Intraoperative type 1 proximal femoral fractures

The Journal of Arthroplasty Vol. 13 No. 6 1998

Intraoperative Type 1 Proximal Femoral Fractures Influence on the Stability of Hydroxyapatite- Coated Femoral Components Francesco

Falez, MD, Nicola Santori,

MD, and Gabriele

Panegrossi,

MD

A b s t r a c t : We reviewed a series of 120 uncemented total hip replacements using the Omniflex stem with hydroxyapatite coating. Twenty minor intraoperative proximal fractures occurred. All fractures were treated with cerclage wiring after removal of the stem. Radiographic and clinical results of these 20 patients were compared with the remaining 100 implants in which this complication did not occur. In 20% of the cases of both groups, a migration of less than 2 m m was observed. No differences were detected in Harris Hip Scores, subsidence o{ the stem, and radiographic behavior. We concluded that a properly stabilized proximal femoral fracture above the lesser trochanter did not influence the clinical and radiographic results at more t h a n 3 years follow-up. K e y w o r d s : u n c e m e n t e d total hip replacement, proximal femoral fracture, subsidence, cerclage wiring.

Until the a d v e n t of press-fit cementless stems, intraoperative p r o x i m a l femoral fractures h a d b e e n a n u n c o m m o n complication during hip arthroplasty: This p r o b l e m , usually described as "intraoperative crack," can occur w h e n trying to obtain a tight fit of the stem, in order to e n h a n c e b o n e g r o w t h on the i m p l a n t surface. Two m a i n causes are associated with the occurrence of this complication. The first is the application of a n oversized final femoral s t e m as c o m p a r e d to the preparing broach. This p r o d u c t design has b e e n u s e d by certain companies to ensure a tight p r o x i m a l fit of the final c o m p o n e n t , a n d it is a recognized source of p r o x i m a l femoral cracks. Fractures h a v e b e e n reported to range f r o m 2 % w i t h the p o r o u s - c o a t e d a n a t o m i c s t e m (Howmedica, Rutherford, N J), w h i c h uses a b r o a c h equal

in size to the final c o m p o n e n t , to 20% with systems such as the Omnifit (Osteonics, AUendale, NJ), w h i c h uses an undersized b r o a c h [1-3]. The second cause of p r o x i m a l cracks is the extent of i m p a c t i o n into the f e m u r of the final prosthesis once the metaphysis has b e e n prepared. In the absence of a collar, the f e m o r a l stern can be p u s h e d further d o w n into the f e m o r a l canal, and the surgeon m a y be t e m p t e d to use this m e t h o d to obtain a tight fit or restore equal leg length. However, the surgeon m u s t also be a w a r e that once the f e m u r has b e e n p r e p a r e d w i t h the last broach, the prosthesis will not be able to go further d o w n into the f e m u r w i t h o u t a significant increase in interface stress [4]. The presence of the collar, o n the other hand, can preclude p r o p e r seating of the i m p l a n t w i t h a p o o r m e t a p h y s e a l fit. The occurrence of a p r o x i m a l femoral fracture decreases initial m e c h a n i c a l stability. If unrecognized, it can multiply the risks of early subsidence of the stem, result in p o o r b o n e a t t a c h m e n t to the implant, a n d can increase the failure rate in the short term.

From the First Orthopaedic Clinic, University "La Sapienza," Rome, Italy. Reprint requests: Francesco Falez, MD, Clinica Ortopedica "La Sapienza," Piazza A. Moro 5, 1-00185 Rome, Italy. Copyright © 2998 by Churchill Livingstone® 0883- 540311306-000953.00/0

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Otani a n d Whiteside [5] h a v e recently d e m o n strated that a linearly displaced p r o x i m a l femoral fracture severely reduces the torsional stability of the stem and, therefore, should n e v e r be left u n treated. Moreover, t h e y f o u n d that the application of circumferential wires m a y significantly restore stability. The p u r p o s e of this retrospective study is i) to d e t e r m i n e if femoral cracks increase the risk of early postoperative subsidence of the stem, and ii) to establish if a properly treated p r o x i m a l crack is associated w i t h a higher failure rate, due to inadequate biological fixation of the implant.

