The contribution of the ligamentum teres to the hip fluid seal: A biomechanics study.

BACKGROUND: The suction seal of the hip plays an important role in maintaining hip stability; however, the function of the ligamentum teres in maintaining this seal remains poorly understood. This study aimed to evaluate the effectiveness of the hip suction seal in ligamentum teres deficient hips for joint positions occurring during gait. METHODS: Six fresh-frozen human cadaveric hips were dissected and mounted to an Instron materials test system. Each specimen was analyzed for average peak distraction force, stiffness, and total energy during hip displacement. Testing was performed in the native intact ligamentum teres state and the deficient ligamentum teres state. Specimens were examined in 20° of flexion, neutral, and 10° of extension. FINDINGS: In the neutral position, the ligamentum teres deficient state displayed a significant decrease in peak distraction force (mean difference: 33.2 N, p < 0.001), average stiffness (mean difference: 63.7 N/mm, p = 0.016), and total energy (mean difference: 82.3 mJ, p = 0.022) compared to the intact controls. In extension, the deficient state exhibited a significant decrease in peak distraction force (mean difference: 42.8 N, p < 0.001) and total energy (mean difference: 72.9 mJ, p = 0.007). In flexion, the deficient state displayed a significant decrease in peak distraction force relative to contols (mean difference: 7.1 N, p = 0.003). INTERPRETATION: The ligamentum teres plays a significant role in maintaining the suction seal of the hip, with its effect being most prominent when the hip is in neural alignment or in extension. The findings suggest that ligamentum teres deficiency may be a relevant treatment target in the clinical setting.

Clinical and radiographic long-term outcomes of hemiarthroplasty for complex proximal humeral fractures.

BACKGROUND: Hemiarthroplasty (HA) is a treatment option for complex proximal humeral fractures not suitable for conservative treatment or open reduction-internal fixation. Long-term outcomes using a large-metaphyseal volume prosthesis in the management of proximal humeral fractures have not been reported thus far. METHODS: Between 2006 and 2010, 41 patients with proximal humeral fractures were treated with HA at our institution (average age, 62 years; age range, 38-85 years). Nine patients underwent revision surgery, 3 were lost to follow-up, and 7 died unrelated to the index surgical procedure. Twenty-two patients were reviewed clinically and radiographically after a mean period of 10.4 years (range, 9-13 years). RESULTS: Of the 9 HA failures, 7 occurred within the first 2 postoperative years: 2 patients had infections and 5 had greater tuberosity nonunions or malunions. The other 2 patients underwent revision for rotator cuff deficiency >5 years after initial surgery. Among the patients available for final follow-up, the implant survival rate was 71% (22 of 31 patients). At final follow-up, these patients showed a mean relative Constant score of 76% (range, 49%-96%), mean active elevation of 116° (range, 60°-170°), and mean external rotation of 28° (range, 0°-55°). The majority had good or excellent internal rotation, with internal rotation to the 12th thoracic vertebra in 13 patients (59%) and to the eighth thoracic vertebra in 7 (31%). The mean Subjective Shoulder Value was 76% (range, 40%-100%). Clinical outcomes did not significantly deteriorate over a period of 10 years, except for flexion (P < .001) and internal rotation (P = .002). On analysis of greater tuberosity healing, 1 patient had a nonunion and 10 patients (45%) had a malunion, whereas the greater tuberosity had healed in an anatomic position in 12 patients (55%). Patients with a displaced malunion of the greater tuberosity did not have inferior clinical results at last follow-up. Only 2 patients showed glenoid erosion, and in no patients could stem loosening be identified at final follow-up. CONCLUSION: The revision rate following large-metaphyseal volume HA to treat a proximal humeral fracture was 29% after 10 years postoperatively, with failure within 2 years largely related to greater tuberosity nonunion or malunion and failure later related to rotator cuff insufficiency. Patients with a retained implant showed good clinical and radiographic long-term results, without relevant deterioration over time even when the greater tuberosity healed in a nonanatomic position.

The moment arms and lines of action of subscapularis after the Latarjet procedure.

