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Alloplastic Total Joint Replacement: AManagement Option in TemporomandibularJoint Condylar ResorptionLouis G. Mercuri

A variety of options have been proposed for the surgical management of

temporomandibular joint (TMJ) idiopathic/progressive condylar resorption

(ICR/PCR) cases in the past. Various developments in understanding the

molecular biology of the TMJ and the postulated role of estrogen in bone

biology have led to a proposed pathophysiology model for ICR/PCR of the

TMJ, which is also based on the established orthopedic bone biology re-

modeling/resorption paradigm. Therefore, a critical review of the ICR/PCR

and TMJ total alloplastic joint replacement surgery literature, as well as the

author’s experience, suggests that TMJ total alloplastic joint replacement

can provide enhanced long-term surgical outcomes in the management of

end-stage ICR/PCR pathology. (Semin Orthod 2013;19:116-126.) © 2013

Elsevier Inc. All rights reserved.

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I diopathic condylar resorption (ICR), alsoknown as progressive condylar resorption

PCR), has been described by Arnett et al1-3 as asevere form of dysfunctional remodeling of thetemporomandibular joint (TMJ). It is mani-fested radiographically and clinically by decreasein condylar head volume, decreased ramusheight, and either progressive mandibular retru-sion in the adult or decreased mandibulargrowth in the juvenile. Some cases of this diseasecan begin spontaneously, but patients undergo-ing orthodontic treatment and/or orthognathicsurgery can also develop ICR/PCR, resulting inocclusal instability, maxillomandibular skeletalmalrelationships, TMJ dysfunction, and pain.4

A variety of surgical management options forICR/PCR cases have been proposed and at-tempted in the past. They include distractionosteogenesis,5 orthognathic surgery,6 combined

Professor of Surgery, Division of Oral and Maxillofacial Surgery,Loyola University Medical Center, Maywood, IL (Retired); and Clini-al Consultant, TMJ Concepts, Ventura, CA.

Address correspondence to Louis G. Mercuri, DDS, MS, TMJoncepts, 2233 Knoll Drive, Ventura, CA 93003. E-mail: lgm@

mjconcepts.com© 2013 Elsevier Inc. All rights reserved.1073-8746/13/1902-0$30.00/0

mhttp://dx.doi.org/10.1053/j.sodo.2012.11.007

116 Seminars in Orthodontics, Vol 19, N

orthognathic and TMJ disk repositioning sur-gery,4,7 total TMJ reconstruction with autoge-

ous tissue grafts,8 and TMJ total alloplastic jointreplacement (TMJ TJR) with alloplastic materi-als.9,10 This article will discuss the potential rolefor TMJ TJR in the management of this condi-tion. An analytical review of the scientific andclinical literature (given later in the text), as wellas the author’s experience in dealing with thesecases, suggests that TMJ TJR may deliver en-hanced long-term surgical outcomes in the man-agement of end-stage ICR/PCR pathology.

Pathophysiology of ICR/PCR—CurrentConcepts

Arnett et al1-3 postulate that the pathophysiologyf this condition may be due to dysfunctionalrticular remodeling resulting from excessive orustained physical stress to the TMJ articulartructures that exceeds normal adaptive capac-ty, or a decreased adaptive capacity of the artic-lating structures of the joint (refer to the articley Arnett and Gunson in this issue of Seminars).

The cellular basis of the modeling and re-odeling cycle was described by Frost, who

amed this physiological relationship the basic

ulticellular unit (BMU).11,12 The BMU de-

o 2 (June), 2013: pp 116-126

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117Alloplastic Total Joint Replacement

scribes the sequential activities of osteoclasts andosteoblasts that are spatially and temporally cou-pled to ensure that the removal of mineralizedmatrix is replaced by an equivalent quantity ofnew bone.13,14 Thus, over innumerable remod-ling cycles, the collective activities of individualMUs ensure that an organism’s bone mass re-ains in constant structural and metabolic bal-

nce, thereby maintaining its skeletal architec-ure relatively unchanged.15-17 Based on these

facts, it has been established that functionalloading of the articular surfaces of normal bonebeyond the capacity of the BMU to remodel willlead to breakdown of the articular cartilage andunderlying bone. Such changes will then be-come manifested clinically as pain, dysfunction,and skeletal malrelationships.

