Injury to the Main Branch of the Saphenous Nerve following Hamstring Tendon Graft Harvesting: A Report of 3 Cases

Abstract

Background:

Hamstring tendon grafts are commonly utilized tendon autografts; however, the harvesting procedure can result in saphenous nerve injury due to its proximity to the semitendinosus and gracilis tendons. Injury to the main branch of the saphenous nerve is a less commonly reported and understood injury during these procedures.

Purpose:

This case report aimed to identify and present cases of iatrogenic injury to the main branch of the saphenous nerve during hamstring tendon graft harvesting.

Methods:

A retrospective chart review of a tertiary-care hospital over the past 10 years was conducted. The search included clinical notes mentioning “saphenous neuropathy, neuralgia or neuritis” and magnetic resonance imaging (MRI) reports indicating saphenous nerve involvement. Patients with a history of a hamstring graft harvesting procedure and radiographically confirmed injury to the main branch of the saphenous nerve were included. Injury characteristics, symptoms, and sequential treatment were evaluated.

Results:

Three cases of iatrogenic injury to the main branch of the saphenous nerve during hamstring graft harvesting were identified. Reported symptoms included pain, paresthesia, numbness, hypersensitivity, swelling, and discoloration. All 3 patients had persistent symptoms despite non-operative treatment and therefore underwent surgical intervention, which involved resection and reconstruction using allograft or burial into adjacent musculature. Postoperatively, 2 of 3 patients demonstrated resolution of symptoms.

Conclusion:

Iatrogenic injury to the main branch of the saphenous nerve is a complication that can occur during hamstring tendon harvesting procedures, leading to severe, persistent symptoms. A better understanding of the mechanism of injury is needed to minimize the risk of iatrogenic injury.

Introduction

Hamstring tendon grafts are one of the most frequently utilized autografts for tendon and ligament reconstructions. These autografts are regularly used in a variety of reconstructive shoulder, elbow, hip, ankle, and knee procedures. Some applications of hamstring tendon grafts include anterior cruciate ligament (ACL), medial collateral ligament (MCL), and ulnar collateral ligament (UCL) reconstruction of the elbow, lateral ligament repair of the ankle, Achilles tendon reconstruction, sternoclavicular joint stabilization, and labral reconstruction of the hip [4,13]. Depending on the indication, hamstring tendon grafts are composed of the gracilis tendon or semitendinosus tendon or both.

Hamstring tendon grafts offer several advantages over other autografts and allografts. One is the harvesting procedure itself. Hamstring tendon graft harvesting is technically straightforward, involves a relatively small incision, and is associated with low donor site morbidity [11,14]. Compared with allografts, hamstring tendon grafts demonstrate earlier engraftment due to decreased inflammatory response, lower rates of graft failure, and have no risk of donor rejection [2,3,14]. In addition, allografts are expensive and availability may be limited. Therefore, hamstring tendon grafts offer a cost and accessibility advantage [2,7,14]. Biomechanically, hamstring tendon grafts have demonstrated superiority to both allografts and other autograft options in ultimate tensile load, stiffness, and cross-sectional area [7,14].

Although hamstring tendon grafts offer numerous advantages, the harvesting procedures are not without risk. The most commonly reported complication is injury to the adjacent saphenous nerve, in particular, injury to the infrapatellar branch [6]. This is explained by the course of the saphenous nerve and the anatomical proximity to the gracilis and semitendinosus tendons.

The saphenous nerve originates from the femoral nerve and enters the adductor canal, coursing medially over the femoral artery [12]. The saphenous nerve then runs parallel to the gracilis on the deep surface of the sartorial fascia [10]. Distally, the saphenous nerve crosses over the gracilis [8,10]. Around the level of the joint line, the saphenous nerve bifurcates into 2 branches, the infrapatellar branch (IPBSN) and the sartorial branch (SBSN) (Fig. 1). The infrapatellar branch courses anteriorly. The sartorial branch is a continuation of the main branch that courses distally on the medial aspect of the knee along with the gracilis and semitendinosus tendons and continues distally along the medial aspect of the lower leg [5].

Fig. 1.

Anatomic diagram of the medial knee: Lateral view highlighting the relationship of the saphenous nerve with the gracilis and semitendinosus.

Given the proximity of the saphenous nerve to the gracilis and semitendinosus, iatrogenic injury during hamstring harvesting graft procedures can occur. The most frequent and least severe consequence of saphenous nerve injury during hamstring graft harvesting procedures is sensory loss, which reportedly occurs in 74% of patients [10]. A recent study by Sanders et al [10] found injury rates for IPBSN, SBSN, and combined IPBSN and SBSN to be 19%, 23%, and 32%, respectively. These injury rates were calculated based upon patient-reported sensory deficits, so no specific data on the site of nerve of injury could be discerned. Other literature reporting main branch or SBSN injury and resulting sensory deficits is sparse.

