Significantly reduced leg length discrepancy and increased femoral offset by application of a head-neck adapter in revision total hip arthroplasty.

Head-neck adapters in total hip arthroplasty (THA) promise the reconstruction of optimal femoral offset and leg length in revision THA while retaining stable implants. Radiological parameters after adapter implantation in THA revision were determined in 37 cases. Significant reduction of leg length discrepancy and improvement of femoral offset (P < 0.001) were found. Clinical endpoints were determined in 20 cases (mean follow-up 4.0 years). Clinical scores were rather poor (median Harris hip score 54, WOMAC score 41) due to age and comorbidities, postoperative dislocation occurred in 3 cases. Only one stable femoral stem had to be revised due to recurrent postoperative dislocation. In conclusion, a head-neck adapter can be a valuable tool in certain cases of revision THA with acceptable dislocation rates while allowing the retention of stable implants.

Femoral head-neck offset measurements in 339 subjects: distribution and implications for femoroacetabular impingement.

PURPOSE: The α-angle is a frequently used measurement to quantify head-neck offset pathology in cam-type femoroacetabular impingement. However, diverging norm values and reference intervals have been described, especially in men. METHODS: The α-angle, the head-neck offset ratio and the triangular index were measured on anteroposterior and lateral radiographs of 339 (170 men and 169 women) subjects without evident underlying hip pathology. RESULTS: For male subjects, the mean α-angle was 49.4° (SD 10.5°) on anteroposterior and 49.1° (SD 10.6°) on lateral radiographs, whereas for female subjects, it was 45.0° (SD 8.0°) and 46.1° (SD 9.9°), respectively. Thus, calculated upper limits of reference intervals in the population screened were 70° for both radiographic projections in men and 61° (anteroposterior) and 66° (lateral) in women. CONCLUSION: These data substantiate recent findings that the pathological threshold of the α-angle in male subjects may be lower than that previously assumed. LEVEL OF EVIDENCE: Diagnostic, Level III.

The aetiology of total knee arthroplasty failure influences the improvement in knee function.

BACKGROUND: Some indications for revision total knee arthroplasty (TKA), e.g. arthrofibrosis, have been identified to yield inferior results. The aim of this study was to analyse the results of revision TKA according to aetiology of TKA failure. PATIENTS AND METHODS: The results of 97 consecutive revision TKA in 97 patients stratified according to the aetiology of primary TKA failure (periprosthetic infection, aseptic loosening, instability and arthrofibrosis), were compared using the Knee Society Score (KSS). The effect of patient age, gender, BMI, American Society of Anesthesiologists (ASA) classification, interval to revision and the occurrence of complications on the outcome were also analysed. RESULTS: After a mean follow-up of 29 months, the KSS had significantly improved in all patient groups (p < 0.001). The analysis of variance among patient groups depicted no significant differences between preoperative KSS (p = 0.618) and postoperative KSS (p = 0.915), while the magnitude of pre- to postoperative improvement showed significant differences between the groups (p = 0.006). The aetiology of primary TKA failure had an independent influence on pre- to postoperative improvement (p = 0.014). Of the other factors analysed, only the ASA classification had an independent impact on postoperative KSS (p = 0.045). CONCLUSION: The aetiology of TKA failure has an effect on the improvement in knee function from revision TKA. As no difference was observed between patient groups postoperatively, similar clinical results can be expected independent of the aetiology of primary TKA failure.

Reduced head-neck offset in nontraumatic osteonecrosis of the femoral head.

