Elifho Obopilwe

Intra-articular Partial-Thickness Rotator Cuff Tears: Analysis of Injured and Repaired Strain Behavior

Background There are few biomechanical studies regarding partial-thickness rotator cuff tears and subsequent repair. Hypothesis Partial-thickness intra-articular supraspinatus tendon tears increase articular-sided tendon strain as they increase in size. Repair of these tears will return strain to the intact state. Study Design Controlled laboratory study. Methods Twenty fresh-frozen human cadaveric shoulders were prepared by dissecting to the supraspinatus tendon and leaving the native footprint intact. The tendon footprint was measured with digital calipers and divided into thirds (anterior, middle, and posterior). The middle third was the area where a consistent partial tear was created based on the thickness of the specimens’ particular footprint. Created were 25%, 50%, and 75% tears. Image analysis software and differential variable reluctance transducers strain gauges were used to measure strain. A 100 N load at 1 Hz for 30 cycles was conducted for glenohumeral angles of 45°, 60°, and 90°. This was completed for the intact tendon, 25%, 50%, and 75% tears. Shoulders were then repaired using the in situ fixation method. The in situ method consisted of either a parachute anchor or metal corkscrew anchor. Eight shoulders were examined for load-to-failure testing with the Materials Testing System. Results There was a significant difference (P < .05) in rotator cuff strain between the intact rotator cuff tendon and 50% and 75% partial-thickness tears. The cuff strain was returned to the intact state with repair. This was consistent for 3 different glenohumeral abduction angles and for all 3 intra-articular tendon areas. The bursal strain did not have any significant differences between groups. Conclusion Articular-sided tendon strain increases consistently across the supraspinatus tendon with greater partial tears. Repair returned strain close to the intact state. Clinical Relevance This study may add credence to the clinical practice of repairing intra-articular partial-thickness rotator cuff tears greater than 50%.

The Effect of Medial Meniscectomy and Meniscal Allograft Transplantation on Knee and Anterior Cruciate Ligament Biomechanics

PURPOSE Our purpose was to evaluate the effect of meniscectomy and meniscal allograft transplant on anterior cruciate ligament (ACL) and knee biomechanics. METHODS A differential variable reluctance transducer was placed in the ACL of 10 human cadaveric knees to record strain. Tibial displacement from a neutral reference was recorded relative to the position of the femur. Testing was performed at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Six cycles of anterior-posterior loads were applied to the limit of 150 N. After a testing cycle, a medial meniscectomy was performed and the testing cycle was repeated. A meniscal allograft transplant was performed, and a final testing cycle was conducted. ACL strain and tibial displacement in the meniscectomy and meniscal allograft states were compared with the intact-knee state. RESULTS Tibial displacement after meniscectomy significantly increased at all angles. The meniscal allograft transplant restored tibial displacement to normal values at 30 degrees and 90 degrees. ACL strain increased significantly after meniscectomy at 60 degrees and 90 degrees of flexion, and meniscal allograft transplant returned the strain values to normal at 60 degrees and 90 degrees. CONCLUSIONS In most cases medial meniscectomy produced a significant increase in tibial displacement relative to the femur, and meniscal allograft transplantation restored displacement values to normal. Meniscectomy increased ACL strain and meniscal allograft transplant restored strain values to normal in 2 of 3 tested flexion angles. CLINICAL RELEVANCE The absence of the medial meniscus exposes the ACL to increased strain, whereas meniscal allograft lowered the strain on the native ACL. This could have implications for those patients undergoing ACL reconstruction who have concomitant removal of the medial meniscus.

Biomechanical Comparison of Arthroscopic Repairs for Acromioclavicular Joint Instability Suture Button Systems Without Biological Augmentation

