Christopher H. Allan

Kienböck's Disease: Diagnosis and Treatment

&NA; Kienböck’s disease, or osteonecrosis of the lunate, can lead to chronic, debilitating wrist pain. Etiologic factors include vascular and skeletal variations combined with trauma or repetitive loading. In stage I Kienböck’s disease, plain radiographs appear normal, and bone scintigraphy or magnetic resonance imaging is required for diagnosis. Initial treatment is nonoperative. In stage II, sclerosis of the lunate, compression fracture, and/or early collapse of the radial border of the lunate may appear. In stage IIIA, there is more severe lunate collapse. Because the remainder of the carpus is still uninvolved, treatment in stages II and IIIA involves attempts at revascularization of the lunate ¯either directly (with vascularized bone grafting) or indirectly (by unloading the lunate). Radial shortening in wrists with negative ulnar variance and capitate shortening or radial‐wedge osteotomy in wrists with neutral or positive ulnar variance can be performed alone or with vascularized bone grafting. In stage IIIB, palmar rotation of the scaphoid and proximal migration of the capitate occur, and treatment addresses the carpal collapse. Surgical options include scaphotrapeziotrapezoid or scaphocapitate arthrodesis to correct scaphoid hyperflexion. In stage IV, degenerative changes are present at the midcarpal joint, the radiocarpal joint, or both. Treatment options include proximal‐row carpectomy and wrist arthrodesis.

Development and Regeneration of the Neonatal Digit Tip in Mice

The digit tips of children and rodents are known to regenerate following amputation. The skeletal structure that regenerates is the distal region of the terminal phalangeal bone that is associated with the nail organ. The terminal phalanx forms late in gestation by endochondral ossification and continues to elongate until sexual maturity (8 weeks of age). Postnatal elongation at its distal end occurs by appositional ossification, i.e. direct ossification on the surface of the terminal phalanx, whereas proximal elongation results from an endochondral growth plate. Amputation through the middle of the terminal phalanx regenerates whereas regenerative failure is observed following amputation to remove the distal 2/3 of the bone. Regeneration is characterized by the formation of a blastema of proliferating cells that appear undifferentiated and express Bmp4. Using chondrogenic and osteogenic markers we show that redifferentiation does not occur by endochondral ossification but by the direct ossification of blastema cells that form the rudiment of the digit tip. Once formed the rudiment elongates by appositional ossification in parallel with unamputated control digits. Regenerated digits are consistently shorter than unamputated control digits. Finally, we present a case study of a child who suffered an amputation injury at a proximal level of the terminal phalanx, but failed to regenerate despite conservative treatment and the presence of the nail organ. These clinical and experimental findings expand on previously published observations and initiate a molecular assessment of a mammalian regeneration model.

Mammalian regeneration and regenerative medicine

Mammals are generally considered to be poor regenerators, yet there are a handful of mammalian models that display a robust ability to regenerate. One such system is the regenerating tips of digits in both humans and mice. In vitro studies of regenerating fetal human and mouse digit tips display both anatomical and molecular similarities, indicating that the mouse digit is a clinically relevant model. At the same time, genetic studies on mouse digit tip regeneration have identified signaling pathways required for the regeneration response that parallel those known to be important for regeneration in lower vertebrates. In addition, recent studies establish that digit tip regeneration involves the formation of a blastema that shares similarities with the amphibian blastema, thus establishing a conceptual bridge between clinical application and basic research in regeneration. In this review we discuss how the study of endogenous regenerating mammalian systems is enhancing our understanding of regenerative mechanisms and helping to shed light on the development of therapeutic strategies in regenerative medicine.

Efficiency of the flexor tendon pulley system in human cadaver hands

The efficiency of the flexor tendon system was examined in a human cadaver model. Pulleys were randomly sectioned, and the results were evaluated on the basis of the tendon excursion, force generated at the fingertip, and the work (force multiplied by distance) involved, as compared to the intact pulley system. When a single minor pulley (A1 or A5) was cut, there was no statistical difference in work efficiency or excursion efficiency from controls. Cutting all minor pulleys (A1, A3, A5) lead to a significant loss in excursion efficiency. The intact three pulley systems of A2, A3, and A4 were near normal and statistically better than A2 and A4 together for work efficiency. Cutting one of the major pulleys (A2, A4) resulted in significant changes in efficiency, but what was unexpected was to find an 85% loss of both work and excursion efficiency for the loss of A4 but only an excursion difference of 94% for the loss of A2. Our findings demonstrated that in this model, with the influence of the skin removed, A4 absence produced the largest biomechanically measured efficiency changes and that a combination of A2, A3, and A4 was necessary to preserve both work and excursion efficiency.

Complications associated with distraction plate fixation of wrist fractures.

This article discusses the major and minor complications of distal plating in the light of a cohort study carried out by the authors, who reviewed all patients undergoing bridge distraction plate fixation of distal radius fractures by three surgeons in a single level I trauma center. The article discusses the effectiveness and the complication rates associated with the technique.

