Invited Article
Hand Surgery 2015;20(2):210-214 • DOI: 10.1142/S021881041540002X
Operative Treatment of Acute Scaphoid Fractures Lana Kang Attending Surgeon Hospital for Special Surgery, Weill Cornell Medical College & New York Presbyterian Hospital, New York, USA
Optimal treatment of acute scaphoid fractures is a necessary goal for many reasons. One is that the scaphoid is the most commonly fractured carpal bone. Another is that a missed diagnosis of an acute scaphoid fracture leads to the more challenging situation of a delayed union, non-union and risk for premature radiocarpal arthrosis. Because the scaphoid has an inherent risk for nonunion due to its the tenuous blood supply, timely diagnosis and appropriate treatment are considered critical to achieving acceptable results and to avoiding the consequences of failed union. Keywords: Acute scaphoid fracture, Treatment, Operative, Surgical fixation, Review
ANATOMIC CONSIDERATIONS IN ACUTE FRACTURES The scaphoid is an asymmetric bone with a complicated three-dimensional structure. Fractures are commonly described according to location within the scaphoid: the proximal pole, the waist, and the distal pole or tubercle. The proximal pole articulates with the radius and lunate, and the waist and distal pole articulate with the capitate, trapezium, and trapezoid. Eighty percent of the scaphoid surface is covered by cartilage and articulates with surrounding carpal bones. Thus, the scaphoid has minimal soft tissue attachments explains its limited vascular access. The dorsoradial vessels from the vascular arches of the dorsal wrist capsule provide 70% to 80% of the scaphoid's blood supply.1-3) The volar nutrient arteries from the radial artery penetrate the area of the scaphotrapezium ligament attachment and enter the distal pole of the scaphoid. This tenuous retrograde pattern of vas-
Received: Mar. 9, 2015; Revised: Apr. 8, 2015; Accepted: Apr. 15, 2015 Correspondence to: Lana Kang Attending Surgeon Hospital for Special Surgery, Weill Cornell Medical College & New York Presbyterian Hospital, New York, USA Tel: +1-212-203-0747, Fax: +1-212-203-0739 E-mail: [email protected]
cularity (Fig. 1) contributes to the well-known risks of nonunion and avascular necrosis of the proximal pole of the scaphoid.
BIOMECHANICAL CONSIDERATIONS IN THE TREATMENT OF ACUTE SCAPHOID FRACTURES Scaphoid fractures frequently occur after a fall on an outstretched hand. The scaphoid is the most threedimensionally mobile bone in the carpus linking the proximal row to the distal row. Disruption of its normal articulations results in abnormal kinematics and load distributions. Cadaveric models have shown that excess
Volar
Superficial palmar branch radial artery
Radial artery
Fig. 1. Scaphoid blood supply.
Dorsal
Dorsal carpal branch radial artery
211 Hand Surgery • Vol. 20, No. 2, 2015 • www.jhs-ap.org
tension results in failure to the volar scaphoid and excess compression results in failure to the dorsal scaphoid.4) Scaphoid fractures lead to opposing rotational moments on the proximal and distal poles,5) creating the angulation, or the “humpback” deformity, of scaphoid nonunions and malunions. The lunate and the remainder of the proximal row shifts into a position of extension referred to as a dorsally intercalated scaphoid instability (DISI) deformity.6) Abnormally increased flexion of the distal scaphoid pole increases loading with the radial styloid leading to radial styloid arthrosis.7,8) The predictable stages of the progressive development of arthritis has been termed as scaphoid non-union advanced collapse (SNAC) which is associated with a progressive increase in wrist stiffness, swelling, deformity, and pain.