Background: Arthroscopic procedures for reconstruction of acromioclavicular (AC) joint separations are increasingly used in clinical practice. Multiple surgical techniques exist, but there are still few data on biomechanical performances of commonly used arthroscopic techniques and fixation methods. Hypothesis: Single and double clavicular tunnel reconstructions show comparable primary stability with a modified Weaver-Dunn procedure, and double tunnel constructs show superior horizontal stability. Study Design: Controlled laboratory study. Methods: The AC joints of 40 cadaveric shoulders were tested for anterior, posterior, and superior translation (70-N load) and maximal load to failure (superior) with the MTS 858 Bionix II Servohydraulic testing system. Shoulders were assigned to 4 groups: (1) native (n = 18), (2) coracoclavicular (CC) reconstruction with 1 clavicular and 1 coracoid tunnel (SCT) fixed with a suture pulley and 2 buttons (n = 8), (3) CC reconstruction with 2 clavicular and 1 coracoid tunnel (DCT) fixed with a suture pulley and 3 buttons (n = 8), and (4) modified Weaver-Dunn reconstruction (n = 6). Results: Native specimens showed a mean anterior translation of 7.92 mm (±1.69 mm), a mean posterior translation of 7.84 mm (±2.09 mm), and a superior translation of 4.28 mm (±1.81 mm). Maximal load to failure was 579.44 N (±148.01 N). The SCT technique showed a mean anterior translation of 5.81 mm (±1.16 mm), posterior translation of 8.30 mm (±1.94 mm), and a superior translation of 2.28 mm (±0.52 mm). The maximal load to failure was 591.35 N (±231.17 N). Anterior and superior translations were significantly less compared with the native specimen (P = .005 and P = .003). The DCT technique had an anterior translation of 4.68 mm (±0.6 mm), posterior translation of 6.85 mm (±0.83 mm), and superior translation of 2.09 mm (±0.86 mm). The mean maximal load to failure was 651.16 N (±226.93 N). Anterior and superior translations were significantly less compared with the native specimens (P = .000 and P = .001). No statistically significant differences were shown between SCT and DCT reconstruction for all measurements (P > .05). One reconstruction of the modified Weaver-Dunn procedure failed directly after mounting it into the testing device. The remaining 5 showed a mean anterior translation of 11.36 mm (±3.17 mm), a mean posterior translation of 13.51 mm (±2.21 mm), and a mean superior translation of 3.31 mm (±0.47 mm). Anterior and posterior translations were significantly increased compared with the native specimen (P = .019 and P = .000). The mean maximal load to failure measured 311.13 N (±52.2 N) and was significantly less compared with the native specimen (P = .000). The Weaver-Dunn technique showed significantly less maximal load to failure and more anterior and posterior translation compared with SCT and DCT (P ≤ .05). Conclusion: Isolated reconstruction of the CC ligaments using single and double clavicular tunnel techniques results in a high load to failure for superior translation, which is equal to the native stability, and less translation in all 3 directions as well as higher superior stability when compared with the modified Weaver-Dunn procedure. A potential drawback is the risk of coracoid fracture, as the high load to failure of the device may exceed load to failure of cortical bone prior to device breakage. Clinical Relevance: Single clavicular tunnel arthroscopic reconstructions of the coracoacromial ligaments show good biomechanical results.

Biomechanical Evaluation of Arthroscopic Rotator Cuff Repairs Over Time

PURPOSE The aim of this study was to assess the contact pressure, force, and area over time for 4 common arthroscopic rotator cuff repair techniques. METHODS The transosseous-equivalent, single-row, triangle double-row, and suture-chain transosseous repair techniques were used to repair a full-thickness tear of the supraspinatus in 16 cadaveric shoulders. Continuous data points were collected immediately after repair and for 160 minutes at set time intervals by use of a custom thin film pressure sensor. RESULTS Each of the 4 rotator cuff repair techniques showed decreased contact force, pressure, and area 160 minutes after the repair was performed. The transosseous-equivalent construct had the highest contact pressure and force initially and at all time points up to 160 minutes. Although the 3 double-row constructs had greater pressure and force at all time points compared with the single-row repair, only the transosseous-equivalent group showed a statistically greater pressure and force when compared with single-row repair (P < .05). CONCLUSIONS Contact pressure, force, and pressurized footprint area decrease 160 minutes after repair regardless of repair technique. The transosseous-equivalent group had the highest contact pressure and force at all time points. CLINICAL RELEVANCE The decrease in contact pressure and force after rotator cuff repair may have important implications in evaluating tendon-to-bone healing and determining the optimal rehabilitation protocol.

Biomechanical evaluation of distal biceps reconstruction with cortical button and interference screw fixation.

