Posterolateral rotatory instability (PLRI) is the most common type of elbow instability. It is caused by an insufficiency of the lateral ligamentous complex, which consists mainly of the radial collateral ligament (RCL) and the lateral ulnar collateral ligament (LUCL). Investigate the influence of serial sectioning of the lateral ligamentous complex on elbow stability in a cadaveric model of PLRI. Kinematics of six fresh frozen cadaveric elbow specimens were measured by digitizing anatomical marks with a Microscribe 3DLX digitizing system (Revware Inc, Raleigh, NC). Each specimen was tested under four conditions: Intact, LUCL tear, LUCL and RCL tear, and complete Tear (LUCL, RCL and capsule tear). Each specimen was tested in 30°, 60° and 90° elbow flexion angles. Varus- laxity was measured in supination, pronation, and neutral forearm rotation positions and total forearm rotation was measured with 0.3 Nm of torque. Statistical significant differences between the conditions were detected using a two-way ANOVA with Tukey's post-hoc test. The radial head dislocated in all specimens in LUCL and RCL tear and Comp but not in LUCL tear. Total forearm ROM did not increase form intact to LUCL tear (p>0.05) but significantly increased in LUCL and RCL tear (p=0.0002) and complete tear (p<0.0001) in all flexion angles. Additionally, ROM in LUCL tear significantly differed from LUCL and RCL tear and complete tear (p=0.0027 and p=0.0002). A similar trend was seen with the varus angle. While there was a significant difference when the intact condition was compared to both the LUCLand RCL tear and complete tear conditions (p<0.0001 and p<0.0001), there was no difference between the intact and LUCL tear conditions. LUCL tear alone is not sufficient to cause instability and increase ROM and varus angle, meanwhile the increase of ROM and varus angle with additional capsular tear was not significant compared to LUCL and RCL tear. The increase of ROM after LUCL and RCL tear is an unknown symptom of PLRI.
Insufficiency of the lateral collateral ligamentous complex causes posterolateral rotatory instability (PLRI). During reconstruction surgery the joint capsule is repaired, but its biomechanical influence on elbow stability has not been described. We hypothesized that capsular repair reduces ROM and varus angle after reconstruction of the lateral collateral complex. Six fresh frozen cadaveric elbow specimens were used. Varus laxity in supination, pronation and neutral forearm rotation with 1 Nm load and forearm rotaitonal range of motion (ROM) with 0.3 Nm torque were measured using a Microscribe 3DLX digitizing system (Revware Inc, Raleigh, NC). Each specimen was tested under four different conditions: Intact, Complete Tear with LUCL, RCL and capsule tear, LUCL/RCL reconstruction + capsule repair and LUCL/RCL reconstruction only. Reconstruction was performed according to the docking technique (Jones, JSES, 2013) and the capsule was repaired with mattress sutures. Each condition was tested in 30°, 60° and 90° elbow flexion. A two-way ANOVA with Tukey's post-hoc test was used to detect statistical differences between the conditions. Total ROM of the forearm significantly increased in all flexion angles from intact to Complete tear (p<0.001). ROM was restored to normal in 30° and 60° elbow flexion in both reconstruction conditions (p>0.05). LUCL/RCL Reconstruction + capsule repair in 90° elbow flexion was associated with a significantly lower ROM compared to intact (p=0.0003) and reconstruction without capsule repair (p=0.015). Varus angle increased significantly from intact to complete tear (p<0.0001) and restored to normal in both reconstruction conditions (p>0.05) in 30° and 60° elbow flexion. In contrast varus angle was significantly lower in 90° elbow flexion in both reconstruction conditions compared to intact (both p<0.0001). Reconstruction of the lateral collateral complex restores elbow stability, ROM and varus laxity independent of capsular repair. Over tightening of the elbow joint occurred in 90° elbow flexion, which was aggravated by capsular repair. Over all capsular repair can be performed without negatively affecting elbow joint mobility.
