K. Nakata

A Clinical Comparative Study of the Direct Anterior With Mini-Posterior Approach: Two Consecutive Series

We classified 182 consecutive patients (195 hips) treated by primary cementless minimally invasive total hip arthroplasty (MIS-THA) into 2 groups via the surgical approaches: direct anterior approach (DAA, 99 hips) and a mini-posterior approach (MPA, 96 hips). Ninety-nine percent of the cups in the DAA group and 91% in the MPA group had been implanted within the safe zone (P = .008). Patients in the DAA group could get single-leg stance of more than 5 seconds by 16.6 days (P = .0004), had positive Tredelenburgs sign by 29%, got 50-m walking time of 52.3 seconds (P = .017), and showed improvement in the use of assistive walking aids (P = .031) at 3 weeks postoperatively. The results of this study suggest more rapid recovery for hip function and gait ability after MIS-THA via a DAA when compared to an MPA.

Second-look arthroscopy after meniscal repair. Review of 132 menisci repaired by an arthroscopic inside-out technique

From 1986 to 1993, we repaired 278 torn menisci in 264 patients using an arthroscopically assisted inside-out technique. A total of 132 meniscal repairs in 122 patients were evaluated by second-look arthroscopy. At review, only nine patients had meniscal symptoms, such as locking, swelling or pain. Ninety-seven menisci (73%) had healed completely at the repair site, but there were new tears in different areas of 21 menisci, some of which had complete healing at the repair site. Incomplete healing, seen in 23 menisci (17%), was frequently near the popliteus tendon, most commonly where there had been an associated anterior-cruciate-ligament injury. Arthroscopically-assisted meniscal repair seems to be a reliable procedure, but some clinically successful cases had incomplete healing at the repair site or a newly-formed tear in the meniscal body or both. These lesions may cause meniscal symptoms to appear at a later date.

Differential in situ expression of α2(XI) collagen mRNA isoforms in the developing mouse

Abstract Type XI collagen is an essential structural component of the extracellular matrix of cartilage and plays a role in collagen fibril formation and skeletal morphogenesis. The expression of all three type XI collagen genes is not restricted to cartilage. In addition, alternative exon usage seems to increase the structural diversity and functional potential of type XI collagen during development. In order to investigate type XI collagen expression during development, we have examined α2(XI) and α1(XI) collagen genes by in situ hybridization in mice. Transcripts of the α2(XI) collagen gene were first detected in the notochord of mouse embryos after 11.5 days of gestation. Subsequently, α2(XI) mRNA was mainly found in the cartilaginous tissues of the developing limbs and axial skeleton together with transcripts of the α1(XI) gene. The α2(XI) transcripts seemed to be alternatively spliced isoforms lacking exons 6–8, which code for an acidic domain. Expression of α2(XI) outside the cartilage was relatively restricted, whereas expression of the α1(XI) gene was widespread. However, expression of α2(XI) transcripts containing exons 6–8 was found in non-chondrogenic tissues, including the calvarium and periosteum where intramembranous ossification occurs. These results indicate that α2(XI) mRNA isoforms are differentially expressed in various tissues during development. In addition, α2(XI) mRNA isoforms containing alternative exons are present in osteogenic cells, and their expression may be closely related to the formation of bone or cartilage.

Contralateral hip in patients with unilateral nontraumatic osteonecrosis of the femoral head

To clarify the risk of the development of osteonecrosis of the femoral head in the contralateral hip of patients with unilateral nontraumatic osteonecrosis of the femoral head, a followup study was performed using magnetic resonance imaging. Forty-six asymptomatic contralateral hips with no evidence of osteonecrosis on magnetic resonance imaging, in patients with unilateral osteonecrosis, were subjects of this study. The period from the onset of unilateral osteonecrosis to entrance in this study ranged from 1 month to 20 years (mean, 3.1 years). There were 29 males and 17 females ranging in age from 16 to 71 years (mean, 41 years). Twenty-three patients had previous steroid therapy for various conditions: 16 had alcoholism and 7 had no etiologic factors. The followup term ranged from 3 to 8 years (average, 5.5 years). During the followup period, 1 patient (2%) had a band of low signal intensity demarcating the lesion of normal fat intensity on T1 weighted images, which progressed to collapse of the femoral head. These results suggest that in unilateral osteonecrosis cases, osteonecrosis rarely develops in the contralateral hip that has appeared normal on magnetic resonance imaging. The contralateral hip with a negative magnetic resonance imaging scan is not in Stage 0 of osteonecrosis, but is normal.

