Isolated adductor longus avulsion in a young semi‐professional football player: Imaging contribution and therapeutic considerations

Adductor longus injuries are usually observed at the proximal musculo‐tendinous junction, but isolated tendinous ruptures (i.e., avulsion) at the origin on the pubic bone are uncommon. In this article, we report a new case of isolated adductor longus avulsion that occurred in a young athlete and was treated with conservative therapy. An 18 years old semi‐professional football player, in the attempt to reach the ball with his right leg, reported acute pain and functional limitation in his left adductor area. Clinical examination showed tenderness on palpation associated with mild swelling. Manual strength testing of adductor muscles showed weakness and elicited moderate pain in the proximal groin region near the pubic bone. The diagnostic evaluations (ultrasound [3–14 MHz linear probe] and magnetic resonance imaging [1.5 Tesla magnetic field]), performed a few days after the event, showed a complete isolated avulsion of the proximal adductor longus tendon associated with a fluid collection, with a gap of about 9.5 mm from its insertion on the pubic bone. Degenerative alterations (sub‐chondral sclerosis, bone edema, erosions, cortical irregularities, calcifications) were found. These findings were crucial in the treatment choice because conservative management is suggested when the gap is below 1 cm and when no important displacement of proximal torn tendon's end at dynamic ultrasound is appreciated. A structured rehabilitation protocol was implemented, allowing the player to come back to his full athletic activity after 146 days. Return to play was allowed when several subjective and objective parameters were fully satisfied (full hip range of motion, pain‐free football‐specific activities, less than a 5%–10% difference in hip adduction strength between the injured and uninjured legs, advanced anatomical healing of the adductor longus tendon seen on diagnostic exams, and Hip And Groin Outcome Score [HAGOS] scores similar to baseline data). This case report emphasizes the importance of diagnostic imaging and clinical assessments in the management of an adductor longus avulsion with short retraction (about 1 cm). Both imaging techniques are non‐invasive and without risks, allow contra‐lateral examination and may guide in the treatment choice; moreover, they significantly influence the post‐care approach by enabling to fine‐tune a safe return to full athletic activity with minor re‐injury rate. While US can be used as primary imaging modality, MRI offers a higher level of accuracy.

examination showed tenderness on palpation associated with mild swelling. Manual strength testing of adductor muscles showed weakness and elicited moderate pain in the proximal groin region near the pubic bone. The diagnostic evaluations (ultrasound [3][4][5][6][7][8][9][10][11][12][13][14] linear probe] and magnetic resonance imaging [1.5 Tesla magnetic field]), performed a few days after the event, showed a complete isolated avulsion of the proximal adductor longus tendon associated with a fluid collection, with a gap of about 9.5 mm from its insertion on the pubic bone. Degenerative alterations (sub-chondral sclerosis, bone edema, erosions, cortical irregularities, calcifications) were found. These findings were crucial in the treatment choice because conservative management is suggested when the gap is below 1 cm and when no important displacement of proximal torn tendon's end at dynamic ultrasound is appreciated. A structured rehabilitation protocol was implemented, allowing the player to come back to his full athletic activity after 146 days. Return to play was allowed when several subjective and objective parameters were fully satisfied (full hip range of motion, pain-free football-specific activities, less than a 5%-10% difference in hip adduction strength between the injured and uninjured legs, advanced anatomical healing of the adductor longus tendon seen on diagnostic exams, and Hip And Groin Outcome Score [HAGOS] scores similar to baseline data). This case report emphasizes the importance of diagnostic imaging and clinical assessments in the management of an adductor longus avulsion with short retraction (about 1 cm). Both imaging techniques are non-invasive and without risks, allow contra-lateral examination and may guide in the treatment choice; moreover,

| INTRODUCTION
The adductor longus (AL) is an uni-articular muscle that originates from the anterior aspect of the pubic bone, at the angle between the pubic crest and the symphysis. The muscle fibers expand into a broad fleshy belly before inserting into the linea aspera of the femur via an aponeurosis. 1,2 The fibrocartilage footprint of the muscle appears triangular on sagittal views and measures approximately 2.5 Â 1.5 cm; it exhibits the classical four zones from a histological point of view. 3 Cadaveric studies have shown that the attachment of the AL is composed of both tendon and muscle fibers on the anterior and posterior (and often lateral) surfaces, respectively. 2 The posterior branch of the obturator nerve, arising from the second to fourth lumbar nerve roots, primarily innervates the AL, with a minor contribution from the tibial portion of the sciatic nerve. 4 In addition to stabilizing the pelvis along with the muscles of the lower abdomen, the AL is involved in the adduction, flexion, and internal rotation of the hip. 5,6 Electromyographic studies have shown minimal AL activity during sprinting, suggesting that other muscles may support this function. 5,7 Adductor injuries are usually observed at the proximal musculotendinous junction, but tendinous ruptures at the origin on the pubic bone, known as avulsions, are uncommon. 8 These injuries can occur in isolation or with associated lesions of the pyramidal and/or pectineus muscles or anterior pubic ligament, forming the so-called pyramidalisanterior pubic ligament-AL complex (PLAC). 9 In football (also called soccer in the United States), these lesions are commonly observed (about 23% of the muscle injuries) in middleaged athletes (22-30 years old) who engage in activities that require strenuous and vigorous movements, particularly in a position of wide hip adduction with extension and internal rotation (kicking, shooting, sprinting, and change of direction). This can cause a powerful adductors eccentric contraction and may result in tendon avulsion. 1 The clinical picture (acute onset of symptoms, sharp pain, tightness, "snap" or "pop" sensation, stop playing) is suggestive of an AL avulsion. Pain at palpation and a gap at the injury site associated with reduced hip range of motion (ROM) and strength, compared to the opposite side, are frequently detected; an hematoma in the pubic and proximal medial thigh could be observed later.
