Christopher Got

In Vivo Kinematics of the Thumb Carpometacarpal Joint During Three Isometric Functional Tasks

BackgroundThe thumb carpometacarpal (CMC) joint is often affected by osteoarthritis—a mechanically mediated disease. Pathomechanics of the CMC joint, however, are not thoroughly understood due to a paucity of in vivo data.Questions/purposesWe documented normal, in vivo CMC joint kinematics during isometric functional tasks. We hypothesized there would be motion of the CMC joint during these tasks and that this motion would differ with sex and age group. We also sought to determine whether the rotations at the CMC joint were coupled and whether the trapezium moved with respect to the third metacarpal.MethodsForty-six asymptomatic subjects were CT-scanned in a neutral position and during three functional tasks (key pinch, jar grasp, jar twist), in an unloaded and a loaded position. Kinematics of the first metacarpal, third metacarpal, and the trapezium were then computed.ResultsSignificant motion was identified in the CMC joint during all tasks. Sex did not have an effect on CMC joint kinematics. Motion patterns differed with age group, but these differences were not systematic across the tasks. Rotation at the CMC joint was generally coupled and posture of the trapezium relative to the third metacarpal changed significantly with thumb position.ConclusionsThe healthy CMC joint is relatively stable during key pinch, jar grasp, and jar twist tasks, despite sex and age group.Clinical RelevanceOur findings indicate that directionally coupled motion patterns in the CMC joint, which lead to a specific loading profile, are similar in men and women. These patterns, in addition to other, nonkinematic influences, especially in the female population, may contribute to the pathomechanics of the osteoarthritic joint.

The morphology of the thumb carpometacarpal joint does not differ between men and women, but changes with aging and early osteoarthritis

The high prevalence of thumb carpometacarpal (CMC) joint osteoarthritis (OA) in women has been previously linked to the articular morphology of the trapezium. Studies report conflicting results on how the articular shapes of male and female trapezia compare to one another, however, mainly because their findings are based on data from older cadaveric specimens. The purpose of this in vivo study was to dissociate the effect of sex from that of aging and early OA by using cohorts of healthy young and healthy older subjects, as well as patients with early stage OA. Computed tomography scans from 68 healthy subjects and 87 arthritic subjects were used to obtain 3-D bone models. The trapezial and metacarpal articular surfaces were manually delineated on scaled bone models and compared between sex, age, and health groups by using polar histograms of curvature and average curvatures. We found no sex-related differences, but significant age-group and health-group differences, in the articular surfaces of both bones. Older healthy subjects had higher curvature in the concave and lower curvature in the convex directions of both the trapezial and metacarpal saddles than healthy young subjects. Subjects with early OA had significantly different metacarpal and trapezial articular shapes from healthy subjects of the same age group. These findings suggest that aging and OA affect the articular shape of the CMC joint, but that, in contrast to previously held beliefs, inherent sex differences are not responsible for the higher incidence of CMC OA in women.

Fluoroscopic Evaluation of Intra-Articular Screw Placement During Locked Volar Plating of the Distal Radius: A Cadaveric Study

PURPOSE To evaluate specific fluoroscopic views for assessment of intra-articular screw placement during locked volar plating of the distal radius. METHODS The distal radius of a cadaver forearm was plated with a fixed-angle volar plate according to the surgical technique guide of the manufacturer. A goniometer was used to place the specimen at various described angles in the fluoroscope including standard posteroanterior (PA), tilt PA (11 degrees ), standard lateral, and tilt lateral (15 degrees , 23 degrees , 30 degrees ) views. Radiographic images of each screw individually and in various combinations were digitally captured. RESULTS Only the tilt PA view correctly showed all 4 screws to be extra-articular. On the standard PA view, the 2 ulnar screws appeared intra-articular. Lower angle tilt lateral views (15 degrees and 23 degrees ) correctly visualized the ulnar screws but not the styloid screw. The highest angle lateral view (30 degrees ) correctly visualized the radial screws but not the sigmoid (most ulnar) screw. The styloid screw appeared to be intra-articular on every lateral view except at 30 degrees and was correctly visualized on both the PA and tilt PA views. CONCLUSIONS Multiple oblique views are required for evaluation of intra-articular screw placement during locked volar plating of the distal radius. Lower angle tilt lateral views are more specific for the ulnar screws, and higher angle views are more specific for the radial screws. We suggest first placing the ulnar screws whenever possible, using lower angle tilt lateral views (15 degrees to 23 degrees ) to evaluate for intra-articular placement. The styloid screw may be placed last and can then be evaluated on the PA and tilt PA views.

