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Proximal hamstring avulsion (PHA) is an injury mostly occurring with slip-and fall accidents. MRI is important for the diagnosis, and MRI-findings together with patient characteristics are used for the allocation of treatment, but little is known about their prognostic value. The treatment can be either operative or nonoperative, but the evidence for the treatment options is limited. There is also no data on incidence and on trends in treatment of hamstring injuries, including PHA.

In paper I we analyzed data from the Swedish National Patient Register between 2001 and 2020 for patients aged 18–90 diagnosed with hamstring injuries (ICD-10 code S76.3), with operative treatment identified using the NOMESCO classification NFL49. The incidence of hamstring injuries increased from 2.2 to 7.3 per 100,000 person-years between 2001 and 2020, with the rate of surgical treatment rising from 3.0% to 14.2%.

In paper II we conducted a survey of 125 orthopedic surgeons from Sweden, Norway, Finland, and Denmark to explore current practices and rationales for PHA treatment decisions. Surgical decision-making was largely influenced by patient-specific factors, including age, BMI and lifestyle, and MRI-findings such as, degree of tendon retraction and number of avulsed tendons.

In paper III we conducted a randomized noninferiority trial at 10 centers that compared operative tendon reinsertion versus non-operative management in patients aged 30–70 with PHA. The primary outcome was the Perth Hamstring Assessment Tool (PHAT) at 24 months. The RCT demonstrated that nonoperative treatment was noninferior to surgery in terms of PHAT, but also in secondary outcomes, such as Lower Extremity Functional Scores (LEFS) and functional test, and with more adverse events in the operative group.

In paper IV we investigated if MRI findings at time of diagnosis had an association with muscle degeneration at 24 months of follow up with tendon retraction emerging as a key factor in predicting muscle degeneration in nonoperatively treated patients.