TGF-ß3 Loaded Electrospun Polycaprolacton Fibre Scaffolds for Rotator Cuff Tear Repair: An in Vivo Study in Rats.

Biological factors such as TGF-ß3 are possible supporters of the healing process in chronic rotator cuff tears. In the present study, electrospun chitosan coated polycaprolacton (CS-g-PCL) fibre scaffolds were loaded with TGF-ß3 and their effect on tendon healing was compared biomechanically and histologically to unloaded fibre scaffolds in a chronic tendon defect rat model. The biomechanical analysis revealed that tendon-bone constructs with unloaded scaffolds had significantly lower values for maximum force compared to native tendons. Tendon-bone constructs with TGF-ß3-loaded fibre scaffolds showed only slightly lower values. In histological evaluation minor differences could be observed. Both groups showed advanced fibre scaffold degradation driven partly by foreign body giant cell accumulation and high cellular numbers in the reconstructed area. Normal levels of neutrophils indicate that present mast cells mediated rather phagocytosis than inflammation. Fibrosis as sign of foreign body encapsulation and scar formation was only minorly present. In conclusion, TGF-ß3-loading of electrospun PCL fibre scaffolds resulted in more robust constructs without causing significant advantages on a cellular level. A deeper investigation with special focus on macrophages and foreign body giant cells interactions is one of the major foci in further investigations.

Reverse shoulder arthroplasty for fracture sequelae: Clinical outcome and prognostic factors.

BACKGROUND: The reverse total shoulder arthroplasty (RTSA) is a common therapy for the fracture sequelae (FS) of the proximal humerus. The aim of this study was to show the short and midterm clinical outcome of the RTSA for FS and to identify prognostic factors. METHODS: Data from 46 patients with chronic FS who underwent RTSA were analysed. The clinical follow-up included the Constant score and radiographic examination. Patients were divided into groups based on the Boileau classification of FS, and the degree of metaphyseal bone loss was measured (Boileau type I 9 patients; type II 3 patients; type III 8 patients and type IV 16 patients). Scapular notching was assessed according to the classification of Sirveaux. RESULTS: The mean postoperative Constant score was 57. Clinical outcomes were similar among the various FS groups, as defined according to the Boileau classification, but patients who had undergone revision arthroplasty had a significantly inferior mean Constant score than patients with type IV FS. There were no significant differences between patients who were initially managed with conservative therapy and those treated surgically. Patients with metaphyseal bone loss >3 cm showed inferior clinical scores. Inferior scapular notching was seen in 25 patients, and had a negative effect on the clinical outcome. Complications included five infections and one dislocation. CONCLUSION: Metaphyseal bone loss was unfavourable prognostic factors in patients with FS treated with RTSA. However, the Boileau classification did not serve as a prognostic criterion. Previous operative or conservative treatment had no influence on the outcome and scapular notching was associated with inferior clinical results.

Arthroscopic posterior bone block stabilization-early results of an effective procedure for the recurrent posterior instability.

PURPOSE: In the current study the clinical outcome of an arthroscopic posterior bone block augmentation in combination with a posterior capsular repair was investigated. METHODS: Twenty-four shoulders (18 patients) with unidirectional posterior shoulder instability were treated with an arthroscopic posterior bone block and capsular reconstruction. The mean follow up period was 26 months. The patients were examined pre- and postoperatively using the Constant-Murley score, the Rowe score, Walch-Duplay score and Western Ontario Shoulder index. RESULTS: At the follow up examination 21 shoulders were classified to be stable, while one patient reported a single redislocation and two further patients reported recurrent posterior subluxation or posterior apprehension. Thus, the recurrence rate was defined to be 12.5%. The Rowe-Score significantly improved from 50 points preoperatively to 75 points postoperatively (p = 0.0003). The WOSI-score significantly improved from 37% preoperatively to 66% postoperatively (p = 0.0001). Revision surgery commonly was required for screw removal. CONCLUSION: The early clinical results of this arthroscopic bone block augmentation and capsular repair are promising. LEVEL OF EVIDENCE: IV.

The effect of rotator cuff malreduction on tendon tension: an evaluation of a custom-made digital tensiometer clamp.

