Femoral Components:
Cemented Stems with Femoral Osteotomy
Colin Howie
Summary
Femoral deformities are common and predictable in developmental dysplasia of the hip (DDH), particularly in high dislocations and previously operated femora.
Standard (if small) cemented implants can be used with good results. Femoral osteotomy is a useful and reliable technique during THA for DDH. In this chapter we will review the results of femoral osteotomy and a cemented stem.
Anatomical Considerations
When reviewing the results of total hip replacement in DDH with respect to the femoral component, consid- eration should be given to the femoral anatomy. It was noted earlier (
chapter 2.3) that in the presence of minor dysplasia the femur can often be regarded as »normal« and therefore suitable for standard total hip replacement tech- niques using standard cemented or uncemented implants.
In these cases long-term results should equate with those of standard age adjusted joint replacement. However, even in these circumstances small straight components may be necessary. In all cases, it is important to restore offset and therefore improve abductor function and reduce joint reaction force. In the more severe forms of dysplasia, or occasionally where the femur has been assaulted at an ear- lier operation to prevent the progression of osteoarthritis, the femur itself can be grossly abnormal.
Noble et al. [12 ] noted that much of the femoral change in the unoperated high dislocation occurred in the subtrochanteric region of the hip. Sugano et al. [18 ] showed that the antero-posterior diameter of the dysplas-
tic femur was much greater than the medial-lateral diam- eter of the femur. Both these »diameters« are markedly reduced and special straight implants may be required for these small and deformed femora. Furthermore, the asymmetrical shape of the diaphysis makes the inser- tion of an uncemented implant difficult, as the diameter used will be that of the smallest internal diameter. In the previous
chapter 8.2excellent long-term results for cemented Charnley hip arthroplasty in the presence of DDH without osteotomy was noted. Where there has been a high dislocation or surgical interference with the proximal femur osteotomy may be necessary (though the technique described by Lai et al. [9] could be used for lengthening alone).
If the acetabulum has been brought down to the true level from a high position, subtrochanteric shortening osteotomy will be necessary (
⊡Fig. 8.32). In the author’s series, no case has required an abductor slide or release (unless for severe post surgical fibrosis), because the reduction osteotomy reduces tension in the adductors and repositions the trochanter, laterally swinging the abductors round to their true anatomical position. In every case commercially available, if small, implants have been used attempting to insert the implant with the largest offset that the femur will allow. In the 92 femora where no osteotomy was performed in the author’s series small cemented implants were used in every case (with offset from 30 to 37.5 mms and correspondingly small stems). To date none has fractured, been revised, or become loose.
In this section, we will consider only those cases
where femoral osteotomy has been carried out, to restore
anteversion and offset and to improve abductor function
and leg length.
⊡ Fig. 8.33. Surgically lengthened femur where accurate leg lengths may be difficult to achieve
Nerve Palsies
There is considerable debate as to the causes and inci- dence of nerve palsy (femoral or sciatic) following THA for DDH, with the range from 3–15% not all of which re- cover [6]. Most authors associate this devastating compli- cation with leg lengthening of greater than 4 cm however just as important is the presence of pre-existing scarring from previous surgery. In a series of 27 sciatic palsies post THA from Finland [15] only 8 were associated with lengthening however 9 were in patients undergoing sur- gery for DDH. 8 patients recovered fully, 7 had a fair result and 12 had a poor long-term result. A further paper [5]
concludes that nerve damage is caused by direct damage not stretching. While intra-operative monitoring has been suggested we review nerve tension and mobilise the nerve from around osteotomy sites (usually pelvic) at the time of surgery. Full exposure may not be necessary (and may interfere with the nerves blood supply) however the nerve should at least be palpated and protected. In our series of 132 Primary THA’s for DDH no case had a persisting nerve palsy, several had transient palsies mostly femoral, and in every case the patient had undergone multiple pelvic and femoral surgeries previously and no significant Leg Length
It can be extremely difficult to ascertain true leg length both preoperatively and post surgery. Clinically, the pelvis may have been used in childhood as roof graft and sig- nificant positional deformity may be present both of which will result in extreme difficulty with accurate measure- ment. Furthermore, it should be noted that any surgery on the limb in childhood may result in relative overgrowth of the limb leading to an unexpected over lengthening after reconstruction to a normal hip. Occasionally the other limb may have undergone surgery to restrict growth to prevent significant discrepancy in childhood (
⊡Fig. 8.33).
