Subtrochanteric fracture after fixation of slipped capital femoral epiphysis: a complication of unused drill holes

The Universal Entry Point with oblique screw is superior to fixation perpendicular to the physis in moderate slipped capital femoral epiphysis

PURPOSE

Stable slipped capital femoral epiphysis (SCFE) is often treated with in situ pinning, with the current gold standard being stabilization with a screw perpendicular to the physis. However, this can lead to impingement and a potentially unstable construct. In this study we model the biomechanical effect of two screw positions used for SCFE fixation. We hypothesize that single screw fixation into the centre of the femoral head from the anterior intertrochanteric line (the Universal Entry Point or UEP) provides a more stable construct than single screw fixation perpendicular to the physis with an anterior starting point.

METHODS

Sawbone models of moderate SCFE were used to mechanically test the two screw constructs and an unfixed control group. Models were loaded to failure with a shear load applied through the physis in an Instron mechanical tester. The primary outcomes were maximum load, stiffness and energy to failure.

RESULTS

Screw fixation into the centre of the femoral head from the UEP resulted in a greater load to failure (+19%), stiffness (+13%) and energy to failure (+45%) than screw fixation perpendicular to the physis.

CONCLUSIONS

In this sawbone construct, screw fixation into the centre of the femoral head from the UEP provides greater biomechanical stability than screw fixation perpendicular to the physis. This approach may also benefit by avoiding an intracapsular entry point in soft metaphyseal bone and subsequent risk of impingement and loss of position.

Extra-articular proximal femur fractures in children and adolescents treated by elastic stable intramedullary nailing

PURPOSE

Extra-articular proximal femur fractures (EPFF) remain challenging for their intrinsic instability. The aim of this study is to evaluate the results of elastic stable intramedullary nailing (ESIN) of extra-articular proximal femur fractures in children and adolescents.

METHODS

A retrospective monocentric study of children treated by ESIN for EPFF between 2012 and 2018 was conducted. We included all patients sustaining a fracture within 10% of the femur length below the lesser trochanter. Studied data were age, sex, femur length, fracture distance below the lesser trochanter, number of days of hospitalization, time to nail removal, and complications. Beaty's criteria and the titanium elastic nailing (TEN) outcome measure scale were used to evaluate radiologic outcome and assess clinical recovery, respectively.

RESULTS

A total of 24 cases were reviewed (18 males, 6 females). Mean age was 8.23 years (range 5-13). Mean duration of hospitalization was 3.7 days (range 2-12). Mean time to nail removal was 28 weeks (range 12-53). Malalignment was observed in five patients, but in all cases, angulation did not exceed 10°. No limb length discrepancy was observed. Twenty out of 24 patients had excellent Beaty's radiological and TEN clinical outcome scores. No poor results were observed.

CONCLUSIONS

The results of our study show that good outcomes following surgical treatment by ESIN should be expected in children younger than 14 years of age with displaced EPFF. Excellent radiological and clinical outcomes were observed in 83.7% of the cases, with a low rate of complications and short hospital stay.

Outcomes after slipped capital femoral epiphysis: a population-based study with three-year follow-up

PURPOSE

To evaluate outcomes three years after treatment for slipped capital femoral epiphysis (SCFE): development of avascular necrosis (AVN), subsequent surgery, hip function and the contralateral hip.

METHODS

This prospective cohort study included a total national population of 379 children treated for SCFE between 2007 and 2013. A total of 449 hips treated for SCFE and 151 hips treated with a prophylactic fixation were identified. The Barnhöft questionnaire, a valid patient-reported outcome measure (PROM), was used.

RESULTS

In all, 90 hips had a severe slip, 61 of these were clinically unstable. AVN developed in 25 of the 449 hips. Six of 15 hips treated with capital realignment developed AVN. A peri-implant femur fracture occurred in three slipped hips and in two prophylactically pinned hips. In three of these five hips technical difficulties during surgery was identified. In 43 of 201 hips scheduled for regular follow-up a subsequent SCFE developed in the contralateral hip. Implant extraction after physeal closure was performed in 156 of 449 hips treated for SCFE and in 51 of 151 prophylactically fixed hips. Children with impaired hip function could be identified using the Barnhöft questionnaire.

CONCLUSION

Fixation in situ is justified to remain as the primary treatment of choice in SCFE. Overweight is more common in children with SCFE than in the average population. Prophylactic fixation is a safe procedure when performed using a correct technique. The number of patients who developed AVN after capital realignment is of concern. We recommend rigorous follow-up of both hips, including PROM evaluation, until physeal closure.

LEVEL OF EVIDENCE

II - prospective cohort study.

