An Alternative Approach To Plantar Plate Derangement

Author(s): 
By Kerry Zang, DPM

     Plantar plate derangement with synovitis of the metatarsophalangeal joint complex is a progressively degenerative condition with an inflammatory component.1 Recent clinical experience suggests that one can treat these pathologies successfully using plasma-mediated, radiofrequency-based microdebridement.

     While the plantar plate of the metatarsophalangeal joint shows signs of degeneration, the metatarsophalangeal joint complex itself is inflamed (i.e. synovitis). Clinicians often find this condition in conjunction with the triad of hallux abductovalgus deformity, metatarsalgia secondary to prominence of the metatarsal head and digital deformity.

     During the physical examination, the physician will notice the following findings:
     • medial deviation of the appropriate digits;
     • contracture with pain on palpation of the dorsal medial aspect of the second metatarsophalangeal joint complex;
     • increased pain on palpation in the metatarsophalangeal joint complex upon distraction of the involved digit;
     • pain on palpation at the lateral plantar aspect of the capsule of the second and/or other metatarsophalangeal joint complexes;
     • clinically prominent and painful metatarsal heads;
     • pain with rotational forces at the base of the proximal phalanx on the head of the corresponding metatarsal;
     • positive vertical instability with stress testing of the involved metatarsophalangeal joint. With plantar plate derangement, the instability is up to approximately 3 mm. Over 3 mm indicates rupture of the plantar plate.

     One may also note frictional keratosis inferior to the metatarsal head.

     It is important to note that the most commonly involved joint for plantar plate derangement in the foot is the second metatarsophalangeal joint but sometimes one may see involvement of other lesser metatarsophalangeal joints. This is usually a direct result of either long metatarsals or other structural imbalances that lead to increased pressure at the level of the metatarsophalangeal joints, and repetitive stress from the biomechanical imbalances that are present.

     Diagnostic ultrasound is also a valuable tool in diagnosing plantar plate derangement. It clearly enables visualization of the plantar plate to determine whether there is early derangement, degenerative changes or rupture. Doppler enhancement will also help the physician ascertain if the process is of an inflammatory nature or degenerative capsulopathy. With the ultrasound, we can also determine the presence and extent of the inflammatory synovitis on the dorsal aspect of the involved metatarsophalangeal joint.

     The normal ultrasound appearance of the plantar plate is one of ligament and tissue continuity at the metatarsophalangeal joint without significant fluid in the joint space. When it comes to a tear in the plantar plate, the clinician will see a disruption in the continuity (hypoechogenicity) of the tissues at the metatarsophalangeal joint. Varying degrees of derangement are categorized as small, moderate or large tears of the plantar plate depending on the amount of disruption. Clinicians will also see increased edema or synovitis within the joint, which one can confirm via the use of power Doppler. If you diagnose the plantar plate derangement early on in the disease process, conservative treatment efforts might be beneficial.

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