Biomechanical study on the functional performance of a new microprocessor-controlled prosthetic knee joint

Abstracts / Gait & Posture 36 (2012) S1–S101

S5

anterior pelvic tilt is explained by concomitant medial hamstings lengthening procedures. Flexed knee gait can be corrected effectively by PTS in cerebral palsy (CP) but maximum knee flexion in swing and the range of knee flexion are reduced by this procedure. For correction of flexed knee gait in CP we recommend PTS although the range of knee flexion during the gait cycle is reduced. The trace for knee flexion–extension kinematics is shifted approximately 20◦ towards extension during the whole gait cycle. Disclosure: No significant relationships. References [1] Stout JL, et al. J Bone Joint Surg Am 2008;90(11):2470–84. [2] Tirosh O, et al. Comput Biol Med 2010;40(2):201–7.

doi:10.1016/j.gaitpost.2011.10.187 O08 Biomechanical study on the functional performance of a new microprocessor-controlled prosthetic knee joint T. Schmalz 1,∗ , M. Bellmann 2 , E. Ludwigs 2 , S. Blumentritt 3 1

Research, Otto Bock Healthcare GmbH, Göttingen, Germany Research, Otto Bock Healthcare, Göttingen, Germany 3 Research, Otto Bock Healthcare, Duderstadt, Germany 2

Fig. 1.

It has recently been described that inclusion of patellar tendon advancement is necessary to achieve optimal results in the surgical management of persistent crouch gait [1]. The aim of this study is to evaluate the outcome of patellar tendon shortening (PTS) in BSCP. Patients/materials and methods: Retrospective cohort study: a total of 24 patients (8 females/16 males) with a mean age of 16.1 ± 5.8 years (range 10.5–40 years at time of surgery) were included. 19 patients had additional surgery and 10 had supracondylar extension osteotomies (SEO). Two patients had unilateral surgery. 18 patients had GMFCS level II and 6 patients had GMFCS level III. All participants had pre- and postoperative 3D gait analysis including a thorough clinical assessment and collection of 3D gait data. From the 3D gait data temporal parameters (cadence, stride length, and walking speed) and joint angles for the sagittal, coronal and transverse planes were calculated. All data was uploaded into Gaitabase [2]. Results: The temporal parameters did not change postoperatively. Clinical assessment of joint angles revealed statistically significant changes in the following parameters (Table 1). The graph (Fig. 1) of knee flexion–extension kinematics is approximately 20◦ shifted towards more extension. Discussion and conclusion: PTS has shown significant improvement in four highly relevant gait parameters and is elegantly demonstrated by the shift in the kinematic knee curve towards normal. The improvements of hip internal rotation is explained by concomitant femoral derotation osteotomies. The deterioration of

Introduction: Due to microprocessor-controlled prosthetic knee joints, the fitting quality of transfemoral amputees has been effectively increased in the past years [1–3]. The high functionality and the safety potential of the C-LEG have been scientifically proven in extensive studies [1,2]. Equipped with an improved sensor system and control algorithms, the newly developed GENIUM prosthetic knee joint increases the functional possibilities of the C-LEG considerably. The article presents the results of a biomechanical study that aimed at examining the new functions of the GENIUM compared to the C-LEG and their advantages for the patient. Patients/materials and methods: For the study, 10 patients of mobility grades 3 and 4 with unilateral transfemoral amputation could be recruited. All of them were fitted with the C-LEG. On the first day of the procedure, the following situations were biomechanically analyzed (C-LEG): standing on a slope (10◦ ), walking on a level surface as well as ascending and descending ramps and stairs. Then all subjects were fitted with the GENIUM. After a familiarization phase of one day, all tests were repeated with this joint (G1). In the following three months, the patients used the GENIUM every day and then they were tested again (G2). Measurements were performed by means of an optoelectronic camera system (VICON460) in combination with 2 force plates (KISTLER 9287A). The WILCOXON test was used for the statistical test procedure. Results: C-LEG–G1: the new standing mode of the GENIUM makes standing significantly more constant and safe (30 s test: load on prosthetic side 44%BW (G1) vs. 31%BW (C-LEG). With the GENIUM, the initial contact during walking is characterized for the first time by physiological pre-flexion of the knee of approximately 4◦ , which supports the subsequent possible stance phase flexion. With the GENIUM, the velocity-dependent maximum knee flexion angle increase during the swing phase is lower (<1◦ /1 m/s) than with the C-LEG (approximately 11◦ /1 m/s). Both findings are reflected in a more physiological gait pattern. On the ramp, the GENIUM allows for significantly increased knee flexion (downwards: flexion increased by 9◦ , upwards: flexion increased by 7◦ ) and higher foot clearance. The kinematic characteristics come closer to that of healthy persons. The results of stair descent show only slight differences between the C-LEG and G1. Due to the new stair mode of the GENIUM, walking up stairs step-over-step is made possible for the first time even with a passive system, which is more natu-

S6

Abstracts / Gait & Posture 36 (2012) S1–S101

Table 1

Preop Postop. p-Value a b

Internal hip rot. in stancea

Knee flex. at initial contacta

Max. knee ext. in stancea

Knee flex. in mid stancea

Max. knee flex. in swingb

Range knee flex.b

Average pelvic tiltb

13.9 ± 15.2◦ 7.2 ± 11.3◦ 0.02

51.1 ± 18.2◦ 32.4 ± 1.8◦ <0.001

42.5 ± 22.8◦ 20.5 ± 13.9◦ <0.001

46.0 ± 24.4◦ 22.9 ± 14.5◦ <0.001

71.9 ± 16.5◦ 57.8 ± 10.0◦ <0.001

55.0 ± 19.0◦ 37.6 ± 12.2◦ <0.001

14.1 ± 6.8◦ 21.6 ± 6.6◦ <0.001

An improvement. A deterioration.

