Background

The inherently high stiffness of locked plate constructs is increasingly recognized as a potential cause of deficient healing observed in patients with periarticular locked plating systems.

The objective of this study is to perform a biomechanical comparison of distal femur locked plating systems.

Introduction: Drilling of the femoral bone tunnel in anterior cruciate ligament reconstruction may be performed in a transtibial drilling technique or via the anteromedial portal.

Purpose: To determine the accuracy of the radiographic bone tunnel position using either a transtibial or anteromedial drilling technique.

Materials & methods: The postoperative lateral radiographs of 100 patients after anterior cruciate ligament reconstruction were reviewed. In each patient, the femoral bone tunnel was created either through the tibial tunnel or via the anteromedial standard arthroscopy portal. The resulting position of the femoral tunnel was evaluated according to reference values reported by Aglietti (65 % of the cortical femoral A-P distance along Blumenstaat’s line), Amis (60 % of the A-P diameter of the posterior lateral femoral condyle parallel to Blumensaat’s line), and Harner (80 % of the A-P length of Blumensaat’s line). The mean deviation of the radiographic tunnel position from the referenced values was statistically evaluated.

Results: Radiographic bone tunnel positions with transtibial drilling were 62.42 ± 8.36, %, 54.53 ± 8.43 %, and 75.84 ± 9.56 % according to Aglietti, Amis, and Harner, respectively. Bone tunnel positions with anteromedial drilling were 65.46 ± 5.29 %, 59.59 ± 4.18 %, and 79.93 ± 4.24 %, respectively. The mean deviation from the reference values was significantly higher when comparing transtibial to anteromedial drilling. Transtibial drilling resulted in a significantly more anterior bone tunnel position.

Conclusion: Precise bone tunnel placement is a prerequisite for proper postoperative knee function and stability. The results of this study indicate that the accuracy of femoral bone tunnel placement through the anteromedial arthroscopy portal was superior to transtibial drilling. It may therefrore be concluded that drilling the femoral tunnel through the anteromedial portal is recommended when using fixation techniques not depending upon placement of a transtibial guide.

Introduction: This study was initiated to evaluate cortical and cancellous bone density (BD) changes of the acetabulum after cemented and uncemented total hip arthroplasty (THA) using computer tomography (CT)-assisted osteodensitometry in-vivo.

Materials and Methods: 15 cemented ZCA Pfannen cups (Zimmer, USA) (age 78 years) and 21 press-fit Trilogy cups (Zimmer, USA) (age 72 years) were implanted by one surgeon. All hips were investigated by a standardized CT-mode (slice thickness 2 mm, table feed 5 mm, extended CT-scale). 6 CT-scans at the level of the cup and 4 scans above the dome of the cup were analyzed 2 weeks and 2 years after surgery. Cancellous and cortical bone mineral density (BMD) (CaHA mg/ml) were elaborated with a special software tool (CAPPA postOP, CAS Innovations AG, Erlangen).

Results: 2 years after index operation cemented cups showed mild cancellous BD loss (−8% to −20%) and no significant cortical BD changes cranial, significant cortical (−4% to −20%) and cancellous (−16% to −44%) BD loss ventral and no significant BD changes dorsal to the cup.

For press-fit cups we observed highly significant (p< 0,01) cancellous BD loss in all sectors (−17% to −53%), cortical BD loss ventral and dorsal to the cup (−12% to −23%) and very limited BD loss cranial (−4% to −13%) to the cup.

Conclusions CT-assisted osteodensitometry allows a thorough assessment of the actabular bone in-vivo. Different patterns of stress shielding were observed for cemented and press-fit cups. For the press-fit cup high BD loss for both cortical and cancellous bone was observed in all areas adjacent to the pelvic implant, except for cortical BD at the acetabular dome, suggesting fixation of the cup in the cranial cortical bone. Comparetively less BD loss was seen for cemented cups in all sectors, especially for cancellous bone, suggesting a more physiological stress transfer to both cortical and cancellous pelvic bone.