The Latarjet procedure is an established surgical treatment for recurrent glenohumeral joint instability with glenoid bone loss. Intraoperatively, the conjoint tendon and its attachement on the coracoid bone graft is routed through a split in subscapularis where the graft is fixed to and augments the anteroinferior glenoid. The objective of this in vitro study was to quantify the influence of glenohumeral joint position and conjoint tendon force on the lines of action and moment arms of subscapularis muscle sub-regions after Latarjet surgery. Eight fresh-frozen, entire upper extremities were mounted onto a testing apparatus, and a cable-pulley system was used to apply physiological muscle loading to the major shoulder muscles. The lines of action and moment arms of four subregions of subscapularis (superior, mid-superior, mid-inferior, and inferior) were quantified radiographically with the conjoint tendon unloaded and loaded while the shoulder was in (i) 0° abduction (ii) 90° abduction (iii) 90° abduction and full external rotation (ABER), and (iv) the apprehension position, defined as ABER with 30° horizontal extension. Conjoint tendon loading after Latarjet surgery significantly increased the inferior inclination of the lines of action of the mid-inferior and inferior subregions of subscapularis in the scapular plane in ABER and apprehension positions (p < 0.001), as well as decreased the horizontal flexion moment arm of the inferior subscapularis (p = 0.040). Increased subscapularis inferior inclination may ultimately increase inferior joint shear potential, while smaller horizontal flexion leverage may reduce joint flexion capacity. The findings have implications for Latarjet surgical planning and postoperative rehabilitation prescription.

Transcutaneous compression suture with iodine gauze for wound closure in revision surgery for therapy-resistant periprosthetic shoulder infections.

Background: To successfully treat a periprosthetic infection, successful bacteria eradication and successful wound closure are mandatory. Despite adequate surgical débridement in the deep, persistence of wound drainage and subsequent persistence of periprosthetic infection may occur, especially in patients with compromised soft tissue conditions. This study presents a transcutaneous compression suture technique with iodine gauze that was used in patients with persistent wound secretion in therapy-resistant periprosthetic shoulder infections in order to achieve successful infection control and wound healing. Methods: All patients with persistent periprosthetic or implant-associated shoulder joint infections despite correct previous surgical and antibiotic therapy attempts were included in the study. In all patients, in addition to repeat deep surgical débridement, a transcutaneous "iodine-gauze-compression-suture" was performed with postoperative antibiotic therapy. The primary endpoint was infection control; the secondary endpoint was wound healing rate; and the third endpoint was complication rate after index surgery. Results: Ten consecutive patients with a mean age of 74 (±7.6) years and a mean follow-up of 14 (±2) months were included. All ten patients showed infection control and successful wound healing, with no need for further revision surgery. In 8 out of 10 patients, the wound healing was fast and completely uncomplicated. Two out of 10 patients showed delayed wound healing with fibrin coatings for 3 and 4 weeks, respectively. No additional intervention was necessary in both patients. Conclusions: Transcutaneous iodine gauze compression sutures were used to achieve successful infection control without additional revision surgery in 10 out of 10 patients who previously underwent surgery with failed infection control. This wound closure technique is a reliable adjunctive therapy method in the treatment of implant-associated infections of the shoulder in patients with fragile wound conditions.

Biomechanical Comparison of Distal Biceps Tendon Repair Techniques: Extracortical Single-Button Inlay Fixation Versus Intracortical Double-Button Onlay Anatomic Footprint Fixation.

BACKGROUND: Extracortical single-button (SB) inlay repair is a commonly used distal biceps tendon technique. However, complications (eg, neurovascular injury) and nonanatomic repairs have led to the development of intracortical fixation techniques. PURPOSE: To compare the biomechanical stability of extracortical SB repair with an anatomic intracortical double-button (DB) repair technique. STUDY DESIGN: Controlled laboratory study. METHODS: The distal biceps tendon was transected in 18 cadaveric elbows from 9 donors. One elbow of each donor was randomly assigned to the extracortical SB or anatomic DB group. Both groups were cyclically loaded with 60 N over 1000 cycles between 90° of flexion and full extension. The elbow was then fixed in 90° of flexion and the repair construct loaded to failure. Gap formation and construct stiffness during cyclic loading and ultimate load to failure were analyzed. RESULTS: When compared with the extracortical SB technique after 1000 cycles, the anatomic DB technique showed significantly less gap formation (mean ± SD, 2.7 ± 0.8 vs 1.5 ± 0.9 mm; P = .017) and significantly more construct stiffness (87.4 ± 32.7 vs 119.9 ± 31.6 N/mm; P = .023). Ultimate load to failure was not significantly different between the groups (277 ± 93 vs 285 ± 135 N; P = .859). The failure mode in the anatomic DB group was significantly different from that of the extracortical SB technique (P = .002) and was due to fracture avulsion of the cortical button in 7 of 9 specimens (vs none in the SB group). CONCLUSION: Our study shows that the intracortical DB technique produces equivalent or superior biomechanical performance to that of the SB technique. The DB technique may offer a clinically viable alternative to the SB repair technique. CLINICAL RELEVANCE: This study suggests, at worst, an equivalent and, at best, a superior biomechanical performance of intracortical anatomic DB footprint repair at the time of surgery. However, the mode of failure suggests that this technique should not be used in patients with poor bone quality.

