Editorial Commentary: Superior Capsular Reconstructions in Cases of Irreparable Rotator Cuff Tendons Only Partially Restore Anatomy, Yet Significantly Normalize Biomechanics-Without Resorting to Reverse Anatomy

The goal of shoulder superior capsular reconstruction and/or anterior cable reconstructions, at least in terms of biomechanics, is to primarily restore a fulcrum to assist with pain control and functional optimization, with the secondary hope of maintaining cartilage. Fully restoring glenohumeral joint loads with SCR cannot be expected in the setting of persistent tendon insufficiency. Biomechanical studies characterizing shoulder capsular reconstructions have demonstrated anatomic and functional restorations toward normalization when tested with standard biomechanical methods. Glenohumeral abduction, superior humeral head migration, deltoid forces, and glenohumeral contact pressure and area, can be optimized toward the normal intact condition, as measured by motion tracking and pressure mapping in real time, using dynamic actuators. Insofar as restoring normal native anatomy is considered a fundamental priority, with the idea that joint functional longevity is enhanced by preserving anatomy, as surgeons, we should not lose sight of reconstruction over replacement (such as nonanatomic reverse total shoulder arthroplasty) as a favored goal. Anatomy-based reconstructions such as superior capsule or anterior cable reconstruction, may prove over time to be the best primary treatment as knowledge and innovations (technical and medical) develop, with nonanatomic arthroplasty truly being a last resort (yet a clinically viable option when indicated).

Anterior Cable Reconstruction: Prioritize Rotator Cable and Tendon Cord When Considering Superior Capsular Reconstruction

Although distinct in name, the anterior cable of the superior capsule and tendon cord of the supraspinatus are structurally one in the same at the attachment on the greater tuberosity footprint. Force transmission through both structures where they converge and interdigitate at this location is disproportionately high, which has implications on functional impact. Superior capsule reconstruction, and, specifically, the anterior cable of the superior capsule, has been shown to assist in maintaining superior stability and a functional fulcrum of the glenohumeral joint, without overconstraining range of motion. Anterior cable reconstructions have been described for specific indications, including full-thickness tears of the supraspinatus and anterior one-half of the infraspinatus. Cord-like grafts, including long head biceps tendon autografts and semitendinosus allografts, can provide relative technical ease during surgery compared to sheet-like grafts for this indication. Side-to-side sutures between anterior cable reconstruction graft and posterosuperior capsule retension the native capsule to optimize its natural functional role. Accounting for abduction and rotation at the time of fixation and employing "loop-around" fixation sutures (no sutures through the graft), are critical concepts to consider in terms of kinematics and limiting graft failure. With both the biomechanically and clinically based literature demonstrating functionality with maintenance of the superior capsule (and specifically the anterior cable of the capsule), despite rotator cuff tendon insufficiency or irreparability, the anterior cable of the superior capsule should be prioritized when considering full-thickness rotator cuff tears that naturally involve both the capsular cable and the supraspinatus tendon cord. LEVEL OF EVIDENCE: Level V (expert opinion).

Biomechanical Assessment of a V-Shaped Semitendinosus Allograft Anterior Cable Reconstruction for Irreparable Rotator Cuff Tears

PURPOSE

The purpose of this study was to biomechanically assess superior stability, subacromial contact pressures, and glenohumeral kinematics of a V-shaped anterior cable reconstruction with semitendinosus allograft (VST) in a massive rotator cuff tear (MCT) model.

METHODS

Eight cadaveric shoulders (mean age, 66 years; range, 48 to 72 years) were tested with a custom testing system used to evaluate superior translation, subacromial contact pressure, and glenohumeral kinematics at 0°, 20°, and 40° glenohumeral abduction and 0°, 30°, 60°, and 90° of external rotation (ER). Conditions tested included (1) native state, (2) MCT (complete supraspinatus and ½ infraspinatus), a (3) VST. The VST was secured medially on the glenoid with 1 anchor and on the greater tuberosity with a double-row configuration using 4 anchors.

RESULTS

The VST significantly decreased superior translation compared to the MCT at 0° and 20° glenohumeral abduction for 0°, 30°, and 60° humeral rotation and at 40° abduction and 0° degrees humeral rotation (P < .05). Superior translation following the VST remained significantly greater than the intact state at 0° abduction and 60° and 90° ER (P = .039 and 0.007, respectively) and 20° abduction and 30°, 60°, and 90° ER (P = .048, .003, and .004, respectively). The VST restored peak subacromial contact pressure to intact levels for all positions except 40° abduction and 60° ER. The VST did not statistically affect humeral head kinematics compared to the intact condition.

CONCLUSIONS

In a biomechanical model, a VST anterior cable reconstruction partially restores superior stability and reduces peak subacromial contact pressure associated with an MCT, without affecting glenohumeral kinematics. The technique may be a consideration in the treatment of an irreparable MCT with isolated anterior cable disruption.

CLINICAL RELEVANCE

The VST may provide an option for treatment of irreparable MCTs with anterior rotator cable disruption.

Biomechanical analysis of progressive rotator cuff tendon tears on superior stability of the shoulder

BACKGROUND

The biomechanical relationship between irreparable rotator cuff tear size and glenohumeral joint stability in the setting of superiorly directed forces has not been characterized. The purpose of this study was to quantify kinematic alterations of the glenohumeral joint in response to superiorly directed forces in a progressive posterosuperior rotator cuff tear model.

METHODS

Nine fresh-frozen cadaveric shoulders (mean age; 58 years) were tested with a custom shoulder testing system. Three conditions were tested: intact, stage II (supraspinatus) tear, stage III (supraspinatus + anterior half of infraspinatus) tear. At each condition, range of motion and humeral head positions were measured with a "balanced" loading condition, and with a superiorly directed force ("unbalanced loading condition"). At each of the 0°, 20°, and 40° of glenohumeral abduction positions, all measurements were made at 0°, 30°, 60°, and 90° of external rotation (ER). Two-way repeated measures analysis of variance with Tukey post hoc tests were performed for statistical analyses.

RESULTS

With the balanced load, no significant change in superior humeral head position was observed in stage II tears. Stage III tears significantly changed the humeral head position superiorly at 30° and 60° ER at each abduction angle compared with the intact condition (P ≤ .028). With superiorly directed load, stage II and stage III tears both showed statistically significant increases in superior translation at all degrees of ER for all degrees of abduction (P ≤ .035), except stage II tears at 0° ER and 40° abduction (P = .185) compared with the intact condition. Stage II tears showed posterior translations with 30° and 60° ER, both at 20° and 40° of abduction. Stage III tears also showed posterior translations with 90° ER for all abduction angles (P ≤ .039).

CONCLUSION

With superiorly directed loads, complete supraspinatus tendon tears created superior translations at all abduction angles, and posterior instability in the middle ranges of rotation for 20° and 40° of abduction. Larger tears involving the anterior half of the infraspinatus tendon caused significant superior and posterior translations within the middle ranges of ER for all abduction angles. In addition to superior instability, posterior translation should be considered when selecting or developing surgical techniques for large posterosuperior rotator cuff tears.

Anterior Cable Reconstruction Using the Proximal Biceps Tendon for Large Rotator Cuff Defects

Tears of the rotator cuff tendons can occur that do not allow anatomic footprint restoration yet may not be large enough to require a superior capsular reconstruction technique. Typically, these intermediate-sized tears are addressed with a medialized repair or partial repair technique. A partially repaired rotator cuff tendon, however, can lead to a high retear rate, as the repaired tendon is required to serve as both a dynamic tendon and a static ligamentous stabilizer. One potential static support, as a nearby autologous graft donor, is the proximal long head biceps tendon. The purpose of this Technical Note is to describe a surgical technique for an anterior cable reconstruction using the proximal biceps tendon for large rotator cuff defects.

