[Principles of fixation of the cementless modular revision stem Revitan]

Technical Note for Transfemoral Implantation of Tapered Revision Stems. The Advantage to Stay Short

Background

The aim was to test the hypothesis that during transfemoral implantation of a conical revision stem, the fixation of the stem at the distal tip leads to a low rate of periprosthetic fractures.

Material and Methods

Two hundred eighty-two stem revisions by a transfemoral approach in cases of Paprosky Type II and IIIA-defects (with a sufficient isthmus) were carried out and analyzed during and radiographically after the surgery for unintentional periprosthetic fractures below the osteotomy.

Results

In all cases, fixation was always achieved at the tip of the distal component in the isthmus of the femur. No periprosthetic fractures were observed.

Conclusions

When the isthmus of the femur is intact, a transfemoral implantation of a tapered revision stem at the distal end reduces the risk of periprosthetic fractures by preventing bypassing the isthmus with the stem. Knowing the difference between the nominal diameter and the diameter at the distal start of the conical zone can help to create this fixation technique resulting in short revision stems.

Common hip conditions requiring primary total hip arthroplasty and comparison of their post-operative functional outcomes

BACKGROUND

Primary osteoarthritis of hip has been widely reported to be the leading cause for total hip replacement (THR) in the world. The other common causes are avascular necrosis of hip, inflammatory diseases and trauma sequelae. We report the prevalence of these disease as studied retrospectively at a tertiary healthcare centre and discuss the common age groups and sex ratios of these patients as compared to the West. Additionally, we compare the outcomes of these surgeries based on the aetiologies for which they were done.

METHODOLOGY

Patients who underwent primary THR in our institute within six years were called and retrospectively analysed. Revision cases were excluded. All the surgeries were done by a single experienced arthroplasty surgeon. On follow ups, functional scores were assessed using standard Harris hip score (HHS) and quality of life scores were assessed using the Short musculoskeletal functional assessment (SMFA) score.

RESULTS

118 hips in 99 patients (M:F- 3.2:1) with a mean age group of 43.22 years, were operated over a period of six years. Non traumatic avascular necrosis (AVN) of hip topped the list in our study with 42.4% of cases, followed by post-traumatic sequelae (30.5%). These were followed subsequently by primary osteoarthritis (OA) (14.4%) and the remaining were inflammatory pathologies (IA). The HHS of patients with non traumatic AVN hip, traumatic sequelae and primary osteoarthritis were significantly superior to inflammatory arthritis with a p value of 0.001, 0.001 and 0.016 respectively. Additionally the short musculoskeletal functional assessment score was also significantly higher in IA than AVN, OA and post trauma groups (p = 0.001, 0.037 and 0.002 respectively); where a higher score denotes inferior outcomes.

CONCLUSION

In our part of the world, non traumatic AVN hip is the commonest indication for primary hip arthroplasty, followed by traumatic sequelae. The frequency of males undergoing hip arthroplasty is much more than females and at a younger age as compared to the West. Additionally, the functional outcomes in cases of inflammatory arthritis are inferior as compared to the other indications, probably because of associated contractures, deformity and spinal issues.

Anchoring of a Kinked Uncemented Femoral Stem after Preparation with a Straight or a Kinked Reamer

Objective

To investigate a stem‐adjusted preparation of the femur with a kinked reamer and to determine whether this approach results in higher primary stability of a kinked stem than straight reaming of the intramedullary canal.

Methods

Ten cementless stems with a kinked design were implanted in synthetic femurs after preparation of the femoral canal with 2 different reamer designs (straight reaming [SR] group vs kinked reaming [KR] group). The specimens were analyzed using CT to determine the anchoring length and examined with a mechanical testing system to establish their axial stiffness, torsional stiffness, and migration distance after 10 000 gait cycles.