Introduction: The aim of this study was to analyze the periprosthetic bone remodeling of the femoral component after implantation of an uncemented taper-design stem using CT-assisted osteodensitometry. This method allows accurate three-dimensional evaluation of cortical and cancellous bone with high resolution.

Material and methods: We followed 21 consecutive Patients with osteoarthritis who received primary total hip replacement using 21 uncemented three-dimensionally shaped taper stems (TiAl6V4-Cerafit, Ceraver, France). CT-evaluation was performed 2 weeks, 1 and 6 years post-op. Bone mineral density (BMD) [mg/ml] was determined separately for both cortical and cancellous bone using a special software.

Results: Mean decrease of cortical BMD in the proximal (metaphyseal) area 6 years post-op was −25%, (1 year post-op −15%). Only slight changes of BMD were observed in the distal (diaphyseal) area. Cancellous BMD decreased progressively from −26% 1 year post-op to −49% 6 years after index operation in the proximal area. Cortical bone density loss was lower and non-progressive at the diaphysis (Ø −7% 1 year, −9% 6 years post-OP) and the distal region (Ø −6% 1 year, −4% 6 years post-OP) of the stem. All stems showed no signs of loosening on plain radiography and good clinical results according to the Harris hip score.

Conclusion: Computertomography assisted osteoden-sitometry is the only method which allows discrimination between periprosthetic cortical and cancellous bone density changes in vivo. The analyzed uncemented stem is anchored at the diaphysis and distal region. Due to the changed biomechanical loading after stem implantation, progressive proximal cancellous bone density loss was measured for the first time in vivo. Its role in the pathogenesis of implant loosening is still unknown and needs to be further elucidated.

INTRODUCTION: Patients undergoing total knee arthroplasty may experience significant blood loss and are at risk of receiving blood transfusions. A bipolar sealing device designed to reduce intraoperative and postoperative blood loss, was compared to conventional electrocautery to determine its efficacy in maintaining hemoglobin levels and reducing transfusions in minimally invasive unilateral total knee arthroplasty.

METHODS: A retrospective, matched control review of one hundred patients undergoing primary total knee arthroplasty by a single surgeon. Conventional electrocautery was used for hemostasis in 50 patients and bipolar sealing technology used in another 50 patients.

RESULTS: Patients in the bipolar sealing group had a significantly lower mean decline in hemoglobin compared to the control group (3.3 ± 1.1 g/dL vs. 3.9 ± 1.2 g/dL; p = 0.0085). The prevalence of autologous transfusion was significantly lower for the bipolar sealing group (16%) compared to the controls (44%) (p < 0.001). The prevalence of allogeneic transfusion was also significantly lower for the bipolar sealing group (8%) compared to control group (22%) (p < 0.001). The prevalence of transfusion as a whole was significantly reduced by 64 percent (p < 0.001). While not statistically significant the break through allogeneic transfusion rate was reduced by 75 percent (4 controls compared to 1 treatment).

DISCUSSION/CONCLUSION: The use of bipolar sealing technology in patients undergoing minimally invasive primary unilateral total knee arthroplasty is associated with a significant reduction in blood loss and transfusion rates compared to the use of conventional electrocautery.

No funds were received in support of this study.

Background Context: One of the main postulated basic principles of total disc replacement (TDR) is the preservation of flexion/extension ability. In neutral position the ideal disc prosthesis should not stay in maximal possible extension which would imply an impingement of the prosthesis. An impingement would cause shear strains on the prosthesis endplates which probably accelerate loosening. Moreover an additional extension ability from the neutral position would indicate no impingement in the facet joints in neutral position and a physiological movement capability.

Purpose: The purpose of study was to evaluate a possible impingement of the prosthesis or facet joints after TDR in neutral position.

Study design: Prospective evaluation of radiological outcome measures after total disc replacement.

