Eon K. Shin

Mechanical Properties of the Human Cervical Spine as Shown by Three-dimensional Load–displacement Curves

Study Design. The mechanical properties of multilevel human cervical spines were investigated by applying pure rotational moments to each specimen and measuring multidirectional intervertebral motions. Objectives. To document intervertebral main and coupled motions of the cervical spine in the form of load–displacement curves. Summary of Background Data. Although a number of in vivo and in vitro studies have attempted to delineate normal movement patterns of the cervical spine, none has explored the complexity of the whole cervical spine as a three-dimensional structure. Methods. Sixteen human cadaveric specimens (C0–C7) were used for this study. Pure rotational moments of flexion–extension, bilateral axial torque, and bilateral lateral bending were applied using a specially designed loading fixture. The resulting intervertebral motions were recorded using stereophotogrammetry and depicted as a series of load–displacement curves. Results. The resulting load–displacement curves were found to be nonlinear, and both rotation and translation motions were coupled with main motions. With flexion–extension moment loading, the greatest degree of flexion occurred at C1–C2 (12.3°), whereas the greatest degree of extension was observed at C0–C1 (20.2°). With axial moment loading, rotation at C1–C2 was the largest recorded (56.7°). With lateral bending moments, the average range of motion for all vertebral levels was 7.9°. Conclusions. The findings of the present study are relevant to the clinical practice of examining motions of the cervical spine in three dimensions and to the understanding of spinal trauma and degenerative diseases.

Internal morphology of human cervical pedicles.

STUDY DESIGN The internal architecture of cervical spine pedicles was investigated by thin sectioning and digitization of radiographic images. OBJECTIVES To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles. SUMMARY OF BACKGROUND DATA Although there have been a number of studies presenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness along the pedicle axis. METHODS Twenty-five human cervical vertebrae (C3-C7) were secured to a thin-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized to facilitate measurement of the internal dimensions. Computer software was specifically developed to determine the external dimensions (i.e., pedicle height and width) and the internal dimensions (i.e., cortical shell thicknesses of the superior, inferior, lateral, and medial walls and the cancellous core height and width) of cervical pedicles. RESULTS Superior and inferior wall cortical thicknesses of pedicle thin slices were similar, whereas the lateral wall cortical thickness was significantly smaller than the medial wall thickness. The medial cortical shell (average value range: 1.2-2.0 mm) was measured to be 1.4 to 3.6 times as thick as the lateral cortical shell (average value range: 0.4-1.1 mm). When medial and lateral cortical thicknesses were normalized for external dimensions, the combined cortical shell thickness was thinnest at C7 (average value range: 18. 6-25.6% of the external width), and this result was statistically significant when compared with other vertebral levels. CONCLUSIONS The cervical pedicle is a complex, three-dimensional structure exhibiting extensive variability in internal morphology. Characteristics of the cervical pedicle at different spinal levels must be noted before transpedicular screw fixation.

The cortical shell architecture of human cervical vertebral bodies.

Study Design. An anatomic study of cervical vertebral bodies. Objectives. To provide quantitative information on the cortical shell architecture of the middle and lower cervical vertebral bodies. Summary of Background Data. Some external dimensions have been measured, but little quantitative data exists for the cortical shell architecture of the vertebral bodies of the cervical spine. Methods. Twenty-one human cervical vertebral bodies (C3–C7) were sectioned along parasagittal planes into five 1.7-mm thin slices for each vertebra. Radiographs of each slice were digitized, and external and internal dimensions were measured. Averages and standard deviations were computed. Single factor analysis of variance was used to determine significant (P < 0.05) differences between the vertebral levels. Results. The superior endplate was thickest in the posterior region (range 0.74–0.89 mm) and thinnest in the anterior region (range 0.44–0.56 mm). The inferior endplate was thickest in the anterior region (range 0.61–0.81 mm) and thinnest in the posterior region (range 0.49–0.62 mm). In the central region, the superior endplate (range 0.42–0.58 mm) was thinner than the inferior endplate (range 0.53–0.64 mm). Variation with vertebral level was dependent on the dimension studied. Conclusions. Comprehensive quantitative anatomic data of the middle and lower cervical vertebral bodies have been obtained. This may be useful in improving the understanding of the three-column and other vertebral-fracture theories, the fidelity of the finite element models of cervical spine, and the designs of surgical instrumentation.

Ulnar Shortening Osteotomy for Ulnar Impaction Syndrome

THE PATIENT A 46-year-old right hand–dominant woman presents with left ulnar-sided wrist pain following a fall from a standing height onto her outstretched hand 6 months before. The examination is normal except for pain with ulnar deviation and axial loading of the wrist. A posteroanterior radiograph of the wrist taken with the forearm in full pronation demonstrates ulnar-positive variance measuring 4 mm. Magnetic resonance imaging reveals increased signal intensity over the proximal ulnar aspect of the lunate and distal ulna along with a central defect of the triangular fibrocartilage complex.

