Correction of Lesser Toe Deformity

Abstract

The correction of a lesser toe deformity is dependent on multiple factors. Foremost is to determine if the deformity is flexible or rigid. The location(s) of the deformity must be evaluated, whether isolated to the PIP or both the MTP and PIP joint. Dislocation or subluxation of the MTP will alter the surgical algorithm as well as in most cases an additional osteotomy of the metatarsal will be required. Failure to properly determine these factors can lead to undercorrection of the deformity and lead to patient dis-satisfaction. Unfortunately, despite adhering to sound principles for lesser toe correction, the results can be difficult to predict with cosmesis and patient satisfaction difficult to achieve and preoperative counseling is critical.

Key Words

Hammertoe, Claw toe, PIP fusion, PIP arthroplasty, Weil osteotomy

Claw Toe and Hammertoe Correction

We follow a simple algorithm for correction of claw toe and hammertoe:

Is the deformity fixed or flexible?
Is the deformity at the proximal interphalangeal (PIP) joint, the metatarsophalangeal (MTP) joint, or both?
Is there a dislocation of the MTP joint?

In patients with claw toe or hammertoe deformities, a resection arthroplasty or a rthrodesis can be performed at the PIP joint. The benefits of a resection arthroplasty is that slight flexion will remain in most patients and the risk of mallet toe is negligible. However, there is a higher risk of recurrence and a temporary pin is required to stabilize the toe during the first 4 weeks. Arthrodesis allows for a more predictable alignment of the toe, however, it is less forgiving if a malunion occurs. In addition, the risk of mallet toe is present and patients may not appreciate having a rigid digit. Intramedullary fixation can be used in the setting of a fusion minimizing the risk of infection and annoyance with the use of a Kirschner wire (K-wire). Arthrodesis is preferred in patients with the following indications:

1.

recurrence of deformity
2.

deformity of the PIP joint in the transverse plane
3.

neuromuscular etiology of the deformity
4.

inadequate flexion strength at the MTP joint when stiffness of the IP joint will be acceptable to the patient
5.

requirement for a degree of predictability of surgery when the patient may not object to a stiff toe

In terms of the functional result, there does not appear to be much difference between a successful arthroplasty or arthrodesis of the interphalangeal (IP) joint. Strength is improved with an arthrodesis because the force of the long flexor tendon is then transmitted to the MTP joint to improve plantar flexion of the MTP joint. However, this advantage has a downside, given that the only flexible joint remaining is the distal interphalangeal (DIP) joint, and this is the reason why a mallet toe can occur. The grip strength of the toe at the level of the PIP joint is better with an arthroplasty, provided that the toe remains flexible. However, the toe is rarely flexible. The potential for complications of both arthroplasty and arthrodesis also has to be considered. Although arthrodesis leaves the toe rigid, it is indeed straight, and depending on how the operation is performed, arthrodesis can avoid the toe shortening that is inherent with some arthroplasty procedures. A mallet toe occurs in approximately 10% of patients as a result of overpull or contracture of the flexor digitorum longus tendon on the DIP joint. For this reason, in many cases we prefer to transect the long flexor when an IP arthrodesis is performed. Although this may compromise the flexion power of the lesser toes, it does seem to mitigate the risk of mallet toe. The flexor is easily identified once the bone has been resected for the fusion and can be transected through the dorsal incision without difficulty.

In establishing the optimal approach to a claw toe or hammertoe deformity, it is important to distinguish a vertical plane deformity from a horizontal plane deformity such as the crossover toe deformity ( ). The latter can never be corrected with an IP joint arthroplasty/arthrodesis, because the apex of the deformity is not the IP, but the MTP joint ( Fig. 7.1 ).

