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IN VIVO KINEMATICS AND KINETICS OF THE NORMAL AND IMPLANTED TMJ
R.D. Komistek’,‘, D.A. Dennis’~*, J.A. Mabel, D.T. Anderson’, ‘Rose Musculoskeletal Research Laboratory,
‘Colorado School of Mines
INTRODUCTION: The objective of this present study is to assess the in viva kinematics and kinetics of the temporomandibular joint (TMJ). METHODS: Fifteen subjects (5 normal, 5 metal-on-metal implants, 5 fossa-only implants) were evaluated using fluoroscopic videos (TMJ Implants, Denver, CO). Under fluoroscopic surveillance, the subjects were asked to onen and close their iaw on a force transducer olaced between their molars &rest the joint (
Figure 1. Fluoroscopy image of a total TMJ subject A data acquisition system recorded the force applied between the subject’s teeth during biting. Video images were analyzed using a digitization technique of designating discrete points on the jaw and tcmporomandibular joint [l]. The kinematic data derived from fluoroscopy and the data output from the force tmnsducer were input to a mathematical model of the human jaw to determine the kinetics of the TMJ ioint (Figure 2)
TIBIOCALCANEAL EVERSION IN BAREFOOT VS. SHOD RUNNING
A. Stacoff’, B.M. Nigg’, C. Reinschmidt’*3, A.J. van den Bogert’, A. Lundberg’, J. Denoth’, E. Stiissi3
‘Human Performance Laboratory, The University of Calgary, Calgary, Canada, ‘Karolinska Institute, Dept. of Orthopaedics, University Hospital,
Huddinge, Sweden, ‘Laboratory for Biomechanics, Dept. of Materials, ETH Ziirich, Schlieren, Switzerland
INTRODUCTION: Running with shoes has been reported to increase eversion compared to barefoot running [I]. However, recent studies have shown that skeletal kinematics are masked by skin and shoe movement artefacts [2]. Thus, it is presently unknown, whether differences between barefoot and shod running exist at the bone level. Therefore, the purpose of this study was to compare skeletal eversion between barefoot and shod running. METHODS: Intracortical bone pins with triads of reflec-tive markers were inserted under local anesthetic into the calcaneus and tibia of five healthy male subjects. Subjects were running barefoot and with a standard running shoe (adidas equ. tush.). Using 3D marker recon-struction and a joint coordinate system app-roach, tibiocalcaneal eversion was calculated for the stance phase. Test variables were de-fined for eversion at touchdown, max. ever-sion, total eversion and max. eversion velocity. RESULTS AND DISCUSSION: No significant differences were found bet-ween barefoot and shod running in any of the test variables (except for shoe*subjects inter-actions for touchdown and max. eversion). Generally, inter-subject differences were found considerably larger than differences between the shod and barefoot condition (Fig. 1). The fact that tibiocalcaneal movement patterns were found similar for shod and barefoot running is in contrast to previous investigations using skin and shoe markers
RESULTS: Figure 2. Mathematical model schematic
The normal joints had more translation than the fossa and the total TMJ joints (Table 1). All five subjects having a total TMJ joint experienced minimal translation, leading to the conclusion that total TMJ implants only rotate and do not translate. The applied force at the TMJ for the normal subjects was much greater than those subjects having fossa or total TMJ joints. The average values were 388 Newtons for the normal group, and 200 and 91 Newtons for the fossa and total TMJ group, respectively. The maximum force values were 621, 536, and 212 Newtons for the normal, fossa, and total TMJ groups respectively.
Subjects A/P ROM Force Angle Torque
(mm) @-kg) (N C- ) (N-m) Nomal 11.9 26.1 387.9 17.4 23.5 Fossa 7.1 21.8 199.9 23.5 12.9 Total 1.0 18.6 90.8 23.9 5.0
Table 1. Average kinematic and kinetic data CONCLUSION: As expected, the average translation and joint reaction force of a normal TMJ joint were noticeably different when compared to the implanted joint averages. Therefore, it can bc concluded the muscles are not applying similar forces at the joint when a subject has a total TMJ joint, compared to a subject who has a normal, nondamaged TMJ joint. The subjects having a total TMJ implant were only able to apply a minimal torque during the biting exercise. REFERENCES: [l] Dennis DA, et al.: Clin Orthop 1996 ACKNOWLEDGEMENTS: TMJ Implants, Golden, CO. VF Works, Palm Harbor FL CORRESPONDENCE: Richard D. Komistek, Ph.D., 2425 So Colorado Blvd, Suite 280, Denver, CO 80222 USA. phone: (303) 759-1490, fax: (303) 7.59-2316, [email protected]
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Figure 1. Total eve&on during barefoot running vs. shod running (repetitions: 3 barefoot, 5 shod).
Preliminary results indicate that when using non standard shoes (with modifications of in serts and sole construction) intra-individual effects for some variables between barefoot and shod running may be present. CONCLUSION: It is concluded that the wearing of a standard running shoe does neither have a substantial nor a systematic effect on tibiocalcaneal eversion compared to barefoot running. REFERENCES: 1 Edington et al. In: Cavanagh, &mechanics of dist. running, H. Kinetics, Ill. 1990.2 Rein-Schmidt et al. Clin. Biomech. 12, 1%. 1997. CORRESPONDENCE: Stacoff, Biomechanics Lab., ETH Ziirich, Wagistr. 4, CH-8952 Schlieren. Fax: ++41 1 633 11 24. [email protected]
I I”’ Conference of the ESB, July 8-11 98, Toulouse. France 13
