A comparison of joint line height after revision total knee replacement using a rotating hinge versus a condylar revision knee system.

Purpose: This retrospective study aimed to assess the effects of two differing revision total knee implants designs (condylar and rotating hinge) on joint line height. Method: The use of distal augmentation and pre and post revision radiographic joint line heights were compared in 19 condylar type knee replacements (Zimmer NexGen Legacy Constrained Condylar Knee - LCCK) and 40 LINK-Endo-rotating hinge knee replacements. Joint line and patellar heights were determined for each implant using four validated methods. For comparison within a group a two tailed paired Student's t-test was used, for comparison between the groups an unpaired, two tailed Student's t-test was used. A p value of less than 0.05 was deemed statistically significant. Results: In 15 of 19 NexGen revision knee replacements distal augments were used. No distal augments were used in the LINK-Endo RHK group. In both systems there was no tendency to elevate the joint line relative to the tibia. The joint line was distalised relative to the femur in the NexGen group and proximalised in the rotating hinge knee group. Measurements using antero-posterior radiographs were found to be the most reliable method of assessing joint line height when compared to lateral radiographs. Conclusion: Both revision knee implant systems adequately restored joint line height. In condylar type knee revision implants elevation of the joint line height may be avoided through the use of distal augmentation. We found AP radiographs to be the most reliable method of accurately assessing joint line height.

Evaluation and Management of Periprosthetic Joint Infection-an International, Multicenter Study.

BACKGROUND: Controversies still exist regarding the optimal diagnostic and therapeutic strategies in patients with prosthetic joint infections (PJI). QUESTIONS/PURPOSES: How effective are preoperative and intraoperative cultures in isolating organisms and how do these culture results compare to one another? What are the results of surgical treatment of PJI in the hip and knee in an international, tertiary referral center cohort? PATIENTS AND METHODS: One hundred sixteen patients (N = 59 hip PJI, N = 57 knee PJI) were recruited prospectively to registries at three international, tertiary referral centers between December 2008 to November 2011. Retrospective review of prospective registry data including demographics, microbiology results, and operative reports was performed. RESULTS: Preoperative synovial fluid aspiration yielded an organism in only 45.2% and 44.4% of cases, respectively, for knee and hip PJI. False-negative rates of preoperative aspiration relative to intraoperative culture were 56% and 46% in hip and knee PJI, respectively, with discordance rates of 25% and 21.4%, respectively. Rates of negative intraoperative cultures were 15% in hip PJI and 20.7% in knee PJI. Open debridement with prosthetic retention was the most common initial revision procedure performed (48.3% of hip PJI and 63.8% of knee PJI). This method of revision was successful in 41.3% of hip PJI and 59.4% of knee PJI. Initial failure rates for prosthetic revision was lower than debridement with prosthetic retention but remained substantial in both hip PJI (initial success of one-stage exchange 60% and two-stage exchange 70%) and knee PJI (initial success of one-stage exchange 80% and two-stage exchange 75%). CONCLUSION: Diagnosis and treatment of PJI remains challenging with difficulty in isolating the offending organism and with high rates of prosthetic revision and initial treatment failures. Future advances in organism isolation and international standardization of treatment protocols may improve patient outcomes.

The association between Femoral Tilt and impingement-free range-of-motion in total hip arthroplasty.

BACKGROUND: There is a complex interaction among acetabular component position and antetorsion of the femoral stem in determining the maximum, impingement-free prosthetic range-of-motion (ROM) in total hip arthroplasty (THA). By insertion into the femoral canal, stems of any geometry follow the natural anterior bow of the proximal femur, creating a sagittal Femoral Tilt (FT). We sought to study the incidence of FT as measured on postoperative computed tomography scans and its influence on impingement-free ROM in THA. METHODS: The incidence of the postoperative FT was evaluated on 40 computed tomography scans after cementless THA. With the help of a three-dimensional computer model of the hip, we then systematically analyzed the effects of FT on femoral antetorsion and its influence on calculations for a ROM maximized and impingement-free compliant stem/cup orientation. RESULTS: The mean postoperative FT on CT scans was 5.7° ± 1.8°. In all tests, FT significantly influenced the antetorsion values. Re-calculating the compliant component positions according to the concept of combined anteversion with and without the influence of FT revealed that the zone of compliance could differ by more than 200%. For a 7° change in FT, the impingement-free cup position differed by 4° for inclination when the same antetorsion was used. CONCLUSIONS: A range-of-motion optimized cup position in THA cannot be calculated based on antetorsion values alone. The FT has a significant impact on recommended cup positions within the concept of "femur first" or "combined anteversion". Ignoring FT may pose an increased risk of impingement as well as dislocation.

The effect of component positioning on intrinsic stability of the reverse shoulder arthroplasty.