INTRODUCTION: Rotator cuff tears are common and good-to-excellent clinical outcome is reported after subsequent repair. However, the retear rate of rotator cuff repairs has been shown to be as high as 20%. The reasons for retear seem to be multifactorial, mainly comprised by mechanical and biological aspects. Regarding mechanical causes, the role of the tendon tension and malreduction is so far unknown. First, we hypothesized that the tendon tension depends on the technique of tendon reposition and that malreduction of the tendon results in an increased tendon tension. Second, we aimed to demonstrate the inter- and intraobserver reliability of a novel custom-made digital tensiometer clamp. MATERIALS AND METHODS: A tendon defect of posterosuperior rotator cuff (reverse L-shaped) was simulated in seven cadaveric human shoulder specimens. By use of a custom-made tensiometer clamp, the supraspinatus tendon was reduced by pulling it in (1) an anterolateral direction (anatomical reduction) and (2) in a straight lateral direction (malreduction) until the footprint was completely covered. The reduction procedure was consecutively repeated to evaluate the inter- and intraobserver reliability. RESULTS: The mean traction forces for anatomical reduction and malreduction were 16.02 N (SD 8.06) and 19.52 N (SD 9.95), respectively. The difference between the two groups was statistically significant (p = 0.028). The interobserver reliability showed a correlation of r = 0.757 [95% confidence interval (CI) 0.092-0.955]. The intraobserver reliability of the three surgeons was observed to be between r = 0.905 and 0.986. CONCLUSIONS: The malreduction of the rotator cuff has a significant influence on the tendon tension and may therefore affect the healing rate of the tendon after the repair, so that a tension-balanced repair could improve the clinical results. Furthermore, the application of a novel custom-made tensiometer clamp showed good interobserver and excellent intraobserver reliabilities.

[Options in joint-preserving surgical treatment of osteoarthritis]. / Optionen der gelenkerhaltenden operativen Omarthrosetherapie.

BACKGROUND: The treatment of glenohumeral arthritis represents a major challenge in highly active younger patients. In these patients, an endoprosthetic treatment often achieves only unsatisfactory results with a limited lifetime of the implant. OBJECTIVES: The aim of the study was to identify joint-preserving therapies for glenohumeral arthritis. MATERIALS AND METHODS: For this study, an extensive and selective literature search was performed. RESULTS: There are several options available for joint-preserving treatment of glenohumeral arthritis. In addition to arthroscopic debridement with treatment of concomitant pathologies, CAM procedures (CAM: comprehensive arthroscopic management) according to Millett, as well as the interposition of allografts are other options. For all therapy options, an improved range of motion and pain reduction is described. A joint gap of <2 mm, bipolar cartilage lesions and age are described as risk factors for failure of the therapies. DISCUSSION: Short and mid-term results have been described for arthroscopic debridement, but there are no long-term and high-quality studies to enable us to make clear recommendations. The CAM procedure and the interposition of an allograft are demanding procedures that should be reserved for experienced arthroscopists. The therapies are an option for younger patients in accordance with individual decisions and realistic expectations.

Anterior stability of the reverse shoulder arthroplasty depending on implant configuration and rotator cuff condition.

INTRODUCTION: The aim of this study was to investigate the stabilizing influence of the rotator cuff as well as the importance of glenosphere and onlay configuration on the anterior stability of the reverse total shoulder replacement (RTSR). MATERIALS AND METHODS: A reverse total shoulder replacement was implanted into eight human cadaveric shoulders, and biomechanical testing was performed under three conditions: after implantation of the RTSR, after additional dissection of the subscapularis tendon, and after additional dissection of the infraspinatus and teres minor tendon. Testing was performed in 30° of abduction and three rotational positions: 30° internal rotation, neutral rotation, and 30° external rotation. Furthermore, the 38-mm and 42-mm glenospheres were tested in combination with a standard and a high-mobility humeral onlay. A gradually increased force was applied to the glenohumeral joint in anterior direction until the RTSR dislocated. RESULTS: The 42-mm glenosphere showed superior stability compared with the 38-mm glenosphere. The standard humeral onlay required significantly higher anterior dislocation forces than the more shallow high-mobility onlay. External rotation was the most stable position. Furthermore, isolated detachment of the subscapularis and combined dissection of the infraspinatus, teres minor, and subscapularis tendon increased anterior instability. CONCLUSIONS: This study showed superior stability with the 42-mm glenosphere and the more conforming standard onlay. External rotation was the most stable position. Detachment of the subscapularis as well as dissection of the complete rotator cuff decreased anterior stability.

