74.BJRBJR0010.1302/2046-3758.74.BJR-2017-0331 research-article2018 Follow us @BoneJointRes Freely available online OPEN ACCESS BJR SYSTEMATIC REVIEW A systematic review of surgical methods to restore articular cartilage in the hip W. E. Hotham, This systematic review examines the current literature regarding surgical techniques for A. Malviya restoring articular cartilage in the hip, from the older microfracture techniques involving perforation to the subchondral bone, to adaptations of this technique using nanofractures Newcastle University, and scaffolds. This review discusses the autologous and allograft transfer systems and the Newcastle Upon Tyne, autologous matrix-induced chondrogenesis (AMIC) technique, as well as a summary of the United Kingdom previously discussed techniques, which could become common practice for restoring articu- lar cartilage, thus reducing the need for total hip arthroplasty. Using the British Medical Jour- nal Grading of Recommendations, Assessment, Development and Evaluation (BMJ GRADE) system and Grade system. Comparison of the studies discussed shows that microfracture has the greatest quantity and quality of research, whereas the newer AMIC technique requires more research, but shows promise. Cite this article: Bone Joint Res 2018;7:336–342. Keywords: Hip, Cartilage regeneration, Surgical Article focus different methods especially in regards to This article focuses on the different surgi- microfracture. The longevity of the studies cal methods available to restore articular is of benefit as they allow us to see long cartilage in hips. term benefits of the techniques. This article shows what method appears There are some studies with short follow to be best for restoring articular cartilage up periods and small cohort sizes. These and our reasons for it. This is backed up may mask some pitfalls in their techniques, by a full literature review showing the dif- especially when evaluating the long-term ferent clinical trials that have been done success of the technique in question. regarding the techniques. There are different scoring systems used Finally we highlight where research should to measure the efficacy of the studies. now be aimed. This can lead some difficulty in compar- ing different studies and techniques Key messages against each other. There is an abundance of research into the microfracture technique but they all Introduction show the same floor. There is some relief The cause of symptomatic hip pain in the W. E. Hotham, BSc (Hons), Student, Newcastle University , of symptoms however this only lasts a young population is commonly due to a Newcastle, UK. short duration in time due to type 1 col- labral tear.1 These tears often occur anteri- A. Malviya, PhD, FRCS (T&O), lagen formation not the natural type 2. orly, and are frequently associated with chon- MS, MSc, MRCS, Consultant Orthopaedic Surgeon, Wansbeck The work done using the AMIC shows it dral lesions and early-onset osteoarthritis General Hospital, Northumbria to have great potential. (OA) secondary to impingement disorders.2,3 Healthcare NHS Foundation Trust, The potential of coupling cell therapies to Inheritance patterns have been identified in Ashington, UK. scaffolds has strong potential and could OA upon examination of concordance rates Correspondence should be sent to W. E. Hotham; be a potential line of enquiry. between monozygotic (MZ) and dizygotic email: [email protected] (DZ) twins, and show increased incidence in doi: 10.1302/2046-3758.75.BJR- Strengths and limitations MZ. OA does not simply result from exposure 2017-0331 There are several studies with long follow to environmental factors such as body 2 Bone Joint Res 2018;7:336–342. up periods and large cohort sizes for weight. Similarly, genetic influence has been VOL. 7, NO. 5, MAY 2018 336 337 W. E. HOTHAM, A. MALVIYA noted in impingement disorders of the hip.4 Whether this Following this, McGill et al8 undertook a two-year information can be used in the future to identify and treat follow-up of 21 hip microfracture surgeries. This study these problems early, remains to be seen. did not investigate the success of the surgery; rather, it Once chondral cartilage is lost, there are few cur- showed surgery was technically possible without causing rent surgical measures available that aim to restore the harm to the patient. These data were unpublished. cartilage, making the need for total hip arthroplasty Philippon et al12 showed that in a 20-month period, (THA) seem inevitable. However, arthroscopic tech- the mean fill of acetabular chondral lesions was 91%, niques have evolved, allowing us to perform interven- however, the scope of results between patients varied tions which initially would not be possible because from 25% to 100%. Concerns