Kazutaka So

A porous bioactive titanium implant for spinal interbody fusion: an experimental study using a canine model

OBJECT Porous biomaterials with adequate pore structure and appropriate mechanical properties are expected to provide a new generation of devices for spinal interbody fusion because of their potential to eliminate bone grafting. The purpose of this study was to evaluate the fusion characteristics of porous bioactive titanium implants using a canine anterior interbody fusion model. METHODS Porous titanium implants sintered with volatile spacer particles (porosity 50%, average pore size 303 microm, compressive strength 116.3 MPa) were subjected to chemical and thermal treatments that give a bioactive microporous titania layer on the titanium surface (BT implant). Ten adult female beagle dogs underwent anterior lumbar interbody fusion at L6-7 using either BT implants or nontreated (NT) implants, followed by posterior spinous process wiring and facet screw fixation. Radiographic evaluations were performed at 1, 2, and 3 months postoperatively using X-ray fluoroscopy. Animals were killed 3 months postoperatively, and fusion status was evaluated by manual palpation and histological examination. RESULTS Interbody fusion was confirmed in all five dogs in the BT group and three of five dogs in the NT group. Histological examination demonstrated a large amount of new bone formation with marrowlike tissue in the BT implants and primarily fibrous tissue formation in the NT implants. CONCLUSIONS Bioactive treatment effectively enhanced the fusion ability of the porous titanium implants. These findings, coupled with the appropriate mechanical properties in load-bearing conditions, indicate that these porous bioactive titanium implants represent a new generation of biomaterial for spinal interbody fusion.

Effects of high-velocity resistance training on muscle function, muscle properties, and physical performance in individuals with hip osteoarthritis: a randomized controlled trial

Objective: To investigate the effects of high-velocity resistance training on muscle function, muscle properties, and physical performance in patients with hip osteoarthritis by comparison with those of low-velocity resistance training. Design: Single-blind randomized controlled trial. Setting: Home-based exercise programmes. Subjects: A total of 46 women with hip osteoarthritis were randomly assigned to the high-velocity (n = 23) or low-velocity (n = 23) training group. Interventions: Both groups underwent an eight-week daily home-based resistance training programme using an elastic band. Exercises involved hip abduction, extension, and flexion and knee extension. Participants in the high-velocity group performed the concentric phase of each repetition as rapidly as possible and returned to the initial position eccentrically in 3 s. Participants in the low-velocity group performed both the concentric and eccentric phases in 3 s. Main measures: The following outcome measures were evaluated: isometric muscle strength, muscle power, muscle thickness, muscle echo intensity, maximum walking speed, Timed Up and Go test, 3-minute walking test, Harris Hip Score, and hip pain. Results: Decreases in the time for performing the Timed Up and Go test (mean changes: high-velocity group −0.46 s, low-velocity group −0.23 s) and echo intensity of the gluteus maximus (mean changes: high-velocity group −6.8, low-velocity group −1.0) were significantly greater in the high-velocity group than in the low-velocity group. No significant difference was observed in changes of other outcome measures between the groups. Conclusion: This study revealed that high-velocity training for patients with hip osteoarthritis has partially a greater effect on muscle properties and physical performance than low-velocity training.

Muscle Mass and Composition of the Hip, Thigh and Abdominal Muscles in Women With and Without Hip Osteoarthritis

The objective of this study was to compare muscle mass and composition between individuals with and without hip osteoarthritis. Twenty-four women with hip osteoarthritis (OA group) and 16 healthy women (healthy group) participated in this study. Muscle thickness (MT) and echo intensity (EI) were measured as indices of muscle mass and composition, respectively, using ultrasound imaging. Seven muscles were examined: gluteus maximus, gluteus medius, quadriceps femoris, rectus abdominis, external oblique, internal oblique and transversus abdominis. MT of only quadriceps femoris in the OA group was significantly thinner than that in the healthy group. EIs of gluteus medius, quadriceps femoris and rectus abdominis were significantly higher in the OA group than those in the healthy group. Thus, actual contractile tissue of gluteus medius and rectus abdominis substantially decreased, although muscle mass was similar, whereas both quantitative and qualitative changes occurred in quadriceps femoris in patients with hip OA.