Mid-term to long-term results of open posterior bone block grafting in recurrent posterior shoulder instability: a clinical and CT-based analysis.

Background: There is little consensus on the best treatment after failed conservative management of recurrent posterior shoulder instability. The purpose of this study was to analyze our clinical and radiological mid-term to long-term results of an open, posterior bone block procedure for the treatment of recurrent posterior shoulder instability. Methods: From 1999 to 2015, 14 patients were included in the study and available for clinical and radiographic follow-up (FU). FU included a standardized physical examination, assessment of the Constant-Murley-Score, subjective shoulder value, American Shoulder and Elbow Surgeons score, and Western Ontario Shoulder Instability Index. Conventional radiographs and a computed tomography (CT)-scan were performed preoperatively and at latest FU. Glenohumeral arthropathy was classified as per Samilson and Prieto. The CT scans were used to evaluate the structure of the graft (resorption, union), graft positioning, glenoid version, centering of the humeral head, and glenoid erosion and morphology. Results: The median age at the time of surgery was 26 years (range 16-41 years) and the median FU period was 9 years (range 4-20 years). The rate of reported dynamic postoperative subluxation and instability was 46% (n = 6) and the rate of dynamic posterior instability during clinical testing at FU was 31% (n = 4). The tested instability rate in the traumatic group was 14% (n = 1) compared to the atraumatic group with 50% (n = 3) during clinical FU. The mean Constant-Murley-Score increased from preoperatively (77 ± 11 points) to postoperatively (83 ± 14 points, P = .158). The last FU showed an American Shoulder and Elbow Surgeons score of 85 ± 12; the Western Ontario Shoulder Instability Index score was 715 ± 475 points. The mean subjective shoulder value increased from 58% ± 19 preoperatively to 73% ± 17 at final FU (P = .005). Degenerative changes increased by at least one grade in 67% of the patients. Mean preoperative glenoid retroversion (CT) was 7.5° ± 6°. The position of the graft was optimal in 86% (n = 12). In 62% of the cases, a major resorption of the graft (Zhu grade II) was observed. Conclusion: The rate of tested recurrent instability at last FU was as high as 31% (n = 4, atraumatic [n = 3] vs. traumatic [n = 1]) after a median FU of 9 years. Given the moderate improvement of clinical outcome scores, shoulder stability and the increase of degenerative joint changes by at least one grade (Samilson/Prieto) in 67% of patients, a posterior bone block procedure is not a uniformly satisfying treatment option for recurrent posterior shoulder subluxation, especially in cases of atraumatic posterior instability.

A Systematic Review of Long-term Clinical and Radiological Outcomes of Arthroscopic and Open/Mini-open Rotator Cuff Repairs.

BACKGROUND: Arthroscopic rotator cuff repair (aRCR) has shown similar midterm functional results and retear rates as open/mini-open rotator cuff repair (oRCR). A pooled analysis of long-term results of both techniques is yet missing. PURPOSE: To evaluate the long-term results of aRCR and oRCR for full-thickness rotator cuff tears. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: The systematic review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The CENTRAL (Cochrane), MEDLINE (PubMed), and Embase databases were searched for studies that reported on long-term clinical and radiographic outcomes of full-thickness aRCR and oRCR with a minimum follow-up of 9 years. RESULTS: Eleven studies were included: 5 studies on aRCR and 6 studies on oRCR. Studies were based on 550 shoulders (539 patients) with a mean patient age of 56.3 years (range, 25-77). After a mean follow-up of 14.0 years (range, 9-20), the mean preoperative absolute Constant score (CS) and American Shoulder and Elbow Surgeons (ASES) shoulder score were significantly improved postoperatively (CS, 44 to 78 points; ASES, 52% to 91%; both comparisons, P < .001). The retear rate was 41% (141 of 342 shoulders) without a significant difference between groups (aRCR, 43%; oRCR, 39%) (P = .364). A retear was associated with significantly reduced CS as compared with a healed repair (P = .004). No significant differences were found in postoperative functional scores, complications, and retear rates after failed cuff repairs between the arthroscopic and open/mini-open repair groups. CONCLUSION: Pooled analysis of arthroscopic and open rotator cuff repairs demonstrated sustained improvement in long-term shoulder scores and pain with a substantial retear rate in both groups, which was associated with inferior shoulder function. There were no significant differences in long-term functional outcomes, retear rates, and complications. Both surgical techniques may be used on the basis of factors such as patient or surgeon preference and cost. Further studies using a more robust randomized controlled trial or larger cohort design are recommended to ascertain whether one surgical repair technique is superior to the other. REGISTRATION: CRD42020180448 (PROSPERO).