Finite element analysis of the impact of screw insertion distal to the trochanter minor on the risk of iatrogenic subtrochanteric fracture

Iatrogenic subtrochanteric fractures are rarely encountered after cannulated screw fixation of femoral neck fractures; however, when they do occur, there can be several complications. Many orthopedic surgeons have concerns about the potential for iatrogenic subtrochanteric fractures after screw fixation distal to the trochanter minor; therefore, some surgeons are typically reluctant to perform this procedure. This study focused on the risk of an iatrogenic subtrochanteric fracture after treating femoral neck fractures with cannulated screws. The main purpose of the study was to understand iatrogenic subtrochanteric fractures and evaluate the effects on these fractures of an inverted triangular–shaped configuration for placement of the cannulated screws. A femur bone with an femoral neck fracture at a 40° incline to the horizontal plane was generated along with a representation of a three-dimensional finite element model, and three inverted triangular–shaped configurations for placement of the cannulated screws were investigated using finite element analyses. Statistical results indicated that the occurrence risk of ISF increases when the screw is located distal to the trochanter minor. Moreover, the risk of occurrence of intertrochanteric fracture increases when the screw is located medial to the trochanter minor because of local concentrated stress on the surface of the screw canals. To avoid the vulnerability of the subtrochanteric region, it was found that proximal placement of the screws using the inverted triangular–shaped configuration could yield better results. In addition, the results of this study provide suggestions on improved screw configurations.

Current concepts in management of slipped capital femoral epiphysis

Slipped capital femoral epiphysis (SCFE) is a common hip condition that can be disabling. In this review, we provide an orientation on current trends in the clinical management of SCFE including conventional procedures and specialised surgical developments. Different methods of fixation of the epiphysis, risks of complications, and the rationale of addressing deformity, primarily or secondarily, are presented. Although improved understanding of the anatomy, vascularity and implications of residual deformity have changed management strategies, the best modality of treatment that would restore complete vascularity to the femoral head and prevent any residual deformity, impingement and early osteoarthritis remains elusive.

Biomechanical Comparison of Perpendicular Versus Oblique In Situ Screw Fixation of Slipped Capital Femoral Epiphysis

BACKGROUND

Percutaneous in situ single screw fixation is the preferred treatment for stable and unstable slipped capital femoral epiphysis (SCFE). The recommended screw placement is in the center of the epiphysis and perpendicular to the physis, which necessitates an anterior starting point for most SCFEs. A recent clinical study has shown good clinical results with a laterally based screw for SCFE, which is oblique to the physis. We sought to biomechanically compare these 2 techniques for load to failure and hypothesized that the laterally based oblique screw is equivalent or superior to an anteriorly based perpendicular screw.

METHODS

Twenty-two paired immature porcine femurs were used to compare the techniques. A SCFE model was created in all femurs using a previously published technique by performing a 30-degree posterior closing wedge osteotomy through the proximal physis. In the control group, a screw was placed perpendicular to the slip with an anterior starting point. In the experimental group, the screw was started as close to the mid-lateral cortex of the proximal femur as possible while maintaining the screw anterior to the posterior cortex of the femoral neck and ending at the apex of the epiphysis ignoring the resultant angle to the physis for the experimental group. The specimens were then potted and loaded in a physiologically relevant posteroinferior direction (30 degrees posterior from vertical) to determine load to failure (N) and stiffness (N/mm).

RESULTS

No statistical difference was found between the 2 groups in maximum load to failure or stiffness (P>0.05).

CONCLUSIONS

A laterally based screw oblique to the physis for in situ fixation in mild SCFE is not significantly different than an anteriorly based screw perpendicular to the physis in load to failure and stiffness in our study model.

CLINICAL RELEVANCE

In light of no difference in load to failure of these 2 constructs, surgeons may be more comfortable with the traditional lateral entry point while still aiming for screw placement in the center of head.

A fatigue loading model for investigation of iatrogenic subtrochanteric fractures of the femur

BACKGROUND

Biomechanics of iatrogenic subtrochanteric femur fractures have been examined. Previously-described loading models employed monotonic loading on the femoral head, which is limited in emulating physiological features. We hypothesize that cyclic loading combined with the engagement of abductor forces will reliably cause iatrogenic subtrochanteric fractures.

METHODS

Finite element analysis determined the effects of adding the abductor muscle forces to the hip contact force around holes located in the lateral femoral cortex. Finite element analysis predictions were validated by strain gage measurements using Sawbones™ femurs (Pacific Research Laboratories, Inc., Vashon, Washington, USA) with or without abductor muscle forces. The newly developed physiologically-relevant loading model was tested on cadaveric femurs (N=8) under cyclic loading until failure.

FINDINGS

Finite element analysis showed the addition of the abductor muscle forces increased the maximum surface cortical strain by 107% and the strain energy density by 332% at the lateral femoral cortex. Strain gages detected a 72.9% increase in lateral cortical strain using the combined loading model. The cyclic, combined loading led to subtrochanteric fractures through the drill hole in all cadaveric femurs.

