Femoral neck fracture following hardware removal

The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

BACKGROUND

The incidence of aggravation or occurrence of avascular necrosis (AVN) following hardware removal in surgically treated pediatric femoral neck fractures who achieved radiologic consolidation is unknown. This study aimed to investigate the risk factors for this complication.

METHODS

Seventy-one pediatric (mean age: 9.8±3.9 y) were retrospectively analyzed. Risk factors (age, sex, laterality, severity of initial displacement, type of fracture, time from trauma to reduction, reduction and fixation method, quality of reduction, time required to achieve radiologic union, duration of hardware retention, presence of AVN before hardware removal and follow-up time) were recorded. The severity of AVN was assessed based on radiographs with Ratliff's classification.

RESULTS

Following hardware removal, the aggravation/occurrence of AVN was detected in 11 hips (15.5%). Among the 5 hips (7%) with aggravation of AVN, 1 (1.4%) with type II AVN and 3 (4.2%) with type III AVN exhibited aggravation of type I AVN, while the remaining hip (1.4%; type I) showed enlargement of the involved AVN area. Six hips (8.5%) developed AVN following hardware removal: 2 (2.8%) were classified as type I and 4 (5.6%) as type III. Receiver operating characteristic curve analysis indicated that hardware retention >7 months after union is associated with a decreased rate of aggravation or occurrence of AVN of the femoral neck or head following hardware removal.

CONCLUSIONS

The incidence of aggravation or occurrence of AVN following hardware removal in surgically treated pediatric femoral neck fractures is 15.5%; hardware retention >7 months after radiologic union may reduce the risk of aggravation or occurrence of AVN of the femoral neck or head postimplant removal.

LEVEL OF EVIDENCE

Level III.

Hounsfield Unit-Calculated Bone Mineral Density Loss Following Combat-Related Lower Extremity Amputations

BACKGROUND

After combat-related lower extremity amputations, patients rapidly lose bone mineral density (BMD). As serial dual x-ray absorptiometry (DXA) scans are rarely performed in this setting, it is difficult to determine the timeline for bone loss and recovery or the role of interventions. However, a strong correlation has been demonstrated between DXA BMD and computed tomography (CT) signal attenuation. We sought to leverage multiple CT scans obtained after trauma to develop a predictive model for BMD after combat-related lower extremity amputations.

METHODS

We reviewed amputations performed within the United States military between 2003 and 2016 in patients with multiple CT scans. We collected pertinent clinical information, including amputation level(s), complications, and time to weight-bearing. The primary outcome measure was the development of low BMD, estimated in Hounsfield units (HU) from CT scans with use of a previously validated method. One hundred and twenty-eight patients with 613 femoral neck CT scans were available for analysis. A least absolute shrinkage and selection operator (LASSO) multiple logistic regression analysis was applied to determine the effects of modifiable and non-modifiable variables on BMD. A random-effects model was applied to determine which factors were most predictive of low BMD and to quantify their effects.

RESULTS

Both amputated and non-amputated extremities demonstrated substantial BMD loss, which stabilized approximately 3 years after the injury. Loss of BMD followed a logarithmic pattern, stabilizing after 1,000 days. On average, amputated limbs lost approximately 100 HU of BMD after 1,000 days. Other factors identified by the mixed-effects model included nonambulatory status (-33.5 HU), age at injury (-3.4 HU per year), surgical complications delaying weight-bearing (-21.3 HU), transtibial amputation (20.9 HU), and active vitamin-D treatment (-19.7 HU).

