Fig. 8.1
Illustrates the dorsal wrist with potential pedicle sites and their corresponding arterial donors. 1, 2 ICSRA; 2, 3 ICSRA; 4th ECA; 5th ECA. RA radial artery, UA ulnar artery, PIA posterior interosseous artery, AIA anterior interosseous artery, ODUA oblique dorsal artery of the distal ulna
Vascular bone grafts taken from distant sites, such as the iliac crest, distal medial femur and fibula have also been described [6, 9]. These grafts have the advantage of having a greater volume of bone available for transportation and, as such, can “obliterate dead space; enhance bone healing and resist infection by ensuring blood supply” [2].
Scaphoid Injuries and Vascularised Bone Grafts
The scaphoid is the most commonly injured bone of the carpus (60 % of all carpal injures) and 5–15 % of these go on to non-union [10]. Fractures involving the proximal pole of the scaphoid are particularly susceptible to avascular necrosis, due to the tenuous blood supply of the scaphoid entering from its distal, dorsal aspect. Scaphoid fractures may also go onto non-union if there is fracture displacement (≥2 mm), or associated carpal instability. Pedicled (pronator quadratus), vascularised bone grafts for the non-union of scaphoid fractures have been reported since the early 1980s [11, 12]. Since then, several other sites have been used to provide VBGs – including 1,2 ICSRA, palmar carpal artery, iliac crest with implantation of the second dorsal vascular bundle, dorsal metacarpal arteries and free vascularised bone.
VBGs may also be of use in revision surgery, where primary fixation has failed and a non-union is clinically present, in proximal pole fractures and in AVN of the proximal pole. Even when VBG are used for scaphoid pathologies, non-union remains a problem in smokers, females and when significant carpal collapse is present [13].
The 1,2 – intercompartmental supraretinacular artery graft (1,2 – ICSRA) is a pedicled, distal, dorsal radius vascularised bone graft based on a consistent and reliable arterial network, initially described by Zaidemberg et al. and further delineated and defined by Sheetz et al. [8, 14] (see Fig. 8.2). Waitayawinyu et al. in a recent study noted that the origin of the 1,2 – ICSRA from the radial artery was approximately 2 mm proximal to the tip of the radial styloid and gave a mean pedicle length of 22.5 mm (range 15–31 mm) [15]. The origin of the 1,2 – ICSRA was often noted to be separate, but could be combined or shared with the origin of the dorsal scaphoid branch. As the 1,2 – ICRSA courses on top of the extensor retinaculum between the first and second extensor compartments, there is an average of five to six perforating branches.
Fig. 8.2
Illustrates the 1, 2 intercompartmental supraretinacular arterial (1, 2 ICSRA) pedicle. RA radial artery
Pedicle grafts from the volar aspect of the distal radius have also been used [7]. These grafts are based on the palmar carpal artery, which lies between the palmar periosteum of the radius and the distal part of the superficial aponeurosis of the pronator quadratus. The bone graft is harvested from the ulna aspect of the distal radius and incorporates a 5 mm wide strip of fascia and periosteum. This has the advantage of allowing a corticocancellous graft to be harvested, which can be used to correct flexion deformity to the scaphoid.
Avascular Necrosis of the Scaphoid (Preiser’s Disease) and Vascularised Bone Grafts
Preiser’s Disease is idiopathic AVN of the scaphoid and is postulated to be due to a fault with the blood supply to the scaphoid, as yet unknown. Similarly to using VBGs for scaphoid fractures, VBGs for Preiser’s disease were also described by Braun in the 1980s, again from the volar distal radius (pronator pedicle). Patients with localised AVN, as opposed to global AVN do better with VBG [16].
As with scaphoid fractures, VBGs for Preiser’s disease are not recommended in the presence of carpal instability and radiocarpal osteoarthritis [17]. At the time of surgery, as with scaphoid non unions, if significant degenerative change is present, salvage procedures, such as proximal row carpectomy, or scaphoid excision with four-corner fusion, should be considered.
Kienböck’s Disease and Vascularised Bone Grafts
Kienböck’s disease is AVN of the lunate bone and is more common than Preiser’s disease. The exact aetiology is still unknown. However, both mechanical (such as negative ulnar variance) and biological abnormalities (tenuous blood supply) have been implicated. In the earlier stages of the disease, that is when there is little collapse or fragmentation of the lunate, reconstructive surgery is an option. This would take the form of procedures to unload the lunate, such as radial or capitate shortening, together with vascularised bone graft. VBGs for the lunate were described 40 years ago (pedicled bone graft using the scaphoid tubercle on the abductor pollicis brevis muscle) [18].
Subsequently, many other types of vascular bone graft have been used, although the most common is the 4 and 5 ECA (see Fig. 8.3).