Acute Hill-Sachs (HS) reduction represents a potential alternative method to remplissage for the treatment of an engaging HS lesion. The purpose of this study is to biomechanically compare the stabilising effects of a acute HS reduction technique and remplissage in a complex instability model. This was a comparative cadaveric study of 6 shoulders. For the acute HS lesion, a unique model was used to create a 30% defect, compressing the subchondral bone while preserving the articular surface in a more anatomic fashion. In addition, a 15% glenoid defect was made in all specimens. The HS lesion was reduced through a lateral cortical window with a bone tamp, and the subchondral void was filled with Quickset (Arthrex) bone cement to prevent plastic deformation. Five scenarios were tested; intact specimen, bipolar lesion, Bankart repair, remplissage with Bankart repair and HS reduction technique with Bankart repair. Translation, kinematics and dislocation events were recorded. For all 6 specimens no dislocations occurred after either remplissage or the reduction technique. At 90 degrees of abduction and external rotation (ABER), anterior-inferior translation was 11.1 mm (SD 0.9) for the bipolar lesion. This was significantly reduced following both remplissage (5.1±0.7mm; p<0.001) and HS reduction (4.4±0.3mm; p<0.001). For anterior-inferior translation there was no significant difference in translation between the reduction technique and remplissage (p=0.91). At 90 degrees of ABER, the intact specimens average joint stiffness was 7.0±1.0N/mm, which was not significantly different from the remplissage (7.8±0.9 N/mm; p=0.9) and reduction technique (9.1±0.6 N/mm; p=0.50). Compared with an isolated Bankart repair, the average external rotation loss after also performing a remplissage procedure was 4.3±3.5 deg (p=0.65), while average ER loss following HS reduction was 1.1±3.3 deg (p=0.99). There was no significant difference in external rotation between remplissage and the reduction technique (p=0.83). Similar joint stability was conferred following both procedures, though remplissage had 3.2-degree loss of ER in comparison. While not statistically significant, even slight ER loss may be clinically detrimental in overhead athletes. Overall, the acute reduction technique is a more anatomic alternative to the remplissage procedure with similar ability to prevent dislocation in a biomechanical model, making it a viable treatment option for engaging Hill-Sachs lesions.
Total knee arthroplasty (TKA) is a very successful procedure with good clinical outcomes. However, the effects of obesity on TKA outcomes remain controversial and inconclusive. The objective of this study was to quantify the biomechanical effects of simulated obesity on Cruciate Retaining (CR) and Posterior Stabilized (PS) TKA in human cadaveric knees. We hypothesized that biomechanical characteristics of CR TKA will be less dependent on simulated obesity compared to PS TKA. Eight cadaveric knees (4 male, 4 female) average age 68.4 years (range, 40–86 years) underwent TKA and were tested using a custom knee testing system. Specifically, Cruciate Retaining (CR) and Posterior Stabilized (PS) Lospa Knee System (Corentec Inc.) were implanted and tested sequentially using internal control experimental design. The muscle loading was determined based on the physiological cross-sectional area ratio of the quadriceps and hamstring muscles. The ratios were then applied to CDC data representing the average male height and used to simulate a BMI of 25, 30, and 35 at knee flexion angles (KFA) of 15, 30, 45, 60, 75, and 90 degrees. Patellofemoral and tibiofemoral joint contact areas and pressures were measured using the K-scan sensor system (Tekscan Inc, South Boston, MA). Contact area, force, pressure and peak contact pressure were obtained and analyzed for each specimen. Knee kinematics were quantified using a Microscribe 3DLX digitizer (Revware Inc, Raleigh, North Carolina). Repeated measure analysis of variance with a Tukey post hoc test was used to compare loading conditions. Comparisons between the CR and PS TKA groups were made with a paired INTRODUCTION
METHODS
Reverse total shoulder arthroplasty continues to have a high complication rate, specifically with component instability and scapular notching. Therefore, the purpose of this study was to quantify the effects of humeral component neck angle and version on impingement free range of motion. A total of 13 cadaveric shoulders (4 males and 9 females, average age = 69 years, range 46 to 96 years) were randomly assigned to two studies. Study 1 investigated the effects of humeral component neck angle (n=6) and Study 2 investigated the effects of humeral component version (n=7). For all shoulders, Tornier Aequalis® Reversed Shoulder implants (Edina, MN) were used. For study 1, the implants were modified to 135, 145 and 155 degree humeral neck shaft angles and for Study 2 a custom implant that allowed control of humeral head version were used. For biomechanical testing, a custom shoulder testing system that permits independent loading of all shoulder muscles with six degree of freedom positioning was used. (Figure 1) Internal control experimental design was used where all conditions were tested on the same specimen.Introduction
Methods
The purpose of this study was to compare the biomechanical effects of the trapezius transfer and the latissimus dorsi transfer in a cadaveric model of a massive posterosuperior rotator cuff tear. Eight cadaveric shoulders were tested at 0°, 30°, and 60° of abduction in the scapular plane with anatomically based muscle loading. Humeral rotational range of motion and the amount of humeral rotation due to muscle loading were measured. Glenohumeral kinematics and joint reaction forces were measured throughout the range of motion. After testing in the intact condition, the supraspinatus and infraspinatus were resected, simulating a massive rotator cuff tear. The lower trapezius transfer was then performed. Three muscle loading conditions for the trapezius (12N, 24N, 36N) were applied to simulate a lengthened graph as a result of excessive creep, a properly tensioned graph exerting a force proportional to the cross-sectional area of the inferior trapezius, and an over-constrained graph respectively. Next the latissimus dorsi transfer was performed and tested with one muscle loading condition 24N. A repeated-measures analysis of variance was used for statistical analysis.Background:
Methods:
