J Oral
Maxillofac
49442443,
Surg
1991
KEEPING AN EYE ON THE
OCULOCARDIAC REFLEX To the Editor:-1 recently read the article “Oculocardisc Reflex During Treatment of an Orbital Blowout Fracture” (J Oral Maxillofac Surg 47:522, 1989). We have found a 25% incidence (25 of 100 patients) of the oculocardiac reflex (OCR) occurring during esthetic blepharoplasty surgery, and reported this.’ Indeed, the OCR is a ubiquitous reflex that may occur during a variety of stimulatory events on or around the globe.* It is incumbent upon the practitioner to be aware of this reflex and monitor all patients undergoing eye surgery. In our series of 100 patients, we found that cessation of the stimulus was adequate to reverse the condition in the majority of patients. However, the possibility of emergency intervention does exist. The OCR is a well-documented complication of eye muscle surgery with which anesthesiologists and ophthalmologists are familiar. It is now evident that it occurs in an eclectic array of situations and everyone operating in the region needs to be aware of this potentially serious condition. ALAN MATARASSO,MD, FACS New York, New York
References 1. Matarasso A: The OCR in blepharoplasty. Plast Reconstr Surg 83~243,1989 2. Anderson RL: The blepharocardiac reflex. Arch Ophthalmol%:1418, 1978 AN IMPORTANT LESSON ABOUT BIOMATERIALS
IN THE TMJ To the Editor:-Silicone rubber and Proplast (Vitek Inc, Houston, TX) II sheeting were advocated as disc replacements by numerous clinicians at the 1982 AAOMS Clinical Congress on TMJ disorders. These materials had previously been used as condylar caps with few problems. However, since 1985, an increasing number of clinical and animal studies have reported biomechanical failure, with microscopic wear debris causing a macrophage and foreign-body giant cell reaction asso-
ciated with pain, bone resorption, hypomobility, and malocclusion. What went wrong; why was there such a stampede towards the use of these devices by the profession from 1982 to 1986? Did clinicians understand the biomechanics of the TMJ? Were clinicians knowledgeable about the testing procedures required of manufacturers by the Food and Drug Administration (FDA) before devices could be marketed? Based on recent information obtained as a result of the FDA Freedom of Information Act, the answer is probably no to all of the above. Surgeons were not satisfied with 15% to 20% disc repair failure in the early 1980s and began to excise and replace the disc with devices known to be biocompatible in nonloaded anatomical sites. Early reports were gratifying and the leap to an alloplastic TMJ disc device was fast. However, biomechanical device failures reported at the 1986 annual AAOMS Meeting slowed this trend, and today the use of alloplastic permanent disc replacement has nearly stopped. Controversy surrounds the issue of TMJ loading. Is the TMJ a load-bearing joint or not? This issue is critical to the design and laboratory testing of a device for this joint; and to be safe, the biomedical engineer must assume that the joint is loaded. Our recent wear testing of Vitek’s implant, using a TMJ simulator at a 20-lb load, produced rapid failure rates. Had Vitek tested the implant under these conditions, it might not have marketed a TMJ disc replacement. Oral and maxillofacial surgeons are not adequately trained in joint biomechanics, material behavior, and device performance. They must rely on the validity of results from the manufacturer regarding the mechanobiological performance of devices. To guard against deficiencies in device testing, our specialty should become knowledgeable about joint biomechanics and material behavior testing under load. There are four phases of testing of a loaded alloplastic device before general usage. Phase 1 is a screening process wherein candidate materials meet or exceed minimum standards for laboratory wear testing. Wear debris may be collected for biocompatibility testing in animals. Phase 2 is the in vitro screening process for the proposed device design. Using joint simulators to wear-test a device intended for in vivo use is one example of an appropriate laboratory test. If loads and frequency are known, in vivo service life predictions can be estimated from results of in vitro wear testing. Phase 3 concentrates on animal testing of a device satisfying phase 2 requirements for design. However, animal model problems include uncontrollable device loading, unknown device load history, compromised design integrity from small animal anatomy, and device miniaturization. Nevertheless, animal testing must bring the device and material to failure, to study mechanisms of failure and subsequent biologic result. In the case of the Vitek implant, requests by us and other clinicians to perform animal tests were rejected because of animal model problems and the fact that the device had per-
