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Avascular necrosis of the proximal scaphoid after fracture union
A V A S C U L A R N E C R O S I S OF T H E P R O X I M A L S C A P H O I D AFTER FRACTURE UNION S. L. FILAN and T. J. HERBERT From the St Luke's Hospital Hand Unit, Sydney, Australia
We report four cases of late avascular necrosis (AVN) of the proximal part of the scaphoid following apparent healing of acute scaphoid fractures. One patient had been treated conservatively, by plaster immobilization, and the other three had undergone internal fixation of their acute fractures. The onset of symptoms associated with AVN varied, being as late as 2 years in one patient. Late AVN following healing of a scaphoid fracture does not appear to have been previously recognized, perhaps due to the fact that patients are seldom followed up for long enough. We feel that this condition is in many ways analogous to late AVN following femoral neck fractures and as such is a special complication related to the fact that both bones are intracapsular and have a precarious blood supply.
Journal of Hand Surgery (British and European Volume, 1995) 20B." 4:551-556
The uneven cystic/sclerotic X-ray appearance correlates with the patchy histological configuration of scaphoid AVN reported by Urban et al (1993).
Late avascular necrosis (AVN) of the femoral head is a relatively common phenomenon, occurring in as many as 50% of cases after fracture union (Calandruccio and Anderson, 1980). While AVN of the proximal scaphoid is a well-recognized complication of scaphoid non-union, idiopathic avascular necrosis is a rare condition (Ferlic and Morin, 1989; Herbert and Lanzetta, 1993). Stothard and Kumar (1993) reported a case of late AVN with pathological fracture of the proximal scaphoid following successful reconstruction of a scaphoid non-union; apart from this we were unable to find any further reference to this phenomenon in the literature. We report four cases of proximal pole AVN occurring following union of acute scaphoid fractures (Table 1). Three patients received primary internal fixation of their scaphoid fractures using a Herbert screw and the fourth was managed conservatively. All patients had symptoms and signs characteristic of AVN, with severe radial-sided wrist pain, synovitis and an "irritable wrist". Three patients had ongoing symptoms from the time of injury, whereas the fourth had been pain-free for 2 years before the onset of symptoms. Radiographic diagnosis was made according to the description of Herbert (1990). Important radiographic features of AVN include a shrinking, deformed proximal pole, and cystic and sclerotic changes with loss of trabeculation leading to a "ground glass" appearance.
CASE REPORTS Case 1
A 28-year-old right-handed service station manager and motocross racer sustained unstable fractures of both scaphoids and his right clavicle, as a result of a motorcycle accident. Initially both wrists were immobilized in plaster, which was removed 3 weeks later when the patient elected to have his scaphoid fractures internally fixed. On the right side there was a very unstable oblique fracture with soft tissue interposition. The fracture was carefully reduced and held with a K-wire and Herbert screw. The left scaphoid fracture was operated on 1 week later; a stable reduction was achieved, the Herbert screw providing rigid fixation without the need for an additional K-wire. Within the first 2 weeks after surgery, the patient was gardening and using a wheelbarrow. 6 weeks after surgery both fractures appeared to have united, but he was still experiencing occasional sharp pains in his right wrist where range of motion remained significantly
Table 1--Patients with late AVN
Case l 2 3 4
Age
Hand
Occupation
Cause of injury
Surgery
Other injury
28 21 30 24
R (D) L (ND) L (ND) L (ND)
Service station Plumber Doctor Cab/student
Motorcycle Skateboard Football Motorcycle
4 weeks POP 11 days 11 days
# R clavicle # L clavicle
D = dominant. ND = non-dominant. 551
Diagnosis 36 24 26 3
months months months months
552
THE JOURNAL OF HAND SURGERY VOL. 20B No. 4 AUGUST 1995
restricted compared with the left wrist, which was symptom free. The right wrist improved slowly after removal of the K-wire and screw in separate procedures. 7 months post-operatively, the patient had regained 85% of flexion and extension and was using the wrist normally. However, 15 months later he returned complaining of increased pain following relatively minor trauma. There was some irregularity of the proximal pole (Fig la), although this was not diagnosed as AVN at that time. By 2 years after the injury, he was complaining of increasing pain with loss of grip strength. A leather work splint was provided, but 3 years after surgery the wrist deteriorated to the stage that he was functionally disabled. By this time X-rays showed clear signs of avascular necrosis of the proximal pole (Fig lb), confirmed on MRI. 4 months later, the proximal pole of the scaphoid was excised and replaced with a silicone prosthesis. At that time the fracture was noted to be soundly healed without deformity. Macroscopically, the proximal pole was found to have undergone segmental avascular necrosis, the dorsal part being the most severely affected; adjacent to this, a tear was noted in the dorsal part of the scapho-lunate ligament. Histology
Fig 1
confirmed the diagnosis of segmental AVN of the proximal pole fragment.
