The biomechanical consequence of posterior interventions at the thoracolumbar spine on the passively stabilized flexed posture

In the flexed end-of-range position (e.g., during slumped sitting), the trunk is passively stabilized. Little is known about the biomechanical consequence of posterior approaches on passive stabilization. The aim of this study is to investigate the effect of posterior surgical interventions on local and distant spinal regions. While being fixed at the pelvis, five human torsos were passively flexed. The change in spinal angulation at Th4, Th12, L4 and S1 was measured after level-wise longitudinal incisions of the thoracolumbar fascia, the paraspinal muscles, horizontal incisions of the inter- & supraspinous ligaments (ISL/SSL) and horizontal incision of the thoracolumbar fascia and the paraspinal muscles. Lumbar angulation (Th12-S1) was increased by 0.3° for fascia, 0.5° for muscle and 0.8° for ISL/SSL-incisions per lumbar level. The effect of level-wise incisions at the lumbar spine was 1.4, 3.5 and 2.6 times greater compared to thoracic interventions for fascia, muscle and ISL/SSL respectively. The combined midline interventions at the lumbar spine were associated with 2.2° extension of the thoracic spine. Horizontal incision of the fascia increased spinal angulation by 0.3°, while horizontal muscle incision resulted in a collapse of 4/5 specimens. The thoracolumbar fascia, the paraspinal muscle and the ISL/SSL are important passive stabilizers for the trunk in the flexed end-of-range position. Lumbar interventions needed for approaches to the spine have a larger effect on spinal posture than thoracic interventions and the increase of spinal angulation at the level of the intervention is partially compensated at the neighboring spinal regions.

Medial Meniscal Extrusion Evaluation With Weight-Bearing Ultrasound: Correlation With MR Imaging Findings and Reported Symptoms: Correlation With MR Imaging Findings and Reported Symptoms

OBJECTIVES

To compare medial meniscal extrusion on weight-bearing ultrasound (US) with supine US and magnetic resonance (MR) imaging correlating with meniscal pathology and reported symptoms.

METHODS

IRB approved study with informed consent. Patients obtaining routine knee MR imaging for suspected knee pathology were prospectively evaluated with supine and weight-bearing US of the medial meniscus. Meniscal extrusion was measured independently by two fellowship-trained musculoskeletal radiologists. Correlation was made to presence or absence of meniscal degeneration or tear on MR imaging, as well as reported symptoms. Statistical significance was calculated via intraclass correlation coefficient (ICC) and analysis of variance (ANOVA).

RESULTS

Ninety-nine knees from 95 subjects (50 males, 45 females; mean age 45 ± 15 years) were included. Mean medial meniscal extrusion measured at US for a normal meniscus (n = 36) was 0.8 mm when supine, increasing to 1.6 mm on weight-bearing. Mean meniscal extrusion in subjects with mucoid degeneration (n = 20) and those with meniscal tears (n = 43) was 1.6 mm, increasing to 2.3 mm with weight bearing. Inter-reader reliability showed ICC values of 0.853 to 0.940. There was a significant difference in medial meniscal extrusion comparing subjects with a normal medial meniscus at magnetic resonance imaging (MRI) and subjects with either meniscal degeneration or tear. There was no significant difference in degree of meniscal extrusion between subjects with meniscal degeneration or tear. There was trend of worsening symptoms and increasing functional limitations moving from normal meniscus to meniscal degeneration to meniscal tear.

CONCLUSIONS

A normal meniscus shows lesser mobility between supine and upright position, than a pathologic meniscus. Both mucoid degeneration and meniscal tear demonstrate extrusion in the supine position, which increases with weight-bearing position.

Imaging Characteristics of the Proximal Lateral Collateral Ligament of the Knee: Findings on Ultrasound and MRI With Histologic Correlation

OBJECTIVES

Determine prevalence of increased signal intensity of the lateral collateral ligament (LCL) of the knee on MRI and decreased echogenicity on ultrasound, and compare with cadaveric histologic evaluation.

