Joshua W. Giles

Moderate to large engaging Hill-Sachs defects: an in vitro biomechanical comparison of the remplissage procedure, allograft humeral head reconstruction, and partial resurfacing arthroplasty

BACKGROUND The management of engaging Hill-Sachs defects (HSD) is controversial. The purpose of this study was to biomechanically compare 3 treatment strategies. MATERIALS AND METHODS Eight specimens were tested on a shoulder simulator. The protocol involved testing 2 unrepaired HSD (30% and 45%), which were then treated with remplissage, humeral head allograft (HHA), and partial resurfacing arthroplasty (PRA). Stability (defect engagement and glenohumeral stiffness) and range of motion (ROM) were measured. RESULTS All 30% and 45% HSDs engaged and dislocated. Remplissage and HHA effectively prevented engagement in all specimens; however, 62% of PRA engaged. No repair exhibited stiffness significantly greater than intact, but 30% and 45% remplissage produced a 74% and 207% increase, respectively, and were significantly greater than the unrepaired states (P ≤ .047). Stiffness results for HHA and PRA closely matched those of intact. In adduction, remplissage reduced internal-external ROM compared with both defects (P ≤ .01), but only 30% remplissage caused a significant decrease compared with intact (P = .049). In abduction, all repairs reduced ROM compared with HSD (P ≤ .04), but none compared with intact (P ≥ 0.05). In extension, remplissage had significantly less ROM than either HHA or PRA (P ≤ .02). CONCLUSION All procedures improved stability; however, unlike remplissage, results from HHA and PRA closely resembled intact. Remplissage (30% and 45%) improved stability and eliminated engagement but caused reductions in ROM. HHA and PRA re-established intact ROM, but PRA could not fully prevent engagement. The effects of each technique are not equivalent and further studies are required.

Does the dynamic sling effect of the Latarjet procedure improve shoulder stability? A biomechanical evaluation

INTRODUCTION Glenohumeral instability with glenoid bone loss is commonly treated with the Latarjet procedure. The procedure involves transfer of the coracoid and conjoint tendon, which is thought to provide a stabilizing sling effect; however, its significance is unknown. This study evaluated the effects of the Latarjet procedure, with and without conjoint tendon loading, on shoulder stability and range of motion (ROM). MATERIALS AND METHODS A custom simulator was used to evaluate anterior shoulder stability and ROM in 8 cadaveric shoulders. Testing conditions included intact, 30% glenoid defect, and Latarjet with and without conjoint loading. Unloaded and 10-N loaded states were tested in adduction and 90° abduction. Outcome variables included dislocation, stiffness (neutral and 60° external rotation), and internal-external rotational ROM. RESULTS All 30% defects dislocated in abduction external rotation. The loaded Latarjet prevented dislocation in all specimens, whereas the unloaded Latarjet stabilized 6 of 8 specimens. In abduction external rotation, there were no significant differences in stiffness between loaded and unloaded transfers (P = .176). In adduction, there were no significant differences between the intact and the loaded Latarjet (P ≥ .228); however, in neutral rotation, the unloaded Latarjet (P = .015) and the 30% defects (P = .011) were significantly less stiff. Rotational ROM in abduction was significantly reduced with the loaded Latarjet (P = .014) compared with unloaded Latarjet, and no differences were found in adduction. CONCLUSIONS These findings indicate that glenohumeral stability is improved, but not fully restored to intact, with conjoint tendon loading. The results support the existence of the sling effect and its importance in augmenting stability provided by the transferred coracoid.

