- Email: [email protected]
Histologic Assessment of Acetabular Labrum Healing
Histologic Assessment of Acetabular Labrum Healing Emmanuel A. Audenaert, M.D., Ph.D., Aad A. M. Dhollander, M.D., Ph.D., Ramses G. Forsyth, M.D., Ph.D., Kristoff Corten, M.D., Gust Verbruggen, M.D., Ph.D., and Christophe Pattyn, M.D., Ph.D.
Purpose: The purpose of this study was to histologically examine the human healing response of arthroscopically repaired acetabular labrum tears. Methods: Biopsy specimens were retrieved from 6 patients during total hip arthroplasty after clinical failure of the index arthroscopic procedure. All patients were diagnosed as having femoroacetabular impingement with a concomitant labral tear. In all cases severe chondral damage was observed during arthroscopy (Beck grades 3 to 4). Despite successful technical repair of the labral tear, chondral damage in these patients was so advanced that the clinical progress after the procedure was unsatisfactory and arthroplasty of the joint was required. Biopsy specimens of the repaired acetabular labra were harvested during the arthroplasty surgery and processed for standard histologic evaluation. Results: Macroscopically and histologically, all repaired labra kept their triangular shape more or less and appeared to have healed. All harvested biopsy specimens displayed a typical fibrocartilaginous appearance with limited vascular supply. Calcifications were present in only 1 biopsy specimen. In 3 cases neovascularization of the labral tissue was noticed in the proximity of the sutures. In the superficial and deep parts of the labral body, small clefts were observed in all cases. Conclusions: In this study the histologic aspects of arthroscopically repaired human labral tears were addressed. It was shown that human labral tears show healing potential after surgical repair. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of the repaired structures were noticed in all cases. Level of Evidence: Level IV, therapeutic case series.
H
ip arthroscopy has evolved from an experimental and mainly diagnostic tool to a standard and effective surgical procedure for the diagnosis and
From the Department of Orthopaedic Surgery and Traumatology (E.A.A., A.A.M.D., C.P.), N. Goormaghtigh Institute of Pathology (R.G.F.), and Laboratory of Connective Tissue Biology, Department of Rheumatology (A.A.M.D., G.V.), Ghent University Hospital, Ghent; Department of Orthopaedics, AZ Groeninge (E.A.A.), Kortrijk; and Department of Orthopaedics (K.C.), University Hospitals Leuven, Pellenberg, Belgium. E.A.A. and A.A.M.D. have contributed equally to this article and share first authorship. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received November 30, 2011; accepted June 4, 2012. Address correspondence to Aad A. M. Dhollander, M.D., Ph.D., Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, De Pintelaan 185 (P5), 9000 Ghent, Belgium. E-mail: [email protected] © 2012 by the Arthroscopy Association of North America 0749-8063/11795/$36.00 http://dx.doi.org/10.1016/j.arthro.2012.06.012
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treatment of a variety of disorders not only within the hip but also outside the hip.1 Labral tears are among the most commonly identified pathologies in patients undergoing hip arthroscopy. In contrast to the hip cartilage, there is a neural supply to the acetabular labrum, making it potentially an important source of mechanical symptoms in the hip.2-5 Although labral tears may occur as an isolated problem, they are usually associated with traumatic injury (e.g., hip dislocation or subluxation) or bony abnormality (e.g., hip dysplasia or femoroacetabular impingement).6 Tears of the acetabular labrum were first reported by Paterson in 1957.7 They have, however, only begun to emerge as a significant source of groin pain in the last decade. Resection of the torn labrum was the earliest treatment for symptomatic labral tears of the hip. Partial labrectomy may relieve pain and eliminate mechanical symptoms; however, the outcomes have been suggested to be better when (1) there is no chondral
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 28, No 12 (December), 2012: pp 1784-1789
ACETABULAR LABRUM HEALING TABLE 1. FAI Type Patient Patient Patient Patient Patient Patient
1 2 3 4 5 6
Mixed Mixed Mixed Pincer Mixed Mixed
Osteoplasty Acetabular Acetabular Acetabular Acetabular Acetabular Acetabular
and femoral and femoral and femoral and femoral and femoral
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Case-Specific Information
Anchor Type
Anchor Diameter
No. of Sutures
Chondral Damage (Beck Grade)
Chondral Treatment
Bioraptor Bio-PushLock Bio-PushLock Bioraptor Bio-PushLock Bio-PushLock
2.9 mm 3.5 mm 3.5 mm 2.9 mm 3.5 mm 3.5 mm
3 2 3 4 3 3
3 4 4 3 4 4
Microfracture Microfracture Microfracture Microfracture Microfracture Microfracture
Abbreviation: FAI, femoroacetabular impingement.
