External Rotation Stiffness Research Articles

An assessment of factors associated with early postoperative stiffness in arthroscopic rotator cuff repair.

Postoperative stiffness affects up to 20% of patients following arthroscopic rotator cuff repair. Recent evidence indicates that early postoperative stiffness may associated with lower retear rates. This study aimed to identify the independent predictors of early postoperative stiffness. A retrospective cohort study of 1526 rotator cuff repairs was performed. Range of motion at 6-week postop was used to identify stiff patients. Stiffness was defined as external rotation <27.5o or forward flexion <145o . Multiple logistic regression analysis was used to identify the independent predictors of 6-week stiffness. The independent predictors for external rotation stiffness at 6-week postop were more recent cases (Wald = 60), restricted preoperative external rotation (Wald = 36), younger age (Wald = 21) and poorer surgeon-ranked tissue quality (Wald = 15). The independent predictors for forward flexion stiffness were more recent cases (Wald = 101), restricted preoperative forward flexion (Wald = 16) and external rotation (Wald = 13) and female patients (Wald = 12). All patients that developed early postoperative stiffness had recovered range of motion by 6 months to preoperative levels (P < 0.0001). A significantly greater proportion of younger patients (40-49) developed postoperative stiffness when compared to older patients aged 50-59 (P < 0.0062), 70-79 (P < 0.0126) and 80-89 (P < 0.004). Patients that retore had significantly greater average 6-week postoperative range of motion. Patients earlier in the study were found to have greater postoperative range of motion, which coincided with a more aggressive rehabilitation program with less immobilization. Thus, the data supports the hypothesis that a temporary period of shoulder stiffness facilitates tendon repair and ultimately a better outcome post rotator cuff repair.

Comparative study between close reduction internal fixation and open reduction internal fixation in lower fibula with medial mallolus fracture

Comparative study between close reduction internal fixation and open reduction internal fixation in lower fibula with medial mallolus fracture - IJOS- Print ISSN No: - 2395-1354 Online ISSN No:- 2395-1362 Article DOI No:- 10.18231/j.ijos.2020.055, Indian Journal of Orthopaedics Surgery-Indian J Orthop Surg

Biomechanical Assessment of Three Osteosynthesis Constructs by Periprosthetic Humerus Fractures.

Background Biomechanical stability assessment of 3 different constructs for proximal fixation of a locking compression plate (LCP) in treating a Worland type C periprosthetic fracture after total shoulder arthroplasty. Methods 27 Worland type C fractures after shoulder arthroplasty in synthetic humeri were treated with 14-hole LCP that is proximally fixed using the following: (1) 1 × 1.5 mm cerclage wires and 2x unicortical-locking screws, (2) 3 × 1.5 mm cerclage wires, or (3) 2x bicortical-locking attachment plates. Torsional stiffness was assessed by applying an internal rotation moment of 5 Nm and then after unloading the specimen, an external rotation moment of 5 Nm at the same rate was applied. Axial stiffness was assessed by applying a 50 N preload, and then applying a cyclic load of 250 N, then increasing the load by 50 N each time, until a maximum axial load of 2500 N was reached or specimen failure occurred. Results With regard to internal as well as external rotational stiffness, group 1 showed a mean stiffness of 0.37 Nm/deg and 0.57 Nm/deg, respectively, group 2 had a mean stiffness of 0.51 Nm/deg and 0.39 Nm/deg, respectively, while group 3 had a mean stiffness of 1.34 Nm/deg and 1.31 Nm/deg, respectively. Concerning axial stiffness, group 1 showed an average stiffness of 451.0 N/mm, group 2 had a mean stiffness of 737.5 N/mm, whereas group 3 had a mean stiffness of 715.8 N/mm. Conclusion Group 3 displayed a significantly higher torsional stiffness while a comparable axial stiffness to group 2.

Staple-Plate Plus Screw vs Screw Alone in Talonavicular Arthrodesis: A Cadaveric Biomechanical Study.