HYPOTHESIS Tension slide repair maintains the strength of the standard cortical button repair but reduces gap formation at the repair. Distal biceps tendon repair with a suspensory cortical button has yielded the strongest published repair, despite observed gap formation and tendon pistoning. The tension slide technique (TST) was described to reduce gap formation while maintaining the strength of cortical button repair. This study evaluates the biomechanics of the TST compared with previously described EndoButton (Smith & Nephew, Memphis, TN) repair and the TST with and without an interference screw. MATERIALS AND METHODS The study used 20 matched specimens: 5 had a standard cortical button repair, and 5 had biceps repair with the TST. An additional 10 specimens underwent a TST, 5 with an interference screw and 5 without. All were cyclically loaded for 3600 cycles. Gap formation and load to failure were measured. RESULTS The mean (SD) load to failure for standard technique was at 389 (148) N vs 432 (66) N for the TST (P = .28). The mean (SD) gap formation was 2.79 (1.43) mm with the standard repair and 1.26 (0.61) mm with the TST (P = .03). The mean (SD) load to failure with TST repair was 436 (103) N without the interference screw and 439 (94) N (P = 0.48) with the screw. The mean gap formation was 1.63 (1.09) mm without the screw and 1.45 (0.67) mm with the screw (P = .38.) CONCLUSION This TST maintains the strength of the standard cortical button repair, but significantly reduces gap formation and motion at the repair site. LEVEL OF EVIDENCE Basic science study.

The Distal Triceps Tendon Footprint and a Biomechanical Analysis of 3 Repair Techniques

Background Anatomic repair of tendon ruptures is an important goal of surgical treatment. There are limited data on the triceps brachii insertion, footprint, and anatomic reconstruction of the distal triceps tendon. Hypothesis An anatomic repair of distal triceps tendon ruptures more closely imitates the preinjury anatomy and may result in a more durable repair. Study Design Descriptive and controlled laboratory studies. Methods The triceps tendon footprint was measured in 27 cadaveric elbows, and a distal tendon rupture was created. Elbows were randomly assigned to 1 of 3 repair groups: cruciate repair group, suture anchor group, and anatomic repair group. Biomechanical measurement of load at yield and peak load were measured. Cyclic loading was performed for a total of 1500 cycles and displacement measured. Results The average bony footprint of the triceps tendon was 466 mm2. Cyclic loading of tendons from the 3 repair types demonstrated that the anatomic repair produced the least amount of displacement when compared with the other repair types (P < .05). Load at yield and peak load were similar for all repair types (P > .05). Conclusion The triceps bony footprint is a large area on the olecranon that should be considered when repairing distal triceps tendon ruptures. Anatomic repair of triceps tendon ruptures demonstrated the most anatomic restoration of distal triceps ruptures and showed statistically significantly less repair-site motion when cyclically loaded. Clinical Relevance Anatomic repair better restores preinjury anatomy compared with other types of repairs and demonstrates less repair-site motion, which may play a role in early postoperative management.

The Effect of a Combined Glenoid and Hill-Sachs Defect on Glenohumeral Stability A Biomechanical Cadaveric Study Using 3-Dimensional Modeling of 142 Patients