An Ultrasonically Powered Implantable Microprobe for Electrolytic Ablation

Electrolytic ablation (EA) is a promising nonthermal tumor ablation technique that destroys malignant cells through induction of a locoregional pH change. EA is typically performed by inserting needle electrodes inside the tumor followed by application of direct current (DC), thus inducing electrolysis and creating localized pH changes around the electrodes. In this paper, we report an ultrasonically powered implantable EA microprobe that may increase the clinical relevance of EA by allowing wireless control over device operation (capability to remotely turn the device on and off) and providing flexibility in treatment options (easier to administer fractionated doses over a longer period). The wireless EA microprobe consists of a millimeter-sized piezoelectric ultrasonic receiver, a rectifier circuit, and a pair of platinum electrodes (overall size is 9 × 3 × 2 mm³). Once implanted through a minimally invasive procedure, the microprobe can stay within a solid tumor and be repeatedly used as needed. Ultrasonic power allows for efficient power delivery to mm-scale devices implanted deep within soft tissues of the body. The microprobe is capable of producing a direct current of 90 µA at a voltage of 5 V across the electrodes under low-intensity ultrasound (~200 mW/cm²). The DC power creates acidic (pH < 2) and alkaline (pH > 12.9) regions around the anode and the cathode, respectively. The pH change, measured using tissue-mimicking agarose gel, extends to 0.8 cm³ in volume within an hour at an expansion rate of 0.5 mm³/min. The microprobe-mediated EA ablative capability is demonstrated in vitro in cancer cells and ex vivo in mouse liver.

Anterior Cable Reconstruction Using the Proximal Biceps Tendon for Large Rotator Cuff Defects Limits Superior Migration and Subacromial Contact Without Inhibiting Range of Motion: A Biomechanical Analysis

PURPOSE

To assess an anterior cable reconstruction (ACR) using autologous proximal biceps tendon for large to massive rotator cuff tears.

METHODS

Nine cadaveric shoulders (mean age, 58 years) were tested with a custom testing system. Range of motion, superior translation of the humeral head, and subacromial contact pressure were measured at 0°, 30°, 60°, and 90° of external rotation (ER) with 0°, 20°, and 40° of glenohumeral abduction. Five conditions were tested: intact, stage II tear (supraspinatus), stage II tear + ACR, stage III tear (supraspinatus + anterior half of infraspinatus), and stage III tear + ACR. ACR involved a biceps tendon tenotomy at the transverse humeral ligament, preserving its labral attachment. ACR included nonpenetrating suture-loop fixation using 2 side-to-side sutures and an anchor at the articular margin to restore anatomy and secure the tendon along the anterior edge of the cuff defect. ACR was performed in 20° glenohumeral abduction and 60° ER.

RESULTS

ACR for both stage II and stage III showed significantly higher total range of motion compared with intact at all angles (P ≤ .001). ACR significantly decreased superior translation for stage II tears at 0°, 30°, and 60° ER for both 0° and 20° abduction (P ≤ .01) and for stage III tears at 0° and 30° ER for both 0° and 20° abduction (P ≤ .004). ACR for stage III tear significantly reduced peak subacromial contact pressure at 30° and 60° ER with 0° and 40° abduction and at 30° ER with 20° abduction (P ≤ .041).

CONCLUSIONS

ACR using autologous biceps tendon biomechanically normalized superior migration and subacromial contact pressure, without limiting range of motion.

CLINICAL RELEVANCE

ACR may improve rotator cuff tendon repair longevity by providing basic static ligamentous support to the dynamic tendon while helping to limit superior migration without restricting glenohumeral kinematics.

Knotless Transosseous-Equivalent Rotator Cuff Repair Improves Biomechanical Self-reinforcement Without Diminishing Footprint Contact Compared With Medial Knotted Repair

PURPOSE

To assess the effect of medial-row knots on self-reinforcement and footprint contact characteristics for transosseous-equivalent repair compared with the same construct without knots.

METHODS

In 8 fresh-frozen human shoulders, transosseous-equivalent repairs with and without medial-row mattress knots were performed in each specimen. A pressure sensor was fixed at the tendon-footprint interface for all repairs. Parameters measured included footprint contact area, force, and pressure. The supraspinatus tendon was loaded sequentially from 0 to 60 N at 0° and 30° of abduction.

RESULTS

Both repairs provided a linear progression (slope) of footprint force and pressure as increasing tendon loads were applied. However, the knotless repair had a significantly higher progression ("self-reinforcement" effect) than the knotted repair at both abduction angles (P = .006 at 0° and P = .021 at 30°). The addition of medial-row knots did not significantly change the footprint contact area (in square millimeters), contact force (in newtons), contact pressure (in kilopascals), or peak pressure (in kilopascals) at each load tested, as well as at both abduction angles. For a given repair, only the knotless repair had significant decreases in contact area, contact force, contact pressure, and peak pressure with increasing abduction angles from 0° to 30° (P = .004 and P = .048).

CONCLUSIONS

Knotless transosseous-equivalent repair shows an improved self-reinforcement effect, without diminishing footprint contact, compared with the same repair with medial knots. Although knotless repair itself can show diminished footprint contact with abduction, medial knots show an adverse biomechanical effect by inhibiting self-reinforcement, without improving contact characteristics compared with knotless repair at each abduction angle tested. Clinical outcomes with specific indications, on the basis of these findings, require further investigation.

CLINICAL RELEVANCE

This study biomechanically helps to validate studies that have shown clinical success with knotless transosseous-equivalent repair. The inhibition of self-reinforcement may provide a quantified biomechanical rationale for medial tear patterns seen with knotted repairs.

Editorial Commentary: Can Passive Muscle Stiffness in a Cadaveric Study Be Clinically Related to Using Knotted Versus Knotless Rotator Cuff Repair?

Is a biomechanical cadaveric study to assess the effect of rotator cuff tear size and repair technique on supraspinatus muscle stiffness clinically relevant? A study in this issue compared double-row and knotless transosseous-equivalent repairs, but notably, muscle loading was not simulated. Results showed that the knotless transosseous-equivalent repair for larger tears demonstrated a more uniform stiffness distribution across the supraspinatus muscle compared with the double-row repair. However, given the inherently asymmetrical functional anatomy and morphology of the supraspinatus tendon-muscle unit, when muscle tone exists, the effect of the repair technique on muscle stiffness in vivo may not be determined based on the findings of this study.

Does transosseous-equivalent rotator cuff repair biomechanically provide a "self-reinforcement" effect compared with single-row repair?

BACKGROUND

Transosseous-equivalent (TOE) rotator cuff repair has been theorized to be "self-reinforcing" against potentially destructive and increasing tendon loads. The goal of this study was to biomechanically verify and characterize the effect of increasing tendon load on frictional resistance over a repaired footprint for single-row (SR) and TOE repair techniques.

METHODS

In 10 fresh frozen human shoulders, TOE and SR supraspinatus tendon repairs were performed in each specimen. For all repairs, a pressure sensor was secured at the tendon-footprint interface. The supraspinatus tendon was loaded with 0, 20, 40, 60, and 80 N at 0° and 30° abduction. Paired t tests and multivariate regression analyses were used for comparisons.

RESULTS

The SR repair had significant increases in footprint contact force, area, and pressure between each and all tendon-loading conditions (P < .05). The TOE repair similarly demonstrated increases in footprint contact force with increasing tendon load (P < .05). Comparing between repairs, TOE repair had more footprint contact force, area, pressure, and peak pressure at each load for both abduction angles (P < .05). With increasing load, the TOE repair had a significantly higher progression (slope) of footprint force and pressure compared with the SR repair.

