Long head of biceps tenodesis at the superior aspect of the biceps groove: A biomechanical comparison of inlay and onlay techniques

Abstract

Purpose

Pathology involving the long head of the biceps tendon is a common source of shoulder pain. Biceps tenodesis has been successfully used in areas below the pectoralis, above the pectoralis, and above the biceps groove. However, clinical data are lacking for additional techniques for tenodesis at the superior aspect of the biceps groove.

Methods

A biomechanical comparison was completed examining six matched pairs of cadaveric shoulders. The ultimate load to failure was compared between an inlay and onlay biceps tenodesis at the superior aspect of the biceps groove.

Results

The results demonstrate an average construct strength of 215 N for the inlay technique and 210 N for the onlay technique. The difference between the two techniques was not significant.

Conclusions

This study demonstrates similar biomechanical strength for both constructs.

Introduction

The proximal tendon of the long head of the biceps is a common source of shoulder pain. Surgical treatment of this pathology has historically involved either tenotomy or tenodesis. Despite equal clinical outcomes in terms of function and patient-rated outcomes,^1,2 the concern regarding residual shoulder pain and cosmetic deformity associated with tenotomy is predictive of patients choosing tenodesis.³ Perhaps as a result of this, the incidence of biceps tenodesis has been increasing yearly compared to tenotomy.⁴

Surgeons performing a biceps tenodesis may choose to perform the fixation at the superior aspect of the bicipital groove, in the suprapectoral region, in the subpectoral region, to the conjoint tendon, or to other soft tissue sites. Biomechanical and clinical data have demonstrated conflicting results in regard to the preferred tenodesis location. Werner et al.⁵ found that an open subpectoral position resulted in less overtensioning, increased load to failure, and reduced number of failures compared to a suprapectoral position. Lutton et al.⁶ agreed with this assessment as they showed better clinical outcomes with less patient pain with lower tenodesis sites. Yet, a systematic review comparing patient outcomes between open versus arthroscopic tenodesis techniques, and thus suprapectoral versus subpectoral positions, demonstrated no clinical difference,⁷ which mirrors other studies as well.⁸ Some authors contend that the increased risk of complications with an open subpectoral technique, along with its more invasive nature, leads to arthroscopic techniques being preferred,^8,9 while others argue that the complication rate is negligible.¹⁰

Once a location is chosen, a decision needs to be made regarding the construct used for fixation such as interference screws, suture anchors, cortical buttons, or all soft tissue techniques. For construct type, interference screws have been shown to have higher loads to failure than suture anchors.^11–14 However, Tashjian and Henninger¹⁵ found similar loads to ultimate failure when comparing the two. Conflicting results have been found comparing interference screws to cortical buttons with some studies finding interference screws to be the better fixation choice,¹⁶ while other studies found no difference.¹⁷ Newer techniques, such as a “soft anchor” have also been found to be similar to interference screws in regard to failure strength^18,19 and clinical outcomes.²⁰ Regardless of location or construct characteristics, fixation strength is of utmost importance. In previous biomechanical studies, ultimate load to failure values have ranged from 68.5 to 310 N.^5,9,11–22

Choosing to perform a tenodesis proximal to the biceps grove has the advantage of ease of location identification during routine arthroscopic imaging. An interference screw utilized in the region of the shoulder has shown reliable clinical results.²³ However, use of an interference screw often requires externalization of the tendon and an approximation of the appropriate length–tension relationship. A fixation construct using sutures fixed to a suture anchor has the unique opportunity to perform the biceps tenodesis at the superior aspect of the biceps groove before releasing the biceps from the superior glenoid tubercle. This allows for the tendon to maintain an anatomic relationship and does not require externalization. Fixation strength of such a construct has not been assessed. In this biomechanical trial, a comparison is made between an interference screw “inlay” technique and a suture anchor “onlay” technique. We hypothesized there would be no significant difference in the ultimate load to failure.

