Anterior shoulder dislocation with avulsion fracture of the greater tuberosity results in reliable good outcomes after closed reduction.

Background: Avulsion of the greater tuberosity (GT) due to traumatic anterior shoulder dislocation (ASD) is a commonly observed fracture pattern. After closed reduction of the dislocated humerus, the GT typically reduces itself into its anatomic position enabling the patient to undergo conservative treatment. The aim of this study was to retrospectively review a consecutive series of patients with conservatively treated GT avulsion fractures after closed reduction of an ASD and analyze radiographic outcome, shoulder function and glenohumeral stability and the conversion rate to surgical treatment. Methods: All patients who underwent closed reduction of a GT avulsion fracture after ASD with the primary intention of conservative treatment between 2017 and 2022 were included. Complications (i.e. conversion to surgical treatment), shoulder function assessed with the American Shoulder and Elbow Surgeons score and subjective shoulder value, instability assessed with the Western Ontario Shoulder Instability score, radiological impingement (greater tuberosity index = GTI and impingement index = II) and GT fracture pattern were assessed as outcome measurements. Results: A total of 29 patients (mean age 44 years, 27% female) with a mean follow-up of 32.6 (range, 8-96) months were enrolled. Seven patients (24%) underwent surgery due to secondary displacement (n = 4, 14%) or impingement symptoms (n = 3, 10%). All patients who underwent secondary surgery showed a multifragmentary fracture pattern of the GT. Shoulder stiffness (n = 7) and neuropraxia of the axillary nerve (n = 3) were observed temporarily and resolved during the follow-up period. The American Shoulder and Elbow Surgeons and subjective shoulder value of the conservatively treated patients at the last follow-up was 89.2 ± 19.1 respectively 86 ± 18.2%. No recurrent glenohumeral dislocation was documented. The mean Western Ontario Shoulder Instability score at last follow-up was 8(0-71). The mean GTI decreased from 1.2 ± 0.1 after ASD to 1.1 ± 0.1 at the last follow-up (P = .002). The mean II decreased from 0.6 ± 0.5 after ASD to 0.4 ± 0.3 at the last follow-up (P = .110). Conclusion: The GT avulsion fragment reduces typically into a close to anatomic position after closed reduction and the GTI even improves with further conservative treatment over time. Close radiological follow-up is necessary to rule out secondary displacement which occurs typically in a multifragmentary fracture pattern. Patients without the need for surgery showed good clinical outcomes without recurrence of glenohumeral instability.

Biomechanical evaluation of fixation of the coracoclavicular stand-alone cow-hitch suture reconstruction in comparison to two established techniques for highly unstable distal clavicle fractures (Neer type V).

Background: Treatment of displaced distal clavicle fractures with bony avulsion of the coracoclavicular (CC) ligaments often warrants surgical fixation, yet a gold standard surgical technique is to be defined. The purpose of this study was to compare the biomechanical fixation strength of a new fixation technique, the CC stand-alone cow-hitch suture reconstruction, and to compare this technique with a clavicle hook plate and a lateral locking plate with CC suture reconstruction. Methods: Simulated Neer type V distal clavicle fractures of the clavicle were created in 18 cadaveric shoulders, which were matched by age and gender in 3 groups: (1) clavicle hook plate (group HP), (2) lateral locking plate fixation with CC suture reconstruction (group LPCC), and (3) CC stand-alone suture reconstruction using the cow-hitch technique (group CH). After preconditioning with 25 N for 10 cycles, the specimens were cycled in the coronal plane for 500 cycles from 10N to 70N. Displacement and ultimate load to failure were documented and analyzed with the data acquisition system. Results: There was a significant difference in the fracture displacement during cyclic loading between the LPCC group and the HP group (0.6 vs. 1.7 mm; P = .02) and between the CH and HP groups (0.5 vs. 1.7 mm; P = .004). Fracture displacement was not different between the LPCC and the CH groups (P = .544). The CH group and the LPCC group showed a significantly higher stiffness compared to the HP group (P < .001 and P = .003, respectively). The CH group showed a significantly higher ultimate load to failure compared with the HP group (429 vs. 172 N; P = .005) and showed a tendency toward higher ultimate load to failure when compared with the LPCC group (429 vs. 258 N; P = .071). Conclusion: The CC stand-alone cow-hitch suture reconstruction and the locking plate with CC reconstruction showed higher fixation strength compared with the hook plate for simulated Neer type V distal clavicle fractures. There was a tendency of higher ultimate load to failure with the cow-hitch technique compared with the lateral locking plate with CC suture reconstruction, and given the potential advantages of less soft tissue stripping, metal-free fixation, low costs, and simple surgical technique, clinical application of the all-suture CC reconstruction using the cow-hitch for Neer type V distal clavicle fractures appears warranted.

