Pertinent Insights On Treating Second MPJ Pathology

Author(s): 
Christopher L. Reeves, DPM, FACFAS, Amber M. Shane, DPM, FACFAS, Larissa McDonough, DPM, AACFAS, and Francesca Zappasodi, DPM, AACFAS

A wide range of pathologies can arise at the second MPJ, making an accurate diagnosis vital. Accordingly, these authors offer diagnostic insights, a guide to conservative and surgical treatment options, and an intriguing case study.

Understanding second metatarsophalangeal joint (MPJ) pathology, a comprehensive term that includes multiple pathological entities, requires the ability to identify and discern particular clinical attributes associated with each condition. A variety of pathologies arise at this anatomic location. A few of these pathologies include synovitis, plantar plate tears, osteochondritis dissecans and crossover toe deformities.

   As with any initial workup, a thorough history is important to understand whether the condition is acquired, idiopathic, traumatic, congenital or progressive. Understanding and identifying the appropriate etiology is imperative in order to establish an effective treatment plan.

   The physical exam must start with a general assessment of the lower extremity. A detailed biomechanical exam helps identify lower extremity structural and soft tissue deformities that can be contributing factors in the development of second MPJ pathologies. Genu varum, genu valgum, equinus contracture and dropfoot are all clinical abnormalities that one should evaluate during the initial physical assessment. Pedal examination should include an inspection for presence of callosities indicative of sub-second metatarsal head pressure, hammering of the digits, hallux valgus deformity, edema, ecchymosis or widening of the gap between web spaces (Sullivan’s sign).

   Additional clinical tests include palpation of the affected area to isolate the location of pain as well as evaluation of the joint as it goes through range of motion. The Lachman vertical stress test is a specific exam that is available to evaluate joint instability and assess the integrity of the plantar plate and periarticular structures. Pain that occurs with the dorsal-plantar translational stress during this test can be indicative of plantar plate attenuation. Pain with passive range of motion within the joint can signify synovitis, capsulitis or cartilage defects.

   Evaluating the first ray is also critical when trying to determine the etiology of second MPJ pain as there are various underlying conditions at this location that can cause second MPJ pathologies. Hallux abductovalgus, hallux rigidus, first ray hypermobility and metatarsus primus elevatus have the ability to cause an imbalance in the forefoot contributing to overloading of the second MPJ. Additionally, an equinus deformity may be a potential contributing cause of forefoot and specifically second MPJ overload. These conditions all cause a biomechanical shift of the plantar pressures to the area beneath the second metatarsal head and joint, causing increased loading and strain to the joint and periarticular structures.

   With hallux valgus deformities, the deviated hallux can allocate the space occupied by the second toe, causing the lesser toe to contract dorsally and deviate medially over time.1 Researchers have demonstrated that increased second metatarsal length is a factor in the development of second MPJ instability with increased plantar plate pressures and medial deviation of the second toe as a result of the attenuation of plantar structures.2

   In addition, hypermobility of the first ray places a large amount of pressure on the second metatarsophalangeal joint complex. Though no standard device can determine hypermobility at this location, one effective clinical technique includes dorsiflexion of the hallux to engage the windlass mechanism while stabilizing the lateral forefoot and manually mobilizing the first metatarsocuneiform joint in the sagittal plane and observing for excessive motion.

What You Should Know About Imaging And Ancillary Tests

Initial imaging should start with a standard radiographic evaluation including weightbearing AP, lateral and medial oblique views. In certain instances, a sesamoid axial view may be beneficial in visualizing pressure distributions under the metatarsal heads. Long leg axial views can additionally demonstrate lower extremity positioning.

   On AP radiographs, one should assess the metatarsal parabola, first MPJ congruity, intermetatarsal angle, second MPJ space congruity and overall shape of the metatarsal heads. On lateral views, evaluate digital contractures, metatarsus primus elevatus and metatarsal declination angles. Consider serial radiographs spaced between appointments to check for articular changes and second metatarsophalangeal joint deviation.

   Researchers have shown that longitudinal ultrasound imaging identifies plantar plate tears better in comparison to contralateral non-affected feet. Ultrasound has a sensitivity of 91.1 percent and specificity of 25 percent.3 One may also use joint arthrography to evaluate for plantar plate tears. Although clinicians usually use magnetic resonance imaging (MRI) for confirmation, it is also effective in identifying early osteochondral changes to the joint to assist in validation of a plantar plate tear. Studies are reporting sensitivity and specificity as high as 95 percent and 100 percent respectively with the use of MRI in identifying plantar plate tears.4

Conservative Care Options For The Second MPJ

Physicians should always exhaust conservative approaches as a first line of treatment before mentioning surgical intervention. Placing metatarsal pads proximal to the metatarsal heads can provide the offloading that is needed in cases of synovitis or capsulitis. In addition, splinting or taping the second toe into a reduced position may provide some temporary relief of symptoms at the affected joint. Silicone gel toe sleeves can relieve pressures on dorsally contracted digits that are prominent and aggravated by shoe gear.