Methods

Six matched pair cadaveric proximal humerus samples were utilized. Rotator cuff and deltoid tissue were removed and the long head of the biceps was excised at the insertion onto the superior glenoid tubercle. Two different biceps tenodesis techniques were utilized. The onlay group contained two left-sided samples and four right-sided samples, and the inlay group was composed two right-sided samples and four left-sided samples from the matched pair set.

To perform the onlay technique the bicep was sutured with a #2 FiberLoop (Arthrex, Naples, FL) once to perform a grasping stitch. The two tails were then again passed distal to the grasping loop (Figure 1(a)). The proximal humerus was then prepared with a punch and a subsequent tap designed for a 4.75 mm BioComposite SwiveLock Anchor (Arthrex, Naples, FL). This was placed at the superior aspect of the biceps groove (Figure 1(b)). The suture tails were then passed through the anchor and reduced (Figure 1(c)). After anchor reduction, one limb of the suture was again passed through the biceps and the two tails were tied (Figure 2). A final example of the finished onlay construct is demonstrated in Figure 2(c).

Figure 1.

(a) The biceps has been sutured with a grasping stitch, (b) a tap prepares the top of the biceps groove for anchor implantation, and (c) suture tails are reduced with the anchor.

Figure 2.

(a) Following anchor placement a suture passer is used to pass one limb of through the remaining tendon, (b) the ends of the sutures are tied reinforcing the construct, and (c) a demonstration of the final onlay construct.

To perform the inlay interference screw technique a 7 mm BioComposite SwiveLock Anchor was utilized (Arthrex, Naples, FL). The biceps tendon was sutured with a #2 FiberLoop (Arthrex, Naples, FL). Four passes were made through the tendon and the suture tails were directed through the terminal end of the tendon (Figure 3). The proximal humerus was prepared with a 7 mm reamer. A tunnel 20 mm in depth was created at the superior aspect of the biceps groove (Figure 4(a)). With the suture tails were passed through the anchor, the biceps was then reduced into the tunnel with the anchor (Figure 4(b)). An example of the final inlay construct is demonstrated in Figure 4(c).

Figure 3.

(a) The biceps is sutured in with a grasping technique and (b) the sutures are passed through the end of biceps tendon preparing for inlay fixation.

Figure 4.

(a) A 7 mm tunnel is prepared, (b) a 7 mm anchor is used to reduce and fix the biceps tendon in the tunnel, and (c) a demonstration of a final inlay construct.

Each construct was then tested for ultimate load to failure as measured in Newtons (N) (Figure 5(a)). The samples were loaded and carefully secured using an Instron materials testing system (Instron, Norwood, MA).

Figure 5.

(a) An example of the starting position before load testing, (b) failure of onlay construct demonstrating the tied knot pulled through the tendon and the suture pulled past the anchor, and (c) failure of an inlay construct demonstrating the tendon and suture pulled past the anchor.

Descriptive statistics were calculated for the data. In consideration of the sample size, the Shapiro–Wilk test was used to assess normality for both groups. Levene’s test for equality of variances was also performed. Independent sample two-tailed t-tests were then calculated for all loads. Statistical significance was determined by an alpha = 0.05.

Results

Data in both groups were normally distributed (Shapiro–Wilk test: p > 0.05). All specimens were loaded to failure and the resulting data demonstrated an average ultimate load of 210 N (range: 125–295, standard error of the mean: 23) for the onlay group and 215 N (range: 60–329, standard error of the mean: 41) for the inlay group. Equal variances were assumed for both groups (p > 0.05). The mean load to failure of each group was compared with a two-sided t-test which demonstrated the difference between the groups was not significant (p > 0.05). The mode of failure for all samples in the onlay group occurred by the suture knot pulling through the tendon and then the sutures pulling past the anchor. No anchor grossly changed position at time of failure. The initial grasping suture did not lose fixation in any specimen (Figure 5(b)). In Figure 5(b), the final suture knot can be appreciated to have been disrupted. In addition, the sutures are demonstrated to have pulled past the anchor while the anchor position is unchanged grossly. The mechanism of failure for all specimens in the inlay group was also identical. Failure occurred by the tendon pulling past the anchor (Figure 5(c)). In all inlay constructs, the anchor did not grossly change position during failure.