Antidegenerative effects of partial disc replacement in an animal surgery model

Study Design. In vivo degenerative changes of rabbit intervertebral discs after partial disc replacements were evaluated radiologically and histologically in a controlled trial. Objective. To demonstrate the therapeutic effects of partial disc replacement in an animal surgical model. Summary of Background Data. Although some authors reported that partial disc replacements have beneficial clinical outcomes, there are few controlled animal studies in which the therapeutic effects of this procedure have been demonstrated. Methods. The implants for partial disc replacements were made of poly (vinyl alcohol) hydrogel and rod-shaped. The L2–L3 or L3–L4 intervertebral discs of Japanese white rabbits were pierced with a 2.0-mm Kirschner wire and implants were inserted into the holes. For comparative purposes, the adjacent discs underwent sham treatments or control treatments in which the disc was pierced but no implant was inserted. Sixty discs from 30 rabbits were analyzed radiologically and histologically for degenerative changes at 1, 3, or 6 months after surgery. Results. Radiologic analysis revealed that significantly less disc height was lost with the replacement treatment than with the control treatment. Change in disc height after the replacement treatment was not significantly different from that after the sham treatment. Histologic degeneration of the replaced discs was delayed in comparison with that of the control discs but progressed with time. Conclusions. The antidegenerative effects of partial disc replacement surgery were demonstrated by quantitative radiologic and histologic analyses. Degeneration of the anulus fibrosus after the replacement treatment was delayed by preserving disc height and occupying the space of the nucleus pulposus. Properly designed implants and minimally invasive techniques are necessary for long-term success.

Minimum 10-Year Wear Analysis of Highly Cross-Linked Polyethylene in Cementless Total Hip Arthroplasty

Fifty-four patients (64 hips) underwent cementless total hip arthroplasty between 2000 and 2003 with a 22-mm zirconia ceramic bearing on highly cross-linked polyethylene, and were evaluated with a mean 11.9-year postoperative follow-up (range, 10-14 years). Linear wear was measured on the anteroposterior radiograph of the hip. No evidence of osteolysis and loosening was found on the final radiograph in any of the cases, and the steady-state linear wear rate was 0.017±0.018 mm/year. No significant correlation was found between the linear wear rate and age, body weight, cup inclination angle, or polyethylene thickness. Highly cross-linked polyethylene showed excellent wear resistance for >10 years when used in combination with 22-mm zirconia heads.

Pelvic instability and trunk and hip muscle recruitment patterns in patients with total hip arthroplasty.

Hip and lumbar spine disorders often coexist in patients with total hip arthroplasty (THA). The current study aimed to reveal pelvic motion pathology and altered trunk and hip muscle recruitment patterns relating to pelvic motion in patients with THA. Twenty-one women who underwent THA and 12 age-matched healthy women were recruited. Pelvic kinematics and muscle recruitment patterns (i.e., amplitude, activity balance, and onset timing) of the gluteus maximus, semitendinosus, multifidus, and erector spinae were collected during prone hip extension. Compared with healthy subjects, the patients showed increased pelvic motion, especially ventral rotation, decreased multifidus muscle activity relative to the hip extensors, and delayed onset of multifidus activity, despite reaction times and speeds of leg motion not being significantly different between the groups. Furthermore, while contributing factors associated with ventral pelvic rotation were not found, delayed onset of multifidus activity was detected as a factor related to the increased anterior tilt of the pelvis (r = 0.47, p < 0.05) in patients with THA. These results suggest that patients with THA have dysfunction of the stabilizer muscles of the lumbopelvic region along with increased pelvic motion.

