Acute median nerve compression secondary to lacertus fibrosis syndrome following distal biceps tendon reconstruction: a case report

Case presentation

The patient was a 32-year-old male who presented with a complete left distal biceps tendon tear that occurred 6 months prior to presentation while playing basketball; however, he did not initially seek medical care. At the time of presentation, he was complaining of left arm weakness and antecubital discomfort. On physical examination, pain was elicited by resisted supination. There also was an abnormal hook test, with obvious retraction of the distal biceps when compared to the right side. The remainder of the physical examination was unremarkable, and the neurovascular examination was intact. Magnetic resonance imaging (MRI) of the elbow revealed a complete tear of the distal bicep insertion with surrounding edema, retraction of more than 8 cm, and coiling of the tendon upon itself at the myotendinous junction (Fig. 1). Given the chronicity of the tear and the degree of retraction, we discussed the possible need for autograft versus allograft tendon reconstruction. Of the choices, the patient preferred an autograft from his ipsilateral hamstring.

Figure 1.

Preoperative T2 sagittal oblique image showing the retraction and healing of the tendon to itself at the myotendinous junction (arrow).

The patient underwent general anesthesia as well as a supraclavicular block with Bupivacaine combined with bupivacaine liposome injectable suspension (Exparel; Pacira Pharmaceuticals Inc., Parsippany, New Jersey, USA). Intraoperatively, the torn long and short heads of the biceps tendon were retracted and entrapped in scar tissue, consistent with a Type VIA tear.³ The lacertus fibrosus was not clearly identified as the distal biceps tendon was significantly retracted. The lacertus was not resected. We were able to reconstitute length in the long head of the biceps; however, the short head was encased in mature scar tissue without the ability to restore its anatomic length. Therefore, the ipsilateral semitendinosus tendon autograft was harvested for reconstruction. The semitendinosus autograft was repaired to the native tendon by a Pulvertaft weave through the myotendinous junction. The long head of the biceps and the 2 ends of the semitendinosus autograft were then woven together with a running locking whipstitch using a #2 FiberWire suture (Arthrex, Naples, FL, USA). The reconstruction was fixed distally using a single, unicortical tunnel approach secured with a cortical button construct. The surgery was performed through a single, anterior approach.

The patient was placed in a well-padded posterior splint and discharged home. The postoperative block lasted for 72 hours. A multimodal regimen was used including Gabapentin 300 mg each evening, Methocarbamol 500 mg every 8 hours as needed, Acetaminophen 1000 mg every 8 hours as needed, Meloxicam 15 mg once daily, Tramadol 50 mg once daily for break-through pain, and Aspirin 81 mg once daily. Six days after surgery, the patient contacted the office due to left thumb, index, and middle finger pain and numbness, and the dose of gabapentin was increased to 300 mg twice daily. At his postoperative visit, 2 weeks after surgery, he reported continued pain, but intact sensation on physical examination. At that time, he was prescribed a course of oral steroids in addition to the previously noted multimodal pain regimen. He lived 2 hours away and was to return in another 4 weeks. Over the phone, 5 weeks after surgery, the patient continued to report radiating pain to his left thumb, index, and middle fingers despite these interventions. He endorsed that his neurogenic pain was worsening since his last visit. He was brought in for examination which demonstrated a progressive decrease in sensation in the median nerve distribution from his prior examinations. He was noted at that appointment to have a normal distal biceps contour, no pain at the elbow, and full pronation and supination. He did exhibit a positive Tinel’s at the antecubital fossa at the level of the lacertus. An electrodiagnostic study, performed 6 weeks after surgery, revealed left median nerve compression neuropathy at the elbow. MRI demonstrated an intact distal biceps reconstruction with scar tissue and thickening in the region of the lacertus fibrosus (Fig. 2). Because of continued pain and failure to respond to conservative managements, a second surgery was planned for proximal median nerve release considering lacertus fibrosis as the common proximal site of compression neuropathy.

Figure 2.

(A) Sagittal T2 image showing the biceps reconstruction healed. (B) T2 axial image demonstrating edema and denervation in the pronator teres (arrow). (C) Axial image demonstrating increased caliber of the median nerve proximal to the lacertus fiborosus.

During the second surgery, there was noted to be thickened tissue at the level of the lacertus compressing the median nerve. This tissue was completely released (Fig. 3). The median nerve was noted to be compressed under the aponeurosis over a length of 3 cm, but as the nerve was decompressed, it returned to normal caliber both proximally and distally (Fig. 4). The patient admitted immediate relief in the postoperative care unit and continued to improve postoperatively. After 6 months from the second surgery, the patient has returned to weightlifting and continued resolution of his left hand and finger pain. The patient gained full elbow range of motion and biceps force of 5 of 5.

Figure 3.

Scar tissue at the region of the lacertus compressing the medial nerve.

Figure 4.

After release of the lacertus and surrounding scar tissue, the nerve is seen in continuity with equal caliber proximal and distal to the site of compression.

