Pistol Grip Research Articles

Exposures and Physiological Responses in Power Tool Operations: Fastening vs. Unfastening Threaded Hardware

Powered hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders. This study examined and compared the kinetic and physiological impacts on operator upper extremities between the fastening and unfastening operations. Thirty-two healthy, right-handed male operators used four tools on two joint simulators at different working heights and distances in the laboratory. Three work configurations were simulated: pistol grip tools on a vertical and horizontal surface, and right angle tools on a horizontal surface. Grip force was measured on an instrumented handle attached to each tool. Muscle activity was monitored at the wrist flexor and extensor and the upper trapezius of the right arm. Paired comparisons showed that when pistol grip tools were used, the peak torque to unfasten a joint (3.7 Nm) was significantly less than to fasten the same joint (5.7 Nm). However, the exposure time was longer for unfastening cycles (98 ms more on the horizontal surface, and 107 ms more on the vertical surface). The average grip force scaled to corresponding peak tool torque revealed that the effort to react against torque was greater in unfastening cycles than in fastening cycles for all work configurations. It also showed that as a proximal stabilizer, the upper trapezius muscle had a greater activity in unfastening cycles. The kinetic and physiological responses demonstrated that unfastening fasteners, which has been neglected in the literature, have the potential to increase risk for musculoskeletal disorders and should be considered in ergonomics assessment in the workplace.

Radiographic Prevalence of Femoroacetabular Impingement in a Young Population with Hip Complaints Is High

Femoroacetabular impingement (FAI) is reportedly a prearthritic condition in young adults that can progress to osteoarthritis. However, the prevalence of FAI is unknown in the young, active population presenting with hip complaints. We sought to determine (1) the prevalence of radiographic findings of FAI in a young, active patient population with complaints localized to the region of the hip presenting to primary care and orthopaedic clinics; (2) the percentage of films with FAI with an official reading suggesting the diagnosis; and (3) whether the Tönnis grades of osteoarthritis corresponded to the findings of FAI. We performed a database review of pelvic and hip radiographs obtained from 157 young (mean age 32 years; range, 18-50 years) patients presenting with hip-related complaints to primary care and orthopaedic clinics. Radiographs were analyzed for signs of FAI (herniation pits, pistol grip deformity, center-edge angle, alpha angle, and crossover sign) and Tönnis grade. Radiology reports were reviewed for a diagnosis of FAI. At least one finding of FAI was found in 135 of the 155 patients (87%). Four hundred thirteen of 487 radiographs (85%) had been read as normal and one read as showing FAI. Tönnis grades did not correlate with radiographic signs of FAI. Radiographic evidence of FAI is common in active patients with hip complaints. Increased awareness of FAI in primary care, radiology, and orthopaedic clinics and additional research into the long-term effects of management are warranted. Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Prevalence of radiological signs of femoroacetabular impingement in patients presenting with long-standing adductor-related groin pain

ObjectiveA decreased range of motion (ROM) of the hip joint is known to predispose to athletic groin injury. Femoroacetabular impingement (FAI) of the hip leads to a reduced ROM. This...

Accuracy of Computer-assisted Navigation for Femoral Head Resurfacing Decreases in Hips with Abnormal Anatomy

Computer-assisted navigation systems for hip resurfacing arthroplasty are designed to minimize the chance of implant malposition. However, there is little evidence computer navigation is useful in the presence of anatomical deformity. We therefore determined the accuracy of an image-free resurfacing hip arthroplasty navigation system in the presence of a pistol grip deformity of the head and femoral neck junction and of a slipped upper femoral epiphysis deformity. We constructed an artificial phantom leg from machined aluminum with a simulated hip and knee. The frontal and lateral plane implant-shaft angles for the guide wire of the femoral component reamer were calculated with the computer navigation system and with an electronic caliper combined with micro-CT. There was a consistent disagreement between the navigation system and our measurement system in both the frontal plane and lateral plane with the pistol grip deformity. We found close agreement only for the frontal plane angle calculation in the presence of the slipped upper femoral epiphysis deformity, but calculation of femoral head size was inaccurate. The use of image-free navigation for the positioning of the femoral component appears questionable in these settings.

