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Symposium: Papers Presented at the Annual Meetings of The Hip Society

A Short Tapered Stem Reduces Intraoperative Complications in Primary Total Hip Arthroplasty

Molli, Ryan G. DO1, 4, 5; Lombardi, Adolph V. Jr MD, FACS1, 2, 3, 4, a; Berend, Keith R. MD1, 2, 4; Adams, Joanne B. BFA1; Sneller, Michael A. BS1

Author Information

1 Joint Implant Surgeons, Inc, 7277 Smith’s Mill Road, Suite 200, 43054, New Albany, OH, USA

2 Department of Orthopaedics, The Ohio State University, Columbus, OH, USA

3 Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA

4 Mount Carmel Health System, New Albany, OH, USA

5 Orthopedic Institute of Michigan, 14555 Levan Road, Suite 116, 48154, Livonia, MI, USA

a e-mail; [email protected]

One or more of the authors (AVL, KRB) receive royalties and institutional research support from and have consulting agreements with Biomet, Inc (Warsaw, IN, USA). One author (KRB) has consulting agreements with Salient Surgical Technologies (Portsmouth, NH, USA). One author (AVL) receives royalties from Innomed, Inc (Savannah, GA, USA).

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.

Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.

Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.

This work was performed at Joint Implant Surgeons, Inc.

Clinical Orthopaedics and Related Research: February 2012 - Volume 470 - Issue 2 - p 450-461
doi: 10.1007/s11999-011-2068-7
  • Free

Abstract

Introduction

Although THA is continually noted as one of the most successful procedures performed by orthopaedic surgeons worldwide, current research and development continue to strive to improve on the biologic and mechanical designs of modern total hip prostheses. A multitude of published studies report overall survivorship of several standard-length tapered femoral components ranging from 94% to 100% at up to 20 years’ followup [10-12, 17-20, 25, 27-29, 33, 35, 42, 43, 47, 52-55, 58-60]. We recently reported femoral implant survival rates of 98.6% at 5 years, 98.4% at 10 years, 97.1% at 15 years, and 95.5% at 20 years in 2000 standard-length tapered titanium porous plasma-sprayed femoral components (Mallory-Head® Porous [MHP]; Biomet, Inc, Warsaw, IN, USA) [43]. Cementless femoral fixation with tapered-geometry designs has evolved over the past several decades with a recent surge of interest in shorter stems.

Short stems are thought to preserve more native host bone and optimize proximal load transfer, and while not a novel concept, they have become increasingly utilized with the advent of less invasive surgery and rapid-recovery protocols [15, 24, 40, 56, 62, 66]. There are several proposed advantages of short stems, including easier insertion through smaller incisions and less invasive techniques, simpler femoral preparation with a “broach only” system, and their basic inherent bone-conserving nature allowing for more favorable conditions in the potential revision setting. Several studies have demonstrated overall survivorship of short stems ranging from 94% to 100% at up to 18 years’ followup and incidences of thigh pain ranging from 0% to 4% [13, 15, 28, 33, 52, 54]. To justify using shorter tapered stems when more traditional standard-length tapered stems provide pain relief, restore function, and have high survivorship [9-11, 17-19, 25, 42, 43, 58, 60], it is important to show advantages with equal long-term survivorship and demonstrate similar intraoperative reproducibility with equivalent and/or decreased perioperative complications.

We therefore compared short, flat-wedge, tapered, broach-only femoral stems to standard-length, double-tapered, ream and broach femoral stems in terms of intraoperative and perioperative complications, short-term survivorship, and pain and function scores.