While sensory disturbances are most common, iatrogenic damage can also cause more severe consequences, such as complex regional pain syndrome (CRPS) [9]. Poehling et al. [9] reported 35 cases of CRPS affecting the knee with demonstrated injury to the IPBSN. However, not all patients in this study had previously undergone a hamstring graft harvesting procedure and no reports of main branch or SBSN injury were included. Focusing specifically at SBSN involvement following hamstring graft harvesting, Betram et al [1] reported a case of saphenous neuralgia following ACL reconstruction with semitendinosus and gracilis autograft. An open revision revealed scar tissue entrapment of both the main branch and IPBSN at the medial joint line, but no evidence of definitive injury.

While the studies mentioned investigated IPBSN and SBSN sensory deficits, IPBSN injury and associated CRPS, and an isolated case of SBSN neuralgia, to our knowledge, no study has addressed a relationship between confirmed main branch or SBSN injury and the resulting consequences. The purpose of this case report is to present 3 cases of confirmed iatrogenic SBSN or main branch injury and the resulting complications.

Methods

A retrospective chart review of patients at a tertiary hospital over the past 10 years was conducted. The search criteria included clinical notes mentioning “saphenous neuropathy, neuralgia, or neuritis” or MRI reports indicating involvement of the saphenous nerve. This search resulted in approximately 1600 patients. Of these patients, only 3 patients had undergone prior hamstring tendon graft harvesting procedures and had radiographically confirmed injury to the main branch of the saphenous nerve. The hamstring tendon graft harvesting procedure was performed by a different surgeon in each of the 3 identified cases. In all 3 cases, both the gracilis and semitendinosus tendons were harvested using standard technique. No further details on the harvesting procedure, such as position of the leg or brand of tendon stripper used, were available. At this particular institution, there are about 800 hamstring graft harvesting procedures performed each year.

Case Report

Case 1

A 26-year-old female underwent a left ACL reconstruction with a semitendinosus and gracilis hamstring autograft. Intraoperatively, a femoral nerve block was performed. The following day she presented with severe pain extending down her medial leg. Symptoms initially improved with pain medication; however, 9 months later, she reported persistent pain, hyperesthesia, and paresthesia from her medial knee along her medial leg to her ankle, which impacted activities of daily living, work, and sleep.

Electromyography (EMG) demonstrated absent saphenous nerve sensory response, suggestive of saphenous nerve injury. Magnetic resonance imaging (MRI) revealed scarring along the saphenous nerve. A high-resolution ultrasound showed a 4 × 3 × 2 mm neuroma of the saphenous nerve as it emerged from the adductor canal, along with segmental thickening and fascicular prominence proximal to the neuroma (Fig. 2). The distal stump could not be visualized due to scarring. A diagnostic ultrasound-guided anesthetic injection of the saphenous nerve provided pain relief for 8 hours.

Fig. 2.

Ultrasound imaging of the nerve injury, demonstrating 4 × 3 × 2 mm neuroma of the saphenous nerve as it emerges from the adductor canal.

Two years after the initial injury and failed non-operative treatment, a neuroma resection and nerve reconstruction with allograft (Axogen, Alachua, FL, USA) was performed. Intraoperatively, abundant scar tissue was noted, and the 2 nerve ends were found terminating in a large neuroma. Immediately postoperatively, the patient continued to have neurogenic pain with hypersensitivity. However, 8 months post operatively, the patient had major improvement in neuroma symptoms, reporting no pain or paresthesia and minimal hyperesthesia at rest. The patient-reported relief of initial symptoms and was pleased with the outcome of the second procedure.

Case 2

A 46-year-old female underwent right ACL reconstruction with a semitendinosus and gracilis hamstring autograft and partial meniscectomy with an ultrasound-guided adductor canal block. At her 2-week postoperative follow-up, she reported severe neurogenic pain, including skin hypesthesia, sharp electrical sensations, paresthesia from her medial knee down the medial leg to her ankle. She also noted hypersensitivity to light touch, clothing, and running water, along with intermittent discoloration, swelling, increased hair growth, and fluctuating temperature. The patient was diagnosed with CRPS type II based on this constellation of symptoms, which interfered with activities of daily living, sleep, and work.

Electromyography revealed an absent left saphenous nerve sensory response. An MRI demonstrated a 10 mm segment of focal saphenous nerve enlargement along the far inferomedial border of the sartorius muscle (Fig. 3). Dense scarring was observed distally, just inferior to the joint line, along with additional scarring of the deep infrapatellar branch. Ultrasound revealed scaring of the saphenous nerve after emerging from the adductor canal with a 4.3-cm segment demonstrating poor visibility of fascicular architecture. An ultrasound-guided anesthetic injection provided temporary relief. Further treatment with a lumbar sympathetic block did not improve symptoms.

Fig. 3.

Magnetic resonance imaging of the nerve injury for case 2. (a) Non-injured saphenous nerve located at distal femur. (b) and (c) Thickened 10 mm segment of the saphenous nerve just distal to knee joint. (d) Scarring of the saphenous nerve along the crural fascia located distal to the knee joint.

