Activation of a chondrocyte volume-sensitive Cl(-) conductance prior to macroscopic cartilage lesion formation in the rabbit knee anterior cruciate ligament transection osteoarthritis model

OBJECTIVE

The anterior cruciate ligament transection (ACLT) rabbit osteoarthritis (OA) model confers permanent knee instability and induces joint degeneration. The degeneration process is complex, but includes chondrocyte apoptosis and OA-like loss of cartilage integrity. Previously, we reported that activation of a volume-sensitive Cl(-) current (ICl,vol) can mediate cell shrinkage and apoptosis in rabbit articular chondrocytes. Our objective was therefore to investigate whether ICl,vol was activated in the early stages of the rabbit ACLT OA model.

DESIGN

Adult Rabbits underwent unilateral ACLT and contralateral arthrotomy (sham) surgery. Rabbits were euthanized at 2 or 4 weeks. Samples were analyzed histologically and with assays of cell volume, apoptosis and electrophysiological characterization of ICl,vol.

RESULTS

At 2 and 4 weeks post ACLT cartilage appeared histologically normal, nevertheless cell swelling and caspase 3/7 activity were both significantly increased compared to sham controls. In cell-volume experiments, exposure of chondrocytes to hypotonic solution led to a greater increase in cell size in ACLT compared to controls. Caspase-3/7 activity, an indicator of apoptosis, was elevated in both ACLT 2wk and 4wk. Whole-cell currents were recorded with patch clamp of chondrocytes in iso-osmotic and hypo-osmotic external solutions under conditions where Na(+), K(+) and Ca(2+) currents were minimized. ACLT treatment resulted in a large increase in hypotonic-activated chloride conductance.

CONCLUSION

Changes in chondrocyte ion channels take place prior to the onset of apparent cartilage loss in the ACLT rabbit model of OA. Further studies are needed to investigate if pharmacological inhibition of ICl,vol decreases progression of OA in animal models.

A Ferromagnetic Foreign Body at the Lateral Aspect of the Mandibular Ramus in a Medically Compromised Patient

A case of a ferromagnetic foreign body in a medically compromised patient was reported. The patient was a 45-year-old male who consulted our department complaining of a foreign body accidentally impacted in the right cheek. X-ray examination revealed a foreign body at the lateral aspect of the right mandibular ramus. The removal of the foreign body was scheduled, but the patient did not return for the procedure. After 8 years he revisited our department for the removal of the foreign body, because it had been found to be ferromagnetic and a barrier to MRI examination. X-ray examination confirmed the foreign body was located at the same site as 8 years prior. Although the patient was suffering from liver cirrhosis with thrombocytopenia and leukopenia, the foreign body was successfully removed under general anesthesia. The foreign body was 12 × 5 × 1 mm, weighed 0.48 g, and was ferromagnetic. The patient’s postoperative course was uneventful. X-ray examination confirmed the removal of the foreign body. Since the surgery, the patient has been in generally stable condition with no complications. This case was a rare example of a foreign body that needed to be removed for medical examination.

A new form of surgical treatment for patients with avascular necrosis of the talus and secondary osteoarthritis of the ankle

A new method of vascularised tibial grafting has been developed for the treatment of avascular necrosis (AVN) of the talus and secondary osteoarthritis (OA) of the ankle. We used 40 cadavers to identify the vascular anatomy of the distal tibia in order to establish how to elevate a vascularised tibial graft safely. Between 2008 and 2012, eight patients (three male, five female, mean age 50 years; 26 to 68) with isolated AVN of the talus and 12 patients (four male, eight female, mean age 58 years; 23 to 76) with secondary OA underwent vascularised bone grafting from the distal tibia either to revascularise the talus or for arthrodesis. The radiological and clinical outcomes were evaluated at a mean follow-up of 31 months (24 to 62). The peri-malleolar arterial arch was confirmed in the cadaveric study. A vascularised bone graft could be elevated safely using the peri-malleolar pedicle. The clinical outcomes for the group with AVN of the talus assessed with the mean Mazur ankle grading scores, improved significantly from 39 points (21 to 48) pre-operatively to 81 points (73 to 90) at the final follow-up (p = 0.01). In all eight revascularisations, bone healing was obtained without progression to talar collapse, and union was established in 11 of 12 vascularised arthrodeses at a mean follow-up of 34 months (24 to 58). MRI showed revascularisation of the talus in all patients. We conclude that a vascularised tibial graft can be used both for revascularisation of the talus and for the arthrodesis of the ankle in patients with OA secondary to AVN of the talus.

Developmental changes in desensitisation of c-Fos expression induced by repeated maternal separation in pre-weaned mice

Early-life stress has long-lasting effects on neuroendocrine and behaviour in adulthood. Maternal separation (MS) is used as a model of early-life stress and daily repeated MS (RMS) for 3 h during the first two postnatal weeks is widely used in rodent studies. However, it is not fully understood whether early-life animals desensitise/habituate to repeated stress. In the present study, we investigated the effects of daily RMS for 3 h and acute/single time MS (SMS) for 3 h on the plasma corticosterone level and c-Fos expression in the brain in mice at different postnatal ages. Mice were subjected to: (i) RMS from postnatal day (PND) 1 to 14 (RMS14); (ii) RMS from PND14 to 21 (RMS21); (iii) SMS on PND14 (SMS14); and (iv) SMS on PND21 (SMS21). Plasma corticosterone and c-Fos expression were examined on the final day in each experiment. The basal corticosterone levels in RMS14 and RMS21 were equal to those in respective age-matched controls. After the final separation, the levels were significantly increased and were comparable with those after SMS14 and SMS21, respectively. Histological analysis indicated that c-Fos expression significantly increased in many brain regions, including the paraventricular nucleus, prefrontal cortex, hippocampus, and basolateral and medial amygdale in both SMS14 and SMS21 mice. However, c-Fos expression in RMS14 mice significantly increased in many regions, whereas such increases were hardly seen in RMS21 mice. These results indicate that repeated early-life stress neither increases basal corticosterone, nor decreases the magnitude of the corticosterone response during the first three postnatal weeks, although desensitisation of c-Fos expression induced by repeated stress is changed during postnatal development.

