Conjoint Tendon Lengthening Improves Internal Rotation Following Reverse Total Shoulder Arthroplasty: A Cadaveric Study

INTRODUCTION

Reverse Shoulder Arthroplasty (RSA) is a common procedure for treating a variety of shoulder pathologies. However, many patients struggle with postoperative internal rotation deficits, which often hinder their activities of daily living. The conjoint tendon provides an anatomic barrier that can impede the postoperative internal rotation of the shoulder, and this study aims to evaluate the effect of a conjoint tendon lengthening on the glenohumeral range of motion following RSA.

METHODS

This study used ten fresh-frozen cadaver specimens of the upper extremity. An RSA was implanted using a standard deltopectoral approach, and the range of motion was assessed post-implantation. Following this, the conjoint tendon was identified and lengthened using a tendon sheath z-plasty, and the range of motion was re-recorded. Statistical significance for the range of motion gains after conjoint tendon lengthening was determined with a significance level of p < 0.05.

RESULTS

Following the lengthening of the conjoint tendon, there were statistically significant improvements in all ranges of motion (p < 0.05). Subjects demonstrated a notable gain in internal rotation to the back by 10.3 cm (p < 0.01), and all ranges of motion increased by at least 10°, except for forward flexion, which increased by 6° (p < 0.001).

CONCLUSIONS

This study suggests that lengthening the conjoint tendon improves postoperative range of motion of the glenohumeral joint after RSA, offering a potential solution to a considerable internal rotation deficits that are commonly encountered post-RSA. Subsequent clinical and biomechanical studies should assess the stability of the shoulder joint following conjoint tendon lengthening.

Assessment of 2 distinct anatomical landmarks for suprascapular nerve injection: a cadaveric study

BACKGROUND

The suprascapular nerve block (SSNB) is a commonly used procedure for the management of pain in various shoulder pathologies. Both image-guided and landmark-based techniques have been utilized successfully for SSNB, though more consensus is needed regarding the optimal method of administration. This study aims to evaluate the theoretical effectiveness of a SSNB at 2 distinct anatomic landmarks and propose a simple, reliable way of administration for future clinical use.

METHODS

Fourteen upper extremity cadaveric specimens were randomly assigned to either receive an injection 1 cm medial to the posterior acromioclavicular (AC) joint vertex or 3 cm medial to the posterior AC joint vertex. Each shoulder was injected with a 10 ml methylene blue solution at the assigned location, and gross dissection was performed to evaluate the anatomic diffusion of the dye. The presence of dye was specifically assessed at the suprascapular notch, supraspinatus fossa, and spinoglenoid notch to determine the theoretic analgesic effectiveness of a SSNB at these 2 injection sites.

RESULTS

Methylene blue diffused to the suprascapular notch in 57.1% of the 1-cm group and 100% of the 3-cm group, the supraspinatus fossa in 71.4% of the 1-cm group and 100% of the 3-cm group, and the spinoglenoid notch in 100% of the 1-cm group and 42.9% of the 3-cm group.

CONCLUSION

Given its superior coverage at the more proximal sensory branches of the suprascapular nerve, a SSNB injection performed 3 cm medial to the posterior AC joint vertex provides more clinically adequate analgesia than an injection site 1 cm medial to the AC junction. Performing a SSNB injection at this location allows for an effective method of anesthetizing the suprascapular nerve.

Is the radial groove a myth? Is the radial nerve in direct contact with the posterior humerus?

BACKGROUND

The radial groove is known as a sulcus on the posterior humerus and protects the radial nerve from adjacent muscle and soft tissue. In the literature, there exists heterogeneity regarding the presence of an actual radial groove and the radial nerve's interaction with the periosteum of the humerus. This study aimed to determine if there is a real radial groove, "sulcus," and define the relationship between the radial nerve and the periosteum of the posterior humerus.

METHODS

Eighteen fresh-frozen cadaveric specimens were dissected using a posterior triceps splitting approach. The radial nerve's interaction with the periosteum of the humerus was determined. The presence of a visible and palpable radial groove was also examined.

