Prosthetic Condyle with Concurrent Microvascular Reconstruction for Mandibular Disarticulation Defects: A Retrospective Series

Abstract

Introduction

Reconstruction of mandibular disarticulation defects is a challenging area of head and neck surgery, with a variety of options available for replacement of the condylar head. The gold standard is autogenous reconstruction of the condyle-ramus unit. The use of a prosthetic condylar head is controversial, but in challenging cases, and those with a likely poor prognosis it may be considered and can achieve a good functional result. The objective of this study is to evaluate the outcomes of its use in a high volume head and neck reconstructive unit.

Materials and methods

A retrospective analysis of all patients treated at the Queen Elizabeth Hospital, Birmingham who underwent mandibular disarticulation resections and prosthetic condylar reconstruction from January 2008 to December 2019 were included.

Results

This retrospective review included 25 patients; 16 for malignant disease (16), osteoradionecrosis (4), osteomyelitis (2), medication related osteonecrosis (1), and secondary reconstruction(2). Free flap reconstruction was performed in 23 cases; 18 bony composite free flaps, 3 patients required double flap reconstruction, and 2 underwent soft tissue flaps only. Mean follow up was 43 months. Prosthesis related complications were encountered in 6 patients, all malignant cases. Four prosthetic condyles required removal due to recurrent infections and glenoid fossa perforation, This appeared to be related to significant surrounding dead space, and limited bony reconstruction. Rate of complications was lowest for non-malignant cases, and patients who had concurrent bony reconstruction extending up the ascending ramus. Functional outcomes were good with majority of patients having a balanced occlusion and oral intake.

Conclusion

Prosthetic condyle outcomes are best when concurrent bony free flap reconstruction is performed with ascending ramus reconstruction. Avoid prosthetic condyles in cases where the articular disc is removed, and cases where a large amount of dead space is expected around the prosthesis. Careful attention to occlusal factors and vertical support of the reconstruction plate can lead to good functional outcomes. A review of the literature and potential future advances is also presented.

Introduction

Ablative surgery of the ascending ramus of the mandible for pathology such as malignancy, osteoradionecrosis or osteomyelitis may require disarticulation of the temporomandibular joint (TMJ) and resection of the condylar head. The use of condylar prostheses for replacement of the temporomandibular joint (TMJ) in the management of ablative disarticulation defects of the mandible is controversial, particularly in the context of malignant disease or patients who have undergone radiotherapy. Early studies of using a prosthesis alone demonstrated significant complications such as heterotopic bone formation and perforation through the glenoid fossa into the middle cranial fossa [1–3]. These reports led to concern that condylar replacement with a prosthesis alone is high risk. Instead, autologous options have been promoted, such as fibula free flap reconstruction directly to the glenoid fossa, with mixed results [4, 5]. This option has other risks including ankylosis, heterotopic bone formation, and more challenging control of the post-operative occlusion.

Combined use of prosthetic condyles and composite microvascular free flaps may be used to achieve predictable and reliable outcomes in this complex scenario [6]. The goal of adding a condylar prosthesis is that it provides better vertical seating within the glenoid fossa for maintaining the occlusion and in turn achieve better functional outcomes, and the vascularized tissue surrounding or fixated to the plate reduces the chance of infection and plate exposure.

The objective of this series is to evaluate the outcomes of all patients who underwent prosthetic condylar replacement for ablative disarticulation defects, with or without concurrent microvascular reconstruction, and to identify factors that contributed to success or failure.

Methods

A retrospective review of all patients who had undergone prosthetic reconstruction of a condyle, by the Maxillofacial team at the Queen Elizabeth Hospital, Birmingham between January 2008 until December 2019 was performed (Approval CARMS-00091). All cases were operated on by the same team of Maxillofacial Surgeons. All cases were planned and managed post-operatively by a multidiskiplinary team that involved the input of surgeons, dieticians, speech and language therapists, specialist support nurses and a prosthetics team.

Data collected included patient demographics, diagnosis, indication for treatment, the type of flap utilized in the reconstruction, level of bony reconstruction, complications and functional outcomes. The Functional Glasgow Intra-oral Scale self-assessment of speech, chewing and mouth opening was completed at most recent follow up to determine subjective outcomes [7].

