Conventional cemented acetabular components are reported to have a high rate of failure when implanted into previously irradiated bone. We recommend the use of a cemented reconstruction with the addition of an acetabular reinforcement cross to improve fixation.
We reviewed a cohort of 45 patients (49 hips) who had undergone irradiation of the pelvis and a cemented total hip arthroplasty (THA) with an acetabular reinforcement cross. All hips had received a minimum dose of 30 Gray (Gy) to treat a primary nearby tumour or metastasis. The median dose of radiation was 50 Gy (Q1 to Q3: 45 to 60; mean: 49.57, 32 to 72).
The mean follow-up after THA was 51 months (17 to 137). The cumulative probability of revision of the acetabular component for a mechanical reason was 0% (0 to 0%) at 24 months, 2.9% (0.2 to 13.3%) at 60 months and 2.9% (0.2% to 13.3%) at 120 months, respectively. One hip was revised for mechanical failure and three for infection.
Cemented acetabular components with a reinforcement cross provide good medium-term fixation after pelvic irradiation. These patients are at a higher risk of developing infection of their THA.
Cite this article: Bone Joint J 2015;97-B:177–84.
Pelvic irradiation is commonly used in the treatment of genitourinary and gastro--intestinal malignancies and for metastatic bone disease.1 Radiation injuries occur in mature bone in a dose-dependent manner, from 30 gray (Gy) upward.2,3 Radiotherapy causes injury to blood vessels with occlusion of the microcirculation. It also causes a reduction in the number of osteoblasts and is associated with decreased collagen production and alkaline phosphatase activity which play a major role in mineralisation.4 These injuries range in severity from radiation osteitis through stress fractures and avascular osteonecrosis to pathological fractures: their prevalence increases with the passage of time.5 Degenerative arthritis is also accelerated by radiotherapy.6 Given the improvement in survivorship of patients with cancer, the effects of irradiation of the hip joint are becoming more common and are encountered by all hip surgeons.7
Conventional total hip arthroplasty (THA) after radiotherapy is associated with frequent and early failure of the acetabular component. The reported rates of loosening, between two and six years post-operatively, range from 44% to 52% for both cemented and uncemented components8-10 (Table I). The reasons for the failure of cemented acetabular components include inadequate interdigitation of the cement with dense and sclerotic bone and insufficient trabecular support over time. Some authors have used a reinforcement device to reduce the rate of failure with moderate success.8-10 The failure of uncemented components is due to the difficulty in achieving primary stability in bone that is poorly elastic, has decreased capability for osseous integration and has limited ability to remodel over time.9
|Authors (year of publication)||Number of hips||Mean radiation dose (cGy)||Mean time between radiation and THA (months) (range)||Type of acetabular reinforcement||Acetabular fixation||Mean follow-up (mths) (range)||Number of acetabular aseptic loosening (%)||Number of prosthetic joint infection (%)||Number of patients revised (%)||Note|
|Massin and Duparc10||42 (49)* / 16 (22)*||5500||73||No / Müller, Eichler and Burch rings||Cemented / Cemented||69 (6 to 240) / 40 (6 to 132)||22 (52) / 3 (19)||0 / 2 (12)||20 (48) / 2 (12)||Predominantly gynaecological malignancies|
|Jacobs et al9||9||4783||77||No||Non-cemented||37 (17 to 78)||4 (44)||NR||2 (22)||Predominantly gynaecological malignancies|
|Cho et al8||14 / 4||5250 / 5250||68 (7 to 130) / 68 (7 to 130)||No / Müller Ring||Non-cemented / Cemented||58 (20 to 139) / 34 (20 to 41)||7 (50) / 2 (50)||NR / NR||6 (42) / 1 (25)||All cervical cancer|
|Kim et al27||58||7065||67||No||Non-cemented||58 (24 to 90)||0||1 (2)||3 (5)||All prostate -cancer|
|Joglekar et al12||22 (34)*||6300||90 (2 to 800)||Trabecular metal||Non-cemented||78 (57 to 116)||0||0||0||Variety of -malignancies|
|Present series||49||5000||57 (3 to 372)||Kerboull Cross||Cemented||51 (17 to 137)||1 (2)||3 (6)||4 (8)||Variety of -malignancy|
*number of hips (N) included in the initial cohort before exclusions cGy,10-2 Gray; THA, total hip arthroplasty; NR, not reported
In order to reduce the risk of failure of the acetabular component, we advocate the use of a cemented reconstruction with the addition of a Kerboull reinforcement cross (CMK, Lépine, Genay, France; CMK, Biomet; Valence, France). This device has both rigidity and elasticity.13,14 It fits the acetabulum adequately, shares the load transmitted through the acetabulum, and overcomes the loss of elasticity of the inert irradiated bone matrix. We hypothesised that it overcomes the decreased mechanical properties of irradiated bone and achieves good medium-term fixation.
This retrospective study evaluates the cumulative incidence of failure of reconstruction using a cemented acetabular component and a reinforcement cross in a group of patients who developed complications following irradiation of the pelvis as a result of the treatment of a nearby cancer.
Materials and methods
The study was undertaken between 1 January 1995 and 31 December 2011. All consecutive operations were performed at two tertiary centres which specialise in joint reconstruction and in the treatment of bone tumours (Cochin Hospital Paris, France and Edouard Herriot Hospital Lyon, France). All patients were operated on by senior surgeons or by fellows with significant experience in joint reconstruction. Patients were included in the study if they had undergone pelvic irradiation with a minimum dose of 30 Gy and THA was undertaken using a cemented acetabular reconstruction and a Kerboull reinforcement cross (CMK, Lépine, Genay, France; CMK, Biomet; Valence, France); were aged > 18 years and had follow-up of > 24 months.
The indications for THA were: symptomatic radiation osteitis causing incapacity (n = 20; 41%), symptomatic avascular necrosis of the femoral head (n = 17; 35%) and pathological fracture of the femoral neck or acetabulum (n = 12; 24%) (Figs 1 and 2). Radiation osteitis was confirmed radiologically before the operation (Fig. 1) or at the time of the acetabular reaming by finding alternating zones of bleeding bone and dense sclerotic bone. A total of 45 patients (49 hips) met these inclusion criteria. There were 28 women (29 hips: 59%) and 17 men (20 hips: 41%) with a mean age of 69 years (19 to 85). Two hips (4%) were American Society of Anesthesiology (ASA) grade 1;15 24 (53%) grade 2; 18 (40%) grade 3, and one (2%) grade 4. The median pre-operative Postel Merle d’Aubigné (PMA) score was 9 (Q1-Q3: 7 to 11).16 The median dose of radiation was 50 Gy (Q1 to Q3: 45 to 60;) with a median time from radiation to THA of 27 months (Q1 to Q3: 10 to 91;). Most patients underwent pelvic radiotherapy for prostate cancer; uterine cancer and metastasis from breast cancer to the femoral neck (n = 8; 18%) (Table II).
Figs. 1a - 1b
Figs. 2a - 2b
|Age/sex||Malignancy||Radiation dose||Radiation to THA||Follow-up||ASA score||Patient status|
|77/female||Breast cancer metastasis||40||16||22||2||Deceased|
|56/female||Breast cancer metastasis||46||13||21||2||Deceased|
|41/female||Breast cancer metastasis||48||6||32||3||Deceased|
|49/female||Breast cancer metastasis||40||6||21||2||Deceased|
|43/female||Breast cancer metastasis||40||24||25||3||Deceased|
|76/female||Breast cancer metastasis||40||10||22||2||Deceased|
|50/female||Breast cancer metastasis||40||9||25||2||Deceased|
|38/female||Breast cancer metastasis||45||9||18||2||Ill|
|ASA, American Society of Anesthesiology; THA, total hip arthroplasty|
The hip was approached through a partial anterior hemi-trochanteric osteotomy in 24 patients (49%), a trochanteric osteotomy in 11 (23%), an anterolateral approach in nine (18%) and a posterolateral approach in five patients (10%). The surgical approach to the hip was at the discretion of the surgeon. The Kerboull reinforcement cross (CMK, Lépine, Genay, France; CMK, Biomet; Valence, France) has a hook which is placed at the inferior margin of the acetabulum (Fig. 3). The superior arm is positioned against the roof of the acetabulum and fixed with between one and four 5 mm screws angled at 45° towards the sacro-iliac joint (Figs 1 and 2). Usually, because no graft was used, two screws were sufficient. The bearing surface used was metal on an all-polyethylene component (MKIII, Howmedica, Herouville Saint-Clair, France; SN, Smith & Nephew, Le Mans, France), among which there were ten (20%) dual mobility components (SATURNE, Amplitude, Valence, France).