Patients and Materials

Institutional review board approved informed consent for historical prospective clinical study was obtained from all patients undergoing THA. We performed a retrospective analysis from a query of our electronic medical record system (DocuMed, Inc, Ann Arbor, MI), revealing 879 consecutive patients (953 hips) who underwent primary THA from January 2006 through March 2008 by two surgeons (AVL, KRB). All patients were managed with a rapid-recovery protocol [8, 41]. The majority of cases (70%; 671 hips) were performed via a less invasive direct lateral approach (LIDL) [6], while a standard direct lateral approach was used in 10% (100 hips), and one surgeon (KRB) beginning in February 2007 used an anterior supine intermuscular approach in 182 hips (19%). To eliminate the possible confounding variable of different surgical approaches as an influence on complication incidence and functional outcome, only cases performed via the LIDL approach were included. Thirteen LIDL cases were excluded in which other femoral stem types were implanted: four cemented stems, six hydroxyapatite-coated stems, two modular stems with a porous proximal sleeve, and one device which was part of a US Food and Drug Administration (FDA) investigational feasibility study. Therefore, our cohort was 606 patients (658 hips) who underwent primary THA using tapered, titanium, porous plasma-sprayed femoral components inserted via a single LIDL approach (Table 1). There were a total of 51 staged bilateral procedures and one simultaneous bilateral procedure. In terms of operative side, 357 (54%) were right hips and 301 (46%) were left hips. A standard-length taper, the MHP femoral component, was implanted in 389 hips (59%), with 110 (28%) being a lateralized offset option. The MHP was introduced and has been used in our practice since 1984. The TaperLoc® stem (Biomet) was introduced in 1982, and a shortened version, the TaperLoc® Microplasty™ femoral component received FDA approval in 2005 and was introduced into clinical use in our practice in January 2006. The lateralized option became available in May 2007. The short stem was implanted in 269 hips (41%), with 173 (64%) being a lateralized offset option. The stem type for patients during the study period was chosen by the surgeons in a nonsystematic manner consistent with the typical process of trialing and implementing any newly available approved device into clinical use. The two groups were similar in age, body mass index, sex, and underlying diagnosis including rheumatoid arthritis. One surgeon (AVL) performed a higher proportion of arthroplasties within the short-stem group, because while the other surgeon (KRB) continued to use the short stem, he began to use the anterior supine intermuscular approach. More ceramic heads and fewer metal-on-metal bearings were used in the short stem group as ceramic heads became available in larger sizes and awareness increased regarding adverse reactions to metal-on-metal. More lateralized option stems were required in the short-stem group because the standard offset neck shaft angle of that device is more valgus (138° versus 136.5°) than the standard-length taper standard offset neck. The minimum followup for the standard-length group was 0.8 months (average, 30.9 months; range, 0.8-61.2 months) and the minimum followup for the short-stem group was 0.9 months (average, 26.9 months; range, 0.9-62.2 months). Twenty-six patients (28 hips) died within the study period at an average of 22 months postoperatively, with none related to the arthroplasty procedure and no THA failures. Two of the patients who died had not returned for a postoperative evaluation. Of the surviving patients, 74% (469) had minimum 2-year followup. Four living patients, with two from each group, did not return for clinical evaluation and could not be located. Clinical data from all patients were included. No patients were recalled specifically for this study; all data were obtained from medical records and radiographs.

T1-17
Table 1:
Characteristics of standard-length taper and short taper stem groups

The MHP femoral component is a titanium collarless stem with a proximal-to-distal taper in both the coronal and sagittal planes (double taper) and three separate surface finishes (Fig. 1). The proximal 1/3 is plasma-sprayed with titanium alloy, the midsection is grit-blasted, and the distal surface is a smooth satin finish. The system requires both reaming and broaching. The design features fins proximally that engage the cortical-cancellous junction to resist rotational moments about the implant in the proximal femur. There are seven different neck length options available and a lateralized neck offset option that allows for increased abductor tension and hip stability without lengthening of the limb.

F1-17
Fig. 1:
The MHP femoral component, introduced in 1984, is a double-tapered titanium stem with a proximal porous plasma-sprayed surface applied circumferentially around the stem. The middle section is grit-blasted and the distal section has a matte finish. The device is available in 14 standard offset sizes with a neck angle of 136.5°, diameters from 6 to 19 mm, and lengths from 135 to 180 mm, and 10 lateralized offset sizes with a neck angle of 131.5°, diameters from 8 to 17 mm, and lengths from 145 to 180 mm. (Reproduced with permission of Joint Implant Surgeons, Inc, New Albany, OH.)

The TaperLoc® Microplasty™ femoral component is a titanium collarless stem with a flat, tapered-wedge geometry (3° medial to lateral taper) with a proximal, titanium, porous plasma-sprayed surface (Fig. 2). This is a broach-only system. The collarless feature allows for optimal component seating and enhanced rotational stability. There are seven neck length options, and a lateralized neck offset option is available.