Case 2
A 21-year-old plumber injured his non-dominant left wrist in a fall on a skateboard ramp, sustaining an undisplaced fracture of the scaphoid (Fig 2a). The fracture was treated conservatively, by immobilization in a scaphoid-type cast for 6 weeks. Following removal of the plaster, X-rays appeared to show sound union, and the patient made an uneventful recovery. 2 years later he came back complaining of increasing pain and swelling in the wrist. On examination he was noted to have marked swelling and tenderness around the scaphoid associated with an irritable wrist joint. X-rays showed signs of progressive avascular necrosis of the proximal pole of the scaphoid, the original fracture being soundly healed (Figs 2b and c). Bone scans showed increased uptake in the radio-carpal joint and a CT scan confirmed the diagnosis of AVN with fissuring and sclerosis of the proximal part of the scaphoid, with a defect in the cortex. At operation, the proximal pole of the scaphoid was excised and replaced with an osteochondral rib graft.
Case 1. (a) 15 m o n t h s after internal fixation, 10 m o n t h s after screw removal. There is some irregularity of the proximal scaphoid. (b) Before salvage. Note the loss of trabecular structure and narrowing of the proximal pole, as well as the increased scapho-lunate gap.
SCAPHOID AVN AFTER FRACTURE UNION
Fig 2
553
Case 2. (a) Acute scaphoid fracture. (b) 2 years later the fracture has united, but there is residual deformity and fissuring of the proximal pole (arrow) with some avulsion at the scapho-lunate ligament attachment. (c) 2.5 years after the original injury the proximal pole is losing density and trabecular structure.
554
Histology confirmed the diagnosis of segmental AVN affecting the proximal pole. Case 3
A 30-year-old doctor and first grade football player sustained an unstable proximal scaphoid fracture in his non-dominant left hand after relatively minor trauma while playing football. At operation 11 days after injury marked synovitis and synovial effusion were noted; the fracture was found to be completely unstable and was fixed with some difficulty using a Herbert bone screw inserted freehand. His wrist remained stiff and swollen after surgery, gradually improving over the following 7 months. At that stage the fracture appeared soundly healed, but the proximal pole started to show radiographic signs of progressive ischaemia. At his last review, 26 months post-operatively, the fracture remained healed and there was no screw loosening; however the proximal pole of the scaphoid had the characteristic appearances of avascular necrosis. The patient remains under review. Interestingly, he had previously sustained a similar fracture to his opposite (right) scaphoid which had failed to heal following conservative treatment. Reconstruction was undertaken 18 months later, but at surgery the proximal pole was noted to be completely ischaemic; the end result being asymptomatic non-union. Case 4
A 24-year-old right-handed student and cab driver presented with a fractured left scaphoid and clavicle following a motorcycle accident (Fig 3a). 11 days after the injury, the scaphoid was fixed using a Herbert screw with a radial bone graft. At operation the fracture was noted to be highly unstable and displaced. Fixation proved difficult and the bone was noted to be abnormally soft; post-operative X-ray showed incomplete reduction of the fracture (Fig 3b). Nevertheless, by 3.5 months the fracture appeared to be united (Fig 3c). The patient's wrist was slow to improve, with extension limited to 20 ° 6 weeks postoperatively. He remained symptomatic, and X-rays at 5 and 8 months demonstrated progressive cystic change around the screw thread in the proximal pole of the scaphoid, narrowing of the proximal pole, and loss of trabecular structure characteristic of AVN (Fig 3d). At his last visit, 8 months postoperatively, the range of motion had improved, but he still had pain and swelling in the wrist. Despite residual symptoms, the patient was reasonably happy with his wrist and was subsequently lost to review. DISCUSSION In a review of more than 500 scaphoid fixations performed by the senior author (TJH), we have identified
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995
three cases of late AVN. All of these followed open reduction and internal fixation of acute unstable scaphoid fractures, in contrast to the case reported by Stothard and Kumar (1993) which followed scaphoid reconstruction for established non-union. The fourth case presented here had been treated conservatively and was subsequently referred for treatment of his symptomatic avascular necrosis. In the femoral head, late AVN after fracture-union is a recognized complication with an incidence of 14% for undisplaced fractures, or 50% for displaced fractures (Calandruccio and Anderson, 1980). In contrast to femoral head fractures, we could find only one report (Stothard and Kumar, 1993) of late AYN after union of a scaphoid fracture. Fractures of the scaphoid have been compared to those of the femoral neck because of the relatively precarious blood supply and intracapsular