Stability of novel cow-hitch suture button coracoid bone graft fixation in Latarjet procedures: a biomechanical study.

BACKGROUND: The Latarjet procedure is widely used to address anterior shoulder instability, especially in case of glenoid bone loss. Recently, cortical suture button fixation for coracoid transfer has been used to mitigate complications seen with screw placement. The aim of this biomechanical study was to evaluate the stability of a novel and cost-effective cow-hitch suture button technique, designed to be performed through a standard open deltopectoral approach, and compare this to a well-established double suture button technique. MATERIALS AND METHODS: We randomly assigned 12 fresh frozen cadaveric shoulders to undergo the Latarjet procedure with either 4 suture button (S&N EndoButton) fixations (SB group; n = 6, age 72 ± 9.8 years) or cow-hitch suture button technique using a 1.7-mm FiberTape looped sequentially in 2 suture buttons (Arthrex Pectoralis Button) placed from anterior on the posterior glenoid (CH-SB group; n = 6, age 73 ± 9.3 years). After fixation, all shoulders underwent biomechanical testing with direct loading on the graft via a material testing system. Cyclic loading was performed for 100 cycles (10-100 N) to determine axial displacement with time; each graft was then monotonically loaded to failure. RESULTS: The maximum cyclic displacement was 4.3 ± 1.6 mm for the cow-hitch suture button technique and 5.0 ± 1.7 mm for the standard double suture button technique (P = .46). Ultimate load to failure and stiffness were, respectively, 190 ± 82 N and 221 ± 124 N/mm for the CH-SB technique and 172 ± 48 N and 173 ± 34 N/mm for the standard double SB technique (P = .66 and .43). The most common failure mode was suture cut-through at the anteroinferior aspect of the glenoid for both fixation groups. CONCLUSIONS: The cow-hitch suture button technique resulted in a similar elongation, stiffness, and failure load compared to an established double suture button technique. Therefore, this cost-effective fixation may be an alternative, eligible for open approaches, to the established double suture button techniques.

Predictive factors of acromial fractures following reverse total shoulder arthroplasty: a subgroup analysis of 860 shoulders.

Background: Acromion stress fractures (ASF) or scapular spine fractures (SSF) following reverse total shoulder arthroplasty (RTSA) are common complications with impaired clinical outcome. The underlying biomechanical factors remain unclear. The aim of this study was to evaluate basic demographic and radiographic parameters predicting occurrence of different types of ASF/SSF in a large single-center study cohort. Methods: A total of 860 RTSA (805 patients) with available minimum follow-up of 2 years were implanted between 2005 and 2018 at a tertiary academic center. All RTSA with subsequent ASF/SSF (n = 45 in 43 shoulders [42 patients, 5%]) were identified and classified as Levy I to III. Predictive demographic, surgical, and radiographic factors were evaluated for each subtype and compared to the control group (817 RTSA, 763 patients). The radiographic analysis included critical shoulder angle, lateralization shoulder angle (LSA), distalization shoulder angle (DSA), acromio-humeral distance (ACHD), acromial thickness, deltoid tuberosity index, deltoid length, and center of rotation. Results: Of the 45 ASF/SSF in 42 patients, 8 were classified as Levy I, 21 as Levy II, and 16 as Levy III. Demographic analysis revealed indication as risk factor for Levy I fractures, higher American Society of Anesthesiologists score as risk for Levy type II fractures and higher age as risk factor for Levy type III fractures. None of the measured radiographic parameters were predictive for occurrence of Levy type I and Levy type II ASF. However, analysis of Levy III SSF revealed a higher postoperative LSA (89° ± 10° vs. 83° ± 9°, P = .015), a lower postoperative DSA (45° ± 8° vs. 53° ± 12°, P = .002), less distalization (ACHD of 33 ± 8 mm vs. 38 ± 10 mm, P = .049), and a more medial center of rotation preoperatively (COR-LA 16 ± 8 mm vs. 12 ± 7 mm, P = .048) as predictive radiographic factors. Conclusion: The present analysis showed a significant association of higher postoperative LSA, lower DSA, a lower ACHD, and higher age as predictive factor only for Levy type III fractures. Some of these factors can be surgically influenced and this knowledge can be of value for preoperative planning and surgical execution to avoid these complications.

