Aims

Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component.

The purposes of this study were to report the accuracy of stem anteversion for Exeter cemented stems with the Mako hip enhanced mode and to compare it to Accolade cementless stems.

We reviewed the data of 25 hips in 20 patients who underwent THA through the posterior approach with Exeter stems and 25 hips in 19 patients with Accolade stems were matched for age, gender, height, weight, disease, and approaches. There was no difference in the target stem anteversion (20°–30°) between the groups. Two weeks after surgery, CT images were taken to measure stem anteversion.

The difference in stem anteversion between the plan and the postoperative CT measurements was 1.2° ± 3.8° (SD) on average with cemented stems and 4.2° ± 4.2° with cementless stems, respectively (P <0.05). The difference in stem anteversion between the intraoperative measurements and the postoperative CT measurements was 0.75° ± 1.8° with Exeter stems and 2.2° ± 2.3° with Accolade stems, respectively (P <0.05).

This study demonstrated a high precision of anteversion for Exeter cemented stems with the Mako enhanced mode and its clinical accuracy was better with the cemented stems than that with the cementless stems. Although intraoperative stem anteversion measurements with the Mako system were more accurate with the cemented stems than that with the cementless stem, the difference was about 1° and the accuracy of intra-operative anteversion measurements was quite high even with the cementless stems. The smaller difference in stem anteversion between the plan and postoperative measurements with the cemented stems suggested that stem anteversion control was easier with cemented stems under the Mako enhanced mode than that with cementless stems.

Intraoperative stem anteversion measurement with Mako total hip enhanced mode was accurate and it was useful in controlling cemented stem anteversion to the target angle.

The purposes of this study were to evaluate the accuracy and feasibility of a robotic preparation for acetabular metal augments in patients with developmental dysplasia of the hip (DDH). Mako robotic arm reaming was used in 7 DDH to prepare the bony cavities for both Trident PSL cups and Tritanium acetabular wedge augments in six hips with Crowe 2 or 3 DDH. In CT-based planning, a properly sized cup was placed in the original acetabulum, and the same sized cup was also placed to fit the superolateral acetabular defect. The coordinates of the planned positions of cup and augment were recorded to manage the robotic arm reaming. After registration of the patient's pelvis, robotic reaming was performed first for the augment, then, for the cup by changing the target position of reaming as planned. The accuracy of the cup and augment placement was assessed on postoperative CT. To evaluate the feasibility of the robotic procedure, the OR time and blood loss were compared with those of 13 patients who received the same cup and augment systems with a conventional technique. All procedures were done without fracture or fixation failure. There were no differences in OR time or blood loss between the two procedures. Postoperative CT measurements of the distance between the cup center and the augment sphere center showed less than 2mm difference from the Mako preoperative planning.

Although a longer time of follow up evaluation is mandatory, our robotic acetabular augment preparation technique is accurate and feasible.

The purposes of this study were to review retrospectively the 10-year outcome of cementless total hip arthroplasty (THA) using an active robot system in the femoral canal preparation for an anatomic short stem and navigation in the cup placement through a mini incision posterior approach. We reviewed all patients who underwent THA with this procedure in 53 hips between 2004 and 2007. There were no intraoperative fracture nor navigation- or robotic-related complications. All implant sizes were same as planned ones. All cases were followed up at least two years and all implants showed bone ingrowth stable according to the Engh's criteria. After then, six patients died of unrelated causes. Two patients (three hips) could not come to the 10-year follow-up examination. The remaining 44 hips were followed for 10 to 12 years (11 years on average). There is no dislocation. The average JOA hip score improved from 48 preoperatively to 96 at the final examination. On the postoperative x-ray measurements, the average cup radiographic inclination was 39° and the radiographic anteversion was 14°. There was no stem which showed more than 2° of varus or valgus alignment. There was no case who showed more than 5mm of limb length discrepancy. Postoperative CT images of 38 hips were obtained at 2 weeks. After matching the coordinates of the pelvis and femur with the preoperative planning, we got very small differences in alignment parameters between the measured values and the planed ones. The difference differences between the plan and measured values were −0.1° in cup inclination, −1.4° in cup anteversion, stem 0.5° in coronal alignment, 0.6° in stem sagittal alignment, and −1.6° in stem anteversion, respectively. We conclude that our robotic femoral preparation for a short anatomical stem and navigated cup placement thru a mini-posterior approach was safe and feasible without affecting the accuracy of the procedure. There were no long term adverse effect of the procedure.