position of the bone (Calandruccio and Anderson, 1980; Herbert, 1990). In both the femoral head (Sevitt, 1964; Sevitt and Thompson, 1965) and the scaphoid (Gelberman and Menon, 1980), damage to the blood supply following fracture is a recognized cause of avascular necrosis. However, at both sites idiopathic avascular necrosis may also occur rarely, and this is thought to be related to anatomical variants in blood supply causing susceptibility in certain individuals (femoral head: Ficat and Arlet, 1980; Arlet, 1992; scaphoid: Herbert and Lanzetta, 1993). The fact that three of our four cases, together with that reported by Stothard and Kumar (1993), occurred after Herbert screw fixation leads one to question whether surgery may have affected the blood supply in some way. However, in all cases the palmar approach was used and there is no evidence that this can adversely affect the blood supply to the scaphoid (Gelberman and Menon, 1980). As mentioned previously, in a personal series of scaphoid reconstructions using the votar approach, we have only been able to identify three cases of late AVN, all of which were associated with grossly unstable acute fractures. For this reason, we believe that late AVN is the result not of surgical trauma, but rather of failure of primary revascularization of the proximal fragment following injury. It appears that several factors may contribute to this failure including severe trauma, gross instability, anatomical variation (patients with bilateral fractures) and damage to the scaphoqunate ligament. Cases 1 and 4 sustained ipsilateral clavicular fractures in addition to unstable and displaced scaphoid fractures, suggesting that the impact force was greater than that normally associated with a scaphoid fracture. Simultaneous ipsilateral clavicular fractures were found only in these two cases among the 73 acute scaphoid fractures eligible for this study. All three fractures which were treated by open reduction and internal fixation were highly unstable, requiring a supplementary K-wire in Case 1, freehand
SCAPI-IOIDAVN AFTER FRACTURE UNION
Fig 3
555
Case 4. (a) Acute scaphoid fracture. (b) Post-operative X-ray showing bone graft and residual deformity. (c) 3.5 months post-operatively the fracture has united, but there is some radio-lucency around the proximal screw thread. (d) 8 months after surgery there is increased cystic change around the proximal screw thread and narrowing of the proximal pole, indicating avascular necrosis.
556
screw insertion in Case 3 and a radial bone graft in Case 4. Case 3 is typical of the problems we see in patients with bilateral scaphoid injuries in whom we have noted an abnormally high rate of complications. Relatively minor trauma led to both fractures and the established non-union failed to heal following surgery. This suggests that there may be an underlying anatomical variation of the scaphoid which increases the likelihood of fracture, as well as non-union and AVN. This is similar to Ficat and Arlet's (1980) observation that in cases of idiopathic necrosis of the femoral head "bilateral cases have a much worse prognosis with three-quarters of the cases undergoing spontaneous progression." As previously noted in our study of patients with idiopathic avascular necrosis of the scaphoid (Herbert and Lanzetta, 1993), we suspect that damage to the scapho-lunate ligament may be a key factor in the development of AVN of the scaphoid. The high impact injury which resulted in these highly unstable and often displaced fractures may well have caused damage to the scapho-lunate ligament, compromising its contribution to the proximal scaphoid vasculature. Hixson and Stewart (1990) and Berger et al (1991) concluded that the scapho-lunate ligament did not supply the proximal pole of the scaphoid, but they described vessels which might become important in the course of fracture healing. Although the scapho-lunate ligament was not examined during open reduction and internal fixation, late scapho-lunate ligament failure in Cases 3 and 4 is consistent with previous damage. We did not routinely examine the ligament because it had been thought that scaphoid fracture and scapho-lunate ligament injuries were mutually exclusive. Since these cases were noted, however, the ligament has been examined during internal fixation of all acute fractures and in several cases tears and/or oedema of the scapho-lunate ligament have been noted. A diagnosis of late AVN following conservative treatment (Case 2) was only made because the patient was referred with a diagnosis of occult wrist pain. We suggest that other cases of late AVN following conservative
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995
treatment must exist, but remain unreported because of inadequate follow-up or because late pathological fractures are confused with true scaphoid non-union. The risk of possible late avascutar necrosis and of unrecognized non-union (Dias et al. 1989) emphasize the importance of keeping patients under review following treatment of scaphoid fracture. Acknowledgement S. L. Filan was supported by a grant from Zimmer, Inc.
