What is next generation sequencing?

Next generation sequencing (NGS), massively parallel or deep sequencing are related terms that describe a DNA sequencing technology which has revolutionised genomic research. Using NGS an entire human genome can be sequenced within a single day. In contrast, the previous Sanger sequencing technology, used to decipher the human genome, required over a decade to deliver the final draft. Although in genome research NGS has mostly superseded conventional Sanger sequencing, it has not yet translated into routine clinical practice. The aim of this article is to review the potential applications of NGS in paediatrics.

The prevalence of a large Hill-Sachs lesion that needs to be treated

BACKGROUND

A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence of shoulder instability. However, there are few reports describing the prevalence of Hill-Sachs lesions that engage with the glenoid. The purpose of this study was to clarify the prevalence of engaging Hill-Sachs lesions using the concept of the glenoid track.

MATERIALS AND METHODS

The computed tomography images of 100 consecutive patients with unilateral recurrent anterior shoulder dislocations were assessed. An image in the plane perpendicular to the rotator cuff attachment was reconstructed from the DICOM (Digital Imaging and Communications in Medicine) data, and the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured. The location of the Hill-Sachs lesion in the glenoid track was assessed, and when the Hill-Sachs lesion extended medially over the glenoid track, it was defined as an "engaging Hill-Sachs lesion."

RESULTS

Engaging Hill-Sachs lesions were observed in 7 of 100 cases (7%). There were 2 types of Hill-Sachs lesions: a large and wide type (3 cases) and a narrow but medially located type (4 cases). All cases with an engaging Hill-Sachs lesion had a large bony defect of the glenoid at the same time.

CONCLUSIONS

In our series of consecutive 100 cases, the prevalence of engaging Hill-Sachs lesions was 7%. There were 2 types of Hill-Sachs lesions: a wide and large type and a narrow but medially located type.

Access to outpatient care for adult rotator cuff patients with private insurance versus Medicaid in North Carolina

BACKGROUND

Access to orthopaedic care for pediatric patients has been shown in previous studies to be decreased for patients with Medicaid compared with those with private insurance. The relationship between type of insurance and access to care for adult patients with acute rotator cuff tears has not yet been examined. This study aimed to determine if type of health insurance would have an impact on access to care for an adult patient with an acute rotator cuff tear.

METHODS

Seventy-one orthopaedic surgery practices within the state of North Carolina were randomly selected and contacted on 2 different occasions separated by 3 weeks. The practices were presented with an appointment request for a fictitious 42-year-old man with an acute rotator cuff tear. Insurance status was reported as Medicaid for the first call and as private insurance during the second call.

RESULTS

Of the 71 practices contacted, 51 (72%) offered the patient with Medicaid an appointment, whereas 68 (96%) offered the patient with private insurance an appointment. The difference in these rates was statistically significant (P < .001). The likelihood of patients with private insurance obtaining an appointment was 8.8 times higher than that of patients with Medicaid (95% CI: 2.5, 31.5).

CONCLUSION

For patients with acute rotator cuff tears, access to care is decreased for those with Medicaid compared with those with private insurance. Patients with private insurance are 8.8 times more likely than those with Medicaid to obtain an appointment.

LEVEL OF EVIDENCE

Basic science, survey study.

Elbow-specific clinical rating systems: extent of established validity, reliability, and responsiveness

BACKGROUND

The modern standard of evaluating treatment results includes the use of rating systems. Elbow-specific rating systems are frequently used in studies aiming at elbow-specific pathology. However, proper validation studies seem to be relatively sparse. In addition, these scoring systems might not always be used for appropriate populations of interest. Both of these issues might give rise to invalid conclusions being reported in the literature. Our aim was to investigate the extent to which the available elbow-specific outcome measurement tools have been validated and the quality of the validation itself. We also aimed to provide characteristics of the populations used for validation of these scales to enable clinicians to use them appropriately.

