George L. Lucas

Fat embolism syndrome.

Since it was initially described, fat embolism syndrome (FES) has remained one of the least clearly understood complications of trauma. This article is a review of the classic and current literature on FES with regard to its causes, pathophysiology, clinical presentation, diagnosis, and treatment. FES is associated with many traumatic and nontraumatic conditions, but is most commonly associated with fractures of long bones of the lower extremity. The pathophysiology is thought to be a cascade of events which can lead to adult respiratory distress syndrome (ARDS). Signs and symptoms of clinical FES usually begin within 24 to 48 hours after trauma. The classic triad involves pulmonary changes, cerebral dysfunction, and petechial rash. Clinical diagnosis is key because laboratory and roentgenographic diagnosis is not specific. Treatment consists of careful initial handling, early stabilization of fractures, careful volume replacement, analgesia, respiratory support, and perhaps steroids. The vast majority of patients today survive FES without sequelae.

Isolated Arthroscopic Meniscal Repair: A Long-Term Outcome Study (More Than 10 Years):

A single surgeons consecutive series of 50 arthroscopically repaired meniscal tears in 48 patients was retrospectively reviewed. None of these patients had concomitant ligament damage to the knee. The average follow-up period was 10 years, 9 months. Criteria for clinical success included 1) history of pain of grade 1 or less and absence of locking, catching, or giving way; 2) a physical examination demonstrating no significant effusion and a painless and negative jump sign; and 3) no subsequent surgical procedures on the repaired meniscus. Patient satisfaction was quite high, although clinical confirmation was possible in only 38 knees, indicating a clinical success rate of 76%. Bilateral standing radiographs were obtained on these 38 operated knees and were evaluated using Fairbanks classification. Evaluation of the radiographs revealed that 8% of the operated knees had minimal joint changes, as compared with 3% in the contralateral, nonoperated knee. This study demonstrates that arthroscopic meniscal repair in knees with isolated meniscal tears has the potential for a long-term successful clinical and radiographic outcome.

Biomechanical and computer analysis of radial head prostheses.

Radial head fractures can lead to significant upper extremity disability. A comminuted radial head fracture with a medial collateral ligament tear presents a clinical conundrum. The radiocapitellar (RC) joint should be maintained, yet the head frequently cannot be reduced and stabilized. The silicone rubber implant currently available is not biomechanically or clinically satisfactory, and thus there is a need for a more suitable prosthetic replacement for the radial head. We have attempted to design such a prosthesis and have examined prosthetic design with various materials that would best transmit force of the RC joint. Design configurations based on our cadaveric and radiographic measurements were tested with structural finite element method computer analyses. Materials examined included titanium alloy, cobalt-chrome alloy, alumina ceramic, and ultrahigh molecular weight polyethylene (UHMWPE). Metals and ceramic transmitted force at the distal bone and implant interface and strain shielded the proximal radial cortex while UHMWPE distributed load uniformly through the cortex and along the entire bone and implant interface. In addition, load transmission comparisons were made with the intact radial head, with a silicone prosthesis, and with 6 and 10 mm thick UHMWPE prostheses in cadaveric specimens. UHMWPE prostheses transmit more force to the RC joint than the silicone prosthesis and with leads closer to physiologic levels at all flexion angles. UHMWPE prostheses not only transmit much more force than silicone, but because of substantially less deformation under load, also provide more stability to the joint.

The pattern of venous drainage of the digits

The transosseous injection of colored latex through 36 fingers demonstrated that the venous system consists of a series of arcades on the dorsal and palmar surface of the digit with connecting oblique and transverse anastomotic veins. The caliber of the palmar veins was smaller than that of the dorsal and their route did not consistently run with the digital artery and nerve. Venous channels were also found in the vincula. The anastomotic veins and especially the commissural veins provide a venous return for the digit if the major dorsal system has been divided.

Structural properties of a novel design of composite analogue humeri models.

Background Mechanical analogue composite bone models have been used as cadaveric bone substitutes in a wide variety of biomechanical tests. The objective of this study was to compare the structural properties of two types (Third- and Fourth-Generation) of commercially available composite analogue humeri. Methods Eighteen of each generation composite analogue humeri were evaluated for flexural rigidity, torsional rigidity, and failure strength. Three tests were performed: medial–lateral four-point bending, anterior–posterior four-point bending, and external rotational torque. Results The Fourth-Generation analogue humeri performed more closely to the biological average with respect to failure strength, flexural rigidity, and torsional stiffness when compared to the Third-Generation humeri. Both the Third- and Fourth-Generation analogues were within the range of published human bone values. There was a statistically significant difference in strength in all modes of testing between the Fourth-Generation humeri and the Third-Generation humeri. Conclusion These composite analogue humeri are ideal for standardization in biomechanical analyses. The advantage of these humeri is that their variability is significantly lower than that of cadaveric specimens for all loading regimens. The widely varying results observed when comparing composite analogue humeri to cadaveric humeri might be derived from the use of different ranges of applied load, varied test methodologies, and diverse methods of computing the stiffness. Mechanical validation of whole Fourth-Generation humeri bone models would be an appropriate follow-up to this study with a direct comparison to cadaveric humeri. Clinical relevance This study validated and advanced our overall understanding of the capacity of composite analogue humeri to model the structural properties of human bone.