Structural Musculotendinous Parameters That Predict Failed Tendon Healing After Rotator Cuff Repair.

Background: Healing of the rotator cuff after repair constitutes a major clinical challenge with reported high failure rates. Identifying structural musculotendinous predictors for failed rotator cuff repair could enable improved diagnosis and management of patients with rotator cuff disease. Purpose: To investigate structural predictors of the musculotendinous unit for failed tendon healing after rotator cuff repair. Study Design: Cohort study; Level of evidence, 2. Methods: Included were 116 shoulders of 115 consecutive patients with supraspinatus (SSP) tear documented on magnetic resonance imaging (MRI) who were treated with an arthroscopic rotator cuff repair. Preoperative assessment included standardized clinical and imaging (MRI) examinations. Intraoperatively, biopsies of the joint capsule, the SSP tendon, and muscle were harvested for histological assessment. At 3 and 12 months postoperatively, patients were re-examined clinically and with MRI. Structural and clinical predictors of healing were evaluated using logistic and linear regression models. Results: Structural failure of tendon repair, which was significantly associated with poorer clinical outcome, was associated with older age (ß = 1.12; 95% CI, 1.03 to 1.26; P = .03), shorter SSP tendon length (ß = 0.89; 95% CI, 0.8 to 0.98; P = .02), and increased proportion of slow myosin heavy chain (MHC)-I/fast MHC-II hybrid muscle fibers (ß = 1.23; 95% CI, 1.07 to 1.42; P = .004). Primary clinical outcome (12-month postoperative Constant score) was significantly less favorable for shoulders with fatty infiltration of the infraspinatus muscle (ß = -4.71; 95% CI, -9.30 to -0.12; P = .044). Conversely, a high content of fast MHC-II muscle fibers (ß = 0.24; 95% CI, 0.026 to 0.44; P = .028) was associated with better clinical outcome. Conclusion: Both decreased tendon length and increased hybrid muscle fiber type were independent predictors for retear. Clinical outcome was compromised by tendon retearing and increased fatty infiltration of the infraspinatus muscle. A high content of fast MHC-II SSP muscle fibers was associated with a better clinical outcome. Registration: NCT02123784 (ClinicalTrials.govidentifier).

MRI findings of traumatic and degenerative rotator cuff tears and introduction of the "cobra sign".

Background: A rotator cuff tear (RCT) is a common shoulder diagnosis and its etiology may be acute, traumatic, or chronic degenerative. Differentiation between the 2 etiologies may be important for multiple reasons, but remains difficult based on imaging. Further knowledge about radiographic and magnetic resonance findings to distinguish traumatic from degenerative RCT is needed. Methods: We analyzed magnetic resonance arthrograms (MRAs) of 96 patients with traumatic or degenerative superior RCT, which were matched according their age and the affected rotator cuff muscle into the 2 groups. Patients older than 66 years of age were excluded from the study to avoid including cases with pre-existing degeneration. In the case of traumatic RCT, the time between the trauma and MRA had to be less than 3 months. Various parameters of the supraspinatus (SSP) muscle-tendon unit were assessed (tendon thickness, presence of a remaining tendon stump at the greater tubercle, magnitude of retraction, layer appearance). The retraction of the 2 SSP layers were individually measured to determine the difference of retraction. Additionally, edema of the tendon and muscle, the tangent- and kinking-sign as well as the newly introduced Cobra-sign (bulging of the distal part of the ruptured tendon with slim configuration of the medial part of the tendon) were analyzed. Results: Edema within the SSP muscle (sensitivity 13%, specificity 100%, P = .011) or the tendon (sensitivity 86%, specificity 36%, P = .014) are more frequent in traumatic RCT. The same association was found for the kinking-sign (sensitivity 53%, specificity 71%, P = .018) and the Cobra sign (sensitivity 47%, specificity 84%, P = .001). Even though not statistically significant, tendencies were observed toward thicker tendon stumps in traumatic RCT, and greater difference in retraction between the 2 SSP layers in the degenerative group. The cohorts had no difference in the presence of a tendon stump at the greater tuberosity. Conclusion: Muscle and tendon edema, as well as tendon kinking appearance and the newly introduced cobra-sign are suitable MRA parameters to distinguish between traumatic and degenerative etiology of a superior RTC.