Prosthetic Planning and Construction

All cases were planned using Materialize™ SurgiCase software. Stereolithographic 3D acrylic models were constructed from computed tomography scans.

Where indicated the condyle and mandible resection was pre-planned on the model and the fossa left unmodified. The reconstruction plates comprised of three components, a plate, carrier plate and condyle. A 2.5 mm Synthes™ Unilock plate was used and locking screws used to secure the carrier plate and condylar component. All plates were contoured to the three-dimensional (3D) models by hand within the laboratory (Fig. 1). Where it was felt to be advantageous, 3D printed cutting guides were prepared to aid osteotomies during reconstruction.

Fig. 1.

Case 2. Patient who presented with a T4aN0M0 SCC of Left mandible. a, b Pre-operative case planning on a stereolithographic model. Laboratory putty is used to allow for a stable platform for accurate condylar positioning. c Intra-operative photo showing the condylar prosthesis in position. d Immediate post-operative OPG showing prosthesis in position, fibula free flap reconstruction, and arch bars in situ. e OPG 10 years after reconstruction. f post-operative photo showing maximal mouth opening. g Post-operative photo showing final occlusion after removal of arch bars

Surgical Technique

The resection was planned and performed according to the extent of disease and amount of involved bone. At the time of reconstruction, the alloplastic condyle was directly inserted into the glenoid fossa against the preserved native temporomandibular articular disk. Where possible, the disk was preserved where it did not compromise the oncological resection. The plate was secured to the remaining native mandible with 2.0 mm locking screws. Intermaxillary fixation (IMF) with Enrich arch bars (Fig. 1) were applied in dentate patients to maintain the vertical position of the condylar head within the fossa and preventing condylar sag. Where additional vertical support was necessary due to concurrent resection of the pterygomasseteric sling, PDS suspension sutures or fascia lata slings were used, positioned to the approximate position of the lingula on the plate. In benign cases, vertical control was supported by re-suturing of the pterygomasseteric sling during closure. Intra-operative and post-operative occlusal support was utilized in all dentate patients where the post-operative occlusion was deemed critical with elastic guidance for 6–8 weeks.

Post-operative Management

Post-operative management included 5 days of intravenous (IV) broad-spectrum antibiotics and two doses of IV dexamethasone. Patients had post-operative enteric feeding via nasogastric or gastrostomy tubes until adequate oral feeding was achieved. All patients were reviewed in outpatient clinics within 1–2 weeks of diskharge, and encouraged to perform mouth opening exercises with tongue depressors and TherabiteTM devices within 4 weeks of surgery. Dental rehabilitation was considered only after 12 months of recurrence-free survival in malignant cases.

Results

Demographics and Indications

A total of 25 cases were included, consisting of 12 males and 13 females with a mean age of 57 (range 20–77). 23 of these were immediate reconstructions at the same time as resection for: neoplastic disease (16), osteoradionecrosis (4), bisphosphonate related osteochemonecrosis (1) and osteomyelitis (2). The remaining two had previously undergone resections with disarticulation of the condyle elsewhere and had been referred for definitive reconstruction by our unit. One had a reconstruction plate fracture, the other had undergone resection without immediate reconstruction. Eight cases had been exposed to radiotherapy prior to their reconstructive surgery. Adjunctive post-operative radiotherapy was required for 11 patients (Table 1).

Table 1.

