Surgical release for lacertus syndrome in a pediatric patient: A case report and review of the literature

INTRODUCTION

The lacertus fibrosus is a fibrous band located slightly distal to the elbow joint. As illustrated in Figure 1, adapted from Al-Hashimi et al.^[1] It can trap the median nerve, resulting in lacertus syndrome (LS), a compressive neuropathy of the median nerve. First described by Seyffarth in 1951^[2] as part of the broader pronator syndrome, LS is now recognized as a distinct clinical entity resulting from focal compression at the level of the lacertus fibrosus.^[3] Clinical presentations vary, ranging from isolated motor symptoms to combined motor and sensory deficits.^[4] Patients typically present with forearm pain, fatigue, and hand weakness, particularly involving the flexor digitorum profundus of the second digit (FDP2), flexor pollicis longus (FPL), and flexor carpi radialis (FCR), as well as occasional sensory disturbances in the median nerve territory.^[4]

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Figure 1:

Illustration of the lacertus fibrosus sheath (drawn by the author [RMA]).

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This condition is often underdiagnosed due to its symptomatic overlap with carpal tunnel syndrome (CTS). The “double-crush” hypothesis, introduced by Upton and McComas in 1973,^[5] suggests that compression at multiple sites along a nerve can intensify symptoms. In a study of 275 upper limbs, 78% showed combined LS and CTS, while isolated LS and CTS were observed in 5% and 17% of cases, respectively. This indicates that LS is more commonly part of a double-crush syndrome.^[5,6] In addition, 12.7% of patients who underwent lacertus release had previously undergone unsuccessful carpal tunnel surgery, underscoring the need to evaluate for proximal compression in unresolved cases.^[6] A retrospective study emphasized the role of occupational and recreational factors, such as sports involving repetitive forearm motion and manual work like dentistry or surgery, in predisposing individuals to LS.^[7] Demographic findings vary: Hagert et al.^[6] reported no gender difference while Ahmad et al.^[7] reported a 77.4% female predominance. However, both studies showed that the majority of cases were in middle-aged people, usually between the ages of 38^[7] and 47.^[6]

Clinically, LS can often be identified by a triad of findings: Pain over the lacertus fibrosus, weakness in hand muscles, and a positive scratch collapse test (SCT).^[6] The SCT detects nerve dysfunction by triggering transient muscle inhibition in response to skin stimulation at the suspected entrapment site.^[8] While diagnostic technologies such as ultrasound and magnetic resonance imaging (MRI) can aid with clinical suspicion, providing dynamic and high-resolution soft tissue imaging, their utility remains limited. Similarly, electrodiagnostic studies, such as electromyography (EMG) and nerve conduction studies (NCSs), frequently produce inconsistent results in LS, making a thorough clinical examination the cornerstone of diagnosis.^[6,7] Despite its clinical significance, LS is still underreported globally, with a notable absence of pediatric cases. To fill this knowledge gap, the current report presents the second pediatric case ever reported, following the first case in an 18-year-old patient,^[4] and the first pediatric case reported in Saudi Arabia. The report includes the difficulties in diagnosing the condition, the treatment strategy, and the results after surgery.

CASE REPORT

A 13-year-old right-handed, healthy, active female presented with left-hand numbness, weakness, forearm fatigue with activity, and pain. Physical examination revealed tenderness over the lacertus fibrosus, hand muscle weakness, and a positive SCT. Six sessions of occupational therapy, which included nerve gliding exercises and myofascial release, were part of the initial treatment. The patient’s active lifestyle, which included swimming, gymnastics, and playing the guitar, made complying with activity modifications difficult.

Electrodiagnostic studies, including EMG and NCS, were normal, ruling out ulnar neuropathy and cervical radiculopathy. MRI confirmed median nerve compression under the lacertus fibrosus [Figure 2]. In addition, a diagnostic local injection with 1% lidocaine was performed at the site of the lacertus fibrosus in the clinic, which resulted in immediate symptom relief and further supported the diagnosis. Pre-operative assessments showed significant functional limitations, with QuickDASH scores of 70.45 (mean), 68.75 (Work), and 75 (sports/performing arts). The SF-36 scores showed significant impairment, especially in physical functioning (70%), emotional well-being (28%), and social functioning (12.5%). Surgical release of the lacertus fibrosus resulted in rapid relief of symptoms. The procedure was performed under the wide-awake local-anesthesia no-tourniquet technique. The surgical site was marked on the volar ulnar side of the elbow, and a 2–3 cm transverse incision was made medial to the biceps tendon, approximately two fingerbreadths below the elbow crease. Dissection was carried out with careful protection of the medial antebrachial cutaneous nerve. The pronator fascia was released first, followed by identification of the lacertus aponeurosis, which was divided with blunt scissors through gentle cutting and spreading after meticulous superficial and deep dissection, with particular attention to the underlying median nerve. Complete release was confirmed by palpation with the index finger, both proximally and distally. Intraoperatively, the lacertus fibrosus was found to be taut and thick, and immediate bulging of the muscle with restoration of strength in the affected muscles (FDP2, FPL, and FCR) was observed following release.