F2-17
Fig. 2:
The TaperLoc® Microplasty™ femoral component is a tapered, titanium, porous plasma-sprayed device available with either standard or lateralized offset and in 13 sizes, with diameters ranging from 5 to 25 mm and lengths ranging from 95 to 135 mm. The neck shaft angle is 138° for both standard and lateralized offset options, with lateralization achieved by shifting the trunnion medially. (Reproduced with permission of Joint Implant Surgeons, Inc, New Albany, OH.)

We used the same surgical approach for every case in this series: the LIDL approach [6], a less invasive modification of the direct lateral approach previously described by Frndak et al. [23] (Fig. 3). We performed preoperative templating in each case to assist in determining component size (both femoral and acetabular) and the appropriate neck resection level. The LIDL approach utilized a more oblique skin incision centered over the tip of the greater trochanter and angled from anterodistally to posteroproximally. The surgeons then incised the fascia lata in line with the skin incision, with minimal undermining between the subcutaneous fat and fascia lata to minimize dead space. The assistants then simultaneously abducted and slowly externally rotated the leg as the surgeon began taking down the anterior-most insertional fibers of the gluteus medius from distal to proximal beginning at the vastus ridge. At this stage, dissection was performed with electrocautery to allow for hemostasis. The anterior aspect of the vastus lateralis was incised in line with its fibers to allow for one continuous sleeve to be elevated off of the anterior femur. Working proximally toward the anterior-proximal-most tip of the greater trochanter, the fibers of the gluteus medius were split at an angle of 45° and bluntly dissected in an anterior and proximal direction for a few centimeters, directly in line with the femoral neck. A blunt Homan-type retractor was then placed deep to the gluteus medius, exposing the anterior-most fibers of the gluteus minimus and anterior hip capsule. The capsule was incised proximally along the superior aspect of the femoral neck, possibly including a small portion of the gluteus minimus tendon. This generally corresponded to a 1 o’clock position in a right hip. Then, the femoral head was resected and standard acetabular and femoral preparation was performed with either the standard-length or short tapered instrumentation and implants. We encountered a femoral or trochanteric fracture during femoral preparation in 13 patients; in these patients, we stabilized the fracture with one or more cerclage cables or wires [9].

F3-17
Fig. 3:
The LIDL approach to the hip is performed by elevating the gluteus medius insertion along with the capsule in one continuous soft tissue sleeve from the anterior aspect of the trochanter. The origin of the vastus lateralis is left intact and dissection proceeds anterior and medial below the vastus muscle. (Reproduced with permission of Joint Implant Surgeons, Inc, New Albany, OH.)

We allowed patients full weightbearing as tolerated with a walker or crutches immediately postoperatively and advised them to progress to a cane and eventually without any ambulatory assistance once they were pain-free and without a limp.

We saw patients at approximately 6 weeks postoperatively and yearly thereafter, unless a problem arose in which case patients were seen as soon as possible. At each clinical examination, radiographs were obtained, including an AP view of the pelvis and a lateral view of the involved hip. In addition, a standard physical examination was performed, including evaluation of the wound and strength assessment of the involved hip. Pain, deformity, ROM, and function were rated using the Harris hip score (HHS) [26] and activity level rated using the Lower Extremity Activity Scale (LEAS) of Saleh et al. [61]. We reviewed perioperative records for incidence of intraoperative complications, operative times, and estimated blood loss; and discharge and office notes for hemoglobin level at discharge, length of acute stay, discharge disposition, implant-related complications, and need for further surgery. Intraoperative records were available for all THAs. Discharge notes were available for 95%.

We used chi square analysis to compare difference in incidence of intraoperative complications between the two groups. We used a two-tailed Student’s t test to compare differences in mean HHSs, pain scores, and LEAS scores between the two groups.