References ARLET, J. (1992). Nontraumatic avascular necrosis of the femoral head: Past, present, and future. Clinical Orthopaedics and Related Research, 277: 12 21. BERGER, R. A., KAUER, J. M. G. and L A N D S M E E R , J. M. F. (t991). Radioscaphohmate ligament: A gross anatomic and histologic study of fetal and adult wrists. Journal of H a n d Surgery, 16A: 2: 350-355. C A L A N D R U C C I O , R. A. and A N D E R S O N W. E. (1980). Post-fracture avascular necrosis of the femoral head: Correlation of experimental and clinical studies. Clinical Orthopaedics and Related Research, 152: 49-84. DIAS, J. J., BRENKEL, I. J. and FINLAY, D. B. L. (1989). Patterns of union in fractures of the waist of the scaphoid. Journal of Bone and Joint Surgery, 71B: 2: 307-310. FERLIC, D. C. and MORIN, P. (1989). Idiopathic avascular necrosis of the scaphoid: Preiser's disease? Journal of H a n d Surgery, 14A: 1: 13-16. FICAT, R. P. and ARLET, J. Ischemia and Necrosis of Bone. Baltimore, Williams and Wilkins, 1980: 196. G E L B E R M A N , R. H. and MENON, J. (1980). The vascularity of the scaphoid bone. Journal of H a n d Surgery, 5: 5: 508-513. HERBERT, T. J. The Fractured Seaphoid. St Louis, Quality Medical Publishing, 1990: 202. HERBERT, T. J. and LANZETTA, M. (1993). Idiopathic avascular necrosis of the scaphoid. Journal of Hand Surgery, 19B: 2: 174-182. HIXSON, M. L. and STEWART, C. (1990). Microvascular anatomy of the radio-scapho-lunate ligament of the wrist. Journal of H a n d Surgery, 15A: 2:279 282. SEVITT, S. (1964). Avascular necrosis and revascularisation of the femoral head after intracapsular fractures. Journal of Bone and Joint Surgery, 46B: 2: 270 296. SEVITT, S. and THOMPSON, R. G. (1965). The distribution and anastomoses of arteries supplying the head and neck of the femur. Journal of Bone and Joint Surgery, 47B: 3:560 573. STOTHARD, J. and K U M A R , A. (1993). Scaphoid fracture at the tip of a Herbert screw. Journal of Bone and Joint Surgery, 75B: 6: 974-975. URBAN, M. A., GREEN, D. P. and A U F D E M O R T E , T. B. (1993). The patchy configuration of scaphoid avascular necrosis. Journal of H a n d Surgery, 18A: 4: 669-674.
Accepted: 2 February 1995 Dr T. J. Herbert, Hand Unit, St Luke's Hospital, 18 Roslyn Street, Potts Point, NSW 2011, Australia. © 1995 The British Society for Surgery of the Hand
We report four cases of late avascular necrosis (AVN) of the proximal part of the scaphoid following apparent healing of acute scaphoid fractures. One patient had been treated conservatively, by plaster immobilization, and the other three had undergone internal fixation of their acute fractures. The onset of symptoms associated with AVN varied, being as late as 2 years in one patient. Late AVN following healing of a scaphoid fracture does not appear to have been previously recognized, perhaps due to the fact that patients are seldom followed up for long enough. We feel that this condition is in many ways analogous to late AVN following femoral neck fractures and as such is a special complication related to the fact that both bones are intracapsular and have a precarious blood supply.