Demographic data, preoperative history and adjunct treatment for included cases

Patient	Age (years)	Gender	Comorbidities	Smoking history	Past diagnosis/prior treatment	Pre-operative treatment	Pre-operative diagnosis	Post-operative adjunct treatment
1	70	F	Asthma	Unknown	Resected ameloblastoma*	–	Fractured reconstruction tray	–
2	71	M	Asthma	Unknown	–	–	T4N0M0 SCC	RT
3	41	M	Asthma	Unknown	–	–	T4N1M0 SCC	RT
4	52	M	None	Unknown	T3N2aM0 tonsillar SCC External fixation*	RT	Osteoradionecrosis Pathological fracture	–
5	20	M	None	No	Resected cementifying fibroma*	–	Ramus deformity	–
6	75	M	Atrial fibrillation Myocardial infarction	Yes	Resection SCC right maxilla DCIA reconstruction	RT	Osteoradionecrosis	–
7	57	F	Ischemic heart disease Diabetes mellitus	Betel nut	–	–	T4N0M0 SCC	RT
8	24	M	None	Yes	Myositis ossificans Bisphosphonates *	–	Medication related Osteonecrosis	–
9	74	F	Hypertension Hypercholesterolemia	No	–	–	pT3 pN2b pR1 parotid adenocarcinoma	RT
10	58	F	Myocardial infarction	Yes	Osteomyelitis Debridement and wound toilet	–	Chronic osteomyelitis with fibrosis Condyle ramus fracture
11	61	F	Osteoarthritis	Yes	–	–	pT4a pN2b Mx SCC	CRT
12	69	M	Hypertension Hypercholesterolemia	Yes	Odontogenic cyst resected and reconstructed with an iliac bone graft*	–	Clear cell odontogenic tumor	RT
13	50	F	Lower limb thrombophlebitis	No	–	CT	High grade osteosarcoma	–
14	47	F	None	No	–	–	Leiomyosarcoma	CRT
15	71	F	Hypercholesterolemia	Yes	–	–	T4N2b SCC	CRT + IMT
16	59	M	Ischemic heart disease	No	–	–	T4N0 SCC	RT
17	66	F	Breast carcinoma	No	T4N0 SCC resection, Scapula flap reconstruction	CRT	T4N0 SCC	–
18	47	M	Hypertension	No	Tonsillar cancer	CRT	High grade chondroblastic osteosarcoma	–
19	77	M	Hypertension	No	T2N2b oropharyngeal carcinoma P16 positive	RT + CT	Osteoradionecrosis	–
20	65	F	None	Unknown	BCC parotidectomy and lateral temporal bone resection, ALT reconstruction	RT	Morphoeic BCC recurrence	–
21	58	M		Yes		–	T4N2b Maxillary SCC	RT
22	71	M	Diabetes mellitus Hypertension	Yes	T3N2b tonsillar SCC	CRT	Osteoradionecrosis	–
23	60	F	Hypertension	Unknown	–	CT	High grade spindle cell carcinoma	RT
24	22	F	Osteopetrosis	Unknown	Osteomyelitis debridement	–	Chronic osteomyelitis	–
25	58	F	Hypertension	Yes	T4N1M0 nasopharyngeal carcinoma	CRT	High grade chondroblastic osteosarcoma	–

ALT Anterolateral thigh flap, DCIA deep circumflex iliac artery flap, SCC squamous cell carcinoma, BCC Basal cell carcinoma, RT Radiotherapy, CT Chemotherapy, CRT Chemoradiotherapy, IMT Immunotherapy,

*Procedures performed by external units

The mean follow-up was 43 months (range 24–146 months).

Four patients have died, none related to the reconstruction, but either succumbed to disease recurrence (1 case), or died of other causes (3 cases).

Classification of Defects

Mandibular defects were classified using the Brown classification [16]. Eleven were classified as ‘Ic’, where the defect extends from the condyle toward but not including the ipsilateral canine; twelve were ‘IIc’, or hemimandibulectomy; and two were ‘IVc’, an extensive resection extending beyond the contralateral canine region (Table 2).

Table 2.

Surgical details for included cases

Cases	Brown’s classification of mandibular defects	Flap type	Bony subunits	Extent of bony replacement of ascending ramus	Radiographic condylar position within the fossa
1	Ic	Fibula	2	Type 3	Normal
2	Ic	Fibula	2	Type 3	Low
3	Ic	Fibula	2	Type 2	Normal
4	Ic	Fibula	2	Type 3	Normal
5	Ic	Fibula	1	Type 2	Low
6	Ic	Fibula	2	Type 2	Normal
7	IIc	ALT	–	–	Normal
8	Ic	Composite lateral border scapula	1	Type 2	Normal
9	Ic	RFFF	–	–	Normal
10	Ic	Fibula	1	Type 2	Low
11	IVc	Fibula + ALT	4	Type 2	Low
12	Iic	Fibula	2	Type 1	Low
13	Iic	Fibula	1	Type 1	Low
14	Ic	Fibula	1	Type 1	Normal
15	IIc	Fibula	2	Type 2	Low
16	Iic	Fibula	1	Type 1	Low displaced
17	IIc	RFFF + Composite lateral border scapula	2	Type 1	Normal
18	IIc	RFFF + Composite lateral border scapula	1	Type 1	Low
19	IIc	Fibula	1	Type 1	Normal
20	Ic	No flap	–	–	Normal
21	Iic	Composite lateral border scapula	1	Type 1	Low
22	IVc	Fibula	3	Type 1	Normal
23	IIc	Fibula	2	Type 1	Normal
24	IIc	No flap	–	–	Normal
25	IIc	Fibula	2	Type 1	Low