Certain deformities are very difficult to correct as a result of intrinsic contracture. These include, for example, the deformities associated with the complications of crush injuries of the forefoot or secondary to a compartment syndrome. The muscle fibrosis and intrinsic contractures shorten the flexor brevis muscle, and tenotomy is never sufficient. Correction of the fixed IP joint deformity will straighten the toe but will not improve flexibility at the MTP joint, and the stiffness is frequently more debilitating. If indeed the toe is straightened, and the MTP joint is stiff, toe pain will be worse, because the pressure on the tip of the toe increases. Typically, the toe can be extended slightly with the MTP joint in flexion, but if the toe is extended, then the fixed, contracted nature of this deformity becomes more apparent ( Fig. 7.2 ). In addition to correction of the fixed contracture at the PIP joint, the MTP joint requires release by shortening the metatarsal and relative lengthening of the intrinsic muscles. Even this procedure is not always sufficient, and metatarsal head resection may be necessary, particularly after crush injuries of the forefoot.

What is the best approach to toe deformities in the elderly associated with asymptomatic hallux valgus? Clearly, the incidence of recurrent deformity of the toes will be high if the hallux is not simultaneously corrected. It is frequently the second or third toe, however, that is markedly dislocated or fixed at the PIP joint. Can an isolated toe procedure be performed with any expectation of a predictable result? If the hallux is overriding the second toe, it is possible to perform the toe surgery without correcting the hallux deformity, as illustrated in Fig. 7.3 . In this case, the patient had bilateral painful second and third toe deformities, but the hallux was fairly rigid after a previous resection arthroplasty. After the corrective surgery, the toes are straight and the hallux lies dorsal to the toes. In some cases, the deformed but asymptomatic hallux is impinging on the symptomatic second toe, and isolated correction cannot be performed. In the elderly, the use of an Akin osteotomy in conjunction with correction of the second PIP deformity can be quite effective and minimize morbidity to the patient.

Another option for surgical management of the painful second toe is amputation ( Fig. 7.4 ). This is an excellent treatment in the presence of an isolated painful toe deformity or a fixed asymptomatic hallux valgus, or cases in which the hallux cannot realistically move into any further valgus because it is already abutting the third or fourth toes (see Fig. 7.4B ). Toe amputation may also work well in the patient who has undergone an arthrodesis of the hallux MTP joint (see Fig. 7.4C ). This approach is a good alternative, particularly with a grade IV crossover second toe dislocation. When the amputation of the second toe is performed, it is very important to eliminate all sources of pain, including the plantar surface of the metatarsal head. A logical assumption might be that with amputation, there is no pressure on the metatarsal, so metatarsalgia will be relieved. This is not the case, however, and we have encountered patients who experienced persistent pain under the metatarsal head after amputation. The likely cause is subluxation of the fat pad from under the metatarsal head, so that even after amputation, pain under the head can persist. In such patients, we always remove the plantar condyles at the same time as the amputation, typically in the form of a metatarsal head resection.

Correction of the Metatarsophalangeal Joint Deformity

One must be assess whether this is an intrinsic or secondary deformity. With the foot elevated off the floor, weight bearing should be simulated by gentle pressure under the metatarsal head. If the MTP joint remains extended (dorsiflexed), then this is an intrinsic contracture of the MTP ( Fig. 7.5 ). A flexion deformity the IP joint with an intrinsic deformity of the MTP joint is most appropriately termed a claw toe. In this setting, an extensor lengthening with capsulotomy is quite effective as long as the MTP can be manually reduced. A flexor to extensor tendon transfer can be considered to prevent recurrence; however, it does result in stiffness and thickening of the MTP joint, which may be unsatisfactory for the patient. If the MTP deformity is fixed and unreducible, then a shortening osteotomy of the metatarsal is required in addition to extensor lengthening with capsulotomy. Given that the floor is a fixed surface, any flexion of the IP joint will result in extension of the MTP during stance. In a secondary deformity, gentle plantarly directed pressure on the dorsal aspect of the proximal phalanx corrects the deformity. Therefore correction of the PIP joint will result in a neutral toe position for these patients. Concomitant deformities should be noted, including the presence of callosities along the metatarsal heads that may indicate metatarsal overload and the need for metatarsal shortening osteotomies or gastrocnemius recession. In all cases of prior hallux surgery, evaluation for instability, excessive shortening, or dorsal malunion of the hallux should be performed as pathology of the first ray is a primary cause of transfer metatarsalgia and deformity of the lesser toes. A second hammer toe may be secondary to hallux valgus or interphalangeus. It should be determined whether there is enough room for the toe if it was straightened ( Fig. 7.6 ). If not, the patient should be counseled regarding correction of the hallux. The Silfverskiöld method is used to evaluate for contracture of the gastrocnemius and the gastrocnemius-soleus complex ( Fig. 7.7 ). Ankle dorsiflexion is tested with the knee in full extension and in 90 degrees of flexion; the foot is maintained in an inverted position to avoid dorsiflexion movements at the midtarsal joints. Increased ankle dorsiflexion with the knee flexed indicates contracture of the gastrocnemius. In these patients, a gastrocnemius recession should be considered to prevent recurrence and minimize pain along the forefoot.

