Determination of a Safe Zone for Ischial Screw Placement in Total Hip Arthroplasty

BACKGROUND

Implantation of acetabular components with supplemental screw fixation is commonly performed to improve osteointegration and long-term stability in total hip arthroplasty (THA). Placement of ischial screws improves stability in biomechanical studies, but can be technically challenging. The study aimed to provide a safe zone for ischial screw placement with reference to easily identifiable intra-operative landmarks.

METHODS

A retrospective review of patients was performed and 27 preoperative pelvis computed tomography scans were collected. After converting these images to 3-dimensional reconstructions of the pelvis, a safe zone for ischial screw placement was established with reference to the anterior superior iliac spine (ASIS) and the acetabular center and rim.

RESULTS

The safe zone of an ischial screw in the en face sagittal plane was a median of 17 degrees (interquartile range [IQR]: 11,23) anterior to 13 degrees (IQR: 10,18) posterior to the reference line from the ASIS through the center of the acetabulum. The safe zone in the coronal plane was 34 degrees (IQR: 18,68) medial to 13 degrees (IQR: 8,19) lateral from a start point 1 centimeter medial to the inferior acetabular rim with a screw length of 25 millimeters. An ischial screw optimized for length directed down the center of the ischium was qualitatively demonstrated to have a start point unobtainable intraoperatively, originating within the cotyloid fossa.

CONCLUSION

The ASIS, center of the acetabulum, and acetabular rim provide identifiable intraoperative landmarks for guiding ischial screw placement in hip arthroplasty.

Dual Bracing for Ulnar Collateral Ligament Injuries Restores Native Valgus Laxity and Native Medial Joint Gapping of the Elbow

Background

Despite growing evidence on the role of the posterior ulnar collateral ligament (pUCL) in elbow stability, current ligament bracing techniques are mainly focused on the anterior ulnar collateral ligament (aUCL). A dual-bracing technique combines the repair of the pUCL and aUCL with a suture augmentation of both bundles.

Purpose

To biomechanically assess a dual-bracing approach addressing aUCL and pUCL for humeral-sided complete UCL lesions to restore medial elbow laxity without overconstraining.

Study Design

Controlled laboratory study.

Methods

A total of 21 unpaired human elbows (11 right, 10 left; 57.19 ± 11.7 years) were randomized into 3 groups to compare dual bracing with aUCL suture augmentation and aUCL graft reconstruction. Laxity testing was performed with 25 N applied 12 cm distal to the elbow joint for 30 seconds at randomized flexion angles (0°, 30°, 60°, 90°, and 120°) for the native condition and then for each surgical technique. A calibrated motion capture system was used for assessment, allowing the 3-dimensional displacement during the complete valgus stress cycle between the optical trackers to be quantified as joint gap and laxity. The repaired constructs were then cyclically tested through a materials testing machine starting with 20 N for 200 cycles at a rate of 0.5 Hz. The load was increased stepwise by 10 N for 200 cycles until displacement reached 5.0 mm or complete failure occurred.

Results

Dual bracing and aUCL bracing resulted in significantly (P = .045) less joint gapping at 120° of flexion compared with aUCL reconstruction. No significant differences in valgus laxity were found among the surgical techniques. Within each technique, there were no significant differences between the native and the postoperative state in valgus laxity and joint gapping. No significant differences between the techniques were observed in cycles to failure and failure load.

Conclusion

Dual bracing restored native valgus joint laxity and medial joint gapping without overconstraining and provided similar primary stability regarding failure outcomes as established techniques. Furthermore, it was able to restore joint gapping in 120° of flexion significantly better than aUCL reconstruction.

Clinical Relevance

This study provides biomechanical data on the dual-bracing approach that may help surgeons to consider this new method of addressing acute humeral UCL lesions.

Clinical Outcomes After Arthroscopic Rotator Cuff Repair With a Fibrin Scaffold Containing Growth Factors and Autologous Progenitor Cells Derived from cBMA

Purpose

To report the clinical outcomes after biologically augmented rotator cuff repair (RCR) with a fibrin scaffold derived from autologous whole blood and supplemented with concentrated bone marrow aspirate (cBMA) harvested at the proximal humerus.

Methods

Patients who underwent arthroscopic RCR with biologic augmentation using a fibrin clot scaffold (“Mega- Clot”) containing progenitor cells and growth factors from proximal humerus BMA and autologous whole blood between April 2015 and January 2018 were prospectively followed. Only high-risk patients in primary and revision cases that possessed relevant comorbidities or physically demanding occupation were included. Minimum follow-up for inclusion was 1 year. The visual analog score for pain (VAS), American Shoulder and Elbow Surgeons (ASES), Simple Shoulder Test (SST), Single Assessment Numerical Evaluation (SANE), and Constant-Murley scores were collected preoperatively and at final follow-up. In vitro analyses of the cBMA and fibrin clot using nucleated cell count, colony forming units, and live/dead assays were used to quantify the substrates.