Expression of Vascular Endothelial Growth Factor correlates with the advance of clinical osteosarcoma

PurposeOsteosarcoma is the most common primary malignancy in orthopaedic surgery. Studies suggest that expression of VEGF and high vascularity within osteosarcoma may correlate with poor prognosis. The purpose of this study was to determine whether there was a correlation of VEGF expression with clinical tumour stage and metastasis.MethodsThis retrospective case series examined 54 cases of osteosarcoma patients who were treated during a ten-year period. Relevant clinical information included age, gender, tumour location, stage, adjuvant therapy, morbidity, mortality, and tumour subtypes. The clinical information was analysed for correlation of VEGF expression and tumour prognosis. Tumour sections were examined by routine H&E and by immunohistochemistry for VEGF, CD31, and the oncogenes c-myc and c-fos.ResultsThere was a significantly positive correlation between VEGF expression and tumour stages among these cases (p < 0.01). The data also suggested a higher cancer recurrence and more frequent cases of remote metastasis in the high-VEGF group compared to the low-VEGF group. VEGF expression also positively associated with c-fos and c-myc expressions in the primary tumour sections.ConclusionThe results of this study highlight the role of VEGF in angiogenesis and tumour burden. Data also suggest the influence of VEGF may associate with the elevations of c-fos and c-myc expression. The development of novel therapies to target the VEGF pathway in osteosarcoma may lead to improved survival.

Role of the coracoacromial ligament as restraint after shoulder hemiarthroplasty.

Patients with an irreparable rotator cuff tear and glenohumeral degeneration often are treated with hemiarthroplasty. This procedure has proven effective as long as the coracoacromial ligament remained intact. The ligament reportedly acts as a restraint against anterosuperior dislocation. The purpose of the current study was to test the role of the coracoacromial ligament as an anterosuperior restraint after hemiarthroplasty in shoulders from cadavers with simulated irreparable rotator cuff tears. Six fresh-frozen shoulders were dissected to mimic a massive rotator cuff tear. After a hemiarthroplasty was done, each shoulder was mounted in a fixture, which was attached to a materials testing device. Using this device, the role of the coracoacromial ligament was evaluated by loading the shoulders in various positions and then measuring displacement before and after excision of the ligament. The mean difference in anterosuperior displacement was 3.44 mm. In all shoulders, subjective observation revealed that the humeral head often becomes wedged between the coracoid and the acromion during axial loading after excision of the coracoacromial ligament. Therefore, the coracoacromial ligament should be preserved to enhance the stability of the joint and to preserve the superior fulcrum.

Value of cervical spine radiographs as a screening tool

A review of the reports of 848 cervical spine radiographs was done to assess the yield of useful and critical information in a group of patients without trauma. In 470 of these patients the clinical record also was reviewed; 54.2% of the radiographs were read as having degenerative change, 35% were read as normal, and 8.5% were read as being consistent with muscle spasm. The remaining 2.3% included diagnoses of anatomic or congenital variants, soft tissue calcification, or old compression fractures. There were no serious diagnoses such as acute fracture, dislocation, or neoplasm that, had they not been identified, would have put the patient in jeopardy. Thus, for most outpatients with nontraumatic symptoms of a nonspecific or nonlocalizing nature, the use of cervical spine radiographs as a screening tool is not justified.

Osteoblastoma of the scaphoid: A case report☆

Abstract Wrist pain is a common complaint that is rarely due to a tumor. We have treated a patient whose wrist pain was caused by a rare tumor, osteoblastoma. The purpose of this report is to emphasize the need to uncover obscure causes of wrist pain.

ARP2/3 complex is required for directional migration of neural stem cell-derived oligodendrocyte precursors in electric fields

IntroductionThe loss of oligodendrocytes in a lesion of the central nervous system causes demyelination and therefore impairs axon function and survival. Transplantation of neural stem cell-derived oligodendrocyte precursor cells (NSC-OPCs) results in increased oligodendrocyte formation and enhanced remyelination. The directional migration of grafted cells to the target can promote the establishment of functional reconnection and myelination in the process of neural regeneration. Endogenous electric fields (EFs) that were detected in the development of the central nervous system can regulate cell migration.MethodsNSCs were isolated from the brains of ARPC2+/+ and ARPC2−/− mouse embryo and differentiated into OPCs. After differentiation, the cultured oligospheres were stimulated with EFs (50, 100, or 200 mV/mm). The migration of OPCs from oligospheres was recorded using time-lapse microscopy. The cell migration directedness and speed were analyzed and quantified.ResultsIn this study, we found that NSC-OPCs migrated toward the cathode pole in EFs. The directedness and displacement of cathodal migration increased significantly when the EF strength increased from 50 to 200 mV/mm. However, the EF did not significantly change the cell migration speed. We also showed that the migration speed of ARPC2−/− OPCs, deficient in the actin-related proteins 2 and 3 (ARP2/3) complex, was significantly lower than that of wild type of OPCs. ARPC2−/− OPCs migrated randomly in EFs.ConclusionsThe migration direction of NSC-OPCs can be controlled by EFs. The function of the ARP complex is required for the cathodal migration of NSC-OPCs in EFs. EF-guided cell migration is an effective model to understanding the intracellular signaling pathway in the regulation of cell migration directness and motility.