September 2007  Volume XXXVI No. 9 pISSN:1078-4519 eISSN:1934-3418

E-PUBLISHING

128	Biomechanical Analysis of Flexor Digitorum Profundus and Superficialis in Grip-Strength Generation Robert A. Kaufmann, MD, Scott H. Kozin, MD, Adam Mirarchi, BS, Burt Holland, PhD, and Scott Porter, Med Robert A. Kaufmann, MD, Kaufmann Medical Building, 3471 Fifth Avenue, Suite 1010, Pittsburgh, PA 15213 (tel, 412-605-3209; fax, 412-687-3724; e-mail, kaufra@upmc.edu). Grip strength is generated through extrinsic flexor tendon and intrinsic muscle actuation. In the study reported here, we analyzed the grip-generating properties of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons during grip-strength generation. In vivo gripping was reproduced in 11 cadaveric forearms through pneumatic tensioning of flexor tendons. A Jamar dynamometer (TEC, Clifton, NJ) was positioned in the hand at varying degrees of angulation measured between the Jamar compression axis and the second metacarpal. Maximum gripping strength during isolated FDP and FDS tensioning generated maximum compressive forces at different angles (P<.0001). The isolated FDP showed continued increased grip strength with larger angles and was most effective when the dynamometer handle was in contact with the distal phalanx. The isolated FDS was most effective at smaller angles when the handle made contact with the middle phalanx. The isolated FDS shows an initial increase in grip strength as the contact point moves toward the middle phalanx (P<.01) and then a tendency for grip strength to decline as the contact point moves over the distal phalanx (P<.01). The FDP and FDS tendons demonstrate unique abilities to generate compression on a dynamometer. This knowledge is important to consider when evaluating grip strength in patients who have injured the extrinsic finger flexors. Am J Orthop. 2007;36(9):E128-E132
133	Iatrogenic Propagation of Anterior Fracture-Dislocations of the Proximal Humerus: Case Series and Literature Review With Suggested Guidelines for Treatment and Prevention Anil S. Ranawat, MD, Gregory S. DiFelice, MD, Michael Suk, MD, JD, MPH, Dean G. Lorich, MD, and David L. Helfet, MD David L. Helfet, MD, Orthopaedic Trauma Service, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021 (tel, 212-606-1888; fax, 212-628-4473; e-mail, helfetd@hss.edu). Abstract not available. Introduction provided instead. Fracture-dislocations of the proximal humerus, though rare, are difficult to manage. An unfortunate and challenging subset of these injuries includes fractures that are iatrogenically created, or worsened, during reduction maneuvers for an anterior shoulder dislocation. Iatrogenic fracture-dislocations have 2 basic mechanisms. In the first, a shoulder dislocation with or without a concomitant tuberosity fracture or Hill-Sachs lesion is converted to a more complicated fracture dislocation with the creation of a new fracture line during a reduction maneuver; in the second, a shoulder dislocation with an unrecognized neck fracture is converted to a more complicated fracture-dislocation with displacement or propagation of the neck fracture during a reduction maneuver. In both cases, the patient is left with a more complicated, higher-grade fracture-dislocation of the proximal humerus—an injury most likely significantly displaced and in need of surgical intervention. In this article, we report on a series of 6 cases of iatrogenic fracture-dislocations. All 6 cases originally were anterior dislocations. Four of the 6 had concomitant greater tuberosity fractures; the other 2 had large Hill-Sachs lesions. Five of the 6 were converted to severely displaced fracture-dislocations of the proximal humerus after unsuccessful reduction attempts; 4 of the 5 required a shoulder hemiarthroplasty, and the fifth required open reduction and internal fixation (ORIF). In the sixth and final case, we applied a new technique to prevent the complication of iatrogenic displacement: We used prophylactic percutaneous fixation to prevent fracture propagation so that we could safely perform closed reduction of the dislocation. In retrospect, at least 2 and perhaps 3 cases had unrecognized anatomical or surgical neck fractures. Am J Orthop. 2007;36(9):E133-E137
138	Ankle Dislocation Without Fracture in a Child John M. Mazur, MD, Eric A. Loveless, MD, and R. Jay Cummings, MD John M. Mazur, MD, Nemours Children’s Clinic, 807 Children’s Way, Jacksonville, FL (tel, 904-390-3600; fax, 904-390-3477; e-mail, jmazur@nemours.org). Abstract not available. Introduction provided instead. Ankle injuries in children are most commonly associated with fractures of the growth plates. Pure ankle dislocations without fracture are extremely rare, especially in children with open growth plates. The ankle joint is intrinsically stable, making an isolated ankle dislocation a rare injury. The ankle ligaments are mechanically stronger than the growth plates.1 A fracture through the growth plate is more likely to occur than a dislocation without an associated fracture. There have been only 2 other reports of an ankle dislocation without associated fracture in a child.2,3 Here we describe the case of a girl with a closed posterior dislocation of the ankle without fracture. We have obtained the informed consent of the patient whose case is described. Am J Orthop. 2007;36(9):E138-E140