Results

The stem migration distances did not differ significantly between the groups (SR group 0.51 ± 0.16 mm vs KR group 0.36 ± 0.03 mm, P = 0.095). Only for the SR group, a correlation was found between the completely conical anchorage length and absolute stem migration (P < 0.05, R = 0.89). Regarding the torsional stiffness, no differences were observed between the study groups (SR group 6.48 ± 0.17 Nm/° vs KR group 6.52 ± 0.25 Nm/°, P = 0.398). In the KR group, significantly higher axial stiffness values were measured than in the SR group (SR group 1.68 ± 0.14 kN/mm vs KR group 2.09 ± 0.13 kN/mm, P = 0.008).

Conclusions

The implantation of a kinked stem after kinked conical intramedullary preparation of the proximal femur showed equivalent results regarding anchoring length, stem migration, and torsional stiffness to those for straight conical reaming. The specimens with kinked reaming showed significantly higher axial stiffness values.

Hemiarthroplasty for neck of femur fractures: to cement or not? A systematic review of literature and meta-analysis

BACKGROUND

Management of fractures of neck of femur in the elderly is largely joint sacrificing, with hemiarthroplasties being the most common entity used. Cemented and uncemented, both the techniques, are universally accepted; however, the former has been more time tested, despite its theoretical disadvantage in the form of cement embolism leading to intra-operative complications. Uncemented stems have been ever evolving with newer designs to increase incorporation, stability and durability. They have their own reported sets of disadvantages like subsidence and fractures. However, overall there is no established gold standard out of the two.

OBJECTIVE

The present systematic review and meta-analysis of current literature was conducted, so as to determine the superiority of one technique over the other by comparing the primary outcomes like hip function, residual pain, local and general complications and mortality. Additionally secondary outcomes like duration of surgery, blood loss and re-operations were analysed as well.

METHODOLOGY

Three databases of PubMed, EMBASE and SCOPUS were searched for relevant articles of last 10 years that directly compare uncemented and cemented hemiarthroplasties, and based on our inclusion and exclusion criteria, article selection was done.

RESULTS

We analysed a total of six randomised controlled studies dated from 2008 to 2017.

PRIMARY OUTCOMES

There was a significant difference in post-operative ability to ambulate at 1 year, between 2 groups with odds ratio 0.45 (95% CI 0.29-0.67, p = 0.0001) favouring cemented hemiarthroplasty. Prosthesis-related complications like fractures and subsidence and general complications like lung complications were more in uncemented group. Mortality at 1 year was more in cemented group.

SECONDARY OUTCOMES

Mean surgical time was lesser in uncemented cases. There was no difference in blood loss and re-operation rates.

CONCLUSION

Cementing techniques are here to stay, until a better, durable and more stable uncemented stem evolves, that could lessen the complications related to uncemented surgeries and match the cemented implants in pain relief and ambulation.

Fixation of a modular curved revision stem with a taper of 2° in the femur

INTRODUCTION

Modular revision stems with a short distal component can prevent the bypassing of the femoral isthmus and hereby theoretically have advantages concerning risk of periprosthetic fractures, breakage of the junction and a technically easier revision procedure.

MATERIALS AND METHODS

Radiological evaluation of 202 stem revision operations with the modular curved revision stem "Revitan Curved" with a 2° taper was carried out after a mean follow-up period of 7.44 ± 2.09 years (3-13 years) to investigate whether short-stem combinations are effective in Paprosky 2 and 3A defects with respect to rate of subsidence and loosening.

RESULTS

Sixty of 62 endofemoral (96.8%) and 137 of 140 transfemoral implantations (97.9%) involved the short, 140 mm distal component. Significant subsidence was seen in 3.3% of cases following endofemoral implantation and in 2.1% of cases following transfemoral implantation. Neither aseptic loosening nor periprosthetic fracture were observed.

CONCLUSION

The use of combinations of short modular components leads to reproducibly good outcomes in femoral revision with respect to subsidence and loosening.

