Abstract
We systematically reviewed the published literature on the complications of closing wedge high tibial osteotomy for the treatment of unicompartmental osteoarthritis of the knee. Publications were identified using the Cochrane Library, MEDLINE, EMBASE and CINAHL databases up to February 2012. We assessed randomised (RCTs), controlled group clinical (CCTs) trials, case series in publications associated with closing wedge osteotomy of the tibia in patients with osteoarthritis of the knee and finally a Cochrane review. Many of these trials included comparative studies (opening wedge versus closing wedge) and there was heterogeneity in the studies that prevented pooling of the results.
Introduction
High tibial osteotomy (HTO) remains a popular treatment method in unicompartmental (medial) osteoarthritis of the knee. There are three main procedures for high tibial osteotomy (HTO); lateral closing wedge, medial opening wedge and dome osteo-tomy.1 The HTO closing wedge was first described by Jackson and Waugh2 in 1961 and then further popularised by Coventry in 1965.3 The function of these osteotomies is to correct the mechanical axis and off-load force from the medial compartment onto the less affected, lateral part of the joint. In the closing wedge procedure, this is achieved by performing an osteotomy above the tibial tubercle and removing an appropriate wedge of bone. Mechanical axis is therefore shifted laterally, theoretically improving function and pain scores.
An in-depth comparison between both closing- and open-wedge osteotomy is beyond the remit of this paper, however, the advantages are thought to be a shorter time to begin weight-bearing and to healing, better control of maintaining posterior tibial slope and less patella baja. In addition there is no need for bone graft or synthetic bone substitute.
Of the papers reviewed, pooled complication rate ranges between 5%4 and 34%5 with a mean of 15.2%.6-9 The complications are listed in Table I and discussed individually at greater length below.
Table I
Mean rates of complications from the reviewed articles
| Complication | Rate (%) |
|---|---|
| Infection | 4.7 |
| Thromboembolic event | 3.1 |
| Fractures (opposite cortex and intra-articular) | 63 |
| Neurovascular complications | 9.8 |
| Under-correction/recurrence of deformity | N/A* |
| Conversion to total knee replacement | N/A* |
| Nonunion | 2.2 |
| Delayed union | 6.6 |
-
* N/A, not available (the amount of correction depends on initial severity, and conversions are time-dependent). See text for further details
Infection
Reported rates of infection range from 0.8% to 10.4%.5,6,8-10 The majority of these are super-ficial wound infections that can be treated successfully with oral antibiotics. Deep infections are more problematic and may require irrigation and debridement with the use of intra-venous antibiotics. Eradication of deep infection is possible by debridement, intravenous antibiotics and bone grafting.5 Fixation devices should be left in situ if at all possible.
Thromboembolic events
The incidence of deep-vein thrombosis (DVT) ranges from 2% to 5%,5-11 a similar rate to that of major joint replacement. A post-HTO venographic study indicated that the rate of DVT may be as high as 41%,12 but that the vast majority of these thrombi are located distally in the calf with little chance of progression more proximally. Of those few in the proximal veins, only 15% were clinically detectable (with patients complaining of calf pain). Isolated fatal pulmonary emboli have been reported.7,11 The use of a tourniquet did not seem to have any significant effect on the incidence of thromboembolic disease.13
With the above information, the use of a thromboprophylaxis regimen similar to that of a knee arthroplasty may be prudent.12
Fractures
An osteotomy is a controlled fracture. In HTO, a wedge of bone is resected, leaving a hinge of bone on the opposite side that helps to maintain stability. Options for this include leaving the osteotomy 5 mm from the opposite cortex. Two things must occur in the process of angular correction. Plastic deformation occurs in the hinge and microfractures occur in this region of bone as the osteotomy is closed. Propagation of the fracture to the opposite cortex or the intra-articular region is to be avoided. In their series of 44 cases, van Raaij et al14 reported opposite cortex fracture in 36 patients (82%) undergoing closing wedge HTO. The authors state that this complication is ‘not entirely preventable’. The notion that a valgus osteotomy greater than 7° or 8° will inevitably cause an extension fracture is supported by other authors.15-17 Importantly, van Raaij et al14 noted in their cohort of 44 patients that despite the high numbers of medial cortical fractures at one year, they did not cause a recurrence in varus angulation or significant malunion in any case. Of the closing wedge group, the desired angular correction was maintained more often in those cases complicated by fracture than in those without fracture (seven of 18 (39%) versus six of 18 (33%)) than in those without fracture. They postulated that ‘With the closing wedge technique, posteromedial bony remnants may act like a more lateral hinge when closing the wedge, and probably cause fracture and gaping at the medial osteo-tomy site with pronounced valgisation’.14 Despite this, the majority of surgeon aim to leave the posteromedial hinge of bone, as described by Slocum et al.18