Inducible osteonecrosis in a rabbit serum sickness model: Deposition of immune complexes in bone marrow

We established inducible osteonecrosis in a rabbit serum sickness model. Osteonecrosis with marrow necrosis could be induced by the intravenous injection of horse serum in two doses separated in time by a period of three weeks. In this model, osteonecrosis could be successfully produced in rabbit femoral metaphysis. The incidence of marrow necrosis was 45% (9 of 20 rabbits) and trabecular necrosis occurred in 6 of 20 rabbits (30%) at 7 days after the second injection of the horse serum. In bone marrow of the femoral metaphysis, extravasation of erythrocytes and the formation of micro-thrombi in arterioles were often observed in an early stage of the present model and both findings correlate well each other (p = 0.0001). Immune complexes could be demonstrated using immunohistochemistry in bone marrow of the femoral metaphysis as well as in glomeruli of the kidney. Extravasation of erythrocytes in bone marrow of the femoral metaphysis was observed in 8 of 12 (67%) cases with immune complex deposition in the sinusoidal space of the femoral metaphysis and in 12 of 21 (57%) cases with immune complex deposition in glomeruli of the kidney. Immune complex deposition both in the sinusoidal space of femoral bone marrow (p = 0.0385) and in glomeruli of the kidney (p = 0.0209) closely related to extravasation of erythrocytes and microthrombi in arterioles in the early stage of this model. Early microcirculatory injury (extravasation of erythrocytes and microthrombi in arterioles) adjacent to osteonecrosis could be induced by immune complex deposition in femoral bone marrow and might be predictable characteristics for the inducible osteonecrosis in the present serum sickness model. The important findings in this study were that early microcirculatory injury was closely related to the deposition of immune complexes in femoral bone marrow, and that early microcirculatory injury associated with immune complex deposition was located close to osteonecrotic regions.

Dome (modified Chiari) pelvic osteotomy. 10- to 18-Year Followup Study

Ninety-six dome (modified Chiari) pelvic osteotomies in 87 patients with pain and disability because of osteoarthrosis secondary to hip dysplasia were reviewed. The mean age of the patients at the time of surgery was 29 years (range, 16–55 years). The mean followup was 13 years (range, 10–18 years). Forty-one hips were classified into a hip dysplasia stage, 32 hips into an early stage of osteoarthrosis, and 23 hips into an advanced stage of osteoarthrosis according to the radiographic grading of the Japanese Orthopaedic Association. The average preoperative Merle d’Aubigné and Postel hip score was 13.8, and the average score at final followup was 16.6. Excellent or good results with a score greater than 14 were achieved in 96% of the hips at final followup. Radiographically, signs of progression of osteoarthrosis were not seen in 87% of the hips. Osteoarthrosis progressed during the postoperative course in 13% of the hips. Four patients (four hips) eventually had a total hip arthroplasty at 13.8 years (range, 12.5–15.3 years) after surgery. The survival rate of dome pelvic osteotomy, using clinical failure as an end point, was 82% at 15 years. Using radiologic failure as an end point, 61 hips in 54 patients (survival rate, 78%) survived at 15 years. Using hip replacement as an end point, 92 hips in 83 patients (survival rate, 82%) survived at 15 years. Dome pelvic osteotomy is an excellent and effective operation for pain relief and functional maintenance of the hip.