damage to the articular surfaces and (2) associated bony pathology is addressed concomitantly.2,8-10 In recent years, there has been mounting evidence that labral repair provides a superior result to labral resection.11,12 On the basis of basic science data that confirm that the labrum has many important functions in the hip, one can infer that it is beneficial to remove as little of the labrum as possible because the remaining labral tissue still may function.13-17 Given the presence of vascular supply in the labrum, one can expect that labral tears can heal after surgical repair. However, the ability of arthroscopically repaired lesions to heal is currently still unknown in humans. Philippon et al.18 studied the histologic healing process in an arthroscopically repaired acetabular-labral detachment in an ovine model. They concluded that arthroscopically repaired acetabular-labral lesions in sheep are capable of healing. Depending on the location of the lesion, the labrum appears to heal by way of fibrovascular repair tissue that originates from the capsular tissues (for intralabral lesions) or reattachment by direct new bone formation (for labral lesions that are repaired to exposed acetabular bone). The purpose of this study was to examine histologically the human healing response of arthroscopically repaired lesions of the acetabular labrum removed during total hip arthroplasty after clinical failure of the index arthroscopic procedure. We hypothesized that human labral tears could be arthroscopically repaired and would subsequently heal. METHODS Biopsy specimens retrieved from 6 patients were available for histologic assessment. The study design was multicentric, and samples were obtained from 2 university hospitals and 1 regional hospital. All 6 patients (4 women and 2 men) underwent an arthroscopic procedure for femoroacetabular impinge-
ment including repair of the acetabular labrum. The median age of these patients was 37 years (range, 30 to 40 years). All patients had a longitudinal buckethandle tear. During the arthroscopic repair, a capsulotomy from portal to portal was performed. The labrum was detached by completion of the tear, and the acetabular rim was trimmed. The tears were then refixed by means of simple looped sutures (2.9-mm Bioraptor anchor [Smith & Nephew Endoscopy, Andover, MA] and 3.5-mm Bio-PushLock [Arthrex, Naples, FL] with FiberWire [Arthrex]) (Table 1).19 The anchors were placed as close as possible to the acetabular rim without penetrating the articular surface. The labrum was tightly fixed with inevitable bunching and thereby deformation of its triangular shape. At the time of the arthroscopy, extensive chondral damage was observed (Beck grades 3 to 4), which was treated by debridement and microfracturing.20-23 The repairs were performed by 2 different surgeons. Postoperative rehabilitation consisted of partial weight bearing and restriction of range of motion to 90° during the first 6 weeks. After 6 weeks, patients were allowed full weight bearing and range of motion was not restricted anymore. Muscle-strengthening exercises were initiated. The surgical attempts for joint preservation of the index arthroscopy were realistically considered as salvage procedures for severely damaged joints. Despite a successful technical procedure, the clinical outcome was unsatisfactory, and the patients were scheduled for joint replacement after a short period. The median duration between the arthroscopic treatment and the arthroplasty procedure was 10 months (range, 8 to 14 months). Biopsy specimens of the acetabular labrum were harvested during arthroplasty surgery. Two tissue samples were obtained from the area of the repaired labrum, 1 close to the suture anchor and 1 more distally. A third tissue sample was taken from a distant healthy area and served as a control. The harvested
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E. A. AUDENAERT ET AL.