Figs. 3a - 3d
There were eight (16%) uncemented femoral components (INTEGRALE, Amplitude, Valence, France), and 41 (84%) cemented components (5 MKIII Howmedica, Herouville Saint-Clair, France; 9 CMK, Smith & Nephew, Le Mans, France; 6 GENERIC, Amplitude, Valence, France; INITIALE, 5 Amplitude, Valence, France; 16 OCEANE, Tornier, Montbonnot Saint-Martin, France). All patients received six weeks of thrombo-embolic prophylaxis with low molecular weight heparin. Post-operative rehabilitation was the same as that for a standard THA. Patients were mobilised fully weight-bearing immediately after the operation unless a trochanteric osteotomy had been performed.
The primary outcome measure was the cumulative incidence of revision for mechanical failure of the acetabular component. The time to revision was the interval between the index operation and revision, if undertaken. Patients who died during follow-up or underwent revision for another reason were treated as competing events; the observations of patients for whom the event of interest, or a competing event, were not seen during follow-up were censored. Revision for mechanical reasons was defined as revision of the acetabular component for loosening, fracture, instability or wear.
Secondary outcomes included the cumulative incidence of revision of the acetabular component for any reason; the Postel Merle d’Aubigné (PMA) score;16 the radiological evaluation of loosening according to De Lee and Charnley17 and Grüen et al18 and patient survival. Patients alive at the time of the study were contacted by the authors by telephone and/or had a clinical review on a voluntary basis.
The survival of the patients was estimated using the Kaplan–Meier method. The cumulative incidence function was used to estimate the incidences in the presence of competing risks.19-21 Survival probabilities are given with 95% confidence intervals (CI). Categorical variables are reported with counts and proportions and continuous variables with median, and quartile values. All computations were made with R.22 The study had ethical approval.
The mean follow-up was 51 months (17 to 137). A total of 19 patients (42%) died during follow up. Patient survival at 24, 60 and 120 months was 71% (95% CI 0.57 to 0.86), 52% (95% CI 0.37 to 0.71), and 41% (95% CI% 0.26 to 0.65), respectively (Fig. 4). At final follow-up, 18 patients (40%) were alive and free of disease and eight (18%) were alive with disease.
The median PMA score was 15 (Q1 to Q3 14 to 17) at final follow-up with a median score of 5 for hip mobility (Q1 to Q2 5 to 6), 6 for pain (Q1 to Q2 5 to 6) and 5 for walking (Q1 to Q2 4 to 6). Patients who did not undergo revision showed no sign of migration of the components or of progressive lucency. A stable lucency was found around eight acetabular components (16%) and around 16 femoral components (33%). A total of five hips (10%) showed heterotopic ossification: two (4%) grade 1, one (2%) grade 2 and two (4%) grade 3.
The cumulative probability of revision for mechanical reasons at 12, 24, 60 and 120 months was 0% (0% to 0%), 0% (0% to 0%), 2.9% (0.2% to 13.3%), and 2.9% (0.2% to 13.3%), respectively (Fig. 5). One patient underwent a -revision for acetabular loosening 34 months post-operatively (Fig. 6). This 56 year-old woman had a total radiation dose of 60 Gy for a uterine cancer 12 years before her hip surgery. At final follow-up (38 months) she was doing well with a PMA score of 14 (mobility = 6, pain = 4, walk = 4) and no radiological or clinical signs of loosening.
The cumulative probability of revision of the acetabular component for any reason at 12, 24, 60 and 120 months was 2.2% (0.2% to 10.3%), 2.2% (0.2% to 10.3%), 8.1% (2% to 20%), and 20.2% (2.9% to 48.6%), respectively (Fig. 5). Three (6%) patients underwent revision for infection.
A 70-year-old man treated for cancer of the bladder by surgery and irradiation with 50 Gy developed an Escherichia coli (E. coli) periprosthetic joint infection 18 months post-operatively. He developed a radiation-induced rectovesical fistula after the THA and underwent a two-stage revision to allow the fistula to heal before the second stage. At final follow-up (9.4 years) he was doing well with a PMA score of 15 (mobility = 6, pain = 5, walk = 4).
A 71-year-old woman who had undergone surgery for a soft-tissue sarcoma of the buttock with resection of a considerable amount of muscle followed by irradiation with 30 Gy developed a periprosthetic infection with a methicillin sensitive Staphylococcus caprae nine months after THA. She underwent a one-stage revision and was doing poorly at final follow-up (9.5 years) with a PMA score at 6 (mobility = 3, pain = 2, walk = 1).