FOCUS ON FRACTURE MANAGEMENT

459	Guest Editorial—Challenging Conventional Wisdom David L. Helfet, MD David L. Helfet, MD, Orthopaedic Trauma Service, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021 (tel, 212-606-1888; fax, 212-628-4473; e-mail, helfetd@hss.edu). Abstract not available. Am J Orthop. 2007;36(9):459
460	Second-Generation Concepts for Locked Plating of Proximal Humerus Fractures Michael J. Gardner, MD, Dean G. Lorich, MD, Clément M. L. Werner, MD, and David L. Helfet, MD Michael J. Gardner, MD, Harborview Medical Center, 325 9th Ave, Seattle, WA 98105 (tel, 206-731-3267; fax, 206-731-3227; e-mail, michaelgardnermd@gmail.com). Displaced fractures of the proximal humerus remain particularly difficult to treat. Because of the poor quality of cancellous bone, it seemed that locking plates would be ideally suited for fixation in this region. However, as clinical reports begin to become available, it appears that these plates are not a panacea for these fractures and may be associated with a high complication rate. Coupled with the generally poor long-term outcomes of hemiarthroplasty, new fixation methods must be sought. Several technical factors, techniques, and alternative approaches have recently been described as possibly improving fixation stability in these fractures. Specifically, the anterolateral acromial approach, which avoids vascularity exposure, allows direct access to the lateral plating zone, and minimizes soft-tissue dissection, may be useful. Mechanical support of the medial column when anatomic cortical contact is not possible is also critical to maximizing stability. This may be achieved either with purposeful inferomedial humeral head screws or endosteal fibula allograft augmentation. Am J Orthop. 2007;36(9):460-465
466	5 Points on Ankle Fractures: It Is Not Just a “Simple” Ankle Fracture Clément M. L. Werner, MD, Dean G. Lorich, MD, Michael J. Gardner, MD, and David L. Helfet, MD Clément M. L. Werner, MD, Department of Orthopaedics, University of Zurich, Uniklinik Balgrist, Forchstrasse 340, 8008 Zurich, Switzerland (tel, 41-44-386-1111; fax, 41-44-386-1609; e-mail, clement.werner@balgrist.ch). Abstract not available. Am J Orthop. 2007;36(9):466-469
473	Effect of Wire Tension on Stiffness of Tensioned Fine Wires in External Fixation: A Mechanical Study Valentin Antoci, MD, PhD, Michael J. Voor, PhD, Valentin Antoci, Jr., BS, and Craig S. Roberts, MD Craig S. Roberts, MD, Department of Orthopaedic Surgery, University of Louisville School of Medicine, 210 E Gray St, Suite 1003, Louisville, KY 40202 (tel, 502-852-6964; fax, 502-852-7227; e-mail, craig.roberts@louisville.edu, klmaye01@louisville.edu). To determine the effect of changes in magnitude of transfixion wire tension on stiffness of fine-wire external-fixation load deformation, we compared results obtained with different wire tensions (50-140 kg) under identical conditions of central axial compression, medial compression-bending, posterior compression- bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. Tension of 140 kg provided the most stiffness, and there was a trend toward increasing overall stiffness with increasing wire tension. The 1.8-mm wires should be tensioned to at least 110 kg in most cases of fine-wire external fixation; compared with all tensions less than 110 kg, this tension provides significantly more mechanical stability in all loading modes. Am J Orthop. 2007;36(9):473-476
477	Clinical Results of Minimal Screw Plate Fixation of Forearm Fractures Bradley D. Crow, MD, Gregory Mundis, MD, and Jeffrey O. Anglen, MD Jeffrey O. Anglen, MD, 541 Clinical Drive, Suite 600, Indianapolis, IN, 46202 (tel, 317-274-7913; fax, 317-274-3702; e-mail, janglen@iupui.edu). Traditional plating technique for forearm fractures specifies implant selection based on achieving a minimum number of “cortices” of screw fixation on either side of the fracture. Recent biomechanical data suggest that plates with fewer screws provide equivalent strength of fixation compared with standard compression plating techniques in forearm fractures. As described in this article, we retrospectively reviewed a surgeon’s experience at a regional level I trauma center to evaluate the clinical outcome of this newer fixation strategy. Seventy-eight fractured bones were plated using “minimal” screw technique—less than the traditionally recommended 6 cortices of screw purchase. Nonunion or fixation failure occurred in 7 fractures (5 patients), producing a union rate of 91% (71/78). All nonunions were atrophic and occurred in open fractures with bone loss. No construct failed because of fixation loss caused by having too few screws. Minimal screw plate technique was stable fixation, despite not having 6 cortices on both sides of the fracture. Technical emphasis should be on adequate plate length rather than number of cortices of fixation in each segment. Am J Orthop. 2007;36(9):477-480
