SYMPOSIUM ON ADVANCES IN THE MANAGEMENT OF SCAPHOID PROBLEMS Scaphoid malunion

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1 Hong HKJOS Kong Journal of Orthopaedic Surgery 2002;6(2): SYMPOSIUM ON ADVANCES IN THE MANAGEMENT OF SCAPHOID PROBLEMS Scaphoid malunion Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong. ABSTRACT Scaphoid malunion may be more common than one might expect, because many cases initially are asymptomatic. In advanced cases, functional impairment and posttraumatic arthritis are highly likely. This article discusses the causes, diagnosis, and management of scaphoid malunion. Key Words: Humpback deformity; Scaphoid malunion; Scaphoid INTRODUCTION In the normal wrist, the distal carpal row is under stress to palmar flex with reference to the proximal row. This is prevented by the very strong scaphotrapezial ligament distally and the scapholunate ligament proximally. In a way, the scaphoid also functions as a stabilising structure to maintain the relationship between the proximal and distal carpal rows, so that despite the lack of strong ligaments binding the capitate and lunate in addition to the very large degree of freedom of movement in the capitolunate joint, the normal carpus does not go into collapse pattern deformity. 6 In scaphoid fractures, when the strong linkage provided by the scaphoid is disrupted, the two bone fragments are under stress to become displaced from one another. The proximal fragment, while remaining attached to the lunate, will be dorsiflexed with the lunate. The distal fragment, being attached to the trapezium by the strong scaphotrapezial ligament, will be flexed. This creates the typical palmar flexed displacement of scaphoid fracture, and if this position persists in delayed union or nonunion, it will result in the typical humpback deformity of scaphoid. There is usually also a persistent dorsiflexion of the lunate, producing the classical dorsiflexed intercalated segment instability (DISI) deformity of the carpus. 10,12 Sometimes there is comminution of the anterior cortex of scaphoid, making the fracture more unstable and with a higher tendency to palmar flex in the course of time. When a fracture initially displaced in such a manner eventually progresses into bone union, malunion of the scaphoid results. Malunion of the scaphoid is difficult to diagnose and is frequently missed. In the long run, many cases of malunion will develop arthritis. DIAGNOSIS OF MALUNION Malunion of the scaphoid occurs when there is flexion deformity of the scaphoid with an increase in flexion of the lateral intrascaphoid angle in the sagittal plane. The Correspondence: Prof. L.K. Hung, Department of Orthopaedics and Traumatology, Prince of Wales Hospital, Shatin, Hong Kong Hong Kong Orthopaedic Association & Hong Kong College of Orthopaedic Surgeons.

2 Scaphoid malunion Figure 2 Ulnar-deviated view of the wrist. For clarity, the increased intrascaphoid angle (posteroanterior) is shown in (B). Figure 1 Posteroanterior view of a case of scaphoid malunion showing the shortened and twisted appearance of the bone and the prominent signet ring appearance of the tubercle. bone is also excessively bent in the coronal plane. In addition, when the distal fragment is flexed, it is forced into pronation by its articulation with the capitate. 4,5 On the anteroposterior view of the plain radiograph, the first sign of malunion is a shortening of the scaphoid and a prominent ring sign, indicating the palmarly flexed attitude of the distal fragment (Fig. 1). The profile of the bone may also appear distorted and twisted. The ulnar-deviated view will show the whole scaphoid in a rather exaggerated curve, and the intrascaphoid angle is also markedly increased (Fig. 2). The more significant abnormality is seen on the lateral view: an increase in flexion of the intrascaphoid angle (Fig. 3). 1 The normal angle is less than 35, but in malunion, it can be increased to more than 60. There is also a DISI deformity, with dorsal tilting of the lunate, an increase in the capitolunate angle, and an increase of the scapholunate angle to more than 60. It is difficult to diagnose rotational deformity. There is slight disproportion between the distal and proximal fragments in the posteroanterior view, but to accurately discern that, a computed tomography scan with 3-dimensional reconstruction is necessary. 11,13 Similarly, it is sometimes difficult to differentiate whether the bone has fully united or not or whether it is a delayed union, a nonunion, or a full-blown malunion. The computed tomography scan with 3-dimensional reconstruction would provide ideal imaging to show the status of the union, as well as the different degrees of deformities that exist within the scaphoid and the arthritic changes that may occur in the adjacent joints. 10 Comparison with the opposite wrist is necessary to fully appreciate these abnormalities and to differentiate a true malunion from an abnormally bent scaphoid, which occasionally occurs. EFFECTS OF MALUNION Scaphoid malunion results in a state of nondissociative collapse of the carpus. The usual causes of carpal collapse, namely, scapholunate dissociation or scaphoid nonunion, are characterised by dissociation of bony components and abnormal mobility between them. In these situations, DISI is formed, and in the long run arthritis will develop around the scaphoid, resulting in either the scapholunate advanced collapse (SLAC) or scaphoid nonunion advanced collapse (SNAC) patterns. 4 These two collapse patterns are similar. There will be arthritis of the capitolunate joint as the capitate articulates on the dorsally tilted lunate. There will be scaphocapitate arthritis as the scaphoid is now flexed and forced to pronate by the capitate, and there will be radioscaphoid arthritis caused by stress between the radial styloid on the malrotated and flexed scaphoid fragment. In scaphoid malunion all these changes arise as a result of malpositioning of the scaphoid. There is a DISI pattern together with flexion and malrotation of the distal scaphoid. Since in this case the scaphoid and the surrounding ligaments are intact, initially there is little abnormal mobility, yet there may be more stiffness. It is, therefore, a form of nondissociative disorder. 105