Materials and Methods F r o m N o v e m b e r 1990 to N o v e m b e r 1993, 120 p r i m a r y u n c e m e n t e d total hip replacements w e r e p e r f o r m e d o n i13 patients. Seven patients underw e n t a two-stage bilateral procedure. Of 120 prostheses, 20 p r o x i m a l fractures occurred during stem insertion (group 1). To d e t e r m i n e the influence of this complication on i m p l a n t stability, s t e m subsidence, a n d final clinical results, these cases w e r e c o m p a r e d w i t h the r e m a i n i n g 93 patients (100 operated hips) (group 2). Age, gender, a n d p r i m a r y cause for surgery w e r e carefully recorded. Before surgery, a n t e r o p o s t e r i o r v i e w and lateral view radiographs w e r e taken, as well as an anteroposterior standing pelvic v i e w to assess leg length discrepancy. Magnification m a r k e r s w e r e used with the focal distance fixed at 120 cm. Careful templating following the m a n u f a c t u r e r ' s instructions was carried out by the s a m e e x a m i n e r w h o was not the operating surgeon. All patients w e r e operated on by the same surgeon t h r o u g h the direct lateral app r o a c h as described b y Hardinge [6]. In all cases, the Omniflex h y d r o x y a p a t i t e - c o a t e d (Osteonics, Rutherford, NJ) stem was implanted. Special a t t e n t i o n was m a d e as to the depth of rasp insertion, a n d particular p r u d e n c e was t a k e n to seat the final c o m p o n e n t at the same level. Protective wiring of the p r o x i m a l f e m u r before rasping was n e v e r p e r f o r m e d in this series. Proximal femoral fractures w e r e classified, according to K a v a n a g h [3], in t h r e e types. Type I fractures, or "proximal cracks," occur on the femoral n e c k above the lesser trochanter. Type II fractures e x t e n d below the lesser t r o c h a n t e r but p r o x i m a l to the isthmus. Fractures that occur at or b e l o w the isthm u s are classified as type III. In addition, these fractures are described according to the a m o u n t of displacement; if displacement is less t h a n 2 ram, it is

a type A fracture, but if it is greater t h a n 2 m m , it is classified as type B. Once recognized during surgery, the fracture was e x a m i n e d by inspection and palpation, a n d further surgically dissected. Any q u e r y as to the e x t e n t or displacement of the fracture was c o n f i r m e d w i t h an intraoperative radiograph. Only type IA a n d type IB fractures w e r e included in this study. All fractures occurred during i m p l a n t insertion a n d n e v e r during femoral rasping a n d w e r e treated w i t h cerclage wiring after r e m o v a l of the stem. The n u m b e r of wires e m p l o y e d was d e p e n d e n t o n the e x t e n s i o n of the fracture r i m a n d the stability obtained during surgery. I m p l a n t steadiness after cerclage wiring was tested o n applying r e p e a t e d strains to the b o n e - i m p l a n t interface either t h r o u g h a rotational load o n the n e c k of the prosthesis with a d y n a m o m e t e r or by gentle further impaction on the implant. The stem was considered stable w h e n n o m o t i o n was detected after three consecutive assessments of torsion with greater t h a n 60 N applied w i t h the d y n a m o m e t e r on the i m p l a n t neck. After surgery, all patients u n d e r w e n t the s a m e rehabilitation protocol regardless of the occurrence of an intraoperative type I fracture. This consisted of i m o n t h of partial weight-bearing w i t h crutches, followed b y a n o t h e r m o n t h of one crutch assistance o n the contralateral side. Hip strengthening exercises w e r e started as soon as tolerated a n d c o n t i n u e d for the first 3 m o n t h s . Patients h a v e b e e n clinically evaluated w i t h the Harris Hip Score [7] before surgery, a n d at 3, 6, 12 m o n t h s , a n d each year after surgery. Clinical evaluation consisted of a s s e s s m e n t of pain, presence of a limp, n e e d for external support, activity level, ability to ambulate, joint range ot~ m o t i o n , and patient satisfaction. All the radiographs w e r e t a k e n in o u r institution u n d e r the care of the same t e a m of radiologists. At each control, standardized a n t e r o p o s t e r i o r a n d lateral radiographs w e r e t a k e n at a focal distance of 120 cm. In order to d e t e r m i n e a n y position changes of the i m p l a n t into the femur, careful a t t e n t i o n was paid w h e n positioning the patient, being certain to predictably flex and rotate the leg, on the x - r a y table because n o radiopaque m a r k e r s w e r e placed at the t i m e of surgery. Stem subsidence was d e t e r m i n e d b y the following radiographic m e a s u r e m e n t s (Fig. 1): A) the distance b e t w e e n the p r o x i m a l lateral corner of the stem and the greater trochanter, B) the distance b e t w e e n the tip of the s t e m and the greater trochanter,