Milam and Schmitz18 applied a similar boneresponse model to the TMJ. They state that me-chanical stress on the TMJ can induce metabolicresponses in TMJ articular tissues that lead toadaptive remodeling. These responses allow af-fected joint tissues to maintain efficient functionin the presence of changing functional loads.However, adaptive TMJ mechanisms can be ad-versely affected by factors such as age, previoustrauma, enhanced sympathetic tone, and hor-mones, which can then lead to compromisedlocal tissue nutrition resulting in impaired cellu-lar function and ultimately tissue damage.

Arnett et al2 and Gunson et al19 discuss theeffect of concomitant endocrine and immunerelated systemic disorders that can affect bonegrowth, maturation, and remodeling. These fac-tors can lead to a decreased adaptive capacity ofthe articulating components of the TMJ. Owingto the female demographic bias in TMJ disor-ders and postmenopausal osteoporosis, the ef-fect of sex hormones, specifically estrogen, onTMJ disorders and bone resorption in the gen-eral skeleton has been studied extensively.20-24

Animal studies have implicated estrogen as apotential mediator of degraded TMJ remodel-ing, decreased bone volume, and osteophyte for-mation.25,26 Puri et al27 studied the estrogeneceptor-alpha (ER-�) protein content in theMJ in vivo. They found an increased number ofells expressing ER-�, measured in 17�-estrad-

iol–treated rats after TMJ inflammation was in-duced; 17�-estradiol is the predominant estro-en during reproductive years both in terms of

bsolute serum levels as well as in terms of es- “

rogenic activity. These investigators concludedhat inflammation and 17�-estradiol can modu-

late ER-� expression in the TMJ and that theseffects were tissue specific.

Based on Frost’s BMU paradigm, it has beenheorized that there is a mediator mechanism inancellous bone that senses estrogen. In re-ponse to estrogen, the normal physiologicalodeling and remodeling process occurs as the

esult of normal joint loading and function.owever, in the face of estrogen deficiency, that

one maintenance process would switch to adisuse mode,” resulting in expanded marrowavities, thinning cortices, and reduced trabecu-ar bone mass. The result of these changes is lossf joint articular architecture and the loss of thebility of the remaining articulation to withstandhe normal functional demands placed on it.his would manifest clinically as pain, dysfunc-

ion, and deformity, and on imaging as jointurface degeneration.28 The exact role estrogen

plays in ICR/PCR has yet to be elucidated, butits role in degeneration of other joints may pro-vide a working hypothesis for further study ofthis pathology in the TMJ.

Incidence of Relapse After Reoperationfor ICR After Orthognathic Surgery

Huang and Ross29 evaluated 28 adult patientsho had developed ICR 2 years after orthog-athic surgery. After condylectomy, 22 of theseatients were reconstructed with autogenousostochondral grafting (n � 5) or orthognathicurgery (n � 18). One patient initially had or-hognathic surgery and subsequently underwentondylectomy and costochondral grafting, mak-ng a total of 23 procedures on 22 patients. Ofhe 18 patients who underwent orthognathicurgery, 4 (22%) developed a recurrence ofCR, whereas 4 others developed TMJ symp-oms. Therefore, 8 of 18 (45%) ICR patients hadnsatisfactory results after orthognathic surgery.

Merkx and Van Damme30 retrospectively re-orted finding signs and symptoms of ICR in 8f 329 (2%) sagittal split osteotomy (SSO) pa-ients. All four patients who underwent SSO re-peration had unsatisfactory esthetic and occlu-al results (100%). The other 4 who receivednly orthodontics and/or prosthetic therapyere reported to have functional occlusions and

tolerable” TMJ complaints.

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Crawford et al31 reported the reoperation re-ults of 7 post-SSO advancement osteotomy ICRatients. All underwent SSO advancement os-

eotomy reoperation. Five (71%) developedCR again, and 1 showed further PCR after a

hird SSO advancement osteotomy.Hoppenreijs et al32 evaluated 26 patients who

eveloped ICR, 19 after bilateral SSO advance-ent and 7 after bimaxillary surgery. Thirteen

atients (50%) received nonsurgical manage-ent (orthotics, orthodontics, restorative den-

istry). Their results were considered satisfac-ory, but with dental compensations, as only 323%) maintained Class I occlusions. The other3 patients (50%) underwent a second orthog-athic surgery. Four of them (31%) had a 40%-0% skeletal relapse; 2 (15%) had 120% and00% relapse, respectively, and required a thirdrthognathic surgical procedure. One of theseatients had a 30% relapse and the other had00% relapse after the third surgery.

Morales-Ryan et al7 followed 44 ICR patientsfor 37 months. Ten of them (23%) had under-gone bimaxillary orthognathic surgery but noTMJ surgery, and all of them had statisticallysignificant relapse owing to PCR.