biopsy specimens were processed for standard histologic evaluation. Paraffin-embedded (5-m-thick) sections of labral tissue were stained with H&E for general histology and examined under polarized light microscopy by an anatomopathologist who specialized in musculoskeletal disorders. This study was approved by the hospital ethics committee. Informed consent to participate in the study was obtained from all patients. RESULTS All arthroscopically repaired labral tears appeared stable and grossly healed at the time of the arthroplasty surgery. Macroscopically, no clear splits or clefts were visible at the articular surface of the repaired labrum. The operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the body. Macroscopically, some diffuse capsule-labral adhesions were observed. However, this phenomenon was not confirmed by histology. Histologically, the labral tears appeared to be healed. All harvested labral tissues displayed a typical fibrocartilaginous appearance with a limited vascular supply. Calcifications were present in 1 of the repaired labral tissues. The surfaces of the treated structures were intact in all cases (Fig 1). Fibrovascular scar tissue was not seen in any of the labral bodies. All cases displayed normal fibrocartilaginous tissue in the areas around the suture (Fig 2). Interestingly, the sutures were partly incorporated and surrounded by labral tissue in all biopsy specimens. No formation of giant cells and no signs of a foreignbody reaction against the sutures were observed. However, in 3 tissue samples neovascularization in the labral tissue was noticed in close proximity to the sutures (Fig 3). In the superficial part and in the deep parts of the labral body near the acetabular-labral attachment (Figs 1 and 4), some small clefts were observed within the tissue in all cases. However, no remnants of labral detachment were observed. The center of the labral body appeared to consist of intact, dense fibrocartilaginous tissue (Fig 5). DISCUSSION Basic science studies confirm that the labral-chondral junction has many functions. The labrum serves as a joint seal that allows for joint lubrication and cartilage nutrition, and it helps in providing joint stability,
FIGURE 1. Histologic image showing an intact surface (arrows) and formation of clefts in the superficial part of the labrum (star) (H&E stain, original magnification ⫻100).
assists in load sharing, and likely has a role in joint proprioception.13-17,24,25 Therefore one can infer that it is beneficial to save as much of the torn labrum as possible. Moreover, recently, mounting evidence has shown that labral repair provides a superior result to labral resection.11,12 These data provide the orthopaedic community with additional evidence to support surgical repair of the symptomatic torn labrum over resection to maintain its biomechanical function. Until now, the histologic healing of labral tears has only been studied in sheep.18 The data presented in this study might be considered as the first attempt to characterize the histologic healing of surgically repaired labral tears in humans. It was shown in an ovine model that labral tears are capable of healing but that this healing was incomplete at 12 weeks. The repaired labra either healed by fibrovascular scar tissue that originated from the joint capsule or underwent direct healing to the acetabulum through new bone formation.18 In general, the histologic aspects of the human labral repair are similar to those observed in the ovine model but with some particularities. It was
ACETABULAR LABRUM HEALING
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FIGURE 4. Histologic image showing cleft formation (star) in the deep part of the labrum at the acetabular-labral attachment (H&E stain, original magnification ⫻100).
FIGURE 2. Histologic image showing fibrocartilaginous tissue of the labrum surrounding the suture remnants (star) (H&E stain, original magnification ⫻40).
shown in this study that human labral tears can be surgically repaired and heal. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of this structure were noticed in all cases. This might indicate some degenerative changes in the repaired tissue. Another remarkable finding was the fact that 3 cases displayed neovascularization in the proximity of the sutures without the presence of giant cells. This type of neovascularization can explain the relatively good healing response of the labrum tear. In contrast to the findings in the ovine model,18 signs of endochondral ossification were observed in only 1 of the human repaired labral tissues. Philippon et al.18 concluded that the healing in sheep was still incomplete at 12 weeks. There was
FIGURE 3. Histologic image showing multiple vessel formation (arrows) in the proximity of the suture remnants (H&E stain, original magnification ⫻200).
