Session II - Tibia

Fri., 10/8/04 Tibia, Paper #15, 11:51 am

Prevalence of Chronic Pain Seven Years after Limb-Threatening Lower-Extremity Trauma

Renan C. Castillo, MD¹ (n); Ellen J. MacKenzie, PhD¹ (n);

Michael J. Bosse, MD² (n); and The LEAP Study Group;

¹ Center for Injury Research & Policy, Johns Hopkins Bloomberg School of

Public Health, Baltimore, Maryland, USA;

²Carolinas Medical Center, Charlotte, North Carolina, USA

Purpose: Chronic pain is one of the leading causes of disability and medical costs in the United States and affects millions of working-age adults. Although a number of chronic-pain syndromes have been described, their cause is poorly understood. Numerous retrospective studies have shown that a significant proportion of patients with chronic pain have a history of traumatic injury. The present analysis examines the prevalence and early predictors of chronic pain in a cohort of patients who were prospectively selected after sustaining severe trauma to the lower extremity.

Methods: Patients treated at one of eight participating level I trauma centers were enrolled in a study of outcomes after limb-threatening unilateral lower-extremity trauma, including Gustilo grade IIIB and IIIC fractures, selected grade IIIA fractures, dysvascular limbs, major soft tissue injuries to the tibia, and severe foot injuries (N = 569). Extensive information regarding patient, injury, and treatment characteristics was collected at baseline. Patients were observed at 3, 6, 12, 24, and 84 months after hospital discharge. Chronic pain was measured by using the Graded Chronic Pain Scale, which measures both pain severity and level of pain-related interference with activities. Chronic Pain Grade (CPG) 0 represents no pain, CPG I and II represent low and high pain intensity with no interference, CPG III represents moderate pain interference, and CPG IV represents high pain interference. Multiple regression techniques were used to identify early correlates of chronic pain.

Table. Prevalence of Chronic Pain Seven Years after Limb-Threatening Lower-Extremity Trauma

	N	% pain-free	Total with pain	% with pain reporting chronic pain grade
				I	II	III	IV
Salvages
Tibia fractures	78	23.1	60	56.7	13.3	13.3	17.7
Knee and ankle fractures	114	16.7	95	46.3	17.9	13.7	22.1
Foot fractures	33	21.2	26	46.2	19.2	19.2	15.4
Soft tissue injuries	55	10.9	49	51.0	16.3	14.3	18.4
Amputations
Foot	7	14.3	6	50.0	0.0	16.7	33.3
Below the knee	67	29.9	47	40.4	12.8	14.9	31.9
Through the knee	15	46.7	8	37.5	12.5	37.5	12.5
Above the knee	28	46.4	15	60.0	0.0	26.7	13.3
Total lower-extremity trauma	397	22.9	306	48.7	14.7	15.7	20.9
Back pain population norms			1213	34.9	27.9	20.0	17.2
Headache population norms			779	29.7	40.1	20.2	10.0
General population norms	803	42.3	463	34.6	38.2	22.7	4.5

Results: Chronic Pain Grade (CPG) results by injury group are summarized in the table above. Patients who have experienced limb-threatening lower-extremity trauma exhibit statistically significantly higher levels of chronic pain than does the general population (P <0.001), comparable to that found in primary care populations with headache and back pain. Patients with amputations at the knee and above reported the lowest levels of chronic pain within the study group (P <0.01), with pain-free percentages comparable to those of the general population. Among the patients who reported at least some pain, those with amputations below the knee, including partial foot amputations, reported the highest levels of chronic pain interference (P <0.05). Among amputees in general, chronic pain grade was strongly associated with phantom pain (P <0.001). In addition to amputation level, a number of strong early predictors of chronic pain were identified, including: less than a high-school education (P <0.01), less than a college education (P <0.001), low self efficacy (P <0.01), and high levels of average alcohol consumption (P <0.05). In addition, high reported pain intensity and elevated levels of depression and anxiety at 3 months after discharge were also strong predictors of chronic pain at 7 years (P <0.001 for all three predictors).

Conclusion/Significance: These results demonstrated high levels of chronic pain among patients who had sustained limb-threatening lower-extremity trauma. Patients treated with amputation at the knee or above reported levels of chronic pain comparable to that of the general population. The results also identify a set of early predictors of chronic pain (low education and self efficacy, high alcohol consumption, and high reported pain intensity and psychologic distress at 3 months after the trauma). It is possible that, for patients within this high-risk group, early referral to pain management or psychologic intervention or both may reduce the likelihood or severity of chronic pain.