[Cement-free diaphyseal fixation principle for hip shaft exchange in large bone defects--analysis of 12 years experience with the Wagner revision shaft]

The transfemoral approach for controlled removal of well-fixed femoral stems in hip revision surgery

BACKGROUND

For the removal of well fixed femoral stems, various standard and extended approaches are possible, all of which have their advantages and disadvantages. They should allow good visualization and avoid uncontrolled damage to the bone (especially devascularization and fractures) and to the musculature (especially the gluteus medius). As an extended approach we prefer the transfemoral approach in a modified Wagner technique. It is indicated for the controlled removal of broken endoprosthetic stems, a significantly thinned bone at risk of fracture, a stable cement mantle, a partially fixed cementless prosthetic stem with a coarse, rough surface, and infected, fixed total hip endoprostheses. In this review article we describe our experience with our technique of the transfemoral approach.

MATERIAL AND RESULTS

In 68 patients with hip revisions using the modified transfemoral approach, the Harris Hip Score increased continuously from 41.4 points preoperatively to 85.9 points 24 months postoperatively. The bony flap showed bone consolidation in 98.5% of cases. In 76 patients with transfemoral two-stage septic hip revisions, with closure of the flap around the interim prosthesis with cerclage wires and reopening of the flap during second stage revision, the Harris Hip Score was 62.2 ± 12.6 points before the replacement of the spacer and 86.6 ± 15.5 points two years after reimplantation. The healing rate of the bony flap after reimplantation was 98.7%, the absence of infection 93.4%, the rate of stem subsidence 6.6%, and the dislocation rate 6.6%; there was no aseptic loosening of the implants.

CONCLUSION

The transfemoral approach allows a reliable protection of the gluteus medius and the vastogluteal sling, and enables reproducibly good clinical outcomes.

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.

Custom uncemented revision stems based on a femoral classification

From the outcome of 175 cases, a group of 4 types of custom-designed HA-coated hip stems, based upon an incremental scale of bone condition, was demonstrated to be sufficient for use with the variety of cavitary defects encountered in revision hip surgery. Harris Hip Score evaluation showed a significant improvement in hip pain and function. Radiographic measurements of axial migration over a 4-year period were less than 2 mm. The migration data were similar across the 4 types of revision stem. A follow-up using DEXA scans showed preservation of bone in all regions up to 4 years, which justifies the design rationale for the close fit of the stems in the proximal region in achieving initial stability and strain transfer.

Rationale for one stage exchange of infected hip replacement using uncemented implants and antibiotic impregnated bone graft

Infection of a total hip replacement (THR) is considered a devastating complication, necessitating its complete removal and thorough debridement of the site. It is undoubted that one stage exchange, if successful, would provide the best benefit both for the patient and the society. Still the fear of re-infection dominates the surgeons decisions and in the majority of cases directs them to multiple stage protocols. However, there is no scientifically based argument for that practice. Successful eradication of infection with two stage procedures is reported to average 80% to 98%. On the other hand a literature review of Jackson and Schmalzried (CORR 2000) summarizing the results of 1,299 infected hip replacements treated with direct exchange (almost exclusively using antibiotic loaded cement), reports of 1,077 (83%) having been successful. The comparable results suggest, that the major factor for a successful outcome with traditional approaches may be found in the quality of surgical debridement and dead space management. Failures in all protocols seem to be caused by small fragments of bacterial colonies remaining after debridement, whereas neither systemic antibiotics nor antibiotic loaded bone cement (PMMA) have been able to improve the situation significantly. Reasons for failure may be found in the limited sensitivity of traditional bacterial culturing and reduced antibiotic susceptibility of involved pathogens, especially considering biofilm formation. Whenever a new prosthesis is implanted into a previously infected site the surgeon must be aware of increased risk of failure, both in single or two stage revisions. Eventual removal therefore should be easy with low risk of additional damage to the bony substance. On the other hand it should also have potential of a good long term result in case of success. Cemented revisions generally show inferior long term results compared to uncemented techniques; the addition of antibiotics to cement reduces its biomechanical properties. Efficient cementing techniques will result in tight bonding with the underlying bone, making eventual removal time consuming and possibly associated with further damage to the osseous structures. All these issues are likely to make uncemented revisions more desirable. Allograft bone may be impregnated with high loads of antibiotics using special incubation techniques. The storage capacities and pharmacological kinetics of the resulting antibiotic bone compound (ABC) are more advantageous than the ones of antibiotic loaded cement. ABC provides local concentrations exceeding those of cement by more than a 100fold and efficient release is prolonged for several weeks. The same time they are likely to restore bone stock, which usually is compromised after removal of an infected endoprosthesis. ABC may be combined with uncemented implants for improved long term results and easy removal in case of a failure. Specifications of appropriate designs are outlined. Based on these considerations new protocols for one stage exchange of infected TJR have been established. Bone voids surrounding the implants may be filled with antibiotic impregnated bone graft; uncemented implants may be fixed in original bone. Recent studies indicate an overall success rate of more than 90% without any adverse side effects. Incorporation of allografts appears as after grafting with unimpregnated bone grafts. Antibiotic loaded bone graft seems to provide sufficient local antibiosis for protection against colonisation of uncemented implants, the eluted amounts of antibiotics are likely to eliminate biofilm remnants, dead space management is more complete and defects may be reconstructed efficiently. Uncemented implants provide improved long term results in case of success and facilitated re-revision in case of failure. One stage revision using ABC together with uncemented implants such should be at least comparably save as multiple stage procedures, taking advantage of the obvious benefits for patients and economy.