Maxillofac
49442443,
Surg
1991
KEEPING AN EYE ON THE
OCULOCARDIAC REFLEX To the Editor:-1 recently read the article “Oculocardisc Reflex During Treatment of an Orbital Blowout Fracture” (J Oral Maxillofac Surg 47:522, 1989). We have found a 25% incidence (25 of 100 patients) of the oculocardiac reflex (OCR) occurring during esthetic blepharoplasty surgery, and reported this.’ Indeed, the OCR is a ubiquitous reflex that may occur during a variety of stimulatory events on or around the globe.* It is incumbent upon the practitioner to be aware of this reflex and monitor all patients undergoing eye surgery. In our series of 100 patients, we found that cessation of the stimulus was adequate to reverse the condition in the majority of patients. However, the possibility of emergency intervention does exist. The OCR is a well-documented complication of eye muscle surgery with which anesthesiologists and ophthalmologists are familiar. It is now evident that it occurs in an eclectic array of situations and everyone operating in the region needs to be aware of this potentially serious condition. ALAN MATARASSO,MD, FACS New York, New York
References 1. Matarasso A: The OCR in blepharoplasty. Plast Reconstr Surg 83~243,1989 2. Anderson RL: The blepharocardiac reflex. Arch Ophthalmol%:1418, 1978 AN IMPORTANT LESSON ABOUT BIOMATERIALS
IN THE TMJ To the Editor:-Silicone rubber and Proplast (Vitek Inc, Houston, TX) II sheeting were advocated as disc replacements by numerous clinicians at the 1982 AAOMS Clinical Congress on TMJ disorders. These materials had previously been used as condylar caps with few problems. However, since 1985, an increasing number of clinical and animal studies have reported biomechanical failure, with microscopic wear debris causing a macrophage and foreign-body giant cell reaction asso-
ciated with pain, bone resorption, hypomobility, and malocclusion. What went wrong; why was there such a stampede towards the use of these devices by the profession from 1982 to 1986? Did clinicians understand the biomechanics of the TMJ? Were clinicians knowledgeable about the testing procedures required of manufacturers by the Food and Drug Administration (FDA) before devices could be marketed? Based on recent information obtained as a result of the FDA Freedom of Information Act, the answer is probably no to all of the above. Surgeons were not satisfied with 15% to 20% disc repair failure in the early 1980s and began to excise and replace the disc with devices known to be biocompatible in nonloaded anatomical sites. Early reports were gratifying and the leap to an alloplastic TMJ disc device was fast. However, biomechanical device failures reported at the 1986 annual AAOMS Meeting slowed this trend, and today the use of alloplastic permanent disc replacement has nearly stopped. Controversy surrounds the issue of TMJ loading. Is the TMJ a load-bearing joint or not? This issue is critical to the design and laboratory testing of a device for this joint; and to be safe, the biomedical engineer must assume that the joint is loaded. Our recent wear testing of Vitek’s implant, using a TMJ simulator at a 20-lb load, produced rapid failure rates. Had Vitek tested the implant under these conditions, it might not have marketed a TMJ disc replacement. Oral and maxillofacial surgeons are not adequately trained in joint biomechanics, material behavior, and device performance. They must rely on the validity of results from the manufacturer regarding the mechanobiological performance of devices. To guard against deficiencies in device testing, our specialty should become knowledgeable about joint biomechanics and material behavior testing under load. There are four phases of testing of a loaded alloplastic device before general usage. Phase 1 is a screening process wherein candidate materials meet or exceed minimum standards for laboratory wear testing. Wear debris may be collected for biocompatibility testing in animals. Phase 2 is the in vitro screening process for the proposed device design. Using joint simulators to wear-test a device intended for in vivo use is one example of an appropriate laboratory test. If loads and frequency are known, in vivo service life predictions can be estimated from results of in vitro wear testing. Phase 3 concentrates on animal testing of a device satisfying phase 2 requirements for design. However, animal model problems include uncontrollable device loading, unknown device load history, compromised design integrity from small animal anatomy, and device miniaturization. Nevertheless, animal testing must bring the device and material to failure, to study mechanisms of failure and subsequent biologic result. In the case of the Vitek implant, requests by us and other clinicians to perform animal tests were rejected because of animal model problems and the fact that the device had per-