Results

Thirteen patients (56.9 ± 7.7 years) were included. The mean follow-up was 26.9 ± 17.7 months (n = 13). There were significant improvements in all outcome scores from the preoperative to the postoperative state: VAS (5.6 ± 2.5 to 3.1 ± 3.2; P < .001), ASES (42.0 ± 17.1 to 65.5 ± 30.6; P < .001), SST (3.2 ± 2.8 to 6.5 ± 4.7; P = .002), SANE (11.5 ± 15.6 to 50.3 ± 36.5; P < .001), and Constant-Murley (38.9 ± 17.5 to 58.1 ± 26.3; P < .001). Six patients (46%) had retears on postoperative MRI, despite all having improvements in pain and function except one. All failures were chronic rotator cuff tears, and all were revision cases except one (1.6 ± 0.5 previous RCRs). The representative sample of harvested cBMA showed an average of 28.5 ± 9.1 × 10⁶ nucleated cells per mL.

Conclusions

Arthroscopic rotator cuff repairs that are biologically augmented with a fibrin scaffold containing growth factors and autologous progenitor cells derived from autologous whole blood and humeral cBMA can improve clinical outcomes in primary, as well as revision cases in high-risk patients. However, the incidence of retears remains a concern in this population, demanding further improvements in biologic augmentation.

Level of Evidence

IV, therapeutic case series.

Semitendinosus vs Gracilis Grafts With 1- vs 2-Tunnel Techniques for Coracoclavicular Ligament Reconstruction: A Biomechanical Study

BACKGROUND

Despite the evolution of acromioclavicular joint surgery to a more anatomic coracoclavicular (CC) ligament reconstruction, no definitive guidance regarding the number and position of bone tunnels in the clavicle, as well as the ideal graft choice, is established.

PURPOSE/HYPOTHESIS

The purpose of this study was to biomechanically compare the reconstruction of the CC ligament complex between gracilis- and semitendinosus-tendon grafts in 1- and 2-tunnel techniques. It was hypothesized that the gracilis tendon graft will provide comparable primary stability in both tunnel techniques while utilizing a smaller tunnel diameter.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 24 cadaveric shoulders (13 men, 11 women; 66 ± 7.5 years) were randomly allocated to 4 repair groups: gracilis with 1 tunnel (GT-1), gracilis with 2 tunnels (GT-2), semitendinosus with 1 tunnel (ST-1), and semitendinosus with 2 tunnels (ST-2). First, specimens were tested for native anterior, posterior, and superior translations. Then, specimens were randomly assigned to 1 of the 4 CC reconstruction groups before undergoing the same testing, followed by cyclic loading and load to failure (LTF).

RESULTS

The GT-2 reconstruction demonstrated significantly less translation when compared with ST-2 in anterior (P = .024) and posterior (P = .048) directions. GT-1 and ST-2 both showed significantly less translation than ST-1 in anterior and superior directions (P < .001). All reconstructions demonstrated less superior translation compared with native testing, with GT-1 and ST-2 significantly less than ST-1 (P < .001). There were no significant differences for peak displacement and LTF between groups.

CONCLUSION

Gracilis tendon grafts using a 1- or 2-tunnel technique for CC ligament reconstruction provided comparable translation, displacement, and LTF as corresponding semitendinosus grafts. Therefore, the gracilis tendon should be considered as a biomechanical equivalent graft choice for the reconstruction of the CC ligament complex.

CLINICAL RELEVANCE

In a cadaveric model, the gracilis tendon demonstrated adequate fixation with minimal translation in CC ligament reconstruction while utilizing smaller diameter bone tunnels, which may help minimize the risk of complications such as loss of reduction and fracture.

Biologically Augmented Suture for Ligament Bracing Procedures Positively Affects Human Ligamentocytes and Osteoblasts In Vitro

PURPOSE

The purpose was to evaluate the response of human ligamentocytes and osteoblasts after biological augmentation with thrombin, concentrated bone marrow aspirate (cBMA), or platelet-rich plasma (PRP) on two different types of nonresorbable flat braided suture used for ligament bracing.

METHODS

Uncoated (U) and collagen-coated (C) flat braided suture material was augmented with either thrombin (T), cBMA (B), PRP (P), or a combination of these three (A), while platelet-poor plasma was used as a source for fibrin (F) in each assay. Previously cultured ligamentocytes and osteoblasts were added with a defined density and assayed after the required time period for adhesion, proliferation, and alkaline phosphatase activity.

RESULTS

Biological augmentation of uncoated [(UFT, UFBT, UFA; P < .001), (UFPT; P = .017)] and collagen-coated suture (CFT, CFPT, CFBT, CFA; P < .001) led to a significantly higher ligamentocyte adhesion. Significantly higher adhesion was also observed for osteoblasts (UFT, UFPT, UFBT, UFA; P < .001; CFT, CFPT, CFBT, CFA; P < .001). Similarly, ligamentocyte proliferation was significantly higher [(UFT, UFPT, UFA; P = .009), (UFBT; P = .001), (CFT; P = .009), (CFBT; P = .001), and (CFA; P = .01)]. Osteoblasts showed significantly higher proliferation as well [(UFT, UFPT, UFA; P = .002), (UFBT; P = .001); (CFT: P = .003), and (CFPT, CFBT, CFA; P = .001)]. Augmentation with thrombin, PRP, and BMA for uncoated (UFT; P = .006, UFPT; P = .035, UFBT; P = .001) and BMA for coated suture (CFBT; P = .027) led to significantly higher alkaline phosphatase activity.