An option to maximise the amount of valgus deformation before fracture is to place a drill hole from anterior to posterior. This is positioned 1 cm from the media cortex and 2 cm below the articular cartilage. The authors report the stress relieving hole allows a further 3° of valgus deformation than without one.15
Intra-articular fractures during closing wedge osteo-tomies have a reported incidence of between 0% and 20%.5,7,8,10 This occurs when the osteotomy is too shallow and the medial hinge is too wide, causing excessive resistance during closure of the osteotomy, which can direct the applied force into the joint resulting in an intra-articular fracture. Also, an osteotomy too close to the joint with a resultant thin proximal fragment will offer little resistance to fracture. In general, the width of the medial hinge should be less than the distance from the end of the osteotomy to the joint line.18 It is critical to recognise the occurrence of this complication, as congruity of the articular surface must be preserved. Most intra-articular fractures remain reduced and require no additional fixation.10,18 Assessment can be made with fluoroscopy and/or directly with arthroscopy. Displacement of an intra-articular fracture necessitates reduction and fixation, usually in the form of compression screws.
Nerve injury
The incidence of symptomatic peroneal nerve injury is reported between 3.3% and 11.9%; EMG demonstrates nerve damage in up to 27% of patients.19-21 While many of these are temporary deficits, some report that 50% of those with early peroneal symptoms are left with some permanent deficit.19
Reasons for nerve injury following an HTO include neuro-praxia secondarily to tourniquet use,22 tight bandages/plaster casts,3,23 compartment syndrome21,24 and finally from iatrogenic peroneal nerve palsy.25 While pressures in the compartment do increase (up to 50 mmHg – maximally between the six hour and 24 hour post--operative period) the use of a drain can significantly reduce this complication.21,25
Most authors agree the most frequent cause of nerve injury is iatrogenic damage to the peroneal nerve in particular with the inclusion and location of the fibular osteoto-my.19,26 The extensor hallucis longus is the most affected muscle after HTO. Anatomical studies have confirmed that there are two or three branches to this -muscle.26,27 However, in some instances there may only be the one branch from the deep peroneal nerve,19 and injury to it may cause permanent palsy. This division is typically located 7 mm to 8 mm from the fibular styloid process. Another danger area is the close relationship between the common peroneal nerve and the neck of the fibula. The nerve is on average only 4 mm posterolateral to the fibular head.19 Very proximal detachments of the fibular head may cause tractional pressure on the nerve as it adherent to the periosteum. Around 2.5 mm from the fibular styloid, the nerve divides into its deep and superficial parts and again is at jeopardy.27
As a result, the so-called safe zone of fibular osteotomy is suggested to be at the junction of the middle and distal thirds (around 16 cm distal to the fibular head).19,20,25,27 Osteotomy at this level requires a separate incision.
Vascular injury
Vascular injuries during closing wedge osteotomies are rare occurrences, but case reports of direct damage to the posterior tibial artery (both complete transaction and pseudoaneurysm) are documented.20,25,27 Damage to the anterior tibial artery by poorly placed retractors or osteotomy jigs is a more common occurrence due to its relatively proximal and unprotected origin. Careful use of these instruments is therefore suggested to avoid vascular complications.
Undercorrection/recurrence of deformity
The goal of any HTO for varus malalignment is to shift the load from the medial to the lateral compartment of the knee. Biomechanically, 70% of the load is borne by the medial compartment when the mechanical axis passes through the centre of the knee,28 This load decreases to 50% in 4° of valgus with a further reduction to 40% in 6° of valgus.29
Given these data, most authors recommend an alignment range between 2° and 6° of mechanical valgus.3,30-34 Coventry3 recommended 8° of valgus. Hernigou et al35 achieved best results at between 3° and 6° of mechanical valgus and showed deterioration when correction was > 6°. Fujisawa, Masuhara and Shiomi36 used a different approach, aiming for the mechanical axis to pass through a point 30% to 40% lateral to the midpoint of the knee (the so-called Fujisawa point). Much controversy still remains regarding the ideal mechanical alignment. Many authors aim for an overcorrection of at least 5° with results showing better long-term outcomes.4,37,38
Regardless, pre-operative planning and adherence to that plan may be the key to a better outcome. Therefore the use of jigs and computer navigation may well be the more accurate way to attain the desired goal.39-41 -Ultimately, undercorrection of the HTO is related to higher rates of revision and conversion to total knee replacement (TKR).