What can the surgeon do to reduce the risk of junction breakage in modular revision stems?

Modular revision stems are very common in hip arthroplasty, but junction fracture remains a known failure mechanism. A review of the literature with description of cases with junction breakage of modular revision stems showed that in all 24 analyzed cases, there was a common finding: the combination of an effective osteointegration of the distal component and missing medial bone support of the proximal component. The result was a bending stress point of the stem construction in the region of the junction. A technique using the combination of short distal component and longer proximal components may alter this stress pattern, allow proximal implant support, and reduce the risk of junction fracture. Moreover, filling of gaps between the modular component and the medial region of the femoral calcar in endofemoral implantation, a double osteotomy in significant bowed femurs, and treating medial bone defects with structural allografts additionally can reduce the risk of junction breakage.

Femoral Bone Restoration Patterns in Revision Total Hip Arthroplasty Using Distally Fixed Modular Tapered Titanium Stems and an Extended Trochanteric Osteotomy Approach

BACKGROUND

Mechanical failure of modular revision stems is a serious complication in revision total hip arthroplasty. The lack of adequate osseous support to the proximal component, especially in cases of an extended trochanteric osteotomy approach, is considered a risk factor for stem failure. In this study, we analyze proximal bone regeneration patterns in patients undergoing revision total hip arthroplasty for aseptic stem loosening through an extended trochanteric osteotomy approach using an uncemented dual modular stem.

METHODS

Fifty-four patients treated for aseptic stem loosening were radiologically reviewed. The femur was divided according to the Gruen zones. Preoperative bone loss, formation of new cancellous bone, and presence of direct osseous contact to the stem were noted right away for each Gruen zone. The presence of osseous support at the modular junction and the proximal component were examined.

RESULTS

All patients showed restoration of proximal bone mass at final follow up. New bone formation was first seen in more distally located Gruen zones. Cases with longer proximal components had a trend toward earlier osseous support at the modular junction. Overall, 75% of patients showed osseous support at the modular junction 2 years after surgery.

CONCLUSION

Restoration of proximal bone occurs in a distal to proximal direction. Shorter proximal components require more time until osseous support to the modular junction is achieved, which may result in a higher risk of mechanical failure. Based on this study, bony support at the modular junction should not be expected in 25% of cases 2 years after surgery.

The Proximal and Distal Femoral Canal Geometry Influences Cementless Stem Anchorage and Revision Hip and Knee Implant Stability

Although cementless revision arthroplasty of the hip has become the gold standard, revision arthroplasty of the distal femur is controversial. This study evaluated the anchoring principles of different femoral revision stem designs in extended bone defect situations, taking into account the anatomical conditions of the proximal and distal femur, and the resulting primary stability. Cementless press-fit stems of 4 different designs were implanted in synthetic femurs. The specimens were analyzed by computed tomography and were tested considering axial/torsional stiffness and migration resistance. Different stem designs anchored in different femoral canal geometries achieved comparable primary stability. Despite considerably different anchorage lengths, no difference in migration behavior or stiffness was found. Both in the distal femur and in the proximal femur, the conical stems showed a combination of conical and 3-point anchorage. Regarding the cylindrical stem tested, a much shorter anchorage length was sufficient in the distal femur to achieve comparable primary stability. In the investigated osseous defect model, the stem design (conical vs cylindrical), not the geometry of the femoral canal (proximal vs distal), was decisive regarding the circumferential anchorage length. For the conical stems, it can be postulated that there are reserves available for achieving a conical-circular fixation as a result of the large contact length. For the cylindrical stems, only a small reserve for a stable anchorage can be assumed. [Orthopedics. 2018; 41(3):e369-e375.].