Patient sample: The patients (19 female, 10 male) ranged from 29 to 56 years of age (mean: 42.46.5 years). The mean follow up interval averaged 13.2 months (range: 6 – 35 months). The diagnosis of degenerative disc disease was confirmed by MRI (black disc) and discography (positive „Memory pain“). Pain relief after facet joint infiltration was an exlucsion criteria. All patients had a single-level disc replacement (Prodisc II, Spine Solutions) with the same angulation (6).

Outcome measures: Evaluation of a possible impingement of the prosthesis and impingement of facet joints in neutral position.

Methods: A computer based analysis of pre- and postoperative lateral X-rays in neutral position and dynamic x-rays. The angulation of prosthesis in neutral position and the extension ability in dynamic x-rays were measured.

Results: 15 patients showed no extension ability on dynamic x-rays and 10 of these 15 patients had an impingement with maximum extension of the prosthesis on x-rays in neutral position. In the remaining 14 patients the extension ability averaged pre-/postoperatively 2.3/1.3 (p=0.115). In 4 of the 14 patients the pros-thesis showed an impingement in maximum extension and in 10 patients the prosthesis was not in maximum possible extension.

Conclusion: Due to the constrained design of the Pro-Disc an impingement is possible and was recognized in nearly 30% of the cases. The imbalance of flexion vs extension bending moments with increase in extension bending moments due to resection of the anterior longitudinal ligament and anterior anulus seems to be a possible explanation. It still remains unclear if an impingement will result in facet joint protection or will trigger a loosening of the implant. A prosthesis design which preserves the anterior longitudinal ligament would be probably a possible solution.

The present study was conducted to analyze the specific morphological features of press-fitted quadriceps tendon-patellar bone grafts that determine primary graft stability in ACL-reconstruction.

Ten quadriceps tendon-patellar bone grafts were harvested from fresh frozen human cadaveric knees (age 52–82) and fixed to porcine femora in a press-fit technique. Four specimens were prepared for histological analysis of the bone-tendon junction, while a modified technique for tissue-plastination was applied to 6 specimens to investigate the microscopic and microradiographic features of the bone-to-bone interface.

Analysis of the bone-tendon junction revealed a serious damage of the fibrocartilage at the attachment zone according to the impaction of the patellar bone plug with implantation. Microradiographs and microscopy of the plastinated specimens showed that there is a trabecular interaction between the bony interfaces of the graft and the femoral tunnel, representing an early osseous integration with local increase of radiopacity. In consequence, both elevated compressive forces as well as increased frictional resistance seem to contribute to the primary stability of press-fit fixated grafts.

The stability of quadriceps tendon-patellar bone grafts in press-fit technique to a certain degree depends on bone quality, allowing compressive forces to arise at the bone-to-bone interface. Loss of graft stability, however, is caused by disturbance of the integrity of the bone-tendon junction while impacting the patellar bone plug into the femoral tunnel.

Background Context: Total disc replacement (TDR) gained enormous popularity as a treatment option for symptomatic degenerative disc disease in the last few years. But the impact of the prosthesis design on the segmental biomechanics in most instances still remains unclear. As TDR results in a distraction of the capsuloligamentous structures, the disc height seems to be of crucial importance for the further biomechanical function of the operated level. Yet the biomechanical role of disc height after TDR still remains unclear.

Purpose: The purpose of study was to evaluate the influence of prosthesis height after total disc replacement on: 1) the sagittal balance and 2) the range of motion.

Study design: A radiological and an in-vitro biomechanical study.

Method: 6 human, lumbar spines L4–L5 were tested in vitro.The segmental lordosis of the specimen were measured on plain radiographs and the range of motion was measured for all six degrees of freedom with a previously described spine tester. The segmental lordosis and the range of motion at level L4–L5 was evaluated for following settings: 1) intact state 2) after implantation of a prosthesis with 5mm endplate 3) after implantation of a prosthesis with 7mm endplate.

The prosthesis used was a prototyp and had a constrained design with a ball and socket principle.