Biomechanical analysis of plating techniques for unstable lateral clavicle fractures with coracoclavicular ligament disruption (Neer type IIB).

BACKGROUND: Neer type IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. Because of the high rate of nonunion and malunion, surgical fixation is recommended; however, no consensus has been reached regarding the optimal fixation method. A new plating technique using a superior lateral locking plate with anteroposterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment, has been designed to enhance stability and reduce implant failure. The purpose of this study was to biomechanically compare 3 different clavicle plating constructs within a fresh frozen human cadaveric shoulder model. METHODS: Twenty-four fresh frozen cadaveric shoulders were randomized into 3 groups (n = 8 specimens): group 1, lateral locking plate only (Medartis Aptus Superior Lateral Plate); group 2, lateral locking plate with CC stabilization (No. 2 FiberWire); and group 3, lateral locking plate with 2 AP locking screws stabilizing the lateral fragment. All specimens were subject to cyclic loading of 70 N for 500 cycles. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, defined by a marked decrease in the load displacement curve. RESULTS: After 500 cycles, there was no statistically significant difference between the 3 groups in gap formation (P = .179). No specimen (0/24) failed during cyclic loading. Ultimate load to failure was significantly higher in group 3 compared to group 1 (286 N vs. 167 N; P = .022), but not to group 2 (286 N vs. 246 N; P = .604). There were no statistically significant differences in stiffness (group 1: 504 N/mm; group 2: 564 N/mm; group 3: 512 N/mm; P = .712). Peri-implant fracture was the primary mode of failure for all 3 groups, with group 3 demonstrating the lowest rate of peri-implant fractures (group 1: 6/8; group 2: 7/8; group 3: 4/8; P = .243). CONCLUSION: Biomechanical evaluation of the clavicle plating techniques showed effective fixation across all specimens at 500 cycles. The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. This new plating technique showed compatible stiffness and gap formation when compared to conventional lateral locking plates as well as plates with CC fixation. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications.

Biomechanical Analysis of Posterior Open-Wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-Free, J-Shaped Iliac Crest Bone Graft.

BACKGROUND: Posterior open-wedge osteotomy and glenoid reconstruction using a J-shaped iliac crest bone graft showed promising clinical results for the treatment of posterior instability with excessive glenoid retroversion and posteroinferior glenoid deficiency. PURPOSE: To evaluate the biomechanical performance of the posterior J-shaped graft to restore glenoid retroversion and posteroinferior deficiency in a cadaveric shoulder instability model. STUDY DESIGN: Controlled laboratory study. METHODS: A posterior glenoid open-wedge osteotomy was performed in 6 fresh-frozen shoulders, allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At each of these 3 preset angles of glenoid retroversion, the following conditions were simulated: (1) intact joint, (2) posterior Bankart lesion, (3) 20% posteroinferior glenoid deficiency, and (4) posterior J-shaped graft (at 0° of retroversion). With the humerus in the Jerk position (60° of glenohumeral anteflexion, 60° of internal rotation), stability was evaluated by measuring posterior humeral head (HH) translation (in mm) and peak translational force (in N) to translate the HH over 25% of the glenoid width. Glenohumeral contact patterns were measured using pressure-sensitive sensors. Fixation of the posterior J-graft was analyzed by recording graft micromovements during 3000 cycles of 5-mm anteroposterior HH translations. RESULTS: Reconstructing the glenoid with a posterior J-graft to 0° of retroversion significantly increased stability compared with a posterior Bankart lesion and posteroinferior glenoid deficiency in all 3 preset degrees of retroversion (P < .05). There was no significant difference in joint stability comparing the posterior J-graft with an intact joint at 0° of retroversion. The posterior J-graft restored mean contact area and contact pressure comparable with that of the intact condition with 0° of retroversion (222 vs 223 mm2, P = .980; and 0.450 vs 0.550 MPa, P = .203). The mean total graft displacement after 3000 cycles of loading was 43 ± 84 µm, and the mean maximal mediolateral graft bending was 508 ± 488 µm. CONCLUSION: Biomechanical analysis of the posterior J-graft demonstrated reliable restoration of initial glenohumeral joint stability, normalization of contact patterns comparable with that of an intact shoulder joint with neutral retroversion, and secure initial graft fixation in the cadaveric model. CLINICAL RELEVANCE: This study confirms that the posterior J-graft can restore stability and glenohumeral loading conditions comparable with those of an intact shoulder.

Long-Term Results and Failure Analysis of the Open Latarjet Procedure and Arthroscopic Bankart Repair in Adolescents.

