Advancing Recovery by Incorporating Physiological Insights into the Surgical Management of Chronic Proximal Rectus Femoris Tendon Avulsion

Abstract

Background: Tendon lesions affecting the proximal rectus femoris (PRF) muscle represent about 1.5% of hip injuries. Most acute cases are managed conservatively with physiotherapy. There is a lack of consensus regarding surgical intervention for chronic injuries. This article, alongside a literature review, presents a case of anatomical surgical reinsertion for chronic complete avulsion rupture of the PRF tendon. Case Report: A 34-year-old amateur athlete experienced acute inguinal pain from overexertion, with conservative treatment having failed over 3 months. Seven months later, proximal tendon rupture involving both PRF muscle heads was confirmed. An anterior Hueter approach released the tendon from the adhesions and fibrosis. The direct portion was reinserted into the inferior anterior iliac spine, and the reflex portion was reattached to the supraacetabular groove. The patient showed excellent improvement on the modified Harris Hip and Lysholm–Tegner scales. The quadriceps muscle force decreased by 20% compared to the contralateral leg at 3 months, reducing to 4% by 12 months. Normal activities resumed after six weeks, and sports resumed after 4 months. Conclusions: The patient experienced significant postoperative improvement, as shown by the enhanced functional scores and muscle force recovery over one year. The success of the anatomical reconstruction in restoring tendon continuity underscores the importance of tendon healing mechanisms, including tissue remodeling and revascularization, in chronic avulsion injuries. This case highlights the efficacy of anatomical reconstruction for chronic PRF tendon avulsion. The literature review offers further insights into treatment options and the physiological basis of recovery for such injuries.

1. Introduction

Understanding the anatomy and physiology of the quadriceps muscle is pivotal in grasping its injury mechanism and optimizing treatment. The rectus femoris muscle, part of the quadriceps group, plays a unique role as it crosses both the hip and knee joints, making it particularly vulnerable to injury during eccentric loading. The straight head of the rectus femoris originates from the anterior lower iliac spine, while the reflected head arises from the upper region of the acetabulum [1,2] (see Figure 1A). Its tendon extends from the distal third of the quadriceps femoris, forming an extensive myotendinous junction before attaching to the superior pole of the patella. The muscle fibers are innervated by branches of the femoral nerve and vascularized by the external circumflex femoral artery and the quadriceps artery. Functionally, the rectus femoris is essential for knee extension and hip flexion.

Physiologically, tendon healing involves complex inflammation, proliferation, and remodeling stages, with vascular and neural supply playing critical roles in regeneration and tissue repair. In rectus femoris tendon injury cases, particularly in the proximal portion, the muscle–tendon unit must undergo remodeling and revascularization to regain strength and function [3,4]. Disruption in these processes, such as in tendon retraction or fibrosis cases, can significantly impair the healing response [5].

Injuries in the proximal portion of the anterior rectus femoris represent approximately 1.5% of hip injuries incurred as a consequence of a sudden and eccentric contraction [6], mainly in adults and young patients during power sports activities such as soccer or rugby with the hip in extension and knee in flexion [1,7,8]. These injuries are predominantly seen in adults and young athletes. Conservative treatment for acute proximal rectus femoris (PRF) injuries focuses on reducing hematoma, managing inflammation, and optimizing muscle–tendon healing, followed by structured rehabilitation to restore normal function and facilitate a return to sports. However, surgical intervention is warranted in cases involving bone avulsion with nonunion, malunion, heterotopic ossification, or tendon retraction greater than 2 cm or as a second-line treatment when conservative methods fail [9].

Chronic PRF lesions, which present unique physiological challenges due to extensive fibrosis and retraction, may also be managed conservatively. However, no consensus exists regarding surgical indications or chronic PRF tendon rupture techniques. Chronic injuries are more likely to require intervention to address the altered tissue mechanics, diminished vascular supply, and impaired healing potential associated with long-standing injuries [10,11].

This article aims to present and assess a case involving anatomical surgical reinsertion for a chronic complete avulsion rupture of the PRF tendon. It also provides a comprehensive literature review, emphasizing the physiological mechanisms underlying tendon healing in chronic cases.