Prolonged mechanical and physiological changes in the upper extremity following short-term simulated power hand tool use

This study investigated in-vivo changes in upper limb dynamic mechanical properties and magnetic resonance imaging (MRI) parameters following short-term power hand tool operation. Previous studies have found reduction in mechanical properties following short-term power tool usage at long build-up times. This study advances that work by having participants operate a simulated pistol grip power hand tool and evaluating changes in mechanical properties, strength, discomfort level and MRI prior to tool operation and daily for 3 d after tool operation. Twenty-four participants were randomly assigned to operate a simulated power hand tool for either a high peak reaction force of 123 N (peak torque = 8 Nm, build-up time = 250 ms) or at a low peak reaction force of 5 N (peak torque = 2 Nm, build-up time = 50 ms). Subjects operated the tool for 60 min at the rate of six times per min. A reduction in stiffness (27%, p < 0.05) was observed 24 h after tool operation for the high force group and this change persisted (26%, p < 0.05) up to 72 h after tool operation. Similar changes were not observed for the low force group. No changes were observed in mass moment of inertia, damping, isometric strength and damping for either group (p > 0.05). There was a signal intensity increase (12%, CI 19%, 5.06%) in the supinator muscle MRI for both groups 24 h after tool operation but only the high force group remained elevated (10%, CI 13.7%, 0.06%) 72 h after tool operation. Persistent short-term changes in mechanical and MRI parameters at high force levels could indicate increased strain on the upper limb and may negatively affect ability to react during rapid forceful loading of the upper limb. This research can ultimately lead to better ergonomic interventions through quantitative power hand tool design guidelines and work practices based on understanding the damaging effects of exposure to specific levels of reaction force, build-up time and repetition, as well as providing new outcome measures for epidemiological studies.

Nonspherical femoral head shape (pistol grip deformity), neck shaft angle, and risk of hip osteoarthritis: A case–control study

To determine whether 2-dimensional measures of femoral head shape and angle are associated with hip osteoarthritis (OA). We compared cases with symptomatic radiographic hip OA with asymptomatic controls with no radiographic hip OA. On anteroposterior pelvis radiographs, we measured "pistol grip deformity" for each hip (visually categorized as nonspherical, indeterminate, or spherical), the femoral head-to-femoral neck ratio as an interval measure of femoral head shape, and the femoral neck shaft angle. The relative risk of hip OA associated with each feature was estimated using odds ratios (ORs) and 95% confidence intervals (95% CIs), adjusted for possible confounders using a logistic regression model. Of 1,007 cases, 965 had definite radiographic hip OA; of 1,123 controls, 1,111 had no radiographic OA. The prevalence of pistol grip deformity in at least 1 hip was 3.61% in controls and 17.71% in cases (OR 6.95 [95% CI 4.64-10.41]), and the prevalence of abnormal femoral head-to-femoral neck ratio in at least 1 hip was 3.70% in controls and 24.27% in cases (OR 12.08 [95% CI 8.05-18.15]). The risk of hip OA increased as the femoral head-to-femoral neck ratio decreased (P for trend<0.001) and with each extreme of neck shaft angle (P<0.05). In cases with unilateral hip OA, the prevalence of abnormal femoral head-to-femoral neck ratio in the unaffected hip was 2 times greater than that in controls (OR 1.82 [95% CI 1.07-3.07]); in contrast, an abnormally low, but not abnormally high, neck shaft angle was more common in unaffected hips than in controls (OR 1.79 [95% CI 1.03-3.14]). Our findings indicate that pistol grip deformity is associated with hip OA. The increased prevalence of pistol grip deformity and an abnormally low neck shaft angle in unaffected hips of cases with unilateral OA suggests that they are risk factors for development of hip OA. However, both a nonspherical head shape and an increase in neck shaft angle may occur as a consequence of OA.

Predicting subjective perceptions of powered tool torque reactions

Powered hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders. In this study, subjective ratings of discomfort and acceptability of reaction forces were collected in an attempt to identify their associations with factors such as work location, and response covariates such as grip force and tool handle displacement. Three work configurations using pistol grip and right angle pneumatic nutrunners on horizontal and vertical surfaces were set up in the laboratory. Twenty healthy right-handed male participants operated four tools at nine locations and the corresponding subjective responses were collected. The results indicate that normalized grip force during the torque buildup period was a significant factor for both subjective ratings. For the unacceptable torque reactions across the three tool configurations, the ratio of hand moment impulse over tool torque impulse was significantly greater than for the acceptable reactions. For pistol grip tools used on the vertical surface, as the working height increased 30 cm, the odds of an unacceptable rating over an acceptable rating increased 1.6 times. Prediction models for subjective ratings of discomfort and acceptability provide insight regarding either workstation design or exposure control. These models can further be used to establish exposure limits based on handle displacement and grip force.