The Effect of the Remplissage Procedure on Shoulder Stability and Range of Motion: An in Vitro Biomechanical Assessment

BACKGROUND The remplissage procedure may be performed as an adjunct to Bankart repair to treat recurrent glenohumeral dislocation associated with an engaging Hill-Sachs humeral head defect. The purpose of this in vitro biomechanical study was to examine the effects of the remplissage procedure on glenohumeral joint motion and stability. METHODS Cadaveric shoulders (n = 8) were mounted on a biomechanical testing apparatus that applies simulated loads to the rotator cuff and the anterior, middle, and posterior heads of the deltoid muscle. Testing was performed with the shoulder intact, after creation of the Bankart lesion, and after repair of the Bankart lesion. In addition, testing was performed after Bankart repair with and without remplissage in shoulders with 15% and 30% Hill-Sachs defects. Shoulder motion and glenohumeral translation were recorded with an optical tracking system. Outcomes measured included stability (joint stiffness and defect engagement) and internal-external glenohumeral rotational motion in adduction and in 90° of composite shoulder abduction. RESULTS In specimens with a 15% Hill-Sachs defect, Bankart repair combined with remplissage resulted in a significant reduction in internal-external range of motion in adduction (15.1° ± 11.1°, p = 0.039), but not in abduction (7.7° ± 9.9, p = 0.38), compared with the intact condition. In specimens with a 30% Hill-Sachs defect, repair that included remplissage also significantly reduced internal-external range of motion in adduction (14.5° ± 11.3°, p = 0.049) but not in abduction (6.2° ± 9.3°, p = 0.60). In specimens with a 15% Hill-Sachs defect, addition of remplissage significantly increased joint stiffness compared with isolated Bankart repair (p = 0.038), with the stiffness trending toward surpassing the level in the intact condition (p = 0.060). In specimens with a 30% Hill-Sachs defect, addition of remplissage restored joint stiffness to approximately normal (p = 0.41 compared with the intact condition). All of the specimens with a 30% Hill-Sachs defect engaged and dislocated after Bankart repair alone. The addition of remplissage was effective in preventing engagement and dislocation in all specimens. None of the specimens with a 15% Hill-Sachs defect engaged or dislocated after Bankart repair. CONCLUSIONS In this experimental model, addition of remplissage provided little additional benefit to a Bankart repair in specimens with a 15% Hill-Sachs defect, and it also reduced specific shoulder motions. However, Bankart repair alone was ineffective in preventing engagement and recurrent dislocation in specimens with a 30% Hill-Sachs defect. The addition of remplissage to the Bankart repair in these specimens prevented engagement and enhanced stability, although at the expense of some reduction in shoulder motion.

An anatomic, computed tomographic assessment of the coracoid process with special reference to the congruent-arc latarjet procedure.

PURPOSE The purpose of this study was to determine the dimensions of the coracoid and to compare the radius of curvature (ROC) of the intact glenoid to the ROC of the coracoid undersurface, as oriented in the congruent-arc Latarjet procedure. The ROC of the coracoid undersurface was also compared with various glenoid bone loss scenarios. METHODS Thirty-four computed tomography-based 3-dimensional models of the shoulder were examined by use of commercially available software. The mean dimensions of the coracoid were determined, and the ROC was calculated for the coracoid undersurface, the intact glenoid, and 20%, 35%, and 50% anterior glenoid bone loss scenarios. Intra-rater and inter-rater statistics were calculated. RESULTS The mean length, width, and thickness of the coracoid were 16.8 mm (SD, 2.5 mm), 15.0 mm (SD, 2.2 mm), and 10.5 mm (SD, 1.7 mm), respectively. The mean ROC values were 13.6 mm (SD, 3.4 mm) for the coracoid, 13.8 mm (SD, 2.1 mm) for the intact glenoid, 27.6 mm (SD, 5.3 mm) for 20% anterior glenoid bone loss, 30.5 mm (SD, 5.2 mm) for 35% bone loss, and 33.3 mm (SD, 5.2 mm) for 50% bone loss. The coracoid ROC was not significantly different from the intact glenoid (P = .75); however, it was significantly less (P < .01) when compared with all glenoid bone loss scenarios. Intra-rater reliability and inter-rater reliability were good or excellent. A coracoid oriented in the congruent-arc manner can reconstitute a significantly greater glenoid bone defect than a coracoid oriented in the classic manner (P < .001). CONCLUSIONS This image-based anatomic study found that the ROC of the coracoid undersurface matches the ROC of the intact anterior glenoid articular margin. In conditions with anterior glenoid bony deficiency, the radii of curvature differ significantly at the graft-native glenoid interface; however, the coracoid graft placed in the congruent-arc manner reconstitutes the ROC of the missing anterior glenoid rim. In addition, orienting the coracoid in the congruent-arc manner can reconstitute a greater glenoid bone defect than a coracoid placed in the original manner as described by Latarjet. CLINICAL RELEVANCE The congruent-arc Latarjet procedure, a modification of the original procedure, is truly congruent in relation to the intact anterior glenoid rim. In addition, the congruent-arc modification can reconstitute a greater glenoid bone defect when compared with the original Latarjet procedure.