METHODS

A literature search identified 17 studies of 12 different elbow-specific scoring systems. These were assessed for validity, reliability, and responsiveness characteristics. The quality of these assessments was rated according to the Consensus Based Standards for the Selection of Health Measurement Instruments (COSMIN) checklist criteria, a standardized and validated tool developed specifically for this purpose.

RESULTS

Currently, the only elbow-specific rating system that is validated using high-quality methodology is the Oxford Elbow Score, a patient-administered outcome measure tool that has been validated on heterogeneous study populations.

CONCLUSION

Other rating systems still have to be proven in the future to be as good as the Oxford Elbow Score for clinical or research purposes. Additional validation studies are needed.

Biomechanical evaluation of subpectoral biceps tenodesis: dual suture anchor versus interference screw fixation

BACKGROUND

Subpectoral biceps tenodesis has been reliably used to treat a variety of biceps tendon pathologies. Interference screws have been shown to have superior biomechanical properties compared to suture anchors; although, only single anchor constructs have been evaluated in the subpectoral region. The purpose of this study was to compare interference screw fixation with a suture anchor construct, using 2 anchors for a subpectoral tenodesis.

METHODS

A subpectoral biceps tenodesis was performed using either an interference screw (8 × 12 mm; Arthrex) or 2 suture anchors (Mitek G4) with #2 FiberWire (Arthrex) in a Krackow and Bunnell configuration in seven pairs of human cadavers. The humerus was inverted in an Instron and the biceps tendon was loaded vertically. Displacement driven cyclic loading was performed followed by failure loading.

RESULTS

Suture anchor constructs had lower stiffness upon initial loading (P = .013). After 100 cycles, the stiffness of the suture anchor construct "softened" (decreased 9%, P < .001), whereas the screw construct was unchanged (0.4%, P = .078). Suture anchors had significantly higher ultimate failure strain than the screws (P = .003), but ultimate failure loads were similar between constructs: 280 ± 95 N (screw) vs 310 ± 91 N (anchors) (P = .438).

CONCLUSION

The interference screw was significantly stiffer than the suture anchor construct. Ultimate failure loads were similar between constructs, unlike previous reports indicating interference screws had higher ultimate failure loads compared to suture anchors. Neither construct was superior with regards to stress; although, suture anchors could withstand greater elongation prior to failure.

A proposal for classification of the superior transverse scapular ligament: variable morphology and its potential influence on suprascapular nerve entrapment

BACKGROUND

The suprascapular region is the most common site of suprascapular nerve entrapment. The aim of the present study was to determine the morphologic variation of the superior transverse scapular ligament (STSL) and measure the reduction in size of the suprascapular opening. Other structures that might be potentially significant during open and arthroscopic procedures in this region are also described.

MATERIALS AND METHODS

The study used 86 randomized formalin-fixed human cadaveric shoulders. After dissection of the suprascapular region, the following measurements were defined and collected for every STSL: length, proximal width, distal width, and thickness at the proximal and distal ends. Measurements were also taken of the area of the suprascapular opening (aSSO) and the middle width of the suprascapular opening (mwSSO).

RESULTS

Three types of STSL may be distinguished: a fan-shaped type (54.6%), a band-shaped type (41.9%), and a bifid type (3.5%). Statistically significant differences between the specimens with fan-shaped and band-shaped types of STSL were observed in aSSO and mwSSO of the suprascapular opening. Anterior coracoscapular ligaments (ACSL) were present in 44 of 86 shoulders. The aSSO and mwSSO were smaller in specimens with an ACSL than in those without; however, this difference was only significant in the band-shaped type of STSL.

CONCLUSION

Knowledge of the morphologic variations of STSL presented in this study is important for better understanding the possible anatomic conditions that can promote suprascapular nerve entrapment and should be taken into particular consideration during surgical and arthroscopic procedures around the suprascapular notch.

The effects of prosthetic humeral head shape on glenohumeral joint kinematics: a comparison of non-spherical and spherical prosthetic heads to the native humeral head

BACKGROUND

The purpose of this study was to quantitatively evaluate the effect of the prosthetic humeral head shape on rotational range of motion and glenohumeral joint kinematics.