Ring and Little Finger Metacarpal Fractures: Mechanisms, Locations, and Radiographic Parameters

PURPOSE To describe a series of ring and little finger metacarpal fractures with regard to mechanism, location, midshaft diameter, and isthmus diameter, to better define injury patterns and assist the surgeon in selection of appropriately sized implants. METHODS We reviewed all metacarpal fractures in skeletally mature patients who presented to a single surgeon over a 2-year period. Fractures of the ring and little finger metacarpals were analyzed with regard to mechanism and fracture location. Metacarpal midshaft and minimum isthmus diameters were measured on posteroanterior radiographs. RESULTS A total of 101 fractures involved the ring and little finger metacarpals. Punching-type injuries accounted for most fractures in the little finger metacarpal (49 of 67) and ring finger metacarpal (26 of 34). Among these punching-related ring and little finger metacarpal fractures, the most common fracture location was the little finger metacarpal neck (34 of 75), followed by the ring finger metacarpal shaft (21 of 75). Among men in this series, the metacarpal midshaft and minimum isthmus diameters were significantly narrower in the ring finger metacarpal than in the little finger (7.4 vs 8.7 mm, p < .001; and 2.2 vs 3.8 mm, p < .001). CONCLUSIONS Whereas punching injuries tended to cause neck fractures in little finger metacarpals in this series, they caused shaft fractures in ring finger metacarpals, which may thus be considered a variant boxers fracture. Furthermore, in men with fractures, the ring finger metacarpal is significantly narrower than the little finger, both in midshaft diameter and isthmus diameter, which surgeons should consider when planning internal fixation. TYPE OF STUDY/LEVEL OF EVIDENCE Prognostic IV.

Biomechanical Comparison of Parallel Versus 90-90 Plating of Bicolumn Distal Humerus Fractures With Intra-Articular Comminution

PURPOSE To compare the biomechanical properties of 90-90 versus mediolateral parallel plating of C-3 bicolumn distal humerus fractures. METHODS We created intra-articular AO/Orthopaedic Trauma Association C-3 bicolumn fractures in 10 fresh-frozen matched pairs of cadaveric elbows. We determined bone mineral density of the metaphyseal region with dual-energy x-ray absorptiometry. The matched pairs of elbows were randomly assigned to either 90-90 or parallel plate fixation. We tested anteroposterior displacement at a rate of 0.5 mm/s to a maximum load of ± 100 N for both the articular and entire distal humerus segments. We tested torsional stability at a displacement rate of 0.1 Hz to a maximum torque of ± 2.5 Nm. After cyclical testing, we loaded the specimens in torsion to failure. RESULTS There was no significant difference in the bone density of the paired specimens. Compared with parallel fixation, 90-90 plate fixation had significantly greater torque to failure load. Both plating constructs were equally sensitive to bone density. Both techniques had the same mode of failure in torsion, a spiral fracture extending from the medial plate at the metaphyseal-diaphyseal junction. There was no significant difference in the stiffness of fixation of the articular fragment or the entire distal segment in anteroposterior loading. CONCLUSIONS This study demonstrated that 90-90 and parallel plating had comparable biomechanical properties for fixation of comminuted intra-articular distal humerus fractures, and that 90-90 plating had greater resistance to torsional loading.

A thumb carpometacarpal joint coordinate system based on articular surface geometry

The thumb carpometacarpal (CMC) joint is a saddle-shaped articulation whose in vivo kinematics can be explored more accurately with computed tomography (CT) imaging methods than with previously used skin-based marker systems. These CT-based methods permit a detailed analysis of the morphology of the joint, and thus the prominent saddle geometry can be used to define a coordinate system that is inherently aligned with the primary directions of motion at the joint. The purpose of this study was to develop a CMC joint coordinate systems that is based on the computed principal directions of curvature on the trapezium and the first metacarpal. We evaluated the new coordinate system using bone surface models segmented from the CT scans of 24 healthy subjects. An analysis of sensitivity to the manual selection of articular surfaces resulted in mean orientation differences of 0.7±0.7° and mean location differences of 0.2±0.1mm. Inter-subject variability, which mostly emanates from anatomical differences, was evaluated with whole bone registration and resulted in mean orientation differences of 3.1±2.7° and mean location differences of 0.9±0.5mm. The proposed joint coordinate system addresses concerns of repeatability associated with bony landmark identification and provides a robust platform for describing the complex kinematics of the CMC joint.

Predictors of failure of nonoperative treatment for type-2 supracondylar humerus fractures.

Background Closed reduction and casting for type-2 supracondylar fractures is a viable treatment option, but studies have shown that some patients will fail to maintain the initial reduction in a cast. This study sought to identify predictors of failed treatment of closed reduction and casting for these fractures. Methods We performed a retrospective case-control study of type-2 supracondylar fractures treated by closed reduction and casting. Using radiographic failure of reduction as our primary outcome measure, we examined injury, postreduction, and follow-up films evaluating the anterior humeral line, cast flexion angle, and degree of cast padding in an attempt to identify predictors of failure. Results We reviewed 645 fractures. Of 126 type-2 fractures, 61 fractures were included in the study. There were 49 (80%) nonoperative treatment successes and 12 failures (20%) with an average follow-up of 41 days (range, 20 to 161 d). We found that (1) the degree of fracture extension using an index based on the anterior humeral line on the injury film was significantly related to failure of cast treatment (P=<0.01), and (2) the width of the soft tissue shadow of the upper arm on the postreduction film was of borderline significance (P=0.02). Cast flexion angle and cast padding were not predictive of radiographic loss of reduction (P=0.94 and 0.70). Conclusions Despite adequate reduction and casting of type-2 supracondylar fractures, some fractures will lose reduction and require delayed pinning. The degree of extension of the distal fragment at the time of injury may help to predict the likelihood of failure of nonoperative treatment. Level of Evidence III.

