Summary

Retrospective case series of 22 patients at 5.8 years follow-up demonstrates that early treatment of stress fractures with teriparatide is associated with good efficacy, low recurrence, and low rates of conversion to surgery.

Abstract

Introduction

Stress fractures are commonly encountered in athletes. While nutrition, sex, hypovitaminosis D and biomechanics have been implicated in stress fractures, it is clear that overuse is central to the pathoetiology of stress fractures, as stress injuries do not occur in low-activity states. As relative skeletal insufficiency likely underpins stress fractures, bone anabolic agents may play an important but under-recognized role in the treatment of these injuries. This study retrospectively evaluates the off-label use of teriparatide in the treatment of primary lower extremity stress fractures in a younger population, and determines efficacy in relation to treatment timing.

Methods

This was a telephone retrospective single cohort study of teriparatide in the treatment of stress fractures of the pelvis and lower extremity. Patients 18 to 55 years of age were included from a retrospective search of 3258 patients with a documented history of PTH receptor agonist use in a single academic institution. Minimum telephone follow-up was 24 months. Inclusion criterion was primary treatment of symptomatic lower extremity and pelvic stress fractures with teriparatide. Exclusion criteria included secondary stress fractures due to endocrine, metabolic, or connective tissue disorder, pain disorders, prior surgery, impending surgery, and pre-existing osteoporosis. Comparisons were made between early treatment (<6 months symptom duration; Group E) and late treatment (≥6 months symptom duration; Group L) groups. Primary outcome was time to symptom resolution. Secondary outcomes include rates of and time to return to sport, rates of fracture recurrence, and rates of conversion to surgery.

Results

22 patients were found to meet criteria (Group E, n=10; Group L, n=12). Median Tegner activity scale was 6. Mean follow up duration was 5.8 years. Mean age was 42.1 versus 40.3 (p=0.82) respectively for Groups E and L. Mean symptom duration was 3.1 and 9.0 months prior to treatment initiation (p=0.0002). Time to symptom resolution (3.0±0.7 versus 4.0±2.1 months, respectively, p=0.70), treatment duration (4.8±1.1 versus 11.3±3.9 months, respectively, p=0.38), time to return to sport (4.4±0.7 versus 7.5±1.6, respectively, p=0.33) were not different. Rates of conversion to surgery (0 versus 2, p=0.18) and fracture recurrence (1 versus 3, p=0.36) were also not different. Rate of non-response to treatment, defined as no improvement in pain, was 0 in Group E and 4 in Group L (p=0.044). Rate of return to sport trended higher in Group E (100%) than in Group L (75%, p=0.089). Overall good rates of pain relief were equivalently reported in both groups, decreasing from a median numeric pain score of 5 pre-treatment to 0 post-treatment in Group E, and from 7 to 2 in Group L (p=0.82). 80% of patients were satisfied that teriparatide improved their healing in Group E versus 50% in Group L (p=0.095). No severe adverse events were encountered.

CONCLUSION/DISCUSSION: Though an off-label indication, this study cautiously suggests that expeditious limited-duration treatment with teriparatide for primary lower extremity stress fractures in 18-55 year old patients may be efficacious. This work represents one of the first reports of a longer-term follow up study of stress fractures treated with teriparatide.