INTERPRETATION

Finite element analysis simulations, strain gage measurements, and cyclic loading of fresh-frozen femurs indicate the inclusion of abductor forces increases the stress and strain at the proximal-lateral femoral cortex. Furthermore, a cyclic loading model that incorporates a hip contact force and abductor muscles force creates the clinically encountered subtrochanteric fractures in vitro. This physiologically-relevant loading model may be used to further study iatrogenic subtrochanteric femur fractures.

Oblique in situ screw fixation of stable slipped capital femoral epiphysis

BACKGROUND

Percutaneous in situ single screw fixation is the preferred treatment for stable slipped capital femoral epiphysis. The recommended screw placement is in the center of the epiphysis and perpendicular to the physis. We reviewed the results of in situ fixation with the screw placed oblique to the physis.

METHODS

Thirty-six stable slips were treated with a modified technique. The screw was started as close to the mid lateral cortex of the proximal femur as possible while maintaining the screw anterior to the posterior cortex of the femoral neck and ending at the apex of the epiphysis ignoring the resultant angle to the physis. Thirty-five of these hips were followed till physeal closure.

RESULTS

Thirty-five of the 36 hips showed physeal closure at an average of 5 months. There were no screw-related complications or symptoms. The oblique screw path allowed for an extra screw thread to be placed in the epiphysis and also allowed adequate femoral neck osteoplasty.

CONCLUSIONS

Oblique placement of the screw for in situ fixation in stable slipped capital femoral epiphysis did not cause any deleterious effects and offered several potential advantages.

LEVEL OF EVIDENCE

IV - Case series.

Subtrochanteric femur fracture after slipped capital femoral epiphysis pinning: a novel treatment

Slipped capital femoral epiphysis is a common injury suffered by adolescents worldwide. Treatment of most slips can be accomplished by percutaneous screw fixation, as this is an accepted and proven method associated with minimal morbidity. Complications, although limited, can be problematic for both the patient and treating physician. These include avascular necrosis, chondrolysis, infection, and fracture. We report a case of an individual who sustained a subtrochanteric femure fracture three weeks after in situ pinning of his left hip treated with a reconstruction intramedullary nail. This option allowed both the subtrochanteric fracture and SCFE to be treated concomitantly with minimized morbidity.

[Immediate weight bearing after treatment of stable epiphysiolysis]

PURPOSE OF THE STUDY

The purpose of this study was to ascertain whether immediate weight bearing after surgery for chronic or stable epiphysiolysis treated with a single percutaneous screw increases the risk of greater displacement.

MATERIAL AND METHODS

Epiphysiolysis procedures (n=30) performed in 25 patients were reviewed retrospectively. One percutaneous screw was inserted under fluoroscopic control in all cases. For ten patients (from 2002), weight bearing was allowed immediately after surgery. The Southwick grading system was applied to classify each epiphysiolysis into one of three stages according to the cervicoepiphyseal angle measured on the lateral radiograph. Clinical and radiographic controls were obtained in all children at 1, 3, 6, and 12 months. Outcome was assessed using the Heyman and Herndon criteria.

RESULTS

The study population included 17 boys and 8 girls (mean age 12 years 18 months). The left side was involved in 12, the right in 8 and both in 5. Weight bearing was allowed immediately after surgery in 10 patients with a stable epiphysiolysis (4 stage I, 5 stage II, 2 stage III). Time to weight bearing was 3 months on average for the others. Mean follow-up was 4 years (range 1-8 years). Clinically, none of the ten patients presented pain or limping at last follow-up. Abduction was limiting in 9 and internal rotation in 19. There was no increase in the displacement for patients with immediate weight bearing.

DISCUSSION

Most teams advise against weight bearing for 6 weeks to 3 months. We were unable to find any pathophysiological reason for this attitude. It would be more logical to wait until complete fusion of the subcapital growth cartilage before authorizing weight bearing. This raises the question of the effect of this practice on postoperative displacement For stable epiphysiolysis, there is no evidence that not allowing weight bearing had an effect on the evolution if the screw is correctly positioned and at least 4 or 5 spires are engaged within the epiphysis.

Biomechanical analysis of single screw fixation for slipped capital femoral epiphysis: are more threads across the physis necessary for stability?

PURPOSE

To evaluate single screw fixation stability, in the treatment of slipped capital femoral epiphysis, as a function of screw thread distribution across the physis.

STUDY DESIGN

In vitro biomechanical study.

METHODS

Thirty porcine proximal femurs were sectioned through the physeal line and stabilized with a cannulated 7.3-mm stainless steel AO screw. The distal 16 mm of each screw was threaded (5 threads). The femurs were randomized into 5 groups (1, 2, 3, 4, or 5 threads across the physis) and biomechanically tested to determine failure load (N) and stiffness (N/mm).

