Biomechanical comparison of 3 latissimus dorsi transfer sites for reverse total shoulder arthroplasty in the absence of teres minor

Morphological Analysis of the Latissimus Dorsi Tendon Insertion: Implications for Optimizing Tendon Transfer Surgeries in Rotator Cuff Repair

Latissimus dorsi (LD) tendon transfer is widely used to treat irreparable rotator cuff tears, particularly in cases with posterosuperior and anterosuperior tear patterns. We conducted a comprehensive anatomical analysis of the attachment of the LD tendon to the humerus, focusing on its morphological patterns and morphometric features, which are critical for optimizing the surgery. Dissection of 32 LD tendons in 16 Korean cadavers revealed three insertion patterns: fully combined (40.6%), partially combined (34.4%), and fully separated (25.0%). The mean width, length, and thickness of the tendons were 48.4, 56.2, and 6.2 mm, respectively. There were significant asymmetries in tendon dimensions. There were also tendinous slips connecting the LD tendon to the triceps tendon, adjacent brachial fascia, coracoid process, and anterior joint capsule of the shoulder in nine specimens, emphasizing the anatomical variability relevant to surgical planning. These findings provide insights for determining surgical approaches on the basis of patient anatomy, and whether to use LD transfer alone or combined LD and teres major transfers. Understanding the anatomical variations will help to make interventions more precise, which in turn should enhance the efficacy of tendon transfer procedures and improve functional outcomes for patients with complex shoulder pathologies.

Tendon transfers in reverse total shoulder arthroplasty: A systematic review and descriptive synthesis of biomechanical studies

BACKGROUND

The role of tendon transfer and ideal insertion sites to improve axial rotation in reverse total shoulder arthroplasty (RTSA) is debated. We systematically reviewed the available biomechanical evidence to elucidate the ideal tendon transfer and insertion sites for restoration of external and internal rotation in the setting of RTSA and the influence of implant lateralization.

PATIENTS AND METHODS

We queried the PubMed/MEDLINE, Embase, Web of Science, and Cochrane databases to identify biomechanical studies examining the application of tendon transfer to augment shoulder external or internal rotation range of motion in the setting of concomitant RTSA. A descriptive synthesis of six included articles was conducted to elucidate trends in the literature.

RESULTS

Biomechanics literature demonstrates that increasing humeral-sided lateralization optimized tendon transfers performed for both ER and IR. The optimal latissimus dorsi (LD) transfer site for ER is posterior to the greater tuberosity (adjacent to the teres minor insertion); however, LD transfer to this site results in greater tendon excursion compared to posterodistal insertion site. In a small series with nearly 7-year mean follow-up, the LD transfer demonstrated longevity with all 10 shoulders having>50% ER strength compared to the contralateral native shoulder and a negative Hornblower's at latest follow-up; however, reduced electromyography activity of the transferred LD compared to the native contralateral side was noted. One study found that transfer of the pectoralis major has the greatest potential to restore IR in the setting of lateralized humerus RTSA.

CONCLUSION

To restore ER, LD transfer posterior on the greater tuberosity provides optimal biomechanics with functional longevity. The pectoralis major has the greatest potential to restore IR. Future clinical investigation applying the biomechanical principles summarized herein is needed to substantiate the role of tendon transfer in the modern era of lateralized RTSA.

LEVEL OF EVIDENCE

IV; systematic review.

How important is the teres minor in reverse total shoulder arthroplasty combined with latissimus dorsi transfer?

BACKGROUND

The utility of latissimus dorsi (LD) transfer combined with reverse total shoulder arthroplasty to restore external rotation (ER) strength is clinically well-established, but studies directly comparing LD and intact teres minor (TM) strength are lacking. Also, variations in eccentricity in the glenoid components have been under-estimated.

METHODS

We used 8 fresh-frozen cadaveric shoulders in this study. LD transfer to the posterolateral aspect of the greater tuberosity was simulated using a cable pulley system. We explored 6 possible conditions: massive rotator cuff tears (RCTs) (supraspinatus and infraspinatus tears), massive RCTs with TM tears, massive RCTs with TM tears and LD transfer, and all 3 conditions complicated by concentric and eccentric glenoid components. We measured the impingement-free range of motion, the ER torque (N∗m), the maximum abduction angle on successive loading of the middle deltoid (the abduction capacities), and the anterior dislocation forces.

RESULTS

Use of an eccentric glenosphere was associated with greater impingement-free range of motion in all directions, but the differences in ER strength, abduction capability, and anterior dislocation force compared with a concentric design were not significant. LD transfer with TM tears showed significantly greater ER strength than massive RCTs condition at 30° (P < .05) and 60° (P < .05) of abduction. TM tears, with or without LD transfer, had less anterior stability than an intact TM (P < .05). Massive RCTs combined with TM tears tended to be associated with an increased abduction angle under the same deltoid load across all tested loads, revealing the key role played by the TM in joint stability and ER.

CONCLUSIONS

LD transfer enhanced ER abduction strength in the absence of an intact TM, in contrast to a massive RCT with an intact TM. The TM was found to play a significant role in stability. Greater range of motion in all directions was achieved with an eccentric rather than with a concentric glenosphere.