The shoulder remplissage procedure for Hill-Sachs defects: does technique matter?

BACKGROUND This biomechanical study evaluated the effects of 3 remplissage techniques on shoulder stability and motion in a Hill-Sachs (HS) instability model. MATERIALS AND METHODS Cadaveric forequarters were tested on an active shoulder simulator. Three remplissage techniques were performed for 15% and 30% HS defects. Testing conditions included intact and 15% and 30% HS defects, and the 3 remplissage techniques: T1, anchors in the defect valley; T2, anchors in humeral head rim; and T3, anchors in valley with medial suture placement. Outcomes included stability, internal-external rotation range of motion (IE-ROM), and joint stiffness. RESULTS All remplissage techniques improved shoulder stability. In 15% HS defects tested in adduction, T3 significantly reduced IE-ROM (P = .037), whereas T1 and T2 did also (mean IE-ROM reductions: T1, 14°; T2, 11°; T3, 21°), but not to significance (P ≥ .088). In abduction, no significant reductions in IE-ROM occurred (P ≥ .060). In 30% HS defects tested in adduction (mean reduction IE-ROM: T1, 11°; T2, 19°; T3, 28°) and abduction (mean reduction: T1, 9°; T2, 15°; T3, 21°), all techniques significantly reduced IE-ROM (P ≤ .046). All techniques increased joint stiffness from 100% to 320% beyond the Bankart repair alone. A significant increase in joint stiffness was observed for T3 compared with the 30% HS group (P = .004), whereas T2 trended toward an increase (P = .078). There was no significant increase in joint stiffness with T1 (P = .249). CONCLUSIONS All remplissage techniques enhanced shoulder stability, restricted ROM, and increased joint stiffness. No significant differences were found between anchors placed in the valley (T1) vs those placed in the humeral head rim (T2). Medial suture placement (T3) resulted in the greatest joint stiffness values and mean restriction in motion.

The effect of the conjoined tendon of the short head of the biceps and coracobrachialis on shoulder stability and kinematics during in-vitro simulation

The kinematics and stability of the shoulder during in-vitro simulation are affected by the muscles chosen for simulation and their loads. Existing simulators have commonly actuated the rotator cuff and deltoids; however, the contribution of secondary muscles, such as those which form the conjoined tendon, are not well understood. The conjoined tendon consists of the origins of the short head of the biceps and coracobrachialis (SH&C), and is thought to produce an anterior stabilizing effect. This study investigated the effect of SH&C tension at four loading levels: 0, 5, 10, 15N. Our primary outcome variable was glenohumeral stiffness for anterior loading but internal/external rotation and extension ranges of motion were also measured. Four joint configurations were tested: adduction and 90° combined abduction, each in neutral and maximal external rotation. Increasing SH&C load resulted in a significant trend of increased glenohumeral stiffness across the average of all joint configurations (p=0.008). In abduction, neutral rotation differences were found between the stiffness at 10 and 15N compared to 0N (p=0.038 and 0.043, respectively); however, no differences were found for the three other joint configurations. There was a tendency for a decrease in the range of shoulder extension with increasing SH&C load, but this did not achieve significance (p=0.065). These findings demonstrate that the SH&C provides a stabilizing barrier effect, but only in configurations when it wraps directly anterior to the humeral head. Thus SH&C loading is likely critical to in-vitro simulation due to its effect on joint stability and kinematics.