Osteocyte-derived HB-GAM (pleiotrophin) is associated with bone formation and mechanical loading

HB-GAM (also known as pleiotrophin) is a cell matrix-associated protein that is highly expressed in bone. It affects osteoblast function, and might therefore play a role in bone development and remodeling. We aimed to investigate the role of HB-GAM in bone in vivo and in vitro. The bones of HB-GAM deficient mice with an inbred mouse background were studied by histological, histomorphometrical, radiological, biomechanical and mu-CT analyses and the effect of immobilization was evaluated. HB-GAM localization in vivo was studied. MLO-Y4 osteocytes were subjected to fluid shear stress in vitro, and gene and protein expression were studied by subtractive hybridization, quantitative PCR and Western blot. Human osteoclasts were cultured in the presence of rhHB-GAM and their formation and resorption activities were assayed. In agreement with previous reports, the skeletal structure of the HB-GAM knockout mice developed normally. However, a growth retardation of the weight-bearing bones was observed by 2 months of age, suggesting a link to physical activity. Adult HB-GAM deficient mice were characterized by low bone formation and osteopenia, as well as resistance to immobilization-dependent bone remodeling. HB-GAM was localized around osteocytes and their processes in vivo and furthermore, osteocytic HB-GAM expression was upregulated by mechanical loading in vitro. HB-GAM did not affect on human osteoclast formation or resorption in vitro. Taken together, our results suggest that HB-GAM is an osteocyte-derived factor that could participate in mediating the osteogenic effects of mechanical loading on bone.

A novel exogenous concentration-gradient collagen scaffold augments full-thickness articular cartilage repair

OBJECTIVES

A collagen scaffold has been long used in order to enhance the regeneration of articular cartilage. In the present study, we investigate the effectiveness of a concentration-gradient (CG) collagen that is designed to recruit efficiently the mesenchymal stem cells (MSCs) to the central region of the full-thickness cartilage defects via haptotaxis.

METHODS

The present study used Cellmatrix (0.3% type I collagen; Nitta gelatin, Osaka, Japan) as the collagen material. We prepared 33%CG collagen gel and 50%CG collagen gel. No gradient collagen gel served as negative control. Full-thickness cartilage defects were created at the patella groove of the rabbit knee, to which the three different collagen gels were transplanted. Bromodeoxyuridine (BrdU) positive, proliferating cells were enumerated and localized, whereas the histological grading score for cartilage regeneration was counted. The expression of type I and type II collagens was evaluated by immunohistochemistry. We also confirmed that the MSCs migrate toward the collagen substrate of higher concentration in a stringently in vitro haptotactic manner.

RESULTS

Enumeration of the BrdU-positive cells demonstrated that 33%CG collagen gel recruited a significantly larger number of proliferating cells to the central region of the cartilage defect. The histological grading score for the regenerated cartilage treated with 33%CG collagen gel was superior to the other groups.

CONCLUSIONS

CG collagen scaffold recruits effectively the MSCs to the center of full-thickness cartilage defect and enhances regeneration of the full-thickness cartilage defect.

Congenital unilateral upper limb muscular hypertrophy associated with contracture of an extrinsic extensor tendon

We report a case of congenital unilateral upper limb muscular hypertrophy which presented with loss of extensor tendon excursion of a single digit in late adolescence. The reason for the problem arising is not clear and is not clearly explained by the underlying congenital pathology.

Closed reduction for traumatic posterior dislocation of the shoulder using the 'lever principle': two case reports and a review of the literature

Traumatic posterior dislocation of the shoulder is frequently missed because of its rarity and the absence of characteristic symptoms. Several signs should be emphasised: an overlap of the humeral head and glenoid rim in a true anteroposterior view and the light-bulb sign in the anteroposterior view. To make an accurate and early diagnosis, use of multidirectional radiographs combined with computed tomography is recommended. Closed reduction was successfully performed under general anaesthesia using the DePalma method with slight modification--the lever principle--by pushing the medial side of the upper arm laterally to adduct the shoulder as far as possible. The dynamics of the lever principle make it a safer and more effective method of achieving a closed reduction of a posterior dislocation of the shoulder than the conventional method of solely pushing the humeral head anteriorly, especially in patients with locking of the glenohumeral joint and impression fractures.

Perforated appendicitis causing thigh emphysema: a case report

We report a case of thigh emphysema resulting from perforated appendicitis. The patient was an 83-year-old man who had no apparent abdominal signs and was initially misdiagnosed as having psoas abscess. Magnetic resonance imaging of the pelvis revealed appendicitis, and a barium enema showed a leakage of enhanced contrast material from the appendix region down into the thigh. A retroperitoneal perforation of the retrocaecal appendix without peritonitis was diagnosed. The patient underwent an appendectomy and curettage of the retroperitoneal and psoas muscle spaces, as well as the thigh. He recovered gradually, though the abscess had extended into the hip joint and resulted in osteomyelitis, requiring an additional procedure of resection arthroplasty. The patient fully recovered with no signs of infection one year postoperatively.

Intramedullary spinal cord metastasis of ovarian tumor

STUDY DESIGN

Case report.

OBJECTIVES

To report a case of a thoracic intramedullary spinal cord metastasis of ovarian tumor in a 59-year-old woman.

SETTING

Shiga, Japan.

CASE REPORT

A case of a thoracic intramedullary spinal cord metastasis of ovarian tumor in a 59-year-old woman is reported. She received abdominal ovariectomy for the ovarian adenocarcinoma 4 years before she suffered from back pain and showed neurological symptoms. The thoracic intramedullary lesion was confirmed by preoperative magnetic resonance imaging. She showed complete paralysis before operation. The excision of the tumor was achieved through the posterior approach. Histologically, the diagnosis of metastasis of adenocarcinoma was made.

CONCLUSION

Although she did not show any postoperative neurologic recovery, her general condition was good and there was no evidence of recurrence 24 months after surgery.

A case of Arnold–Chiari syndrome with flaccid paralysis and huge syringomyelia

STUDY DESIGN

A case report.

SETTING

Department of Orthopaedic Surgery, Shiga University of Medical Science, Japan.

PATIENT

A 13-year-old woman presented progressive weakness in the lower extremities, with predominance on the right. Magnetic resonance (MR) imaging revealed a huge syrinx. The patient also showed scoliosis, cleft palate, hearing impairment, excessive sweating, hairiness, dural ectasia, and malformation of the skull. METHOD AND OBJECTIVES: We treated a very rare case of Arnold-Chiari syndrome, which presented with flaccid paralysis. Methods of differential diagnosis and suitable treatment are discussed.

RESULTS AND CONCLUSION

Both the syrinx and muscle strength were quickly improved following placement of a syringo-peritoneal (S-P) shunt, after which the patient recovered the ability to walk. However, transient hypesthesia in the right hand occurred after the operation. The syrinx around the conus was thought to play a crucial role in the etiology of the patient case, which showed unique symptoms.

Cytokine production in the infrapatellar fat pad: another source of cytokines in knee synovial fluids

BACKGROUND

Recent studies have shown that adipose tissue is an endocrine organ that releases various cytokines.

OBJECTIVE

To investigate the production of growth factors and proinflammatory cytokines in infrapatellar fat pad specimens.

METHODS

Infrapatellar fat pad tissues were obtained from patients during knee surgery. Protein levels of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), tumour necrosis factor (TNF)alpha, and interleukin (IL)6 in homogenised tissues were measured by an enzyme immunoassay. Gene expressions for those cytokines were examined by reverse transcription-polymerase chain reaction (RT-PCR). Localisation of bFGF and VEGF was evaluated by immunohistochemistry and in situ hybridisation.

RESULTS

Infrapatellar fat pads were found to contain various protein levels of bFGF, VEGF, TNF alpha, and IL6. Further, gene expressions for these cytokines were detected by RT-PCR. Immunohistochemistry and in situ hybridisation showed that the expressions of both bFGF and VEGF were localised in immature adipocytes, interstitial undifferentiated mesenchymal cells, and vascular endothelial cells.

CONCLUSION

The production of bFGF, VEGF, TNF alpha, and IL6 in the infrapatellar fat pad was demonstrated. Although synovial cells and articular chondrocytes are thought to be primary sources of cytokines found in knee synovial fluids, the results suggest that they may also originate from this fat pad.

Decrease in serum nucleotide pyrophosphatase activity in ankylosing spondylitis

OBJECTIVE

Ankylosing spondylitis (AS) is a prototype of a group of rheumatic diseases referred to as spondyloarthropathy. AS patients show marked ectopic ossification in the spine, occasionally resulting in so-called bamboo spine. Although a strong association with HLA-B27 has been reported, its aetiology remains undetermined. Another rheumatic disease, ossification of the posterior longitudinal ligament of the spine (OPLL), demonstrates ectopic ossification of the spinal ligaments very similar to that of AS. Recently, nucleotide pyrophosphatase (NPPS) was implicated in the aetiology of OPLL: an Npps mutation was found to cause OPLL in mice, and an association between a polymorphism of the human NPPS gene and OPLL was identified. The clinical similarities between AS and OPLL led us to hypothesize that NPPS may also be implicated in the aetiology of AS. To elucidate the role of NPPS in the pathogenesis of AS, we examined serum NPPS activity and the possible association of the NPPS gene with AS.

METHODS

Forty-four Japanese patients with AS, 43 patients with OPLL, and age- and sex-matched normal volunteers took part in this study. We determined serum NPPS activity using high-performance liquid chromatography and examined the association between AS and NPPS using single nucleotide polymorphisms (SNPs) of the NPPS gene.

RESULTS

Serum NPPS activity in AS patients was significantly decreased compared with the controls (P < 0.0001). However, there was no association between AS and NPPS gene SNPs.

CONCLUSION

NPPS is implicated in the pathogenesis of AS.

Articular cartilage degradation and de-differentiation of chondrocytes by the systemic administration of retinyl acetate-ectopic production of osteoblast stimulating factor-1 by chondrocytes in mice

OBJECTIVE

Vitamin A derivatives are widely used therapeutic agents for the treatment of dermatological and rheumatological disorders. Long-standing administration of these drugs, in turn, causes skeletal changes including ossification of ligaments, premature fusion of epiphyses and abnormalities of modeling. Recent in vitro experiments have further suggested that retinoid treatment of cultured chondrocytes may cause apoptotic cell death. The present study aims to address detailed cartilage changes associated with in vivo administration of vitamin A derivatives.

METHODS

Retinyl acetate was administrated to experimental mice, C3H-Heston, for more than 12 months. Modified morphometry on the articular cartilage and fluorescent labeling of the subchondral bone were carried out to address the changes in the articular cartilage and subchondral bone. In order to address the detailed chondrocytes phenotypes, electron microscopy was carried out. Since findings of these studies suggested that biological properties of the cartilage matrix might be altered, the present study also immunolocalized functional matrix molecules, type I collagen and osteoblast-stimulating factor-1 (OSF-1).

RESULTS

Histomorphometry demonstrated that retinoid administration lead to progressive atrophy of the articular cartilage with concomitant proliferation of subchondral bone. Furthermore, detailed light and electron microscopy suggested that the subchondral bone proliferates into the degenerating cartilage. The affected articular cartilage also resembled that of osteoarthritis in terms of ectopic type I collagen production. Furthermore, the affected articular cartilage produced a developmentally regulated matrix molecule, osteoblast-stimulating factor-1 (OSF-1) that is normally expressed in both the fetal cartilage and the epiphyseal growth plate cartilage but not in the articular cartilage.

CONCLUSION

The present results indicate that the systemic retinoid administration may alter the biological properties of the articular cartilage.

Effects of serotonin 1A agonist on acute spinal cord injury

STUDY DESIGN

We evaluated the effects of serotonin (5-HT) agonists on in vitro models of spinal cord compressive injury. Evoked potentials in injured rat spinal cords (n=24) were recorded during perfusion with 5-HT agonists.

OBJECTIVES

To evaluate the therapeutic effects of 5-HT agonists on the recovery of compound action potentials in injured spinal cords.

METHODS

Rat dorsal columns were isolated, placed in a chamber, and injured by extradural compression with a clip. Conducting action potentials were activated by supramaximal constant current electrical stimuli and recorded during perfusion with 5-HT agonists and antagonists.

RESULTS

After inducing compression injuries, mean action potential amplitudes were reduced to 33.9+/-5.4% of the pre-injury level. After 120 min of perfusion with Ringer's solution, the mean amplitudes recovered to 62.8+/-8.4% of the pre-injury level. At a concentration of 100 micro M, perfusion with tandospirone (a 5-HT1A agonist) resulted in a significantly greater recovery of mean action potential amplitudes at 2 h after the injury (86.2+/-6.9% of pre-injury value) as compared with the control Ringer's solution (62.8+/-8.4% of pre-injury value, P<0.05). In contrast, quipazine (a 5-HT2A agonist) accelerated the decrease of amplitude (54.5+/-11.7% of pre-injury value). 5-HT1A and 5-HT2A agonist did not consistently alter latencies of the action potentials.

CONCLUSION

The 5-HT1A receptor agonist was effective for the recovery of spinal action potential amplitudes in a rat spinal cord injury model.

Arthroscopic osteochondral autograft transplantation for chondral lesion of the tibial plateau of the knee

Arthroscopic osteochondral autograft transplantation is often used to treat chondral/osteochondral lesions of the femoral condyle of the knee. However, arthroscopic autologous osteochondral grafting to the tibial plateau has not been reported. We report the surgical technique and the clinical course of a patient who underwent engraftment by this method. A 26-year-old man developed symptoms of pain and catching in his knee. Arthroscopy revealed a deep chondral lesion, 10 x 15 mm in size, down to the subchondral bone on the posterocentral area of the lateral tibial plateau. The injured cartilage was debrided using a curette and an abrader until normal healthy cartilage bordered the debrided defect. An osteochondral plug, 10 mm in diameter and 20 mm long, the chondral surface of which was orientated 25 degrees obliquely, was harvested from the most peripheral and proximal part of the lateral patellar groove. A bony hole was created in the center of the defect through the tibia using a core reamer. The osteochondral plug was inserted from the tibial window through the bony hole. To enhance the stability of the osteochondral fragment, bioactive ceramic fillers were used to fill the space below the plug. A second-look arthroscopy 10 months after surgery showed that the grafted osteochondral plug was well adapted and integrated into the surrounding cartilage on the lateral tibial plateau.

Bridging a peripheral nerve defect using collagen filaments

We describe bridging a peripheral nerve defect using collagen filaments instead of a tube. Cords of collagen filaments were grafted to bridge 20-mm defects of rat sciatic nerves. Nerve autografts were grafted as the control. The mean number and the mean fiber diameter of regenerated myelinated axons were approximately 4,800 and 3.3 microm, respectively, in the distal end of the nerve autograft and approximately 5,500 and 2.3 microm, respectively, in the distal end of the collagen-filaments nerve guide 8 weeks after surgery. The mean number and the mean fiber diameter of regenerated myelinated axons were approximately 6,900 and 3.1 microm, respectively, in the distal end of the nerve autograft and approximately 6,300 and 3.3 microm, respectively, in the distal end of the collagen-filaments nerve guide 25 weeks after surgery. Histologic studies suggested that the collagen filaments guided regenerating axons effectively. This new procedure offers a possible solution for the need to sacrifice a healthy nerve and for the shortage of graft material available for the repair of severed nerves.

The Bisurface total knee replacement: a unique design for flexion. Four-to-nine-year follow-up study

BACKGROUND

The Bisurface knee prosthesis was designed in 1989 to improve knee flexion without affecting the durability of the prosthesis. The prosthesis has a unique ball-and-socket joint in the midposterior portion of the femoral and tibial components, which functions as a posterior stabilizing cam mechanism and causes femoral rollback. The femoral component was made of alumina ceramic. The purpose of this study was to review the clinical results of the first 223 arthroplasties performed with this prosthesis in order to assess whether this new implant had achieved its design objectives.

METHODS

From December 1989 to May 1994, all patients who were scheduled for primary total knee arthroplasty were enrolled in a prospective study of the Bisurface knee. The patients were evaluated clinically according to The Hospital for Special Surgery knee-rating system and with a self-administered questionnaire, and they were evaluated radiographically according to the system of the Knee Society. Kaplan-Meier survivorship analysis was performed with revision of the knee or recommendation for revision as the end point.

RESULTS

One hundred and sixty-six patients treated with a total of 223 consecutive primary total knee arthroplasties were enrolled in the study, and 182 knees were followed for 3.9 to 9.0 years (mean, 5.8 years). Preoperatively, the mean Hospital for Special Surgery knee score was 44.5 points. At the time of latest follow-up, the mean knee score was 86.3 points. The mean preoperative and postoperative ranges of flexion were 119 and 124 degrees, respectively. The patients, even those with a good preoperative range of motion, rarely lost deep flexion of the knee after the procedure. A revision operation was performed in eight knees (because of infection in five, instability in two, and breakage of the peg of the patellar component in one). Two knees had recurrent medial-lateral subluxations of the femorotibial articulation, which were treated nonoperatively. No prosthesis had loosened aseptically and no alumina ceramic femoral component had broken by the time of latest follow-up. The rate of survival of the implant was 94 percent (95 percent confidence interval, 90 to 98 percent) at six years. According to the patient questionnaires, 20 percent of the knees sometimes felt loose in daily living activities, which prompted us to improve the intrinsic stability of the prosthesis by improving the congruity of the ball-and-socket joint.

CONCLUSIONS

Total knee arthroplasty with the Bisurface prosthesis resulted in an excellent range of motion and a high level of satisfaction with the operation; the durability of the prosthesis is promising.

Bone bonding ability of a new biodegradable composite for internal fixation of bone fractures

Hydroxyapatite particles and poly(L-lactide) composites for internal fixation of bone fractures have been developed based on the hypothesis that incorporation of hydroxyapatite particles in a poly(L-lactide) matrix might enhance bone bonding. This study evaluated the bone bonding ability of these biodegradable composites. Two types of hydroxyapatite and poly(L-lactide) composite were used in this study: calcined hydroxyapatite/poly(L-lactide) and uncalcined hydroxyapatite/poly(L-lactide). Rectangular plates (2 x 10 x 15 mm) of each composite or poly(L-lactide) were implanted into the metaphysis of the tibiae of 33 male rabbits, and the failure load was measured by conducting a detaching test 8, 16, and 25 weeks after implantation. The failure loads of calcined hydroxyapatite/poly(L-lactide), uncalcined hydroxyapatite/poly(L-lactide), and poly(L-lactide), respectively, were 13.60, 13.95, and 0.46 N at 8 weeks; 29.84, 24.09, and 2.86 N at 16 weeks; and 25.50, 29.67, and 2.43 N at 25 weeks. Histologic observation revealed that the composites formed direct contact with the bone. The results in this study indicate that the composites improved the strength of the interface between bone and plate. This improved interfacial strength lead to a substantial decrease in the frequency of implant loosening in the treatment of fractured bones by internal fixation.