METHODS

Six fresh-frozen cadaveric shoulders were tested in multiple positions under anatomic muscle loading. Specimens were tested for the native head, and then the spherical and non-spherical prosthetic heads were randomly implanted in the same stem to preserve the center of rotation. Rotational range of motion was measured with 3.3 Nm of torque. Glenohumeral joint kinematics was quantified by the position vectors of the humeral head apex (HHA) and geometric center of the humeral head (GCHH) to calculate translation of HHA and GCHH per degree of humeral rotation.

RESULTS

The non-spherical prosthetic head replicated the native head shape more accurately than the spherical prosthetic head. Between the non-spherical and native heads, there was no statistical difference in rotational range of motion (P > .05), but a statistical difference in HHA and GCHH translation was found at 60° of scapular plane abduction in the interval from 30° of internal rotation to neutral rotation and at 30° of forward flexion plane abduction in the interval from 30° of external rotation to maximum external rotation, respectively (P < .05). The spherical head significantly decreased rotational range of motion (P < .05), increased HHA translation per degree (P < .05), and decreased GCHH translation per degree (P < .05) in multiple positions compared with the native humeral head.

CONCLUSION

The custom, non-spherical prosthetic head more accurately replicated the head shape, rotational range of motion, and glenohumeral joint kinematics than the commercially available, spherical prosthetic head compared with the native humeral head.

Combining tissue repair and tissue engineering; bioactivating implantable cell-free vascular scaffolds

Synthetic replacement grafts for heart valves and small-diameter blood vessels such as coronary arteries have the potential to circumvent many of the limitations of currently available autologous grafting materials. Cell-free material incorporating biologically active compounds may guide the formation of fully autologous new tissue in situ derived from host cells after implantation. Inspiration for such bioactive compounds and their dynamics can be found in in vivo repair processes. Molecules such as stromal cell-derived factor 1α (SDF1α) that can attract progenitor cells from the bloodstream and modulate immune responses may be able to improve neotissue development in cell-free vascular and valvular grafts. Advances in the development of fully synthetic molecules and scaffold materials allow the spatial and temporal control of biologically active factors, enabling tissue engineers to mimic complex cellular signalling. This review focuses on combining knowledge of the molecular dynamics of factors involved in in vivo damage repair with the possibilities offered by newly developed synthetic materials. This approach has lead to encouraging results in the field of in situ vascular tissue engineering, and can ultimately lead to the development of off-the-shelf available vascular and valvular replacement grafts.

Electromyographic analysis of reverse total shoulder arthroplasties

BACKGROUND

Understanding how reverse total shoulder arthroplasty (RTSA) affects muscle activation may help refine it. This study evaluated deltoid and upper trapezius activity during shoulder abduction, flexion, and external rotation in RTSA recipients.

METHODS

Fifty individuals were recruited for this study: 33 were ≥6 months postunilateral RSTA, and 17 comprised our control group. Control individuals easily performed all functional tasks and had no history of shoulder pathology or pain. RTSA participants were divided into 3 groups according to implant design. Participants performed weighted and unweighted abduction in the coronal plane, forward flexion in the sagittal plane, and unweighted external rotation. Electromyography activation of the anterior, lateral, and posterior aspects of the deltoid and the upper trapezius muscles was recorded bilaterally. Motion capture using passive reflective markers quantified 3-dimensional motions of both shoulders.

RESULTS

During abduction and flexion, deltoid and upper trapezius activity was significantly increased in RTSA shoulders. Posterior deltoid activation was highest in shoulders with the medial glenosphere/lateral humerus implant. Medial glenosphere/medial humerus shoulders were most similar to the control group's anterior, lateral, and posterior deltoid muscle activation during weighted flexion.