CONCLUSION

Biological enhancement of suture used for ligament bracing significantly increased ligamentocyte and osteoblast adhesion and proliferation, as well as alkaline phosphatase activity of osteoblasts in an in vitro model. After biological augmentation, cellular adhesion, proliferation, and alkaline phosphatase activity changed up to 1,077%, 190%, and 78%, respectively. Furthermore, no overall superiority between uncoated or collagen-coated suture material was observed for cellular adhesion, proliferation, or alkaline phosphatase activity.

CLINICAL RELEVANCE

This study provides in vitro data on a new treatment concept of biologic augmentation for acute ligamentous lesions treated with ligament bracing that has not been widely described. This concept may improve the healing of injured ligaments, in addition to providing immediate biomechanical stabilization.

Clinical and Radiological Outcomes in Reverse Total Shoulder Arthroplasty by Inclination Angle With a Modular Prosthesis

The influence of the humeral inclination in reverse total shoulder arthroplasty (RTSA) is not well understood. The purpose of this study was to determine outcomes and complications after RTSA with an inclination of 135° or 155° in a modular prosthesis. American Shoulder and Elbow Surgeons (ASES), visual analog scale (VAS), Single Assessment Numeric Evaluation (SANE), and Simple Shoulder Test (SST) scores, as well as forward elevation (FE), abduction (ABD), and external rotation (ER), were assessed after a minimum 2-year follow-up. Scapular notching and radiolucency were assessed according to Sirveaux and Lévigne. A total of 121 patients with a mean age of 69.7±7.3 years were evaluated after a mean of 36.5±8 months. The inclination was set to 135° in 80.2% and to 155° in 19.8% of patients. There was no significant difference between the groups for ASES, VAS, SANE, and SST scores. The FE (P=.022) and ABD (P=.002) were significantly higher for the 155° inclination group. Complication rates were not significantly different between the groups. Scapular notching was significantly more common with a 155° inclination (P=.01), whereas humeral radiolucency was not correlated. All outcome scores improved significantly from pre- to postoperative (P≤.001). Reverse total shoulder arthroplasty leads to significant improvements in pain, range of motion, and outcome scores after mid-term follow-up. Overall, the inclination angle does not significantly affect clinical outcomes or the complication rate after RTSA at mid-term follow-up. However, an inclination of 155° shows significantly greater FE and ABD, although it results in a significantly higher rate of scapular notching. Cases with scapular notching are associated with significantly reduced mean ASES scores and ER as well as significantly higher VAS scores. [Orthopedics. 2021;44(4):e527-e533.].

Subacromial Bursa-Derived Cells Demonstrate High Proliferation Potential Regardless of Patient Demographics and Rotator Cuff Tear Characteristics

PURPOSE

To investigate the influence of patient demographics and rotator cuff tear characteristics on the cellular proliferation potential of subacromial bursa-derived cells (SBDCs).

METHODS

Patients undergoing arthroscopic rotator cuff repair between December 2017 and February 2019 were considered for enrollment in the study. Basic demographic information as well as medical and surgical history were obtained for each patient. Subacromial bursa was harvested from over the rotator cuff tendon. Cellular proliferation was evaluated after 3 weeks of incubation by counting nucleated SBDCs. Fluorescence-activated cell sorting (FACS) analysis was performed to confirm the presence of mesenchymal stem cell (MSC) specific surface markers. Using preoperative radiographs and magnetic resonance imaging (MRI), acromiohumeral distance (AHD), severity of cuff tear arthropathy, and rotator cuff tear characteristics were evaluated.

RESULTS

Seventy-three patients (mean age: 57.2 ± 8.5 years) were included in the study. There was no significant difference in cellular proliferation of SBDCs when evaluating the influence of age, sex, body mass index (BMI), smoking status, and presence of systemic comorbidities (p > .05, respectively). Similarly, there was no significant difference in cellular proliferation of SBDCs when looking at rotator cuff tear characteristics (size, tendon retraction, fatty infiltration, muscle atrophy), AHD, or severity of cuff tear arthropathy (p > .05). FACS analysis confirmed nucleated SBDCs to have a high positive rate of MSC specific surface markers.

CONCLUSION

Subacromial bursa consistently demonstrated a high cellular proliferation potential regardless of patient demographics, rotator cuff tear characteristics, and severity of glenohumeral joint degeneration.

CLINICAL RELEVANCE

These findings may alleviate concerns that subacromial bursa might lose cellular proliferation potential when being used for biologic augmentation in massive and degenerated rotator cuff tears, thus assisting in predicting tendon healing and facilitating surgical decision-making.

All-suture anchor and unicortical button show comparable biomechanical properties for onlay subpectoral biceps tenodesis

Hypothesis

The purpose of this study was to biomechanically evaluate onlay subpectoral long head of the biceps (LHB) tenodesis with all-suture anchors and unicortical buttons in cadaveric specimens.

Methods

After evaluation of bone mineral density, 18 fresh-frozen, unpaired human cadaveric shoulders were randomly assigned to 2 groups: One group received an onlay subpectoral LHB tenodesis with 1 all-suture anchor, whereas the other group received a tenodesis with 1 unicortical button. The specimens were mounted in a servo-hydraulic material testing system. Tendons were initially loaded from 5 N to 100 N for 5000 cycles at 1 Hz. Displacement of the repair constructs was observed with optical tracking. After cyclic loading, each specimen was loaded to failure at a rate of 1 mm/s.