Intraoperative Proximal Femoral Fractures

Fig. 1. Measurement employed to quantify stem subsidence. (A) Distance between the proximal lateral corner of the stem and the greater trochanter. (B) Distance between the tip of the stem and the greater trochanter,

C) the diameter of the femoral head, D) the ratio b e t w e e n A and C, a n d E) the ratio b e t w e e n B and C. M e a s u r e m e n t of the femoral head diameter (C) was used to m a t c h radiographic magnification. If a different magnification was detected, this was corrected relating the m e a s u r e m e n t s of (A) and (B) with the w i d t h of the diameter of the femoral head, w h i c h was always 28 m m (C). All m e a s u r e m e n t were taken by the same observer (G.P.). Radiological assessment included the appearance of lucency, osteolysis, stem subsidence, or a n y o t h e r signs of implant loosening.

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(60%) and 8 females (40%). Primary cause for joint replacement was osteoarthritis in 16 cases, avascular necrosis in 1 case, a Garden IV fracture in i case, r h e u m a t o i d arthritis in 1 case, a n d 1 case of pseudoarthrosis of a femoral neck fracture. Average foll o w - u p was 38 m o n t h s (range, 13-42 months). In group 2, the average age was 61.9 (range, 29-84), 55 w o m e n (59%) a n d 38 m e n (41%). Primary cause for replacement was osteoarthritis in 66 hips, displaced femoral neck fracture in 14, previous acetabular fracture in 7, avascular necrosis in 6, pseudoarthrosis after femoral neck fracture in 4, and r h e u m a t o i d arthritis in the remaining 3 hips. Average follow-up was 37 m o n t h s (range, 15-42 months). Age distribution in the two groups is s h o w n in Table 1. In Group 1, there were 16 type IA fractures and 4 type IB fractures. A single wire was used in 12 cases, while 2 wires were used in the remaining 8 cases. All implants in group 1 appeared intraoperatively stable after wiring. Pre- and postoperative Harris Hip scores are reported in Table 2. We n e v e r detected a n y postoperative statistically significant difference b e t w e e n the two groups (P > .05). No patients in either group were lost to follow-up. At 6 months, pain was not present in 90% of patients in group 1 and in 89% in group 2. At 1 yea], 80% of patients in both groups did not need a cane, while at 2 years 90% and 94% in groups 1 and 2, respectively, were walking independently. Again, these data were not statistically different in the two groups (P > .05). Overall results were classified as excellent in 93% and fair in 7% in group 1 and 95% excellent and 5 % fair in group 2. Magnification corrections employing the femoral head diameter were done in 22 cases at 3 months, in 31 cases at 6 months, in 12 cases at 12 months, and in 16 cases at 2 years. At 6 months, in 20% of patients of both groups, we f o u n d an average stem subsidence of 2 m m

Results This series consisted of 65 w o m e n and 48 men, with an average age of 62.3 years (range, 2 9 - 8 4 years). Indications for surgery were osteoarthritis in 82 cases, femoral neck fractures in 15 cases, previous acetabular fracture in 7 cases, avascular necrosis in 7 cases, pseudoarthrosis after femoral neck fracture in 5 cases, and r h e u m a t o i d arthritis in the remaining 4 cases. The average age in group 1, patients with intraoperative cracks, was 63.3 (range, 42-76), 12 males

Table 1. Distribution of Patients, According to Age, in the Two Groups Groups of Age

Group 1 (%)

Group 2 (%)

40-49 50-59 60-69 70-79 80-89

2 (I0) 5 (25) 7 (35) 6 (30) -- (0)

12 (12.9) 38 (40.8) 34 (36.6) 9 (9.7) 0 (0)

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The Journal of Arthroplasty Vol. 13 No. 6 September 1998 Table 2. Average Preoperative and Later Harris

