Masaaki Maruyama

Morphologic features of the acetabulum and femur: Anteversion angle and implant positioning

Morphologic features of the hips, in particular those features germane to determination of acetabular and femoral anteversion angles and femoral head offset, were studied in 50 male and 50 female human skeletons with bilateral normal joints. Four distinct configurations were identified relative to the anterior acetabular ridge. The majority (121, 60.5%) were curved; 51 (25.5%) were angular; 19 (9.5%) were irregular; and nine (4.5%) were straight. The acetabular anteversion angle measured 19.9° ± 6.6° (range, 7°–42°) and was significantly larger in females (21.3° ± 7.1°) versus males (18.5° ± 5.8°). The notch acetabular angle, which can be identified easily intraoperatively, was defined as the angle created at the intersection of a line from the sciatic notch along the posterior acetabular ridge and a line from the posterior to the anterior acetabular wall. This angle is almost perpendicular (89.0° ± 3.5°) and, therefore, may provide an accurate estimate of acetabular anteversion during cup placement. Awareness of the anatomic differences between genders for acetabular anteversion angle, anterolateral bowing of the femur, and neck shaft angle may help reduce the relatively higher incidence of dislocation in females and may lead to different implant designs for male and female patients.

In vitro properties of a chitosan-bonded self-hardening paste with hydroxyapatite granules.

A new self-hardening paste was made by using a combination of chitosan, hydroxyapatite (HA) granules, ZnO, and CaO. The sol was made by dissolving 0.1 g of chitosan in a solution of 0.1 g malic acid and 2.0 mL physiological saline solution. Mixed with 0.03 g of CaO and 0.04 g of ZnO powders was 2.77 g (55 wt %) of HA granules which had a homogeneous pore distribution and a porosity of 35-48%. The size of the granules was set for 0.1-0.3 mm. Kneading and setting of the paste generated a little amount of heat (32.8 degrees C) as compared with the heat produced by polymethyl-methacrylate (PMMA) bone cement (114.5 degrees C). The pH value of chitosan-HA-hardened composite after setting was nearly equal to that of human plasma (pH 7.4), while that of PMMA bone cement maintained an acid pH of 4.7. Hydroxyapatite granules less than 0.1 mm, 0.1-0.3 mm, or 0.3-0.6 mm were set using chitosan sol. The size of the granules did not influence the compressive strength of the set chitosan-HA-hardened composite. The greatest compressive strength of chitosan-HA-hardened composite was obtained by using 55 wt % of HA granules. The strength of the chitosan-HA-hardened composite was comparable to that of the cancellous bone derived from tibial eminentia, but was considerably lower than that of the PMMA bone cement.

The all-inside meniscal suture technique using new instruments

The all-inside meniscal suture was performed by using new arthroscopic instruments with a soft and fine (4-0 gauge) polyfilament thread that yielded relatively small knots so as to be innocuous to articular cartilage. No neurovascular injury, infection, or any other complication had occurred intraoperatively and postoperatively in this technique.

Hydroxyapatite clay used to fill the gap between implant and bone

A clay containing hydroxyapatite (HA) was developed for use as a filling material between an uncemented implant and bone. It consists of 55% HA granules greater than 0.1 mm in size with a homogeneous pore distribution and a porosity of 35% to 48% in a saline solution of sodium alginate (6%). Ti-6A1-4V alloy rods with smooth surfaces were implanted into the distal medullary canal of one osteotomised tibia of 32 Japanese white rabbits. Sixteen rods were inserted with HA clay and 16 without the clay to act as a control group. Six of each group were killed at one week and ten at 12 weeks postoperatively. The pull-out strength of the implants with HA clay was significantly greater at 12 weeks (p < 0.05), as was the percentage of the area of the new bone (p < 0.05). The study suggests that HA clay has an osteoconductive property, allowing adequate bone fixation across a gap at an early stage. The use of HA clay to enhance the early stability of uncemented components may help to improve the functional outcome of total joint arthroplasty.

Hydroxyapatite Block for Reconstruction of Severe Dysplasia or Acetabular Bone Defects in Total Hip Arthroplasty: Operative Technique and Clinical Outcome

Fourteen hips in 14 patients (all female; average age, 64 years) with severe bone defects due to developmental dysplasia of the hip or migration of the socket were treated with hydroxyapatite block with impacted morselized bone graft in conjunction with a cemented socket. All patients were followed clinically in a prospective fashion, and radiographs were analyzed retrospectively. One initial patient had 17-year follow-up, whereas the remaining 13 patients had follow-up between 4 and 6.5 years. No acetabular components were revised, including the socket of a 17-year postoperative case that remains rigidly fixed and supported by the graft and hydroxyapatite block with only mild polyethylene wear and minor osteolysis. Osteointegration and good clinical outcome were achieved in all cases by reconstruction with this technique in total hip arthroplasty.

Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty

The linear penetration rates for ceramic femoral heads on conventional and highly cross-linked polyethylene were measured and compared with radiographs taken in the standing and supine position taken three weeks postoperatively and at final follow-up. Seventy-five patients (83 hips) with conventional polyethylene (group-1) and two hundred and seventy five patients (300 hips) with highly cross-linked polyethylene (group-2) were studied. Follow-up periods were 14.5years in group-1 and 8.6years in group-2. The average penetration rates in group-1 were 0.17mm/year in supine position and 0.18mm/year in standing position (P<0.05). On the other hand, the rates in group-2 were 0.03mm/year and 0.04mm/year respectively (P<0.05). Although there were statistical differences between groups, 0.01mm differences are probably not clinically relevant.

Reconstruction of the Shallow Acetabulum With a Combination of Autologous Bulk and Impaction Bone Grafting Fixed by Cement

BackgroundAcetabular bone deficiency, especially proximal and lateral deficiency, is a difficult technical problem during primary total hip arthroplasty (THA) in developmental dysplasia of the hip (DDH). We report a new reconstruction method using a medial-reduced cemented socket and additional bulk bone in conjunction with impaction morselized bone grafting (additional bulk bone grafting method).Questions/purposesIn a population of patients with acetabular dysplasia undergoing THA using a medial-reduced cemented socket and additional bulk bone with impacted morselized bone grafting, we evaluated (1) the radiographic appearance of bone graft; (2) the proportion of cups that developed loosening and subsequent revision; and (3) clinical results (outcome scores and complications).MethodsForty percent of 330 THAs for DDH performed at one center between 1999 and 2009 were defined as shallow dysplastic hips. The additional bulk bone grafting method was performed on 102 THAs with shallow acetabulum (31% for DDH) at one center between 1999 and 2009. We used this approach and technique for shallow acetabuli when a cup protruded from the lateral acetabular edge in preoperative templating. The other 132 dysplastic hips without bone grafting had THA performed at the same periods and served as a control. Acetabuli were defined as shallow when the depth was less than or equal to one-fifth of the pelvic height (cranial-caudal length on radiograph). The additional bulk bone grafting technique was as follows: the resected femoral head was sectioned at 1 to 2 cm thickness, and a suitable size of the bulk bone graft was placed on the lateral iliac cortex and fixed by poly-l-lactate absorbable screws. Autologous impaction morselized bone grafting, with or without hydroxyapatite granules, was performed along with the implantation of a medial-reduced cemented socket. We defined an “incorporated” graft as remodeling and trabeculation including rounding off of the protruding edge of a graft beyond the socket. Radiographic criteria used for determining loosening were migration or a continuous radiolucent zone between the prosthesis/bone cement and host bone. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) and the Merle d’Aubigne and Postel score; complications were tallied from chart review. The followup was 10 ± 3 years (range, 6–15 years).ResultsOne acetabular component (1%) with severe shallow and steep acetabuli showed definite radiographic evidence of loosening and was revised. Clinically, the mean JOA score for the hips treated with additional bulk bone grafting THA in this study improved from 39 ± 10 points preoperatively to 95 ± 5 points postoperatively (p < 0.05, paired t-test). The mean Merle d’Aubigne and Postel score for the hips improved from 7 ± 2 points to 17 ± 1 points (p < 0.05, paired t-test). Complications included a Trendelenburg sign in one hip, dislocation in one, and transient partial sciatic nerve palsy in one. Within 3 years 6 months postoperatively, 101 of 102 additional bulk bone grafting cases showed successful bone remodeling and bone graft reorientation without collapse on radiographs. Partial resorption of the additional bone graft on the lateral side was observed in two hips (2%) with socket abduction angles of < 35°.ConclusionsAchieving stable acetabular fixation is often challenging in the dysplastic hip, especially shallow acetabulum, and a variety of techniques have been described. Early results of combining bulk graft with impaction of morselized graft are promising. Although each surgical technique was well established, further investigation for clinical results of a combination of these techniques might be necessary to confirm longer term outcomes.Level of EvidenceLevel IV, therapeutic study.

CORR Insights(®): Does Tranexamic Acid Reduce Blood Loss and Transfusion Requirements Associated With the Periacetabular Osteotomy?

I ntraoperative blood loss can occur in many different ways—hypotensive anesthesia or continuous epidural anesthesia methods, surgical technique, or prolonged operation time can all influence bleeding during surgery. In fact, patients undergoing periacetabular osteotomy (PAO) lose more blood during surgery and receive transfusions more frequently [3] compared to patients undergoing total joint arthroplasty. Although blood management strategies such as blood donation and blood salvage have been used to curb intraoperative blood loss for patients undergoing PAO, these approaches carry their own risks. Another approach to reducing intraoperative bleeding is the use of an antifibrinolytic agent, such as tranexamic acid (TXA). TXA has been shown to reduce blood loss and minimize transfusions in various surgical subspecialties [1, 2]. However, one concern associated with TXA is the possible increased risk of thrombosis. Additionally, there are no studies in the literature that have examined the effects of TXA on blood loss associated with PAO.