Anchoring and resulting primary stability of a kinked compared to a straight uncemented femoral stem

INTRODUCTION

The number of revision hip arthroplasties being performed is growing and implantation of a cementless stem has become established as the gold standard. For producing a primary stability, the press-fit procedure is the method of choice, but also can be achieved by multiple-point impactions. Specific femoral stems should follow the anatomical shape and provide a more extensive anchorage. The objective of this study was to evaluate the type, localization of the impaction and resulting primary stability of two different femoral revision stem designs (kinked vs. straight) after implantation via an endofemoral approach in the case of more extensive defects of the proximal femur.

MATERIALS AND METHODS

Cementless stems of two different designs were implanted in synthetic femurs. The specimens were analyzed by CT and tested considering axial/torsional stiffness and migration resistance in a servohydraulic testing machine.

RESULTS

The present data do not show any significant differences between the two endofemorally implanted conical stems in contact area or in biomechanics with regard to migration and axial or torsional stiffness, despite having different designs.

CONCLUSIONS

The location, type and length of the stem anchorage are not only influenced by the kinked or straight design, but in particular also by the surgical approach. Also in the case of an extensive proximal bone defect, in the endofemoral approach, both a conical and a three-point anchorage occur. Here, the length of the conical anchorage determines the primary stability and should be at least 55 mm.

The Transfemoral Approach for Removal of Well-Fixed Femoral Stems in 2-Stage Septic Hip Revision

BACKGROUND

The value of a transfemoral approach for removal of well-fixed infected hip arthroplasties in 2-stage revision is unclear, especially whether cerclages for closure of the flap in the first step lead to higher reinfection rates and whether reopening of the flap for reimplantation of a hip arthroplasty leads to a lower union rate of the bony flap.

METHODS

Seventy-six septic 2-stage revisions via a transfemoral approach with cerclages for closure of the flap in the first step and reopening of the flap for reimplantation were followed prospectively for a mean period of 51.2 ± 23.2 (24-118) months.

RESULTS

The union rate of the bony flap after reimplantation was 98.7%, and no recurrence of reinfection was recorded in 93.4% of all cases. Subsidence of the stem occurred at a rate of 6.6%, dislocation at a rate of 6.6%, and there was no aseptic loosening of the implants. The Harris Hip Score was 62.2 ± 12.6 points with the spacer and 86.6 ± 15.5 points 2 years after reimplantation. Nine fractures (11.8%) of the flap occurred during the operation because of osteolytic or osteoporotic weakness of the flap itself, but these all healed without further intervention.

CONCLUSION

The transfemoral approach is a safe method for septic revision of well-fixed hip prostheses, and the use of cerclage wires for closing the osteotomy flap in the first stage does not appear to lead to a higher reinfection rate. Similarly, the reopening of the flap does not appear to decrease the union rate of the flap.

Mid term results with the curved modular tapered, fluted titanium Revitan stem in revision hip replacement

We report our experience of revision total hip replacement (THR) using the Revitan curved modular titanium fluted revision stem in patients with a full spectrum of proximal femoral defects. A total of 112 patients (116 revisions) with a mean age of 73.4 years (39 to 90) were included in the study. The mean follow-up was 7.5 years (5.3 to 9.1). A total of 12 patients (12 hips) died but their data were included in the survival analysis, and four patients (4 hips) were lost to follow-up. The clinical outcome, proximal bone regeneration and subsidence were assessed for 101 hips. The mean Harris Hip Score was 88.2 (45.8 to 100) after five years and there was an increase of the mean Barnett and Nordin-Score, a measure of the proximal bone regeneration, of 20.8 (-3.1 to 52.7). Five stems had to be revised (4.3%), three (2.9%) showed subsidence, five (4.3%) a dislocation and two of 85 aseptic revisions (2.3%) a periprosthetic infection. At the latest follow-up, the survival with revision of the stem as the endpoint was 95.7% (95% confidence interval 91.9% to 99.4%) and with aseptic loosening as the endpoint, was 100%. Peri-prosthetic fractures were not observed. We report excellent results with respect to subsidence, the risk of fracture, and loosening after femoral revision using a modular curved revision stem with distal cone-in-cone fixation. A successful outcome depends on careful pre-operative planning and the use of a transfemoral approach when the anatomy is distorted or a fracture is imminent, or residual cement or a partially-secured existing stem cannot be removed. The shortest appropriate stem should, in our opinion, be used and secured with > 3 cm fixation at the femoral isthmus, and distal interlocking screws should be used for additional stability when this goal cannot be realised.