The last patient was an 81-year-old woman who underwent surgery and irradiation with 68 Gy for uterine cancer. She developed ureteric stenosis with frequent pyelonephritis and a periprosthetic infection with E. coli 35 months after THA. She underwent a one-stage revision after surgery for stenosis of the ureter and was doing well at final follow-up (40 months) with a PMA score of 14 (mobility = 5, pain = 6, walk = 3). There has been no recurrent infection in any of these three patients and none has required further revision.
We recommend the use of a cemented reconstruction with the addition of an acetabular reinforcement cross to improve the medium-term results after THA in patients who have received radiation to the pelvis.
At ten years, we report a cumulative probability of revision for mechanical failure of 3%. Massin et al10 in a retrospective study which included 42 THAs, reported a rate of acetabular failure for mechanical reasons of 52% at six years using a standard cemented THA for an irradiated hip. Cho et al8 in a retrospective series of 18 patients, reported a failure rate of 50% at a mean follow-up of 58 months (Table I). We suspect that the reasons for these poor results include both inadequate cement interdigitation at the time of the procedure and a structure of bone which was, or eventually became, unable to withstand the stress around the implant.
Radiation osteitis is characterised by mixed areas of dense sclerotic bone together with zones of focal demineralisation.4 Previous in vitro studies have shown that the penetration of cement is compromised when the bone is less porous.23,24 Therefore, the abnormal bone structure seen in patients after radiation is likely to reduce the interdigitation between cement and bone. Moreover, damage to the microvasculature of the bone and cells leave a bone matrix with a reduced capacity to remodel.25 The resultant sclerotic structure is prone to microfracture.6,26 Because the bone cannot heal, the forces around the implant are transmitted through an interface with an increasingly incompetent surface; consequently the stress increases, more microfractures are created, and the cycle continues until the implant fails. The effects of irradiation also increase with the passage of time.8 Therefore, bone that appears adequate at the time of THA involving bleeding bone without signs of radiation osteitis on imaging studies, may become incompetent after a few years.8
The use of the Kerboull reinforcement cross reduces the risk of implant failure because it decreases the stress applied to the peri-acetabular bone, allows fixation over a large surface area and gives elasticity to the reconstruction.13,14 The inferior hook and the long screws passing through the plate allow transmission of forces to the supra- and infra-acetabular regions where resistance is better.14 Kawanabe et al13 have shown in a finite element analysis that the areas under high stress are the hook and the plate of the Kerboull-type device rather than the outer surface of the cemented acetabular component. With other reinforcement rings the stress is mainly transmitted around the screw holes and to the central part of the outer surface of the acetabular component.13 This may explain why we have seen better results in our series than in those which used other types of reinforcement ring.8,10
Given the poor results of conventional cemented reconstruction, surgeons have looked at uncemented implants as an alternative. Conflicting survival results have been reported.9,27 The proposed reasons for their poor results are the presence of a paucicellular and sclerotic matrix with decreased properties for osseous integration and the progression of cellular damage over time leading to a debonded interface.8 Recently, surgeons have been using trabecular metal implants which have shown better primary stability and bone ingrowth because of their high coefficient of friction and porosity.11,12,28,29 The long-term survival of such uncemented reconstructions has yet to be seen given the potential for the progression of radiation damage over time. Joglekar et al12 reported no direct proof of osseous integration five years post-operatively. We also believe that the benefits of uncemented components are limited in patients in whom the mortality is approximately 50% at five years.8,10
We noted a 6% rate of prosthetic infection. This is unusually high and compares unfavourably with the expected 1% or less after conventional THA.30 In other series it ranges between 0% and 12%8,10 (Table I). These patients are often immunodeficient and present with modifications of their urinary tract microflora resulting in frequent infections which are difficult to treat.31-33 Furthermore, the presence of radiation-induced entero-urinary fistulae, an increased rate of wound fistula and lymphatic stasis increase the risk of implant colonisation10,34,35 These patients should be subject to extra care pre- and post-operatively with repeated mid-stream urine examinations and careful management with prophylactic antibiotics.36 Bacteriological culture of joint fluid obtained at operation may be helpful because septic arthritis in irradiated hips is frequently misdiagnosed as radionecrosis.37
This study has some limitations. First, the size of the series is limited to provide a precise estimate of the rate of revision.38,39 However, it remains the second largest series published to date. A second limitation is the design of the study: it is a non-comparative study and we cannot rule out that the improved survival of this series over non-reinforced cemented acetabular reconstruction is due to chance alone. However, given the mechanical and biophysical backgrounds, previous reports in the literature and the low mechanical failure rate, we believe that our results are significant. A third limitation is that there is no way of determining the extent of radiation injury at the time of surgery. This may be one explanation for the differences in survival reported in the literature. In the present series, we included only patients who had received a minimum of dose of 30 Gy: radiation osteitis was confirmed either radiologically or at the time of reaming of the acetabular bone. Fourthly, all operations were carried out at two centres for hip reconstruction and bone tumour and it cannot be inferred that similar results would be obtained at other centres. However, the surgical technique is straightforward and can be performed as easily as a primary THA. Lastly, although two different acetabular components were used in the study, there was no difference in survival between the two (log rank test, p = 1). The use of a dual mobility cup is increasingly popular: we would recommend its more frequent use in this group of patients with a limited life expectancy.
