Monteggia fractures: analysis of patient-reported outcome measurements in correlation with ulnar fracture localization.

BACKGROUND: Monteggia fractures and Monteggia-like lesions result after severe trauma and have high complication rates. Preliminary biomechanical studies suggested a correlation between ulnar fracture localization and clinical result. OBJECTIVES: Key objective was to evaluate whether the site of the ulnar fracture can be correlated to clinical outcome after open reduction and internal stabilization. METHODS: In a retrospective, monocentric study 35 patients who underwent surgical treatment after suffering a Monteggia injury or Monteggia-like lesion were included. Fractures were classified according to Bado and Jupiter, the site of the fracture location at the proximal ulna and regarding the potential accompanying ligamentary injury. In a follow-up examination validated patient-reported outcome measures and functional parameters were evaluated. Furthermore, treatment strategy and complications were analysed. RESULTS: Mean patient age was 51.9 years (± 18.0). 69% were females (n = 24). Follow-up took place after 50.5 months (± 22.1). Fractures were classified according to Bado (I:2, II:27, III:4, IV:2). Bado II-fractures were further classified according to Jupiter (A:7, B:16, C:3, D:1). Cases were divided into subgroups depending upon the distance of the ulnar fracture site in respect to its distal endpoint (A: < 7 cm and B: > 7 cm). Average overall MEPS was 84.1 (± 19.0). Oxford elbow score and DASH were 37.2 (± 10.5) and 20.4 (± 20.5). Average extension capability reached - 7° (± 7.5). Mean flexion was 134.8° (± 19.7). Average pain according to visual analogue scale was 1.6 (± 1.9). We found no differences between the subgroups regarding the PROMs. Subgroup A displayed a worse extension capability (p = 0.027) and patients were significantly older (p < 0.01). Comparing patients with and without fracture of the radial head, we observed no differences. Patients with an accompanying injury of the coronoid process displayed higher pain levels (p = 0.011), a worse functionality (p = 0.027) and overall lower scoring in PROM. CONCLUSION: The presented results suggest that in Monteggia fractures and Monteggia-like lesions, the localization of the ulna fracture can give a hint for its postoperative outcome. However, we could not confirm the hypothesis of an increasing instability in ulnar fractures located further distally (high severity of the potential ligamentous injury). Intraarticular fractures or injuries with a close relation to the joint have a worse prognosis, especially if the coronoid process is injured. Trial registration Registration was done with ClinicalTrials.gov under NCT05325268.

Modeling muscle function using experimentally determined subject-specific muscle properties.

Muscle models are commonly based on intrinsic properties pooled across a number of individuals, often from a different species, and rarely validated against directly measured muscle forces. Here we use a rich data set of rat medial gastrocnemius muscle forces recorded during in-situ and in-vivo isometric, isotonic, and cyclic contractions to test the accuracy of forces predicted using Hill-type muscle models. We identified force-length and force-velocity parameters for each individual, and used either these subject-specific intrinsic properties, or population-averaged properties within the models. The modeled forces for cyclic in-vivo and in-situ contractions matched with measured muscle-tendon forces with r2 between 0.70 and 0.86, and root-mean square errors (RMSE) of 0.10 to 0.13 (values normalized to the maximum isometric force). The modeled forces were least accurate at the highest movement and cycle frequencies and did not show an improvement in r2 when subject-specific intrinsic properties were used; however, there was a reduction in the RMSE with fewer predictions having higher errors. We additionally recorded and tested muscle models specific to proximal and distal regions of the muscle and compared them to measures and models from the whole muscle belly: there was no improvement in model performance when using data from specific anatomical regions. These results show that Hill-type muscle models can yield very good performance for cyclic contractions typical of locomotion, with small reductions in errors when subject-specific intrinsic properties are used.

Biomechanical comparison of bi- and tricortical k-wire fixation in tension band wiring osteosynthesis.