Borstlap et al33 reported a 2-year prospectivestudy of 222 patients who underwent SSO ad-vancement with rigid internal fixation (RIF).Eight patients (4%) developed PCR postopera-tively. The data revealed that in their cohort,patients undergoing this treatment at a youngage (�14 years) appeared to be more at risk forthe occurrence of condylar alterations and PCR.A steep mandibular plane angle and low facialheight ratio (posterior:anterior) were signifi-cantly related to the occurrence of condylar al-terations. They also noted that the appearanceof TMJ sounds in the first few months postoper-atively were highly correlated to future condylechanges and temporomandibular joint disorders(TMD).

The contribution of maxillomandibular os-teotomy stabilization and fixation and their rolesin the development of ICR/PCR have also beenconsidered. Ellis and Hinton34 studied the his-ologic effects of RIF after mandibular advance-

ent on the TMJ of the adult Macaca mulattaonkey. They reported finding that alteration

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119Alloplastic Total Joint Replacement

different stresses and strains suddenly being im-posed on the condyle.

Suuronen et al35 compared the TMJ condylesof osteotomized sheep mandibular condylarnecks with and without screw RIF over 24 weekswithout maxillomandibular fixation (MMF). Ra-diographically and histologically, they foundbony destruction, osteophytes, and flattening ofthe condylar heads on the RIF sides. They con-cluded that RIF without MMF might result indegenerative joint disease.

Clinical studies have questioned the role ofremodeling or degenerative changes in pos-torthognathic surgical relapse.36,37 Kersey et al38

reviewed the literature on TMJ morphologychanges after SSO advancement with RIF. Theyconcluded that the norms for condylar and fossaremodeling as well as changes in TMJ disk posi-tion and morphology have not been established,and in addition, the changes in condylar posi-tion present with individual variability; conse-quently, there is a need for further research inthis area.

Van Strijen et al39 reported a case of ICR 1year after distraction osteogenesis to advancethe mandible in a 15-year-old male patient. Thiscase report is complicated by the fact that therewas associated postdistraction trauma in this pa-tient. However, as osteoclastic activity in the TMJhas been reported after gradual distraction of themandible, distraction osteogenesis may make its

Figure 1. Preoperative phot

own contribution to ICR.40,41 The authors39 sug-est that in the future, patients being consideredor surgical management of mandibular hyp-plasia be critically evaluated for any traumatic,unctional, or metabolic risk factors for ICR.

Rationale for the Use of TMJ TJR in theSurgical Management of End-StageICR/PCR

End-stage disease is the worst condition of anorgan or disease state; at this point, the organ isbarely functioning. Examples include end-stagekidney disease, where the kidneys have shutdown and the patient requires dialysis, or end-stage cardiac disease, where the heart is func-tioning poorly and may need mechanical sup-port or transplantation for the patient to survive.Applying this term to joints, end-stage diseaseconnotes a joint that is so negatively affectedarchitecturally by disease or injury that it resultsin a severe functional impairment to the patient.For the ICR/PCR patient, the local adaptive ca-pacity of the TMJ condyle BMU has been me-chanically and biologically tested in vivo, and ithas failed. This failure is demonstrated by theload-compromised bony architecture havingend-stage pathologic changes as seen on imag-ing, and clinically, it is manifested in the pa-tient’s signs and symptoms.

os (2005)—patient SC.

120 Mercuri

Long-term successful outcomes for both non-surgical and surgical ICR/PCR management op-tions ultimately rely on the stability and strengthof pathologically altered local TMJ articular andsoft-tissue elements. In cases where a surgeonselects costochondral grafting, orthognathic sur-gery, or distraction osteogenesis, the long-termoutcomes rely on the ability of an avascular graftor an end-stage diseased condylar remnant towithstand potentially greater loads and func-tional forces. All this is complicated by not know-ing whether that end-stage diseased TMJ willadapt despite what is possibly a local manifesta-tion of systemic pathology.

Placing already functional load compromisedarticular bone into a mechanically stressful en-vironment may account for the less than satisfac-tory outcomes cited with orthognathic surgery,distraction osteogenesis, and autogenous tissue

Figure 2. SC: occlusion preoperative (2005).

replacement surgical options. This kind of me-

chanically and biologically unfavorable environ-ment can occur as a result of many factors thatare inherent in various surgical procedures. Forexample, it is well known that reorientation ofpositional, muscular, and/or RIF loading forcesinvariably occurs after orthognathic and/or dis-traction surgical manipulation of the maxillofa-cial skeleton, and also after autogenous TMJreconstruction. Therefore, an ICR/PCR man-agement option that is not dependent on thecompromised mechanical and biological adap-tive capacity of the TMJ and surrounding tissuesshould be considered.

