Abstract
Introduction: Adult acquired flat foot deformity is recognised as a spectrum of pathology related to tibialis posterior dysfunction (TPD) and plantar ligament insufficiency. Cobb has described a method of reconstruction in pure Johnson and Strom type II TPD using a split Tibialis Anterior musculo-tendinous graft.
Methods: We describe a prospective study of 32 patients treated by the Cobb technique and a medial displacement translational os calcis osteotomy for Johnson and Strom type II TPD. There were 28 females and four males (age range 44–66, average 54) each with unilateral disease. The average follow up was 5.1 years, range 3 to 7.2 years. Each patient had failed conservative management and the staging was confirmed clinically and radiologically (ultrasound scanning and MRI). The surgery was performed as described by Cobb but with a bone tunnel in the navicular rather than the medial cuneiform. Postoperative immobilisation in plaster was for eight weeks followed by orthotics and physiotherapy.
Results: All the os calcis osteotomies healed uneventfully. 29 of the 32 patients were able to perform a single heel rise test (none prior to surgery) at twelve months follow-up. These patients had grade 5 power of the tibialis posterior tendon. The others had grade 4 power and were also happy with the result. The mean American orthopaedic foot and ankle society (AOFAS) hindfoot score was 82. There was one superficial wound infection successfully treated by antibiotics and a temporary dysaesthesia in the medial plantar nerve in another.
Discussion: This prospective study confirms that the Cobb technique is an excellent method of treating pure Johnson and Strom type II TPD after failed conservative management. The procedure is performed with a medial displacement os calcis osteotomy but in selected cases may be combined with spring ligament repair and lateral column lengthening. An updated classification will be presented designed to facilitate the decision making process in this difficult condition.
Correspondence should be addressed to A.H.N. Robinson, BOX 37, Department of Orthopaedics, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Trust, Hills Road, Cambridge. CB2 0QQ, England.
