Bone integration in acetabular revision hip arthroplasty using equine-derived bone grafts: a retrospective study.

PURPOSE: During the last decade, total hip arthroplasty has become a common procedure performed in young patients, as well as elderly ones. This has led to an increase in total hip arthroplasty revisions. Loosening of primary components with associated bone loss represents the major cause of total hip arthroplasty revision. This study evaluates the safety and performance of an enzyme-deantigenic equine-derived bone graft material in acetabular defect reconstruction. METHODS: Records of 55 patients who were treated for Paprosky type II or III acetabular bone defects with arthroplasty revisions using equine-derived bone and followed for an average of 34 months (range from 24 to 48 months) were analyzed. RESULTS: Of the 55 revisions, 49 (89%) were regarded as successful, showing good osteointegration without signs of mobilization. Failures included six cases (11%) of mobilization: five cases of aseptic mobilization (9.1% of revisions, 83% of failures) and one case of septic mobilization (1.9% of revisions, 17% of failures). These results are consistent with those of studies having a similar follow-up period for allografts used in combination with trabecular metal components. CONCLUSIONS: Results of the present study suggest that enzyme-treated equine-derived bone grafts may be a valid alternative to autogenous and homologous bone grafts in total hip arthroplasty revision.

The effects of femoral component design on the patello-femoral joint in a PS total knee arthroplasty.

INTRODUCTION: Anterior knee pain following TKA performed utilizing the PFC Sigma system still represents a cause of failure. The purpose of this study was to evaluate whether or not a recent change in the femoral design (PFC Sigma PS) had a positive impact on the patello-femoral complication rate. MATERIALS AND METHODS: A consecutive series of 100 TKA using the PFC Sigma PS system was followed prospectively for a minimum of 3 years. All patellae were replaced and a standard lateral release was never performed. Radiographic analysis following the Knee Society Score (KSS) included antero-posterior weight-bearing, lateral and bilateral axial radiographs. TKA rotational alignment was recorded at the final follow-up in 30 consecutive knees by performing a CT evaluation. RESULTS: Good to excellent clinical results according to the KSS were achieved in 94% of the knees. Survival without need of reoperation for any reason was 98% at 3 years minimum follow-up; two reoperations were done for removal of fibromatous intra-articular tissue ("Clunk syndrome"). There were no revisions for septic or aseptic loosening of the components. The mean ROM improved from 104° preoperatively to 115° (97°-132°) postoperatively: postoperative flexion was 120° or more in 58 % of the knees. Severe anterior knee pain was present in 9% of patients. Radiographic evaluation showed 90 knees with a tibio-femoral anatomical axis between 8° and 2° of valgus (±3° from the intraoperative goal). CT evaluation of 30 consecutive knees showed that the femoral component positioning in relationship to the trans-epicondylar axis had only 2.80° of external rotation (±2.10°) with respect to a planned external rotation of 3°. This difference was statistically significant. CONCLUSIONS: Although the PFC Sigma PS system provides good and predictable results for tricompartmental arthritis of the knee, anterior mechanism complications still represent a reason for dissatisfaction in a substantial group of patients.

A multimodal approach in total hip arthroplasty preoperative templating.

OBJECTIVES: Accurate preoperative planning is mandatory for a successful total hip arthroplasty (THA). Templating helps to achieve multiple technical goals, including offset restoration, leg-length equality, and components positioning. This study aims to measure how successful a new stepwise method for preoperative radiographic templating is in achieving postoperative restoration of anatomy. METHODS: We measured the relationship of several radiographic landmarks on the affected limb in comparison to the unaffected limb to define the appropriate position of the components. One hundred consecutive patients with unilateral disease undergoing THA were retrospectively analyzed. The preoperative templates were compared with the postoperative radiographs. RESULTS: Accuracy in achieving the desired offset, leg-length discrepancy within 5 mm, was 93 % and 100 % respectively. Acetabular component positioning within 2° was replicated in 92 %. CONCLUSION: We conclude that this technique can help the surgeon to accurately reproduce the anatomy of the contralateral unaffected hip.

Contemporary femoral designs in total knee arthroplasty: effects on the patello-femoral congruence.