Do the Traditional and Modified Latarjet Techniques Produce Equivalent Reconstruction Stability and Strength

Background: The Latarjet procedure has been described as a reconstructive option for instability associated with substantial glenoid bone defects. A modification, termed the Congruent-Arc, is thought to improve glenoid reconstruction through better articular congruency and greater bone reconstitution. The strengths of these techniques, however, have not been reported. Purpose/Hypothesis: To compare the fixation stability, strength, glenoid vault load transfer, and joint contact between the Classic and Congruent-Arc techniques. The authors hypothesized that the Classic Latarjet would exhibit inferior joint contact characteristics while having greater stability and strength and more normal glenoid vault strain. Study Design: Controlled laboratory study. Methods: Sixteen shoulder specimens (8 pairs) were tested by loading the glenohumeral joint with the glenoid intact, following creation of a 25% anterior bone defect, and after random assignment to the Classic or Congruent-Arc Latarjet techniques. Specimens were mounted to a testing apparatus that allowed concentric, centralized loading and loading 30° anterior on the glenoid rim. Cyclic loading (100 cycles at 1 Hz) was applied with a staircase protocol (50, 100, 150, and 200 N). Graft interface displacement and glenoid load transfer, quantified in terms of strain, were recorded during loading. Contact was quantified during 50-N loading using a thin pressure sensor. After cyclic loading, specimens were loaded to failure, defined as 5 mm of graft interface displacement. Results: The 30° loading ≥100 N resulted in significantly greater graft displacement (P < .004) in the Congruent-Arc group as compared with the Classic (mean displacement range, 0.9-2.6 vs 0.1-0.5 mm, respectively). Failure testing yielded a significantly (P = .010) greater ultimate strength for the Classic (557 N) as compared with the Congruent-Arc (392 N). Load-transfer measurements demonstrated that neither technique’s glenoid vault strain values significantly differed from intact (P ≥ .076). Both techniques resulted in contact areas significantly less than intact (P < .035); however, the Congruent-Arc trended toward better contact characteristics (P = .074). Conclusion: The Congruent-Arc results in significantly poorer fixation stability as compared with the Classic technique but did more closely reproduce intact joint contact, which may yield more favorable long-term outcomes. Clinical Relevance: Care must be taken in balancing the consideration of initial fixation stability and joint contact for the Congruent-Arc and Classic Latarjet, as these factors have opposing implications for each of the 2 reconstructions’ outcomes.

Utility of an image-based technique to detect changes in joint congruency following simulated joint injury and repair: An in vitro study of the elbow

BACKGROUND Investigating joint mechanics is important when determining the etiology of osteoarthritis, as degenerative changes are thought to occur due to altered joint mechanics. The objective of this study was to demonstrate the utility of an x-ray computed tomography-based approach to evaluate joint congruency in the setting of subtle kinematic alterations, employing an in vitro model of collateral ligament repair of the elbow. METHODS Active and passive elbow flexion was performed in 4 and 5 fresh-frozen cadaveric upper extremities respectively using an elbow motion simulator in the valgus gravity dependent positions. The collateral ligaments were sectioned and repaired. A registration and inter-bone distance algorithm were then used to examine ulnohumeral joint congruency (quantified as surface area) throughout elbow flexion. Valgus angulation was also measured. FINDINGS Following ligament sectioning and repair, there was a 1.2±1.0° increase in valgus angulation in active flexion and a 21.2±26.2% decrease in surface area. In passive flexion, valgus angulation increased 3.3±2.2° and surface area decreased 57.9±39.9%. INTERPRETATION The technique described to quantify joint congruency proved to be sensitive enough to detect large changes in joint surface interactions inspite of only small changes in traditionally measured kinematics. These changes in joint congruency may, in part, explain the high incidence of arthritis that has been reported following ligament injuries of the elbow, even in the absence of clinically detectable instability. This technique, when adapted for in vivo use, will be a useful tool to evaluate joint function and the effectiveness of treatments non-invasively.