Conversion to total knee replacement
Survivorship of the HTO procedure is often measured by the conversion to TKR. There are few large number prospective studies with substantial follow-up. The largest series so far followed a group of 301 knees for a mean of 18 years (minimum of 12 years) after a closing wedge HTO.30 Survival was 85% at 20 years with revision as the endpoint. Knee function was considered satisfactory by 77% of patients. Their population was a younger group than other studies (mean age of 42 years), with an equal gender mix. Their multivariate analysis showed that an age > 50 years and a pre-operative Ahlback grade42 for arthritis of ≥ 3 were predictors of poor outcomes.30
Another large series followed 118 knees for a mean of 16.4 years.31 They reported survivorship of 97.6% (95% confidence interval (CI) 95.0 to 100) at ten years and 90.4% (95% CI 84.1 to 96.7) at 15 years. Their cohort had a mean age of 63, and the Cox’s proportional hazards model gave a relative risk ratio of 1.196 for an age > 65 years. Excellent and good results, as assessed by the Hospital for Special Surgery (HSS) knee score,43 were achieved in 87 knees (73.7%).31 Of the 11 patients (9%) who required conversion to TKR, three had an inadequate angle of correction at one year, one had a hyper-valgus correction and seven had good correction despite poor HSS knee scores. In this study, a pre-operative body mass index > 27.5 kg/m2 and range of movement < 100° were risk factors predicting early failure.31 These results are similar to those from a smaller series also from Japan,32 with a similar patient cohort (four times as many women as men, and a mean age of approximately 60 years).
Other studies demonstrate less successful survivorship. Tang and Henderson33 described a cumulative survival probability of 89.5% at five years, 74.7% at ten years and 66.9% for both 15 and 20 years, based on a cohort of 67 knees with a follow-up between one and 21 years. A similar survivorship is reported by other studies in younger patient cohort.5,34
Most series report a deterioration in both functional outcome and conversion to TKR rates after ten years.3,10,44
The results of TKR after HTO are variable. Some studies have found poor results when compared with primary TKR45-47 and others have found no difference.48-50 Parvizi et al50 have a large series of post-HTO arthroplasties with a 15-year follow-up and revision rate of 92%, but also report a high rate of radiological evidence of tibial loosening but without revision.
Most authors agree that the surgical approach to arthroplasty after any type of HTO is more complex, with time for careful dissection being paramount.51 The presence of scars, patella baja, ligamentous laxity, remaining hardware and fibrosis are all issues that may have to be addressed. The use of a cruciate-sacrificing system is advocated after HTO, as ligamentous instability is thought to attribute to poorer outcomes in those with implants retaining the posterior cruciate ligament.52
Nonunion
The major benefit of the closing wedge over the opening wedge is the lower rates of non- or delayed union. This is because there is good bone apposition and the osteotomy is in compression.2,10,14 Nonetheless, rates of nonunion have been reported between 1% and 5%, with a mean pooled rate of 2.2%.5,8,10,31,32,53 The usual general risk factors for non- or delayed-union must be considered in patient selection i.e. smokers, diabetics, arteriopaths, and those that are non-compliant.
From a surgical point of view it is considered that an osteotomy distal to the tibial tubercle has a higher rate of delayed/ nonunion compared with those made proximal to it (14% versus 3%).53 Treatment options include the use of adjuvants such as BMP, electrical stimulation and distraction osteogenesis.54,55
Summary
The closing wedge high tibial osteotomy remains a relevant treatment option in the option of unicompartmental osteoarthritis. While the criteria for patient choice remain contentious, most authors agree that in a younger patient with varus or flexion deformity of < 15°, no ligamentous instability and no other degenerative changes, a closed HTO may still be a suitable procedure. While the survivorship rates are variable, most authors agree that the levels of analgesia and failure increase after ten years.
