Prosthetic replacement of the aortic arch.

Four patients are reported in whom the aortic arch and variable portions of the ascending and descending aorta were replaced with a prosthesis. In three patients the preoperative diagnosis was dissecting aneurysm of the aortic arch and in one an arteriosclerotic aneurysm of the aortic arch was present. A combination of surface cooling and cardiopulmonary bypass was utilized to produce total body hypothermia. Arch replacement was carried out during a period of total circulatory arrest. Cardiopulmonary bypass was then utilized to warm the patient and resuscitate the heart. The average duration of cerebral ischemia was 43 minutes and the average duration of myocardial ischemia was 74 minutes. The average lowest esophageal temperature was 14 degrees C., and the average lowest rectal temperature was 18 degrees C. Three patients are alive and well 4 to 13 months following surgery. One patient died 4 days postoperatively of pulmonary insufficiency. This experience indicates that by utilizing total body hypothermia and circulatory arrest aortic arch replacement can be carried out with an acceptable mortality rate. Corrective surgery could be offered to patients with life-threatening enlarging aneurysms of the aortic arch.     

Prosthetic replacement of the patellofemoral joint.

We are just beginning to fully appreciate the significant role of the patellofemoral joint in total knee replacement surgery. Most of the new generation prostheses have a flanged femoral component. The tendency is to make the flange more anatomic in shape as more attention is paid to patellar tracking. Most systems have an optional polyethylene button to resurface the patellar side of the patellofemoral joint, and indications for its use are increasing. Although pain relief with patellar buttons seems uniform, the potential complications of stress fracture, loosening, and wear must temper our enthusiasm for their use until there is longer follow-up. Vitallium hemiarthroplasty of the patella is available in prostheses with and without the requirement for cement fixation. Most investigators have good results in chondromalacia (as a secondary procedure), but the experience in the literature is small. Results have been poor when the femoral side of the joint has been involved. Metal to plastic isolated patellofemoral prostheses have been designed to treat disease on both sides of the patellofemoral joint or to salvage unflanged total knee replacements with residual patellofemoral symptoms. Short term experience has been promising.     

Prosthetic valve replacement in children.

Reported clinical experience with prosthetic valve replacement in children have suggested a high operative mortality. We placed 25 valves in 24 children with one operative death. There has been one late death related to pacemaker malfunction, but the remainder of the patients have generally done extremely well. The children have not undergone elective anticoagulation, and the long-term embolism rate has not exceeded the incidence of systemic embolization in adults who have been controlled on warfarin sodium (Coumadin) therapy. The objective of prosthetic valve replacement is myocardial preservation. We believe that valve replacement with currently available prostheses should be undertaken in any child with valvular malfunction who is not well controlled with good medical management.     

Prosthetic replacement of the proximal humerus

Eighteen patients had prosthetic proximal humeral replacement with either a metal or ceramic prosthesis. Three replacements were performed for fracture nonunions, five for benign neoplasms, six for low-grade malignancies, and four for high-grade malignancies. Retention of elbow and hand function was good. In five of the 11 ceramic prostheses, failure occurred at the humeral-prosthetic junction even though it was designed for biologic fixation. Ten of 18 prostheses subluxated or dislocated. Twelve of 18 patients have had revision operations. While the revision rate in this initial series was high, valuable experience was gained for further investigations of shoulder arthroplasty.     

Prosthetic replacement of the inferior vena cava. Current controversies

A ringed polytetrafluoroethylene (PTFE) graft is currently the most widely used replacement for the inferior vena cava, although clinical studies comparing this technique with non-ringed prostheses are lacking. There is no consensus on the need to use an anticoagulant or associate a temporary distal arteriovenous fistula to increase venous flow. At present, the best therapeutic strategy cannot be determined. We present a case of retroperitoneal sarcoma infiltrating the infrarenal vena cava, right colon and ureter that was surgically treated in our hospital. En bloc resection was performed and the vena cava was reconstructed using a non-ringed PTFE graft associated with systemic anticoagulation.     

Prosthetic replacement of the proximal interphalangeal joint

The first proximal interphalangeal joint (PIPJ) replacements were hinged devices allow-ing only single-axis motion. Newer implant arthroplasties of the PIPJ have anatomically designed proximal phalangeal and middle phalangeal components. Constrained devices have typically lead to failure at the hinge mechanism or the prosthetic bone interface. A need to create balanced forces across the joint was the rationale behind the semicon-strained PIPJ prosthesis, which uses an anatomic design. Limitations of the silicone PIPJ implant include its lack of resistance to valgus loading at the index and long digits during the pinch maneuver. It is generally believed that a PIPJ surface replacement arthro-plasty that preserves the collateral ligaments will achieve greater PIPJ stability.     

Prosthetic replacement of the upper ankle joint

Results after total ankle arthroplasty in the 1970s and 1980s were poor. The outcomes of these surgeries deteriorated rather dramatically with time. Causes of failure were multifactorial, but the two main reasons for failure were constrained designs and cement fixation. Today, the design of total ankle arthroplasty is unconstrained and the fixation is uncemented. Total ankle arthroplasties are considered technically demanding procedures, with relatively high early postoperative complication rates. As yet, the ideal total ankle patient remains to be defined. Good alignment and ligamentous stability are essential. Osteonecrosis and profound osteoporosis are associated with poor results due to problems with bony fixation. Patients should be advised that the implant may fail and that this may require further surgery, including the potential need for an ankle fusion. The results of ankle fusions, although usually initially good, seem to deteriorate with time. Not uncommonly, patients frequently develop peritarsal degenerative joint disease several years after an ankle arthrodesis. Because of the associated pain and functional limitations that can follow ankle fusion, efforts to develop a workable total ankle replacement continue. At present, the long-term results of new designs are unknown. Today, total ankle arthroplasty should be limited to centers where patient volume and infrastructure allows critical review and prospective clinical trials to determine the factors leading to successful and unsuccessful outcomes.