gms | German Medical Science

Objectives: Leg length discrepancy (LLD) following total hip arthroplasty (THA) can contribute to poor hip function and serious medical legal problems. With the introduction of minimal invasive surgical techniques and thus limited exposure, the risk for leg length discrepancy increases. A major disadvantage of direct anterior approach (DAA) with a leg positioner is the inability to evaluate the LLD intraoperatively. The purpose of the present study was: to 1) estimate the accuracy of an intraoperative method of LLD determination and 2) evaluate whether a higher LLD was associated with the worse functional outcomes.

Methods: The medical records of 1385 patients were retrospectively reviewed. All cases were performed via a standardized minimally invasive DAA in a supine position using a leg positioner. The optimal leg length was planned preoperatively and confirmed intraoperatively by measuring the distance between the lesser trochanter and the conus of the prosthesis. A t-test was applied to investigate a potential difference in LLD between experienced and less-experienced surgeons, in trauma and elective setting, between patients with a THA or native hip on the contralateral side. Functional outcomes included Harris hip score (HHS) at 3 months, 1 year and 5 years.

The HHS at the final follow-up was compared between patients with a LLD>10mm and patients with a LLD<10 mm.

Results and Conclusion: The average LLD was 4,5 ± 3,5mm. In 1273 patients (91,9%) LLD was smaller than 10mm of which 951 (68,7%) had a LLD < 5mm. In 112 (8.1%) patients LLD was greater than 10mm. Patients operated by an experienced surgeon had an average LLD of 4,8±3,9 mm whereas patients operated by a less-experienced surgeon had an average LLD of 4,4±3,7 mm (p=0.1). The LLD was 4,4 ± 3,7mm and 7,7±4,2 mm in patients who underwent a THA elective or due to a femoral neck fracture, respectively (p< 0.01). The LLD was 4,4 ± 3,7mm and 4.8±4,1 mm in patients with a native hip or THA in the contralateral side, respectively (p=0.1). Patients with LLD >10mm were associated with a worse HHS at final follow-up than patients with a LLD<5mm (p< 0.05).

Measuring the distance between lesser trochanter-conus of the prothesis might be a simple, reproducible and reliable intraoperative method to assess the LLD, even by less experienced surgeons, in both elective and trauma setting. The presence of a THA on the contralateral side doesn't influence the results of the measurement. The post-operative HHS was satisfactory in over 90% of cases. However, patients with LLD >10mm scored markedly lower than patients with a LLD<10 mm.