Journal of Hand Surgery (British and European Volume, 1995) 20B." 4:551-556
The uneven cystic/sclerotic X-ray appearance correlates with the patchy histological configuration of scaphoid AVN reported by Urban et al (1993).
Late avascular necrosis (AVN) of the femoral head is a relatively common phenomenon, occurring in as many as 50% of cases after fracture union (Calandruccio and Anderson, 1980). While AVN of the proximal scaphoid is a well-recognized complication of scaphoid non-union, idiopathic avascular necrosis is a rare condition (Ferlic and Morin, 1989; Herbert and Lanzetta, 1993). Stothard and Kumar (1993) reported a case of late AVN with pathological fracture of the proximal scaphoid following successful reconstruction of a scaphoid non-union; apart from this we were unable to find any further reference to this phenomenon in the literature. We report four cases of proximal pole AVN occurring following union of acute scaphoid fractures (Table 1). Three patients received primary internal fixation of their scaphoid fractures using a Herbert screw and the fourth was managed conservatively. All patients had symptoms and signs characteristic of AVN, with severe radial-sided wrist pain, synovitis and an "irritable wrist". Three patients had ongoing symptoms from the time of injury, whereas the fourth had been pain-free for 2 years before the onset of symptoms. Radiographic diagnosis was made according to the description of Herbert (1990). Important radiographic features of AVN include a shrinking, deformed proximal pole, and cystic and sclerotic changes with loss of trabeculation leading to a "ground glass" appearance.
CASE REPORTS Case 1
A 28-year-old right-handed service station manager and motocross racer sustained unstable fractures of both scaphoids and his right clavicle, as a result of a motorcycle accident. Initially both wrists were immobilized in plaster, which was removed 3 weeks later when the patient elected to have his scaphoid fractures internally fixed. On the right side there was a very unstable oblique fracture with soft tissue interposition. The fracture was carefully reduced and held with a K-wire and Herbert screw. The left scaphoid fracture was operated on 1 week later; a stable reduction was achieved, the Herbert screw providing rigid fixation without the need for an additional K-wire. Within the first 2 weeks after surgery, the patient was gardening and using a wheelbarrow. 6 weeks after surgery both fractures appeared to have united, but he was still experiencing occasional sharp pains in his right wrist where range of motion remained significantly
Table 1--Patients with late AVN
Case l 2 3 4
Age
Hand
Occupation
Cause of injury
Surgery
Other injury
28 21 30 24
R (D) L (ND) L (ND) L (ND)
Service station Plumber Doctor Cab/student
Motorcycle Skateboard Football Motorcycle
4 weeks POP 11 days 11 days
# R clavicle # L clavicle
D = dominant. ND = non-dominant. 551
Diagnosis 36 24 26 3
months months months months
552
THE JOURNAL OF HAND SURGERY VOL. 20B No. 4 AUGUST 1995
restricted compared with the left wrist, which was symptom free. The right wrist improved slowly after removal of the K-wire and screw in separate procedures. 7 months post-operatively, the patient had regained 85% of flexion and extension and was using the wrist normally. However, 15 months later he returned complaining of increased pain following relatively minor trauma. There was some irregularity of the proximal pole (Fig la), although this was not diagnosed as AVN at that time. By 2 years after the injury, he was complaining of increasing pain with loss of grip strength. A leather work splint was provided, but 3 years after surgery the wrist deteriorated to the stage that he was functionally disabled. By this time X-rays showed clear signs of avascular necrosis of the proximal pole (Fig lb), confirmed on MRI. 4 months later, the proximal pole of the scaphoid was excised and replaced with a silicone prosthesis. At that time the fracture was noted to be soundly healed without deformity. Macroscopically, the proximal pole was found to have undergone segmental avascular necrosis, the dorsal part being the most severely affected; adjacent to this, a tear was noted in the dorsal part of the scapho-lunate ligament. Histology
Fig 1
confirmed the diagnosis of segmental AVN of the proximal pole fragment.