The effect of radial head implant shape on radiocapitellar kinematics during in vitro forearm rotation

BACKGROUND A number of radial head implants are in clinical use for the management of radial head fractures and their sequelae. However, the optimal shape of a radial head implant to ensure proper tracking relative to the capitellum has not been established. This in vitro biomechanical study compared radiocapitellar joint kinematics for 3 radial head implant designs as well as the native head. METHODS Eight cadaveric upper extremities were tested using a forearm rotation simulator with the elbow at 90° of flexion. Motion of the radius relative to the capitellum was optically tracked. A stem was navigated into a predetermined location and cemented in place. Three unipolar implant shapes were tested: axisymmetric, reverse-engineered patient-specific, and population-based quasi-anatomic. The patient-specific and quasi-anatomic implants were derived from measurements performed on computed tomography models. RESULTS Medial-lateral and anterior-posterior translation of the radial head with respect to the capitellum varied with forearm rotation and radial head condition. A significant difference in medial-lateral (P = .03) and anterior-posterior (P = .03) translation was found between the native radial head and the 3 implants. No differences were observed among the radial head conditions except for a difference in medial-lateral translation between the axisymmetric and patient-specific implants (P = .04). CONCLUSIONS Radiocapitellar kinematics of the tested radial head implants were similar in all but one comparison, and all had different kinematics from the native radial head. Patient-specific radial head implants did not prove advantageous relative to conventional implant designs. The shape of the fixed stem unipolar radial head implants had little influence on radiocapitellar kinematics when optimally positioned in this testing model.

Development and Performance Evaluation of a Multi-PID Muscle Loading Driven In Vitro Active-Motion Shoulder Simulator and Application to Assessing Reverse Total Shoulder Arthroplasty

In vitro active shoulder motion simulation can provide improved understanding of shoulder biomechanics; however, accurate simulators using advanced control theory have not been developed. Therefore, our objective was to develop and evaluate a simulator which uses real-time kinematic feedback and closed loop proportional integral differential (PID) control to produce motion. The simulators ability to investigate a clinically relevant variable-namely muscle loading changes resulting from reverse total shoulder arthroplasty (RTSA)-was evaluated and compared to previous findings to further demonstrate its efficacy. Motion control of cadaveric shoulders was achieved by applying continuously variable forces to seven muscle groups. Muscle forces controlling each of the three glenohumeral rotational degrees of freedom (DOF) were modulated using three independent PID controllers running in parallel, each using measured Euler angles as their process variable. Each PID controller was configured and tuned to control the loading of a set of muscles which, from previous in vivo investigations, were found to be primarily responsible for movement in the PIDs DOF. The simulators ability to follow setpoint profiles for abduction, axial rotation, and horizontal extension was assessed using root mean squared error (RMSE) and average standard deviation (ASD) for multiple levels of arm mass replacement. A specimen was then implanted with an RTSA, and the effect of joint lateralization (0, 5, 10 mm) on the total deltoid force required to produce motion was assessed. Maximum profiling error was <2.1 deg for abduction and 2.2 deg for horizontal extension with RMSE of <1 deg. The nonprofiled DOF were maintained to within 5.0 deg with RMSE <1.0 deg. Repeatability was high, with ASDs of <0.31 deg. RMSE and ASD were similar for all levels of arm mass replacement (0.73-1.04 and 0.14-0.22 deg). Lateralizing the joints center of rotation (CoR) increased total deltoid force by up to 8.5% body weight with the maximum early in abduction. This simulator, which is the first to use closed loop control, accurately controls the shoulders three rotational DOF with high repeatability, and produces results that are in agreement with previous investigations. This simulators improved performance, in comparison to others, increases the statistical power of its findings and thus its ability to provide new biomechanical insights.