We approach the MTP joint release sequentially ( Fig. 7.8 ). A dorsal longitudinal incision is made in the second interspace for approach to the second and third and in the fourth interspace for the fourth and fifth. The dissection is deepened down to the relevant extensor tendons. The procedure begins with a release of the long and short extensor tendons, followed by a transverse dorsal capsulotomy. If a contracture still persists, we release the collateral ligaments dorsally and then, finally, release the volar plate contracture, if present. If the toe is now reduced and stable in position, the long extensor is sutured loosely to restore balance to the MTP joint. If the MTP release is performed as an isolated procedure, in the absence of correction of the IP joint, then a decision has to be made whether to secure the MTP joint with a K-wire, which should be used judiciously. There is always the potential for breakage of the wire, and in particular, infection with consequent chronic swelling may be a problem ( Fig. 7.9 ). These infections take a very long time to settle down, and the toe may remain swollen for months. If we detect any unusual swelling or inflammation in the toe after placement of a K-wire, it is removed promptly, and a debridement of the joint performed if necessary. The K-wire should never be used to reduce an unstable joint, because the subluxation will recur promptly once the wire is removed. In other words, the K-wire can facilitate scarring of the MTP joint, but it should not be relied on to correct deformity.

If the joint is unstable or dislocated, soft tissue releases as described for a contracture are not sufficient, and a shortening osteotomy of the metatarsal needs to be performed ( ). The exposure for the MTP joint is the same as discussed earlier for the joint release, with subperiosteal exposure of the distal metatarsal shaft. The first cut can be made with the oscillating saw: the cut starts dorsal and slightly proximal to the metatarsal head-neck junction, just where the cartilage ends. The plane of the cut parallels the plantar foot surface in the frontal plane and is oriented obliquely in the sagittal plane. The cut should exit proximal to the capsular attachment on the plantar aspect of the MTP. In some cases, elevation of the metatarsal is desired to decrease the plantar prominence to decrease metatarsalgia, we term this a modified Weil osteotomy . This maneuver may also decrease the risk of a “floating toe” as it elevates the center of rotation of the metatarsal head. 2–4 mm of the metatarsal head is resected depending on the amount of desired elevation. The amount of articular cartilage to be resected is determined and the oscillating saw used to remove the wedge. The metatarsal head is grasped with a Kocher and taken proximally ensuring that bone-on-bone apposition is maintained. A 0.045 K-wire is used to determine if sufficient shortening has occurred. A twist-off screw or 2.0-/2.4-mm standard screw is used to fix the osteotomy. The screw is directed distal and plantar given the obliquity of the osteotomy. The length of the screw can vary between 12–15 mm. We commonly use the 12–13-mm screw to avoid the risk of overpenetration of the plantar metatarsal head. Fluoroscopy is used to ensure that the metatarsal head is neutrally rotated and that the screw is not long and penetrating the metatarsal head. The dorsal overhanging bone is removed with a rongeur or bone cutter to prevent impingement of the phalanx ( Figs. 7.10–7.14 ).