The remodelling process of allogeneic and autogenous patellar tendon grafts in rats: a radiochemical study

In order to study the remodelling of collagen fibres of transplanted tendons, one-half of the patellar tendon of the knee in 54 rats was replaced with a radioisotope (3H-proline)-labelled patellar tendon procured from a donor rat. Three transplantation models were used in this study: fresh-frozen allograft, fresh-frozen autograft (fresh-frozen isograft), and fresh autograft (fresh isograft). The percentage of old collagen was calculated as an indicator of collagen turnover from the amount of hydroxyproline and the radioactivity level of 3H-bydroxyproline in the transplanted tendons at 4, 12 and 24 weeks postoperatively. Histological evaluation was also performed at 2, 4, 12 and 24 weeks. At 4 weeks, the percentage of old collagen in the grafts from the fresh-frozen allograft group was significantly lower than in the autograft groups (20% vs. 48%). Although the percentage of old collagen in the fresh-frozen autograft group had decreased to the same level as in the fresh-frozen allograft group by 12 weeks (approximately 10%), the value was still high in the fresh autograft group at 12 weeks and remained higher (38%). Histologically, at 2 weeks, the cellularity in the fresh-frozen allograft was higher than in the fresh-frozen autograft. After 4 weeks, however, no significant difference was found between these two groups. In the fresh autograft group, the cellularity was lower than in the fresh-frozen groups at all times. In conclusion, the collagen turnover rate in the fresh-frozen allograft was the most rapid of the three transplantation models based on hydroxyproline turnover.

The immune reaction to heterologous serum causes osteonecrosis in rabbits

Osteonecrosis (ON) was produced experimentally in rabbits by intravenous injection of horse serum. Eighty adult rabbits were used: 16 were injected twice with isotonic saline (Group A), 24 were injected once with saline and once with horse serum (Group B), and 40 were injected twice with horse serum (Group C). Both femurs of each rabbit were obtained from 2 h to 7 weeks after the final injection an were subjected to histological examination. No pathological changes were seen in Groups A and B. In Group C, 5 of 15 rabbits (33%) showed ON (necrosis of trabecula and bone marrow) in the femoral metaphysis. In Group C, the early major pathological findings in bone marrow are extravasation of erythrocytes in sinusoidal spaces and microthrombi in small arteries and arterioles near the lesion of extravasation. Immune complexes were demonstrated in the kidney within 24 h of the final injection of horse serum. The present study suggests that immunological reaction associated with serum sickness may play an important role in inducible ON and this model will contribute toward clarifying the pathogenesis of ON.

Serial change of sliding in intertrochanteric femoral fractures treated with sliding screw system.

We investigated the serial change of the extent of sliding of the compression screw in 42 intertrochanteric femoral fractures fixed with a sliding screw system. Neither age, gender, bone density, fracture type nor quality of fracture reduction could accurately predict healing time. There was a significant correlation between the extent of sliding at union and healing time (correlation coefficient r = 0.505). The average healing time in group B (the extent of sliding at union of 8 mm or greater) was 13.8 weeks postoperatively, and that in group A (the extent of sliding at union of less than 8 mm) was 8.9 weeks. There was a significant difference in the average healing time between groups A and B (P = 0.0004). The extent of sliding at union had a influence on the healing time. The phenomenon of sliding progressed mainly during the first 2 weeks postoperatively. There was a significant positive correlation between the extent of sliding at union and the extent of sliding at 2 weeks postoperatively (r = 0.977). An assessment using the extent of sliding at 2 weeks postoperatively can accurately predict the extent of sliding at union and the healing time. It is important to examine the phenomenon of sliding during the early postoperative course, especially until 2 weeks postoperatively, in order to predict fracture repair.

Involvement of platelet activation in experimental osteonecrosis in rabbits

Osteonecrosis (ON) was produced experimentally in rabbits by intravenous injection of platelet activating factor (PAF) in combination with lipopolysaccharides (LPS) on two occasions separated by a week‐long interval. Eleven of 15 rabbits (73%), with administration of both LPS (50 µg/kg) and PAF (10 µg/kg), exhibited microcirculatory injuries including extravasation of erythrocytes into sinusoidal spaces and formation of microthrombi in arterioles near regions of erythrocyte extravasation. Seven of 15 rabbits (47%), which received both LPS (50 µg/kg) and PAF (10 µg/kg), exhibited necrosis of trabeculae and 8 of 15 (53%) exhibited bone marrow necrosis. In addition, PAF receptor antagonist (0.3 and 3.0 mg/kg) significantly reduced the incidence of trabecular necrosis (0%) in this model. The findings of the present study suggest that platelet activation may play an important role in inducible ON, and that suppression of platelet activation may contribute prevention of ON.