481	Two-Screw Femoral Neck Fracture Fixation: A Biomechanical Analysis of 2 Different Configurations Virak Tan, MD, Kirk L. Wong, MD, Christopher T. Born, MD, Robert Harten, PhD, and William G. DeLong, Jr., MD Virak Tan, MD, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, 140 Bergen St, ACC D-1626, Newark, NJ 07103 (tel, 973-972-0763; fax, 973-972-8860; e-mail, tanvi@umdnj.edu). In the study reported here, we evaluated 2-screw femoral neck fixation. Femoral necks from 5 paired fresh-frozen cadavers were fractured and then fixed with two 7.3-mm cannulated cancellous screws. Vertical (parallel screws in sagittal plane of femoral neck) and horizontal (parallel screws in superior aspect of femoral neck) configurations were used for each matched pair. Mechanical testing was performed. Load, displacement, and stiffness at the yield point were significantly higher in the horizontal group, which also had a higher mean maximal failure load (P = .019). Preliminary data suggest that 2 horizontal screws in the superior aspect of the femoral neck provide more secure fixation than 2 vertical screws. Am J Orthop. 2007;36(9):481-485
489	Concomitant, Distinct Fractures of the Capitellum and Trochlea Separating the Whole Articular Surface of the Distal Humerus in the Coronal Plane Emmanouil D. Stamatis, MD, MC, FHCOS, FACS, and Kalomoira N. Konstantinidou, MD Emmanouil D. Stamatis, MD, Plastira 17, Nea Smyrni, 17121, Athens, Greece (tel, 0030-6977-717895; e-mail, mstamatis66@yahoo.com). Abstract not available. Am J Orthop. 2007;36(9):489-491
492	Intramedullary Bone Fragment Preventing Passage of Reaming Guide Wire Michael Salamon, MD, and Christopher G. Finkemeier, MD Michael Salamon, MD, 4003 Kresge Way, Suite 300, Louiville, KY 40207 (tel, 502-212-2663; fax, 502-212-2004; e-mail, mlsalamon@aol.com). Abstract not available. Am J Orthop. 2007;36(9):492-493
494	Characterization of a Consistent Radiographic Finding in Chronic Anterior Cruciate Ligament Deficiency: The Posteromedial Osteophyte Brian H. Mullis, MD, Spero G. Karas, MD, and Scott S. Kelley, MD Often found in patients undergoing total knee arthroplasty (TKA) is an osteophyte, at the posterior lateral corner of the medial tibial plateau, that prevents anterior translation. This osteophyte does not occur in the presence of an entirely normal anterior cruciate ligament (ACL) with normal vascularity. Although similar findings have been reported in animal studies, to our knowledge this has never been documented in humans. To determine the incidence of this finding in our patient population, anteroposterior and lateral x-rays of the affected knee of 90 patients undergoing TKA were reviewed. Forty-two percent (43/102 knees) had radiographic signs of this stabilizing osteophyte. This finding confirms previous animal research and may lead to a better understanding of how the knee adapts to improve stability in a chronic ACL-deficient state. Am J Orthop. 2007;36(9):494-497
498	Making Better Hiring Decisions Karen Zupko, BSJ Abstract not available. Am J Orthop. 36(9):498-499
500	Exchange Femoral Nailing: A New Technique for Removal of a Broken Nail Rodney K. Alan, MD, Rafath Baig, MD, and Frank R. Voss, MD Rodney K. Alan, MD, 595 W. Wesmark Blvd, Sumter, SC 29153 (tel, 803-469-4028; fax, 803-469-2663; e-mail, rka0822@yahoo.com). Exchange femoral nailing is the preferred method for treating femoral nonunions. When the index femoral nail is broken, the difficulty of exchange nailing increases dramatically. In this article, we describe a new technique for removing a broken retrograde nail—advancing it out of the proximal end of the femur. Am J Orthop. 36(9):500-502

MIS HIP, MIS KNEE, DVT PROPHYLAXIS—GETTING IT JUST RIGHT

Supported by an independent educational grant from sanofi-aventis U.S.