CONCLUSIONS

Patients with combat-related lower extremity amputations experience an initially rapid decline in BMD in both intact and amputated limbs as a result of both modifiable and non-modifiable influences, including time to walking, amputation level, surgical complications, and age. The paradoxical association of vitamin-D supplementation with lower HU likely reflects this treatment being assigned to patients with low BMD. This model may assist with clinical decision-making prior to performing lower extremity amputation and also may assist providers with postoperative decision-making to optimize management for prophylaxis against osteoporosis.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Use of calcium phosphate cement after removal of a cephalomedullary nail: A case report

Femoral neck fracture in the absence of trauma is a rare, but known complication after hardware removal. This complication may be due to the boney defect created by the hardware removal itself, or the increase in femoral neck strain that occurs after removal of the hardware. Previous biomechanical studies have suggested that filling the defect with calcium phosphate cement after removal of hardware may prevent the development of a femoral neck fracture. However, there are no reports on the use of calcium phosphate cement after removal of hardware in the clinical setting. The purpose of this case discussion is to present the first reported case, to our knowledge, of the use of calcium phosphate cement augmentation of the boney defect after lag screw removal, and the subsequent failure resulting in atraumatic femoral neck fracture.

Should cannulated screws be removed after a femoral neck fracture has healed, and how? A finite element analysis of the femur before and after cannulated screw removal

PURPOSE

The removal of three inverted triangular parallel cannulated screws after the femoral neck fracture healing is sometimes accompanied by osteonecrosis of the femoral head (ONFH) or its refracture. The purpose of this study was to determine the biomechanical changes of the femur before and after the screw removal using a finite element analysis.

METHODS

The CT data of the femurs were obtained from a 69-year-old healthy female to establish the femur models. The established finite element models consisted of N, C, and R groups: N group, the normal femur; C group (to simulate the femoral neck fracture healing after the internal fixation), the normal femur with three inverted triangular parallel cannulated screws (C1) or with two upper parallel screws (C2). For the R1 or R2 groups, the screws in the model of the C1 or C2 individuals were gradually removed in seven or three types of different screw combinations, respectively. The stresses and displacements of the femur were determined.

RESULTS

(1) Compared with the N group, a uniform stress distribution was stopped by the addition of three screws in the C1 group; in contrast, all screw removals resulted in the stress concentration on the screw holes and the disappearance of stress shielding. Moreover, the average stress of the femoral head in C1 group increased by 37.85%, while that of the femoral neck decreased by 23.03%. (2) Compared with the C1 group, while only the lowest femoral calcar screw was removed, there was a similar stress distribution in the proximal femur, and the average stress of the femoral head increased only by 0.35% although that of the femoral neck increased by 63.62%; however, removal by any other means resulted in a significant stress concentration in the proximal femur and a significant increase in the average stresses of the femoral head and neck (5.96-40.95% and 12.82-75.46%, respectively). (3) Compared with the N or C1 group, there was a significant stress concentration on the screws and its surrounding proximal femur in the C2 group. (4) Compared with the C2 group, the simultaneous removal of two upper screws not only did not cause a significant stress concentration on the proximal femur but also significantly reduced the average stresses of the femoral head and neck by 87.49% and 65.51% respectively. On the contrary, the gradual removal of two screws caused a significant stress concentration on the screw and its surrounding proximal femur although the average stresses of the femoral head and neck decreased by 88.79-89.06% and 67.00-67.22%, respectively. (5) Compared with the N group, the average displacements of the femoral head and neck in the C1 group increased only by 3.12% and 3.37%, respectively. Additionally, compared with the C1 group, while three, two, or one screw was simultaneously removed, the average displacements of the femoral head and neck only fluctuated - 5.51-1.65% and 1.78-9.03%, respectively.

CONCLUSIONS

Residual internal fixation after femoral neck fracture healing may lead to stress concentration on screws and stress shielding around screws. The first removal of the lowest femoral calcar screw and then the second removal of two upper residual screws have a minimum effect on the stress concentration on the proximal femur and the average stress on the femoral head. The incorrect screw removal and resulting femoral load may well be closely related to occurrence in ONFH or its refracture.

Femoral Neck Hounsfield Units as an Adjunct for Bone Mineral Density After Combat-Related Lower Extremity Amputation

OBJECTIVES

To correlate femoral neck Hounsfield units (HUs) measured on a computed tomography (CT) scan to dual-energy x-ray absorptiometry (DEXA) T-scores allowing evaluation of bone mineral density (BMD) over time after lower extremity trauma-related amputation.