Salvage Reconstruction of Congenital Pseudarthrosis of the Clavicle With Vascularized Fibular Graft After Failed Operative Treatment: A Case Report

Congenital pseudarthrosis of the clavicle is a rare condition present at birth but often diagnosed later in childhood. Indications for surgical treatment include deformity, pain, or neurovascular compromise. Reconstruction usually involves resection of the pseudarthrosis, placement of iliac crest bone graft, and internal fixation. We report a case of congenital pseudarthrosis of the clavicle that failed initial surgical management at another institution using bone marrow aspirate, bone graft substitute, and internal fixation with plate and screws. Treatment failure was associated with significant osteolysis resulting in a large defect of the midclavicle with only small areas of residual bone remaining at the medial and lateral ends, and the remaining hardware was mobile. The defect was judged to be too large for placement of an iliac crest bone graft and was therefore spanned with a free vascularized fibular graft. At 15 months postoperatively, the patient has clinical and radiographic unions, and is symptom-free with an excellent cosmetic result. This unique application of a well-established technique provided a successful solution to this difficult revision situation. Level of Evidence: Level V, case report

Treatment of Thumb Metacarpophalangeal and Interphalangeal Joint Arthritis

Degenerative joint disease affecting the thumb metacarpophalangeal and interphalangeal joints is a debilitating condition, which can significantly restrict activities of daily living. Conservative measures to address symptoms include oral anti-inflammatory medications, activity modification and splinting, and intraarticular corticosteroid injections. Surgical interventions include arthroscopic synovectomy, arthroplasty, and finally arthrodesis of the affected articulations. Although short-term results from synovectomy and arthroplasty seem promising, long-term data are not yet available. Arthrodesis of the metacarpophalangeal and interphalangeal joints yields a stable yet functional thumb with reliably good pain relief.

Management of complications of wrist arthroplasty and wrist fusion.

The human wrist joint is unique from functional and anatomic standpoints. Numerous articulations exist within the wrist that allow for many options for partial wrist fusion and arthroplasty. In cases of pancarpal disease, fusion or arthroplasty of the entire wrist joint can be performed. Because of the high functional demand of the wrist, many of these surgical options can fail, leading to devastating complications. This article addresses the types of fusions and arthroplasties available for the wrist and discusses the potential complications associated with each. Methods to prevent these complications are presented and those to treat them once they have occurred are discussed.

Wrist Arthroscopy for Athletic Injuries

Management of hand and wrist injuries for athletes often places emphasis on an expeditious return to sport. Arthroscopic techniques have the advantage of directly visualizing joint derangements and correcting them via a minimally invasive approach. This article discusses the evaluation and management of common wrist injuries treated with arthroscopy in athletes, including scapholunate and lunotriquetral injury, triangular fibrocartilage complex tears, hamatolunate impingement, and arthroscopic-assisted reduction of wrist fractures.

Nonbridging External Fixation of Distal Radius Fractures

Surgical management of distal radius fractures continues to evolve because of their high incidence in an increasingly active elderly population. Traditional radiocarpal external fixation relies on ligamentotaxis for fracture reduction but has several drawbacks. Nonbridging external fixation has evolved to provide early wrist mobility in the setting of anatomic fracture reduction. Several studies of the nonbridging technique have demonstrated satisfactory results in isolated nonbridging external fixation series and in comparison with traditional spanning external fixation. Nonbridging external fixation for surgical treatment of distal radius fractures can be technically demanding and requires at least 1 cm of intact volar cortex in the distal fracture fragment for successful implementation.

Prognostic Variables for Patient Return-to-Work Interval Following Carpal Tunnel Release in a Workers’ Compensation Population

Background: We hypothesize that depressive and anxiety disorders, chronic pain conditions, and work-related factors are significant determinants of the time interval for return to work (RTW) in the workers’ compensation (WC) population following carpal tunnel release (CTR) surgery. Methods: We retrospectively reviewed records of all WC patients who underwent open CTR surgery over a 5-year period by 1 of 3 fellowship-trained hand surgeons. One hundred fifty-two wrists in 108 patients (64 unilateral, 44 bilateral) met the inclusion criteria. Demographic, medical, and surgical data were obtained from patient records. Bivariate and multivariate analyses were performed to assess predictors of RTW. Results: Eighty-nine percent of all patients returned to work full-duty. Average RTW duration in all wrists was 12.5 ± 11.3 weeks. Predictors of delayed RTW in bivariate and multivariate analyses were depression with or without anxiety, chronic pain disorders including fibromyalgia, preoperative opioid use, and modified preoperative work status. Job type, motor nerve conduction velocity, and bilateral surgery were not predictive of delayed RTW interval. Conclusions: WC patients with depression, anxiety, or fibromyalgia and other chronic pain disorders were significantly more likely to have delayed RTW following CTR than were WC patients without these conditions. In addition, those who use opioid medications preoperatively and those with preoperative work restrictions were also found to have a significantly delayed RTW after CTR. Knowledge of these risk factors may help care providers and employers identify those WC patients who are most likely to have a protracted postoperative recovery period.