The purpose of this preliminary study was to evaluate the feasibility and accuracy of HipAlign (OrthAlign, Inc., USA) system for cup orientation in total hip arthroplasty (THA). The subjects of this study were 5 hips that underwent primary cementless THA via a posterior approach in the lateral decubitus position. Evaluation 1; after reaming acetabular bone, a trial cup was placed in the reamed acetabulum in an aimed alignment using HipAlign. Then, the trial cup alignment was measured using HipAlign and CT-based navigation system in the radiographic definition. Evaluation 2; a cementless cup was placed in the reamed acetabular in an aimed alignment using CT-based navigation and cup alignment was measured using both methods. After operation, we measured the cup alignment using postoperative CT in each patient. In the results, the average cup inclination measured with HipAlign was around 5 degrees of true cup inclination angles. The average cup anteversion with HipAlign tended to be larger than that with CT-based navigation or postoperative CT in both evaluations. That is because there is a difference in the pelvic sagittal tilt between the lateral position and supine position. In conclusion, this study suggests that guiding cup alignment with the use of HipAlign is feasible through a posterior approach and the mean cup inclination measured with HipAlign showed an acceptable level of accuracy, but the mean cup anteversion is not reliable. We need a further modification for pelvic registration to improve the accuracy of cup anteversion.

Aims

To determine the normal values and usefulness of the C1/4 space available for spinal cord (SAC) ratio and C1 inclination angle, which are new radiological parameters for assessing atlantoaxial instability in children with Down syndrome.

The purpose of this retrospective study was to estimate the outcome improvements after Total Hip Arthroplasty (THA) using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients who underwent THA with a navigation system in our institutions, and to compare them with those undergoing THA without a navigation system that had been reported in the literatures. The subjects in this study comprised 245 patients (39 males, 206 females; mean age, 59.9±12.0 years; mean BMI, 22.8±3.2 kg/m2) who underwent THA. All patients had adequate data to allow complete scoring of the WOMAC for a minimum one-year postoperative follow-up. CT-based navigation was used in all THAs. Postoperatively, no restrictions were imposed. A MEDLINE search was conducted using the search terms ‘Total hip’, ‘Quality of life (QOL)’, and ‘WOMAC’. 10 articles evaluated all WOMAC subscales one to two years after THA. The WOMAC subscale scores were compared statistically between our study and the results reported in the 10 articles using Welch's t-test. The present physical function subscale scores were the best of the 10 studies, and in 8 of the 10 studies, the differences were significant. WOMAC subscale results in our study were significantly better than those reported in most articles in which THA was performed without navigation. These results show that THA using navigation can improve patients' postoperative QOL.

The robotic-assisted system (ROBODOC) is the first active robot that was designed to reduce potential human errors in performing cementless total hip arthroplasty (THA). We have reported minimum five years follow-up clinical results. However, to our knowledge, there have been no longer follow-up reports. The purpose of this study was to prospectively compare the minimum ten years follow-up results of robotic-assisted and hand-rasping stem implantation techniques.

Between 2000 and 2002, we performed 146 THA on 130 patients who were undergoing primary THA. Robot assisted primary THA was performed on 75 hips and a hand-rasping technique was used on 71 hips. Among them, 112 hips (53 hips in the robotic milling group and 59 hips in the hand-rasping group) were followed more than 10 years. Follow-up periods ranged from 120–152 months (average 135). Preoperatively, we plan the position and the size of the stem three-dimensionally for both groups. At the operation, posterolateral approach was used. We evaluated survivorship and compared clinical results.