TJR, because it is a biomechanical rather thanbiological solution to the management of jointsthat are anatomically distorted, end-stage dis-eased, and dysfunctional, provides such an op-tion. It has been recognized for decades thatwithout TJR for the management of end-stagejoint disease, the modern practice of orthopedicsurgery would be inconceivable. TMJ TJR has

Figure 3. SC: right and left temporomandibular joint(TMJ) coronal computed tomography scan images

preoperatively (2005).

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121Alloplastic Total Joint Replacement

similarly been demonstrated to be a long-termsafe and effective option for the reconstructivemaxillofacial surgeon managing end-stage TMJdisease.42

The goals of any TMJ replacement, whetherautogenous or alloplastic, are to (1) improvemandibular function and form, (2) reduce suf-fering and disability, (3) contain excessive treat-ment and cost, and (4) prevent morbidity.43 TMJ

JR as a management option for end-stage ICR/CR meets all of them.

The advantages of TMJ TJR are as follows: (1)hysical therapy can begin immediately; (2)

here is no need for a secondary donor site andecreased surgery time; and (3) they are able toimic normal anatomy.42 In the ICR/PCR pa-

ient, there is the added advantage that the ma-erials from which these devices are constructedre not susceptible to the pathophysiology of theisease process.

Autogenous tissue TMJ replacement involvesarvesting an avascular free bone graft (rib),

Figure 4. Left TMJ Concepts (Ventura, CA) patient-fit

surgery.

sing RIF to fixate and stabilize it against theost ramus, cortex to cortex. MMF is requiredhile the free graft vascularizes and integrates

nto the host bone and surrounding soft tissues.eitzik43 reported that despite ideal healing cir-umstances, the return to full-strength cortex-to-ortex healing took 20 weeks in a monkey; there-ore, he postulated it would probably require 25eeks in man. This would rule out early masti-atory muscle rehabilitation, because any graft-o-host-bone mobility leads to graft failure.44

Long-term functional immobility is contraryto all the principles of physical rehabilitationafter joint surgery of any kind. Salter45 unambig-

ously demonstrated with his continuous passiveotion theory that early active physical therapy

fter orthopedic joint surgery is essential foruccessful long-term improved functional out-omes. Early physical therapy after conventionalurgical procedures can lead to mechanicallynfavorable stresses and strains on the host boneMU in the compromised biological environ-

custom) fossa and ramal components at implantation

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122 Mercuri

ment, resulting in failure and relapse in ICR/PCR cases. In contrast, TMJ TJR, because of itsinherent immediate fixation stability, permitsimmediate startup of active physical therapy,leading to improved long-term functional out-comes.46

Patient-fitted (custom) TMJ TJR fossa and ra-mus (condyle) components are designed andmanufactured from a stereolaser model gener-ated from the patient’s computed tomographyscan data to mimic the normal anatomical con-tours of the structures they are intended to re-place. At implantation, these TMJ TJR compo-nents are adapted and fixed in a stable and closemanner to the bony surfaces of the temporalbone and mandibular ramus.9,47

There is always a component of counterclock-wise mandibular rotation in the surgical man-agement of ICR/PCR. This fact has negativeimplications for the outcome of most traditionalICR/PCR treatments, as one cannot predictablyexpect an avascular autogenous rib graft or acompromised condyloid process to withstandthe muscle and other soft-tissue forces gener-ated in these new anatomic relationships. Underfunctional loading in the short term as well asthe long-term, there is a significant potential forrelapse if one considers the effects of muscleforces on bone.48 However, the long-term stabil-ity using a customized patient-fitted TMJ TJR insuch cases is well documented.49-52

Figure 5. SC: postopera

The relative disadvantages of TMJ TJR are (1)cost of the device, (2) material wear and failure,(3) limited longevity, and (4) that alloplasticimplants will not follow a patient’s growth.42

Considering the young average age of ICR/PCRpatients, longevity of any TMJ TJR must be animportant consideration. Because this is a bio-mechanical rather than a biological solution,future planning for revision surgery to removescar tissue from the articulating components ofthe implant, or even replacement of the implantover time owing to material wear and/or failure,may be required. At present, patients are advisedthat these devices may have a functional life spanof 10-15 years based on the orthopedic experi-ence in total joint arthroplasty53 and recent TMJ

JR long-term outcomes results.9,42,46,47,54-62

In orthopedics, advancement in surgical tech-niques, implant materials, and designs has led toexcellent long-term function and quality-of-lifeimprovement results. Total joint replacementsurvival rates of other joints exceeding 90% after10 years in younger patients have been re-ported.63,64 Therefore, orthopedists are no lon-ger deterred from replacing end-stage diseasedjoints in younger patients to provide these pa-tients with an improved function and quality oflife. The same consideration should be given toICR/PCR patients when making the decision forhow to manage the skeletal consequences oftheir end-stage TMJ disease process.

tive photos (2012).