CONCLUSIONS

Self-reinforcing capacity in rotator cuff repair has been biomechanically characterized and verified. The TOE repair, with tendon-bridging sutures fixed medially and spanning the footprint, provides disproportionately more progressive footprint frictional resistance with increasing tendon loads compared with the SR repair secured over isolated fixation points. This self-reinforcing effect could help sustain structural integrity and potentially improve healing biology.

Biomechanical effects of a 2 suture-pass medial inter-implant mattress on transosseous-equivalent rotator cuff repair and considerations for a "technical efficiency ratio"

BACKGROUND

Rotator cuff repair involving fewer tendon suture passes without compromising biomechanical performance would represent a technical advancement. An inter-implant "medial pulley-mattress" transosseous-equivalent (MP-TOE) repair requiring fewer tendon suture-passes was hypothesized to provide equivalent biomechanical characteristics compared to the control.

METHODS

In 6 human cadaveric shoulders, a transosseous-equivalent (TOE) repair (control) was performed utilizing 2 separate medial mattresses resulting in 4 tendon-bridging sutures. In 6 matched-pairs, 2 single-loaded anchors were used to create a medial inter-implant mattress construct (all sutures shuttled in 1 tendon pass per anchor)-after knot-tying, the same tendon-bridging pattern as the control was created. A materials testing machine cyclically loaded each repair from 10-180 N for 30 cycles; each repair subsequently underwent failure testing. Gap and strain were measured with a video digitizing system. A "technical efficiency ratio" (TER) was defined as: (#knots + #suture passes + #suture limbs)/#fixation points.

RESULTS

Cyclic and failure testing demonstrated no significant differences between constructs. Gap formation at cycle 30 was 5.3 ± 0.8 mm (TOE) and 5.0 ± 0.3 mm (MP-TOE) (P = .62). Cycle 30 anterior strain values were -16.0 ± 7.3% (TOE) and -15.8 ± 6.6% (MP-TOE) (P = .99). Yield loads were 208.7 ± 2.7 N (TOE) and 204.0 ± 1.3 N (MP-TOE) (P = .17). Mode of failure demonstrated less tendon cut-out with the MP-TOE repair. The MP-TOE repair has a TER of 2.0 vs 2.5 for the control.

CONCLUSION

The MP-TOE repair requiring fewer tendon suture passes, yet creating an additional inter-implant mattress configuration, is biomechanically equivalent to the original TOE technique, and may limit failure with improved medial load-sharing capacity. A TER may help quantify technical ease and help standardize comparisons between repair techniques.

Biomechanical validation of rotator cuff repair techniques and considerations for a "technical efficiency ratio"

Biomechanical studies are commonly used to validate new or modified rotator cuff repair techniques. Additional knots, more tendon suture passes, and obligatory suture management requirements are often the "cost" for improved biomechanical results. This cost can amount to increased technical difficulty and surgical times. However, technical ease or difficulty as a measurable variable has not been quantified. A basic measure for technical ease would allow surgeons the ability to objectively assess and compare rotator cuff repair practicality and potentially help in the design of future studies to standardize repair techniques alongside biomechanical measures. A proposed rotator cuff repair "technical efficiency ratio" is defined as follows: (No. of knots + No. of tendon suture passes + No. of suture limbs)/No. of pilot holes created. This can give a measure of "work" or utility achieved per fixation point created for a particular type of repair (e.g., single or double row), with a smaller number representing relatively more efficiency per anchor or fixation point used. If repairs validated in the laboratory are too cumbersome to perform in vivo from a practical standpoint, technical ease should be a prerequisite measure, and the success of a repair technique should not necessarily be based on biomechanics alone.

Rotator cuff tendon repair morphology comparing 2 single-anchor repair techniques

PURPOSE

To compare the effect of 2 common rotator cuff repair techniques, for smaller tears limited to the use of a single anchor, on tendon morphology in relation to the footprint.

METHODS

Six matched pairs of human shoulders were dissected, and a standardized 10-mm supraspinatus tendon tear was created. Two single-anchor repairs were performed: simple repair with the anchor on the footprint or inverted-mattress repair with the anchor 1 cm distal-lateral to the footprint. The repaired specimens were frozen in situ with liquid nitrogen. Coronal cross sections through the intact and repaired tendon were made. A digitizer was used to measure variables including tendon area and radius of tendon curvature.

RESULTS

Comparing between repairs, we found significantly more gap formation for the simple repair at the repair cross section (3.67 ± 0.32 mm v 0.68 ± 0.10 mm, P = .00050). The simple repair had less tendon area (38.28 ± 2.50 mm(2)v 58.65 ± 4.06 mm(2), P = .0036) and a smaller radius of curvature (8.47 ± 1.39 mm v 32.51 ± 3.94 mm, P = .0046). For the simple repair, there was significantly more gap formation, less tendon area, and a smaller radius of tendon curvature for all repair cross sections compared with the intact cross sections (P < .05). For the inverted-mattress repair, there was more gap formation compared with the intact condition (P < .05), although it was less than 1 mm on average; for tendon area, radius of curvature, and tendon height, the cross section centered on the repair showed no differences compared with the intact control.

CONCLUSIONS

For rotator cuff tears that are 10 mm or smaller and limited to the use of a single anchor, using a distal-lateral anchor position with tape-type suture can provide better maintenance of native tendon morphology and footprint dimensions when compared with repair that uses standard sutures and places the anchor on the footprint.

CLINICAL RELEVANCE

For smaller tears, the inverted-mattress repair described in this article may provide a relatively improved healing environment compared with a simple repair on the footprint, potentially optimizing the prevention of early tear progression.

Revision ulnar collateral ligament reconstruction using a suspension button fixation technique

BACKGROUND

Revision ulnar collateral ligament reconstruction remains a challenging problem. The objective of this study was to biomechanically evaluate an ulnar collateral ligament reconstruction technique using a suspension button fixation technique that can be used even in the case of ulnar cortical bone loss.

HYPOTHESIS

An ulnar suspension fixation technique for ulnar collateral ligament reconstruction can restore elbow kinematics and demonstrate failure strength comparable to that of currently available techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine pairs of cadaveric elbows were dissected free of soft tissue and potted. After simulating ulnar cortical bone loss, ulnar collateral ligament reconstruction was performed in 1 elbow of each pair using palmaris longus autograft and a 30-mm RetroButton suspended from the far (lateralmost) ulnar cortex. A docking technique was used for humeral fixation of the graft. Elbow valgus angle was quantified using a Microscribe 3DLX digitizer at multiple elbow flexion angles. Valgus angle was measured with the ulnar collateral ligament intact, transected, and reconstructed. In addition, load-to-failure testing was performed in 1 elbow of each pair.

RESULTS

Release of the ulnar collateral ligament caused a significant increase in valgus angle at each flexion angle tested (P < .002). Reconstructed elbows demonstrated no significant differences in valgus angle from the intact elbow at all flexion angles tested. Load-to-failure tests showed that reconstructed elbows had an ultimate torque (10.3 + or - 5.7 N x m) significantly less than intact elbows (26.4 + or - 10.6 N x m) (P = .001).

CONCLUSION

Ulnar collateral ligament reconstruction using a suspension button fixation technique reliably restored elbow kinematics to the intact state. Load-to-failure testing demonstrated comparable fixation strength to several historic controls of primary reconstruction techniques despite the simulated ulnar cortical bone loss.