Results: Even the implantation of the lowest possible prosthesis height (5mm endplate) resulted in an increase of segmental lordosis (intact: 6.9; 5mm endplate: 8.8; p=0,027). Using a higher prosthesis (7mm endplate) further increased the segmental lordosis (10.5, p=0.041). The implantation of the lowest prosthesis resulted in significant increase of movement capability compared to the intact status for flexion-extension (8.6 vs 11.4; p=0.046) and axial rotation (2.9 vs 5.1; p=0.028). Lateral bending did not changed significantly (9.4 vs 8.6; p=0.345). The implantation of the higher prosthesis (7mm endplate) resulted in similar movement capability compared to intact status for flexion-extension (8.4 vs 8.6; p=0.116) and axial rotation (3.3 vs 2.9; p=0.600). Lateral bending decreased significantly compared to the intact status (5.1 vs 8.6; p=0.028).

Conclusion: Total disc replacement with the lowest prosthesis height inherently increases segmental lordosis. Further increase of disc height results in a significant enhancement of segmental lordosis by decreasing the range of motion for all three degrees of freedom. Yet, methods for scheduling the ideal disc height preoperatively, to provide a physiological lordosis thereby maintaining physiological range of motion postoperatively, seems not to be established already.

Introduction and Aims: Recently, concerns have emerged regarding the high stiffness of acetabular components inserted with alumina ceramic liners, which might potentially cause early migration and loosening. This study was designed to investigate in-vivo the migration pattern of these constructs

Method: Fifty patients (50 hips) operated on using the same surgical technique and the same prosthesis were randomised in two groups. The study group of hips was treated with an alumina ceramic liner, the control group of hips received a polyethylene liner. An alumina femoral head with a diameter of 28mm was used in all hips. Radiostereometric analysis (RSA) was performed to assess migration using serial follow-up radiographs.

Results: The median pre-operative Harris hip score (HHS) was rated 48.9 points in the alumina group, and 47.7 points in the polyethylene group. At the two-year follow-up, the median HHS of the alumina group was rated 94.1 points, and was rated 93.7 points in the polyethylene group. There were no clinical or radiological signs of aseptic loosening. RSA of the alumina group of cups showed a median axial displacement of 0.026 mm (SD 0.35mm). The median axial displacement of the polyethylene group was 0.047 mm (SD 0.26 mm) (p=0.9). The median tilting of the cup was 0.21 degrees (SD 0.54 degrees) in the alumina group, and 0.35 degrees (SD 0.71 degrees) in the polyethylene group (p=0.12).

Conclusion: At an average of two years post-operatively, the cups inserted with an alumina ceramic liner appeared stable, RSA showed low rates of non-progressive migration. Results did not differ from those observed using the same cup inserted with a polyethylene liner.

Introduction and Aims: Little is known about peri-acetabular bone remodelling after insertion of the acetabular cup in total hip arthroplasty. This study was designed to analyse retroacetabular bone changes using quantitative CT-assisted osteodensitometry. This is a new method for a detailed measurement of bone density (BD) changes around the implants.

Method: Prospective cohort study. Operations were performed on 26 consecutive hips (26 patients) using an uncemented prosthesis with alumina-alumina pairing (Cerafit, Ceraver Osteal, France). The average age of patients was 58.4 years. There were 15 men and 11 women. CT investigations were performed within two weeks of surgery and then one year and three years post-operatively. Cancellous, cortical and total bone density (mgCaHA/ml) were assessed using specific software (Impact-Hip, VAMP, Moehrendorf, Germany).

Results: All 26 hips were available for follow-up at one year, seven patients were available at three years. At three-year follow-up we found an 18.4% decrease of cancellous BD proximal to the upper rim of the cup. Cortical BD increased by + 5.2% in this region. Cortical BD decreased ventral to the cup by −5.0% and by −2.3% dorsal to the cup. Of more interest, cancellous BD was observed to decrease by −40.9% in the ventral region and −32.2% in the dorsal region.