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123Alloplastic Total Joint Replacement

When calculating cost, it is critical that notonly is the cost of the device considered, but alsoall factors associated with its implantation. Themajor advantage of TMJ TJR over autogenousreconstruction is that there is no need for asecondary surgical donor site (rib). Donor sitemorbidity is therefore eliminated, as are the ex-penses associated with prolonged intraoperativeand postoperative hospitalization stretches.Therefore, although these devices may be con-sidered expensive, the relative cost involved withTMJ TJR overall is either equal to or eventuallyless than autogenous reconstruction.

Cases Managed by the Author

Between 1985 and 2010, 14 ICR/PCR patients pre-sented to the author for management (Table 1).All were female and were 13-34 years old (meanage � 23.4 years, standard deviation �7.1 years).

t their initial visit, all of them had a history,linical characteristics, and imaging characteristicsf ICR/PCR, and they also had negative rheuma-oid factor serology results. All but one (YF) wereaking oral contraceptive pills either to control

enstrual dysfunction or prevent conception. Theetails of one case are as follows:

SC, a 29-year-old Native American woman, pre-ented for consultation in 2005 with chief com-laints of increasing bilateral TMJ pain andysfunction, headaches, progressive mandibularetrusion, and developing anterior open bite overhe past 16 months (Figs 1 and 2). Maximal incisalpening was 15 mm. She denied any history ofrevious orthodontics, arthritic disease, micro- oracro-mandibular trauma, previous TMD symp-

oms, clenching, or bruxism. A review of systemsas unremarkable except for a history of dysmen-rrhea managed by oral contraceptive pills. Rheu-atoid factor and serology results were negative.Computed tomography scan imaging revealed

ilateral severe end-stage degenerative condylarhanges (Fig 3). A working diagnosis of ICR/PCRas made, and she was prepared for TMJ TJRsing the TMJ Concepts (Ventura, CA) patient-tted (custom) system. Articulated study modelsevealed that a good occlusion could be estab-ished at surgery by autorotation of the mandiblend placement of the TMJ TJR devices withoutreimplantation orthodontia.

In 2006, SC underwent uneventful bilateral

MJ TJR (Fig 4). After implantation, she has d

onsistently reported no further TMJ pain oreadaches. At routine yearly follow-up appoint-ents, she has maintained a stable, repeatable,

nd functional occlusion since having the TMJJR surgery (Figs 5 and 6). Maximal incisalpening was 38 mm at 6 years after implanta-ion. Six years postimplantation imaging (Fig 7)

Figure 6. SC: occlusion postoperatively (2012).

emonstrates excellent integration of the fixa-

124 Mercuri

tion screws, no evidence of osteolysis around thefossa or ramus/condyle components, and ac-ceptable facial esthetics.

Conclusion

By combining the pathophysiologic mecha-nisms of ICR/PCR with the reported outcomesof past surgical procedures for treating thatcondition, the frequent failure of those proce-dures is now better understood. Because it isunlikely that altering those traditional proce-dures will do much to change the predictabil-ity of outcomes, the use of TMJ TJR shouldbe considered as a feasible choice. This isespecially true if there has already been oneor more recurrences of ICR/PCR in a casetreated by either orthognathic or autogenousreplacement surgery. Although the track re-cord for TMJ TJR is shorter than that for otherjoints, the same general principles apply;therefore, TMJ surgeons should consider us-ing the new technologies of custom design andload-bearing materials that can be obtainedwith current TMJ TJR systems.

Future investigative efforts must include morestudies about the role of 17�-estradiol and theassociated cytokines in ICR/PCR. Furthermore,

Figure 7. SC: posterior-anterior and lateral cephalommolecular-weight polyethylene component of the titacomponent is not radiopaque.

long-term prospective studies should be devel-

oped to evaluate outcomes with all nonsurgicaland surgical management options for the man-agement of ICR/PCR.

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