3 HKJOS A B C Figure 3 Lateral views of the wrist. For clarity the deformities are marked separately. (A) The DISI deformity and the increased lunocapitate angle; (C) the markedly increased intrascaphoid angle. Nonetheless, this change in articulation will create the kinds of stress observed in the SLAC and SNAC collapse patterns as well as subsequent arthritis in the adjacent joints. A clinical study has shown that for scaphoid fractures that were reduced well, there were good clinical outcomes in 83% of the cases, with posttraumatic arthritis arising in only 22%. However, when there is a palmar flexion deformity of the scaphoid of more than 35, satisfactory clinical outcomes dropped to 27% of the cases and posttraumatic arthritis occurred in 54%. 1 CLINICAL FEATURES OF SCAPHOID MALUNION Most cases of scaphoid malunion arise from acute fractures that were previously treated conservatively with plaster casts. It is highly probable that some degrees of displacement and comminution of the fracture occur initially, which results in flexion deformity at the fracture site that is unrecognised at first, and then the fracture gradually heals in flexion. For an unstable fracture, it is also possible that the fracture displaces inside the cast, resulting in malalignment and subsequent malunion of the bone. It is difficult to check the bone positions accurately inside a cast. Another potential cause of malunion is inadequate reduction during bone grafting surgery for scaphoid nonunion. 8,14 The most likely reason for this is the failure to clear all dorsal osteophytes during excision of the nonunion, so the humpback deformity is not completely corrected. At the same time, the degree of varus deformity and rotational deformity of the distal fragment are difficult to assess and may not be corrected adequately. The nonunion will then be allowed to heal in an abnormal manner. Clinically, the patient will experience stiffness of the wrist, in particular at the mid-carpal joint, along with limitation of radial deviation. 3 Such symptoms may be misinterpreted as a consequence of immobilisation. In fact, if there is only selective limitation in these dimensions, the surgeon should make a careful radiological examination of the scaphoid to check for malunion. In a simulated study, a 15 increase in palmar flexion of scaphoid will result in loss of radiocarpal extension, and a 30 increase in palmar flexion will result in loss of midcarpal extension as well. 3 The degree of impairment will depend on the degrees of deformity, previous treatment, and any associated injuries. Some patients may adjust to it very well, with arthritis presenting very late, whereas other patients may find it very incapacitating from the start and develop arthritis very quickly. Clinical studies have shown that if there is a significant degree of humpback deformity, it is associated with a high incidence of posttraumatic arthritis in the wrist. 1,8 THE DILEMMA OF TREATMENT To correct scaphoid malunion, the logical solution is to perform an open corrective osteotomy, which normally requires wedge bone grafting. The problem that most surgeons fear is that an osteotomy is merely the tradeoff of a malunion for the likelihood of a nonunion and avascular necrosis of the scaphoid. 7 Some surgeons also feel that cheilectomy of the dorsal osteophyte is suffi- 106