macroscopic evidence of a shallow, superficial cleft along the articular surface of the repair site in all specimens. These findings were not seen in the human biopsy specimens, probably because the arthroplasty surgery was performed at a median of 10 months after the repair surgery. In other words, the time to heal was much longer in this study compared with the 12 weeks in the ovine study. This might explain the more complete healed aspect of the repaired labra in this study. It was previously shown in an animal model that a partially resected acetabular labrum can regenerate spontaneously.26 Ovine labral tears repaired with single suture anchors are capable of healing, but they did not maintain their triangular cross-sectional geometry and appeared “bunched” and misshapen.18 The human operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the labral body. A possible explanation could be that the suture cut into the labrum and left a healed scar behind. However, this phenomenon was not observed at the index arthroscopy but could have occurred
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E. A. AUDENAERT ET AL. study, but the findings can serve as a base for future research under the same theme. CONCLUSIONS In this study the histologic aspects of arthroscopically repaired human labral tears were addressed. It was shown that human labral tears show healing potential after surgical repair. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of the repaired structures were noticed in all cases. REFERENCES
FIGURE 5. Histologic image showing an intact fibrocartilaginous structure in the central body of the labrum (H&E stain, original magnification ⫻100).
afterward. Currently, different labral suture techniques are available.19 Labral repair with a simple looped stitch that passes over the free edge of the labrum was considered to cause bunching of the labrum and distortion of the normal triangular cross-sectional anatomy of the labrum. In this way, the labral sealing function would be disrupted. However, in this study the operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the body. In this way, one might suppose that the labral seal is still functioning. More research concerning the outcome of the different suture techniques is needed. It was the purpose of this study to document the histologic aspects of human acetabular labrum repair. It must be emphasized that the attainability of the presented data is very limited in the human setting, and therefore biopsy specimens from only 6 patients were available for histologic assessment. Moreover, the biopsy specimens were harvested from patients who underwent a salvage arthroscopically labral repair. The chondral damage in these patients was so advanced that the clinical progress after the procedure was not satisfactory. These patients therefore elected to undergo joint replacement. In other words, the patients included in this study were not the ideal candidates for optimal assessment of the histologic repair of labral tears. These limitations do not allow a broad generalization of the findings observed in this
1. Hutchinson MR, Safran MR. On the shoulders of giants. Am J Sports Med 2011;39:5-6 (Suppl). 2. Safran MR. The acetabular labrum: Anatomic and functional characteristics and rationale for surgical intervention. J Am Acad Orthop Surg 2010;18:338-345. 3. Putz R, Schrank C. Anatomy of the labro-capsular complex. Orthopade 1998;27:675-680 (in German). 4. Hosokawa O. Histological study on the type and distribution of the sensory nerve endings in human hip joint capsule and ligament. Nippon Seikeigeka Gakkai Zasshi 1964;38:887-901 (in Japanese). 5. Kim YT, Azuma H. The nerve endings of the acetabular labrum. Clin Orthop Relat Res 1995;320:176-181. 6. Wenger DE, Kendell KR, Miner MR, Trousdale RT. Acetabular labral tears rarely occur in the absence of bony abnormalities. Clin Orthop Relat Res 2004;426:145-150. 7. Paterson I. The torn acetabular labrum; a block to reduction of a dislocated hip. J Bone Joint Surg Br 1957;39:306-309. 8. Farjo LA, Glick JM, Sampson TG. Hip arthroscopy for acetabular labral tears. Arthroscopy 1999;15:132-137. 9. Santori N, Villar RN. Acetabular labral tears. Result of arthroscopic partial limbectomy. Arthroscopy 2000;16:11-15. 10. Fitzgerald RH Jr. Acetabular labrum tears: Diagnosis and treatment. Clin Orthop Relat Res 1995;60-68. 11. Schilders E, Dimitrakopoulou A, Bismil Q, Marchant P, Cooke C. Arthroscopic treatment of labral tears in femoroacetabular impingement: A comparative study of refixation and resection with a minimum two-year follow-up. J Bone Joint Surg Br 2011;93:1027-1032. 12. Larson CM, Giveans MR. Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement. Arthroscopy 2009;25:369-376. 13. Crawford MJ, Dy CJ, Alexander JW, et al. The 2007 Frank Stinchfield Award. The biomechanics of the hip labrum and the stability of the hip. Clin Orthop Relat Res 2007;465:16-22. 14. Konrath GA, Hamel AJ, Olson SA, Bay B, Sharkey NA. The role of the acetabular labrum and the transverse acetabular ligament in load transmission in the hip. J Bone Joint Surg Am 1998;80:1781-1788. 15. Ferguson SJ, Bryant JT, Ganz R, Ito K. The acetabular labrum seal: A poroelastic finite element model. Clin Biomech (Bristol, Avon) 2000;15:463-468. 16. Ferguson SJ, Bryant JT, Ganz R, Ito K. The influence of the acetabular labrum on hip joint cartilage consolidation: A poroelastic finite element model. J Biomech 2000;33:953-960. 17. Ferguson SJ, Bryant JT, Ganz R, Ito K. An in vitro investiga-
ACETABULAR LABRUM HEALING
18. 19. 20.