AR Ascending ramus, LAR low ascending ramus, NAR No ascending ramus, ALT anterolateral thigh flap, RFFF radial forearm flap

Surgical Factors, Microvascular Bone Level and Supplementary Procedures

All cases had preservation of the native articular disk except one (Case 11). 23 cases underwent concurrent free flap reconstruction. Microvascular reconstruction with single free flaps were completed in 20 cases; 18 bony reconstructions (fibula (16), and composite scapula (2)), and 2 soft tissue flaps only (radial forearm (1), and anterolateral thigh (1)). Three cases underwent simultaneous two flap reconstruction with a composite free flap and an additional soft tissue flap due to large multi-subunit resections (Cases 11, 17 and 18. The remaining 2 cases had no free flap reconstruction (Cases 20 and 24). Case 20 involved a ramus resection only due to deep Basal cell carcinoma recurrence where only the condyle and a small part of the posterior ramus was resected. The second case was a hemimandibulectomy with disarticulation in a patient with osteomyelitis in the setting of congenital osteopetrosis (case 24). Bony reconstruction was deemed inappropriate for this patient.

Classification of Reconstruction

The extent of bony reconstruction of the ascending ramus for each case is summarized in Table 2. The classification used relates to the position of the bone in relation to the prosthesis and the ascending ramus it is replacing (Fig. 2). In 11 cases the bone only extended toward the angle of the plate (Type 1), in 7 cases it extended toward the lower aspect of the ascending ramus (Type 2) and in 3 cases extended beyond the condylar carrier plate toward the glenoid fossa (Type 3).

Fig. 2.

Postoperative orthopantomographs (OPGs) showing the amount of ramus reconstructed when a bony composite free flap was used in conjunction with a condylar prosthesis and reconstruction plate. a Type 1—No ascending ramus (bone reaches only up to the angle of the mandible). b Type 2– Low ascending ramus (bone reaches half way up the ramus, up to the carrier plate, but not beyond it). Type 3—Ascending ramus (bone reaches past the point of the carrier plate close do the condylar prosthesis)

Post-operative Management

The mean post-operative hospital stay was 14 nights (7–31 nights). The mean interincisal distance was 25.9 mm (n = 21). Adjunctive post-operative radiotherapy was required for 11 patients (Table 1).

Complications

Eight patients had prosthesis/plate related complications (8/25), most commonly infection (6/8). Of these, 6 were related to the condylar prosthesis all of whom were malignant cases. Two cases returned to theater within 30 days: one due to lateral displacement of the prosthesis on post-operative day 2 (case 15); the other due to intraoral dehiscence. This defect was repaired with a lateral tongue flap (case 16) (Table 3).

Table 3.

