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The dynamic helical hip system (DHHS; Synthes, Paoli, Pennsylvania) differs from the standard dynamic sliding hip screw (SHS) in that in preparing for its insertion, reaming of the femoral head is not performed, thereby preserving bone stock. It also requires less torque for insertion of the helical screw. The associated plate has locking options to allow locking screw fixation in the femoral shaft, thereby decreasing the chance of the plate pulling off. While biomechanical studies have shown improved resistance to cutout and increased rotational stability of the femoral head fragment when compared with traditional hip lag screws, there is limited information on clinical outcome of the implant available in the literature.
We report a single surgeon series of 87 patients who were treated for their per-trochanteric hip fractures with this implant to evaluate their clinical outcome and compare it with a cohort of 344 patients who were treated with the standard SHS. All data were prospectively collected, most as part of a structured Geriatric Fracture Care Program.
The 2 groups were similar demographically, and medically, with similar rates of in-hospital complications and implant failure. Failure in the DHHS group was attributable to use of the implant outside its indications and repeated fall of the patient.
This limited case series showed that the DHHS outcomes are comparable with that of the SHS. Whether there is any benefit to its use will require larger, prospective randomized controlled trials.
As the post–World War II “baby boomer” population ages, there is an anticipated fracture epidemic, with data indicating that hip fractures account for 330 000 admissions costing an estimated 10.3 billion/year.1 Hip fracture patterns define treatment, with extracapsular fractures with an unstable fracture pattern and loss of the medial buttress believed to be most effectively treated with an intramedullary device.2 Extracapsular fractures of a “stable” configuration are treated with a dynamic or sliding hip screw (SHS) with high success rates being reported in the literature.3
The SHS is a stainless steel screw implant with a barrel that slides over the attachment to the lateral wall plate, thus allowing medial displacement of shaft in relation to head and neck fragments, which reduces the bending moment and resulting forces that potentially lead to collapse of medial buttress and varus displacement. Its use was described and popularized in the second half of the 20th century,4,5 and it rapidly gained widespread use as the gold standard for treatment of intertrochanteric hip fractures, until the introduction of trochanteric entry intramedullary devices in the past 15 years.6
The dynamic helical hip screw (DHHS; Synthes, Paoli, Pennsylvania) is a stainless steel implant designed to permit controlled impaction of fracture fragments and is similar to the traditional SHS design. The DHHS has both short and long barrel options and offers the added potential benefit of locking head screws in the sideplate. The helical blade can be rotationally locked in the barrel with a collet mechanism using a cylindrical impactor. The DHHS device was first introduced in 2004. The recommended indications for the device are similar to those for an SHS. The device is offered in varying neck shaft angles similar to those available with an SHS and the helical blade implants are offered in 5 mm increments, again similar to those of an SHS.
Reasons for failure of the SHS have been well described as cutout of the screw from the femoral head, loss of reduction with shaft medialization, nonunion and plate pull off. Lag screw cutout has been related to incorrect technique, such as a poor tip–apex distance and also to poor quality osteoporotic bone.7 Modifications and augmentations such as retractable talons,8 twin hooks,9 expansion devices10 as well as augmentation of the screw with cement11 of the SHS have been developed to minimize the failure rate of this common procedure, but none have gained widespread use. The DHHS utilizes a helical blade implant which does not require reaming or tapping of bone in the femoral head, thus theoretically preserving femoral head bone mass for fixation. Helical implants also theoretically offer higher areas of surface area contact with osteoporotic bony trabeculae to maximize purchase and decrease cutout.
Biomechanical studies have shown improved resistance to cutout and increased rotational stability of the femoral head fragment with helical implants when compared with traditional hip lag screws,12–17 but limited published studies18 are available on the clinical outcome of this implant.
We present a single surgeon series of patients who were treated for their pertrochanteric hip fractures with this implant and compare it with a group treated with an SHS. None of the authors have any financial or intellectual allegiances to either implant. The aim of the study is to compare the rates of implant-related complication between an SHS and a DHHS devices in elderly patients with fracture.
We report a series of patients treated with a DHHS by the senior author. The study was conducted after approval by the local institutional review board.
The primary source of data was a Geriatric Fracture Database, the results of which have been previously published.19 A secondary source was data collected in the surgeon’s office charts before the implementation of the Geriatric Fracture Database, 30 patients were sourced from this cohort. Their charts were reviewed by a nurse data collector so that the standard and quality of collected data were consistent with the previously prospectively collected information.
All geriatric patients with a fracture admitted to our institution since 2004 are treated with the same protocols of the Geriatric Fracture Care (GFC) Program. This ensures early evaluation and treatment, decreased time to surgery, and standardized order sets with comanagement by both the orthopedic and geriatric team with all patients prospectively enrolled in a quality management database. The program has been shown to improve patient outcomes, decreased complications, mortality, and costs.19–21 As this is a retrospective review, the choice of implant was at the discretion of the operating surgeon. Two groups were established from the database for study purposes (ie, SHS and DHHS) and were compared based on in-hospital complications and rates of reoperation or failure. The scoring systems used for analysis in the GFC program are the Parker Mobility Score22 (an assessment tool that ranks mobility on a scale of 0-9) and the Charlson Score23(a validated tool used to predict 1-year mortality based on weighted scores for medical comorbidities).