PURPOSE: The objective of this study was to evaluate the radiological and clinical correlations between implant design and patellar positioning in patients who underwent TKA utilizing femoral implants with modern designs. METHODS: Thirty consecutive PFC PS Sigma TKAs, characterized by a new prolonged anterior flange and a "smoother" trochlea, were prospectively reviewed. All patellae were replaced. All patients were evaluated pre-operatively and prospectively at two years follow-up both clinically according to the Knee Society score as well as radiographically. This included computed tomography (CT); patellar tilt, patellar conformity angle, patellar lateralization, and femoral component external-rotation in relation to the clinical trans-epicondylar axis. RESULTS: Average patellar tilt at follow-up was 3° (±7.5°) with respect to a pre-operative 18.5° (±8.5°). Average patellar congruence angle at follow-up was -3° (range, -11° to +9°) with respect to a pre-operative 10.3° (range, + 1.5° to 25.5°). Average lateralization index at follow-up was 2.7 mm (range, -3.4 mm to +7.1 mm) with respect to a pre-operative 12.2 mm (± 4.8 mm). Femoral component positioning related to the trans-epicondylar axis showed an external rotation of 2.80° (± 2.10°) at follow-up with respect to 5.7° (± 1.80°). Clinically, two (6.6%) patients reported patello-femoral complications related to imperfections in the surgical technique more than the implant's design. CONCLUSIONS: This study highlighted that modern femoral designs in TKA allow for a correct reproducibility of a normal patello-femoral conformity. Strict surgical principles are paramount to avoid patello-femoral complications even when modern implants are used.

Biomechanical analysis on total knee replacement patients during gait: Medial pivot or posterior stabilized design?

BACKGROUND: Total Knee Replacement surgery restores joint function in patients with advanced osteoarthritis. There are several prostheses available based on different mechanisms, which guarantee knee stability during Activities of Daily Living. The aim of this study is to compare ball-in-socket (or Medial Pivot) and post-cam mechanisms to detect possible differences in terms of biomechanical parameters between these two prosthesis designs and to evaluate which design is closer to physiological biomechanics. METHODS: A kinematics, kinetics and electromyography lower limb analyses were performed during gait on sixty subjects: twenty with Medial Pivot prosthesis, twenty with posterior stabilized prosthesis and twenty healthy subjects to obtain a physiologic reference. FINDINGS: Total Knee Replacement gait pattern for both patient groups were characterized by reduced walking speed, reduced stride length and increased stance time respect to control group. Comparison between Medial Pivot and Posterior Stabilized groups showed a reduction of knee flexion and flexor moment in patients with ball-in-socket mechanism. A prolonged muscular activity of rectus femoris was observed in Medial Pivot patients compared to Posterior Stabilized and control groups. INTERPRETATION: "Stiff knee pattern" mechanism was showed for both patient groups but more enhanced in Medial Pivot patients. Even though the Posterior Stabilized design introduces the non-physiological paradoxical motion and the Medial Pivot design seems to better reproduce the physiological condylar movement as gait analysis parameters, including kinematics, kinetics and electromyographic parameters were closer to control group and, in turn, to physiological gait for the Posterior Stabilized than Medial Pivot group parameters.

Shoulder joint loadings in post total hip replacement surgery patients during assisted walking: The influence of the crutch setup.

A crutch is prescribed to permit the patient to walk safely and independently immediately after total hip replacement (THR) surgery. Purpose of this study is to evaluate the influence of the crutch setup on upper limbs biomechanics, including shoulder joint kinematics and kinetics parameters that will be evaluated to detect possible differences related to the crutch length. Thirty patients were randomly assigned to elbow flexed (EF) or elbow extended (EE) forearm crutch setup. Subjects were asked to walk on the laboratory path, instrumented with motion tracking system and force platforms. Spatiotemporal gait parameters, crutch ground reaction force (GRF) and crutch displacement (measured as the relative distance between the crutch position on the floor and the shoulder joint center), were evaluated. A three-dimensional (3D) biomechanical model was implemented to determine shoulder joint kinematics and kinetics during crutch walking. Results showed that the stride length significantly decreased, and base of support width increased for the EF group when compared to the EE group. Crutch forces and distance to the body significantly decreased in the EE group. Furthermore, shoulder joint moments in all planes of motion, vertical and lateral forces were significantly reduced in the EE group. The present study showed that crutch setup influenced performance and upper limb loading during walking, with EE setup allowing a more stable walking and reducing stress on the shoulder joint when compared to the EF setup. Results may help therapists in rationalizing crutch length adjustments for patients after THR surgery.

