Kevin Eng

External and internal bone micro-architecture in normal and Kienböck's lunates: A whole-bone micro-computed tomography study

Kienböcks disease is idiopathic osteonecrosis of the lunate, leading to its fracture and collapse. This study compares internal and external bone micro‐architecture of normal and fractured lunates (Kienböcks), by using high‐resolution three‐dimensional (3D) micro‐computed tomography (micro‐CT) on the whole bone of the two lunate types, and histology.

The Effect of Lunate Morphology on the 3-Dimensional Kinematics of the Carpus

PURPOSE To assess carpal kinematics in various ranges of motion in 3 dimensions with respect to lunate morphology. METHODS Eight cadaveric wrists (4 type I lunates, 4 type II lunates) were mounted into a customized platform that allowed controlled motion with 6 degrees of freedom. The wrists were moved through flexion-extension (15°-15°) and radioulnar deviation (RUD; 20°-20°). The relative motion of the radius, carpus, and third metacarpal were recorded using optical motion capture methods. RESULTS Clear patterns of carpal motion were identified. Significantly greater motion occurred at the radiocarpal joint during flexion-extension of type I wrist than a type II wrist. The relative contributions of the midcarpal and radiocarpal articulations to movement of the wrist differed between the radial, the central, and the ulnar columns. During wrist flexion and extension, these contributions were determined by the lunate morphology, whereas during RUD, they were determined by the direction of wrist motion. The midcarpal articulations were relatively restricted during flexion and extension of a type II wrist. However, during RUD, the midcarpal joint of the central column became the dominant articulation. CONCLUSIONS This study describes the effect of lunate morphology on 3-dimensional carpal kinematics during wrist flexion and extension. Despite the limited size of the motion arcs tested, the results represent an advance on the current understanding of this topic. CLINICAL RELEVANCE Differences in carpal kinematics may explain the effect of lunate morphology on pathological changes within the carpus. Differences in carpal kinematics due to lunate morphology may have implications for the management of certain wrist conditions.

Cable-augmented, quad ligament tenodesis scapholunate reconstruction: rationale, surgical technique, and preliminary results.

Eight patients underwent scapholunate reconstruction using tensionable suture anchors. Adapted from a modified Brunelli technique, the anchors provide a fixed cable that reduces the scapholunate diastasis and maintains reduction during the healing phase. The flexor carpi radialis tendon graft is advanced through the scaphoid and stabilizes the volar scaphotrapezial ligament, dorsal scapholunate ligament, dorsal intercarpal ligament, and dorsal radiocarpal ligament. The ligament-sparing approach is closed using an ulnar advancement capsulodesis that further reinforces the dorsal intercarpal and dorsal radiocarpal ligament. Good clinical results were obtained. Measured on a visual analog scale (0 to 10), the average pain score improved from 5.8 to 2.1, average patient satisfaction was 7.6, average extension was 56 degrees (91% of contralateral side), flexion was 44 degrees (70% of contralateral side), and grip was strength 41 kg (95% of contralateral side). Radiographic parameters were less favorable. The average scapholunate angle was 71 degrees, radiolunate angle 16 degrees, and scapholunate interval 3.0 mm. The cable-augmented, quad ligament scapholunate ligament reconstruction offers theoretical advantages over previously published techniques, but long-term follow-up is required.

Anatomic foveal reconstruction of the triangular fibrocartilage complex with a tendon graft

An acute injury to the triangular fibrocartilage complex (TFCC) with avulsion of the foveal attachment can produce distal radioulnar joint (DRUJ) instability. The avulsed TFCC is translated distally so the footprint will be bathed in synovial fluid from the DRUJ and will become covered in synovitis. If the TFCC fails to heal to the footprint, then persistent instability can occur. The authors describe a surgical technique indicated for the treatment of persistent instability of the DRUJ due to foveal detachment of the TFCC. The procedure utilizes a loop of palmaris longus tendon graft passed through the ulnar aspect of the TFCC and into an osseous tunnel in the distal ulna to reconstruct the foveal attachment. This technique provides stability of the distal ulna to the radius and carpus. We recommend this procedure for chronic instability of the DRUJ due to TFCC avulsion, but recommend that suture repair remain the treatment of choice for acute instability. An arthroscopic assessment includes the trampoline test, hook test, and reverse hook test. DRUJ ballottement under arthroscopic vision details the direction of instability, the functional tear pattern, and unmasks concealed tears. If the reverse hook test demonstrates a functional instability between the TFCC and the radius, then a foveal reconstruction is contraindicated, and a reconstruction that stabilizes the radial and ulnar aspects of the TFCC is required. The foveal reconstruction technique has the advantage of providing a robust anatomically based reconstruction of the TFCC to the fovea, which stabilizes the DRUJ and the ulnocarpal sag.