METHODS

After IRB approval of this prospective study with informed consent, patients having knee MRI were additionally evaluated with ultrasound. Signal intensities of LCL on MRI (low, intermediate, high), echogenicity at ultrasound (hyperechoic, hypoechoic, anechoic), and extent of findings were assessed. Descriptive statistics, Wilcoxon signed ranked test, and intraclass correlation coefficient (ICC) were calculated. Two cadaveric knees were imaged with MRI and ultrasound, including histologic LCL evaluation.

RESULTS

Seventy-three subjects were included (39 males, 34 females; mean age 48 ± 14 years) with 77 knee examinations. On MRI, low, intermediate, and high signals were present in 21% (16/77), 75% (58/77), and 4% (3/77), respectively. On ultrasound, echogenicity was assessed as hyperechoic, hypoechoic, and anechoic in 62% (48/77), 38% (29/77), and 0% (0/77), respectively. Mean length of increased signal was 8.6 mm (±4.9) on MRI, and 6.5 mm (±4.8) on ultrasound. The ICC showed a good to excellent intermodality reliability (0.735-0.899) without statistically significant difference for interreader measurements (P = .163-.795). Histology evaluation showed transition of ligament fibers to fibrocartilage at its insertion with increased connective tissue mucin corresponding to MRI and ultrasound findings.

CONCLUSIONS

Increased signal intensity of the proximal LCL on ultrasound and MRI is common and corresponds to normal connective tissue mucin.

MR imaging of the quadriceps femoris tendon: distal tear characterization and clinical significance of rupture types

Objective

To characterize quadriceps femoris tendon tears on magnetic resonance (MR) imaging regarding tear extent, location, and presence of bony avulsion.

Materials and methods

IRB approval was obtained and informed consent was waived for this retrospective case series. Electronic medical records from all patients in our hospital system were searched for keywords: knee MR imaging, and quadriceps tendon rupture or tear. MRI studies were randomized and independently evaluated by two fellowship-trained musculoskeletal radiologists. MR imaging was used to characterize each individual quadriceps tendon as having tendinosis, tear (location, partial versus complete, size, and retraction distance), and bony avulsion. Knee radiographs were reviewed for presence or absence of bony avulsion. Descriptive statistics and inter-reader reliability (Cohen’s Kappa and Wilcoxon-signed-rank test) were calculated.

Results

Fifty-two patients with 53 quadriceps tears were evaluated (45 males, 7 females; mean age: 51 ± 13 years). The vastus intermedius (VI) tendon more often incurred a partial rather than a complete tear (39.6% vs. 37.7%), while the rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) incurred complete tears more commonly (64.2–66%). Subjects with bony avulsion on radiographs had higher-grade tears of the RF, VM, and VL tears (p = 0.020–0.043) but not the VI. Most tendons tore at or immediately proximal to the patella (84.8–93.6%). Gaps in retracted torn tendons measured between 2.3 and 2.7 cm. Inter-reader reliability was substantial to almost perfect (κ = 0.624–0.953).

Conclusion

Quadriceps femoris tendon tears most commonly involve the RF or VL/VM layers usually in proximity to the patella. A bony avulsion correlates with a more extensive tear.

Key Points

• Quadriceps femoris tendon tears most commonly involve the rectus femoris or vastus lateralis/vastus medialis layers.

• A rupture of the quadriceps femoris tendon usually occurs in proximity to the patella.

• A bony avulsion of the patella correlates with a more extensive tear of the superficial and middle layers of the quadriceps tendon.

Mid-term results after in situ pinning and hip arthroscopy for mild slipped capital femoral epiphysis: a minimum five-year follow-up

PURPOSE

In situ pinning of mild slipped capital femoral epiphysis (SCFE) results in an aspherical head-neck junction and arthroscopic osteochondroplasty can successfully correct the head-neck junction. However, whether the correction stays stable over at least five years remains unknown.