BACKGROUND: Patients with a simple transversal fracture of the olecranon are often treated with a tension band wiring (TBW), because it is known as a biomechanically appropriate and cost-effective procedure. Nevertheless, the technique is in detail more challenging than thought, resulting in a considerable high rate of implant-related complications like k-wire loosening and soft tissue irritation. In the literature, a distinction is generally only made between transcortical (bi-) and intramedullary (mono-) fixation of the wires. There is the additional possibility to fix the proximal bent end of k-wire in the cortex of the bone and thus create a tricortical fixation. The present study investigates the effectiveness of bi- and tricortical k-wire fixation in a biomechanical approach. METHODS: TBW of the olecranon was performed at 10 cadaver ulnas from six donors in a usual manner and divided into two groups: In group 1, the k-wire was inserted by bicortical fixation (BC), and in group 2, a tricortical fixation (TC) was chosen. Failure behavior and maximum pullout strength were assessed and evaluated by using a Zwick machine. The statistical evaluation was descriptive and with a paired t test for the evaluation of significances between the two techniques. RESULTS: The average age of the used donors was 81.5 ± 11.5 (62-92) years. Three donors were female, and three were male. Ten k-wires were examined in BC group and 10 in the TC group. The mean bone density of the used proximal ulnas was on average 579 ± 186 (336-899) HU. The maximum pullout strength was 263 ± 106 (125-429) N in the BC group and increased significantly in the TC group to 325 ± 102 (144-466) N [p = .005]. CONCLUSION: This study confirms for the first time biomechanical superiority of tricortical k-wire fixation in the olecranon when using a TBW and may justify the clinical use of this method.

Prospective randomized controlled trial in the treatment of lateral epicondylitis with a new dynamic wrist orthosis.

BACKGROUND: In the treatment of lateral epicondylitis (LE), the role of a new dynamic wrist orthosis is unclear. PATIENTS AND METHODS: Patients suffering from a LE longer than 3 months were multicentrically and prospectively randomized into a physiotherapeutic group (PT group) and in a physiotherapy group plus wrist orthosis (PT + O group). Physiotherapy consisted of daily eccentric strengthening exercises under initial professional supervision. Inclusion criteria were a Placzek score greater than 4. Exclusion criteria were previous surgery, rheumatic arthritis, elbow instability, radicular symptoms, higher-grade extensor tendon rupture, or cervical osteoarthritis. The clinical evaluation was performed after 12 weeks and 12 months. The Patient-Rated Tennis Elbow Evaluation (PRTEE) scale, Placzek Score, the pain rating (VAS), range of motion and the Subjective Elbow Score were evaluated. RESULTS: Of the initially 61 patients, 31 were followed up after 12 weeks and 22 after 12 months. Twenty-nine patients (43%) were male, the mean age was 46, and 44 patients (66%) had the right elbow involved. At 12 weeks, there was a pain reduction on the VAS in both groups (PT + O: 6.5-3.7 [p = .001]; PT: 4.7-4.1 [p = .468]), albeit it was only significant for the PT + O group. At 12 months, reduction was significant in both groups (PT + O: 1.1 [p = .000]; PT: 1.3 [p = .000]). The painless maximum hand strength in kg improved in both groups significant after 3 and 12 months. The Placzek score was reduced from 8.25 to 3.5 [p = .001] after 12 weeks for the PT + O group and from 8.1 to 3.8 [p = .000] in the PT group, as well as after 12 months in the PT + O group to 0 [p = .000] and in the PT group to 2.0 [p = .000]. The PRTEE improved in both groups after 12 weeks (PT + O: 52.8--31.3 [p = .002]; PT: 48.6-37.6 [p = .185]) and 12 months (PT + O: 16.15 [p = .000]; PT: 16.6 [p = .000]), although the reduction at 12 weeks was not significant for the PT group. CONCLUSION: The elbow orthosis appears to accelerate the healing process with respect to the PRTEE and pain on the VAS (12 weeks follow-up), although there is an adjustment after 12 months in both groups and a significant improvement of symptoms is achieved in all endpoints.

Different Segments within Vertebrate Muscles Can Operate on Different Regions of Their Force-Length Relationships.

