Tomas Smith

Dynamic versus static reconstruction of the medial patellofemoral ligament for recurrent lateral patellar dislocation

PurposeTo compare clinical and radiological outcomes of static and dynamic medial patellofemoral ligament (MPFL) reconstruction techniques.MethodsIn a retrospective, matched-paired, cohort analysis, 30 patients surgically treated for recurrent lateral patellar dislocation were divided into two groups of 15 patients matched for inclusion and exclusion criteria. The static technique group underwent rigid fixation of the gracilis tendon at the anatomic femoral MPFL insertion and the superomedial border of the patella; the dynamic technique group underwent detachment of the gracilis tendon at the pes anserinus with fixation to the proximal medial patellar margin via tunnel transfer obliquely through the patella. Kujala, Lysholm, and Tegner scores; pain level; and pre- and postoperative radiographic changes of patellar height, patellar tilt, and bisect offset were compared.ResultsNo significant between-group differences were found in mean Kujala, Tegner, Lysholm, or visual analogue scale scores or radiographic parameters. One case of resubluxation was observed in the dynamic group. All but one patient in each group would have been willing to undergo the procedure again.ConclusionsBoth techniques provided satisfactory short-term outcomes.Level of evidenceIII.

Arthroscopic posterior shoulder stabilization with an iliac bone graft and capsular repair: a novel technique.

Several surgical approaches have been described for the treatment of recurrent posterior shoulder instability. Many authors have performed posterior bone block procedures with good results not only in the presence of glenoid bone loss or dysplasia but also in the case of capsular hyperlaxity and poor soft-tissue quality. Open techniques often require an extensive approach with the disadvantage of a poor cosmetic result and possible insufficiency of the deltoid muscle. Furthermore, the treatment of concomitant pathologies and the correct placement of the bone graft are difficult. Therefore we describe an all-arthroscopic posterior shoulder stabilization technique with an iliac bone graft and capsular repair that is intended to improve the pre-existing open procedure. The key steps of the operation are the precise placement and screw fixation of the bone block at the posterior glenoid under arthroscopic control and the subsequent posterior capsular refixation and plication using 2 suture anchors to create an extra-articular graft position.

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.

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

IntroductionThe 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 methodsA 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.ResultsThe 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.ConclusionsThis 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.

Biomechanical evaluation of inferior scapula notching of reverse shoulder arthroplasty depending on implant configuration and scapula neck anatomy.

Purpose: The presence of inferior scapula notching is significantly affected by the anatomy the scapula and can be influenced by the glenosphere design and position and the onlay type. Materials and Methods: A biomechanical study was undertaken with 13 human shoulder specimens in a robot-assisted shoulder simulator. Inferior scapula contact during adduction of the humerus was detected using a contact pressure film. Computed tomography scans with three-dimensional reconstructions of each specimen were performed. Results: The greatest improvement of the scapula notching angle (SNA) was achieved by simultaneous implantation of a shallow humeral onlay and an eccentric glenosphere design: 16.3-19.0° (P < 0.005). The SNA was significantly decreased by 5.8° when shifting from a 38 mm centric glenosphere to a 42 mm centric glenosphere (P < 0.005) and by 8.9° comparing the 38 mm centric glenosphere with 38 mm eccentric glenosphere (P < 0.005). The solitary implantation of a shallow onlay significantly decreased the SNA depending on the glenosphere size between 7.4° and 8.0° (P = 0.001). A more inferior position of the metaglene as well as a long scapula neck (P = 0.029) and a large lateral scapula pillar angle (P = 0.033) were correlated with a lower SNA. Conclusion: This study demonstrates the importance of inferior glenosphere placement and the benefit of eccentric glenosphere and shallow humeral cup design to reduce the adduction deficit of the reverse shoulder. The presence of a short neck of the scapula can have a negative prognostic effect on inferior impingement during adduction of the arm. Level of Evidence: Basic Science Study

Total Versus Hemiarthroplasty for Glenohumeral Arthritis According to Preoperative Glenoid Erosion.