Hip Score Harris Hip Score Preoperative Group 1 Range Group 2 Range

23.2 5-51 24.6 6-63

1 year 91.2 67-100 89 76-100

2 years

Final

94.1 80-100 92.9 73-100

94.3 78-100 93.4 78-100

(range, 1.8-2.7 m m ) w h i c h s h o w e d no increase within the following 6 m o n t h s (Figs. 2 and 3). In group 1, no correlation was f o u n d b e t w e e n radiological findings a n d type of fracture (IA or IB), age, gender, or level of activity. At 1 a n d 3.5 years follow-up all cases with s t e m subsidence w e r e clinically s y m p t o m free, a n d no further subsidence was recorded. Three patients in group 2 h a v e had f u r t h e r surgery for acetabular loosening. Seven patients s h o w e d radiolucency in acetabular zones 1 a n d 3 at the last control; t w o of these w e r e in group 2. No femoral radiolucent lines h a v e b e e n identified in either group. I n c o m p l e t e pedestal f o r m a t i o n has b e e n n o t e d in 1 case of g r o u p 1 a n d 8 cases of group 2, while calcar resorption greater t h a n 5 m m was

p r e s e n t in patients of b o t h groups, but n o n e of these was associated with subsidence of the implant. Cortical h y p e r t r o p h y was n o t e d in zones 4a a n d 4b facing the distal tip of the i m p l a n t in- 3 cases in g r o u p 1 a n d 13 cases in group 2.

Discussion A substantial r e q u i r e m e n t for a successful c e m e n t less i m p l a n t is to achieve s o u n d initial p r o x i m a l stability. This minimizes i m p l a n t m i c r o m o t i o n along the entire length of the s t e m and e n h a n c e s b o n e remodeling. Several investigations h a v e identified the i m p o r t a n c e of p r o x i m a l stress transfer as a p r o m i n e n t feature of any f e m o r a l i m p l a n t [5,8]. Unlike c e m e n t e d femoral c o m p o n e n t s , cementless f e m o r a l s t e m insertion can produce substantial h o o p strains in the p r o x i m a l f e m o r a l cortex, d e p e n d i n g o n h o w tight the prosthesis is i m p a c t e d into the f e m o r a l canal [9]. An excessive increase of stresses can ultimately lead to a p r o x i m a l femoral crack. This complication m a y occur w h e n trying to obtain a tight p r o x i m a l fit or w h e n the surgeon is facing a m i s m a t c h i n g b e t w e e n the patient's f e m o r a l m o r p h o l o g y a n d i m p l a n t g e o m e t r y [4]. I n t r a o p e r a t i v e f e m o r a l fractures appear to be m o r e c o m m o n with certain implants [2,10-14] a n d it is possible that the

-

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Fig. 2. (A) Type 1A fracture treated with cerclage wiring. (B) One-year follow-up. Stem subsidence of greater than 2 m m is not seen.

Intraoperative Proximal Femoral Fractures

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Fig. 3. Postoperative (A) and I year (B) radiographic control of a case with no proximal femoral fracture. No evidence of stem subsidence.

true incidence is e v e n higher, as m a n y of these fractures go u n d e t e c t e d at the time of surgery [15]. E v e n t h o u g h Martell et al. [16] h a v e recently reported a correlation b e t w e e n the occurrence of intraoperative fracture a n d early aseptic loosening, the influence of a p r o x i m a l femoral crack on the clinical o u t c o m e of a n o n c e m e n f e d hip r e p l a c e m e n t is still u n k n o w n . No studies h a v e addressed the clinical a n d radiographic o u t c o m e of patients in w h o m a m i n o r fracture occurred a n d c o m p a r e d this data w i t h patients in w h i c h this complication did not occur. The u n u s u a l l y high incidence of femoral fractures that occurred in our series (16.6%) m a y be due to the b i o m e c h a n i c a l characteristics a n d geometric shape of the Omniflex (Osteonics, Allendale, NJ) m o d u l a r femoral stem. This c o m p o n e n t was designed to transfer the load p r o x i m a l l y and to address the issue of a proximal-distal mismatch. To m a x i mize i m m e d i a t e p r o x i m a l b o n e - m e t a l contact, the femoral i m p l a n t is oversized in respect of the corresponding broach. As a result of this mismatch, this s t e m is apt to produce p r o x i m a l cracks during insertion. Capello et al. [I I] h a v e recently reported 6 m a j o r fractures, five subtrochanteric and I i m i n o r undisplaced cracks in the first 86 hips. O t h e r authors [2,10] h a v e reported an e v e n higher percentage of m i n o r p r o x i m a l fractures w i t h the Omnifit