Neuromuscular Electrical Stimulation-Enhanced Physical Therapist Intervention for Functional Posterior Shoulder Instability (Type B1): A Multicenter Randomized Controlled Trial.

OBJECTIVE: Functional posterior shoulder instability (FPSI) (type B1) is a severe type of instability, mainly in teenagers and young adults, that leads to loss of function, pain, and stigmatization among peers. An experimental nonsurgical treatment protocol based on neuromuscular electrical stimulation (NMES) showed very promising early results in the treatment of FPSI. The hypothesis of this study was that NMES-enhanced physical therapy leads to better outcomes than physical therapy alone as the current gold standard of treatment in patients with FPSI. METHODS: In this multicenter randomized controlled trial, patients with FPSI were randomly allocated in a 1:1 ratio to either 6 weeks of physical therapy or 6 weeks of physical therapy with simultaneous motion-triggered NMES. Baseline scores as well as outcome scores at 6 weeks, 3 months, 6 months, and 12 months after the intervention were obtained. The predefined primary outcome of this trial was the Western Ontario Shoulder Instability Index (WOSI) at the 3-month time point. RESULTS: Forty-nine patients were randomized and eligible for the trial. The group that received physical therapy with simultaneous motion-triggered NMES showed a significantly better main outcome measurement in terms of the 3-month WOSI score (64% [SD = 16%] vs 51% [SD = 24%]). Two-thirds of the patients from the physical therapist group crossed over to the group that received physical therapy with simultaneous motion-triggered NMES due to dissatisfaction after the 3-month follow-up and showed a significant increase in their WOSI score from 49% [SD = 8%] to 67% [SD = 24%]. The frequency of instability episodes showed a significant improvement in the group that received physical therapy with simultaneous motion-triggered NMES at the 3-month follow-up and beyond, while in the physical therapist group, no significant difference was observed. CONCLUSION: The current study shows that NMES-enhanced physical therapy led to statistically significant and clinically relevant improvement in outcomes in the treatment of FPSI compared to conventional physical therapy alone-from which even patients with prior unsatisfactory results after conventional physical therapy can benefit. IMPACT: Based on the results of this study, NMES-enhanced physical therapy is an effective new treatment option for FPSI, a severe type of shoulder instability. NMES-enhanced physical therapy should be preferred over conventional physical therapy for the treatment of patients with FPSI.

Results of arthroscopic partial repair of large retracted rotator cuff tears.

PURPOSE: To evaluate the midterm results of partial rotator cuff repair using the Constant score and the acromiohumeral radiographic measurement. METHODS: Thirty-eight patients with a mean age of 65 years and a large retracted rotator cuff tear (at least 2 tendons) were included in the study. Patients underwent clinical examination, standard radiography, and isometric strength testing at a mean follow-up of 47 months. The rotator cuff tears were classified as posterosuperior, anterosuperior, or global tears (≥3 tendons), and an arthroscopic partial repair was performed. RESULTS: The mean Constant score significantly increased from 56 points before surgery to 71 points after surgery (P = .041); the mean age- and sex-adjusted Constant score significantly improved from 63% to 90% at a mean follow-up of 47 months after arthroscopic partial rotator cuff repair (P = .003); and the subcategories pain and activity significantly improved (P = .001, P = .014, respectively). The active range of motion improved from 133° of flexion and 111° of abduction before surgery to 163° of forward flexion and 156° of abduction after surgery (P < .001). However, the active range of external rotation decreased from 44° before surgery to 36° after surgery. Further, there was a trend toward a decrease in the mean acromiohumeral distance from 7.0 mm before surgery to 5.6 mm after surgery. The abduction strength did not significantly improve after surgery (4.2 kg before surgery and 4.8 kg after surgery; P = .116). CONCLUSIONS: An arthroscopic partial repair of the rotator cuff is an effective tool to improve the Constant score by restoring active forward flexion and abduction and through pain relief. Further, we found that a pathologically decreased acromiohumeral distance cannot be reversed by a partial rotator cuff repair. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Biomechanical comparison of open and arthroscopic Latarjet procedures.

PURPOSE: To biomechanically compare the effectiveness of the standard open and arthroscopic techniques of the Latarjet procedure to address a critical anterior glenoid defect in combination with a capsular insufficiency. METHODS: Translation testing of 12 human cadaveric shoulder specimens was performed in a robot-assisted setup under 3 different conditions: (1) intact/vented shoulder joint, (2) combined anterior glenoid bone and capsular defect, and (3) open and arthroscopic Latarjet procedures. Testing was performed for each condition in 2 test positions: 60° of glenohumeral abduction with neutral rotation (ABD position) and 60° of abduction and external rotation (ABER position). Each position was tested with a passive humerus load of 30 N in the anterior, inferior, and anteroinferior directions. Translational movement of the humeral head was evaluated with and without the application of a 10-N load to the conjoint tendon (CJT). RESULTS: In the ABD position, translations after the open Latarjet procedure significantly differed from the arthroscopic technique in the anterior and anteroinferior directions when testing was performed with loading of the CJTs (CJT loading). Without CJT loading, the open Latarjet technique showed significantly lower translations in the anterior, inferior (P = .004), and anteroinferior (P = .001) testing directions in the ABD position. In the ABER position, the arthroscopic procedure showed no significant difference compared with the standard open procedure. CONCLUSIONS: We found a superior stabilization effect of the open Latarjet technique in the ABD position. The difference is ascribed to the anterior capsular repair, which was performed within the open technique and omitted during the arthroscopic procedure. CLINICAL RELEVANCE: The reduction of translation in a pure abduction position of the arm is more effectively performed with a conventional open Latarjet technique that includes a capsular repair. In combined ABER position, there was no difference found between the open and arthroscopic Latarjet techniques.

Short and midterm results of reverse shoulder arthroplasty according to the preoperative etiology.

BACKGROUND: Reverse shoulder arthroplasty (RSA) has shown promising results for cuff tear arthropathy but the indication has been extended to fracture sequelae and revision shoulder arthroplasty with different preconditions. Further, the clinical relevance of inferior scapular notching for different etiologies is uncertain. Our hypothesis was that preoperative etiology as well as the occurrence of scapular notching would significantly influence the clinical outcome. METHODS: We reviewed 76 reverse shoulder arthroplasties for cuff tear arthropathy (45 patients), fracture sequelae (10 patients) and revision arthroplasty (21 patients) retrospectively. The follow-up consisted of 71 patients and the mean follow-up period was 23 months (±14 months). All patients were evaluated postoperatively using the Constant score adjusted for age and gender and the simple shoulder test. A radiological investigation was performed preoperatively and at the time of the final follow-up including the evaluation of scapular notching according to Sirveaux. For further evaluation of scapular notching, patients were separated into three groups according to the inferior glenosphere overlap: negative or no inferior overlap -6-0 mm), mild overlap (1-4 mm) and pronounced overlap (5-9 mm). RESULTS: After a mean follow-up of 23 months the average age- and gender-adjusted Constant score (CS) was 77.8 % (±26 %). According to the etiology, patients with cuff tear arthropathy (CTA) showed a higher CS of 83 % compared with patients with fracture sequelae (CS 73 %) and compared with patients who had undergone RSA as a revision for failed shoulder arthroplasty (CS 69 %). The difference was significant comparing the cuff tear arthropathy patients with the revision surgery patients (p = 0.035). Within the group of fracture sequelae, patients with type three sequelae according to the Boileau classification (surgical neck nonunion) had a significantly worse outcome compared with the type four fracture sequelae patients (severe tuberosity dislocation) (CS 57 vs. 87 %, p = 0.01). The overall complication rate was 27 % with 8 % infections and 9 % dislocations. Revision surgery was necessary in 11.5 % with removal or replacement of the implants in 8 %. Inferior scapular notching was detected in 43 % of the patients. These patients had an inferior CS (70 ± 18 %) compared with patients without scapular notching (84 ± 25 %, p = 0.015). The incidence of scapular notching was significantly reduced with an increasing inferior overlap of the glenosphere. CONCLUSIONS: In conclusion, we found the preoperative etiology to influence the clinical results after RSA with superior results given for cuff tear arthropathy and inferior results for revision arthroplasty and fracture sequelae type three. Further, we found a correlation between scapular notching and the clinical outcome. The inferior scapular notching was significantly reduced by an increased inferior glenosphere overlap. LEVEL OF EVIDENCE: Level IV, case series, treatment study.

Humeral surface replacement for osteoarthritis.