EXAMINATION Acute scaphoid fractures commonly occur in a youn ger patient population but can occur at any age. Displaced fractures are more likely to be associated with pronounced wrist swelling and edema, but mild swelling and subtle findings should prompt suspicion of a scaphoid fracture. Tenderness may be focal at the snuffbox dorsally or at the tuberosity volarly, but it may also be nonspecific in the radial side of the wrist. Limited passive motion and guarding with extremes of wrist motion are also common exam findings. The specificity of physical examination has been reported to be 74 to 80%.9)
RADIOGRAPHIC EVALUATION Acute scaphoid fractures can be difficult to visualize with the standard posteranterior (PA), lateral and oblique radiographs of the wrist. The postero-anterior ulnar-deviated or 'scaphoid view' with the wrist positioned in ulnar deviation extends the scaphoid and, thereby, addresses the overhang of the tubercle with the remainder of the scaphoid that can obscure visualization of nondisplaced fractures with the standard PA view. The semipronated and 45o supinated oblique views also provide enhanced visualization of the scaphoid waist. Historically, for suspect fractures, ordering repeat plain radiographs approximately two to several weeks from the time of injury or a proceeding with a technicium-99 bone scan was standard practice. Bone scans have been reported to have a zero false negative rate when obtained more than 48 hours after injury.10,11) Currently, magnetic resonance imaging (MRI) is co mmonly used to diagnose occult scaphoid fractures. MRI
is particularly helpful when the degree of proximal pole viability and cartilage loss are questionable when considering primary fracture fixation.12) While MRI avoids the use of ionizing radiation and is cost effective in the diagnosis of occult fractures,13) hand surgeons are facing an increased number of administrative constraints that preclude authorization of MR imaging. It remains to be determined how to optimize and avoid over-utilization of MRI in the treatment of acute scaphoid fractures. The use of computer tomography (CT) provides a unique three-dimensional understanding of fracture personality, pattern, and displacement is proving to be critical in the acute treatment of scaphoid fractures.14,15) Thus, CT evaluation of acute scaphoid fractures to diagnose and to confirm fracture healing is continuing to increase. CT scanning of the wrist should include coronal, sagittal and axial images, and along the long axis of the scaphoid with the arm held in 45o across the gantry.16) Cuts should not be greater than one millimeter in width.16)
CLASSIFICATION Management of acute of scaphoid fractures can be based on classifying these fractures according to fracture pattern, location, and degree of instability. Fracture instability has been classified according to Herbert’s classification system17) that divides fractures into four types: Type A, stable acute fractures; Type B, unstable acute fractures; Type C, delayed unions; and Type D, established non-unions. Fractures with more than 1 mm of displacement are considered unstable.18)
MANAGEMENT OF ACUTE SCAPHOID FRACTURES In patients who are acceptable candidates for anesthesia and for surgery, the treatment of acute scaphoid fractures can be guided by the location of the fracture and the degree of displacement and angulation. Distal pole fractures are typically avulsion fractures of the tuberosity or impaction fractures of the distal articular surface which are well-vascularized. Thus, most of these fractures heal with thumb spica short-arm cast immobilization. Any clinically significant long-term effect on the distal articulating surface remains unproven.19) The traditional treatment of cast treatment for nondisplaced waist fractures has been supported by studies that report a healing rate over variable lengths of time of greater than 90%.20-23) The effect of including the thumb in the cast remains unclear.24) While clinical studies as-
212 Lana Kang. Acute Scaphoid Fractures
sessing the difference in incidence of nonunion between short-arm and long-arm casting show contradictory data.25) There is a low threshold to operatively treat acute fractures in order to minimize the risk of nonunion; the reby, the use of long arm casting has likely become reserved for skeletally immature patients. Our patients today have variable needs and desires to avoid the risks associated with cast immobilization. Surgical fixation has become a readily offered choice of treatment for non-displaced fractures.26-28) Early surgical fixation offers to minimize wrist stiffness and to potentially accelerate healing, and a considerable proportion of patients will find surgical treatment preferable to cast immobilization due to pressures of work- and other activity- related reasons.28,29) A percutaneous or mini-in cision may be appropriate for these non-displaced fractures, and minimally invasive methods require fractures that are nondisplaced or ability to achieve a reduction that is anatomic.30-33) Arthroscopically aided reduction with limited exposures may provide surgeons with direct