Technique of Insertion: After administration of anesthesia, spinal or general at the anesthetistś preference and prophylactic antibiotics (cefalosporin or vancomycin if penicillin allergic), each patient was positioned supine on the fracture table with a padded traction boot applied to the side of the hip fracture, and the contralateral uninjured side held in flexion and abduction in a padded well-leg holder to allow imaging of the hip fracture site with an image intensifier.
Reduction by traction and internal rotation or manipulative maneuvers24 was confirmed with imaging before sterile preparation and draping of the skin. A longitudinal incision was made through the skin and fat, from just distal to the greater trochanter to the fascia layer, with hemostasis by cautery. A longitudinal split was created in the line of the fascia lata and exposure of the vastus lateralis was obtained. The vastus lateralus is split in line with its fibers and was retracted to expose the femoral shaft distal to the fracture site. A variable angle guide allowed placement of a 2.5-mm guide wire centrally in the femoral head, confirmed on anterior-posterior (AP) and lateral imaging. Each implant was then inserted per manufacturer’s instructions, with differences between both techniques as follows.
After measuring the length of the screw of the guide wire, the femoral neck is reamed, using an SHS triple reamer, which reams the trochanteric area and the femoral neck. The lag screw of the appropriate length is screwed into position without tapping. Imaging confirms appropriate positioning and a satisfactory tip–apex distance in both the AP and lateral views. The appropriate sized sideplate is then inserted over the SHS barrel and affixed onto the femoral shaft with 4.5 mm cortex screws.
After measuring the length of the guide wire, a tapered reamer is used to ream the trochanter and lateral femoral neck. A DHHS helix blade of exact measured length is impacted into position with the insertion device which applies a torsional force to the helical blade as it is inserted over the guide wire. Images of the helical blade resemble a “teardrop” on the AP projection and a helix on the lateral projection (Figure 1). Using an insertion device, the appropriate DHHS side plate is then inserted over the helix blade and fastened to the femoral shaft with screws. The DHHS has the option of utilizing a 5-mm locking screw or standard 4.5 mm cortex screws. The DHHS is then rotationally locked within the barrel with the impactor, which still permits axial collapse as for the SHS.
Final images were obtained to confirm satisfactory implant placement prior to closure in layers. No drains were inserted. All patient postoperative care is standardized per the unit’s care pathway,19 with discharge from the hospital to a rehabilitation or skilled nursing facility.
Clinical characteristics and postoperative outcomes within each operative approach were assessed using an independent samples t test, a Mann-Whitney U test, or chi-square analysis as appropriate to the data. These statistical analyses were performed using the SPSS software version 19 (SPSS Inc, Chicago, IL).
In total, 87 patients older than 60 years were identified who were treated with a DHHS for a hip fracture over a period of 6 years. Surgery of 30 patients predated the introduction of the GFC program. Their care was per the surgeon who developed the pathway, in the same institution and can be considered to be of the same standard. The remaining 57 patients had surgery after the introduction of the organized program. Periprosthetic and pathological fractures were excluded from both groups. In all, 344 patients older than 60 years were identified who had an SHS for the same fracture pattern. Details and characteristics of the groups are outlined in Table 1.
There were 17 males and 70 females in the DHHS group with a mean age of 87 years, ranging from 61 to 105 years. Within the expected context of the local community, most patients were whites and female. Just over 50% of both groups were community dwellers prior to their fracture. The mean Parker Mobility Scores22(a tool to assess preinjury mobility function and help stratify 1-year mortality after proximal femur fractures) were low (overall 3.51 in SHS group and 3.49 in the DHHS group), likely reflecting the high percentage of noncommunity dwellers.
Time to surgery (Table 2) was within 24 hours for both groups, per the standard of care within the GFC. Average length of stay was 4.2 days (range 2-23 days) in the DHHS group, less than that of the SHS group despite an outlier who waited 23 days before definitive treatment. There was no statistically significant difference between the 2 groups, except that the mean of the Charlson morbidity score was higher in the DHHS group, implying them to be a “sicker” cohort than the SHS group.
Table Table22 also demonstrates no difference in the rate of in-hospital complications, that is, postoperative infection (ie, urinary tract infection, surgical site infection, and pneumonia), bleeding (ie, wound hematoma, gastrointestinal bleed, retroperitoneal hematoma, intracranial bleeding, or hemorrhagic stroke), renal insufficiency, cardiac complications (ie, new arrhythmia, acute myocardial infarction, or congestive heart failure) hypoxia, or delirium between both groups. Implant-related complications (reoperation or hardware fixation failure), including the need for revision surgery, were also comparable between the 2 cohorts at 2% for the SHS group and 2.3% for the DHHS group.