Case 2
A 21-year-old plumber injured his non-dominant left wrist in a fall on a skateboard ramp, sustaining an undisplaced fracture of the scaphoid (Fig 2a). The fracture was treated conservatively, by immobilization in a scaphoid-type cast for 6 weeks. Following removal of the plaster, X-rays appeared to show sound union, and the patient made an uneventful recovery. 2 years later he came back complaining of increasing pain and swelling in the wrist. On examination he was noted to have marked swelling and tenderness around the scaphoid associated with an irritable wrist joint. X-rays showed signs of progressive avascular necrosis of the proximal pole of the scaphoid, the original fracture being soundly healed (Figs 2b and c). Bone scans showed increased uptake in the radio-carpal joint and a CT scan confirmed the diagnosis of AVN with fissuring and sclerosis of the proximal part of the scaphoid, with a defect in the cortex. At operation, the proximal pole of the scaphoid was excised and replaced with an osteochondral rib graft.
Case 1. (a) 15 m o n t h s after internal fixation, 10 m o n t h s after screw removal. There is some irregularity of the proximal scaphoid. (b) Before salvage. Note the loss of trabecular structure and narrowing of the proximal pole, as well as the increased scapho-lunate gap.
SCAPHOID AVN AFTER FRACTURE UNION
Fig 2
553
Case 2. (a) Acute scaphoid fracture. (b) 2 years later the fracture has united, but there is residual deformity and fissuring of the proximal pole (arrow) with some avulsion at the scapho-lunate ligament attachment. (c) 2.5 years after the original injury the proximal pole is losing density and trabecular structure.
554
Histology confirmed the diagnosis of segmental AVN affecting the proximal pole. Case 3
A 30-year-old doctor and first grade football player sustained an unstable proximal scaphoid fracture in his non-dominant left hand after relatively minor trauma while playing football. At operation 11 days after injury marked synovitis and synovial effusion were noted; the fracture was found to be completely unstable and was fixed with some difficulty using a Herbert bone screw inserted freehand. His wrist remained stiff and swollen after surgery, gradually improving over the following 7 months. At that stage the fracture appeared soundly healed, but the proximal pole started to show radiographic signs of progressive ischaemia. At his last review, 26 months post-operatively, the fracture remained healed and there was no screw loosening; however the proximal pole of the scaphoid had the characteristic appearances of avascular necrosis. The patient remains under review. Interestingly, he had previously sustained a similar fracture to his opposite (right) scaphoid which had failed to heal following conservative treatment. Reconstruction was undertaken 18 months later, but at surgery the proximal pole was noted to be completely ischaemic; the end result being asymptomatic non-union. Case 4
A 24-year-old right-handed student and cab driver presented with a fractured left scaphoid and clavicle following a motorcycle accident (Fig 3a). 11 days after the injury, the scaphoid was fixed using a Herbert screw with a radial bone graft. At operation the fracture was noted to be highly unstable and displaced. Fixation proved difficult and the bone was noted to be abnormally soft; post-operative X-ray showed incomplete reduction of the fracture (Fig 3b). Nevertheless, by 3.5 months the fracture appeared to be united (Fig 3c). The patient's wrist was slow to improve, with extension limited to 20 ° 6 weeks postoperatively. He remained symptomatic, and X-rays at 5 and 8 months demonstrated progressive cystic change around the screw thread in the proximal pole of the scaphoid, narrowing of the proximal pole, and loss of trabecular structure characteristic of AVN (Fig 3d). At his last visit, 8 months postoperatively, the range of motion had improved, but he still had pain and swelling in the wrist. Despite residual symptoms, the patient was reasonably happy with his wrist and was subsequently lost to review. DISCUSSION In a review of more than 500 scaphoid fixations performed by the senior author (TJH), we have identified
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995
three cases of late AVN. All of these followed open reduction and internal fixation of acute unstable scaphoid fractures, in contrast to the case reported by Stothard and Kumar (1993) which followed scaphoid reconstruction for established non-union. The fourth case presented here had been treated conservatively and was subsequently referred for treatment of his symptomatic avascular necrosis. In the femoral head, late AVN after fracture-union is a recognized complication with an incidence of 14% for undisplaced fractures, or 50% for displaced fractures (Calandruccio and Anderson, 1980). In contrast to femoral head fractures, we could find only one report (Stothard and Kumar, 1993) of late AYN after union of a scaphoid fracture. Fractures of the scaphoid have been compared to those of the femoral neck because of the relatively precarious blood supply and intracapsular position of the bone (Calandruccio and Anderson, 1980; Herbert, 1990). In both the femoral head (Sevitt, 1964; Sevitt and