1 Amendola A . Unicompartmental osteoarthritis in the active patient: the role of high tibial osteotomy. Arthroscopy2003;19:109–116.CrossrefPubMed Google Scholar
2 Jackson JP , WaughW. Tibial osteotomy for osteoarthritis of the knee. J Bone Joint Surg [Br]1961;43-B:746–751.PubMed Google Scholar
3 Coventry MB . Osteotomy of the upper portion of the tibia for degenerative arthritis of the knee: a preliminary report. J Bone Joint Surg [Am]1965;47-A:984–990. Google Scholar
4 Wu LD , HahneHJ, HassenpflugT. A long-term follow-up of study of high tibial osteotomy for medial compartment osteoarthrosis. Chin J Traumatol2004;7:348–353. Google Scholar
5 Naudie D , BourneRB, RorabeckCH, BourneTJ. Survivorship of the high tibial valgus osteotomy: a 10-to 22-year followup study. Clin Orthop Relat Res1999;367:18–27. Google Scholar
6 Ivarsson I , MyrnertsR, GillquistJ. High tibial osteotomy for medial osteoarthritis of the knee: a 5 to 7 and 11 year follow-up. J Bone Joint Surg [Br]1990;72-B:238–244. Google Scholar
7 Aglietti P , BuzziR, VenaLM, BaldiniA, MondainiA. High tibial osteotomy for medial gonarthrosis: a 10- to 21-year study. J Knee Surg2003;16:21–26. Google Scholar
8 Bettin D , KarbowskiA, SchweringL, MatthiassHH. Time-dependent clinical and roentgenographical results of Coventry high tibial valgisation osteotomy. Arch Orthop Trauma Surg1998;117:53–57.CrossrefPubMed Google Scholar
9 Song EK , SeonJK, ParkSJ, JeongMS. The complications of high tibial osteotomy: closing- versus opening-wedge methods. J Bone Joint Surg [Br]2010;92-B:1245–1252.CrossrefPubMed Google Scholar
10 Sprenger TR , DoerzbacherJF. Tibial osteotomy for the treatment of varus gonioarthrosis: survival and failure analysis to twenty-two years. J Bone Joint Surg [Am]2003;85-A:469–474. Google Scholar
11 Insall JN , JosephDM, MsikaC. High tibial osteotomy for varus gonarthrosis: a long-term follow-up study. J Bone Joint Surg [Am]1984;66-A:1040–1048. Google Scholar
12 Turner RS , GriffithsH, HeatleyFW. The incidence of deep-vein thrombosis after upper tibial osteotomy: a venographic study. J Bone Joint Surg [Br]1993;75-B:942–944. Google Scholar
13 Motycka T , EggerthG, LandsiedlF. The incidence of thrombosis in high tibial osteotomies with and without the use of a tourniquet. Arch Orthop Trauma Surg2000;120:157–159.CrossrefPubMed Google Scholar
14 van Raaij TM , BrouwerRW, de VliegerR, ReijmanM, VerhaarJA. Opposite cortical fracture in high tibial osteotomy: lateral closing compared to the medial opening-wedge technique. Acta Orthop2008;79:508–514.CrossrefPubMed Google Scholar
15 Kessler OC , JacobHA, RomeroJ. Avoidance of medical cortical fracture in high tibial osteotomy: improved technique. Clin Orthop Relat Res2002;395:180–185. Google Scholar
16 Pape D , AdamF, RuppS, SeilR, KohnD. Stability, bone healing and loss of correction after valgus realignment of the tibial head: a roentgen stereometry analysis. Acta Orthop2010;81:193–198. Google Scholar
17 Mathews LS , GoldsteinSA, MalvitzTA, KatzBP, KauferH. Proximal tibial osteotomy: factors that influence the duration of satisfactory function. Clin Orthop Relat Res1998;229:193–200. Google Scholar
18 Slocum DB , LarsonRL, JamesSL, GrenierR. High tibial osteotomy. Clin Orthop Relat Res1974;104:239–243.CrossrefPubMed Google Scholar
19 Aydogdu S , YercanH, SaylamC, SurH. Peroneal nerve dysfunction after high tibial osteotomy: an anatomical cadaver study. Acta Orthop Belg1996;62:152–156. Google Scholar
20 Wootton JR , AshworthMJ, MacLarenCA. Neurological complications of high tibial osteotomy: the fibular osteotomy as a causative factor:a clinical and anatomical study. Ann R Coll Surg Engl1995;77:31–34. Google Scholar