DESIGN

Retrospective cohort study.

SETTING

United States military trauma referral center.

PATIENTS

Military combat-related lower extremity amputees with both DEXA and CT scans within 6 months of each other.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Correlation between femoral neck comprehensive mean HUs and BMD and HUs threshold for low BMD.

RESULTS

Regression model correlation (r) between CT HU and DEXA T-score was r = 0.84 [95% confidence interval (CI) 0.52-0.94] and r = 0.81 (95% CI 0.57-0.92) when CT imaging was separated from DEXA by less than 4 and 5 months, respectively. Beyond 5 months separation, correlation decreased to r = 0.60 (95% CI 0.29-0.80). Using a receiver operator characteristic curve for mean comprehensive HUs to determine low BMD with 4-month cut-off, a threshold of 151 HUs was 97% sensitive and 84% specific to identify low BMD, whereas 98 HUs was 100% sensitive and 100% specific to identify osteoporosis.

CONCLUSION

Using opportunistic CT, clinicians can reliably estimate BMD in trauma-related amputees. This information will inform providers making decisions regarding weightbearing and bisphosphonate therapy to limit further loss. Future phases of this study will aim to use this correlation to study the effects of weightbearing advancement timing, bisphosphonate therapy, and interventions on the natural history of bone density after amputation.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Unexpected iatrogenic fracture of the femoral neck during subtrochanteric fracture fixation in a patient on bisphosphonate treatment for osteoporosis: Case report

Osteoporotic patients being treated with bisphosphonates present an interesting dilemma when removing hardware such as dynamic hip screws “DHS”. In this paper, we describe the case of a 66-year-old osteoporotic patient who was placed on long term bisphosphonate therapy after sustaining an intertrochanteric hip fracture which was stabilized with a DHS. She presented with a subtrochantric fracture on the ipsilateral side. She was planned for DHS removal and intramedullary nailing. Removal of the dynamic hip screw proved to be difficult, likely due to possible cold welding of the DHS to the barrel of the side plate and sclerotic bone formation around the hardware secondary to the extended bisphosphonate use. The patient had an intra-operative femoral neck fracture while attempting the DHS removal. We had to convert to an unanticipated total hip replacement. Careful considerations should be taken when removing hardware from patients on long term bisphosphonate treatment.

Femoral neck fractures after removal of hardware in healed trochanteric fractures

INTRODUCTION

Hardware removal in healed trochanteric fractures (TF) in the absence of infection or significant mechanical complications is rarely indicated. However, in patients with persistent pain, prominent material and discomfort in the activities of daily living, the implant is eventually removed. Publications of ipsilateral femoral neck fracture after removal of implants from healed trochanteric fractures (FNFARIHTF) just because of pain or discomfort are rare. The purpose of this systematic review of the literature is to report on the eventual risk factors, the mechanisms, the clinical presentation, and frequency, and to pay special emphasis in their prevention.

MATERIALS AND METHODS

A comprehensive review of the literature was undertaken using the PRISMA guidelines with no language restriction. Case reports of FNFARIHTF and series of TF with cases of FNFARIHTF due to pain or discomfort published between inception of journals to December 2016 were eligible for inclusion. Relevant information was divided in two parts. Part I included the analysis of cases of FNFARIHTF, with the objective of establishing the eventual risk factors, mechanisms and pathoanatomy, clinical presentation and diagnosis, treatment and prevention. Part II analyzed series of TF which included cases of FNFARIHTF for assessing the incidence of femoral neck fractures in this condition.