visualization that an anatomic reduction has been achieved.34-36) More recent studies suggest that computernavigation techniques provide for greater accuracy in the percutaneous placement of screws.37-39) Theoretically, the compressive effect of headless screw fixation offers a biomechanical means to achieve a more rapid time to union compared to cast immobilization alone. Return to work has been faster with surgical fixation compared to casting.26,27) The degree of displacement may be underestimated by plain radiographs alone, and the risk for nonunion may not be not worth the complications of surgical fixation. These include hardware prominence, osteonecrosis, failure of fixation, and nonunion.40) Percutaneous fixation of scaphoid fractures is performed by either a volarly or dorsally placed screw.41) Studies have shown advantages and disadvantages for both. 42-44) With the percutaneous volar approach, the starting point for the guidewire is the scaphotrapezial joint. Extension of the wrist over a rolled towel may enhance proper wire placement.31) The major drawback of the volar percutaneous approach is that the trapezium may impede wire and screw placement and a portion of the base of the trapezium may need to be resected. The dorsal percutaneous approach poses risks to the extensor tendons and branches of the posterior interosseous nerve, as well as other complications of hardware issues and post-fixation fracture, the incidence of which is not clearly the result of technique rather than approach.45,46) Open reduction and internal fixation is indicated for
scaphoid fractures that are displaced and angulated.40,47,48) Both dorsal and volar approach can be used for scaphoid waist fractures, however, a volar exposure may be preferable to directly visualize reduction of significant flexion deformities associated with angulated waist fractures. The volar approach allows optimal exposure for distal third fractures; the dorsal approach allows optimal exposure for proximal pole fractures.41) Traditionally considered advantages for the traditional Russe volar approach may be that to circumvent disruption of the dorsal blood supply, but the dorsal could approach achieve the same by avoiding soft tissue stripping distal to the site of the fracture. Since the original Herbert screw was introduced, surgical fixation of acute fractures continue to depend on the principle that the differential pitch of the threads comprising a single screw exerts compression across the fracture.44,47,48) Different from the original Herbert screw, most screws today are not cannulated.49) Different designs among systems may vary according to the presence of a central barrel (versus continuous threads), screw diameters, screw lengths, and need for countersinking and/or pre-drilling.46,50,51) While studies have emphasized screw placement down the central axis as critical to successful healing, several reports have offered varying conclusions as to the preferred screw position, screw length, patient gender and surgical approach.52-54) Screw position relative to the line of the fracture has also been proposed to be more critical.53,54) The goal to bury these headless screws beneath the cortical surface of the scaphoid cannot be overemphasized since screw prominence will erode the opposing cartilage. Both a 45-degree supination oblique and a pronated oblique view has been suggested to be most useful for assessing length of the screw and avoiding screw prominence.33,52) Patients should be informed that the need for a return trip to the operating room for screw removal under these circumstances is not uncommon or unexpected.40) Fracture pattern and radiographic healing will dictate the post-operative course of recovery. Imaging should confirm fracture healing. CT has been shown to be a reliable method of assessing healing.55) This can be utilized when desiring to graduate the patients to the next stage of rehabilitation, particularly for those who want to resume sports and/or perform manual labor. Acute fractures are ideally treated within two weeks and less than six weeks from the time of injury with surgical methods of acute fracture treatment. Conversely, time to union using cast immobilization can require
213 Hand Surgery • Vol. 20, No. 2, 2015 • www.jhs-ap.org
greater than 6 months. Proximal pole fractures have a higher risk of nonunion even with surgical fixation, and time to union with casting alone may be as long as 9 months. These, therefore, serve as additional indications for acute surgical fixation.
SUMMARY Timely and appropriate treatment of acute scaphoid fractures is necessary for successful healing. Indications for surgical fixation of non-displaced fractures can be variable and the consensus opinion continues to evolve. In contrast, displaced, angulated, and comminuted fractures are unequivocal indications in the appropriate surgical candidate. While surgeon preference and fracture pattern may dictate choice of surgical approach and choice of implant, there are only a limited number of surgical exposures and surgical techniques, and the wellequipped hand surgeon should feel comfortable using them all.