Results

More intraoperative complications (fractures) occurred when the standard-length tapers (n = 12; 3.1%) were implanted compared with the short tapers (n = 1; 0.4%). The location of these fractures utilizing the Mallory classification [9, 46] were three trochanteric avulsions, seven Type I femoral fractures, and two Type III fractures within the standard-length stem group. One Type I femoral and two of the trochanteric avulsions were in patients with rheumatoid arthritis. The fracture in the short-stem group was a Type I femoral fracture in a patient with rheumatoid arthritis (Table 2). Other complications within the standard-length stem group included four acetabular revisions (three for loosening, one for metal sensitivity) (1.0%), one temporary (< 12 hours) sciatic nerve palsy (0.2%), and one chronic sciatic nerve palsy (0.2%). Other complications in the short-stem group included two acetabular revisions (0.7%), one for cup migration and one for acetabular fracture/cup protrusion. There was no difference in incidence of complications between the two surgeons.

T2-17
Table 2:
Results for standard-length taper and short taper stem groups

We observed two stem failures requiring revision, one from each group for an overall incidence of stem failure for any reason of 0.26% in the standard-length stem group and 0.37% in the short-stem group. There were no patients with aseptic loosening in either group. The first failure was a periprosthetic femur fracture in the standard-length stem group, which we identified 2 weeks after the primary procedure (Fig. 4). We revised the patient to a larger MHP stem with cerclage cables and she was doing well at latest followup. The second patient was in the short-stem group and had continued pain, radiolucencies around the femoral component on plain radiographs, and a bone scan with increased uptake, suggesting aseptic loosening versus infection. Laboratory analysis demonstrated elevated erythrocyte sedimentation rate and C-reactive protein 19 months after the index procedure and we performed a radical débridement with antibiotic spacer placement. The patient subsequently underwent reimplantation with a standard-length stem and revision acetabular component and was doing well at most recent followup.

F4-17
Fig. 4A-E:
(A) A preoperative radiograph of the left hip of a 79-year-old female patient who presented with severe pain and discomfort secondary to osteoarthritis shows severe joint space narrowing, sclerosis, and osteophyte and cyst formation. (B) An immediate postoperative radiograph shows treatment of cementless primary left THA with an 11- by 160-mm standard-length taper stem with lateralized offset and a 36-mm cobalt-chromium head with +6-mm neck articulated against highly crosslinked polyethylene. (C) At 2 weeks postoperative, the patient presented emergently with severe pain. A radiograph reveals a periprosthetic femoral fracture. (D) The patient’s femoral component was revised to a 14- by 175-mm standard-length tapered stem with lateralized offset, and the bone was secured with five cerclage cables. (E) A radiograph at 3 years after revision shows well-fixed components in satisfactory position and alignment. The patient had a HHS of 94 at latest followup.

Between groups, there were no differences in preoperative or postoperative HHSs or LEAS scores at 6 weeks and most recent followup (Table 2).

Discussion

There has been much evidence demonstrating standard-length, tapered, titanium, porous plasma-sprayed components perform well in the short, mid, and long term [10-12, 17-20, 25, 27-29, 33, 35, 42, 43, 47, 52-55, 58-60]. With recent interest in less invasive surgery through smaller incisions, shorter cementless stems have been popularized and utilized to achieve femoral fixation [15, 24, 40, 56, 62, 66]. We therefore compared the intraoperative and perioperative complication rate, short-term survival, and preoperative and postoperative HHSs and LEAS scores for pain and function between groups receiving standard-length double-tapered stems and shorter, flat-wedge, “microplasty” tapered stems.

Our study does contain several limitations. First, although both stems are titanium, porous plasma-sprayed, tapered designs, they are two completely different stems, not just a shorter version of the standard-length stem. The standard-length stem requires both reaming and broaching, while the short stem is a broach-only system. This extra-preparation and geometric design may influence the tendency for the standard-length stem to have a higher fracture risk [9, 40, 59, 63]. Second, the short-term followup for this study was a limiting factor in terms of comparing differences in survivorship and functional outcomes. Third, although this was not the intent of this study, there was no specific analysis of radiographs with regard to positioning and sizing of stems, although studies have shown stem position is not correlated with increased incidence of early component failure [11, 34].