Ultrasound (US) and magnetic resonance imaging (MRI) can be used to detect tendinous avulsion. 10,11 A retracted AL tendon stump located at the proximal insertion near the pubic bone, associated with a fluid collection (sero-hematoma), is usually seen. 10,11 Among the advantages of both diagnostic techniques (not invasive, no risk of radiations, contra-lateral examination), US can be used as The optimal management of a complete proximal AL tear is controversial and challenging, especially in the athletic population. 12 The surgical option is considered mandatory when there is a retraction of more than 3 cm between the AL and pubic bone, or when other structures are damaged (e.g., PLAC structures). 13 Conversely, conservative therapy is preferred when the AL tendon's torn end is less retracted. 14 However, there are gray zones (when the size of retraction is between 2 and 3 cm, when there is a high functional request, or when there is significant loss of adductor strength), where the decision is difficult and depends on the clinician's experience. Functional outcomes appear to be good with both treatments, with different recovery times and return-to-play (RTP) between the two options (from 6 to 13 and 12 to 21 weeks with conservative and surgical options, respectively). 12 However, it should be noted that the criteria used for RTP are often subjective and generic, some lacking objective measures.
Considering the limited number of studies on this topic, the aim of this report is to describe a new case of isolated AL avulsion that occurred in a very young (18 years old) semi-professional player and was treated with conservative therapy. Serial diagnostic (US and MRI) and objective (strength measurements) evaluations were carried out to monitor the muscle-tendon-bone healing process before RTP. Describing this case provides an opportunity to discuss several aspects of this uncommon injury, which was carefully monitored with imaging and objective evaluations during the entire rehabilitation period.

| CASE REPORT
This case report is a retrospective review of a clinical record and diagnostic images. Informed written consent was obtained from the subject described in this article.
An 18-year-old semi-professional football player (contact sport with almost five training sessions plus one official game every week; increased risk of injury to the high demanding physical activity requested) experienced acute pain in his left adductor area during the last few minutes of an official game. The injury occurred when he was pushed from the side by a striker while attempting to defend. The player tried to maintain balance and reach the ball with his right leg, but all his weight shifted onto his left leg due to the push. Although the player did not feel any "snap" or "pop" sound in the left adductor region, he was unable to continue playing.
It is worth noting that the player had reported mild pain in the groin-pubic area for a month before the injury, which was treated conservatively according to Holmich et al. protocol 15  The player's initial treatment consisted of the PRICE protocol (protection, rest, ice, compression, and elevation). Weight-bearing was allowed as tolerated in uni-directional movements, and no cast or brace was used. In case of pain, the patient was advised to take analgesic drugs like paracetamol (1000 mg). Following the diagnosis, a structured and supervised rehabilitation protocol was started. The rehabilitation plan was based on standardized criteria and, to ensure a safe recovery, progression to the next level was allowed only when the preceding activities were reported to be pain-free. It consisted of three phases.
In the first phase (0-25 days after injury), the focus was on hip ROM and isometric exercises in standing, sitting, and lying positions.
