Abstract
Metacarpal and phalangeal fracture malunions with significant angulation deformity are associated with bone shortening, prominence of the metacarpal head in the palm or pseudoclaw deformity and may be symptomatic. If so, they may need corrective osteotomy procedures. Conventional methods of closing, or opening, wedge osteotomy do not restore the length of the bone exactly. Simultaneous correction of the angular deformity and restoration of bone length can be addressed by a trapezoid rotational bone graft osteotomy. A double osteotomy is done and the segment of bone is rotated and re-inserted as a bone graft. This was done successfully in four metacarpal and two phalangeal fracture malunions with angulation deformities.
Malunion of metacarpal fractures with dorsal angulation deformity may result in significant metacarpal shortening and/or prominence of the metacarpal head in the distal palm. Proximal phalangeal fracture malunion with volar angulation deformity may result in bone shortening, pseudoclaw deformity and decrease in range of motion of the joints of the finger. Both of these malunions may result in painful hand grasp and/or decreased grip strength. These problems are usually experienced when the angle in the metacarpal shaft is greater than 30° or the shortening is greater than 2 to 5 mm and when the angle is greater than 25 to 30° in the proximal phalanx (Green, 1986; Lee and Jupiter, 2000; Stern, 2005; Wolfe and Elliot, 1996). Correction of these angular deformities has previously been achieved by either a closing wedge or an opening wedge osteotomy at the fracture site. However, these procedures do not restore the length of the bone to its initial pre-fracture length. In a closing wedge osteotomy of 30° or greater, there may be significant shortening in the length of the bone as a result of removal of the wedge of bone (Fig 1). The geometrical gain in length by straightening the bone is, to some extent, negated by this shortening. In an opening wedge osteotomy, there is lengthening of the bone, resulting in an over-correction of bone length (Fig 2). The latter procedure also involves harvesting a bone graft from a distant site, with the inherent risk of donor site morbidity (Cockin, 1971). Stabilisation of the bone graft can also be difficult.
Restoration of the bone length, whilst correcting the angular deformity, can be addressed by the trapezoid rotational bone graft osteotomy technique (Fig 3), the use of which is illustrated in five patients in this study.
PATIENTS AND METHOD
Three patients with four metacarpal fracture malunions with dorsal angulation presented with painful hand grasp function, although they had normal ranges of motion of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. Their pre-operative malunion angles averaged 38° (range 32° –45° ). Another two patients with two proximal phalangeal fracture malunions with volar angulation of the little fingers had pseudoclaw deformities. One of them complained of having decreased grip strength and the other of painful grasp function. The former had decreased range of motion of the MCP joint and the latter had decreased range of motion of the PIP joint. In addition, the former patient had a volar subluxation of the proximal phalanx at the MCP joint. This may have occurred following two previous attempted operations to correct the deformity in his right little finger. He had sustained the injury to his little finger more than ten years earlier and the last operation was approximately five years ago. Their pre-operative malunion angles were 60° and 50° , respectively. All five patients were men of average age 32.5 (range 20–51) years (Table 1).
Corrective osteotomies, as described below, were carried out to the metacarpals and phalanges at the sites of angulation.
Surgical technique for metacarpal dorsal angulation (Figs 3 and 4)
Pre-operatively, the angle of deformity α° is measured on the lateral view radiograph of the metacarpal. The operative angle of osteotomy is then calculated. In a closing wedge osteotomy, the osteotomy is performed at two sites, proximal and distal to the apex of the dorsal angulation, at an angle perpendicular to the bone such that they meet at the far cortex and each osteotomy corrects ½α°. In our procedure, the osteotomies are done further apart to cut out a trapezoid segment of bone and the angle of osteotomy from the perpendicular to the bone should be ¼α°, as this segment of bone is removed, rotated and re-inserted as a free bone graft. The two sites of the osteotomy are placed at a distance apart such that the shorter cortex of this trapezoid segment of bone is of a sufficient length for the stable placement of a screw, i.e. three times the diameter of the screw-being used. For example, if the diameter of the screw is 1.5 mm, then this cortex length should be at least 4.5 mm. The fixation of the corrective osteotomy is by metal plate and screw internal fixation. A 1.5 mm or 2.0 mm mini-plate may be used, depending on the size of the bone and the surgeon’s choice. A straight plate is used for the metacarpal bone and should be, at least, a six-hole plate.
The malunited fracture site is exposed from a dorsal approach. The trapezoid segment of bone is marked out for osteotomy, as described above, such that the palmar cortex will be at least three times the diameter of the metal screws which will be used later for internal fixation of the bone. The angle of osteotomy is measured from the perpendicular to the bone towards the angle of the deformity, proximally and distally (Fig 3B). Placing a K-wire perpendicular to the axis of the bone may facilitate this marking process.