CLINICAL RELEVANCE

Ulnar collateral ligament reconstruction using a suspension button fixation technique can be considered in the case of ulnar cortical bone loss in a primary or revision setting.

Influence of distinct anatomic subregions of the supraspinatus on humeral rotation

The supraspinatus, having distinct anterior and posterior subregions, is most commonly considered an abductor of the humerus, but it has also been shown to induce humeral rotation. The objective of this study was to quantify the magnitude and direction of humeral rotation that results from loading the distinct anterior and posterior subregions of the supraspinatus. Fourteen cadaver specimens were tested under four loading conditions based on physiological cross section area of the supraspinatus: (1) anterior only; (2) posterior only; (3) physiologic (each subregion loaded simultaneously); and (4) nonphysiologic (the tendon loaded as a whole). Each specimen was tested at 0, 15, 30, 45, and 60 degrees of glenohumeral abduction in the scapular plane and from 60 degrees of internal to 45 degrees of external rotation in 15 degrees increments. The humeral rotation that occurred with loading from the initial starting rotation position was measured using a rotary variable inductance transducer. In the scapular plane, the anterior subregion of the supraspinatus acts as both an internal and external rotator depending on the initial position of the humerus. The posterior subregion either acted as an external rotator or did not induce rotation. This study demonstrated a distinct functional difference between the anatomic subregions of the supraspinatus. This understanding will help to improve testing methods and the development of repair strategies of the supraspinatus.

Biomechanical analysis of a knotless transtendon interimplant mattress repair for partial-thickness articular-sided rotator cuff tears

BACKGROUND

A transtendon interimplant mattress repair along the medial row for partial-thickness rotator cuff repairs has been described with clinical success. However, the biomechanical characteristics for such a repair have not been elucidated.

HYPOTHESIS

A knotless interimplant mattress repair may show improved or equivalent load and strain characteristics, compared with a repair using isolated mattress repairs over each of 2 anchors.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven matched pairs of human cadaveric shoulders were dissected. Articular-sided tears were created involving 50% of the supraspinatus footprint. In 7 shoulders, repairs were performed with mattress configurations isolated over each of 2 anchor sites (control group). In 7 contralateral shoulders, a knotless interimplant mattress suture configuration was employed creating bridging sutures between implants. For all specimens, a materials-testing machine was used to cyclically load each repair from 10 to 180 N for 30 cycles; each repair was then loaded to failure. A deformation rate of 1 mm per second was employed for all tests. A video-digitizing system was employed to quantitatively measure the gap formation and strain on the footprint area of the repair. For detecting gap formation, 7 matched pairs were necessary for achieving a power of at least 90%.

RESULTS

During cyclic loading, gap formation at the anterior tendon was significantly lower in the control group (P < .05) but did not exceed 0.5 mm. There were no significant differences for linear stiffness, hysteresis, and strain between the 2 constructs. During tensile load-to-failure testing, there were no significant differences at yield load between the control and knotless techniques (293.90 + or - 132.72 N and 320.38 + or - 237.01 N, respectively; P > .05). There were no differences for stiffness, ultimate load, and energy absorbed to failure between the 2 repairs (P > .05). Gap formation in 3 regions was not significantly different between groups at yield and ultimate loads (P > .05). The anterior regions of the repair were the first to fail in all constructs.

CONCLUSION

A transtendon interimplant mattress rotator cuff repair for partial articular-sided tendon tears involving 50% of the footprint has biomechanical characteristics similar to those of a repair employing 2 isolated mattress configurations. An interim-plant mattress repair can protect tendon strain; it also exhibits yield loads that exceed those typically experienced in the early postoperative period.

CLINICAL RELEVANCE

A medial-row interimplant mattress repair configuration that is knotless may facilitate repair without compromising biomechanical characteristics.

Subungual glomus tumours of the hand: diagnosis and outcome of the transungual approach

We report 17 patients with a subungual glomus tumour. All complained of pain and tenderness when touched, and nine patients experienced severe pain in the cold. A transungual approach with nail plate avulsion on one side was used in all cases. A surgical microscope was used to localise and dissect the tumour and to repair the nail bed and matrix. This method has produced good results, without local recurrence or postoperative nail plate deformity.

The effect of abduction and rotation on footprint contact for single-row, double-row, and modified double-row rotator cuff repair techniques

BACKGROUND

An abduction pillow and abduction and rotation exercises are commonly used after rotator cuff repair. The effect of glenohumeral abduction and rotation on footprint contact has not been elucidated.

HYPOTHESIS

Abduction will decrease tendon-to-bone contact for all repairs. A modified double-row repair will maintain footprint contact more effectively at each position of humeral abduction and rotation than double- or single-row repairs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 6 fresh-frozen human shoulders, a modified double-row supraspinatus tendon repair was performed; a suture limb from each of 2 medial anchors was bridged over the tendon and fixed laterally. Double- and single-row repairs were performed sequentially; a total of 3 repairs were tested. For all repairs, a Tekscan pressure sensor was fixed at the tendon-footprint interface. The tendon was loaded with 30 N. The shoulders were tested at 0 degrees , 30 degrees , and 60 degrees of abduction with 0 degrees of rotation. For both dual-row repairs, 5 rotation positions were tested.

RESULTS

The greatest contact areas at neutral rotation were achieved at 0 degrees of abduction for the modified double-row, double-row, and single-row repairs (151.3 +/- 10.7 mm2, 80.7 +/- 30.0 mm2, and 61.3 +/- 26.1 mm2, respectively), with values decreasing as abduction increased. Each repair was significantly different from one another at each abduction angle (P < .05), except between single- and double-row repairs at 0 degrees of abduction. Mean interface pressure exerted over the footprint was greater for the modified double-row technique than for the other techniques at each abduction angle (P < .05). With respect to rotation, the modified double-row repair had significantly more footprint contact than did the double-row repair at each position tested (P < .05).

CONCLUSION

For a given repair, increasing abduction at neutral rotation reduced footprint contact. Internal rotation to 60 degrees provided among the highest contact measurements. The modified double-row technique provided the most contact.

CLINICAL RELEVANCE

Results are consistent with the practice of immobilizing the shoulder with 30 degrees or less of abduction and up to 60 degrees of internal rotation to optimize footprint contact. A dual-row repair may maximize contact when initiating rehabilitation that involves abduction and rotation.

The effect of dynamic external rotation comparing 2 footprint-restoring rotator cuff repair techniques

BACKGROUND

Allowing for humeral external rotation while loading rotator cuff repairs has been shown to affect tendon biomechanics when compared with testing with the humerus fixed. Adding dynamic external rotation to a tendon-loading model using footprint-restoring repairs may improve our understanding of rotator cuff repair response to a common postoperative motion.

HYPOTHESIS

A tendon suture-bridging repair will demonstrate better load sharing compared to a double-row repair, and there will be a differential gap formation between the anterior and posterior tendon regions.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 6 fresh-frozen human cadaveric shoulders, a tendon suture-bridging rotator cuff repair was performed; a suture limb from each of 2 medial anchors was bridged over the tendon and fixed laterally with an interference screw. In 6 contralateral match-paired specimens, a double-row repair was performed. For all specimens, a custom jig was employed that allowed dynamic external rotation (0 degrees to 30 degrees ) with loading. A materials testing machine was used to cyclically load each repair from 0 N to 90 N for 30 cycles; each repair was then loaded to failure. A deformation rate of 1 mm/s was employed for all tests. Gap formation between tendon edge and insertion was measured using video digitizing software.