REFERENCES 1. Gelberman RH, Menon J. The vascularity of the scaphoid bone. J Hand Surg Am. 1980;5(5):508-13. 2. Puopolo SM, Rettig ME. Management of acute scaphoid fractures. Bull Hosp Jt Dis. 2003;61(3-4):160-3. 3. Taleisnik J, Kelly PJ. The extraosseous and intraosseous blood supply of the scaphoid bone. J Bone Joint Surg Am. 1966;48(6):1125-37. 4. Weber ER, Chao EY. An experimental approach to the mechanism of scaphoid waist fractures. J Hand Surg Am. 1978;3(2):142-8. 5. Smith DK, Cooney WP, 3rd, An KN, Linscheid RL, Chao EY. The effects of simulated unstable scaphoid fractures on carpal motion. J Hand Surg Am. 1989;14(2 Pt 1):283-91. 6. Mack GR, Bosse MJ, Gelberman RH, Yu E. The natural history of scaphoid non-union. J Bone Joint Surg Am. 1984;66(4):504-9. 7. Ruby LK, Stinson J, Belsky MR. The natural history of scaphoid non-union. A review of fifty-five cases. J Bone Joint Surg Am. 1985;67(3):428-32. 8. Vender MI, Watson HK, Wiener BD, Black DM. Degenerative change in symptomatic scaphoid nonunion. J Hand Surg Am. 1987;12(4):514-9. 9. Adams JE, Steinmann SP. Acute scaphoid fractures. Orthop Clin North Am. 2007;38(2):229-35, vi. 10. Dias JJ, Taylor M, Thompson J, Brenkel IJ, Gregg PJ. Radiographic signs of union of scaphoid fractures. An analysis of inter-observer agreement and reproducibility. J Bone
Joint Surg Br. 1988;70(2):299-301. 11. Ganel A, Engel J, Oster Z, Farine I. Bone scanning in the assessment of fractures of the scaphoid. J Hand Surg Am. 1979;4(6):540-3. 12. Breitenseher MJ, Metz VM, Gilula LA, et al. Radiographically occult scaphoid fractures: value of MR imaging in detection. Radiology. 1997;203(1):245-50. 13. Dorsay TA, Major NM, Helms CA. Cost-effectiveness of immediate MR imaging versus traditional follow-up for revealing radiographically occult scaphoid fractures. AJR Am J Roentgenol. 2001;177(6):1257-63. 14. Compson JP. The anatomy of acute scaphoid fractures: a three-dimensional analysis of patterns. J Bone Joint Surg Br. 1998;80(2):218-24. 15. Nakamura R, Imaeda T, Horii E, Miura T, Hayakawa N. Analysis of scaphoid fracture displacement by threedimensional computed tomography. J Hand Surg Am. 1991;16(3):485-92. 16. Sanders WE. Evaluation of the humpback scaphoid by computed tomography in the longitudinal axial plane of the scaphoid. J Hand Surg Am. 1988;13(2):182-7. 17. Herbert TJ, Fisher WE. Management of the fractured scaphoid using a new bone screw. J Bone Joint Surg Br. 1984;66(1):114-23. 18. Cooney WP, Dobyns JH, Linscheid RL. Fractures of the scaphoid: a rational approach to management. Clin Orthop Relat Res. 1980(149):90-7. 19. Prosser AJ, Brenkel IJ, Irvine GB. Articular fractures of the distal scaphoid. J Hand Surg Br. 1988;13(1):87-91. 20. Alho A, Kankaanpaa. Management of fractured scaphoid bone. A prospective study of 100 fractures. Acta Orthop Scand. 1975;46(5):737-43. 21. Hambidge JE, Desai VV, Schranz PJ, Compson JP, Davis TR, Barton NJ. Acute fractures of the scaphoid. Treatment by cast immobilisation with the wrist in flexion or extension? J Bone Joint Surg Br. 1999;81(1):91-2. 22. Kaneshiro SA, Failla JM, Tashman S. Scaphoid fracture displacement with forearm rotation in a short-arm thumb spica cast. J Hand Surg Am. 1999;24(5):984-91. 23. Langhoff O, Andersen JL. Consequences of late immo bilization of scaphoid fractures. J Hand Surg Br. 1988; 13(1):77-9. 24. Clay NR, Dias JJ, Costigan PS, Gregg PJ, Barton NJ. Need the thumb be immobilised in scaphoid fractures? A randomised prospective trial. J Bone Joint Surg Br. 1991;73(5):828-32. 25. Gellman H, Caputo RJ, Carter V, Aboulafia A, McKay M. Comparison of short and long thumb-spica casts for nondisplaced fractures of the carpal scaphoid. J Bone Joint Surg Am. 1989;71(3):354-7.