HYPOTHESIS: Anterior instability is one of the most common complications in reverse shoulder replacement. This study hypothesized that intrinsic stability of a reverse prosthesis varies with the degree of version of the humerus and glenoid components. This should provide guidelines on how to best position the implant components to decrease the rate of dislocation. MATERIALS AND METHODS: Resistance to anterior dislocation of a reverse implant was measured in a mechanical testing machine by means of the stability ratio (ratio of peak dislocation/axial compressive forces). Versions of the humeral and glenoid components were modified in 10 degrees steps in the 90 degrees abducted and resting positions. RESULTS: In both tested positions, the effect of humeral component version was highly significant. Only a glenoid component retroversion of 20 degrees led to a statistically significant drop in stability ratio for the 20 degrees abducted position. Intrinsic stability in the typical component positioning (neutral glenoid version and 20 degrees humeral retroversion) yielded comparably low intrinsic stability, which could only be improved by increasing anteversion of the humeral component. DISCUSSION: Version of the humeral component is the critical factor for intrinsic stability. Version of the glenoid component is less important for intrinsic stability, but special care should be given to avoid retroversions of more than 10 degrees . Within this range, the surgeon can concentrate primarily on other parameters critical for long-term outcome (range of motion, secure fixation) when choosing the appropriate glenoid version. CONCLUSION: Anterior stability can be improved by implanting the humeral component in neutral or with some anteversion.

Challenges for Large Orthopaedic Hospitals Worldwide-An ISOC Position Statement.

Since the foundation of the International Society of Orthopaedic Centers in 2006, the group has continued to grow, with currently 11 members worldwide. During the 2008 annual meeting, the bylaws and mission of the group were approved as well as the acceptance of two additional members. Strict inclusion criteria were established to keep the group both small and effective. The goal of the 2008 meeting and this position statement is to identify current challenges in both research and education for large-volume orthopedic hospitals and to discuss possible approaches and solutions.

How accurately can the acetabular rim be trimmed in hip arthroscopy for pincer-type femoral acetabular impingement: a cadaveric investigation.

PURPOSE: The purpose of this study was to evaluate the precision of central hip arthroscopy in the assessment and treatment of pincer-type femoroacetabular impingement (FAI) avoiding the posterolateral portal, with its close proximity to the main arterial blood supply of the femoral head, the medial circumflex femoral artery. METHODS: Seven human cadaveric hips underwent arthroscopic trimming of the acetabular labrum and rim along a preoperatively defined 105 degrees arc of resection for treatment of a presumed pincer-type lesion. After the arthroscopic procedure, all specimens were dissected and measured for evaluation of the location, quantity, and quality of the area undergoing resection. RESULTS: The difference between the actual and planned arc of resection was 18.7 degrees +/- 4.7 degrees (range, 2 degrees to 34 degrees). This was mainly because of a lack of accuracy in the presumed posterior starting point (PSP), with a mean deviation of 19 degrees +/- 3.4 degrees (range, 10 degrees to 36 degrees). Correlation analysis showed that variance in the arc of resection was mainly dependent on the PSP (r = 0.739, P = .058). CONCLUSIONS: Central hip arthroscopy is a feasible option in treating anterosuperior pincer-type FAI by use of the anterior and anterolateral portals only. This cadaveric study showed that there is a significant risk of underestimating the actual arc of resection compared with the planned arc of resection for posterosuperior pincer-type lesions because of the modest accuracy in determining the PSP of the resection. CLINICAL RELEVANCE: Accurate preoperative planning and arthroscopic identification of anatomic landmarks at the acetabular side are crucial for the definition of the appropriate starting and ending points in the treatment of pincer-type FAI. Whereas anterosuperior pincer-type lesions can be addressed very precisely with our technique, the actual resection of posterosuperior lesions averaged 19 degrees less than the planned resection, which may have clinical implications.

Adipogenic and myogenic gene expression in rotator cuff muscle of the sheep after tendon tear.

Chronic rotator cuff tendon tears lead to fatty infiltration and muscle atrophy with impaired physiological functions of the affected muscles. However, the cellular and molecular mechanisms of corresponding pathophysiological processes remain unknown. The purpose of this study was to characterize the expression pattern of adipogenic (PPARgamma, C/EBPbeta) and myogenic (myostatin, myogenin, Myf-5) transcription factors in infraspinatus muscle of sheep after tenotomy, implantation of a tension device, refixation of the tendon, and rehabilitation, reflecting a model of chronic rotator cuff tears. In contrast to human patients, the presented sheep model allows a temporal evaluation of the expression of a given marker in the same individual over time. Semiquantitative RT/PCR analysis of PPARgammaã, myostatin, myogenin, Myf-5, and C/EBPbeta transcript levels was carried out with sheep muscle biopsy-derived total RNA. We found a significantly increased expression of Myf-5 and PPARgamma after tenotomy and a significant change for Myf-5 and C/EBPbeta after continuous traction and refixation. This experimental sheep model allows the molecular analysis of pathomechanisms of muscular changes after rotator cuff tear. The results point to a crucial role of the transcription factors PPARgamma, C/EBPbeta, and Myf-5 in impairment and regeneration of rotator cuff muscles after tendon tears in sheep.

