This study was a prospective non-randomized study conducted on 95 elderly patients (95 hips) with displaced femoral neck fracture who were treated with cemented BHA in our institute from September 2013 to December 2017. This study adhered to CONSORT guidelines. Sample size was determined that p1=0.3, p2=0.6, α=0.05, 1-β=0.8 resulted 42. Inclusion criteria were diagnosed of displaced femoral neck fracture, then 114 patients (114 hips) were met the criteria. Exclusion criteria were patients who had osteoarthritis or dysplasia (Sharp angle over 45 degrees) of the same side of fracture and patients who had no tolerance of surgery. 6 patients (6 hips) met the former exclusion criteria, then they were treated with cemented THA. 13 patients (13 hips) met the latter exclusion criteria, then they were treated conservative. The knot position was changed from anterior (Fig 1) to posterior (Fig 2) alternately, and the surgeon did not know which knot position to adopt until just before the knotting. A third party other than the doctor or nurse assigned the knot position. The anterior position was used in 47 hips and the posterior position in 48 hips. This study was approved by our institutional review board, and Informed consent was obtained from each patient.
All operations were performed using the modified Dall approach. A chisel was used to cut the greater trochanter partially. The fragment thickness was maintained at 10 mm, and the fragment was not cut through entirely. In this manner, the osteotomy surface had a ramp, which prevented the fragment from shifting anteriorly. The fragment of the greater trochanter was measured using Vernier calipers: length (maximum cranio-caudal length), width (maximum antero-posterior length), and thickness before the fragment was reattached. The estimated volume of the fragment was calculated as follows: length × width × thickness.
In order to pull the fragment 15mm posterior to the original position, the tendinous portion of the gluteus minimus was cut before reattaching. For the fixation method, two 3.0-mm-width UHMWPE fiber cables were pathed around the femur using anterior loops; thereafter, the cables were tied up using a double-loop sliding knot. The gun tensioning system (Tightning Gun TGL, Alfresa Pharma Co., Osaka, Japan) at more than 20 kg was used, and the cables were later tied four times by hand and finally tied once using the gun tensioning system at more than 20 kg.
Eleven Exeter stems (Stryker Orthopedics, Mahwah, New Jersey) and 84 SC stems (KYOCERA Medical, Osaka, Japan) were used. Exeter stem is the cemented polished double-tapered stem, and it has excellent outcomes in Japan [6,7]. SC stem is the cemented polished triple-tapered stem. All stems were implanted with two packs of Simplex P bone cement (Stryker Orthopedics, Mahwah, New Jersey) and using the interface bioactive bone cement technique [8-10].
The antero-posterior supine-positioned X-ray images obtained immediately after the operation were compared with those obtained at 3 months postoperatively, without informing the surgeons, patients, physical therapists, and radiologists which knot positions were applied. Osteotomy healing or union of the greater trochanter was then classified into three types: type A, no apparent shifting of the trochanteric fragment and fracture of the greater trochanter; type C (Fig 3), over 1-mm shifting of the trochanteric fragment; and type F (Fig 4), fracture of the greater trochanter. Three doctors (HH, MK, and HF) classified the status of the greater trochanter. Disagreements were resolved by consultation. The patients’ age at operation, sex, and body mass index (BMI); size of the greater trochanteric fragment; type of the stem; and experience of the surgeon (surgeon A: 20 years of experience, surgeon B: 15 years of experience; “others”, C： 5 years of experience and D: 15 years of experience) were analyzed using the t-test and chi-square test. C and D performed operations in fewer than five hips; thus, they were classified as “others”.
All analyses were performed using Statcel 4 (OMS Publ., Tokyo, Japan), which is an add-in software of Excel (Microsoft, Redmond, Washington). The statistical significance level was set at a value of <5%.