The surgeon, as part of preoperative assessment, should ensure that he has assessed the true leg lengths and that the lumbar spine deformity is correctable (by check- ing the seated position). As a general rule full correction is neither possible nor desirable in cases of high dislocation (greater than 4 cm), as the patient will feel extremely long if fully corrected. It is probably wise to correct offset and as a result reduce joint reaction force (and wear) rather than length. Patients do not feel comfortable overcor- rected. We counsel all our patients that the length will be significantly better but not perfect.
⊡ Fig. 8.32a,b. High dislocation brought down with osteotomy 8 years post surgery (acetabular grafts probably unnecessary)
a
b
Uncemented Series
There are a number of reports of uncemented stem re- placement in the presence of DDH (11) including some where custom designed implants have been used (7).
Recent reports of soft tissue lengthening followed by uncemented primary surgery have reported on 56 cases with 9 revisions (5 for polyethylene wear) [9]. This inter- esting paper showed that considerable lengthening could be carried out using an external fixator as the first stage procedure.
Paavilainen et al. [13] described osteotomy and fixa- tion with a specially designed straight uncemented stem in 67 cases (including a number of cases where a longitu- dinal osteotomy was carried out to increase the femoral diameter). Many of these cases included severely deformed post surgical femora. With a three to five year follow up 4 stems were loose and 2 had been revised. Recently using a technique similar to Paavilainen et al [13], Carlsson et al.
[2] reported an extended osteotomy by removing the tro- chanter and shortening the femur followed by insertion of a conical titanium stem all with good mid-term results.
Della Valle et al. [4] using an extended trochanteric oste- otomy in 6 patients with maximum 4-year follow-up and an uncemented stem had one non-union but all implants were stable. Masonis et al. [10] described 10 cemented and 11 uncemented hip replacements with a follow-up of 5–8 years and 91% of the osteotomies had united. They reported 3 dislocations and that one-cemented stem had
2 stems had been revised, one for leg lengthening and one for cup loosening. Huo et al. [8] described an oblique osteotomy using a cementless stem in 26 cases, but only three were primary cases with a follow up of 3 to 5 years.
The technique involved distal fix and distal osteotomies.
There was a 24% failure rate, though it is not clear what the results were for the three primaries. Cameron [1]
reported 71 cases using a distal fit and adjustable proximal segment, which can customised at the table to fit the prox- imal fragment. However only 17 were Crowe grade 4 and would be considered for the femoral osteotomy described here. Of these 17 there was a 50% complication rate with 2 sciatic palsies, one femoral fracture and one osteotomy collapse. Only two of these cases had a shortening oste- otomy the anteversion being corrected by the customis- able proximal segment. A report of osteotomy in severe deformity [17] in 28 cases using uncemented stems was presented: two developed non unions and they recom- mended grafting the osteotomy site. This was an interest- ing series where the stem size used was 10–13 mm, larger than many of the medullary canals met in our practice though they reported no fractures (
⊡Table 8.20).