Results

The mean displacement after cyclic loading was 6.77 ± 3.15 mm in the all-suture anchor group and 8.41 ± 3.17 mm in the unicortical button group (P = not significant). The mean load to failure was 278.05 ± 38.77 N for all-suture anchor repairs and 291.36 ± 49.69 N for unicortical button repairs (P = not significant). The most common mode of failure in both groups was LHB tendon tearing. There were no significant differences between the 2 groups regarding specimen age (58.33 ± 4.37 years vs. 58.78 ± 5.33 years) and bone mineral density (0.50 ± 0.17 g/cm² vs. 0.44 ± 0.19 g/cm²).

Conclusion

All-suture anchors and unicortical buttons are biomechanically equivalent in displacement and load-to-failure testing for LHB tenodesis. All-suture anchors can be considered a validated alternative for onlay subpectoral LHB tenodesis.

Proximal Humerus and Ilium Are Reliable Sources of Bone Marrow Aspirates for Biologic Augmentation During Arthroscopic Surgery

PURPOSE

The purpose of this study was to evaluate the number of colony-forming units (CFUs) derived from concentrated bone marrow aspirates (BMAs) that were processed following arthroscopic harvest from either the proximal humerus or the body of the ilium during biologic augmentation of the rotator cuff and acetabular labral repairs.

METHODS

Between November 2014 and January 2019, BMA was harvested from the proximal humerus (n = 89) and the body of the ilium (n = 30) during arthroscopic surgery. Following concentration of the aspirate, a 0.5-mL aliquot was further processed and the number of nucleated cells (NC) was counted. Each aliquot was cultured until CFUs were quantifiable. Fluorescence-activated cell sorting analysis and quantitative polymerase chain reaction was performed to confirm presence of mesenchymal stem cells. BMA harvest sites were prospectively assessed and evaluated for differences in age, sex, volume of aspirated BM, and CFUs per milliliter of BMA.

RESULTS

The prevalence (38.57 ± 27.92_ilium vs. 56.00 ± 25.60_humerus CFUs per 10⁶ nucleated cells) and concentration (979.17 ± 740.31_ilium vs. 1,516.62 ± 763.63_humerus CFUs per 1.0 mL BMA) of CFUs was significantly higher (P < .001, respectively) for BMA harvested from the proximal humerus. Additionally, the estimated total number of cells was significantly higher (P = .013) in BMA from the proximal humerus (97,529.00 ± 91,064.01_ilium vs. 130,552.4 ± 85,294.2_humerus). There was no significant difference between groups regarding BMA volume (91.67 ± 18.77_ilium vs. 85.63 ± 35.61_humerus mL; P = .286) and NC count (24.01 ± 5.13_ilium vs. 27.07 ± 6.28_humerus × 10⁶ per mL BMA; P = .061). The mean age was significantly lower (P < .001) in patients with BMA being harvested from the ilium (30.18 ± 7.63_ilium vs. 56.82 ± 7.08_humerus years). Patient sex and age had no significant influence on cellular measures within groups (P > .05, respectively).

CONCLUSION

Both proximal humerus and the body of the ilium can be considered reliable sources of bone marrow aspirate for the use in biologic augmentation during their respective arthroscopic surgery. Samples of bone marrow aspirate from the proximal humerus yielded a significantly higher amount of CFUs when compared with samples of BMA obtained from the ilium.

LEVEL OF EVIDENCE

Level II- prospective laboratorial study.

Intraoperative and In Vitro Classification of Subacromial Bursal Tissue

PURPOSE

To classify subacromial bursal tissue using intraoperative and in vitro characteristics from specimens harvested during arthroscopic shoulder surgery.

METHODS

Subacromial bursa was harvested over the rotator cuff from 48 patients (57 ± 10 years) undergoing arthroscopic shoulder surgery. Specimens were characterized intraoperatively by location (over rotator cuff tendon or muscle), tissue quality (percent of either fatty or fibrous infiltration), and vascularity before complete debridement. Nucleated cell counts were determined after 3 weeks incubation and histological sections were reviewed for degree of fatty infiltration and vascularity. Mesenchymal stem cell surface markers were counted via flow cytometry (n = 3) and cellular migration was observed using a fluoroscopic assay (n = 3).

RESULTS

Intraoperatively, muscle bursa was found most often to have >50% fatty infiltration (n = 39), whereas tendon bursa showed majority fibrous tissue (n = 32). Cellular proliferation did not significantly differ according to intraoperative tissue quality. Intraoperative vascularity was associated with greater proliferation for highly vascular samples (P = 0.023). Tendon bursa demonstrated significantly greater proliferation potential than muscle bursa (P = 0.00015). Histologic assessment of fatty infiltration was moderately correlated with gross tissue fattiness (ρ = -0.626, P = 7.14 × 10^-11). Flow cytometry showed that 90% to 100% of bursal cells were positive for MSC surface markers. Peak cellular migration rates occurred between 18 and 30 hours' incubation.

CONCLUSIONS

Intraoperative and in vitro subacromial bursa characteristics were not found to reliably correlate with the degree of cellular proliferation. However, the anatomic location of subacromial bursa was consistently predictive of increased proliferation potential. Bursa-derived nucleated cells were confirmed to include mesenchymal stem cells with migratory potential.

