Wrist flexion and extension strength in patients with work-related chronic elbow pain: the isokinetic effort factor and its implications.

BACKGROUND: The validity of isokinetic strength findings relating to forearm muscles in patients with chronic elbow pain and/or epicondylitis is not well established. Furthermore, given the nature of this disorder, ensuring maximal effort in performing the tests is an essential prerequisite. The isokinetic-based DEC parameter (defined as the difference between high- and low-velocity eccentric-to-concentric ratios of a given muscle) has been shown to efficiently detect maximal effort. The purpose of this study was therefore to assess the validity of isokinetic strength tests in patients with chronic elbow pain and/or epicondylitis. METHODS: A cohort consisting of 44 male patients with chronic elbow pain (average evolution time, 262 ± 193.04 days) was recruited. The wrist extensor and flexor concentric and eccentric isokinetic strength of the involved and uninvolved sides was measured. The involved-uninvolved and flexor-extensor (F/E) ratios, as well as the DEC (eccentric-concentric difference), were computed based on peak moment values. Work disability and relapse within the first year were registered. In maximal performers, associations between deficits, F/E ratios, work disability, and symptom relapse were explored applying multiple comparisons. RESULTS: Of the patients, 68.2% met the maximal-effort criteria, with the involved-side muscles being significantly weaker than their uninvolved-side counterparts in most cases. Although the mean deficit in this group was not associated with either work disability or relapse, patients with a relapse of symptoms within the first year had a significantly higher F/E ratio than those without relapse. CONCLUSION: In patients presenting with chronic elbow pain who perform at the maximal level of effort, high wrist F/E strength ratios may predict symptom relapse.

Does knee revision after an articulated spacer implant provide normal gait restoration?

PURPOSE: The aim of this study was to quantitatively evaluate gait parameters in patients who underwent a revision procedure after an interval articulated spacer for septic knee prosthesis. METHODS: Ten adult subjects underwent three-dimensional computerized gait analysis 12 months after second-stage knee revision procedure. Kinematic and kinetic parameters were acquired and compared with a normal reference population. Data were also compared with those collected in a previous study, in which the same cohort of patients underwent gait analysis 8-14 weeks after spacer implantation. RESULTS: Kinematic and kinetic parameters did not show any significant difference between the affected and unaffected limb. Compared to normal reference population, patients treated with revision knee prosthesis showed a reduced mean gait velocity, step frequency, stride and step length, average knee range of motion, knee power and ground reaction forces. When comparing average data with those observed after spacer implant, no difference was observed in kinematic variables, while kinetic analysis demonstrated a significant improvement in knee power. CONCLUSIONS: This study shows that 1 year after second-stage knee revision surgery, kinematic and kinetic values remain lower than those observed in a normal reference population. Only slight improvements in walking ability are shown, when analysing data in comparison with those collected after a preformed articulated knee spacer. This finding points out the long time to full functional recovery after knee revision surgery and the limited improvement of gait when compared to the one achieved at the time of spacer implant.

Quantitative gait analysis in patients with Parkinson treated with deep brain stimulation: the effects of a robotic gait training.

BACKGROUND: Despite Deep Brain Stimulation (DBS) improves cardinal symptoms of Parkinson's Disease (PD), its effect on walking impairment is less evident. Robotic-assisted rehabilitation systems could serve as "add-on" physical therapy for PD patients. This systems are able to anticipate and correct the trajectory of patients' motion to improve their motor function recovery. OBJECTIVE: Aim of the present study was the quantitative assessment of the effects of a Robotic-Assisted Rehabilitation Protocol (RARP) on gait patterns by means of three-dimensional gait analysis on PD patients treated with DBS. METHODS: 9 patients with PD treated with DBS were submitted to 5 weeks robotic-assisted rehabilitation sessions. Three-dimensional gait analysis was performed before the starting session, and one day after the last session using an optoelectronic system with passive markers. RESULTS: The RARP showed significant improvements on spatio-temporal gait parameters and on the Unified Parkinson's Disease Rating Scale motor score. CONCLUSIONS: The RARP with Lokomat may have positive effects on spatio-temporal gait parameters of PD patients and it could be an adjunct therapy for patients treated with DBS. On the other hand kinematic and kinetic gait parameters did not show significant improvements, remaining almost comparable before and after the RARP.