RESULTS

The yield load for the suture-bridging technique (161.88 +/- 35.09 N) was significantly larger than the double-row technique (135.17 +/- 24.03 N) (P = .026). The yield gap between tendon and lateral footprint was significantly greater anteriorly than posteriorly (1.62 +/- 0.82 mm and 0.68 +/- 0.47 mm, respectively) for the suture-bridging technique (P = .024) but not for the double-row technique (1.35 +/- 0.52 mm and 1.05 +/- 0.50 mm, respectively) (P = .34). There were no differences for gap formation, stiffness, ultimate load to failure, and energy absorbed to failure between the 2 repairs (P > .05). The anterior regions of the repair were the first to fail in all constructs. The suture-bridging repair remained interconnected for 5 of 6 repairs.

CONCLUSIONS

The tendon suture-bridging rotator cuff repair has a yield load that is higher than the double-row repair when allowing for external rotation during load testing. External rotation can accentuate gap formation anteriorly at a repaired rotator cuff footprint.

CLINICAL RELEVANCE

Based on the tension of repair, there may be a role for reinforcing the repair anteriorly and limiting external rotation postoperatively.

The biomechanical effects of dynamic external rotation on rotator cuff repair compared to testing with the humerus fixed

BACKGROUND

Biomechanical testing without humeral motion is a standard method for evaluating rotator cuff repair constructs. This cannot elucidate the effects of dynamic external rotation on the repair, which is a common postoperative motion.

HYPOTHESIS

Biomechanical properties and gap formation of rotator cuff repairs will be different when dynamic external rotation is allowed to occur during loading.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 6 matched pairs of human cadaveric shoulders, a commonly used single-row rotator cuff repair was performed. In 6 shoulders, a materials testing machine and a custom testing apparatus that permits cyclic rotation (0 degrees -30 degrees ) were employed (group 1). In contralateral shoulders, the apparatus was fixed to prevent humeral rotation (group 2). All repairs were cyclically loaded from 0 to 60 N at a displacement rate of 1 mm/s for 30 cycles. The constructs were then loaded to failure. Repair strength, gap formation, and strain were compared between groups.

RESULTS

Cyclic loading revealed no difference in linear stiffness between testing conditions. Hysteresis was significantly greater when dynamic external rotation was allowed to occur. With load to failure, there were no differences in yield or ultimate load. Anterior tendon gap formation was greater at end rotation (30 degrees of humeral external rotation) and at yield load, and strain on the posterior tendon was less with dynamic external rotation. With dynamic external rotation, gap formation and tendon strain were significantly greater in the anterior region of the supraspinatus tendon compared with the posterior region.

DISCUSSION

External rotation using postoperative physiologic loads affects gap formation and tendon strain between anterior and posterior supraspinatus tendon regions. Previous testing models without humeral rotation may underestimate gap formation and anterior tendon strain and overestimate posterior tendon strain.

CLINICAL RELEVANCE

Understanding regional differences with respect to these variables, depending on quality of repair, may provide the surgeon a framework from which to prescribe guidelines for postoperative rehabilitation.

Part I: Footprint contact characteristics for a transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique

Rotator cuff repair via transosseous tunnels can improve footprint contact area and pressure when compared with suture anchor techniques. A double-row technique has been used clinically to improve footprint coverage by a repaired tendon. We hypothesized that a transosseous-equivalent rotator cuff repair via tendon suture bridges would demonstrate improved pressurized contact between the tendon and tuberosity when compared with a double-row technique. In 6 fresh-frozen human shoulders, a transosseous-equivalent rotator cuff repair was performed: a suture limb from each of 2 medial anchors was bridged over the tendon and fixed laterally with an interference screw (4 suture bridges). In 6 of the contralateral specimens, two types of repair were performed randomly in each specimen: (1) a double-row repair and (2) a transosseous-equivalent repair with a single screw (2 suture bridges). For all repairs, pressure-sensitive film was placed at the tendon-footprint interface, and software was used to obtain measurements. The mean pressurized contact area between the tendon and insertion was significantly greater for the 4-suture bridge technique (124.2 +/- 16.3 mm2, 77.6% footprint) compared with both the double-row (63.3 +/- 28.5 mm2, 39.6% footprint) and 2-suture bridge (99.7 +/- 22.0 mm2, 62.3% footprint) techniques (P < .05). The mean interface pressure exerted over the footprint by the tendon was greater for the 4-suture bridge technique (0.27 +/- 0.04 MPa) than for the double-row technique (0.19 +/- 0.01 MPa) (P = .002). The transosseous-equivalent rotator cuff repair technique can improve pressurized contact area and mean pressure between the tendon and footprint when compared with a double-row technique. A transosseous-equivalent technique, using suture bridges, may help optimize the healing biology at a repaired rotator cuff insertion.

Part II: Biomechanical assessment for a footprint-restoring transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique

We hypothesized that a transosseous-equivalent repair would demonstrate improved tensile strength and gap formation between the tendon and tuberosity when compared with a double-row technique. In 6 fresh-frozen human shoulders, a transosseous-equivalent rotator cuff repair was performed: a suture limb from each of two medial anchors was bridged over the tendon and fixed laterally with an interference screw. In 6 contralateral matched-pair specimens, a double-row repair was performed. For all repairs, a materials testing machine was used to load each repair cyclically from 10 N to 180 N for 30 cycles; each repair underwent tensile testing to measure failure loads at a deformation rate of 1 mm/sec. Gap formation between the tendon edge and insertion was measured with a video digitizing system. The mean ultimate load to failure was significantly greater for the transosseous-equivalent technique (443.0 +/- 87.8 N) compared with the double-row technique (299.2 +/- 52.5 N) (P = .043). Gap formation during cyclic loading was not significantly different between the transosseous-equivalent and double-row techniques, with mean values of 3.74 +/- 1.51 mm and 3.79 +/- 0.68 mm, respectively (P = .95). Stiffness for all cycles was not statistically different between the two constructs (P > .40). The transosseous-equivalent rotator cuff repair technique improves ultimate failure loads when compared with a double-row technique. Gap formation is similar for both techniques. A transosseous-equivalent repair helps restore footprint dimensions and provides a stronger repair than the double-row technique, which may help optimize healing biology.

Vagus nerve stimulation for depression: rationale, anatomical and physiological basis of efficacy and future prospects

Treatment-resistant depression (TRD) is a major public health concern due to its high costs to society. One of the novel approaches for the treatment of depression is the vagus nerve stimulation (VNS). Therapeutic brain stimulation through delivery of pulsed electrical impulses to the left cervical vagus nerve now has established safety and efficacy as an adjunct treatment for medication-resistant epilepsy and has recently been approved as an adjunct long-term treatment for chronic or recurrent depression. There is considerable evidence from both animal and human neurochemical and neuroimaging studies, that the vagus nerve and its stimulation influence limbic and higher cortical brain regions implicated in mood disorders, providing a rationale for its possible role in the treatment of psychiatric disorders. Clinical studies (open-label and comparator with treatment in naturalistic setting) in patients with TRD have produced promising results, especially when the response rates at longer-term (one- and two-year) follow-up time points are considered. Ongoing research efforts will help determine the place of VNS in the armament of therapeutic modalities available for major depression.

"Transosseous-equivalent" rotator cuff repair technique

In order to optimize healing biology at a repaired rotator cuff footprint, we have developed a "transosseous-equivalent" rotator cuff repair that can be performed arthroscopically. What the arthroscopically repaired tendon experiences is "equivalent" to what is experienced with a traditional open suture-bridge technique. This repair maximizes the utility of a single-row repair technique by preserving the suture limbs of the medial single-row and bridging these sutures over the footprint insertion with distal-lateral interference screw suture fixation; the medial row uses a mattress suture configuration. The geometry of the construct compresses the tendon, optimizing tendon-to-tuberosity contact dimensions, while providing strength sufficient to withstand immediate postoperative rehabilitation.