2. Case Presentation

After we obtained institutional review board approval, clinical data were retrospectively retrieved from a prospectively maintained institutional surgical repository comprising a 34-year-old male skier and amateur soccer athlete, who presented with two episodes of inguinal pain after sports activities, was initially evaluated in the emergency department and in another hospital, where he was diagnosed with a ruptured PRF tendon and treated conservatively with rehabilitation, without any improvement after 6 months of treatment. He returned for consultation 7 months after the initial injury, presenting with pain in hip flexion, gait disturbance, and an inability to perform sports activities. Physical examination showed loss of the normal contour of the rectus femoris. This was tender to palpation at the anterior inferior iliac spine (AIIS) level with a tendon gap. When performing hip flexion against resistance, muscle retraction was observed on the distal side. The lesion was confirmed by a Magnetic Resonance Image (MRI) without gadolinium enhancement, with a complete rupture of the proximal insertion of the anterior rectus femoris, with a muscle retraction of 72 mm associated with extensive fibrosis (see Figure 1B,C).

Anatomical surgical reconstruction was performed using an anterior (Hueter) approach with the patient in dorsal decubitus. A longitudinal skin incision was made using the AIIS and fibula head as reference points, protecting the lateral femoral cutaneous nerve away from the surgical field. The rectus femoris was identified by utilizing the interval between the tensor fasciae lata and sartorius, appearing distally retracted with abundant surrounding fibrous scar tissue. At this stage, protecting the surrounding circumflex vessels in the surgical field and exercising extreme caution is essential to avoid iatrogenic injuries to the lateral femoral cutaneous nerve branches. Once the retracted tendon was identified, it was marked with two strands of 2-0 Vicryl sutures, which were used for traction while removing the scar tissue from proximal to distal. Then, the direct portion of the tendon was reinserted into the AIIS, and the reflex portion was fixed into the supraacetabular groove using two 5 mm anchors (5 mm Griphon, MITEK), reinforcing it with a Krackow-type suture (see Figure 2).

The postsurgical rehabilitation protocol was implemented with assisted ambulation with two crutches with proprioceptive load and using an articulated knee orthosis in extension for three weeks. Subsequently, a progressive load was applied to the affected limb for up to four weeks, and a rehabilitation protocol was followed with eccentric exercises with a progressive range of motion and full load from the sixth week. Closed kinetic chain exercises were allowed between the sixth and twelfth weeks (cycling, swimming, and jogging) and subsequent return to playing soccer after 16 weeks. At 3 months post-operation, the patient fully recovered quadriceps strength with knee flexion and extension from 0° to 120°, and the range of hip motion fully recovered.

The patient demonstrated progress at 3, 6, and 12 months according to the modified Harris scale and Lysholm–Tegner scale, with scores increasing from 46 to 84, 88, and 91, and from 50 to 86, 92, and 100, respectively. The maximal muscle force of the quadriceps decreased by 20% compared to the contralateral quadriceps at 3 months, reducing to 4% at the final follow-up compared to the contralateral quadriceps measured with the ActivForce 2 dynamometer^®. (See Figure 3). A control MRI was performed at 6 months, showing the injury’s complete healing (see Figure 4).

3. Discussion

The most relevant finding of the present study is that surgical treatment showed satisfactory postoperative outcomes and a complete return to sports at 4 months in a young patient with moderate-intensity sports activity and a chronic PRF injury with complete tendon avulsion.

The literature review indicated that PRF injury was uncommon and that a consensus on its treatment has yet to be established. One reason for the underdiagnosis of this injury is its challenging clinical diagnosis, which leads to frequent misrecognition and delayed treatment. In this regard, imaging can be a crucial tool for diagnosis (X-rays, ultrasound, and MRI) and analyzing the characteristics of the injury [12]. Specifically, MRI has shown significant diagnostic power in cases of sequelae and chronic injuries, as it can delineate the area of scar tissue in greater detail. Furthermore, it allows for the diagnosis of labral lesions that may be associated with avulsion of the rectus femoris muscle, as in the case of the so-called HALTAR (hip anterosuperior labral tear with avulsion of the rectus femoris lesion) [13].