The influence of the crutch setup on stability and weight-bearing parameters in post total hip replacement surgery patients during quiet standing.

PURPOSE: The purpose of this study is to evaluate the influence of the crutch setup on standing, in post total hip replacement (THR) surgery patients. MATERIALS AND METHODS: Thirty patients after THR were randomly assigned to walking with the elbow flexed (EF) or elbow straight (ES) crutch setup. Subjects were asked to stand on a force platform in a comfortable position with the crutch positioned on the unaffected side, facing forward for 10 seconds. Centre of pressure total path and maximal excursion were evaluated in both medio-lateral and anterior-posterior planes. Difference in the asymmetry of left/right acromial height, measured with and without the crutch, was calculated (ACdiff). Percentage of body weight borne by the crutch (Fcr), symmetry (SIload) between operated and healthy limbs loading during the trial, together with shoulder forces and moments were measured. RESULTS: No significant differences between the two groups (p > .05) were found for stability parameters. ACdiff, Fcr and shoulder load increased significantly (p < .05) in EF group compared to ES group. In addition leg loading symmetry was significantly reduced in the EF group. CONCLUSIONS: The present study showed that the ES setup reduced the force borne by the crutch, the load on the shoulder joint and it minimized postural and loading asymmetries when compared to EF setup. Conversely, postural stability was not influenced by the crutch setup. Implications for Rehabilitation Static posture and weight-bearing parameters are influenced by crutch setup during quiet standing. Crutch setup does not influence postural stability. Adjusting the crutch according to the elbow straight setup reduces the force borne by the crutch and the asymmetry in lower limbs loading. Forces and moments at the shoulder joint were reduced for the elbow straight setup group.

Does crutch length influence gait parameters after total hip replacement surgery?

After total hip replacement surgery, crutches are often prescribed to enable patients to walk independently. Purpose of this study was to evaluate possible crutch length influence on gait performance and symmetry, including spatiotemporal and kinetics parameters. Thirty patients were randomly assigned to elbow flexed (EF) or elbow extended (EE) crutch setup. Subjects were asked to walk on the laboratory path, instrumented with motion tracking system and force platforms. Spatiotemporal gait parameters and ground reaction force (GRF) parameters for both limbs and crutch support were evaluated. In addition, limb symmetry was evaluated for both gait and force parameters using the symmetry index. Variability was quantified for base of support width, stride time and length as the coefficient of variation. Results showed that cadence and walking speed were not significantly different, but stride length significantly decreased and base of support width increased for the EF group when compared to the EE group. Operated limb GRF parameters were significantly decreased for the EF group, while crutch force parameters decreased for the EE group. Furthermore, the EF group showed greater stride length variability and asymmetry of force and spatiotemporal parameters than EE group did. The results of the present study showed that EF and EE setups did not assist patients equally during walking, with EE setup allowing more load bearing on the operated side, reducing load on the crutch and asymmetries in gait parameters when compared to the EF setup. This may help clinicians in rationalizing crutch setup for patients after total hip replacement surgery.

Unassisted quiet standing and walking after crutch usage in patients with total hip replacements: Does crutch length matter?