21.
tion of the acetabular labral seal in hip joint mechanics. J Biomech 2003;36:171-178. Philippon MJ, Arnoczky ST, Torrie A. Arthroscopic repair of the acetabular labrum: A histologic assessment of healing in an ovine model. Arthroscopy 2007;23:376-380. Fry R, Domb B. Labral base refixation in the hip: Rationale and technique for an anatomic approach to labral repair. Arthroscopy 2010;26:81-89. Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of damage to the acetabular cartilage: Femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br 2005;87:1012-1018. Beck M, Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R. Anterior femoroacetabular impingement: Part II. Midterm results of surgical treatment. Clin Orthop Relat Res 2004: 67-73.
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22. Konan S, Rayan F, Meermans G, Witt J, Haddad FS. Validation of the classification system for acetabular chondral lesions identified at arthroscopy in patients with femoroacetabular impingement. J Bone Joint Surg Br 2011;93:332-336. 23. Philippon MJ, Schenker ML, Briggs KK, Maxwell RB. Can microfracture produce repair tissue in acetabular chondral defects? Arthroscopy 2008;24:46-50. 24. Takechi H, Nagashima H, Ito S. Intra-articular pressure of the hip joint outside and inside the limbus. Nippon Seikeigeka Gakkai Zasshi 1982;56:529-536. 25. Terayama K, Takei T, Nakada K. Joint space of the human knee and hip joint under a static load. Eng Med 1980;9:66-74. 26. Miozarri HH, Clark JM, Jacob HA, von Rechenberg B, Notzli HP. Effects of removal of the acetabular labrum in a sheep. Osteoarthritis Cartilage 2004;12:419-430.
Purpose: The purpose of this study was to histologically examine the human healing response of arthroscopically repaired acetabular labrum tears. Methods: Biopsy specimens were retrieved from 6 patients during total hip arthroplasty after clinical failure of the index arthroscopic procedure. All patients were diagnosed as having femoroacetabular impingement with a concomitant labral tear. In all cases severe chondral damage was observed during arthroscopy (Beck grades 3 to 4). Despite successful technical repair of the labral tear, chondral damage in these patients was so advanced that the clinical progress after the procedure was unsatisfactory and arthroplasty of the joint was required. Biopsy specimens of the repaired acetabular labra were harvested during the arthroplasty surgery and processed for standard histologic evaluation. Results: Macroscopically and histologically, all repaired labra kept their triangular shape more or less and appeared to have healed. All harvested biopsy specimens displayed a typical fibrocartilaginous appearance with limited vascular supply. Calcifications were present in only 1 biopsy specimen. In 3 cases neovascularization of the labral tissue was noticed in the proximity of the sutures. In the superficial and deep parts of the labral body, small clefts were observed in all cases. Conclusions: In this study the histologic aspects of arthroscopically repaired human labral tears were addressed. It was shown that human labral tears show healing potential after surgical repair. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of the repaired structures were noticed in all cases. Level of Evidence: Level IV, therapeutic case series.