At the final follow-up, no stem was revised in either group. Plain radiographs showed bone ingrowth fixation for all the stems of both groups. There were no signs of mechanical loosening in any implant. Preoperatively, there were no significant differences in the Japanese Orthopedic Association (JOA) hip scores between the two groups. Ten years postoperatively, it was significantly better in the robotic milling group (98 points and 96 points, respectively) (Mann-Whitney U-test; p<0.05). The main difference was observed in the category of range of motion (19 points and 18 points, respectively) (p=0.01).

In the previous study, we have reported that the JOA hip score was significantly better in the robotic milling group up to three years postoperatively. In the present study, we found that it was still significantly better at ten years postoperatively. In conclusion, robotic milling THA was associated with better clinical scores until ten years postoperatively.

Objective

Excessive mechanical stress on synovial joints causes osteoarthritis (OA) and results in the production of prostaglandin E2 (PGE2), a key molecule in arthritis, by synovial fibroblasts. However, the relationship between arthritis-related molecules and mechanical stress is still unclear. The purpose of this study was to examine the synovial fibroblast response to cyclic mechanical stress using an in vitro osteoarthritis model.

The occurrence of impingement can lead to instability, accelerated wear, and unexplained pain after THA. While implant and bony impingement were widely investigated, importance of soft tissue impingement was unclear. In the THA through posterior approach, it is known that posterior soft tissue repair can decrease the risk of dislocation. However, it is not known whether anterior soft tissue impingement by anterior hip capsule will influence hip ROM. The purpose of this study is to quantitatively measure the effect of anterior capsule resection on hip ROM in vivo during posterior approach THA using hip navigation system.

From June 2011, 26 hips (25 patients) that underwent primary THA using Stryker CT-based hip navigation system were the subjects. All were female osteoarthritis patients and the average age at the operation was 59 (47–76) years. Intraoperatively, acetabular cup and femoral stem placement were performed through posterior approach under the navigation system. After reduction of the joint, we measured hip ROM using the same navigation system. We measured them before and after the resection of anterior hip capsule and compared the difference.

After the resection of anterior hip capsule, the average increases of ROM were 0.7±3.5 degrees for flexion, 2.3±2.3 degrees for extension, 1.1±2.3 degrees for abduction and 2.1±2.9 degrees for external rotation at flexion 0 degree compared with ROM before the resection. However, it significantly increased 7.5±5.1 degrees for internal rotation at flexion 90 degree (range; −3–20, paired t-test p<0.001) and 6.1±5.5 degrees for internal rotation at flexion 45 degree (range; −4–18, p<0.001).

In this study, we used navigation system for assessment of soft tissue impingement. We found that during posterior approach THA, resection of anterior hip capsule brought about significant increase of ROM, especially in the direction of flexion with internal rotation. We also found that this procedure did not change ROM of flexion, extension, abduction and external rotation. These results indicated that, during THA through posterior approach, resection of anterior hip capsule could reduce the risk of posterior instability without increasing the risk of anterior instability.

We developed a custom-made template for corrective femoral osteotomy during THA in a patient with a previous Schanz osteotomy.

A seventy-year-old woman presented to our clinic with a chief complaint of right hip, left knee and left ankle pain with marked limp. She had undergone Schanz osteotomy of the left femur because of high dislocation of the left hip when she was 20 years old. After right THA was performed, we decided to perform left THA with corrective femoral osteotomy. A custom-made osteotomy template was designed and manufactured with use of CT data. During surgery, we placed the template on the bone surface, cut the bone through a slit on the template, and corrected the deformity as preoperatively simulated. Two years after surgery, she had no pain in any joints, could walk more than one hour without limp. Japanese Orthopedic Association hip score were 100 points for both hips.

THA in patients with previous Schanz osteotomy was reported to be technically demanding and the rate of complications was high. In 2008, Murase T et al. developed a system, including a 3D computer simulation program and a custom-made template to corrective osteotomy of malunited fractures of the upper extremity. We applied the system to corrective femoral osteotomy during THA in a patient with a previous Schanz osteotomy. The surgical procedure was technically easy and accurate osteotomy brought the patient to acquire good alignment of lower extremities with good clinical results.