Discussion

Lacertus syndrome is commonly missed and likely underdiagnosed, as its symptoms closely overlap with carpal tunnel syndrome.⁷ Cline et al found that unconscious bias of the clinician favors the diagnosis of carpal tunnel syndrome and some patients with proximal median nerve entrapment are being misdiagnosed with carpal tunnel syndrome.⁵ Additionally, Lalonde suggests that carpal tunnel syndrome and lacertus syndrome can coexist, which further complicates appropriate diagnosis of lacertus syndrome.⁹

The lacertus fibrosus is an aponeurosis originating from the medial border of the distal biceps brachialis tendon. It has an oblique orientation, coursing medially. It overlies the median nerve, brachial artery, and common flexor mass.⁸ A cadaveric study found the lacertus fibrosus in direct contact with the median nerve in about half of the upper extremities examined.² Lacertus syndrome manifests clinically by symptomatic compression of the median nerve under the lacertus fibrosus with both sensory and motor deficits. A positive Tinel’s distal to the lacertus aponeurosis with numbness in the palmar cutaneous nerve distribution and weakness in the muscles innervated by the median nerve distal to the lacertus including the flexor pollicus longus, flexor digitorum profundus, and flexor carpi radialis.

This specific patient developed symptoms of lacertus syndrome after distal biceps tendon reconstruction. He also endorsed early neurogenic symptoms that were at first confused for residual effects from his block, yet became progressive in nature over the ensuing weeks. Amarasooriya et al performed a systematic review of complications after distal biceps tendon repair and found 4.6% major complication rate including 0.3% median nerve injury. They did not specifically report if there was median nerve compression secondary to lacertus fibrosus but noted that 2 cases underwent decompression with resolution of symptoms.¹ Lin et al presented a case of a patient who specifically developed median nerve symptoms after distal biceps repair; however, upon surgical exploration, the median nerve was found to be compressed by the biceps tendon. They found the distal biceps tendon was incorrectly placed between the median and ulnar nerves rather than in its anatomic position, thus leading to compression.¹⁰ Daskalakis et al reported a case of median nerve neuropathy secondary to heterotopic ossification after distal biceps tendon repair.⁶ Seitz et al found evidence of partial rupture of the myotendinous junction of the biceps causing increased tension across the median nerve due to a tethered lacertus fibrosus. They found that a partial tear resulted in a change in the vector of pull of the biceps, resulting in the lacertus fibrosus shifting proximally and medially. This created a secondary compression of the median nerve, specifically as the elbow extended and the forearm pronated.¹¹ This study most closely resembles our patient; however, the lacertus was not clearly identified at the time of biceps reconstruction, yet may have been present but grossly attenuated given the great degree of retraction of the biceps on initial presentation. At the time of the second MRI, there was scar tissue and thickening of the lacertus causing compression of the median nerve (Fig. 5).

Figure 5.

An axial fat-suppressed image 6 weeks after the index surgery shows a thin aponeurosis (green arrow) overlying the median nerve (thin white arrow) which shows slight enlargement of the caliber of the median nerve, measuring up to 7 mm in diameter, with increased signal, consistent with neuritis. As shown, the biceps myotendinous junction with interwoven graft (thick white arrow) is well away from the nerve with no evidence of mass effect or compression to the median nerve.

Given that the patient lived 2 hours away, his management was delayed longer with confirmation from EMG and MRI coming at 6 weeks postoperatively. In the present case, one may argue that the short head of the biceps remained contained in chronic scar tissue may have created a mass effect on the median nerve. This may have been compounded by mass effect with the addition of the Pulvertaft weave of autologous hamstring graft. Certainly, these factors may have contributed to the patient’s symptoms and the more immediate postoperative neurological complaints. However, the postoperative MRI and exploration of the median nerve at surgery showed no evidence of mass effect from the reconstruction on the median nerve. Similarly, there was a noted very thickened aponeurosis across the anterior elbow from the medial epicondyle most consistent tissue in continuity with the lacertus. Once the aponeurosis alone was released with a neurolysis, without any debulking of the reconstruction, the patient’s symptoms immediately improved and ultimately resolved further implicating the lacertus aponeurosis.

Tendon healing consists of 3 overlapping steps: inflammation, proliferation, and finally remodeling. The inflammatory stage takes place during the first 48 hours and then transitions to the proliferative stage from days 7-21, and finally the remodeling stage can last longer than 12 months.⁴ It is unlikely the degree of scar tissue and thickening of the lacertus seen on the second MRI started at the time of the first surgery, but rather at the time of the initial injury. We propose that the lacertus was attenuated yet still with fibers attached to the retracted biceps and was brought over the median nerve at the time of the index surgical reconstruction. Often the senior surgeon will release the lacertus carefully to help regain excursion of a retracted distal biceps. However, with the use of an autologous reconstruction and given the high degree of proximal retraction of the torn tendon, excision of the lacertus which was poorly defined at the index surgery seemed less critical. Similarly, while the senior surgeon has extensive experience with both distal biceps repairs and reconstructions, he has not experienced median nerve compression as a postoperative issue or complication after reconstruction, primary repair, or revision surgery. Therefore, resection of the lacertus in this setting of tendon reconstruction for a chronically torn, retracted tendon was not deemed necessary except in circumspect evaluation of this case.

Conclusion

Although median nerve symptoms have been reported in the literature, there appears to be a lack of literature regarding median nerve symptoms secondary to lacertus fibrosus syndrome after distal biceps repair or reconstruction. This case presents a unique case which demonstrates pathology that should be considered when evaluating patients who are status post distal biceps tendon repair presenting with median nerve symptoms. The authors recommend taking a more aggressive approach to lacertus release or resection in chronic cases in which chronic scar tissue is encountered or significant postoperative swelling is expected.

Disclaimers:

Funding: No funding was disclosed by the authors.

Conflicts of interest: The authors, their immediate families, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

Patient consent: Obtained.