Does soccer cleat design influence the rotational interaction with the playing surface?

Non-contact injuries in soccer players may be related to the interplay between cleat type and playing surface, and bladed shoes were often blamed for non-contact injuries with no research support. The aim of this study was to compare the rotational resistance (stiffness and peak sustainable torque) among three types of soccer cleats (metal studs, molded rubber studs, and bladed) in a controlled laboratory environment. The shoes were tested on both natural and artificial turfs under a compressive preload of 1000 N and with internal and external rotations. The three shoe models showed comparable performances with a good repeatability for each individual test on both playing surfaces. A less stiff behavior was observed for the natural turf. A tendency toward highest peak torque was observed in the studded model on natural surface. The bladed cleats provided peak torque and rotational stiffness comparable to the other models. Studded and bladed cleats did not significantly differ in their interaction with the playing surface. Therefore, soccer shoes with bladed cleats should not be banned in the context of presumed higher risk for non-contact injuries.

No difference in gait recovery after THA with different head diameters: a prospective randomized study.

BACKGROUND: Larger femoral heads are commonly presumed to improve joint stability and hip biomechanics; some studies have suggested they may hasten recovery of a normal gait. To our knowledge, no gait analysis studies have compared different size head diameters in THA. QUESTIONS/PURPOSES: We compared (1) spatiotemporal gait parameters, (2) kinematic and kinetic gait parameters, and (3) Harris hip scores in patients undergoing THA randomized to receive a 28-, 36-, or ≥ 42-mm bearing couple. We hypothesized a larger femoral head would restore an earlier, more physiologic gait pattern. METHODS: This randomized, blinded study involved 60 patients who received the same cementless THA except for the size of the bearing. Inclusion criteria were primary hip arthritis, female sex, and age between 55 and 70 years. Exclusion criteria were other problems influencing walking ability. The patients were randomized into three groups of 20 each (28- and 36-mm ceramic-on-crosslinked polyethylene, ≥ 42-mm metal-on-metal). All patients underwent the same postoperative rehabilitation protocol. Gait evaluation using an optoelectronic system was performed preoperatively and at 2 and 4 months postoperatively. RESULTS: With the numbers available, no differences in spatiotemporal gait parameters, kinematic or kinetic gait parameters, or Harris hip scores emerged among the three groups. All variables assessed at 4 months postoperatively showed improvements across all groups, but the differences among them were not significant. CONCLUSIONS: The hypothesis that a larger femoral head results in improved early gait performance was not supported by this study.

Primary stability of pedicle screws depends on the screw positioning and alignment.

BACKGROUND CONTEXT: There is no universal consensus regarding the biomechanical aspects and relevance on the primary stability of misplaced pedicle screws. PURPOSE: The study is aimed to the determination of the correlation between axial pullout forces of pedicle screws with the possible screw misplacement, including mild and severe cortical violations. METHODS: Eighty-eight monoaxial pedicle screws were implanted into 44 porcine lumbar vertebral bodies, paying attention on trying to obtain a wide range of placement accuracy. After screw implantation, all specimens underwent a spiral computed tomography scan, and the screw placements were graded following the scales of Laine et al. and Abul Kasim et al. Axial pullout tests were then performed on a servohydraulic material testing system. RESULTS: Decreasing pullout forces were determined for screws implanted with increasing cortical violation. A smaller influence of cortical violations in the medial direction with respect to the lateral direction was observed. Screws implanted with a large cortical violation and misplacement in the craniocaudal direction were found to be significantly less stable than screws having comparable cortical violation but in a centered sagittal position. CONCLUSIONS: These results provide adjunctive criteria to evaluate more accurately the fate of a spine instrumentation. Particular care should be placed in the screw evaluation regarding the craniocaudal positioning and alignment.

Rigid and flexible spinal stabilization devices: a biomechanical comparison.