METHODS

In a retrospective and consecutive series, 11 patients with a mean age of 12 years (range, 10 years to 15 years) were included. All patients were treated for mild SCFE with in situ pinning and staged hip arthroscopy correcting the head-neck junction. All patients were assessed clinically and radiographically (radiograph and magnetic resonance imaging (MRI)) pre-operatively, 12 weeks and at least five years' post-operatively.

RESULTS

The mean range of motion (ROM) for flexion and internal rotation was stable over time with 100° (sd 4) and 21° (sd 6), respectively at the last follow-up. The mean alpha angle decreased from pre-operative 64° (range 61° to 68°) to 12 weeks post-operative 49° (range 46° to 52°; p = 0.001) and stayed stable over time. New superficial cartilage damage on either the acetabular or femoral side was seen in each three patients. Progressive labral degeneration was present in two patients.

CONCLUSION

In situ pinning and staged hip arthroscopy for the correction of mild SCFE is safe, restores normal alpha angles and reveals stable morphological correction at mid-term follow-up. Furthermore, the clinical results were excellent with almost normalized internal hip rotation at mid-term follow-up in patients who had reached adulthood. However, there was some joint deterioration, but without negative impact on subjective and clinical outcome after at least five years.

LEVEL OF EVIDENCE

IV.

Cartilage icing and chondrocalcinosis on knee radiographs in the differentiation between gout and calcium pyrophosphate deposition

Objective

To determine if findings of “cartilage icing" and chondrocalcinosis on knee radiography can differentiate between gout and calcium pyrophosphate deposition (CPPD).

Methods

IRB-approval was obtained and informed consent was waived for this retrospective study. Electronic medical records from over 2.3 million patients were searched for keywords to identify subjects with knee aspiration-proven cases of gout or CPPD. Radiographs were reviewed by two fellowship-trained musculoskeletal radiologists in randomized order, blinded to the patients’ diagnoses. Images were evaluated regarding the presence or absence of cartilage icing, chondrocalcinosis, tophi, gastrocnemius tendon calcification, and joint effusion. Descriptive statistics, sensitivity, specificity, positive and negative predictive values, and accuracy were calculated.

Results

From 49 knee radiographic studies in 46 subjects (31 males and 15 females; mean age 66±13 years), 39% (19/49) showed gout and 61% (30/49) CPPD on aspiration. On knee radiographs, cartilage icing showed a higher sensitivity for CPPD than gout (53–67% and 26%, respectively). Chondrocalcinosis also showed a higher sensitivity for CPPD than gout (50–57% versus 5%), with 95% specificity and 94% positive predictive value for diagnosis of CPPD versus gout. Soft tissue tophus-like opacities were present in gout at the patellar tendon (5%, 1/19) and at the popliteus groove in CPPD (15%, 4/27). Gastrocnemius tendon calcification was present in 30% (8/27) of subjects with CPPD, and 5% (1/19) of gout.

Conclusion

In subjects with joint aspiration-proven crystal disease of the knee, the radiographic finding of cartilage icing was seen in both gout and CPPD. Chondrocalcinosis (overall and hyaline cartilage) as well as gastrocnemius tendon calcification positively correlated with the diagnosis of CPPD over gout.

Hand-Held Portable Versus Conventional Cart-Based Ultrasound in Musculoskeletal Imaging

Background:

Portable ultrasound machines are now common, used for point-of-care applications and needle guidance for percutaneous procedures; however, the effectiveness of portable ultrasound in evaluation of the musculoskeletal system has not been fully assessed.