Reverse Total Shoulder Arthroplasty for Proximal Humeral Fractures and Sequalae Compared to Non-Fracture Indications: A Matched Cohort Analysis of Outcome and Complications.

BACKGROUND: With the increase in utility and popularity of the reverse total shoulder arthroplasty (RTSA) within the last decades, indications for RTSA have expanded. As well as the established indications such as cuff tear arthropathy and massive irreparable rotator cuff tears, RTSA for complex proximal humeral fractures in elderly patients has been proven to be a reliable treatment option. METHODS: A prospectively enrolled RTSA database of 1457 RTSAs implanted between September 2005 and November 2020 was reviewed. Patients treated with RTSA for a complex proximal humerus fracture and fracture sequalae (F-RTSA) were 1:1 matched with a group of patients who were treated electively with RTSA for indications other than a fracture (E-RTSA). Matching criteria included sex, age, length of follow-up and body mass index. Evaluation after a minimum of 2 years follow-up included evaluation of the absolute and relative Constant-Murley score (aCS; rCS), subjective shoulder value (SSV), range of motion (ROM) assessment and complications. RESULTS: Each of the matched cohorts comprised 134 patients with a mean follow-up of 58 ± 41 months for the fracture group and 58 ± 36 months for the elective group. The mean age for both groups was 69 ± 11 years in the F-RTSA and 70 ± 9 years for the E-RTSA group. There were no significant differences in clinical outcome measures including aCS, rCS and SSV (p > 0.05). There was a significant difference in mean active external rotation with 20° ± 18° in the F-RTSA group compared with 25° ± 19° in the E-RTSA group (p = 0.017). The complication rate was not significantly different, with 41 complications in 36 shoulders in the F-RTSA and 40 complications in 32 shoulders in the E-RTSA group (p = 0.73). The main complication for the F-RTSA group was dislocation of the greater tuberosity (6%), whereas acromial fractures (9%) were the leading complication in the E-RTSA group. There was also no significant difference in revision rate comparing F-RTSA with E-RTSA (10% vs. 14%; p = 0.25). CONCLUSIONS: RTSA for complex proximal humeral fractures and its sequalae leads to a comparable clinical outcome as that for patients treated electively with RTSA for indications other than fracture. There was, however, a significant difference in active external rotation, with inferior rotation in patients undergoing RTSA for fracture. This valuable information can help in requesting informed consent of patients with proximal humeral fractures.

Greater Tuberosity Fractures after RTSA: A Matched Group Analysis.

Periprosthetic fractures, such as acromial and spine fractures, are known complications following implantation of reverse shoulder arthroplasty (RTSA). The entity of greater tuberosity fractures (GTF) has rarely been studied in the literature. The purpose of this study was to analyze the outcome of postoperative greater tuberosity fractures after RTSA compared to a matched control group. The main findings of this study are that a GTF after RTSA is associated with worse clinical outcome scores (mean absolute CS 50 ± 19 (p = 0.032); SSV 63% ± 26 (p = 0.022); mean force 1 kg ± 2 kg (p = 0.044)) compared with the control group (mean absolute CS 62 ± 21; SSV 77% ± 29; mean force 2 kg ± 2 kg). In terms of postoperative range of motion, the fracture group was significantly worse in terms of external rotation (17° ± 19° vs. 30° ± 19° (p = 0.029)). Internal rotation, flexion, as well as abduction of the shoulder appear to be unaffected (internal rotation GTF 4 ± 2, control group 5 ± 3 (p = 0.138); flexion GTF 102° ± 28°, control group 114° ± 27° (p = 0.160); abduction GTF 109° ± 42°, control group 120° ± 39° (p = 0.317)).

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.

Return to Play After Surgical Treatment of High-Grade Acromioclavicular Joint Injuries in the Australian Football League.