Introduction

Current standard cups of metal on metal resurfacing hip arthroplasty (RHA) have no dome holes and it is very difficult for surgeons to confirm full seating of these cups. This sometimes results in gap formation between the cup and acetabular floor. Although the incidence of initial gaps using modular press-fit cups with dome screw holes has been reported to range from 20 to 35%, few studies have reported the incidence of gap formation with monoblock metal cups and its clinical consequences in RHA. The purpose of this study was to investigate retrospectively the incidence of initial gap formation and whether the initial gap influences the clinical results in RHA.

Introduction

Lesion location and volume are critical factors to select patients with osteonecrosis for whom resurfacing arthroplasty is appropriate. However, no reliable surgical planning system which can assess relationship between necrotic lesions and the femoral component has been established. We have developed a 3D-MRI-based planning system for resurfacing arthroplasty. The purpose of the present study was to evaluate its feasibility.

Introduction

Femoral neck fracture (FNF) is a common trauma in the elderly individuals. When the blood supply to the femoral head is impaired with a fracture event, the reduction or disruption of blood supply to the bone, hypoxia, leads to death of the bone marrow and trabecular bone, and eventual late segmental collapse. In the reparative process, osteoblasts and osteoclasts perform the important function of repairing the fracture site at the femoral neck. However, the reparative reaction including angiogenesis and osteogenesis remains unknown. In order to investigate the reparative reaction in patients with FNF, the distribution of tartrate resistant acid phosphatase (TRAP)-positive cells and expression of HIF-1 alpha, VEGF, and FGF-2 were observed in 36 hips in 35 patients.

Using a larger diameter femoral head in total hip arthroplasty (THA) has advantages in terms of the increased joint stability and range of motion. And the wear resistance of highly cross-linked polyethylene (HXLPE) even combined with a larger head has already been demonstrated by in vitro studies. The purpose of this study was to compare the in vivo wear of Longevity HXLPE sockets against 32 mm and 26 mm heads at a 5-year follow-up.

From November 2000 to November 2001, 51 primary cementless THAs were performed with a 26 mm cobalt-chromium head and a Longevity HXLPE socket (Zimmer). A cohort of 32 mm cobalt-chromium heads was comprised of 51 THAs with the same prosthesis performed from December 2001 to December 2003. No significant differences between the groups were observed in gender, age, and BMI, however, polyethylene liners with 32 mm heads were significantly thinner than those with 26 mm heads. Two-dimensional linear wear was measured using PolyWare software on annual x-rays, and total head penetration rates at postoperative 5-year and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated.

At the 5-year follow-up, the total head penetration rates were 0.047±0.022 mm/year with 26 mm heads and 0.048±0.026 mm/year with 32 mm heads. The steady state wear rates were −0.008 mm/year with 26 mm heads and 0.001 mm/year with 32 mm heads. No significant differences were seen between the two groups (p=0.82 and p=0.24). Osteolysis was not observed around pros-theses in any hips.

At the 5-year follow-up, the wear rate of Longevity HXLPE was very low. A Longevity HXLPE socket will undergo the same level of wear whether with a 32 mm head or a 26 mm head.

Ceramic heads and highly cross-linked polyethylene (HXLPE) as bearing surface materials have been introduced to reduce the production of polyethylene wear particles. The present study hypothesized that the wear rate of HXLPE could be further reduced when combined with a ceramic head. The purpose of this study was to compare the in vivo wear of Longevity HXLPE against cobalt-chromium and zirconia heads after a minimum 5-year follow-up.

A prospective cohort study was performed in 102 cementless total hip arthroplasties (THAs) with the Longevity HXLPE socket (Zimmer) between June 2000 and October 2001. Same prostheses were used in all cases both acetabular cups (Trilogy; Zimmer) and femoral stems (Versys Fiber Metal Taper; Zimmer). 26-mm zirconia heads (NGK) or 26-mm cobalt-chromium heads (Zimmer) were randomly used in 51 hips each. A minimum 5-year follow-up was completed for 47 hips with zirconia heads and 46 hips with cobalt-chromium heads. Two-dimensional linear wear of Longevity HXLPE was measured using computer-assisted methods (PolyWare) on annual x-rays, and total head penetration rates and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated.