H
ip arthroscopy has evolved from an experimental and mainly diagnostic tool to a standard and effective surgical procedure for the diagnosis and
From the Department of Orthopaedic Surgery and Traumatology (E.A.A., A.A.M.D., C.P.), N. Goormaghtigh Institute of Pathology (R.G.F.), and Laboratory of Connective Tissue Biology, Department of Rheumatology (A.A.M.D., G.V.), Ghent University Hospital, Ghent; Department of Orthopaedics, AZ Groeninge (E.A.A.), Kortrijk; and Department of Orthopaedics (K.C.), University Hospitals Leuven, Pellenberg, Belgium. E.A.A. and A.A.M.D. have contributed equally to this article and share first authorship. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received November 30, 2011; accepted June 4, 2012. Address correspondence to Aad A. M. Dhollander, M.D., Ph.D., Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, De Pintelaan 185 (P5), 9000 Ghent, Belgium. E-mail: [email protected] © 2012 by the Arthroscopy Association of North America 0749-8063/11795/$36.00 http://dx.doi.org/10.1016/j.arthro.2012.06.012
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treatment of a variety of disorders not only within the hip but also outside the hip.1 Labral tears are among the most commonly identified pathologies in patients undergoing hip arthroscopy. In contrast to the hip cartilage, there is a neural supply to the acetabular labrum, making it potentially an important source of mechanical symptoms in the hip.2-5 Although labral tears may occur as an isolated problem, they are usually associated with traumatic injury (e.g., hip dislocation or subluxation) or bony abnormality (e.g., hip dysplasia or femoroacetabular impingement).6 Tears of the acetabular labrum were first reported by Paterson in 1957.7 They have, however, only begun to emerge as a significant source of groin pain in the last decade. Resection of the torn labrum was the earliest treatment for symptomatic labral tears of the hip. Partial labrectomy may relieve pain and eliminate mechanical symptoms; however, the outcomes have been suggested to be better when (1) there is no chondral
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 28, No 12 (December), 2012: pp 1784-1789
ACETABULAR LABRUM HEALING TABLE 1. FAI Type Patient Patient Patient Patient Patient Patient
1 2 3 4 5 6
Mixed Mixed Mixed Pincer Mixed Mixed
Osteoplasty Acetabular Acetabular Acetabular Acetabular Acetabular Acetabular
and femoral and femoral and femoral and femoral and femoral
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Case-Specific Information
Anchor Type
Anchor Diameter
No. of Sutures
Chondral Damage (Beck Grade)
Chondral Treatment
Bioraptor Bio-PushLock Bio-PushLock Bioraptor Bio-PushLock Bio-PushLock
2.9 mm 3.5 mm 3.5 mm 2.9 mm 3.5 mm 3.5 mm
3 2 3 4 3 3
3 4 4 3 4 4
Microfracture Microfracture Microfracture Microfracture Microfracture Microfracture
Abbreviation: FAI, femoroacetabular impingement.
damage to the articular surfaces and (2) associated bony pathology is addressed concomitantly.2,8-10 In recent years, there has been mounting evidence that labral repair provides a superior result to labral resection.11,12 On the basis of basic science data that confirm that the labrum has many important functions in the hip, one can infer that it is beneficial to remove as little of the labrum as possible because the remaining labral tissue still may function.13-17 Given the presence of vascular supply in the labrum, one can expect that labral tears can heal after surgical repair. However, the ability of arthroscopically repaired lesions to heal is currently still unknown in humans. Philippon et al.18 studied the histologic healing process in an arthroscopically repaired acetabular-labral detachment in an ovine model. They concluded that arthroscopically repaired acetabular-labral lesions in sheep are capable of healing. Depending on the location of the lesion, the labrum appears to heal by way of fibrovascular repair tissue that originates from the capsular tissues (for intralabral lesions) or reattachment by direct new bone formation (for labral lesions that are repaired to exposed acetabular bone). The purpose of this study was to examine histologically the human healing response of arthroscopically repaired lesions of the acetabular labrum removed during total hip arthroplasty after clinical failure of the index arthroscopic procedure. We hypothesized that human labral tears could be arthroscopically repaired and would subsequently heal. METHODS Biopsy specimens retrieved from 6 patients were available for histologic assessment. The study design was multicentric, and samples were obtained from 2 university hospitals and 1 regional hospital. All 6 patients (4 women and 2 men) underwent an arthroscopic procedure for femoroacetabular impinge-