CONCLUSIONS

RTSA increases muscle activation compared with normal shoulders. RTSA often restores stability and motion but not normal deltoid or upper trapezius activation. Increased muscle activation in shoulders with RTSA suggests less efficiency. RTSAs with lateral or medial glenosphere centers of rotation had mostly similar muscle activation. Average posterior deltoid activation did not exceed 20% of maximal voluntary isometric contraction for any group during unweighted external rotation, and differences between groups were <5% maximal voluntary isometric contraction.

Development and validation of a new method of 3-dimensional assessment of glenoid and humeral component position after total shoulder arthroplasty

HYPOTHESIS

This study evaluates the intrarater and inter-rater reliability of 3-dimensional (3D) computed tomography (CT) measurements of component position and alignment after total shoulder arthroplasty (TSA).

MATERIALS AND METHODS

Two patients and one whole-body cadaver with anatomic TSA implants underwent CT scans of the shoulder with a 0.6-mm slice thickness in two different arm positions (supine arm down or lateral decubitus arm up) on the same day. Test-retest reliability of component measurements within and between 5 observers was determined, as were any differences in measurements based on arm position. Precision and 95% confidence intervals were determined for the following measurements: glenoid component position (anterior-posterior, superior-inferior, and medial-lateral), glenoid component orientation (version, inclination, and roll), and humeral-glenoid alignment (HGA). HGA was defined in the anterior-posterior and superior-inferior dimensions.

RESULTS

The range of precision for measurement of the position of the glenoid implant across observers was between 0.2 and 0.5 mm, and for orientation, it was between 1.2° and 1.5°. The range of precision for measurement of HGA across observers was between 0.7 and 1.2 mm. There was no significant difference in the precision of measurements between the two imaged arm positions.

DISCUSSION AND CONCLUSION

The described method of 3-dimensional CT imaging can provide very precise and reproducible assessment of component position after TSA. Ultimately, correlation of these measurements with clinical outcome, anatomic factors, prosthetic design, and surgical factors will allow for better understanding of the causes of implant failure.

Bone strength in children: understanding basic bone biomechanics

The term 'bone strength' is often used to explain why some children's bones fracture while others do not. Bone strength describes the general integrity of bone; a complex organ with multiple structural levels and an array of biomechanical properties. Key biomechanical properties of bone include stiffness, toughness, ductility and mechanical strength. When measured in bone tissue, these properties are known as the intrinsic biomechanical properties of bone, while the extrinsic biomechanical properties reflect the structural behaviour of a whole bone. The fine balance between various and often opposing intrinsic and extrinsic biomechanical properties of bone is crucial for fracture resistance. When clinically evaluating a child with a fracture, an understanding of basic bone biomechanics helps determine the likely mechanism of injury and whether underlying reduced fracture resistance exists.

Achieving fixation in glenoids with superior wear using reverse shoulder arthroplasty

BACKGROUND

Superior glenoid wear is a common challenge with reverse shoulder arthroplasty and, if left uncorrected, can result in superior glenoid tilt, which increases the risk of aseptic glenoid loosening. This study evaluates the impact of an E2 superior defect on reverse shoulder glenoid fixation in composite scapulae after correction of glenoid tilt by use of 2 different glenoid reaming techniques: eccentric reaming and off-axis reaming.

MATERIALS AND METHODS

A superior glenoid defect was created in 14 composite scapulae. The superior defect was corrected by 2 different glenoid reaming techniques: (1) eccentric reaming with implantation of a standard glenoid baseplate and (2) off-axis reaming with implantation of a superior-augment glenoid baseplate. Each corrected superior-defect scapula was then cyclically loaded (along with a control group consisting of 7 non-worn scapulae) for 10,000 cycles at 750 N; glenoid baseplate displacement was measured for each group to quantify fixation before and after cyclic loading.

RESULTS

Regardless of the glenoid reaming technique or the glenoid baseplate type, each standard and superior-augment glenoid baseplate remained well fixed in this superior-defect model scenario after cyclic loading. No differences in baseplate displacement were observed either before or after cyclic loading between groups.