At a mean 6-year follow-up, the total head penetration rates were 0.034±0.016 mm/year (zirconia) and 0.031±0.015 mm/year (cobalt-chromium). The steady state wear rates were −0.01 mm/year (zirconia) and −0.01 mm/year (cobalt-chromium). No significant difference was seen between the two groups (p=0.4 and p=0.91). Osteolysis was not observed around prostheses in any hips.

In conclusion, no advantage was seen for the zirconia head compared with the cobalt-chromium head in this time period.

The anterior pelvic plane (APP) through the bilateral anterior superior iliac spines (ASIS) and pubic tuberosities is often used as a pelvic reference in measuring orientation of the acetabular cup in total hip arthroplasty. Apophyses such as ASIS are, however, anatomically variable among patients and APP does not always represent the functional pelvic tilt in the sagittal plane in each patient. Therefore, malposition of the cup and recurrent dislocation may occur even though the cup is placed in a safe zone when measured against APP. We analyzed dynamic pelvic tilt angle in the sagittal plane using a motion analysis system after THA and we found a case of recurrent dislocation due to an unusual APP tilt.

A 77-year-old woman underwent primary THA 3 years ago and cup re-implantation was done with the use of a 10-degree elevated liner and the head diameter was increased from 26mm to 28 mm after two anterior dislocations. However, posterior dislocation occurred 11 times after this. A second revision was performed with a 36 mm head and cup anteversion was optimized against APP. Further posterior dislocations occurred twice again. To probe the cause of recurrent dislocation, we performed motion analysis using a 6-camera VICON system and the markers were registered to the bone and implant models based on the postoperative CT images. This system visually represents four-dimensional dynamic motions that include the time sequential transitions of components and their posture. The cup had been placed in 6 degrees of radiographic anteversion against APP, and in −13 degrees of radiographic retroversion in supine (FPP), because the pelvic flexion angle in supine was 17.6 degrees. Furthermore, when standing, the pelvic flexion angle increased 10 degrees.

Malposition of the acetabular cup in THA is the most common cause of dislocation. To avoid errors in cup placement, computer navigation systems have been introduced and most of the navigation systems refer APP to establish cup orientation. There are two drawbacks in using APP as the reference. One is that apophyses such as ASIS develop variably in each patient with a resulting variability in APP tilt in the sagittal plane in supine. The other is significant changes in pelvis tilt during various activities of daily living such as standing, walking, and sitting. Therefore, even if cup orientation is acceptable when referencing APP, it can be mal-oriented in a functional position of the pelvis as in this case, which showed proper anteversion against APP but retroversion in supine, standing and sitting.

In conclusion, we found that there exists a case in which APP is not a suitable pelvic reference in determining orientation of the cup.

Introduction: In order to investigate the reparative reaction process in patients with osteonecrosis of the femoral head (ONFH), we performed tartrate resistant acid phosphatase (TRAP) staining for the femoral head retrieved from the patients at the surgery.

Methods: This study included 21 hips in 19 patients. There were 15 women and 4 men who had a mean age of 42 years (range, 22 to 79 years). Associated risk factors included corticosteroids (n=15), alcohol (n=4), and idiopathic (n=1). Radiologic staging according to the Japanese Orthopaedic Classification included one stage 1, six stage 3A (collapse < 3mm), five stage3B (collapse> 3mm), and nine stage 4 (osteoarthritic change). After femoral head samples were fixed in formalin, 15 samples were decalcified by EDTA, while 6 were not decalcified. All samples were stained by Haematoxylin and Eosin and TRAP.

