 7 epiphyseal strains, 2 Salter-Harris I fractures, and 28 Salter-Harris III fractures (UIAA 1, n = 7; UIAA 2, n = 30). Thirty-six injuries developed through repetitive stress, while 1 had an acute onset. Twenty-eight injuries were treated nonoperatively and 9 surgically. Osseous union was achieved in all cases, and there were no recurrences. The time between the start of treatment and the return to sport was 40.1 ± 65.2 days. The climbing-specific outcome score was excellent in 34 patients and good in 3. VAS decreased from 2.3 ± 0.6 to 0.1 ± 0.4 after treatment and QuickDASH from 48.1 ± 7.9 to 28.5 ± 3.3.

CONCLUSION

The proposed management algorithm led to osseous union in all cases. Effective treatment of EGPIs of the fingers may include nonsurgical or surgical intervention, depending on the time course and severity of the injury. Further awareness of EGPI is important to help prevent these injuries in the future.

Self-heating phenomenon of piezoelectric elements excited by a tone-burst electric field

Tone-burst excitation is often used for ultrasonic transducers of specific operation modes or for overcoming transducer overheating problems associated with continuous wave (CW) excitation. In this study, a theoretical model for the self-heating phenomenon of a piezoelectric disc element is established to estimate the temperature rise induced by a tone-burst electric field. An analytical solution for the temperature rise of the piezoelectric element is obtained by using Laplace transform method. Numerical simulations and experimental measurements are performed to investigate the influence of different excitation parameters on the temperature rise. By comparing the experimental results with the simulation results, the temperature-rise difference between tone-burst and CW excitations is quantified, and the validity of the theoretical model is verified. Furthermore, a multiparameter estimation method is proposed for the heat convection coefficient and dielectric properties under high-field operating conditions. These results are useful in both optimization of heat dissipation performance and characterization of high-power ultrasonic transducers.

The role of ultrasound in the management of flexor tendon injuries

The use of ultrasound scanning to establish tendon pathologies was assessed retrospectively in 17 patients in 18 digits. The ultrasound scan demonstrated four patterns: (1) normal intact tendons in four, (2) ruptured tendons in three, (3) tendons in continuity but attenuated in five and (4) tendons in continuity but thickened with fibrosis and decreased movement representing adhesions in five patients. Surgery was undertaken in only three cases, confirming the ultrasound diagnosis in two. Surgery was offered to all three patients with ruptures but was declined by two. Ultrasound imaging helped to avoid surgery in 14 cases by excluding flexor tendon re-ruptures. This allowed on-going mobilisation, leading to recovery of function.