Transverse Plane Digital Deformities

Transverse Plane Digital Deformities

Michael S. Downey

Michael C. McGlamry

Sarah A. Spizzirri

Until recent years, discussion of the transverse plane deviation of lesser digits was given nothing more than a cursory mention in the literature. Whether this resulted from limited observation or oversight, unwillingness to describe a condition that was poorly understood, or overshadowing by the more common sagittal plane contracture and subluxation of the toes can only be speculated. Fortunately, this condition is now readily recognized as a significant deformity that can not only be debilitating to patients but also be refractory to treatment. The goal of treatment is to produce a less painful, more rectus digit with reproducible, dependable, and longlasting results.

In this chapter, transverse plane digital deformity is defined as the medial or lateral deviation of the longitudinal axis of the proximal phalanx compared with the longitudinal axis of the metatarsal both clinically and radiographically (Fig. 20.1). This condition most commonly affects the second digit with medial deviation at the metatarsophalangeal joint (MTPJ), and this deformity is referred to as the “crossover second toe” (1). Even though transverse plane digital deformities are most frequently seen in the second toe, other rays are often affected (Fig. 20.2).

Although transverse plane deformity of the lesser MTPJ is now well documented, its etiology is not clearly understood and its treatment is not universally agreed upon. In recent years, many articles have suggested potential causes and proposed treatment options. This chapter reviews the currently popular ideas for the etiology, evaluation, and treatment of this still developing and very challenging clinical pathology.


The exact etiology of a transverse plane digital deformity is often difficult to identify and is likely multifactorial. Whatever the cause, the linking element between these factors is damage to the lesser MTPJ capsule, collateral ligaments, and/or plantar plate (PP). Trauma has been implicated as the most frequent underlying cause of this condition, but a focal initiating incident is rarely identified. More commonly, repetitive microtrauma is credited for causing the deformity. Branch (2) and Coughlin (1) correlated high-heeled or narrow-toed shoes with chronic hyperextension or transverse plane forces at the MTPJ that destabilize the joint over time. Not surprisingly then, the incidence has been noted to be greatest in women over the age of 50 (2,3).

Biomechanically, a long or plantarflexed metatarsal, a structurally or functionally short adjacent ray, or the presence of a previous stress fracture of an adjacent metatarsal can lead to increased mechanical forces through the MTPJ and the potential for inflammatory synovitis of the joint (4). Inflammatory synovitis, in turn, may cause rupture or attenuation of the collateral ligaments, capsule, and/or PP, creating a clinically evident transverse plane digital deformity. Johnson and Price (5) recognized that a foot with a vertical oblique midtarsal joint axis creates a medial pull of the flexor digitorum longus tendon inserting into the second digit, thus leading to medial deviation. Close apposition of the metatarsal heads, as in metatarsus adductus, may also play a contributing role in the development of transverse plane deformities (6,7).

When hallux valgus deformity is present, medial deviation of the second digit is easier to explain (Fig. 20.3). With the first metatarsal relatively displaced medially, significant tension is applied to the sesamoid apparatus. The deep transverse intermetatarsal ligament receives medial pull from the sesamoid apparatus, which, in turn, causes medial subluxation of the second MTPJ capsular structures and PP. As the PP shifts medially, it carries with it the flexor tendons. As this imbalance proceeds, the first dorsal interosseous muscle and lumbrical muscle gain mechanical advantage and contribute to the adduction deformity. Over time, the medial second MTPJ structures contract and the thicker lateral structures stretch. Miller noted a similar process associated with a short first metatarsal or a short adjacent lesser metatarsal (8).

Numerous iatrogenic causes have also been associated with transverse plane digital deformities. Due to the presence of several important structures in a confining space, inadvertent injury to an interosseous tendon (IT), the collateral ligaments, or the PP intraoperatively can produce medial or lateral deviation of a lesser digit (9,10). Following the amputation of a digit, adjacent toes have been observed to transversely deviate secondary to loss of the neighboring digit’s “buttressing effect” (11).

Anatomic considerations possibly predisposing the second digit to deviation include an anomalous tendon described as running medial to the extensor digitorum longus tendon and inserting into the base of the proximal phalanx dorsomedially, thus creating a pull not only in the transverse plane but also in the sagittal and coronal planes (12). Also important to note is the shape of the plantar metatarsal head. The lateral plantar condyle is larger than the medial condyle, thus making it easier for the flexor apparatus, once injured, to translocate medially (5).

Inflammatory joint disease and nontraumatic synovitis have been offered as causes of MTPJ deformity in the transverse plane (13). Inflammatory conditions such as rheumatoid arthritis, psoriatic arthritis, Reiter syndrome, and nontraumatic synovitis can cause synovial tissue hypertrophy with eventual joint distention and later disruption of joint capsular and ligamentous structures. This can ultimately result in a transverse MTPJ deformity. Typically, these deformities begin as a
subtle medial or lateral deviation of the digit at the MTPJ. Yu and Judge (14) coined the term “predislocation syndrome” to describe the acute, subacute, or chronic inflammatory condition of a lesser MTPJ, which they felt was a precursor to a lesser MTPJ dislocation.

Figure 20.1 Severe transverse plane deformity of the second MTPJ with medial deviation or adduction at the MTPJ. In C, note the medial deviation of the longitudinal axis of the proximal phalanx of the second toe in relation to the longitudinal axis of the second metatarsal. The angle formed between these two axes has been referred to as the digital deviation angle.


Evaluation of the transverse plane digital deformity includes the standard history and physical examination. Of particular importance are any history of prior inflammatory joint
conditions, history of metabolic disease, past surgical history, and history of any local trauma to the involved area. Careful evaluation should include inspection and palpation, evaluation of the local tissue temperature, active and passive range of motion evaluation, stance evaluation, and radiographs.