This study evaluated whether the addition of a nitinol staple-plate to a single cannulated screw increased the mechanical stability for a talonavicular fixation construct. Twenty matched pairs of cadaveric feet were randomized to fusion with either a single 5.5-mm cannulated screw or a screw and a plate with 2 screws and a slot with an 18-mm nitinol staple. After in situ fusion procedure, the talonavicular joint complex was dissected free and the ends were embedded in epoxy. The specimens were then cyclically loaded on a servohydraulic load frame (1000 cycles at 20 N, increasing at intervals of 20 N until failure), half of them for cantilever bending and the other half for torsion. In the bending arm of the study, the staple-plate group showed significantly higher stiffness, failure load, and cycles to failure. In the torsion arm of the study, the staple-plate group also had higher cycles to failure, stiffness in external rotation, and torque to failure. No significant difference was noted in stiffness in internal rotation. We found a significant increase in stability of the talonavicular joint when a nitinol staple-plate construct was placed to augment a single cannulated screw for the purpose of a talonavicular fusion. This information may be helpful to surgeons in implant selection for this common arthrodesis procedure.

Hip external rotation stiffness and midfoot passive mechanical resistance are associated with lower limb movement in the frontal and transverse planes during gait

BackgroundHip external rotation stiffness, midfoot passive mechanical resistance and foot alignment may influence on ankle, knee and hip movement in the frontal and transverse planes during gait. Research questionAre hip stiffness, midfoot mechanical resistance and foot alignment associated with ankle, knee and hip kinematics during gait? MethodsHip stiffness, midfoot mechanical resistance, and foot alignment of thirty healthy participants (18 females and 12 males) with average age of 25.4 years were measured. In addition, lower limb kinematic data during the stance phase of gait were collected with the Qualisys System (Oqus 7+). Stepwise multiple linear regressions were performed to identify if hip stiffness, midfoot torque, midfoot stiffness and foot alignment were associated with hip and knee movement in the transverse plane and ankle movement in the frontal plane with α = 0.05. ResultsReduced midfoot torque was associated with higher hip range of motion (ROM) in the transverse plane (r2 = 0.18), reduced hip stiffness was associated with higher peak hip internal rotation (r2 = 0.16) and higher ROM in the frontal plane (r2 = 0.14), reduced midfoot stiffness was associated with higher peak knee internal rotation (r2 = 0.14) and increased midfoot torque and midfoot stiffness were associated with higher peak knee external rotation (r2 = 0.36). SignificanceThese findings demonstrated that individuals with reduced hip and midfoot stiffness have higher hip and knee internal rotation and higher ankle eversion during the stance phase of gait. On the other hand, individuals with increased midfoot torque and stiffness have higher knee external rotation. These relationships can be explained by the coupling between ankle movements in the frontal plane and knee and hip movements in the transverse plane. Finally, this study suggests that midfoot passive mechanical resistance and hip stiffness should be assessed in individuals presenting altered ankle, knee and hip movement during gait.

Correlation between retear after arthroscopic rotator cuff repair and stiffness of the shoulder

BackgroundThe purpose of this study was to investigate the relationship between retear after arthroscopic rotator cuff repair and passive range of motion of the shoulder. MethodsPassive range of motion before and after surgery was compared between the two groups. ResultsThe healed and retear groups comprised 86.4% and 13.6% shoulders, respectively. Passive external rotation with the arm at the side at 3 months postoperatively was significantly smaller in the healed group than retear group. ConclusionsThis difference seemed to be associated with stiffness in external rotation of the shoulder and the process of cuff healing after surgery. Level of evidenceLevel III, Case-Control Study, Treatment Study.

Calcar screw position in proximal humerus fracture fixation: Don’t miss high!

IntroductionIn locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of “missing” the calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model. Materials and methodsThis experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups. ResultsCadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p = 0.003, p = 0.034) and axial stiffness (p = 0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p = 0.020), increased axial stiffness (p = 0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement. DiscussionThe distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness. Resultsfrom the Sawbones model were more definitive and provided further evidence that proximal calcar screw placements are undesirable and distal implant placement may provide improved construct stability. ConclusionSuccessful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.

CORR Insights®: What Factors are Associated With Clinically Important Improvement After Shoulder Hemiarthroplasty for Cuff Tear Arthropathy?

CORR Insights®: What Factors are Associated With Clinically Important Improvement After Shoulder Hemiarthroplasty for Cuff Tear Arthropathy?

