Intertrochanteric femoral fractures are common in clinical practice and the key to treatment is timely stable fixation and early rehabilitation to prevent bedridden complications. At present, the failure of common internal fixation system in the treatment of unstable intertrochanteric femoral fractures is not rare. The authors think that for the normal anatomical type of leverage structure of human proximal femur, pivot can bear weight and complete multidirectional activities because its pivot is close to the center of the body. The intertrochanteric femoral fractures destroyed the trabecular structure on the tension side and pressure side. At the same time, the physiological lever of the proximal femur was destroyed. The cause for the failure of the existing internal fixation is the inability to reconstruct the physiological pivot. Based on the anatomical and biomechanical characteristics of the proximal femur, the author reviewed the previous literatures and analyzed the problems in the treatment of intertrochanteric femoral fractures, and for the first time raised the " lever-pivot balance" theory for the treatment of intertrochanteric femoral fractures. This theory opens a new way for solving the problems in treatment of intertrochanteric femoral fractures.

Objective:To investigate the characteristics of postoperative internal fixation failures of femoral intertrochanteric fractures and analyze the related reasons using the leverage-balance-reconstruction theory.Methods:A retrospective case series study was performed for 40 patients suffering from implant failure after internal fixation of femoral intertrochanteric fractures admitted to Peking University People's Hospital from January 1999 to December 2019. There were 20 males and 20 females, aged from 43 to 92 years [(74.1±11.5)years]. The patients were assigned to extramedullary fixation (extramedullary fixation group, 17 patients) and intramedullary fixation (intramedullary fixation group, 23 patients). Complications associated with internal fixation were recorded, including internal fixation cutout, coxa vara deformity of hip joint, internal fixation withdrawal, femoral heck shortening and internal fixation breakage. Based on the lever-balance-reconstruction theory, the failure reasons of internal fixation were analyzed in combination with the change of arm length and outward shift of fulcrum measured before operation, after internal fixation and after fixation failure.Results:Among 40 patients, internal fixation cutout occurred in 18 patients, coxa vara deformity of hip joint in 37, internal fixation withdrawal in 29, femoral neck shortening in 37 and internal fixation breakage in 3. In extramedullary fixation group, the lengths of primary power arm and resistance arm were (8.0±1.0)mm and (59.4±10.9)mm, the lengths of power arm and resistance arm after fixation were (72.7±21.7)mm and (8.9±7.4)mm, the lengths of power arm and resistance arm after fixation failure were (50.3±14.9)mm and (33.6±17.6)mm. In intramedullary fixation group, the lengths of primary power arm and resistance arm were (6.7±0.6)mm and (49.8±9.9)mm, the lengths of power arm and resistance arm after fixation were (51.5±7.0)mm and (19.8±5.9)mm, the lengths of power arm and resistance arm after fixation failure were (41.6±9.6)mm and (32.4±7.7)mm. In each group, the lengths of power arm and resistance arm after internal fixation showed significant differences from that of normal ones and from that after fixation failure ( P<0.05). The length of power arm in extramedullary fixation group was larger than that in intramedullary fixation group ( P<0.05). The shortening of power arm in extramedullary fixation group was larger than that in intramedullary fixation group after fixation failure ( P<0.05). Conclusions:The extramedullary and intramedullary fixation of femoral intertrochanteric fractures result in the displacement of reconstruction fulcrum. The shortening of power arm is observed after fixation failure. The leverage-balance-reconstruction theory is helpful to analyze the cause of complications. The power arm after extramedullary fixation is longer than that after intramedullary fixation and is therefore more prone to fixation failure. The primary cause of postoperative internal fixation complications is to achieve a new balance of leverage.

Objective:To explore the curative effects of Nice knot fixation on tuberosity healing in hemiarthroplasty for complex proximal humeral fractures.Methods:A retrospective analysis was conducted of the eligible 32 complex proximal humeral fractures which had been treated at Department of Trauma and Orthopedics, Peking University People's Hospital between May 1, 2016 and May 1, 2019. Nice knot fixation was used to repair greater and lesser tuberosities in hemiarthroplasty for all the patients. There were 6 males and 26 females, aged from 60 to 90 years (mean, 74.9 years). By the Neer classification, there were 4 three-part fractures combined with dislocation, 20 four-part fractures, and 8 four-part fractures combined with dislocation. Shoulder joint X-rays were taken at postoperative 1, 2, 3, 6, and 12 months at the outpatient clinic to evaluate the patients' shoulder joint mobility, visual analog scale (VAS) pain score and Constant-Murley shoulder score. Tuberosity healing was assessed based on the X-rays and related complications were recorded.Results:The 32 patients received complete follow-up for 12 to 25 months (average, 17.82 months). At the 12-month follow-up, their shoulder flexion averaged 131.3° (from 80° to 155°), abduction 126.9° (from 80° to 155°), external rotation 48.4° (from 30° to 60°), internal rotation the L2 level, VAS pain score 0.9 (from 0 to 5), and Constant-Murley score 83.4 (from 58 to 96). The rate of patient satisfaction was 87.5%(28/32). Tuberosity-related complications were observed in 6 cases with an incidence of 18.8%. Complications like infection and prosthetic loosening were found in none of the patients.Conclusion:In hemiarthroplasty for complex proximal humeral fractures, application of Nice knot to fixate greater and lesser tuberosities can lead to rigid fixation, definite curative effects and a low incidence of tuberosity-related complications.