2	Venous Thromboembolism Prophylaxis: Who’s Right—Orthopedic Surgeons or Chest Physicians? Peter D. McCann, MD Abstract not available. Am J Orthop. 2007;36(9S):2-3
4	A Comprehensive Approach to Outpatient Total Hip Arthroplasty Richard A. Berger, MD Minimally invasive surgery (MIS) techniques for total hip arthroplasty (THA) have the potential for reduced tissue trauma, leading to more rapid recovery and return to function than with traditional approaches to THA. However, to achieve these potential benefits, all other aspects of patient care need to be modernized. Development and implementation of these newer anesthetic and rehabilitation protocols allow MIS-THA to be done safely on an outpatient basis in select patients. Am J Orthop. 2007;36(9S):4-5
6	Minimally Invasive Total Knee Arthroplasty: Past, Present, and Future Alfred J. Tria, Jr., MD Choices for a limited approach to total knee arthroplasty (TKA) now include the mini-arthrotomy, the mini-midvastus, the subvastus, and the quadriceps-sparing technique. These newer approaches suggest use of modified instruments at least smaller in overall size; call for early ambulation and range of motion with modified pain management protocols; demonstrate improved early recovery of the knee; and lead to less visualization and can contribute to an increase in outliers. Use of navigation for TKA remains controversial. Prophylaxis against deep venous thrombosis is necessary and is used at the discretion of the operating surgeon. Complications are sometimes higher with these approaches, and patient preference and choice of surgical technique are extremely important. Minimally invasive surgery approaches are still evolving for TKA, and long-term results are not available. These techniques are certainly not for all patients or all surgeons, and the indications are still being developed. Am J Orthop. 2007;36(9S):6-7
8	The Impact of Smart Tools on Total Knee Arthroplasty Giles R. Scuderi, MD Smart tools and robotic surgery are helping us take a step into the operating room of the future. As this technology develops, it can potentially help surgeons perform total knee arthroplasty (TKA) faster and with increased accuracy. In addition, this technology will reduce the number of instruments needed for the procedure, thus improving efficiency. As technology advances, smart tools may become commonplace in the operating room and may fulfill their potential to transform the way TKA is performed. Such potential is important, as there has been an exponential rise in the number of TKAs performed annually. The resulting demand on surgeons and hospital systems will necessitate improving technology so that it can be used to treat more patients while maintaining quality of care. Smart tools and robotic surgery may represent one answer to this demand. Am J Orthop. 2007;36(9S):8-10
11	Rationale for Thromboprophylaxis in Lower Joint Arthroplasty Clifford W. Colwell, Jr., MD Without prophylaxis, rates of deep vein thrombosis (DVT) after major orthopedic surgery range from 40% to 60%. Randomized clinical trials over the past 30 years have provided evidence that primary thromboprophylaxis reduces DVT, pulmonary embolism (PE), and fatal PE, and prophylaxis to prevent venous thromboembolism (VTE) in patients at risk has been ranked as the highest safety practice for hospitalized patients. Since 1986, some type of prophylaxis has been recommended for total knee arthroplasty (TKA), total hip arthroplasty (THA), and hip fracture surgery. Orthopedic guidelines published in Chest provide a current evidence-based guide for prophylaxis for TKA, THA, and hip fracture surgery. In addition to following these recommendations for routine prophylaxis, surgeons should assess patients for additional VTE risk. Patients at higher risk may need more intense prophylaxis. Data from meta-analyses and placebo-controlled, blinded, randomized clinical trials have demonstrated little or no increase in rates of clinically important bleeding with prophylaxis. Am J Orthop. 2007;36(9S):11-13
14	Aspirin Prophylaxis for Thromboembolic Disease After Total Joint Arthroplasty Paul A. Lotke, MD The most appropriate prophylactic regimen for thromboembolic disease has not been determined. There appear to be several good alternatives, all of which yield similar results as determined by the incidence of symptomatic pulmonary embolism, but all are associated with various bleeding-related risks. Results from past research of almost 3500 total knee arthroplasties demonstrated a low risk for pulmonary emboli (0.1%) and a reduced risk for postoperative bleeding with use of aspirin and foot pumps as prophylaxis against thromboembolic disease. We continue to remain comfortable recommending this regimen for our patients. Am J Orthop. 2007;36(9S):14-15

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