The exercises were designed to be pain-tolerant and the resistance was gradually increased. Core stability exercises and additional nongroin exercises targeting other muscle groups (hip abductors, extensors, hamstrings, and calves) were also prescribed.  I G U R E 1 US images of complete AL avulsion occurred in a semi-professional football player. After 48 hours from the injury (panel A, transverse; B, longitudinal scan), a complete AL tear is observed. At the site of lesion (*) an anechoic area (sero-hematoma) can be seen. ATs appear thickened and irregularly hypo-echoic. Calcifications (^) into the ATs and few signals at Color Doppler vascularization (+1), are also detected. In panel C (transverse) and D (longitudinal scan), at day 14, the sero-hematoma is clearly depicted and vascularization is appreciated. AddMs, adductor muscles; AL, adductor longus; ATs, adductor tendons; P, pubic bone.
F I G U R E 2 MRI images of complete left AL lesion (STIR, PD fat sat, and T2 TSE images). After 3 days, in panel A (coronal), B (axial), and C (sagittal), a complete avulsion of AL tendon (yellow circle) from the P can be observed; at the site of lesion a fluid collection (hyper-intense area), attributable to a sero-hematoma, is present (*). Proximal portion (white arrow) of AL tendon is retracted. Inter-fibrillar edema (hyper-intense areas) can be appreciated in the surrounding adductor muscles (B). AL, adductor longus; P, pubic bone. un-injured side were determined 2 weeks after the injury and were used as a reference for monitoring the loss and recovery of hip muscle strength. The average force for the right and left leg was 100 and 74 N/m, respectively, resulting in an asymmetry of 28.3%. During the entire rehabilitation period, the patient underwent US and MRI evaluations at 2 and 4 months after the injury to monitor the anatomical healing of the tendon. The Copenhagen Hip And Groin Outcome Score (HAGOS) questionnaire was also collected as a measure of selfreported disability at the time of injury and before RTP (defined as the time the player could resume his sport's activity with a minimum risk of re-injury).
RPT was fixed according to the following parameters: full hip ROM without pain, pain-free football specific activities with no limitations or worsening of symptoms the following day, less than a 5-10% difference in hip adduction strength between the injured and un-injured legs, advanced anatomical healing of the AL tendon seen on diagnostic exams (US and MRI), and HAGOS scores similar to baseline data. By day 115, the HAGOS score had fully recovered to pre-injury levels (data collected in July, before the beginning of the competitive season: 100% vs. 99.4%), indicating that the player's ability to participate in sport activity had been fully restored.
Even it was not calculated, a positive correlation between objective and subjective parameters (strength, imaging, and HAGOS score) F I G U R E 3 US follow-up of AL tendon avulsion. After 84 days (panel A, transverse; B, longitudinal scan), the anechoic area consistent with serohematoma is significantly reduced (yellow circle) but still present. Some calcific deposits (^) can be appreciated into the ATs. Color Doppler evaluation showed only few flow signals into the ATs (B). At day 118 (panel C, transverse; D, longitudinal scan), US imaging shows advanced healing process. In particular, ATs are thickened and hypo-echoic while, in the previous area of injury, no interruption of the fibrillar tendon pattern can be observed. AddMs, adductor muscles; ATs, adductor tendons; P, pubic bone. was probably present as at every follow-up time these variables improved accordingly.
After considering all objective and subjective parameters, the player gradually resumed specific athletic preparation with the team from day 120 and was able to come back to full activity after 146 days. 16

| DISCUSSION
This article presents a new case of isolated AL avulsion in a young player who was treated with conservative therapy. While the diagnosis of AL avulsion is relatively straightforward, the optimal management of a complete tear can be controversial. Indeed, AL can be treated with both conservative and operative strategies with good clinical results. In our case, we decided to follow a conservative protocol based on several anatomical, imaging, and outcome measures.
First, after 48 hours (acute phase), we observed a mean retraction of the tendon stump of about 10 mm, which is below the cut-off measures suggested for surgery in the literature (>2-3 cm). 15,17 Indeed, a functional sufficient reattachment of a ruptured tendon to its proximal origin after conservative treatment can be observed when the mean retraction is less than 2 cm. 18 This information was obtained with both the imaging modalities used. However, compared to US, MRI offered an higher level of accuracy in measuring the tendinous gap and provided additional information regarding the quality of the surrounding tissues (tendons, muscles, bone) which may guide in the treatment choice. On the other hand, US was used as primary imaging modality and allowed a dynamic evaluation of the tendon involved which showed minor displacement.