False magnetic resonance imaging persistence of a biodegradable anterior cruciate ligament interference screw with chronic inflammation after 4 years in vivo

Surgeons should be aware that the degradation kinetics of biodegradable implants likely influence the rate of osseous integration, and depend on numerous factors such as polymer weight, crystallinity, and stereocopolymer ratio. We present a case of inflammatory reaction at a polylactide tibial interference screw site more than 4 years after primary anterior cruciate ligament (ACL) reconstruction. This inflammation was presumptively treated as an infection with surgical irrigation and debridement. Preoperatively, the screw was clearly delineated by magnetic resonance imaging (MRI), yet was grossly absent at surgery. Postoperative MRI confirmed thorough debridement and complete absence of the screw. This report shows that not only can a late inflammatory reaction occur, after up to 4 years in vivo, but that the MRI may show a persistent screw despite significant biodegradation. False MRI-persistent screws should be considered when critically reviewing studies that use MRI in the methods for evaluating biodegradable implants. More importantly, false MRI-persistent screws may have significant ramifications when planning revision surgery after primary ACL reconstruction having used interference screws that can degrade over several years.

Serum cytokine profiles and their correlations with disease activity in Takayasu's arteritis

OBJECTIVE

To investigate serum profiles of inflammatory cytokines in patients with Takayasu's arteritis (TA) and to determine their correlations with disease activity of TA.

METHODS

Forty-nine patients with TA and 12 age- and sex-matched controls were studied. Blood samples were obtained and were divided into active and stable disease groups. Paired blood samples were available in 19 patients at the active stage before treatment and at the remitted stage after treatment. Serum tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-6, IL-12 and IL-18 levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum TNF-alpha, IL-6 and IL-18 levels of patients with TA were significantly higher than those of controls (P<0.05), but IFN-gamma and IL-12 levels were not. Serum IL-6 and IL-18 levels were significantly higher in the active disease group than in the stable disease group (P<0.05), but the levels of TNF-alpha were not different between the groups. In the 19 patients with paired samples, serum IL-18 levels at the remitted stage after treatment were significantly decreased compared with the active stage before treatment (P<0.001). The changes in IL-18 levels between active and remitted stages correlated well with changes in erythrocyte sedimentation rate (P<0.001).

CONCLUSION

Serum IL-18 and IL-6 levels were elevated in patients with TA, especially in those with active disease. Serum IL-18 levels correlated well with disease activity of TA. These results suggest that IL-6 and IL-18 might contribute to the pathogenesis of TA and that IL-18 could be a useful marker for monitoring disease activity of TA.

Post-interventional immunosuppressive treatment and vascular restenosis in Takayasu's arteritis

OBJECTIVE

To investigate the outcome of vascular interventions and the effect of post-interventional immunosuppressive treatment on the occurrence of vascular restenosis in patients with Takayasu's arteritis (TA).

METHODS

Forty-two patients with TA who had undergone vascular intervention and had serial angiographies before and after intervention were enrolled. The demographic and clinical data were collected at the time when the interventions were performed, and the intervention modalities and post-interventional medical treatments were evaluated.

RESULTS

Sixty-three interventions were performed in 42 patients. Twenty (31.7%) interventions restenosed 24.0 +/- 21.9 months after intervention; the likelihood decreasing as time passed. Estimates of arterial patency after intervention were 90.1% at 1 yr, 75.5% at 2 yr, 68.4% at 3 yr, 61.6% at 5 yr and 49.3% at 10 yr. According to the log rank test, interventions that were performed during the stable stage of the disease (P = 0.039) and those that were followed by treatment with glucocorticoids and immunosuppressive agents (P = 0.044) were independent variables for the maintenance of arterial patency. Their hazard ratios were 0.30 and 0.41, respectively.

CONCLUSION

Restenosis occurred in 31.7% of TA patients after intervention. A lower restenosis rate was observed when the vascular interventions were performed at the stable stage and when post-interventional immunosuppressive treatment was implemented.

Tendon-to-bone pressure distributions at a repaired rotator cuff footprint using transosseous suture and suture anchor fixation techniques

BACKGROUND

Interface contact pressure between the tendon and bone has been shown to influence healing. This study evaluates the interface pressure of the rotator cuff tendon to the greater tuberosity for different rotator cuff repair techniques.

HYPOTHESIS

The transosseous tunnel rotator cuff repair technique provides larger pressure distributions over a defined insertion footprint than do suture anchor techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Simulated rotator cuff tears over a 1 x 2-cm infraspinatus insertion footprint were created in 25 bovine shoulders. A transosseous tunnel simple suture technique (n = 8), suture anchor simple technique (n = 9), and suture anchor mattress technique (n = 8) were used for repair. Pressurized contact areas and mean pressures of the repaired tendon against the tuberosity were determined using pressure-sensitive film placed between the tendon and the tuberosity.

RESULTS

The mean contact area between the tendon and tuberosity insertion footprint was significantly greater for the transosseous technique (67.7 +/- 5.8 mm(2)) compared with the suture anchor simple (34.1 +/- 9.4 mm(2)) and suture anchor mattress (26.0 +/- 5.3 mm(2)) techniques (P < .05). The mean interface pressure exerted over the footprint by the tendon was also greater for the transosseous technique (0.32 +/- 0.05 MPa) compared with the suture anchor simple (0.26 +/- 0.04 MPa) and suture anchor mattress (0.24 +/- 0.02 MPa) techniques (P < .05).

CONCLUSION

The transosseous tunnel rotator cuff repair technique creates significantly more contact and greater overall pressure distribution over a defined footprint when compared with suture anchor techniques.

CLINICAL RELEVANCE

Stronger and faster rotator cuff healing may be expected when beneficial pressure distributions exist between the repaired rotator cuff and its insertion footprint. Tendon-to-tuberosity pressure and contact characteristics should be considered in the development of improved open and arthroscopic rotator cuff repair techniques.

Dynamic contributions of the flexor-pronator mass to elbow valgus stability

BACKGROUND

Previous studies have indicated that the demands placed on the medial ulnar collateral ligament of the elbow when it is subjected to valgus torque during throwing exceed its failure strength, which suggests the necessary dynamic contribution of muscle forces. We hypothesized that the flexor-pronator mass assists the medial ulnar collateral ligament in stabilizing the elbow against valgus torque.

METHODS

Six cadaveric elbows were tested at 30 degrees and 90 degrees of flexion with no other constraints to motion. A full medial ulnar collateral ligament tear was simulated in each elbow. Muscle forces were simulated on the basis of the centroids and physiological cross-sectional areas of individual muscles. The biceps, brachialis, and triceps were simulated during flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum superficialis and flexor carpi ulnaris, and pronator teres-loading conditions. Kinematic data were obtained at each flexion angle with use of a three-dimensional digitizer.

RESULTS

Release of the medial ulnar collateral ligament caused a significant increase in valgus instability of 5.9 degrees +/- 2.4 degrees at 30 degrees of elbow flexion and of 4.8 degrees +/- 2.0 degrees at 90 degrees of elbow flexion (p < 0.05). The differences in valgus angulation between each muscle-simulation condition and the medial ulnar collateral ligament-intact condition were significantly different from each other (p < 0.05), except for the difference between the flexor carpi ulnaris contraction condition and the flexor digitorum superficialis-flexor carpi ulnaris co-contraction condition. This co-contraction provided the most correction of the valgus angle in comparison with the intact condition at both 30 degrees and 90 degrees of elbow flexion (1.1 degrees +/- 1.8 degrees and 0.38 degrees +/- 2.3 degrees , respectively). Simulation of the flexor carpi ulnaris alone provided the greatest reduction of the valgus angle among all individual flexor-pronator mass muscles tested (p < 0.05), whereas simulation of the pronator teres alone provided the least reduction of the valgus angle (p < 0.05).