Own Results Using a Cemented Stem
We will report on a modified version of the technique (
⊡Fig. 8.34) described by Reikeraas et al. [16] and out- lined earlier in this book (
chapter 2.3). In his original series Reikeraas et al. reviewed 25 cases using a press fit uncemented prosthesis and found one sciatic palsy, one
8
⊡ Table 8.20. Comparison of published series
Authors Femoral Special Technique N= FU Loosening Non- Revisions
Implant union
Paavalainen [13] uncemented Various osteotomies 67 3–5 y 4 0 2
Carlsson [2] uncemented Ext. trocht. Osteot. 22 8–94 mos 0 0 5
Lai [9] uncemented Ext. fixator 56 Avge 147 mos 0 0 9
Della Valle [4] uncemented Extended troch osteotomy 6 Avge 50 mos4 0 1 1
Huo [8] uncemented Custom made stem 26 3–5 5 1 6
Oblique osteotomy
Matsui [11] uncemented Custom stem 51 5–9 18 N/A 2
Masonis [10] uncemented Sub trochanteric osteotomy 11 5–9 2 2
cemented Sub-trochanteric osteotomy 10 5–9 1 1
Decking [13] uncemented Straight stem, sub-trochanteric 12 Mean 5.1 yrs 1 0 2
Sener [17] uncemented Step cut osteotomy 28 7–92 mos 4 2 3
Howie cemented Subtrochanteric; straight stem 40 6–120 mos 0 0 3
non-union and one malunion. Yasgur et al. [19] also re- ported the technique augmented by cables and strut grafts with uncemented stems with similar results.
We have undertaken 40 femoral osteotomies in pri- mary cemented total hip replacements for DDH (from a series of 132 cases) to correct length, rotational or align-
ment problems. 5 had retained metalwork (
⊡Fig. 8.35) at the time of osteotomy and the osteotomy was used to remove some of the metalwork. The femoral loosening rate in those cases without metalwork removal is zero, the deep infection rate zero, we had no osteotomy non- unions and no cases of aseptic loosening. However using
⊡ Fig. 8.34a,b. High dislocation treated with femoral osteotomy and acetabular grafting
a b
⊡ Fig. 8.35. Femoral osteotomy remo- ving screws from inside and retaining plate to support cortex
a b
the double taper stem we have subsidence of the stem within the cement mantle. This gives 100% stem survival at 6 months to 10 year follow up when metalwork has not been removed and femoral osteotomy has been carried out (accepting two late periprosthetic fractures treated successfully by plating and retention of the hip implant).
The grafted osteotomy site, however, has taken up to 2 years to show evidence of union.
In cases where ingrown metalwork was present at the time of hip replacement there were some difficult com- plications, in one case reactivation of a previous infection at the osteotomy site occurred, resulting in two stage revision and successful proximal femoral replacement.
In another the distal femur fractured on insertion of the implant through holes created by the removal of screws and subsequently became infected, again resolving after a two stage revision. In both cases the plate and screws lay entirely within bone at the time of surgery, but staged removal would have resulted in fracture of the femur.
Intraoperative fracture or perforation of the femur can occur because of the thin and abnormal anatomy. Often the risks are increased by the presence of metalwork or holes created by the previous removal of metalwork. Some have suggested prophylactic wiring and strut grafting of the femur, particularly when using uncemented implants
[14]. Our current practice is that any ingrown plates or irremovable screws are left where possible and the screws burred from the inside if necessary leaving the cortical segments to reduce stress risers and maintain femoral tube integrity. Of the five cases with retained metalwork two became infected and were revised (20%) the other three all healed without event.
Two patients in our series, both with united oste- otomies, have fallen and sustained late (greater than 9 months post THR) periprosthetic fractures which have both been successfully treated with plating.
Conclusion
Full correction of leg length is less desirable than increas- ing offset, soft tissue tightness is more marked in the ad- ductors and soft tissue structures leaving the pelvis than the abductors. Abductor release is rarely if ever required.
Complications of all varieties are more common and the soft tissue continuity between abductors and Vastus lateralis should be maintained. It is our belief that the hip should be made to look normal (by osteotomy) then the surgeon should implant his normal device to obtain good long term results.
8
⊡ Fig. 8.36. Ugly femur post osteotomy for SUFE (not included in this series) showing deformity, corrective osteotomy and cutting of screws
from within (via osteotomy). On the post operative film note retained screw parts in both cortices
Take Home Messages
I I
▬
Shortening osteotomy in CDH is required to cor- rect deformity.▬
Restoration of offset is important – leg length is secondary.▬
Non-union and fracture can occur after osteotomy.▬
Small implant sizes must be available.▬
Both uncemented and cemented femoral stems are successful.References
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