Background: Acromioclavicular joint (ACJ) injuries are the second most common upper limb injuries in the Australian Football League (AFL); however, there is little evidence on the return-to-sport results after surgical stabilization of the ACJ in this sporting population. Purpose: To investigate the return-to-sport time, on-field performance, and patient-reported outcomes in a series of professional AFL players after undergoing ACJ stabilization. Study Design: Case series; Level of evidence, 4. Methods: We conducted a retrospective case series of all AFL players who had undergone open twin-tailed dog-bone ACJ stabilization by a single surgeon between September 2013 and April 2017. Outcome measures included time to return to sport, on-field performance indicators (handballs, tackles, kicks, and AFL Fantasy and Supercoach scores), the Nottingham Clavicle Score, Oxford Shoulder Score, and the Specific Acromioclavicular Score. Patient-reported outcomes were evaluated at a minimum follow-up of 12 months. Results: Of 13 senior listed AFL players who underwent twin-tailed dog-bone surgery, 9 players were included. Mean follow-up was 24.8 months (range, 5-41 months) postoperatively. Mean return-to-sport time was 8.6 weeks for injuries that occurred within the season. The number of kicks, marks, handballs, and tackles as well as AFL Supercoach and Fantasy scores did not significantly change after surgery (P > .05). Outcome measures showed a high level of patient satisfaction after surgery, with a mean Nottingham Clavicle Score of 92.2, Oxford Shoulder Score of 47.7, and the Specific Acromioclavicular Score of 7.5. Conclusion: In a collective of professional AFL players with ACJ injury, our twin-tailed dog-bone technique revealed return to competitive play could be achieved at a mean of 8.6 weeks without compromising on-field performance or patient-reported pain, function, and satisfaction.

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.].

Fixation of distal clavicle fractures with coracoclavicular instability: a comparative biomechanical study in human cadavers.

BACKGROUND: The need for coracoclavicular (CC) stabilization in the fixation of fractures with CC instability (Neer type IIB and V) was biomechanically demonstrated by higher construct strength than isolated locking plate osteosynthesis. It was the purpose of this study to prove noninferiority of the new cow-hitch suture repair technique compared with the well-established suture tape double-button fixation with regard to overall fixation strength and cyclic loading properties. METHODS: Twelve human cadaver shoulders (7 right and 5 left) were matched for sex and age (mean age: 75 ± 5 years). An oblique parasagittal fracture line 20 mm medial to the acromioclavicular joint line was created, and the CC ligaments were dissected. Six shoulders were reconstructed by a double FiberTape fixation with two suture buttons (group DB), and the remaining six shoulders by a cow-hitch suture repair using a double FiberWire with only coracoid button fixation (group CH). Both reconstruction techniques were tested in a servo-hydraulic material testing machine for cyclic displacement (mm), stiffness (N/mm), and maximum load-to-failure (N) after 500 cycles at 3 mm/s and inferosuperior load between 15 and 70 N. Superior fragment displacement in space was recorded using a MicroScribe digitizer. RESULTS: There were no statistically significant differences regarding cyclic displacement (group DB: 0.7 mm; group CH: 1.3 mm; P = .36), stiffness (group DB: 177 N/mm; group CH: 116 N/mm; P = .17), maximum load-to-failure (group DB: 560 N; group CH: 492 N; P = .59), and superior displacement in space of the medial fragment (group DB: 3.2 mm; group CH: 1.6 mm; P = .48). CONCLUSION: Fixation of unstable distal clavicle fractures using a double FiberWire cow-hitch suture repair with isolated coracoid button fixation for stand-alone CC stabilization resulted in similar biomechanical properties to a double-suture button fixation with FiberTapes while avoiding prominent clavicular implants.

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.

Incidence, radiographic predictors, and clinical outcome of acromial stress reaction and acromial fractures in reverse total shoulder arthroplasty.

BACKGROUND: Acromial and scapular spine fractures (ASFs) are known complications following implantation of reverse total shoulder arthroplasty (RTSA). The entity of acromial stress reaction (ASR) without fracture has recently been described. The purpose of this study was to analyze the incidence, radiographic predictors, treatment options, healing rates, and clinical outcomes of ASF and ASR compared with a control group. METHODS: A total of 854 primary RTSAs were implanted between 2005 and 2018 in a single shoulder unit of a tertiary referral hospital and retrospectively reviewed for the incidence of ASF and ASR. ASR was defined as pain at the acromion or scapular spine after fracture exclusion on computed tomography scans. The ASF group was matched to a control group. Preoperative and postoperative radiographs were analyzed for radiographic predictors of ASF or ASR. The impact of ASF and ASR, operative vs. nonoperative treatment, and fracture union on clinical outcomes (Constant-Murley score [CS], Subjective Shoulder Value [SSV], and range of motion) with a minimum follow-up period of 2 years was analyzed. RESULTS: A total of 46 ASFs (5.4%) in 44 patients and 44 ASRs (5.2%) in 43 patients were detected at a mean of 16 ± 24 months and 20 ± 23 months postoperatively, respectively. Predictive radiographic factors were an increased critical shoulder angle and lateralization shoulder angle. The overall union rate was 55% (22 of 40) but was significantly higher following operative treatment (9 of 11, 82%) compared with nonoperative treatment (13 of 29, 45%). Patients with ASF or ASR demonstrated inferior clinical outcomes (CS, 44 ± 21 and 48 ± 18; SSV, 52% ± 25% and 57% ± 27%) compared with the control group (CS, 66 ± 14; SSV, 82% ± 22%) independent of bony union or treatment at a mean of 59 ± 33 months (ASF) and 61 ± 38 months (ASR). CONCLUSION: ASF and ASR are frequent complications following RTSA implantation with similar poor clinical outcome measures. The healing rate was shown to be much higher with a surgical approach. Nevertheless, fracture consolidation does not result in better clinical outcomes compared with nonunion.