21 Gibson MJ , BarnesMR, AllenMJ, ChanRN. Weakness of foot dorsiflexion and changes in compartment pressures after tibial osteotomy. J Bone Joint Surg [Br]1986;68-B:471–475.CrossrefPubMed Google Scholar
22 Weingarden SI , LouisDL, WaylonisGW. Electromyographic changes in post-meniscectomy patients: role of the pneumatic tourniquet. JAMA1979;241:1248–1250. Google Scholar
23 Devas MB . High tibial osteotomy for arthritis of the knee: a method specially suitable for the elderly. J Bone Joint Surg [Br]1969;51-B:95–99. Google Scholar
24 Bauer T , HardyP, LemoineT, et al.Drop foot after high tibial osteotomy: a prospective study of aetiological factors. Knee Surg Sports Traumatol Arthrosc2005;13:23–33.CrossrefPubMed Google Scholar
25 Curley P , EyresK, BrezinovaV, et al.Common peroneal nerve dysfunction after high tibial osteotomy. J Bone Joint Surg [Br]1990;72-B:405–408.CrossrefPubMed Google Scholar
26 Kirgis A , AlbrechtS. Palsy of the deep peroneal nerve after proximal tibial osteotomy: an anatomical study. J Bone Joint Surg [Am]1992;74-A:1180–1185. Google Scholar
27 Georgoulis AD , MakrisCA, PapageorgiouCD, et al.Nerve and vessel injuries during high tibial osteotomy combined with distal fibular osteotomy: a clinically relevant anatomic study. Knee Surg Sports Traumatol Arthrosc1999;7:15–19.CrossrefPubMed Google Scholar
28 Johnson F , LeitlS, WaughW. The distribution of load across the knee: a comparison of static and dynamic measurements. J Bone Joint Surg [Br]1980;62-B:346–349. Google Scholar
29 Kettelkamp DB , WengerDR, ChaoEY, ThompsonC. Results of proximal tibial osteotomy: the effects of tibiofemoral angle, stance-phase flexion-extension, and medial-plateau force. J Bone Joint Surg [Am]1996;58-A:952–960. Google Scholar
30 Flecher X , ParratteS, AubaniacJM, ArgensonJN. A 12-28-year followup study of closing wedge high tibial osteotomy. Clin Orthop Relat Res2006;452:91–96.CrossrefPubMed Google Scholar
31 Akizuki S , ShibakawaA, TakizawaT, YamazakiI, HoriuchiH. The long-term outcome of high tibial osteotomy: a ten- to 20-year follow-up. J Bone Joint Surg [Br]2008;90-B:592–596.CrossrefPubMed Google Scholar
32 Koshino T , YoshidoT, AraY, SaitoI, SaitoT. Fifteen to twenty-eight years’ follow-up results of high tibial valgus osteotomy for osteoarthritic knee. Knee2004;11:439–444. Google Scholar
33 Tang WC , HendersonIJ. High tibial osteotomy: long term survival analysis and patients’ perspective. Knee2005;12:410–413. Google Scholar
34 Papachristou G , PlessasS, SourlasJ, et al.Deterioration of long-term results following high tibial osteotomy in patients under 60 years of age. Int Orthop2006;30:403–408.CrossrefPubMed Google Scholar
35 Hernigou P , MedevielleD, DebeyreJ, GoutallierD. Proximal tibial osteotomy for osteoarthritis with varus deformity: a ten to thirteen-year follow-up study. J Bone Joint Surg [Am]1987;69-A:332–354. Google Scholar
36 Fujisawa Y , MasuharaK, ShiomiS. The effect of high tibial osteotomy on osteoarthritis of the knee: an arthroscopic study of 54 knee joints. Orthop Clin North Am1979;10:585–608. Google Scholar
37 Pfahler M , LutzC, AnetzbergerH, et al.Long-term results of high tibial osteotomy for medial osteoarthritis of the knee. Acta Chir Belg2003;103:603–606.CrossrefPubMed Google Scholar
38 Myrnerts R . High tibial osteotomy with overcorrection of varus alalignment in medial gonarthrosis. Acta Orthop Scand1980;51:557–560. Google Scholar
39 Keppler P , GebhardF, GrütznerPA, et al.Computer aided high tibial open wedge osteotomy. Injury2004;35(Suppl):SA68–SA78.CrossrefPubMed Google Scholar
40 Wang G , ZhengG, KepplerP, et al.Implementation, accuracy evaluation, and preliminary clinical trial of a CT-free navigation system for high tibial opening wedge osteotomy. Comput Aided Surg2005;10:73–85.CrossrefPubMed Google Scholar