The Etiology of Osteoarthritis of the Hip

More than 90% of patients with so-called primary or idiopathic osteoarthritis of the hips in whom sufficient data were available to make an assessment of the normality of the hip joint at the cessation of growth clearly showed demonstrable abnormalities in the hip joint. The most common are mild acetabular dysplasia and/or pistol grip deformity. This latter deformity is associated with mild slipped capital femoral epiphysis (recognized or unrecognized at the time), Legg-Perthes' disease (recognized or unrecognized at the time), multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia, and/or the presence of an intraacetabular labrum, as well as, in certain instances, acetabular dysplasia. When these abnormalities are taken in conjunction with the detection of other metabolic abnormalities that can lead to osteoarthritis of the hip and which may not be recognized readily, such as hemochromatosis, ochronosis, calcium pyrophosphate disease, and monarticular rheumatoid arthritis, it seems clear that either osteoarthritis of the hip does not exist at all as a primary disease entity or, if it does, is extraordinarily rare.

Femoroazetabuläres Impingement - Behandlung des FAI bei Epiphyseolysis capitis femoris durch chirurgische Hüftgelenksluxation

Spencer S, Millis MB, Kim YJ (2006): Early results of treatment for hip impingement syndrome in slipped capital femoral epiphysis and pistol grip deformity of the femoral head-neck junction using the surgical dislocation technique. J Ped Orth 26:281-28

Power grip strength as a function of tool handle orientation and location

Thirty male volunteers participated in a study evaluating the effect of workspace envelope (work height and reach distance) and handle orientation on grip force capacity. Maximum voluntary power grip exertions were recorded using instrumented tool handles under three conditions: a pistol grip tool handle oriented horizontally and vertically and a right angle tool handle oriented horizontally. Significant main effects of handle height and reach location on normalized grip force capacity were observed with the horizontally oriented pistol grip and right angle handles, whereas only an interaction effect was observed with the vertically oriented pistol grip handle. Comparison of results to scores produced with a job assessment tool (RULA) is included as an appendix. The proposed methodology can provide information useful to job, workstation or tool design directed toward best accommodating the physical capacities of workers performing hand tool tasks.

Effects of user experience, working posture and joint hardness on powered nutrunner torque reactions

Powered hand tools produce reaction forces that may be associated with upper extremity musculoskeletal disorders. The handle displacement, grip force and upper limb muscle activity (electromyography (EMG)) due to the effects of operator experience, working height and distance, type of tool and fastener joint hardness were measured in this study with 15 experienced and 15 novice nutrunner users. The results show that when pistol grip handles were used to work on a horizontal surface, experienced users allowed an average handle displacement of 7.9°, while novice users allowed 11.5°. Average EMG scaled by reference voluntary contraction (RVC) at forearm flexors, forearm extensors and biceps were greater for experienced users (318% RVC, 285% RVC, 143% RVC, respectively) than for novice users (246% RVC, 219% RVC, 113% RVC, respectively). Experienced users exerted more grip force than novice users when using right angle handles, but less force when using pistol grip handles. The results suggest that it is possible to minimize tool handle displacement by adapting the workplace layout to permit different working postures for each user group.

Power Hand Tool Kinetics Associated with Upper Limb Injuries in an Automobile Assembly Plant

This study investigated the relationship between pneumatic nutrunner handle reactions, workstation characteristics, and prevalence of upper limb injuries in an automobile assembly plant. Tool properties (geometry, inertial properties, and motor characteristics), fastener properties, orientation relative to the fastener, and the position of the tool operator (horizontal and vertical distances) were measured for 69 workstations using 15 different pneumatic nutrunners. Handle reaction response was predicted using a deterministic mechanical model of the human operator and tool that was previously developed in our laboratory, specific to the measured tool, workstation, and job factors. Handle force was a function of target torque, tool geometry and inertial properties, motor speed, work orientation, and joint hardness. The study found that tool target torque was not well correlated with predicted handle reaction force (r = 0.495) or displacement (r = 0.285). The individual tool, tool shape, and threaded fastener joint hardness all affected predicted forces and displacements (p < 0.05). The average peak handle force and displacement for right-angle tools were twice as great as pistol grip tools. Soft-threaded fastener joints had the greatest average handle forces and displacements. Upper limb injury cases were identified using plant OSHA 200 log and personnel records. Predicted handle forces for jobs where injuries were reported were significantly greater than those jobs free of injuries (p < 0.05), whereas target torque and predicted handle displacement did not show statistically significant differences. The study concluded that quantification of handle reaction force, rather than target torque alone, is necessary for identifying stressful power hand tool operations and for controlling exposure to forces in manufacturing jobs involving power nutrunners. Therefore, a combination of tool, work station, and task requirements should be considered.