Post-surgical complications and management

Cases	Post-surgical complications	Management of complication
1	None	None
2	None	–
3	None	–
4	Absolute trismus	Mouth opening exercises
5	Slight malocclusion	None—mild unilateral open bite. No functional problem
6	None	None
7	Left partial facial nerve palsy	None. Offered static facial slings. Refused
8	Pan left facial weakness—resection related	None. Offered static facial slings Refused
9	None	–
10	None	–
11	Delayed Pan facial weakness*—4 years post-operatively Multiple Infections with draining sinuses* Perforation of condylar prosthesis through glenoid fossa*	Condylar Prosthesis removed and static slings performed– at 4 years post-operatively
12	None	–
13	Small sinus buccal aspect of right mandible	Managed with antibiotics—granulated, and infection resolved
14	Fistula in the right neck communicating with prosthesis*	Condylar Prosthesis removed—at 3 months post-operatively
15	Displacement of prosthesis day 2 post-op*	return to theater for repositioning
16	Intraoral wound dehiscence (not condylar prosthesis related) Malocclusion*	Return to theater for Right lateral tongue flap to close the soft tissue defect Plan for further intervention
17	Retromandibular orocutaneous fistula* Delayed facial nerve palsy*—4 months post-operatively	Condylar Prosthesis removed—at 10 months post-operatively
18	Dehiscence superior aspect of the scapula skin paddle* Orocutaneous fistula* Trismus	Condylar Prosthesis removed—at 7 months post-operatively
19	None	–
20	None	–
21	None	–
22	Myofascial pain Right neck dehiscence and infection (plate infection without involving the condylar prosthesis)	Neck infection resolved with antibiotics alone
23	None	–
24	Intraoral plate exposure with intermittent infections	Symptomatic management and intermittent antibiotics
25	None	–

*Complication related to prosthetic condylar head

Displacement of the prosthesis was seen in the latter case described 2 months after reconstruction (Case 16). This patient is planned for a further procedure to reposition the mandible.

There were no cases of flap failure, or return to theater for issues of vascular compromise. Of the 6 patients who had post-operative infections, 2 had received pre-operative radiotherapy (Cases 17 and 18), 3 had adjuvant radiotherapy (Cases 11, 14, and 16), and 1 had no history of radiotherapy (Case 24). The latter patient had osteopetrosis, and so plate infection and exposure was more likely. There were no cases of significant plate/prosthesis related complications in the patients who had reconstruction for osteoradionecrosis (Cases 4, 6, 19 and 22).

Four patients with infection required removal of the prosthetic condylar head (4/25). All of these patients had experienced infection that communicated with the prosthesis. It is notable that the infections resolved in all of these cases by removal of the temporary prosthesis alone, not necessitating removal of the whole reconstruction plate. One case (case 11) also showed radiographic signs of erosion of the condylar head through the glenoid fossa of the temporal bone at 4 years post-surgery (Fig. 3). This was the only case where the articular disk was removed during the resection. Three of the four cases were in patients who underwent double flap reconstruction, three of the four cases had type 1 reconstructions. There were 2 cases of delayed facial nerve palsy, with both believed to be related to the direct contact of the prosthesis with the facial nerve. In both of these cases the prosthetic head was removed. The facial nerves did not recover post-removal. There were no cases with evidence of heterotopic bone formation, and no cases of ankylosis.

Fig. 3.

Coronal CT scan demonstrating perforation of the glenoid fossa by the condylar prosthesis at 4 years post-reconstruction

Functional Outcomes and Rehabilitation

The Functional Intraoral Glasgow Scale findings showed a mean total score of 12.7, for 18 cases who were able to be contacted and were happy to complete the questionnaire (Table 4). Four patients underwent placement of osseointegrated dental implants and prosthetic rehabilitation, with evidence of good balanced occlusions. In dentate patients, occlusal control with IMF and accurate vertical ascending ramus height reconstruction led to a balanced occlusion in all but two patients.

Table 4.

Post-operative nutritional, functional, rehabilitation outcomes and follow up time

Case	Nutritional route	Functional Intraoral Glasgow Scale Scores			Post op mouth opening (mm)	Post op occlusion	Oral rehabilitation (implants)	Total postoperative follow up (months)
		Speech	Chewing	Swallowing
1	Oral	5	3	5	20	Balanced	Y	90
2	Oral	5	4	4	30	Balanced	N	146
3	Oral	4	5	4	30	Balanced	N	42
4	Oral	–	–	–	10	Balanced	N	32
5	Oral	–	–	–	20	Right slight open bite	N	64
6	Oral	–	–	–	30	–	N	26
7	Oral	4	3	3		Edentulous	N	86
8	Oral	–	–	–	0	–	N	32
9	Oral	–	–	–	30	–	N	46
10	Oral	–	–	–	35	–	N	24
11	Oral	5	4	5	–	Edentulous	N	75
12	Oral	5	4	5	30	Balanced	N	44
13	Oral	4	5	4	30	Balanced	N	29
14	Oral	5	5	5	30	Balanced	N	33
15	Oral + G	4	3	3	25	Balanced	N	25
16	Oral	4	4	4	25	Occlusion deranged	N	27
17	PEG	3	2	2		Balanced	Y	63
18	Oral + G	3	2	2	30	Balanced	N	27
19	Oral	5	5	5	30	Balanced	N	27
20	Oral	5	5	5	24	Balanced	N	25
21	Oral	4	–	2		Edentulous	N	28
22	Oral	5	3	3	35	Balanced	Y	36
23	Oral	5	4	3	30	Balanced	N	53
24	Oral + PEG	5	3	3	20	Balanced	N	56
25	Oral	5	4	3	40	Edentulous	Y	54