INTRODUCTION: Risk factors for nontraumatic osteonecrosis of the femoral head have in common that they trigger intravascular coagulation and thus lead to devascularization of the femoral head. In part of the patients, however, no risk factors seem to be evident. Mechanical reasons contributing to nontraumatic osteonecrosis have not been discussed so far. We hypothesized that recurrent traumatization of the vessels supplying the femoral head by a cam-type mechanism as in femoroacetabular impingement could add to intravascular coagulation. We, therefore, asked whether structural abnormalities at the femoral head-neck junction indicative of such a mechanism could be observed in radiographs of patients with osteonecrosis of the femoral head. MATERIALS AND METHODS: The preoperative anteroposterior and lateral radiographs of 77 patients who underwent surgery because of osteonecrosis of the femoral head were retrospectively screened for a reduced head-neck offset by measuring the α-angle. For comparison, the α-angle was measured on anteroposterior and lateral radiographs of 339 control subjects without evident underlying hip pathology. RESULTS: The mean α-angle was 62.8° (SD 18.7°) for anteroposterior and 67.6° (SD 13.2°) for lateral radiographs in patients with nontraumatic osteonecrosis of the femoral head, whereas in control subjects, the mean α-angle was 47.2° (SD 9.6°) (p < 0.0001) and 47.6° (SD 10.3°) (p < 0.0001), respectively. CONCLUSIONS: A reduced head-neck offset in patients with nontraumatic osteonecrosis of the femoral head may act as a mechanical (co-)factor in developing osteonecrosis of the femoral head.

Can femoroacetabular impingement and hip dysplasia be distinguished by clinical presentation and patient history?

PURPOSE: Hip dysplasia and femoroacetabular impingement may both lead to disability and hip osteoarthritis. The purpose of the current study was to compare the two entities in order to define differences in their clinical presentation. METHODS: The clinical presentation and WOMAC items, subscales and overall sum score were compared between 37 patients with femoroacetabular impingement and 37 patients with hip dysplasia. RESULTS: The average duration of symptoms was 33.3 ± 31.6 months in patients with femoroacetabular impingement and 34.5 ± 39.0 months in patients with dysplasia (p = 0.885). The anterosuperior impingement test was positive in all patients with femoroacetabular impingement and in 92% of hip dysplasia patients (p = 0.061). Mean internal rotation and abduction was significantly less in patients with femoroacetabular impingement (p = 0.001 and 0.007). The WOMAC subscales for pain, stiffness, and functionality as well as the overall sum score were not significantly different between patients with femoroacetabular impingement and patients with hip dysplasia. The qualitative analysis of WOMAC items revealed that symptoms related to sitting were significantly more often rated to be present in femoroacetabular impingement than in hip dysplasia patients. In the quantitative analysis, only the item 'getting in or out of a car' was rated significantly more severe in patients with femoroacetabular impingement. CONCLUSION: In addition to obtaining a detailed history and examination, radiographic studies are needed for differentiation of the two entities and for the decision on treatment strategy.

Radiographic risk factors for labral lesions in femoroacetabular impingement.

BACKGROUND: Tears of the acetabular labrum can lead to pain, disability, and osteoarthritis. Several pathomechanisms have been proposed, including femoroacetabular impingement (FAI). Labral tears have been reported to occur in the presence of even subtle deformities of the acetabulum and femoral head-neck junction. QUESTIONS/PURPOSES: We analyzed the association of the extent of bony deformity and presence and extent of labral lesions in hips with FAI. PATIENTS AND METHODS: Radiographs of 123 hips in 116 patients receiving surgical treatment for FAI were analyzed and correlated to the presence and extent of labral lesions. Radiographic parameters of the acetabulum included acetabular index of the weightbearing zone, center-edge angle, inclination of the acetabulum, lateral head extrusion index, and retroversion. On the femoral side, neck-shaft angle, asphericity of the femoral head, superior and anterior alpha angle, offset, and offset ratio were measured. Osteoarthritis was graded according to Tönnis and Kellgren and Lawrence. Labral lesions were graded according to the modified Beck classification. A correlation between labral lesions and age, gender, affected side, type of impingement, and presence and extent of chondromalacia also was tested. RESULTS: No correlation was found between presence or extent of labral lesions and any radiographic parameter tested, except osteoarthritis classification. The severity of labral lesions correlated to the severity of acetabular chondromalacia as well as patient age (Beck Grade 0 versus Grade 1, Beck Grade 0 versus Grades 1 and 2). CONCLUSIONS: In the presence of impingement-inducing deformity, the extent of deformation is not associated with the incidence of labral lesions. Labral lesions are associated with early degenerative hip disease in FAI. LEVEL OF EVIDENCE: Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Corrosion at the stem-sleeve interface of a modular titanium alloy femoral component as a reason for impaired disengagement.