Bonding of alkali- and heat-treated tantalum implants to bone

Alkali- and heat-treated tantalum (Ta) has been shown to bond to bone. The purpose of this study was to investigate the effects of chemical treatments on the bone-bonding ability of tantalum implants in rabbit tibiae. Miyazaki et al. reported in vitro that alkali- and heat-treated tantalum had an apatite forming ability in an acellular simulated body fluid (SBF). In this study, smooth-surfaced rectangular plates (15 x 10 x 2 mm) of pure tantalum and treated tantalum were prepared. The plates were implanted transcortically into the proximal metaphyses of bilateral rabbit tibiae, alkali- and heat-treated plates for one limb and untreated plates for the contralateral limb, which served as a paired control. Bone bonding at the bone/implant interface was evaluated by tensile testing and undecalcified histological examination, at 8 and 16 weeks after implantation. The treated implants showed weak bonding to bone at 8 weeks, and exhibited significantly higher tensile failure loads compared with untreated tantalum implants at 16 weeks. The untreated implants showed almost no bonding, even at 16 weeks. Histological examination by Giemsa surface staining, contact microradiography (CMR), and scanning electron microscopy (SEM) revealed that treated tantalum implants bonded directly to bone tissue. In contrast, the untreated tantalum implants had a intervening fibrous tissue layer between the bone and the plate and did not bond to bone at 8 and 16 weeks. It is clear from these results that alkali and heat treatment induce the bone-bonding ability of tantalum. This new bioactive tantalum should be an effective material for weight-bearing and bone-bonding orthopedic devices.

Histomorphometric study on high-strength hydroxyapatite/poly(L-lactide) composite rods for internal fixation of bone fractures

The purpose of this study was to investigate the bone-implant interface of high-strength hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite rods. As reinforcing particles, two types of HA particles-calcined HA (c-HA) and uncalcined HA (u-HA)-were applied to allow comparison of their suitability as bioactive fillers. Four types of composites (c-HA30, c-HA40, u-HA30, and u-HA40), which contained 30 or 40% by weight of each HA particle, were used. Unfilled PLLA rods were used as controls. A hole was drilled in the distal femora of 50 rabbits, and a composite or unfilled PLLA rod was implanted in a press-fit manner. Two, 4, 8, and 25 weeks after implantation, the samples were examined histologically by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An image analyzer was used for histomorphometric analysis of the bone-implant interface. An affinity index was calculated for each material; this was the length of bone directly apposed to the rods expressed as a percentage of the total length of the rod surface. In all the composites, histologic examination showed new bone formation at 2 weeks after implantation. The bone gradually grew along the composite surface. SEM showed direct bone contact with the composites without intervening fibrous tissue. During follow-up, the affinity indices of all the composite rods were significantly higher than those of the unfilled PLLA rods (p < 0.01; two-way ANOVA). The maximum affinity index (41%) was attained at 4 weeks in c-HA40 rods. In contrast, little bone contact was seen in unfilled PLLA rods. The only significant difference in affinity indices among the composites was that c-HA40 had a higher affinity index than u-HA40 (p < 0.05 at 4 weeks). No disintegration of rods or polymer debris, which could elicit inflammatory tissue reactions, was observed even at 25 weeks. Our results indicate that osteoconductive bone formation on composites could enhance the stability between bone and implant in fracture repair.

Histomorphometric study on high-strength hydroxyapatite/poly(L-lactide) composite rods for internal fixation of bone fractures

The purpose of this study was to investigate the bone-implant interface of high-strength hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite rods. As reinforcing particles, two types of HA particles-calcined HA (c-HA) and uncalcined HA (u-HA)-were applied to allow comparison of their suitability as bioactive fillers. Four types of composites (c-HA30, c-HA40, u-HA30, and u-HA40), which contained 30 or 40% by weight of each HA particle, were used. Unfilled PLLA rods were used as controls. A hole was drilled in the distal femora of 50 rabbits, and a composite or unfilled PLLA rod was implanted in a press-fit manner. Two, 4, 8, and 25 weeks after implantation, the samples were examined histologically by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An image analyzer was used for histomorphometric analysis of the bone-implant interface. An affinity index was calculated for each material; this was the length of bone directly apposed to the rods expressed as a percentage of the total length of the rod surface. In all the composites, histologic examination showed new bone formation at 2 weeks after implantation. The bone gradually grew along the composite surface. SEM showed direct bone contact with the composites without intervening fibrous tissue. During follow-up, the affinity indices of all the composite rods were significantly higher than those of the unfilled PLLA rods (p < 0.01; two-way ANOVA). The maximum affinity index (41%) was attained at 4 weeks in c-HA40 rods. In contrast, little bone contact was seen in unfilled PLLA rods. The only significant difference in affinity indices among the composites was that c-HA40 had a higher affinity index than u-HA40 (p < 0.05 at 4 weeks). No disintegration of rods or polymer debris, which could elicit inflammatory tissue reactions, was observed even at 25 weeks. Our results indicate that osteoconductive bone formation on composites could enhance the stability between bone and implant in fracture repair.

Biodegradation behavior of ultra-high-strength hydroxyapatite/poly (L-lactide) composite rods for internal fixation of bone fractures

The purpose of this study was to investigate the biodegradation behavior of the ultra-high-strength hydroxyapatite/poly(L-lactide) (HA/PLLA) composite rods for fracture repair. Two kinds of composite materials were used in this study: u-HA/PLLA. which contained 30% by weight of uncalcined HA as reinforcing particles, and c-HA/PLLA, which contained 30% by weight of calcined HA as reinforcing particles. These composite rods were implanted in the subcutis and in the medullary cavities of rabbits. The specimens were removed at specific intervals between 2 and 52 weeks and the mechanical strength was measured for the rods in the subcutis, and the molecular weight and crystallinity were measured for the rods in both the subcutis and medullary cavities. The rod surfaces were examined using a scanning electron microscope (SEM). The specimens were examined histologically by light microscopy. The bending strength of the composites implanted in the subcutis was maintained at more than 200 M Pa at 25 weeks and at 150 MPa at 52 weeks. The molecular weight dropped to 45% of the initial values at 8 weeks and to approximately 10% at 52 weeks. Significant differences in the molecular weight were seen between c-HA/PLLA and u-HA/PLLA, with u-HA/PLLA showing a faster rate of decrease than c-HA/PLLA after 8 weeks. SEM demonstrated that HA particles disappeared increasingly from the rod surfaces over time and that the spaces left by these HA particles formed many pores in the composite surfaces at 52 weeks. Histologically, a fibrous tissue layer was formed around the composite rod from 4 weeks in the subcutis and in the diaphyseal area of the medullary canal. This became more mature over time. Bony tissue contact to the composites without fibrous tissue layers was seen in the metaphyseal area of the medullary canal. During the experimental period, there were no inflammatory cells such as mono- or multi-nuclear phagocytes. Although further long-term studies for degradation are needed, the composites have promising mechanical strength and no adverse tissue reaction for use as fracture-fixation devices during the experimental periods.