Bone regeneration in the proximal femur following implantation of modular revision stems with distal fixation

INTRODUCTION

A quantitative analysis of the response of proximal femur bone to implantation of revision stems with distal fixation and of the factors that affect that response has not previously been published.

MATERIALS AND METHODS

A prospective study of 138 stem revision operations involving replacement with cementless, modular, titanium revision stems with distal fixation (Revitan, Zimmer GmbH, Winterthur, Switzerland) was designed to assess Barnett and Nordin scores at the proximal femur obtained immediately after surgery and at a 3-year follow-up examination in order to analyze bone regeneration in the proximal femur and associated response-modifying factors.

RESULTS

In general, a bone formation with increase of the Barnett and Nordin score was observed. However, stress shielding occurred in cases of osteoporosis or more severe bone defects. A statistical analysis of possible factors that might affect the bone response revealed that the degree of bone regeneration was directly related to the Barnett and Nordin score obtained immediately post-surgery and the severity of the bone defect and only indirectly to the length of the stem, which is determined by the type of bone defect, and to the necessity of interlocking screws.

CONCLUSION

Distally fixed titanium revision stems do not result in stress shielding per se. Proximal bone response depends mostly on the condition of the bone before and immediately after the operation and not, as stated in many reports, on surgical procedures such as method of approach or the thickness of the prosthesis.

[Periprosthetic fractures after total hip arthroplasty : classification, diagnosis and therapy strategies]

The number of periprosthetic fractures following hip replacement is increasing due to longer life expectancy and the rising number of joint replacements. The main causes of periprosthetic fractures include trauma, implant specific factors or loosening of the endoprosthesis. When planning therapy, surgeons should consider specific and general implant- and patient-related risk factors to ensure the best possible treatment. Established classification systems can facilitate preoperative planning. At present, the Vancouver classification system probably comes closest to the ideal, as it considers fracture configuration, stability of the implant and quality of the bone stock. Depending on these factors, therapeutic options include conservative treatment, fracture stabilisation or replacement of the endoprosthesis. The problems associated with periprosthetic fractures of varying etiology and the available treatment options are discussed against the background of the established classification systems.

[Replacement of femoral hip prostheses]

Femoral revision of total hip arthroplasty is a technically demanding procedure. Therefore, accurate preoperative planning is essential for good clinical results. With many reconstruction methods available, the decision-making process can be complex. Well established classification systems can facilitate preoperative planning. At the time of revision surgery appropriate implants and instruments have to be available ensuring the possibility of managing operative complications. Primary goals of revision arthroplasty are restoration of the physiological joint biomechanics and primary stable fixation of the revision implant. In consideration of possible repeat revision surgery, cementless stem fixation should be preferred. Modular stems provide significant flexibility in restoring the center of rotation. Depending on the pre-existing femoral defect, osseous grafts can be necessary.The scope and classification systems of femoral osseous defects in revision arthroplasty will be discussed and different treatment options will be outlined, which guide the surgeon in selecting an appropriate method of reconstruction.

Revision of late periprosthetic infections of total hip endoprostheses: pros and cons of different concepts

Many concepts have been devised for the treatment of late periprosthetic infections of total hip prostheses. A two-stage revision with a temporary antibiotic-impregnated cement spacer and a cemented prosthesis appears to be the most preferred procedure although, in recent times, there seems to be a trend towards cementless implants and a shorter period of antibiotic treatment. Because of the differences in procedure, not only between studies but also within studies, it cannot be decided which period of parenteral antibiotic treatment and which spacer period is the most suitable. The fact that comparable rates of success can be achieved with different treatment regimens emphasises the importance of surgical removal of all foreign materials and the radical debridement of all infected and ischaemic tissues and the contribution of these crucial procedures to the successful treatment of late periprosthetic infections.