Thompson, 1965) and the scaphoid (Gelberman and Menon, 1980), damage to the blood supply following fracture is a recognized cause of avascular necrosis. However, at both sites idiopathic avascular necrosis may also occur rarely, and this is thought to be related to anatomical variants in blood supply causing susceptibility in certain individuals (femoral head: Ficat and Arlet, 1980; Arlet, 1992; scaphoid: Herbert and Lanzetta, 1993). The fact that three of our four cases, together with that reported by Stothard and Kumar (1993), occurred after Herbert screw fixation leads one to question whether surgery may have affected the blood supply in some way. However, in all cases the palmar approach was used and there is no evidence that this can adversely affect the blood supply to the scaphoid (Gelberman and Menon, 1980). As mentioned previously, in a personal series of scaphoid reconstructions using the votar approach, we have only been able to identify three cases of late AVN, all of which were associated with grossly unstable acute fractures. For this reason, we believe that late AVN is the result not of surgical trauma, but rather of failure of primary revascularization of the proximal fragment following injury. It appears that several factors may contribute to this failure including severe trauma, gross instability, anatomical variation (patients with bilateral fractures) and damage to the scaphoqunate ligament. Cases 1 and 4 sustained ipsilateral clavicular fractures in addition to unstable and displaced scaphoid fractures, suggesting that the impact force was greater than that normally associated with a scaphoid fracture. Simultaneous ipsilateral clavicular fractures were found only in these two cases among the 73 acute scaphoid fractures eligible for this study. All three fractures which were treated by open reduction and internal fixation were highly unstable, requiring a supplementary K-wire in Case 1, freehand
SCAPI-IOIDAVN AFTER FRACTURE UNION
Fig 3
555
Case 4. (a) Acute scaphoid fracture. (b) Post-operative X-ray showing bone graft and residual deformity. (c) 3.5 months post-operatively the fracture has united, but there is some radio-lucency around the proximal screw thread. (d) 8 months after surgery there is increased cystic change around the proximal screw thread and narrowing of the proximal pole, indicating avascular necrosis.
556
screw insertion in Case 3 and a radial bone graft in Case 4. Case 3 is typical of the problems we see in patients with bilateral scaphoid injuries in whom we have noted an abnormally high rate of complications. Relatively minor trauma led to both fractures and the established non-union failed to heal following surgery. This suggests that there may be an underlying anatomical variation of the scaphoid which increases the likelihood of fracture, as well as non-union and AVN. This is similar to Ficat and Arlet's (1980) observation that in cases of idiopathic necrosis of the femoral head "bilateral cases have a much worse prognosis with three-quarters of the cases undergoing spontaneous progression." As previously noted in our study of patients with idiopathic avascular necrosis of the scaphoid (Herbert and Lanzetta, 1993), we suspect that damage to the scapho-lunate ligament may be a key factor in the development of AVN of the scaphoid. The high impact injury which resulted in these highly unstable and often displaced fractures may well have caused damage to the scapho-lunate ligament, compromising its contribution to the proximal scaphoid vasculature. Hixson and Stewart (1990) and Berger et al (1991) concluded that the scapho-lunate ligament did not supply the proximal pole of the scaphoid, but they described vessels which might become important in the course of fracture healing. Although the scapho-lunate ligament was not examined during open reduction and internal fixation, late scapho-lunate ligament failure in Cases 3 and 4 is consistent with previous damage. We did not routinely examine the ligament because it had been thought that scaphoid fracture and scapho-lunate ligament injuries were mutually exclusive. Since these cases were noted, however, the ligament has been examined during internal fixation of all acute fractures and in several cases tears and/or oedema of the scapho-lunate ligament have been noted. A diagnosis of late AVN following conservative treatment (Case 2) was only made because the patient was referred with a diagnosis of occult wrist pain. We suggest that other cases of late AVN following conservative
T H E J O U R N A L OF H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995
treatment must exist, but remain unreported because of inadequate follow-up or because late pathological fractures are confused with true scaphoid non-union. The risk of possible late avascutar necrosis and of unrecognized non-union (Dias et al. 1989) emphasize the importance of keeping patients under review following treatment of scaphoid fracture. Acknowledgement S. L. Filan was supported by a grant from Zimmer, Inc.
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Accepted: 2 February 1995 Dr T. J. Herbert, Hand Unit, St Luke's Hospital, 18 Roslyn Street, Potts Point, NSW 2011, Australia. © 1995 The British Society for Surgery of the Hand