Results: TRAP positive multinucleated cells were existed at not only necrotic trabecular bone but also new appositional trabecular bone. TRAP positive cells were mainly located at the reactive interface (revascularized) zone while they did not exist in the necrotic zone. They were sometimes located at the normal bone marrow area near the retinacula or teres. While subchondral fractures were detected in two stage 3A hips, five stage 3B hips, and three stage 4 hips, TRAP positive cells around the subchondral fracture were detected in only two stage 3B hips and three stage 4 hips. In one stage 1 hip, TRAP positive mononuclear cells were detected around the enlarged adipocytes at the reactive interface zone. In six stage 3A hips, TRAP positive cells were detected at the reactive interface zone just around the subchondral area. In five stage 3B hips, they were detected along the reactive interface zone in the femoral head. In nine stage 4 hips, they were detected through the subchondral area and along the reactive interface zone.

Discussion: The expression mode of TRAP positive cells changes according to the radiologic stages in ONFH, represents the reparative reaction process.

While numerous studies have examined dislocation caused by basic everyday movements, no objective studies have investigated body positions to minimize risk of dislocation during intercourse. We therefore used a four-dimensional motion analysis system to assess sexual activities in patients who had undergone total hip arthroplasty (THA), to identify body positions displaying less risk of dislocation.

Five body-surface infrared sensors were placed on five healthy female volunteers, and maximum hip joint angle was measured. Subjects were asked to take the following three body positions: supine (missionary); top (woman on top); and kneeling (doggy-style). Angle data obtained using body surface markers were combined with three-dimensional skeletal models extracted using CT images obtained from the 24 joints of 16 patients who had undergone THA, to ascertain angles at which collision with the artificial joint or skeleton would occur.

Collision angle for: supine position at maximum abduction in flexion was 77±16° in flexion and 82±57° in medial rotation; top position at maximum extension was 36±16° in flexion and 68±53° in medial rotation; top position at maximum flexion was 12±9° in flexion and 14±11° in medial rotation; kneeling position at maximum extension was 115±1° in flexion and 127±44° in medial rotation; and kneeling position at maximum flex-ion was 14±8° in flexion and 17±11° in medial rotation.

The present study only assessed risk for dislocation caused by collision with the artificial joint or skeleton, and did not take into account the effects of soft tissue. However, we were able to quantitatively assess angle of the hip joint for some leg positions involved with various common coital positions. The results showed that the supine position at maximum abduction in flexion is relatively safe, since the range of motion before collision would occur was relatively wide. In addition, top and kneeling positions at maximum extension were relatively safe, but caution must be exercised at maximum flexion, as not much extra angle was available in flexion and medial rotation.

We have been using a Charnley type hip prosthesis with an alumina ceramic head. Three sizes of alumina head, 28, 26 and 22mm, were employed and the Ortron 90 Charnley total hip prosthesis was used at the same period. The objective of this study was to compare the survival rate and the wear rate of those four groups. There were 90, 62, 322 and 88 hips in 28, 26, 22mm alumina head and 0rtron 90 head group. Average age at operation was 49.5, 57.8, 58.0 and 60.6, respectively. A 28 mm prosthesis was indicated for relatively young patients. The mean duration of follow-up was 156, 97, 49 and 110 months, respectively. Twenty patients were chosen at random for each of four groups and the linear wear as seen on X-ray film was measured every two years with a computer and scanner.

Results: The average linear wear rate (mm/yr) was 0.179 for the 28mm, 0.112 for the 26mm, 0.115 for the 22mm alumina head and 0.075 for the Ortron 90 head. The difference between the 28mm group and the other three groups was analyzed statistically. The Kaplan-Meier survivorship analysis, with revision for aseptic loosening as the endpoint, showed the survival rate of the 28mm group appeared to be inferior to that of the other three groups.

Discussion: Our study showed that the wear rate of the 28mm alumina group was highest because low grade alumina was used. In addition, the polyethylene socket used for the 28mm group was thinner than that for the other groups. No clinical superiority of ceramics to metal in terms of polyethylene wear can be shown in this study. A randomized prospective study should be carried out to determine whether an alumina ceramic head is clinically superior to a metallic head in terms of polyethylene wear.