RESULTS

Femurs with 2 or 3 threads across the physis had a significantly greater load to failure and stiffness compared with femurs with 1, 4, or 5 threads across the physis (P < 0.05).

CONCLUSIONS

Thread distribution across the physis seems to be important. When using screws with a 16-mm thread, greatest strength and stiffness are achieved when 40%-60% of threads engage the epiphysis, with a significant decrease when greater than 80% of threads cross the physis. Too few threads in the epiphysis as well as too few in the metaphysis both lead to decreased stability.

CLINICAL RELEVANCE

This study challenges the belief that compression across the physis maximizes slipped capital femoral epiphysis fixation stability. We recommend equal distribution of threads across the physis when using 16-mm thread screws, and we postulate that screws with a greater thread length (32 mm or fully threaded) would increase fixation stability even further. Optimizing purchase may decrease the incidence of slip progression, especially as the prevalence of obesity increases in the adolescent population.

[Intertrochanteric femoral fractures in children]

Based on two cases and a review of the literature, we describe a rare injury in childhood, intertrochanteric femoral fracture. Because of the insertion and traction of muscles at the proximal femur, conservative treatment is difficult. The hip muscles pull the proximal fragment into flexion, abduction and external rotation. In our opinion, surgical stabilization is the therapy of choice. We use an angular stable, locking compression plate for the stabilization of these fractures. Postoperatively, mobilization with full weight bearing is possible.

Femoral neck fracture in a child with autosomal-dominant osteopetrosis: failure of spica cast treatment and successful outcome by internal fixation

A case report of a 6-year-old child with autosomal dominant osteopetrosis who sustained a closed femoral neck fracture initially treated with a spica cast with subsequent fracture displacement is presented. Further treatment included closed reduction and operative fixation, first, with a guide pin placement for a cannulated screw insertion that was abandoned because of the hardness of the bone. Three Kirschner wires were then inserted to maintain the closed reduction, followed by immobilization in a spica cast. At the 2-year follow-up, the child was completely free of any complications resulting from her injury and treatment. Radiographs showed no evidence of avascular necrosis in the affected femoral head. Review of the literature supports evidence for early operative fixation of such cases, whether or not the femoral neck fracture is nondisplaced or displaced.

Subtrochanteric fracture after cannulated screw fixation of femoral neck fractures: a report of four cases

Subtrochanteric fractures after screw or pin fixation of femoral neck fractures are a recognized complication. No literature is available on this complication after fixation using the recently popularized cannulated screws. We present our experience in treating four of these complications. The common denominator for all four patients seemed to be an entry point in the lateral cortex below the level of the most inferior edge of the lesser trochanter.

Fixation failure in femoral neck fractures

Fixation of femoral neck fractures is associated with a higher incidence of complications than any other fracture. The rates of nonunion and avascular necrosis with open reduction and internal fixation continue to be unacceptably high. These complications are the main reason for resorting to primary endoprosthetic replacement of the femoral head in the presence of displaced fractures in elderly patients. However, with the increasing life span of the patients with these prostheses, late complications of endoprosthetic replacement of the femoral head are becoming significant. With these complications, it may be argued that the most cost-effective solution to the femoral neck fracture in the majority of patients is open reduction and internal fixation, with elective conversion, when necessary, to total hip arthroplasty in patients who have a complication. Because the literature does not contain a systematic review of reasons for failure of internal fixation, the authors will attempt to review the common means of failure of internal fixation in young and older patients in an attempt to better understand and prevent these complications.

Custom 95 degree condylar blade plate for pediatric subtrochanteric femur fractures

Subtrochanteric fractures in the older child and adolescent often are not amenable to conservative methods of treatment. The anatomic constraints of the proximal femur including the small diameter of the femoral neck and the presence of the capital femoral physis may limit the type of internal fixation used in these patients. This article presents our preliminary experience with a custom 95 degree condylar blade plate for subtrochanteric fractures in older children and adolescents.

Displaced femoral neck fractures at the bone-screw interface after in situ fixation of slipped capital femoral epiphysis

Two patients had displaced femoral neck fractures at the bone-screw interface after in situ fixation of slipped capital femoral epiphysis. Both fractures required closed reduction and internal fixation. Inadvertent derotation of the femur occurred in both patients and allowed fixation of the fracture through the intramedullary canal of the femoral neck without anterior penetration of the pins into the joint; a nonunion occurred in this patient. The other patient developed chondrolysis and avascular necrosis. Because the femoral neck is vulnerable to stress fractures in young adults, there is some question whether pins placed anteriorly through the femoral neck cortex should be removed.