CLINICAL RELEVANCE

The anatomic distinction between muscle and tendon bursa provides a simple classification for predicting cellular activity.

Acellular dermal matrix augmentation significantly increases ultimate load to failure of pectoralis major tendon repair: a biomechanical study

BACKGROUND

Biomechanical studies have demonstrated that standard pectoralis major tendon (PMT) repairs have inferior strength compared with native tendon.

HYPOTHESIS

Augmentation of PMT repair with an acellular dermal matrix (ADM) will increase the ultimate load to failure.

METHODS

Eighteen cadaveric specimens were allocated to 3 repair groups: standard repair (SR); augmented repair (AR) with ADM; and intact, native tendon (NT). Specimens were tested for cyclic elongation, linear stiffness, load to 5 mm displacement, maximum load to failure, and method of failure.

RESULTS

Maximum load to failure in AR (1450 ± 295 N) was significantly higher than SR (921 ± 159 N; P = .0042) and equivalent to NT (1289 ± 240 N; P = .49). NT required the highest load to displace 5 mm (709 ± 202 N), which was higher than AR (346 ± 95 N; P < .001) and SR (375 ± 55; P = .0015). NT stiffness (125 ± 42 N/mm) was greater than the AR (69 ± 19 N/mm; P = .0073) or SR (75 ± 11 N/mm; P = .015). The mode of failure for SR was suture pullout from the PMT as opposed to button pullout from the humerus (fracture) for AR.

CONCLUSION

ADM augmentation of PMT repair significantly increases ultimate load to failure.

The Effect of Glenohumeral Fixation Angle on Deltoid Function During Superior Capsule Reconstruction: A Biomechanical Investigation

PURPOSE

To evaluate the effect of dermal allograft fixation at different angles of glenohumeral abduction on deltoid forces during superior capsule reconstruction (SCR).

METHODS

Fifteen cadaveric specimens were tested using a dynamic shoulder simulator. Following testing in the native state, shoulders underwent SCR in 2 of 5 possible fixation angles; 0°, 15°, 30°, 45°, or 60° of glenohumeral abduction, allowing for 6 specimens per group. Angles were measured radiographically with the glenoid fixed perpendicular to the floor. Maximum mean deltoid abduction force was compared among 5 separate conditions within each angle group: (1) native shoulder, (2) complete supraspinatus (SSP) and superior capsule tear, (3) SCR alone, (4) SCR with posterior margin sutured, and (5) SCR with anterior and posterior margins sutured.

RESULTS

SSP tears significantly increased the maximum deltoid forces for all 5 fixation angles compared with the native state (P < .05). Specimens repaired at 0°, 30°, and 45° were unable to restore deltoid forces compared with the native state in any condition (P < .05). SCR at 15° with anterior and posterior margin convergence showed similar abduction forces compared with the native state (P = .19). When fixed at 60° abduction, SCR alone significantly reduced deltoid forces compared to SSP (Δ143N, P < .001) and native (Δ48N, P < .001). No significant differences were found between the 3 repair subtypes (SCR ± anterior/posterior margin repair) in the 60° group.

CONCLUSIONS

SCR with anterior and posterior margin convergence tensioned at 15° of glenohumeral abduction showed similar deltoid abduction force requirements compared with the native state, whereas graft fixation in 60° significantly reduced deltoid force in all SCR conditions.

CLINICAL RELEVANCE

Increased graft tension with a greater abduction angle may provide greater functional outcome by placing less load on the deltoid. In contrast, graft fixation in lower abduction angles may require additional margin convergence to reproduce native forces.

Biomechanical Comparison of Anterograde and Retrograde Lesser Trochanter Avulsion Repair

Background:

Lesser trochanter avulsions are rare injuries in adolescents. Severe cases with relevant fragment displacement can be treated surgically. However, no standard approach is available in the literature. Operative techniques are presently limited to anterograde fixations. A new retrograde approach to reduce operative difficulty and postoperative morbidity has been proposed. So far, no biomechanical comparison of these techniques is available.

Hypothesis:

Retrograde repair of the lesser trochanter with a titanium cortical button will produce superior stability under load to failure and similar displacement under cyclic loading compared with anterograde fixation with titanium suture anchors.

Study Design:

Controlled laboratory study.

Methods:

Sixteen paired hemipelvic cadaveric specimens (mean age, 62.5 ± 10.7 years) were dissected to isolate the lesser trochanter and iliopsoas muscle. After repair of a simulated lesser trochanter avulsion, specimens were tested under cyclic loading between 10 and 125 N at 1 Hz for 1500 cycles before finally being loaded to failure at a rate of 120 mm/min in a material testing machine. Motion tracking was used to assess displacement at the superior and inferior aspects of the iliopsoas tendon under cyclic loading.

Results:

Load to failure was significantly greater for the retrograde repair compared with the anterograde repair (1075.24 ± 179.39 vs 321.85 ± 62.45 N; P = .012). Mean displacement at the superior repair aspect (retrograde vs anterograde: 3.29 ± 1.84 vs 4.39 ± 4.50 mm; P = .779) and mean displacement at the inferior aspect (3.54 ± 2.13 vs 4.22 ± 4.48 mm; P = .779) of the iliopsoas tendon did not significantly differ by the type of repair. Mode of failure was tendon tearing by the sutures for each retrograde repair and anchor pullout for each anterograde repair.