Osteonecrosis of the resurfaced patella following bilateral total knee arthroplasty. A case report and review of the literature

A 77-year-old woman with severe varus and flexion deformity of both knee joints, hypertension, and arteriosclerosis underwent bilateral total knee arthroplasty. Six weeks after the operation on the right knee and four months after the operation on the left knee, osteolysis of the patellas was seen on the radiographs. Three years after the operations, the lateral and inferior poles of both patellas were sclerotic and displaced. There was no knee pain and no extension lag throughout the follow-up period. This case suggests that the prognosis of patellar osteonecrosis after total knee arthroplasty is good if the continuity of the retinaculum and the extensor mechanism are preserved, and if instability of the knee does not occur.

Cemented total hip arthroplasty with acetabular bone graft for developmental dysplasia. Long-term results and survivorship analysis

Although the technique of autogenous acetabular bone grafting has been widely used to augment containment of the acetabulum in total hip arthroplasty (THA) for developmental dysplasia, the role of this technique in improving long-term results remains controversial. We present the long-term results of cemented THA with acetabular bone grafting in 112 patients (133 hips) in order to clarify the factors which affect the outcome. The mean follow-up was for 12.3 years (8 to 24). Kaplan-Meier survivorship analysis predicted a rate of survival of the acetabular component at 15 years of 96% (95% confidence interval (CI) 92 to 99) with revision for aseptic loosening as the endpoint, and of 75% (95% CI 65 to 85) when radiological loosening was used. Parametric survivorship analysis using the Cox proportional-hazards model indicated that trochanteric nonunion, lateral placement of the socket, and delayed trabecular reorientation of the bone graft were risk factors for loosening of the acetabular component. Our findings have shown that autologous acetabular bone grafting is of value for long-term success provided that the risk factors are reduced.

Inflammatory cytokines induced down-regulation of m-calpain mRNA expression in fibroblastic synoviocytes from patients with osteoarthritis and rheumatoid arthritis

Our previous reports revealed that calpain has proteoglycanase activity and exists in synovial fluid in osteoarthritis and rheumatoid arthritis. We examined the effects of cytokines on expression of the calpain-calpastatin system in fibroblastic synoviocytes (FLS). Primary cultures of human FLS from osteoarthritis (OA) and rheumatoid arthritis (RA) patients were stimulated with inflammatory cytokines and the amounts of m-calpain and calpastatin mRNAs expressed were determined by Northern blotting. Northern blots were subjected to computerized densitometer and band intensities were determined. Interleukin-1 (IL-1) down-regulated m-calpain and tissue-type calpastatin mRNA expression in OA and RA FLS. In RA FLS, although IL-6 did not alter m-calpain mRNA expression, IL-1 + tumor necrosis factor (TNF) and IL-1 + transforming growth factor (TGF) down-regulated m-calpain mRNA expression. These results provide new information about the effects of inflammatory cytokines on calpain and calpastatin system in OA and RA pathology.

Bonding behavior of ultrahigh strength unsintered hydroxyapatite particles/poly(L-lactide) composites to surface of tibial cortex in rabbits

Unsintered hydroxyapatite particles/poly(L-lactide) (u-HA/PLLA) composites with an initial bending strength of up to 270 MPa were developed based on the hypothesis that inclusion of u-HA particles in a PLLA matrix might enhance bone bonding. The purpose of this study was to examine the bonding strength and behavior of these u-HA/PLLA composites on the surface of the bone cortex. Composites containing 30 (u-HA30), 40 (u-HA40), or 50 wt % (u-HA50) of fine u-HA particles (3-microm average particle size) were prepared. Semicolumnar plates of these composites and control PLLA plates were fixed with metal screws to the surface of both proximal tibial cortices in 45 rabbits. The loads required to detach the plates from the bone cortex surface, defined as the bonding strengths, were measured at 4, 8, and 25 weeks after implantation. Bonding strengths in the u-HA30 group at 8 weeks and in the u-HA40 and u-HA50 groups at each postimplantation time were significantly greater than in the PLLA group (post hoc test using Fisher's protected least significant difference method). At each postimplantation time histological examinations revealed direct contact between the bone and the u-HA/PLLA composite plates without any intervening fibrous tissue. There was no evidence of any inflammatory or foreign-body response in any group throughout the follow-up periods. The results of this study suggest that the biodegradable PLLA fixation plates amended with u-HA particles could be functionally superior to PLLA plates without particles.

Effect of rotational alignment on patellar tracking in total knee arthroplasty

Forty-four consecutive patients (65 knees) who underwent identical condylar type total knee arthroplasty were evaluated retrospectively. In 22 of the patients (32 knees), the femoral component was set parallel to the posterior condylar axis (neutrally aligned group). In the remaining 22 patients (33 knees), it was set in an external rotation position of 3 degrees to 5 degrees relative to the axis (externally aligned group). Of the total knee arthroplasties in the neutrally aligned group, 34% required lateral release, compared with only 6% in the externally aligned group; patellar tracking in the externally aligned group was significantly better than that in the neutrally aligned group. Postoperative measurements performed using computed tomography scans showed that the mean angle between the prosthetic posterior condylar axis and the transepicondylar axis was 7.9 degrees in the neutrally aligned group and 3.2 degrees in the externally aligned group. The external rotation setting of the femoral component diminished the need for lateral retinacular release and may decrease the rate of patellofemoral complications that occur after total knee arthroplasty.

Biodegradable screw fixation of rabbit tibia proximal osteotomies

The purpose of this study was to evaluate a biodegradable poly(L-lactide) (P-L-LA) screw for osteosynthesis under a load-bearing condition. A proximal tibial osteotomy on 25 rabbits was fixed with a biodegradable screw made of P-L-LA. A follow-up study was done at 1, 2, 4, 8, and 16 weeks. In another 25 rabbits, the tibial osteotomy was fixed with stainless steel (SUS) screws of the same size as the P-L-LA screws with a similar follow-up period. Radiographic, histological, microradiographic, and oxytetracycline-labeling studies showed healing of the osteotomy within 4 to 8 weeks. The displacement of fragments and the mass of newly formed bone around the screws were measured by histomorphometric analysis. There was no significant difference in the displacement of the fragments in these two groups and new bone was more abundantly detected in the P-L-LA group than in the SUS group. Histologically, no inflammatory lesion was detected in either group. All osteotomies united without delay and the displacement was minimal, although no external support was applied and the rabbits were allowed to move freely after the operation. The results of this study suggest a possible use for a P-L-LA screw in the clinical treatment of human bone fractures.