G Gastrostomy, PEG Percutaneous endoscopic gastrostomy

Discussion

In the setting of malignant neoplastic disease, or irradiated patients, reconstructive options for disarticulation defects pose a significant challenge for the reconstructive surgeon. The options available depend on several factors including the extent of resection, predicted survival, state of dentition and occlusion, economic factors, and surgeon preference. The options that exist are as follows:

First, leave the mandible to ‘swing’ without reconstructing the TMJ. This has the advantage of simplicity and low surgical complication rates, but with large defects, significant functional impairment is likely, with malocclusion, facial asymmetry, and difficulty with chewing and swallowing.

The second option is the use of condylar prosthesis alone to replace the resected condyle. This approach has been shown to preserve facial symmetry, maintain occlusion, and with good case selection may have good short to medium term outcomes[8, 9], but is prone to complications. Key complications from prosthetic condylar replacement only include infection, plate exposure, glenoid fossa perforation, facial nerve injury, and hypertrophic bone formation [10]. Additionally, the condylar attachments to reconstruction plates that are available in the market are currently approved as temporary devices only (TMCRP, 21 CFR 872.4770), for a period of up to 24 months until definitive TMJ reconstruction is performed. However, apart from a formal total joint replacement, there are no rapidly available prosthetic alternatives to this temporary prosthesis.

The third option is direct bony microvascular replacement (Autogenous) of the condyle and ramus which is regarded the gold standard. With the development of microvascular reconstruction techniques, options for reconstruction with autologous bone include the fibula, DCIA (Deep circumflex iliac artery), scapula, second metatarsal-phalangeal joints, and lateral femoral condyle free flaps [11–15]. In the setting of ablative surgery, the fibula free flap has most commonly been used. The main advantage of the fibula is its length allowing for condylar replacement at the same time as potentially angle to angle mandibular reconstruction. Using the fibula alone as a condylar replacement secured to a reconstruction plate achieves similar functional results to a prosthetic condyle, although occlusal control may be more difficult [4, 10, 16, 17]. Although it is the gold standard, it is also associated with significant complications including displacement, ankylosis and malocclusion due to difficulty controlling the occlusion [4, 5, 18, 19]. Additionally, alternative options are needed where a bony free flap of adequate length such as a fibula is not a viable options due to peripheral vascular disease, or vascular anomalies (which was the case in 4 of our patients who underwent scapula reconstructions instead).

A fourth option includes combining the use of prosthetic condyles with microvascular techniques as presented in this series. With the use of virtual planning, a bony free flap secured to the plate along the ascending ramus with a prosthetic condylar component can allow accurate control of vertical ramus height. The main advantage over autologous reconstruction alone is that the prosthetic condyle reduces the risk of ankylosis and heterotopic bone formation, and improves vertical control of the neo-ascending ramus, in turn achieving better control of the post-operative occlusion and hence functional improvement. Few studies have evaluated the use of concurrent free flaps and prosthetic condylar replacements. Bredell et al. reported a series of 15 patients who had condylar reconstruction, among whom 4 had fibula free flaps with metal condylar replacements [10]. These patients had comparable outcomes to those who had autogenous reconstructions extending to the glenoid fossa. These findings are consistent with findings in some recent studies, where condylar prostheses and reconstruction plates with concurrent bony free flap reconstruction including the ascending ramus (type 3), have shown good short to medium-term outcomes [6, 20]. Similar to our findings, the best outcomes with reduced complications were observed when bony reconstruction extended up the ascending ramus. Results are likely to improve with improving technology, with recent studies showing good results when employing virtual planning with CAD-CAM techniques with accurate printed anatomic condyles and accurate ramus height restoration [6, 20]. 3D printing the reconstruction plate with the condylar segment as part of the reconstruction plate would be the ideal way to perform this technique without using the temporary condylar prosthesis currently available.