Fig. 8.3
Illustrates the position of the second and third intercompartmental supraretinacular arterial (2, 3 ICSRA) pedicle and the fourth and fifth extracompartmental (ECA) pedicle. S scaphoid
Surgical Techniques and Rehabilitation
Pedicled VBGs can be a technically demanding procedure. Any surgeon undertaking this particular operation should have a thorough knowledge of the microvascular supply around the wrist and, obviously, access to magnification. Of greatest concern, is that vessels can easily be damaged during insertion and kinking of the pedicle, or vessel damage can lead to the bone graft effectively becoming devascularised. The graft needs to be fixed in a stable fashion (for example, with a Kirschner wire) when it reaches its final destination.
Free VBG (such as iliac crest) allows for a larger volume of bone to be transported and this may be of more use when treating problems such as severe humpback deformities in the case of chronic scaphoid pathologies. Evidence has suggested that the incidence of humpback deformity is significantly greater in VBGs that go onto non-union [13].
If capitolunate wear is identified at the time of surgery, then VBGs are probably not suitable and a salvage procedure should be considered instead. However, if degenerative changes are isolated to the radial styloid, then a radial styloidectomy can be undertaken in conjunction with a VBG. Finally, any inter-osseous scaphoid cysts need to be fully excised prior to the introduction of any graft.
Moran and Shin (2007) described the technical difficulties in the use of VBG for the treatment of Preiser’s disease [19]. Perforation of the proximal part of the scaphoid can occur when attempting to remove the necrotic/sclerotic bone. This, in itself, can also present a problem as significant defects may be left once necrotic bone is removed, necessitating large volumes of VBG.
In Kienböck’s disease, the use of dorsal VBG may be the most simple as a single incision can be utilised, without compromise to the volar carpal ligaments. An unloading procedure, such as capitate shortening, may aid in revascularisation, as it is thought that the initial stages of bony healing increase osteoclast response and bony absorption and may in turn lead to initial weakening, causing further collapse [20].
Clinical Pearls
Ensure knowledge of the microvascular supply around the wrist and that access to magnification is available prior to embarking on VB grafting.
Ensure that the pedicle is not kinked.
Make sure that the graft is stably fixed (may need adjuncts to aid this).
Try and utilise a single incision for both harvesting of the bone graft and treatment of the pathology.
Outcome Including Literature Review
Scaphoid Pathology
Reports describing the use of the pronator muscle as a pedicle from the volar radius for bone grafting of (chronic) scaphoid non-unions were first described in the 1980s and “excellent” results with good bony union were reported [11, 12]. A Brazilian study (number (n) = 80) compared distal radial VBGs with non-vascularised bone graft from the iliac crest for treating scaphoid fracture non-union. Functional results (in terms of range of motion, grip strength) and radiographic findings were compared, with similar results and negligible difference in the mean time to union (9 months in the vascularised group versus 8 in the non-vascularised group) [21]. Another Brazilian group concluded that VBG (from the dorsal, distal radius) had superior results (in terms of function and time to union) for the treatment of scaphoid non-union (n = 86) in the presence of a sclerotic, poorly-vascularised proximal pole [22]. The literature often represents small patient numbers, so it may be difficult to ascertain their significance, but Boyer (n = 10) reported a 40 % non-union rate for AVN of the scaphoid proximal pole when treated with a 1,2 ICSRA VBG [23]. Other series (using the 1, 2 ICSRA VBG) have reported more ambitious rates of 90–100 % with regard to union, but again numbers of patients have been small (n = 11, 22) [8, 24]. Gras and Mathoulin (2011) have reported their use of the pedicled volar carpal artery graft in the treatment of 111 scaphoid waist or proximal pole non-unions, of which 73 were primary procedures and 38 were secondary, with a mean non-union period of 26 and 33 months respectively [25]. Sixty-four patients had no instability or malalignment (Alnot grade IIA), 42 had a mobile non-union with anterior defect resulting in DISI deformity (Alnot grade IIB) and five had a mobile non-union and DISI deformity with isolated radioscaphoid arthritis (Alnot grade IIIA). None of the patients had proximal pole AVN. Seventy of seventy-three patients (96 %) treated primarily and 34 of 38 patients (90 %) treated secondarily, achieved union at a mean of 9.7 weeks (range, 6–24 weeks) and 10.8 weeks (range, 6–24 weeks), respectively. Although statistical values were not reported, patients in both the primary and secondary groups had improved grip strength (26.8–42.3 and 20.4–39.5 kg, respectively), improved range of motion (18° and 28° increased flexion-extension arc, respectively) and most had complete resolution of their pain (96 and 56 % of patients respectively). In the primary treatment group, 95 % of patients had excellent or good results, based on the Mayo wrist score, compared with only 74 % of patients in the secondary treatment group. Radiographic carpal measures and arthritis were not reported.
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