Conclusion:

Surgical repair of lesser trochanter avulsion fractures with retrograde fixation using a titanium cortical button demonstrated superior load to failure and similar displacement under cyclic loading compared with anterograde fixation using suture anchors.

Clinical Relevance:

The retrograde approach provides a biomechanically validated alternative to other surgical techniques for this injury.

Biomechanical Evaluation of Proximal Hamstring Repair: All-Suture Anchor Versus Titanium Suture Anchor

Background:

Proximal hamstring avulsions are severe tendon injuries and are commonly sports-related. Open and endoscopic techniques as well as different anchor configurations have already been described for proximal hamstring repair. Novel all-suture anchors have been developed to provide decreased bone loss during placement and reduced occupied bone volume when compared with titanium suture anchors.

Hypothesis:

Complete proximal hamstring avulsions repaired with all-suture anchors will demonstrate equal load to failure and comparable displacement under cyclic loading when compared with titanium suture anchors.

Study Design:

Controlled laboratory study.

Methods:

Complete proximal hamstring avulsions were created in 18 paired cadaveric specimens (mean ± SD age, 63.0 ± 10.4 years). Either all-suture anchors or titanium suture anchors were used for repair. Cyclic loading from 10 to 125 N at 1 Hz was performed for 1500 cycles with a material testing machine. Displacement was assessed along anterior and posterior aspects of the tendon repair with optical tracking. Specimens were loaded to failure at a rate of 120 mm/min. Displacement, load to failure, and repair construct stiffness were compared between matched pairs with the Wilcoxon signed-rank test. Correlations were determined by Spearman rho analysis.

Results:

The all-suture anchors showed significantly higher load-to-failure values when compared with the titanium anchor repairs (799.64 ± 257.1 vs 573.27 ± 89.9 N; P = .008). There was no significant difference in displacement between all-suture anchors and titanium suture anchors at the anterior aspect (6.60 ± 2.2 vs 5.49 ± 1.1 mm; P = .26) or posterior aspect (5.87 ± 2.08 vs 5.23 ± 1.37 mm; P = .678) of the repaired hamstring tendons.

Conclusion:

All-suture anchors demonstrated similar displacement and superior load to failure when compared with titanium suture anchors.

Clinical Relevance:

The results of this study suggest that all-suture anchors are an equivalent alternative to titanium suture anchors for proximal hamstring avulsion repair.

Comparison of Preparation Techniques for Isolating Subacromial Bursa-Derived Cells as a Potential Augment for Rotator Cuff Repair

PURPOSE

To identify an effective, nonenzymatic method for maximizing the yield of subacromial bursa-derived nucleated cells for augmenting rotator cuff repair.

METHODS

Subacromial bursa (minimum 0.2 g) was collected prospectively over the supraspinatus from patients (n = 7) with at least one full-thickness tendon tear undergoing arthroscopic primary rotator cuff repair. Samples were processed and analyzed prospectively using 4 different methods: (1) mechanical digestion with scissors (chopping), (2) collagenase digestion, (3) mechanical digestion with a tissue homogenizer, and (4) whole tissue with minimal manipulation. Tissue from each method were plated and cultured in a low oxygen tension, humidified incubator for 7 days. Following incubation, cellularity was assessed with nucleated cell count using a Coulter Counter. Flow cytometry was performed on the non-enzymatic method that demonstrated the greatest cell count to confirm the presence of mesenchymal stem cells (MSCs). The Kruskal-Wallis H test and post hoc Dunn's test were used for statistical analysis.

RESULTS

Following incubation, mean nucleated cell counts (cells/mL) were (1) 102,681 ± 73,249 for chopping, (2) 76,190 ± 66,275 for collagenase, (3) 31,686 ± 29,234 for homogenization, and (4) 11,162 ± 4016 for whole tissue. There was no significant difference between chopping and collagenase (P = .45) or between homogenization and collagenase (P = .52). Both chopping (P = .003) and collagenase (P = .03) produced significantly more cells when compared with whole tissue. Flow cytometry confirmed the presence of MSC markers on samples processed by chopping.

CONCLUSIONS

Mechanical isolation of subacromial bursa-derived cells using a chopping technique demonstrated similar nucleated cell count compared with collagenase, along with the confirmed presence of MSCs.

CLINICAL RELEVANCE

This study demonstrated a nonenzymatic, mechanical method for isolating subacromial bursa-derived cells to potentially augment rotator cuff repair. Further clinical studies are required to assess its possible advent in the tendon-bone healing process.

The effect of a single consecutive volume aspiration on concentrated bone marrow from the proximal humerus for clinical application

BACKGROUND

Low aspiration volumes have been recommended to allow for higher concentrations of progenitor cells during bone marrow harvesting. However, these guidelines then require multiple aspiration attempts in order to maximize cellular yield. The purpose of this study was to investigate the effect of a single, high-volume aspiration with four consecutive aliquots on the number of nucleated cells (NCs) and colony-forming units (CFUs) in concentrated bone marrow aspirate (cBMA) taken from the proximal humerus.