In the literature review, seven articles analyzed patients with chronic injuries to PRF. Most of these were heterogeneous articles of low-to-medium scientific quality, including case series and clinical cases, where the treated patients were high-performance athletes. Due to the lack of standard guidelines, surgical approaches have varied based on individual surgeons’ preferences, making it challenging to compare functional outcomes. Generally, in the case of chronic injuries, especially for professional athletes, reconstruction with anchors has been preferred over tendon suturing. Lempainen et al. [14] studied five cases of tendon reinsertion. The ruptured rectus femoris stump was reinserted into the anterior inferior iliac spine with one to two suture anchors using simple stitches. All patients returned to their pre-injury level of play (mean follow-up, 2.8 years; range, 1–11 years) (

Table A1. Summary of surgical techniques and post-operative RTP outcomes of the review of the literature.

Author/Year	N° Chronic Patients	Approach	Technique	RTP (months)	Observations/Complications
Hughes [22] (1995)	2 chronic	Not described	1 tenotomy 1 suture	36 18	Athletes amateur
Irmola [18] (2007)	5 overall 2 chronic	SP	Anchor	5 to 10	FCN lesion, hematoma, seroma
Wittstein [19] (2011)	5 chronic	Anterior	Reflex portion tenotomy	7 to 10	Femoral nerve injury
Ueblacker [17] (2014)	4 overall 1 chronic	Not described	Anchor	5 to 10	Elite athletes
Gazi Huri [15] (2014)	1 chronic	Anterior	Suture (polydioxanone)	6	Professional athlete
Lasse Lempainen [14] (2018)	19 overall 5 chronic	Anterior	Anchor	12 to 24	FCN injury
Choufani [7] (2021)	67 overall 41 chronic	37 Hueter 4 SP	23 releases 1 allograft 7 tenotomy 2 screws 6 sutures 2 labral lesion resections	6 to 24	2 LFCN injury 1 hematoma

References: SP: Smith–Petersen. LFCN: lateral femoral cutaneous nerve, RTP: return to play.

). Gazi et al. [10] analyzed a case of a professional soccer player with chronic complete avulsion of the reflected head of the rectus femoris that was reinserted with polydioxanone (PDS) sutures at its footprint. In this case, excellent functional results were achieved within a 24-month follow-up period.

Positive functional results were observed in all reviewed studies (Table A1). There appears to be a notable absence of standardized guidelines, leading to the variability of treatment regarding timing and technique. Nonetheless, surgical reconstruction is emphasized as a valid option for addressing chronic PRF injuries. Choufani et al., 2022, conducted a systematic literature review which showed that, at the moment, it is impossible to define a reference technique due to the absence of comparative or comparable studies [7]. Similarly, there is currently no significant difference in functional outcomes between conservative and surgical treatments, particularly for acute injuries. In this regard, the main distinction lies in the postoperative recovery times, which appear shorter in the case of conservative treatment, even in high-performance athletes. As a result, conservative treatment appears to be the first-line approach, even in cases of bone avulsion achieving optimal results and resuming sports activity in estimated times between 3 and 6 months [15]. Gamradt et al., 2009, published a study in which they reviewed eleven cases of professional athletes with complete rectus femoris avulsion who were treated successfully with conservative measures, with the mean return to play being 69.2 days [16]. Choufani et al., 2022, proposed a threshold for surgical treatment of avulsions greater than 2 cm and 3 months of conservative treatment without clinical functional improvement [7].

In establishing objective criteria to assess the extent of muscle rupture, bone avulsion, the involvement of one or both muscle heads, and the timeline of the injury is crucial. Additionally, measuring muscle retraction is essential for effective surgical planning [14].

The authors’ technique includes the use of anchors to reinsert the tendon anatomically, suturing the partial lesion, or performing a tenotomy of the head of the ruptured tendon without determining the superiority of one technique or another, or establishing an algorithm for decision making [17,18,19].