1 Smithers DW . Radiotherapy and cancer. Postgrad Med J1946;22:127–144. Google Scholar
2 Dalinka MK , EdeikenJ, FinkelsteinJB. Complications of radiation therapy: adult bone. Semin Roentgenol1974;9:29–40. Google Scholar
3 Bragg DG , ShidniaH, ChuFC, HiginbothamNL. The clinical and radiographic aspects of radiation osteitis. Radiology1970;97:103–111. Google Scholar
4 Mitchell MJ , LoganPM. Radiation-induced changes in bone. Radiographics1998;18:1125–1136. Google Scholar
5 Kwon JW , HuhSJ, YoonYC, et al.Pelvic bone complications after radiation therapy of uterine cervical cancer: evaluation with MRI. AJR Am J Roentgenol2008;191:987–994. Google Scholar
6 Phillips TW , RaoDR. Destructive arthropathy of the hip following pelvic irradiation: report of four cases. Can J Surg1989;32:353–357. Google Scholar
7 No authors listed. Center for Disease Control and Prevention. US Cancer Working Group. http://www.cdc.gov (date last accessed 22 February 2014). Google Scholar
8 Cho MR , KwunKW, LeeDH, KimSY, KimJD. Latent period best predicts acetabular cup failure after total hip arthroplasties in radiated hips. Clin Orthop Relat Res2005;438:165–170. Google Scholar
9 Jacobs JJ , KullLR, FreyGA, et al.Early failure of acetabular components inserted without cement after previous pelvic irradiation. J Bone Joint Surg [Am]1995;77-A:1829–1135. Google Scholar
10 Massin P , DuparcJ. Total hip replacement in irradiated hips. A retrospective study of 71 cases. J Bone Joint Surg [Br]1995;77-B:847–852. Google Scholar
11 Bobyn JD , PoggieRA, KrygierJJ, et al.Clinical validation of a structural porous tantalum biomaterial for adult reconstruction. J Bone Joint Surg [Am]2004;86-A(Suppl 2):123–129. Google Scholar
12 Joglekar SB , RosePS, LewallenDG, SimFH. Tantalum acetabular cups provide secure fixation in THA after pelvic irradiation at minimum 5-year follow-up. Clin Orthop Relat Res2012;470:3041–3047. Google Scholar
13 Kawanabe K , AkiyamaH, GotoK, MaenoS, NakamuraT. Load dispersion effects of acetabular reinforcement devices used in revision total hip arthroplasty: a simulation study using finite element analysis. J Arthroplasty2011;26:1061–1066. Google Scholar
14 Kerboull M , HamadoucheM, KerboullL. The Kerboull acetabular reinforcement device in major acetabular reconstructions. Clin Orthop Relat Res2000;378:155–168. Google Scholar
15 No authors listed. New classification of physical status Anesthesiol1963;24:111. Google Scholar
16 Merle D'Aubigne R . Numerical classification of the function of the hip. 1970 Rev Chir Orthop Reparatrice Appar Mot1990;76-6:371–374 (In French). Google Scholar
17 DeLee JG , CharnleyJ. Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop Relat Res1976;121:20–32. Google Scholar
18 Gruen TA , McNeiceGM, AmstutzHC. “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop Relat Res1979;141:17–27. Google Scholar
19 Biau DJ , HamadoucheM. Estimating implant survival in the presence of competing risks. Int Orthop2011;35:151–155. Google Scholar
20 Biau DJ , LatoucheA, PorcherR. Competing events influence estimated survival probability: when is Kaplan-Meier analysis appropriate?Clin Orthop Relat Res2007;462:229–233. Google Scholar
21 Prentice RL , KalbfleischJD, PetersonAV Jr, et al.The analysis of failure times in the presence of competing risks. Biometrics1978;34:541–554. Google Scholar
22 Dean CB , NielsenJD. Generalized linear mixed models: a review and some extensions. Lifetime Data Anal2007;13:497–512. Google Scholar
23 Markolf KL , AmstutzHC. Penetration and flow of acrylic bone cement. Clin Orthop Relat Res1976;121:99–102. Google Scholar
24 Noble PC , SwartsE. Penetration of acrylic bone cements into cancellous bone. Acta Orthop Scand1983;54:566–573. Google Scholar
25 Pelker RR , FriedlaenderGE. The Nicolas Andry Award-1995. Fracture healing. Radiation induced alterations. Clin Orthop Relat Res1997;341:267–282. Google Scholar