To relate in vivo behavior of fascicle segments within a muscle to their in vitro force-length relationships, we examined the strain behavior of paired segments within each of three vertebrate muscles. After determining in vivo muscle activity patterns and length changes of in-series segments within the semimembranosus muscle (SM) in the American Toad (Bufo americanus) during hopping and within the sternohyoid (SH) muscle in the rat (Rattus rattus) during swallowing, and of spatially separated fascicles within the medial gastrocnemius (MG) muscle in the rat during trotting, we measured their corresponding in vitro (toad) or in situ (rat) force-length relationships (FLRs). For all three muscles, in vivo strain heterogeneity lasted for about 36-57% of the behavior cycle, during which one segment or fascicle shortened while the other segment or fascicle simultaneously lengthened. In the toad SM, the proximal segment shortened from the descending limb across the plateau of its FLR from 1.12 to 0.91 of its optimal length (Lo), while the distal segment lengthened (by 0.04 ± 0.04 Lo) before shortening down the ascending limb from 0.94 to 0.83 Lo. In the rat SH muscle, the proximal segment tended to shorten on its ascending limb from 0.90 to 0.85 Lo while the distal segment tended to lengthen across Lo (0.96-1.12 Lo). In the rat MG muscle, in vivo strains of proximal fascicles ranged from 0.72 to 1.02 Lo, while the distal fascicles ranged from 0.88 to 1.11 Lo. Even though the timing of muscle activation patterns were similar between segments, the heterogeneous strain patterns of fascicle segments measured in vivo coincided with different operating ranges across their FLRs simultaneously, implying differences in force-velocity behavior as well. The three vertebrate skeletal muscles represent a diversity of fiber architectures and functions and suggest that patterns of in vivo contractile strain and the operating range over the FLR in one muscle region does not necessarily represent other regions within the same muscle.

[Corrective osteotomies for posttraumatic elbow deformities]. / Korrekturosteotomien bei posttraumatischen Fehlstellungen des Ellenbogengelenks.

OBJECTIVES: Correcion of elbow joint deformities that usually develop secondary to direct or indirect trauma of the arm or elbow with subsequent inadequate healing and consecutive axial/rotational malalignment and may be associated with cosmetic or functional deficits of the arm. INDICATIONS: Relevant malalignment of the arm axis with corresponding cosmetic or functional deficits for the patient. CONTRAINDICATIONS: Pre-existing degenerative and chronic inflammatory changes. SURGICAL TECHNIQUE: Generally, two-dimensional supracondylar open or closed wedge osteotomies are used. In the presence of a three-dimensional deformity (with rotational component), an additional derotational correction is necessary. Extra-articular deformities following extension fractures should be treated preferably with an open wedge osteotomy, extra-articular deformities of flexion fractures with a closed wedge osteotomy. Valgus/varus deformities may also require a closed/open wedge osteotomy primarily through a dorsal or alternatively radial approach. POSTOPERATIVE MANAGEMENT: The arm should be immobilized with a brachial cast splint for 2-3 weeks, with passive exercises of the elbow starting on postoperative day 7. RESULTS: In general, the results for a three-dimensional osteotomy of the distal humerus are expected to be good to very good. Only in rare cases (2.5%) is a mostly transient irritation of the ulnar nerve observed.

The effect of fast and slow motor unit activation on whole-muscle mechanical performance: the size principle may not pose a mechanical paradox.

The output of skeletal muscle can be varied by selectively recruiting different motor units. However, our knowledge of muscle function is largely derived from muscle in which all motor units are activated. This discrepancy may limit our understanding of in vivo muscle function. Hence, this study aimed to characterize the mechanical properties of muscle with different motor unit activation. We determined the isometric properties and isotonic force-velocity relationship of rat plantaris muscles in situ with all of the muscle active, 30% of the muscle containing predominately slower motor units active or 20% of the muscle containing predominately faster motor units active. There was a significant effect of active motor unit type on isometric force rise time (p < 0.001) and the force-velocity relationship (p < 0.001). Surprisingly, force rise time was longer and maximum shortening velocity higher when all motor units were active than when either fast or slow motor units were selectively activated. We propose this is due to the greater relative effects of factors such as series compliance and muscle resistance to shortening during sub-maximal contractions. The findings presented here suggest that recruitment according to the size principle, where slow motor units are activated first and faster ones recruited as demand increases, may not pose a mechanical paradox, as has been previously suggested.

A constitutive description of the anisotropic response of the fascia lata.

In this paper we propose a constitutive model to analyze in-plane extension of goat fascia lata. We first perform a histological analysis of the fascia that shows a well-organized bi-layered arrangement of undulated collagen fascicles oriented along two well defined directions. To develop a model consistent with the tissue structure we identify the absolute and relative thickness of each layer and the orientation of the preferred directions. New data are presented showing the mechanical response in uniaxial and planar biaxial extension. The paper proposes a constitutive relation to describe the mechanical response. We provide a summary of the main ingredients of the nonlinear theory of elasticity and introduce a suitable strain-energy function to describe the anisotropic response of the fascia. We validate the model by showing good fit of the numerical results and the experimental data. Comments are included about differences and analogies between goat fascia lata and the human iliotibial band.