Computed tomography-based navigation for curved periacetabular osteotomy

Curved periacetabular osteotomy (CPO), a modifi ed Bernese periacetabular osteotomy, has been developed to treat developmental dysplasia of the hip. CPO achieves good anterior and lateral acetabular coverage of the femoral head, resulting in prevention of osteoarthritic progression in the hip. 1 With this procedure, an outward curved osteotomy from the quadrilateral space is considered technically demanding because of limited visualization, with surgeons having to perform the curved osteotomy out of their fi eld of view. A computed tomography (CT)-based navigation system allows surgeons to provide positional information about the surgical instruments to target bones during the operation. This system offers three-dimensional (3D) images and real-time guidance, which improve the accuracy and safety of diffi cult operations. In this report, we present a technique for CPO using CT-based navigation.

Compensatory turning strategies while walking in patients with hip osteoarthritis

The ability to change directions while walking is an integral component of adaptive locomotor behavior. Patients with hip osteoarthritis (OA) experience prolonged hip dysfunction. Gait compensation adopted by the patients with hip OA may become more pronounced while they turn. The purposes of this study were to identify the turning strategy while walking in patients with hip OA, and to examine the relationship between the turning strategy and the patients functional level. Fourteen patients with hip OA and 13 age-matched healthy controls were recruited. The hip, knee, and ankle joint angles and moments, and the foot progression angle were measured under three walking conditions (straight walking, 45° step turn, and 45° crossover turn), and the gait variables for each walking condition were compared between the 2 groups. The relationship between the increasing rate of knee and ankle joint moments in the turning to the straight walking and the functional point in the Harris hip score (HHS) was examined. The OA group showed decreased hip flexion, extension, and abduction angles, and hip flexion moment during the step turn, and decreased hip flexion, extension, and adduction angles, and hip abduction moment during the crossover turn. Furthermore, the ankle plantarflexion moment and the change in the foot angle during the stance phase were significantly increased during the crossover turn in the OA group. The increasing rate of the ankle plantarflexion moment correlated significantly with the functional point in the HHS. Patients with hip OA rely primarily on the ankle plantarflexors to compensate for the hip dysfunction while changing the walking direction.

Long-Term Results of Cemented Total Hip Arthroplasty for Dysplasia, With Structural Autograft Fixed With Poly-l-Lactic Acid Screws

This study reviewed a series of cemented total hip arthroplasty (THA) for dysplasia, with structural autograft fixed with poly-L-lactic acid screws. Grafted bone union was confirmed radiologically in every case, and there were no cases of early collapse or extravasation of grafted bone. Kaplan-Meier survivorship analysis of socket revision, radiologic loosening of the socket, and the appearance of a radiolucent line greater than 1 mm in the graft-socket interface as the end points indicated survival rates of 99%, 97.1%, and 63.5% at 10 years and 96.6%, 90.2%, and 56.1% at 15 years, respectively. The results of this study indicated that poly-L-lactic acid screws are safe and useful for the fixation of acetabular bone graft concomitant to cemented THA with a careful rehabilitation program.

Hip external rotator exercise contributes to improving physical functions in the early stage after total hip arthroplasty using an anterolateral approach: a randomized controlled trial

Abstract Purpose: The purpose of this study was to investigate the effects of an exercise program focusing on hip external rotator muscle on physical recovery in the early post-operative period of total hip arthroplasty (THA). Methods: Patients who underwent THA were randomized to an exercise group (n = 14) or a control group (n = 14). In exercise group, the hip external rotator exercise program was performed 5 times per week for four weeks. Outcome measures were hip pain, hip range of motion, muscle strength of lower extremity and Timed Up and Go (TUG) test. Results: Both the hip abductor strength (effect size = 0.60) and TUG test (effect size= −0.53) in the exercise group improved significantly after the intervention. Conclusions: The results of the present study demonstrated that exercise program focusing on hip external rotator muscle was an effective intervention, especially in improving both hip abductor strength and walking ability in the acute post-THA stage. Implication for Rehabilitation After THA, in order to safely progress patients back to their desired activity level, there is a need to develop rehabilitation strategies to expedite and promote the recovery during the acute postoperative period. Exercise program focusing on hip external rotator muscle may lead to significant improvement of hip abductor muscle strength and gait ability in the acute post-THA stage.