Modularity in sleeved femoral components allows the exchange of the stem without disruption of the fixation between the sleeve and the surrounding bone at revision surgery. Failure to disengage the stem from the sleeve would represent an unnecessary compromise from the intended usefulness of the modular design. We report the results of an examination of 22 modular titanium alloy femoral components retrieved after 0.0 to 8.8 years in vivo. In 7 implants, the stem-sleeve interface could not be disengaged without cutting through the components or using mechanical force. Moderate to severe corrosion was detected in all 7 of these cases. Corrosive surface changes were observed in an additional 6 interfaces. There was no correlation with the length of time that the devices had been implanted. When only the stem is to be revised, orthopedic surgeons should be aware of difficulties in disengagement and anticipate alternative surgical procedures.

Time course of biological activity in fresh murine osteochondral allografts paralleled to the recipient's immune response.

The use of fresh osteochondral allografts is a popular approach to treat articular cartilage lesions. Immunological reactions of the recipient elicited by the allograft's osseous portion, however, frequently result in their deterioration. So far, little emphasis has been put on describing morphology and biological activity in fresh allografts and paralleling these to the immunological processes triggered in the host. Therefore, in the present study murine neonatal femora, serving as osteochondral grafts, were transplanted as fresh isografts (controls) or allografts (the latter in non- or presensitized mice) and retrieved after 2, 5, 10, and 20 days. It was shown that (1) in isografts active bone cells (osteoblasts, osteoclasts) were present, the bone marrow was repopulated with hematopoietic cells, the diaphysis increased in length, and no specific immunological reaction by the recipient was evoked. (2) Allografts transplanted into nonsensitized hosts initially appeared similar as isografts, but activated T lymphocytes at the transplantation site preceded loss of active bone cells within the graft and development of fibrosis within the marrow cavity. (3) In allografts transplanted into presensitized recipients, severe deterioration of the graft was observed with very few active bone cells, accompanied by an invasion of T lymphocytes and fibrosis in the marrow cavity already in early stages. Similar to vital organ transplantation, the function of cells within osteochondral allografts is severely impaired after being recognized by the immune system. Therefore, emphasis has to be placed on the development of procedures preserving cartilage biology while reducing the antigenicity of the allograft's osseous portion.

The asymptomatic contralateral hip in unilateral slipped capital femoral epiphysis: morbidity of prophylactic fixation.

Prophylactic contralateral fixation in unilateral slipped capital femoral epiphysis (SCFE) remains a controversial issue. In this study, 66 patients treated for unilateral SCFE (July 1997-April 2009) were screened for complications with need for surgical reintervention in the asymptomatic contralateral hip. Except for one patient, prophylactic fixation was performed in all cases. Major complications such as avascular necrosis were not seen; minor complications such as wound revision occurred in 4.6% (three of 65). In 16.9% (11/65) secondary loss of fixation with need for second fixation occurred. As the need for second fixation arose mostly bilaterally (10.7%, 7/65), only four patients (6.2%) required an additional surgical procedure for second fixation. Children who needed second fixation were significantly younger (11.8 years) than those who did not (13.1 years, P=0.013). In conclusion, this retrospective analysis shows that prophylactic contralateral fixation in SCFE is a safe procedure with no major complications and an acceptable rate of minor complications. When Kirschner wires are used for prophylactic pinning, there is a possibility of secondary loss of fixation due to length growth at the level of the physis. To avoid the need for secondary fixation, screw epiphysiodesis might be considered.

Index level mobility after total lumbar disc replacement: is it beneficial or detrimental?