RESULTS

Overall 24 publications with 45 cases of FNFARIHTF met the inclusion criteria. We found that the only prevalent factors for FNFARIHTF were: 1) preexisisting systemic osteoporosis, as most patients were older and elder females, with lower bone mineral density and bone mass; 2) local osteoporosis as a result of preloading by the fixation device in the femoral neck, leading to stress protection, reducing the strain at the neck, and increasing bone loss and weakness; and 3) the removal of hardware from the femoral neck, with reduction of the failure strength of the neck. The femoral neck fractures were spontaneous, i.e. not related to trauma or fall, in 87.5% of the cases, mostly subcapital, and with no prevalence between displaced and undisplaced fractures. The clinical presentation was that of a spontaneous fracture, and most of the patients consulted because of hip pain and presented in the emergency room walking by themselves which led to delayed diagnosis in several instances. Radiological diagnosis was mostly with radiographs, though in some cases CT scans or MRI were necessary. The overall median incidence of this complication was 14.5% after hardware removal because of pain or discomfort in healed trochanteric fractures.

CONCLUSION

The risk factors for FNFARIHTF seem to be preexisisting systemic osteoporosis, local osteoporosis as a result of preloading by the fixation device in the femoral neck, and the removal of hardware from the femoral neck, with reduction of the strength of the neck. The clinical presentation may be obscure as most of the patients complain of hip pain of some days or weeks, and arrive in the hospital walking. Therefore, the attending physician should be alert in order to request the appropriate radiological investigation and if this is not clear CT scan or MRI should be done in order to diagnose promptly these "spontaneous" fractures. Treatment should be replacement surgery in most cases; however, there is some place for internal fixation especially in undisplaced fractures or younger patients. The occurrence of the femoral neck fracture after hardware removal may be prevented with re-osteosynthesis and the use of bone chips or bone substitutes. Finally, the relatively high incidence of this complication should alert orthopaedic surgeons to reduce the removal of hardware in healed trochanteric fractures to very selected cases.

Complications following implant removal in patients with proximal femur fractures - an observational study over 16 years

BACKGROUND

Fractures of the proximal femur commonly occur but the majority of orthopaedic surgeons do not consider general hardware removal as a routine necessity. Indications and time interval for hardware removal in this special selected patient group is still controversial. Therefore we performed a retrospective study to address the following questions: 1) Is there a difference between the medically- (infection, mechanical problems, implant failure) and non-medically indicated group (patients demand, meteoro-sensitivity, foreign body sensation) in relation to complications? 2) Is there a correlation regarding time interval between implantation and removal comparing these two groups? 3) Is there a context related refracture rate? 4) Should non-medically indicated implant removal (IR) be performed due to persistent pressure from the patient?

HYPOTHESIS

We hypothesized that non-medically indicated implant removals should be avoided due to a significantly higher number of associated complications.

PATIENTS AND METHODS

A total of 371 consecutive patients with 424 hardware removal procedures following a proximal femur fracture, between 08/1992 and 11/2008, have been included. Study population was divided into two groups according to their indication for implant removal: medically indicated group (MIR) consisted of 299 patients (80.59%) and 72 patients (19.41%) were assigned to the non-medically indicated (NMIR) group.

RESULTS

In the NMIR subgroup a total of (n = 21) 28% complications occurred compared to 11.46% in the MIR subgroup; (P < 0.005), 86.51% of IR in the MIR group were performed within 1.5 years, compared to 79.17% in the NMIR group after 2 to 3.5 years (NS). In the MIR group 1 refracture occurred, compared to 4 in the NMIR group (NS).

CONCLUSION

Non-medically indicated implant removal should be avoided due to the higher complication rate of 28%. Surgeons and patients should be aware of the imminent complications and therefore implant removal should only be performed for good medical reasons.

LEVEL OF EVIDENCE

Level IV. Historical case study.

A Novel Surgical Technique for Removing Buried Cannulated Screws Using a Guidewire and Countersink: A Report of Two Cases

Removal of metal implants is a common procedure that is performed for a variety of indications. However, problems such as a buried screw head may occasionally arise and render hardware removal difficult or even impossible. The problem is further compounded when the initial screw was inserted percutaneously or via a minimally-invasive (MIS) technique. In the present paper, we introduce a novel, minimally invasive technique to remove buried cannulated screws which obviates the need for excessive extension of the skin incision, surgical exploration, soft tissue dissection or excess bone removal, which surgeons may otherwise have to undertake to uncover the buried screw head. This technique is especially useful in removing cannulated screws which have been inserted using small stab incisions and MIS techniques initially. This technique can be applied to the removal of buried cannulated screws which are placed into any bone in the body.