The authors do not advocate this technique for all cases with mandibular disarticulation, but present it as a viable option that can be considered with appropriate case selection. All of those with significant condylar prosthesis related infections and complications occurred in our series were in malignant cases. Hence, we would caution its use in malignant cases. It can be considered a viable option however in patients where alternative autologous options are not available, and those with a poor prognosis and unlikely long term survival. In our cohort, very challenging cases were managed with this technique with a sustainable functional outcome (see Table 1 and 4). Several of the malignant cases were advanced malignant tumors or high grade recurrences with poor long term expected survival and prognosis (patients 9, 11, 13, 14, 15, 17, 18, 20, 21, 23, 25). Additionally, several of the non malignant cases had no alternative option apart from resection and leaving the mandible to swing such as patient 8 with advanced myositis ossificans and bisphosphonate induced osteonecrosis, and patient 24 who had osteopetrosis since birth who was miserably suffering from chronic osteomyelitis. Resecting the infected side of her mandible and reconstructing her with a reconstruction plate with a prosthetic condyle gave her good function, and significant symptomatic improvement.

In the rare cases where large multi-subunit resections are required necessitating more than one concurrent free flap to reconstruct the defect, having a prosthesis seems to be a recipe for infection and ultimately the need for prosthesis removal. The likely explanation for the increased risk of infection in all of these cases is the amount of dead space around the prosthesis. The dead space fills with haematoma or seroma, an environment highly conducive to bacterial proliferation and resultant infection, especially in the presence of a prosthesis and saliva. The risk seems higher when the prosthesis and reconstruction plate are located between two microvascular free flaps. Special attention should be given to eliminating this dead space with vascularized tissue, either by extending the bony reconstruction (with its associated muscular tissue) as high up the ascending ramus as possible, or using a soft tissue flap (local or distant) to wrap the prosthesis and plate and eliminate the dead space.

Radiotherapy is a relative contraindication for prosthetic condylar reconstruction [10], and post-operative radiotherapy in malignant cases appears to increase the risk of prosthetic infection. However, unexpectedly, it is notable how few complications arose from our cases who underwent prosthetic condylar reconstruction for osteoradionecrosis. The 4 patients in this series all had good outcomes. None had undergone previous mandibular or oral cavity resections, allowing us to preserve the surrounding soft tissue, including the pterygomasseteric sling and the articular disk. This may explain the good outcomes seen in these cases.

Rare complications of prosthetic condyle replacement such as perforation of the glenoid fossa and facial nerve palsy need to also be discussed. Perforation of the temporal bone is a known complication of prosthetic condylar prostheses [3, 8, 9]. Several factors appear to contribute to the risk of glenoid fossa perforation including radiotherapy, articular disk removal and lack of posterior occlusal support [21]. Conversely, more anatomically accurate prostheses may reduce the risk. Virtual planning and CAD-CAM condylar prostheses designed to the mirrored condylar shape with accurate ramus height reconstruction led to better pressure distribution, and avoided maladaptive biodynamic changes to the glenoid fossa and residual joint components as demonstrated by a team in Bologna, Italy [6]. Ipsilateral posterior occlusal support may also reduce vertical condylar pressure on the glenoid fossa from unopposed masticatory forces. Preservation of the articular disk is also critical [9, 20, 21]. In our series, one patient developed a late perforation into the middle cranial fossa following two flap reconstruction for a large mandibular SCC, and was the only patient in our cohort whose resection included the articular disk at the time of resection. She had post-operative adjuvant chemo-radiotherapy, and suffered from recurrent infections. At 4 years after surgery, CT imaging demonstrated perforation of the prosthesis through the glenoid fossa. The prosthesis was removed without complication. Careful case selection and pre-operative planning is needed to reduce the risk of glenoid fossa perforation. A glenoid fossa prosthetic component could be considered for the prosthetic head to not directly contact the bone of the glenoid fossa. This should be seriously considered in cases where the articular disk is sacrificed in the resection.

