In the past, the clinical outcome of earlier types of resurfacing hip arthroplasty was often characterised by a high percentage of failures and early mobilisations. An implant retrieval of a Co-Cr head and UHMWPE cup cemented resurfacing hip prosthesis was analysed. The implant was in place 11 years, without any clinical problem for nearly 10 years. The cup was highly worn. There was a complete fracture of the interface between cement and bone at the base of the femural neck. A significant hyperplastic reaction was present at the level of the synovial membrane, with fibrin deposits, hyperplasia of lining cells and a cellular infiltrate formed mostly by macrophages, with occasional giant cells and localised groups of perivascular lymphocytes. Immunohistochemical analysis showed that all lymphocytes were of the T type and that the largest part of macrophages containing debris were not activated. Inside the prosthetic head there were only traces of ossified tissue. This picture indicated that for a long time no viable bone tissue had been in contact with the cement and bone rarefaction was massive. The study shows an important cause of the failure of earlier types of hip resurfacing arthroplasty, namely the abnormal stress distribution that caused the complete bone rarefaction.
The authors studied the characteristics that would be desirable for a metacarpo-phalangeal joint prosthesis to be used in patients with rheumatoid disease. In these patients the severe destruction of the capsulo-ligamentous structures of the joint often makes prosthetic substitution dissatisfactory, particularly for the index finger. Such a prosthesis should be restricted in its range of motion, actually abolishing any ulnar deviation. Axial rotaion should be coupled to flexion-extension and radial deviation to gain an adequate stress dissipation at the interface. Both distal and proximal stems should be conical, for the best possible distribution of shear stresses at the interface. A flattening surface should accommodate properly the externsor apparatus without interfering with it. The greatest possible congruence should be required for the articulated components. The rationale of such a design for a rheumatoid patient lies in the fact rheumatoid arthritis is the most important indication for a metacarpo-phalangeal joint arthroplasty, due to the highly incapacitating condition that may ensue. Then, despite limitations required by the proposed design, an improvement in the functional ability of the rheumatoid patient will be obtained.
A case is reported of an 18-year-old man with a post-traumatic radial shortening of about 10 cm with 40° of radial deviation as a consequence of an epiphyseal arrest that occurred when the patient was 8 years old. In the past the patient and his parents had refused all corrective treatment which would result in a permanent shortening; then a treatment by the Ilizarov external fixator was proposed. The forearm assembly was made by two fixed rings (one proximal and one medial) and one hinged distal ring. A closed corticotomy was performed parallel to the distal ring, whose fulcrum was at the ulnar styloid. Correction and lengthening were obtained by elongating two opposite threaded bars about 0.5 mm per day. Minor revisions were made on an out-patient basis. Time of correction and lengthening was 113 days, followed by 70 days in the fixator and a further 44 days of plaster cast after fixator removal. The complete correction of deformity and concurrent lengthening showed that Ilizarov‘s method is a definite but very demanding option in the treatment of severe deformities of the upper limb.