Possible predictors for difficult removal of locking plates: A case-control study

INTRODUCTION

Difficult removal of locking plates including less invasive stabilisation systems (LISSs) and locking compression plates (LCPs) sometimes occur. However, investigations of the mechanisms and correlated factors of complicated removal remain scant. This study aims to identify correlated factors for the difficult removal of locking plates and to propose suggestions for decision making regarding implant removal and the prevention of complicated removal.

MATERIALS AND METHODS

In total, 308 consecutive patients who underwent LCP/LISS removal from Sep. 2004 to Nov. 2013 were assessed. Using the Mann-Whitney U test, we analysed the correlation between difficult removal and the duration between open reduction and internal fixation (ORIF) and implant removal as well as the correlation between difficult removal and the patients' age. Using Chi Square test, we assessed the correlations between complicated removal and the size, location, insertion technique and cortical purchase of the locking head screw (LHS). Correlated factors were separately determined in upper and lower extremities. Rates of difficult removal in different fracture locations were evaluated, and postoperative complications were documented.

RESULTS

Of the total 308 patients, thirty-seven had intra-operative difficulties, and six patients experienced postoperative complications. Six out of fifteen patients with peri-elbow fractures and five out of seventeen patients with femur fractures suffered difficult removal, while four out of one hundred patients with malleolar fractures had intra-operative difficulties. Difficulties were experienced with 30 of 338 LCPs, 7 of 32 LISSs, 67 of 1533 small-diameter (≤ 3.5-mm) LHSs, and 12 of 442 large-diameter (≥ 4.5-mm) LHSs. Three LCPs and seventeen small-diameter LHSs were retained. A longer interval between ORIF and removal, younger age and bicortical screws correlated with difficult removal in the upper extremities, and a longer duration before removal, small-diameter LHS and minimally invasive insertion of LHS were predictors in the lower extremities.

CONCLUSIONS

Complications occur with LCP/LISS removal, and it should not be a routine procedure. If removal is indicated, performing surgery as soon as radiographs show fracture healing is recommended. Different considerations should apply when making decisions and removing implants from patients with different fracture sites.

Femoral neck fracture after removal of the compression hip screw from healed intertrochanteric fractures

OBJECTIVES

To evaluate the incidence of femoral neck fracture (FNF) after removal of a compression hip screw (CHS) without trauma and to determine the risk factors for this type of fracture.

DESIGN

Retrospective study of consecutive patient series.

SETTING

University teaching hospital.

PATIENTS

Sixty-seven patients with a mean age of 65.3 years (45 women and 22 men).

INTERVENTION

A total of 67 implants were removed in the presence of bony consolidation of the fracture site; most of them were due to hardware pain.

MAIN OUTCOME MEASURES

The incidence of FNF after a CHS removal, clinical parameters (age, gender, bone mineral density, body mass index, and fracture stability), and radiologic parameters (the femoral neck-shaft angle, femoral neck width, distance between thread of lag screw, and neck cortex). Univariate analysis was performed for those parameters of the fracture group and the nonfracture group. To assess which variables were associated with FNF, a multiple logistic regression was used.

RESULTS

Six (9.0%) FNFs occurred within 1 month after a CHS removal. The mean anterior and lateral neck widths were significantly smaller, and the mean anterior and inferior thread-to-cortex distances were significantly shorter in the fracture group compared with the nonfracture group. The risk factor significantly associated with FNF was the inferior thread-to-cortex distance (odds ratio, 0.462; 95% confidence interval, 0.217-0.988).

CONCLUSIONS

CHS should not be removed routinely due to the risk of FNF. Furthermore, attention should be paid to at-risk patients with a hip screw positioned close to the inferior femoral neck cortex.

LEVEL OF EVIDENCE

Prognostic level II.