The effects of distal interlocking screws on torsional stability in three-part intertrochanteric hip fractures

ObjectiveMany surgeons currently use long cephomedullary nails for the treatment of intertrochanteric fractures. The optimal indications for deploying distal interlocks are still debatable. This study examined the torsional biomechanical properties of 3-part intertrochanteric femur fractures in a cadaveric bone model using two different distal fixation strategies, an unlocked long cephalomedullary nail versus a dynamically locked nail. Our hypothesis is that a long cephalomedullary nail does not require distal locking fixation when used for treatment of a 3-part intertrochanteric fracture.MethodsFive matched pairs of cadaveric femora were randomly assigned to one of two distal fixation treatment groups; a single distal interlock screw placed in the dynamic orientation or no distal fixation. A 3-part intertrochanteric fracture was produced. Specimens were potted and mounted in a double gimbal fixture facilitating unconstrained motion in the sagittal and coronal planes. Specimens were cyclically loaded dynamically in both internal and external rotation. Range of motion, internal and external rotation stiffness, torsion stiffness, torsion yield and ultimate torsion magnitude were calculated.ResultsThe samples instrumented with a distal locking screw reported statistically greater external rotational stiffness than the unlocked samples in nondestructive testing. The results of the destructive data demonstrated no statistical difference between the locked and unlocked group with regard to yield torque (p = 0.282), peak torque (p = 0.340), stiffness (p = 0.220), displacement at yield torque (p = 0.0605), and displacement at peak torque (p = 0.280).ConclusionDistal locking of a long cephalomedullary nail increases the stiffness of the nail-femur construct in a 3-part biomechanical fracture model. However, our testing illustrates that an unlocked construct will tolerate at least equal stress before catastrophic failure in a torsional loading model.

A biomechanical comparison of locked and unlocked long cephalomedullary nails in a stable intertrochanteric fracture model.

This study compared the torsional properties of stable intertrochanteric femur fractures in a cadaveric bone model using 2 different distal fixation strategies: unlocked long cephalomedullary nailing versus dynamically locked nailing. Fourteen matched pairs of cadaveric femora were randomly assigned to 1 of 2 distal fixation treatment groups: a single distal interlock screw placed in the dynamic orientation or no distal screw fixation. A stable 2-part intertrochanteric fracture was produced. Specimens were potted and mounted in a double gimbal fixture, facilitating unconstrained motion in the sagittal and coronal planes. Specimens were cyclically loaded dynamically in both internal and external rotation. Range of motion, internal and external rotation stiffness, torsion stiffness, torsion yield, and ultimate torsion magnitude were calculated. The samples instrumented with a distal locking screw reported statistically significantly greater internal (1.54 ± 0.81 N·m per degree vs. 1.08 ± 0.35 N·m per degree; P = 0.026) and external rotational stiffness (1.42 ± 0.72 N·m per degree vs. 0.86 ± 0.36 N·m per degree; P = 0.009). Samples with locked distal fixation were statistically stiffer and displayed statistically less displacement at the yield and peak torque. The yield torque was statistically significantly higher in the samples without distal fixation (14.2 ± 3.3 N·m per degree vs. 10.6 ± 3.8 N·m per degree; P = 0.037). The peak torque was comparable between locked and unlocked samples (15.0 ± 4.6 N·m per degree vs. 16.2 ± 4.2 N·m per degree; P = 0.492). Distal locking of femoral intramedullary nails increases the stiffness of the nail-femur construct. Unlocked samples displayed statistically significant higher yield torque while maintaining comparable peak torque as the locked samples. This study indicates that treating stable intertrochanteric fractures with unlocked long intramedullary nails may be an acceptable option, although further clinical study will be needed to test this assertion.

Rotational and peak torque stiffness of rugby shoes

ObjectiveSports people always strive to avoid injury. Sports shoe designs in many sports have been shown to affect traction and injury rates. The aim of this study is to demonstrate the differing stiffness and torque in rugby boots that are designed for the same effect. MethodsFive different types of rugby shoes commonly worn by scrum forwards were laboratory tested for rotational stiffness and peak torque on a natural playing surface generating force patterns that would be consistent with a rugby scrum. ResultsThe overall internal rotation peak torque was 57.75±6.26Nm while that of external rotation was 56.55±4.36Nm. The Peak internal and external rotational stiffness were 0.696±0.1 and 0.708±0.06Nm/deg respectively. Our results, when compared to rotational stiffness and peak torques of football shoes published in the literature, show that shoes worn by rugby players exert higher rotational and peak torque stiffness compared to football shoes when tested on the same natural surfaces. There was significant difference between the tested rugby shoes brands. ConclusionIn our opinion, to maximize potential performance and lower the potential of non-contact injury, care should be taken in choosing boots with stiffness appropriate to the players main playing role.