DISCUSSION

Our results suggest that either glenoid reaming technique may be used to achieve fixation in the clinically challenging situation of superior wear with reverse shoulder arthroplasty.

LEVEL OF EVIDENCE

Basic science, biomechanical study.

Percutaneous balloon humeroplasty for Hill-Sachs lesions: a novel technique

INTRODUCTION

Hills-Sachs lesions are commonly associated with anterior shoulder dislocations and can be a source of recurrent instability. Studies have shown that, even after soft tissue repair of a Bankart lesion, there is still a risk for redislocation in a patient with significant bony defects. The purpose of this study is to ascertain whether balloon humeroplasty is an effective technique of reducing acute Hill-Sachs defect in a cadaveric model.

METHODS

Eighteen cadaveric humerii dissected free of soft tissue were used for this study. Hill-Sachs lesions were created in a reproducible manner in the anatomical posterolateral aspect of the head with a mallet edge. An inflatable balloon tamp (balloon, IBT) was used to reduce the lesion via a small transcortical window. Cement was used to fill the void created by the balloon. We utilized computed tomography (CT) to collect volume data of each humeral head pre- and post-procedure. From this data, we calculated the volume of the Hill-Sachs defect and the percent corrected. A paired t test was performed to analyze the data statistically.

RESULTS

The average prereduction Hill-Sachs defect volume was 1515.5 mm(3). The average post-reduction lesion residual volume was 31 mm(3) with 99.3% reduction to the original humeral head volume. The Hill-Sachs lesion reduction was statistically significant with P value of .0004.

CONCLUSION

Balloon humeroplasty proved to be an effective technique for reducing Hill-Sachs lesions in a cadaveric model. This technique may be used as an adjunct to arthroscopic versus open Bankart procedure for engaging acute Hill-Sachs lesions.

Endoscopic DCR using bipedicled interlacing mucosal flaps

OBJECTIVE

Obstruction of the nasolacrimal duct is a relatively common condition that affects patients of all ages, races, and sexes. The surgical gold standard for complete nasolacrimal duct obstruction and dacryocystitis is dacryocystorhinostomy (DCR). The purpose of this study was to describe a novel, bipedicled interlacing mucosal sparing flap technique for endoscopic DCR (eDCR).

METHODS

A posteriorly based mucosal flap over the fundus is combined with a novel, anteriorly based mucosal flap over the intraosseus portion of the nasolacrimal duct (NLD). This exposes a wide area of the maxillary bone, allowing for exposure and identification of the NLD/sac complex in a safer, more inferior position. The interlacing mucosal flaps may be replaced at the conclusion of the procedure, thereby minimizing bone exposure and maintaining excellent long-term patency.

RESULTS

The authors have utilized this technique in 55 procedures with 100% positive identification of the NLD and lacrimal sac, 0% complication rate, 100% anatomical patency rate, and 96.4% success rate after a minimal follow-up of 6 months.

DISCUSSION

The bipedicled interlacing flap technique for eDCR provides for safe and reproducible identification of the NLD and lacrimal sac while minimizing bone exposure and restenosis rate.

CONCLUSION

The bipedicled interlacing flap technique for eDCR provides for safe and reproducible identification of the NLD and lacrimal sac while minimizing bone exposure and restenosis rate.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:794-797, 2018.

Age-related changes affect rat rotator cuff muscle function

BACKGROUND

The influence of age on rotator cuff function and muscle structure remains poorly understood. We hypothesize that normal aging influences rotator cuff function, muscle structure, and regulatory protein expression in an established rat model of aging.

METHODS

Seventeen rats were obtained from the National Institute on Aging. The supraspinatus muscles in 11 middle-aged (12 months old) and 6 old (28 months old) rats were studied for age-related changes in rotator cuff neuromuscular function by in vivo muscle force testing and electromyography (EMG). Changes in muscle structure and molecular changes were assessed with quantitative immunohistochemistry for myogenic determination factor 1 (MyoD) and myogenic factor 5 (Myf5) expression.