214 Lana Kang. Acute Scaphoid Fractures
26. Bond CD, Shin AY, McBride MT, Dao KD. Percutaneous screw fixation or cast immobilization for nondisplaced sca phoid fractures. J Bone Joint Surg Am. 2001;83(4):483-8. 27. Rettig AC, Kollias SC. Internal fixation of acute stable scaphoid fractures in the athlete. Am J Sports Med. 1996; 24(2):182-6. 28. Saeden B, Tornkvist H, Ponzer S, Hoglund M. Fracture of the carpal scaphoid. A prospective, randomised 12-year follow-up comparing operative and conservative treatment. J Bone Joint Surg Br. 2001;83(2):230-4. 29. Bhandari M, Hanson BP. Acute nondisplaced fractures of the scaphoid. J Orthop Trauma. 2004;18(4):253-5. 30. Haddad FS, Goddard NJ. Acute percutaneous scaphoid fixation. A pilot study. J Bone Joint Surg Br. 1998;80(1):95-9. 31. Shin AY, Hofmeister EP. Percutaneous fixation of stable scaphoid fractures. Tech Hand Up Extrem Surg. 2004; 8(2):87-94. 32. Wu WC. Percutaneous cannulated screw fixation of acute scaphoid fractures. Hand Surg. 2002;7(2):271-8. 33. Yip HS, Wu WC, Chang RY, So TY. Percutaneous cannulated screw fixation of acute scaphoid waist fracture. J Hand Surg Br. 2002;27(1):42-6. 34. Shih JT, Lee HM, Hou YT, Tan CM. Results of arthroscopic reduction and percutaneous fixation for acute displaced scaphoid fractures. Arthroscopy. 2005;21(5):620-6. 35. Slade JF, 3rd, Gillon T. Retrospective review of 234 scaphoid fractures and nonunions treated with arthroscopy for union and complications. Scand J Surg. 2008;97(4):280-9. 36. Slade JF, 3rd, Grauer JN, Mahoney JD. Arthroscopic reduction and percutaneous fixation of scaphoid fractures with a novel dorsal technique. Orthop Clin North Am. 2001; 32(2):247-61. 37. Kam CC, Greenberg JA. Computer-assisted navigation for dorsal percutaneous scaphoid screw placement: a cadaveric study. J Hand Surg Am. 2014;39(4):613-20. 38. Smith EJ, Ellis RE, Pichora DR. Computer-assisted percutaneous scaphoid fixation: concepts and evolution. J Wrist Surg. 2013;2(4):299-305. 39. Walsh E, Crisco JJ, Wolfe SW. Computer-assisted navigation of volar percutaneous scaphoid placement. J Hand Surg Am. 2009;34(9):1722-8. 40. Meyer C, Chang J, Stern P, Osterman AL, Abzug JM. Complications of distal radial and scaphoid fracture treatment. J Bone Joint Surg Am. 2013;95(16):1517-26. 41. Polsky MB, Kozin SH, Porter ST, Thoder JJ. Scaphoid fractures: dorsal versus volar approach. Orthopedics. 2002; 25(8):817-9. 42. Adamany DC, Mikola EA, Fraser BJ. Percutaneous fixation of the scaphoid through a dorsal approach: an anatomic
study. J Hand Surg Am. 2008;33(3):327-31. 43. Bedi A, Jebson PJ, Hayden RJ, Jacobson JA, Martus JE. Internal fixation of acute, nondisplaced scaphoid waist fractures via a limited dorsal approach: an assessment of radio graphic and functional outcomes. J Hand Surg Am. 2007; 32(3):326-33. 44. Jeon IH, Micic ID, Oh CW, Park BC, Kim PT. Percutaneous screw fixation for scaphoid fracture: a comparison bet ween the dorsal and the volar approaches. J Hand Surg Am. 2009;34(2):228-36 e1. 45. Bushnell BD, McWilliams AD, Messer TM. Complications in dorsal percutaneous cannulated screw fixation of nondisplaced scaphoid waist fractures. J Hand Surg Am. 2007; 32(6):827-33. 46. Gardner AW, Yew YT, Neo PY, Lau CC, Tay SC. Interfragmentary compression profile of 4 headless bone screws: an analysis of the compression lost on reinsertion. J Hand Surg Am. 2012;37(9):1845-51. 47. Herbert TJ, Fisher WE, Leicester AW. The Herbert bone screw: a ten year perspective. J Hand Surg Br. 1992;17(4): 415-9. 48. O'Brien L, Herbert T. Internal fixation of acute scaphoid fractures: a new approach to treatment. Aust N Z J Surg. 1985;55(4):387-9. 49. Trumble TE, Clarke T, Kreder HJ. Non-union of the scaphoid. Treatment with cannulated screws compared with treatment with Herbert screws. J Bone Joint Surg Am. 1996;78(12):1829-37. 50. Dodds SD, Panjabi MM, Slade JF, 3rd. Screw fixation of scaphoid fractures: a biomechanical assessment of screw length and screw augmentation. J Hand Surg Am. 2006; 31(3):405-13. 51. Hart A, Harvey EJ, Lefebvre LP, Barthelat F, Rabiei R, Martineau PA. Insertion profiles of 4 headless compression screws. J Hand Surg Am. 2013;38(9):1728-34. 52. Kim RY, Lijten EC, Strauch RJ. Pronated oblique view in assessing proximal scaphoid articular cannulated screw penetration. J Hand Surg Am. 2008;33(8):1274-7. 53. Luria S, Lenart L, Lenart B, Peleg E, Kastelec M. Optimal fixation of oblique scaphoid fractures: a cadaver model. J Hand Surg Am. 2012;37(7):1400-4. 54. Meermans G, Verstreken F. Influence of screw design, sex, and approach in scaphoid fracture fixation. Clin Orthop Relat Res. 2012;470(6):1673-81. 55. Grewal R, Frakash U, Osman S, McMurtry RY. A quantitative definition of scaphoid union: determining the interrater reliability of two techniques. J Orthop Surg Res. 2013;8:28.