One month after the initial injury, a neuroma resection and nerve reconstruction with allograft (Axogen, Alachua, FL, USA) was performed. Intraoperatively, abundant scar tissue was observed with the 2 nerve ends found in continuity within the neuroma (Fig. 4). Postoperatively, the initial neuroma symptoms returned after 2 weeks along with a fluid collection of the proximal medial calf. The source of fluid was inconclusive despite MRI evaluation and was treated with 4 repeated ultrasound-guided aspirations. She also underwent 3 lumbar sympathetic blocks for nerve-related symptoms, which provided decreasing short-term relief. At final follow-up, 18 months after surgery, the patient reported major improvement in pain and resolution of her calf swelling. She reported mild pain and minor numbness and tingling at the medial ankle, corresponding to the distribution of the saphenous nerve.

Fig. 4.

(a) Preoperative marking of the operative site of the injured saphenous nerve along the medial aspect of the lower leg. (b) Intraoperative visualization of the neuroma of the saphenous nerve at the site of injury. (c) Intraoperative imaging of the saphenous nerve reconstruction using nerve allograft.

Case 3

A 44-year-old male underwent right ACL reconstruction with semitendinosus and gracilis autograft and lateral meniscectomy with a guided adductor canal block. Immediately postoperatively, the patient reported burning pain in his leg. Two weeks later, the patient had persistent numbness. At 6 weeks, the patient reported neurogenic symptoms in the medial aspect of his lower leg that increased with weightbearing and palpation. These symptoms were also accompanied by discoloration, hyperesthesia, hyperalgesia, allodynia, and temperature changes of the anteromedial leg. Given these symptoms, the patient was diagnosed with CRPS. These symptoms affected the patient’s activities of daily living, work, and sleep.

Magnetic resonance imaging demonstrated mild hyperintensity of the saphenous nerve within the distal adductor canal with maintained fascicular architecture. Scarring was observed only along the course of the deep infrapatellar nerve. Ultrasound revealed segmental thickening and fascicular prominence of the saphenous approximately at the level of the adductor canal. An ultrasound-guided injection provided 5 hours of symptom reduction. Similarly, a lumbar sympathetic block resulted in diminished pain for 2 days.

Approximately, 6 months after initial injury, the patient underwent saphenous nerve neuroplasty and resection. The saphenous nerve was resected distally in the thigh, capped, and buried deep into the thigh musculature. Two weeks post operatively, the patient had increasing nerve pain. An MRI 6 months after surgery revealed scarring distally along the adductor canal. An EMG demonstrated saphenous nerve conduction distally, despite prior resection, raising suspicion for aberrant, or accessory branch of the saphenous nerve. An ultrasound confirmed 2 distinct branches in the upper inner thigh: a buried posterior branch and a continuous anterior branch. A perineural injection of the anterior branch provided 85% to 90% pain relief temporarily.

A second surgical procedure was performed to resect the saphenous nerve from medial knee to medial ankle. Despite continued treatment, the patient continued to have persistent pain, hypersensitivity, and swelling 3.5 years after initial saphenous nerve injury.

Discussion

As demonstrated by the presented cases, injury to the main branch of the saphenous nerve during hamstring graft harvesting procedures is a challenging and devastating injury. The symptoms following injury interfered significantly with activities of daily living, work, and sleep. However, the first and second cases highlight the symptom relief obtained from surgical intervention of the saphenous nerve.

These 3 cases also highlight the apparent low frequency at which this injury occurs. At our particular institution, about 800 hamstring graft harvesting procedures are performed each year. Given this, the rate of this injury is approximately 3 in 8000. Since this injury to the saphenous nerve is not reported in current literature, neither incidence nor prevalence rates are available. The search and chart review conducted in this study, which revealed only 3 cases, gives an indication of the low prevalence of this complication. While the apparent low prevalence of this injury may be in part due to under-recognition or underreporting of these injuries, our medical record search illustrates the rarity of this injury.

Despite the low prevalence of this injury, the associated consequences are severe enough to warrant a better understanding of the cause of saphenous nerve injury. Understanding the mechanism of injury provides insight on how to minimize risk of injury during hamstring graft harvesting procedures.

The injuries occurred either at the level of the joint or at the distal aspect of the adductor canal. Both sites were proximal to the skin incision and blunt dissection used during hamstring graft harvesting, which excludes these 2 steps as the mechanism of injury. The location of these injuries suggests that they were likely caused by blunt trauma to the nerve sustained during the proximal advancement of the tendon stripper.

Given this hypothesis, the trajectory of the tendon stripper and its proximity to the saphenous nerve during hamstring graft harvesting is a concern. Prior literature has recommended utilizing the leg position to decrease tension on the saphenous nerve [8]. Besides this, there is sparse literature providing guidance on the proximal advancement of the tendon stripper. Specifically, there are no recommendations on trajectory. Future studies are needed to identify the trajectory of the tendon stripper that maximizes distance from the saphenous nerve and as a result minimizes risk of injury. This knowledge would improve the safety of hamstring graft harvesting procedures with the goal of improving patient outcomes.