BACKGROUND: The purpose of this study was to analyze the long-term results of arthroscopic Bankart repair compared with an open Latarjet procedure in adolescents who are at high risk for recurrent anterior shoulder instability. We hypothesized that the long-term stability rate of an open Latarjet procedure would be superior to that of arthroscopic Bankart repair. METHODS: Forty eligible patients (41 shoulders) with a mean age of 16.4 years (range, 13 to 18 years) underwent arthroscopic Bankart repair, and 37 patients (40 shoulders) with a mean age of 16.7 years (range, 14 to 18 years) underwent an open Latarjet procedure. Of these, 34 patients (35 shoulders) in the Bankart group and 30 patients (31 shoulders) in the Latarjet group with long-term follow-up were compared; the overall follow-up rate was 82%. Clinical and radiographic results were obtained after a mean follow-up of 12.2 years (range, 8 to 18 years). RESULTS: Treatment failure occurred in 20 shoulders (57%) in the Bankart repair group and in 2 shoulders (6%) in the open Latarjet procedure group (p < 0.001), representing a significantly higher revision rate for instability in the Bankart group (13) compared with the Latarjet group (1) (p < 0.001). In patients without recurrent shoulder instability (15 in the Bankart group and 29 in the Latarjet group), there was a significant improvement in the Constant score (p = 0.006 in the Bankart group and p < 0.001 in the Latarjet group) and Subjective Shoulder Value (p = 0.009 in the Bankart group and p < 0.001 in the Latarjet group), without any significant difference between the 2 groups. Younger age was the only variable significantly correlated with failure following a Bankart repair (p = 0.01). CONCLUSIONS: Adolescents are at a high risk for treatment failure after Bankart repair, and, therefore, the Latarjet procedure should be strongly considered as a primary procedure for recurrent anterior shoulder instability in this population. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Case Report: Midshaft clavicle fracture with concomitant high grade (Type V) acromioclavicular joint dislocation.

Introduction: Concomitant acromioclavicular joint dislocation and midshaft clavicle fracture are rare injuries, generally resulting from high energy trauma, with limited previous experience in management. Case: A 30 year old male presented following a pushbike accident. He had suffered a head on collision with another cyclist. Radiographic examination demonstrated a displaced midshaft clavicle fracture with a Rockwood Type V acromioclavicular joint dislocation. Operative management was undertaken using a dual plating technique. At six month follow up the patient demonstrated full range of motion and had no pain. Conclusion: Appropriate radiographic evaluation and careful intraoperative assessment are required using the principles of management for acromioclavicular joint injuries, along with stabilization of the mid-clavicular fracture to reduce the risk of non-union.

Risk Factors for Dislocation After Reverse Total Shoulder Arthroplasty: A Systematic Review and Meta-Analysis.

Instability after reverse total shoulder arthroplasty (RTSA) is a dreaded complication. Risk factors for postoperative instability are uncertain. The goal of this systematic review was to quantitatively and qualitatively analyze the risk factors for instability after RTSA. Of 1183 studies identified, 12 studies involving 3810 patients were included. The mean age was 68.8 years, and the mean follow-up was 46 months. The pooled rate of dislocation after RTSA was 4.0%. Several patient-specific and implant-specific risk factors have been identified, and especially the implant-specific risk factors appear avoidable with current knowledge, implant design, and technology. [Orthopedics. 2022;45(6):e303-e308.].

Osteoarthritis Progression after ACL Reconstruction Was Significantly Higher Than That of the Healthy Contralateral Knees: Long-Term Follow Up Study of Mean 16.4 Years.

BACKGROUND: This study aimed to assess long-term progression of osteoarthritis (OA) after isolated anterior cruciate ligament (ACL) reconstruction in athletes compared to the healthy contralateral side. METHODS: The study included 15 patients and 30 knees with a mean age of 40 years (range, 35-46) years, none of whom had had revision surgery or an injury to the contralateral side. The mean follow-up period was 16.4 years (range, 13-22). Clinical and radiographic assessment included the Tegner activity scale (TAS), International Knee Documentation Committee (IKDC) score, Knee injury and Osteoarthritis Outcome Score (KOOS), and Kellgren and Lawrence (KL) grade. The long-term results of the injured knees were compared with the status of the healthy contralateral side and compared with previously published mid-term results of the same cohort of patients. RESULTS: Patients generally remained clinically asymptomatic or mildly symptomatic at final follow-up, which is reflected by a KOOS pain score of 33 points (maximum 36 points) and an IKDC total subjective score of 87% (maximum 100%). There was a significant difference between mid-term and final follow-up in terms of the function score of the IKDC subjective questionnaire (p = 0.031), compartment findings and donor site morbidity of the IKDC functional examination (both p = 0.034), and the total KOOS score (p = 0.047). The KL score indicated significant progression of OA from mid-term to final follow-up in the injured knees (p = 0.004) and healthy contralateral knees (p = 0.014). Mean OA grades of the injured knees were significantly higher compared with the healthy contralateral side (p = 0.006) at final follow-up, and two patients showed moderate to severe signs of OA in the injured knee. CONCLUSIONS: Although most patients remained clinically asymptomatic or mildly symptomatic, long-term progression of OA after isolated ACL reconstruction in athletes was significantly higher compared with the healthy contralateral knee.