Latissimus dorsi tendon transfer and reverse shoulder arthroplasty: restoring mechanical advantage by transfer posterior to the long head of the triceps tendon

BACKGROUND

Patients undergoing reverse total shoulder arthroplasty (rTSA) for rotator cuff arthropathy may present with an external rotation (ER) lag due to posterior rotator cuff insufficiency. As a result, the addition of a latissimus dorsi (LD) tendon transfer in combination with rTSA has become increasingly utilized. Initial descriptions of LD tendon transfer involved rerouting of the LD tendon posterior to the long head of the triceps tendon. However, more recent techniques involve rerouting the LD tendon anterior to the long head of the triceps tendon via the deltopectoral approach utilized for rTSA. The purpose of this cadaveric study was to assess the biomechanical effect on ER force of LD tendon transfer anterior vs. posterior to the long head of the triceps tendon in combination with rTSA.

METHODS

Eight fresh frozen cadaveric shoulders were utilized. A shoulder fellowship trained orthopedic surgeon performed rTSA in each specimen. The rotator cuff tendon attachments were cut to simulate a massive rotator cuff tear. The LD tendon was transferred to the greater tuberosity first anterior to the long head of the triceps, and then posterior to the long head of the triceps. The specimens underwent biomechanical testing for each condition using an established cadaveric shoulder simulator with 6 degrees of freedom for glenohumeral joint motion.

RESULTS

Both anterior and posterior LD tendon transfers successfully achieved ER of the humerus when force was applied to the LD tendon. Posterior LD tendon transfer resulted in less required force to achieve ER of the arm throughout range of motion compared to anterior LD tendon transfer (33.4 N vs. 48.6 N, P < .001), which was maintained irrespective of glenohumeral abduction angle. Loading of the long head of the triceps tendon was associated with significantly increased force required for generation of ER only in the anterior LD tendon transfer condition (48.6 N loaded vs. 39.4 N unloaded; P < .001).

CONCLUSION

LD tendon transfer posterior to the long head of the triceps resulted in more efficient humeral ER movements in the setting of rTSA, irrespective of degree of shoulder abduction. Our results also demonstrate that long head of the triceps tension results in decreased efficiency of the LD tendon transfer when performed anterior to the long head of the triceps. While technically more difficult, transfer of the LD tendon posterior to the long head of the triceps provides a mechanical advantage that may improve clinical outcomes in patients with rTSA lacking ER.

Insertion sites of latissimus dorsi tendon transfer performed during reverse shoulder arthroplasty: A systematic review and meta-analysis

BACKGROUND

Reverse shoulder arthroplasty (RSA) with concurrent latissimus dorsi transfer (LDT) is a potential treatment option for restoration of external rotation (ER). Biomechanical studies have emphasized the importance of the insertion site location for achieving optimal outcomes. In this systematic review and meta-analysis, we aimed to describe what insertion sites for LDT are utilized during concomitant RSA and their associated clinical outcomes.

METHODS

A systematic review and meta-analysis were performed per PRISMA guidelines. We queried PubMed/MEDLINE, Embase, Web of Science, and Cochrane databases to identify articles reporting on patients who received RSA with LDT to restore ER and specified the site of tendon transfer insertion on the humerus. We first describe reported insertion sites in the literature. Secondarily, we present preoperative and postoperative range of motion and Constant score for different insertion sites as well as reported complications.

RESULTS

Sixteen studies, analyzed as 19 separate cohorts (by insertion site and tendon-transfer), reporting on 264 RSAs with LDT (weighted mean age 66 years, follow-up 39 months, 61% female) were evaluated. Of these, 143 (54%) included a concomitant teres major transfer (LDT/TMT) and 121 (46%) were LDT-only. Fourteen cohorts (14/19, 74%) reported insertion at the posterolateral aspect of the greater tuberosity, four cohorts (4/19, 21%) reported insertion site at the lateral bicipital groove, and one cohort (1/19, 5%) reported separate LDT and TMT with insertion of the TMT to the posterolateral aspect of the greater tuberosity and LDT to the lateral bicipital groove. Meta-analysis revealed no differences in range of motion or Constant score based on humeral insertion site or whether the LDT was transferred alone or with TMT. Leading complications included dislocation, followed by infection and neuropraxia. No discernible correlation was observed between postoperative outcomes and the strategies employed for tendon transfer, prosthesis design, or subscapularis management.

CONCLUSION

The posterolateral aspect of the greater tuberosity was the most-utilized insertion site for LDT performed with RSA. However, in the current clinical literature, LDT with or without concomitant TMT result in similar postoperative ROM and Constant score regardless of insertion site. Analysis of various proposed transfer sites reinforce the ability of LDT with RSA to restore both FE and ER in patients with preoperative active elevation and external rotation loss. Meta-analysis revealed significant improvements in range of motion and Constant score regardless of humeral insertion site or whether the LDT was transferred alone or with TMT, although future studies are needed to determine whether an ideal tendon transfer technique exists.

LEVEL OF EVIDENCE

IV.