BACKGROUND: Crutch use is prescribed early in the rehabilitation process following total hip replacement (THR) surgery to improve safety and promote return to active living. RESEARCH QUESTION: Purpose of this study was to understand mid-term effects of crutch length setup on quiet standing and walking two months post-op when crutch use was no longer required. METHODS: Thirty patients were evaluated 2 months post-surgery when they had been walking without crutch for a month. The patients had previously been assigned randomly to elbow flexed (EF) or elbow extended (EE) crutch set-ups and evaluated 3 days post-surgery. Quiet standing stability was assessed with participants standing in a comfortable position with each foot on separated force platforms, facing forward for 10 s. In addition, participants walked on the laboratory path, instrumented with motion tracking system and force platforms. For the quiet standing trial, centre of pressure measure, acromial height and lower limbs load bearing symmetry were evaluated. For the walking trial, spatiotemporal and ground reaction force (GRF) parameters were evaluated together with side symmetry indices. RESULTS: Results showed no significant differences in any standing trial variables between groups. For walking, GRF parameters and symmetry indices were similar for both groups. However, increased base of support width, reduced self-selected walking speed and stride length were found for the EF group. SIGNIFICANCE: This study showed that crutch set-up influenced gait after patients started to walk unassisted. Patients that previously used crutch adjusted according to the EE setup, demonstrated a more efficient gait with higher self-selected speed and longer and narrower stride. Clinicians may use these results for a proper crutch height adjustment, which improves walking and, in turn, functional recovery in post THR patients.

Rotational alignment of the tibial component in total knee arthroplasty.

Many surgical techniques, correlated to different anatomical landmarks, have been proposed to allow a satisfactory rotational alignment of the tibial component in primary total knee arthroplasty (TKA). Unfortunately, an accurate landmark has not yet been established although many computer models using CT reconstructions and standard radiologic studies have been performed. In this review article, the authors propose a new anatomical rotational reference for a correct positioning of the tibial component during primary TKA; the authors compared the results of their studies with the current literature on rotational alignment references and previously proposed surgical techniques. The authors also analyzed the correlation between classic and newer tibial baseplate designs and different tibial rotational landmarks.

Posterior-stabilized total knee arthroplasty: a matched pair analysis of a classic and its evolutional design.

BACKGROUND: Total knee arthroplasty (TKA) designs continue to be modified to optimize patient's outcome. This study was designed to compare clinical and radiological results of classic worldwide used TKA posterior-stabilized (PS) design to those of its recent evolution. METHODS: A consecutive group of 100 patients undergoing TKA using a classic cemented fixed-bearing PS TKA system was matched by age, gender, body max index to 100 patients having the newer cemented fixed-bearing PS design, both by the same manufacturer. Patients were assessed preoperatively, at 12 months and at 24 months minimum follow-up (range, 24-46) in a standard prospective fashion. The outcome assessments used were the Oxford Knee Score, the Knee Society Score, range of motion, and a satisfaction survey. A 2-sample t test comparing the 2 groups was performed. RESULTS: No patients were lost at follow-up. At 2-year follow-up, differences in clinical and radiological Knee Society Score (P = .09), Oxford Score (P = .08), and overall satisfaction rate did not reach statistical significance. Implant group 2 showed a statistically significant decrease in postoperative anterior knee pain (P = .006). At final follow-up, 16% of group 1 knees achieved > 130° flexion compared with 37% in group 2 (P = .0009). There were 2 revisions for any reason in group 1 and none in group 2. CONCLUSIONS: Design modifications applied to the newer TKA system allowed greater flexion and lower patellofemoral complications but did not appear to achieve better overall clinical scores.

Clinical outcome of design modifications to the CLS Spotorno Stem in total hip replacement.

PURPOSE: historically, the original CLS Spotorno Stem has demonstrated excellent survival. The design of this stem was recently modified, resulting in the introduction of a shorter, modular version (CLS Brevius). The purpose of the current study was to evaluate the functional, radiological and survivorship outcomes of the cementless CLS Brevius Stem in a multi-surgeon, single center, consecutive series study at two years post-surgery. METHODS: the Authors performed 170 total hip arthroplasties in 155 patients using the shorter, triple-taper stem design (CLS Brevius). The patients' diagnoses were primary hip osteoarthritis (OA) in 74.4%, secondary hip OA in 22.6%, and post-traumatic hip OA in 3%. All operations were performed through a mini-posterior approach, with the patient in the lateral decubitus position. The mean follow-up was 32 months (24-44 months). Outcome was assessed using the Harris Hip Score (HHS). RESULTS: the mean HHS improved from 32 preoperatively to 92 points at final follow-up, while the stem survival rate was 99.4%. Overall, the results were excellent in148 hips (87%), good in 14 hips (8.2%), fair in six hips (3.6%), and poor in two hips (1.2%). Intraoperative complications included a calcar fissure in three hips (1.7%). Correct femoral offset was reproduced in 97% while the planned center of hip rotation was achieved in 98%. Only one hip underwent early stem revision; this was due to major subsidence. CONCLUSIONS: the modified CLS stem design showed excellent short-term results with a low rate of early postoperative complications. One of the main findings of this study was the high correlation between the planned femoral offset and center of hip rotation and the final radiographic measurements. This high reproducibility, which indicates the ability of the system to restore normal hip anatomy, is indeed due to the extensive modularity that characterizes this stem system. Long-term follow-up studies are necessary to fully compare the outcomes of the new design with its highly successful predecessor. LEVEL OF EVIDENCE: Level IV, therapeutic cases series.