Structural and Functional Results of Subscapularis and Conjoint Tendon After Latarjet Procedure at 8-Year Average Follow-up.

BACKGROUND: The Latarjet procedure involves initial dissection through a longitudinal split of the subscapularis tendon with only a final partial closure to accommodate the transferred coracoid bone. Furthermore, by transferring the coracoid bone block to the anterior glenoid, the surgeon completely alters the resting and dynamic route of the attached conjoint tendon. The eventual structural and functional integrity of the subscapularis and conjoint tendons is currently unknown. PURPOSE: To examine the structural and functional integrity of the subscapularis and the conjoint tendon after the Latarjet procedure at an 8-year average follow-up. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Twenty patients with anterior shoulder instability at a mean age of 30 years (range, 19-50 years) underwent the open Latarjet procedure. Clinical examination at the final follow-up included quantitative isometric measurement of abduction and internal rotation strength compared with the nonoperative side. Patients were assessed via radiograph examination and preoperative computed tomography. Final position and healing of the transferred coracoid bone block were evaluated using standard radiographs. At follow-up, the subscapularis and conjoint tendon were evaluated via magnetic resonance imaging (MRI) with metal artifact reduction techniques and via ultrasound. RESULTS: Nineteen of the 20 shoulders remained stable at the final follow-up; there was 1 redislocation (5%) after 14 months. The mean Rowe score was 83 points (SD, 17.9 points), the mean Constant score was 85 points (SD, 8.1 points), and the Subjective Shoulder Value was 80% (SD, 18%). The mean abduction strength of the operative shoulder was 7.41 ± 2.06 kg compared with 8.33 ± 2.53 kg for the nonoperative side (P = .02). The mean internal rotation strength at 0° for the operative shoulder was 8.82 ± 3.47 kg compared with 9.06 ± 3.01 kg for the nonoperative side (P = .36). The mean internal rotation strength in the belly-press position for the operative shoulder was 8.12 ± 2.89 kg compared with 8.50 ± 3.03 kg (P = .13). Four of 20 shoulders showed mild tendinopathic changes of the subscapularis tendon but no partial or complete tear. One patient exhibited fatty degeneration Goutallier stage 1. Conjoint tendon was in continuity in all 20 shoulders on MRI scans. CONCLUSION: Abduction, but not internal rotation strength, was slightly reduced after the Latarjet procedure at a mean of 8 years of follow-up. The subscapularis tendon was intact based on ultrasound examination, and the conjoint tendon was intact based on MRI scans. Subscapularis muscle girth relative to the supraspinatus muscle remained intact from preoperative measurements based on MRI scans.

Acromial Morphology and Its Relation to the Glenoid Is Associated with Different Partial Rotator Cuff Tear Patterns.