RESULTS

Old animals revealed significantly decreased peak tetanic muscle force at 0.5 N and 0.7 N preload tension (P < .05). The age of the animal accounted for 20.9% of variance and significantly influenced muscle force (P = .026). Preload tension significantly influenced muscle force production (P < .001) and accounted for 12.7% of total variance. There was regional heterogeneity in maximal compound motor action potential (CMAP) amplitude in the supraspinatus muscle; the proximal portion had a significantly higher CMAP than the middle and distal portions (P < .05). The expression of muscle regulatory factors MyoD and Myf5 was significantly decreased in old animals compared with middle-aged animals (P < .05).

CONCLUSIONS

The normal aging process in this rat model significantly influenced contractile strength of the supraspinatus muscle and led to decreased expression of muscle regulatory factors. High preload tensions led to a significant decrease in force production in both middle-aged and old animals.

Geometry of the proximal humeral articular surface in young children: a study to define normal and analyze the dysplasia due to brachial plexus birth palsy

BACKGROUND

Little is known regarding the morphology of the proximal humerus in growing children. This study reports bilateral magnetic resonance imaging measurements in children with internal rotation contractures from birth palsy, hypothesizing that dysplasia alters normal humeral sphericity and symmetry.

METHODS

We studied 25 children with unilateral internal rotation contractures (mean age, 3.7 years) for humeral shape by bilateral magnetic resonance imaging studies at the mid-glenoid level. Local radii of curvature were compared for symmetry and orientation.

RESULTS

Neither side showed uniform radii (sphericity), but normal humeri showed symmetry lost in dysplasia. Internal rotation contractures were correlated with flattening of the anterior humeral head (P = .0002). All heads were flatter in the region of articular contact. The skew axis (the largest cross-sectional diameter of the proximal humerus) was collinear with the articular surface centerline in normal humeri, an alignment often lost with dysplasia, resulting in a skew axis angle. The severity of glenoid deformity correlated with progressive posterior displacement of the humeral head center (P < .0003).

CONCLUSION

The normal humeral articular surface in the young child is not spherical and is flatter in the middle than at the periphery but is symmetric about its central axis. Internal rotation contractures result in loss of this symmetry with characteristic flattening of the anterior humeral head and development of a skew axis angle.

CLINICAL RELEVANCE

Posterior displacement of the humeral head center of rotation beyond 50% of the calculated head radius warrants vigilance and possibly surgical intervention because there is a high likelihood for development of a pseudoglenoid.

Increased interleukin 1β levels in the subacromial fluid in diabetic patients with rotator cuff lesions compared with nondiabetic patients

BACKGROUND

Diabetic patients have a high prevalence of shoulder pain and stiffness. Interleukin (IL) 1β was reportedly correlated with shoulder stiffness and decreased shoulder function. We retrospectively compared the expression of IL-1β in the subacromial synovial fluid between diabetic and nondiabetic patients with rotator cuff tearing.

MATERIALS AND METHODS

We enrolled 68 patients with rotator cuff tearing (23 diabetic patients and 45 nondiabetic patients). The preoperative sum of range-of-motion deficit (SROMD), Constant score, and visual analog scale (VAS) score were obtained. Intraoperatively, subacromial synovial fluid was collected for the IL-1β level measurement. Comparisons of IL-1β levels, Constant scores, SROMD, and VAS scores between diabetic and nondiabetic patients were analyzed with the Mann-Whitney U test.

RESULT

Diabetic patients with rotator cuff tearing had significantly increased subacromial IL-1β levels (P = .048), SROMD (P < .001) and VAS scores (P = .022) and lower Constant scores (P < .001) than nondiabetic patients. The IL-1β levels in the subacromial fluid were significantly correlated with the Constant score (r = -0.477, P < .001), VAS score (r = 0.698, P < .001), and SROMD (r = 0.293, P = .015) in all patients.

CONCLUSION

The elevated IL-1β levels in the subacromial fluid of patients with diabetes may explain the likelihood of pain and shoulder stiffness developing in these patients. We suggest more aggressive treatment for rotator cuff lesions in diabetic patients.