Discussion

This study demonstrated a comparison of techniques for a proximal biceps tenodesis. The data suggest that both the inlay and the onlay techniques described have statistically similar ultimate load to failure values. In addition, both techniques failed in a very similar way. In all specimens, the anchor remained grossly unchanged in position. Failure in the onlay technique group required the final knot fixation to fail and subsequent passage of the suture tails past the anchor. The inlay group also demonstrated all specimens failed by the tendon suture construct pulling past the anchor. This exhibits the failure point to be the fixation of the tendon or suture to the anchor as opposed to the fixation strength of the anchor or breakage of the grasping suture in the tendon. This provides important information about how biceps tenodesis constructs fails.

These findings also illustrate values which are comparable to published values for suprapectroral and subpectoral tenodesis techniques.^{5,9,11–15,17–22} Werner et al.⁵ randomized arthroscopic suprapectoral and open subpectoral biceps tenodesis in 18 matched cadaveric shoulders and demonstrated improved fixation strength in the open subpectoral group. They described implant pullout as a more frequent model of failure in the arthroscopic suprapectoral group. When this result is carefully examined, the difference may have been correlated with the bone quality in the metaphyseal region compared to the diaphysis region. This lends an important implication, as utilizing the bone at the superior aspect of the biceps grove for fixation may theoretically help avoid this type of failure. This was true in our data set as anchor pullout was not appreciated in any of the specimens. Thus, by demonstrating the values in this study to be similar to established values and by providing a construct which did not demonstrate anchor pullout, the inlay and onlay techniques at the superior aspect of the biceps grove were both demonstrated to be biomechanically stable enough to be considered for clinical application.

As with many tenodesis techniques, the treating surgeon has the option of using an arthroscopic or an open approach. Arthroscopic biceps tenodesis at the articular margin has been shown to be a reliable clinical technique with a low revision rate using an interference screw technique, and a tenodesis at the superior aspect of the biceps groove may have a distinct advantage when performed arthroscopically.²³ The superior aspect of the biceps can easily be reached through standard anterior and lateral portal sites. This may decrease the number of incisional sites necessary during surgery. In addition, by working in the space at the top of the groove, the treating surgeon does not need to perform the additional dissection needed for a suprapectoral or subpectoral tenodesis, thus decreasing morbidity. Finally, the onlay fixation may even offer a more distinct advantage, as the onlay technique can be performed with the biceps still intact. By then releasing the tendon after the fixation has occurred, accurate length–tension relationships can be assured.

Of note, there are several limitations to this study. The sample size was small. However, with respect to using a small sample size, the average strength of the constructs were similar to standards published in the literature. Another limitation is the fact that the techniques were performed as an open procedure and not arthroscopically. The transition to performing the techniques arthroscopically may add additional technical hurdles, possibly confounding the results. The model is also a limitation. Though this model demonstrated a single force to failure, failure in the clinical setting may also occur by cyclic loading. Finally, the right and left side distribution was not equal between the matched pair. As the samples were matched pairs, we do not believe this altered the biomechanical testing.

This study indicates that the ultimate load strength of a biceps tenodesis at the superior aspect of the biceps groove is similar for an onlay and an inlay technique. In addition, the load values were similar to those published for suprapectoral and subpectoral biceps tenodesis. Thus, the treating surgeon may consider the onlay and inlay techniques as viable options for biceps tenodesis procedures. In addition, the utilization of a proximal tenodesis site has the added advantage of avoiding the morbidity associated with an additional incision frequently needed in suprapectoral and subpectoral techniques. High-level clinical trials are needed to further compare a tenodesis at the superior aspect of the biceps grove to suprapectoral and subpectoral techniques.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Bradford O Parsons, MD is a consultant for Arthrex and has royalties from Arthrex.

Ethical Review and Patient Consent

All of the authors certify that all investigations were conducted in conformity with ethical principles of research. Patient consent was not sought or required as this was a cadaver biomechanics study.