How To Address Predislocation Syndrome Of Lesser MPJs
- Volume 20 - Issue 3 - March 2007
- 64519 reads
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Metatarsalgia is a diagnostic term used to describe pain in the ball of the foot. Gerard V. Yu, DPM, eloquently described and illustrated predislocation syndrome in 1995. What Dr. Yu described was a clinical syndrome characterized by focal pain under a lesser metatarsophalangeal joint (MPJ), most often affecting the second toe joint.1
Subjective symptoms reported by those afflicted with this syndrome would be described as a “grape-like” swelling under the affected toe joint, and a feeling as if there were a stone bruise on the ball of the foot. More often than not, the patient would be apologetic about wasting the doctor’s time with what seemed trivial as there was no obvious problem looking at the foot.
Clinical findings with predislocation syndrome include pain upon palpation of the plantar plate, and subtle dorsal and/or transverse plane subluxation of the toe (exacerbated with loading of the foot) without frank hammertoe formation. Usually, there is no callus but one may see mild edema in the region of the plantar plate. With this condition, the clinician will also note that range of motion of the metatarsophalangeal joint is painful with end-range plantarflexion of the digit.
In contrast to metatarsalgia without predislocation syndrome, there is pain upon palpation of the metatarsal head, which is more proximal than the plantar plate. One would also usually see callus formation and note that range of motion
of the metatarsophalangeal joint is not painful. In these cases, podiatrists may also note a lack of fat padding and a longstanding, non-reducible hammertoe deformity.
Essentially, predislocation syndrome describes the evolution of a hammertoe deformity if it is left untreated. Inflammation of the plantar structures of the metatarsophalangeal joint can eventually lead to attenuation or rupture of the stabilizing plantar structures, which leads to ensuing deformity of the toe. As the plantar capsular structures rupture, the proximal phalanx will eventually dorsally migrate and the flexor tendons may deviate medially. If you think of the plantar plate as analogous to the sesamoid apparatus of the great toe joint, then you can appreciate that where the plantar plate migrates, the flexor tendons migrate in similar fashion.
This ultimately can lead to a flexion contracture and transverse plane drift of the toe. If there is concomitant hallux valgus, then the mechanical force of the crowding great toe will undermine the second toe, encouraging it to sit on top of the great toe. This process can exacerbate the medial drift of the second toe.
Getting A Strong Grasp On Lesser MPJ Anatomy
Understanding the anatomy of the lesser metatarsophalangeal joint is necessary to appreciate the syndrome. The normal anatomy has been well described in the literature.2-4 Yao has described pathological findings on MRI.5 The plantar plate is a thickening of the plantar capsule consisting of a fibrocartilage material. This provides a shock-absorbing weightbearing structure. The distal attachment of the plantar plate is to the base of the proximal phalanx, which is relatively strong, and the proximal attachment site is behind the condyles of the metatarsal neck, which is the weakest attachment.