A straightforward guide to the basic science behind cardiovascular cell-based therapies

It has been over a decade since the concept of cell-based therapy was coined as a method to treat patients who suffered the consequences of myocardial infarction (MI). Shortly after promising preclinical results emerged, a rapid translation to the clinic was made using stem cells isolated from a variety of sources, including bone marrow mononuclear cells (BM-MNC), mesenchymal stem cells (MSC) and cardiac progenitor cells (CPC). The hypothesis was that transplanted stem cells would provide cues that enhance the wound healing process, and locally differentiate into new contractile cardiac tissue. However, although the clinical trials have been shown to be safe, only a relatively small effect on cardiac function has been observed. It has become clear that each cell type applied in cell-based therapy has its own ability for cardiac repair. Basic knowledge of each cell population's behaviour and its ability to interfere in different stages of post-MI wound healing may enable us to design an optimised cell-based therapy.

Coracoid process x-ray investigation before Latarjet procedure: a radioanatomic study

BACKGROUND

The purpose of this study was to determine whether a preoperative radiologic assessment of the coracoid process is predictive of the amount of bone available for coracoid transfer by the Latarjet procedure.

MATERIAL

Thirty-five patients with anterior instability undergoing a Latarjet procedure were included. A preoperative radiologic assessment was performed with the Bernageau and true anteroposterior (true AP) views.

METHODS

The length of the coracoid process was measured on both radiographic views and the values were compared with the length of the bone block during surgery. Statistical analysis was carried out by ANOVA and Wilcoxon tests (P < .05).

RESULTS

On radiologic examination, the mean coracoid process length was 29 ± 4 and 33 ± 4 mm on the Bernageau and true AP views, respectively. The mean bone block length during surgery was 21.6 ± 2.7 mm. A significant correlation was found (P = .032) between the coracoid process length on the true AP view and the intraoperative bone block length.

DISCUSSION

Preoperative planning for the Latarjet procedure, including graft orientation and screw placement, requires knowledge of the length of coracoid bone available for transfer. This can be facilitated with the use of preoperative standard radiographs, thus avoiding computed tomography. This planning allows the detection of coracoid process anatomic variations or the analysis of the remaining part of the coracoid process after failure of a first Latarjet procedure to avoid an iliac bone graft.

CONCLUSION

Radiologic preoperative coracoid process measurement is an easy, reliable method to aid preoperative planning of the Latarjet procedure in primary surgery and reoperations.

Effect of immobilization on rotator cuff reconstruction with acellular dermal matrix grafts in an animal model

INTRODUCTION

Using a rat model we determined whether immobilization improves tendon-to-bone healing and tendon maturation after rotator cuff reconstruction with acellular dermal matrix (ADM) grafts.

METHODS

Sprague-Dawley rats were randomly assigned to 3 equal groups. All rats were subjected to rotator cuff reconstruction and their shoulder was not immobilized (N-IM controls) or immobilized for 2- or 6 weeks immediately thereafter (2- and 6-IM groups, respectively). After detaching the rotator cuff including the full-thickness supraspinatus tendon at its insertion on the greater tuberosity, a defect was created. ADM patches were used for rotator cuff reconstruction. Specimens obtained 2, 6, and 12 weeks after surgery were subjected to semiquantitative histomorphological measurements to assess cellularity, vascularity, and collagen organization. In addition, specimens at 12 weeks were submitted for biomechanical analysis.

RESULTS

Cell density decreased over time in all 3 groups; there was no significant difference among the groups at 2 weeks. However, the 6-IM group harbored more cells in the tendon-to-bone interface than the 2-IM group at 6 weeks and the N-IM group at 12 weeks. Vascularity in the interface decreased over time in the N-IM and 2-IM groups but not the 6-IM rats. At 6 and 12 weeks, the 2-IM group manifested better collagen organization than the other groups. The 2-IM group exhibited higher ultimate load-to-failure than the other groups. Stiffness was similar in the 3 groups.