Ganglia of the posterior cruciate ligament. A report of three cases and a review of the literature

Two cases of isolated symptomatic ganglia and one case of a combined asymptomatic ganglion arising from the posterior cruciate ligament (PCL) are reported. One patient was a 29-year-old male who complained of posteromedial radiating knee pain. The medial McMurray test was positive. A cystic mass, 1.5 cm in diameter, arising from the femoral insertion of the PCL was removed piece-by-piece. The second case involved a 29-year-old female who complained of medial knee pain and limitation of flexion. MR scans detected a soft mass around the PCL. This was found to be a ganglion cyst surrounding the PCL, measuring 30 mm by 25 mm; it was excised using a power shaver. The third patient was a 17-year-old male who had knee pain due to a large medial synovial plica. Two small cystic masses were present on the intermediate portion of the PCL, but they seemed to be asymptomatic because of their small size. Whether or not a ganglion produces symptoms is determined by its size and location. Intra-articular ganglia can be cured by piecemeal resection and do not recur.

A-W glass ceramic as a bone substitute in cemented hip arthroplasty: 15 hips followed 2-10 years

We retrospectively reviewed hip arthroplasties in 13 patients (15 hips), in whom we had used apatite-wollastonite (A-W) glass ceramic together with auto- or allograft for augmentation of severe bone deficiency. 11 cemented sockets and 4 stem revisions were included and followed for 2-9.6 years. There were no radiolucent lines between A-W glass ceramic and surrounding bone, and remodeling of the bone graft containing A-W glass ceramic was observed. No migration of cemented sockets was seen except in 1 case, which was revised. In this case, direct bonding between bone and A-W glass ceramic granules was present histologically. In 4 stem revisions, 5 mm subsidence occurred in 1 case. However, the stem became stable and remodeling of the grafted bone occurred. An artificial bone material, such as A-W glass ceramic, can be used under high-load conditions, because of its good mechanical properties.

Treatment of osteomyelitis with antibiotic-soaked porous glass ceramic

We have developed a new drug delivery system using porous apatite-wollastonite glass ceramic (A-W GC) to treat osteomyelitis. A-W GC (porosity, 70% and 20% to 30%), or porous hydroxyapatite (HA) blocks (porosity 35% to 48%) used as controls, were soaked in mixtures of two antibiotics, isepamicin sulphate (ISP) and cefmetazole (CMZ) under high vacuum. We evaluated the release concentrations of the antibiotics from the blocks. The bactericidal concentration of ISP from A-W GC was maintained for more than 42 days, but that from HA decreased to below the detection limit after 28 days. The concentrations of CMZ from both materials were lower than those of ISP. An in vivo study using rabbit femora showed that an osseous concentration of ISP was maintained at eight weeks after implantation. Osteoconduction of the A-W GC block was good. Four patients with infected hip arthroplasties and one with osteomyelitis of the tibia have been treated with the new delivery system with excellent results.

Treatment of osteomyelitis with antibiotic-soaked porous glass ceramic

We have developed a new drug delivery system using porous apatite-wollastonite glass ceramic (A-W GC) to treat osteomyelitis. A-W GC (porosity, 70% and 20% to 30%), or porous hydroxyapatite (HA) blocks (porosity 35% to 48%) used as controls, were soaked in mixtures of two antibiotics, isepamicin sulphate (ISP) and cefmetazole (CMZ) under high vacuum.

We evaluated the release concentrations of the antibiotics from the blocks. The bactericidal concentration of ISP from A-W GC was maintained for more than 42 days, but that from HA decreased to below the detection limit after 28 days. The concentrations of CMZ from both materials were lower than those of ISP. An in vivo study using rabbit femora showed that an osseous concentration of ISP was maintained at eight weeks after implantation. Osteoconduction of the A-W GC block was good.

Four patients with infected hip arthroplasties and one with osteomyelitis of the tibia have been treated with the new delivery system with excellent results.

Anti-tumour effects of localized hyperthermia on an experimental bone tumour using an intramedullary nail

A new localized hyperthermia system for an experimental bone tumour in the rabbit tibia was developed. This system was composed of an induction coil, generator and a Kirschner wire, which was inserted into the medullary canal of the tibia as a heat-generating ferromagnetic implant. The metastatic bone tumour model was created by implantation of VX2 carcinoma in the medullary canal of the tibia diaphysis. The days after VX2 implantation, hyperthermia was induced for 50 min. Three weeks after the treatment, rabbits were sacrificed for histological and radiological evaluation. According to the semi-quantitative scoring system, anti-tumour effects of the single dose of hyperthermia was noted radiologically (p < 0.01) and histologically (p < 0.05) where the temperature was at a sufficient level to cause hyperthermia (> 42.5 degrees C). This new heating method, which is relatively simple and clinically applicable, appears to be promising for the treatment of metastatic tumours of the long bone.

Septum-like structures in lipoma and liposarcoma: MR imaging and pathologic correlation

OBJECTIVE

To investigate the septum-like structures in predominantly lipomatous tumors, by correlating fat-suppressed MR images with histopathologic findings.

DESIGN AND PATIENTS

The MR findings of three cases of well-differentiated liposarcoma (atypical lipoma), one case of lipoma-like component of dedifferentiated liposarcoma, and nine cases of lipoma were analyzed. T1-, T2-, and fat-suppressed T1-weighted images after Gd-DTPA administration were obtained. Surgical specimens from five patients (four with liposarcoma and one with lipoma) were also scanned with a MR unit, and compared with the pathologic findings.

RESULTS AND CONCLUSIONS

Enhancement features of lipoma and liposarcoma were well visualized on fat-suppressed T1-weighted images after Gd-DTPA administration. The septum-like structures of liposarcoma are thick and enhanced considerably, while septa of lipoma are thin and enhanced only slightly. Pathologically, the septum-like structures of liposarcoma contained muscle fibers and the septa of lipoma represented fibrous capsule. Identification of well-enhanced septa in a predominantly lipomatous tumor helps to differentiate malignant tumors from lipomas. As the septum-like structures of liposarcoma contain a skeletal muscle component the tumor might need more extensive surgical procedures including resection of adjacent muscles.