   Wide toe boxes, decreased heel heights and rocker bottom shoes are simple shoe gear modifications that one can attempt with an early deformity to slow its progression. Partial or complete offloading in a fracture boot can assist in cases of Freiberg’s infraction to treat symptoms of pain and acute inflammation. Non-steroidal anti-inflammatory drugs can also be a safe first-line treatment in alleviating inflammation at the second MPJ. The use of corticosteroids, both systemically and as an intra-articular injection, is controversial. Multiple authors have documented a prevalence of decreased ligamentous structure strength after intra-articular injection of corticosteroids.5-7 Reserve the use of intra-articular corticosteroid injections for the most severe and recalcitrant cases.

Essential Surgical Considerations

After exhausting conservative modalities, one can discuss surgical intervention as the next line of treatment. Making the correct diagnosis and determining the appropriate etiology of the second MPJ pathology are critical to formulating surgical plans for correction.

   In patients with digital contractures or crossover toe deformities, often the initial culprit is a hallux abductovalgus deformity. This deformity, while not always symptomatic in the patient, may necessitate surgery if it is a direct contributing factor to the dorsal medial migration of the second toe. In addition, one must evaluate the second ray to specify the correction of the hammertoe deformity that is present. If a callus or plantar pain is present upon palpation of the second metatarsal head, surgeons may utilize a decompression or dorsiflexory metatarsal osteotomy.

   When second MPJ plantar callosities are present, evaluate instability in the first tarsometatarsal joint. If instability is apparent on clinical exam, a procedure such as a first tarsometatarsal joint arthrodesis may correct and stabilize the mechanics of the forefoot, and reduce the excessive pressure at the second metatarsophalangeal joint complex.

   A large number of contracted digits result from a long second metatarsal. These elongated metatarsals experience chronic overload and ultimately result in weakened plantar capsular structures that allow for joint instability, which can progress to dislocation. In this situation, we recommend a metatarsal decompression osteotomy to restore an anatomic parabola and the appropriate allocation of plantar pressures.

   The retrograde subluxation of the proximal phalanx of a rigidly contracted toe on the corresponding metatarsal head only further exacerbates the overloading of the joint. By already addressing the metatarsal position, one can correct the hammertoe deformity of the second toe with either proximal interphalangeal joint arthroplasty or arthrodesis. A variety of implants are available to keep an arthrodesis site internally aligned and compressed until fusion occurs. Also, one can release contractures in the soft tissue structures with the use of a skin plasty, such as a V-Y incision. If there is a residual transverse plane deformity of the second toe after decompression osteotomies and hammertoe repair, consider a lateral second MPJ capsulorrhaphy and or a medial capsulotomy.

   If there is instability through the Lachman vertical stress test when evaluating the second toe, surgical strategies may have to incorporate a plantar plate repair or a flexor tendon transfer. In patients with plantar plate rupture, historical approaches for repair of the plantar plate apparatus include both dorsal and plantar incisions. A more popular surgery includes a dorsal approach with concomitant metatarsal osteotomy to create temporary intraoperative exposure to the plantar plate and postoperative shortening of the metatarsal length. Reefing the plantar tissues with a suture while holding the toe in a slight plantarflexory position allows for a better repair.

   A flexor tendon transfer such as the Girdlestone procedure is typically indicated with flexible digital deformities. This tendon transfer enables the tendon to plantarflex the MPJ and extends the distal digital joints. The procedure can also aid in stabilization when sagittal plane instability is present at the second MPJ or a complete plantar plate tear is beyond repair. One can perform this procedure with a one or two incision technique. The surgeon can harvest the tendon and pass it through the proximal phalanx with the security of a suture anchor, or split the tendon longitudinally and tie it dorsally on the proximal phalanx.

   For patients who demonstrate progressive radiographic destruction of the articular surface of the second metatarsal head, one should suspect an acute Freiberg’s infraction. Initial radiographs early on may only demonstrate an area of linear subchondral lucency in the second metatarsal head. This radiographic feature signifies osseous resorption and is referred to as the crescent sign. Longer periods of non-weightbearing and offloading are initially required until symptoms acquiesce.

   In later stages, when the metatarsal head has undergone changes in shape and degeneration, surgeons have discussed multiple surgical modalities in the literature. More conservative initial approaches include simple joint debridement, arthroplasties and decompression osteotomies of the metatarsal. As the condition evolves to a later stage in which joint preservation is no longer possible, procedures such as implant arthroplasty and even metatarsal head resection are viable options for surgeons to consider.

   Literature regarding the indications, efficacy and complications of arthrodesis of the lesser metatarsophalangeal joint is deficient both in amount and long-term data. While there are currently limited studies, a more recent study reported a statistically significant reduction in pain after lesser metatarsophalangeal joint arthrodesis.8 The authors proposed that the procedure obviates the need for plantar plate repair and flexor tendon transfers while having complication rates similar to first metatarsophalangeal joint arthrodesis procedures.

   Just as important as any surgical approach, a strict and well-communicated postoperative course is imperative for success. One would typically remove sutures after two weeks and Kirschner wires at three to four weeks. Depending on the procedure, allow passive range of motion after the first four to six weeks postoperatively.