Purpose:

To prospectively evaluate the use of portable hand-held ultrasound in comparison with conventional cart-based ultrasound in evaluation of the musculoskeletal system.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

In this institutional review board–approved, prospective study, 100 consecutive patients with informed consent were imaged through use of both portable and cart-based ultrasound equipment using 12-5 MHz linear transducers. Agreement in ultrasound diagnosis was documented along with expected clinical changes in management if there was disagreement (definitely no, probably no, uncertain, probably yes, definitely yes). Imaging details of disagreement cases were recorded, and descriptive statistics were calculated.

Results:

There were 42 male and 58 female patients (mean ± SD age, 53 ± 13 years) imaged over a time period of 20 months. Anatomic areas scanned were the shoulder (n = 30), elbow (n = 11), hand and wrist (n = 15), hip (n = 10), knee (n = 11), foot and ankle (n = 12), and others (n = 11). Scanning with conventional ultrasound revealed abnormality in 92% of patients. Agreement in diagnosis made between portable versus cart-based ultrasound was found in 65% of patients. In the 35% of patients with discordant results, the change in diagnosis resulted in no change in clinical management in 46%, probably no change in 29%, uncertain change in 14%, probable change in 11%, and definite change in 0%. The diagnoses changing management (4%; 4/100) included nondetection of a satellite nodule (n = 1), ganglion cyst (n = 1), hernia (n = 1), and underestimated tendon tear (n = 1).

Conclusion:

When compared with conventional cart-based ultrasound, a musculoskeletal diagnosis using portable hand-held ultrasound was concordant or was discordant without clinical relevance in 96% (96/100) of patients. Knowledge of benefits and limitations of portable hand-held ultrasound will help determine areas where specific types of ultrasound equipment can be used.

Ultrasound characterization of pseudoerosions and dorsal joint recess morphology of the hand and wrist in 100 asymptomatic subjects

PURPOSE

To sonographically characterize pseudoerosions and dorsal joint recess and capsule morphology of the hand and wrist in 100 asymptomatic subjects.

METHOD

The metacarpal heads, and dorsal aspects of the lunate, triquetrum, and ulna were evaluated for pseudoerosions including measurements and sonographic characterization. The dorsal recesses of the metacarpophalangeal, radiocarpal, and midcarpal joints were also characterized with regards to echogenicity, fibrillar pattern, hyperemia, and measurements.

RESULTS

100 subjects were included (average age 47 years, range 19-82 years; 52% male, 48% female). Pseudoerosions of metacarpophalangeal heads were seen in every subject, in all metacarpal heads, but most commonly the second and third (99% were bilateral, 97% were multiple); 81.5% involved at least three metacarpal heads; 99% were central with maximum depth of 2.6 mm. At the wrist, in 92% of subjects a bilateral pseudoerosion was present at the dorsal triquetrum, lunate, or ulna. Dorsal joint capsules and recesses at the metacarpophalangeal joints were isoechoic to subdermal fat and fibrillar measuring 3.1-6.3 mm in maximal thickness. The dorsal capsules and recesses of the radiocarpal and midcarpal joints were hypoechoic to subdermal fat, non-fibrillar and with maximal thickness of 3.9 and 3.4 mm, respectively. No hyperemia on color Doppler imaging was noted.

CONCLUSIONS

Pseudoerosions are common at the dorsal metacarpal heads, lunate, triquetrum, and ulna, which should not be mistaken for true inflammatory erosions. The characteristic appearances of dorsal joint capsules and recesses should not be confused with synovial hypertrophy.

Sonography of Wrist Ganglion Cysts: Which Location Is Most Common?

OBJECTIVES

The literature states that wrist ganglion cysts are most commonly dorsal; however, our experience suggests a volar location is more common. The purpose of this study was to identify the locations of ganglion cysts of the wrist as imaged with sonography.

METHODS

After Institutional Review Board approval with informed consent waived, retrospective review of wrist sonography reports from January to April 2016 was completed. Only patients who had a comprehensive evaluation that included the dorsal and volar wrist were included. Ultrasound images were reviewed to characterize wrist ganglion cysts.