Biomechanical Comparison of 4 Different Lateral Plate Constructs for Distal Fibula Fractures

Displaced lateral malleolar fractures are often treated with reduction and surgical stabilization. However, there has not been a comprehensive laboratory comparison to determine the most appropriate device for treating these patients. This study subjected a range of contemporary lateral fibular plates to a series of mechanical tests designed to reveal performance differences. Forty fresh frozen lower extremities were divided into 4 groups. A Weber B distal fibula fracture was simulated with an osteotomy and stabilized using 1 of 4 plate systems: a standard Synthes one-third tubular plate with interfragmentary lag screw, a Synthes LCP locking plate with lag screw, an Orthohelix MaxLock Extreme low-profile locking plate with lag screw, or a TriMed Sidewinder nonlocking plate. Controlled monotonic bending and cyclic torsional loading were applied and bending stiffness, torsional stiffness, and fracture site motion were quantified. Resistance to cyclic torsional loading was determined by quantifying the number of loads withstood before excessive rotation occurred. Correlation between bone mineral density and each of the mechanical measures was determined. There was no difference in angulation or bending stiffness between plates. All plates except the LCP showed greater lateral deflection than in the other bending directions. Bending stiffness was lowest in lateral distal fragment deflection for all 4 plates. There was a positive correlation between bone mineral density and bending stiffness for all plate types. There was no difference in fracture site rotation between plate types in internal or external torsion, but internal rotation of the distal fragment consistently exceeded external rotation. Torsional stiffness in external rotation exceeded stiffness in internal rotation in nearly all specimens. LCP plates performed relatively poorly under cyclic torsion. Significant differences in plate performance were not demonstrated. The effects of bone quality variability and differences in interfragmentary screw purchase resulted in data dispersion that confounded absolute ranking of plate performance. Identification of an optimal lateral fibular plating system has the potential to improve the clinical outcome of malleolar fracture fixation, particularly when patient conditions are unfavorable.

The Biomechanics of Ipsilateral Intertrochanteric and Femoral Shaft Fractures: A Comparison of 5 Fracture Fixation Techniques

The aim of the present study was to examine biomechanically 5 different construct combinations for fixation of ipsilateral intertrochanteric and femoral shaft fractures. Twenty-five fresh-frozen adult human femora (age range = 58-91 years, average age = 75.4 years) were tested in physiological bending and in torsion to characterize initial bending and torsional stiffness and stiffness following fixation of combined intertrochanteric and femoral shaft fractures. Five fracture fixation device constructs were assessed-construct A: long dynamic hip screw (long DHS); construct B: reconstruction nail; construct C: DHS plus low-contact dynamic compression plate; construct D: DHS plus retrograde intramedullary nail; and construct E: long intramedullary hip screw. Axial stiffness, torsional stiffness, and axial load-to-failure were the main measurements recorded. There were no differences between constructs in terms of axial stiffness (P = 0.41), external rotation stiffness (P = 0.13), and axial load-to-failure (P = 0.16). However, there was a borderline statistically significant difference in internal rotation stiffness between the constructs (P = 0.048). Specifically, construct C was significantly stiffer than construct E (P = 0.04). All constructs showed no statistical differences when compared with one another, with the exception of construct E, which provided the least torsional stiffness. However, the current in vitro model did not simulate fracture healing or support offered by soft tissues, both of which would affect the stiffness and load-to-failure levels reached.

Shoulder External Rotation Flexibility in Tennis Players

Novotny etal., (J Orthop Res. 2000 Mar;1 8(2): 190–4) showed it is possible to develop a device and protocols to quantify shoulder internal/external rotation range of motion (ROM) and resistance to the associated motion. PURPOSE: The purpose of this project was to develop a device to measure shoulder external rotation (ER) flexibility in an orientation relevant to overhand athletics. A secondary purpose was to determine if relationships exist among flexibility measures in advanced tennis players. METHODS: Twenty-seven advanced (NTPR rating >5.0) male tennis players (age = 22.4 ± 7.3 yrs) participated in the study. The device was built to measure both ER range of motion and the associated resistance in an overhand orientation (upper arm abducted at 90° and in the scapular plane). A load cell measured resistance to ER (torque) and a potentiometer was mounted to the device to measure external rotation ROM (degrees). Flexibility measures included the resistance onset angle (ER angle at 1 N-m of resistance), ER ROM (end ROM), and ER stiffness (slope of torque vs. angle best fit line). Pearson product moment correlations were used to determine if significant relationships existed among flexibility measures. RESULTS: All flexibility measures were highly variable. The resistance onset angle ranged from 80–124° (mean = 100 ± 13°), ER ROM ranged from 87–162° (122 ± 17°), and stiffness ranged from 1.6–4.0 °/N-m (2.4 ± 0.7 °/N-m). No relationship was found between the resistance onset angle and ER stiffness (r = 0.14, p = 0.43), however, a significant positive correlation was found between the resistance onset angle and ER ROM (r = 0.83, p <0.01). No relationship was found between ER ROM and ER stiffness (r = 0.11, p = 0.60). CONCLUSIONS: To our knowledge, this is the first study to objectively quantify resistance to shoulder external rotation in overhand athletes. In this study, tennis players with early resistance onset angles tended to cease ER ROM sooner. Interestingly, the resistance onset angle and ER stiffness appear to be independent.