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Figure 2:

(a) Sagittal view: The arrow points to the median nerve, which is being compressed anterior to the elbow joint by a low-signal, band-like structure consistent with the lacertus fibrosus. (b) A axial view: The arrow points to the median nerve, which appears flattened and displaced deep to the hypointense fibrous structure (lacertus fibrosus) in the anterior compartment of the forearm, just distal to the elbow.

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Skin closure was achieved with absorbable sutures, and the patient was placed in a soft circular dressing for 3 days, after which unrestricted mobilization was permitted. Recovery was rapid, with full resolution of symptoms, demonstrating the effectiveness of surgical decompression when conservative management fails. Her complete recovery further supported the diagnosis, as persistent or recurrent symptoms would have been expected if an alternative entrapment, such as pronator teres syndrome (PTS), had been the underlying pathology.

Postoperatively, the patient’s pain was completely relieved, with the Visual Analog Scale score improving from 8/10 to 0/10. Grip strength increased from 27.9 kg preoperatively to 37 kg in the affected hand, reaching 48 kg at 3 months. Functional outcomes also improved markedly: QuickDASH scores decreased to 22.72 (mean), 18.75 (work), and 12.5 (sports/performing arts), while short form-36 health survey (SF-36) scores demonstrated significant recovery across all domains. At the final follow-up, 6 months after surgery, the patient remained pain-free, showed sustained functional improvement, and had a negative SCT, indicating continued resolution of symptoms.

DISCUSSION

A review of the seven previously reported cases reveals several consistent trends [Table 1].^[4,9-12] Previous reports have largely involved adult patients, with only a single pediatric case described in an 18-year-old;^[4] our case is the first reported instance of LS in a pediatric Saudi patient. With four females and three males reported, the distribution suggests no clear sex predilection. High levels of hand use, whether occupational or lifestyle-related, were common across cases. Our pediatric patient shared this characteristic, as she had an active lifestyle that included swimming, gymnastics, and playing guitar. This supports the theory that repetitive upper limb activity may contribute to the pathogenesis of the condition, regardless of age.^[7]

While our patient demonstrated the classic features of LS, the recent report by Chlebanowski et al.^[12] highlights how the condition may also manifest with atypical symptoms. Their adult patient presented predominantly with lateral elbow and shoulder pain, a pattern that initially led to misdiagnoses of cervicalgia and tennis elbow. In contrast, our pediatric case resembled the traditional description, reinforcing that LS may follow either a textbook or misleading course. Taken together, these cases illustrate the wide clinical spectrum of LS and underscore the importance of considering proximal median nerve compression in both typical and atypical presentations.

Electrodiagnostic testing was used in most cases; however, the results were inconsistent, with both positive and negative findings reported. MRI was not consistently utilized. These diagnostic inconsistencies highlight the limitations of imaging and NCS in LS, underscoring the continued importance of clinical judgment, particularly in atypical populations. Indeed, as reported in the literature and in our own practice, MRI can contribute to the diagnosis when positive, but it is not essential, as many patients show negative findings despite typical clinical features. In our patient, the MRI revealed flattening of the median nerve beneath the lacertus fibrosus, which reinforced the clinical impression.

Diagnosis in this case was confirmed using the Hagert Triad: First, tenderness over the lacertus fibrosus at the level of the elbow; second, a positive SCT; and finally, the weakness of FPL, FDP2, and FCR. All of which were present in our patient. In addition, a diagnostic local injection at the site of the lacertus fibrosis resulted in immediate symptomatic relief, providing a valuable confirmatory tool.

It is also important to note that while LS is classically a motor-predominant neuropathy, occasional sensory symptoms such as palm numbness may occur. This has been documented in prior series (Ahmad et al.^[7], Hagert et al.^[13]) and reflects the mixed motor and sensory function of the median nerve. Such symptoms can lead to diagnostic confusion with PTS or CTS. In our case, the localization of symptoms, the absence of nocturnal finger numbness typical of CTS, normal EMG/NCS, and the immediate improvement after local injection at the lacertus site all supported LS over PTS or CTS.

In previously reported cases, non-operative management of LS was uniformly unsuccessful, whereas surgical treatment consistently resulted in complete symptom resolution. Our case aligns with this pattern, further supporting surgical decompression as the most reliable and effective intervention. Surgical release of the lacertus fibrosus is typically performed under local or regional anesthesia and has demonstrated consistently favorable outcomes.^[9]

While our findings are consistent with prior reports regarding clinical presentation and treatment response, this case contributes to the literature by documenting LS in a pediatric Saudi patient and by emphasizing the value of thorough clinical assessment supported by appropriate diagnostic tools in establishing an accurate diagnosis.

CONCLUSION

This case shows the diagnostic challenges of LS, a rare and overlooked condition involving median nerve compression. Given the diversity in presentation and limitations of electrodiagnostic investigations, careful clinical examination remains essential, especially in unusual populations. This instance highlights the necessity of increased clinical awareness of LS in all age groups and promotes early surgical intervention in appropriate situations. Further reporting and research are needed to improve recognition and optimize care, particularly in underrepresented populations.