CONCLUSIONS

The flexor-pronator mass dynamically stabilizes the elbow against valgus torque. The flexor carpi ulnaris is the primary stabilizer, and the flexor digitorum superficialis is a secondary stabilizer. The pronator teres provides the least dynamic stability.

Elbow medial ulnar collateral ligament insufficiency alters posteromedial olecranon contact

BACKGROUND

The effect of elbow medial ulnar collateral ligament injury on posteromedial compartment contact is unknown.

HYPOTHESIS

Medial ulnar collateral ligament injury causes altered contact area and pressure in the posteromedial compartment of the elbow.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven elbow cadaveric specimens were tested in an apparatus that positioned the elbow at 30 degrees and 90 degrees of flexion. Partial and full tears were simulated by releasing the medial ulnar collateral ligament. Pressure-sensitive film was placed in the posteromedial compartment for each condition. Valgus torques of 1.25 and 2.0 N.m were applied for each ligament condition, and kinematic data were obtained at each flexion angle using a 3-dimensional digitizer.

RESULTS

Both ligament condition and valgus load had significant effects on contact area and pressure (P<.05). For a given load and flexion angle, the contact area decreased and the pressure increased with increasing medial ulnar collateral ligament insufficiency. Within these trends, statistical significance was found at 30 degrees of elbow flexion for both area and pressure (P<.05); at 90 degrees of elbow flexion, increasing medial ulnar collateral ligament insufficiency did not significantly affect contact area or pressure (P>.05).

DISCUSSION

Medial ulnar collateral ligament insufficiency alters contact area and pressure between the posteromedial trochlea and olecranon and helps explain the development of posteromedial osteophytes.

Two-part and three-part fractures of the proximal humerus treated with suture fixation

OBJECTIVE

To evaluate the radiographic and clinical outcomes of patients with displaced proximal humerus fractures (two-part and three-part) treated with nonabsorbable rotator cuff-incorporating sutures.

DESIGN

Retrospective.

SETTING

University hospital.

PATIENTS

There were 27 patients (28 shoulders) with displaced proximal humerus fractures. There were 13 greater tuberosity (GT) and 9 surgical neck (SN) two-part fractures and 6 GT/SN three-part fractures. The average age was 64 years (range 38 to 84 years). The average follow-up was 4.4 years (range 1.0 to 11.5 years).

INTERVENTION

All patients were surgically treated solely with heavy polyester nonabsorbable sutures.

MAIN OUTCOME MEASUREMENTS

Functional assessment was obtained using the American Shoulder and Elbow Surgeons (ASES) score and Neer's criteria, which grade outcomes as excellent, satisfactory, or unsatisfactory.

RESULTS

Overall, there were 22 (78%) excellent, 3 (11%) satisfactory, and 3 (11%) unsatisfactory results, and the average ASES score was 87.1 (range 35.0 to 100.0). All shoulders healed radiographically without evidence of avascular necrosis of the humeral head. Twenty-four shoulders (86%) had anatomic alignment on postoperative radiographs. Of four shoulders with nonanatomic alignment, three had ASES scores of >/=90, with excellent Neer scores. When comparing patients with isolated two-part GT fractures (n = 13) with patients having two-part SN or three-part SN/GT fractures (n = 15), there were no statistically significant differences with respect to range of motion (P > 0.05) and outcome measures (P > 0.05). All patients who had unsatisfactory outcomes were noncompliant with physical therapy, with ASES scores averaging 39.4 (range 35.0 to 43.3).

CONCLUSION

Two-part and three-part GT and SN fractures can be treated satisfactorily with heavy nonabsorbable rotator cuff-incorporating sutures, particularly in elderly patients. Hardware-associated complications are obviated. Patients with SN fractures treated with sutures can have outcomes similar to patients with two-part GT fractures. Although the goal is to reconstruct a "one-part" fracture pattern, some residual deformity does not preclude an excellent outcome. A compliant patient is crucial for a successful result.

Shoulder dislocation in young athletes: current concepts in management

A fall onto an outstretched arm or a collision on the playing field often leads to an acute anterior shoulder dislocation for high school- and college-age athletes. The diagnosis is usually made by history and physical exam. The angle of impact is an important diagnostic clue. If no neurologic contraindications or signs of acute fracture are seen, radiographs are unnecessary, and early reduction before the onset of muscle spasm is essential. Recent advances in arthroscopic techniques have dramatically reduced the high incidence of recurrent instability in young elite athletes, though nonoperative management with immobilization is still an excellent option.

Quantifying risk of transfusion in children undergoing spine surgery

BACKGROUND CONTEXT

The risks and costs of transfusion are a great concern in the area of pediatric spine surgery, because it is a blood-intensive procedure with a high risk for transfusion. Therefore, determining the predictors of transfusion in this patient population is an important first step and has the potential to improve upon the current approaches to reducing transfusion rates. In this study, we reveal several predictors of transfusion in a pediatric patient population undergoing spine surgery. In turn, we present a general rule of thumb ("rule of two's") for gauging transfusion risk, thus enhancing the surgeon's approach to avoiding transfusion in certain clinical scenarios.

PURPOSE

This study was conducted to determine the main factors of transfusion in a population of pediatric patients undergoing scoliosis surgery. The goal was to present an algorithm for quantifying the true risk of transfusion for various patient groups that would highlight patients "at high risk" for transfusion. This is especially important in light of the various risks associated with undergoing a transfusion, as well as the costs involved in maintaining and disposing of exogenous blood materials.

STUDY DESIGN/SETTING

This is a retrospective review of a group of children who underwent scoliosis surgery between 1988 and 1995 at an academic institution.

PATIENT SAMPLE

A total of 290 patients were analyzed in this study, of which 63 were transfused and 227 were not.

OUTCOME MEASURES

No outcomes measures were used in this study.

METHODS

A retrospective review of 290 patients presenting to our institution for scoliosis surgery was conducted, with a focus on socioclinical data related to transfusion risk. Univariate analysis and logistic regression were used to quantify the determinants of transfusion risk.

RESULTS

Univariate analysis identified many factors that were associated with the risk of transfusion. However, it is clear that several of these factors are dependent on each other, obscuring the true issues driving transfusion need. We used multivariate analysis to control for the various univariate predictors of transfusion. Our logistic regression model suggested that the type of scoliosis (odds ratio [OR], 2.02; 95% confidence interval [CI], 1.07 to 3.82), degree of curvature (OR, 1.012/degree curve; 95% CI, 1.01 to 1.03), and use of erythropoietin (OR, 0.29; 95% CI, 0.14 to 0.62) were the main determinants of transfusion risk for our population.

CONCLUSIONS

The main risk factors of transfusion were used to formulate a simple algorithm, which can be used to quantify transfusion risk and to guide efforts to avoid transfusion in children undergoing spinal surgery. Given a 10% baseline risk for transfusion, our "rule of two's" indicates that each risk factor approximately doubles the chance of transfusion, whereas the administration of recombinant human erythropoietin roughly halves the risk of transfusion.