The 2 failures noted in the DHHS group are shown in Figures 2 and 33 . . The first occurred after a fall, within 8 weeks of the index operation and demonstrates superior cutout of the helical blade. Both patient and her health care proxy refused further surgery and further treatment consisted of conservative comfort measures. The second failure (Figure 3) was attributable to the incorrect implant being used at the index operation resulting in medial cut through—a cephalomedullary device was indicated due to the unstable fracture pattern. Revision to a hemiarthroplasty was performed due to progressive symptoms.
There are some reports in the literature of the biomechanical assessment of the DHSS, but very little information with regard to its clinical use.
The helical blade construct is reported to be superior to that of the “traditional” lag screw,15,25,26 however, these articles report on the use of the helical blade with an intramedullary construct and do not compare it to the lag screw with a lateral sideplate. With the increasing use of trochanteric entry nails in conjunction with a helical blade, whether the helical blade could be used cost-effectively in conjunction with the lateral plate of the SHS has been investigated27 and shown that it is implant position rather than fracture reduction or type or generation of implant which is most important for osteosynthesis. This is consistent with previous work regarding the importance of the tip–apex distance in prediction of cutout.7,28 Also, Stern et al report29 their findings comparing the DHHS implant with a trochanteric entry nail, their objective being to determine the degree of accuracy in placement of the device in the femoral head, as well as reporting on the rates of reoperation and cutout of the 2 implants. They found that in AO 31-A1 and AO 31-A2 pertrochanteric fractures, both the screw and blade performed equally well in terms of implant placement in the femoral head and radiographic outcome. Lenich et al30 recently described their investigation into the effect of rotational torque as the initiating factor in femoral cutout and report that both screw systems (SHS and Gamma 3) and helical blades (proximal femoral nail [PFNA] and trochanteric fixation nail [TFN]), fail if not optimally positioned, and thus that the center–center position in the head of femur of any kind of lag screw or blade is to be achieved to minimize rotation of the femoral head and to prevent further mechanical complications.
With specific regard to a helical implant, in vitro experiments demonstrating its superior implant anchorage under cyclical loading17 and a delayed onset of migration of the implant14 which can lead to cutout and thus failure have been published. However, another in vitro study by Wahnert et al16 revealed no differences in the primary stability of the proximal femora instrumented with the helical blade implant with different degrees of cancellous bone compaction, that is, predrilled or nonpredrilled and did not show that predrilling compromises fixation.
As previously reported, the results of our subgroup show the benefits of elderly patients with a hip fracture being treated within a GFC program,13 with a decreased length of stay when compared with the national average of 6.43 days (standard error: 0.05)31The mean Parker Mobility Scores22 were low (overall 3.51 in SHS group and 3.49 in the DHHS group), likely reflecting the high percentage of noncommunity dwellers. The rates of complications between the 2 groups were comparable, with no significant statistical differences noted. Although there is a higher in-hospital mortality rate in the SHS group, it can be attributed to the larger group being analyzed and is still equivalent to nationally reported rates.31
A recent report of a small randomized trial of 51 patients18 recognized that both the SHS and DHHS perform well in the majority of cases. However, the authors observed a higher incidence of failure in the DHHS group, but note that despite failure, the mechanics of the implant left sufficient bone stock for revision fixation. The outcome of our larger series is in accordance with these findings.
Author experience with the device showed the device to be straightforward to insert but to require experience with the device for proficiency. This opinion will differ among surgeons and ultimately must be verified by strong evidence of the outcome of the implant through a randomized controlled trial. Both failures occurred in the subset of patients treated before the implementation of the Geriatric Fracture Database and can be considered to be a part of the learning curve.
The device is similar in cost to the standard traditional SHS, if standard 4.5 mm cortex screws are utilized to fasten the sideplate to the femoral shaft. However, if three 5.0-mm locking head screws are used in the femoral sideplates, the cost for the DHHS implant is considerably higher. Total implant cost (list price) of an SHS is $1252.50, a DHHS with 4 standard cortex screws is $1312.50 while a DHHS with locking screws is $1901.25 (prices as of January 2012). We have not shown any clinical benefit to justify the increased cost given the 2 implant failures occurred in the DHHS group not in the SHS group.
In this limited series, the DHHS device was found to be comparable with the traditional SHS with similar rates of failure for both devices. While the DHHS was seen to fail, these failures appear to be related to repeated injury and incorrect usage or positioning. In summary, the DHHS device appears to be a safe and reasonable alternative to use of an SHS for the elderly osteoporotic patient with a stable pattern pertrochanteric hip fracture. A large, well-designed, sufficiently powered randomized controlled trial would be required to validate our findings.
Declaration of Conflicting Interests: Dr. Kates has received institutional research grant support from Synthes, USA not related to this project. He has also received grant support from AO Research Foundation and AOCID has helped create the Geriatric Fracture database.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.