A new all-suture tension band tape fixation technique for simple olecranon fractures versus conventional tension band wire fixation: a comparative biomechanics study.

HYPOTHESIS: Simple transverse or short oblique olecranon fractures without articular comminution are classified as Mayo type IIA fractures and are typically treated with a tension band wire construct. Because of the high reoperation rates, frequently because of prominent hardware, all-suture tension band constructs have been introduced. It was the purpose to compare the biomechanical performance of conventional tension band wire fixation with a new all-suture tension band tape fixation for simple olecranon fractures. METHODS: Mayo type IIA olecranon fractures were created in 20 cadaveric elbows from 10 donors. One elbow of each donor was randomly assigned to the tension band wire technique (group TBW) or tension band tape (Arthrex, 1.3-mm SutureTape) technique (group TBT). Both groups were cyclically loaded with 500 N over 500 cycles, after which a uniaxial displacement was performed to evaluate load to failure. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, where failure was defined as fracture gap formation greater than 4.0 mm. RESULTS: There was no significant difference in gap formation after 500 cycles between the TBW (1.8 mm ± 1.3 mm) and the TBT (1.9 mm ± 1.1 mm) groups (P = .854). The TBT showed a tendency toward greater construct stiffness compared with the TBW construct (mean difference: 142 N/mm; P = .053). Ultimate load to failure was not significantly different comparing both groups (TBW: 1138 N ± 286 N vs. TBT: 1126 N ± 272 N; P = .928). In both groups, all repairs failed because of >4.0-mm gap formation at the fracture site and none because of tension band construct breakage. CONCLUSIONS: Our study shows that the TBT technique produces equivalent or superior biomechanical performance to the TBW for simple olecranon fractures. The TBT approach reduces the risk of hardware prominence and as a result mitigates against the need for hardware removal. The TBT technique offers a clinically viable alternative to TBW.

The Effect of Patellar Positioning on Femoral Component Rotation when Performing Flexion Gap Balancing Using a Tensioning Device for Total Knee Arthroplasty.

There is an increasing interest in new devices such as tensiometers for flexion gap balancing during total knee arthroplasty (TKA). The purpose of this study was to determine the influence of patella positioning during flexion gap balancing on femoral component rotation. We prospectively evaluated 32 consecutive knees in 31 patients who underwent primary TKA for degenerative osteoarthritis and where soft tissue balancing was performed using the same tensiometer. Preoperative measurements included valgus/varus deformation, mechanical axis, epicondylar axis, and tibial slope. Intraoperatively, measurement of femoral component rotation in 90 degrees of knee flexion was conducted in three different positions of the patella: (1) patella reduced, (2) patella dislocated but not everted, and (3) patella dislocated and everted. The femoral component had significantly higher rotation when the patella was reduced compared with a dislocated patella (4.9 ± 2.1 degrees vs. 4.2 ± 2.2 degrees; p = 0.006) and compared with a dislocated and everted patella (4.9 ± 2.1 degrees vs. 4.1 ± 2.3 degrees; p = 0.006). Varus knees (n = 22) demonstrated significantly increased femoral component rotation if the patella was reduced (5.3 ± 2.2 degrees) compared with dislocated patella without eversion (4.7 ± 2.3 degrees; p = 0.037) and with eversion (4.4 ± 2.5 degrees; p = 0.019). As such, the measurement of the mediolateral flexion gap stability with a laterally dislocated patella leads to a statistically significant overestimation of the lateral ligament stability and an underestimation of the external rotation positioning of the femoral component of approximately 1 degree, which is aggravated in varus knees. This is a Level II, prospective consecutive series study.

Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability.