Following the osteotomy, the trapezoid segment of bone is removed, rotated 180º and re-inserted as an interposition bone graft (Fig 3C and D). The bone segments are aligned, reduced and internally fixed with a compression metal plate and screws (Fig 3D). The centre screw to the bone graft segment is placed first, followed by compression fixation to the proximal segment with an eccentrically placed screw. This is repeated for compression fixation of the distal bone segment to the middle bone graft segment. The alignment of the reduction and the fingers are checked and confirmed. The remaining screws are then inserted in neutral positions. This procedure restores the bone to its initial pre-fracture length whilst correcting the angulation deformity: no bone is removed or added. Stable ‘‘rigid’’ bone fixation with a mini-plate and screws allows immediate postoperative mobilisation.
Surgical technique for proximal phalangeal volar angulation (Fig 5)
Similar pre-operative measurements are done. The proximal phalanx is exposed through a dorsal skin incision and the extensor tendon split. Commonly, the fracture malunion site is at the base of the phalanx and the proximal osteotomy site is placed such that there is sufficient length of bone proximally for placement of the transverse arm of the T-plate, which will be used for internal fixation of the bone. Since the apex of the angulation deformity is volar and the surgical approach is dorsal, the angle of osteotomy from the perpendicular to the bone is measured away from the angle of the deformity. Otherwise, the procedure is similar to that for the metacarpal, described above, except that a T-plate and screws are used for stable bone fixation. The longitudinal arm of the plate should have at least four-holes. Care should be taken when using the power saw for the osteotomy of the proximal phalanx as the flexor tendon lies in a shallow trough on the volar surface of the bone. The flexor tendon was partially cut in case 4 (Table 1) and required repair primarily. He subsequently required flexor tendon rehabilitation incorporated into the post-operative therapy programme. An osteotome was used for completion of the osteotomy in case 5 to avoid this problem.
Active and passive joint mobilisation therapy commences on the first postoperative day. It has been our experience that patients will mobilise only the joints that are painless on mobilising through the full range of motion. Thus, therapy is focused on the joints that are expected to be painful with full range of motion. This frequently occurs at the MCP joint in metacarpal fractures and at both the MCP and PIP joints in phalangeal fractures. After the proximal phalangeal osteotomy, a PIP joint extension splint is used between exercise sessions if full active extension is not achieved by two weeks after surgery, to help prevent PIP joint volar plate contracture.
The ranges of motion at the MCP and PIP joints were measured at one week and, thereafter, monthly until fracture union was seen on X-rays of the osteotomy. Grip strength was measured at grip position 2 of a Jamar dynamometer (TEC, New Jersey 07012, USA). Radiographs of the metacarpals or phalanges were done postoperatively and at six weeks, three months and, thereafter, monthly to confirm retention of the correction and assess bony union.
RESULTS
Radiographic illustration of case 1, with malunion of the fifth metacarpal, is shown in Fig 4. The angle of deformity is measured in the lateral view (Fig 4A). The trapezoid shaped rotational bone graft is about the optimal size for placement of one screw i.e. the shorter cortex is about 4.5 mm long which is three times the diameter of the 1.5 mm screw used (Fig 4B and C). Radiographic illustration of cases 2, with fourth and fifth metacarpal malunions, and 5, with proximal phalanx malunion in the little finger, are shown in Figs 5 and 6, respectively.
Table 1 shows the details of measurements pre- and postoperatively. The angulation deformities were fully corrected in all the metacarpals and one proximal phalanx and 75% corrected in the other proximal phalanx, which had the largest angle of deformity.
The postoperative periods were uneventful. Bone union was achieved by three to four months, except for the proximal interface of the bone graft in case 3 and the distal interface in case 5. These achieved bone union on X-ray at eight and six months, respectively. Considering that this is a bone grafting procedure, we consider bony union at four months to be acceptable. Thus, there was delayed union in 2 out of the 12 of the osteotomy sites, or interfaces of the cortical bone grafts. All of the patients, except case 1, had removal of the implants carried out at seven months to one and a half years after surgery. There were no cases of re-fracture after removal of the implants.
Painful grasp was completely relieved in all the cases. The pseudoclaw deformities were corrected in the two cases with proximal phalangeal malunion. The MCP joint ranges of motion were all maintained at the pre-operative full range of motion. The PIP joint ranges of motion for the cases of proximal phalangeal malunion improved by 20° and 25° , respectively. However, they remained short of the normal range by 10° and 15° , respectively. Grip strength improved post-operatively in the two cases who had comparative measurements done pre-operatively. Case 4 who suffered an accidental partial cut flexor tendon did not have any complications arising from it and there were no trophic or sensory problems.