Hand-Handle Interface Force and Torque Measurement System for Pneumatic Assembly Tool Operations: Suggested Enhancement to ISO 6544

A hand-handle interface force and torque measurement system is introduced to fill the void acknowledged in the international standard ISO 6544, which governs pneumatic, assembly tool reaction torque and force measurement. This system consists of an instrumented handle with a sensor capable of measuring grip force and reaction hand moment when threaded, fastener-driving tools are used by operators. The handle is rigidly affixed to the tool in parallel to the original tool handle allowing normal fastener-driving operations with minimal interference. Demonstration of this proposed system was made with tools of three different shapes: pistol grip, right angle, and in-line. During tool torque buildup, the proposed system measured operators exerting greater grip force on the soft joint than on the hard joint. The system also demonstrated that the soft joint demanded greater hand moment impulse than the hard joint. The results demonstrate that the measurement system can provide supplemental data useful in exposure assessment with power hand tools as proposed in ISO 6544.

Subjective Perceptions toward Selected Power Nutrunner Torque Reactions

Power hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders (UEMSDs). The reaction forces affect the subjective ratings of perceived exertions associated with tool operations. This paper addresses how operators perceived power nutrunner torque reactions. Two work configurations using pistol grip and right angle tools were tested in the laboratory. Twenty male participants operated four automatic shutoff pneumatic nutrunners on two different task joints using various postures. Handle displacement and the grip force for each torque reaction was monitored. Subjective ratings of discomfort and acceptance toward the given reaction were recorded. The results show that discomfort and acceptance for torque reactions were significantly affected by grip force but not by handle displacement. Odds ratios using grip force as a predictor were calculated. This study can helping setting physical exposure limits encountered in power nutrunner operations.

Early Results of Treatment of Hip Impingement Syndrome in Slipped Capital Femoral Epiphysis and Pistol Grip Deformity of the Femoral Head-Neck Junction Using the Surgical Dislocation Technique

Pistol grip deformity of the femoral head-neck junction and slipped capital femoral epiphysis can cause anterior impingement leading to pain, cartilage damage and eventual osteoarthritis. Osteoplasty of this metaphyseal prominence, with or without concomitant intertrochanteric osteotomy, using a surgical dislocation approach, can effectively treat this problem. Clinical and radiographic outcomes were assessed in 19 patients who underwent osteoplasty or osteoplasty/intertrochanteric osteotomy via Ganz-type surgical dislocation with average 12-month follow-up. Preoperative and postoperative Western Ontario and McMaster Osteoarthritis Index (WOMAC) questionnaires and radiographs were obtained and evaluated. In the osteoplasty group, 7 patients improved, 4 were unchanged, and 2 worsened. In the osteoplasty/osteotomy group, 5 of 6 patients improved. Patients with chondral flaps had less improvement. No avascular necrosis was noted postoperatively, and all trochanteric osteotomies healed. The surgical dislocation approach, combined with osteoplasty and/or bony realignment, is a safe efficacious treatment option for symptomatic pistol grip deformity. Outcomes are worse if there is preexisting cartilage damage.

Arthroscopic Treatment of Osseous Abnormalities as a Cause of Femoroacetabular Impingement: Preliminary Clinical Results

Purpose : To report the preliminary clinical results for arthroscopic treatment of osseous abnormalities as a cause of femoroacetabular impingement (FAI). Materials and Methods : We evaluated 26 patients diagnosed with FAI who were treated by arthroscopic debridement of the labrum, spur resection, and bump resection from March 2004 to March 2005. Osseous abnormalities of FAI were evaluated for the presence or absence of asphericity, pistol grip deformity, coxa vara, coxa valga, retroversion of the acetabulum, and protrusion of acetabulum were present or not. We evaluated the clinical manifestations based on patient satisfaction, sequential JOA pain scores and ranges of motion of the hips. Results : 24 patients were satisfied postoperatively. The average JOA pain score preoperatively and postoperatively at 2 weeks, 6 weeks, 3 months, and 6 months, were 0.85, 0.71, 1.50, 1.71, and 1.86, respectively. At 2 weeks preoperatively, the clinical symptoms were aggravated and 6 months postoperatively, the clinical symptoms were improved. 11 patients could not take a cross-legged position preoperatively: but 10 of the 11 patients could take a cross-legged position postoperatively. Conclusion : Preliminary clinical results for arthroscopic treatment of osseous abnormalities were satisfactory. We need to perform a follow-up study of the clinical results about the early detection of which findings and decompression of which osseous abnormalities will prevent or delay the progression of osteoarthritis through mid and long-term follow up.

