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Animal experiment: Radiological analysis of the LPM reattachment1797IntroductionSince the first total temporomandibular joint replacement (TMJR) method was conceived in 1965 by Christensen, many more systems have been devised. Twenty-seven different TMJR systems are currently in use. (1,2) However, none provides for reinsertion of the lateral pterygoid muscle (LPM), which is surgically detached during the condylar resection phase. The importance of the LPM is apparent when examining the different phases of mastication. The incisor and canine teeth first cut and tear the food, respectively. The premolars and molars then crush and chew the food, which is ground to the point where it can easily be swallowed and further improve digestion. Mastication efficiency is the number of chews necessary to grind down the food. It is dependent on good articular and muscular function and on the individual’s dental condition. (3,4)The lateral pterygoid muscle participates in the cutting and tearing phases of mastication by performing protrusion. It also performs laterotrusive motions during the chewing and grinding phase. Laterotrusive motions occur via unilateral contraction of the LPM. Protrusion results from bilateral contraction of the lateral pterygoid muscle. Loss of the lateral pterygoid muscle results in impaired laterotrusive and protrusive functions. For example, the average laterotrusion in humans is 10 mm, but Mercuri’s et al. (5) long-term follow-up study found that significant post-operative decreases in laterotrusion occur after TMJR procedures. They reported an average laterotrusion of 3.07 mm (95%, 2.09 to 4.04) to the contralateral side after unilateral, right TMJR and 3.04 mm (95% CI, 1.98 to 4.10) after unilateral, left TMJR procedures. Similar findings were reported by Dimitroulis et al. (6). They found that laterotrusion can be limited to a mean value of 1.6 mm (range 0 - 2.9 mm). Correct mastication occurs bilaterally. During unilateral mastication, the TMJs are subjected to an uneven load, and further deterioration of the TMJ that experiences most of the load can result.(7)In an attempt to reinstall laterotrusive movement after joint replacement, Mommaerts reconstructed the LPM enthesis using direct reinsertion Nikolas de Meurechy NW.indd 179 05-06-2024 10:14