were that there was no of technical limitations. The procedures available comparison group, the ages were not stated, and there range from microfracture to cartilage scaffold. The last were only nine participants. review on hip cartilage regeneration was performed in Through observations in mammalian models, microf- 2012.5 We therefore felt the need to perform an update racture of the acetabulum leads to an increase in type II of the literature to see if the results favour any one collagen micro RNA (mRNA) after six weeks. This looked particular method. promising, however, mRNA does not always lead to more We found several gaps in the literature regarding sur- protein, and there was no significant increase in other gical techniques to manage chondral defects during Extra Cellular Matrix (ECM) products such as aggrecan.11 arthroscopy, and this provided the starting point for our Unfortunately, an animal study has shown strong evi- review: to outline and evaluate the gaps in the literature dence for bone cyst formation.10 Bone cysts are common using the Grade6 guidelines. markers for OA.13 However, we found no documented human cases, possibly because the cyst formation is Materials and Methods being accredited to the chondral lesion rather than to the On 26 June 2017, we performed a PubMed search using surgery. the keywords ‘hip’, ‘cartilage’, ‘regeneration’ and ‘sur- The effectiveness of microfracture is highly disputed. gery’. This returned 115 papers, but only 14 were McDonald’s14 case control study of young male athletes deemed relevant (review papers and those referring to returning to sport following microfracture surgery the knee were excluded). These 14 papers were evalu- showed no significant improvements over those who did ated using the Grade6 guidelines. The GRADE system is not undergo surgery (77% vs 88%).14 Of concern with used as a method to grade studies against each other in McDonald’s case control study, is the patient group: they terms of methodological floors, generalizability to the are male, young and active, and thus have better recov- public, effectiveness of treatment, and consistency with ery time with or without the surgery due to the rest other studies, and have also devised a system of catego- period. rizing studies according to the level of evidence (from 1++ An important study by Byrd and Jones15 examined 220 to 4) and classification of recommendation (A to D) patients undergoing hip arthroscopy for CAM impinge- (Tables I and II). ment. All patients showed improvements, however, Surgical techniques: microfracture. This is the oldest there was no difference between those undergoing technique for cartilage restoration in weight-bearing microfracture surgery and those not. Despite the large regions of the joint, performed in over 1800 patients.7 study population, only 58 hips underwent microfracture Unfortunately, only a small proportion of these were in surgery. There was no loss to follow-up. Nevertheless, the hip and these were on lesions smaller than 4 cm2.7,8 given the inclusion of a comparison group, this study This surgery is low in complexity with a low risk of associ- holds the advantage over others. ated patient morbidity.7 Haviv’s16 similar study involved 381 patients with ace- The operation involves specially designed awls perfo- tabular chondral defects, of whom only 29 had microf- rating the subchondral bone of the femoral head or the racture surgery. These patients did have a mean acetabulum. The perforations are made as close together improvement in modified Harris Hip Scores (mHHS) and as possible, while ensuring they do not infringe and ‘rup- Non-Arthritic Hip Scores, however, patient scores were ture into’ each other. The perforations are normally 2 not statistically significant. Perhaps with a larger study mm deep, as deeper holes show no significant effect on and a smaller loss to follow-up, there could be a statisti- cartilage production, but may reduce the integrity of the cally significant improvement. These large studies, show- subchondral bone and cause osteocyte necrosis.7-10 ing little impact and possible bone cyst formation, explain Immediately, a blood clot rich in stem cells is formed, why microfracture is not currently a common surgical leading to fibrocartilage production, not the original hya- method. line.11 Fibrocartilage is less flexible, and may explain why There is strong evidence for this technique above, and it pain relief following surgery is limited to approximately is used commonly in other joints. We would recommend five years.8 using this technique on chondral lesions of size no greater BONE & JOINT RESEARCH A SYSTEMATIC REVIEW OF SURGICAL METHODS TO RESTORE ARTICULAR CARTILAGE IN THE HIP 338 Table I. Levels of evidence Level