Quality Measures in Upper Limb Surgery.

BACKGROUND Quality measures are now commonplace and are increasingly tied to financial incentives. We reviewed the existing quality measures that address the upper limb and tested the null hypothesis that structure (capacity to deliver care), process (appropriate care), and outcome (the result of care) measures are equally represented. METHODS We systematically reviewed MEDLINE/PubMed, Embase, Google Scholar, the American Academy of Orthopaedic Surgeons Clinical Practice Guidelines, the National Quality Forum, the Agency for Healthcare Research and Quality, and the Physician Quality Reporting System for quality measures addressing upper limb surgery. Measures were characterized as structure, process, or outcome measures and were categorized according to their developer and their National Strategy for Quality Improvement in Health Care (National Quality Strategy) priority as articulated by the U.S. Department of Health & Human Services. RESULTS We identified 134 quality measures addressing the upper limb: 131 (98%) process and three (2%) outcome measures. The majority of the process measures address the National Quality Strategy priority of effective clinical care (90%), with the remainder addressing communication and care coordination (5%), person and caregiver-centered experience and outcomes (4%), and community/population health (1%). CONCLUSIONS Our review identified opportunities to develop more measures in the structure and outcome domains as well as measures addressing patient and family engagement, public health, safety, care coordination, and efficient use of resources. The most common existing measures-process measures addressing care-might not be the best measures of upper limb surgery quality given the relative lack of evidence for their use in care improvement.

Complications associated with retained implants after plate fixation of the pediatric forearm.

Objective: Our present study examines the complications of pediatric patients treated with plate fixation for forearm fractures. Design: Case series of pediatric patients after their forearm fracture was fixed using a plate, with the majority of patients retaining their implants. Setting: Level 1 Trauma Center. Methods: From 1999 to 2009, 58 patients between the ages of 6 and 15 years had fixation of their forearm fracture with plates. Thirty-three of these patients were available for a long-term follow-up with an average of 6.4 years. The patients were interviewed over the phone, and a physician filled out a questionnaire with regard to their clinical course. Records and x-ray data were reviewed for each patient. Factors such as implant complications, functional activity level, pain score, and clinical symptoms were studied. Results: Fractures occurred in 7.1% (2/28) of the patients who chose to retain their implants. Of the 28 patients who initially chose to leave the implants in place, 17.9% (5/28) had a partial or complete removal of the implants because of irritation. These patients reported the following symptoms: mild pain 42.3% (11/26), clicking 34.6% (9/26), ability to feel the plates 73.1% (19/26), and mild weakness 26.9% (7/26). The number of patients who reported return to the preinjury level of activity was 88.5% (23/26), and 96.2% (25/26) reported being satisfied with their clinical outcome when implants were retained. Females had a significantly greater subjective weakness of 60.0% (6/10) compared with that of males, which was 14.3% (3/21; P = 0.009) after a forearm fracture. The inability to return to the preinjury level of activity was significantly greater for females, which was 30.0% (3/10) versus 0.0% (0/21) for males (P = 0.008). Conclusions: We concluded that retaining the plates in pediatric forearm fractures does not increase the refracture rate compared with the removal from the historical rates in the literature. Patients should be warned of possible symptoms and complications that may be present with retained plates. Also, a more aggressive physical therapy may be considered for females because they were observed to have more subjective weakness and dysfunction at long-term follow-up. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Flexor Tendon Repair With Looped Suture: 1 Versus 2 Knots

PURPOSE To assess the strength of flexor tendon repair with looped suture. We hypothesized that, after passing the intact looped suture in the desired repair configuration, splitting the loop and tying 2 independent knots would increase the strength of flexor tendon repair. METHODS Thirty-two flexor tendons were harvested and were sharply transected in zone II. The tendons were repaired with a 4-strand core suture repair using 3-0 looped nonabsorbable nylon suture. The harvested tendons were randomly assigned and repaired with either a 1- or a 2-knot construct. The repaired flexor tendons were fixed in a servohydraulic material testing system and were loaded to failure either with uniaxial tension or cyclically. RESULTS The average force at failure was 43 N for the 1-knot repair and 28 N for the 2-knot repair. The mode of failure of 15 of the flexor tendon repairs that were cyclically loaded to failure was suture pull-out. The average number of cycles and force in cyclic testing that caused failure of flexor tendon repairs was 134 cycles and 31 N for tendons repaired with looped 3-0 suture tied with 1 knot and 94 cycles and 33 N for tendons repaired with looped 3-0 suture tied with 2 knots. CONCLUSIONS Our hypothesis was disproved by the results of this study. CLINICAL RELEVANCE This study suggests that, when using looped suture, tying 2 independent knots instead of tying a single knot does not increase the strength of the flexor tendon repair.