CONCLUSION

Remodeling of ADM grafts placed in rat rotator cuff defects was promoted by 2- but not 6-week immobilization.

The effect of stem surface treatment and material on pistoning of ulnar components in linked cemented elbow prostheses

BACKGROUND

The ulnar component of a total elbow replacement can fail by "pistoning." Stem surface treatments have improved stability at the stem-cement interface but with varied success. This study investigated the role of surface treatment and stem substrate material on implant stability under axial loading.

MATERIALS AND METHODS

Sixty circular stems (diameter, 8 mm) made of cobalt chrome (n = 30) or titanium (n = 30) had different surfaces: smooth, sintered beads, and plasma spray. The surface treatment length was either 10 mm or 20 mm. Stems were potted in bone cement, allowed to cure for 24 hours, and tested in a materials testing machine under a compressive staircase loading protocol. Failure was defined as 2 mm of push-out or completion of the protocol. Two-way analyses of variance compared the effects of surface treatment and substrate material on interface strength and motion.

RESULTS

Significant interactions were found between surface treatment and substrate material for both interface strength and motion (P < .05). For titanium, the 20-mm beaded stems had greater interface strength than all other stems (P < .05) and had less motion than the 10-mm plasma-spray and smooth stems (P < .05). For cobalt chrome, the 20-mm beaded stems showed greater interface strength (P < .05) and similar motion (P > .05) to the 20-mm plasma-spray stems (P < .05), which outperformed all other stems (P < .05). Mechanisms of catastrophic failure varied: smooth stems debonded at the stem-cement interface, beaded stems experienced debonding of the beads from the stem, and plasma-spray stems showed loss of frictional force between the surface treatment and cement.

DISCUSSION AND CONCLUSION

Stem surface treatment can enhance ulnar component stability but is dependent on substrate material.

Pulse oximetry in children

Pulse oximetry is routinely used in hospitals in high-income settings, but its theoretical basis is often poorly understood. This paper summarises the physiological background, technological basis and limitations of pulse oximetry.

Measurements of the ispilateral capitellum can reliably predict the diameter of the radial head

BACKGROUND

There is no validated method to determine the correct diameter of a radial head implant when the radial head is too comminuted to function as a template or during revision surgery when the radial head has been previously excised. The purpose of this study was to determine if ipsilateral capitellar dimensions could be used to predict the diameter of the radial head; and hence to assist with implant selection.

METHODS

Computer tomography scans of 50 normal elbows were used to generate 3D models. Measurements of the radial head included the maximum (Dmax) and minimum (Dmin) outer diameters and the maximum (Dishmax) and minimum (Dishmin) articular dish diameters. Measurements of the humerus included the width of the capitellum (CAPwidth), and the width from the lateral aspect of the capitellum to the lateral trochlear ridge (CAP-TROCHridge). Relationships were determined with Pearson bivariate coefficients.

RESULTS

The mean radial head dimensions were Dmax = 24.7 ± 2.3 mm, Dmin = 23.5 ± 2.3 mm, Dishmax = 18.2 ± 1.9 mm and Dishmin = 16.8 ± 1.7 mm. The mean capitellar measurements were CAPwidth (18.4 ± 1.4 mm) and CAP-TROCHridge (23.0 ± 2.1 mm). The most significant correlations were found between Dmax and CAP-TROCHridge (R = .90, P < .001) and Dmin and CAP-TROCHridge (R = .90, P < .001).

DISCUSSION

Radiologic measurements of the capitellum are useful in the estimation of native radial head diameter. The CAP-TROCHridge measurement was very strongly correlated with both the maximum and minimum diameters of the radial head. This suggests that CAP-TROCHridge may be useful to accurately predict the native radial head diameter. These morphological relationships were plotted to produce an implant selection chart for radial head sizing applicable to any implant system.

LEVEL OF EVIDENCE

Basic science, anatomy study, CT imaging.