(Osteonics, Allendale, N J) stem, w h i c h has the same m e t h a p h y s e a l g e o m e t r y of the Omniflex system. Once it occurs, a p r o x i m a l fracture m u s t be properly treated. Otani a n d Whiteside [5] h a v e e x p e r i m e n t a l l y d e m o n s t r a t e d t h a t the m o s t stable condition is obtained w h e n cerclage wires are applied after s t e m removal. Both our experience and that of other investigators [10,17] s e e m to confirm the efficacy of this approach. Careful assessment of the crack and a stable fixation after s t e m r e m o v a l are, in our opinion, responsible for the low rate of complication a n d the absence of subsidence in this series of 20 fractures. On the contrary, the role of the h y d r o x y a p a t i t e coating in e n h a n c i n g fracture healing can't be appraised in this study considering the lack of a control group. In the future we feel it could be interesting, to assess the i m p o r t a n c e of the h y d r o x y a p a t i t e in this situation. Recently, Schutzer et al. [2,1] investigated implant stability and b o n e i n g r o w t h w h e n a p r o x i m a l fracture was p r o d u c e d in the f e m u r of a group of 10 m o n g r e l dogs. They f o u n d that the occurrence of the fracture had deleterious effects on b o n e ing r o w t h e v e n after a perfect reduction and cerclage wiring. However, their retrievals h a v e b e e n e x a m ined only at 3 a n d 6 w e e k s f r o m surgery and therefore results m a y h a v e b e e n significantly affected by the short follow-up.

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The Journal of Arthroplasty Vol. 13 No. 6 September 1998

In this retrospective study we have no direct histological evidence of b o n e i n g r o w t h or k n o w l edge of w h e t h e r this process has been affected or not by the occurrence of the fracture. Nevertheless, we have n o t seen a n y radiolucent lines a r o u n d the implant. The absence of radiolucent lines and a n y other radiological signs of aseptic loosening are considered indirect but reliable signs of bone integration [22]. The only significant radiographic finding has been a progressive calcar resorption, w h i c h was not correlated to the occurrence of the fracture, but suggests implant b o n d i n g and load transfer with remodeling. The most accurate m e t h o d to determine position changes of the prosthesis is r o e n t g e n stereophotogrammetric analysis (RSA) [I8,19]. This procedure was not e m p l o y e d in this study. However, extreme attention was taken in positioning the patient o n the x-ray table, and all radiographs were done in the same institution u n d e r the care of the same team of radiologists. Walker et al. [20] have recently d e m o n strated that the most accurate landmarks for determining stem susidence are those w h i c h are close together o n the f e m u r a n d the stem, and in the same plane. They d e t e r m i n e d that the most reproducible landmarks are the greater trochanter o n the f e m u r and the lateral proximal corner on the stem. According to this study, it is possible, allowing for variations of up to 10 ° rotation of the femur in a n y directions b e t w e e n successive radiographs, to have a m a x i m u m error of 0.37 m m . These same landmarks were employed in our investigation. Furthermore, any magnification was corrected with the femoral head diameter, w h i c h is a fixed l a n d m a r k n o t influenced by rotation and located on the same plane of the stem. Similar to other investigators, we believe that an undetected and u n t r e a t e d proximal femoral crack must be considered as a reason for decreased mechanical stability [5] and decreased bone i n g r o w t h of an apparently stable prosthesis [15]. The clinical evidence that at 3.5 years follow-up there are n o significant differences in Harris Hip Score in the two groups, confirms our belief that a proximal femoral fracture, if properly treated, must be considered simply as an intraoperative complication with n o effects in the short term. Moreover, once the proximal cracks has healed w i t h o u t causing stem subsidence, it is likely that it will also n o t influence the results in the longer follow-up. It is still questionable w h e t h e r prophylactic wiring is preferable w h e n using an implant with such a high rate of intraoperative fractures. The reason in favor of that approach is the evidence of the surgical

technique. Besides, it is still possible that some fractures could go u n d e t e c t e d at the time of surgery. However, it m u s t be r e m e m b e r e d that it is a timec o n s u m i n g step, can increase blood loss, and the c e r d a g e itself m a y represent a cause of pain and inflammation of the surrounding soft tissue. In conclusion, we observed the following: 1. No significant difference was n o t e d in the a m o u n t of subsidence in comparing patients with a n d w i t h o u t intraoperative proximal femoral fractures. 2. The occurrence of a proximal crack, w h e n properly treated, did not increase the rate of loosening. 3. W h e n using implants with significant mism a t c h i n g (>2 m m ) of broaches and final c o m p o nent, routine prophylactic cerclage wiring m a y be considered.