METHODS

cBMA was taken from the proximal humerus of patients undergoing arthroscopic rotator cuff surgery. Four 12-mL double syringes were used consecutively from a single trocar to obtain four 10 cc aliquots. Each then underwent centrifugation to create a fractionated layer rich in nucleated cells. Following cellular separation, NCs were counted and CFUs were evaluated after incubation of 7-10 days. Cellular comparisons between each aliquot were performed along with their interaction with patient age and sex.

RESULTS

Twenty-nine patients (55.9 ± 4.6 years) were included in this study. The number of NCs and CFUs showed significant differences between the four aliquots of aspirate, with the first 10 cc aliquot providing the highest amount (p < 0.001, respectively). No significant differences were found between the sum of the three sequential aliquots compared to the initial 10 cc sample. There were no significant differences between male and female patients (p > 0.05). Increasing age resulted in no significant decrease in the number of NCs and CFUs across the four consecutive aliquots (p > 0.05).

CONCLUSION

In conclusion, while the initial aliquot provided the greatest number of nucleated cells and cultured CFUs, the addition of each sequential volume aspirate yielded similar amounts in total. This demonstrates the potential effectiveness of obtaining of higher volume aspirates from the proximal humerus during rotator cuff repair.

Examining the Potency of Subacromial Bursal Cells as a Potential Augmentation for Rotator Cuff Healing: An In Vitro Study

PURPOSE

To compare the potency of mesenchymal stem cells between the cells derived from the subacromial bursa to concentrated bone marrow aspirate (cBMA) taken from patients undergoing rotator cuff (RC) repair.

METHODS

Subacromial bursa and cBMA were harvested arthroscopically from 13 patients (age 57.4 ± 5.2 years, mean ± standard deviation) undergoing arthroscopic primary RC repair. Bone marrow was aspirated from the proximal humerus and concentrated using an automated system (Angel System; Arthrex). Subacromial bursa was collected from 2 sites (over the RC tendon and muscle) and digested with collagenase to isolate a single cellular fraction. Proliferation, number of colony-forming units, differentiation potential, and gene expression were compared among the cells derived from each specimen.

RESULTS

The cells derived from subacromial bursa showed significantly higher proliferation compared with the cells derived from cBMA after 5, 7, and 10 days (P = .018). Regarding colony-forming units, the subacromial bursa had significantly more colonies than cBMA (P = .002). Subacromial bursal cells over the RC tendon produced significantly more colonies than cells over both the RC muscle and cBMA (P = .033 and P = .028, respectively). Moreover, when compared with cBMA, cells derived from subacromial bursa showed significantly higher differentiation ability and higher gene expression indicative of chondrogenesis, osteogenesis, and adipogenesis.

CONCLUSION

The subacromial bursa is an easily accessible tissue that can be obtained during RC repair, with significant pluripotent stem cell potency for tendon healing. Compared with cBMA taken from the proximal humerus, bursal cells showed significantly increased differentiation ability and gene expression over time.

CLINICAL RELEVANCE

Failed RC repairs have been partly attributed to a poor healing environment. Biologic augmentation of the repair site may help increase healing potential and incorporation of the cuff at the tendon-bone interface.

Flexor Hallucis Longus Transfer Improves Achilles Tendon Load to Failure in Surgery for Non-Insertional Tendinopathy: A Biomechanical Study

BACKGROUND

Non-insertional Achilles tendinopathy is a common disorder that may be treated with surgical debridement. A flexor hallucis longus (FHL) transfer is recommended if debridement of ≥50% is performed; however, there are no biomechanical data to support this. The purpose of this study was to assess the added biomechanical strength provided by an FHL transfer with incrementally sized non-insertional Achilles tendon defects.

METHODS

Thirty matched-pair below-the-knee cadaveric specimens (n = 60) (mean age at the time of donor death, 67 years; range, 36 to 74 years) were obtained and randomly divided into 3 groups according to whether the defect was 25%, 50%, or 75% of the tendon width. One specimen of each pair was then randomly selected to undergo FHL transfer using interference screw fixation. All specimens then underwent cyclic loading of 100 N, and elongation of the medial and lateral limbs of the tendon defect was recorded. The constructs were then loaded to failure to measure stiffness, ultimate strength, and peak elongation before failure.

RESULTS

The specimens with a 75% defect had significantly less elongation of the medial and lateral tendon-defect limbs when an FHL transfer had been done (p < 0.05). Ultimate load to failure was significantly increased in all groups (by 242 to 270 N depending on the defect size) following FHL transfer. Failures usually occurred through the tendon defect in the 75% and 50% defect groups, whereas all failures occurred at the Achilles tendon insertion when a 25% defect had been created. No significant differences were found in peak elongation with the addition of an FHL transfer. FHL augmentation resulted in significantly greater stiffness in the 25% and 75% defect groups (p < 0.05).

CONCLUSIONS

This study showed that an FHL transfer significantly increased load to failure of Achilles tendons with a non-insertional defect involving 25%, 50%, and 75% of the tendon width. The mechanism of failure was usually through the defect in the specimens with a 50% or 75% defect, supporting the use of FHL augmentation with debridement of ≥50%.

CLINICAL RELEVANCE

The present study supports the mechanical concept that FHL transfer is indicated when debridement of the Achilles tendon is ≥50%.