[Control of diffuse bleeding in unstable pelvic fractures with compression plate packing: presentation of the surgical technique]. / Kontrolle diffuser Blutungen bei instabiler Beckenfraktur mittels Kompressionsplattentamponade: Vorstellung der chirurgischen Technik.

Current recommendations on surgical management of unstable pelvic fracture with hemorrhagic shock include reduction and fixation, i.e., with a C-clamp and external fixator, angiographic embolization of injured pelvic arteries, and preferably extraperitoneal packing to control diffuse bleeding from the venous plexus and fracture site. However, the recently reported lethality at 40-60% remains seriously high. One possible reason could be the unsatisfactory efficiency of extraperitoneal packing in the case of a traumatically or surgically opened retroperitoneal compartment. In this paper, a new approach, so-called compression plate packing, is proposed to control diffuse bleeding. In this technique, the essential pressure of the packing on the bleeding site is set up with small fragment plates with screw fixation to the pelvic ring. In two first clinical cases of severe pelvic trauma the hemorrhage could be controlled reliably.

Ovine bone marrow mesenchymal stem cells: isolation and characterization of the cells and their osteogenic differentiation potential on embroidered and surface-modified polycaprolactone-co-lactide scaffolds.

The current study was undertaken with the goal being isolation, cultivation, and characterization of ovine mesenchymal stem cells (oMSC). Furthermore, the objective was to determine whether biological active polycaprolactone-co-lactide (trade name PCL) scaffolds support the growth and differentiation of oMSC in vitro. The oMSC were isolated from the iliac crest of six merino sheep. Three factors were used to demonstrate the MSC properties of the isolated cells in detail. (1) Their ability to proliferate in culture with a spindle-shaped morphology, (2) presence of specific surface marker proteins, and (3) their capacity to differentiate into the three classical mesenchymal pathways, osteoblastic, adipogenic, and chondrogenic lineages. Furthermore, embroidered PCL scaffolds were coated with collagen I (coll I) and chondroitin sulfate (CS). The porous structure of the scaffolds and the coating with coll I/CS allowed the oMSC to adhere, proliferate, and to migrate into the scaffolds. The coll I/CS coating on the PCL scaffolds induced osteogenic differentiation of hMSC, without differentiation supplements, indicating that the scaffold also has an osteoinductive character. In conclusion, the isolated cells from the ovine bone marrow have similar morphologic, immunophenotypic, and functional characteristics as their human counterparts. These cells were also found to differentiate into multiple mesenchymal cell types. This study demonstrates that embroidered PCL scaffolds can act as a temporary matrix for cell migration, proliferation, and differentiation of oMSC. The data presented will provide a reliable model system to assess the translation of MSC-based therapy into a variety of valuable ovine experimental models under autologous settings.

[Perspectives of clinical stem cell therapy in the treatment of musculoskeletal diseases in Germany]. / Perspektiven klinischer mesenchymaler Stammzelltherapie bei muskuloskeletalen Erkrankungen in Deutschland.

AIM: The treatment of large bone defects remains a challenge for the orthopaedic surgeon. Regenerative therapies with the use of mesenchymal stem cells (MSC) may provide an alternative to autogenous bone transplantation, callus distraction or the use of allografts. MATERIAL AND METHODS: On the occasion of an expert workshop of the German Society for Orthopaedic and Trauma Surgery, a literature search regarding studies with the use of MSC was performed to evaluate its potential for future clinical studies. Furthermore, the legislative requirements were examined. RESULTS: Various in vitro and animal studies showed the benefit of MSC in bone regeneration. However, there are sparse data from clinical studies. Due to recent legislative changes there are several regulatory demands to meet if clinical studies are performed with MSC. CONCLUSIONS: For further evaluation of the role of MSC in the treatment of bone defects there is a need for clinical trials. The current paper provides some assistance for the successful application for clinical trials with MSC. Planning and performance of these studies may require early consultation with the regulatory authorities and cooperation of research centres in order to obtain authorisation for the evaluation of MSC. Preclinical data have to be obtained according to good laboratory practice with equivalent protocols that will be used in the clinical trials. In the latter the implementation of the guidelines for good clinical practice are mandatory.

