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.
Our clinical experience in treating lower limb deformities by external fixation started in 1982 by applying an Ilizarov external fixation frame. Correcting lower limb deformity by gaining the proper length and the optimal mechanical performance is of the outmost importance and essential for valid restoration of the articular function. We treated 145 patients: 25 patients affected by post-traumatic deformities; 12 patients affected by axial deviation of the knee; 82 patients affected by limb shortening and associated limb deformities; eight patients with lower limb deformities and shortening following pathological hip alterations; and 18 patients affected by severe foot deformities. It is important to stress that in congenital lower limb deformities both axial deviation and limb shortening contribute to the final picture of the deformity. Combined (hybrid) external fixation provides an adequate correction of the mechanical axis and a proper lengthening of the shorter limb by a corticotomy followed by a gradual distraction.
We performed 55 operations in 40 patients affected by diabetic foot and referred to the Diabetic Day Hospital from 1998 to 2003. Surgical procedures can be grouped as: (a) emergency operations: mostly for surgical debridment; (b) operations such as functional amputation of the limb at various levels; and (c) conservative operations such as preventive correction of deformities or restoration of morphology and function. We performed 39 amputations; 15 conservative procedures (including ring external fixation in “Charcot foot”); and one emergency procedure (sepsis). We never used local ischaemia while operating diabetic patients. Patients follow-up ranges from 6 months to 6 years. One fourth of patients died for reasons not directly associated with diabetic foot but often related to the diabetes. The vast majority of patients mantained adequate control of the disease, wore special “diabetic shoes”, and judged the result of the operation very positively and consider their situation much improved after the operation. Surgical wound closure took from 2 to 20 weeks (mean 6 weeks). More than half of the patients can walk without support. It is relevant to note that about half of the patients had previous operations for the same problem but about 90% of the patients required no further operation after the one we performed. Orthopaedic surgical treatment may effectively restore walking ability in those patients who lost it because of diabetic foot problems.
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 new class of soybean-based biomaterials has been presented to the scientific community (patent PCT/GB01/03464) that shows good mechanical properties and an intrinsic anti-inflammatory potential, probably related to the phyto-hormone Genistein. This plant iso-flavone is also reported to inhibit osteoclastic activity. De-fatted soybean curd was prepared into granules which were subsequently implanted in a cylindrical cavity drilled into the femoral canal of New Zealand White rabbits. Retrieved femurs were embedded in polymethyl-meta-acrylate and samples were analysed by back-scattered electron microscopy (BSEM). Retrieved, operated femurs showed a macroscopic appearance similar to the non-operated controls. BSEM showed that granules were still present at the site of implantation after 8 weeks, but a clear progressive degradation took place from the periphery to the centre of the femural canal already after 3 weeks. The degradation of the granule was accompanied by the production of new trabeculae apposed to the surface of the material. It can be hypothesised that the released Genistein shifts the metabolic balance towards bone production by inhibiting the macrophagic and osteoclastic activities and that the material degrading surface supports the apposition and mineralisation of the newly formed bone.
Coatings for endo-osseous implants have been developed based on phospholipids. Such coatings promote the formation of a very thin superficial rim which is highly enriched with calcium phosphates. Two phospholipid-based preparations have been compared with a standard hydroxyapatite coating. Preparation S was based on phosphatidyl-serine; preparation C was based on a mixture of phosphatidyl-serine, phosphatidyl-choline and cholesterol. Titanium cylinders spammed with titanium foam were the metallic substrate for the coatings; they were implanted in the femoral canal of New Zealand White rabbits and retrieved after 4, 8 and 26 weeks. A back scattered electron microscopy analysis followed. Both phospholipid preparations were shown not to have any inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction. Pictures of bone in-growth into the cavities of the titanium foam are present. A truly tight apposition between bone and coating was evident only in the comparative group sprayed with hydroxyapatite, but this latter coating was often fragmented and its constituent granules were evident. The phospholipid-based coatings did not show inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction.
The rationale for a degradable bioactive glass coating is to lead the bone to appose gradually to the metal without the release of non-degradable particles. Two formulations of bioactive glasses, already described in the literature, have been studied: bg A and bg F. A non-bioactive glass (glass H) was sprayed as a control. Glass-coated Ti6Al4V cylinders were implanted in the femoral canal of New Zealand White rabbits. Samples were analysed by back scattered electron microscopy (BSEM) and electron dispersive analysis (EDX). Bone was in tight apposition with the coating. As time progressed, images were found where bone showed features of physiological remodelling (newly formed bone filling areas of bone resorption) close to the coating. At the interface the apposition was so tight that it was not possible to discern a clear demarcation, even at higher magnification (more than 2500x). There was a gradual degradation during time and at 10 months bone was found apposed directly to the metal in more than half of the samples. In contrast, the non-bioactive glass coating showed complete integrity at any time examined and a clear demarcation with the coating was evident. Two peculiar features of the behaviour of bioactive glass coatings in vivo are: (a) degradation during time; and (b) promotion of a tight apposition with the newly formed bone.
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.
