Long-term analysis of chronic pain associated with lower extremity injuries

Due to advances in prehospital care, modern intensive care concepts, formation of specialized trauma centers, and improved surgical management, the survival rate of severely injured patients has increased from 60 to 85–88% in recent decades [1, 2]. With increased survival rates, the long-term functional outcomes of polytrauma patients have gained importance [3]. Specifically, lower extremity injuries have been associated with significant functional impairments and low satisfaction scores in polytrauma patients [4‐7]. A detailed investigation of long-term outcome and their influencing factors after lower extremity injury was performed within the Lower Extremity Assessment Project (LEAP) [8‐11].

The impact of lower extremity injuries on outcome has also already been described by our group [12]. It has been reported that fractures below the knee are frequently associated with persistent functional deficits in trauma patients [13]. It was also suggested that not only the individual fracture but more importantly fracture patterns influence long-term outcome [13]. Furthermore, it was emphasized that delayed treatment, a thin soft tissue envelope below the knee, high energy trauma, unfavorable blood supply and complex fracture patterns may contribute to unfavorable outcomes [13]. However, studies providing detailed information on the impact of the injury pattern of lower extremity and pelvic fractures on the functional outcomes in polytrauma patients remain limited. Therefore, the goal of this study is to examine the relationship between the injury pattern of lower extremity fractures and the functional long-term outcomes in polytrauma patients. The main objective of this study is to identify chronic pain associated with lower extremity injury patterns that have not been previously reported. We hypothesize that fracture pattern and location of lower extremity and pelvis fractures of multiple injured patients influence their long-term pain outcome.

We performed a retrospective cohort study of prospective acquired data involving patients with multiple fractures of the lower limb and pelvis that were initially treated in a Level 1 Trauma center and followed up for a minimum of 10 years postinjury. The standardized follow-up evaluation was performed by a trauma surgeon. All Patients provided written consent and the study protocol was approved by the local Institutional Review Board (No. 2326-2000/03/22).

Patients treated between 01/01/1973 and 12/31/1990 were retrospectively reviewed. If inclusion and exclusion criteria were met, patients were invited for physical examinations. Further details of patient recruitment and measures against biases were previously published [14, 15]. Out of the initial cohort (n = 637) 525 patients met the inclusion criteria: age 3–58 years at the time of injury, multiple injured patients and associated fractures to the lower limb and/or pelvis.

Influencing variables were obtained using the patient charts including: Fracture location, patients age at the time of injury, gender, cause of injury and injury severity measured by Abbreviated Injury Score (AIS) [16]. Target variables were obtained using self-administered patient questionnaires as well as standardized physical examinations of all injured locations as performed by a trauma surgeon. The following functional variables were recorded: lower leg pain subdivided into persistent pain, load-dependent pain and intermittent pain, as well as limping.

Accordingly, the patients were divided into subgroups.

Within these subgroups, the most common fracture combinations were obtained. The rest were categorized in a separate cohort defined as “other.”

More than half of the study cohort still demonstrated lower limb pain 10 years postinjury (n = 301; 57.3%). This most commonly manifested as load-dependent pain (n = 151; 50.2%), followed closely by intermittent pain (n = 120; 39.9%). Persistent lower limb pain was seen in 9.9% (n = 30).

Load-dependent pain was most prevalent at 50% and was most common in patients with femoral shaft fractures (40%; n = 60), foot fractures (29%; n = 44) and distal tibia fractures (28%; n = 42) (Fig. 1A). The most common fracture combinations were fractures of the foot combined with femoral shaft fractures or distal tibia fractures. Each making up 11% (n = 17) of the group cohort (Fig. 2A).

Intermittent pain was present in 40% of all patients with pain with multiple lower limb fractures. Out of these, 47% (n = 56) presented with a femoral shaft fracture and 42% (n = 50) a tibia shaft fracture (Fig. 1B). Fracture combinations involving the shaft of the tibia with either the femoral shaft or distal tibia occurred most frequent with at 9% each, respectively (n = 11) (Fig. 2B).