Functional Outcomes Following Bridge Plate Fixation for Distal Radius Fractures

PURPOSE To determine the functional outcomes of patients treated with dorsal spanning distraction bridge plate fixation for distal radius fractures. METHODS All adult patients at our institution who underwent treatment of a unilateral distal radius fracture using a dorsal bridge plate from 2008 to 2012 were identified retrospectively. Patients were enrolled in clinical follow-up to assess function. Wrist range of motion, grip strength, and extension torque were measured systematically and compared with the contralateral, uninjured wrist. Patients also completed Quick-Disabilities of the Arm, Shoulder, and Hand and Patient-Rated Wrist Evaluation outcomes questionnaires. RESULTS Eighteen of 100 eligible patients, with a minimum of 1 year from the time of implant removal, were available for follow-up (mean, 2.7 y). All fracture patterns were comminuted and intra-articular (AO 23.C3). There were significant decreases in wrist flexion (43° vs 58°), extension (46° vs 56°), and ulnar deviation (23° vs 29°) compared with the contralateral uninjured wrist. Grip strength was 86% and extension torque was 78% of the contralateral wrist. Comparison of dominant and nondominant wrist injuries identified nearly complete recovery of grip (95%) and extension (96%) strength of dominant-sided wrist injuries, compared with grip (79%) and extension (65%) strength in those with an injured nondominant wrist. Mean Quick-Disabilities of the Arm, Shoulder, and Hand and Patient-Rated Wrist Evaluation scores were 16 and 14, respectively. There were 2 cases of postoperative surgical site pain and no cases of infection, tendonitis, or tendon rupture. CONCLUSIONS Distraction bridge plate fixation for distal radius fractures is safe with minimal complications. Functional outcomes are similar to those published for other treatment methods. TYPE OF STUDY/LEVEL OF EVIDENCE Therapeutic IV.

Botulinum Toxin Induces Muscle Paralysis and Inhibits Bone Regeneration in Zebrafish

Intramuscular administration of Botulinum toxin (BTx) has been associated with impaired osteogenesis in diverse conditions of bone formation (eg, development, growth, and healing), yet the mechanisms of neuromuscular‐bone crosstalk underlying these deficits have yet to be identified. Motivated by the emerging utility of zebrafish (Danio rerio) as a rapid, genetically tractable, and optically transparent model for human pathologies (as well as the potential to interrogate neuromuscular‐mediated bone disorders in a simple model that bridges in vitro and more complex in vivo model systems), in this study, we developed a model of BTx‐induced muscle paralysis in adult zebrafish, and we examined its effects on intramembranous ossification during tail fin regeneration. BTx administration induced rapid muscle paralysis in adult zebrafish in a manner that was dose‐dependent, transient, and focal, mirroring the paralytic phenotype observed in animal and human studies. During fin regeneration, BTx impaired continued bone ray outgrowth, morphology, and patterning, indicating defects in early osteogenesis. Further, BTx significantly decreased mineralizing activity and crystalline mineral accumulation, suggesting delayed late‐stage osteoblast differentiation and/or altered secondary bone apposition. Bone ray transection proximal to the amputation site focally inhibited bone outgrowth in the affected ray, implicating intra‐ and/or inter‐ray nerves in this process. Taken together, these studies demonstrate the potential to interrogate pathological features of BTx‐induced osteoanabolic dysfunction in the regenerating zebrafish fin, define the technological toolbox for detecting bone growth and mineralization deficits in this process, and suggest that pathways mediating neuromuscular regulation of osteogenesis may be conserved beyond established mammalian models of bone anabolic disorders.

Imaging Key Wrist Ligaments: What the Surgeon Needs the Radiologist to Know

OBJECTIVE Although much attention is paid to the scapholunate ligament, lunotriquetral ligament, and the triangular fibrocartilage complex, additional intrinsic and extrinsic ligaments in the wrist play an important part in carpal stability. With improved MRI techniques, the radiologist can increasingly visualize these ligaments. CONCLUSION The anatomy, MRI appearance, and clinical significance of the scapholunate ligament, lunotriquetral ligament, triangular fibrocartilage complex, carpal metacarpal ligaments, and volar and dorsal extrinsic ligaments are reviewed.

Radial Nerve Injuries

Radial nerve injuries continue to challenge hand surgeons. The course of the nerve and its intimate relationship to the humerus place it at high risk for injury with humerus fractures. We present a review of radial nerve injuries with emphasis on their etiology, workup, diagnosis, management, and outcomes.

Fracture of the distal radius: epidemiology and premanagement radiographic characterization.

OBJECTIVE Fractures of the distal radius are common and frequently encountered by the radiologist. We review the epidemiology, classification, as well as the concept of instability. Salient qualitative and quantitative features of the distal radius fracture identifiable on the routine radiography series are highlighted. We conclude with a synopsis of descriptors that are of greatest utility to the clinician for treatment planning and that should be addressed in the radiology report. CONCLUSION A detailed understanding of the intricacies of the distal radius fracture is necessary for the radiologist to provide a clinically relevant description.