BACKGROUND AND PURPOSE: Humeral resurfacing has shown promising results for osteoarthritis, but revisions for glenoid erosion have been reported frequently. We investigated the hypothesis that preoperative glenoid wear and postoperative progress of glenoid erosion would influence the clinical outcome. METHODS: We reviewed 61 resurfacing hemiarthroplasties (55 patients) for primary osteoarthritis. 6 patients were lost to follow-up and 5 had undergone revision arthroplasty. This left 50 shoulders in 44 patients (mean age 66 years) that were followed for mean 30 (12-44) months. Complications, revisions, and the age- and sex-related Constant score were assessed. Radiographs were evaluated for loosening and glenoid erosion according to Walch. RESULTS: Of the 50 shoulders that were functionally assessed, the average age- and sex-related Constant score was 73%. In patients with preoperative type-B2 glenoids, at 49% it was lower than in type-A1 glenoids (81%, p = 0.03) and in type-B1 glenoids (84%, p = 0.02). The average age- and sex-related Constant score for patients with type-A2 glenoids (60%) was lower than for type-A1 and -B1 glenoids and higher than for type-B2 glenoids, but the differences were not statistically significant. In the total population of 61 shoulders, the radiographs showed postoperative glenoid erosion in 38 cases and no humeral prosthetic loosening. Revision arthroplasty was performed in 11 cases after 28 (7-69) months. The implant size had no statistically significant influence on the functional outcome. The size was considered to be adequate in 28 of the 50 functionally assessed shoulders. In 21 cases, the implant size was too large and in 1 case it was too small. INTERPRETATION: We found frequent postoperative glenoid erosion and a high rate of revision arthroplasty after humeral resurfacing for primary osteoarthritis. Oversizing of the implants was common, but it had no statistically significant influence on the functional outcome. Inferior results were found in the presence of increased eccentric preoperative glenoid wear. Total shoulder arthroplasty should be considered in these patients.

The influence of superior labrum anterior to posterior (SLAP) repair on restoring baseline glenohumeral translation and increased biceps loading after simulated SLAP tear and the effectiveness of SLAP repair after long head of biceps tenotomy.

HYPOTHESIS: Biomechanical studies have shown increased glenohumeral translation and loading of the long head biceps (LHB) tendon after superior labrum anterior to posterior (SLAP) tears. This may explain some of the typical clinical findings, including the prevalence of humeral chondral lesions, after SLAP lesions. The first hypothesis was that SLAP repair could restore the original glenohumeral translation and reduce the increased LHB load after SLAP lesions. The second hypothesis was that SLAP repair after LHB tenotomy could significantly reduce the increased glenohumeral translation. MATERIALS AND METHODS: Biomechanical testing was performed on 21 fresh frozen human cadaveric shoulders with an intact shoulder girdle using a sensor-guided industrial robot to apply 20 N of compression in the joint and 50 N translational force at 0°, 30°, and 60° of abduction. LHB loading was measured by a load-cell with 5 N and 25 N preload. Type IIC SLAP lesions were created arthroscopically, and a standardized SLAP repair was done combined with or without LHB tenotomy. RESULTS: No significant difference of glenohumeral translation and increased LHB load in SLAP repair compared with the intact shoulder was observed under 5 N and 25 LHB preload, except for anterior translation under 25 N LHB preload. After LHB tenotomy after SLAP lesions, no significant difference of translation was observed with or without SLAP repair. CONCLUSIONS: SLAP repair without associated LHB tenotomy helps normalize glenohumeral translation and LHB loading. The stabilizing effect of the SLAP complex is dependent on the LHB. After biceps tenotomy, SLAP repair does not affect glenohumeral translation.

Suprapectoral or subpectoral position for biceps tenodesis: biomechanical comparison of four different techniques in both positions.