Translunate Perilunate Injuries—A Spectrum of This Uncommon Injury

Purpose To review a series of translunate perilunate dislocations to analyze the, mechanism of injury, diagnosis, management, and outcome. Methods A literature review and a survey of the International Wrist Investigators Workshop were performed to locate cases. Results Translunate perilunate injuries are rare. There is a spectrum of severity. The mechanism of injury is usually high-energy, and multiple fractures are the norm. High-energy mechanism, perilunate dislocation, comminuted lunate fracture and delayed presentation greater than 7 days are associated with a higher likelihood of a salvage procedure being required. Discussion Translunate injuries are a complex variant of perilunate dislocations. Early diagnosis is critical in understanding the complexity of the injury. Lunate fixation should be performed prior to bony and ligamentous stabilization of the proximal row. In delayed or highly comminuted cases, salvage procedures are the preferred option. Including a translunate arc in addition to the greater and lesser carpal arc would lead to a more inclusive classification. Level of Evidence Level IV.

Anatomic study of the superior glenoid labrum.

The purpose of the study was to describe the normal anatomy of the glenoid labrum to help identification of pathology and guide surgical repair. Twenty dry bone scapulae and 19 cadaveric shoulders were examined. Light microscopy was performed on 12 radial slices through the glenoid. An external capsular circumferential ridge, 7–8 mm medial to the glenoid rim marks the attachment of the capsule. A separate internal labral circumferential ridge 4 mm central to the glenoid rim marks the interface between the labrum and articular cartilage. A superior–posterior facet was found consistently on the glenoid. Two thirds of the long head of biceps arises from the supraglenoid tubercle, 6.6 mm from the glenoid face, the remainder from the labrum. The superior labrum is concave and is loosely attached to the articular cartilage and glenoid rim. Clefts and foramens are common superiorly. In contrast the anterior–inferior labrum is convex, attaches 4 mm central to the glenoid rim and has a strong attachment to articular cartilage and bone. Sublabral clefts, recesses, and holes are common, but only in the superior–anterior labrum. Lesions in other regions of the labrum are potentially pathological. A complex superior labrum tear that extends to involve the biceps anchor, should have the biceps anchor repaired to the supraglenoid tubercle (mean 6.6 mm off the glenoid face) and the labrum be repaired to the glenoid rim. The anteroinferior labrum should be repaired 4 mm onto the glenoid face. This study will aid in identifying pathological labral lesions and guide anatomic repairs. Clin. Anat., 2013.

A novel method to replicate the kinematics of the carpus using a six degree-of-freedom robot

Understanding the kinematics of the carpus is essential to the understanding and treatment of wrist pathologies. However, many of the previous techniques presented are limited by non-functional motion or the interpolation of points from static images at different postures. We present a method that has the capability of replicating the kinematics of the wrist during activities of daily living using a unique mechanical testing system. To quantify the kinematics of the carpal bones, we used bone pin-mounted markers and optical motion capture methods. In this paper, we present a hammering motion as an example of an activity of daily living. However, the method can be applied to a wide variety of movements. Our method showed good accuracy (1.0-2.6°) of in vivo movement reproduction in our ex vivo model. Most carpal motion during wrist flexion-extension occurs at the radiocarpal level while in ulnar deviation the motion is more equally shared between radiocarpal and midcarpal joints, and in radial deviation the motion happens mainly at the midcarpal joint. For all rotations, there was more rotation of the midcarpal row relative to the lunate than relative to the scaphoid or triquetrum. For the functional motion studied (hammering), there was more midcarpal motion in wrist extension compared to pure wrist extension while radioulnar deviation patterns were similar to those observed in pure wrist radioulnar deviation. Finally, it was found that for the amplitudes studied the amount of carpal rotations was proportional to global wrist rotations.

Repair of the acutely unstable elbow: use of tensionable anchors.