Figure 20.2 Severe transverse plane, adduction deformity of all the lesser MTPJs.

Of specific interest, especially in the early stages of this problem, are localized edema and calor in the flexor tendon sheath or PP at the base of the involved digit or in the joint area. With a local increase in temperature or edema, an early joint problem can often be suspected, even if deformity is not yet apparent. Similarly, fairly significant tenderness is often appreciated with palpation of the base of the proximal phalanx and plantar flexor plate area at the MTPJ level. In the visual absence of deformity, these findings can suggest problems that may ultimately result in deformity.

Neuritic symptoms may often be present and the diagnosis of an interdigital neuroma must be differentiated from a transverse plane digital deformity. Patients with interdigital neuritis often complain of pain radiating into the toes, have pain more localized to the interdigital space than the MTPJ, and have greater pain with Mulder compression technique (15). A diagnostic injection of local anesthetic into the joint will typically help the deviated MTPJ problem, but not the interdigital neuritis (16).

Gentle, passive range of motion evaluation should show an accentuation of the deformity at the dorsal end range of motion as might be seen with a trackbound hallux valgus deformity. This is of particular interest since the primary underlying pathologic force with lesser MTPJ transverse plane deviation seems to be dislocation of the flexor apparatus and PP. Additionally, passive range of motion examination may confirm any abnormality in the quality or quantity of motion. Poor quality of motion or crepitus and/or decreased joint motion might be produced by an articular defect associated with local trauma, such as transient dislocation with cartilage damage at the time of injury or relocation. Passive range of motion examination may also include the Lachman test (4,17), dorsal drawer test (18), or vertical stress test (19) of the lesser MTPJ. These tests are similar and are performed with the metatarsal immobilized firmly in one hand and the proximal phalanx held firmly in the other hand with approximately 20 to 25 degrees of dorsiflexion at the MTPJ (i.e., longitudinal axis of the proximal phalanx relative to the longitudinal axis of the metatarsal) (Fig. 20.4). A vertical shear force is then applied with an attempt made to
vertically dislocate the proximal phalanx at the MTPJ. Deland et al (19) defined a significantly positive test as more than 2 mm of dorsal displacement.

Figure 20.3 “Crossover” second toe deformity with associated hallux abductovalgus deformity.

Active range of motion will often suggest dislocation of the flexor apparatus and PP as the toe will medially or laterally deviate with flexion of the MTPJ. McGlamry (20) found that eliciting the plantar Babinski reflex by stroking the plantar surface of the foot would result not in pure plantarflexion of the toes, but limited flexion along with medial or lateral deviation in patients with transverse plane deformities. Limited motion or pain with either passive or active range of motion can also suggest joint damage or arthritis.

The stance examination is particularly important, as many of these deformities are not evident, especially in the early stages, on non-weight-bearing examination. If weight-bearing evaluation is not possible, the stance position can be reproduced with the use of the Kelikian push-up test (i.e., manual loading of the PPs by applying pressure to the plantar aspects of the metatarsals). Note should be taken of the transverse plane position as well as sagittal plane deviation of each of the lesser rays. Sagittal plane contracture is often associated with the transverse plane deformity. A gap will often be noted between toes when an isolated transverse plane deformity is present. In other instances, all of the toes will deviate in the same direction (see Fig. 20.2). Often with transverse plane deformity, there is concomitant sagittal plane deformity, and the toe will deviate medially or laterally during stance and also will not purchase the weight-bearing surface.

Radiographic evaluation should be undertaken in relaxed stance. For obvious reasons, non-weight-bearing radiographs may not adequately reflect the degree of the deformity. Though no standard angle has been reported in the literature, it is often helpful to record the “digital deviation angle” or the angle created by the longitudinal axis of the proximal
phalanx of the toe and the longitudinal axis of the metatarsal shaft (see Fig. 20.1C).

Figure 20.4 Clinical stress test of the lesser MTPJ to check for stability. A: Initial position to evaluate the second MTPJ. B: Dorsal stress applied. Note dorsal dislocation of proximal phalangeal base at the second MTPJ. More than 2 mm of displacement is considered to be abnormal. The stress test may also be done with radiography or fluoroscopy. Radiographic appearance before stress (C) and with stress applied (D).

Other diagnostic imaging techniques have also been described, but are usually unnecessary as the clinical findings typically provide the clinician with the means to make the diagnosis. In the early stages of the process, when suspicion of the condition is present without significant clinical deviation of the MTPJ, magnetic resonance imaging (MRI) may be helpful in cases where the diagnosis is equivocal (21,22 and 23). MRI will show gross pathologic changes within the tendon apparatus, joint, and/or PP, but will also demonstrate increased signal intensity even prior to any rupture or displacement of the flexor apparatus (Fig. 20.5). Arthrography has also been noted to demonstrate partial or complete damage to the PP as well as small defects in the joint surfaces (21). More recently, several investigations have shown that musculoskeletal ultrasound can be used to assess the lesser MTPJ joint structures and help differentiate PP pathology from interdigital neuromas and other sources of forefoot pain (24,25,26,27 and 28). Due to the dynamic nature of ultrasonography, it may actually become the modality of choice for such clinical assessments in the not too distant future.

The early condition which potentially leads to transverse plane deviation of the digit has been well described by Yu and Judge (14) as “predislocation syndrome.” Coughlin (17) similarly described various stages of crossover deformity: stage I, synovitis and mild deformity; stage II, dorsomedial deviation; stage III, overlapping of the hallux; and stage IV, frank MTPJ dislocation. As with many conditions early understanding and diagnosis may be the key to the most successful treatment.

Jul 26, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Transverse Plane Digital Deformities
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