4 Scaphoid malunion cient to improve wrist extension, the deficiency of which is the main complaint of most patients. 1,7 Any long-standing scaphoid malunion in which there are already advanced arthritic changes is not a good candidate for corrective osteotomy. Instead, salvage procedures should be considered. Corrective osteotomy should only be considered for relatively young patients. Two surgical approaches have been used for corrective osteotomy. The classical palmar approach is commonly used for bone grafting of scaphoid nonunion and is familiar to most surgeons. However, with this approach it is difficult to assess the degree of palmar flexion of the scaphoid intraoperatively, and the degree of rotational deformity is difficult to assess as well. Careful preoperative planning is therefore essential. The palmar approach further runs the risk of devascularising the proximal part of the scaphoid because the main blood supply that comes in through the dorsum is not visualised. The osteotomy can easily be placed too proximally, resulting in devascularisation of the proximal pole. The dorsal-radial approach provides a side-view of the scaphoid. It also allows easier manipulation of the distal fragment back into greater supination. At the same time, the capsular reflexion that brings in the blood supply and attaches along the dorsal ridge of the scaphoid can be seen and protected, and if necessary only detached slightly over the radial side to allow exposure of the bone. The osteotomy can be placed distal to this capsular reflexion to ensure a better preservation of blood supply to the proximal pole. Experience with corrective osteotomy of the scaphoid is still limited. 2,5,9,10,12 Among the cases reported, there was an increase in range of movement after surgery by 20 to 40, and an improvement of grip strength by 90% to 100%. The majority of patients were pain free with only a minority having mild to moderate pain. 10 These results are very encouraging and further clinical studies are worthwhile. SALVAGE PROCEDURES Depending on symptoms and requirements of the patient, one may do a joint debridement and excision of osteophytes (cheilectomy). 7 In fact, in many patients pain arises mainly from impingement of the dorsal osteophytes and will be much improved after excision of the prominences. In some patients, the pain arises from impingement of the radial styloid. With the aid of arthroscopy, a systematic assessment of the wrist can be carried out. With mid-carpal arthroscopy, the scaphocapitate, scapholunate, and scapho-trapezial-trapezoid joints can be assessed. Through radiocarpal joint arthroscopy, impingement of the radial styloid can be assessed. Cheilectomy can be carried out in a less traumatic manner in arthroscopic surgery, without opening up the joint. Internal styloidectomy of the radial styloid can also be performed arthroscopically. For more advanced and symptomatic cases, an excision of the scaphoid and intercarpal fusion, as in the case of a long-standing scaphoid nonunion, may be done, and good results can be expected. This procedure can also be carried out arthroscopically, thereby reducing tissue trauma, which can speed up recovery. SUMMARY Scaphoid malunion may be more common than expected and it can be difficult to diagnose and manage. Therefore, in management of acute scaphoid fractures or nonunions, this problem should be kept in mind and reduction of the fracture should be as anatomical as possible. Management of established malunion is controversial. The results of corrective osteotomy in carefully selected cases appear to be satisfactory. This is a demanding and potentially risky surgery and should be carefully planned and carried out by experienced surgeons. On the other hand, symptoms in scaphoid malunion may arise from arthritic changes or bone deformities that may be dealt with adequately by cheilectomy. Careful assessment is the key. REFERENCES 1. Amadio PC, Berquist TH, Smith DK, Ilstrup DM, Cooney WP, Linscheid RL. Scaphoid malunion. J Hand Surg Am 1989; 14: Birchard D, Pichora D. Experimental corrective scaphoid osteotomy for scaphoid malunion with abnormal wrist mechanics. J Hand Surg Am 1990;15: Burgess RC. The effect of a simulated scaphoid malunion on wrist motion. J Hand Surg Am 1987;12: Fernandez DL, Eggli S. Scaphoid nonunion and malunion. How to correct deformity. Hand Clin 2001;17: Fernandez DL, Martin CJ, Gonzalez del Pino J. Scaphoid malunion: the significance of rotational malalignment. J Hand Surg Br 1998;23: Garcia-Elias M. Carpal instabilities and dislocations. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green s Operative Hand Surgery. 4th ed. New York: Churchill Livingstone; 1999:

5 HKJOS 7. Gunal I, Barton NJ, Calli I, eds. Scaphoid fractures: twenty questions answered. London: The Royal Society of Medicine Press; 2002: Jiranek WA, Ruby LK, Millender LB, Bankoff MS, Newberg AH. Long-term results after Russe bone-grafting: the effect of malunion of the scaphoid. J Bone Joint Surg Br 1992;74: Lynch NM, Linscheid RL. Corrective osteotomy for scaphoid malunion: technique and long-term follow-up evaluation. J Hand Surg Am 1997;22: Nakamura R. Scaphoid mal-union: current concept and perspectives. Hand Surgery 2000;5: Nakamura R, Imaeda T, Horii E, Miura T, Hayakawa N. Analysis of scaphoid fracture displacement by three-dimensional computed tomography. J Hand Surg Am 1991;16: Nakamura R, Imaeda T, Miura T. Scaphoid malunion. J Bone Joint Surg Br 1991;73: Sanders WE. Evaluation of the humpback scaphoid by computed tomography in the longitudinal axial plane of the scaphoid. J Hand Surg Am 1988;13: Tomaino MM, Pizillo M. Correction of lunate malalignment when bone grafting scaphoid nonunion with hympback deformity: rationale and results of a technique revisited. J Hand Surg Am 2000;25: The Author HUNG Leung-Kim, MBBS, FHKAM (Orth Surg), Professor, Department of Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong. 108