Acute ruptures of the medial or lateral collateral ligaments of the elbow associated with elbow dislocations have traditionally been repaired back to their respective epicondyles using suture anchors or transosseous sutures. Tensioning of those ligaments using conventional techniques had been difficult because of the need to maintain tension while tying and securing sequential knots. Tensionable anchors are a new generation of anchors that have been used for rotator cuff repair, but can be employed for the repair of collateral ligaments and capsular tears. It allows fine control and sequential tensioning of the ligament repair, and on-table assessment of stability before locking the anchor. We present a modified surgical technique for the repair of collateral ligaments repair using tensionable anchors in acute elbow dislocations or fracture dislocations.

Optimal Lateral Row Anchor Positioning in Posterior-Superior Transosseous Equivalent Rotator Cuff Repair: A Micro-Computed Tomography Study.

Background: The optimal placement of suture anchors in transosseous-equivalent (TOE) double-row rotator cuff repair remains controversial. Purpose: A 3-dimensional (3D) high-resolution micro–computed tomography (micro-CT) histomorphometric analysis of cadaveric proximal humeral greater tuberosities (GTs) was performed to guide optimal positioning of lateral row anchors in posterior-superior (infraspinatus and supraspinatus) TOE rotator cuff repair. Study Design: Descriptive laboratory study. Methods: Thirteen fresh-frozen human cadaveric proximal humeri underwent micro-CT analysis. The histomorphometric parameters analyzed in the standardized volumes of interest included cortical thickness, bone volume, and trabecular properties. Results: Analysis of the cortical thickness of the lateral rows demonstrated that the entire inferior-most lateral row, 15 to 21 mm from the summit of the GT, had the thickest cortical bone (mean, 0.79 mm; P = .0001), with the anterior-most part of the GT, 15 to 21 mm below its summit, having the greatest cortical thickness of 1.02 mm (P = .008). There was a significantly greater bone volume (BV; posterior, 74.5 ± 27.4 mm3; middle, 55.8 ± 24.9 mm3; anterior, 56.9 ± 20.7 mm3; P = .001) and BV as a percentage of total tissue volume (BV/TV; posterior, 7.3% ± 2.7%, middle, 5.5% ± 2.4%; anterior, 5.6% ± 2.0%; P = .001) in the posterior third of the GT than in intermediate or anterior thirds. In terms of both BV and BV/TV, the juxta-articular medial row had the greatest value (BV, 87.3 ± 25.1 mm3; BV/TV, 8.6% ± 2.5%; P = .0001 for both) followed by the inferior-most lateral row 15 to 21 mm from the summit of the GT (BV, 62.0 ± 22.7 mm3; BV/TV, 6.1% ± 2.2%; P = .0001 for both). The juxta-articular medial row had the greatest value for both trabecular number (0.3 ± 0.06 mm–1; P = .0001) and thickness (0.3 ± 0.08 μm; P = .0001) with the lowest degree of trabecular separation (1.3 ± 0.4 μm; P = .0001). The structure model index (SMI) has been shown to strongly correlate with bone strength, and this was greatest at the inferior-most lateral row 15 to 21 mm from the summit of the GT (2.9 ± 0.9; P = .0001). Conclusion: The inferior-most lateral row, 15 to 21 mm from the tip of the GT, has good bone stock, the greatest cortical thickness, and the best SMI for lateral row anchor placement. The anterior-most part of the GT 15 to 21 mm below its summit had the greatest cortical thickness of all zones. The posterior third of the GT also has good bone stock parameters, second only to the medial row. The best site for lateral row cortical anchor placement is 15 to 21 mm below the summit of the GT. Clinical Relevance: Optimal lateral anchor positioning is 15 to 21 mm below the summit of the greater tuberosity in TOE.

Reconstruction of Chronic Foveal TFCC Tears with an Autologous Tendon Graft

Background A triangular fibrocartilage complex (TFCC) injury can produce distal radioulnar joint (DRUJ) instability. If the foveal attachment is avulsed, it translates distally. The footprint is separated from its origin and will become covered in synovitis, preventing healing. The authors describe a surgical technique for the treatment of instability of the DRUJ due to chronic foveal detachment of the TFCC. Technique The procedure utilizes a loop of autologous palmaris longus tendon graft passed through the ulnar aspect of the TFCC and through an osseous tunnel in the distal ulna to reconstruct the fovel attachment. Patients and Methods We report on nine patients with a mean age of 42. Median follow-up was 13 months. Results The median pain scores measured were reduced from 8 to 3 postoperatively, and all had a stable DRUJ. Conclusions This technique provides stability of the distal ulna to the radius and carpus, with potential for biologic healing through osseous integration. It is a robust, anatomically based reconstruction of the TFCC to the fovea that stabilizes the DRUJ and the ulnar-carpal sag.