Hind limb scaling of kangaroos and wallabies (superfamily Macropodoidea): implications for hopping performance, safety factor and elastic savings.

The aim of this study was to examine hind limb scaling of the musculoskeletal system in the Macropodoidea, the superfamily containing wallabies and kangaroos, to re-examine the effect of size on the locomotor mechanics and physiology of marsupial hopping. Morphometric musculoskeletal analyses were conducted of 15 species and skeletal specimens of 21 species spanning a size range from 0.8 to 80 kg that included representatives of 12 of the 16 extant genera of macropodoids. We found that unlike other groups, macropodoids are able to match force demands associated with increasing body size primarily through a combination of positive allometry in muscle area and muscle moment arms. Isometric scaling of primary hind limb bones suggests, however, that larger species experience relatively greater bone stresses. Muscle to tendon area ratios of the ankle extensors scale with strong positive allometry, indicating that peak tendon stresses also increase with increasing body size but to a lesser degree than previously reported. Consistent with previous morphological and experimental studies, large macropodoids are therefore better suited for elastic strain energy recovery but operate at lower safety factors, which likely poses an upper limit to body size. Scaling patterns for extant macropodoids suggest that extinct giant kangaroos (approximately 250 kg) were likely limited in locomotor capacity.

Differential design for hopping in two species of wallabies.

Hindlimb musculoskeletal anatomy and steady speed over ground hopping mechanics were compared in two species of macropod marsupials, tammar wallabies and yellow-footed rock wallabies (YFRW). These two species are relatively closely related and are of similar size and general body plan, yet they inhabit different environments with presumably different musculoskeletal demands. Tammar wallabies live in relatively flat, open habitat whereas yellow-footed rock wallabies inhabit steep cliff faces. The goal of this study was to explore musculoskeletal differences between tammar wallabies and yellow-footed rock wallabies and determine how these differences influence each species' hopping mechanics. We found the cross-sectional area of the combined ankle extensor tendons of yellow-footed rock wallabies was 13% greater than that of tammar wallabies. Both species experienced similar ankle joint moments during steady-speed hopping, however due to a lower mechanical advantage at this joint, tammar wallabies produced 26% more muscle force. Thus, during moderate speed hopping, yellow-footed rock wallabies operated with 38% higher tendon safety factors, while tammar wallabies were able to store 73% more elastic strain energy (2.18 J per leg vs. 1.26 J in YFRW). This likely reflects the differing demands of the environments inhabited by these two species, where selection for non-steady locomotor performance in rocky terrain likely requires trade-offs in locomotor economy.

Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). I. Kinematic and neuromuscular control of turning.

Maneuvering flight has long been recognized as an important component of the natural behavior of many bird species, but has been the subject of little experimental work. Here we examine the kinematics and neuromuscular control of turning flight in the rose-breasted cockatoo Eolophus roseicapillus (N=6), testing predictions of maneuvering flight and control based on aerodynamic theory and prior kinematic and neuromuscular studies. Six cockatoos were trained to navigate between two perches placed in an L-shaped flight corridor, making a 90 degrees turn midway through each flight. Flights were recorded with three synchronized high-speed video cameras placed outside the corridor, allowing a three-dimensional reconstruction of wing and body kinematics through the turn. We simultaneously collected electromyography recordings from bilateral implants in the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis muscles. The cockatoos maneuvered using flapping, banked turns with an average turn radius of 0.92 m. The mean rate of change in heading during a complete wingbeat varied through the turn and was significantly correlated to roll angle at mid-downstroke. Changes in roll angle were found to include both within-wingbeat and among-wingbeat components that bear no direct relationship to one another. Within-wingbeat changes in roll were dominated by the inertial effects while among-wingbeat changes in roll were likely the result of both inertial and aerodynamic effects.

Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). II. Inertial and aerodynamic reorientation.