41 Hankemeier S , HufnerT, WangG, et al.Navigated open-wedge high tibial osteotomy: advantages and disadvantages compared to the conventional technique in a cadaver study. Knee Surg Sports Traumatol Arthrosc2006;14:917–921.CrossrefPubMed Google Scholar
42 Ahlbäck S . Osteoarthritis of the knee: a radiographic investigation. Acta Radiol Diagn (Stockh)1968;227(Suppl):7–72. Google Scholar
43 Insall JN , RanawatCS, AgliettiP, ShineJ. A comparison of four models of total knee-replacement prostheses. J Bone Joint Surg [Am]1976;58-A:754–765.CrossrefPubMed Google Scholar
44 Sherman C , CabanelaME. Closing wedge osteotomy of the tibia and the femur in the treatment of gonarthrosis. Int Orthop2010;34:173–184.CrossrefPubMed Google Scholar
45 Katz MM , HungerfordDS, KrackowKA, LennoxDW. Results of total knee arthroplasty after failed proximal tibial osteotomy for osteoarthritis. J Bone Joint Surg [Am]1987;69-A:225–233.PubMed Google Scholar
46 Mont MA , AntonaidesS, KrackowKA, HungerfordDS. Total knee arthroplasty after failed high tibial osteotomy: a comparison with a matched group. Clin Orthop Relat Res1994;299:125–130. Google Scholar
47 Windsor RE , InsallJN, VinceKG. Technical considerations of total knee arthroplasty after proximal tibial osteotomy. J Bone Joint Surg [Am]1988;70-A:547–555.PubMed Google Scholar
48 Haddad FS , BentleyG. Total knee arthroplasty after high tibial osteotomy: a medium-term review. J Arthroplasty2000;15:597–603.CrossrefPubMed Google Scholar
49 Meding JB , KeatingEM, RitterMA, FarisPM. Total knee arthroplasty after high tibial osteotomy: a comparison study in patients who had bilateral total knee replacement. J Bone Joint Surg [Am]2000;82-A:1252–1259. Google Scholar
50 Parvizi J , HanssenAD, SpangehlMJ. Total knee arthroplasty following proximal tibial osteotomy: risk factors for failure. J Bone Joint Surg [Am]2004;86-A:474–479.CrossrefPubMed Google Scholar
51 Whitehead TS , WillitsK, BryantD, GriffinJR, FowlerPJ. Impact of medial opening or lateral closing tibial osteotomy on bone resection and posterior cruciate ligament integrity during knee arthroplasty. J Arthroplasty2009;24:979–989.CrossrefPubMed Google Scholar
52 Akasaki Y , MatsudaS, MiuraH, et al.Total knee arthroplasty following failed high tibial osteotomy: mid-term comparison of posterior cruciate-retaining versus posterior stabilized prosthesis. Knee Surg Sports Traumatol Arthrosc2009;17:795–799.CrossrefPubMed Google Scholar
53 Vainionpää S , LäikeE, KirvesP, TiusanenP. Tibial osteotomy for osteoarthritis of the knee: a five to ten-year follow-up study. J Bone Joint Surg [Am]1981;63-A:938–946. Google Scholar
54 Tsumaki N , KakiuchiM, SasakiJ, OchiT, YoshikawaH. Low-intensity pulsed ultrasound accelerates maturation of callus in patients treated with opening-wedge high tibial osteotomy by hemicallotasis. J Bone Joint Surg [Am]2004;86-A:2399–2405.CrossrefPubMed Google Scholar
55 Rozbruch SR , HerzenbergJE, TetsworthK, TutenHR, PaleyD. Distraction osteogenesis for nonunion after high tibial osteotomy. Clin Orthop Relat Res2002;394:227–235.CrossrefPubMed Google Scholar
Funding statement:
None declared
Author contributions:
A. Atrey: Writing the paper
Z. Morison: Researching papers, Data collection, Data analysis
J. P. W. Waddell: Supervision of the project, Critical revision and editing
T. Tosounidis: Researching papers
J. Tunggal: Writing and editing the paper
ICMJE Conflict of Interest:
None declared
©2012 British Editorial Society of Bone and Joint Surgery. This is an open-access article distributed under the terms of the Creative Commons Attributions licence, which permits unrestricted use, distribution, and reproduction in any medium, but not for commercial gain, provided the original author and source are credited.