STUDY DESIGN: Analysis of segmental and total lumbar range of motion (ROM) before and after total lumbar disc replacement. OBJECTIVE: To examine the relationship between absolute segmental and total lumbar ROM and evolution of ROM on clinical outcome. SUMMARY OF BACKGROUND DATA: At the moment, data are scarce with regard to the evolution of total lumbar ROM (t-ROM) and segmental ROM (s-ROM) after total lumbar disc replacement. Moreover, the influence of ROM on clinical outcome still is unclear and remains a matter of controversial debate. METHODS.: Forty patients operated on for mono- or bisegmental symptomatic degenerative disc disease with a total of 45 artificial discs (ProDisc-L, Synthes) were analyzed. Pre- and postoperative s-ROM and t-ROM were measured on flexion/extension radiographs. The Oswestry Low Back Pain Disability Questionnaire and the Short Form 36 Health Survey were obtained pre- and postoperatively with a minimum follow-up of 3 years (37-64 months). RESULTS: Neither the s-ROM (pre-/postoperatively: 6.9 degrees/7.3 degrees) nor the t-ROM (pre-/postoperatively: 34.9 degrees/35.8 degrees) did change significantly after implantation of an artificial disc. Postoperatively, there was an increase of s-ROM (t-ROM) in 40% (40%), a decrease in 35% (30%), and no change in 25% (30%) of the patients. A significant inferior clinical outcome only was observed in patients with decreased t-ROM. The resulting postoperatively s-ROM had no significant impact on outcome. CONCLUSION: Neither the absolute s-ROM nor the evolution of s-ROM (increase, decrease, unchanged) was positively correlated with better clinical outcome. Although a positive correlation was observed with regard to t-ROM.

Reperfusion injury in free bone grafts after tourniquet-induced ischemia.

For successful revascularization, incorporation, and survival of fracture fragments or free nonpedicled bone grafts, the first days after surgery seem to be most critical. Using intravital fluorescence microscopy, the effects of 3 hours of tourniquet-induced ischemia were assessed on newly formed angiogenic microvessels 4, 8, and 12 days after isogeneic transplantation of metatarsal bones into dorsal skin fold chambers of adult inbred C57BL/6 mice. The microvascular perfusion index of newly formed microvessels was quantified 30 and 120 minutes after initiation of reperfusion. Four days after transplantation, a complete breakdown of the perfusion of all grafts was found accompanied by hemorrhage as a sign of microvascular damage. In contrast, at 8 and 12 days after transplantation a complete breakdown of graft perfusion rarely occurred. Therefore, the tourniquet-induced ischemia was most pronounced in early stages of development of angiogenic microvessels. These experimental data provide rationale for critical application of tourniquets in revision surgery shortly after initiation of fracture treatment or transplantation of free nonpedicled grafts so as not to compromise angiogenesis-induced tissue revascularization.

Potential role of pre-existing blood vessels for vascularization and mineralization of osteochondral grafts: an intravital microscopic study in mice.

BACKGROUND: The aim of this study was to develop an experimental model that allows to elude the potential role of the preexisting graft microvasculature for vascularization and mineralization of osteochondral grafts. ANIMALS AND METHODS: For that purpose, the II-IV metatarsals of fetal DDY-mice known to be nonvascularized at day 16 of gestation (M16) but vascularized at day 18 (M18) were freshly transplanted into dorsal skin fold chambers of adult DDY mice. Using intravital microscopy angiogenesis, leukocyte-endothelium interaction and mineralization were assessed for 12 days. RESULTS: Angiogenesis occurred at 32 hours in M18, but not before 57 hours in M16 (p = 0.002), with perfusion of these vessels at 42 hours (p = 0.005) and 65 hours (p = 0.1), respectively. Vessels reached a density three times as high as that of the recipient site at day 6, remaining constant until day 12 in M18, whereas in M16 vascular density increased from day 6 and reached that of M18 at day 12 (p = 0.04). Leukocyte-endothelium interaction showed sticker counts elevated by a factor of 4-5 in M18 as compared to M16. Mineralization of osteochondral grafts did not differ between M16 and M18, which significantly increased in both groups throughout the observation period. INTERPRETATION: We propose the faster kinetics in the angiogenic response to M18 and the elevated counts of sticking leukocytes to rest on the potential of establishing end-to-end anastomoses (inosculation) of the vascularized graft with recipient vessels.