The reconfigurable, flapping wings of birds allow for both inertial and aerodynamic modes of reorientation. We found evidence that both these modes play important roles in the low speed turning flight of the rose-breasted cockatoo Eolophus roseicapillus. Using three-dimensional kinematics recorded from six cockatoos making a 90 degrees turn in a flight corridor, we developed predictions of inertial and aerodynamic reorientation from estimates of wing moments of inertia and flapping arcs, and a blade-element aerodynamic model. The blade-element model successfully predicted weight support (predicted was 88+/-17% of observed, N=6) and centripetal force (predicted was 79+/-29% of observed, N=6) for the maneuvering cockatoos and provided a reasonable estimate of mechanical power. The estimated torque from the model was a significant predictor of roll acceleration (r(2)=0.55, P<0.00001), but greatly overestimated roll magnitude when applied with no roll damping. Non-dimensional roll damping coefficients of approximately -1.5, 2-6 times greater than those typical of airplane flight dynamics (approximately -0.45), were required to bring our estimates of reorientation due to aerodynamic torque back into conjunction with the measured changes in orientation. Our estimates of inertial reorientation were statistically significant predictors of the measured reorientation within wingbeats (r(2) from 0.2 to 0.37, P<0.0005). Components of both our inertial reorientation and aerodynamic torque estimates correlated, significantly, with asymmetries in the activation profile of four flight muscles: the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis (r(2) from 0.27 to 0.45, P<0.005). Thus, avian flight maneuvers rely on production of asymmetries throughout the flight apparatus rather than in a specific set of control or turning muscles.

Modulation of proximal muscle function during level versus incline hopping in tammar wallabies (Macropus eugenii).

We examined the functional role of two major proximal leg extensor muscles of tammar wallabies during level and inclined hopping (12 degrees, 21.3% grade). Previous in vivo studies of hopping wallabies have revealed that, unlike certain avian bipeds, distal hindlimb muscles do not alter their force-length behavior to contribute positive work during incline hopping. This suggests that proximal muscles produce the increased mechanical work associated with moving up an incline. Based on relative size and architectural anatomy, we hypothesized that the biceps femoris (BF), primarily a hip extensor, and the vastus lateralis (VL), the main knee extensor, would exhibit changes in muscle strain and activation patterns consistent with increased work production during incline versus level hopping. Our results clearly support this hypothesis. The BF experienced similar activation patterns during level and incline hopping but net fascicle shortening increased (-0.5% for level hopping versus -4.2% for incline hopping) during stance when the muscle likely generated force. Unlike the BF, the VL experienced active net lengthening during stance, indicating that it absorbs energy during both level and incline hopping. However, during incline hopping, net lengthening was reduced (8.3% for level hopping versus 3.9% for incline hopping), suggesting that the amount of energy absorbed by the VL was reduced. Consequently, the changes in contractile behavior of these two muscles are consistent with a net production of work by the whole limb. A subsidiary aim of our study was to explore possible regional variation within the VL. Although there was slightly higher fascicle strain in the proximal VL compared with the distal VL, regional differences in strain were not significant, suggesting that the overall pattern of in vivo strain is fairly uniform throughout the muscle. Estimates of muscle work based on inverse dynamics calculations support the conclusion that both the BF and VL contribute to the additional work required for incline hopping. However, on a muscle mass-specific basis, these two muscles appear to contribute less than their share. This indicates that other hindlimb muscles, or possibly trunk and back muscles, must contribute substantial work during incline hopping.

Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control.

We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle-tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor control. This control strategy allows limb cycling to remain constant, whereas limb posture, loading and energy performance are interdependent. We propose that this control strategy provides simple, rapid mechanisms for managing energy and controlling velocity when running over rough terrain.

[Internal fixation of meta- and diaphyseal intercalary bone defects after tumour resection with intramedullary nailing and porous polymethylmetacrylate (PMMA) spacer]. / Stabilisierung von meta- und diaphysären Segmentdefekten nach Tumorresektion durch Marknagelung und Polymethylmetacrylat- (PMMA-)Formkörper.