Relationship between Tibial Baseplate Design and Rotational Alignment Landmarks in Primary Total Knee Arthroplasty.

This study evaluated the influence of modern tibial baseplate designs when using the anterior tibial cortex as a primary rotational landmark for the tibial baseplate in TKA. Eighty patients undergoing TKA were randomized in two groups. Group 1 included 25 females and 15 males receiving a posterior-stabilized (PS) symmetric tibial baseplate while Group 2 included 24 females and 16 males receiving a PS anatomical tibial component. Identical surgical technique, including the use of the surgical transepicondylar femoral axis (sTEA) and the anterior tibial cortex ("Curve-on-Curve") as rotational alignment landmarks, was used. All patients underwent CT evaluation performed with the knee in full extension. Three observers independently measured the rotational alignment of the tibial component in relation to the sTEA. The rotational alignment of the symmetric baseplate showed an average external rotation of 1.3° (minimum 5°, maximum -1°): 91% of the knees showed 0 ± 3° with respect to the surgical sTEA, being internally rotated in 20%. The rotational alignment of the anatomical baseplate showed an average external rotation of 4.1° (minimum 0.4°, maximum 8.9°): only 47.5% of the knees showed 0 ± 3°, being externally rotated in 100%. The difference between the two groups was statistically significant. This study confirms the reliability of the "Curve-on-Curve" technique as an adequate rotational alignment anatomical landmark in TKA: the use of an asymmetric tibial baseplate might lead to external rotation of the tibial component when this technique is intraoperatively chosen.

Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation.

BACKGROUND: Intercondylar femoral bone removal during posterior stabilized (PS) total knee arthroplasty (TKA) makes many cruciate substituting implant designs less appealing than cruciate retaining implants. Bone stock conservation is considered fundamental in the prevision of future revision surgeries. The purpose of this study was to compare the quantity of intercondylar bone removable during PS housing preparation using three contemporary PS TKA instrumentations. METHOD: We compared different box cutting jigs which were utilized for the PS housing of three popular PS knee prostheses. The bone removal area from every PS box cutting jig was three-dimensionally measured. RESULTS: Independently from the implant size, the cutting jig for a specific PS TKA always resected significantly less bone than the others: this difference was statistically significant, especially for small- to medium-sized total knee femoral components. CONCLUSION: This study does not establish a clinical relevance of removing more or less bone at primary TKA, but suggests that if a PS design is indicated, it is preferable to select a model which possibly resects less distal femoral bone.

Analysis of differences in bone removal during femoral box osteotomy for primary total knee arthroplasty.

PURPOSE: this study was conducted to compare the quantity of intercondylar bone removed during femoral box osteotomy for implantation of three contemporary posterior stabilized (PS) total knee arthroplasty designs: Sigma PS (DePuy), Vanguard (Biomet) and Persona (Zimmer). METHODS: we compared the maximum volumetric bone resection required for the housing of the PS mechanism of these three designs. Bone removal by each PS box cutting jig was three-dimensionally measured. The differences between the three designs were analyzed by the Kruskal-Wallis test. The Mann-Whitney U-test was used for pairwise comparisons. The level of significance was set at p<0.05. RESULTS: for small-size implants, the average box osteotomy volume of Persona was significantly smaller than the Vanguard and Sigma PS volumes (p=0.003). The mean difference between Vanguard and Sigma PS (p=0.01) was also significant. For medium size implants, the mean difference between Persona and Sigma PS (p=0.008) and the mean difference between Vanguard and Sigma PS (p=0.01) were statistically significant. For large size implants, the mean difference between Vanguard and Sigma PS (p=0.01) and the mean difference between Sigma PS and Persona (p=0.008) were statistically significant. CONCLUSIONS: irrespective of implant size, the Persona cutting jig always resected significantly less bone than did Vanguard and Sigma PS. CLINICAL RELEVANCE: although this study does not establish any clinical relevance of removing more or less bone at primary TKA, its results suggest that if a PS design is indicated, it is preferable to select a model which resects less distal femoral bone.