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Hand Surgery 2015;20(2):210-214 • DOI: 10.1142/S021881041540002X
Operative Treatment of Acute Scaphoid Fractures Lana Kang Attending Surgeon Hospital for Special Surgery, Weill Cornell Medical College & New York Presbyterian Hospital, New York, USA
Optimal treatment of acute scaphoid fractures is a necessary goal for many reasons. One is that the scaphoid is the most commonly fractured carpal bone. Another is that a missed diagnosis of an acute scaphoid fracture leads to the more challenging situation of a delayed union, non-union and risk for premature radiocarpal arthrosis. Because the scaphoid has an inherent risk for nonunion due to its the tenuous blood supply, timely diagnosis and appropriate treatment are considered critical to achieving acceptable results and to avoiding the consequences of failed union. Keywords: Acute scaphoid fracture, Treatment, Operative, Surgical fixation, Review
ANATOMIC CONSIDERATIONS IN ACUTE FRACTURES The scaphoid is an asymmetric bone with a complicated three-dimensional structure. Fractures are commonly described according to location within the scaphoid: the proximal pole, the waist, and the distal pole or tubercle. The proximal pole articulates with the radius and lunate, and the waist and distal pole articulate with the capitate, trapezium, and trapezoid. Eighty percent of the scaphoid surface is covered by cartilage and articulates with surrounding carpal bones. Thus, the scaphoid has minimal soft tissue attachments explains its limited vascular access. The dorsoradial vessels from the vascular arches of the dorsal wrist capsule provide 70% to 80% of the scaphoid's blood supply.1-3) The volar nutrient arteries from the radial artery penetrate the area of the scaphotrapezium ligament attachment and enter the distal pole of the scaphoid. This tenuous retrograde pattern of vas-
Received: Mar. 9, 2015; Revised: Apr. 8, 2015; Accepted: Apr. 15, 2015 Correspondence to: Lana Kang Attending Surgeon Hospital for Special Surgery, Weill Cornell Medical College & New York Presbyterian Hospital, New York, USA Tel: +1-212-203-0747, Fax: +1-212-203-0739 E-mail: [email protected]
cularity (Fig. 1) contributes to the well-known risks of nonunion and avascular necrosis of the proximal pole of the scaphoid.
BIOMECHANICAL CONSIDERATIONS IN THE TREATMENT OF ACUTE SCAPHOID FRACTURES Scaphoid fractures frequently occur after a fall on an outstretched hand. The scaphoid is the most threedimensionally mobile bone in the carpus linking the proximal row to the distal row. Disruption of its normal articulations results in abnormal kinematics and load distributions. Cadaveric models have shown that excess
Volar
Superficial palmar branch radial artery
Radial artery
Fig. 1. Scaphoid blood supply.
Dorsal
Dorsal carpal branch radial artery
211 Hand Surgery • Vol. 20, No. 2, 2015 • www.jhs-ap.org
tension results in failure to the volar scaphoid and excess compression results in failure to the dorsal scaphoid.4) Scaphoid fractures lead to opposing rotational moments on the proximal and distal poles,5) creating the angulation, or the “humpback” deformity, of scaphoid nonunions and malunions. The lunate and the remainder of the proximal row shifts into a position of extension referred to as a dorsally intercalated scaphoid instability (DISI) deformity.6) Abnormally increased flexion of the distal scaphoid pole increases loading with the radial styloid leading to radial styloid arthrosis.7,8) The predictable stages of the progressive development of arthritis has been termed as scaphoid non-union advanced collapse (SNAC) which is associated with a progressive increase in wrist stiffness, swelling, deformity, and pain.
