ONE-STEP FUNCTIONAL REGISTRATION FOR KINEMATIC ANALYSIS IN COMPUTER AIDED SURGERY

Nicola Lopomo(1,2), Francesca Colle(1,2), Cecilia Signorelli(1,3), Marco Bontempi(1), Matteo Baracchi(1), Andrea Visani(1)

1. Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Italy; 2. Laboratorio di Nano Biotecnologie – NaBi, Istituto Ortopedico Rizzoli,

Italy; 3. Dipartimento di Bioingegneria, Politecnico di Milano, Italy.

Introduction

Registration phase is a critical point both in gait

analysis and in computer assisted surgery.

Landmarks are usually necessary to define the

anatomic model specific for each patient. This

phase is quite time-costing and subjected to

operator errors. Several methods have been

implemented to define knee functional joint model,

starting from kinematic data [Reichl, 2010;

Martelli, 2002]. The goal of this study was to

describe a novel registration method able to define

through a single movement a knee functional

reference system.

Materials and Methods

25 patients undergoing ACL reconstruction were

included in the study. A standard registration

technique [Martelli, 2006] was performed and a

passive flexion/extension movement (PROM)

starting from full-extension position was acquired

by means of a navigation system (KLEE, BLU-

IGS, Orthokey, DE, USA). Hip joint center (HJC)

was identified using a transformation technique

[Siston, 2006] and, similarly, knee

flexion/extension axis (FEA) was estimated using a

novel symmetrical axis approach. The knee center

(KC) was identified through a 1-lambda evolution

strategy method [Cerveri, 2005] on the FEA,

minimizing varus-valgus angle and medial-lateral

displacement during the PROM. Internal/External

rotation axis (IEA) was defined as the axis joining

HJC and KC, whereas valgus/varus rotation axis

(VVA) was identified as the cross product between

IEA and FEA. We compared the differences in

kinematic decomposition [Grood, 1983] between

standard and functional registration on the PROM.

Figure 1: Mean angular and displacement

deviation with respect to the kinematics defined by

the standard registration.

Results

The mean differences in kinematics are reported in

figure 1. Maximum and minimum differences

between the kinematic are reported in table 1 and

table 2.

MAX MIN

f/e v/v i/e f/e v/v i/e

Mean 0.2 2.6 4.5 -0.2 -3.3 -3.5

STD 0.2 3.1 4.0 0.3 3.0 5.4

Table 1: Max/min angles deviations from

kinematics defined by the standard registrations.

MAX MIN

m/l a/p p/d m/l a/p p/d

Mean 1.3 14.2 3.7 -0.7 -1.5 -3.7

STD 1.2 4.8 3.7 0.8 2.3 3.8

Table 1: Max/min displacements deviations from

kinematics defined by the standard registrations.

Difference in the estimation of HJC is 34.5 ± 17.6

mm. Computational time is 15.7 ± 2.8 sec. The

average time for a complete functional registration

thus is about 22.7 ± 4.1 sec compared to 228 sec of

standard registration [Martelli, 2007].

Conclusions

The presented method reported good results when

compared to the standard registration technique;

only a/p displacement report important mean

difference, due to the estimation of KC position in

the sagittal plane. KC position can be better

estimated allowing in the optimization model not-

intersecting rotation axes. The procedure is

extremely time saving. Critical points are: the

correct estimation of the HJC (that can be improved

considering the introduction of some

abduction/adduction movement while flexing the

limb) and the limb starting position.

References

Cerveri P et al, Ann Bio Eng, 33(3):402-12, 2005.

Grood ES et al, J Bio Eng, 105:136-44, 1983.

Martelli S et al, CMBB, 5:175-85, 2002.

Martelli S et al, CBM, 37:872-8, 2007.

Herig RM et al, J Biomech, 40:2150-2157, 2007.

Reichl et al, MCMDS, 16:403-15, 2010

Siston et al, J Biomec, 39:125-30, 2006.

Presentation 1414 − Topic 06. Biomechanics for computer integrated surgery systems S65

ESB2012: 18th Congress of the European Society of Biomechanics Journal of Biomechanics 45(S1)