Periprosthetic joint infections: a clinical practice algorithm.

PURPOSE: periprosthetic joint infection (PJI) accounts for 25% of failed total knee arthroplasties (TKAs) and 15% of failed total hip arthroplasties (THAs). The purpose of the present study was to design a multidisciplinary diagnostic algorithm to detect a PJI as cause of a painful TKA or THA. METHODS: from April 2010 to October 2012, 111 patients with suspected PJI were evaluated. The study group comprised 75 females and 36 males with an average age of 71 years (range, 48 to 94 years). Eighty-four patients had a painful THA, while 27 reported a painful TKA. The stepwise diagnostic algorithm, applied in all the patients, included: measurement of serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels; imaging studies, including standard radiological examination, standard technetium-99m-methylene diphosphonate (MDP) bone scan (if positive, confirmation by LeukoScan was obtained); and joint aspiration with analysis of synovial fluid. RESULTS: following application of the stepwise diagnostic algorithm, 24 out of our 111 screened patients were classified as having a suspected PJI (21.7%). CRP and ESR levels were negative in 84 and positive in 17 cases; 93.7% of the patients had a positive technetium-labeled bone scan, and 23% a positive LeukoScan. Preoperative synovial fluid analysis was positive in 13.5%; analysis of synovial fluid obtained by preoperative aspiration showed a leucocyte count of > 3000 cells µ/l in 52% of the patients. CONCLUSIONS: the present study showed that the diagnosis of PJI requires the application of a multimodal diagnostic protocol in order to avoid complications related to surgical revision of a misdiagnosed "silent" PJI. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Rotational alignment of the tibial component in total knee arthroplasty: the anterior tibial cortex is a reliable landmark.

PURPOSE: to compare the anterior tibial surface curvature, the Akagi's line and the medial third of the tibial tubercle in order to assess which is the most reliable landmark for correct tibial component rotational positioning in total knee arthroplasty. METHODS: three independent investigators reviewed 124 knee MRI scans. The most suitable tibial baseplate tracing for the Nexgen Total Knee System (Zimmer, Warsaw, USA) was superimposed on the scan matching the anterior tibial cortex with the anterior aspect of the baseplate. The rotation of the tibial baseplate tracing was calculated with respect to the transepicondylar axis (TEA), the medial third of the tibial tubercle line, Akagi's line and the femoral posterior condylar axis (PCA). Customized software was created and used for analysis of the MRI datasets. The reliability of each measurement was then calculated by using the intraclass correlation coefficient for interobserver agreement. RESULTS: observer agreement on the position of the Akagi's line was within 3° in 64% of the cases and within 5° in 85% of the cases. Agreement on the position of the medial third of the tibial tubercle was within 3° in 29% of the cases and within 5° in 70% of the cases. Agreement on the localization of the anterior tibial surface curvature was within 3° in 89% of the cases and within 5° in 99% of the cases. Component alignment along the anterior cortex guaranteed full matching ± 3° with the epicondylar axis in 75% of the knees. CONCLUSIONS: the anterior tibial surface curvature was found to be a more reliable and more easily identifiable landmark for correct tibial component alignment than either Akagi's line or the medial third of the tibialtubercle. LEVEL OF EVIDENCE: level III, retrospective cohort study.

Candida glabrata prosthetic hip infection.

We present a case of a 60-year-old Caucasian woman carrying a 2-year-old hip prosthesis infected by Candida glabrata dose-dependent susceptible to fluconazole and voriconazole. Resection arthroplasty was performed. Six weeks of caspofungin plus liposomal amphotericin combination therapy achieved joint sterilization and allowed a successfully reimplantation arthroplasty. In addition we review 9 cases of C. glabrata prosthetic joint infection described to date in the literature.