ment including repair of the acetabular labrum. The median age of these patients was 37 years (range, 30 to 40 years). All patients had a longitudinal buckethandle tear. During the arthroscopic repair, a capsulotomy from portal to portal was performed. The labrum was detached by completion of the tear, and the acetabular rim was trimmed. The tears were then refixed by means of simple looped sutures (2.9-mm Bioraptor anchor [Smith & Nephew Endoscopy, Andover, MA] and 3.5-mm Bio-PushLock [Arthrex, Naples, FL] with FiberWire [Arthrex]) (Table 1).19 The anchors were placed as close as possible to the acetabular rim without penetrating the articular surface. The labrum was tightly fixed with inevitable bunching and thereby deformation of its triangular shape. At the time of the arthroscopy, extensive chondral damage was observed (Beck grades 3 to 4), which was treated by debridement and microfracturing.20-23 The repairs were performed by 2 different surgeons. Postoperative rehabilitation consisted of partial weight bearing and restriction of range of motion to 90° during the first 6 weeks. After 6 weeks, patients were allowed full weight bearing and range of motion was not restricted anymore. Muscle-strengthening exercises were initiated. The surgical attempts for joint preservation of the index arthroscopy were realistically considered as salvage procedures for severely damaged joints. Despite a successful technical procedure, the clinical outcome was unsatisfactory, and the patients were scheduled for joint replacement after a short period. The median duration between the arthroscopic treatment and the arthroplasty procedure was 10 months (range, 8 to 14 months). Biopsy specimens of the acetabular labrum were harvested during arthroplasty surgery. Two tissue samples were obtained from the area of the repaired labrum, 1 close to the suture anchor and 1 more distally. A third tissue sample was taken from a distant healthy area and served as a control. The harvested
1786
E. A. AUDENAERT ET AL.
biopsy specimens were processed for standard histologic evaluation. Paraffin-embedded (5-m-thick) sections of labral tissue were stained with H&E for general histology and examined under polarized light microscopy by an anatomopathologist who specialized in musculoskeletal disorders. This study was approved by the hospital ethics committee. Informed consent to participate in the study was obtained from all patients. RESULTS All arthroscopically repaired labral tears appeared stable and grossly healed at the time of the arthroplasty surgery. Macroscopically, no clear splits or clefts were visible at the articular surface of the repaired labrum. The operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the body. Macroscopically, some diffuse capsule-labral adhesions were observed. However, this phenomenon was not confirmed by histology. Histologically, the labral tears appeared to be healed. All harvested labral tissues displayed a typical fibrocartilaginous appearance with a limited vascular supply. Calcifications were present in 1 of the repaired labral tissues. The surfaces of the treated structures were intact in all cases (Fig 1). Fibrovascular scar tissue was not seen in any of the labral bodies. All cases displayed normal fibrocartilaginous tissue in the areas around the suture (Fig 2). Interestingly, the sutures were partly incorporated and surrounded by labral tissue in all biopsy specimens. No formation of giant cells and no signs of a foreignbody reaction against the sutures were observed. However, in 3 tissue samples neovascularization in the labral tissue was noticed in close proximity to the sutures (Fig 3). In the superficial part and in the deep parts of the labral body near the acetabular-labral attachment (Figs 1 and 4), some small clefts were observed within the tissue in all cases. However, no remnants of labral detachment were observed. The center of the labral body appeared to consist of intact, dense fibrocartilaginous tissue (Fig 5). DISCUSSION Basic science studies confirm that the labral-chondral junction has many functions. The labrum serves as a joint seal that allows for joint lubrication and cartilage nutrition, and it helps in providing joint stability,
FIGURE 1. Histologic image showing an intact surface (arrows) and formation of clefts in the superficial part of the labrum (star) (H&E stain, original magnification ⫻100).