Persistent pain was still present in 10% of all patients with multiple injuries of the lower extremity. Tibia shaft fractures (37%; n = 11), proximal tibia fractures (30%; n = 9) and femoral shaft fractures (30%; n = 9) predominated this group (Fig. 1C). The combination of a fracture of the tibial shaft with either the femoral shaft or proximal tibia was most common at 13% (n = 4) (Fig. 2C).

Forty-one percent of patients still showed a persistent limp 10 years postinjury (n = 215). Of those demonstrating a persistent limp, a one-sided limp was seen in 65% of cases (n = 140), while a bilateral limp was seen in 35% of cases (n = 75). The most common fractures resulting in a persistent limp involved fractures of the femoral shaft (n = 41; 19%), fractures of the tibia shaft (n = 37; 17%) and fractures of the pelvis (n = 32; 15%).

Identifying and analyzing risk factors influencing the long-term outcomes can produce important information for establishing new treatment strategies and guidelines improving long-term functional results.

Our study revealed the following results:

The degree of soft tissue injury is certainly a crucial contributory factor affecting long-term outcome in patients with lower extremity injuries. Thus, the studies of the Lower Extremity Assessment Project (LEAP) described factors that influence the long-term outcome of limb-threatening lower extremity injuries and showed that patients with amputations had comparable functional outcomes to patients with reconstructions [8‐11]. However, information about the long-term pain outcome of patients with multiple fractures of the lower limb and pelvis is sparse.

Continuous pain is very frequently reported following multiple trauma of the lower extremity. This is in accordance with recent studies showing a significant impact on functional recovery of polytrauma patients with fractures below the knee [13]. Persistent hip pain is known in patients with a history of femoral shaft fractures [20]. Possible attributions to cause continuous pain is osteoporosis due to immobility [21] and the development of arthritis [22‐24].

Chronic persistent and load-dependent pain were both frequently associated with femoral shaft fracture in combination with articular fractures. Studies differentiating between stress induced and continuous pain after femoral shaft fracture are scarce. Heel pain after weight bearing can be caused by tarsal tunnel, nerve entrapment or Achilles tendinopathy as a result of soft tissue damage [25]. Foot fractures can be more easily overlooked in the initial diagnostics of a polytrauma patient. Delayed treatment can cause chronic pain.

Studies suggest the presence of intra-articular hip pathology in patients with chronic pain following femoral shaft fractures, which may provide a possible explanation as to why this fracture type is the most common fracture overall in our study involving patients exhibiting any chronic or stress induced pain [20]. All fractures healed while nonunion was not a relevant factor. Heterotopic ossification may result in limited mobility, thereby causing weight bearing chronic pain. Several studies show a higher rate of heterotopic joint ossification in ventilated patients or patients with a head injury, which is a common occurrence in patients of polytrauma [26‐28]. Furthermore, muscle weakness due to immobility can be attributed as a cause of stress induced pain [29, 30].

A remarkable 41% of patients still exhibited a persistent limp 10 years post trauma. This demonstrates the value in the examination of gait abnormalities, especially when considering that one of the primary factors influencing patient satisfaction is extremity function [31]. Long bone shaft fractures were shown to be the most common cause of an abnormal gait in patients.

Pelvic ring instability is a known cause of gait abnormality [32]. Research on long-term gait abnormality for long bone fractures is scarce. It is suggested that gait abnormality after femoral shaft fractures may also be due to intraarticular hip pathologies such as labral tears or osseous bumps of the femoral neck [20]. A difference in length between both legs resulting from long bone shaft fractures could possibly also explain the cause of limping [32].

Abnormal gait can be caused by immobility of the joints following muscle contracture or pain disorder [33]. Heterotopic ossification also generates restriction in mobility [26]. Additionally, head injuries can also lead to heterotopic ossification [27, 28] which are common in polytrauma patients. High rates are also noted in ventilated patients [26].

In multiple injured patients with lower extremity injuries, the combination of fractures and their location are critical factors in long-term outcome. Patients with chronic persistent or load-dependent pain often had underlying femoral shaft fractures in combination with joint fractures.

Patients with the types of injury patterns described here may benefit from structured and targeted long-term physiotherapy to prevent the development of chronic pain.