PURPOSE: Upper third tears of the subscapularis tendon can be repaired successfully with a single anchor according to previous literature. The aim of the present study was to compare three single anchor repair techniques regarding fixation strength, footprint coverage and contact pressure in a biomechanical test set-up on human cadaveric shoulders. METHODS: Eighteen human cadaveric shoulders were randomized in three groups with respect to the repair technique; group 1: knotted lasso-loop mattress, group 2: knotted mattress and group 3: knotless tape repair. Upper third tears of the subscapularis tendon (Lafosse type 2) were created and repairs were performed with additional contact pressure and area measurement using a pressure mapping system. Cyclic testing was performed by loading the subscapularis from 10 to 100 N for 300 cycles. A position-controlled ramp protocol up to 30 and 50 N was used to allow for pressure measurements. Finally, specimens were loaded to failure and failure modes were recorded. RESULTS: The three groups were not significantly different regarding age, gender, bone mineral density at the lesser tuberosity, subscapularis footprint size and defect area created at the upper subscapularis insertion. A significant difference was detected between group 1 (48.6 ± 13.8%) and group 2 (25.9 ± 5.7%) regarding pressurized footprint coverage (p = 0.028). Ultimate load to failure was 630.8 ± 145.3 N in group 1, 586.9 ± 220.7 N in group 2 and 678.2 ± 236.5 N in group 3, respectively. Cyclic displacement was similar in all three groups with an average displacement of 1.2 ± 0.6 mm. The highest stiffness was found in group 1 with 88 ± 30.3, which was not statistically significantly different to group 2 (65 ± 27 N/mm) and group 3 (83.9 ± 32.9 N/mm). The most common mode of failure was suture cut-through at the suture-tendon interface (44%). Failures in group 3 were less common associated with suture cut-through (33% vs. 50% in group 1 and 2), but no significant differences were found. CONCLUSIONS: All three tested single anchor repair techniques of upper third subscapularis tears were able to provide sufficient biomechanical stability. Knotted lasso-loop mattress and knotless tape repair were superior regarding pressurized footprint coverage compared to a knotted horizontal mattress technique and are, therefore, preferable techniques for upper subscapularis repair.

Acromioclavicular joint stabilization with a double cow-hitch technique compared to a double tight-rope: a biomechanical study.

INTRODUCTION: The aim of the present biomechanical study was to evaluate the stability of a novel simple and cost-effective mini-open double cow-hitch suture button technique of acromioclavicular (AC) joint stabilization in comparison to a well-established double tight-rope technique. MATERIALS AND METHODS: A total of 12 fresh-frozen cadaveric shoulders were randomized into two treatment groups. In either a coracoclavicular stabilization with a standard double tight-rope technique (Group 1; n = 6, age 78 years ± 10) or a double cow-hitch with two No. 5 FiberWire strains looped in a bicortical button placed at the bottom of the coracoid process (Group 2; n = 6, age 80 years ± 13). Both techniques were equally augmented with an AC joint cerclage using a FiberTape. All shoulders were tested in a servo-hydraulic material testing machine for elongation/cyclic displacement (in mm) after cyclic loading (70 N cyclical load, 1500 cycles), stiffness (N/mm) and ultimate load to failure (N). The mechanism of failure was recorded. All tests were performed in a previously published testing setup. RESULTS: After 1500 cycles, group 2 showed a cyclic displacement of 1.67 mm (SD 0.85), compared to 1.04 mm (SD 0.23) cyclic displacement in group 1 (p = 0.11). The cyclic displacement after AC reconstruction in group 1 was 0.36 mm lower than in the native state with intact ligaments (p = 0.19), whereas the cyclic elongation in group 2 was 0.05 mm higher compared to the native situation (p = 0.87). Stiffness after reconstruction was significantly higher in group 1 compared to the native specimen (p = 0.001), in group 2 it was similar as before the reconstruction (p = 0.64). Ultimate load to failure and stiffness were higher in group 1 with 424 N (SD 237) and 68.6 N/mm (SD 8.2), compared to 377 N (SD 152) and 68 N/mm (SD 13.3) in group 2, without reaching statistical significance (p = 0.69 and 0.89). The most common failure modes were clavicular fractures at the tight rope drill holes (n = 2) and clavicular fractures medially at the fixation site (n = 2) in group 1, and coracoid button break-through (n = 3) and clavicular fractures medially at the fixation site (n = 2) in group 2. CONCLUSIONS: Stabilization of the AC joint with a novel mini-open double cow-hitch suture button technique resulted in a similar low elongation, high stiffness and ultimate load to failure compared to a double tight-rope technique. This cost-effective technique for AC joint stabilization could demonstrate a sufficient biomechanical stability with especially high stiffness and load-to-failure. LEVEL OF EVIDENCE: Biomechanical study.

Biomechanical stability of complex coronal plane fracture fixation of the capitellum.