Clinical studies on primary osteoarthritis have shown better results of total shoulder arthroplasty (TSA) compared to hemiarthroplasty (HA) regarding the function, revision rate and postoperative pain relief. However, a clear recommendation for implantation of TSA or HA, depending on the glenoid type of erosion, does not exist. The aim of the study was to compare the results of TSA and HA with respect to the preoperative glenoid type. In this study, 41 patients were examined retrospectively; among them, 25 patients were treated with stemmed anatomic TSA and 16 with stemmed anatomic HA. The degree of osteoarthritis was determined according to Samilson and the glenoid erosion was classified according to Walch. The clinical outcome of the patients was determined by using the Constant Score (CS) and the Simple Shoulder Test at final follow-up. Patients after TSA demonstrated a significantly improved internal rotation compared to HA patients. Patients with preoperative B1 glenoid showed better pain relief after TSA compared to HA. For patients with preoperative type A2 glenoid a significantly higher CS was found after TSA compared to HA. We were able to show good short-term results after TSA and HA. Our findings suggest a better internal rotation for TSA compared to HA, superior clinical outcome for patients with preoperative A2 glenoid and lower pain level for patients with a preoperative B1 glenoid. However, these results need to be confirmed by further studies.

The effects of a dynamic patellar realignment brace on disease determinants for patellofemoral instability in the upright weight-bearing condition.

BackgroundPatellar stabilizing braces are used to alleviate pain and prevent subluxation/dislocation by having biomechanical effects in terms of improved patellar tracking. The purpose of this study is to analyze the effects of the dynamic patellar realignment brace, Patella Pro (Otto Bock GmbH, Duderstadt, Germany), on disease determinants in subjects with patellofemoral instability using upright weight-bearing magnetic resonance imaging (MRI).MethodsTwenty subjects (8 males and 12 females) with lateral patellofemoral instability were studied in an open-configuration magnetic resonance imaging scanner in an upright weight-bearing position at full extension (0° flexion) and 15° and 30° flexion with and without the realignment brace. Disease determinants were defined by common patellofemoral indices that included the Insall–Salvati Index, Caton–Deschamps Index, and the Patellotrochlear Index to determine patella height and patella tilt angle, bisect offset, and tuberositas tibiae–trochlear groove (TT–TG) distance to determine patellar rotation and translation with respect to the femur and the alignment of the extensor mechanism.ResultsAnalyses of variance revealed a significant effect of the brace with reduction of the three patellar height ratios, patella tilt angle, and bisect offset as well as TT–TG distance. Post hoc pairwise comparisons of the corresponding conditions with and without the realignment brace revealed significantly reduced patella height ratios, patella tilt angles, and bisect offsets at full extension and 15° and 30° flexion. No significant differences between the TT–TG distances at full extension but significant reductions at 15° and 30° flexion were observed when using the realignment brace compared to no brace.ConclusionsThis study suggests that the dynamic patellar realignment brace is capable of improving disease determinants in the upright weight-bearing condition in the range of 0° to 30° flexion in patients with patellofemoral instability.

Transfer of the long head of biceps to the conjoint tendon. A biomechanical study

BACKGROUND Tenodesis of the long head of biceps has been intensively investigated and various surgical options exist. The aim of this biomechanical study was to compare the maximum strength of two different techniques for biceps tenodesis. Our hypothesis was that the two procedures have the same biomechanical properties. METHODS We performed the two different tenodesis techniques using 12 fresh frozen shoulders divided into two groups of six. In the first group, the biceps was transferred to the conjoint tendon. In the second group, an intraossous suprapectoral tenodesis was performed. After a preload of 10 N, cyclical loading with a maximum of 60 N and 100 N with 100 cycles and 0.5 Hz was applied to the tendons for both groups. An axial ultimate loading to failure was conducted subsequently. RESULTS No significant differences were found in age, bone mineral density, or weight between the two groups. During the cyclical loading with 60 N, one slippage of the tendon was observed in the suprapectoral group. The mean ultimate load to failure was 294.15N in the transposition group and 186.76 N in the suprapectoral group, but this difference was not significant (P=0.18). INTERPRETATION The biomechanical results demonstrated equal biomechanical properties postoperatively for both transposition of the tendon and the current standard suprapectoral tenodesis procedure. The transposition can be performed as a primary or a salvage procedure in order to potentially reduce the proportion of patients with persistent postoperative bicipital groove pain and is comparable in strength to a standard tenodesis.

Adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon anterior cruciate ligament reconstruction – A biomechanical in vitro study

Background: This biomechanical cadaveric in vitro study aimed to evaluate and compare the dynamic elongation behavior and ultimate failure strength of tibial adjustable‐length loop cortical button versus interference screw fixation in quadriceps tendon‐based anterior cruciate ligament reconstruction. Methods: Sixteen human quadriceps tendons were harvested and fixed into porcine tibiae using either biodegradable interference screw (n = 8) or adjustable loop device (n = 8) fixation. An acrylic block was utilized for femoral adjustable loop device fixation for both groups. All constructs were precycled for 10 times at 0.5 Hz and manually retensioned before tested in position and force control mode each for 1000 cycles at 0.75 Hz according to in vitro loading conditions replicating the in vivo ACL environment. Subsequently, an ultimate failure test at 50 mm/min was performed with mode of failure noted. Findings: Tibial IS fixation showed no statistically significant differences in the initial (−0.46 vs. −0.47 mm; P = 0.9780), dynamic (2.18 mm vs. 2.89 mm; P = 0,0661), and total elongation (1.72 mm vs. 2.42 mm; P = 0,0997) compared to adjustable loop device fixation. The tibial button fixation revealed an increased ultimate failure load (743.3 N vs. 606.3 N; P = 0.0027), while stiffness was decreased in comparison to screw fixation (133.2 N/mm vs. 153.5 N/mm; P = 0,0045). Interpretation: Anterior cruciate ligament reconstruction for quadriceps tendon graft using a tibial adjustable‐length loop cortical button provides for comparable dynamic stabilization of the knee with increased ultimate failure load at decreased stiffness compared to screw fixation. HighlightsTibial cortical button shows advantages in ultimate failure load.Biodegradable interference screw fixation provides greater stiffness.No significant difference in elongation behavior between button and screw fixation

Implant impingement during internal rotation after reverse shoulder arthroplasty. The effect of implant configuration and scapula anatomy: A biomechanical study

BACKGROUND Internal rotation after reverse shoulder arthroplasty is essential to perform fundamental daily living activities. The purpose of this study was to examine the impact of anatomical and implant related factors on impingement-free internal rotation of the glenohumeral joint. METHODS CT-scans of 13 human shoulder specimens with implanted reverse shoulder prostheses were carried out and scapula neck length, lateral pillar angle, and implantation height of the metaglene were measured. Internal rotation testing of all specimens was performed by the use of a robot assisted shoulder simulator. Biomechanical variables were analyzed using a three-way ANOVA. Spearmans rank correlations were performed to determine the relationship between biomechanical and anatomical data. FINDINGS The maximum internal rotation angle for a 38 mm centric glenosphere and a standard onlay was 93.4(SD 34.9°). The change of the diameter of the glenosphere resulted in no significant increase of the maximum rotation angle (P=0.16), while change of the glenosphere type from concentric to eccentric (P=0.005) as well as the change of the onlay type from standard to a more shallow one (P=0.002) both had a significant effect on the internal rotation. The distance between the inferior rim of the metaglene and the inferior aspect of the glenoid (P=0.21), scapula pillar angle (P=0.13) as well as the scapula neck length (P=0.81) showed no significant correlation with the maximum internal rotation angle. INTERPRETATION Implant component selection shows strong influence on the impingement-free internal rotation. The use of an eccentric glenosphere and a shallow humeral cup may improve internal rotation after reverse shoulder arthroplasty.