Conclusion: We have observed a progressive decrease of cancellous BD after insertion of an uncemented ace-tabular component. These phenomenon could explain the onset of late migration and implant failure of pressfit cups. Only minor changes have been observed in cortical BD. Further investigations are required to define the role of implant design and material in periprosthetic bone remodelling of the acetabulum.

The purpose of this study was to evaluate the clinical outcome of a hydroxyapatite (HA)-coated tapered stem and to assess bone remodelling of the proximal femur using quantitative computed tomography osteodensitometry.

Fifty consecutive hips were managed with total hip replacement using the Cerafit Multicone H-A.C. stem with HA coating and the Cerafit Triradius-M press-fit cup (Ceraver Osteal, Paris, France). The mean follow-up was 3 years (range, 2.9 to 4 years). Current criteria were used for clinical and radiological assessment.

Forty-nine hips (98%) were clinically rated good or excellent. The mean preoperative Harris Hip Score was rated 57, and it has improved to 96 at the time of follow-up. The radiographs showed stable fixation by bone ingrowth in all hips. Fifteen patients (15 hips) were eligible for osteodensitometry. The mean decrease of the overall bone density (BD) in the metaphyseal portion of the femur 3 years after insertion of the stem was rated 14.21%, and the mean decrease of the cortical BD was rated 15.52%. The mean decrease of the overall BD in the diaphyseal portion of the femoral component was rated 10.00%, and the mean decrease of cortical BD was rated 7.76%. Little changes were observed underneath the tip of the stem.

The clinical and radiological outcomes of the tapered stem with HA coating at a mean follow-up of 3 years compares favourably with other reports. Results of osteodensitometry show less proximal femur BD loss in comparison to similar investigations performed using uncemented stems.

The first Ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopedic Clinic at the University of Jena, Germany in 1972 [1]. In 1980, Drs. Oonishi and Hasegave began using a Alumina femoral component on a polyethylene tibial component [2]. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by the demand of thin components. In the present feasibility study the in vitro wear behavior of a knee concept with a novel Alumina Matrix Composite (AMC) Ceramic was examined [3,4].

The wear behavior of the Ceramic components for the knee system were tested in accordance to ISO/WD 14243-3 for 5*106 cycles. Six samples were tested. The lubricant was calf serum diluted with deionized water. All tests have been performed with components made of the novel AMC Ceramic.

The wear test performed showed an average gravimetric wear rate below 1 mg/1*106 cycles on each of the six components. A change of geometry was not measurable after 5 million cycles. No significant change of the surface structure was detectable with a conventional surface tracer. SEM and AFM pictures show traces of ultra mild abrasive wear at the surface. The performed investigation on the novel knee concept shows the following potential benefits for a Ceramic knee bearing:

approx. 500 times lower volumetric wear

The novel AMC Ceramic offers a solution to minimize the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are to be realized. The use of knee endo-prosthesis with Ceramic on Ceramic combination is an option for îzeroî wear bearings in the knee. These first results motivate to start further R& D on Ceramic on Ceramic bearings for total knee implants.

The first Ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopedic Clinic at the University of Jena, Germany in 1972 [1]. In 1980, Drs. Oonishi and Hasegave began using an Alumina femoral component on a polyethylene tibial component [2]. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by the demand of thin components. In the present feasibility study the in vitro wear behavior of a knee concept with a novel Alumina Matrix Composite (AMC) Ceramic was examined [3,4].

The wear behaviour of the Ceramic components for the knee system were tested in accordance to ISO/WD 14243-3 for 5*106 cycles. Six samples were tested. The lubricant was calf serum diluted with deionized water. All tests have been performed with components made of the novel AMC Ceramic. The wear test performed showed an average gravimetric wear rate below 1 mg/1*106 cycles on each of the six components. A change of geometry was not measurable after 5 million cycles. No significant change of the surface structure was detectable with a conventional surface tracer. SEM and AFM pictures show traces of ultra mild abrasive wear at the surface.