Two-stage cementless revision of infected hip endoprostheses

Cementless two-stage revision of infected total hip prostheses lacks the possibility of local antibiotic protection of the implant at the time of reimplantation, which leads to the concern that this protocol may not sufficiently eradicate periprosthetic infection. Moreover, early implant loosening as much as 18% and stem subsidence as much as 30% have been reported. To determine whether a cementless revision could eradicate infection and achieve sufficient implant stability, we prospectively followed 36 patients with two-stage revisions for septic hip prostheses. We used a uniform protocol of a 6-week spacer interval, specific local and systemic antibiotic therapies, and cementless modular revision stems. The minimum followup was 24 months (mean, 35 months; range, 24-60 months). In one patient, the spacer was changed when the C-reactive protein value failed to normalize after 6 weeks, and the reimplantation was performed after an additional 6 weeks. No infections recurred. There was no implant loosening and a 94% bone-ingrowth fixation of stems. Subsidence occurred in two patients. The Harris hip score increased from a preoperative mean of 41 to 90 at 12 months after reimplantation and later. Using cementless prostheses in two-stage revisions of periprosthetic infections of the hip in combination with a specific local and systemic antibiotic therapy seems to eradicate infection and provide implant stability.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Short-term results of hip revisions with a curved cementless modular stem in association with the surgical approach

INTRODUCTION

A prospective study was designed to test the hypothesis that short-term results after hip revisions are in association with the surgical approach with lower clinical scores for the transfemoral approach.

MATERIALS AND METHODS

A total of 120 hip revision operations with the modular cementless revision stem "Revitan Curved" (Zimmer GmbH, Winterthur, Switzerland), of which 42 replacements involved an endofemoral (posterolateral) approach and 78 implantations a transfemoral approach, were followed up over a period of at least 24 months.

RESULTS

In the early post-operative stage, stems implanted transfemoral were associated with significantly lower Harris Hip Scores and a significantly more frequent appearance of Trendelenburg signs. The differences lessened at the end of the follow-up period. Within the group of transfemoral implantation, all six stems with a circular fixation zone measuring less than 3 cm had subsided and two of these had become loose; none of the stems with greater fixation zones exhibited these properties. In the case of the endofemoral implants, three stems exhibited sinking but there did not appear to be any relationship between this event and length of fixation zone.

CONCLUSION

The surgical approach has an association with the short-time outcomes of hip revsions using cementless modular stems. Transfemoral implantation of the "Revitan curved" stem requires a fixation zone of at least 3 cm and a longer period of rehabilitation.

A modified transfemoral approach using modular cementless revision stems

The transfemoral approach in its traditional form, using a nonmodular Wagner self-locking revision stem, has the disadvantages of a less predictable union rate of the bony flap and a high rate of stem subsidence. To investigate whether this situation can be improved by using a modified transfemoral approach and modular curved cementless revision stems, we prospectively analyzed 68 hip revisions and followed them clinically and radiographically for a minimum of 24 months (mean +/- standard deviation, 32.4 +/- 11.2 months). One year after the operation, the osteotomy showed bony consolidation in all but one case (98.5%). We noted subsidence in six cases (8.8%) and two of these stems became loose. In all of these cases, the circular fixation zone of the stem in the isthmus of the femur was less than 3 cm. The Harris hip score improved continuously from 41.4 +/- 14.5 points preoperatively to 85.9 +/- 14.6 points 24 months postoperatively. The modified transfemoral approach in combination with a curved, modular revision stem showed reproducibly good results concerning union of the bony flap and subsidence of the stem if the fixation zone was not less than 3 cm.