References 1. Cabanela ME: Results of uncemented THA with the Osteonics prosthesis. Present at the Closed Meeting of the Hip Society. Scottsdale, AR, September, 1990. 2. Fitzgerald RH, Brindley GW, Kavanagh BF: The uncemented total hip arthroplasty Intraoperative femoral fractures. Clin Orthop 235:61, 1988 3. Kavanagh BF: Intraoperative femoral fractures, fn Morrey BF (ed): Joint replacement arthroplasty. Churchill Livingstone, New York, 1991 4. Jasty M, Henshaw RM, O'Connor DO, Harris WH: High assembly strains and femoral fractures produced during insertion of uncemented femoral component J Arthroplasty 8:479, 1993 5. Otani t, Whiteside LA: Failure of cementless fixation of the femoral component in total hip arthroplas~. Orthop Clin North Am 23:335, 1992 6. Hardinge K: The direct lateral approach to the hip. J Bone Joint Surg [Br] 64:I7, 1982 7. Harris WH: Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end study using a new method of result evaluation. J Bone Joint Surg [Am] 51:737, 1969 8. Oh I, Harris WH: Proximal strain distribution in the loaded femur J Bone Joint Surg [Am] 60:75, 1978 9. Skinner HB, Kilgus DJ, Keyak J, Shimaoka EE, Kim AS, Tipton JS: Correlation of computed finite element stresses to bone density after remodeling around cementless femoral implants. Clin Orthop 305:178, 1994 10. Baldurrson H, Egund N, Hansson LI, Selvik G: Instability and wear of total hip prosthesis determined with roentgen stereophotogrammetry. Arch Orthop Trauma Surg 95:257, 1979 i 1. Capello WN, Sallay PI, Feinberg JR: Omniflex modular femoral component: two to five years follow-up. Clin Orthop 298:54, 1994

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12. Harrington IJ, Tountas AA, Cameron HU: Femoral fracture associated with the Moore's prosthesis. Injury 11:23, 1979 13. Jensen JS, Retpen JB: Failures with the Judet noncem e n t e d total hip. Acta Orthop Scand 58:23, 1987 14. Schwartz Jr JT, Mayer JG, Engh CA: Femoral fracture during n o n c e m e n t e d total hip arthroplasty. J Bone Joint Surg [Am] 71:1135, 1989 15. Jasty M, Bragdon CR, Rubash H, Schutzer SF, Haire T, Harris W: Unrecognised femoral fractures during cementless total hip arthroplasty in the dog and their effect on bone ingrowth. J Arthroplasty 7:501, 1992 16. Martell JM, Pierson RHI, Jacobs JJ et al: Primary total hip replacement with a cementless titanium fiber metal coated prostheses. J Bone Joint Surg [Am] 75:554, 1993. 17. Kavanagh BF, Ilstrup DM, Fitzgerald MH: Uncem e n t e d PCA total hip replacement: 2 years results. Orthop Rev 18(suppl):39, 1989

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18. Mj6berg B, Selvik G, Hansson LI et al: Mechanical loosening of total hip prosthesis a radiographic and roentgen-stereophotogrammetric study. J Bone Joint Surg [Br] 68:770, 1986 19. W y k m a n A, Lundberg A: Subsidence of porous coated noncemented femoral components in total hip arthroplasty: a roentgen stereophotogrammetric analysis. J Arthroplast 7:197, 1992 20. Walker PS, Mai SF, Cobb AG, Bentley G: Prediction of clinical outcome of THR from migration measurements on standard radiographs. J Bone Joint Surg [Br] 77:705, 1995 21. Schutzer SE Grady-Benson J, Jasty M, O'Connor DO, Bragadon C, Harris WH: Influence of intraoperative femoral fractures and cerclage wiring on bone ingrowth into canine porous-coated femoral components. J Arthroplasty 10:823, 1995 22. Engh CA, Massin P: Cementless total hip arthroplasty using the anatomic medullary system: results using a suvivorship analysis. Clin Orthop 249:141, 1989