RESULTS

In 56% of specimens, the radial nerve was directly seated over the periosteum of the posterior humerus (direct contact between the nerve and bone). In comparison, 44% of specimens had a layer of the medial head of the triceps brachii muscle fibers interposition between the nerve and bone. 89% of specimens had no visible or palpable radial groove. In 11% of specimens, there was mild palpable depression.

CONCLUSION

This study shows that the radial groove may not exist and is probably not a true anatomical structure. In addition, the nerve is in direct contact with the posterior periosteum of the humerus in most specimens. These anatomic relationships and findings add to the anatomical understanding of the radial nerve, which helps during operative approaches and fixation of the humerus.

Does Morbid Obesity (BMI ≥40 kg/m2) Impact Operative Time, Blood Loss, Length of Stay, or Complications Following Anatomic Total Shoulder Arthroplasty?

Objectives

There have been conflicting reports regarding the effects of obesity on both surgical time and blood loss following anatomic shoulder arthroplasty. Varying categories of obesity has made comparison amongst existing studies difficult.

Methods

A retrospective review of consecutive anatomic shoulder arthroplasty cases (aTSA) was undertaken. Demographic data, including age, gender, body mass index (BMI), age-adjusted Charleson Comorbidity Index (ACCI), operative time, hospital length of stay (LOS), and both POD#1 and discharge visual analogue score (VAS) was collected. Intra-operative total blood volume loss (ITBVL) and need for transfusion was calculated. BMI was categorized as non-obese (<30 kg/m²), obese (30-40 kg/m²) and morbidly obese (≥40 kg/m²). Unadjusted associations of BMI with operative time, ITBVL and LOS were examined using Spearman correlation coefficients. Regression analysis was used to identify factors associated with hospital LOS.

Results

There were 130 aTSA cases performed, including 45 short stem and 85 stemless implants, of which 23 (17.7%) were morbidly obese, 60 (46.2%) were obese and 47 (36.1%) were non-obese. Median operative time for the morbidly obese cohort was 119.5 minutes (IQR 93.0, 142.0) versus 116.5 minutes (IQR 99.5, 134.5) for the obese cohort versus 125.0 minutes (IQR, 99.0, 146.0) for the non-obese cohort. (P=0.61) The median ITBVL for the morbidly obese cohort was 235.8 ml (IQR 144.3, 329.7) versus 220.1 ml (IQR 147.7, 262.7) for the obese cohort versus 216.3 ml (IQR 139.7, 315.5) for the non-obese cohort. (P=0.72). BMI ≥40kg/m² (IRR 1.32, P=0.038), age (IRR 1.01, P=0.026), and female gender (IRR 1.54, P<0.001) were predictive of increased LOS. There was no difference with regards to in-hospital medical complications (P=0.13), surgical complications (P=1.0), need for re-operation (P=0.66) and 30-day return to the ER (P=0.06).

Conclusion

Morbid obesity was not associated with increased surgical time, ITBVL and perioperative medical or surgical complications following aTSA, though it was predictive of increased hospital LOS.

Chondrogenic differentiation of human bone marrow MSCs in osteochondral implants under kinematic mechanical load is dependent on the underlying osteo component

Chondrogenic models utilizing human mesenchymal stromal cells (hMSCs) are often simplistic, with a single cell type and the absence of mechanical stimulation. Considering the articulating joint as an organ it would be beneficial to include more complex stimulation. Within this study we applied clinically relevant kinematic load to biphasic constructs. In each case, the upper layer consisted of fibrin embedded hMSCs retained within an elastomeric polyurethane (PU) scaffold. These were randomly assigned to five base scaffolds, a cell-free fibrin PU base, viable bone, decellularized bone, 3D printed calcium phosphate or clinically used cement. This allowed the study of cross talk between viable bone and chondrogenically differentiating MSCs, while controlling for the change in stiffness of the base material. Data obtained showed that the bulk stiffness of the construct was not the defining factor in the response obtained, with viable and decellularized bone producing similar results to the softer PU base. However, the stiff synthetic materials led to reduced chondrogenesis and increased calcification in the upper MSC seeded layer. This demonstrates that the underlying base material must be considered when driving chondrogenesis of human cells using a clinically relevant loading protocol. It also indicates that the material used for bony reconstruction of osteochondral defects may influence subsequent chondrogenic potential.