Rotational control of various pediatric femur fractures stabilized with titanium elastic intramedullary nails.

This study investigated the torsional stability of transverse, oblique, spiral, butterfly, and comminuted pediatric femur fractures reduced with titanium elastic nails. Twenty-five fractures were created in synthetic analog pediatric femora (five of each fracture type); each fracture was reduced with two 4-mm-diameter titanium elastic nails. Each reduced femur was tested for rotational stability using an MTS. Angular displacements and torques were recorded, plotted, and regressed, and the slope (torsional stiffness) was determined; analysis of variance was performed between fracture groups and rotational testing direction. The oblique fracture pattern exhibited the greatest torsional stiffness in internal rotation, the spiral fracture pattern the greatest stiffness in external rotation. All reduced fracture patterns possessed a torsional stiffness statistically equal to or greater than the torsional stiffness of the transverse fracture pattern. These results suggest this method of internal fixation provides a consistent means of rotational stability for a variety of fracture patterns in a synthetic model.

In vivo rotational stability of the kinematic rotating hinge knee prosthesis.

The in vivo rotary laxity and torsional stiffness of the knee joint were measured in 20 patients with wide intraarticular resection of the distal femoral tumor followed by reconstruction with a custom Kinematic rotating hinge endoprosthesis. The contralateral normal knee served as natural control. Twenty patients underwent 29 measurements, including 9 at the first year, 10 at the second year (4 of these also measured at year 1), and 10 at the third year (3 of these also measured at years 1 and 2; 2 also measured at year 2). The mean followup for the 15 survivors was 134 months (range, 102-156 months). The total rotatory laxity of the hinged knee was significantly greater than that of the contralateral knee. The torsional stiffness in external rotation of the hinged knee was 30.4% less than that of the contralateral knee in the first postoperative year, whereas the torsional stiffness in internal rotation was similar to that of the contralateral knee. Torsional stiffness of the hinged knee in the second year was significantly less than that of the contralateral knee whereas it was within the normal range of stiffness in the third year. The total rotatory laxity and torsional stiffness of the hinged knee in the early postoperative years could not predict the risk of late loosening. In vitro rotational stability of the rotating hinge device with axial load bearing was 6.7 and 8.1 Newton-meters (N-m) at 0 degrees and 20 degrees knee flexion, respectively, under an axial tibial load of 945 Newtons.

Stiffness and laxity of the knee--the contributions of the supporting structures. A quantitative in vitro study

Thirty-five normal cadaver knees were tested manually in six positions of the knee using apparatus designed to measure the moment-rotation responses for both varus-valgus angulation and torsion of the tibia, as well as the force-displacement responses for anterior-posterior movement of the tibia. The responses of all knees to all modes of loading were non-linear, reflecting increasing stiffness. With the knee at full extension, stiffness was maximum and laxity was minimum. Hence, it was in this position that changes in stability (laxity and stiffness) were best demonstrated when ligament structures were sectioned. Differences in laxity were observed between right and left knees of intact paired specimens. Torsional laxity and internal rotation stiffness were most affected by sectioning the medial collateral ligament, while external rotation stiffness was only affected by division of both the lateral collateral ligament and the posterior capsule. Varus-valgus laxity was relatively unaffected by removal of the menisci or section of the cruciate ligaments but increased greatly when either collateral ligament was cut. The medial collateral ligament was the main contributor to valgus stiffness, whereas the lateral collateral ligament had no measurable effect on varus stiffness. Anterior-posterior stability was affected to some extent by virtually every sectioning procedure. Isolated section of the anterior cruciate ligament produced the greatest increase in anterior-posterior laxity at full extension and section of the posterior cruciate, the greatest increase at 90 degrees of flexion. Large increases in anterior-posterior laxity were also observed when the medial collateral ligament and posterior capsule were sectioned in combination.