We found a higher incidence of intraoperative femoral and trochanteric fracture with standard-length stems (3.1%) than with short stems (0.4%), which are both within the range of findings reported in other studies of primary cementless THA (Table 3). While these numbers are lower than previous reports of intraoperative fracture with tapered designs, which range from 1.6% to 7% [9, 59, 63], our study demonstrates this particular design of shorter stem does have a lower incidence of intraoperative femur fracture when compared with a standard-length stem. The literature is a bit conflicting when looking at overall outcomes of THAs after intraoperative fractures. Thillemann et al. [67] have shown an overall cumulative failure rate of 0.9% within the first 6 months for patients without intraoperative femoral fractures versus 3.4% for patients with associated intraoperative femoral fractures. The highest cumulative failure rates in that study were 5.7% for the patients when they had osteosynthesis compared to 1.5% in the intraoperative fractures treated nonoperatively [67]. The decision to treat certain intraoperative fractures without osteosynthesis is likely due to less severe fracture morphology with more inherent stability with distal stem fixation [67]. In contrast, we previously reported excellent long-term survival of MHP femoral components after intraoperative fracture with immediate cerclage wire or cable fixation (100% femoral component survival at up to 16 years) [9]. In another experimental study comparing a standard-length, cementless, tapered stem (CLS® Spotorno®; Zimmer, Inc, Warsaw, IN, USA) with a shorter, tapered stem (Mayo®; Zimmer), the authors observed a nonsignificant trend toward lower fracture resistance with the short-stemmed design [30]. This same study showed a much lower average amount of subsidence before fracture in the short stem (7.9 mm) versus the standard-length stem (13.9 mm) [30]. Although these reports show conflicting data, our experience with these two particular stem designs suggests the shorter stems are an equally efficacious alternative to the standard-length stems. While the shorter stems may make the procedure technically easier and more amenable to less invasive approaches, our data also demonstrate a decreased risk of intraoperative fracture when shorter stems are used.

T3A-17
Table 3:
Published studies reporting incidence of intraoperative femoral, trochanteric, and ankle fractures during primary THA
T3B-17
Table 3:
(continued)

The overall stem survivorship at most recent followup with stem revision for any reason as the end point was 99.7%, with only two of 658 stems needing revision for any reason. We performed no revisions for aseptic loosening or failure of ingrowth, for an early rate of stable fixation of 100%. Although this study was predominately designed to compare the intraoperative complication rates between standard-length and short tapered stems, our short-term survival is encouraging. We previously reported a 98.6% overall stem survivorship at 5 years (98.4% at 10 years, 97.1% at 15 years, and 95.5% at 20 years) with the MHP femoral prosthesis, all performed via a direct lateral approach, with stem revision for any reason as the end point [43]. In the same study, stem survivorship, when looking only at aseptic loosening as reason for failure, was 99.4% at 5 years and 99.3% at 10, 15, and 20 years [43]. Further followup is needed to compare the long-term durability in clinical practice of these two devices in terms of survival and patient function and activity level.

With regard to postoperative pain and function scores, no differences in the HHS pain and total scores and LEAS scores were seen between the two groups at the 6-week or most recent followup visit. Both groups saw relatively equivalent improvements in their HHS pain and total scores postoperatively when compared with preoperative levels (Table 2).

In conclusion, the TaperLoc® Microplasty™ femoral stem appears to be a safe and reliable alternative to a more traditional standard-length double-tapered stem (Fig. 5). The risk of major intraoperative complications, particularly iatrogenic femoral fracture, was less with this short stem, making it an attractive alternative to more traditional stems. Although overall stem survivorship in the literature with traditional stems is exceptional, the nearly eight times higher risk of intraoperative fracture associated with these stems in this study certainly lends to more fracture-friendly stem options being sought. Short stems do not appear to compromise either femoral fixation or short-term clinical results and will likely continue to be utilized as many more surgeons and patients seek less invasive techniques for THA. Future studies focused on long-term survivorship and durability of these “short stems” will be important in determining their continued use in THA.

F5-17
Fig. 5A-C:
(A) A preoperative radiograph of the left hip of a 64-year-old female patient who presented with severe pain and discomfort secondary to osteoarthritis shows severe joint space narrowing, sclerosis, and osteophyte and cyst formation. (B) A postoperative radiograph at 6 weeks shows treatment of cementless primary left THA with a 10- by 105-mm short taper stem and a 36-mm BIOLOX® delta ceramic-on-highly-crosslinked polyethylene articulation (Ceramtec AG, Plochingen, Germany). (C) A radiograph at 4 years postoperatively shows well-fixed components in satisfactory position and alignment. The patient had a HHS of 96.5 at latest followup.

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