assists in load sharing, and likely has a role in joint proprioception.13-17,24,25 Therefore one can infer that it is beneficial to save as much of the torn labrum as possible. Moreover, recently, mounting evidence has shown that labral repair provides a superior result to labral resection.11,12 These data provide the orthopaedic community with additional evidence to support surgical repair of the symptomatic torn labrum over resection to maintain its biomechanical function. Until now, the histologic healing of labral tears has only been studied in sheep.18 The data presented in this study might be considered as the first attempt to characterize the histologic healing of surgically repaired labral tears in humans. It was shown in an ovine model that labral tears are capable of healing but that this healing was incomplete at 12 weeks. The repaired labra either healed by fibrovascular scar tissue that originated from the joint capsule or underwent direct healing to the acetabulum through new bone formation.18 In general, the histologic aspects of the human labral repair are similar to those observed in the ovine model but with some particularities. It was
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FIGURE 4. Histologic image showing cleft formation (star) in the deep part of the labrum at the acetabular-labral attachment (H&E stain, original magnification ⫻100).
FIGURE 2. Histologic image showing fibrocartilaginous tissue of the labrum surrounding the suture remnants (star) (H&E stain, original magnification ⫻40).
shown in this study that human labral tears can be surgically repaired and heal. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of this structure were noticed in all cases. This might indicate some degenerative changes in the repaired tissue. Another remarkable finding was the fact that 3 cases displayed neovascularization in the proximity of the sutures without the presence of giant cells. This type of neovascularization can explain the relatively good healing response of the labrum tear. In contrast to the findings in the ovine model,18 signs of endochondral ossification were observed in only 1 of the human repaired labral tissues. Philippon et al.18 concluded that the healing in sheep was still incomplete at 12 weeks. There was
FIGURE 3. Histologic image showing multiple vessel formation (arrows) in the proximity of the suture remnants (H&E stain, original magnification ⫻200).
macroscopic evidence of a shallow, superficial cleft along the articular surface of the repair site in all specimens. These findings were not seen in the human biopsy specimens, probably because the arthroplasty surgery was performed at a median of 10 months after the repair surgery. In other words, the time to heal was much longer in this study compared with the 12 weeks in the ovine study. This might explain the more complete healed aspect of the repaired labra in this study. It was previously shown in an animal model that a partially resected acetabular labrum can regenerate spontaneously.26 Ovine labral tears repaired with single suture anchors are capable of healing, but they did not maintain their triangular cross-sectional geometry and appeared “bunched” and misshapen.18 The human operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the labral body. A possible explanation could be that the suture cut into the labrum and left a healed scar behind. However, this phenomenon was not observed at the index arthroscopy but could have occurred
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E. A. AUDENAERT ET AL. study, but the findings can serve as a base for future research under the same theme. CONCLUSIONS In this study the histologic aspects of arthroscopically repaired human labral tears were addressed. It was shown that human labral tears show healing potential after surgical repair. The surfaces of the labral tissues were intact, and neither remnants of the tear nor the presence of fibrovascular scar tissue was observed. However, some small clefts in the superior and deep parts of the repaired structures were noticed in all cases. REFERENCES
FIGURE 5. Histologic image showing an intact fibrocartilaginous structure in the central body of the labrum (H&E stain, original magnification ⫻100).
afterward. Currently, different labral suture techniques are available.19 Labral repair with a simple looped stitch that passes over the free edge of the labrum was considered to cause bunching of the labrum and distortion of the normal triangular cross-sectional anatomy of the labrum. In this way, the labral sealing function would be disrupted. However, in this study the operated labra kept their triangular shape more or less, because the sutures were partly incorporated in the body. In this way, one might suppose that the labral seal is still functioning. More research concerning the outcome of the different suture techniques is needed. It was the purpose of this study to document the histologic aspects of human acetabular labrum repair. It must be emphasized that the attainability of the presented data is very limited in the human setting, and therefore biopsy specimens from only 6 patients were available for histologic assessment. Moreover, the biopsy specimens were harvested from patients who underwent a salvage arthroscopically labral repair. The chondral damage in these patients was so advanced that the clinical progress after the procedure was not satisfactory. These patients therefore elected to undergo joint replacement. In other words, the patients included in this study were not the ideal candidates for optimal assessment of the histologic repair of labral tears. These limitations do not allow a broad generalization of the findings observed in this
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