EXAMINATION Acute scaphoid fractures commonly occur in a youn ger patient population but can occur at any age. Displaced fractures are more likely to be associated with pronounced wrist swelling and edema, but mild swelling and subtle findings should prompt suspicion of a scaphoid fracture. Tenderness may be focal at the snuffbox dorsally or at the tuberosity volarly, but it may also be nonspecific in the radial side of the wrist. Limited passive motion and guarding with extremes of wrist motion are also common exam findings. The specificity of physical examination has been reported to be 74 to 80%.9)
RADIOGRAPHIC EVALUATION Acute scaphoid fractures can be difficult to visualize with the standard posteranterior (PA), lateral and oblique radiographs of the wrist. The postero-anterior ulnar-deviated or 'scaphoid view' with the wrist positioned in ulnar deviation extends the scaphoid and, thereby, addresses the overhang of the tubercle with the remainder of the scaphoid that can obscure visualization of nondisplaced fractures with the standard PA view. The semipronated and 45o supinated oblique views also provide enhanced visualization of the scaphoid waist. Historically, for suspect fractures, ordering repeat plain radiographs approximately two to several weeks from the time of injury or a proceeding with a technicium-99 bone scan was standard practice. Bone scans have been reported to have a zero false negative rate when obtained more than 48 hours after injury.10,11) Currently, magnetic resonance imaging (MRI) is co mmonly used to diagnose occult scaphoid fractures. MRI
is particularly helpful when the degree of proximal pole viability and cartilage loss are questionable when considering primary fracture fixation.12) While MRI avoids the use of ionizing radiation and is cost effective in the diagnosis of occult fractures,13) hand surgeons are facing an increased number of administrative constraints that preclude authorization of MR imaging. It remains to be determined how to optimize and avoid over-utilization of MRI in the treatment of acute scaphoid fractures. The use of computer tomography (CT) provides a unique three-dimensional understanding of fracture personality, pattern, and displacement is proving to be critical in the acute treatment of scaphoid fractures.14,15) Thus, CT evaluation of acute scaphoid fractures to diagnose and to confirm fracture healing is continuing to increase. CT scanning of the wrist should include coronal, sagittal and axial images, and along the long axis of the scaphoid with the arm held in 45o across the gantry.16) Cuts should not be greater than one millimeter in width.16)
CLASSIFICATION Management of acute of scaphoid fractures can be based on classifying these fractures according to fracture pattern, location, and degree of instability. Fracture instability has been classified according to Herbert’s classification system17) that divides fractures into four types: Type A, stable acute fractures; Type B, unstable acute fractures; Type C, delayed unions; and Type D, established non-unions. Fractures with more than 1 mm of displacement are considered unstable.18)
MANAGEMENT OF ACUTE SCAPHOID FRACTURES In patients who are acceptable candidates for anesthesia and for surgery, the treatment of acute scaphoid fractures can be guided by the location of the fracture and the degree of displacement and angulation. Distal pole fractures are typically avulsion fractures of the tuberosity or impaction fractures of the distal articular surface which are well-vascularized. Thus, most of these fractures heal with thumb spica short-arm cast immobilization. Any clinically significant long-term effect on the distal articulating surface remains unproven.19) The traditional treatment of cast treatment for nondisplaced waist fractures has been supported by studies that report a healing rate over variable lengths of time of greater than 90%.20-23) The effect of including the thumb in the cast remains unclear.24) While clinical studies as-
212 Lana Kang. Acute Scaphoid Fractures
sessing the difference in incidence of nonunion between short-arm and long-arm casting show contradictory data.25) There is a low threshold to operatively treat acute fractures in order to minimize the risk of nonunion; the reby, the use of long arm casting has likely become reserved for skeletally immature patients. Our patients today have variable needs and desires to avoid the risks associated with cast immobilization. Surgical fixation has become a readily offered choice of treatment for non-displaced fractures.26-28) Early surgical fixation offers to minimize wrist stiffness and to potentially accelerate healing, and a considerable proportion of patients will find surgical treatment preferable to cast immobilization due to pressures of work- and other activity- related reasons.28,29) A percutaneous or mini-in cision may be appropriate for these non-displaced fractures, and minimally invasive methods require fractures that are nondisplaced or ability to achieve a reduction that is anatomic.30-33) Arthroscopically aided reduction with limited exposures may provide surgeons with direct visualization that an anatomic