HYPOTHESIS: The aim of this study was to compare different techniques for tenodesis of the long head of biceps tendon (LHB) in the suprapectoral and subpectoral position to test the hypothesis that using shorter screws at the subpectoral position would achieve a similar primary ultimate failure load (UFL) as the longer screws at the suprapectoral position, that both types of tenodesis screws achieve comparable UFL, and that knotless suture anchor techniques can be performed at the subpectoral position in cortical bone and reach a UFL similar to tenodesis screws. METHODS: On 42 fresh frozen human cadavers divided into 6 groups, 4 different techniques for LHB tenodesis were performed localized 10 mm and 50 mm, respectively, distal to the entrance of the bicipital groove. Two techniques with tenodesis screws (Bio-Tenodesis screw, Biceptor) and 2 with knotless suture anchors (Bio-SwiveLock, Footprint PK) were tested. Under a 10-N preload, an axial cyclic load with 100 cycles, 1-Hz frequency, and 50-N maximal load was applied. UFL was evaluated with an axial traction of 0.2 mm/s until decrease of tension. LHB dislocation was measured by 3-dimensional photogrammetry. RESULTS: All techniques except the subpectoral Bio-SwiveLock had a dislocation <3 mm after cyclic loading. The highest mean UFL was measured for the suprapectoral Bio-Tenodesis screw (218.3 ± 59.7 N) and the lowest with the subpectoral Footprint PK (99.1 ± 16.4 N). The UFL of suture anchors were significantly lower than those of interference screws (P < .01). UFL was not significantly different for type of interference screw, the type of suture anchor, or tenodesis localization. Different failure mechanisms were evaluated for suture anchors and interference screws. CONCLUSION: Due to the biomechanical testings interference screws are appropriate devices for suprapectoral and subpectoral biceps tenodesis resisting cyclic loading and attaining a satisfactory, whereas the knotless suture anchors sustained a significant about 50% lower UFL, and can only be recommended conditionally for LHB tenodesis regarding primary stability.

Results of Arthroscopic Revision Rotator Cuff Repair for Failed Open or Arthroscopic Repair: A Prospective Multicenter Study on 100 Cases.

BACKGROUND: Retears after rotator cuff repair (RCR) have been associated with poor clinical results. Meaningful data regarding the role of arthroscopic revision RCR are sparse thus far. PURPOSE/HYPOTHESIS: To investigate results after arthroscopic revision RCR. We hypothesized that (1) arthroscopic revision RCR would lead to improved outcomes, (2) the clinical results would be dependent on tendon integrity and (3) tear pattern, tendon involvement, and repair technique would influence clinical and structural results. STUDY DESIGN: Case series; Level of evidence 4. METHODS: During a 40-month period, 100 patients who underwent arthroscopic revision RCR were prospectively enrolled in this multicenter study. Outcomes were evaluated preoperatively, at 6 months (6M), and at 24 months (24M) using the Constant score (CS), the Oxford Shoulder Score (OSS), and the Subjective Shoulder Value (SSV). Tendon integrity at 2 years was analyzed using magnetic resonance imaging. A total of 13 patients (13%) were lost to follow-up, and 14 patients (14%) had a symptomatic retear before the 24M follow-up. RESULTS: All clinical scores improved significantly during the study period (CS: preoperative, 44 ± 16; 6M, 58 ± 22; 24M, 69 ± 19 points; OSS: preoperative, 27 ± 8; 6M, 36 ± 11; 24M, 40 ± 9 points; SSV: preoperative, 43% ± 18%; 6M, 66% ± 24%; 24M, 75% ± 22%) (P < .01). At 2 years, a retear rate of 51.8% (43/83) and a surgical revision rate of 12.6% (11/87) were observed. Mean full-thickness tear size decreased from 5.00 ± 1.61 cm2 to 3.25 ± 1.92 cm2 (P = .041). Although the Sugaya score improved from 4.5 ± 0.9 to 3.7 ± 1.4 (P = .043), tendon integrity did not correlate with better outcome scores. Previous open RCR, involvement of the subscapularis, chondral lesions of Outerbridge grade ≥2, and medial cuff failure were correlated with poorer SSV scores at 2 years (P≤ .047). Patients with traumatic retears had better CS and OSS scores at 2 years (P≤ .039). CONCLUSION: Although arthroscopic revision RCR improved shoulder function, retears were frequent but usually smaller. Patients with retears, however, did not necessarily have poorer shoulder function. Patient satisfaction at 2 years was lower when primary open RCR was performed, when a subscapularis tear or osteoarthritis was present, and when the rotator cuff retear was located at the musculotendinous junction. Patients with traumatic retears showed better functional improvement after revision.

The biomechanical effect of specific labral and capsular lesions on posterior shoulder instability.