26 Barth HD , ZimmermannEA, SchaibleE, et al.Characterization of the effects of x-ray irradiation on the hierarchical structure and mechanical properties of human cortical bone. Biomaterials2011;32:8892–8904. Google Scholar
27 Kim K , KleinGR, SleeperJ, et al.Uncemented total hip arthroplasty in patients with a history of pelvic irradiation for prostate cancer. J Bone Joint Surg [Am]2007;89-A:798–805. Google Scholar
28 Bobyn JD , StackpoolGJ, HackingSA, TanzerM, KrygierJJ. Characteristics of bone ingrowth and interface mechanics of a new porous tantalum biomaterial. J Bone Joint Surg [Br]1999;81-B:907–914. Google Scholar
29 Abolghasemian M , TangsatapornS, SternheimA. Combined trabecular metal acetabular shell and augment for acetabular revision with substantial bone loss: a mid-term review. Bone Joint J2013;95-B:166–172. Google Scholar
30 Hailer NP , GarellickG, KarrholmJ. Uncemented and cemented primary total hip arthroplasty in the Swedish Hip Arthroplasty Register. Acta Orthop2010;81:34–41. Google Scholar
31 Bessell EM , Granville-WhiteM. The effect of prophylactic trimethoprim on aerobic urinary tract infection during pelvic radiotherapy and the incidence of infections due to fastidious or anaerobic organisms. Clin Oncol1994;6:116–120. Google Scholar
32 Prasad KN , PradhanS, DattaNR. Urinary tract infection in patients of gynecological malignancies undergoing external pelvic radiotherapy. Gynecol Oncol1995;57:380–382. Google Scholar
33 Wisplinghoff H , SeifertH, WenzelRP, EdmondMB. Current trends in the epidemiology of nosocomial bloodstream infections in patients with hematological malignancies and solid neoplasms in hospitals in the United States. Clin Infect Dis2003;36:1103–1110. Google Scholar
34 Johnson JT , BloomerWD. Effect of prior radiotherapy on postsurgical wound infection. Head Neck1989;11:132–136. Google Scholar
35 Passick J . Hirsh DM. Recurrent infection of a total hip arthroplasty associated with radiation-induced ulcerative colitis: a case report. J Arthroplasty1989;4:87–90. Google Scholar
36 Bialas I , BessellEM, SokalM, SlackR. A prospective study of urinary tract infection during pelvic radiotherapy. Radiother Oncol1989;16:305–309. Google Scholar
37 Yang SH , YangRS, TsaiCL. Septic arthritis of the hip joint in cervical cancer patients after radiotherapy: three case reports. J Orthop Surg (Hong Kong)2001;9:41–45. Google Scholar
38 Biau DJ , KernéisS, PorcherR. Statistics in brief: the importance of sample size in the planning and interpretation of medical research. Clin Orthop Relat Res2008;466:2282–2288. Google Scholar
39 Biau DJ . In brief: Standard deviation and standard error. Clin Orthop Relat Res2011;469:2661–2664. Google Scholar
A. Felden: Acquisition of data; Analysis and interpretation of data; Drafting the article; Final approval of the version to be published.
G. Vaz: Acquisition of data; Drafting the article; Final approval of the version to be published.
S. Kreps: Substantial contributions to conception and design; Revising it critically for important intellectual content; Final approval of the version to be published.
P. Anract: Substantial contributions to conception and design; Revising it critically for important intellectual content; Final approval of the version to be published.
M. Hamadouche: Substantial contributions to conception and design; Revising it critically for important intellectual content; Final approval of the version to be published.
D. J. Biau: Acquisition of data; Analysis and interpretation of data; Drafting the article; Final approval of the version to be published; Revising it critically for important intellectual content.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
This article was primary edited by A. Ross and first proof edited by J. Scott.