reduction has been achieved.34-36) More recent studies suggest that computernavigation techniques provide for greater accuracy in the percutaneous placement of screws.37-39) Theoretically, the compressive effect of headless screw fixation offers a biomechanical means to achieve a more rapid time to union compared to cast immobilization alone. Return to work has been faster with surgical fixation compared to casting.26,27) The degree of displacement may be underestimated by plain radiographs alone, and the risk for nonunion may not be not worth the complications of surgical fixation. These include hardware prominence, osteonecrosis, failure of fixation, and nonunion.40) Percutaneous fixation of scaphoid fractures is performed by either a volarly or dorsally placed screw.41) Studies have shown advantages and disadvantages for both. 42-44) With the percutaneous volar approach, the starting point for the guidewire is the scaphotrapezial joint. Extension of the wrist over a rolled towel may enhance proper wire placement.31) The major drawback of the volar percutaneous approach is that the trapezium may impede wire and screw placement and a portion of the base of the trapezium may need to be resected. The dorsal percutaneous approach poses risks to the extensor tendons and branches of the posterior interosseous nerve, as well as other complications of hardware issues and post-fixation fracture, the incidence of which is not clearly the result of technique rather than approach.45,46) Open reduction and internal fixation is indicated for
scaphoid fractures that are displaced and angulated.40,47,48) Both dorsal and volar approach can be used for scaphoid waist fractures, however, a volar exposure may be preferable to directly visualize reduction of significant flexion deformities associated with angulated waist fractures. The volar approach allows optimal exposure for distal third fractures; the dorsal approach allows optimal exposure for proximal pole fractures.41) Traditionally considered advantages for the traditional Russe volar approach may be that to circumvent disruption of the dorsal blood supply, but the dorsal could approach achieve the same by avoiding soft tissue stripping distal to the site of the fracture. Since the original Herbert screw was introduced, surgical fixation of acute fractures continue to depend on the principle that the differential pitch of the threads comprising a single screw exerts compression across the fracture.44,47,48) Different from the original Herbert screw, most screws today are not cannulated.49) Different designs among systems may vary according to the presence of a central barrel (versus continuous threads), screw diameters, screw lengths, and need for countersinking and/or pre-drilling.46,50,51) While studies have emphasized screw placement down the central axis as critical to successful healing, several reports have offered varying conclusions as to the preferred screw position, screw length, patient gender and surgical approach.52-54) Screw position relative to the line of the fracture has also been proposed to be more critical.53,54) The goal to bury these headless screws beneath the cortical surface of the scaphoid cannot be overemphasized since screw prominence will erode the opposing cartilage. Both a 45-degree supination oblique and a pronated oblique view has been suggested to be most useful for assessing length of the screw and avoiding screw prominence.33,52) Patients should be informed that the need for a return trip to the operating room for screw removal under these circumstances is not uncommon or unexpected.40) Fracture pattern and radiographic healing will dictate the post-operative course of recovery. Imaging should confirm fracture healing. CT has been shown to be a reliable method of assessing healing.55) This can be utilized when desiring to graduate the patients to the next stage of rehabilitation, particularly for those who want to resume sports and/or perform manual labor. Acute fractures are ideally treated within two weeks and less than six weeks from the time of injury with surgical methods of acute fracture treatment. Conversely, time to union using cast immobilization can require
213 Hand Surgery • Vol. 20, No. 2, 2015 • www.jhs-ap.org
greater than 6 months. Proximal pole fractures have a higher risk of nonunion even with surgical fixation, and time to union with casting alone may be as long as 9 months. These, therefore, serve as additional indications for acute surgical fixation.
SUMMARY Timely and appropriate treatment of acute scaphoid fractures is necessary for successful healing. Indications for surgical fixation of non-displaced fractures can be variable and the consensus opinion continues to evolve. In contrast, displaced, angulated, and comminuted fractures are unequivocal indications in the appropriate surgical candidate. While surgeon preference and fracture pattern may dictate choice of surgical approach and choice of implant, there are only a limited number of surgical exposures and surgical techniques, and the wellequipped hand surgeon should feel comfortable using them all.
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