BACKGROUND: Radical resection of bone tumours localized in the meta- or diaphysis of long bones frequently results in segmental defects. Several stabilization techniques with preservation of the adjacent joint have been published, but the failure rate appears to be considerable. The objective of this study is the experimental and clinical testing of a new technique which combines unreamed nailing with support of the defect by a porous polymethylmetacrylate (PMMA) spacer. METHODS: For spacer preparation, PMMA spheres were adhered to a cylindrical spacer (Ø 32 mm) with interconnective porosity. Axial strength was determined, as was the stiffness/strengths of the combination osteosynthesis in human cadaver tibias (defect lengths 6 cm; empty defect served as a control). An experiment was also conducted with sheep. A 3 cm diaphyseal tibia defect was prepared and stabilized by nailing. For the control there was an empty defect. Group A had support of the defect with a PMMA spacer and group B a PMMA spacer coated with osteoconductive RGD-peptide. Evaluation after was made after 6 months including histology and a determination of relative torsional strength. In addition, a clinical study has been under way since October 1998, with 13 patients (defect lengths between 3-15 cm) being operated. RESULTS: Axial stability was 12,750+/-300 N (17.56+/-0.59 MPa). There was an enhancement of 4-point bending stiffness by 35% (P=0.028), of axial stiffness by 36% (ns) and of axial strength by 553% (P=0.028). Histology showed the formation of a new bone at the spacer/muscle interface. For the sheep, relative torsional strength was enhanced by 95% (P=0.08) in group A and by 91% (P=0.047) in group B. For the patients studied, the mean follow-up period was 16.1 months, max. 48 months. One mechanical failure occurred after 24 months, which was solved by callus distraction. CONCLUSIONS: Combination osteosynthesis is suitable for stabilizing segmental bone defects. The risk of mechanical failure appears to be low. Nevertheless, this technique should only be applied as a definitive solution if callus distraction is unfavourable due to advanced age or a poor lifetime prognosis. The method can also be used for temporary internal stabilization during prolonged postoperative chemotherapy.

[Distal radius fracture. Correlation between radiological and functional results]. / Die distale Radiusfraktur. Korrelation zwischen radiologischem und funktionellem Ergebnis.

BACKGROUND: The purpose of the present study was to investigate the influence of the radiological parameters on the functional outcome of patients with a fracture of the distal radius and to find out to which extent a deformity can be tolerated. PATIENTS AND METHODS: A total of 344 patients with an isolated fracture of the distal radius were treated during a 3-year period; 211 of them were evaluated at an average of 16 months after the accident according to the score of Gartland and Werley as modified by Sarmiento. Furthermore, we developed our own score for evaluating the influence of radiological parameters on the functional outcome. RESULTS: According to the AO classification, there were 20 patients with an A2, 71 an A3, 11 a B, 35 a C1, 44 a C2, and 30 a C3 fracture. Of 211 patients, 28 (13%) had a step-off in the articular surface of over 1 mm, resulting in a 24% reduction of the range of motion compared to the non-injured wrist (p<0.05). Patients with a radial shortening of more than 3 mm (n=12) had a 21% reduction of pro- and supination compared to the non-injured side (p<0.05). The radial tilt and the palmar inclination did not have a direct influence on the functional outcome. Patients treated with K-wire pinning and with an initial palmar inclination of less then -15 degrees had a significantly higher secondary loss of palmar inclination of 9 degrees compared to all others (p<0.05) at the final follow-up. CONCLUSION: The main radiological factors influencing the functional outcome of fractures of the distal radius are radial shortening and a step-off in the articular surface.

Effects of load carrying on metabolic cost and hindlimb muscle dynamics in guinea fowl (Numida meleagris).

The goal of this study was to test whether the contractile patterns of two major hindlimb extensors of guinea fowl are altered by load-carrying exercise. We hypothesized that changes in contractile pattern, specifically a decrease in muscle shortening velocity or enhanced stretch activation, would result in a reduction in locomotor energy cost relative to the load carried. We also anticipated that changes in kinematics would reflect underlying changes in muscle strain. Oxygen consumption, muscle activation intensity, and fascicle strain rate were measured over a range of speeds while animals ran unloaded vs. when they carried a trunk load equal to 22% of their body mass. Our results showed that loading produced no significant (P > 0.05) changes in kinematic patterns at any speed. In vivo muscle contractile strain patterns in the iliotibialis lateralis pars postacetabularis and the medial head of the gastrocnemius showed a significant increase in active stretch early in stance (P < 0.01), but muscle fascicle shortening velocity was not significantly affected by load carrying. The rate of oxygen consumption increased by 17% (P < 0.01) during loaded conditions, equivalent to 77% of the relative increase in mass. Additionally, relative increases in EMG intensity (quantified as mean spike amplitude) indicated less than proportional recruitment, consistent with force enhancement via stretch activation, in the proximal iliotibialis lateralis pars postacetabularis; however, a greater than proportional increase in the medial gastrocnemius was observed. As a result, when averaged for the two muscles, EMG intensity increased in direct proportion to the fractional increase in load carried.