The ACL-deficient knee and the prevalence of meniscus and cartilage lesions: a systematic review and meta-analysis (CRD42017076897)

INTRODUCTION

The purpose of this systematic review and meta-analysis was to analyze and compare the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction.

MATERIALS AND METHODS

A systematic search for articles comparing the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction was performed. PubMed central was the database used for the literature review.

RESULTS

Forty articles out of 1836 were included. In 35 trials (88%), there was evidence of a positive correlation between the rate of meniscus and/or cartilage lesions and the time since ACL injury. This correlation was more evident for the medial meniscus in comparison with the lateral meniscus. In particular, a delay of more than 6 months was critical for secondary medial meniscus injuries [risk ratio 0.58 (95% CI 0.44-0.79)] and a delay of more than 12 months was critical for cartilage injuries [risk ratio 0.42 (95% CI 0.29-0.59)]. Additionally, there is evidence that the chance for meniscal repair decreases as the time since ACL rupture increases.

CONCLUSION

Chronic instability in the ACL-deficient knee is associated with a significant increase of medial meniscus injuries after 6 months followed by a significant increase of cartilage lesions after 12 months.

The Effect of Lateral Opening Wedge Distal Femoral Varus Osteotomy on Tibiofemoral Contact Mechanics Through Knee Flexion

BACKGROUND

Lateral opening wedge distal femoral osteotomy (DFO) unloads a diseased lateral compartment of the knee in patients with genu valgum. To the best of our knowledge, there are no biomechanical studies investigating the effect of knee flexion on contact pressure and area after DFO.

HYPOTHESIS

As knee flexion angles increase, DFO will be less effective at unloading the lateral compartment of the knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Lateral opening wedge DFO was performed, correcting a mean of 7°, in 10 cadaveric knees using plate fixation. Tibiofemoral contact pressure was measured in 0°, 15°, 30°, 45°, 60°, and 75° of knee flexion before and after osteotomy using electronic sensors. Peak contact pressure (PCP), mean contact pressure (MCP), and contact area were measured for each condition. Anatomic dissection quantified the tibiofemoral contact position on the distal femur in all degrees of flexion. Mixed-effects regression analyses were used to compare the change in variables before and after osteotomy and between flexion angles.

RESULTS

One sample had to be excluded because of tibiofemoral arthritis. MCP decreased in the lateral compartment after DFO throughout all degrees of flexion (all P < .05) but to the greatest extent in 0° of flexion. When examining the percentage of MCP in the lateral compartment, this decreased after DFO at 0° (70.4% to 40.0%; P < .001), 15° (65.1% to 52.1%; P < .001), 30° (60.7% to 52.0%; P = .003), 45° (55.8% to 49.7%; P = .033), and 60° (51.9% to 44.2%; P = .010) but not at 75° (50.2% to 45.3%; P = .112). PCP decreased in the lateral compartment after DFO at 0° (2.41 to 1.34 MPa; P < .001), 15° (2.50 to 1.81 MPa; P < .001), 30° (2.28 to 1.93 MPa; P = .039), 45° (2.21 to 1.73 MPa; P = .005), 60° (2.15 to 1.71 MPa; P = .009), and 75° (1.95 to 1.49 MPa; P = .012). The percentage of contact area decreased in the lateral compartment in full extension (68.7% to 48.1%; P = .007) but not at any other degree of flexion (all P > .05).

CONCLUSION

DFO decreased lateral compartment pressure. However, it had the greatest effect in full knee extension.

CLINICAL RELEVANCE

DFO decreased contact pressure in the lateral compartment but more effectively decreased contact pressure in the more anterior aspects of the femoral articular cartilage.

A validated hybrid computational fluid dynamics-physiologically based pharmacokinetic model for respiratory tract vapor absorption in the human and rat and its application to inhalation dosimetry of diacetyl

Diacetyl vapor is associated with bronchiolar injury in man but primarily large airway injury in the rat. The goal of this study was to develop a physiologically based pharmacokinetic model for inspired vapor dosimetry and to apply the model to diacetyl. The respiratory tract was modeled as a series of airways: nose, trachea, main bronchi, large bronchi, small bronchi, bronchioles, and alveoli with tissue dimensions obtained from the literature. Airborne vapor was allowed to absorb (or desorb) from tissues based on mass transfer coefficients. Transfer of vapor within tissues was based on molecular diffusivity with direct reaction with tissue substrates and/or metabolism being allowed in each tissue compartment. In vitro studies were performed to provide measures of diacetyl metabolism kinetics and direct reaction rates allowing for the development of a model with no unassigned variables. Respiratory tract uptake of halothane, acetone, ethanol and diacetyl was measured in male F344 rat to obtain data for model validation. The human model was validated against published values for inspired vapor uptake. For both the human and rat models, a close concordance of model estimates with experimental measurements was observed, validating the model. The model estimates that limited amounts of inspired diacetyl penetrate to the bronchioles of the rat (<2%), whereas in the lightly exercising human, 24% penetration to the bronchioles is estimated. Bronchiolar tissue concentrations of diacetyl in the human are estimated to exceed those in the rat by 40-fold. These inhalation dosimetric differences may contribute to the human-rat differences in diacetyl-induced airway injury.