INTRODUCTION: Coronal plane fractures of the distal humerus are relatively rare and can be challenging to treat due to their complexity and intra-articular nature. There is no gold standard for surgical management of these complex fractures. The purpose of this study was to compare the biomechanical stability and strength of two different internal fixation techniques for complex coronal plane fractures of the capitellum with posterior comminution. MATERIALS AND METHODS: Fourteen fresh frozen, age- and gender-matched cadaveric elbows were 3D-navigated osteotomized simulating a Dubberley type IIB fracture. Specimens were randomized into one of two treatment groups and stabilized with an anterior antiglide plate with additional anteroposterior cannulated headless compression screws (group antiGP + HCS) or a posterolateral distal humerus locking plate with lateral extension (group PLP). Cyclic testing was performed with 75 N over 2000 cycles and ultimately until construct failure. Data were analyzed for displacement, construct stiffness, and ultimate load to failure. RESULTS: There was no significant difference in displacement during 2000 cycles (p = 0.291), stiffness (310 vs. 347 N/mm; p = 0.612) or ultimate load to failure (649 ± 351 vs. 887 ± 187 N; p = 0.140) between the two groups. CONCLUSIONS: Posterolateral distal humerus locking plate achieves equal biomechanical fixation strength as an anterior antiglide plate with additional anteroposterior cannulated headless compression screws for fracture fixation of complex coronal plane fractures of the capitellum. These results support the use of a posterolateral distal humerus locking plate considering the clinical advantages of less invasive surgery and extraarticular metalware. LEVEL OF EVIDENCE: Biomechanical study.

Long-term results after posterior open glenoid wedge osteotomy for posterior shoulder instability associated with excessive glenoid retroversion.

BACKGROUND: Treatment of posterior shoulder instability (PSI) associated with excessive glenoid retroversion is a rare, challenging problem in shoulder surgery. One proposed technique is posterior open wedge glenoid osteotomy to correct excessive glenoid retroversion as described by Scott. However, this operation is rarely performed, and limited long-term outcomes using this approach are available. The goal of this study was to analyze the long-term outcomes of posterior open wedge glenoid osteotomy for PSI associated with excessive glenoid retroversion. METHODS: Six consecutive patients (7 shoulders) with a mean age of 24 years (range 19-34) were treated with posterior open wedge glenoid osteotomy for PSI associated with a glenoid retroversion greater than 15° and followed up clinically and radiographically at a mean age of 15 years (range 10-19). RESULTS: Recurrent, symptomatic PSI was observed in 6 of 7 shoulders (86%). One necessitated revision with a posterior (iliac crest) bone block procedure and was rated as a failure and excluded from functional analysis. One patient rated his result as excellent, 3 as good, 1 as fair, and 1 as unsatisfactory. Mean relative Constant Score (CS%) was unchanged from preoperation to final follow-up (CS% = 72%) and pain did not significantly decrease (Constant Score = 7-10 points; P = .969). The mean Subjective Shoulder Value (SSV) improved postoperatively, but with 6 patients the improvement did not reach statistical significance (SSV = 42%-67%, P = .053) and the total Western Ontario Shoulder Instability Index averaged 30% at the final follow-up. Mean glenoid retroversion of all 7 shoulders was corrected from 20° (range 16°-26°) to 3° (range -3° to +8°) (P = .018). In the 5 shoulders with preoperative static posterior subluxation of the humeral head, the humeral head was not recentered. All 7 shoulders showed progression of glenoid arthritic changes. CONCLUSIONS: Posterior open wedge glenoid osteotomy for PSI associated with excessive glenoid retroversion neither reliably restored shoulder stability nor recentered the joint or prevent progression of osteoarthritis. Alternative treatments for PSI associated with excessive glenoid retroversion have to be developed and evaluated.

Complications of Reverse Total Shoulder Arthroplasty: A Computational Modelling Perspective.

Reverse total shoulder arthroplasty (RTSA) is an established treatment for elderly patients with irreparable rotator cuff tears, complex proximal humerus fractures, and revision arthroplasty; however, with the increasing indications for RTSA over the last decade and younger implant recipients, post-operative complications have become more frequent, which has driven advances in computational modeling and simulation of reverse shoulder biomechanics. The objective of this study was to provide a review of previously published studies that employed computational modeling to investigate complications associated with RTSA. Models and applications were reviewed and categorized into four possible complications that included scapular notching, component loosening, glenohumeral joint instability, and acromial and scapular spine fracture, all of which remain a common cause of significant functional impairment and revision surgery. The computational shoulder modeling studies reviewed were primarily used to investigate the effects of implant design, intraoperative component placement, and surgical technique on postoperative shoulder biomechanics after RTSA, with the findings ultimately used to elucidate and mitigate complications. The most significant challenge associated with the development of computational models is in the encapsulation of patient-specific anatomy and surgical planning. The findings of this review provide a basis for future direction in computational modeling of the reverse shoulder.