Facial nerve injury in patients with prosthetic condylar replacements have also been reported [3, 10], and occurred in 2 of our patients. Both had radiotherapy and recurrent infections associated with the condylar prosthesis. The cause remains unknown, but is likely related to direct nerve contact with the prosthesis. Removal of the prosthesis did not to result in recovery. Inadequate soft tissue separating the condylar prosthesis from the nerve is the most likely contributing factor to facial nerve damage. In our series, facial nerve injury never occurred with type 3 reconstructions, likely because of the generous soft tissue and muscle bulk wrapped around the plate and prosthetic condyle. If a bony reconstruction is not concurrently performed, soft tissue interposition could be achieved with tissue from a vascularized soft tissue flap used, or from partial temporalis transposition flap secured around the neck of the condyle.

Functional outcomes in our cohort demonstrate good occlusal and oral intake outcomes. The results of the Functional Intraoral Glasgow score showed comparable results to fibula only reconstructions in patients with benign disease[16]. All patients maintained intelligible speech, and most were able to chew adequately. Chronic swallow dysfunction was secondary to post-operative radiotherapy. Patients who required removal of the condylar prosthesis had the worst functional outcomes. The following recommendations can be made from our experience to achieve good functional outcomes.

• Where dental rehabilitation is considered, we recommend waiting for 12 months following reconstruction to allow for stabilisation of the anteroposterior and vertical position of the mandible prior to planning and insertion of implants.

• Occlusion and condylar position can be controlled with the following:

  • Suspensory sutures or fascial sling from the reconstruction plate to the articular disk and residual joint tissue, or to the zygomatic arch.
  • For dentate patients, intermaxillary fixation intra-operatively and elastic support post-operatively for 6 weeks will guide a balanced post-operative occlusion.
  • Where pterygomasseteric sling muscles are preserved, resuspend the sling during closure, suturing the muscles to the plate or fibula.

The key limitation of this paper is the retrospective nature of the study, the heterogeneity of conditions included, and the small sample size. However, what differentiates this report from others is that it includes a large number of malignant cases, and it demonstrates the potential role of combined prosthetic condyles with microvascular reconstruction to achieve good functional outcomes in both malignant and benign cases. The authors, where possible, prefer autogenous reconstruction alone for disarticulation defects without a prosthetic condyle. However, we believe that the future of reconstruction of disarticulation defects may lie in the use of total joint reconstruction (fossa and condylar components), which has developed rapidly over the years for advanced internal derangement or arthritic conditions of the TMJ with evidence of long term success [22]. Acceptable results have been demonstrated with their use for mandibular disarticulation defects in benign disease [2, 10]. However, in the setting of malignant disease, there is a lack of evidence to demonstrate safety in the setting of radiotherapy, uncertainty regarding the positional stability after significant soft tissue resection, and significant time delays to design and production of a total joint prosthesis making it not suitable for malignant cases. Further development and more rapid CAD-CAM is required before total prosthetic joint replacement can be considered routine in malignant ablative mandibular defects.

Conclusion

Prosthetic condylar reconstruction with concurrent microvascular reconstruction is a viable option for reconstruction of disarticulation defects of the mandible with good functional outcomes in challenging cases. Complications are more commonly encountered in reconstructions for malignant cases. Improved outcomes are experienced when vascularized bony reconstruction extending up the ascending ramus with the plate is used (type 3), and the reconstruction is virtually planned to facilitate accurate vertical height restoration. Careful attention to occlusal factors and vertical support of the reconstruction plate can lead to good functional outcomes. Prosthetic condyles should be avoided in patients where the articular disk is removed, and in double flap patients where a significant dead space around the prosthesis is expected.

Funding

No funding was acquired for this project.

Declarations

Conflict of interest

There are no conflicts of interest to report.

Ethical Approval

Approval for this audit was given by the Queen Elizabeth Hospital ethics committee—Approval Number CARMS-00091.