The primary reported complications were associated with the surgical approach, involving damage to the lateral cutaneous nerve of the thigh, resulting in painful paresthesia and/or hypoesthesia on the anterolateral side of the thigh. This nerve runs adjacent to the anterior inferior iliac spine, and one must be careful not to injure it, especially when planning to extend the surgical approach proximally. General risks related to any surgery should be considered, particularly in cases of abundant fibrotic scar tissue, where bleeding from a potential injury to the circumflex vessels should be considered. No recurrence of rupture was noted in the analysis of the studies examined [14,18,19].

Tendon healing is a complex process involving multiple stages, including inflammation, proliferation, and remodeling. In cases of chronic tendon avulsion, such as the one described here, delayed healing poses unique challenges due to prolonged fibrosis and retraction. The initial inflammatory response, which typically facilitates cellular migration to the injury site, is often insufficient in chronic injuries. This is compounded by the development of scar tissue, which limits vascularization and nutrient delivery to the affected area. Therefore, surgical intervention aims to re-establish continuity between the tendon and bone, enabling the subsequent stages of healing.

The physiological basis for successful tendon reinsertion relies heavily on collagen remodeling and revascularization. Following anatomical reconstruction, fibroblasts play a crucial role in producing new collagen fibers, while angiogenesis supports tissue viability and long-term tendon strength. Recent studies have demonstrated that early mobilization after tendon repair enhances collagen fiber alignment, improving functional outcomes [3]. In chronic cases, the release of adhesions and fibrosis, as performed in this case, further supports improved tissue mechanics by reducing the restriction of movement caused by scar tissue [20]. The case presented highlights the essential role of these physiological mechanisms in achieving successful long-term recovery following surgical intervention.

Anatomical reconstruction in chronic tendon injuries depends on key healing processes like remodeling and revascularization. Recent studies, such as that by Capurro-Soler et al., 2024, report significant functional recovery in gluteus tendon repairs using a double-row technique, with improvements seen in as early as 3 months. These results underscore the importance of biological optimization to support tendon healing in chronic cases, as shown in this proximal rectus femoris repair [21].

The main limitation of this study is its analysis of a single clinical case of tendon reconstruction for chronic detachment of both ends of the rectus femoris muscle. Furthermore, there are few existing studies on chronic injuries, which are often limited to clinical cases with a very small population and insufficient statistical power. Despite this, we have demonstrated that the anatomical reconstruction of both muscle heads yields excellent short-term functional results without recognized international guidelines.

4. Conclusions

Anatomical reinsertion of the proximal rectus femoris (PRF) tendon in chronic injuries has demonstrated excellent functional outcomes, with the patient returning to sports within four months and showing near-complete recovery by the 12-month follow-up. Individualized treatment based on injury characteristics and patient expectations remains crucial. While no consensus exists on surgical versus conservative management, this case supports surgical intervention. Physiological mechanisms such as collagen remodeling, revascularization, and tissue integration at the tendon–bone interface are key to recovery. Further studies are needed to establish treatment guidelines and evaluate long-term outcomes.

5. Clinical Application

The main finding of this case report is the successful anatomical reinsertion of the proximal rectus femoris (PRF) tendon in a chronic injury, demonstrating exceptional functional outcomes. The patient returned to sports within 4 months, with near-complete recovery by the 12-month follow-up. This outcome underscores the effectiveness of surgical intervention in cases of chronic PRF avulsion, adding to the limited literature on operative management for this type of injury.

Strengths of this case report include the detailed documentation of functional recovery, highlighting the role of physiological healing mechanisms such as collagen remodeling, revascularization, and tendon-bone integration. A limitation is the single-case nature, which limits its generalizability and underscores the need for further studies to establish more comprehensive treatment guidelines.

Clinically, this case supports surgical intervention in chronic PRF injuries, especially when conservative treatment fails or tendon retraction exceeds 2 cm. Future directions should include larger studies to refine treatment protocols, assess long-term outcomes, and further clarify the role of individualized surgical approaches for chronic hip tendon injuries.