Arthroscopic versus open osteoplasty of the head-neck junction: a cadaveric investigation.

PURPOSE: Femoroacetabular impingement can be successfully treated by open osteoplasty, although arthroscopic osteoplasty is growing in popularity. We compared the precision and accuracy of arthroscopic versus open osteoplasty. METHODS: We randomly assigned 8 paired fresh-frozen cadaveric pelvises to an open or arthroscopic technique and performed osteoplasty on both anterior femoral head-neck junctions. We calculated the volume and location of the resected bone using digital subtraction of preoperative and postoperative computed tomography. RESULTS: Statistical analysis showed no differences between the techniques regarding volume, depth, or overall arc of resection. The arthroscopic group was closer to the predetermined starting point, and the open group was closer to the end-point. CONCLUSIONS: This study confirms the ability to perform arthroscopic decompressions of the head-neck junction for isolated cam-type impingement with accuracy and precision that approach those of the open surgical technique. CLINICAL RELEVANCE: This report gives important information on the accuracy and precision of arthroscopic osteoplasty of the femoral head-neck junction as a feasible alternative to open resection.

The risk of vascular injury to the femoral head when using the posterolateral arthroscopy portal: cadaveric investigation.

PURPOSE: The aim was to clarify the relationship between the posterolateral arthroscopy portal to the hip joint and the deep branch of the medial femoral circumflex artery (MFCA) and its terminal divisions. METHODS: In 7 fresh fixated human cadavers, the deep femoral arteries were injected with latex. In all specimens, the standard anterior, anterolateral, and posterolateral arthroscopy portals to the central compartment of the hip were established in a standardized procedure as done in our operating room. Subsequently, all specimens underwent surgical dissection to identify the tract of the posterolateral portal, the course of the deep branch of the MFCA, and its terminal divisions. The distance between the portal tract and the deep branch of the MFCA was measured at its shortest point. RESULTS: None of the specimens revealed injury to the deep branch of the MFCA and its terminal divisions; however, 1 specimen did not reveal filling of the MFCA, and did not allow for accurate measurement. For the remaining 6 specimens, the mean distance of the portal tract to the vessels at the closest point was 10.16 mm (standard deviation, 4.4 mm; range, 5 to 15 mm). In all specimens, the greater trochanter seemed to prevent closer contact between the vessel and the portal tract. CONCLUSIONS: As long as the shape of the posterior aspect of the greater trochanter has not been changed by previous surgery, the posterolateral portal to the hip joint can be performed safely with respect to the vital blood supply to the femoral head, because the MFCA is protected by the overhang of the posterior aspect of the greater trochanter, giving a minimum of 3 mm and an average 10 mm of clearance. CLINICAL RELEVANCE: At the level of the piriformis muscle, the posterolateral portal has a minimum of 3 mm and an average of 10 mm of clearance to the deep branch of the MFCA. As long as the shape of the posterior aspect of the greater trochanter has not been changed, and the skin penetration remains close to this bony margin with direction of the portal toward the joint space, this portal can be performed safely with respect to the vital blood supply to the femoral head.

Vascular preservation during arthroscopic osteoplasty of the femoral head-neck junction: a cadaveric investigation.

PURPOSE: The goal of this study was to evaluate the risk of vascular injury with arthroscopic osteoplasty of the femoral head-neck junction in a cadaveric model. METHODS: Eight fresh-frozen cadaveric pelvi were used for arthroscopic osteoplasty of a predetermined 150 degrees arc of resection along the anterior femoral head-neck junction. Postoperatively, injection studies of the deep femoral arteries were performed on all specimens to identify local extravasation of neoprene latex before polymerization as a reproducible indicator of vascular injury. Control specimens included 1 specimen without an osteoplasty and 1 specimen after an "aggressive" open osteoplasty with intention to violate the superior retinacular vessels. RESULTS: The first control specimen showed complete filling of the superior retinacula branches, whereas the second control specimen had evidence of intracapsular latex extravasation. In 7 of 8 experimental specimens, there was near-to-complete filling of the superior and inferior retinacula branches with no signs of latex extravasation. In 1 specimen, no superior retinacular branches were identified; however, no extravasation of the latex material was noted. No injury to the main extracapsular branches of the medial or lateral femoral circumflex vessels was noted. We noted on average 3 superior retinacular vessels penetrating the posterior-superior head-neck junction. CONCLUSIONS: There was no evidence of vascular injury to the main blood supply of the femoral head in any of the 8 experimental specimens as noted by latex extravasation. These findings show that arthroscopic osteoplasty can be performed without disrupting the vascular supply to the femoral head. CLINICAL RELEVANCE: This article has important information on the relation of vascular structures and the resection limit with arthroscopic osteoplasty of the femoral head-neck junction.