DISCUSSION
The common deformity seen in metacarpal shaft fracture malunion is dorsal angulation. In proximal phalanx basal fracture malunion, this volar angulation. These result in shortening of the bone (Fig 1A and B). The metacarpal head may be prominent in the palm, causing discomfort on gripping, and the MCP joint centre of rotation moves more palmar in relation to the intrinsic muscles. A pseudoclaw deformity commonly occurs in angulated fractures of the base of proximal phalanx (Fig 6A). The shortening is greater when the angulation occurs towards the midshaft of the bone. The metacarpal head is more prominent in the palm in distal metacarpal shaft angulation (Wolfe and Elliot, 1996).
These factors contribute to the symptoms of painful grasp and decreased grip strength (Seitz and Froimson, 1988; Stern, 2005; Wolfe and Elliot, 1996). Gropper and Bowen (1984) reported their indications for open reduction and internal fixation of acute metacarpal fractures, which included shortening of more than 2 mm and dorsal angulation of 25° in the fourth metacarpal and 30º in the fifth metacarpal. Most authors report that metacarpal malunion is acceptable if the resultant bone shortening is not greater than 2 to 5 mm and angulation not greater than 20° to 30° (Burkhalter, 1990; Green, 1986; Lee and Jupiter, 2000; Wolfe and Elliot, 1996). In the presence of symptomatic metacarpal and phalangeal shaft fracture malunion with angulation deformity, the surgical procedure should correct the angle of deformity and restore the length of the bone.
Correction of the angle of deformity can be achieved by the conventional methods of either a closing, or an opening, wedge osteotomy at the fracture site (Seitz and Froimson, 1988). However, neither of these procedures restores the length of the bone exactly. In opening wedge osteotomy, there is a significant lengthening of the bone, resulting in an over correction of bone length (Fig 2). It also involves harvesting a bone graft from a distant site, with the inherent risk of donor site morbidity (Cockin, 1971). Stabilisation of the bone graft may also be difficult. In a closing wedge osteotomy of 30° , or greater, there is significant shortening in the length of the bone as a result of the removal of the wedge of bone (Fig 1). Wolfe and Elliot (1996) reported that this dorsal length loss is usually offset by the geometrical length gain achieved by the angular correction. However, this geometrical length gain only offsets the original geometrical length loss resulting from the initial fracture with angulation deformity. It is insufficient to compensate for the additional length of bone loss contributed by the closing wedge osteotomy.
The wedge of bone could simply be rotated through 180º and then re-inserted as a free bone graft. If this is done, the angle of osteotomy should be halved (Yong et al., 2000). However, it is difficult to achieve a stable fixation of the small wedge of bone with the angled edge at the near cortex. If the osteotomy is done similarly at two sites, but further apart, to get a trapezoid block of bone with sufficient length for placement of a screw in a stable plate and screws fixation construct, fixation is easier and more stable. In this reconstruction, the angle of osteotomy will need to be further halved, i.e. one-quarter of the angle of deformity (Fig 3). The smaller angle of osteotomy also facilitates a compression fixation technique to enhance bone union. A metal plate and screw compression fixation is recommended for maximum stable internal fixation of the osteotomy (Black et al., 1985). It also enables immediate postoperative joint mobilisation. The osteotomy is done at the site of malunion and no bone is removed, or added. Therefore, it restores bone length to its initial, pre-fracture length, whilst correcting the angle of deformity.
Our patients had metacarpal shaft angular deformities of 32° to 45° and proximal phalanx basal angular deformities of 50° to 60° . There were no problems at surgery to correct these angulations except in one case, that with a 60° angulation at the base of the proximal phalanx, which only achieved 75% correction. Four out of five of the patients had symptoms of pain on grasp function. These all resolved and none showed deterioration of their symptoms. Grip strength also improved in the patient who complained of weak grip. Delay of union might be considered a complication of this trapezoid osteotomy procedure as this occurred in two of the 12 osteotomy sites. To minimise the likelihood of this occurring, or this having any ill effects, compression plate and screw bone fixation is recommended for this procedure.
In this small series, there were no problems at surgery or with ultimate bony union of the resultant free cortical bone graft. Correction of the angular deformity and precise restoration of the metacarpal and phalangeal bone length are possible using this technique and should contribute to pain relief and improvement in grip strength.