ral than asymmetric ascending with the C-Leg (usually 2 steps at once with the contralateral side). G1–G2: for movements with the GENIUM that require only slight performance changes compared to the C-LEG, no significant differences of the biomechanical parameters were identified (walking on a level surface, walking up and down a slope, walking down stairs). After 3 months, the adaptation effects observed in the subjects with regard to the new function of walking up stairs step-over-step with the GENIUM were significant (e.g. increase of power generated in the hip joint on the affected side during stance phase extension from 105 W to 144 W). Discussion and conclusion: Compared to the C-LEG, the new, intuitively useable functions of the GENIUM contribute to the further approximation of natural movement patterns in all investigated situations; overloading of intact parts of the locomotor system is reduced further. Both effects are confirmed by biomechanical parameters and provide considerable functional benefits for the prosthesis user. Disclosure: The authors are employees of the Research Department of Otto Bock Healthcare GmbH.

References [1] Bellmann, et al. Arch Phys Med Rehab 2010;91:644–52. [2] Blumentritt, et al. J Prosthet Orthot 2009;21:2–15. [3] Bunce, et al. J Prosthet Orthot 2007;19:7–14.

doi:10.1016/j.gaitpost.2011.10.188 O09 Predictive factors to determine the outcome after single event multilevel surgery for gait correction in children with cerebral palsy using the gait profile score E. Rutz 1,∗ , S. Donath 2 , R. Baker 1 , O. Tirosh 3 , H.K. Graham 4 1

Murdoch Childrens Research Institute, The Royal Children’s Hospital, Parkville, Australia 2 Clinical Epidemiology and Biostatistics Unit, The Royal Children’s Hospital, Parkville, Australia 3 Hugh Williamson Gait Laboratory, The Royal Children’s Hospital, Parkville, Australia 4 Orthopaedic Department, The Royal Children’s Hospital, Parkville, Australia

Introduction: The natural history of gait in children with bilateral spastic cerebral palsy (BSCP) is one of deterioration. Single event multilevel surgery (SEMLS) is performed in order to prevent deterioration and to improve gait in patients with BSCP. The Gait Profile Score (GPS) [1] measures how different a gait pattern is from that of typically developing children. The aim of this study is to investigate which factors most predict change in GPS after SEMLS. Patients/materials and methods: All 121 diplegic patients with GMFCS level II or III (48 girls; age 11 ± 3 years at time of surgery) who had SEMLS at our hospital between 1995 and 2008 were included. We hypothesised that the following factors might have a bearing on SEMLS outcome: age at surgery, number of oper-

ative procedures during SEMLS, insurance status: private versus public insurance (as a surrogate for socio-economic status), surgical adverse events, pre-operative GMFCS level, pre-operative GPS (GPS-pre op). Bivariable linear regression was used to identify factors, which might be predictors of the change in GPS from baseline to one year follow-up at a level of p < 0.05. Variables thus identified were subject to a multivariable linear regression. Results: The mean GPS change was 4.3◦ (SD 4◦ ) from 15.5◦ (SD 4◦ ) pre-operatively to 11.2◦ (SD 3◦ ) post-operatively. Bivariable linear regression suggests three factors were related to GPS change. These were: GPS pre-op (b = 0.73, p < 0.001), age at surgery (b = −0.33, p = 0.009) and surgical adverse events (b = −3.17, p = 0.005). Multivariable linear regression revealed that once GPS pre-op had been taken into account the other two variables are not predictors of GPS change (p > 0.1). Discussion and conclusion: Apparent correlations of outcomes with age at surgery and surgical adverse events appear to be a consequence of correlations of these variables with pre-op GPS. This suggests that the small number of adverse events (12 out of 121 children) were also more common amongst the milder children and that milder children have surgery later. GMFCS was not a sufficiently sensitive measure to reveal the relationship between outcome and pre-operative gait pattern. Over 90% of children exhibit an improvement in gait pattern as result of SEMLS. The most severely affected children (high GPS) show the greatest improvements which can be considerably higher than the 4.3◦ change recorded for the cohort as a whole. Incidents of deterioration after surgery in these children are very rare. More mildly affected children show only modest improvements in gait pattern on average and a higher incidence of deterioration after surgery. Gait dysfunction in children with BSCP can be effectively corrected by SEMLS. Not only is the GPS an excellent method to assess the direction and magnitude of change after SEMLS, in itself it is the major predictor of surgical outcome. Disclosure: No significant relationships. Reference [1] Baker R, et al. Gait Posture 2009;30–3:265–9.

doi:10.1016/j.gaitpost.2011.10.189 O10 The effect of distal rectus femoris transfer as a part of multilevel surgery in spastic diplegia—A randomized clinical trial T. Dreher ∗ , S.I. Wolf, J. Korber, F. Braatz Department for Orthopaedic Surgery and Traumatology, University of Heidelberg, Heidelberg, Germany Introduction: Various studies reported satisfying results after distal rectus femoris transfer (DRFT) [1]. However different authors brought into question the effects of DRFT as a procedure suitable for all patients [2,3]. This is underlined by MRI studies showing failure of knee flexion augmentation and persistent extensor momentall