PURPOSE: In contrast to anterior shoulder instability there seems to be no single key lesion in posterior shoulder instability. Therefore, the purpose of this study was to determine the biomechanical effect of specific posterior capsulolabral lesions. Our hypothesis was that a posterior capsule lesion will have a predominant effect compared to a labrum detachment (Bankart lesion). METHODS: Stability testing of 16 cadaveric human shoulders was performed. The specimens were distributed to two groups: the labrum lesion group and the capsular lesion group. In the labrum lesion group three different conditions were tested consecutively: posteroinferior Bankart lesion, additive pHAGL lesion, additive posterosuperior Bankart lesion. In the capsular lesion group two conditions were tested: posteroinferior capsule cut including a glenoidal transection of the pIGHL, additive rotator interval and superior capsule lesion (SGHL and CHL cut). All lesions were set arthroscopically. Biomechanical testing was performed in two positions: the sulcus-test position and the jerk-test position each with a passive humerus load of 50 N in the posterior, posteroinferior and inferior direction. RESULTS: A posteroinferior Bankart lesion resulted in a percentage increase of 86% posterior translation in the jerk position and an increase of 31% inferior translation in the sulcus position. An additional pHAGL lesion resulted in a significant increase of posterior and inferior translation given by 31 and 41% in the jerk position. Regarding the capsular lesions, a cut of the posteroinferior capsule and the pIGHL resulted in a significant increased inferior translation of 53% in the sulcus position but did not cause a significant increase of posterior translation in the jerk position. If an additional rotator interval lesion is set the inferior translation is again significantly increased. CONCLUSIONS: On the basis of our results traumatic posterior shoulder instability must be suspected to be bidirectional posteroinferior independently if a posterior capsule lesion or a posterior Bankart lesion is evident. CLINICAL RELEVANCE: Capsular and labral lesions both have a significant biomechanical effect but differ in the predominant direction of instability, which is posterior for the Bankart lesion and inferior for the capsular lesion. An additional pHAGL or rotator interval lesion aggravates the posteroinferior instability and must be respected in the surgical treatment strategy.

Stabilization of chronic proximal tibiofibular joint instability with a semitendinosus graft.

Although chronic proximal tibiofibular joint instability is a rare condition, it is associated with marked functional impairment. Various surgical options have been reported in literature, all associated with several problems and limitations. We describe a new technique of reconstruction of the proximal tibiofibular joint using the semitendinosus tendon. The key steps of the procedure are the preparation of a proximally released semitendinosus tendon, and its guidance through two transtibial tunnels and one transfibular tunnel. The semitendinosus tendon acts as a soft tissue sling and does not interfere with mobility at the proximal or distal tibiofibular joints as noted after fibular head resection or arthrodesis of the proximal tibiofibular joint. Further advantages are the easy accessibility of the semitendinosus graft and the small surgical scar with better cosmetic results as compared to ligamentous reconstructive procedures using a split biceps femoris tendon or a strip of the iliotibial band.

Possibilities and limitations of electrospun chitosan-coated polycaprolactone grafts for rotator cuff tear repair.

Acute and chronic rotator cuff tears remain challenging for therapy. A wide range of therapeutic approaches were developed but re-tears and postoperative complications occur regularly. Especially in elderly people, the natural regeneration processes are decelerated, and graft materials are often necessary to stabilize the tendon-to-bone attachment and to improve the healing process. We here investigated in a small animal model a newly developed electrospun polycaprolactone fiber implant coated with a chitosan-polycaprolactone graft copolymer and compared these implants biomechanically and histologically with either a commercially available porous polyurethane implant (Biomerix 3D Scaffold) or suture-fixed tendons. Fifty-one rats were divided into three groups of 17 animals each. In the first surgery, the left infraspinatus tendons of all rats were detached, and the animals recovered for 4 weeks. In the second surgery, the tendons were fixed with suture material only (suture-fixed group; n = 17), whereas in the two experimental groups, the tendons were fixed with suture material and the polyurethane implant (Biomerix scaffold group; n = 17) or the modified electrospun polycaprolactone fiber implant (CS-g-PCL scaffold group; n=17), respectively. The unaffected right infraspinatus tendons were used as native controls. After a recovery of 8 weeks, all animals were clinically inconspicuous. In 12 animals of each group, repaired entheses were biomechanically tested for force at failure, stiffness, and modulus of elasticity, and in five animals, repaired entheses were analyzed histologically. Biomechanically, all parameters did not differ statistically significant between both implant groups, and the entheses failed typically at the surgical site. However, with respect to the force at failure, the median values of the two implant groups were smaller than the median value of the suture-fixed group. Histologically, the modified polycaprolactone fiber implant showed no acute inflammation processes, a good infiltration with cells, ingrowth of blood vessels and tendinous tissue, and a normal fibrous ensheathment. Further improvement of the implant material could be achieved by additional implementation of drug delivery systems. Therewith, the used CS-g-PCL fiber mat is a promising basic material to reach the goal of a clinically usable graft for rotator cuff tear repair.

Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.

The purpose of the study was to compare a single-row repair and a double-row repair technique for the specific characteristics of a complete subscapularis lesion. Ten pairs of human cadaveric shoulder human shoulder specimens were tested for stiffness and ultimate tensile strength of the intact tendons in a load to failure protocol. After a complete subscapularis tear was provoked, the specimens were assigned to two treatment groups: single-row repair (1) and a double-row repair using a "suture bridge" technique (2). After repair cyclic loading a subsequent load to failure protocol was performed to determine the ultimate tensile load, the stiffness and the elongation behaviour of the reconstructions. The intact subscapularis tendons had a mean stiffness of 115 N/mm and a mean ultimate load of 720 N. The predominant failure mode of the intact tendons was a tear at the humeral insertion site (65%). The double-row technique restored 48% of the ultimate load of the intact tendons (332 N), while the single-row technique revealed a significantly lower ultimate load of 244 N (P = 0.001). In terms of the stiffness, the double-row technique showed a mean stiffness of 81 N/mm which is significantly higher compared to the stiffness of the single-row repairs of 55 N/mm (P = 0.001). The double-row technique has been shown to be stronger and stiffer when compared to a conventional single-row repair. Therefore, this technique is recommended from a biomechanical point of view irrespectively if performed by an open or arthroscopic approach.

Coracoclavicular ligament reconstruction: biomechanical comparison of tendon graft repairs to a synthetic double bundle augmentation.

For currently presented anatomical coracoclavicular ligament repairs issues such as autologous tendon graft versus synthetic suture augmentation and the optimum fixation strategies for both types of reconstruction are not solved. The purpose of the study was to compare the biomechanical properties of different tendon graft repairs to the characteristics of a synthetic polyester augmentation. Four anatomical coracoclavicular ligament repairs were biomechanically tested: 5 mm coracoclavicular tendon loop with suture fixation, tendon loop with flip button fixation, tendon loop with interference screw fixation versus a double 1.0-mm polyester repair with flip button fixation. The biomechanical testing included cyclic superio-inferior loading and a subsequent load to failure protocol. The ultimate failure loads were significantly higher for the double polyester/flip button repair (927 N) compared to all tendon repair techniques (maximum 640 N). In contrast the stiffness level was higher for the tendon repairs compared to the polyester/flip button repair (68.7 N/mm) but strongly dependent on the fixation technique (interference screw 97.2 N/mm, flip button 84.9 N/mm, side to side suture 60.9 N/mm). A synthetic coracoclavicular augmentation using a polyester suture provides adequate structural properties compared to a tendon repair. Therefore the decision for a tendon graft should be made by the necessity of a biologic substrate rather than by the assumption of a biomechanical advantage.

In vivo analysis of vascularization and biocompatibility of electrospun polycaprolactone fibre mats in the rat femur chamber.

In orthopaedic medicine, connective tissues are often affected by traumatic or degenerative injuries, and surgical intervention is required. Rotator cuff tears are a common cause of shoulder pain and disability among adults. The development of graft materials for bridging the gap between tendon and bone after chronic rotator cuff tears is essentially required. The limiting factor for the clinical success of a tissue engineering construct is a fast and complete vascularization of the construct. Otherwise, immigrating cells are not able to survive for a longer period of time, resulting in the failure of the graft material. The femur chamber allows the observation of microhaemodynamic parameters inside implants located in close vicinity to the femur in repeated measurements in vivo. We compared a porous polymer patch (a commercially available porous polyurethane-based scaffold from Biomerix™) with electrospun polycaprolactone (PCL) fibre mats and chitosan (CS)-graft-PCL modified electrospun PCL (CS-g-PCL) fibre mats in vivo. By means of intravital fluorescence microscopy, microhaemodynamic parameters were analysed repetitively over 20 days at intervals of 3 to 4 days. CS-g-PCL modified fibre mats showed a significantly increased vascularization at Day 10 compared with Day 6 and at Day 14 compared with the porous polymer patch and the unmodified PCL fibre mats at the same day. These results could be verified by histology. In conclusion, a clear improvement in terms of vascularization and biocompatibility is achieved by graft-copolymer modification compared with the unmodified material.