The pathogenesis of subacromial impingement syndrome is controversially discussed. Assuming that bursal sided partial tears of the supraspinatus tendons are rather the result of a direct subacromial impact, the question arises whether there is a morphological risk configuration of the acromion and its spatial relation to the glenoid. Patients who underwent arthroscopic repair of either a partial articular supraspinatus tendon avulsion (PASTA) or bursal-sided supraspinatus tear (BURSA) were retrospectively allocated to two groups. Various previously described and new omometric parameters on standard anteroposterior and axial shoulder radiographs were analyzed. We hypothesized that acromial shape and its spatial relation to the glenoid may predispose to a specific partial supraspinatus tendon tear pattern. The measurements included the critical shoulder angle (CSA), the acromion index (AI), Bigliani acromial type and the new short sclerotic line, acromioclavicular offset angle (ACOA), and AC offset. The ratio length/width of acromion and the medial acromial offset were measured on axial radiographs. A total of 73 patients were allocated to either PASTA (n = 45) or BURSA (n = 28). The short sclerotic line showed a statistically significant difference between PASTA and BURSA (16.2 mm versus 13.1 mm, p = 0.008). The ratio acromial width/length was statistically significant (p = 0.021), with BURSA having slightly greater acromial length (59 vs. 56 mm). The mean acromial offset was 42.9 mm for BURSA vs. 37.7 mm for PASTA (p = 0.021). ACOA and AC offset were both higher for BURSA, without reaching statistical significance. The CSA did not differ significantly between PASTA and BURSA (33.73° vs. 34.56°, p = 0.062). The results revealed an association between a narrow acromial morphology, increased medial offset of the acromion in relation to the glenoid, and the presence of a short sclerotic line in the anteroposterior radiograph in bursal-sided tears of the supraspinatus tendon. Assuming that bursal-sided tears are rather the result of a direct conflict of the tendon with the undersurface of the acromion, this small subgroup of patients presenting with impingement syndrome might benefit from removing a harming acromial spur.

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.

Biomechanical comparison of intramedullary screw fixation, dorsal plating and K-wire fixation for stable metacarpal shaft fractures.

We compared four methods of metacarpal shaft fixation: 2.2 mm intramedullary headless compression screw; 3.0 mm intramedullary headless compression screw; intramedullary K-wire fixation; and dorsal plate fixation. Transverse mid-diaphyseal fractures were created in 64 metacarpal sawbones and were assigned into four groups. Peak load to failure and stiffness were measured in cantilever bending and torsion. We found that dorsal plating had the highest peak load to failure. However, initial bending stiffness of the 3.0 mm intramedullary headless compression screw was higher than that of the dorsal plates. In torsion testing, dorsal plating had the highest peak torque, but there was no significant difference in torsional stiffness between the plate and intramedullary headless compression screw constructs. We concluded that intramedullary headless compression screw fixation is biomechanically superior to K-wires in cantilever bending and torsion; however, it is less stable than dorsal plating. In our study, the initial stability provided by K-wire fixation was sufficient to cope with expected loads in the early rehabilitation period, whereas dorsal plates and IHCS constructs provided stability far in excess of what is required.

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.

Cow-hitch fixation in fracture hemiarthroplasty.

BACKGROUND: The treatment of complex proximal humerus fractures with hemiarthroplasty is associated with a high failure rate due to secondary displacement of the tuberosities. It was the aim of this in-vitro study to compare the mechanical stability of tuberosity reattachment obtained with the so-called "Cow-Hitch" (CH) cerclage compared with conventional tuberosity reattachment. METHODS: A 4-part proximal humerus fracture was created in 10 fresh-frozen, human cadaveric shoulders. The greater and lesser tuberosity were reattached to the hemiarthroplasty stem with in total 4 CH Cerclages in the Cow-Hitch group. The conventional technique-recommended for the tested implant-was used in the control group using 6 sutures. A total of 5000 loading cycles with forces of 350N were applied, while motion (in mm) of the tuberosities was recorded in 3 directions (anteroposterior = AP, mediolateral = ML, inferosuperior = IS) with a telecentric camera. RESULTS: After 5000 loading cycles, the CH group showed less fragment displacement (AP: 2.3 ± 2.3 mm, ML: 1.8 ± 0.9 mm, IS: 1.3 ± 0.5 mm) than the conventional group (AP: 9.8 ± 12.3 mm, ML: 5.5 ± 5.6 mm, IS: 4.5 ± 4.7 mm). The differences were not statistically significant (AP: P = .241; ML: P = .159; IS: P = .216). The lesser tuberosity fragment displacement in the CH group after 5000 cycles was less in the AP (2.3 ± 3.3 vs. 4.0 ± 2.8, P = .359) and IS (1.9 ± 1.2 vs. 3.1 ± 1.8; P = .189) directions but higher in the ML direction (7.2 ± 5.7 vs 6.3 ± 3.6, P = .963). CONCLUSIONS: In-vitro, "Cow-Hitch" cerclage results in mean greater tuberosity displacements of 2 mm and reliably prevents displacements greater than 5 mm. In contrast, the conventional fixation technique yields unreliable, variable stability with low to complete displacement upon cyclical loading.