Improved range of flexion after total knee arthroplasty. The total condylar knee versus the KU knee

One objective of the modification of the total condylar knee is to increase the range of flexion without compromising the durability of the prosthesis. The KU knee prosthesis was designed to improve postoperative range of motion. This prosthesis has a unique ball-and-socket joint in the center of the posterior portion of the femorotibial articulation. A retrospective comparative study was undertaken to determine whether the KU knee prosthesis had achieved its design objectives. The study was based on the clinical observation of two populations: one (the TC group: 31 joints) with total condylar prostheses and the other (the KU group; 31 joints) with KU knee prostheses. At two years postoperatively, the mean postoperative range of flexion was 94 degrees (range: 60 degrees to 120 degrees) in the TC group and 120 degrees (range: 95 degrees to 150 degrees) in the KU group. The mean postoperative range of flexion was 24 degrees better in the KU group than in the TC group (p < 0.01). The mean functional score was 76 points (range: 61 to 86) in the TC group and 81 points (range: 56 to 92) in the KU group. There were no statistically significant difference in pain, walking ability, deformity, extension lag, and activities of daily living (ADL) score between the two groups. However, a statistically significant difference was detected in the range of motion (ROM) score (p < 0.01). No major complications occurred in either of the two groups. Although the follow-up period was not long enough, the KU knee was thought to be a promising modification of the total condylar knee prosthesis.

A long-term clinical study on drawn poly-L-lactide implants in orthopaedic surgery

We have developed an ultra-high-strength drawn poly (L-lactide) (PLLA) with a bending strength of 240 MPa. Seventy-four patients (80 cases) who were treated with this PLLA implant were enrolled in this study. Their ages ranged from 14 to 78 years, and the follow-up period ranged from 4 to 9 years (mean: 5.3 years). Bony union was obtained in all cases. Osteolytic changes were observed in 12 cases (15%) but no late aseptic swelling was noted. Both MRI and roentgenographic findings indicated that the spaces where the PLLA implants were located had not been replaced with bony tissue.

Arthroscopic partial medial meniscectomy in patients over 40 years old: a 5- to 11-year follow-up study

A retrospective analysis of 68 knees from 65 patients older than 40 years, who had undergone a partial medial meniscectomy, was carried out. The average age of the patients was 49.7 years (range, 40 to 74), and the mean follow-up period was 7.8 years (range, 5 to 11). The patients were divided into two groups based on the degree of articular cartilage degeneration. Group I consisted of 53 knees that did not have any significant articular cartilage damage beyond grade I or II. Group II consisted of 15 knees that had grade III or IV cartilage damage. Overall, excellent results were obtained in 44 patients (47 knees), good results in 10 patients, fair results in six patients, and poor results in five patients. In group I, 46 knees (87%) had an excellent outcome, and only one patient had a poor result. In contrast, patients in group II had significantly worse results, with only one knee (7%) having excellent outcome, and four knees had a poor result. A specific history of trauma did not affect the clinical outcome. Forty-two patients (64%) were able to resume normal athletic activities without any restrictions. Arthroscopic partial medial meniscectomy in patients older than 40 years is an acceptable and effective long-term treatment, particularly in patients without significant articular cartilage damage.

Biodegradable pin fixation of osteochondral fragments of the knee

The authors present 3 cases of osteochondritis and 2 cases of osteochondral fracture of the knee. These cases were treated with a bioabsorbable ultra high strength poly (L-lactide) pin, which has the highest mechanical strength value of any nonfiber reinforced poly (L-lactide) reported previously. Three of the patients were male, and 2 were females; their ages ranged from 12 to 21 years. The followup period ranged from 2 years to 7 years 9 months (mean, 4.1 years). Two to 4 poly (L-lactide) pins with a diameter of 2 mm were used to fix the osteochondral fragments or the transplanted autogenous osteochondral grafts. In all cases, satisfactory bone union was obtained, and no inflammatory reaction was observed during the entire followup periods. The ranges of motion were normal, and there was no pain in any of the cases. It is concluded that the poly (L-lactide) pin is safe and useful in the repair of osteochondral fractures of the knee and in fixing grafted osteochondral fragments.

Tissue reaction of bioabsorbable ultra high strength poly (L-lactide) rod. A long-term study in rabbits

Bioabsorbable ultra high strength poly (L-lactide) rods, which were developed for internal fixation of fractures, were fabricated using a drawing technique. These rods were implanted in the subcutaneous tissue and in the medullary cavity of rabbits to investigate tissue reactions to poly (L-lactide) and to study their degradation process. After 18 months, histiocytes were found, and their phagocytic activity continued for as long as 42 months, with maximum activity observed between 24 and 36 months after implantation. At 62 months after intramedullary implantation, the materials had been absorbed almost completely and were replaced by bone marrow cells, with only a small amount of residual tissue reaction. At 69 months after subcutaneous implantation, the materials had been absorbed completely without any scar formation. During degradation, no foreign body giant cells were found and osteolytic expansion caused by liquid degradable materials was not seen.

Biodegradable plate fixation of rabbit femoral shaft osteotomies. A comparative study

Femoral shaft transverse osteotomies in 58 rabbits were fixed with ultrahigh strength poly-L-lactic acid plates made by a drawing technique. Similar osteotomies in another 35 rabbits were fixed using stainless steel plates. The union rate, the mechanical strength of the united bones, bone mineral content and density in the area beneath the plate using dual energy x-ray absorptiometry, and the cortical thickness beneath and opposite the plate using a digitizer was compared between the poly-L-lactic acid and stainless steel groups after postoperative periods of 8, 25, and 40 weeks. The poly-L-lactic acid and stainless steel groups showed union rates of 67% (39 of 58) and 80% (28 of 35) without displacement, respectively. In the poly-L-lactic acid group, plate failure occurred in 14% (8 of 58). The mechanical strength of the specimen was restored to a level equal to that on the untreated side by 25 weeks, and cortical thickness and bone mineral content and density were maintained almost normal for 40 weeks in the poly-L-lactic acid group. The stainless steel group showed significantly lower mechanical strength and led to osteopenia because of stress shielding after 25 weeks.

Bioabsorbable osteosynthetic implants of ultra high strength poly-L-lactide. A clinical study

We have developed reasonably strong but bioabsorbable osteosynthetic screws, pins and nails made of ultra high strength poly-L-lactide (PLLA) and evaluated their use in 143 patients. The PLLA implants have the highest strength among those reported to date. They lose about 10% of their initial strength within 8 weeks, about 40% within 4 weeks and nearly 100% within 20 weeks in vivo. The patients were aged from 9 to 78 years, and the follow up was from 2 to 6 years. The implants were used for fixation of bone grafts in 84 patients, peri- and intra-articular fractures in 49, after osteotomy in 8, and in 2 others. Bony union was not achieved in only one case. In the early stages of the study, breakage of screws occurred in 12 cases (8%), mostly because of an inappropriate size of tap; these problems have not occurred after improvement of the tapping system. There were no cases with abnormal blood tests, infection or foreign body reaction.