Case Study: When A Patient Has Hallux Valgus With A Contracted Second Toe And Second MPJ Instability

A 64-year-old male with diabetes presented to our clinic with complaints of an aching, throbbing right forefoot of six months’ duration. He noted that pain improved when he was non-weightbearing and was aggravated with continued activity. He also complained of a hammered second toe with a callus on the plantar aspect of his right forefoot that was painful.

   Upon physical examination, there was a hallux abductovalgus deformity present with subsequent overcrowding of the second digit. The patient had mild discomfort with palpation over the prominent medial eminence of the first metatarsal. The second toe had a rigid dorsal contracture located at the proximal interphalangeal joint. The contracture extended proximally and also involved the metatarsophalangeal joint. A Lachman vertical stress test demonstrated laxity and exquisite tenderness at the metatarsophalangeal joint. There was a diffuse hyperkeratotic lesion beneath the second metatarsal head and a prominence of the second metatarsal head. Surprisingly, the first ray was stable with range of motion both with and without the windlass mechanism activated.

   An AP radiograph demonstrated a hallux abductovalgus deformity with a short first metatarsal. In addition, there was an increased intermetatarsal angle between the first and second metatarsals. Upon evaluation of the metatarsal parabola, we noted that the second metatarsal was elongated. Medial deviation of the second toe on the corresponding metatarsal head and mild joint space widening were also apparent. The lateral radiograph demonstrated a dorsal contracture of the second toe at the proximal interphalangeal joint. In addition, the first metatarsal was slightly elevated in comparison to the lesser metatarsals.

   The patient had exhausted previous conservative modalities that included diabetic shoes with accommodative toe box and inserts, routine manual debridement of callosities and keratolytic creams. This particular patient did not have taping and strapping due to his diabetes and the risk of skin tearing. With the patient’s consent, we then devised a surgical plan.

   Taking the clinical and radiographic findings into consideration, we believed it was critical to address the hallux abductovalgus deformity as it was both symptomatic and directly contributing to the development of deformity at the second metatarsophalangeal joint. Correcting the hallux abductovalgus deformity restores the function of the first ray and allows for a resultant reduction in plantar pressure at the second metatarsophalangeal joint complex. Upon discussion with the patient we recommended a correction of the second digit, stabilization of the second metatarsophalangeal joint, and a shortening osteotomy of the second metatarsal. Additionally, we recommended repositioning the first ray with a Lapidus procedure. The patient refused the post-op adherence necessary for the Lapidus. As a result, we decided on an aggressive distal metaphyseal osteotomy to reposition the metatarsal in a more aligned position.

   We addressed the hallux abductovalgus deformity with a distal first metatarsal osteotomy followed by a Weil decompression osteotomy at the second metatarsal head. Prior to fixation of the osteotomy, we transposed the capital segment medially (in the direction of the toe subluxation) to facilitate reduction of the deformity. During this portion of the procedure, a careful inspection of the plantar plate revealed a tear. Before addressing the tear, we first isolated the rigid contracture at the proximal interphalangeal joint, prepped it and performed arthrodesis using an internal implant.

   We proceeded to make a plantar linear incision beneath the second MPJ, which helped us access the plantar plate tear. After careful dissection, we did a primary repair of the tear with the use of an absorbable suture anchor that we tacked into the base of the second toe proximal phalanx while maintaining manual reduction of the deformity. Prior to incisional closure, there was significant clinical and radiographic improvement of the forefoot deformities.

   Postoperative radiographic assessment demonstrated osseous union at the arthrodesis and osteotomy sites as well as maintained stability and congruency at the second MPJ. After surgery, the patient was non-weightbearing for four weeks and gradually progressed into protective weightbearing with a short leg controlled ankle motion (CAM) boot for an additional three weeks. Five months post-op, the patient received a custom molded insert. He experienced alleviation of his painful symptoms and has maintained his correction. At one year post-op, he is satisfied overall with the results of his surgical procedure.

In Conclusion

In general, second metatarsophalangeal joint pathology encompasses a broad spectrum of conditions at this anatomic location. A thorough history and physical exam are always an important base to establish when first evaluating the patient. Ancillary imaging and diagnostic testing can further aid in the determination and confirmation of a particular diagnosis. Integration of all of the resulting information is necessary to accurately identify the clinical pathology and ultimately institute a successful treatment plan for the patient.

   Dr. Reeves practices at the Orlando Foot and Ankle Clinic in Orlando, Fla. He is an Attending Physician with the Florida Hospital East Orlando Residency Training Program.

   Dr. Shane practices at the Orlando Foot and Ankle Clinic in Orlando, Fla. She is an Attending Physician with the Florida Hospital East Orlando Residency Training Program.

   Dr. McDonough is a third-year podiatric surgical resident at Florida Hospital East Orlando in Orlando, Fla.

   Dr. Zappasodi is a second-year podiatric surgical resident at Florida Hospital East Orlando in Orlando, Fla.

References

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