Background: Bone loss in anterior glenohumeral instability occurs on both the glenoid and the humerus; however, existing biomechanical studies have evaluated glenoid and humeral head defects in isolation. Thus, little is known about the combined effect of these bony lesions in a clinically relevant model on glenohumeral stability. Hypothesis/Purpose: The purpose of this study was to determine the biomechanical efficacy of a Bankart repair in the setting of bipolar (glenoid and humeral head) bone defects determined via computer-generated 3-dimensional (3D) modeling of 142 patients with recurrent anterior shoulder instability. The null hypothesis was that adding a bipolar bone defect will have no effect on glenohumeral stability after soft tissue Bankart repair. Study Design: Controlled laboratory study. Methods: A total of 142 consecutive patients with recurrent anterior instability were analyzed with 3D computed tomography scans. Two Hill-Sachs lesions were selected on the basis of volumetric size representing the 25th percentile (0.87 cm3; small) and 50th percentile (1.47 cm3; medium) and printed in plastic resin with a 3D printer. A total of 21 cadaveric shoulders were evaluated on a custom shoulder-testing device permitting 6 degrees of freedom, and the force required to translate the humeral head anteriorly 10 mm at a rate of 2.0 mm/s with a compressive load of 50 N was determined at 60° of glenohumeral abduction and 60° of external rotation. All Bankart lesions were made sharply from the 2- to 6-o’clock positions for a right shoulder. Subsequent Bankart repair with transosseous tunnels using high-strength suture was performed. Hill-Sachs lesions were made in the cadaver utilizing a plastic mold from the exact replica off the 3D printer. Testing was conducted in the following sequence for each specimen: (1) intact, (2) posterior capsulotomy, (3) Bankart lesion, (4) Bankart repair, (5) Bankart lesion with 2-mm glenoid defect, (6) Bankart repair, (7) Bankart lesion with 2-mm glenoid defect and Hill-Sachs lesion, (8) Bankart repair, (9) Bankart lesion with 4-mm glenoid defect and Hill-Sachs lesion, (10) Bankart repair, (11) Bankart lesion with 6-mm glenoid defect and Hill-Sachs lesion, and (12) Bankart repair. All sequences were used first for a medium Hill-Sachs lesion (10 specimens) and then repeated for a small Hill-Sachs lesion (11 specimens). Three trials were performed in each condition, and the mean value was used for data analysis. Results: A statistically significant and progressive reduction in load to translation was observed after a Bankart lesion was created and with the addition of progressive glenoid defects for each humeral head defect. For medium (50th percentile) Hill-Sachs lesions, there was a 22%, 43%, and 58% reduction in stability with a 2-, 4-, and 6-mm glenoid defect, respectively. For small (25th percentile) Hill-Sachs lesions, there was an 18%, 27%, and 42% reduction in stability with a 2-, 4-, and 6-mm glenoid defect, respectively. With a ≥2-mm glenoid defect, the medium Hill-Sachs group demonstrated significant reduction in translation force after Bankart repair (P < .01), and for the small Hill-Sachs group, a ≥4-mm glenoid defect was required to produce a statistical decrease (P < .01) in reduction force after repair. Conclusion: Combined glenoid and humeral head defects have an additive and negative effect on glenohumeral stability. As little as a 2-mm glenoid defect with a medium-sized Hill-Sachs lesion demonstrated a compromise in soft tissue Bankart repair, while small-sized Hill-Sachs lesions showed compromise of soft tissue repair with ≥4-mm glenoid bone loss. Clinical Relevance: Bipolar bony lesions of the glenoid and humeral head occur frequently together in clinical practice. Surgeons should be aware that the combined defects and glenoid bone loss of 2 to 4 mm or approximately 8% to 15% of the glenoid could compromise Bankart repair and thus may require surgical strategies in addition to traditional Bankart repair alone to optimize stability.

Rotational and Translational Stability of Different Methods for Direct Acromioclavicular Ligament Repair in Anatomic Acromioclavicular Joint Reconstruction

Background: Many reconstructions of acromioclavicular (AC) joint dislocations have focused on the coracoclavicular (CC) ligaments and neglected the functional contribution of the AC ligaments and the deltotrapezial fascia. Purpose: To compare the modifications of previously published methods for direct AC reconstruction in addition to a CC reconstruction. The hypothesis was that there would be significant differences within the variations of surgical reconstructions. Study Design: Controlled laboratory study. Methods: A total of 24 cadaveric shoulders were tested with a servohydraulic testing system. Two digitizing cameras evaluated the 3-dimensional movement. All reconstructions were based on a CC reconstruction using 2 clavicle tunnels and a tendon graft. The following techniques were used to reconstruct the AC ligaments: a graft was shuttled underneath the AC joint back from anterior and again sutured to the acromial side of the joint (group 1), a graft was fixed intramedullary in the acromion and distal clavicle (group 2), a graft was passed over the acromion and into an acromial tunnel (group 3), and a FiberTape was fixed in a cruciate configuration (group 4). Anterior, posterior, and superior translation, as well as anterior and posterior rotation, were tested. Results: Group 1 showed significantly less posterior translation compared with the 3 other groups (P < .05) but did not show significant differences compared with the native joint. Groups 3 and 4 demonstrated significantly more posterior translation than the native joint. Group 1 showed significantly less anterior translation compared with groups 2 and 3. Group 3 demonstrated significantly more anterior translation than the native joint. Group 1 demonstrated significantly less superior translation compared with the other groups and with the native joint. The AC joint of group 1 was pulled apart less compared with all other reconstructions. Only group 1 reproduced the native joint for the anterior rotation at the posterior marker. Group 4 showed significantly increased distances for all 3 measure points when the clavicle was rotated posteriorly. Conclusion: Reconstruction of the AC ligament by direct wrapping and suturing of the remaining graft around the AC joint (group 1) was the most stable method and was the only one to show anterior rotation comparable with the native joint. In contrast, the transacromial technique (group 3) showed the most translation and rotation. Clinical Relevance: An anatomic repair should address both the CC ligaments and the AC ligaments to control the optimal physiologic function (translation and rotation).