RESULTS

The study group consisted of 98 subjects (78% female, 22% male) (median age, 51 years; range 13-79) with 124 wrist ganglion cysts, where 69% (86 of 124) were volar and 31% (38 of 124) were dorsal. Ganglion cysts were located between the radial artery and flexor carpi radialis in 63% (78 of 124), followed by a dorsal location superficial to the scapholunate ligament in 20% (25 of 124), other dorsal locations in 11% (13 of 124), and other volar locations in 6% (8 of 124). With dorsal ganglion cysts, the scapholunate ligament when imaged appeared normal in 91% (20 of 22). Ganglion cysts were multilocular/multilobular in all subjects.

CONCLUSIONS

The most common location for wrist ganglion cysts is in the volar wrist, particularly between the radial artery and flexor carpi radialis tendon, appearing multilocular or multilobular with a mean largest dimension of 1.0 cm. Given the propensity of ganglion cysts to occur at this site, attention to this area when imaging the wrist with sonography or magnetic resonance imaging should be considered.

[Assessment of ligament and tendon injuries of the elbow using magnetic resonance imaging]

An overview about the normal anatomy and frequent pathologies of tendons and ligaments of the elbow using MRI will be provided. The unique joint configuration and articulation, as well as passive ligamentous and active muscle structures as well as the unique configuration of the articulating components of the elbow contribute to joint stabilization. MRI is an essential imaging modality in patients with ligamentous injuries including the sequelae of joint dislocation as well as chronic pathologies such as long-standing and refractory tendinopathies. Ideally, when reporting MRI of the elbow, the joint is separated into its four compartments, anterior, posterior, medial and lateral, allowing precise, comprehensive and structured reporting.

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.

Greater Trochanteric Pain Syndrome: Abductors, External Rotators

Chronic pain and tenderness at the greater trochanter characterizes trochanteric pain syndrome. For a long time, trochanteric bursitis was thought to be the only underlying pathology; however, investigations have shown that tendinopathy of the abductors is the main cause, followed by iliotibial band thickening and, to a lesser extent, abductor tendon tears. Trochanteric bursitis can be associated with it. On magnetic resonance imaging (MRI), peritrochanteric T2 abnormalities are evident in greater trochanteric pain syndrome. However, this is also frequently encountered in asymptomatic patients. In the postoperative setting, patients with total hip arthroplasties and transtendinous lateral or posterior surgical access are prone to tendon injury. Symptomatic patients typically present with tendon tears, whereas peritrochanteric fluid, thickening, and signal alterations of the abductors and fatty atrophy of the gluteus minimus muscle are often encountered in asymptomatic postoperative hips. MRI and ultrasound are proven and reliable imaging modalities in patients with greater trochanteric pain syndrome. Awareness of typical imaging findings, in particular in postoperative patients, are helpful in the evaluation of patients.

Increased Magnetic Resonance Imaging Signal of the Lateral Patellar Facet Cartilage: A Functional Marker for Patellar Instability?

BACKGROUND

In the knee joint, predisposition for patellar instability can be assessed by an abnormal Insall-Salvati index, tibial tuberosity-trochlear groove (TTTG) distance, and abnormal shape of patella and trochlea. Given the complex anatomic features of the knee joint with varying positions of the patella during motion, the presence of a single or even a combination of these factors does not inevitably result in patellar instability. After trocheoplasty in patients with trochlear dysplasia, assessment of trochlear cartilage and subchondral bone is limited due to postoperative artifacts. Identification of presence of edema in the patellar cartilage may be helpful to identify patellar instability before and after surgery in these patients.