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.

[Revision arthroplasty of the hip: modularity of neck and metaphyseal components]

BACKGROUND

Modular parts in femoral components used for hip arthroplasty are reported to be predilection sites for mechanical failure. The possible benefit of their use is therefore controversial.

PATIENTS AND METHOD

We report the outcome of 97 revision hip arthroplasties using a non-cemented femoral component with a modular metaphyseal part and an interchangeable neck (Profemur). The femoral defects treated included Paprosky types I-III. The average follow-up was 5 years (range 3-10 years).

DISCUSSION

No mechanical failure of the modular parts and taper connections has been observed so far. The percentage of patients with a balanced leg length increased from 32% preoperative to 65% postoperative. The mean leg length discrepancy could be reduced from 1.4 cm preoperative to 0.5 cm postoperative. A total of 5 re-revisions were required, including 2 cases of infection. The cumulative survival of the implants due to aseptic loosening was 96.5%.

CONCLUSION

Because of the achieved results the use of the modular stem investigated in this study can be classified as safe and effective for revision hip arthroplasty. The interchangeable neck proved to be a useful completion of the revision system.

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.

Cementless fixation of megaprostheses using a conical fluted stem in the treatment of bone tumours

We reviewed 25 patients in whom a MUTARS megaprosthesis with a conical fluted stem had been implanted. There were three types of stem: a standard stem was used in 17 cases (three in the proximal femur, nine in the distal femur and five proximal tibia), a custom-made proximal femoral stem in four cases and a custom-made distal femoral stem in four cases. The mean age of the patients was 40.1 years (17 to 70) and the mean follow-up was for 2.5 years (0.9 to 7.4).

At follow-up two patients had died from their disease: one was alive with disease and 22 were disease-free. One of 23 prostheses had been removed for infection and another revised to a cemented stem. The mean Musculoskeletal Tumor Society score was 24.9 (12 to 30) and the mean Karnofsky index was 82% (60% to 100%).

There was no radiological evidence of loosening or subsidence. Stem stress shielding was seen in 11 patients and was marked in five of these.

There were five complications, rupture of the extensor mechanism of the knee after extra-articular resection in two patients, deep venous thrombosis in one, septic loosening in one, and dislocation of the hip in one.

The survival rate after seven years was 87% (95% confidence interval (CI) 83 to 91) for the patients and 95% (95% CI 91 to 99) for the megaprosthesis. A longer follow-up is needed to confirm these encouraging results.

Major femoral bone loss in revision total hip arthroplasty treated with tapered, porous-coated stems

Clinical results of revision total hip arthroplasty using fully porous-coated tapered titanium stems to treat severe proximal femoral bone loss were evaluated in a retrospective review of 39 patients (45 hips). The bone was reinforced with cables in 39 hips, and in 14 hips strut allografts were added. Fixation was successful in 44 hips, and one hip required revision to treat undetected fracture and migration of the stem. All the others had radiographic evidence of bone attachment. Neither bone atrophy nor reconstitution was noted. Three patients (3 hips) had mild thigh pain, but the others had no pain related to the femoral component. Eight hips dislocated; one resolved and seven had recurrent dislocation that was treated with a constrained acetabular component, capsulorrhaphy, or liner reorientation. Ten patients (12 hips) used a walker and 10 patients (12 hips) used a cane at the last postoperative visit. Whereas fixation was successful with this surgical technique, complications related to deficiency of the soft tissue structures were common.