Sequential Resection of the Distal Clavicle and Its Effects on Horizontal Acromioclavicular Joint Translation

Background: Reconstructions of the coracoclavicular (CC) ligament in an open or arthroscopically assisted procedure are often combined with a resection of the distal clavicle to prevent or treat osteoarthritic degenerations of the acromioclavicular (AC) joint. However, increased horizontal translation leading to symptomatic instability may be associated with resection of the distal clavicle. Hypothesis: Horizontal translation increases in direct correlation to subsequent resection of the distal clavicle. Study Design: Controlled laboratory study. Methods: Twelve fresh-frozen specimens (mean age, 82.0 ± 5 years) were examined using a servohydraulic testing system. A 70-N force was applied in the anterior, posterior, and superior directions, and the translations were quantified for all directions. After native testing, sequential resection of the distal clavicle at 5 and 10 mm was performed after incision of the inferior capsule, and anterior-posterior loads were retested. Finally, the AC ligaments were incised, and repeated testing was performed. Results: Native mean (± standard deviation) anterior translation was 7.90 ± 2.62 mm. After section of the inferior AC capsule, anterior translation was 8.05 ± 2.62 mm (P = 1.0). After clavicle resection of 5 mm, anterior translation was 10.75 ± 2.38 mm (P = .122), and after resection of 10 mm, anterior translation was significantly increased to 11.6 ± 2.37 mm (P = .012). Complete AC capsule sectioning led to significantly greater amounts of anterior translation (12.12 ± 3.0 mm; P = .003). Posterior translation for the native specimen was 8.88 ± 2.63 mm. Sectioning of the inferior AC capsule resulted in 9.21 ± 2.71-mm translation (P = 1.0). After clavicle resection of 5 mm, posterior translation was 10.42 ± 2.42 mm (P = 1.0), and after 10-mm resection, it was 11.31 ± 2.86 mm (P = .39). Sectioning of the complete AC capsule led to significantly greater amounts of posterior translation (12.31 ± 3.12 mm; P = .043). Conclusion: Ten millimeters of resection increased anterior translation of the distal clavicle with both the superior and posterior AC capsules as well as the CC ligaments intact. Both anterior and posterior translations increased after 10-mm resection and complete AC capsule sectioning. Clinical Relevance: These results suggest that resection of the distal clavicle leads to increased horizontal translation despite an intact superior and posterior AC capsule. Only sparing resection of the distal clavicle should be performed and only if strictly indicated. Violation of the AC capsule further increases horizontal translation and should therefore be avoided, or if indicated in AC joint dislocations, a reconstruction of the AC capsule should be considered.

A Biomechanical Analysis of Capsular Plication Versus Anchor Repair of the Shoulder: Can the Labrum Be Used as a Suture Anchor?

PURPOSE To determine the biomechanical strength properties of suture capsulolabral plication to an intact labrum versus glenoid bone anchor fixation. METHODS Fourteen paired fresh frozen shoulders with intact glenoid labrum and mean age of 43.3 +/- 11.1 were randomized to capsular plication in the anteroinferior and posteroinferior quadrants using either two suture-anchor fixation versus suture fixation to an intact labrum. The construct was then preconditioned at 10 N for 10 cycles (1 Hz), and then loaded to failure at 3 mm per minute. RESULTS There was no statistical difference in ultimate load to failure between the suture anchor (304.3 +/- 92.8 N) and the intact labrum (285.6 +/- 66.7 N) groups. The suture anchor group demonstrated significantly less mean displacement (2.15 +/- 1.1 mm) than suture plication (3.43 +/- 1.38 mm; P = .007) at failure. There were no statistical differences of labrum strength and stiffness between the anteroinferior and posteroinferior quadrants. CONCLUSIONS An intact labrum provides similar fixation strength to a glenoid anchor; however, the labrum displacement was higher with plication alone. There were no strength differences between the anteroinferior and posteroinferior labrum. However, displacement of up to 1.5 mm may be expected without the use of glenoid anchors. CLINICAL RELEVANCE The intact posteroinferior or anteroinferior labrum provides similar fixation strength to a glenoid anchor; however, the labrum displacement is higher versus plication alone.