Temporomandibular joint (TMJ) replacement is the gold standard for reconstruction of the ankylosed joint, as it provides the facility for early function and a suitably large gap, both aimed at the prevention of recurrence. The recurrence of heterotopic ossification is traditionally managed by resection, a temporary spacer, and remake of the prosthesis, with placement at a second procedure, which adds to costs and morbidity. Atraumatic removal of the prosthesis, resection of the heterotopic tissue, replacement of the prosthesis into its previous position, and the packing of fat around the articulation represents a technique that both minimizes morbidity and reduces costs. This technique has been utilized in three cases, with early improvement in mobility, function, and pain. It is still too early to determine whether the outcomes obtained will be maintained in the long-term.
Temporomandibular joint (TMJ) ankylosis is defined as a reduction in mouth opening due to fusion of the joint structures secondary to the interposition of bone. There are various classifications of TMJ ankylosis, depending on the extent of ankylosis, types of tissue causing it, and its location. The common causes of ankylosis include trauma and infection, although rheumatoid disease and iatrogenic aetiologies have also been implicated. Clinically the patient presents with restricted mouth opening and loss of lateral movements, especially to the contralateral side. Significant heterotopic bone formation causing fusion is not associated with pain; however in the early stages, the body’s desire to move the joint makes this process painful.
There are various management options depending on the age of the patient, clinical findings, costs, and available expertise. Alloplastic TMJ replacement is an option in the management of heterotopic bone formation. The outcome in terms of pain reduction and mandibular range of movement is comparable to resection of the heterotopic mass and interpositional arthroplasty. The advantages of alloplastic replacement of the TMJ include no secondary donor site morbidity, stable occlusion postoperatively, a short hospital stay, and early mobilization due to the decrease in pain and a stable joint. Patients with a prosthetic replacement progress to a normal diet much sooner. The main disadvantage of the alloplastic TMJ replacement is the initial cost of the prosthesis, although the shorter length of stay and reduced morbidity may equalize costs somewhat when compared to autologous reconstruction. In the UK, it is necessary to request individual funding for this procedure. Other disadvantages include the risk of infection (at 2–4%), dislocation of the prosthetic joint, and limited long-term follow-up studies beyond 20 years.
The management of recurrent heterotopic bone formation around the TMJ prosthesis is discussed herein. If the prosthesis in such a case were to be replaced, the patient would need two-stage surgery requiring two inpatient stays, with increased morbidity and overall cost. The standard protocol is resection of the heterotopic mass, removal of the prosthesis, and insertion of a temporary spacer. A repeat computed tomography (CT) scan is performed to construct a new patient-fitted prosthesis and the patient is discharged home. An alternative management strategy comprises removal of the whole prosthesis and subsequent replacement following resection of the recurrent heterotopic mass, with autologous fat placed around the articulation. The use of this strategy in three patient cases is described below.
Three patients who developed disabling recurrent heterotopic bone around their TMJ prostheses underwent single-stage surgery that involved atraumatic removal of the prosthesis, resection of the heterotopic bone, re-insertion of the same prosthesis, and packing of autologous abdominal fat around the articulating surface. Data were collected prospectively in the departmental database, including patient demographics, date of initial surgery, time from the insertion of the prosthesis to the development of restriction or pain, pain score, dietary score, mouth opening, and any prior surgical procedures. The clinical outcomes measured were mouth opening, dietary score, and pain score before surgery and after surgery. Patient permission was obtained for publication of the clinical photograph and CT image. As the prosthesis could be used as a temporary spacer, no ethical approval was required.