The surgical devices for the treatment of degenerative disc disease are based on different concepts (rods for spine fusion, ROM-restricting or load-bearing devices for dynamic stabilization). In the present work, the effects of some stabilization systems on the biomechanics of the lumbar spine were investigated by means of a finite element model of the L2-L5 spine segment. Pedicular screws and stabilization devices were added at L4-L5. Different rods were considered: stainless steel, titanium, PEEK and the composite ostaPek. Two pedicular devices aimed at motion preservation were also considered: the FlexPLUS and the DSS. All models were loaded by using the hybrid protocol in flexion, extension, lateral bending and axial rotation. The spine biomechanics after implantation resulted significantly sensitive to the design and the materials of the device. The impact of all rods in reducing the ROM was found to be critical (>70% in flexion and extension). The dynamic devices were able to preserve the motion of the segment, but with different performances (ROM reduction from 30% (DSS) to 50% (FlexPLUS)). The shared load was more sensitive to the elastic modulus of the device material than the calculated ROMs (from 7% (PEEK) to 48% (stainless steel)). Regarding devices aimed at motion preservation, the authors suggest to distinguish "flexible" devices, which are able to preserve only a minor fraction (e.g. at most 50%) of the physiological ROM, from "dynamic" devices, which induce a smaller ROM restriction. However, the optimal characteristics of a stabilization device for the treatment of degenerative disc disease still need to be determined by means of basic science and clinical studies.

Spine stability after implantation of an interspinous device: an in vitro and finite element biomechanical study.

OBJECT: Interspinous devices are widely used for the treatment of lumbar stenosis. The DIAM spinal stabilization system (Medtronic, Ltd.) is an interspinous implant made of silicone and secured in place with 2 laces. The device can be implanted via posterior access with the sacrifice of the supraspinous ligament (SSL) or via lateral access with preservation of the ligament. The aim of the present work was to evaluate the role of the laces, the SSL, and the device size and positioning to determine the device's ability in reducing segmental lordosis and in stabilizing motion. METHODS: Biomechanical tests were performed in flexion and extension on 8 porcine spines implanted with the DIAM either with or without the laces and the SSL. A finite element model of the human L4-5 spine segments was also created and used to test 2 sizes of the device implanted in 2 different positions in the anteroposterior direction. RESULTS: Implantation of the DIAM induced a shift toward kyphosis in the neutral position. Laces, the SSL, and device size and placement had a significant influence on the neutral position, the stiffness of the implanted spine, and the positions of the instantaneous centers of rotation. CONCLUSIONS: The shift of the neutral position toward kyphosis may be beneficial in reducing symptoms of spinal stenosis such as radicular pain, sensation disturbance, and loss of strength in the legs. The authors recommend preservation of the SSL and the use of the fixation laces, given their relevant mechanical role. Choosing the proper device size and placement should be achieved by using a correct surgical technique.

The influence of the axial, antero-posterior and lateral positions of the center of rotation of a ball-and-socket disc prosthesis on the cervical spine biomechanics.

BACKGROUND: Previous studies documented the importance of the positioning and the design parameters of the prosthesis in determining the biomechanics of the implanted spine. However, a comprehensive biomechanical evaluation of the significance of these parameters is still lacking. Therefore, the paper is aimed to the quantification of their influence on the flexibility of the implanted spine and the force transmitted through the facet joints. METHODS: A finite element model of the C5-C6 spine unit including a ball-and-socket disc prosthesis was built. Three probabilistic variables were considered: the axial, antero-posterior and lateral positions of the center of rotation. Randomized input parameters were generated with the Monte Carlo method. Pure moments of 1.6 Nm in flexion, extension, lateral bending and axial rotation were imposed to the upper endplate of C5; 100 simulations were conducted for the each of the considered loading conditions. FINDINGS: Axial position of the center of rotation influenced the spine flexibility in all loading conditions and the facet force in extension, lateral bending and axial rotation. The antero-posterior position was found to influence the spine flexibility in flexion and extension, and the facet force in lateral bending and axial rotation. The lateral position was not significant. INTERPRETATION: The effects of the positioning of a cervical disc prosthesis were estimated. A wide range of mechanical behaviors can be obtained by the manufacturers by appropriately manipulating the position of the center of rotation. A proper positioning of the artificial disc during the surgery, in particular in the antero-posterior direction, was found to be of critical importance.