How To Treat Lesser MPJ Disorders

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Continuing Education Course #131 — June 2005

I am pleased to introduce the latest article, “How To Treat Lesser MPJ Disorders,” in our CE series. This series, brought to you by the North American Center for Continuing Medical Education (NACCME), consists of regular CE activities that qualify for one continuing education contact hour (.1 CEU). Readers will not be required to pay a processing fee for this course.

In this article, Vincent J. Muscarella, DPM, the Acting Chairman of the Department of Surgery at the Temple University School of Podiatric Medicine, emphasizes having a strong knowledge of forefoot anatomy in order to treat disorders of the lesser metatarsophalangeal joints (MPJs). He discusses the various etiologies of these conditions and key considerations one must weigh in choosing an appropriate treatment course.

At the end of this article, you will find a 10-question exam. Please mark your responses on the enclosed postcard and return it to NACCME. This course will be posted on Podiatry Today’s Web site (www.podiatrytoday.com) roughly one month after the publication date. I hope this CE series contributes to your clinical skills.

Sincerely,

Jeff A. Hall
Executive Editor
Podiatry Today

INSTRUCTIONS: Physicians may receive one continuing education contact hour (.1 CEU) by reading the article on pg. 62 and successfully answering the questions on pg. 66. Use the enclosed card provided to submit your answers or log on to www.podiatrytoday.com and respond via fax to (610) 560-0502.
ACCREDITATION: NACCME is approved by the Council on Podiatric Medical Education as a sponsor of continuing education in podiatric medicine.
DESIGNATION: This activity is approved for 1 continuing education contact hour or .1 CEU.
DISCLOSURE POLICY: All faculty participating in Continuing Education programs sponsored by NACCME are expected to disclose to the audience any real or apparent conflicts of interest related to the content of their presentation.
DISCLOSURE STATEMENTS: Dr. Muscarella has disclosed that he is a member of the Speaker’s Bureau for BioPro.
GRADING: Answers to the CE exam will be graded by NACCME. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam.
TARGET AUDIENCE: Podiatrists.
RELEASE DATE: June 2005.
EXPIRATION DATE: June 30, 2006.
LEARNING OBJECTIVES: At the conclusion of this activity, participants should be able to:
• discuss pertinent aspects of forefoot anatomy as they relate to the lesser MPJs;
• cite examples of metabolic conditions that may cause lesser MPJ pathology;
• describe examples of clinical presentations that may result from direct trauma to the lesser MPJs;
• list possible conservative modalities that one may employ for lesser MPJ disorders;
• compare and contrast surgical procedures for treating lesser MPJ disorders; and
• discuss the steps that are involved in performing a joint replacement procedure for lesser MPJ disorders.

Sponsored by the North American Center for Continuing Medical Education.

The author notes that joint replacement is his procedure of choice for treating lesser MPJ disorders. When the range of motion is acceptable, one can remove the sizer and place the properly sized implant into the proximal phalanx.
A 24-year-old man dropped a 200-lb. iron plate on his right foot. After six weeks of cast immobilization and six weeks of physical therapy, the patient still had extreme pain and stiffness at the second MPJ. This radiograph revealed a non-healed intraarti
Ten months after undergoing a joint replacement procedure with a hemi-implant, the patient had full, non-painful range of motion of the second MPJ and was able to return to construction work.
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Author(s): 
By Vincent J. Muscarella, DPM

   Podiatric physicians routinely see disorders of the forefoot, especially the lesser metatarsophalangeal joints (MPJs). In fact, they are often the presenting complaint of the patient or the reason for the medical referral. Lesser MPJ disorders can also occur as a result of preexisting conditions such as trauma, infection, faulty biomechanics and previous podiatric surgery.

   Unfortunately, the term metatarsalgia has been used as a catch-all term to describe a condition without a true etiology. This can be very frustrating to both the patient and the doctor. Indeed, having a firm grasp of the forefoot anatomy is essential when it comes to understanding lesser MPJ pathology.

   The forefoot consists of the bones and all soft tissue structures from the distal aspect of all five digits to the bases of all five metatarsals at the metatarsocuneiform/cuboid (Lisfranc’s) joint. The MPJs are composed of the articulation between the base of the proximal phalanx of each digit and each metatarsal head. These joints are described as ellipsoid joints, which are created by the rounded metatarsal heads and the shallow cavities on the base of the proximal phalanx of each toe.1

   Articular cartilage covers the distal and plantar portions of the metatarsal heads. There is no articular cartilage on the dorsal surface of the metatarsal. The articular cartilage of the phalangeal bases encompasses the entire cavity of the bone. Two collateral ligaments, running from dorsal proximal to plantar distal, maintain the integrity of the MPJ. These ligaments allow sagittal dorsiflexion and plantarflexion of the proximal phalanx on the metatarsal heads but prevent excessive transverse plane motion of abduction and adduction. Minimal frontal plane motion of inversion and eversion is possible. Disruption of these ligaments causes transverse deviation of the digits as well as dorsal contraction.

   The fibrous capsule surrounds the joints and is relatively thin dorsally but is synonymous with the thick plantar ligaments that comprise the plantar plate. All the MPJs are connected plantarly by the deep transverse intermetatarsal ligament.

   The lesser MPJs are located approximately 2.5 cm proximal to the web of the digits. The amount of joint dorsiflexion of the lesser MPJs can approach 90 degrees and is necessary for the extremes of forefoot function in walking, but most importantly in sports. The lesser MPJs are at a relative 25 degrees of dorsiflexion in stance, owing to the 20- to 25-degree plantarflexion of the metatarsals in stance.

   Muscles associated with this area are divided into extrinsic and intrinsic muscles. The extrinsic muscles at this level are composed entirely of tendinous material. Dorsally, the extensor digitorum longus tendon passes over the lesser MPJ and divides into three slips. The central slip inserts into the base of the intermediate phalanx. The remaining two slips rejoin to insert into the base of the distal phalanx. The extensor hood is comprised of soft tissue at the joint level that connects the extensor tendon to the plantar plate. The extensor tendon does not insert into the proximal phalanx but dorsiflexes the proximal phalanx on the metatarsal head through the extensor hood mechanism. The tendons of the extensor digitorum brevis tendon attach to the long extensor tendons at the level of the second, third and fourth MPJs.

   Plantarly, the tendon of the flexor digitorum longus courses along the long axis of the joint and inserts into the base of the distal phalanx. The tendon of the flexor digitorum brevis inserts into the center area of the middle phalanx. This aids in plantarflexion of the proximal and distal IPJ. There is no insertion of the flexor tendons on the proximal phalanx.

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