In accordance in our case (at the final follow-up, in the chronic phase), US and MRI evaluations showed that the tendinous gap was filled with scar tissue and extended over a larger area on the adjacent soft tissues around the tendon (suggestive of advanced healing process) but was not just by magic tendinous reattachment to the osseus area. Moreover, no major atrophy (similar AL muscle size between sides), as a result of injury and rehabilitation, was detected. These findings (associated with a reduced sero-hematoma and pubic alterations) suggest that healing was ongoing and that the residual AL did not allow tendon retraction but favored scar tissue formation. However, the mechanical properties of the "neo-tendon" were not tested.
In this case, the use of diagnostic images was fundamental as it provide an objective evaluation of the healing process during the whole rehabilitative program.
F I G U R E 4 Control MRI (STIR and PD fat sat images) of AL tendon avulsion. At day 92 (panel A, coronal; B, axial) MRI images, compared to Figure 2, demonstrate a reduced sero-hematoma at the site of injury (yellow circle and *). After 120 days from the injury (panel C, coronal; D, axial), an advanced healing process of AL tendon can be appreciated. Fibrinous scar tissue inside the injured area, associated with mild surrounding edema, is observed. AL, adductor longus; P, pubic bone.
Second, we considered that the conservative treatment usually provides early RTP at the same pre-injury level with no additional risk of recurrence. Comparative studies have shown that athletes undergoing a conservative approach experience a faster recovery compared to those undergoing surgical re-attachment (3-12 vs. 10-16 weeks), 8,12,15 although the surgical group was composed of patients with more severe injuries. However, in our case, the player resumed sport activity after 16 weeks (a longer time compared to other cases where conservative strategies were used), as we waited that all RTP criteria were fully satisfied (subjective and objective measures). According to Pezzotta et al., degenerative changes and bone edema at the pubic bone were present and probably delayed RTP. 19 The third consideration was the potential risk associated with surgery that could be avoided through a non-operative approach. Among the complications related to surgery itself (dehiscence, infection, etc), the development of postoperative adhesions (scar tissue) as well as suture anchors in the pubic bone would cause complaints in this sensitive area, which could hinder RTP, particularly in professional athletes. 12,18 Finally, from an anatomical perspective, we considered that other muscles (adductor brevis, adductor magnus, and pectineus) can support the AL for the same functional movements. Indeed, an electromyography study by Mann et al. 7 revealed minimal activity of AL during sprinting, indicating that other muscles may compensate for its function. Compared to bi-articular muscles (e.g., proximal rectus femoris and proximal hamstrings), which require surgical repair, AL is uni-articular and can likely heal at its anatomical origin if treated conservatively. 20 Therefore, a full anatomical re-approximation of AL may not be critical for high-level athletic performance.
In summary, the conservative option was preferred because the AL avulsion was isolated, the gap between the stumps was minimal, the recovery time was presumably lower, and the functional role of AL was limited.
It is worth noting that in some cases the conservative treatment may not fully restore normal anatomy or allow a complete tendon healing, which may result in functional deficits (decreased adductor muscle strength and activity), as seen in patients with chronic groin pain who underwent tenotomy. 21 However, this was not the case for our player, who at the end of the rehabilitation protocol (day 120), demonstrated full hip ROM, pain-free football-specific activities, no significant hip adduction strength difference in flexion and extension between legs, and no subjective functional limitations (HAGOS score). Ultimately, the player was able to resume sport activities at the same pre-injury level.
This case report highlights the successful conservative treatment of an isolated AL avulsion with short retraction and emphasizes the importance of diagnostic imaging evaluation and of a structured rehabilitation protocol focused on hip adductor function and eccentric strength capacity to facilitate a safe return to full athletic activity.
Diagnostic instrumental assessments should be performed throughout the rehabilitation process, including the use of US and MRI to evaluate anatomical healing. Indeed, both imaging techniques (non-invasive, no risk of radiations, possible contra-lateral examination, dynamic study) may guide in the treatment choice (gap evaluation and quality of surrounding tissues) and influence the post-care approach reducing the risks of re-injury rate.
Moreover, an hand-held dynamometry should be used to measure muscle strength recovery more precisely than subjective reports alone (manual muscle testing has been shown to fail the identification of substantial muscle strength deficits). In this regard, it is important to note that even slight strength deficits can impact RTP in athletes. 11 We recommend that all RTP criteria, as outlined in this report, are met before allowing the athlete to resume activity and to prevent the risk of recurrence. The observation that our player returned to pre-injury level without any complaints serves as evidence of the effectiveness of conservative treatment. Additionally, it is worth mentioning that athletes should not ignore mild symptoms as they can increase the risk of a future groin injury by five-fold, even if they do not always affect performance or result in rupture.