Consistent features in the forelimb representation of primary motor cortex in rhesus macaques

The purpose of this study was to systematically map the forelimb area of primary motor cortex (M1) in rhesus macaques in an effort to investigate further the organization of motor output to distal and proximal muscles. We used stimulus-triggered averaging (StTAing) of electromyographic activity to map the cortical representation of 24 simultaneously recorded forelimb muscles. StTAs were obtained by applying 15 microA stimuli to M1 sites while the monkey performed a reach and prehension task. Motor output to body regions other than the forelimb (e.g., face, trunk, and hindlimb) was identified using repetitive intracortical microstimulation to evoke movements. Detailed, muscle-based maps of M1 revealed a central core of distal (wrist, digit, and intrinsic hand) muscle representation surrounded by a "horseshoe"-shaped zone of proximal (shoulder and elbow) muscle representation. The core distal and proximal zones were separated by a relatively large region representing combinations of both distal and proximal muscles. On the basis of its size and characteristics, we argue that this zone is not simply the result of stimulus-current spread, but rather a distinct zone within the forelimb representation containing cells that specify functional synergies of distal and proximal muscles. Electrode tracks extending medially from the medial arm of the proximal muscle representation evoked trunk and hindlimb responses. No distal or proximal muscle poststimulus effects were found in this region. These results argue against the existence of a second, major noncontiguous distal or proximal forelimb representation located medially within the macaque M1 representation.

Compensation of phase change on reflection in white-light interferometry for step height measurement

We present a method for compensating for the phase change on reflection in scanning white-light inteferometry that practically permits precise three-dimensional profile mapping of composite target surfaces that comprise multiple, dissimilar materials. The compensation method estimates the variation of phase change with the spectral distribution of the light source through a first-order approximation and then directly compensates for the measurement errors by performing two additional quasi-monochromatic phase-measuring interferometric measurements. Experimental results prove that the proposed compensation method is capable of reducing the measurement error in step height gauging to +/-5 nm or less.

Chronic recording of EMG activity from large numbers of forelimb muscles in awake macaque monkeys

Studies of the neural control of movement often require or benefit from long-term recording of EMG activity from large numbers of muscles involved in a particular motor task. While chronic recording of EMG activity has been described in a number of previous monkey studies, the number of muscles recorded has been somewhat limited and the implantation approach has been highly invasive procedures. This paper presents two EMG implant fabrication and surgical implantation methods that are suitable for use in monkeys, relatively non-traumatic and capable of simultaneous recording from 24 or more muscles.

Induction of reproductive organ-preferential histone genes by wounding or methyl jasmonate

A cDNA clone CaH2B, which is highly expressed in floral buds, was isolated from hot pepper plants (Capsicum annuum) by the mRNA differential display method. Sequence analysis of CaH2B revealed that the clone contains an open reading frame of 145 amino acid residues, which are 77% identical to a maize H2B histone. The CaH2B mRNA was barely detectable in roots, was more abundant in anthers than in seedlings, and was expressed highest in floral buds and fruits. An in situ analysis of CaH2B in floral buds indicated that the transcript is highly present in the pollen and petals. Northern analysis of CaH4, a pepper H4 histone cDNA, which was obtained during the expressed sequence tag (EST) analysis of anther tissues, showed that the expression pattern was very similar to that of CaH2B, although the expression level was slightly different. Both histone genes were examined for inducibility by wounding, methyl jasmonate (MJ), or phytohormones. CaH2B and CaH4 were induced by wounding, and maximally induced ca. 3 h after wound treatment both in vitro and in planta. Airborne MJ greatly induced the expression of the genes as well. The inducing effect by wounding was suppressed by MJ, suggesting that wounding and MJ might have different roles in signal transduction for the histone gene induction. Southern blot hybridization showed that both H2B and H4 genes are comprised of multigene families in the hot pepper.

Cra-mediated regulation of Escherichia coli adenylate cyclase

In Escherichia coli, expression of certain genes and operons, including the fructose operon, is controlled by Cra, the pleiotropic catabolite repressor/activator protein formerly known as FruR. In this study we have demonstrated that cra mutant strains synthesize 10-fold less cAMP than isogenic wild-type strains, specifically when grown in fructose-containing minimal media. The glucose-specific IIA protein (IIAglc) of the phosphotransferase system, which activates adenylate cyclase when phosphorylated, is largely dephosphorylated in cra but not wild-type strains growing under these conditions. Dephosphorylation of IIAglc in cra strains apparently results from enhanced fructose operon transcription and fructose uptake. These conclusions were supported by showing that fructose-grown cra strains possess 2.5-fold higher fructose-1-phosphate kinase activity than fructose-grown wild-type strains. Moreover, artificially increasing fructose operon expression in cells transporting fructose dramatically decreased the activity of adenylate cyclase. The results establish that Cra indirectly regulates the activity of adenylate cyclase by controlling the expression of the fructose operon in cells growing with fructose as the sole carbon source.

Intravesical bacille Calmette-Guérin therapy for muscle invasive bladder cancer

OBJECTIVES

This investigation attempted to determine whether the degree of fibronectin expression in the bladders of patients with invasive transitional cell carcinoma correlated with their clinical response to intravesical bacille Calmette-Guerin (BCG) therapy.

METHODS

Following transurethral resection of all invasive disease, 13 patients with Stages T2-T4 bladder cancer were administered intravesical BCG (fo 6 weeks followed by monthly instillations). Fibronectin expression in the patients' resected tumors and normal mucosa was determined by immunohistochemical staining techniques. Minimum disease-free follow-up was 60 months.

RESULTS

Only 1 of 13 patients had neither local nor systemic disease recurrence; 10 of 13 patients developed systemic disease and 7 patients died from metastases. Fibronectin expression was not correlated with the clinical response to BCG.

CONCLUSIONS

Intravesical BCG therapy for the treatment of muscle invasive transitional cell carcinoma of the bladder is ineffective. Fibronectin expression in the bladder of patients with invasive disease is variable and does not correlate significantly with the clinical response to BCG therapy.

Fibronectin expression on surgical specimens correlated with the response to intravesical bacillus Calmette-Guerin therapy

Attachment of bacillus Calmette-Guerin (BCG) organisms to the bladder during intravesical therapy is thought to be mediated exclusively by the glycoprotein fibronectin, which is expressed variably on epithelial surfaces and on basement membranes. We examined the relationship between the degree of fibronectin expressed on surgical specimens obtained from 50 candidates for BCG therapy and the subsequent clinical response. Immunoperoxidase staining for fibronectin was performed on tumor, nonadjacent normal mucosa and basement membrane tissues, and the intensity of the staining was scored on a scale of 0 to 3+ (control 2+). In the absence of recurrence at quarterly surveillance cystoscopy, a course of Tice BCG therapy consisted of 6 weekly and 12 monthly instillations. Recurrence of noninvasive tumor prompted a second BCG course. Followup ranged from 24 to 66 months (median 40 months). Of the 50 patients (11 with carcinoma in situ) disease progression occurred in 9 (none with carcinoma in situ). Compared to the results for tumors or for basement membranes, the degree of fibronectin expression on normal mucosa was well correlated with the clinical response (r = 0.59, p < 0.001 by Kendall Tau B). Routine assessment of fibronectin expression on the normal mucosa associated with superficial bladder cancer may be useful for predicting the clinical response to BCG therapy.

Primary non-Hodgkin's malignant lymphoma of the vulva--a case report

A case of primary non-Hodgkin's malignant lymphoma of the vulva which occurred in a 68-year-old woman is presented. Non-Hodgkin's malignant lymphoma is infrequently involved in the female genital tract. Moreover, primary vulvar involvement of this tumor is very rare. To date only 6 cases have been reported in the literature. To our knowledge this is the first reported case of a non-Hodgkin's malignant lymphoma of the vulva in Korea.