Three-dimensional computed tomography of the hip in the assessment of femoroacetabular impingement

Femoroacetabular impingement secondary to the cam effect is thought to be associated with an insufficient anterior concavity in the sagittal/axial plane of the femoral head-neck junction. Using three-dimensional computed tomography the anterior and posterior concavity of the femoral head-neck junction was assessed in 36 painful non-dysplastic hips (30 patients). The mean age of the symptomatic hips was 40.7 with 13 females and 17 males. Eighteen out of the 36 hips had a pistol grip deformity. Magnetic resonance gadolinium arthrography was performed to assess for labral and cartilage lesions. Alpha and beta angles measuring the anterior and posterior femoral head-neck junction concavities were also determined in 20 asymptomatic hips (12 patients; mean age 37, 5 females and 7 males) using three-dimensional computed tomography. The mean alpha angle for the symptomatic and the control group were: 66.4 versus 43.8 (p=0.001), and for the beta angle 40.2 versus 43.8 (p=0.011), respectively. All but one of the symptomatic hips had a labral tear with 61% of these hips having associated cartilage damage. Three-dimensional computed tomography represents an accurate tool to quantify the femoral head-neck concavity providing a non-invasive assessment of hips at risk of femoroacetabular impingement.

Handle displacement and operator responses to pneumatic nutrunner torque buildup

The objective of this study is to investigate the workstation and tool effects on the responses of the powered hand tool operator reacting against the impulsive reaction forces that may be associated with upper extremity musculoskeletal disorders. The study demonstrated a means of direct measurement of force at the interface between the tool and the operator. Fifteen experienced male operators performed three independent work configurations: pistol grip and right angle tools used on the horizontal surface and pistol grip tools used on the vertical surface, in the laboratory. A full factorial experiment consisting of 36 conditions was designed to examine the effects of working height, distance, tool, and fastener joint hardness on handle displacement and grip forces. The results indicate that operator responses were affected by different factors depending on the work configuration. When pistol grip tools were used on the vertical surface, the mean handle displacement decreased from 9.9° to 7.3° as the working height increased from 30 cm below shoulder to 30 cm above shoulder. When right angle tools were used, the greatest handle displacement (51.1 mm) and grip force (84.7% MVC) during torque reactions were measured at 30 cm below elbow and 40% forward reach away from the operator. This study provides quantitative information that can be used for workstation design and tool selection to reduce the torque reaction experienced by powered nutrunner operators.

Meniscal Repair Using the Polysorb Meniscal Stapler XLS

We present our technique of repair of meniscal tears in 11 patients using a newly designed stapler, the Polysorb Meniscal Stapler XLS (USS Sports Medicine, Norwalk, CT), to increase the effectiveness and ease of repair of tears in the vascular zone while limiting potential complications. The low-profile stapler comes with a reloadable pistol grip device and a disposable straight or 15° upcurved shaft with a single preloaded 10-mm staple. Standard anteromedial and anterolateral portals were used, along with a superomedial portal for inflow. The portal was enlarged slightly to facilitate introduction of the cannula or the stapler directly into the knee. The nose of the stapler was applied to the superior surface of the inner edge of the meniscal tear. The sharp points on the tip of the nose were used to manipulate the inner edge and coapt the tear site. Firm pressure was applied to the meniscal tissue, and the nose of the stapler was embedded in the inner edge of the meniscus no more than 2 to 3 mm from the tear (as measured along the meniscal surface). The handle was pulled slowly as the staple engaged the meniscal tissue. This step was repeated every 3 to 4 mm to ensure ideal tear stabilization.

Effect of User Experience on Powered Nutrunner Torque Reactions

Powered tools are widely used in industries and they produce reaction forces that may be associated with upper extremity musculoskeletal disorders. The handle displacement, grip force, and upper limb EMG during impulsive torque reactions due to the effect of operator experience was examined in the study with 15 experienced and 15 novice tool users. The results show that experienced users allowed an average of 7.9° of handle displacement, while novice users allowed 11.5° when pistol grip tools were used on a horizontal surface. Experienced users exerted more grip force than novice users when using right angle tools, but less when using pistol grip tools. Average EMG magnitudes at flexors, extensors, and biceps were greater for experienced users. Recommendations regarding tool selection and workstation design can be derived from the results to minimize physical exposure for both user groups during power tool usage.