The performed investigation on the novel knee concept shows the following potential benefits for a Ceramic knee bearing:

approx. 500 times lower volumetric wear

The novel AMC Ceramic offers a solution to minimize the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are to be realized. The use of knee endoprosthesis with Ceramic on Ceramic combination is an option for ”zero” wear bearings in the knee. These first results motivate to start further R& D on Ceramic on Ceramic bearings for total knee implants.

Aims: The purpose of this study was to verify a partial bursal-side rupture of the rotator cuff (RC) using different imaging techniques with special emphasis on the validity of a specific method of subacromial arthrography (SAA). Methods: Patients (n=92, age 53.8 years) with a subacromial impingement syndrome underwent sonography, magnetic resonance imaging (MRI), and SAA. All diagnostic results were controlled by subsequent arthroscopic surgery. Results: Out of 31 surgically verified ruptures, 17 cases showed a partial rupture located towards the bursa. These had been detected by MRI and ultrasound with a sensitivity of 64% and 41%, respectively, while SAA as a diagnostic tool yielded a sensitivity of 82%. In 14 cases of complete RC ruptures, all imaging techniques had a similar sensitivity of 86 to 93%. Conclusions: It appears that SAA is a sufficient and valid diagnostic tool for the detection of partial bursa-sided RC ruptures. Ultrasound and MRI showed a comparably lower sensitivity. It is therefore concluded that SAA has clear advantages in the diagnosis of this defect with the consequence that open surgical techniques to the patient can be avoided.

Aims: Aim of this study was to asses the glenohumeral joint internal and external range of motion using ultra-sonographic based kinematic measurement. Methods: 27 male professional tennis players were bilaterally measured for internal and external rotation at 90 degrees of shoulder abduction while negating scapulothoracic motion. The normal control group consisted of 20 asymptomatic volunteers. Results: Both arms had signiþcantly greater degrees of external rotation than internal rotation (p< 0,05). The dominant arm (playing arm) had signiþcantly greater range of external rotation than the nondominant arm (p< 0,01). Analysis of internal rotational deþciency showed highly decreased internal rotation on the dominant arm (p< 0,01). The total rotational range of motion of the dominant arm was also found signiþcantly less (p< 0,01) in the elite tennis players. No signiþcant difference was found for the dominant and nondominant extremity in the control group. Conclusions: The objective measurement of glenohumeral rotational abilities has clinical application for the development of a speciþc treatment protocol that may reduce the risk of shoulder injury.

Introduction: Little is known about periacetabular bone remodelling and stress shielding after total hip arthroplasty.

Aim: To analyse prospectively the bone changes around an acetabular component using high resolution computerised tomography (CT).

Methods: A sequential CT scan mode was used (140kv and 206mA, table feed 10mm, slide thickness 2mm). Special software (IMPACT-HIP, VAMP, Germany) was used for bone density (BD) measurements. Parameters of the assessment were: BD of cancellous, cortical and full bone, bone-implant-contact area, bone-area. Twenty patients with degenerative osteoarthrosis (20 hips) were operated on using an uncemented, pressfit, acetabular component and alumina-alumina pairing (Cerafit, Ceraver Osteal, France). The average age of patients was 57 years. CT examinations were performed after two weeks and again one year after the operation. Measurement of BD of the contralateral hip was conducted as a control.

Results: Cancellous bone showed a decrease of BD ranging from 20% to 23% in the caudal portion of the periacetabular area and a decrease ranging from 8% to 12% in the cranial portion. The cortical BD increased 6% at the cranial portion of the periacetabular area. Only slight changes of cortical BD were observed at the caudal portion.

Conclusions: The study showed a significant atrophy of the cancellous bone around the cup, but limited changes of the cortical bone. Periacetabular stress shielding is a little recognised phenomenon which requires further investigations. The method used in the present study allowed analysis of bone changes by 3D-viewing of the acetabulum and by separation of cancellous and cortical bone.