Comminuted patellar fractures: The role of biplanar fixed angle plate constructs

Background

Comminuted patellar fractures represent a challenging clinical problem. Treatment aims to restore the integrity of the extensor mechanism and the congruity of patellofemoral joint. Controversy exists regarding the ideal fixation method. Metallic constructs aiming to convert pulling forces on the anterior aspect of the patella into compression forces across the fracture site are the standard of care. More recently, low profile plates have been described in the management of comminuted patellar fractures. The aims of this study were to (1) develop a novel unstable patellar fracture model and (2) to compare biomechanically three different constructs for fixation comminuted patellar fractures. We hypothesized that an orthogonal biplanar disposition of the screws within an anteriorly placed locking plate provides the best biomechanical properties in the management of comminuted fractures.

Methods

Six-part complex AO 34–C3 patella fractures were simulated in 18 human cadaveric knees by means of osteotomies including comminution around the distal patellar pole. The specimens were randomly assigned to 3 fixation techniques (n ​= ​6) for either anterior plating, antero-lateral plating, or tension band wiring (TBW). Biomechanical testing was performed over 5000 cycles in active extension and passive flexion, followed by ultimate destructive quasi-static testing. Interfragmentary movements were captured by means of optical motion tracking.

Results

Displacement between the proximal and distal medial patella fragments was lower after anterior plating compared to both antero-lateral plating (P ​= ​0.084) and TBW (P ​< ​0.001). Moreover, displacement between the proximal and distal lateral fragments was significantly lower after anterior plating compared to both other techniques (P ​≤ ​0.032). In addition, it was significantly lower for antero-lateral plating versus TBW (P ​< ​0.001). Rotation around the medio-lateral axis between the proximal and distal medial fragments was significantly lower after anterior plating compared to TBW (P ​= ​0.017).

Conclusions

Anterior mesh plating with biplanar placement of locking screws provides superior stability for fixation of comminuted patellar fractures when compared to both antero-lateral mesh plating and TBW. The latter is associated with considerably inferior performance.

Secondary Perforation Risk in Plate Osteosynthesis of Unstable Proximal Humerus Fractures: A Biomechanical Investigation of the Effect of Screw Length

Secondary perforation of screws into the joint surface is a commonly reported mechanical fixation failure mode in locked plating of proximal humerus fractures (PHF). This study investigated the influence that screws tip to joint distance (TJD) has on the biomechanical risk of secondary screw perforation and the stability of PHF. Ten pairs of cadaveric proximal humeri with a wide range of bone mineral density were used. Each specimen was osteotomized and instrumented with the PHILOS plate, simulating a highly unstable 3-part fracture. Bones were randomized into a long screw group (LSG) with 4 mm TJD, or a short screw group (SSG) with 8 mm TJD. A custom biomechanical setup was used to test the samples to failure cyclically with a constant valley load and an increasing ramp. The number of cycles to the initial screw loosening event was significantly higher for the LSG (mean ± standard deviation: 17,532 ± 6,458) compared with the SSG (11,102 ± 5,440) (p < 0.01). The mode of failure during testing was lateral-inferior displacement combined with varus collapse, with calcar screws perforating first. The number of cycles to failure event for LSG (27,849 ± 5,648) was not significantly different compared with SSG (28,782 ± 7,307) (p = 0.50). Screws that purchase closer to the joint had better initial stability and resistance against loosening. Placing longer screws, within limits dictated by the surgical guide, is expected to decrease the risk of secondary perforation failures in unstable PHF. These findings require clinical corroboration. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2625-2633, 2019.