Protocol for the treatment of heterotopic bone formation in the temporomandibular joint.

The increase in patients with multiply operated temporomandibular joints (TMJs) has led to an increase in associated complications that respond unfavorably to additional attempts at correction. These can present as ankylosis and/or heterotopic bone formation. This has been recognized in other joint reconstruction, to a much more significant degree, and related to decreased vascularity, increased fibrosis and scarring, and decreased cellularity of the tissue in the joint space following multiple surgical procedures. Attempted correction of this problem can often lead to an increase in the etiology and to recurrence of the bone formation in spite of its debridement. Correction in other joints has evolved to include the use of thorough debridement of the heterotopic bone, alloplastic joint reconstruction, autologous fat grafting, and use of NSAIDs and low-dose radiatíon to decreaserecurrence.

Temporomandibular joint reconstruction with a custom total temporomandibular joint prosthesis: use in the multiply operated patient.

The purpose of this article is to report the development and use of the custom Christensen prosthesis (Garrett modification) for total temporomandibular joint reconstruction, its indications, protocol, adjunctive treatment and evolution to present design.

Vascularized osteochondral allografts in an immunosuppressed rat model: graft modulation and host immune tolerance.

The effects of 4 weeks of cyclosporin A (7 mg/kg per day) (CyA) on the survival of vascularized osteochondral grafts between rat strains [DA (donor) and Lewis (recipient)] and the presence and significance of host immune tolerance and graft antigen modulation after cessation of immunosuppression have been examined. Isografts (n = 12) survived without apparent abnormality for 8 weeks but showed signs of wasting after longer periods; unprotected allografts (n = 5) were rejected within 2 weeks. After 4 weeks of CyA, allografts remained healthy for at least 12 weeks but then deteriorated (n = 40). Antigen modulation was examined by graft removal at various intervals after cessation of CyA and reimplantation into a naive recipient (n = 14). All were rejected rapidly. Host tolerance was examined by graft removal at various periods after cessation of CyA and reimplantation of a fresh allograft (n = 15). Some of the second grafts survived at least 4 weeks without immunosuppression. The findings indicate development of incomplete host tolerance but no antigenic modulation of the graft.

Secondary ischaemia in rabbit skin flaps: the roles played by thromboxane and free radicals.

1. Biochemical mechanisms of ischaemia were investigated in rabbit skin flaps subjected to 2 h of primary ischaemia then, 24 h later, to 4 h of secondary ischaemia. During secondary ischaemia, flaps underwent either total ischaemia (arterial and venous blood supply occluded) or partial ischaemia (vein only occluded). Some of these flaps were treated at the time of reperfusion with the free-radical scavenger superoxide dismutase (EC 1.15.1.1) and/or the thromboxane synthetase inhibitor UK-38,485. 2. After 30 min of reperfusion, superoxide dismutase treatment significantly reduced blood thromboxane levels, elevated during ischaemia. Superoxide dismutase also reduced tissue levels of malonyldialdehyde and xanthine oxidase, indicators of free-radical damage, and restored the depleted tissue levels of superoxide dismutase. 3. UK-38,485 treatment failed to significantly alter any of these tissue free-radical parameters, although this agent significantly reduced blood thromboxane levels. 4. Combined superoxide dismutase plus UK-38,485 treatment was not significantly better than either treatment alone with respect to any parameter. 5. Partial ischaemia led to consistently higher levels of tissue free radicals and blood thromboxane than did total ischaemia. Thus partial ischaemia appears to result in greater free-radical damage than total ischaemia. 6. These results are consistent with the hypothesis that thromboxane acts as a mediator for free-radical damage in the ischaemic changes within the flap.

Interaction between thromboxane and free radical mechanisms in experimental ischaemic rabbit skin flaps.

The possible relationship between increased blood levels of thromboxane (TXA2) and tissue levels of free radicals during ischaemia was investigated. Rabbit epigastric skin flaps were subjected to 4 h of body temperature ischaemia, then infused with either the TXA2 synthetase inhibitor UK-38,485, the free radical scavenger superoxide dismutase (SOD), or both immediately prior to reperfusion. After 30 min of reperfusion, increases in the tissue levels of xanthine oxidase (XO) and malonyldialdehyde (MDA), both of which are indices of free radical generation and decreases in the tissue levels of SOD were found. SOD treatment completely restored XO, MDA and SOD levels to normal, whereas UK-38,485 only partially improved all three parameters. None of these changes was statistically significant. Effluent blood thromboxane B2 (TXB2) levels from the flap increased significantly (P less than 0.01) after ischaemia and were reduced significantly by both UK-38,485 and SOD (P less than 0.05). Combined UK-38,485 and SOD treatment was no better than treatment with either agent alone. ATP levels and oedema, which decreased and increased respectively due to ischaemia, were not significantly altered by drug infusion. These results suggest that free radical damage may be related to TXA2-generated thrombosis in ischaemia/reperfusion injury.

The scaphoid allograft: a new operation for treatment of the very proximal scaphoid nonunion or for the necrotic, fragmented scaphoid proximal pole.

This is a preliminary report of eight cases in which an allograft was used to replace half of the scaphoid. The indications for the procedure include the following: (1) Severe necrosis with fragmentation of the proximal pole, (2) Very proximal pole nonunion with small (less than 20% of the bone), unreconstructable proximal fragments, and (3) One case of severely comminuted intra-articular fracture of the scaphotrapezial joint and basal joint of the thumb caused by a gunshot wound. The Herbert scaphoid screw was used to provide rigid fixation. Follow-up ranged from 8 to 30 months. The result was good in six of eight patients. It should be emphasized that this is a preliminary report of the early experience with a new operation for salvage of difficult scaphoid fracture problems.