PURPOSE

To determine whether increased signal intensity of the lateral patellar facet cartilage or measurements of abnormal patellofemoral articulation are associated with patellar instability before and after trochleoplasty.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-two patients with clinical diagnosis of patellar instability who underwent trochleoplasty, with magnetic resonance imaging (MRI) of the knee before and after surgery, were identified. The following observations and measurements were obtained in preoperative imaging: Insall-Salvati ratio, tibial tuberosity-trochlear groove (TTTG) distance, patellar shape (Wiberg), trochlear shape (Hepp), and edema in the lateral patellar facet cartilage. At 3 to 12 months after surgery, the presence or absence of edema in the cartilage of the lateral facet of the patella, the trochlear shape, and TTTG distance were reassessed. Wilcoxon matched-pairs signed rank test and Student t test were used. Interreader agreement was calculated as the Cohen κ or paired Student t test.

RESULTS

Increased cartilage signal was present in 20 patients before trochleoplasty and in 4 after trochleoplasty. Insall-Salvati ratio was greater than 1.20 in 20 patients. Patellar shape was greater than type 2 in 18 patients. Trochlear shape was greater than type 2 in 21 patients before and 7 after trochleoplasty. Mean TTTG distance was 14 mm before and 10 mm after surgery. When results before and after surgery were compared, a significant difference was found for cartilage signal, TTTG distance, and trochlear shape. Agreement for observations was moderate to substantial, and no significant differences were found for interreader agreement ( P > .05).

CONCLUSION

Patellar cartilage at the lateral facet of the patella can be assessed after trochleoplasty despite postoperative artifacts in the trochlea. A decrease of patellar edema seems to be associated with improved femoropatellar articulation. Moreover, patellar edema may be used as a functional criterion of patellofemoral instability. This would provide additional information compared to morphologic criteria which just describe predisposing factors for femoropatellar instability.

4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty

OBJECTIVE

The purpose was to evaluate the intra- and inter-observer reliability of combined quantitative 3D-volumetric single-photon emission computed tomography (SPECT)/CT analysis including size, intensity and localisation of tracer uptake regions and total knee arthroplasty (TKA) position.

MATERIALS AND METHODS

Tc-99m-HDP-SPECT/CT of 100 knees after TKA were prospectively analysed. The anatomical areas represented by a previously validated localisation scheme were 3D-volumetrically analysed. The maximum intensity was recorded for each anatomical area. Ratios between the respective value and the mid-shaft of the femur as the reference were calculated. Femoral and tibial TKA position (varus-valgus, flexion-extension, internal rotation- external rotation) were determined on 3D-CT. Two consultant radiologists/nuclear medicine physicians interpreted the SPECT/CTs twice with a 2-week interval. The inter- and intra-observer reliability was determined (ICCs). Kappa values were calculated for the area with the highest tracer uptake between the observers.

RESULTS

The measurements of tracer uptake intensity showed excellent inter- and intra-observer reliabilities for all regions (tibia, femur and patella). Only the tibial shaft area showed ICCs <0.89. The kappa values were almost perfect (0.856, p < 0.001; 95 % CI 0.778, 0.922). For measurements of the TKA position, there was strong agreement within and between the readings of the two observers; the ICCs for the orientation of TKA components for inter- and intra-observer reliability were nearly perfect (ICCs >0.84).

CONCLUSION

This combined 3D-volumetric standardised method of analysing the location, size and the intensity of SPECT/CT tracer uptake regions ("hotspots") and the determination of the TKA position was highly reliable and represents a novel promising approach to biomechanics.

Isolated pancreatic tuberculosis: a case report and radiological comparison with cystic pancreatic lesions

Pancreatic tuberculosis is rare and can occur in the absence of evidence of tuberculosis elsewhere in the body. Here we review the radiological appearance of pancreatic tuberculosis and compare it with other cystic pancreatic lesions, including common lesions (pseudocysts, serous or mucinous cystadenomas, intraductal papillary mucinous neoplasm) and rare lesions such as solid pseudopapillary tumors, etc. Their typical localizations within the pancreas and their malignant potential are presented. Knowledge of these can assist radiologists and clinicians in selecting the best approach towards making the correct diagnosis.